WO2009145373A1 - Packaging substrate and gas sensing device having the same, and method for manufacturing the same - Google Patents

Packaging substrate and gas sensing device having the same, and method for manufacturing the same Download PDF

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Publication number
WO2009145373A1
WO2009145373A1 PCT/KR2008/003041 KR2008003041W WO2009145373A1 WO 2009145373 A1 WO2009145373 A1 WO 2009145373A1 KR 2008003041 W KR2008003041 W KR 2008003041W WO 2009145373 A1 WO2009145373 A1 WO 2009145373A1
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WO
WIPO (PCT)
Prior art keywords
gas
gas sensing
substrate
flow rate
rate detecting
Prior art date
Application number
PCT/KR2008/003041
Other languages
French (fr)
Inventor
Sang Jin Uhm
Young Geun Park
Original Assignee
M2N Inc.
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 M2N Inc. filed Critical M2N Inc.
Publication of WO2009145373A1 publication Critical patent/WO2009145373A1/en

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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
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof  ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/84—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by variation of applied mechanical force, e.g. of pressure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/02—Containers; Seals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/28—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection
    • H01L23/31—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape
    • H01L23/3107—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape the device being completely enclosed
    • H01L23/315—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape the device being completely enclosed the encapsulation having a cavity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/146—Mixed devices
    • H01L2924/1461—MEMS

Definitions

  • the present invention relates to a packaging of a gas sensing device, and more particularly, relates to a packaging substrate using a MEMS (Micro Electro Mechanical Systems) technique, a gas sensing device having the packaging substrate and a method for manufacturing the gas sensing device.
  • MEMS Micro Electro Mechanical Systems
  • a gas sensing device is in general used to detect a specific gas.
  • a gas sensing portion included in the gas sensing device is exposed to the specific gas, conductivity of a semiconductor as a sensing material of the gas sensing portion may change or an electromotive force may be generated.
  • an electromotive force may be generated.
  • FIG. 1 is a cross-sectional view of a conventional gas sensing device.
  • the conventional gas sensing device 1 includes a printed circuit board 10, a gas sensing substrate 20 and a cover 30.
  • the printed circuit board 10 includes a circuit pattern for gas sensing, and a board pads 11 connected with the circuit pattern is positioned on the printed circuit board 10. A part of the printed circuit board 10 is depressed from its top surface such that the gas sensing substrate 20 is accommodated thereon.
  • the gas sensing substrate 20 includes a substrate 21, an insulating layer 22, a heating portion 23, an insulating portion 24, electrodes 25, a gas sensing portion 26, and electrode pads 27.
  • the substrate 21 is formed of a silicon wafer and the insulating layer 22 is disposed thereon.
  • the insulating layer 22 contains silicon oxide, silicon nitride, and so forth.
  • the heating portion 23 is disposed on the insulating layer 22.
  • the heating portion 23 is used for heating the gas sensing portion 26 up to a temperature at which the performance of the gas sensing portion 26 can be optimized.
  • the heating portion 23 contains a metal material such as platinum (Pt) whose property of electrical conductivity does not deteriorate under high temperature conditions.
  • the heating portion 23 is connected with the electrode pad 27.
  • the insulating portion 24 is disposed between the heating portion 23 and the electrode 25, and serves to prevent a short circuit between the heating portion 23 and the electrode 25.
  • the electrode 25 is used for detecting a change in electrical resistance of the gas sensing portion 26 due to an inflow of a gas from the outside.
  • the electrode 25 is connected with the electrode pads 27.
  • the gas sensing portion 26 indicates the change in electrical resistance by making a direct contact with a gas to be detected and adsorbing the gas, and it contains metal oxide having semiconductor properties.
  • the gas introduced from the outside makes a contact with the gas sensing portion 26 and makes a chemical reaction, electrons are exchanged between the gas and the gas sensing portion 26, so that the electrical resistance of the gas sensing portion 26 is changed.
  • the electrode pad 27 is connected with the heating portion 23 and the electrode 25 and also connected with the board pad 11 positioned on the printed circuit board 10 via a wire w.
  • the heating portion 23 and the electrode 25 are connected with the circuit pattern for gas sensing, which is formed on the printed circuit board 10, via the electrode pad 27, the wire w and the board pads 11.
  • the cover 30 protects the gas sensing substrate 20 from external shocks.
  • the conventional gas sensing device 1 includes therein the printed circuit board 10, the gas sensing substrate 20 and the cover 30 which are manufactured through separate processes and adhered to each other, manufacturing cost increases.
  • the gas sensing device is used in an alcohol sensor, a smoke sensor, a foul breath sensor or the like, it is desirable to activate the gas sensing device only when the amount of a gas introduced from the outside increases equal to or over a predetermined amount.
  • a gas flowmeter for measuring a flow rate of the gas introduced into the gas sensing portion 26 is additionally installed, which causes complication of manufacturing process and an increase of manufacturing cost. Disclosure of Invention Technical Problem
  • the present invention provides a packaging substrate having an improved structure and thus capable of reducing manufacturing cost; a gas sensing device having the packaging substrate; and a method for manufacturing the gas sensing device.
  • the present invention also provides a packaging substrate having an improved connection structure between a circuit pattern for gas sensing and a gas sensing portion and thus capable of improving gas sensing reliability; a gas sensing device having the packaging substrate; and a method for manufacturing the gas sensing device.
  • the present invention also provides a packaging substrate including a gas flow rate detecting portion and thus capable of simplifying a manufacturing process and reducing manufacturing cost; a gas sensing device having the packaging substrate and a method for manufacturing the gas sensing device.
  • a gas sensing device including: a gas sensing substrate including a gas sensing portion whose electrical resistance is changed when it comes into contact with a gas to be detected; and a packaging substrate disposed on the gas sensing substrate, for packaging the gas sensing substrate, and the packaging substrate includes a gas flow rate detecting portion for measuring an amount of the gas introduced into the gas sensing portion.
  • the gas flow rate detecting portion may be of a piezoresistance type in which electrical resistance is changed when pressure is applied by the gas.
  • the gas flow rate detecting portion may activate the gas sensing portion when the amount of the gas exceeds a predetermined value.
  • the gas flow rate detecting portion may include one or more holes through which the gas passes.
  • the gas flow rate detecting portion may contain polysilicon (poly Si) doped with impurities.
  • the gas sensing substrate may further include: a first substrate; an insulating film disposed between the first substrate and the gas sensing portion; and a pad disposed on the insulating film and connected with the gas sensing portion.
  • the gas sensing substrate may further include: a heating portion disposed between the insulating film and the gas sensing portion, for heating the gas sensing portion; and an electrode portion for connecting the pad with the gas sensing portion.
  • the packaging substrate may further include: a second substrate disposed on the first substrate, for forming a detection space between the gas flow rate detecting portion and the gas sensing portion; and an insulating layer disposed between the second substrate and the gas flow rate detecting portion.
  • the insulating layer corresponding to the detection space may be in a floating state.
  • the second substrate may include a through hole corresponding to the pad and passing through the second substrate; the packaging substrate may further include a conductive pattern formed on the second insulating layer; and the gas sensing device may further include a connecting portion disposed within the through hole, for connecting the pad and the conductive pattern via the through hole.
  • a method for manufacturing a gas sensing device including: process (a) of providing a gas sensing substrate including a gas sensing portion whose electrical resistance is changed when it is in contact with a gas to be detected; process (b) of providing a packaging substrate including a gas flow rate detecting portion for measuring an amount of the gas; and process (c) of bonding the packaging substrate onto the gas sensing substrate in order for the gas flow rate detecting portion to measure the amount of the gas introduced to the gas sensing portion.
  • the process (b) may include forming one or more holes in the gas flow rate detecting portion.
  • At least one step of the processes (a) and (b) may be carried out by using a MEMS
  • the process (b) may include: providing a substrate; forming an insulating layer on the substrate; forming the gas flow rate detecting portion on the insulating layer; and forming a through hole passing through the substrate.
  • the process (b) may further include: forming a conductive pattern on the insulating layer, and the process (c) may include: forming a connecting portion within the through hole so as to connect the conductive pattern with the gas sensing portion.
  • a packaging substrate used for a gas sensing device for packaging a gas sensing substrate having a gas sensing portion for detecting gas
  • the packaging substrate including: a gas flow rate detecting portion disposed in a moving route of the gas, for measuring an amount of the gas introduced to the gas sensing portion.
  • the gas flow rate detecting portion may be of a piezoresistance type in which electrical resistance is changed when pressure is applied by the gas.
  • the gas flow rate detecting portion may activate the gas sensing portion when the amount of the gas exceeds a predetermined value.
  • the gas flow rate detecting portion may include one or more holes through which the gas passes.
  • the gas flow rate detecting portion may contain polysilicon (poly Si) doped with impurities.
  • the packaging substrate may further include an insulating layer disposed between the gas flow rate detecting portion and the detection space, and the insulating layer corresponding to the detection space may be in a floating state.
  • the packaging substrate may further include: a conductive pattern; and a through hole for accommodating therein a connecting portion for connecting the gas sensing portion and the conductive pattern.
  • FIG. 1 is a cross-sectional view of a conventional gas sensing device
  • FIG. 2 is a cross-sectional view of a gas sensing device in accordance with an embodiment of the present invention.
  • FIG. 3 is a top plane view of the gas sensing device in accordance with the embodiment of the present invention.
  • FIG. 4 is a flowchart showing a method for manufacturing a gas sensing device in accordance with an embodiment of the present invention.
  • FIGs. 5 to 12 are cross-sectional views to explain the method for manufacturing the gas sensing device in accordance with the embodiment of the present invention. Best Mode for Carrying out the Invention
  • the term “on” that is used to designate a position of one element with respect to another element includes both a case that the one element is adjacent to the another element and a case that any other element exists between these two elements.
  • the term “comprises or includes” and/or “comprising or including” used in the document means that one or more other components, steps, operation and/or existence or addition of elements are not excluded in addition to the described components, steps, operation and/or elements unless context dictates otherwise.
  • Fig. 2 is a cross-sectional view of the gas sensing device in accordance with the embodiment of the present invention
  • Fig. 3 is a top plane view of the gas sensing device in accordance with the embodiment of the present invention.
  • a gas sensing device 1000 in accordance with the embodiment of the present invention includes a gas sensing substrate 100, a packaging substrate 200 and connecting portions 300.
  • the gas sensing substrate 100 includes a first substrate 110, an insulating film 120, a heating portion 130, an insulating portion 140, electrodes 150, a gas sensing portion 160 and pads 170.
  • the first substrate 110 is formed of a wafer made of silicon.
  • the insulating film 120 is disposed on the first substrate 110.
  • the insulating film 120 includes a silicon oxide layer, a silicon nitride layer, and so forth.
  • the heating portion 130 is disposed on the insulating film 120.
  • the heating portion 130 functions to heat the gas sensing portion 160 up to a temperature at which the performance of the gas sensing portion 160 can be optimized.
  • the heating portion 130 contains a metal material such as platinum (Pt) whose property of electrical conductivity does not deteriorate under high temperature conditions and a conductive material such as polysilicon (poly Si).
  • the heating portion 130 is connected with the pad 170.
  • the insulating portion 140 is disposed between the heating portion 130 and the electrode 150 and serves to prevent a short circuit between the heating portion 130 and the electrode 150.
  • the electrode 150 serves to detect a change in electrical resistance of the gas sensing portion 160 due to an inflow of a gas from the outside.
  • the electrode 150 contains a metal material such as platinum (Pt) whose property of electrical conductivity does not deteriorate under high temperature conditions and a conductive material such as polysilicon.
  • the electrode 150 is connected with the pad 170.
  • the gas sensing portion 160 indicates a change in electrical resistance by making direct a contact with a gas to be detected and adsorbing the gas, and it contains metal oxides such as tin oxide (SnO 2 ), tungsten oxide (WO 3 ) and titanium oxide (TiO 2 ), and so forth, which have semiconductor properties.
  • metal oxides such as tin oxide (SnO 2 ), tungsten oxide (WO 3 ) and titanium oxide (TiO 2 ), and so forth, which have semiconductor properties.
  • a part of the pads 170 is connected with the heating portion 130 and the rest are connected with the electrodes 150.
  • the pads 170 are not only connected with the gas sensing portion 160 via the electrodes 150 but also connected with conductive patterns 260 of the packaging substrate 200 to be described below via the connecting portions 300 of the packaging substrate 200.
  • the packaging substrate 200 to be described below is disposed on the above-stated gas sensing substrate 100.
  • the packaging substrate 200 includes a second substrate 210, first insulating layers 220, second insulating layers 230, a bonding layer 240, a gas flow rate detecting portion 250 and the conductive pattern 260.
  • the second substrate 210 is formed of a wafer made of silicon.
  • the second substrate 210 is formed of a wafer made of silicon.
  • the second substrate 210 surrounds the gas sensing portion 160 in a manner such that a detection space S is formed around the gas sensing portion 160 of the gas sensing substrate 100. A gas introduced from the outside stays in the detection space S.
  • the second substrate 210 includes through holes 211 which correspond to the pads 170 on the gas sensing substrate 100 and pass through the second substrate 210 from its top surface to its bottom surface.
  • the connecting portion 300 to be described below is disposed in the through hole 211 of the second substrate 210.
  • the first insulating layers 220 are respectively located on the top surface of the second substrate 210 and the bottom surface opposite thereto.
  • the first insulating layer 220 is made of an insulating material containing silicon oxide (SiO 2 ).
  • the first insulating layer 220 corresponding to the detection space S is in direct contact with the detection space S. That is, the first insulating layer 220 located on the detection space S is facing the gas sensing portion 160 of the gas sensing substrate 100 in a floating state.
  • the second insulating layer 230 is disposed on the first insulating layer 220.
  • the second insulating layer 230 is made of an insulating material containing silicon nitride (SiNx). It is desirable that the second insulating layer 230 is made of an insulating material whose lattice structure intersects that of the first insulating layer 220. That is, the first insulating layer 220 and the second insulating layer 230 serve to reinforce insulation property and elastic strength of each other.
  • the bonding layer 240 is disposed between the second insulating layer 230 and the gas sensing substrate 100.
  • the bonding layer 240 serves to bond the packaging substrate 200 with the gas sensing substrate 100 by using a thermocompression bonding method such as an eutectic bonding method using any one or more conductive metal materials among indium (In), tin (Sn) and gold (Au), or a thermosetting bonding method using an epoxy resin.
  • a thermocompression bonding method such as an eutectic bonding method using any one or more conductive metal materials among indium (In), tin (Sn) and gold (Au), or a thermosetting bonding method using an epoxy resin.
  • an additional insulating material may be disposed between the connecting portion 300 to be described later and the bonding layer 240 in order to prevent a short circuit between the connecting portion 300 and the bonding layer 240.
  • the gas flow rate detecting portion 250 is disposed on the second insulating layer 230 on a top surface of the second substrate 210 opposite to the second insulating layer 230 disposed on the bonding layer 240.
  • the gas flow rate detecting portion 250 is disposed above the detection space S so as to correspond to the gas sensing portion 160 of the gas sensing substrate 100 and located on the second insulating layer 230 disposed on the first insulating layer 220 in the floating state.
  • the gas flow rate detecting portion 250 contains polysilicon (poly Si) doped with impurities such as boron, phosphorus or the like, and is of a piezoresistance type in which electrical resistance is changed when pressure is applied from the outside.
  • the gas flow rate detecting portion 250 includes one or more holes 251 formed to correspond to the gas sensing portion 160 of the gas sensing substrate 100. During a gas detecting process, the gas is introduced into the detection space S through the holes 251 from the outside.
  • the gas flow rate detecting portion 250 disposed on the second insulating layer 230 is bent and receives a pressure applied thereto. That is, as the gas flow rate detecting portion 250 receives the pressure applied thereto due to the inflow of the gas, the electrical resistance thereof is changed, and the flow rate of the gas introduced into the detection space S can be measured from the changed electrical resistance.
  • the gas flow rate detecting portion 250 activates the gas sensing portion 160 of the gas sensing substrate 100 by a signal exchange with the circuit pattern of the conductive pattern 260 to be described below. That is, if the electrical resistance of the gas flow rate detecting portion 250 exceeds the predetermined value due to the gas introduced into the detection space S, the conductive pattern 260 connected with the gas flow rate detecting portion 250 transmits an activation signal to the gas sensing substrate 100 and thus the gas sensing portion 160 becomes activated, whereby it is possible to start sensing the gas in the detection space S due to an activation of the gas sensing portion 160. In this manner, the gas sensing device 1000 can perform the optimal gas sensing operation based on the amount of the gas introduced from the outside.
  • the conductive pattern 260 is disposed nearby the gas flow rate detecting portion
  • the conductive pattern 260 is disposed on the second insulating layer 230, and includes a circuit pattern for sending/receiving an electric signal to/from the heating portion 130 and the electrodes 150 of the gas sensing substrate 100; a circuit pattern for sending/receiving an electric signal to/from the gas flow rate detecting portion 250; and a circuit pattern for performing other additional driving operations.
  • the conductive pattern 260 can be formed to include a plurality of thin film transistors and is connected with the gas sensing substrate 100 in connection with the pads 170 of the gas sensing substrate 100 by way of the connecting portion 300.
  • the conductive pattern 260 can be disposed between the second in- sulating layer 230 and the gas flow rate detecting portion 250 or on the gas flow rate detecting portion 250.
  • the connecting portion 300 is placed within the through hole 211 of the second substrate 210, and serves to connect the pads 170 of the gas sensing substrate 100 with the conductive pattern 260 of the packaging substrate 200 by passing through the second substrate 210 via the through hole 211.
  • the connecting portion 300 contains conductive metal materials such as gold (Au), silver (Ag) and copper (Cu).
  • the gas sensing device 1000 in accordance with an embodiment of the present invention includes therein the conductive pattern 260 for gas sensing on the packaging substrate 200 without an additional printed circuit board, so that it is possible to simplify the manufacturing process in comparison with the conventional device.
  • the device 1000 is fabricated by bonding the gas sensing substrate 100 and the packaging substrate 200 each formed from silicon wafer so that separate gas sensing devices 1000 can be fabricated by bonding silicon wafers in which a plurality of gas sensing substrates 100 and a plurality of packaging substrates 200 are formed respectively and slicing the bonded silicon wafers. Thereby, it is possible to reduce both manufacturing time and cost.
  • the gas sensing substrate 100 and the conductive pattern 260 of the packaging substrate 200 are electrically connected via the connecting portion 300 of the packaging substrate 200, so that such a connection is stronger than an electrical connection through a wire vulnerable to external shocks. That is, the gas sensing reliability becomes improved.
  • the packaging substrate 200 includes the gas flow rate detecting portion 250 for measuring the flow rate of the gas introduced from the outside so as to provide the best performance for gas sensing, it is not necessary to include any further gas flow rate detecting portion. In this way, there is provided a gas sensing device 1000 manufactured in a simplified process at reduced cost.
  • FIG. 4 is a flowchart showing a method for manufacturing a gas sensing device in accordance with an embodiment of the present invention
  • Figs. 5 to 12 are cross- sectional views to explain the method for manufacturing the gas sensing device in accordance with the embodiment of the present invention.
  • a gas sensing substrate 100 is prepared (SlOO).
  • the gas sensing substrate 100 including a first substrate 110, an insulating film 120, a heating portion 130, an insulating portion 140, electrodes 150, a gas sensing portion 160 and pads 170.
  • a packaging substrate 200 is prepared (S200).
  • a top surface and a bottom surface of a second substrate 210 formed of a DSP (Double Side Polished) silicon wafer are oxidized in water (H 2 O) by using a wet thermal oxidation method and then, on each of the top and bottom surfaces of the second substrate 210, there is formed a first insulating layer 220 made of silicon oxide (SiO 2 ) and having a thickness ranging from about 4000A to about 6000A.
  • a second insulating layer 230 made of silicon nitride (SiNx) and having a thickness ranging from about 2000A to about 4000A by using a LPCVD (Low Pressure Chemical Vapor Deposition) method.
  • SiNx silicon nitride
  • an additional insulating layer made of silicon oxide or silicon nitride between the first insulating layer 220 and the second substrate 210 or between the first insulating layer 220 and the second insulating layer 230.
  • a conductive layer 255 made of polysilicon (poly Si) and having a thickness ranging from about 3000A to about 5000A by using the LPCVD method or an ion implant method.
  • a gas flow rate detecting portion 250 is formed by patterning the conductive layer 255 by using a photolithography technique.
  • the gas flow rate detecting portion 250 should have a thickness ranging from about 5000A to about 40000A so as not to be broken by the pressure of the gas introduced from the outside but to be bent in an appropriate manner such that electrical resistance can be changed.
  • the gas flow rate detecting portion 250 can be broken by the pressure of the introduced gas when the gas is introduced from the outside.
  • the gas flow rate detecting portion 250 is not bent by the pressure of the introduced gas and thus the electrical resistance of the gas flow rate detecting portion 250 is not changed when the gas is introduced from the outside.
  • the first insulating layer 220 and the second insulating layer 230 disposed on the top surface of the second substrate 210 are patterned by using the photolithography technique so as to allow the top surface of the second substrate 210 to be exposed at a first area A. Further, the first insulating layer 220 and the second insulating layer 230 disposed on the bottom surface of the second substrate 210 are patterned so as to allow the bottom surface of the second substrate 210 to be exposed at a second area B. In this case, it is desirable to use a RIE (Reactive Ion Etch) process for patterning the first insulating layer 220 and the second insulating layer 230.
  • RIE Reactive Ion Etch
  • the second substrate 210 exposed at the second area A is etched by a wet etching process by using potassium hydroxide (KOH) as an etchant.
  • KOH potassium hydroxide
  • the etched surface of the second substrate 210 can be formed at an acute angle or an obtuse angle, and the first insulating layer 220, the second insulating layer 230 and the gas flow rate detecting portion 250 disposed on the top surface of the second substrate 210 are floated by etching the second substrate 210 at the second area B, whereby the second substrate 210 forms a detection space S.
  • a bonding layer 240 is formed on the second insulating layer 230 disposed on the bottom surface of the second substrate 210.
  • the bonding layer 240 may be formed of metal multi-layers made of indium (In), tin (Sn), gold (Au) and the like, or formed of a resin single layer made of epoxy or the like. It is desirable to form the bonding layer 240 having a thickness ranging from about 3000A to about 5000A.
  • the first insulating layer 220, the second insulating layer 230 and the bonding layer 240 which correspond to the through hole 211 are etched by using the dry etching process or the wet etching process.
  • the bonding layer 240 is formed of metal multi-layers made of indium (In), tin (Sn), gold (Au) and the like, it is desirable to form an insulating material on one surface of the bonding layer 240 to be in contact with the through hole 211 and exposed to the outside after the etching.
  • PECVD Pullasma Enhanced Chemical Vapor Deposition
  • a conductive pattern 260 including a plurality of circuit patterns for sensing a gas or a gas flow rate by using a MEMS technique.
  • the conductive pattern 260 is connected with the gas flow rate detecting portion 250.
  • the conductive pattern 260 can be formed at another position such as within the second substrate 210, on the upper side of the gas flow rate detecting portion 250, or the like. [95] Then, by using a photolithography technique, one or more holes 251 are formed at gas flow rate detecting portion 250 so as to communicate with the detection space S after penetrating the first insulating layer 220, the second insulating layer 230 and the gas flow rate detecting portion 250.
  • the holes 251 may be formed after the packaging substrate
  • the packaging substrate 200 is prepared.
  • the packaging substrate 200 is bonded onto the gas sensing substrate 100 (S300).
  • the packaging substrate 200 is bonded onto the gas sensing substrate
  • the bonding layer 240 in a manner such that the gas sensing portion 160 of the gas sensing substrate 100 is located in the detection space S of the packaging substrate 200 and the pads 170 of the gas sensing substrate 100 is located in the through hole 211 of the packaging substrate 200.
  • the packaging substrate 200 is bonded onto the gas sensing substrate 100 by using a thermocompression bonding method such as a eutectic bonding method using the bonding layer 240. Also, if the bonding layer 240 is formed of a resin single layer made of epoxy or the like, the packaging substrate 200 can be bonded onto the gas sensing substrate 100 by using a thermosetting bonding method using the bonding layer 240.
  • the gas sensing substrate 100 and the packaging substrate 200 can be bonded to each other by using a bonding material such as glass powder.
  • a connecting portion 300 is formed by disposing a conductive material such as copper (Cu) within the through hole 211 through a plating process.
  • the conductive pattern 260 of the packaging substrate 200 is connected with the pads 170 of the gas sensing substrate 100 through the connecting portion 300. That is, the gas sensing portion 160 is connected with the conductive pattern 260.
  • the gas sensing device 1000 in accordance with an embodiment of the present invention is fabricated.
  • the present invention enables omission of an additional printed circuit board by improving the structure of a packaging substrate. Thus, manufacturing cost can be reduced.

Abstract

There is provided a cost-reducible packaging substrate, a gas sensing device having the packaging substrate and a method for manufacturing the gas sensing device. The gas sensing device includes a gas sensing substrate having a gas sensing portion whose electrical resistance is changed when it is in contact with a gas to be detected, and a packaging substrate disposed on the gas sensing substrate, for packaging the gas sensing substrate, and the packaging substrate has a gas flow rate detecting portion for measuring an amount of the gas introduced to the gas sensing portion.

Description

Description
PACKAGING SUBSTRATE AND GAS SENSING DEVICE HAVING THE SAME, AND METHOD FOR MANUFACTURING
THE SAME
Technical Field
[1] The present invention relates to a packaging of a gas sensing device, and more particularly, relates to a packaging substrate using a MEMS (Micro Electro Mechanical Systems) technique, a gas sensing device having the packaging substrate and a method for manufacturing the gas sensing device. Background Art
[2] A gas sensing device is in general used to detect a specific gas. In particular, when a gas sensing portion included in the gas sensing device is exposed to the specific gas, conductivity of a semiconductor as a sensing material of the gas sensing portion may change or an electromotive force may be generated. By measuring such a change in the conductivity of the semiconductor or the generated electromotive force, a change in electrical resistance of the semiconductor is measured, whereby it becomes possible to detect the specific gas.
[3] Fig. 1 is a cross-sectional view of a conventional gas sensing device.
[4] As illustrated in Fig. 1, the conventional gas sensing device 1 includes a printed circuit board 10, a gas sensing substrate 20 and a cover 30.
[5] The printed circuit board 10 includes a circuit pattern for gas sensing, and a board pads 11 connected with the circuit pattern is positioned on the printed circuit board 10. A part of the printed circuit board 10 is depressed from its top surface such that the gas sensing substrate 20 is accommodated thereon.
[6] The gas sensing substrate 20 includes a substrate 21, an insulating layer 22, a heating portion 23, an insulating portion 24, electrodes 25, a gas sensing portion 26, and electrode pads 27.
[7] The substrate 21 is formed of a silicon wafer and the insulating layer 22 is disposed thereon.
[8] The insulating layer 22 contains silicon oxide, silicon nitride, and so forth. The heating portion 23 is disposed on the insulating layer 22.
[9] The heating portion 23 is used for heating the gas sensing portion 26 up to a temperature at which the performance of the gas sensing portion 26 can be optimized. The heating portion 23 contains a metal material such as platinum (Pt) whose property of electrical conductivity does not deteriorate under high temperature conditions. The heating portion 23 is connected with the electrode pad 27. [10] The insulating portion 24 is disposed between the heating portion 23 and the electrode 25, and serves to prevent a short circuit between the heating portion 23 and the electrode 25.
[11] The electrode 25 is used for detecting a change in electrical resistance of the gas sensing portion 26 due to an inflow of a gas from the outside. The electrode 25 is connected with the electrode pads 27.
[12] The gas sensing portion 26 indicates the change in electrical resistance by making a direct contact with a gas to be detected and adsorbing the gas, and it contains metal oxide having semiconductor properties. When the gas introduced from the outside makes a contact with the gas sensing portion 26 and makes a chemical reaction, electrons are exchanged between the gas and the gas sensing portion 26, so that the electrical resistance of the gas sensing portion 26 is changed.
[13] The electrode pad 27 is connected with the heating portion 23 and the electrode 25 and also connected with the board pad 11 positioned on the printed circuit board 10 via a wire w. In other words, the heating portion 23 and the electrode 25 are connected with the circuit pattern for gas sensing, which is formed on the printed circuit board 10, via the electrode pad 27, the wire w and the board pads 11.
[14] The cover 30 protects the gas sensing substrate 20 from external shocks.
[15] As stated above, since the conventional gas sensing device 1 includes therein the printed circuit board 10, the gas sensing substrate 20 and the cover 30 which are manufactured through separate processes and adhered to each other, manufacturing cost increases.
[16] Further, since the printed circuit board 10 and the gas sensing substrate 20 are electrically connected with each other via the wire w, deterioration of gas sensing reliability may be caused.
[17] Furthermore, in case the gas sensing device is used in an alcohol sensor, a smoke sensor, a foul breath sensor or the like, it is desirable to activate the gas sensing device only when the amount of a gas introduced from the outside increases equal to or over a predetermined amount. To this end, in the conventional gas sensing device, a gas flowmeter for measuring a flow rate of the gas introduced into the gas sensing portion 26 is additionally installed, which causes complication of manufacturing process and an increase of manufacturing cost. Disclosure of Invention Technical Problem
[18] In order to solve the above-stated problems, the present invention provides a packaging substrate having an improved structure and thus capable of reducing manufacturing cost; a gas sensing device having the packaging substrate; and a method for manufacturing the gas sensing device.
[19] Further, the present invention also provides a packaging substrate having an improved connection structure between a circuit pattern for gas sensing and a gas sensing portion and thus capable of improving gas sensing reliability; a gas sensing device having the packaging substrate; and a method for manufacturing the gas sensing device.
[20] Further, the present invention also provides a packaging substrate including a gas flow rate detecting portion and thus capable of simplifying a manufacturing process and reducing manufacturing cost; a gas sensing device having the packaging substrate and a method for manufacturing the gas sensing device. Technical Solution
[21] In accordance with a first aspect of the present invention, there is provided a gas sensing device, including: a gas sensing substrate including a gas sensing portion whose electrical resistance is changed when it comes into contact with a gas to be detected; and a packaging substrate disposed on the gas sensing substrate, for packaging the gas sensing substrate, and the packaging substrate includes a gas flow rate detecting portion for measuring an amount of the gas introduced into the gas sensing portion.
[22] The gas flow rate detecting portion may be of a piezoresistance type in which electrical resistance is changed when pressure is applied by the gas.
[23] The gas flow rate detecting portion may activate the gas sensing portion when the amount of the gas exceeds a predetermined value.
[24] The gas flow rate detecting portion may include one or more holes through which the gas passes.
[25] The gas flow rate detecting portion may contain polysilicon (poly Si) doped with impurities.
[26] The gas sensing substrate may further include: a first substrate; an insulating film disposed between the first substrate and the gas sensing portion; and a pad disposed on the insulating film and connected with the gas sensing portion.
[27] The gas sensing substrate may further include: a heating portion disposed between the insulating film and the gas sensing portion, for heating the gas sensing portion; and an electrode portion for connecting the pad with the gas sensing portion.
[28] The packaging substrate may further include: a second substrate disposed on the first substrate, for forming a detection space between the gas flow rate detecting portion and the gas sensing portion; and an insulating layer disposed between the second substrate and the gas flow rate detecting portion.
[29] The insulating layer corresponding to the detection space may be in a floating state. [30] The second substrate may include a through hole corresponding to the pad and passing through the second substrate; the packaging substrate may further include a conductive pattern formed on the second insulating layer; and the gas sensing device may further include a connecting portion disposed within the through hole, for connecting the pad and the conductive pattern via the through hole.
[31] In accordance with a second aspect of the present invention, there is provided a method for manufacturing a gas sensing device, the method including: process (a) of providing a gas sensing substrate including a gas sensing portion whose electrical resistance is changed when it is in contact with a gas to be detected; process (b) of providing a packaging substrate including a gas flow rate detecting portion for measuring an amount of the gas; and process (c) of bonding the packaging substrate onto the gas sensing substrate in order for the gas flow rate detecting portion to measure the amount of the gas introduced to the gas sensing portion.
[32] The process (b) may include forming one or more holes in the gas flow rate detecting portion.
[33] At least one step of the processes (a) and (b) may be carried out by using a MEMS
(Micro Electro Mechanical Systems) technique.
[34] The process (b) may include: providing a substrate; forming an insulating layer on the substrate; forming the gas flow rate detecting portion on the insulating layer; and forming a through hole passing through the substrate.
[35] The process (b) may further include: forming a conductive pattern on the insulating layer, and the process (c) may include: forming a connecting portion within the through hole so as to connect the conductive pattern with the gas sensing portion.
[36] In accordance with a third aspect of the present invention, there is provided a packaging substrate used for a gas sensing device, for packaging a gas sensing substrate having a gas sensing portion for detecting gas, the packaging substrate including: a gas flow rate detecting portion disposed in a moving route of the gas, for measuring an amount of the gas introduced to the gas sensing portion.
[37] The gas flow rate detecting portion may be of a piezoresistance type in which electrical resistance is changed when pressure is applied by the gas.
[38] The gas flow rate detecting portion may activate the gas sensing portion when the amount of the gas exceeds a predetermined value.
[39] The gas flow rate detecting portion may include one or more holes through which the gas passes.
[40] The gas flow rate detecting portion may contain polysilicon (poly Si) doped with impurities.
[41] There may be formed a detection space between the gas flow rate detecting portion and the gas sensing portion. [42] The packaging substrate may further include an insulating layer disposed between the gas flow rate detecting portion and the detection space, and the insulating layer corresponding to the detection space may be in a floating state.
[43] The packaging substrate may further include: a conductive pattern; and a through hole for accommodating therein a connecting portion for connecting the gas sensing portion and the conductive pattern. Brief Description of Drawings
[44] Fig. 1 is a cross-sectional view of a conventional gas sensing device;
[45] Fig. 2 is a cross-sectional view of a gas sensing device in accordance with an embodiment of the present invention;
[46] Fig. 3 is a top plane view of the gas sensing device in accordance with the embodiment of the present invention;
[47] Fig. 4 is a flowchart showing a method for manufacturing a gas sensing device in accordance with an embodiment of the present invention; and
[48] Figs. 5 to 12 are cross-sectional views to explain the method for manufacturing the gas sensing device in accordance with the embodiment of the present invention. Best Mode for Carrying out the Invention
[49] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that the present invention may be readily implemented by those skilled in the art. However, it is to be noted that the present invention is not limited to the embodiments but can be embodied in various other ways. In drawings, parts irrelevant to the description are omitted for the simplicity of explanation, and like reference numerals denote like parts through the whole document.
[50] Through the whole document, the term "on" that is used to designate a position of one element with respect to another element includes both a case that the one element is adjacent to the another element and a case that any other element exists between these two elements. Further, the term "comprises or includes" and/or "comprising or including" used in the document means that one or more other components, steps, operation and/or existence or addition of elements are not excluded in addition to the described components, steps, operation and/or elements unless context dictates otherwise.
[51] Hereinafter, there will be explained a gas sensing device in accordance with an embodiment of the present invention with reference to Figs. 2 and 3.
[52] Fig. 2 is a cross-sectional view of the gas sensing device in accordance with the embodiment of the present invention, and Fig. 3 is a top plane view of the gas sensing device in accordance with the embodiment of the present invention. [53] As illustrated in Fig. 2, a gas sensing device 1000 in accordance with the embodiment of the present invention includes a gas sensing substrate 100, a packaging substrate 200 and connecting portions 300.
[54] The gas sensing substrate 100 includes a first substrate 110, an insulating film 120, a heating portion 130, an insulating portion 140, electrodes 150, a gas sensing portion 160 and pads 170.
[55] The first substrate 110 is formed of a wafer made of silicon. The insulating film 120 is disposed on the first substrate 110.
[56] The insulating film 120 includes a silicon oxide layer, a silicon nitride layer, and so forth. The heating portion 130 is disposed on the insulating film 120.
[57] The heating portion 130 functions to heat the gas sensing portion 160 up to a temperature at which the performance of the gas sensing portion 160 can be optimized. The heating portion 130 contains a metal material such as platinum (Pt) whose property of electrical conductivity does not deteriorate under high temperature conditions and a conductive material such as polysilicon (poly Si). The heating portion 130 is connected with the pad 170.
[58] The insulating portion 140 is disposed between the heating portion 130 and the electrode 150 and serves to prevent a short circuit between the heating portion 130 and the electrode 150.
[59] The electrode 150 serves to detect a change in electrical resistance of the gas sensing portion 160 due to an inflow of a gas from the outside. The electrode 150 contains a metal material such as platinum (Pt) whose property of electrical conductivity does not deteriorate under high temperature conditions and a conductive material such as polysilicon. The electrode 150 is connected with the pad 170.
[60] The gas sensing portion 160 indicates a change in electrical resistance by making direct a contact with a gas to be detected and adsorbing the gas, and it contains metal oxides such as tin oxide (SnO2), tungsten oxide (WO3) and titanium oxide (TiO2), and so forth, which have semiconductor properties. When the gas introduced from the outside makes a contact with the gas sensing portion 160 and makes a chemical reaction, electrons are exchanged between the gas and the gas sensing portion 160, so that the electrical resistance of the gas sensing portion 160 is changed.
[61] A part of the pads 170 is connected with the heating portion 130 and the rest are connected with the electrodes 150. The pads 170 are not only connected with the gas sensing portion 160 via the electrodes 150 but also connected with conductive patterns 260 of the packaging substrate 200 to be described below via the connecting portions 300 of the packaging substrate 200.
[62] The packaging substrate 200 to be described below is disposed on the above-stated gas sensing substrate 100. [63] As illustrated in Figs. 2 and 3, the packaging substrate 200 includes a second substrate 210, first insulating layers 220, second insulating layers 230, a bonding layer 240, a gas flow rate detecting portion 250 and the conductive pattern 260.
[64] The second substrate 210 is formed of a wafer made of silicon. The second substrate
210 surrounds the gas sensing portion 160 in a manner such that a detection space S is formed around the gas sensing portion 160 of the gas sensing substrate 100. A gas introduced from the outside stays in the detection space S. The second substrate 210 includes through holes 211 which correspond to the pads 170 on the gas sensing substrate 100 and pass through the second substrate 210 from its top surface to its bottom surface. The connecting portion 300 to be described below is disposed in the through hole 211 of the second substrate 210. The first insulating layers 220 are respectively located on the top surface of the second substrate 210 and the bottom surface opposite thereto.
[65] The first insulating layer 220 is made of an insulating material containing silicon oxide (SiO2). The first insulating layer 220 corresponding to the detection space S is in direct contact with the detection space S. That is, the first insulating layer 220 located on the detection space S is facing the gas sensing portion 160 of the gas sensing substrate 100 in a floating state. The second insulating layer 230 is disposed on the first insulating layer 220.
[66] The second insulating layer 230 is made of an insulating material containing silicon nitride (SiNx). It is desirable that the second insulating layer 230 is made of an insulating material whose lattice structure intersects that of the first insulating layer 220. That is, the first insulating layer 220 and the second insulating layer 230 serve to reinforce insulation property and elastic strength of each other. The bonding layer 240 is disposed between the second insulating layer 230 and the gas sensing substrate 100.
[67] The bonding layer 240 serves to bond the packaging substrate 200 with the gas sensing substrate 100 by using a thermocompression bonding method such as an eutectic bonding method using any one or more conductive metal materials among indium (In), tin (Sn) and gold (Au), or a thermosetting bonding method using an epoxy resin. In case of using the conductive metal material as the bonding layer 240, an additional insulating material may be disposed between the connecting portion 300 to be described later and the bonding layer 240 in order to prevent a short circuit between the connecting portion 300 and the bonding layer 240. The gas flow rate detecting portion 250 is disposed on the second insulating layer 230 on a top surface of the second substrate 210 opposite to the second insulating layer 230 disposed on the bonding layer 240.
[68] The gas flow rate detecting portion 250 is disposed above the detection space S so as to correspond to the gas sensing portion 160 of the gas sensing substrate 100 and located on the second insulating layer 230 disposed on the first insulating layer 220 in the floating state. The gas flow rate detecting portion 250 contains polysilicon (poly Si) doped with impurities such as boron, phosphorus or the like, and is of a piezoresistance type in which electrical resistance is changed when pressure is applied from the outside. Further, the gas flow rate detecting portion 250 includes one or more holes 251 formed to correspond to the gas sensing portion 160 of the gas sensing substrate 100. During a gas detecting process, the gas is introduced into the detection space S through the holes 251 from the outside. In this way, when the gas passes through the holes 251, the first insulating layer 220 in the floating state and the second insulating layer 230 are shaken due to a gas flow velocity, whereby the gas flow rate detecting portion 250 disposed on the second insulating layer 230 is bent and receives a pressure applied thereto. That is, as the gas flow rate detecting portion 250 receives the pressure applied thereto due to the inflow of the gas, the electrical resistance thereof is changed, and the flow rate of the gas introduced into the detection space S can be measured from the changed electrical resistance. If the amount of the gas introduced into the detection space S exceeds a predetermined value, the gas flow rate detecting portion 250 activates the gas sensing portion 160 of the gas sensing substrate 100 by a signal exchange with the circuit pattern of the conductive pattern 260 to be described below. That is, if the electrical resistance of the gas flow rate detecting portion 250 exceeds the predetermined value due to the gas introduced into the detection space S, the conductive pattern 260 connected with the gas flow rate detecting portion 250 transmits an activation signal to the gas sensing substrate 100 and thus the gas sensing portion 160 becomes activated, whereby it is possible to start sensing the gas in the detection space S due to an activation of the gas sensing portion 160. In this manner, the gas sensing device 1000 can perform the optimal gas sensing operation based on the amount of the gas introduced from the outside.
[69] The conductive pattern 260 is disposed nearby the gas flow rate detecting portion
250.
[70] The conductive pattern 260 is disposed on the second insulating layer 230, and includes a circuit pattern for sending/receiving an electric signal to/from the heating portion 130 and the electrodes 150 of the gas sensing substrate 100; a circuit pattern for sending/receiving an electric signal to/from the gas flow rate detecting portion 250; and a circuit pattern for performing other additional driving operations. The conductive pattern 260 can be formed to include a plurality of thin film transistors and is connected with the gas sensing substrate 100 in connection with the pads 170 of the gas sensing substrate 100 by way of the connecting portion 300.
[71] In another embodiment, there is no specific limitation on a position of the conductive pattern 260, so that the conductive pattern 260 can be disposed between the second in- sulating layer 230 and the gas flow rate detecting portion 250 or on the gas flow rate detecting portion 250.
[72] The connecting portion 300 is placed within the through hole 211 of the second substrate 210, and serves to connect the pads 170 of the gas sensing substrate 100 with the conductive pattern 260 of the packaging substrate 200 by passing through the second substrate 210 via the through hole 211. The connecting portion 300 contains conductive metal materials such as gold (Au), silver (Ag) and copper (Cu).
[73] As stated above, the gas sensing device 1000 in accordance with an embodiment of the present invention includes therein the conductive pattern 260 for gas sensing on the packaging substrate 200 without an additional printed circuit board, so that it is possible to simplify the manufacturing process in comparison with the conventional device. Further, the device 1000 is fabricated by bonding the gas sensing substrate 100 and the packaging substrate 200 each formed from silicon wafer so that separate gas sensing devices 1000 can be fabricated by bonding silicon wafers in which a plurality of gas sensing substrates 100 and a plurality of packaging substrates 200 are formed respectively and slicing the bonded silicon wafers. Thereby, it is possible to reduce both manufacturing time and cost.
[74] Furthermore, the gas sensing substrate 100 and the conductive pattern 260 of the packaging substrate 200 are electrically connected via the connecting portion 300 of the packaging substrate 200, so that such a connection is stronger than an electrical connection through a wire vulnerable to external shocks. That is, the gas sensing reliability becomes improved.
[75] Moreover, since the packaging substrate 200 includes the gas flow rate detecting portion 250 for measuring the flow rate of the gas introduced from the outside so as to provide the best performance for gas sensing, it is not necessary to include any further gas flow rate detecting portion. In this way, there is provided a gas sensing device 1000 manufactured in a simplified process at reduced cost.
[76] Hereinafter, a method for manufacturing a gas sensing device in accordance with an embodiment of the present invention will be explained with reference to Figs. 4 to 12.
[77] Fig. 4 is a flowchart showing a method for manufacturing a gas sensing device in accordance with an embodiment of the present invention, and Figs. 5 to 12 are cross- sectional views to explain the method for manufacturing the gas sensing device in accordance with the embodiment of the present invention.
[78] As illustrated in Figs. 4 and 5, first, a gas sensing substrate 100 is prepared (SlOO).
[79] To be specific, by using a MEMS technique, there is prepared the gas sensing substrate 100 including a first substrate 110, an insulating film 120, a heating portion 130, an insulating portion 140, electrodes 150, a gas sensing portion 160 and pads 170.
[80] Subsequently, as illustrated in Figs. 6 to 11, a packaging substrate 200 is prepared (S200).
[81] To be specific, as illustrated in Fig. 6, first of all, a top surface and a bottom surface of a second substrate 210 formed of a DSP (Double Side Polished) silicon wafer are oxidized in water (H2O) by using a wet thermal oxidation method and then, on each of the top and bottom surfaces of the second substrate 210, there is formed a first insulating layer 220 made of silicon oxide (SiO2) and having a thickness ranging from about 4000A to about 6000A.
[82] Then, on a second insulating layer 230, there is formed a second insulating layer 230 made of silicon nitride (SiNx) and having a thickness ranging from about 2000A to about 4000A by using a LPCVD (Low Pressure Chemical Vapor Deposition) method.
[83] In another embodiment, it may be possible to form an additional insulating layer made of silicon oxide or silicon nitride between the first insulating layer 220 and the second substrate 210 or between the first insulating layer 220 and the second insulating layer 230.
[84] Further, on the second insulating layer 230 disposed on the top surface of the second substrate 210, there is formed a conductive layer 255 made of polysilicon (poly Si) and having a thickness ranging from about 3000A to about 5000A by using the LPCVD method or an ion implant method. [85] Thereafter, as illustrated in Fig. 7, a gas flow rate detecting portion 250 is formed by patterning the conductive layer 255 by using a photolithography technique. [86] It is desirable that the gas flow rate detecting portion 250 should have a thickness ranging from about 5000A to about 40000A so as not to be broken by the pressure of the gas introduced from the outside but to be bent in an appropriate manner such that electrical resistance can be changed. That is, in case the thickness of the gas flow rate detecting portion 250 is equal to or less than 5000A, the gas flow rate detecting portion 250 can be broken by the pressure of the introduced gas when the gas is introduced from the outside. In case the thickness of the gas flow rate detecting portion 250 is equal to or more than 40000A, the gas flow rate detecting portion 250 is not bent by the pressure of the introduced gas and thus the electrical resistance of the gas flow rate detecting portion 250 is not changed when the gas is introduced from the outside.
[87] In another embodiment, it may be possible to form the gas flow rate detecting portion
250 by using a conductive layer containing impurities and having semiconductor properties.
[88] Subsequently, as illustrated in Fig. 8, the first insulating layer 220 and the second insulating layer 230 disposed on the top surface of the second substrate 210 are patterned by using the photolithography technique so as to allow the top surface of the second substrate 210 to be exposed at a first area A. Further, the first insulating layer 220 and the second insulating layer 230 disposed on the bottom surface of the second substrate 210 are patterned so as to allow the bottom surface of the second substrate 210 to be exposed at a second area B. In this case, it is desirable to use a RIE (Reactive Ion Etch) process for patterning the first insulating layer 220 and the second insulating layer 230.
[89] Then, as illustrated in Fig. 9, by etching the second substrate 210 by means of a dry etching process such as the RIE process, through holes 211 are formed through the second substrate 210 to be extended from its top surface exposed at the first area A to its bottom surface.
[90] Thereafter, the second substrate 210 exposed at the second area A is etched by a wet etching process by using potassium hydroxide (KOH) as an etchant. In this case, the etched surface of the second substrate 210 can be formed at an acute angle or an obtuse angle, and the first insulating layer 220, the second insulating layer 230 and the gas flow rate detecting portion 250 disposed on the top surface of the second substrate 210 are floated by etching the second substrate 210 at the second area B, whereby the second substrate 210 forms a detection space S.
[91] Further, as illustrated in Fig. 10, a bonding layer 240 is formed on the second insulating layer 230 disposed on the bottom surface of the second substrate 210. The bonding layer 240 may be formed of metal multi-layers made of indium (In), tin (Sn), gold (Au) and the like, or formed of a resin single layer made of epoxy or the like. It is desirable to form the bonding layer 240 having a thickness ranging from about 3000A to about 5000A.
[92] Furthermore, as illustrated in Fig. 11, the first insulating layer 220, the second insulating layer 230 and the bonding layer 240 which correspond to the through hole 211 are etched by using the dry etching process or the wet etching process. In this case, if the bonding layer 240 is formed of metal multi-layers made of indium (In), tin (Sn), gold (Au) and the like, it is desirable to form an insulating material on one surface of the bonding layer 240 to be in contact with the through hole 211 and exposed to the outside after the etching. When forming the insulating material on the one surface of the bonding layer 240, there is formed an insulating layer made of silicon oxide and having a thickness ranging from about 4000A to about 6000A by using a PECVD (Plasma Enhanced Chemical Vapor Deposition) method.
[93] Thereafter, on the second insulating layer 230 disposed on the top surface of the second substrate 210, there is formed a conductive pattern 260 including a plurality of circuit patterns for sensing a gas or a gas flow rate by using a MEMS technique. The conductive pattern 260 is connected with the gas flow rate detecting portion 250.
[94] In another embodiment, there is no specific limitation on the position of the conductive pattern 260. Thus, besides on the second insulating layer 230, the conductive pattern 260 can be formed at another position such as within the second substrate 210, on the upper side of the gas flow rate detecting portion 250, or the like. [95] Then, by using a photolithography technique, one or more holes 251 are formed at gas flow rate detecting portion 250 so as to communicate with the detection space S after penetrating the first insulating layer 220, the second insulating layer 230 and the gas flow rate detecting portion 250.
[96] In another embodiment, the holes 251 may be formed after the packaging substrate
200 is bonded onto the gas sensing substrate 100.
[97] Through the above-stated processes, the packaging substrate 200 is prepared.
[98] Subsequently, as illustrated in Fig. 12, the packaging substrate 200 is bonded onto the gas sensing substrate 100 (S300).
[99] To be specific, the packaging substrate 200 is bonded onto the gas sensing substrate
100 by using the bonding layer 240 in a manner such that the gas sensing portion 160 of the gas sensing substrate 100 is located in the detection space S of the packaging substrate 200 and the pads 170 of the gas sensing substrate 100 is located in the through hole 211 of the packaging substrate 200.
[100] If the bonding layer 240 is formed of metal multi-layers made of indium (In), tin (Sn), gold (Au) and the like, the packaging substrate 200 is bonded onto the gas sensing substrate 100 by using a thermocompression bonding method such as a eutectic bonding method using the bonding layer 240. Also, if the bonding layer 240 is formed of a resin single layer made of epoxy or the like, the packaging substrate 200 can be bonded onto the gas sensing substrate 100 by using a thermosetting bonding method using the bonding layer 240.
[101] In another embodiment, the gas sensing substrate 100 and the packaging substrate 200 can be bonded to each other by using a bonding material such as glass powder.
[102] Thereafter, a connecting portion 300 is formed by disposing a conductive material such as copper (Cu) within the through hole 211 through a plating process. The conductive pattern 260 of the packaging substrate 200 is connected with the pads 170 of the gas sensing substrate 100 through the connecting portion 300. That is, the gas sensing portion 160 is connected with the conductive pattern 260.
[103] In addition, if one wafer in which a plurality of packaging substrates 200 is formed is bonded to another wafer in which a plurality of gas sensing substrates 100 is formed, it is possible to manufacture a plurality of gas sensing devices 1000 each including the packaging substrate 200 and the gas sensing substrate 100 by dicing the one wafer and the another wafer bonded to each other.
[104] Through the above-stated processes, the gas sensing device 1000 in accordance with an embodiment of the present invention is fabricated.
[105] In view of the foregoing, there is provided a method for manufacturing a gas sensing device capable of improving gas sensing reliability as well as reducing manufacturing cost. [106] The above description of the present invention is provided for the purpose of illustration, and it would be understood by those skilled in the art that various changes and modifications may be made without changing technical conception and essential features of the present invention. Thus, it is clear that the above-described embodiments are illustrative in all aspects and do not limit the present invention. For example, each component describe to be of a single type can be implemented in a distributed manner. Likewise, components described to be distributed can be implemented in a combined manner.
[107] The scope of the present invention is defined by the following claims rather than by the detailed description of the embodiment. It shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention. Industrial Applicability
[108] In accordance with one of the above-stated means for solving the problems, the present invention enables omission of an additional printed circuit board by improving the structure of a packaging substrate. Thus, manufacturing cost can be reduced.
[109] Further, by improving a packaging substrate structure, gas sensing reliability can be improved.
[110] Furthermore, by using a packing substrate including a gas flow rate detecting portion, a manufacturing process can be simplified and manufacturing cost can be reduced.

Claims

Claims
[1] A gas sensing device, comprising: a gas sensing substrate including a gas sensing portion whose electrical resistance is changed when it comes into contact with a gas to be detected; and a packaging substrate disposed on the gas sensing substrate, for packaging the gas sensing substrate, wherein the packaging substrate includes a gas flow rate detecting portion for measuring an amount of the gas introduced into the gas sensing portion.
[2] The gas sensing device of claim 1, wherein the gas flow rate detecting portion is of a piezoresistance type in which electrical resistance is changed when pressure is applied by the gas.
[3] The gas sensing device of claim 2, wherein the gas flow rate detecting portion activates the gas sensing portion when the amount of the gas exceeds a predetermined value.
[4] The gas sensing device of claim 2, wherein the gas flow rate detecting portion includes one or more holes through which the gas passes.
[5] The gas sensing device of claim 2, wherein the gas flow rate detecting portion contains polysilicon (poly Si) doped with impurities.
[6] The gas sensing device of claim 1, wherein the gas sensing substrate further includes: a first substrate; an insulating film disposed between the first substrate and the gas sensing portion; and a pad disposed on the insulating film and connected with the gas sensing portion.
[7] The gas sensing device of claim 6, wherein the gas sensing substrate further includes: a heating portion disposed between the insulating film and the gas sensing portion, for heating the gas sensing portion; and an electrode portion for connecting the pad with the gas sensing portion.
[8] The gas sensing device of claim 6, wherein the packaging substrate further includes: a second substrate disposed on the first substrate, for forming a detection space between the gas flow rate detecting portion and the gas sensing portion; and an insulating layer disposed between the second substrate and the gas flow rate detecting portion.
[9] The gas sensing device of claim 8, wherein the insulating layer corresponding to the detection space is in a floating state. [10] The gas sensing device of claim 8, wherein the second substrate includes a through hole corresponding to the pad and passing through the second substrate; the packaging substrate further includes a conductive pattern formed on the second insulating layer; and the gas sensing device further includes a connecting portion disposed within the through hole, for connecting the pad and the conductive pattern via the through hole. [11] A method for manufacturing a gas sensing device, the method comprising: process (a) of providing a gas sensing substrate including a gas sensing portion whose electrical resistance is changed when it is in contact with a gas to be detected; process (b) of providing a packaging substrate including a gas flow rate detecting portion for measuring an amount of the gas; and process (c) of bonding the packaging substrate onto the gas sensing substrate in order for the gas flow rate detecting portion to measure the amount of the gas introduced to the gas sensing portion. [12] The method of claim 11, wherein the process (b) includes forming one or more holes in the gas flow rate detecting portion. [13] The method of claim 11, wherein at least one step of the processes (a) and (b) is carried out by using a MEMS (Micro Electro Mechanical Systems) technique. [14] The method of claim 11, wherein the process (b) includes: providing a substrate; forming an insulating layer on the substrate; forming the gas flow rate detecting portion on the insulating layer; and forming a through hole passing through the substrate. [15] The method of claim 14, wherein the process (b) further includes: forming a conductive pattern on the insulating layer, and the process (c) includes: forming a connecting portion within the through hole so as to connect the conductive pattern with the gas sensing portion. [16] A packaging substrate used for a gas sensing device, for packaging a gas sensing substrate having a gas sensing portion for detecting gas, the packaging substrate comprising: a gas flow rate detecting portion disposed in a moving route of the gas, for measuring an amount of the gas introduced to the gas sensing portion. [17] The packaging substrate of claim 16, wherein the gas flow rate detecting portion is of a piezoresistance type in which electrical resistance is changed when pressure is applied by the gas. [18] The packaging substrate of claim 17, wherein the gas flow rate detecting portion activates the gas sensing portion when the amount of the gas exceeds a predetermined value. [19] The packaging substrate of claim 17, wherein the gas flow rate detecting portion includes one or more holes through which the gas passes. [20] The packaging substrate of claim 17, wherein the gas flow rate detecting portion contains polysilicon (poly Si) doped with impurities. [21] The packaging substrate of claim 17, there is formed a detection space between the gas flow rate detecting portion and the gas sensing portion. [22] The packaging substrate of claim 21, further comprising: an insulating layer disposed between the gas flow rate detecting portion and the detection space, wherein the insulating layer corresponding to the detection space is in a floating state. [23] The packaging substrate of claim 17, further comprising: a conductive pattern; and a through hole for accommodating therein a connecting portion for connecting the gas sensing portion and the conductive pattern.
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FR3040488A1 (en) * 2015-08-28 2017-03-03 Bosch Gmbh Robert GAS SENSOR
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