WO2016098372A1 - Electrode for limiting current type gas sensors, method for producing same, limiting current type gas sensor, method for manufacturing limiting current type gas sensor, and sensor network system - Google Patents

Electrode for limiting current type gas sensors, method for producing same, limiting current type gas sensor, method for manufacturing limiting current type gas sensor, and sensor network system Download PDF

Info

Publication number
WO2016098372A1
WO2016098372A1 PCT/JP2015/067018 JP2015067018W WO2016098372A1 WO 2016098372 A1 WO2016098372 A1 WO 2016098372A1 JP 2015067018 W JP2015067018 W JP 2015067018W WO 2016098372 A1 WO2016098372 A1 WO 2016098372A1
Authority
WO
WIPO (PCT)
Prior art keywords
gas sensor
limiting current
electrode
current type
metal particle
Prior art date
Application number
PCT/JP2015/067018
Other languages
French (fr)
Japanese (ja)
Inventor
俊輔 赤坂
政人 守分
Original Assignee
ローム株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ローム株式会社 filed Critical ローム株式会社
Publication of WO2016098372A1 publication Critical patent/WO2016098372A1/en

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
    • G01N27/41—Oxygen pumping cells
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/416—Systems

Definitions

  • the present embodiment relates to an electrode for a limiting current gas sensor and a manufacturing method thereof, a limiting current gas sensor and a manufacturing method thereof, and a sensor network system.
  • a resistance change type a capacitance change type, a zirconia (ZrO 2 ) solid electrolyte type, and the like are known as humidity sensors for detecting the concentration of water vapor in a gas to be measured.
  • ZrO 2 zirconia
  • the polymer film resistance variable type is advantageous in that it is inexpensive and easy to make a device.
  • the capacitance change type has the advantage of good linearity, measurement in the entire relative humidity range, and low temperature dependence.
  • the influence of water other than pure water (such as tap water) and organic solvents is great.
  • the capacity at a humidity of 0% RH is several hundred pF
  • the capacity change when 1% RH changes is 1 pF or less, and periodic calibration is required for accurate humidity measurement.
  • it is an effective device when humidity measurement accuracy is not required in a general office environment it is an effective device, while high-accuracy humidity measurement, condensation, and gas exposure (atmospheric observation applications and bathrooms), 100 ° C Use in an atmosphere with such a high temperature is unexpected.
  • Humidity sensors using a zirconia solid electrolyte are sold for measuring humidity at high temperatures.
  • Oxygen sensor using the zirconia solid electrolyte is used for the reduction of the combustion efficiency and NO X of the motor vehicle, durability of the material is proven.
  • zirconia is used after being raised to several hundred degrees Celsius, the power consumption is as high as 100 W and the handling of high-temperature objects is difficult, so the market is limited to some industrial applications.
  • This type of limiting current oxygen sensor has the advantage of high reliability and good linearity.
  • the excessive current intake from the porous electrode of oxygen gas deteriorates the limit current characteristics and decreases the sensor sensitivity.
  • an electrode for a limit current type gas sensor having good limit current characteristics and improved detection sensitivity, and a manufacturing method thereof, and a limit current type gas sensor to which this limit current type gas sensor electrode is applied and a manufacturing method thereof And a sensor network system.
  • an electrode for a limiting current type gas sensor including a dense electrode having a metal particle sintered layer and a fine gas introduction path formed in the metal particle sintered layer.
  • a substrate a porous electrode disposed on the substrate, an insulating film disposed on the porous electrode, and an opening patterned in the insulating film
  • a solid electrolyte layer disposed on the porous electrode and on the insulating film surrounding the opening; and on the solid electrolyte layer, facing the porous electrode and substantially longitudinally with respect to the substrate
  • a limiting current type gas sensor including a metal particle sintered layer and a dense electrode having a fine gas introduction path formed in the metal particle sintered layer.
  • a step of forming a porous electrode on a substrate a step of forming an insulating film on the porous electrode, and patterning the insulating film to form an opening Forming a solid electrolyte layer on the porous electrode in the opening and on the insulating film surrounding the opening; and facing the porous electrode on the solid electrolyte layer;
  • a method of manufacturing a limiting current gas sensor having a step of forming a dense electrode having a metal particle sintered layer and a fine gas introduction path formed in the metal particle sintered layer in a substantially vertical direction.
  • a sensor network system including the above-described limiting current gas sensor is provided.
  • an electrode for a limit current gas sensor with good limit current characteristics and improved detection sensitivity a method for manufacturing the electrode, a limit current gas sensor to which the electrode for the limit current gas sensor is applied, and A manufacturing method and a sensor network system can be provided.
  • a method for producing an electrode for a limiting current gas sensor wherein (a) air is introduced in the middle of temperature lowering (700 ° C.), CNT is burned, and a fine gas introduction path having a diameter of about 0.1 ⁇ m (B) Another process diagram in which air is introduced in the middle of temperature lowering (700 ° C.) and CNTs are burned to form a fine gas introduction path having a diameter of about 0.1 ⁇ m.
  • FIG. 12 is a schematic sectional view taken along the line II of FIG.
  • FIG. 4 (A) Schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) Schematic sectional view taken along line VI-VI in FIG. 5). (A) Schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) Schematic cross-sectional structure diagram taken along line VII-VII in FIG. 6). (A) Schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) Schematic sectional view taken along line VIII-VIII in FIG. 7). Typical cross-section FIG. (8) which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 1st Embodiment.
  • the typical plane pattern block diagram of the limiting current type gas sensor which concerns on 2nd Embodiment Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 1). Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 2). Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 3). Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 4). Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 5).
  • Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 6).
  • A Schematic cross-sectional structure diagram showing one step (beam structure forming step) of the method for manufacturing a limiting current gas sensor according to the embodiment, (b) One step of the method for manufacturing the limiting current gas sensor according to the embodiment The typical cross-section figure which shows (another beam structure formation process).
  • A Layout diagram (top view) of the beam structure of the limiting current type gas sensor according to the embodiment, (b) A schematic cross-sectional structure diagram taken along line IX-IX in FIG. The flowchart figure which shows the operation
  • FIG. 6 is a schematic explanatory diagram of current-voltage characteristics in the limiting current type gas sensor according to the embodiment.
  • FIG. 4 is a schematic cross-sectional view for explaining ion conduction in the limiting current gas sensor according to the embodiment.
  • the typical bird's-eye view block diagram which shows the cover of the package which accommodates the limiting current type gas sensor which concerns on embodiment.
  • the typical bird's-eye view block diagram which shows the main body of the package which accommodates the limiting current type gas sensor which concerns on embodiment.
  • the typical block block diagram which shows the limiting current type gas sensor which concerns on embodiment.
  • the limiting current gas sensor electrode according to Comparative Example 1 includes a solid electrolyte layer 4A, a porous electrode 5R disposed on the upper surface of the solid electrolyte layer 4A, and a solid electrolyte layer 4A. And a porous electrode 5D disposed on the lower surface.
  • the limiting current type gas sensor electrode 14A according to the comparative example 1 includes a porous electrode 5R disposed on the upper surface of the solid electrolyte layer 4A for controlling the oxygen gas inflow to control the oxygen gas inflow amount.
  • the porous electrode 5R has a porous structure, it is difficult to control the inflow amount (pore diameter) of oxygen gas.
  • the limiting current type gas sensor electrode according to Comparative Example 2 includes a solid electrolyte layer 4A, a porous electrode 5PU disposed on the upper surface of the solid electrolyte layer 4A, and a porous electrode 5PU.
  • the porous insulating film or the porous insulating substrate 6P is arranged on the upper surface of the solid electrolyte layer 4A and used to throttle the oxygen gas. It has.
  • the porous insulating film or the porous insulating substrate 6P has a porous structure, it is difficult to control the inflow amount (pore diameter) of oxygen gas. In addition, it is difficult to adopt a MEMS beam structure in a porous insulating substrate.
  • Electrode for limiting current type gas sensor embodiment
  • FIG. 1 A schematic cross-sectional structure of the limiting current gas sensor electrode 14 according to the embodiment is represented as shown in FIG.
  • the limiting current gas sensor electrode 14 includes a metal particle sintered layer 28 and a fine gas introduction path 26 formed in the metal particle sintered layer 28 as shown in FIG. A dense electrode 5U is provided.
  • the fine gas introduction path 26 can be formed by a heat treatment step of nanowires having a nanometer scale contained in the metal particle sintered layer 28, nanotubes, nanoparticles, or the like or an etching treatment step combined with the heat treatment step. Nanowires, nanotubes, and nanoparticles can be formed from, for example, carbon (C), zinc oxide (ZnO), and the like. Note that the metal particle sintered layer 28 and the fine gas introduction path 26 formed in the metal particle sintered layer 28 will be described with reference to FIGS. 5 and 6 in the description of the method of manufacturing the limiting current gas sensor electrode 14. ,explain.
  • the limiting current gas sensor electrode 14 includes a solid electrolyte layer 4 and a porous electrode 5D disposed in contact with the solid electrolyte layer 4 as shown in FIG.
  • the dense electrode 5U is disposed in contact with the surface of the solid electrolyte layer 4 facing the porous electrode 5D.
  • the metal particle sintered layer 28 may include nanowires.
  • the nanowire may include CNT or ZnO.
  • the metal particle sintered layer 28 includes carbon nanotubes or carbon nanoparticles, and the fine gas introduction path 26 burns the carbon nano nanotubes or carbon nanoparticles by the combustion of the metal particle sintered layer 28 in the atmosphere. It may be formed.
  • the metal particle sintered layer 28 may include ZnO, and the fine gas introduction path 26 may be formed by etching ZnO by wet etching after burning the metal particle sintered layer 28 in the atmosphere.
  • the electrode 14 for limiting current type gas sensor according to the embodiment can control the gas permeation amount by the shape of the fine gas introduction path 26.
  • the limiting current type gas sensor electrode 14 can control the gas permeation amount by the content ratio of the fine gas introduction path 26.
  • the metal particles of the metal particle sintered layer 28 may include any of Pt, Ag, Pd, Au, or Ru.
  • the metal particle sintered layer 28 may include nanowires that are confined in the metal particle sintered layer 28 and are not burned by combustion in the atmosphere.
  • the nanowire or nanoparticle has a diameter of about 0.1 ⁇ m or less. Further, the length of the nanowire is, for example, about 10 ⁇ m or less.
  • the merit of using the nanowire is that the gas permeation amount can be controlled by the shape (diameter and length) of the nanowire, and the gas permeation amount can be controlled by the ratio of the nanowire.
  • Oxygen gas uptake control experiment An oxygen gas uptake control experiment using bulk YSZ as the solid electrolyte layer 4 was performed. The purpose of the experiment is to reduce oxygen gas uptake.
  • FIG. 2 An example of a cross-sectional SEM photograph of porous platinum is represented as shown in FIG. 2, and an example of a cross-sectional SEM photograph of dense platinum is represented as shown in FIG.
  • a porous (hole) of about several ⁇ m is observed.
  • Pt is densely formed and no porous is observed.
  • a dense electrode 5U made of dense platinum is disposed on the solid electrolyte layer 4, while the solid electrolyte layer 4
  • a porous electrode 5D made of porous platinum is disposed on the lower surface.
  • Oxygen (O 2 ) gas passes through the dense electrode 5U made of dense platinum under moderate flow rate control, and O 2 ⁇ ions pass through the solid electrolyte layer 4 made of bulk YSZ by ionic conduction, and from porous platinum. Oxygen (O 2 ) gas passes through the porous electrode 5D.
  • the temperature is set to 500 ° C., and an example of current-voltage characteristics in the atmosphere and in nitrogen is expressed as shown in FIG.
  • the oxygen gas introduction amount is reduced by reducing the oxygen inflow amount in order to control diffusion.
  • a dense electrode having a fine gas introduction path is used as an electrode for a limiting current gas sensor.
  • the amount of oxygen inflow can be reduced by a dense electrode film having a fine gas introduction path 26 having a small pore diameter (about 0.1 ⁇ m).
  • FIG. 5 (a) shows a method of manufacturing the limiting current gas sensor electrode 14 according to the embodiment, in which a metal particle paste layer 25 containing CNTs 22 is formed on a solid electrolyte layer (YSZ) 4 by a printing process.
  • the step of removing the binder by firing at 500 ° C. in the atmosphere is expressed as shown in FIG. 5B, and the metal particle sintered layer 28 is formed at 1100 ° C. in an inert gas atmosphere.
  • the step of forming is represented as shown in FIG.
  • the method for manufacturing the limiting current gas sensor electrode 14 includes a step of forming the metal particle paste layer 25 contained in the binder 24 in contact with the solid electrolyte layer 4 and a first temperature in the atmosphere. Firing and removing the binder 24, firing at a second temperature in an inert gas atmosphere to form a metal particle sintered layer 28, and introducing the atmosphere at the third temperature to sinter the metal particles Forming a fine gas introduction path 26 in the layer 28.
  • the process of forming the metal particle paste layer 25 may include a printing process.
  • the first temperature may be about 500 ° C., for example.
  • the second temperature may be about 1100 ° C., for example.
  • the third temperature may be about 700 ° C., for example.
  • the binder 24 may include, for example, an ethyl cellulose-based or acrylic material.
  • the step of forming the fine gas introduction path 26 is performed by CNT combustion by the combustion of the metal particle sintered layer 28 in the atmosphere and the fine gas.
  • a step of forming the introduction path 26 may be included.
  • the metal particle sintered layer 28 includes CNTs 22 or carbon nanoparticles as shown in FIG.
  • the step of forming CNTs may include a step of burning the CNTs 22 or the carbon nanoparticles by burning the sintered metal particle layer 28 in the atmosphere.
  • FIG. 6B even if some of the CNTs 22 are not burned and remain in the metal particle sintered layer 28 due to the combustion of the metal particle sintered layer 28 in the atmosphere, no problem.
  • the metal particle sintered layer 28 includes ZnO, and the step of forming the fine gas introduction path 26 is performed in the atmosphere of the metal particle sintered layer 28. After burning in, there may be a step of etching ZnO by wet etching.
  • a metal particle paste layer 25 containing metal particles 20 and CNTs 22 in a binder 24 is applied onto the solid electrolyte layer 4 on the solid electrolyte layer 4, and a printing step. Formed by.
  • the metal particle paste layer 25 is an electrode paste for controlling the oxygen gas permeation amount.
  • the CNT 22 is a nanowire having a diameter of about 0.1 ⁇ m or less.
  • the binder 24 includes, for example, an ethyl cellulose material or an acrylic material.
  • the binder is removed by heat treatment in the atmosphere at, for example, about 500 ° C.
  • a non-burning material such as ZnO nanowire
  • a similar structure can be formed by wet etching after heat treatment in the atmosphere, and atmosphere control is unnecessary. As shown in FIG. 6B, there is no problem even if there is unburned CNT 22 because the conductivity can be maintained.
  • a zirconia oxygen / humidity sensor electrode According to the method for manufacturing a limiting current gas sensor electrode according to the embodiment, it is possible to form a zirconia oxygen / humidity sensor electrode.
  • FIG. 7 shows a schematic cross-sectional structure of the sensor portion formed in the MEMS beam structure in the limiting current type gas sensor 12A according to the comparative example 3. Moreover, it is the limiting current type gas sensor 12A which concerns on the comparative example 4, Comprising: The typical cross-section of the sensor part formed in a MEMS beam structure is represented as shown in FIG.
  • a limiting current type gas sensor 12A includes a MEMS beam structure substrate 1, a porous electrode 5D disposed on the substrate 1, and a solid electrolyte disposed on the porous electrode.
  • a porous electrode 5PU disposed on the solid electrolyte layer 4 so as to face the porous electrode 5D and substantially vertically with respect to the substrate 1, and the entire surface of the device disposed on the porous electrode 5PU.
  • an insulating film 8D for covering the substrate.
  • the insulating film 8D is formed of a porous insulating film (Al 2 O 3 —SiO 2 ) or a dense insulating film (glass paste).
  • the porous electrodes 5D and 5PU are formed of porous Pt having a pore diameter of several ⁇ m, and the solid electrolyte layer 4 is formed of YSZ having a thickness of about 15 ⁇ m.
  • the thickness of the substrate 1 having the MEMS beam structure is formed of a silicon substrate of about 10 ⁇ m.
  • the limiting current type gas sensor 12A In the limiting current type gas sensor 12A according to Comparative Example 3, as shown in FIG. 7, it is formed of a porous insulating film (Al 2 O 3 , SiO 2 , Al 2 O 3 —SiO 2 ) or a dense insulating film (glass paste).
  • the insulating film 8D has a structure for reducing the amount of oxygen gas introduced.
  • the limiting current characteristic deteriorates due to excessive incorporation of oxygen gas from the porous electrode 5PU, and the sensor sensitivity is lowered. .
  • the limiting current type gas sensor 12A according to the comparative example 4 includes a MEMS beam substrate 1, a porous electrode 5D disposed on the substrate 1, and a solid electrolyte disposed on the porous electrode.
  • an insulating film 8D disposed on the insulating film 8P.
  • the insulating film 8P is formed of a porous insulating film (Al 2 O 3 , SiO 2 , Al 2 O 3 —SiO 2 ), and the insulating film 8D is formed of a dense insulating film (glass paste).
  • the porous electrodes 5D and 5PU are formed of porous Pt having a pore diameter of several ⁇ m, and the solid electrolyte layer 4 is formed of YSZ having a thickness of about 15 ⁇ m.
  • the thickness of the substrate 1 having the MEMS beam structure is formed of a silicon substrate of about 10 ⁇ m.
  • the limiting current type gas sensor 12A according to the comparative example 4 has a structure for taking in oxygen gas from the side surface of the insulating film 8P formed of a porous insulating film (Al 2 O 3 —SiO 2 ).
  • the limiting current characteristic deteriorates due to excessive uptake of oxygen gas from the porous electrode 5PU, and the sensor sensitivity decreases.
  • FIG. 9A shows a schematic cross-sectional structure of the sensor portion formed in the MEMS beam structure, which is the limiting current type gas sensor 12 according to the first embodiment. Further, another schematic cross-sectional structure of the sensor portion formed in the MEMS beam structure of the limiting current gas sensor 12 according to the first embodiment is expressed as shown in FIG.
  • the limiting current type gas sensor 12 includes a substrate 1 having a MEMS beam structure, a porous electrode 5D disposed on the substrate 1, and a porous electrode 5D.
  • a substrate 1 having a MEMS beam structure
  • a porous electrode 5D disposed on the substrate 1
  • a porous electrode 5D On the solid electrolyte layer 4 disposed on the top, on the solid electrolyte layer 4, facing the porous electrode 5 ⁇ / b> D and disposed substantially vertically with respect to the substrate 1, the metal particle sintered layer 28 and the metal particle firing And a dense electrode 5U including a fine gas introduction path 26 formed in the binder layer 28.
  • a limiting current type gas sensor 12 includes a substrate 1 having a MEMS beam structure, a porous electrode 5D disposed on the substrate 1, and a porous material.
  • a dense electrode 5U facing the porous electrode 5D and disposed substantially vertically with respect to the substrate 1, a metal particle sintered layer 28 and a fine gas introduction path 26 formed in the metal particle sintered layer 28 are provided.
  • a dense electrode 5U facing the porous electrode 5D and disposed substantially vertically with respect to the substrate 1, a metal particle sintered layer 28 and a fine
  • the insulating film 8 is not in contact between the end face of the solid electrolyte layer 4 and the porous electrode 5D. It is possible to suppress the uptake of oxygen (O) ions from the end surface of the solid electrolyte layer 4 and reduce the surface conduction current component between the dense electrode 5U and the porous electrode 5D.
  • the insulating film 3 disposed on the substrate 1 may be provided, and the porous electrode 5D may be disposed on the insulating film 3.
  • the porous electrode 5D is formed of porous Pt having a pore diameter of about several ⁇ m, and the thickness is, for example, about 1 ⁇ m or more. This is because Pt aggregates and insulates if it is too thin.
  • the solid electrolyte layer 4 is made of YSZ having a thickness of about 4 ⁇ m or more. This is because if it is thin, the upper and lower Pt electrodes become conductive.
  • the thickness of the substrate 1 having a MEMS beam structure is a silicon substrate having a thickness of about 10 ⁇ m.
  • the Pt electrode itself is formed in a nanostructure. That is, Pt mixed with CNT is sintered, and finally a sintered metal particle layer in which CNTs are burned off to form a fine gas introduction path is applied as the dense electrode 5U. Carbon nanoparticles may be applied instead of CNTs.
  • the thickness of the dense electrode 5U formed of dense Pt is, for example, about 1 ⁇ m or more. This is because Pt aggregates and insulates if it is too thin.
  • a limiting current type gas sensor since the oxygen gas uptake can be controlled by the dense electrode, a limiting current type gas sensor having good limiting current characteristics and improved detection sensitivity is provided. be able to.
  • the metal particle sintered layer 28 includes CNTs 22 or carbon nanoparticles, and the fine gas introduction path 26 is formed by burning the CNTs 22 or carbon nanoparticles by burning the metal particle sintered layer 28 in the atmosphere. Also good.
  • the metal particle sintered layer 28 may include ZnO, and the fine gas introduction path 26 may be formed by etching ZnO by wet etching after burning the metal particle sintered layer 28 in the atmosphere.
  • the limiting current type gas sensor 12 can control the gas permeation amount by the shape of the fine gas introduction path 26.
  • the limiting current type gas sensor 12 can control the gas permeation amount by the content ratio of the fine gas introduction path 26.
  • the metal particles of the metal particle sintered layer 28 may include any one of Pt, Ag, Pd, Au, or Ru.
  • FIG. 10 The schematic plane pattern configuration of the limiting current type gas sensor 12 according to the first embodiment is expressed as shown in FIG. 10, and the enlarged schematic plane pattern configuration of the sensor portion is expressed as shown in FIG.
  • FIG. 10 A schematic cross-sectional structure taken along line II in FIG. 11 is expressed as shown in FIG.
  • the limiting current type gas sensor 12 is disposed on the substrate 1, the porous electrode 5D disposed on the substrate 1, and the porous electrode 5D.
  • the insulating film 8, the solid electrolyte layer 4 disposed on the porous electrode 5 ⁇ / b> D of the opening 7 patterned on the insulating film 8, and the insulating film 8 surrounding the opening 7, and the solid electrolyte layer 4 are porous.
  • the limiting current type gas sensor 12 applies a voltage between the dense electrode 5U and the porous electrode 5D to thereby generate a predetermined gas in the gas to be measured.
  • a detection circuit 18 for detecting the concentration by a limiting current type is provided.
  • the detection circuit 18 can detect the oxygen concentration based on the limit current.
  • the detection circuit 18 can detect the water vapor concentration based on the limit current.
  • the limiting current type gas sensor 12 includes a first stress relaxation low thermal expansion film 6 (5U) disposed on the dense electrode 5U, and a porous film.
  • the second stress relaxation low thermal expansion film 6 (5D) disposed on the porous electrode 5D and the third stress relaxation low thermal expansion film 6 (4) disposed on the solid electrolyte layer 4 may be provided. .
  • the limiting current type gas sensor 12 includes a first stress relaxation low thermal expansion film 6 (5U) and a third stress relaxation low heat expansion in plan view.
  • the first warp-suppressing porous insulating film 10 (5U) disposed on the dense electrode 5U across the expansion film 6 (4), and the second stress relaxation low thermal expansion film 6 (in plan view) 5D) and the second stress-reducing low thermal expansion film 6 (4), the second warp suppressing porous insulating film 10 (5D) disposed on the porous electrode 5D may be provided. good.
  • the limiting current type gas sensor 12 includes a MEMS element structure of a double-supported beam structure as a basic structure. Although a detailed structure will be described later, a sensor portion is disposed in the center portion, and a porous electrode 5D connected to the sensor portion and a dense electrode 5U are disposed in the beam portion of the both-end supported beam structure, and the porous electrode 5D. A detection circuit 18 is connected between the dense electrodes 5U.
  • the sensor part in the center is embedded with a microheater 2 for heating the sensor part, and the heat capacity of the sensor part in the center is reduced by using the MEMS element structure of the double-supported beam structure as a basic structure, The sensor sensitivity is improved.
  • the substrate 1 includes a micro heater 2 as shown in FIG.
  • the microheater 2 may be disposed on the upper part of the substrate 1 or the lower part of the substrate 1. Further, the microheater 2 may be embedded in the substrate 1 as shown in FIG.
  • the micro heater 2 can be formed by, for example, a Pt heater formed by printing or a polysilicon heater. Further, a laminated film 100 of silicon oxide film / silicon nitride film including the microheater 2 made of polysilicon may be formed on the surface of the substrate 1 (FIG. 29).
  • the porous electrode 5D and the dense electrode 5U can be formed of a porous Pt electrode.
  • the porous Pt electrode can be formed by printing, vapor deposition, or sputtering.
  • the thicknesses of the porous electrode 5D and the dense electrode 5U are, for example, about 0.5 ⁇ m to 10 ⁇ m.
  • the insulating film 8 can be formed of any of Al 2 O 3 , Al 2 O 3 —SiO 2 , YSZ—SiO 2 , or YSZ—Al 2 O 3 .
  • the insulating film 8 can be formed by a printing process or a sputtering process.
  • the thickness of the insulating film 8 is, for example, about 1.0 ⁇ m to 10 ⁇ m.
  • YSZ is a yttrium-stabilized zirconia (YSZ: Yttria-Stabilized Zirconia) film.
  • the contact area between the stabilized zirconia (4) / Pt porous electrode (5D) is stabilized, the contact between the end surface of the stabilized zirconia (4) and the Pt porous electrode (5D) is eliminated, and The surface conduction component between the Pt porous electrode (5D) and the Pt porous electrode (5U) can be removed.
  • the solid electrolyte layer 4 can be formed of a stabilized zirconia film containing at least one of YSZ, YSZ—SiO 2 , or YSZ—Al 2 O 3 .
  • the solid electrolyte layer 4 can be formed by a printing process or a sputtering process.
  • the thickness of the solid electrolyte layer 4 is, for example, about 1.0 ⁇ m to 10 ⁇ m.
  • the low thermal expansion film 6 for stress relaxation can adjust the film density depending on the amount of gas to be detected.
  • the low thermal expansion film 6 for stress relaxation can be formed of any one of a dense film, a porous film, or a composite film of a dense film and a porous film.
  • the stress relaxation low thermal expansion film 6 may be formed of a material containing at least one of SiO 2 , Al 2 O 3 , YSZ, or mullite. Moreover, the low thermal expansion film 6 for stress relaxation can be formed by a printing process or a sputtering process. The thickness of the low thermal expansion film 6 for stress relaxation is, for example, about 1.0 ⁇ m to 5.0 ⁇ m.
  • the warp suppressing porous insulating film 10 may be formed of a material containing at least one of SiO 2 , Al 2 O 3 , YSZ, or mullite. Moreover, the warp suppressing porous insulating film 10 can be formed by a printing process or a sputtering process. The thickness of the warp suppressing porous insulating film 10 is, for example, about 1.0 ⁇ m to 5.0 ⁇ m.
  • the substrate 1 may have a MEMS beam structure.
  • the substrate 1 can be formed of a silicon substrate having a thickness of 10 ⁇ m or less, preferably 2 ⁇ m or less. If MEMS is applied, the thickness of the substrate 1 can be reduced to 2 ⁇ m or less, so that the heat capacity is reduced and the power consumption in the microheater 2 can be reduced.
  • the limiting current type gas sensor 12 is formed as a doubly supported beam structure on a cavity C (Cavity) formed in the substrate 1, as shown in FIGS. Has been.
  • the beam structure is a beam structure formed by MEMS and having a thickness of 10 ⁇ m or less, preferably 2 ⁇ m or less.
  • the insulating film 3 disposed on the substrate 1 may be provided, and the porous electrode 5D may be disposed on the insulating film 3.
  • the insulating film 3 can be formed of a porous film containing any of Al 2 O 3 , Al 2 O 3 —SiO 2 , YSZ—SiO 2 , or YSZ—Al 2 O 3 .
  • the insulating film 3 functions as a gas intake film and can be formed by a printing process or a sputtering process.
  • the thickness of the insulating film 3 is, for example, about 0 to 10 ⁇ m.
  • the insulating film 3 is not necessarily provided.
  • a porous electrode 5D that can be formed of a porous Pt electrode can be used as the gas-intake film.
  • Such a limiting current type gas sensor may be manufactured by a method other than MEMS.
  • the thickness of the silicon substrate 1 is, for example, about 600 ⁇ m.
  • the manufacturing method of the limiting current type gas sensor according to the first embodiment includes the step of forming the porous electrode 5D on the substrate 1, and the insulating film 8 on the porous electrode 5D. Forming the opening 7 by patterning the insulating film 8, and forming the solid electrolyte layer 4 on the porous electrode 5D of the opening 7 and on the insulating film 8 surrounding the opening 7. And a fine gas introduction path formed in the metal particle sintered layer 28 and the metal particle sintered layer 28 on the solid electrolyte layer 4 so as to face the porous electrode 5D and substantially in the longitudinal direction with respect to the substrate 1. And the step of forming a dense electrode 5U.
  • the insulating film 8 makes the contact between the end face of the solid electrolyte layer 4 and the porous electrode 5D non-contact, suppresses the intake of oxygen (O) ions from the end face of the solid electrolyte layer 4, and the porous electrode 5U and the porous electrode 5D are porous. It is possible to reduce the surface conduction current component between the porous electrode 5D.
  • the first stress relaxation low thermal expansion film 6 (5U) is formed on the dense electrode 5U, and the porous electrode Forming a second stress relaxation low thermal expansion film 6 (5D) on 5D and forming a third stress relaxation low thermal expansion film 6 (4) on the solid electrolyte layer 4;
  • the manufacturing method of the limiting current type gas sensor according to the first embodiment includes a first stress relaxation low thermal expansion film 6 (5U) and a third stress relaxation low thermal expansion in plan view.
  • the substrate 1 is etched to form a doubly supported beam structure on the cavity formed in the substrate 1. The process of carrying out.
  • the manufacturing method of the limiting current type gas sensor according to the first embodiment may include a step of forming the microheater 2 on the substrate 1 or the lower portion of the substrate 1.
  • the method for manufacturing the limiting current gas sensor according to the first embodiment may include a step of forming the microheater 2 embedded in the substrate 1.
  • the method for manufacturing the limiting current gas sensor according to the first embodiment may include a step of forming the insulating film 3 on the substrate 1, and the porous electrode 5 ⁇ / b> D may be formed on the insulating film 3.
  • the microheater 2 the insulating film 3, the porous electrode 5D and the dense electrode 5U, the insulating film 8, the solid electrolyte layer 4, and the low thermal expansion for stress relaxation.
  • the films 6 and 6 (5U) and 6 (5D) and the warp suppressing porous insulating films 10 and 10 (5U) and 10 (5D) can be formed by a printing process.
  • FIGS. 13A and 13B A method of manufacturing the limiting current type gas sensor according to the first embodiment will be described with reference to FIGS.
  • the insulating film 3 is formed on the substrate 1 in which the microheater 2 is embedded.
  • the insulating film 3 is a porous film, it becomes a gas passage.
  • the formation of the insulating film 3 may be omitted.
  • FIGS. 14A and 14B a porous electrode 5 ⁇ / b> D is formed on the insulating film 3 and the substrate 1. Since the porous electrode 5D is formed of, for example, a porous Pt electrode, gas may pass through the porous Pt electrode.
  • C Next, as shown in FIGS.
  • the insulating film 8 is patterned to form the opening 7.
  • the contact area between the stabilized zirconia (4) / Pt porous electrode (5D) is stabilized, and the contact between the end surface of the stabilized zirconia (4) and the Pt porous electrode (5D) is achieved.
  • the surface conduction component between the Pt porous electrode (5D) and the Pt porous electrode (5U) can be removed.
  • the solid electrolyte layer 4 is formed on the porous electrode 5 ⁇ / b> U of the opening 7 and on the insulating film 8 surrounding the opening 7.
  • the solid electrolyte layer 4 is formed of, for example, YSZ (stabilized zirconia) here.
  • E Next, as shown in FIGS. 17 (a) and 17 (b), on the solid electrolyte layer 4, it is opposed to the porous electrode 5D and is a dense electrode substantially vertically with respect to the substrate 1. 5U is formed.
  • the dense electrode 5U is also formed to extend on the insulating film 8, the insulating film 3, and the substrate 1.
  • the dense electrode 5U is formed by, for example, a porous Pt electrode.
  • a first stress relaxation low thermal expansion film 6 (5U) is formed on the dense electrode 5U, and the first electrode is formed on the porous electrode 5D.
  • the low stress expansion low thermal expansion film 6 (5D) is formed, and the third stress relaxation low thermal expansion film 6 (4) is formed on the solid electrolyte layer 4.
  • the stress relaxation low thermal expansion film 6 can adjust the film density according to the amount of gas to be detected.
  • the low thermal expansion film 6 for stress relaxation can be formed of any one of a dense film, a porous film, or a composite film of a dense film and a porous film.
  • the stress relaxation low thermal expansion film 6 is formed of a material containing at least one of SiO 2 , Al 2 O 3 , YSZ, or mullite. Moreover, the low thermal expansion film 6 for stress relaxation can be formed by a printing process or a sputtering process. The low thermal expansion film 6 for stress relaxation is an insulating film having a low thermal expansion coefficient. By forming the low thermal expansion film 6 for stress relaxation, stress during heating can be relaxed. (G) Next, as shown in FIGS. 19 (a) and 19 (b), between the first low stress thermal expansion film 6 (5U) and the third low stress thermal expansion film 6 (4).
  • the first warp suppressing porous insulating film 10 (5U) is formed on the dense electrode 5U, and the second stress relaxation low thermal expansion film 6 (5D) and the third stress relaxation low thermal expansion film 6 ( 4), the second warp suppressing porous insulating film 10 (5D) is formed on the porous electrode 5D.
  • the warp suppressing porous insulating film 10 is formed of a material containing at least one of SiO 2 , Al 2 O 3 , YSZ, or mullite.
  • the warp suppressing porous insulating film 10 can be formed by a printing process or a sputtering process. By forming the warp-suppressing porous insulating film 10, it is possible to reduce the warp of the beam structure during heating and improve the durability.
  • FIG. 10 A schematic plane pattern configuration of the limiting current type gas sensor according to the second embodiment is expressed as shown in FIG.
  • the porous electrode 5D and the porous electrode 5U are arranged only on one arm of the two arms on one side of the four arms of the doubly supported beam structure. is doing.
  • the porous electrodes 5D 1 and 5D are formed on both arms of the two arms on one side of the four arms of the both-end supported beam structure. 2 ⁇ Precise electrodes 5U 1 ⁇ 5U 2 are arranged.
  • the porous electrodes 5D 1 and 5D 2 are electrically connected to each other.
  • the dense electrodes 5U 1 and 5U 2 are also electrically connected to each other.
  • the limiting current type gas sensor 12 includes a substrate 1, porous electrodes 5D 1 and 5D 2 disposed on the substrate 1, and porous electrodes 5D 1 and 5D. 2 and the solid electrolyte layer 4 disposed on the porous electrodes 5D 1 and 5D 2 of the opening 7 patterned on the insulating film 8 and on the insulating film 8 surrounding the opening 7
  • the fine gas introduction path 26 formed in the metal particle sintered layer 28 and the metal particle sintered layer 28 on the solid electrolyte layer 4 so as to face the porous electrode 5D and substantially in the longitudinal direction with respect to the substrate 1.
  • dense electrodes U 1 and 5 U 2 dense electrodes
  • the insulating film 8 makes the contact between the end face of the solid electrolyte layer 4 and the porous electrodes 5D 1 and 5D 2 in a non-contact manner, and suppresses the uptake of oxygen (O) ions from the end face of the solid electrolyte layer 4 to be dense.
  • the surface conduction current component between the electrodes 5U 1 and 5U 2 and the porous electrodes 5D 1 and 5D 2 can be reduced.
  • the limiting current type gas sensor 12 applies a voltage between the dense electrodes 5U 1 and 5U 2 and the porous electrodes 5D 1 and 5D 2.
  • a detection circuit 18 is provided for detecting a predetermined gas concentration in the gas to be measured by a limiting current type.
  • the detection circuit 18 can detect the oxygen concentration based on the limit current.
  • the detection circuit 18 can detect the water vapor concentration based on the limit current.
  • the limiting current type gas sensor 12 includes a first stress relaxation low thermal expansion film 6 (5U 1 ), which is disposed on the dense electrodes 5U 1 and 5U 2.
  • 6 (5U 2 ) the second low stress expansion film 6 (5D 1 ) ⁇ 6 (5D 2 ) for stress relaxation disposed on the porous electrodes 5D 1 and 5D 2 , and the solid electrolyte layer 4 You may provide the 3rd low thermal expansion film
  • the limiting current type gas sensor 12 has a first stress relaxation low thermal expansion film 6 (5U 1 ), 6 (5U 2 ) and a third one in plan view.
  • the first warp suppressing porous insulating films 10 (5U 1 ) and 10 (5U 2 ) disposed on the dense electrodes 5U 1 and 5U 2 across the low thermal expansion film 6 (4) for stress relaxation
  • the porous electrode 5D 1 ... Spans between the second stress relaxation low thermal expansion film 6 (5D 1 ), 6 (5D 2 ) and the third stress relaxation low thermal expansion film 6 (4).
  • the insulating film 3 disposed on the substrate 1 may be provided, and the porous electrodes 5D 1 and 5D 2 may be disposed on the insulating film 3.
  • Other configurations are the same as those of the first embodiment.
  • the method of manufacturing the limiting current type gas sensor according to the second embodiment includes a step of forming porous electrodes 5D 1 and 5D 2 on the substrate 1 (FIG. 22), forming a quality electrode 5D 1 ⁇ 5D 2 insulating film 8 on a step (23) forming an opening 7 by patterning the insulating film 8, the porous electrode 5D 1 ⁇ 5D 2 opening 7 A step of forming the solid electrolyte layer 4 on the insulating film 8 surrounding the top and the opening 7 (FIG.
  • a step of forming the dense electrodes 5U 1 and 5U 2 including the metal particle sintered layer 28 and the fine gas introduction path 26 formed in the metal particle sintered layer 28 in a substantially vertical direction (FIG. 25).
  • the insulating film 8 makes the contact between the end face of the solid electrolyte layer 4 and the porous electrodes 5D 1 and 5D 2 in a non-contact manner, and suppresses the uptake of oxygen (O) ions from the end face of the solid electrolyte layer 4 to be dense.
  • the surface conduction current component between the electrodes 5U 1 and 5U 2 and the porous electrodes 5D 1 and 5D 2 can be reduced.
  • the manufacturing method of the limiting current type gas sensor according to the second embodiment includes a first stress relaxation low thermal expansion film 6 (5U 1 ) ⁇ 6 on the dense electrodes 5U 1 and 5U 2.
  • (5U 2) to form a porous electrode 5D 1 ⁇ 5D on 2 second stress relieving for a low thermal expansion layer 6
  • 5D 1) ⁇ 6 ( 5D 2) is formed, third stress on the solid electrolyte layer 4 Forming a low thermal expansion film 6 (4) for relaxation.
  • the manufacturing method of the limiting current type gas sensor according to the second embodiment includes the first stress relaxation low thermal expansion films 6 (5U 1 ) and 6 (5U 2 ) in plan view.
  • the first warp-suppressing porous insulating films 10 (5U 1 ) and 10 (5U 2 ) are formed on the dense electrodes 5U 1 and 5U 2 so as to straddle the third low-temperature expansion film for stress relaxation 6 (4).
  • the substrate 1 is etched to form a doubly supported beam structure on the cavity formed in the substrate 1. The process of carrying out.
  • the method for manufacturing a limiting current gas sensor according to the second embodiment includes a step of forming an insulating film 3 on the substrate 1, and the porous electrode 5D is formed on the insulating film 3. 1 ⁇ 5D 2 may be formed.
  • the porous electrodes 5D 1 , 5D 2, and the dense electrode 5U are provided on both arms of the two arms on one side of the four arms of the doubly supported beam structure. Since only the structure in which 1 ⁇ 5 U 2 is arranged is different from that of the first embodiment, the detailed manufacturing process of each part is the same as that of the first embodiment.
  • FIG. 28 (a) A schematic cross-sectional structure showing one step (beam structure forming step) of the manufacturing method of the limiting current type gas sensor according to the embodiment is represented as shown in FIG. 28 (a), and the limiting current type according to the embodiment is shown.
  • One step of the gas sensor manufacturing method (another beam structure forming step) is expressed as shown in FIG.
  • FIG. 28A an open type structure in which the cavity C is formed in the open structure at the bottom of the substrate 1, and as shown in FIG. A boat-shaped structure formed inside the substrate 1 is possible. In either case, for example, anisotropic etching of a silicon substrate can be applied.
  • FIGS. 28A and 28B the microheater 2 is formed on the thinned substrate 1 portion, but the illustration is omitted.
  • the vertical sensor structure of the limiting current type gas sensor according to the embodiment is represented by a device heating unit 200.
  • FIG. 29A The layout diagram (top view) of the beam structure of the limiting current type gas sensor according to the embodiment is represented as shown in FIG. 29A, and is a schematic cross-sectional structure taken along line IX-IX in FIG. Is represented as shown in FIG.
  • a silicon substrate having a (100) surface is used as the substrate 1, and a cavity having a bottom surface of (100) surface and a side surface of (111) surface is formed at the bottom of the device heating unit 200 by anisotropic etching. C is formed.
  • a laminated film 100 of silicon oxide film / silicon nitride film including a microheater made of polysilicon is formed on the surface of the substrate 1.
  • the area of the device heating unit 200 is, for example, about 0.1 mm 2 .
  • a laminated film 100 including a microheater is formed on the bottom of the device heating unit 200 having a vertical sensor structure, and the substrate 1 is removed. Yes. That is, in the first embodiment and the second embodiment, the thinned substrate 1 may be removed and only the laminated film 100 including the microheater may be formed.
  • the microheater 2 of the limiting current type gas sensor according to the embodiment can be formed by the following process flow.
  • a 3 um-PSG (Phosphorus Silicon Glass) film is formed on the silicon substrate 1, SiN is formed, and SiN patterning is performed (SiN removal is performed on the highly doped portion).
  • polysilicon is formed, and phosphorus P is diffused into the polysilicon by, for example, a heat treatment at about 1000 ° C. to form highly doped polysilicon.
  • the portion where SiN is present is lightly doped polysilicon.
  • a vertical sensor structure is formed, and a beam structure is formed by PSG etching with BHF (5: 1).
  • the beam-structured micro heater 2 can be easily formed on the cavity C.
  • the microheater 2 is disposed in the laminated film 100 portion of FIGS. 29 (a) and 29 (b).
  • the micro heater 2 may be formed by the following process flow.
  • a laminated film 100 which is a multilayer insulating film of SiO 2 / SiN / SiO 2 is formed on a Si (100) substrate 1, and a Pt heater (micro heater 2) is formed thereon.
  • the device heating unit 200 is formed on the microheater 2.
  • the cavity C is formed by anisotropically etching the silicon substrate 1 using the TMAH solution.
  • the beam-structured micro heater 2 can be easily formed on the cavity C.
  • the principle of the limiting current type gas sensor is as follows. First, when the zirconia solid electrolyte is heated to several hundred degrees and a voltage is applied to the zirconia solid electrolyte, oxygen ions ionized at the catalyst electrode are conducted from one side of the solid electrolyte to the other side. At this time, if the amount of oxygen gas sucked into the electrolyte is limited using small pores or porous materials, a saturation phenomenon appears in which the current becomes a constant value even when the voltage is increased. This current is called the limiting current and is proportional to the ambient oxygen concentration. Therefore, if a constant voltage is applied, the oxygen concentration can be detected from the flowing current value. If the voltage to be applied is switched, the water vapor concentration can be detected by the same principle.
  • FIG. 31 A flowchart showing an operation of detecting a gas concentration using the limiting current type gas sensor 12 according to the embodiment is expressed as shown in FIG. Further, in the limiting current type gas sensor according to the embodiment, the relationship between the YSZ temperature and the time in the gas concentration detection operation is schematically represented as shown in FIG. 31, and the schematic cross-sectional structure for explaining the operation principle is It is expressed as shown in FIG.
  • the solid electrolyte layer 4 is ripened to several hundred degrees C., for example, about 500 degrees C. by the microheater 2 and a voltage is applied between the dense electrode (cathode) 5U and the porous electrode (anode) 5D to pass the current I, As shown in FIG. 32, in the dense electrode (cathode) 5U, oxygen ions are implanted into the solid electrolyte layer 4 by the electrochemical reaction of O 2 + 4e ⁇ ⁇ 2O 2 ⁇ . On the other hand, in the porous electrode (anode) 5D, oxygen gas is released by the reaction of 2O 2 ⁇ O 2 + 4e ⁇ .
  • oxygen ions (O 2 ⁇ ) are propagated based on hopping conduction.
  • an energy diagram for explaining the hopping conduction of oxygen ions (O 2 ⁇ ) is schematically represented as shown in FIG.
  • the bottom of the conductor will be inclined only -ee X. Accordingly, the height of the conduction barrier of oxygen ions (O 2 ⁇ ) is lowered, and therefore, hopping conduction of oxygen ions (O 2 ⁇ ) is performed together with thermal excitation.
  • the limiting current in the current-voltage characteristic is schematically represented as shown in FIG. That is, in FIG. 34, the current appearing in period T 2 represents the limiting current for oxygen gas, and the current appearing in period T 3 represents the limiting current I W for water vapor. Since the limit currents I O and I W are proportional to the surrounding oxygen concentration and water vapor concentration, the values of the limit currents I O and I W and the oxygen concentration and water vapor concentration values are associated in advance and registered in the detection circuit 8. Keep it.
  • the corresponding oxygen concentration / water vapor concentration can be detected.
  • the voltage applied between the dense electrode (cathode) 5U and the porous electrode 5D is switched, not only the oxygen concentration but also the water vapor concentration can be detected.
  • T on the heater ON period, T off is equivalent to heater off period.
  • Heating power supplied to the heater on time T on is, for example, about 5 mW.
  • the sensor is heated from room temperature to a measurement temperature (for example, 500 ° C.) using the microheater 2 (FIG. 30: Step S1 ⁇ S2: NO ⁇ S1 ⁇ ).
  • B When the measured temperature is reached (FIG.
  • Step S2 YES
  • it waits for a certain time until it stabilizes (FIG. 30: Step S3).
  • C Next, a voltage is applied between the dense electrode 5U and the porous electrode 5D (FIG. 30: step S4).
  • D Next, the value of the limiting current is measured, and the gas concentration corresponding to the limiting current is detected (step S5).
  • heating, standby, measurement, and cooling may be repeated at a cycle of about once per minute.
  • the electrochemical reaction in the limiting current type gas sensor will be described.
  • the (a) YSZ4, the micro-heater 2, for example, ripe pressurized to about 500 ° C., the electric current I and the voltage V is applied between a cathode 5U ⁇ anode 5D, in the period T 1 of the FIG. 34, current is increased The limit current I O is reached.
  • oxygen ions O 2 ⁇ diffuse in YSZ4 by the electrochemical reaction of O 2 + 4e ⁇ ⁇ 2O 2 ⁇ .
  • the flow amount of the oxygen gas O 2 is larger than the diffusion amount of the oxygen ions O 2 ⁇ .
  • YSZ4 the electrolysis of YSZ4 begins.
  • oxygen ions O 2 ⁇ are injected into YSZ4 by an electrochemical reaction of O 2 + 4e ⁇ ⁇ 2O 2 ⁇ at the cathode 5U and the YSZ4 interface.
  • hydrogen is released by an electrochemical reaction of H 2 O + 2e ⁇ ⁇ H 2 + O 2 ⁇ . That is, water vapor (H 2 O) is electrolyzed, and oxygen ions O 2 ⁇ move through the solid electrolyte layer 4 by hopping conduction.
  • oxygen gas O 2 is released by the reaction of 2O 2 ⁇ O 2 + 4e ⁇ due to the electrolysis of the adsorbed oxygen gas O ad .
  • oxygen gas O 2 is released by the reaction of 2O 2 ⁇ O 2 + 4e ⁇ by electrolysis of water vapor (H 2 O).
  • the oxygen vacancy concentration depends on the equilibrium with the atmospheric oxygen partial pressure based on the following formula O O x X1 / 2 ⁇ O 2 (g) + V O .. + 2e ′ .
  • This equation shows that the electronic conductivity depends on the partial pressure of oxygen at equilibrium with the solid, and at high temperatures, the entropy of the production system is larger, so at high temperatures, the reaction is biased to the right, so it also depends on temperature. Show.
  • FIG. 36 A schematic bird's-eye view configuration showing the lid 131 of the package that houses the limiting current type gas sensor according to the embodiment is expressed as shown in FIG. As shown in FIG. 36, the package lid 131 is formed with a large number of through holes 132 that allow gas to pass but not allow foreign matter to pass.
  • a metal mesh, a small hole metal, a porous ceramic, or the like can be applied for the lid 131 of the package.
  • FIG. 37 A schematic bird's-eye view configuration showing a main body 141 of a package that houses a limiting current type gas sensor according to the embodiment is expressed as shown in FIG.
  • a package main body 141 houses a limit current type gas sensor chip 142 having a plurality of terminals, and is electrically connected by a plurality of bonding wires 143.
  • a lid 131 is placed on the top of the package main body 141 and mounted on the printed circuit board 101 by soldering.
  • the limiting current type gas sensor (sensor node) according to the embodiment includes sensors 151, a wireless module 152, a microcomputer 153, an energy harvester power supply 154, and a power storage element 155.
  • the configuration of the sensors 151 is as described in the embodiment.
  • the wireless module 152 is a module including an RF circuit that transmits and receives wireless signals.
  • the microcomputer 153 has a management function of the energy harvester power supply 154, and inputs the power from the energy harvester power supply 154 to the sensors 151. At this time, the microcomputer 153 may input power based on a heater power profile that saves power consumed by the sensors 151.
  • the first power that is relatively large power may be input for the first period T1
  • the second power that is relatively small power may be input for the second period T2.
  • data may be read during the second period T2, and after the second period T2 has elapsed, the power supply may be stopped for the third period T3.
  • the energy harvester power supply 154 collects energy such as sunlight, illumination light, vibration generated by the machine, and heat to obtain electric power.
  • the power storage element 155 is a lithium ion power storage element that can store power.
  • the operation of such a sensor node will be described.
  • the power from the energy harvester power supply 154 is supplied to the microcomputer 153.
  • the microcomputer 153 boosts the voltage from the energy harvester power supply 154, as indicated by (2) in FIG.
  • the microcomputer 153 boosts the voltage from the energy harvester power supply 154, as indicated by (2) in FIG.
  • (3) in FIG. 38 after reading the voltage of the electricity storage element 155, as shown in (4) and (5) in FIG. 38, power supply to the electricity storage element 155, Electric power is drawn from the power storage element 155.
  • power is supplied to the sensors 151 based on the heater power profile, and as shown in (7) in FIG. 38, the sensor resistance value, the Pt resistance value, etc. Read data.
  • a sensor package 96 equipped with the limiting current type gas sensor includes a temperature sensor thermistor 90, a humidity / oxygen sensor YSZ sensor 92, and a thermistor 90 / YSZ.
  • An AD / DA converter 94 that receives analog information SA 2 and SA 1 from the sensor unit 92 and supplies control signals S 2 and S 1 to the thermistor unit 90 and YSZ sensor unit 92; Output signal DI ⁇ DO.
  • thermistor section 90 for example, an NTC thermistor, a PTC thermistor, a ceramic PTC, a polymer PTC, a CTR thermistor or the like can be applied.
  • the limiting current type gas sensor according to the embodiment can be applied to the YSZ sensor unit 92.
  • the YSZ sensor unit 92 can also measure absolute humidity (Absolute Humidity) and relative humidity (RH: Relative Humidity). However, the temperature is used as a reference when detecting the relative humidity (RH). The detected temperature information is required.
  • FIG. 40 A schematic block configuration of a sensor network system to which the limiting current type gas sensor according to the embodiment is applied is expressed as shown in FIG.
  • the sensor network is a network in which a large number of sensors are connected to each other.
  • New initiatives using sensor networks have already begun in various fields such as factories, medical / healthcare, transportation, construction, agriculture, and environmental management.
  • the limiting current type gas sensor for example, humidity sensor
  • the present invention it is possible to provide a limiting current type gas sensor, a manufacturing method thereof, and a sensor network system that reduce the surface conduction current component and consume low power.
  • the present embodiment includes various embodiments that are not described here.
  • NASICON Na Super Ionic Conductor
  • the concentration of carbon dioxide can be detected.
  • the limiting current type gas sensor of the present embodiment can be applied to an oxygen sensor and a humidity sensor. Further, such a sensor can be applied to automobile exhaust gas and sensor networks.
  • Detection circuit 20 Metal particles ( Pt particles) 22 ... Carbon nanotube (CNT) 24 ... Binder 26 ... Fine gas introduction path 28 ... Sintered metal particle layer (Pt sintered layer) 90 ... Thermistor part 92 ... YSZ sensor part (limit current type gas sensor) 94 ... AD / DA converter 96 ... sensor package 100 ... laminated film 131 ... package lid 132 ... through hole 141 ... package body 142 ... limit current type gas sensor chip 143 ... bonding wire 151 ... sensors 152 ... wireless module 153 ... Microcomputer 154 ... Energy harvester power supply 200 ... Device heating part B ... Beam structure C ... Cavity I S ... Surface conduction current

Landscapes

  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)

Abstract

This electrode (14) for limiting current type gas sensors is provided with a dense electrode (5U) which has a metal particle sintered layer (28) and a fine gas introduction path (26) that is formed in the metal particle sintered layer (28). A method for producing this electrode (14) for limiting current type gas sensors comprises: a step for forming a metal particle paste layer (25), which contains carbon nanotubes (22) contained in a binder (24), on a solid electrolyte layer (4); a step for removing the binder (24) by means of sintering at a first temperature in the atmosphere; a step for forming a metal particle sintered layer (28) by means of sintering at a second temperature in an inert gas atmosphere; and a step for forming a fine gas introduction path (26) in the metal particle sintered layer (28) by firing the carbon nanotubes (22) by introducing the atmosphere at a third temperature. The present invention provides: an electrode for limiting current type gas sensors, which enables the achievement of good limiting current characteristics and improved detection sensitivity; a method for producing this electrode for limiting current type gas sensors; and a limiting current type gas sensor which uses this electrode for limiting current type gas sensors.

Description

限界電流式ガスセンサ用電極およびその製造方法、限界電流式ガスセンサおよびその製造方法、およびセンサネットワークシステムLimit current type gas sensor electrode and manufacturing method thereof, limit current type gas sensor and manufacturing method thereof, and sensor network system
　本実施の形態は、限界電流式ガスセンサ用電極およびその製造方法、限界電流式ガスセンサおよびその製造方法、およびセンサネットワークシステムに関する。 The present embodiment relates to an electrode for a limiting current gas sensor and a manufacturing method thereof, a limiting current gas sensor and a manufacturing method thereof, and a sensor network system.
　従来、被測定ガス内における水蒸気の濃度を検出する湿度センサとして、抵抗変化型、容量変化型、ジルコニア（ＺｒＯ2）固体電解質型などが知られている。 Conventionally, a resistance change type, a capacitance change type, a zirconia (ZrO 2 ) solid electrolyte type, and the like are known as humidity sensors for detecting the concentration of water vapor in a gas to be measured.
　高分子膜抵抗変化型は安価であり、デバイス化が容易であるという長所がある。一方で、低湿度領域での測定精度が低く、温度依存性が大きい、また、結露による溶出が素子劣化・破壊の原因になるという短所がある。 The polymer film resistance variable type is advantageous in that it is inexpensive and easy to make a device. On the other hand, there are disadvantages in that measurement accuracy in a low humidity region is low, temperature dependency is large, and elution due to condensation causes deterioration and destruction of the element.
　また、容量変化型はリニアリティが良く、相対湿度全領域で測定可能であり、温度依存性が小さいという長所がある。一方で、純水以外の水（水道水など）や、有機溶媒などの影響が大きいという短所がある。また、湿度０％ＲＨにおける容量が数百ｐＦあるのに対し、１％ＲＨ変化したときの容量変化が１ｐＦ以下であり、正確な湿度測定には定期的な校正が必要となる。一般的な事務環境で湿度測定の精度を求めない場合は、有効なデバイスである一方、高精度の湿度測定や結露、ガス曝露の可能性のある雰囲気（気象観測用途や風呂場）、１００℃以上の高温になる雰囲気での使用は想定外である。耐久性を高くするには新規に高分子材料の開発が必要である。今後の研究開発が期待される一方、新規材料開発には時間・コストが必要である。 Also, the capacitance change type has the advantage of good linearity, measurement in the entire relative humidity range, and low temperature dependence. On the other hand, there is a disadvantage that the influence of water other than pure water (such as tap water) and organic solvents is great. Further, while the capacity at a humidity of 0% RH is several hundred pF, the capacity change when 1% RH changes is 1 pF or less, and periodic calibration is required for accurate humidity measurement. While it is an effective device when humidity measurement accuracy is not required in a general office environment, it is an effective device, while high-accuracy humidity measurement, condensation, and gas exposure (atmospheric observation applications and bathrooms), 100 ° C Use in an atmosphere with such a high temperature is unexpected. In order to increase durability, it is necessary to develop a new polymer material. While future research and development is expected, the development of new materials requires time and cost.
　高温での湿度測定のために、ジルコニア固体電解質を用いた湿度センサが販売されている。ジルコニア固体電解質を用いた酸素センサは、自動車の燃焼効率向上やＮＯXの低減のために使用されており、材料としての耐久性は実績がある。ただ、ジルコニアを数百℃に上げて使用するため、消費電力が１００Ｗと高く、さらに高温物体の取り扱いの難しいことから、市場は一部の産業用途に限られている。 Humidity sensors using a zirconia solid electrolyte are sold for measuring humidity at high temperatures. Oxygen sensor using the zirconia solid electrolyte is used for the reduction of the combustion efficiency and NO X of the motor vehicle, durability of the material is proven. However, since zirconia is used after being raised to several hundred degrees Celsius, the power consumption is as high as 100 W and the handling of high-temperature objects is difficult, so the market is limited to some industrial applications.
　そこで、近年ではジルコニア薄膜限界電流型が注目されている。この種の限界電流式酸素センサは、高信頼性でリニアリティが良いという長所がある。 Therefore, in recent years, the zirconia thin film limiting current type has attracted attention. This type of limiting current oxygen sensor has the advantage of high reliability and good linearity.
米国特許第４４８７６８０号明細書US Pat. No. 4,487,680 特開平５－３１２７７２号公報JP-A-5-312772 特開２００９－７５０１１号公報JP 2009-75011 A 特開２００６－３１７４２９号公報JP 2006-317429 A 特開２０１４－１９６９９５号公報JP 2014-196995 A
　限界電流式ガスセンサにおいて、酸素ガスの多孔質電極からの過剰な取り込みにより、限界電流特性が劣化し、センサ感度を低下する。 In the limit current type gas sensor, the excessive current intake from the porous electrode of oxygen gas deteriorates the limit current characteristics and decreases the sensor sensitivity.
　本実施の形態は、良好な限界電流特性が得られ、検出感度の向上した限界電流式ガスセンサ用電極およびその製造方法、およびこの限界電流式ガスセンサ用電極を適用した限界電流式ガスセンサおよびその製造方法、およびセンサネットワークシステムを提供する。 In the present embodiment, an electrode for a limit current type gas sensor having good limit current characteristics and improved detection sensitivity, and a manufacturing method thereof, and a limit current type gas sensor to which this limit current type gas sensor electrode is applied and a manufacturing method thereof And a sensor network system.
　本実施の形態の一態様によれば、金属粒子焼結層と、前記金属粒子焼結層に形成された微細ガス導入路とを有する緻密電極を備える限界電流式ガスセンサ用電極が提供される。 According to one aspect of the present embodiment, there is provided an electrode for a limiting current type gas sensor including a dense electrode having a metal particle sintered layer and a fine gas introduction path formed in the metal particle sintered layer.
 　本実施の形態の他の態様によれば、固体電解質層に接触して、バインダに含有された金属粒子ペースト層を形成する工程と、大気中で第１温度において焼成し、前記バインダを除去する工程と、不活性ガス雰囲気中で第２温度において焼成し、金属粒子焼結層を形成する工程と、第３温度において大気を導入して、前記金属粒子焼結層中に微細ガス導入路を形成する工程とを有する限界電流式ガスセンサ用電極の製造方法が提供される。 According to another aspect of the present embodiment, a step of forming a metal particle paste layer contained in a binder in contact with the solid electrolyte layer, and firing at a first temperature in the atmosphere to remove the binder. Firing at a second temperature in an inert gas atmosphere to form a metal particle sintered layer, introducing air at a third temperature, and providing a fine gas introduction path in the metal particle sintered layer. There is provided a method of manufacturing an electrode for a limiting current gas sensor having a forming step.
　本実施の形態の他の態様によれば、基板と、前記基板上に配置された多孔質電極と、前記多孔質電極上に配置された絶縁膜と、前記絶縁膜にパターニングされた開口部の前記多孔質電極上および前記開口部を取り囲む前記絶縁膜上に配置された固体電解質層と、前記固体電解質層上に、前記多孔質電極に対向し、前記基板に対して実質的に縦方向に配置され、金属粒子焼結層および前記金属粒子焼結層に形成された微細ガス導入路を備える緻密電極とを備える限界電流式ガスセンサが提供される。 According to another aspect of the present embodiment, a substrate, a porous electrode disposed on the substrate, an insulating film disposed on the porous electrode, and an opening patterned in the insulating film A solid electrolyte layer disposed on the porous electrode and on the insulating film surrounding the opening; and on the solid electrolyte layer, facing the porous electrode and substantially longitudinally with respect to the substrate There is provided a limiting current type gas sensor including a metal particle sintered layer and a dense electrode having a fine gas introduction path formed in the metal particle sintered layer.
　本実施の形態の他の態様によれば、基板上に多孔質電極を形成する工程と、前記多孔質電極上に絶縁膜を形成する工程と、前記絶縁膜をパターニングして開口部を形成する工程と、前記開口部の前記多孔質電極上および前記開口部を取り囲む前記絶縁膜上に固体電解質層を形成する工程と、前記固体電解質層上に、前記多孔質電極に対向し、前記基板に対して実質的に縦方向に、金属粒子焼結層および前記金属粒子焼結層に形成された微細ガス導入路を備える緻密電極を形成する工程とを有する限界電流式ガスセンサの製造方法が提供される。 According to another aspect of the present embodiment, a step of forming a porous electrode on a substrate, a step of forming an insulating film on the porous electrode, and patterning the insulating film to form an opening Forming a solid electrolyte layer on the porous electrode in the opening and on the insulating film surrounding the opening; and facing the porous electrode on the solid electrolyte layer; In contrast, there is provided a method of manufacturing a limiting current gas sensor having a step of forming a dense electrode having a metal particle sintered layer and a fine gas introduction path formed in the metal particle sintered layer in a substantially vertical direction. The
　本発明の他の態様によれば、上記の限界電流式ガスセンサを備えるセンサネットワークシステムが提供される。 According to another aspect of the present invention, a sensor network system including the above-described limiting current gas sensor is provided.
　本実施の形態によれば、良好な限界電流特性が得られ、検出感度の向上した限界電流式ガスセンサ用電極およびその製造方法、およびこの限界電流式ガスセンサ用電極を適用した限界電流式ガスセンサおよびその製造方法、およびセンサネットワークシステムを提供することができる。 According to the present embodiment, an electrode for a limit current gas sensor with good limit current characteristics and improved detection sensitivity, a method for manufacturing the electrode, a limit current gas sensor to which the electrode for the limit current gas sensor is applied, and A manufacturing method and a sensor network system can be provided.
（ａ）比較例１に係る限界電流式ガスセンサ用電極の模式的断面構造図、（ｂ）比較例２に係る限界電流式ガスセンサ用電極の模式的断面構造図、（ｃ）実施の形態に係る限界電流式ガスセンサ用電極の模式的断面構造図。(A) Schematic cross-sectional structure diagram of limit current type gas sensor electrode according to Comparative Example 1, (b) Schematic cross section structure diagram of limit current type gas sensor electrode according to Comparative Example 2, (c) According to the embodiment The typical cross-section figure of the electrode for limiting current type gas sensors. ポーラス白金の断面ＳＥＭ写真例。Cross-sectional SEM photograph example of porous platinum. 緻密白金の断面ＳＥＭ写真例。Example of cross-sectional SEM photograph of dense platinum. 実施の形態に係る限界電流式ガスセンサ用電極を適用した限界電流式ガスセンサにおいて、温度を５００℃とし、大気中および窒素中における電流電圧特性例。The example of the current-voltage characteristic in the atmosphere and nitrogen in temperature limiting 500 degreeC in the limiting current type gas sensor which applied the electrode for limiting current type gas sensors which concerns on embodiment. 実施の形態に係る限界電流式ガスセンサ用電極の製造方法であって、（ａ）固体電解質層上に、カーボンナノチューブ（ＣＮＴ:Carbon Nanotube）入り金属粒子ペースト層を印刷工程により形成する工程図、（ｂ）大気中で５００℃焼成により、バインダを除去する工程図、（ｃ）不活性ガス雰囲気中で１１００℃で金属粒子焼結層を形成する工程図。BRIEF DESCRIPTION OF THE DRAWINGS It is a manufacturing method of the electrode for limiting current type gas sensors which concerns on embodiment, (a) Process drawing which forms the metal particle paste layer containing a carbon nanotube (CNT: Carbon | Nanotube) on a solid electrolyte layer by a printing process, ( b) Process diagram for removing binder by firing at 500 ° C. in the atmosphere, (c) Process diagram for forming a metal particle sintered layer at 1100 ° C. in an inert gas atmosphere. 実施の形態に係る限界電流式ガスセンサ用電極の製造方法であって、（ａ）降温途中（７００℃）で大気を導入して、ＣＮＴを燃焼して、φ約０．１μｍの微細ガス導入路を形成する工程図、（ｂ）降温途中（７００℃）で大気を導入して、ＣＮＴを燃焼して、φ約０．１μｍの微細ガス導入路を形成する別の工程図。A method for producing an electrode for a limiting current gas sensor according to an embodiment, wherein (a) air is introduced in the middle of temperature lowering (700 ° C.), CNT is burned, and a fine gas introduction path having a diameter of about 0.1 μm (B) Another process diagram in which air is introduced in the middle of temperature lowering (700 ° C.) and CNTs are burned to form a fine gas introduction path having a diameter of about 0.1 μm. 比較例３に係る限界電流式ガスセンサであって、メムス（ＭＥＭＳ：Micro Electro Mechanical Systems）梁構造に形成されるセンサ部分の模式的断面構造図。It is a limiting current type gas sensor which concerns on the comparative example 3, Comprising: The typical cross-section figure of the sensor part formed in a MEMS (MEMS: Micro * Electro | Mechanical * Systems) beam structure. 比較例４に係る限界電流式ガスセンサであって、ＭＥＭＳ梁構造に形成されるセンサ部分の模式的断面構造図。It is a limiting current type gas sensor concerning the comparative example 4, Comprising: The typical cross-section figure of the sensor part formed in a MEMS beam structure. （ａ）第１の実施の形態に係る限界電流式ガスセンサであって、ＭＥＭＳ梁構造に形成されるセンサ部分の模式的断面構造図、（ｂ）第１の実施の形態に係る限界電流式ガスセンサのＭＥＭＳ梁構造に形成されるセンサ部分の別の模式的断面構造図。(A) It is a limiting current type gas sensor according to the first embodiment, and is a schematic sectional view of a sensor portion formed in the MEMS beam structure, (b) a limiting current type gas sensor according to the first embodiment. The another typical cross-section figure of the sensor part formed in the MEMS beam structure of. 第１の実施の形態に係る限界電流式ガスセンサの模式的平面パターン構成図。The typical plane pattern block diagram of the limiting current type gas sensor which concerns on 1st Embodiment. 第１の実施の形態に係る限界電流式ガスセンサのセンサ部分の拡大された模式的平面パターン構成図。The typical plane pattern block diagram to which the sensor part of the limiting current type gas sensor which concerns on 1st Embodiment was expanded. 図１１のＩ－Ｉ線に沿う模式的断面構造図。FIG. 12 is a schematic sectional view taken along the line II of FIG. （ａ）第１の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図、（ｂ）図１３（ａ）のＩＩ－ＩＩ線に沿う模式的断面構造図（その１）。(A) A schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) a schematic cross-sectional structure diagram taken along the line II-II in FIG. 1). （ａ）第１の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図、（ｂ）図１４（ａ）のＩＩＩ－ＩＩＩ線に沿う模式的断面構造図（その２）。(A) Schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) Schematic sectional view taken along line III-III in FIG. 2). （ａ）第１の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図、（ｂ）図１５（ａ）のＩＶ－ＩＶ線に沿う模式的断面構造図（その３）。(A) Schematic plan view showing one step of the method for manufacturing the limiting current type gas sensor according to the first embodiment, (b) Schematic sectional view taken along line IV-IV in FIG. 3). （ａ）第１の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図、（ｂ）図１６（ａ）のＶ－Ｖ線に沿う模式的断面構造図（その４）。(A) Schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) Schematic sectional view taken along line VV in FIG. 4). （ａ）第１の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図、（ｂ）図１７（ａ）のＶＩ－ＶＩ線に沿う模式的断面構造図（その５）。(A) Schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) Schematic sectional view taken along line VI-VI in FIG. 5). （ａ）第１の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図、（ｂ）図１８（ａ）のＶＩＩ－ＶＩＩ線に沿う模式的断面構造図（その６）。(A) Schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) Schematic cross-sectional structure diagram taken along line VII-VII in FIG. 6). （ａ）第１の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図、（ｂ）図１９（ａ）のＶＩＩＩ－ＶＩＩＩ線に沿う模式的断面構造図（その７）。(A) Schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) Schematic sectional view taken along line VIII-VIII in FIG. 7). 第１の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的断面構造図（その８）。Typical cross-section FIG. (8) which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 1st Embodiment. 第２の実施の形態に係る限界電流式ガスセンサの模式的平面パターン構成図。The typical plane pattern block diagram of the limiting current type gas sensor which concerns on 2nd Embodiment. 第２の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図（その１）。Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 1). 第２の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図（その２）。Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 2). 第２の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図（その３）。Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 3). 第２の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図（その４）。Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 4). 第２の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図（その５）。Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 5). 第２の実施の形態に係る限界電流式ガスセンサの製造方法の一工程を示す模式的平面図（その６）。Typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 2nd Embodiment (the 6). （ａ）実施の形態に係る限界電流式ガスセンサの製造方法の一工程（梁構造形成工程）を示す模式的断面構造図、（ｂ）実施の形態に係る限界電流式ガスセンサの製造方法の一工程（別の梁構造形成工程）を示す模式的断面構造図。(A) Schematic cross-sectional structure diagram showing one step (beam structure forming step) of the method for manufacturing a limiting current gas sensor according to the embodiment, (b) One step of the method for manufacturing the limiting current gas sensor according to the embodiment The typical cross-section figure which shows (another beam structure formation process). （ａ）実施の形態に係る限界電流式ガスセンサの梁構造のレイアウト図（上面図）、（ｂ）図２９（ａ）のＩＸ－ＩＸ線に沿う模式的断面構造図。(A) Layout diagram (top view) of the beam structure of the limiting current type gas sensor according to the embodiment, (b) A schematic cross-sectional structure diagram taken along line IX-IX in FIG. 実施の形態に係る限界電流式ガスセンサを用いてガス濃度を検出する動作を示すフローチャート図。The flowchart figure which shows the operation | movement which detects gas concentration using the limiting current type gas sensor which concerns on embodiment. 実施の形態に係る限界電流式ガスセンサにおいて、ガス濃度検出動作におけるＹＳＺ温度と時間との関係を示す模式図。The schematic diagram which shows the relationship between YSZ temperature and time in gas concentration detection operation | movement in the limiting current type gas sensor which concerns on embodiment. 実施の形態に係る限界電流式ガスセンサの動作原理を説明する模式的断面構造図。The typical cross-section figure explaining the operation principle of the limiting current type gas sensor which concerns on embodiment. 実施の形態に係る限界電流式ガスセンサにおいて、酸素イオン（Ｏ2-）のホッピング伝導を説明するエネルギーダイアグラム。The energy diagram explaining the hopping conduction of oxygen ion (O 2− ) in the limiting current type gas sensor according to the embodiment. 実施の形態に係る限界電流式ガスセンサにおいて、電流―電圧特性の模式的説明図。FIG. 6 is a schematic explanatory diagram of current-voltage characteristics in the limiting current type gas sensor according to the embodiment. 実施の形態に係る限界電流式ガスセンサにおいて、イオン伝導を説明する模式的断面図。FIG. 4 is a schematic cross-sectional view for explaining ion conduction in the limiting current gas sensor according to the embodiment. 実施の形態に係る限界電流式ガスセンサを収容するパッケージの蓋を示す模式的鳥瞰構成図。The typical bird's-eye view block diagram which shows the cover of the package which accommodates the limiting current type gas sensor which concerns on embodiment. 実施の形態に係る限界電流式ガスセンサを収容するパッケージの本体を示す模式的鳥瞰構成図。The typical bird's-eye view block diagram which shows the main body of the package which accommodates the limiting current type gas sensor which concerns on embodiment. 実施の形態に係る限界電流式ガスセンサを示す模式的ブロック構成図。The typical block block diagram which shows the limiting current type gas sensor which concerns on embodiment. 実施の形態に係る限界電流式ガスセンサを搭載するセンサパッケージの模式的ブロック構成図。The typical block block diagram of the sensor package carrying the limiting current type gas sensor which concerns on embodiment. 実施の形態に係る限界電流式ガスセンサを適用したセンサネットワークの模式的ブロック構成図。The typical block block diagram of the sensor network to which the limiting current type gas sensor which concerns on embodiment is applied.
　次に、図面を参照して、実施の形態を説明する。以下の図面の記載において、同一又は類似の部分には同一又は類似の符号を付している。ただし、図面は模式的なものであり、厚みと平面寸法との関係、各層の厚みの比率等は現実のものとは異なることに留意すべきである。したがって、具体的な厚みや寸法は以下の説明を参酌して判断すべきものである。又、図面相互間においても互いの寸法の関係や比率が異なる部分が含まれていることはもちろんである。 Next, embodiments will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.
　又、以下に示す実施の形態は、技術的思想を具体化するための装置や方法を例示するものであって、構成部品の材質、形状、構造、配置等を下記のものに特定するものでない。この実施の形態は、特許請求の範囲において、種々の変更を加えることができる。 In addition, the embodiment described below exemplifies an apparatus and method for embodying the technical idea, and does not specify the material, shape, structure, arrangement, etc. of the component parts as follows. . This embodiment can be modified in various ways within the scope of the claims.
　[第１の実施の形態]
　（限界電流式ガスセンサ用電極：比較例）
　比較例１に係る限界電流式ガスセンサ用電極の模式的断面構造は、図１（ａ）に示すように表される。比較例２に係る限界電流式ガスセンサ用電極の模式的断面構造は、図１（ｂ）に示すように表される。 [First embodiment]
(Limit current type gas sensor electrode: comparative example)
A schematic cross-sectional structure of a limiting current gas sensor electrode according to Comparative Example 1 is expressed as shown in FIG. A schematic cross-sectional structure of a limiting current gas sensor electrode according to Comparative Example 2 is expressed as shown in FIG.
　比較例１に係る限界電流式ガスセンサ用電極は、図１（ａ）に示すように、固体電解質層４Ａと、固体電解質層４Ａの上面に配置された多孔質電極５Ｒと、固体電解質層４Ａの下面に配置された多孔質電極５Ｄとを備える。比較例１に係る限界電流式ガスセンサ用電極１４Ａでは、酸素ガス流入量を制御するために、固体電解質層４Ａの上面に配置され、酸素ガスを絞るための多孔質電極５Ｒを備えている。しかしながら、多孔質電極５Ｒは、ポーラス構造を有するため、酸素ガスの流入量（ポア径）の制御が難しい。 As shown in FIG. 1A, the limiting current gas sensor electrode according to Comparative Example 1 includes a solid electrolyte layer 4A, a porous electrode 5R disposed on the upper surface of the solid electrolyte layer 4A, and a solid electrolyte layer 4A. And a porous electrode 5D disposed on the lower surface. The limiting current type gas sensor electrode 14A according to the comparative example 1 includes a porous electrode 5R disposed on the upper surface of the solid electrolyte layer 4A for controlling the oxygen gas inflow to control the oxygen gas inflow amount. However, since the porous electrode 5R has a porous structure, it is difficult to control the inflow amount (pore diameter) of oxygen gas.
　比較例２に係る限界電流式ガスセンサ用電極は、図１（ｂ）に示すように、固体電解質層４Ａと、固体電解質層４Ａの上面に配置された多孔質電極５ＰＵと、多孔質電極５ＰＵ上に配置された多孔質絶縁膜若しくは多孔質絶縁基板６Ｐと、固体電解質層４Ａの下面に配置された多孔質電極５Ｄとを備える。比較例２に係る限界電流式ガスセンサ用電極１４Ａでは、酸素ガス流入量を制御するために、固体電解質層４Ａの上面に配置され、酸素ガスを絞るための多孔質絶縁膜若しくは多孔質絶縁基板６Ｐを備えている。しかしながら、多孔質絶縁膜若しくは多孔質絶縁基板６Ｐは、ポーラス構造を有するため、酸素ガスの流入量（ポア径）の制御が難しい。また、多孔質絶縁基板では、ＭＥＭＳ梁構造の採用が難しい。 As shown in FIG. 1B, the limiting current type gas sensor electrode according to Comparative Example 2 includes a solid electrolyte layer 4A, a porous electrode 5PU disposed on the upper surface of the solid electrolyte layer 4A, and a porous electrode 5PU. A porous insulating film or porous insulating substrate 6P, and a porous electrode 5D disposed on the lower surface of the solid electrolyte layer 4A. In the limiting current type gas sensor electrode 14A according to Comparative Example 2, in order to control the oxygen gas inflow amount, the porous insulating film or the porous insulating substrate 6P is arranged on the upper surface of the solid electrolyte layer 4A and used to throttle the oxygen gas. It has. However, since the porous insulating film or the porous insulating substrate 6P has a porous structure, it is difficult to control the inflow amount (pore diameter) of oxygen gas. In addition, it is difficult to adopt a MEMS beam structure in a porous insulating substrate.
　（限界電流式ガスセンサ用電極：実施の形態）
　実施の形態に係る限界電流式ガスセンサ用電極１４の模式的断面構造は、図１（ｃ）に示すように表される。 (Electrode for limiting current type gas sensor: embodiment)
A schematic cross-sectional structure of the limiting current gas sensor electrode 14 according to the embodiment is represented as shown in FIG.
　実施の形態に係る限界電流式ガスセンサ用電極１４は、図１（ｃ）に示すように、金属粒子焼結層２８と、金属粒子焼結層２８に形成された微細ガス導入路２６とを有する緻密電極５Ｕを備える。ここで、微細ガス導入路２６は、金属粒子焼結層２８に含有されるナノメートルスケールを有するナノワイヤ、ナノチューブ、ナノ粒子などの熱処理工程若しくは熱処理工程と組み合わせたエッチング処理工程によって形成可能である。ナノワイヤ、ナノチューブ、ナノ粒子は、例えば、炭素（Ｃ）、酸化亜鉛（ＺｎＯ）などによって形成可能である。なお、金属粒子焼結層２８および金属粒子焼結層２８に形成される微細ガス導入路２６については、限界電流式ガスセンサ用電極１４の製造方法の説明において、図５・図６を参照して、説明する。 The limiting current gas sensor electrode 14 according to the embodiment includes a metal particle sintered layer 28 and a fine gas introduction path 26 formed in the metal particle sintered layer 28 as shown in FIG. A dense electrode 5U is provided. Here, the fine gas introduction path 26 can be formed by a heat treatment step of nanowires having a nanometer scale contained in the metal particle sintered layer 28, nanotubes, nanoparticles, or the like or an etching treatment step combined with the heat treatment step. Nanowires, nanotubes, and nanoparticles can be formed from, for example, carbon (C), zinc oxide (ZnO), and the like. Note that the metal particle sintered layer 28 and the fine gas introduction path 26 formed in the metal particle sintered layer 28 will be described with reference to FIGS. 5 and 6 in the description of the method of manufacturing the limiting current gas sensor electrode 14. ,explain.
　また、実施の形態に係る限界電流式ガスセンサ用電極１４は、図１（ｃ）に示すように、固体電解質層４と、固体電解質層４に接触して配置された多孔質電極５Ｄとを備え、緻密電極５Ｕは、固体電解質層４の多孔質電極５Ｄに対向する面に接触して配置されている。 Further, the limiting current gas sensor electrode 14 according to the embodiment includes a solid electrolyte layer 4 and a porous electrode 5D disposed in contact with the solid electrolyte layer 4 as shown in FIG. The dense electrode 5U is disposed in contact with the surface of the solid electrolyte layer 4 facing the porous electrode 5D.
　金属粒子焼結層２８は、ナノワイヤを備えていても良い。ここで、ナノワイヤは、ＣＮＴ若しくはＺｎＯを備えていても良い。 The metal particle sintered layer 28 may include nanowires. Here, the nanowire may include CNT or ZnO.
　また、金属粒子焼結層２８は、カーボンナノチューブ若しくはカーボンナノ粒子を備え、微細ガス導入路２６は、金属粒子焼結層２８の大気中での燃焼により、カーボンナノナノチューブ若しくはカーボンナノ粒子が燃焼されて形成されていても良い。 Further, the metal particle sintered layer 28 includes carbon nanotubes or carbon nanoparticles, and the fine gas introduction path 26 burns the carbon nano nanotubes or carbon nanoparticles by the combustion of the metal particle sintered layer 28 in the atmosphere. It may be formed.
　また、金属粒子焼結層２８は、ＺｎＯを備え、微細ガス導入路２６は、金属粒子焼結層２８の大気中での燃焼後、ウェットエッチングによりＺｎＯがエッチングされて形成されていても良い。 Further, the metal particle sintered layer 28 may include ZnO, and the fine gas introduction path 26 may be formed by etching ZnO by wet etching after burning the metal particle sintered layer 28 in the atmosphere.
　実施の形態に係る限界電流式ガスセンサ用電極１４は、微細ガス導入路２６の形状によりガス透過量制御可能である。 The electrode 14 for limiting current type gas sensor according to the embodiment can control the gas permeation amount by the shape of the fine gas introduction path 26.
　また、実施の形態に係る限界電流式ガスセンサ用電極１４は、微細ガス導入路２６の含有割合によりガス透過量制御可能である。 Further, the limiting current type gas sensor electrode 14 according to the embodiment can control the gas permeation amount by the content ratio of the fine gas introduction path 26.
　また、金属粒子焼結層２８の金属粒子は、Ｐｔ、Ａｇ、Ｐｄ、Ａｕ、若しくはＲｕのいずれかを備えていても良い。 Further, the metal particles of the metal particle sintered layer 28 may include any of Pt, Ag, Pd, Au, or Ru.
　また、金属粒子焼結層２８は、金属粒子焼結層２８中に閉じ込められて大気中での燃焼により、燃焼されないナノワイヤを備えていても良い。 Further, the metal particle sintered layer 28 may include nanowires that are confined in the metal particle sintered layer 28 and are not burned by combustion in the atmosphere.
　ナノワイヤ若しくはナノ粒子は、直径が約０．１μｍ以下を備える。また、ナノワイヤの長さは、例えば、約１０μｍ以下である。ナノワイヤを使用するメリットは、ナノワイヤの形状（径、長さ）により、ガス透過量制御可能であり、またナノワイヤの割合により、ガス透過量制御可能なことである。 The nanowire or nanoparticle has a diameter of about 0.1 μm or less. Further, the length of the nanowire is, for example, about 10 μm or less. The merit of using the nanowire is that the gas permeation amount can be controlled by the shape (diameter and length) of the nanowire, and the gas permeation amount can be controlled by the ratio of the nanowire.
　（酸素ガス取り込み量制御実験）
　固体電解質層４として、バルクＹＳＺを使った、酸素ガス取り込み量制御実験を実施した。実験の目的は、酸素ガス取込量を減らすことである。 (Oxygen gas uptake control experiment)
An oxygen gas uptake control experiment using bulk YSZ as the solid electrolyte layer 4 was performed. The purpose of the experiment is to reduce oxygen gas uptake.
　ポーラス白金の断面ＳＥＭ写真例は、図２に示すように表され、緻密白金の断面ＳＥＭ写真例は、図３に示すように表される。ポーラス白金の断面ＳＥＭ写真例では、約数μｍのポーラス（孔）が観測されている。一方、緻密白金の断面ＳＥＭ写真例では、緻密にＰｔが形成されており、ポーラスは観測されていない。 An example of a cross-sectional SEM photograph of porous platinum is represented as shown in FIG. 2, and an example of a cross-sectional SEM photograph of dense platinum is represented as shown in FIG. In an example of a cross-sectional SEM photograph of porous platinum, a porous (hole) of about several μm is observed. On the other hand, in the cross-sectional SEM photograph example of dense platinum, Pt is densely formed and no porous is observed.
　実施の形態に係る限界電流式ガスセンサ用電極１４においては、図１（ｃ）に示すように、固体電解質層４の上に緻密白金からなる緻密電極５Ｕが配置される一方、固体電解質層４の下面には、ポーラス白金からなる多孔質電極５Ｄが配置されている。 In the limiting current type gas sensor electrode 14 according to the embodiment, as shown in FIG. 1C, a dense electrode 5U made of dense platinum is disposed on the solid electrolyte layer 4, while the solid electrolyte layer 4 A porous electrode 5D made of porous platinum is disposed on the lower surface.
　酸素（Ｏ2）ガスは、緻密白金からなる緻密電極５Ｕを適度に流量制御されて通過し、バルクＹＳＺからなる固体電解質層４中をイオン電導によって、Ｏ2-イオンが通過し、ポーラス白金からなる多孔質電極５Ｄ中を酸素（Ｏ2）ガスが通過している。 Oxygen (O 2 ) gas passes through the dense electrode 5U made of dense platinum under moderate flow rate control, and O 2− ions pass through the solid electrolyte layer 4 made of bulk YSZ by ionic conduction, and from porous platinum. Oxygen (O 2 ) gas passes through the porous electrode 5D.
　実施の形態に係る限界電流式ガスセンサ用電極１４を適用した限界電流式ガスセンサにおいて、温度を５００℃とし、大気中および窒素中における電流電圧特性例は、図４に示すように表される。 In the limiting current type gas sensor to which the limiting current type gas sensor electrode 14 according to the embodiment is applied, the temperature is set to 500 ° C., and an example of current-voltage characteristics in the atmosphere and in nitrogen is expressed as shown in FIG.
　実施の形態に係る限界電流式ガスセンサ用電極１４を適用した限界電流式ガスセンサにおいては、図４に示すように、緻密電極５Ｕとして緻密白金を適用することによって、プラトー領域が広くなり、良好な限界電流電圧特性が得られている。 In the limiting current type gas sensor to which the limiting current type gas sensor electrode 14 according to the embodiment is applied, by applying dense platinum as the dense electrode 5U as shown in FIG. Current-voltage characteristics are obtained.
　また、実施の形態に係る限界電流式ガスセンサ用電極１４を適用した限界電流式ガスセンサにおいては、図４に示すように、酸素濃度に応じて電流値が変化する特性が得られている。 Further, in the limiting current type gas sensor to which the limiting current type gas sensor electrode 14 according to the embodiment is applied, as shown in FIG. 4, a characteristic that the current value changes according to the oxygen concentration is obtained.
　実施の形態に係る限界電流式ガスセンサにおいては、拡散律速にするために、酸素流入量を減らすことによって、酸素ガス導入量の低減化している。具体的には、限界電流式ガスセンサ用電極として微細ガス導入路を備える緻密電極を用いている。小さな孔径（約～０．１μｍ）の微細ガス導入路２６を有する緻密電極の膜で酸素流入量を絞ることができる。 In the limiting current type gas sensor according to the embodiment, the oxygen gas introduction amount is reduced by reducing the oxygen inflow amount in order to control diffusion. Specifically, a dense electrode having a fine gas introduction path is used as an electrode for a limiting current gas sensor. The amount of oxygen inflow can be reduced by a dense electrode film having a fine gas introduction path 26 having a small pore diameter (about 0.1 μm).
　（限界電流式ガスセンサ用電極の製造方法）
　実施の形態に係る限界電流式ガスセンサ用電極１４の製造方法であって、固体電解質層（ＹＳＺ）４上に、ＣＮＴ２２入り金属粒子ペースト層２５を印刷工程により形成する工程は、図５（ａ）に示すように表され、大気中で５００℃焼成により、バインダを除去する工程は、図５（ｂ）に示すように表され、不活性ガス雰囲気中で１１００℃で金属粒子焼結層２８を形成する工程は、図５（ｃ）に示すように表される。 (Method for manufacturing electrode for limiting current type gas sensor)
FIG. 5 (a) shows a method of manufacturing the limiting current gas sensor electrode 14 according to the embodiment, in which a metal particle paste layer 25 containing CNTs 22 is formed on a solid electrolyte layer (YSZ) 4 by a printing process. The step of removing the binder by firing at 500 ° C. in the atmosphere is expressed as shown in FIG. 5B, and the metal particle sintered layer 28 is formed at 1100 ° C. in an inert gas atmosphere. The step of forming is represented as shown in FIG.
　また、実施の形態に係る限界電流式ガスセンサ用電極１４の製造方法であって、降温途中（７００℃）で大気を導入して、ＣＮＴ２２を燃焼して、φ約０．１μｍの微細ガス導入路２６を形成する工程は、図６（ａ）に示すように表され、降温途中（７００℃）で大気を導入して、ＣＮＴ２２を燃焼して、φ約０．１μｍの微細ガス導入路２６を形成する別の工程は、図６（ｂ）に示すように表される。 Further, it is a method of manufacturing the limiting current type gas sensor electrode 14 according to the embodiment, in which air is introduced in the middle of temperature lowering (700 ° C.), the CNT 22 is combusted, and a fine gas introduction path having a diameter of about 0.1 μm. 6A is represented as shown in FIG. 6A. Air is introduced in the middle of temperature lowering (700 ° C.), the CNT 22 is burned, and a fine gas introduction path 26 having a diameter of about 0.1 μm is formed. Another process to be formed is expressed as shown in FIG.
　実施の形態に係る限界電流式ガスセンサ用電極１４の製造方法は、固体電解質層４に接触して、バインダ２４に含有された金属粒子ペースト層２５を形成する工程と、大気中で第１温度において焼成し、バインダ２４を除去する工程と、不活性ガス雰囲気中で第２温度において焼成し、金属粒子焼結層２８を形成する工程と、第３温度において大気を導入して、金属粒子焼結層２８中に微細ガス導入路２６を形成する工程とを有する。 The method for manufacturing the limiting current gas sensor electrode 14 according to the embodiment includes a step of forming the metal particle paste layer 25 contained in the binder 24 in contact with the solid electrolyte layer 4 and a first temperature in the atmosphere. Firing and removing the binder 24, firing at a second temperature in an inert gas atmosphere to form a metal particle sintered layer 28, and introducing the atmosphere at the third temperature to sinter the metal particles Forming a fine gas introduction path 26 in the layer 28.
　また、金属粒子ペースト層２５を形成する工程は、印刷工程を備えていても良い。 Moreover, the process of forming the metal particle paste layer 25 may include a printing process.
　また、第１温度は、例えば約５００℃であっても良い。 The first temperature may be about 500 ° C., for example.
　また、第２温度は、例えば約１１００℃であっても良い。 The second temperature may be about 1100 ° C., for example.
　また、第３温度は、例えば約７００℃であっても良い。 The third temperature may be about 700 ° C., for example.
　また、バインダ２４は、例えばエチルセルロース系若しくはアクリル系材料を備えていても良い。 Further, the binder 24 may include, for example, an ethyl cellulose-based or acrylic material.
　また、実施の形態に係る限界電流式ガスセンサ用電極１４の製造方法において、微細ガス導入路２６を形成する工程は、金属粒子焼結層２８の大気中での燃焼により、ＣＮＴ燃焼されて微細ガス導入路２６を形成する工程を有していても良い。 Further, in the method of manufacturing the limiting current gas sensor electrode 14 according to the embodiment, the step of forming the fine gas introduction path 26 is performed by CNT combustion by the combustion of the metal particle sintered layer 28 in the atmosphere and the fine gas. A step of forming the introduction path 26 may be included.
　また、実施の形態に係る限界電流式ガスセンサ用電極１４の製造方法において、金属粒子焼結層２８は、図５（ｃ）に示すように、ＣＮＴ２２若しくはカーボンナノ粒子を備え、微細ガス導入路２６を形成する工程は、図６（ａ）に示すように、金属粒子焼結層２８の大気中での燃焼により、ＣＮＴ２２若しくはカーボンナノ粒子が燃焼される工程を有していても良い。なお、図６（ｂ）に示すように、金属粒子焼結層２８の大気中での燃焼により、一部のＣＮＴ２２が燃焼されず、金属粒子焼結層２８中に残存しても特性上は問題ない。 Further, in the method of manufacturing the limiting current gas sensor electrode 14 according to the embodiment, the metal particle sintered layer 28 includes CNTs 22 or carbon nanoparticles as shown in FIG. As shown in FIG. 6A, the step of forming CNTs may include a step of burning the CNTs 22 or the carbon nanoparticles by burning the sintered metal particle layer 28 in the atmosphere. As shown in FIG. 6B, even if some of the CNTs 22 are not burned and remain in the metal particle sintered layer 28 due to the combustion of the metal particle sintered layer 28 in the atmosphere, no problem.
　また、実施の形態に係る限界電流式ガスセンサ用電極１４の製造方法において、金属粒子焼結層２８は、ＺｎＯを備え、微細ガス導入路２６を形成する工程は、金属粒子焼結層２８の大気中での燃焼後、ウェットエッチングによりＺｎＯがエッチングされる工程を有していても良い。 Further, in the method of manufacturing the limiting current gas sensor electrode 14 according to the embodiment, the metal particle sintered layer 28 includes ZnO, and the step of forming the fine gas introduction path 26 is performed in the atmosphere of the metal particle sintered layer 28. After burning in, there may be a step of etching ZnO by wet etching.
　以下に、実施の形態に係る限界電流式ガスセンサ用電極１４の製造方法を詳述する。 Hereinafter, a manufacturing method of the limiting current type gas sensor electrode 14 according to the embodiment will be described in detail.
　（Ａ）まず、図５（ａ）に示すように、固体電解質層４上に、バインダ２４に金属粒子２０とＣＮＴ２２を含有した金属粒子ペースト層２５を固体電解質層４上に塗布し、印刷工程によって形成する。金属粒子ペースト層２５は、酸素ガス透過量を制御するための電極用ペーストである。ＣＮＴ２２は、直径が約０．１μｍ以下のナノワイヤである。バインダ２４は、例えばエチルセルロース系若しくはアクリル系材料を備える。 (A) First, as shown in FIG. 5A, a metal particle paste layer 25 containing metal particles 20 and CNTs 22 in a binder 24 is applied onto the solid electrolyte layer 4 on the solid electrolyte layer 4, and a printing step. Formed by. The metal particle paste layer 25 is an electrode paste for controlling the oxygen gas permeation amount. The CNT 22 is a nanowire having a diameter of about 0.1 μm or less. The binder 24 includes, for example, an ethyl cellulose material or an acrylic material.
　（Ｂ）次に、図５（ｂ）に示すように、大気中で例えば約５００℃で熱処理し、バインダを除去する。 (B) Next, as shown in FIG. 5B, the binder is removed by heat treatment in the atmosphere at, for example, about 500 ° C.
　（Ｃ）次に、図５（ｃ）に示すように、不活性ガス（Ｎ2）雰囲気中で例えば約１１００℃で熱処理し、金属粒子焼結層２８を形成する。この時、不活性ガス（Ｎ2）雰囲気中であるため、金属粒子焼結層２８中にはＣＮＴ２２が含まれている。 (C) Next, as shown in FIG. 5C, heat treatment is performed, for example, at about 1100 ° C. in an inert gas (N 2 ) atmosphere to form the metal particle sintered layer 28. At this time, since the atmosphere is an inert gas (N 2 ) atmosphere, the metal particle sintered layer 28 contains CNT 22.
　（Ｄ）次に、図６（ａ）に示すように、降温動作中に、例えば約７００℃において、大気を導入することによって、金属粒子焼結層２８の大気中での燃焼により、ＣＮＴ２２を燃焼して、微細ガス導入路２６を形成する。図６（ｂ）に示すように、金属粒子焼結層２８の大気中での燃焼により、一部のＣＮＴ２２が燃焼されず、金属粒子焼結層２８中に残存しても特性上は問題ない。 (D) Next, as shown in FIG. 6A, by introducing the atmosphere during the temperature lowering operation, for example, at about 700 ° C., the metal particle sintered layer 28 is burned in the atmosphere, so that the CNT 22 By burning, a fine gas introduction path 26 is formed. As shown in FIG. 6B, there is no problem in characteristics even if some of the CNTs 22 are not burned and remain in the metal particle sintered layer 28 due to the combustion of the metal particle sintered layer 28 in the atmosphere. .
　以上の工程においては、雰囲気を調整して熱処理するだけで、上記の金属粒子焼結層２８中に微細ガス導入路２６を形成する制御が可能である。 In the above steps, it is possible to control the formation of the fine gas introduction path 26 in the metal particle sintered layer 28 only by adjusting the atmosphere and performing heat treatment.
　ＺｎＯナノワイヤなどの燃えないものを用いると、大気中熱処理後ウェットエッチングすることで同様の構造を形成可能であり、雰囲気制御は不要である。図６（ｂ）に示すように、ＣＮＴ２２の燃え残りがあっても、導電性を保てるので問題ない。 If a non-burning material such as ZnO nanowire is used, a similar structure can be formed by wet etching after heat treatment in the atmosphere, and atmosphere control is unnecessary. As shown in FIG. 6B, there is no problem even if there is unburned CNT 22 because the conductivity can be maintained.
　実施の形態に係る限界電流式ガスセンサ用電極の製造方法によれば、ジルコニア酸素・湿度センサ用電極を形成可能である。 According to the method for manufacturing a limiting current gas sensor electrode according to the embodiment, it is possible to form a zirconia oxygen / humidity sensor electrode.
　（限界電流式ガスセンサ：ＭＥＭＳ梁構造）
　（比較例）
　比較例３に係る限界電流式ガスセンサ１２Ａであって、ＭＥＭＳ梁構造に形成されるセンサ部分の模式的断面構造は、図７に示すように表される。また、比較例４に係る限界電流式ガスセンサ１２Ａであって、ＭＥＭＳ梁構造に形成されるセンサ部分の模式的断面構造は、図８に示すように表される。 (Limit current type gas sensor: MEMS beam structure)
(Comparative example)
FIG. 7 shows a schematic cross-sectional structure of the sensor portion formed in the MEMS beam structure in the limiting current type gas sensor 12A according to the comparative example 3. Moreover, it is the limiting current type gas sensor 12A which concerns on the comparative example 4, Comprising: The typical cross-section of the sensor part formed in a MEMS beam structure is represented as shown in FIG.
　比較例３に係る限界電流式ガスセンサ１２Ａは、図７に示すように、ＭＥＭＳ梁構造の基板１と、基板１上に配置された多孔質電極５Ｄと、多孔質電極上に配置された固体電解質層４と、固体電解質層４上に、多孔質電極５Ｄに対向し、基板１に対して実質的に縦方向に配置された多孔質電極５ＰＵと、多孔質電極５ＰＵ上に配置されかつデバイス全面を被覆する絶縁膜８Ｄとを備える。ここで、絶縁膜８Ｄは、ポーラス絶縁膜（Ａｌ2Ｏ3-ＳｉＯ2）若しくは緻密絶縁膜（ガラスペースト）で形成される。多孔質電極５Ｄ・５ＰＵは、孔径数μｍ程度のポーラスＰｔで形成され、固体電解質層４は、厚さ約１５μｍのＹＳＺで形成される。ＭＥＭＳ梁構造の基板１の厚さは、約１０μｍのシリコン基板で形成される。 As shown in FIG. 7, a limiting current type gas sensor 12A according to Comparative Example 3 includes a MEMS beam structure substrate 1, a porous electrode 5D disposed on the substrate 1, and a solid electrolyte disposed on the porous electrode. A porous electrode 5PU disposed on the solid electrolyte layer 4 so as to face the porous electrode 5D and substantially vertically with respect to the substrate 1, and the entire surface of the device disposed on the porous electrode 5PU. And an insulating film 8D for covering the substrate. Here, the insulating film 8D is formed of a porous insulating film (Al 2 O 3 —SiO 2 ) or a dense insulating film (glass paste). The porous electrodes 5D and 5PU are formed of porous Pt having a pore diameter of several μm, and the solid electrolyte layer 4 is formed of YSZ having a thickness of about 15 μm. The thickness of the substrate 1 having the MEMS beam structure is formed of a silicon substrate of about 10 μm.
　比較例３に係る限界電流式ガスセンサ１２Ａにおいては、図７に示すように、ポーラス絶縁膜（Ａｌ2Ｏ3、ＳｉＯ2、Ａｌ2Ｏ3-ＳｉＯ2）若しくは緻密絶縁膜（ガラスペースト）で形成される絶縁膜８Ｄによって、酸素ガスの導入量を絞る構造を備えるが、限界電流特性は、酸素ガスの多孔質電極５ＰＵからの過剰な取り込みにより、限界電流特性が劣化し、センサ感度を低下する。 In the limiting current type gas sensor 12A according to Comparative Example 3, as shown in FIG. 7, it is formed of a porous insulating film (Al 2 O 3 , SiO 2 , Al 2 O 3 —SiO 2 ) or a dense insulating film (glass paste). The insulating film 8D has a structure for reducing the amount of oxygen gas introduced. However, the limiting current characteristic deteriorates due to excessive incorporation of oxygen gas from the porous electrode 5PU, and the sensor sensitivity is lowered. .
　比較例４に係る限界電流式ガスセンサ１２Ａは、図８に示すように、ＭＥＭＳ梁構造の基板１と、基板１上に配置された多孔質電極５Ｄと、多孔質電極上に配置された固体電解質層４と、固体電解質層４上に、多孔質電極５Ｄに対向し、基板１に対して実質的に縦方向に配置された多孔質電極５ＰＵと、多孔質電極５ＰＵ上に配置されかつデバイス全面を被覆する絶縁膜８Ｐと、絶縁膜８Ｐ上に配置された絶縁膜８Ｄとを備える。ここで、絶縁膜８Ｐは、ポーラス絶縁膜（Ａｌ2Ｏ3、ＳｉＯ2、Ａｌ2Ｏ3-ＳｉＯ2）で形成され、絶縁膜８Ｄは、緻密絶縁膜（ガラスペースト）で形成される。多孔質電極５Ｄ・５ＰＵは、孔径数μｍ程度のポーラスＰｔで形成され、固体電解質層４は、厚さ約１５μｍのＹＳＺで形成される。ＭＥＭＳ梁構造の基板１の厚さは、約１０μｍのシリコン基板で形成される。 As shown in FIG. 8, the limiting current type gas sensor 12A according to the comparative example 4 includes a MEMS beam substrate 1, a porous electrode 5D disposed on the substrate 1, and a solid electrolyte disposed on the porous electrode. A porous electrode 5PU disposed on the solid electrolyte layer 4 so as to face the porous electrode 5D and substantially vertically with respect to the substrate 1, and the entire surface of the device disposed on the porous electrode 5PU. And an insulating film 8D disposed on the insulating film 8P. Here, the insulating film 8P is formed of a porous insulating film (Al 2 O 3 , SiO 2 , Al 2 O 3 —SiO 2 ), and the insulating film 8D is formed of a dense insulating film (glass paste). The porous electrodes 5D and 5PU are formed of porous Pt having a pore diameter of several μm, and the solid electrolyte layer 4 is formed of YSZ having a thickness of about 15 μm. The thickness of the substrate 1 having the MEMS beam structure is formed of a silicon substrate of about 10 μm.
　比較例４に係る限界電流式ガスセンサ１２Ａにおいては、図８に示すように、ポーラス絶縁膜（Ａｌ2Ｏ3-ＳｉＯ2）で形成される絶縁膜８Ｐの側面から酸素ガスを取り込む構造を備えるが、限界電流特性は、酸素ガスの多孔質電極５ＰＵからの過剰な取り込みにより、限界電流特性が劣化し、センサ感度が低下する。 As shown in FIG. 8, the limiting current type gas sensor 12A according to the comparative example 4 has a structure for taking in oxygen gas from the side surface of the insulating film 8P formed of a porous insulating film (Al 2 O 3 —SiO 2 ). The limiting current characteristic deteriorates due to excessive uptake of oxygen gas from the porous electrode 5PU, and the sensor sensitivity decreases.
　（限界電流式ガスセンサ：実施の形態）
　第１の実施の形態に係る限界電流式ガスセンサ１２であって、ＭＥＭＳ梁構造に形成されるセンサ部分の模式的断面構造は、図９（ａ）に示すように表される。また、第１の実施の形態に係る限界電流式ガスセンサ１２のＭＥＭＳ梁構造に形成されるセンサ部分の別の模式的断面構造は、図９（ｂ）に示すように表される。 (Limit current type gas sensor: embodiment)
FIG. 9A shows a schematic cross-sectional structure of the sensor portion formed in the MEMS beam structure, which is the limiting current type gas sensor 12 according to the first embodiment. Further, another schematic cross-sectional structure of the sensor portion formed in the MEMS beam structure of the limiting current gas sensor 12 according to the first embodiment is expressed as shown in FIG.
　第１の実施の形態に係る限界電流式ガスセンサ１２は、図９（ａ）に示すように、ＭＥＭＳ梁構造の基板１と、基板１上に配置された多孔質電極５Ｄと、多孔質電極５Ｄ上に配置された固体電解質層４と、固体電解質層４上に、多孔質電極５Ｄに対向し、基板１に対して実質的に縦方向に配置され、金属粒子焼結層２８および金属粒子焼結層２８に形成された微細ガス導入路２６を備える緻密電極５Ｕとを備える。 As shown in FIG. 9A, the limiting current type gas sensor 12 according to the first embodiment includes a substrate 1 having a MEMS beam structure, a porous electrode 5D disposed on the substrate 1, and a porous electrode 5D. On the solid electrolyte layer 4 disposed on the top, on the solid electrolyte layer 4, facing the porous electrode 5 </ b> D and disposed substantially vertically with respect to the substrate 1, the metal particle sintered layer 28 and the metal particle firing And a dense electrode 5U including a fine gas introduction path 26 formed in the binder layer 28.
　別の第１の実施の形態に係る限界電流式ガスセンサ１２は、図９（ｂ）に示すように、ＭＥＭＳ梁構造の基板１と、基板１上に配置された多孔質電極５Ｄと、多孔質電極５Ｄ上に配置された絶縁膜８と、絶縁膜８にパターニングされた開口部７の多孔質電極５Ｄ上および開口部７を取り囲む絶縁膜８上に配置された固体電解質層４と、固体電解質層４上に、多孔質電極５Ｄに対向し、基板１に対して実質的に縦方向に配置され、金属粒子焼結層２８および金属粒子焼結層２８に形成された微細ガス導入路２６を備える緻密電極５Ｕとを備える。 As shown in FIG. 9B, a limiting current type gas sensor 12 according to another first embodiment includes a substrate 1 having a MEMS beam structure, a porous electrode 5D disposed on the substrate 1, and a porous material. An insulating film 8 disposed on the electrode 5D, a solid electrolyte layer 4 disposed on the porous electrode 5D of the opening 7 patterned on the insulating film 8 and on the insulating film 8 surrounding the opening 7, and a solid electrolyte On the layer 4, facing the porous electrode 5D and disposed substantially vertically with respect to the substrate 1, a metal particle sintered layer 28 and a fine gas introduction path 26 formed in the metal particle sintered layer 28 are provided. And a dense electrode 5U.
　別の第１の実施の形態に係る限界電流式ガスセンサ１２においては、図９（ｂ）に示すように、絶縁膜８は、固体電解質層４の端面と多孔質電極５Ｄとの間を非接触化し、酸素（Ｏ）イオンの固体電解質層４端面からの取り込みを抑制し、緻密電極５Ｕと多孔質電極５Ｄとの間の表面伝導電流成分を低減化可能である。 In the limiting current type gas sensor 12 according to another first embodiment, as shown in FIG. 9B, the insulating film 8 is not in contact between the end face of the solid electrolyte layer 4 and the porous electrode 5D. It is possible to suppress the uptake of oxygen (O) ions from the end surface of the solid electrolyte layer 4 and reduce the surface conduction current component between the dense electrode 5U and the porous electrode 5D.
　また、基板１上に配置された絶縁膜３を備え、多孔質電極５Ｄは、絶縁膜３上に配置されていても良い。 Further, the insulating film 3 disposed on the substrate 1 may be provided, and the porous electrode 5D may be disposed on the insulating film 3.
　多孔質電極５Ｄは、孔径数μｍ程度のポーラスＰｔで形成され、厚さは、例えば、約１μｍ以上である。薄すぎるとＰｔが凝集して絶縁化するためである。 The porous electrode 5D is formed of porous Pt having a pore diameter of about several μm, and the thickness is, for example, about 1 μm or more. This is because Pt aggregates and insulates if it is too thin.
　固体電解質層４は、厚さ約４μｍ以上のＹＳＺで形成される。薄いと上下のＰｔ電極間が導通してしまうためである。 The solid electrolyte layer 4 is made of YSZ having a thickness of about 4 μm or more. This is because if it is thin, the upper and lower Pt electrodes become conductive.
　ＭＥＭＳ梁構造の基板１の厚さは、約１０μｍのシリコン基板で形成される。 The thickness of the substrate 1 having a MEMS beam structure is a silicon substrate having a thickness of about 10 μm.
　第１の実施の形態に係る限界電流式ガスセンサ１２においては、Ｐｔ電極自体をナノ構造に形成している。すなわち、ＣＮＴを混ぜたＰｔを焼結し、最後にＣＮＴを焼き飛ばして微細ガス導入路を形成した金属粒子焼結層を緻密電極５Ｕとして適用する。ＣＮＴの代わりに、カーボンナノ粒子を適用しても良い。 In the limiting current type gas sensor 12 according to the first embodiment, the Pt electrode itself is formed in a nanostructure. That is, Pt mixed with CNT is sintered, and finally a sintered metal particle layer in which CNTs are burned off to form a fine gas introduction path is applied as the dense electrode 5U. Carbon nanoparticles may be applied instead of CNTs.
　緻密Ｐｔで形成された緻密電極５Ｕの厚さは、例えば、約１μｍ以上である。薄すぎるとＰｔが凝集して絶縁化するためである。 The thickness of the dense electrode 5U formed of dense Pt is, for example, about 1 μm or more. This is because Pt aggregates and insulates if it is too thin.
　第１の実施の形態に係る限界電流式ガスセンサにおいては、緻密電極により酸素ガスの取り込みを制御可能であるため、良好な限界電流特性が得られ、検出感度の向上した限界電流式ガスセンサを提供することができる。 In the limiting current type gas sensor according to the first embodiment, since the oxygen gas uptake can be controlled by the dense electrode, a limiting current type gas sensor having good limiting current characteristics and improved detection sensitivity is provided. be able to.
　金属粒子焼結層２８は、ＣＮＴ２２若しくはカーボンナノ粒子を備え、微細ガス導入路２６は、金属粒子焼結層２８の大気中での燃焼により、ＣＮＴ２２若しくはカーボンナノ粒子が燃焼されて形成されていても良い。 The metal particle sintered layer 28 includes CNTs 22 or carbon nanoparticles, and the fine gas introduction path 26 is formed by burning the CNTs 22 or carbon nanoparticles by burning the metal particle sintered layer 28 in the atmosphere. Also good.
　また、金属粒子焼結層２８は、ＺｎＯを備え、微細ガス導入路２６は、金属粒子焼結層２８の大気中での燃焼後、ウェットエッチングによりＺｎＯがエッチングされて形成されていても良い。 Further, the metal particle sintered layer 28 may include ZnO, and the fine gas introduction path 26 may be formed by etching ZnO by wet etching after burning the metal particle sintered layer 28 in the atmosphere.
　第１の実施の形態に係る限界電流式ガスセンサ１２は、微細ガス導入路２６の形状によりガス透過量制御可能である。 The limiting current type gas sensor 12 according to the first embodiment can control the gas permeation amount by the shape of the fine gas introduction path 26.
　また、第１の実施の形態に係る限界電流式ガスセンサ１２は、微細ガス導入路２６の含有割合によりガス透過量制御可能である。 Further, the limiting current type gas sensor 12 according to the first embodiment can control the gas permeation amount by the content ratio of the fine gas introduction path 26.
　金属粒子焼結層２８の金属粒子は、Ｐｔ、Ａｇ、Ｐｄ、Ａｕ、若しくはＲｕのいずれかを備えていても良い。 The metal particles of the metal particle sintered layer 28 may include any one of Pt, Ag, Pd, Au, or Ru.
　第１の実施の形態に係る限界電流式ガスセンサ１２の模式的平面パターン構成は、図１０に示すように表され、センサ部分の拡大された模式的平面パターン構成は、図１１に示すように表され、図１１のＩ－Ｉ線に沿う模式的断面構造は、図１２に示すように表される。 The schematic plane pattern configuration of the limiting current type gas sensor 12 according to the first embodiment is expressed as shown in FIG. 10, and the enlarged schematic plane pattern configuration of the sensor portion is expressed as shown in FIG. A schematic cross-sectional structure taken along line II in FIG. 11 is expressed as shown in FIG.
　第１の実施の形態に係る限界電流式ガスセンサ１２は、図１０～図１２に示すように、基板１と、基板１上に配置された多孔質電極５Ｄと、多孔質電極５Ｄ上に配置された絶縁膜８と、絶縁膜８にパターニングされた開口部７の多孔質電極５Ｄ上および開口部７を取り囲む絶縁膜８上に配置された固体電解質層４と、固体電解質層４上に、多孔質電極５Ｄに対向し、基板１に対して実質的に縦方向に配置され、金属粒子焼結層２８および金属粒子焼結層２８に形成された微細ガス導入路２６とを備える緻密電極５Ｕとを備える。 As shown in FIGS. 10 to 12, the limiting current type gas sensor 12 according to the first embodiment is disposed on the substrate 1, the porous electrode 5D disposed on the substrate 1, and the porous electrode 5D. The insulating film 8, the solid electrolyte layer 4 disposed on the porous electrode 5 </ b> D of the opening 7 patterned on the insulating film 8, and the insulating film 8 surrounding the opening 7, and the solid electrolyte layer 4 are porous. A dense electrode 5U that is opposed to the porous electrode 5D and that is disposed substantially longitudinally with respect to the substrate 1 and includes a metal particle sintered layer 28 and a fine gas introduction path 26 formed in the metal particle sintered layer 28; Is provided.
　また、第１の実施の形態に係る限界電流式ガスセンサ１２は、図１０に示すように、緻密電極５Ｕと多孔質電極５Ｄとの間に電圧を印加することにより被測定ガス内における所定のガス濃度を限界電流式で検出する検出回路１８を備える。ここで、検出回路１８は、限界電流に基づいて酸素濃度を検出することができる。また、検出回路１８は、限界電流に基づいて水蒸気濃度を検出することができる。 Further, as shown in FIG. 10, the limiting current type gas sensor 12 according to the first embodiment applies a voltage between the dense electrode 5U and the porous electrode 5D to thereby generate a predetermined gas in the gas to be measured. A detection circuit 18 for detecting the concentration by a limiting current type is provided. Here, the detection circuit 18 can detect the oxygen concentration based on the limit current. The detection circuit 18 can detect the water vapor concentration based on the limit current.
　また、第１の実施の形態に係る限界電流式ガスセンサ１２は、図１０～図１２に示すように、緻密電極５Ｕ上に配置された第１応力緩和用低熱膨張膜６（５Ｕ）と、多孔質電極５Ｄ上に配置された第２応力緩和用低熱膨張膜６（５Ｄ）と、固体電解質層４上に配置された第３応力緩和用低熱膨張膜６（４）とを備えていても良い。 Further, as shown in FIGS. 10 to 12, the limiting current type gas sensor 12 according to the first embodiment includes a first stress relaxation low thermal expansion film 6 (5U) disposed on the dense electrode 5U, and a porous film. The second stress relaxation low thermal expansion film 6 (5D) disposed on the porous electrode 5D and the third stress relaxation low thermal expansion film 6 (4) disposed on the solid electrolyte layer 4 may be provided. .
　また、第１の実施の形態に係る限界電流式ガスセンサ１２は、図１０～図１２に示すように、平面視において、第１応力緩和用低熱膨張膜６（５Ｕ）と第３応力緩和用低熱膨張膜６（４）との間に跨って、緻密電極５Ｕ上に配置された第１反り抑制用多孔質絶縁膜１０（５Ｕ）と、平面視において、第２応力緩和用低熱膨張膜６（５Ｄ）と第３応力緩和用低熱膨張膜６（４）との間に跨って、多孔質電極５Ｄ上に配置された第２反り抑制用多孔質絶縁膜１０（５Ｄ）とを備えていても良い。 Further, as shown in FIGS. 10 to 12, the limiting current type gas sensor 12 according to the first embodiment includes a first stress relaxation low thermal expansion film 6 (5U) and a third stress relaxation low heat expansion in plan view. The first warp-suppressing porous insulating film 10 (5U) disposed on the dense electrode 5U across the expansion film 6 (4), and the second stress relaxation low thermal expansion film 6 (in plan view) 5D) and the second stress-reducing low thermal expansion film 6 (4), the second warp suppressing porous insulating film 10 (5D) disposed on the porous electrode 5D may be provided. good.
　第１の実施の形態に係る限界電流式ガスセンサ１２は、図１０～図１２に示すように、両持梁構造のＭＥＭＳ素子構造を基本構造として備える。詳細構造は後述するが、中央部にはセンサ部分が配置され、両持梁構造の梁部分には、センサ部分に接続された多孔質電極５Ｄと、緻密電極５Ｕが配置され、多孔質電極５Ｄ・緻密電極５Ｕ間には、検出回路１８が接続されている。 As shown in FIGS. 10 to 12, the limiting current type gas sensor 12 according to the first embodiment includes a MEMS element structure of a double-supported beam structure as a basic structure. Although a detailed structure will be described later, a sensor portion is disposed in the center portion, and a porous electrode 5D connected to the sensor portion and a dense electrode 5U are disposed in the beam portion of the both-end supported beam structure, and the porous electrode 5D. A detection circuit 18 is connected between the dense electrodes 5U.
　中央部のセンサ部分には、センサ部分の加熱用のマイクロヒータ２が埋め込まれており、両持梁構造のＭＥＭＳ素子構造を基本構造とすることによって、中央部のセンサ部分の熱容量を低減化し、センサ感度の向上を図っている。 The sensor part in the center is embedded with a microheater 2 for heating the sensor part, and the heat capacity of the sensor part in the center is reduced by using the MEMS element structure of the double-supported beam structure as a basic structure, The sensor sensitivity is improved.
　また、第１の実施の形態に係る限界電流式ガスセンサ１２においては、基板１は、図１２に示すように、マイクロヒータ２を備える。マイクロヒータ２は、基板１上部もしくは基板１下部に配置されていても良い。また、マイクロヒータ２は、図１２に示すように、基板１内部に埋め込まれていても良い。マイクロヒータ２は、例えば、印刷により形成されたＰｔヒータ、またはポリシリコンヒータで形成可能である。また、基板１の表面には、ポリシリコンで形成されたマイクロヒータ２を含むシリコン酸化膜／シリコン窒化膜の積層膜１００が形成されていても良い（図２９）。 Further, in the limiting current type gas sensor 12 according to the first embodiment, the substrate 1 includes a micro heater 2 as shown in FIG. The microheater 2 may be disposed on the upper part of the substrate 1 or the lower part of the substrate 1. Further, the microheater 2 may be embedded in the substrate 1 as shown in FIG. The micro heater 2 can be formed by, for example, a Pt heater formed by printing or a polysilicon heater. Further, a laminated film 100 of silicon oxide film / silicon nitride film including the microheater 2 made of polysilicon may be formed on the surface of the substrate 1 (FIG. 29).
　多孔質電極５Ｄ・緻密電極５Ｕは、多孔質のＰｔ電極で形成可能である。多孔質のＰｔ電極は、印刷、蒸着もしくはスパッタにより形成可能である。多孔質電極５Ｄ・緻密電極５Ｕの厚さは、例えば、約０．５μｍ～１０μｍ程度である。 The porous electrode 5D and the dense electrode 5U can be formed of a porous Pt electrode. The porous Pt electrode can be formed by printing, vapor deposition, or sputtering. The thicknesses of the porous electrode 5D and the dense electrode 5U are, for example, about 0.5 μm to 10 μm.
　絶縁膜８は、Ａｌ2Ｏ3、Ａｌ2Ｏ3－ＳｉＯ2、ＹＳＺ－ＳｉＯ2、もしくはＹＳＺ－Ａｌ2Ｏ3のいずれかで形成可能である。絶縁膜８は、印刷工程若しくはスパッタリング工程により形成可能である。絶縁膜８の厚さは、例えば、約１．０μｍ～１０μｍ程度である。ここで、ＹＳＺは、イットリウム安定化ジルコニア（ＹＳＺ：Yttria-Stabilized Zirconia）膜である。 The insulating film 8 can be formed of any of Al 2 O 3 , Al 2 O 3 —SiO 2 , YSZ—SiO 2 , or YSZ—Al 2 O 3 . The insulating film 8 can be formed by a printing process or a sputtering process. The thickness of the insulating film 8 is, for example, about 1.0 μm to 10 μm. Here, YSZ is a yttrium-stabilized zirconia (YSZ: Yttria-Stabilized Zirconia) film.
　絶縁膜８を形成することによって、安定化ジルコニア（４）／Ｐｔポーラス電極（５Ｄ）間の接触面積の安定化し、安定化ジルコニア（４）端面とＰｔポーラス電極（５Ｄ）の接触を無くし、また、Ｐｔポーラス電極（５Ｄ）とＰｔポーラス電極（５Ｕ）間の表面伝導成分の除去することができる。 By forming the insulating film 8, the contact area between the stabilized zirconia (4) / Pt porous electrode (5D) is stabilized, the contact between the end surface of the stabilized zirconia (4) and the Pt porous electrode (5D) is eliminated, and The surface conduction component between the Pt porous electrode (5D) and the Pt porous electrode (5U) can be removed.
　固体電解質層４は、ＹＳＺ、ＹＳＺ－ＳｉＯ2、もしくはＹＳＺ－Ａｌ2Ｏ3の少なくとも一つが含まれる安定化ジルコニア膜で形成可能である。固体電解質層４は、印刷工程若しくはスパッタリング工程により形成可能である。固体電解質層４の厚さは、例えば、約１．０μｍ～１０μｍ程度である。 The solid electrolyte layer 4 can be formed of a stabilized zirconia film containing at least one of YSZ, YSZ—SiO 2 , or YSZ—Al 2 O 3 . The solid electrolyte layer 4 can be formed by a printing process or a sputtering process. The thickness of the solid electrolyte layer 4 is, for example, about 1.0 μm to 10 μm.
　応力緩和用低熱膨張膜６は、検出するガス量によって、膜密度を調整可能である。 The low thermal expansion film 6 for stress relaxation can adjust the film density depending on the amount of gas to be detected.
　また、応力緩和用低熱膨張膜６は、緻密膜、多孔質膜、もしくは緻密膜と多孔質膜の複合膜のいずれかで形成可能である。 Further, the low thermal expansion film 6 for stress relaxation can be formed of any one of a dense film, a porous film, or a composite film of a dense film and a porous film.
　また、応力緩和用低熱膨張膜６は、ＳｉＯ2、Ａｌ2Ｏ3、ＹＳＺもしくはムライトの少なくとも一種類を含む材料で形成されていても良い。また、応力緩和用低熱膨張膜６は、印刷工程若しくはスパッタリング工程により形成可能である。応力緩和用低熱膨張膜６の厚さは、例えば、約１．０μｍ～５．０μｍ程度である。 The stress relaxation low thermal expansion film 6 may be formed of a material containing at least one of SiO 2 , Al 2 O 3 , YSZ, or mullite. Moreover, the low thermal expansion film 6 for stress relaxation can be formed by a printing process or a sputtering process. The thickness of the low thermal expansion film 6 for stress relaxation is, for example, about 1.0 μm to 5.0 μm.
　反り抑制用多孔質絶縁膜１０は、ＳｉＯ2、Ａｌ2Ｏ3、ＹＳＺもしくはムライトの少なくとも一種類を含む材料で形成されていても良い。また、反り抑制用多孔質絶縁膜１０は、印刷工程若しくはスパッタリング工程により形成可能である。反り抑制用多孔質絶縁膜１０の厚さは、例えば、約１．０μｍ～５．０μｍ程度である。 The warp suppressing porous insulating film 10 may be formed of a material containing at least one of SiO 2 , Al 2 O 3 , YSZ, or mullite. Moreover, the warp suppressing porous insulating film 10 can be formed by a printing process or a sputtering process. The thickness of the warp suppressing porous insulating film 10 is, for example, about 1.0 μm to 5.0 μm.
　また、第１の実施の形態に係る限界電流式ガスセンサ１２においては、基板１は、ＭＥＭＳ梁構造を備えていても良い。基板１は、厚さ１０μｍ以下、望ましくは２μｍ以下のシリコン基板で形成可能である。ＭＥＭＳを応用すれば、基板１の厚さを２μｍ以下にすることができるため、熱容量が小さくなり、マイクロヒータ２での消費電力を低減することが可能である。 In the limiting current type gas sensor 12 according to the first embodiment, the substrate 1 may have a MEMS beam structure. The substrate 1 can be formed of a silicon substrate having a thickness of 10 μm or less, preferably 2 μm or less. If MEMS is applied, the thickness of the substrate 1 can be reduced to 2 μm or less, so that the heat capacity is reduced and the power consumption in the microheater 2 can be reduced.
　また、第１の実施の形態に係る限界電流式ガスセンサ１２は、図１０～図１２に示すように、基板１に形成されたキャビティＣ（Cavity:空洞）上に両持ちの梁構造体として形成されている。梁構造体は、ＭＥＭＳにより形成された厚さ１０μｍ以下、望ましくは２μｍ以下の梁構造体である。 Further, the limiting current type gas sensor 12 according to the first embodiment is formed as a doubly supported beam structure on a cavity C (Cavity) formed in the substrate 1, as shown in FIGS. Has been. The beam structure is a beam structure formed by MEMS and having a thickness of 10 μm or less, preferably 2 μm or less.
　また、基板１上に配置された絶縁膜３を備え、多孔質電極５Ｄは、絶縁膜３上に配置されていても良い。 Further, the insulating film 3 disposed on the substrate 1 may be provided, and the porous electrode 5D may be disposed on the insulating film 3.
　絶縁膜３は、Ａｌ2Ｏ3、Ａｌ2Ｏ3－ＳｉＯ2、ＹＳＺ－ＳｉＯ2、もしくはＹＳＺ－Ａｌ2Ｏ3のいずれかが含まれる多孔質膜で形成可能である。絶縁膜３は、ガス取り込み膜として機能し、印刷工程若しくはスパッタリング工程により形成可能である。ここで、絶縁膜３の厚さは、例えば、約０～１０μｍ程度である。絶縁膜３は必ずしも備えていなくても良い。その場合には、多孔質のＰｔ電極で形成可能な多孔質電極５Ｄをガス取り込み膜として利用することができる。
このような限界電流式ガスセンサは、ＭＥＭＳ以外の方法により製造されても良い。この場合のシリコン基板１の厚さは、例えば６００μｍ程度である。 The insulating film 3 can be formed of a porous film containing any of Al 2 O 3 , Al 2 O 3 —SiO 2 , YSZ—SiO 2 , or YSZ—Al 2 O 3 . The insulating film 3 functions as a gas intake film and can be formed by a printing process or a sputtering process. Here, the thickness of the insulating film 3 is, for example, about 0 to 10 μm. The insulating film 3 is not necessarily provided. In that case, a porous electrode 5D that can be formed of a porous Pt electrode can be used as the gas-intake film.
Such a limiting current type gas sensor may be manufactured by a method other than MEMS. In this case, the thickness of the silicon substrate 1 is, for example, about 600 μm.
　（製造方法）
　第１の実施の形態に係る限界電流式ガスセンサの製造方法は、図１３～図１７に示すように、基板１上に多孔質電極５Ｄを形成する工程と、多孔質電極５Ｄ上に絶縁膜８を形成する工程と、絶縁膜８をパターニングして開口部７を形成する工程と、開口部７の多孔質電極５Ｄ上および開口部７を取り囲む絶縁膜８上に固体電解質層４を形成する工程と、固体電解質層４上に、多孔質電極５Ｄに対向し、基板１に対して実質的に縦方向に、金属粒子焼結層２８および金属粒子焼結層２８に形成された微細ガス導入路２６とを備える緻密電極５Ｕを形成する工程とを有する。 (Production method)
As shown in FIGS. 13 to 17, the manufacturing method of the limiting current type gas sensor according to the first embodiment includes the step of forming the porous electrode 5D on the substrate 1, and the insulating film 8 on the porous electrode 5D. Forming the opening 7 by patterning the insulating film 8, and forming the solid electrolyte layer 4 on the porous electrode 5D of the opening 7 and on the insulating film 8 surrounding the opening 7. And a fine gas introduction path formed in the metal particle sintered layer 28 and the metal particle sintered layer 28 on the solid electrolyte layer 4 so as to face the porous electrode 5D and substantially in the longitudinal direction with respect to the substrate 1. And the step of forming a dense electrode 5U.
　ここで、絶縁膜８は、固体電解質層４の端面と多孔質電極５Ｄとの間を非接触化し、酸素（Ｏ）イオンの固体電解質層４端面からの取り込みを抑制し、緻密電極５Ｕと多孔質電極５Ｄとの間の表面伝導電流成分を低減化可能である。 Here, the insulating film 8 makes the contact between the end face of the solid electrolyte layer 4 and the porous electrode 5D non-contact, suppresses the intake of oxygen (O) ions from the end face of the solid electrolyte layer 4, and the porous electrode 5U and the porous electrode 5D are porous. It is possible to reduce the surface conduction current component between the porous electrode 5D.
　また、第１の実施の形態に係る限界電流式ガスセンサの製造方法は、図１８に示すように、緻密電極５Ｕ上に第１応力緩和用低熱膨張膜６（５Ｕ）を形成し、多孔質電極５Ｄ上に第２応力緩和用低熱膨張膜６（５Ｄ）を形成し、固体電解質層４上に第３応力緩和用低熱膨張膜６（４）を形成する工程を有する。 Further, in the method of manufacturing the limiting current type gas sensor according to the first embodiment, as shown in FIG. 18, the first stress relaxation low thermal expansion film 6 (5U) is formed on the dense electrode 5U, and the porous electrode Forming a second stress relaxation low thermal expansion film 6 (5D) on 5D and forming a third stress relaxation low thermal expansion film 6 (4) on the solid electrolyte layer 4;
　また、第１の実施の形態に係る限界電流式ガスセンサの製造方法は、図１９に示すように、平面視において、第１応力緩和用低熱膨張膜６（５Ｕ）と第３応力緩和用低熱膨張膜６（４）との間に跨って、緻密電極５Ｕ上に第１反り抑制用多孔質絶縁膜１０（５Ｕ）を形成する工程と、平面視において、第２応力緩和用低熱膨張膜６（５Ｄ）と第３応力緩和用低熱膨張膜６（４）との間に跨って、多孔質電極５Ｄ上に第２反り抑制用多孔質絶縁膜１０（５Ｄ）を形成する工程とを有する。 In addition, as shown in FIG. 19, the manufacturing method of the limiting current type gas sensor according to the first embodiment includes a first stress relaxation low thermal expansion film 6 (5U) and a third stress relaxation low thermal expansion in plan view. The step of forming the first warp suppressing porous insulating film 10 (5U) on the dense electrode 5U across the film 6 (4), and the second stress relaxation low thermal expansion film 6 (in plan view) 5D) and the third stress relaxation low thermal expansion film 6 (4), and a step of forming the second warpage suppressing porous insulating film 10 (5D) on the porous electrode 5D.
　また、第１の実施の形態に係る限界電流式ガスセンサの製造方法は、図２０に示すように、基板１をエッチングして、基板１に形成されたキャビティ上に両持ちの梁構造体を形成する工程を有する。 Further, in the method of manufacturing the limiting current type gas sensor according to the first embodiment, as shown in FIG. 20, the substrate 1 is etched to form a doubly supported beam structure on the cavity formed in the substrate 1. The process of carrying out.
　また、第１の実施の形態に係る限界電流式ガスセンサの製造方法は、基板１もしくは基板１下部にマイクロヒータ２を形成する工程を有していても良い。 Further, the manufacturing method of the limiting current type gas sensor according to the first embodiment may include a step of forming the microheater 2 on the substrate 1 or the lower portion of the substrate 1.
　また、第１の実施の形態に係る限界電流式ガスセンサの製造方法は、基板１内部に埋め込まれたマイクロヒータ２を形成する工程を有していても良い。 Further, the method for manufacturing the limiting current gas sensor according to the first embodiment may include a step of forming the microheater 2 embedded in the substrate 1.
　また、第１の実施の形態に係る限界電流式ガスセンサの製造方法は、基板１上に絶縁膜３を形成する工程を有し、絶縁膜３上に多孔質電極５Ｄを形成しても良い。 In addition, the method for manufacturing the limiting current gas sensor according to the first embodiment may include a step of forming the insulating film 3 on the substrate 1, and the porous electrode 5 </ b> D may be formed on the insulating film 3.
　また、第１の実施の形態に係る限界電流式ガスセンサの製造方法において、マイクロヒータ２、絶縁膜３、多孔質電極５Ｄおよび緻密電極５Ｕ、絶縁膜８、固体電解質層４、応力緩和用低熱膨張膜６・６（５Ｕ）・６（５Ｄ）、および反り抑制用多孔質絶縁膜１０・１０（５Ｕ）・１０（５Ｄ）は、印刷工程により形成可能である。 In the method for manufacturing the limiting current gas sensor according to the first embodiment, the microheater 2, the insulating film 3, the porous electrode 5D and the dense electrode 5U, the insulating film 8, the solid electrolyte layer 4, and the low thermal expansion for stress relaxation. The films 6 and 6 (5U) and 6 (5D) and the warp suppressing porous insulating films 10 and 10 (5U) and 10 (5D) can be formed by a printing process.
　第１の実施の形態に係る限界電流式ガスセンサの製造方法について、図１３～図２０を参照して説明する。
（ａ）まず、図１３（ａ）・図１３（ｂ）に示すように、マイクロヒータ２を埋め込んだ基板１上に絶縁膜３を形成する。ここで、絶縁膜３は、多孔質膜であることから、ガスの通り道となる。なお、絶縁膜３の形成を省略しても良い。
（ｂ）次に、図１４（ａ）・図１４（ｂ）に示すように、絶縁膜３および基板１上に多孔質電極５Ｄを形成する。多孔質電極５Ｄは、例えば、ポーラスＰｔ電極によって形成されるため、このポーラスＰｔ電極中をガスが通るようにしても良い。
（ｃ）次に、図１５（ａ）・図１５（ｂ）に示すように、多孔質電極５Ｄ上に絶縁膜８を形成した後、絶縁膜８をパターニングして開口部７を形成する。ここで、絶縁膜８を形成することによって、安定化ジルコニア（４）／Ｐｔポーラス電極（５Ｄ）間の接触面積の安定化し、安定化ジルコニア（４）端面とＰｔポーラス電極（５Ｄ）の接触を無くし、また、Ｐｔポーラス電極（５Ｄ）とＰｔポーラス電極（５Ｕ）間の表面伝導成分の除去することができる。
（ｄ）次に、図１６（ａ）・図１６（ｂ）に示すように、開口部７の多孔質電極５Ｕ上および開口部７を取り囲む絶縁膜８上に固体電解質層４を形成する。固体電解質層４は、例えば、ここではＹＳＺ（安定化ジルコニア）で形成される。
（ｅ）次に、図１７（ａ）・図１７（ｂ）に示すように、固体電解質層４上に、多孔質電極５Ｄに対向し、基板１に対して実質的に縦方向に緻密電極５Ｕを形成する。緻密電極５Ｕは、図１７（ａ）に示すように、絶縁膜８・絶縁膜３・基板１上にも延伸して形成される。緻密電極５Ｕは、例えば、ポーラスＰｔ電極によって形成される。
（ｆ）次に、図１８（ａ）・図１８（ｂ）に示すように、緻密電極５Ｕ上に第１応力緩和用低熱膨張膜６（５Ｕ）を形成し、多孔質電極５Ｄ上に第２応力緩和用低熱膨張膜６（５Ｄ）を形成し、固体電解質層４上に第３応力緩和用低熱膨張膜６（４）を形成する。応力緩和用低熱膨張膜６は、検出するガス量によって、膜密度を調整可能である。また、応力緩和用低熱膨張膜６は、緻密膜、多孔質膜、もしくは緻密膜と多孔質膜の複合膜のいずれかで形成可能である。また、応力緩和用低熱膨張膜６は、ＳｉＯ2、Ａｌ2Ｏ3、ＹＳＺもしくはムライトの少なくとも一種類を含む材料で形成される。また、応力緩和用低熱膨張膜６は、印刷工程若しくはスパッタリング工程により形成可能である。応力緩和用低熱膨張膜６は、低熱膨張係数の絶縁膜であり、応力緩和用低熱膨張膜６を形成することによって、加熱時の応力を緩和することができる。
（ｇ）次に、図１９（ａ）・図１９（ｂ）に示すように、第１応力緩和用低熱膨張膜６（５Ｕ）と第３応力緩和用低熱膨張膜６（４）との間に跨って、緻密電極５Ｕ上に第１反り抑制用多孔質絶縁膜１０（５Ｕ）を形成すると共に、第２応力緩和用低熱膨張膜６（５Ｄ）と第３応力緩和用低熱膨張膜６（４）との間に跨って、多孔質電極５Ｄ上に第２反り抑制用多孔質絶縁膜１０（５Ｄ）を形成する。反り抑制用多孔質絶縁膜１０は、ＳｉＯ2、Ａｌ2Ｏ3、ＹＳＺもしくはムライトの少なくとも一種類を含む材料で形成される。また、反り抑制用多孔質絶縁膜１０は、印刷工程若しくはスパッタリング工程により形成可能である。反り抑制用多孔質絶縁膜１０を形成することによって、加熱時の梁構造の反りを小さくし、耐久性を向上することができる。
（ｈ）次に、図２０に示すように、基板１を矢印方向に裏面からエッチングする。結果として、図１０～図１２に示すように、基板１に形成されたキャビティＣ上に両持ちの梁構造体が形成される。このよぅに、梁構造を形成することによって、センサ部分の熱容量を低減し、かつ熱伝導を低減することができる。結果として、加熱時の低消費電力化が可能である。 A method of manufacturing the limiting current type gas sensor according to the first embodiment will be described with reference to FIGS.
(A) First, as shown in FIGS. 13A and 13B, the insulating film 3 is formed on the substrate 1 in which the microheater 2 is embedded. Here, since the insulating film 3 is a porous film, it becomes a gas passage. The formation of the insulating film 3 may be omitted.
(B) Next, as shown in FIGS. 14A and 14B, a porous electrode 5 </ b> D is formed on the insulating film 3 and the substrate 1. Since the porous electrode 5D is formed of, for example, a porous Pt electrode, gas may pass through the porous Pt electrode.
(C) Next, as shown in FIGS. 15A and 15B, after the insulating film 8 is formed on the porous electrode 5D, the insulating film 8 is patterned to form the opening 7. Here, by forming the insulating film 8, the contact area between the stabilized zirconia (4) / Pt porous electrode (5D) is stabilized, and the contact between the end surface of the stabilized zirconia (4) and the Pt porous electrode (5D) is achieved. In addition, the surface conduction component between the Pt porous electrode (5D) and the Pt porous electrode (5U) can be removed.
(D) Next, as shown in FIGS. 16A and 16B, the solid electrolyte layer 4 is formed on the porous electrode 5 </ b> U of the opening 7 and on the insulating film 8 surrounding the opening 7. The solid electrolyte layer 4 is formed of, for example, YSZ (stabilized zirconia) here.
(E) Next, as shown in FIGS. 17 (a) and 17 (b), on the solid electrolyte layer 4, it is opposed to the porous electrode 5D and is a dense electrode substantially vertically with respect to the substrate 1. 5U is formed. As shown in FIG. 17A, the dense electrode 5U is also formed to extend on the insulating film 8, the insulating film 3, and the substrate 1. The dense electrode 5U is formed by, for example, a porous Pt electrode.
(F) Next, as shown in FIGS. 18A and 18B, a first stress relaxation low thermal expansion film 6 (5U) is formed on the dense electrode 5U, and the first electrode is formed on the porous electrode 5D. The low stress expansion low thermal expansion film 6 (5D) is formed, and the third stress relaxation low thermal expansion film 6 (4) is formed on the solid electrolyte layer 4. The stress relaxation low thermal expansion film 6 can adjust the film density according to the amount of gas to be detected. The low thermal expansion film 6 for stress relaxation can be formed of any one of a dense film, a porous film, or a composite film of a dense film and a porous film. The stress relaxation low thermal expansion film 6 is formed of a material containing at least one of SiO 2 , Al 2 O 3 , YSZ, or mullite. Moreover, the low thermal expansion film 6 for stress relaxation can be formed by a printing process or a sputtering process. The low thermal expansion film 6 for stress relaxation is an insulating film having a low thermal expansion coefficient. By forming the low thermal expansion film 6 for stress relaxation, stress during heating can be relaxed.
(G) Next, as shown in FIGS. 19 (a) and 19 (b), between the first low stress thermal expansion film 6 (5U) and the third low stress thermal expansion film 6 (4). The first warp suppressing porous insulating film 10 (5U) is formed on the dense electrode 5U, and the second stress relaxation low thermal expansion film 6 (5D) and the third stress relaxation low thermal expansion film 6 ( 4), the second warp suppressing porous insulating film 10 (5D) is formed on the porous electrode 5D. The warp suppressing porous insulating film 10 is formed of a material containing at least one of SiO 2 , Al 2 O 3 , YSZ, or mullite. Moreover, the warp suppressing porous insulating film 10 can be formed by a printing process or a sputtering process. By forming the warp-suppressing porous insulating film 10, it is possible to reduce the warp of the beam structure during heating and improve the durability.
(H) Next, as shown in FIG. 20, the substrate 1 is etched from the back surface in the direction of the arrow. As a result, as shown in FIGS. 10 to 12, a doubly supported beam structure is formed on the cavity C formed in the substrate 1. Thus, by forming the beam structure, it is possible to reduce the heat capacity of the sensor portion and reduce heat conduction. As a result, low power consumption during heating is possible.
　[第２の実施の形態]
　第２の実施の形態に係る限界電流式ガスセンサの模式的平面パターン構成は、図２１に示すように表わされる。第１の実施の形態においては、図１０に示すように、両持梁構造の４本のアームの内、片側２本のアームの一方のアームにのみ多孔質電極５Ｄ・多孔質電極 ５Ｕを配置している。これに対して、第２の実施の形態においては、図２１に示すように、両持梁構造の４本のアームの内、片側２本のアームの両方のアームに多孔質電極５Ｄ1・５Ｄ2・緻密電極 ５Ｕ1・５Ｕ2を配置している。また、多孔質電極５Ｄ1・５Ｄ2は、互いに電気的に接続されている。同様に、緻密電極 ５Ｕ1・５Ｕ2も互いに電気的に接続されている。 [Second Embodiment]
A schematic plane pattern configuration of the limiting current type gas sensor according to the second embodiment is expressed as shown in FIG. In the first embodiment, as shown in FIG. 10, the porous electrode 5D and the porous electrode 5U are arranged only on one arm of the two arms on one side of the four arms of the doubly supported beam structure. is doing. On the other hand, in the second embodiment, as shown in FIG. 21, the porous electrodes 5D 1 and 5D are formed on both arms of the two arms on one side of the four arms of the both-end supported beam structure. 2・ Precise electrodes 5U 1・ 5U 2 are arranged. The porous electrodes 5D 1 and 5D 2 are electrically connected to each other. Similarly, the dense electrodes 5U 1 and 5U 2 are also electrically connected to each other.
　第２の実施の形態に係る限界電流式ガスセンサ１２は、図２１に示すように、基板１と、基板１上に配置された多孔質電極５Ｄ1・５Ｄ2と、多孔質電極５Ｄ1・５Ｄ2上に配置された絶縁膜８と、絶縁膜８にパターニングされた開口部７の多孔質電極５Ｄ1・５Ｄ2上および開口部７を取り囲む絶縁膜８上に配置された固体電解質層４と、固体電解質層４上に、多孔質電極５Ｄに対向し、基板１に対して実質的に縦方向に、金属粒子焼結層２８および金属粒子焼結層２８に形成された微細ガス導入路２６を備える緻密電極Ｕ1・５Ｕ2とを備える。 As shown in FIG. 21, the limiting current type gas sensor 12 according to the second embodiment includes a substrate 1, porous electrodes 5D 1 and 5D 2 disposed on the substrate 1, and porous electrodes 5D 1 and 5D. 2 and the solid electrolyte layer 4 disposed on the porous electrodes 5D 1 and 5D 2 of the opening 7 patterned on the insulating film 8 and on the insulating film 8 surrounding the opening 7 The fine gas introduction path 26 formed in the metal particle sintered layer 28 and the metal particle sintered layer 28 on the solid electrolyte layer 4 so as to face the porous electrode 5D and substantially in the longitudinal direction with respect to the substrate 1. And dense electrodes U 1 and 5 U 2 .
　ここで、絶縁膜８は、固体電解質層４の端面と多孔質電極５Ｄ1・５Ｄ2との間を非接触化し、酸素（Ｏ）イオンの固体電解質層４端面からの取り込みを抑制し、緻密電極５Ｕ1・５Ｕ2と多孔質電極５Ｄ1・５Ｄ2間の表面伝導電流成分を低減化可能である。 Here, the insulating film 8 makes the contact between the end face of the solid electrolyte layer 4 and the porous electrodes 5D 1 and 5D 2 in a non-contact manner, and suppresses the uptake of oxygen (O) ions from the end face of the solid electrolyte layer 4 to be dense. The surface conduction current component between the electrodes 5U 1 and 5U 2 and the porous electrodes 5D 1 and 5D 2 can be reduced.
　また、第２の実施の形態に係る限界電流式ガスセンサ１２は、図２１に示すように、緻密電極５Ｕ1・５Ｕ2と多孔質電極５Ｄ1・５Ｄ2との間に電圧を印加することにより被測定ガス内における所定のガス濃度を限界電流式で検出する検出回路１８を備える。ここで、検出回路１８は、限界電流に基づいて酸素濃度を検出することができる。また、検出回路１８は、限界電流に基づいて水蒸気濃度を検出することができる。 Further, as shown in FIG. 21, the limiting current type gas sensor 12 according to the second embodiment applies a voltage between the dense electrodes 5U 1 and 5U 2 and the porous electrodes 5D 1 and 5D 2. A detection circuit 18 is provided for detecting a predetermined gas concentration in the gas to be measured by a limiting current type. Here, the detection circuit 18 can detect the oxygen concentration based on the limit current. The detection circuit 18 can detect the water vapor concentration based on the limit current.
　また、第２の実施の形態に係る限界電流式ガスセンサ１２は、図２１に示すように、緻密電極５Ｕ1・５Ｕ2上に配置された第１応力緩和用低熱膨張膜６（５Ｕ1）・６（５Ｕ2）と、多孔質電極５Ｄ1・５Ｄ2上に配置された第２応力緩和用低熱膨張膜６（５Ｄ1）・６（５Ｄ2）と、固体電解質層４上に配置された第３応力緩和用低熱膨張膜６（４）とを備えていても良い。 Further, as shown in FIG. 21, the limiting current type gas sensor 12 according to the second embodiment includes a first stress relaxation low thermal expansion film 6 (5U 1 ), which is disposed on the dense electrodes 5U 1 and 5U 2. 6 (5U 2 ), the second low stress expansion film 6 (5D 1 ) · 6 (5D 2 ) for stress relaxation disposed on the porous electrodes 5D 1 and 5D 2 , and the solid electrolyte layer 4 You may provide the 3rd low thermal expansion film | membrane 6 (4) for stress relaxation.
　また、第２の実施の形態に係る限界電流式ガスセンサ１２は、図２１に示すように、平面視において、第１応力緩和用低熱膨張膜６（５Ｕ1）・６（５Ｕ2）と第３応力緩和用低熱膨張膜６（４）との間に跨って、緻密電極５Ｕ1・５Ｕ2上に配置された第１反り抑制用多孔質絶縁膜１０（５Ｕ1）・１０（５Ｕ2）と、平面視において、第２応力緩和用低熱膨張膜６（５Ｄ1）・６（５Ｄ2）と第３応力緩和用低熱膨張膜６（４）との間に跨って、多孔質電極５Ｄ1・５Ｄ2上に配置された第２反り抑制用多孔質絶縁膜１０（５Ｄ1）・１０（５Ｄ2）とを備えていても良い。 Further, as shown in FIG. 21, the limiting current type gas sensor 12 according to the second embodiment has a first stress relaxation low thermal expansion film 6 (5U 1 ), 6 (5U 2 ) and a third one in plan view. The first warp suppressing porous insulating films 10 (5U 1 ) and 10 (5U 2 ) disposed on the dense electrodes 5U 1 and 5U 2 across the low thermal expansion film 6 (4) for stress relaxation In the plan view, the porous electrode 5D 1 ... Spans between the second stress relaxation low thermal expansion film 6 (5D 1 ), 6 (5D 2 ) and the third stress relaxation low thermal expansion film 6 (4). 5D for arranged second warp suppressing over 2 porous insulating film 10 (5D 1) · 10 ( 5D 2) and may include a.
　また、基板１上に配置された絶縁膜３を備え、絶縁膜３上に多孔質電極５Ｄ1・５Ｄ2を配置しても良い。その他の構成は、第１の実施の形態と同様である。 Further, the insulating film 3 disposed on the substrate 1 may be provided, and the porous electrodes 5D 1 and 5D 2 may be disposed on the insulating film 3. Other configurations are the same as those of the first embodiment.
　（製造方法）
　第２の実施の形態に係る限界電流式ガスセンサの製造方法は、図２２～図２５に示すように、基板１上に多孔質電極５Ｄ1・５Ｄ2を形成する工程（図２２）と、多孔質電極５Ｄ1・５Ｄ2上に絶縁膜８を形成する工程と、絶縁膜８をパターニングして開口部７を形成する工程（図２３）と、開口部７の多孔質電極５Ｄ1・５Ｄ2上および開口部７を取り囲む絶縁膜８上に固体電解質層４を形成する工程（図２４）と、固体電解質層４上に、多孔質電極５Ｄ1・５Ｄ2に対向し、基板１に対して実質的に縦方向に、金属粒子焼結層２８および金属粒子焼結層２８に形成された微細ガス導入路２６を備える緻密電極５Ｕ１・５Ｕ2を形成する工程（図２５）とを有する。 (Production method)
As shown in FIGS. 22 to 25, the method of manufacturing the limiting current type gas sensor according to the second embodiment includes a step of forming porous electrodes 5D 1 and 5D 2 on the substrate 1 (FIG. 22), forming a quality electrode 5D 1 · 5D 2 insulating film 8 on a step (23) forming an opening 7 by patterning the insulating film 8, the porous electrode 5D 1 · 5D 2 opening 7 A step of forming the solid electrolyte layer 4 on the insulating film 8 surrounding the top and the opening 7 (FIG. 24), and on the solid electrolyte layer 4 facing the porous electrodes 5D 1 and 5D 2 and facing the substrate 1 A step of forming the dense electrodes 5U 1 and 5U 2 including the metal particle sintered layer 28 and the fine gas introduction path 26 formed in the metal particle sintered layer 28 in a substantially vertical direction (FIG. 25).
　ここで、絶縁膜８は、固体電解質層４の端面と多孔質電極５Ｄ1・５Ｄ2との間を非接触化し、酸素（Ｏ）イオンの固体電解質層４端面からの取り込みを抑制し、緻密電極５Ｕ１・５Ｕ2と多孔質電極５Ｄ1・５Ｄ2との間の表面伝導電流成分を低減化可能である。 Here, the insulating film 8 makes the contact between the end face of the solid electrolyte layer 4 and the porous electrodes 5D 1 and 5D 2 in a non-contact manner, and suppresses the uptake of oxygen (O) ions from the end face of the solid electrolyte layer 4 to be dense. The surface conduction current component between the electrodes 5U 1 and 5U 2 and the porous electrodes 5D 1 and 5D 2 can be reduced.
　また、第２の実施の形態に係る限界電流式ガスセンサの製造方法は、図２６に示すように、緻密電極５Ｕ１・５Ｕ2上に第１応力緩和用低熱膨張膜６（５Ｕ1）・６（５Ｕ2）を形成し、多孔質電極５Ｄ1・５Ｄ2上に第２応力緩和用低熱膨張膜６（５Ｄ1）・６（５Ｄ2）を形成し、固体電解質層４上に第３応力緩和用低熱膨張膜６（４）を形成する工程を有する。 In addition, as shown in FIG. 26, the manufacturing method of the limiting current type gas sensor according to the second embodiment includes a first stress relaxation low thermal expansion film 6 (5U 1 ) · 6 on the dense electrodes 5U 1 and 5U 2. (5U 2) to form a porous electrode 5D 1 · 5D on 2 second stress relieving for a low thermal expansion layer 6 (5D 1) · 6 ( 5D 2) is formed, third stress on the solid electrolyte layer 4 Forming a low thermal expansion film 6 (4) for relaxation.
　また、第２の実施の形態に係る限界電流式ガスセンサの製造方法は、図２７に示すように、平面視において、第１応力緩和用低熱膨張膜６（５Ｕ1）・６（５Ｕ2）と第３応力緩和用低熱膨張膜６（４）との間に跨って、緻密電極５Ｕ１・５Ｕ2上に第１反り抑制用多孔質絶縁膜１０（５Ｕ1）・１０（５Ｕ2）を形成する工程と、平面視において、第２応力緩和用低熱膨張膜６（５Ｄ1）・６（５Ｄ2）と第３応力緩和用低熱膨張膜６（４）との間に跨って、多孔質電極５Ｄ1・５Ｄ2上に第２反り抑制用多孔質絶縁膜１０（５Ｄ1）・１０（５Ｄ2）を形成する工程とを有する。 In addition, as shown in FIG. 27, the manufacturing method of the limiting current type gas sensor according to the second embodiment includes the first stress relaxation low thermal expansion films 6 (5U 1 ) and 6 (5U 2 ) in plan view. The first warp-suppressing porous insulating films 10 (5U 1 ) and 10 (5U 2 ) are formed on the dense electrodes 5U 1 and 5U 2 so as to straddle the third low-temperature expansion film for stress relaxation 6 (4). A porous electrode straddling between the second stress relaxation low thermal expansion film 6 (5D 1 ), 6 (5D 2 ) and the third stress relaxation low thermal expansion film 6 (4) in plan view. on 5D 1 · 5D 2 and forming a for second warp suppressing porous insulating film 10 (5D 1) · 10 ( 5D 2).
　また、第２の実施の形態に係る限界電流式ガスセンサの製造方法は、図２１に示すように、基板１をエッチングして、基板１に形成されたキャビティ上に両持ちの梁構造体を形成する工程を有する。 Further, in the method of manufacturing the limiting current gas sensor according to the second embodiment, as shown in FIG. 21, the substrate 1 is etched to form a doubly supported beam structure on the cavity formed in the substrate 1. The process of carrying out.
　また、第２の実施の形態に係る限界電流式ガスセンサの製造方法は、図２１に示すように、基板１上に絶縁膜３を形成する工程を有し、絶縁膜３上に多孔質電極５Ｄ1・５Ｄ2を形成しても良い。 In addition, as shown in FIG. 21, the method for manufacturing a limiting current gas sensor according to the second embodiment includes a step of forming an insulating film 3 on the substrate 1, and the porous electrode 5D is formed on the insulating film 3. 1 · 5D 2 may be formed.
　第２の実施の形態においては、図２１に示すように、両持梁構造の４本のアームの内、片側２本のアームの両方のアームに多孔質電極５Ｄ1・５Ｄ2・緻密電極 ５Ｕ1・５Ｕ2を配置している構造のみが第１の実施の形態と異なるため、各部の詳細な製造工程は、第１の実施の形態と同様である。 In the second embodiment, as shown in FIG. 21, the porous electrodes 5D 1 , 5D 2, and the dense electrode 5U are provided on both arms of the two arms on one side of the four arms of the doubly supported beam structure. Since only the structure in which 1 · 5 U 2 is arranged is different from that of the first embodiment, the detailed manufacturing process of each part is the same as that of the first embodiment.
　以下、第１の実施の形態、第２の実施の形態に共通する説明は、単に実施の形態と記載する。 Hereinafter, the description common to the first embodiment and the second embodiment will be simply referred to as an embodiment.
　（梁構造）
　実施の形態に係る限界電流式ガスセンサの製造方法の一工程（梁構造形成工程）を示す模式的断面構造は、図２８（ａ）に示すように表わされ、実施の形態に係る限界電流式ガスセンサの製造方法の一工程（別の梁構造形成工程）は、図２８（ｂ）に示すように表わされる。 (Beam structure)
A schematic cross-sectional structure showing one step (beam structure forming step) of the manufacturing method of the limiting current type gas sensor according to the embodiment is represented as shown in FIG. 28 (a), and the limiting current type according to the embodiment is shown. One step of the gas sensor manufacturing method (another beam structure forming step) is expressed as shown in FIG.
　ＭＥＭＳ構造を有する梁構造には、図２８（ａ）に示すように、空洞Ｃを基板１の底部に開放構造に形成する開放型構造と、図２８（ｂ）に示すように、空洞Ｃを基板１の内部に形成する船型構造が可能である。いずれも例えばシリコン基板の異方性エッチングなどを適用可能である。図２８（ａ）・図２８（ｂ）においては、いずれも薄層化された基板１部分には、マイクロヒータ２が形成されているが図示は省略する。また、実施の形態に係る限界電流式ガスセンサの縦型センサ構造は、デバイス加熱部２００によって表わされている。 In the beam structure having the MEMS structure, as shown in FIG. 28A, an open type structure in which the cavity C is formed in the open structure at the bottom of the substrate 1, and as shown in FIG. A boat-shaped structure formed inside the substrate 1 is possible. In either case, for example, anisotropic etching of a silicon substrate can be applied. In FIGS. 28A and 28B, the microheater 2 is formed on the thinned substrate 1 portion, but the illustration is omitted. Further, the vertical sensor structure of the limiting current type gas sensor according to the embodiment is represented by a device heating unit 200.
　実施の形態に係る限界電流式ガスセンサの梁構造のレイアウト図（上面図）は、図２９（ａ）に示すように表わされ、図２９（ａ）のＩＸ－ＩＸ線に沿う模式的断面構造は、図２９（ｂ）に示すように表わされる。 The layout diagram (top view) of the beam structure of the limiting current type gas sensor according to the embodiment is represented as shown in FIG. 29A, and is a schematic cross-sectional structure taken along line IX-IX in FIG. Is represented as shown in FIG.
　図２９においては、基板１として（１００）面を有するシリコン基板を使用し、異方性エッチングにより、デバイス加熱部２００の底部には、底面が（１００）面、側面が（１１１）面のキャビティＣが形成されている。 In FIG. 29, a silicon substrate having a (100) surface is used as the substrate 1, and a cavity having a bottom surface of (100) surface and a side surface of (111) surface is formed at the bottom of the device heating unit 200 by anisotropic etching. C is formed.
　この基板１の表面には、ポリシリコンで形成されたマイクロヒータを含むシリコン酸化膜／シリコン窒化膜の積層膜１００が形成されている。デバイス加熱部２００の面積は、例えば、約０．１ｍｍ2である。 On the surface of the substrate 1, a laminated film 100 of silicon oxide film / silicon nitride film including a microheater made of polysilicon is formed. The area of the device heating unit 200 is, for example, about 0.1 mm 2 .
　図２９（ａ）・図２９（ｂ）に示す構造例では、縦型センサ構造のデバイス加熱部２００の底部には、マイクロヒータを含む積層膜１００が形成されており、基板１は除去されている。すなわち、第１の実施の形態および第２実施の形態において、薄層化された基板１を除去し、マイクロヒータを含む積層膜１００のみが形成されていても良い。 In the structural example shown in FIGS. 29A and 29B, a laminated film 100 including a microheater is formed on the bottom of the device heating unit 200 having a vertical sensor structure, and the substrate 1 is removed. Yes. That is, in the first embodiment and the second embodiment, the thinned substrate 1 may be removed and only the laminated film 100 including the microheater may be formed.
　実施の形態に係る限界電流式ガスセンサのマイクロヒータ２は、以下のプロセスフローにより形成することができる。 The microheater 2 of the limiting current type gas sensor according to the embodiment can be formed by the following process flow.
　まず、シリコン基板１上に３ｕｍ－ＰＳＧ（Phosphorus Silicon Glass）膜を形成し、ＳｉＮを形成し、ＳｉＮパターニングを行う（高濃度にドープする部分はＳｉＮ除去）。次に、ポリシリコンを形成し、例えば約１０００℃程度の熱処理により、ポリシリコンへ燐Ｐを拡散して高濃度ドープポリシリコンにする。ＳｉＮがある部分は低濃度ドープポリシリコンにする。更に、縦型センサ構造を形成し、ＢＨＦ（５:１）でＰＳＧエッチチングして梁構造を形成する。 First, a 3 um-PSG (Phosphorus Silicon Glass) film is formed on the silicon substrate 1, SiN is formed, and SiN patterning is performed (SiN removal is performed on the highly doped portion). Next, polysilicon is formed, and phosphorus P is diffused into the polysilicon by, for example, a heat treatment at about 1000 ° C. to form highly doped polysilicon. The portion where SiN is present is lightly doped polysilicon. Further, a vertical sensor structure is formed, and a beam structure is formed by PSG etching with BHF (5: 1).
　以上のように、実施の形態によれば、キャビティＣ上に梁構造のマイクロヒータ２を容易に形成することができる。 As described above, according to the embodiment, the beam-structured micro heater 2 can be easily formed on the cavity C.
　実施の形態に係る限界電流式ガスセンサにおいて、マイクロヒータ２は、図２９（ａ）・図２９（ｂ）の積層膜１００部分に配置されている。以下のプロセスフローによりマイクロヒータ２を形成するようにしても良い。 In the limiting current type gas sensor according to the embodiment, the microheater 2 is disposed in the laminated film 100 portion of FIGS. 29 (a) and 29 (b). The micro heater 2 may be formed by the following process flow.
　まず、Ｓｉ（１００）基板１上にＳｉＯ2／ＳｉＮ／ＳｉＯ2の多層絶縁膜である積層膜１００を形成し、その上にＰｔヒータ（マイクロヒータ２）を形成する。次に、マイクロヒータ２の上にデバイス加熱部２００を形成する。更に、ＴＭＡＨ溶液を用いてシリコン基板１を異方性エッチングすることによりキャビティＣを形成する。 First, a laminated film 100 which is a multilayer insulating film of SiO 2 / SiN / SiO 2 is formed on a Si (100) substrate 1, and a Pt heater (micro heater 2) is formed thereon. Next, the device heating unit 200 is formed on the microheater 2. Furthermore, the cavity C is formed by anisotropically etching the silicon substrate 1 using the TMAH solution.
　以上のように、実施の形態によれば、キャビティＣ上に梁構造のマイクロヒータ２を容易に形成することができる。 As described above, according to the embodiment, the beam-structured micro heater 2 can be easily formed on the cavity C.
　（動作原理）
―ガス濃度を検出する動作―
　限界電流式ガスセンサの原理は次の通りである。まず、ジルコニア固体電解質を数百度に加熱し、ジルコニア固体電解質に電圧を印加すると、触媒電極でイオン化した酸素イオンが、固体電解質の一方の側から他の側へ伝導する。このとき、小孔や多孔質などを利用して電解質に吸入する酸素ガス量を制限すると、電圧を増加しても電流が一定値になる飽和現象が現れる。この電流は限界電流と呼ばれ、周囲の酸素濃度に比例する。そのため、一定の電圧を印加すれば、流れる電流値から酸素濃度を検出することができる。印加する電圧を切り替えれば、同様の原理で水蒸気の濃度を検出することも可能である。 (Operating principle)
-Operation to detect gas concentration-
The principle of the limiting current type gas sensor is as follows. First, when the zirconia solid electrolyte is heated to several hundred degrees and a voltage is applied to the zirconia solid electrolyte, oxygen ions ionized at the catalyst electrode are conducted from one side of the solid electrolyte to the other side. At this time, if the amount of oxygen gas sucked into the electrolyte is limited using small pores or porous materials, a saturation phenomenon appears in which the current becomes a constant value even when the voltage is increased. This current is called the limiting current and is proportional to the ambient oxygen concentration. Therefore, if a constant voltage is applied, the oxygen concentration can be detected from the flowing current value. If the voltage to be applied is switched, the water vapor concentration can be detected by the same principle.
　実施の形態に係る限界電流式ガスセンサ１２を用いてガス濃度を検出する動作を示すフローチャートは、図３０に示すように表される。また、実施の形態に係る限界電流式ガスセンサにおいて、ガス濃度検出動作におけるＹＳＺ温度と時間との関係は、模式的に図３１に示すように表され、動作原理を説明する模式的断面構造は、図３２に示すように表される。 A flowchart showing an operation of detecting a gas concentration using the limiting current type gas sensor 12 according to the embodiment is expressed as shown in FIG. Further, in the limiting current type gas sensor according to the embodiment, the relationship between the YSZ temperature and the time in the gas concentration detection operation is schematically represented as shown in FIG. 31, and the schematic cross-sectional structure for explaining the operation principle is It is expressed as shown in FIG.
　固体電解質層４を、マイクロヒータ２によって、数百℃、例えば５００℃程度に加熟し、緻密電極（陰極）５Ｕ・多孔質電極（陽極）５Ｄ間に電圧を印加して電流Ｉを流すと、図３２に示すように、緻密電極（陰極）５Ｕでは、Ｏ2＋４ｅ-⇔２Ｏ2－の電気化学反応によって固体電解質層４中へ酸素イオンの注入が起こる。一方、多孔質電極（陽極）５Ｄでは、２Ｏ2－⇔Ｏ2＋４ｅ-の反応によって酸素ガスの放出が生じる。 When the solid electrolyte layer 4 is ripened to several hundred degrees C., for example, about 500 degrees C. by the microheater 2 and a voltage is applied between the dense electrode (cathode) 5U and the porous electrode (anode) 5D to pass the current I, As shown in FIG. 32, in the dense electrode (cathode) 5U, oxygen ions are implanted into the solid electrolyte layer 4 by the electrochemical reaction of O 2 + 4e − ⇔2O 2− . On the other hand, in the porous electrode (anode) 5D, oxygen gas is released by the reaction of 2O 2 −⇔O 2 + 4e − .
　固体電解質層４中において、酸素イオン（Ｏ2-）は、ホッピング伝導に基づいて伝播される。ここで、酸素イオン（Ｏ2-）のホッピング伝導を説明するエネルギーダイアグラムは、図３３に示すように模式的に表される。固体電解質層４に電界ＥXが印加されるとその効果によって、伝導体の底は、－ｅＥXだけ傾くことになる。その分だけ、酸素イオン（Ｏ2-）の伝導障壁高さが低下するため、熱励起と共に酸素イオン（Ｏ2-）のホッピング伝導が実施される。 In the solid electrolyte layer 4, oxygen ions (O 2− ) are propagated based on hopping conduction. Here, an energy diagram for explaining the hopping conduction of oxygen ions (O 2− ) is schematically represented as shown in FIG. By its effect when the solid electrolyte layer 4 field E X is applied, the bottom of the conductor will be inclined only -ee X. Accordingly, the height of the conduction barrier of oxygen ions (O 2− ) is lowered, and therefore, hopping conduction of oxygen ions (O 2− ) is performed together with thermal excitation.
　固体電解質層４に吸入する酸素ガス量を制限すると、電圧を増加しても電流が一定値になる飽和現象が現れる。実施の形態に係る限界電流式ガスセンサにおいて、電流―電圧特性における限界電流は、図３４に示すように模式的に表される。すなわち、図３４において、期間Ｔ2で現れる電流が酸素ガスに対する限界電流を表し、期間Ｔ3で現れる電流が水蒸気に対する限界電流ＩWを表す。この限界電流ＩO・ＩWは、周囲の酸素濃度・水蒸気濃度に比例するため、限界電流ＩO・ＩWの値と酸素濃度・水蒸気濃度の値とを予め対応付けて検出回路８に登録しておく。このようにすれば、限界電流ＩO・ＩWの値を測定することにより、それに対応する酸素濃度・水蒸気濃度を検出することができる。また、緻密電極（陰極）５Ｕ・多孔質電極５Ｄ間に印加する電圧を切り替えれば、酸素濃度だけでなく水蒸気濃度を検出することも可能である。 When the amount of oxygen gas sucked into the solid electrolyte layer 4 is limited, a saturation phenomenon appears in which the current becomes a constant value even when the voltage is increased. In the limiting current type gas sensor according to the embodiment, the limiting current in the current-voltage characteristic is schematically represented as shown in FIG. That is, in FIG. 34, the current appearing in period T 2 represents the limiting current for oxygen gas, and the current appearing in period T 3 represents the limiting current I W for water vapor. Since the limit currents I O and I W are proportional to the surrounding oxygen concentration and water vapor concentration, the values of the limit currents I O and I W and the oxygen concentration and water vapor concentration values are associated in advance and registered in the detection circuit 8. Keep it. In this way, by measuring the value of the limit current I O · I W , the corresponding oxygen concentration / water vapor concentration can be detected. Moreover, if the voltage applied between the dense electrode (cathode) 5U and the porous electrode 5D is switched, not only the oxygen concentration but also the water vapor concentration can be detected.
　実施の形態に係る限界電流式ガスセンサ１２を用いてガス濃度を検出する動作を、図３０および図３１を参照して説明する。図３１において、Ｔonはヒータオン期間、Ｔoffはヒータオフ期間に相当する。ヒータオン期間Ｔonに投入される加熱電力は、例えば、約５ｍＷである。
（ａ）まず、マイクロヒータ２を用いて、室温から測定温度（例えば５００℃）までセンサを加熱する（図３０：ステップＳ１→Ｓ２：ＮＯ→Ｓ１→・・・）。図３１に示すように、例えば、時刻ｔ＝０～ｔ＝０．１秒の間にＹＳＺ温度Ｔは、０℃～約５００℃まで上昇する。
（ｂ）測定温度に達したら（図３０：ステップＳ２：ＹＥＳ）、安定するまで一定時間待機する（図３０：ステップＳ３）。図３１に示すように、例えば、時刻ｔ＝０．１秒～ｔ＝０．３秒の待機期間ＴWにＹＳＺ温度Ｔは、約５００℃に保持される。
（ｃ）次に、緻密電極５Ｕ・多孔質電極５Ｄ間に電圧を印加する（図３０：ステップＳ４）。図３１に示すように、例えば、時刻ｔ＝０．３秒～ｔ＝０．５秒の測定期間ＴMにＹＳＺ温度Ｔは、約５００℃に保持される。
（ｄ）次に、限界電流の値を測定し、その限界電流に対応するガス濃度を検出する（ステップＳ５）。
（ｅ）次に、マイクロヒータ２をオフにして、センサを冷却する。図３１に示すように、例えば、時刻ｔ＝０．５秒～にＹＳＺ温度Ｔは、約５００℃から室温まで冷却される。 The operation of detecting the gas concentration using the limiting current type gas sensor 12 according to the embodiment will be described with reference to FIG. 30 and FIG. In Figure 31, T on the heater ON period, T off is equivalent to heater off period. Heating power supplied to the heater on time T on is, for example, about 5 mW.
(A) First, the sensor is heated from room temperature to a measurement temperature (for example, 500 ° C.) using the microheater 2 (FIG. 30: Step S1 → S2: NO → S1 →...). As shown in FIG. 31, for example, the YSZ temperature T rises from 0 ° C. to about 500 ° C. during the time t = 0 to t = 0.1 seconds.
(B) When the measured temperature is reached (FIG. 30: Step S2: YES), it waits for a certain time until it stabilizes (FIG. 30: Step S3). As shown in FIG. 31, for example, YSZ temperature T at time t = 0.1 sec ~ t = 0.3 seconds waiting period T W of is maintained at about 500 ° C..
(C) Next, a voltage is applied between the dense electrode 5U and the porous electrode 5D (FIG. 30: step S4). As shown in FIG. 31, for example, the YSZ temperature T is maintained at about 500 ° C. during the measurement period T M from time t = 0.3 seconds to t = 0.5 seconds.
(D) Next, the value of the limiting current is measured, and the gas concentration corresponding to the limiting current is detected (step S5).
(E) Next, the micro heater 2 is turned off to cool the sensor. As shown in FIG. 31, for example, the YSZ temperature T is cooled from about 500 ° C. to room temperature from time t = 0.5 seconds.
　以上に説明した温度サイクルは、例えば、約１分間に1回程度のサイクルで加熱・待機・測定・冷却を繰り返しても良い。 In the temperature cycle described above, for example, heating, standby, measurement, and cooling may be repeated at a cycle of about once per minute.
　（電気化学反応）
　実施の形態に係る限界電流式ガスセンサにおいて、イオン伝導を説明する模式的断面構造は、図３５に示すように表される。 (Electrochemical reaction)
In the limiting current type gas sensor according to the embodiment, a schematic cross-sectional structure for explaining ion conduction is expressed as shown in FIG.
　図３４・図３５を参照して、実施の形態に係る限界電流式ガスセンサにおける電気化学反応について説明する。
（ａ）ＹＳＺ４を、マイクロヒータ２によって、例えば５００℃程度に加熟し、陰極５Ｕ・陽極５Ｄ間に電圧Ｖを印加して電流Ｉを流すと、図３４の期間Ｔ1において、電流は増加し、限界電流ＩOに到達する。図３４の期間Ｔ1においては、Ｏ2＋４ｅ-⇔２Ｏ2－の電気化学反応によって、ＹＳＺ４中において、酸素イオンＯ2－が拡散する。この時、酸素ガスＯ2のフロー量の方が酸素イオンＯ2－が拡散する量よりも大きい。
（ｂ）限界電流ＩOが保持される図３４の期間Ｔ2においては、酸素ガス分子の電気分解反応が実施され、図３５に示すように、陰極５ＵとＹＳＺ４界面では、Ｏ2＋４ｅ-⇔２Ｏ2－の電気化学反応によってＹＳＺ４中へ酸素イオンＯ2－の注入が起こる。一方、５ＤとＹＳＺ４界面では、２Ｏ2－⇔Ｏ2＋４ｅ-の反応によって酸素ガスＯ2の放出が生じる。
（ｃ）ＹＳＺ４の温度Ｔを、例えば５００℃程度に保持し、さらに電圧Ｖを増加すると、電流Ｉは増加し、図３４の期間Ｔ3において、限界電流ＩWに到達する。
（ｄ）限界電流ＩWが保持される図３４の期間Ｔ3においては、吸着酸素ガスＯadの電気分解反応と水蒸気（Ｈ2Ｏ）の電気分解反応が実施される。ここで、図３５に示すように、陰極５ＵとＹＳＺ４界面では、Ｏ2＋４ｅ-⇔２Ｏ2－の電気化学反応によってＹＳＺ４中へ酸素イオンＯ2－の注入が起こる。また、Ｈ2Ｏ＋２ｅ-⇔Ｈ2＋Ｏ2－の電気化学反応によって水素の放出が生じる。すなわち、水蒸気（Ｈ2Ｏ）が電気分解されて、酸素イオンＯ2－が固体電解質層４内をホッピング伝導により移動していく。 With reference to FIG. 34 and FIG. 35, the electrochemical reaction in the limiting current type gas sensor according to the embodiment will be described.
The (a) YSZ4, the micro-heater 2, for example, ripe pressurized to about 500 ° C., the electric current I and the voltage V is applied between a cathode 5U · anode 5D, in the period T 1 of the FIG. 34, current is increased The limit current I O is reached. In the period T 1 in FIG. 34, oxygen ions O 2− diffuse in YSZ4 by the electrochemical reaction of O 2 + 4e − ⇔2O 2− . At this time, the flow amount of the oxygen gas O 2 is larger than the diffusion amount of the oxygen ions O 2− .
(B) In the period T 2 in FIG. 34 in which the limit current I O is maintained, an oxygen gas molecule electrolysis reaction is performed. As shown in FIG. 35, O 2 + 4e − ⇔ is generated at the cathode 5U and YSZ4 interface. Oxygen ions O 2− are implanted into YSZ4 by 2O 2− electrochemical reaction. On the other hand, at the interface between 5D and YSZ4, oxygen gas O 2 is released by the reaction of 2O 2 −ＯO 2 + 4e − .
(C) When the temperature T of YSZ4 is maintained at, for example, about 500 ° C. and the voltage V is further increased, the current I increases and reaches the limit current I W in the period T 3 of FIG.
(D) In the period T 3 of FIG. 34 in which the limit current I W is maintained, the electrolysis reaction of the adsorbed oxygen gas O ad and the electrolysis reaction of water vapor (H 2 O) are performed. Here, as shown in FIG. 35, oxygen ions O 2− are injected into YSZ4 by an electrochemical reaction of O 2 + 4e − ⇔2O 2− at the cathode 5U and the YSZ4 interface. Further, hydrogen is released by an electrochemical reaction of H 2 O + 2e − ⇔H 2 + O 2− . That is, water vapor (H 2 O) is electrolyzed, and oxygen ions O 2− move in the solid electrolyte layer 4 by hopping conduction.
　一方、陽極５ＤとＹＳＺ４界面では、吸着酸素ガスＯadの電気分解により、２Ｏ2－⇔Ｏ2＋４ｅ-の反応によって酸素ガスＯ2の放出が生じる。同様に、水蒸気（Ｈ2Ｏ）の電気分解により、２Ｏ2－⇔Ｏ2＋４ｅ-の反応によって酸素ガスＯ2の放出が生じる。
（ｅ）ＹＳＺ４の温度Ｔを、例えば５００℃程度に保持し、さらに電圧Ｖを増加すると、電流Ｉは増加し、図３４の期間Ｔ4において、吸着酸素ガスＯadの電気分解反応と水蒸気（Ｈ2Ｏ）の電気分解反応が実施される。さらに、ＹＳＺ４の電気分解が始まる。
ここで、図３５に示すように、陰極５ＵとＹＳＺ４界面では、Ｏ2＋４ｅ-⇔２Ｏ2－の電気化学反応によってＹＳＺ４中へ酸素イオンＯ2－の注入が起こる。また、Ｈ2Ｏ＋２ｅ-⇔Ｈ2＋Ｏ2－の電気化学反応によって水素の放出が生じる。すなわち、水蒸気（Ｈ2Ｏ）が電気分解されて、酸素イオンＯ2－がホッピング伝導により固体電解質層４内を移動していく。 On the other hand, at the interface between the anode 5D and the YSZ4, the oxygen gas O 2 is released by the reaction of 2O 2 −⇔O 2 + 4e − due to the electrolysis of the adsorbed oxygen gas O ad . Similarly, oxygen gas O 2 is released by the reaction of 2O 2 −⇔O 2 + 4e − by electrolysis of water vapor (H 2 O).
(E) When the temperature T of YSZ4 is maintained at, for example, about 500 ° C. and the voltage V is further increased, the current I increases, and during the period T 4 in FIG. 34, the electrolysis reaction of adsorbed oxygen gas O ad and water vapor ( An electrolysis reaction of H 2 O) is carried out. Furthermore, the electrolysis of YSZ4 begins.
Here, as shown in FIG. 35, oxygen ions O 2− are injected into YSZ4 by an electrochemical reaction of O 2 + 4e − ⇔2O 2− at the cathode 5U and the YSZ4 interface. Further, hydrogen is released by an electrochemical reaction of H 2 O + 2e − ⇔H 2 + O 2− . That is, water vapor (H 2 O) is electrolyzed, and oxygen ions O 2− move through the solid electrolyte layer 4 by hopping conduction.
　一方、陽極５ＤとＹＳＺ４界面では、吸着酸素ガスＯadの電気分解により、２Ｏ2－⇔Ｏ2＋４ｅ-の反応によって酸素ガスＯ2の放出が生じる。同様に、水蒸気（Ｈ2Ｏ）の電気分解により、２Ｏ2－⇔Ｏ2＋４ｅ-の反応によって酸素ガスＯ2の放出が生じる。 On the other hand, at the interface between the anode 5D and the YSZ4, the oxygen gas O 2 is released by the reaction of 2O 2 −⇔O 2 + 4e − due to the electrolysis of the adsorbed oxygen gas O ad . Similarly, oxygen gas O 2 is released by the reaction of 2O 2 −⇔O 2 + 4e − by electrolysis of water vapor (H 2 O).
　さらにＹＳＺ４の電気分解によって、酸素空孔濃度は次式ＯO X⇔１／２・Ｏ2（ｇ）＋ＶO ..＋２ｅ’に基づき、雰囲気酸素分圧との平衡にも依存する。この式は、電子的伝導率は、固体と平衡する酸素分圧に依存し、高温では、生成系のエントロピーがより大きいことから高温では、反応が右に偏るので、温度にも依存することを示している。 Furthermore, due to the electrolysis of YSZ4, the oxygen vacancy concentration depends on the equilibrium with the atmospheric oxygen partial pressure based on the following formula O O x X1 / 2 · O 2 (g) + V O .. + 2e ′ . This equation shows that the electronic conductivity depends on the partial pressure of oxygen at equilibrium with the solid, and at high temperatures, the entropy of the production system is larger, so at high temperatures, the reaction is biased to the right, so it also depends on temperature. Show.
　（パッケージ）
　実施の形態に係る限界電流式ガスセンサを収容するパッケージの蓋１３１を示す模式的鳥瞰構成は、図３６に示すように表される。図３６に示すように、パッケージの蓋１３１には、ガスは通過可能であるが異物は通さない多数の貫通穴１３２が形成されている。パッケージの蓋１３１には、メタルメッシュ、小孔開きメタル、ポーラスセラミックなどを適用可能である。 (package)
A schematic bird's-eye view configuration showing the lid 131 of the package that houses the limiting current type gas sensor according to the embodiment is expressed as shown in FIG. As shown in FIG. 36, the package lid 131 is formed with a large number of through holes 132 that allow gas to pass but not allow foreign matter to pass. For the lid 131 of the package, a metal mesh, a small hole metal, a porous ceramic, or the like can be applied.
　実施の形態に係る限界電流式ガスセンサを収容するパッケージの本体１４１を示す模式的鳥瞰構成は、図３７に示すように表される。図３７に示すように、パッケージの本体１４１には、複数の端子を備えた限界電流式ガスセンサのチップ１４２が収容され、複数のボンディングワイヤ１４３により電気的に接続されている。パッケージの本体１４１の上部に蓋１３１を被せ、半田によりプリント基板１０１などに実装する。 37. A schematic bird's-eye view configuration showing a main body 141 of a package that houses a limiting current type gas sensor according to the embodiment is expressed as shown in FIG. As shown in FIG. 37, a package main body 141 houses a limit current type gas sensor chip 142 having a plurality of terminals, and is electrically connected by a plurality of bonding wires 143. A lid 131 is placed on the top of the package main body 141 and mounted on the printed circuit board 101 by soldering.
　（エナジーハーベスタ電源を用いたセンサノードの構成例）
　実施の形態に係る限界電流式ガスセンサ（センサノード）は、図３８に示すように、センサ類１５１と、無線モジュール１５２と、マイコン１５３と、エナジーハーベスタ電源１５４と、蓄電素子１５５とを備える。センサ類１５１の構成は、実施の形態で説明した通りである。無線モジュール１５２は、無線信号を送受信するＲＦ回路などを備えたモジュールである。マイコン１５３は、エナジーハーベスタ電源１５４のマネジメント機能を備え、エナジーハーベスタ電源１５４からの電力をセンサ類１５１に投入する。このとき、マイコン１５３は、センサ類１５１における消費電力を省電力化するヒータ電力プロファイルに基づいて電力を投入しても良い。例えば、相対的に大きな電力である第１の電力を第１の期間Ｔ１だけ投入した後、相対的に小さな電力である第２の電力を第２の期間Ｔ２だけ投入しても良い。また、第２の期間Ｔ２にデータを読み取り、第２の期間Ｔ２が経過した後、第３の期間Ｔ３だけ電力の投入を停止しても良い。エナジーハーベスタ電源１５４は、太陽光や照明光、機械の発する振動、熱などのエネルギーを採取し、電力を得る。蓄電素子１５５は、電力を蓄電することが可能なリチウムイオン蓄電素子などである。 (Configuration example of sensor node using energy harvester power supply)
As shown in FIG. 38, the limiting current type gas sensor (sensor node) according to the embodiment includes sensors 151, a wireless module 152, a microcomputer 153, an energy harvester power supply 154, and a power storage element 155. The configuration of the sensors 151 is as described in the embodiment. The wireless module 152 is a module including an RF circuit that transmits and receives wireless signals. The microcomputer 153 has a management function of the energy harvester power supply 154, and inputs the power from the energy harvester power supply 154 to the sensors 151. At this time, the microcomputer 153 may input power based on a heater power profile that saves power consumed by the sensors 151. For example, the first power that is relatively large power may be input for the first period T1, and then the second power that is relatively small power may be input for the second period T2. Alternatively, data may be read during the second period T2, and after the second period T2 has elapsed, the power supply may be stopped for the third period T3. The energy harvester power supply 154 collects energy such as sunlight, illumination light, vibration generated by the machine, and heat to obtain electric power. The power storage element 155 is a lithium ion power storage element that can store power.
　以下、このようなセンサノードの動作について説明する。まず、図３８中の（１）に示すように、エナジーハーベスタ電源１５４からの電力がマイコン１５３に供給される。これにより、マイコン１５３は、図３８中の（２）に示すように、エナジーハーベスタ電源１５４からの電圧を昇圧する。次に、図３８中の（３）に示すように、蓄電素子１５５の電圧を読み取った後、図３８中の（４）・（５）に示すように、蓄電素子１５５への電力供給や、蓄電素子１５５からの電力引き出しを行う。次に、図３８中の（６）に示すように、ヒータ電力プロファイルに基づいてセンサ類１５１に電力を投入し、図３８中の（７）に示すように、センサ抵抗値およびＰｔ抵抗値などのデータを読み取る。次に、図３８中の（８）に示すように、無線モジュール１５２に電力を供給し、図３８中の（９）に示すように、センサ抵抗値およびＰｔ抵抗値などのデータを無線モジュール１５２に送る。最後に、図３８中の（１０）に示すように、無線モジュール１５２によってセンサ抵抗値およびＰｔ抵抗値などのデータが無線送信される。 Hereinafter, the operation of such a sensor node will be described. First, as shown in (1) of FIG. 38, the power from the energy harvester power supply 154 is supplied to the microcomputer 153. As a result, the microcomputer 153 boosts the voltage from the energy harvester power supply 154, as indicated by (2) in FIG. Next, as shown in (3) in FIG. 38, after reading the voltage of the electricity storage element 155, as shown in (4) and (5) in FIG. 38, power supply to the electricity storage element 155, Electric power is drawn from the power storage element 155. Next, as shown in (6) in FIG. 38, power is supplied to the sensors 151 based on the heater power profile, and as shown in (7) in FIG. 38, the sensor resistance value, the Pt resistance value, etc. Read data. Next, as shown in (8) in FIG. 38, power is supplied to the wireless module 152, and as shown in (9) in FIG. 38, data such as the sensor resistance value and the Pt resistance value is stored in the wireless module 152. Send to. Finally, as shown by (10) in FIG. 38, the wireless module 152 wirelessly transmits data such as the sensor resistance value and the Pt resistance value.
　（センサパッケージ：ブロック構成）
　実施の形態に係る限界電流式ガスセンサを搭載するセンサパッケージ９６の模式的ブロック構成は、図３９に示すように表される。 (Sensor package: block configuration)
A schematic block configuration of a sensor package 96 on which the limiting current type gas sensor according to the embodiment is mounted is expressed as shown in FIG.
　実施の形態に係る限界電流式ガスセンサを搭載するセンサパッケージ９６は、図３９に示すように、温度センサ用のサーミスタ部９０と、湿度・酸素センサ用のＹＳＺセンサ部９２と、サーミスタ部９０・ＹＳＺセンサ部９２からのアナログ情報ＳＡ2・ＳＡ1を受信し、またサーミスタ部９０・ＹＳＺセンサ部９２への制御信号Ｓ2・Ｓ1を供給するＡＤ／ＤＡ変換部９４と、外部からのディジタル入出力信号ＤＩ・ＤＯとを備える。 As shown in FIG. 39, a sensor package 96 equipped with the limiting current type gas sensor according to the embodiment includes a temperature sensor thermistor 90, a humidity / oxygen sensor YSZ sensor 92, and a thermistor 90 / YSZ. An AD / DA converter 94 that receives analog information SA 2 and SA 1 from the sensor unit 92 and supplies control signals S 2 and S 1 to the thermistor unit 90 and YSZ sensor unit 92; Output signal DI · DO.
　サーミスタ部９０は、例えば、ＮＴＣサーミスタ、ＰＴＣサーミスタ、セラミックＰＴＣ、ポリマーＰＴＣ、ＣＴＲサーミスタなどを適用可能である。ＹＳＺセンサ部９２には、実施の形態に係る限界電流式ガスセンサを適用可能である。ＹＳＺセンサ部９２においては、絶対湿度（Absolute Humidity）や相対湿度（ＲＨ：Relative Humidity）も測定可能であるが、特に相対湿度（ＲＨ）の検出では、温度が基準になるため、サーミスタ部９０で検出した温度情報が必要となる。 As the thermistor section 90, for example, an NTC thermistor, a PTC thermistor, a ceramic PTC, a polymer PTC, a CTR thermistor or the like can be applied. The limiting current type gas sensor according to the embodiment can be applied to the YSZ sensor unit 92. The YSZ sensor unit 92 can also measure absolute humidity (Absolute Humidity) and relative humidity (RH: Relative Humidity). However, the temperature is used as a reference when detecting the relative humidity (RH). The detected temperature information is required.
　（センサネットワーク）
　実施の形態に係る限界電流式ガスセンサを適用したセンサネットワークシステムの模式的ブロック構成は、図４０に示すように表される。図４０に示すように、センサネットワークとは、多数のセンサを相互に接続したネットワークである。すでに、工場、医療／ヘルスケア、交通、建設、農業、環境管理など、様々な分野でセンサネットワークを利用した新しい取り組みが始まっている。これらの分野では、耐久性の高いセンサを使用することが望まれるため、実施の形態に係る限界電流式ガスセンサ（例えば、湿度センサ）を適用するのが望ましい。このような湿度センサは、ジルコニアを使用しているため、耐久性に優れている。そのため、信頼性の高いセンサネットワークを提供することが可能である。 (Sensor network)
A schematic block configuration of a sensor network system to which the limiting current type gas sensor according to the embodiment is applied is expressed as shown in FIG. As shown in FIG. 40, the sensor network is a network in which a large number of sensors are connected to each other. New initiatives using sensor networks have already begun in various fields such as factories, medical / healthcare, transportation, construction, agriculture, and environmental management. In these fields, since it is desired to use a highly durable sensor, it is desirable to apply the limiting current type gas sensor (for example, humidity sensor) according to the embodiment. Since such a humidity sensor uses zirconia, it has excellent durability. Therefore, it is possible to provide a highly reliable sensor network.
　以上説明したように、本発明によれば、表面伝導電流成分を低減化し、かつ低電力消費の限界電流式ガスセンサおよびその製造方法、およびセンサネットワークシステムを提供することができる。 As described above, according to the present invention, it is possible to provide a limiting current type gas sensor, a manufacturing method thereof, and a sensor network system that reduce the surface conduction current component and consume low power.
　[その他の実施の形態]
　上記のように、実施の形態によって記載したが、この開示の一部をなす論述および図面は例示的なものであり、この実施の形態を限定するものであると理解すべきではない。この開示から当業者には様々な代替実施の形態、実施例および運用技術が明らかとなろう。 [Other embodiments]
As described above, the embodiments have been described. However, it should be understood that the descriptions and drawings forming a part of this disclosure are illustrative and do not limit the embodiments. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.
　このように、本実施の形態はここでは記載していない様々な実施の形態などを含む。例えば、ジルコニアに代えてＮＡＳＩＣＯＮ（Na Super Ionic Conductor）を固体電解質層４に用いれば、二酸化炭素の濃度を検出することが可能である。 Thus, the present embodiment includes various embodiments that are not described here. For example, if NASICON (Na Super Ionic Conductor) is used for the solid electrolyte layer 4 instead of zirconia, the concentration of carbon dioxide can be detected.
　本実施の形態の限界電流式ガスセンサは、酸素センサや湿度センサに適用することができる。また、このようなセンサは、自動車の排ガス用やセンサネットワーク用に応用することができる。 The limiting current type gas sensor of the present embodiment can be applied to an oxygen sensor and a humidity sensor. Further, such a sensor can be applied to automobile exhaust gas and sensor networks.
１…基板
２…マイクロヒータ
３、８…絶縁膜
４、４Ａ…固体電解質層（安定化ジルコニア）
５Ｕ…緻密電極（陰極）
５Ｒ、５ＰＵ…多孔質電極（陰極）
５Ｄ、５ＰＤ…多孔質電極（陽極）
６Ｐ…多孔質膜絶縁膜（多孔質絶縁基板）
６、６（５Ｕ）、６（５Ｄ）…応力緩和用低熱膨張膜（緻密膜、多孔質膜）
７…開口部
１０、１０（５Ｕ）、１０（５Ｄ）…反り抑制用多孔質絶縁膜
１２、１２Ａ…限界電流式ガスセンサ
１４、１４Ａ…限界電流式ガスセンサ用電極
１８…検出回路
２０…金属粒子（Ｐｔ粒子）
２２…カーボンナノチューブ（ＣＮＴ）
２４…バインダ
２６…微細ガス導入路
２８…金属粒子焼結層（Ｐｔ焼結層）
９０…サーミスタ部
９２…ＹＳＺセンサ部（限界電流式ガスセンサ）
９４…ＡＤ／ＤＡ変換部
９６…センサパッケージ
１００…積層膜
１３１…パッケージの蓋
１３２…貫通穴
１４１…パッケージの本体
１４２…限界電流式ガスセンサのチップ
１４３…ボンディングワイヤ
１５１…センサ類
１５２…無線モジュール
１５３…マイコン
１５４…エナジーハーベスタ電源
２００…デバイス加熱部
Ｂ…梁構造体
Ｃ…キャビティ
ＩS…表面伝導電流
 
  DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... Micro heater 3, 8 ... Insulating film 4, 4A ... Solid electrolyte layer (stabilized zirconia)
5U ... Dense electrode (cathode)
5R, 5PU ... Porous electrode (cathode)
5D, 5PD ... Porous electrode (anode)
6P ... Porous film insulating film (porous insulating substrate)
6, 6 (5U), 6 (5D) ... Low thermal expansion film for stress relaxation (dense film, porous film)
7 ... Openings 10, 10 (5U), 10 (5D) ... Warp suppressing porous insulating films 12, 12A ... Limit current type gas sensor 14, 14A ... Limit current type gas sensor electrode 18 ... Detection circuit 20 ... Metal particles ( Pt particles)
22 ... Carbon nanotube (CNT)
24 ... Binder 26 ... Fine gas introduction path 28 ... Sintered metal particle layer (Pt sintered layer)
90 ... Thermistor part 92 ... YSZ sensor part (limit current type gas sensor)
94 ... AD / DA converter 96 ... sensor package 100 ... laminated film 131 ... package lid 132 ... through hole 141 ... package body 142 ... limit current type gas sensor chip 143 ... bonding wire 151 ... sensors 152 ... wireless module 153 ... Microcomputer 154 ... Energy harvester power supply 200 ... Device heating part B ... Beam structure C ... Cavity I S ... Surface conduction current

Claims (41)

  1. 　金属粒子焼結層と、
    　前記金属粒子焼結層に形成された微細ガス導入路と
    　を有する緻密電極を備えることを特徴とする限界電流式ガスセンサ用電極。     A metal particle sintered layer;
    An electrode for limiting current type gas sensor, comprising a dense electrode having a fine gas introduction path formed in the metal particle sintered layer.
  2. 　固体電解質層と、
    　前記固体電解質層に接触して配置された多孔質電極と
    　を備え、前記緻密電極は、前記固体電解質層の前記多孔質電極に対向する面に接触して配置されたことを特徴とする請求項１に記載の限界電流式ガスセンサ用電極。     A solid electrolyte layer;
    A porous electrode disposed in contact with the solid electrolyte layer, and the dense electrode is disposed in contact with a surface of the solid electrolyte layer facing the porous electrode. The electrode for limiting current type gas sensors according to 1.
  3. 　前記金属粒子焼結層は、ナノワイヤを備えることを特徴とする請求項１または２に記載の限界電流式ガスセンサ用電極。 The electrode for a limiting current gas sensor according to claim 1 or 2, wherein the metal particle sintered layer includes nanowires.
  4. 　前記ナノワイヤは、カーボンナノチューブ若しくはＺｎＯを備えることを特徴とする請求項３に記載の限界電流式ガスセンサ用電極。 4. The limiting current gas sensor electrode according to claim 3, wherein the nanowire comprises a carbon nanotube or ZnO.
  5. 　前記金属粒子焼結層は、カーボンナノチューブ若しくはカーボンナノ粒子を備え、
    　前記微細ガス導入路は、前記金属粒子焼結層の大気中での燃焼により、前記カーボンナノチューブ若しくは前記カーボンナノ粒子が燃焼されて形成されたことを特徴とする請求項１または２に記載の限界電流式ガスセンサ用電極。     The metal particle sintered layer includes carbon nanotubes or carbon nanoparticles,
    3. The limit according to claim 1, wherein the fine gas introduction path is formed by burning the carbon nanotubes or the carbon nanoparticles by burning the sintered metal particle layer in the atmosphere. Electrode for current type gas sensor.
  6. 　前記金属粒子焼結層は、ＺｎＯを備え、
    　前記微細ガス導入路は、前記金属粒子焼結層の大気中での燃焼後、ウェットエッチングにより前記ＺｎＯがエッチングされて形成されたことを特徴とする請求項１または２に記載の限界電流式ガスセンサ用電極。     The metal particle sintered layer comprises ZnO,
    3. The limiting current gas sensor according to claim 1, wherein the fine gas introduction path is formed by etching the ZnO by wet etching after combustion of the metal particle sintered layer in the atmosphere. Electrode.
  7. 　前記微細ガス導入路の形状によりガス透過量制御可能であることを特徴とする請求項１～６のいずれか１項に記載の限界電流式ガスセンサ用電極。 The limit current type gas sensor electrode according to any one of claims 1 to 6, wherein the gas permeation amount can be controlled by the shape of the fine gas introduction path.
  8. 　前記微細ガス導入路の含有割合によりガス透過量制御可能であることを特徴とする請求項１～７のいずれか１項に記載の限界電流式ガスセンサ用電極。 The limit current type gas sensor electrode according to any one of claims 1 to 7, wherein a gas permeation amount can be controlled by a content ratio of the fine gas introduction path.
  9. 　前記金属粒子焼結層の金属粒子は、Ｐｔ、Ａｇ、Ｐｄ、Ａｕ、若しくはＲｕのいずれかを備えることを特徴とする請求項１～８のいずれか１項に記載の限界電流式ガスセンサ用電極。 9. The electrode for a limiting current gas sensor according to claim 1, wherein the metal particles of the sintered metal particle layer include any one of Pt, Ag, Pd, Au, or Ru. .
  10. 　固体電解質層に接触して、バインダに含有された金属粒子ペースト層を形成する工程と、
    　大気中で第１温度において焼成し、前記バインダを除去する工程と、
    　不活性ガス雰囲気中で第２温度において焼成し、金属粒子焼結層を形成する工程と、
    　第３温度において大気を導入して、前記金属粒子焼結層中に微細ガス導入路を形成する工程と
    　を有することを特徴とする限界電流式ガスセンサ用電極の製造方法。     Forming a metal particle paste layer contained in the binder in contact with the solid electrolyte layer;
    Firing at a first temperature in the atmosphere and removing the binder;
    Firing at a second temperature in an inert gas atmosphere to form a metal particle sintered layer;
    And a step of introducing a fine gas introduction path in the metal particle sintered layer by introducing air at a third temperature. A method for producing a limiting current gas sensor electrode, comprising:
  11. 　前記金属粒子ペースト層を形成する工程は、印刷工程を備えることを特徴とする請求項１０に記載の限界電流式ガスセンサ用電極の製造方法。 The method for producing an electrode for a limiting current gas sensor according to claim 10, wherein the step of forming the metal particle paste layer includes a printing step.
  12. 　前記第１温度は、５００℃であることを特徴とする請求項１０または１１に記載の限界電流式ガスセンサ用電極の製造方法。 The method for producing an electrode for a limiting current gas sensor according to claim 10 or 11, wherein the first temperature is 500 ° C.
  13. 　前記第２温度は、１１００℃であることを特徴とする請求項１０～１２のいずれか１項に記載の限界電流式ガスセンサ用電極の製造方法。 The method for producing an electrode for a limiting current gas sensor according to any one of claims 10 to 12, wherein the second temperature is 1100 ° C.
  14. 　前記第３温度は、７００℃であることを特徴とする請求項１０～１３のいずれか１項に記載の限界電流式ガスセンサ用電極の製造方法。 The method for producing an electrode for limiting current gas sensor according to any one of claims 10 to 13, wherein the third temperature is 700 ° C.
  15. 　前記バインダは、エチルセルロース系若しくはアクリル系材料を備えることを特徴とする請求項１０～１４のいずれか１項に記載の限界電流式ガスセンサ用電極の製造方法。 The method for producing an electrode for a limiting current gas sensor according to any one of claims 10 to 14, wherein the binder comprises an ethylcellulose-based or acrylic material.
  16. 　前記金属粒子焼結層は、カーボンナノチューブ若しくはカーボンナノ粒子を備え、
    　前記微細ガス導入路を形成する工程は、前記金属粒子焼結層の大気中での燃焼により、前記カーボンナノチューブ若しくは前記カーボンナノ粒子が燃焼される工程を有することを特徴とする請求項１０～１５のいずれか１項に記載の限界電流式ガスセンサ用電極の製造方法。     The metal particle sintered layer includes carbon nanotubes or carbon nanoparticles,
    The step of forming the fine gas introduction path includes a step of burning the carbon nanotubes or the carbon nanoparticles by burning the sintered metal particle layer in the atmosphere. The manufacturing method of the electrode for limiting current type gas sensors of any one of these.
  17. 　前記金属粒子焼結層は、ＺｎＯを備え、
    　前記微細ガス導入路を形成する工程は、前記金属粒子焼結層の大気中での燃焼後、ウェットエッチングにより前記ＺｎＯがエッチングされる工程を有することを特徴とする請求項１０～１６のいずれか１項に記載の限界電流式ガスセンサ用電極の製造方法。     The metal particle sintered layer comprises ZnO,
    The step of forming the fine gas introduction path includes a step of etching the ZnO by wet etching after burning the sintered metal particle layer in the atmosphere. A method for producing an electrode for a limiting current gas sensor according to item 1.
  18. 　基板と、
    　前記基板上に配置された多孔質電極と、
    　前記多孔質電極上に配置された絶縁膜と、
    　前記絶縁膜にパターニングされた開口部の前記多孔質電極上および前記開口部を取り囲む前記絶縁膜上に配置された固体電解質層と、
    　前記固体電解質層上に、前記多孔質電極に対向し、前記基板に対して実質的に縦方向に配置され、金属粒子焼結層および前記金属粒子焼結層に形成された微細ガス導入路を備える緻密電極と
    　を備えることを特徴とする限界電流式ガスセンサ。     A substrate,
    A porous electrode disposed on the substrate;
    An insulating film disposed on the porous electrode;
    A solid electrolyte layer disposed on the porous electrode of the opening patterned on the insulating film and on the insulating film surrounding the opening;
    On the solid electrolyte layer, facing the porous electrode and disposed in a substantially vertical direction with respect to the substrate, a metal particle sintered layer and a fine gas introduction path formed in the metal particle sintered layer A limiting current type gas sensor comprising: a dense electrode.
  19. 　前記金属粒子焼結層は、カーボンナノチューブ若しくはカーボンナノ粒子を備え、
    　前記微細ガス導入路は、前記金属粒子焼結層の大気中での燃焼により、前記カーボンナノチューブ若しくは前記カーボンナノ粒子が燃焼されて形成されたことを特徴とする請求項１８に記載の限界電流式ガスセンサ。     The metal particle sintered layer includes carbon nanotubes or carbon nanoparticles,
    The limiting current equation according to claim 18, wherein the fine gas introduction path is formed by burning the carbon nanotubes or the carbon nanoparticles by burning the sintered metal particle layer in the atmosphere. Gas sensor.
  20. 　前記金属粒子焼結層は、ＺｎＯを備え、
    　前記微細ガス導入路は、前記金属粒子焼結層の大気中での燃焼後、ウェットエッチングにより前記ＺｎＯがエッチングされて形成されたことを特徴とする請求項１８に記載の限界電流式ガスセンサ。     The metal particle sintered layer comprises ZnO,
    19. The limiting current gas sensor according to claim 18, wherein the fine gas introduction path is formed by etching the ZnO by wet etching after burning the sintered metal particle layer in the atmosphere.
  21. 　前記微細ガス導入路の形状によりガス透過量制御可能であることを特徴とする請求項１８～２０のいずれか１項に記載の限界電流式ガスセンサ。 The limiting current type gas sensor according to any one of claims 18 to 20, wherein a gas permeation amount can be controlled by a shape of the fine gas introduction path.
  22. 　前記微細ガス導入路の含有割合によりガス透過量制御可能であることを特徴とする請求項１８～２１のいずれか１項に記載の限界電流式ガスセンサ。 The limiting current type gas sensor according to any one of claims 18 to 21, wherein the gas permeation amount can be controlled by the content ratio of the fine gas introduction path.
  23. 　前記金属粒子焼結層の金属粒子は、Ｐｔ、Ａｇ、Ｐｄ、Ａｕ、若しくはＲｕのいずれかを備えることを特徴とする請求項１８～２２のいずれか１項に記載の限界電流式ガスセンサ。 The limit current gas sensor according to any one of claims 18 to 22, wherein the metal particles of the metal particle sintered layer include any one of Pt, Ag, Pd, Au, or Ru.
  24. 　前記緻密電極と前記多孔質電極との間に電圧を印加することにより被測定ガス内における所定のガス濃度を限界電流式で検出する検出回路を備えることを特徴とする請求項１８～２３のいずれか１項に記載の限界電流式ガスセンサ。 The detection circuit according to any one of claims 18 to 23, further comprising a detection circuit that detects a predetermined gas concentration in the gas to be measured by a limiting current type by applying a voltage between the dense electrode and the porous electrode. The limiting current type gas sensor according to claim 1.
  25. 　前記基板は、マイクロヒータを備えることを特徴とする請求項１８～２４のいずれか１項に記載の限界電流式ガスセンサ。 The limiting current type gas sensor according to any one of claims 18 to 24, wherein the substrate includes a micro heater.
  26. 　前記マイクロヒータは、前記基板上部もしくは基板下部に配置されることを特徴とする請求項２５に記載の限界電流式ガスセンサ。 26. The limiting current type gas sensor according to claim 25, wherein the microheater is disposed on the upper or lower portion of the substrate.
  27. 　前記マイクロヒータは、前記基板内部に埋め込まれたことを特徴とする請求項２５に記載の限界電流式ガスセンサ。 The limiting current gas sensor according to claim 25, wherein the micro heater is embedded in the substrate.
  28. 　前記マイクロヒータは、印刷により形成されたＰｔヒータ、若しくはポリシリコンヒータを備えることを特徴とする請求項２５～２７のいずれか１項に記載の限界電流式ガスセンサ。 The limiting current gas sensor according to any one of claims 25 to 27, wherein the micro heater includes a Pt heater or a polysilicon heater formed by printing.
  29. 　前記多孔質電極は、印刷、蒸着もしくはスパッタにより形成されたポーラスＰｔ電極を備え、前記緻密電極は、Ｐｔ粒子焼結層を備えることを特徴とする請求項１８～２８のいずれか１項に記載の限界電流式ガスセンサ。 The porous electrode is provided with a porous Pt electrode formed by printing, vapor deposition, or sputtering, and the dense electrode is provided with a Pt particle sintered layer. Limit current type gas sensor.
  30. 　前記絶縁膜は、Ａｌ2Ｏ3、Ａｌ2Ｏ3－ＳｉＯ2、ＹＳＺ－ＳｉＯ2、もしくはＹＳＺ－Ａｌ2Ｏ3のいずれかを備えることを特徴とする請求項１８～２９のいずれか１項に記載の限界電流式ガスセンサ。 30. The insulating film according to claim 18, wherein the insulating film comprises any one of Al 2 O 3 , Al 2 O 3 —SiO 2 , YSZ—SiO 2 , and YSZ—Al 2 O 3. Limit current type gas sensor described in 1.
  31. 　前記固体電解質層は、ＹＳＺ、ＹＳＺ－ＳｉＯ2、もしくはＹＳＺ－Ａｌ2Ｏ3の少なくとも一つが含まれる安定化ジルコニア膜であることを特徴とする請求項１８～３０のいずれか１項に記載の限界電流式ガスセンサ。 The solid electrolyte layer is a stabilized zirconia film containing at least one of YSZ, YSZ-SiO 2 , or YSZ-Al 2 O 3 . Limit current type gas sensor.
  32. 　前記検出回路は、限界電流に基づいて酸素濃度を検出することを特徴とする請求項２４に記載の限界電流式ガスセンサ。 The limit current gas sensor according to claim 24, wherein the detection circuit detects an oxygen concentration based on a limit current.
  33. 　前記検出回路は、限界電流に基づいて水蒸気濃度を検出することを特徴とする請求項２４に記載の限界電流式ガスセンサ。 The limit current type gas sensor according to claim 24, wherein the detection circuit detects a water vapor concentration based on the limit current.
  34. 　前記基板は、ＭＥＭＳ梁構造を備えることを特徴とする請求項１８～３３のいずれか１項に記載の限界電流式ガスセンサ。 The limiting current gas sensor according to any one of claims 18 to 33, wherein the substrate has a MEMS beam structure.
  35. 　前記基板に形成されたキャビティ上に両持ちの梁構造体として形成されていることを特徴とする請求項１８～３４のいずれか１項に記載の限界電流式ガスセンサ。 The limiting current gas sensor according to any one of claims 18 to 34, wherein the gas sensor is formed as a doubly supported beam structure on a cavity formed in the substrate.
  36. 　前記梁構造体は、シリコン酸化膜とシリコン窒化膜の積層膜を備えることを特徴とする請求項３５に記載の限界電流式ガスセンサ。 36. The limiting current gas sensor according to claim 35, wherein the beam structure includes a laminated film of a silicon oxide film and a silicon nitride film.
  37. 　基板上に多孔質電極を形成する工程と、
    　前記多孔質電極上に絶縁膜を形成する工程と、
    　前記絶縁膜をパターニングして開口部を形成する工程と、
    　前記開口部の前記多孔質電極上および前記開口部を取り囲む前記絶縁膜上に固体電解質層を形成する工程と、
    　前記固体電解質層上に、前記多孔質電極に対向し、前記基板に対して実質的に縦方向に、金属粒子焼結層および前記金属粒子焼結層に形成された微細ガス導入路を備える緻密電極を形成する工程と
    　を有することを特徴とする限界電流式ガスセンサの製造方法。     Forming a porous electrode on a substrate;
    Forming an insulating film on the porous electrode;
    Patterning the insulating film to form an opening;
    Forming a solid electrolyte layer on the porous electrode of the opening and on the insulating film surrounding the opening;
    On the solid electrolyte layer, densely provided with a metal gas sintered layer and a fine gas introduction path formed in the metal particle sintered layer, facing the porous electrode and substantially longitudinally with respect to the substrate And a step of forming an electrode. A method of manufacturing a limiting current type gas sensor.
  38. 　前記基板をエッチングして、前記基板に形成されたキャビティ上に両持ちの梁構造体を形成する工程を有することを特徴とする請求項３７に記載の限界電流式ガスセンサの製造方法。 38. The method of manufacturing a limiting current gas sensor according to claim 37, further comprising a step of etching the substrate to form a doubly-supported beam structure on a cavity formed in the substrate.
  39. 　前記基板上部もしくは基板下部にマイクロヒータを形成する工程を有することを特徴とする請求項３７または３８に記載の限界電流式ガスセンサの製造方法。 The method of manufacturing a limiting current gas sensor according to claim 37 or 38, further comprising a step of forming a micro heater on the upper or lower portion of the substrate.
  40. 　前記基板内部に埋め込まれたマイクロヒータを形成する工程を有することを特徴とする請求項３７または３８に記載の限界電流式ガスセンサの製造方法。 The method of manufacturing a limiting current gas sensor according to claim 37 or 38, further comprising a step of forming a micro heater embedded in the substrate.
  41. 　請求項１８～３６のいずれか１項に記載の限界電流式ガスセンサを備えることを特徴とするセンサネットワークシステム。
     
          A sensor network system comprising the limiting current type gas sensor according to any one of claims 18 to 36.

PCT/JP2015/067018 2014-12-16 2015-06-12 Electrode for limiting current type gas sensors, method for producing same, limiting current type gas sensor, method for manufacturing limiting current type gas sensor, and sensor network system WO2016098372A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2014254259A JP6546392B2 (en) 2014-12-16 2014-12-16 Electrode for limiting current type gas sensor and method for manufacturing the same, limiting current type gas sensor and method for manufacturing the same, and sensor network system
JP2014-254259 2014-12-16

Publications (1)

Publication Number Publication Date
WO2016098372A1 true WO2016098372A1 (en) 2016-06-23

Family

ID=56126276

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2015/067018 WO2016098372A1 (en) 2014-12-16 2015-06-12 Electrode for limiting current type gas sensors, method for producing same, limiting current type gas sensor, method for manufacturing limiting current type gas sensor, and sensor network system

Country Status (2)

Country Link
JP (1) JP6546392B2 (en)
WO (1) WO2016098372A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07113782A (en) * 1993-10-18 1995-05-02 Fujikura Ltd Limiting current type oxygen sensor
JPH10197476A (en) * 1996-12-30 1998-07-31 Fujikura Ltd Limiting current-type oxygen sensor
JP2009198410A (en) * 2008-02-25 2009-09-03 Gunze Ltd Hydrogen gas sensor

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6134456A (en) * 1984-07-27 1986-02-18 Hitachi Ltd Air/fuel rate sensor
JPH09257746A (en) * 1996-03-21 1997-10-03 Ngk Spark Plug Co Ltd Method for cleaning limit current type gas sensor and gas concentration detector utilizing the same
JP3517064B2 (en) * 1996-09-30 2004-04-05 日本特殊陶業株式会社 Stabilization method of oxygen sensor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07113782A (en) * 1993-10-18 1995-05-02 Fujikura Ltd Limiting current type oxygen sensor
JPH10197476A (en) * 1996-12-30 1998-07-31 Fujikura Ltd Limiting current-type oxygen sensor
JP2009198410A (en) * 2008-02-25 2009-09-03 Gunze Ltd Hydrogen gas sensor

Also Published As

Publication number Publication date
JP6546392B2 (en) 2019-07-17
JP2016114511A (en) 2016-06-23

Similar Documents

Publication Publication Date Title
JP6403985B2 (en) Limit current type gas sensor, method for manufacturing the same, and sensor network system
Bobinger et al. Flexible and robust laser-induced graphene heaters photothermally scribed on bare polyimide substrates
WO2014136329A1 (en) Limiting current gas sensor, method for producing limiting current gas sensor, and sensor network system
US9354197B2 (en) Micromachined oxygen sensor and method of making the same
JP6730280B2 (en) Limiting current type gas sensor
CN102639993B (en) Rapid response relative humidity sensor using anodic aluminum oxide film
CN103630582B (en) A kind of MEMS humidity sensor and preparation method
KR101403406B1 (en) Fabrication method for gas sensor and temperature sensor based on suspended carbon nanowires
Wu et al. A practical vacuum sensor based on a ZnO nanowire array
KR101878343B1 (en) Method of measuring hydrogen gas using sensor for hydrogen gas
Kim et al. Batch Nanofabrication of Suspended Single 1D Nanoheaters for Ultralow‐Power Metal Oxide Semiconductor‐Based Gas Sensors
KR102125278B1 (en) GAS SENSOR and Method for Manufacturing GAS SENSOR
KR102013825B1 (en) Hydrogen gas sensor and Fabrication method of the same
CN104407034A (en) Gas sensor chip
KR102154291B1 (en) Hydrogen gas sensor and method for manufacturing the same
WO2016098372A1 (en) Electrode for limiting current type gas sensors, method for producing same, limiting current type gas sensor, method for manufacturing limiting current type gas sensor, and sensor network system
JP2005098846A (en) Gas sensor
Guo et al. Response and stability improvement by fusing optimized micro-hotplatform and double layer bowl-like nano arrays
Islam et al. $\gamma-\hbox {Al} _ {2}\hbox {O} _ {3} $-Coated Porous Silicon for Trace Moisture Detection
TWI325054B (en) Gas sensor with diffuse micro cavity structure and method thereof
KR20160125245A (en) Limiting current type oxygen sensor and Method of manufacturing the same
WO2019202528A1 (en) Method for fabrication of mems integrated sensor and sensor thereof
Wang et al. Wafer‐level fabrication of low power consumption integrated alcohol microsensor
CN104597087A (en) Manufacturing method of gas sensor chip
JP2005300470A (en) Manufacturing method of layered gas sensor element

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15869581

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15869581

Country of ref document: EP

Kind code of ref document: A1