CN108844652A - The preparation method of MEMS gas sensor chip, sensor and sensor - Google Patents
The preparation method of MEMS gas sensor chip, sensor and sensor Download PDFInfo
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- CN108844652A CN108844652A CN201810400193.8A CN201810400193A CN108844652A CN 108844652 A CN108844652 A CN 108844652A CN 201810400193 A CN201810400193 A CN 201810400193A CN 108844652 A CN108844652 A CN 108844652A
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- 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
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/333—Ion-selective electrodes or membranes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/19—Control of temperature characterised by the use of electric means
- G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
- G05D23/22—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element being a thermocouple
Abstract
The present invention relates to a kind of MEMS gas sensor chips, the preparation method of sensor and sensor, belong to gas detection technology field, solve the problems, such as that the prior art is expensive, the response time is long, environmental stability is poor.MEMS gas sensor chip includes gas sensitization unit, temperature sensing unit, sensitive structure substrate and temperature control unit.MEMS gas sensor, including MEMS gas sensor chip and control circuit；Control circuit includes microcontroller, N-type MOSFET, p-type MOSFET, positive-negative power again.The actual temperature of the temperature sensitive unit acquisition of microcontroller is compared with preset temperature, control signal is exported according to comparison result, the on-off of N-type MOSFET and p-type MOSFET are controlled, and then controls the current direction and size for flowing through temperature control unit, changes the temperature of sensitive structure substrate surface.MEMS gas sensor of the present invention is easy to operate, versatile, can measure the concentration of multiple gases simultaneously, saves cost, and the response time is short, environmental stability is good.
Description
Technical field
The present invention relates to gas detection technology field more particularly to a kind of MEMS gas sensor chips, sensor and biography
The preparation method of sensor.
Background technique
Gas detection is as a kind of important environmental parameter obtaining means, in atmosphere pollution prevention and treatment, industrial harmful gas
The fields such as monitoring, Internet of Things application value with higher.Currently mainly realized by gas sensor for the detection of gas,
Common gas sensor according to working principle and self structure can be divided into electrochemistry type, metal-oxide, catalytic combustion type,
Semi-conductor type and MEMS gas sensor etc..
MEMS gas sensor had received widespread attention in recent years since small in size, at low cost, structure is simple.But
The sensitive structure of existing MEMS gas sensor is affected by environmental stress, and performance is lower, and stability in long-time service
(being a most important index in sensor stability especially to the adaptability of temperature) is poor, therefore can not expire completely
The related needs of gas detection in sufficient adverse circumstances.
Both at home and abroad in research, the main path of the raising MEMS gas sensor performance of use is to improve gas sensitive material
Specificity and increase gas sensitive structure and the contact area of gas etc., but the specificity for improving gas sensitive material is only applicable
In the detection of portion gas, and the contact area for increasing sensitive structure and gas can then bring itself complexity, cost and it is micro- plus
The raising of work realization difficulty.Currently lack one kind under the premise of not increasing structure complexity, improves MEMS gas sensitive structure
The technological approaches of performance.
Summary of the invention
In view of above-mentioned analysis, the embodiment of the present invention is intended to provide a kind of MEMS gas sensor chip, sensor and biography
The preparation method of sensor, to solve the problems, such as that the prior art is expensive, the response time is long, environmental stability is poor.
The embodiment of the invention provides a kind of MEMS gas sensor chip, including gas sensitization unit, temperature are sensitive single
Member, sensitive structure substrate and temperature control unit；
The gas sensitization unit and temperature sensing unit are in same layer, and the two is respectively arranged at the sensitive structure substrate
Top, and the two bottom surface is directly contacted with the upper surface of the sensitive structure substrate；
The temperature control unit is set to the lower section of the sensitive structure substrate, for controlling sensitive structure substrate surface
Temperature.
Above-mentioned technical proposal has the beneficial effect that：Sensitive structure substrate of the invention has good heating conduction, temperature
Degree sensing unit is used to acquire environment temperature locating for MEMS gas sensor chip, is higher than preset temperature when measuring environment temperature
When, temperature control unit cools down to sensitive structure substrate, otherwise heats up.Temperature control unit is imitated based on Peltier
Answer, can be realized heat it is quick transmitting and lower steady state temperature difference, so that gas sensitization unit is always worked in isoperibol
In, eliminate or reduced influence of the environment temperature to MEMS gas sensor chip, therefore the response time is short, environmental stability
It is good.Moreover, the present invention can be right simultaneously by the way that multiple gas sensitization units realizations are arranged in sensitive structure substrate or encapsulation
The detection of multiple gases concentration reduces compared with directlying adopt a variety of existing discrete gas sensors for gas with various
Cost.
In another embodiment based on the above method, in MEMS gas sensor chip, the gas sensitization unit packet
Include metal electrode and gas-sensitive film；The gas-sensitive film is covered on the surface of metal electrode；
The gas sensitization unit, for the concentration variation of specific gas ingredient in local environment atmosphere to be converted into certainly
The variation of body resistance；
The temperature sensing unit, including at least one set of metal broken line type structure, for by the variation of local environment temperature
It is converted into the variation of self-resistance.
Beneficial effect by adopting the above technical scheme is：Gas sensitization unit and temperature sensing unit of the present invention are complete static
Movable member, therefore reliability with higher is not present in structure.Above scheme can realize that lesser metal electrode thickness is gentle
Sensitive film thickness, gas molecule are easy to go deep into inside air-sensitive film, to change the electric conductivity of gas sensitization unit, therefore advantageous
In sensitivity of the raising to object gas.Moreover, gas sensitization unit of the present invention and temperature sensing unit structure are simple, work is processed
Skill is easy to accomplish, and stability is good.
Further, the metal electrode is the interdigitated electrode structure structure of mutual symmetry, and the interdigital width of the interdigitated electrode structure structure is
5-30 μm, interdigital spacing is 5-30 μm, and metal electrode is with a thickness of 1000-2000A；
The temperature sensing unit uses alloy platinum material, and resistance is directly proportional to the broken line length of metal broken line type structure, with
Fold line cross-section width and thickness is inversely proportional.
Beneficial effect using above-mentioned further scheme is：Platinum itself has good environmental stability, and its resistivity
The linearity in large temperature range is generally preferable, therefore the temperature detecting precision of temperature sensing unit is higher.Moreover, temperature
Metal electrode preparation process in the preparation process and gas sensitization unit of sensing unit can use magnetron sputtering technique system
It is standby, the preparation of gas sensitization unit metal electrode and temperature sensing unit can be completed in same technical process, therefore advantageous
In the manufacturing cost for reducing entire MEMS gas sensor.Since the resistance of temperature sensing unit and its structure size have fixed pass
System, therefore the resistance value of temperature sensing unit can be adjusted in a certain range by changing broken line dimensional parameters.
Further, the temperature control unit is the plate knot made of semiconductor material based on paltie effect
Structure, including upper layer N-type semiconductor and lower layer's P-type semiconductor, the upper layer N-type semiconductor and lower layer's P-type semiconductor are directly connected to；
The length and width of the temperature control unit is greater than the length and width of sensitive structure substrate, with a thickness of 1000 μm or so；
The upper surface of the upper layer N-type semiconductor is attached by the bottom surface of gluey silicone grease and sensitive structure substrate.
Beneficial effect using above-mentioned further scheme is：Temperature control unit is mm grades, and temperature-responsive speed is ms
Grade, and gas sensitization unit and temperature sensing unit size are um to mm grades, therefore temperature control unit and gas sensitization
Heat transfer process between unit and temperature sensing unit has the characteristics that transmission path is short, balancing speed is fast.
Further, the sensitive structure substrate with a thickness of 200 μm or so, the gas sensitization unit and temperature are sensitive single
The distance of member is 100 μm or so.
Beneficial effect using above-mentioned further scheme is：Under the premise of guaranteeing heat-transfer effect, sensitive structure substrate
Thickness can guarantee the electric insulating quality of gas sensitization unit and temperature sensing unit respectively between the external world.Moreover, sensitive knot
The thinner thickness of structure substrate, therefore good heat-transfer.It is not contacted between gas sensitization unit and temperature sensing unit, is conducive to reality
Now gas sensitization unit and temperature sensing unit are individually tested.Distance can preferably eliminate temperature for 100 μm or so
Influence of the sensing unit to gas sensitization unit.
The embodiment of the invention also provides a kind of MEMS gas sensor, including above-mentioned MEMS gas sensor chip, with
And control circuit；
The input terminal of the control circuit receives two-way input signal, is all the way the measurement temperature of temperature sensing unit output
Degree, another way is preset temperature；The control circuit is compared the two-way input signal, is exported and is controlled according to comparison result
Signal processed；The control signal flows through the current direction and size of the temperature control unit by control, changes sensitive structure
The temperature of substrate surface.
Beneficial effect using the above scheme is：The current direction and size of temperature control unit are flowed through by controlling, only
Need to heating and refrigeration can be realized using single temperature control unit, i.e. realization gas sensitization unit and temperature sensing unit
Heating and cooling.When temperature of the preset temperature lower than temperature sensing unit acquisition, control signal makes table on temperature control unit
The heat in face is transferred to lower surface, therefore can reduce the temperature of upper surface, realizes the cooling to MEMS gas sensor.Instead
It, realizes heating.
Further, the control circuit includes microcontroller, N-type MOSFET, p-type MOSFET, positive-negative power；
The input terminal of the microcontroller receives the two-way input signal, the output end of the microcontroller respectively with institute
It states N-type MOSFET to be connected with the grid of p-type MOSFET, controls the N using the temperature deviation result of the two-way input signal
The on-off of type MOSFET and p-type MOSFET；
The source electrode of the N-type MOSFET is connected with the source electrode of the p-type MOSFET；The drain electrode of the N-type MOSFET connects just
The drain electrode of power supply, the p-type MOSFET connects negative supply；
One electric interfaces of the temperature control unit respectively with the source electrode of the N-type MOSFET and the p-type
The drain electrode of MOSFET is connected, another electric interfaces is directly grounded.
Beneficial effect using above-mentioned further scheme is：By microcontroller, the two-way input signal is compared
Compared with according to comparison result output control signal；The control signal is by controlling the logical of the N-type MOSFET and p-type MOSFET
It is disconnected, and then the current direction and size for flowing through the temperature control unit are controlled, change the temperature of sensitive structure substrate surface, into
And make the temperature of gas sensitization unit with faster velocity-stabilization around preset temperature.Pass through the fast of gas sensitization cell temperature
Speed control can reduce influence of the variation of ambient temperature to gas sensitization unit autosensitization, and then improve MEMS gas sensing
The environmental suitability and environmental stability of device.
The embodiment of the invention also provides a kind of methods for preparing above-mentioned MEMS gas sensor, include the following steps：
After cleaning to semiconductor crystal wafer, layer of oxide layer is grown in semiconductor wafer surface by thermal oxidation technology；
Gas sensitization unit is prepared in the oxidation layer surface；
In the oxidation layer surface preparation temperature sensing unit；
The semiconductor crystal wafer is carried out thinned；
Scribing is carried out to the semiconductor crystal wafer, forms sensitive structure substrate, includes gas on the sensitive structure substrate
The complete structure of sensing unit and temperature sensing unit；
Prepare the temperature control unit of plate morphology；
The sensitive structure substrate and the temperature control unit are engaged by heat-conducting silicone grease, obtain MEMS gas
Sensor chip；
Control circuit is built, the MEMS gas sensor chip is accessed into the control circuit, obtains the MEMS gas
Body sensor.
Beneficial effect using the above scheme is：On the basis of chip-scale, gas sensitization unit, temperature are realized
Sensing unit and temperature control unit it is system-level integrated, and can temperature to gas sensitization unit and temperature sensing unit at any time
It is controlled and is adjusted.Moreover, the processing technology of MEMS gas sensor is conventional process, it is easier to realize, and can be
Aoxidize multiple gas sensitization units and temperature sensing unit that layer surface preparation is directed to gas with various.
Further, include the step of the oxidation layer surface prepares gas sensitization unit,
Using sputtering technology in oxide layer Surface Creation nickel simple substance layer；
Golden simple substance layer is generated on the nickel simple substance layer using sputtering technology；
Metal electrode X-Y scheme in gas sensitization unit is transferred to by the golden simple substance layer surface using photoetching process；
Extra metal material and photoresist are removed by etching process, form metal electrode；
After for the sensitive material of specific gas and organic solvent dissolution, made on metal electrode by spin coating proceeding
Standby gas-sensitive film.
Beneficial effect using above-mentioned further scheme is：It repeats the above steps, can be made on sensitive structure substrate
Multiple gas sensitization units for different specific gas realize detection of the same sensor to a variety of gas with various concentration.
Include in the step of oxidation layer surface preparation temperature sensing unit,
Platinum simple substance layer is generated by sputtering technology in the oxide layer；
The two-dimensional structure of temperature sensing unit is being transferred to the platinum simple substance layer surface by photoetching process；
Extra metal material and photoresist are removed by etching process, form the platinum structure of broken line type.
Beneficial effect using above-mentioned further scheme is：It repeats the above steps, can be made on sensitive structure substrate
Multiple temperature sensing units obtain the Temperature Distribution of substrate surface, can more accurately obtain environment temperature.Temperature is sensitive single
The effect of member is environment temperature locating for precise measurement gas sensitization unit.
It in the present invention, can also be combined with each other between above-mentioned each technical solution, to realize more preferred assembled schemes.This
Other feature and advantage of invention will illustrate in the following description, also, certain advantages can become from specification it is aobvious and
It is clear to, or understand through the implementation of the invention.The objectives and other advantages of the invention can by specification, claims with
And it is achieved and obtained in specifically noted content in attached drawing.
Detailed description of the invention
Attached drawing is only used for showing the purpose of specific embodiment, and is not to be construed as limiting the invention, in entire attached drawing
In, identical reference symbol indicates identical component.
Fig. 1 is 1MEMS of embodiment of the present invention gas sensor chip structural schematic diagram；
Fig. 2 is 2MEMS of embodiment of the present invention gas sensor chip structural schematic diagram；
Fig. 3 is 2 gas sensitization cellular construction schematic diagram of the embodiment of the present invention；
Fig. 4 is 2 temperature sensing unit structural schematic diagram of the embodiment of the present invention；
Fig. 5 is the structural schematic diagram of 2 temperature control unit of the embodiment of the present invention；
Fig. 6 is 3MEMS of embodiment of the present invention gas sensor composition schematic diagram；
Fig. 7 is 4MEMS of embodiment of the present invention gas sensor preparation method schematic diagram；
Fig. 8 is the preparation method schematic diagram of 4 gas sensitization unit of the embodiment of the present invention；
Fig. 9 is the preparation method schematic diagram of 4 temperature sensing unit of the embodiment of the present invention；
Appended drawing reference：
A, B- metal electrode；The length of L- gas sensitization unit；The width of D- gas sensitization unit；
The adjacent interdigital spacing of d-；The interdigital width of w-；M1-N type MOSFET；M2-P type MOSFET；
V+- positive supply, V-- negative supply, M, the interface of N- temperature control unit.
Specific embodiment
Specifically describing the preferred embodiment of the present invention with reference to the accompanying drawing, wherein attached drawing constitutes the application a part, and
Together with embodiments of the present invention for illustrating the principle of the present invention, it is not intended to limit the scope of the present invention.
Embodiment 1
As shown in Figure 1, a specific embodiment of the invention, discloses a kind of MEMS gas sensor chip, including gas
Body sensing unit, temperature sensing unit, sensitive structure substrate and temperature control unit.
The gas sensitization unit and temperature sensing unit are in same layer, and the two is respectively arranged at the sensitive structure substrate
Top, and the two bottom surface is directly contacted with the upper surface of sensitive structure substrate.
Temperature control unit is set to the lower section of sensitive structure substrate, including two electric interfaces.Temperature control unit is used
In the temperature of control sensitive structure substrate surface.
When implementation, the electrical electric interfaces ground connection of one of temperature control unit, another connects control signal.When temperature sensitivity
When the actual temperature of unit acquisition is higher than the preset temperature of working sensor, temperature control unit cools down, i.e., temperature controls
The heat of unit upper surface is transferred to lower surface, realizes cooling.When the actual temperature of temperature sensing unit acquisition is lower than sensor
When the preset temperature of work, temperature sensing unit generates heat, realizes heating.
Compared with prior art, it is gentle to be integrated with temperature control unit for MEMS gas sensor chip provided in this embodiment
Body sensitive structure, and temperature control unit has a refrigerating/heating effect, control by the current direction of temperature control unit with
Size, can efficiently and quickly control temperature control unit refrigerating/heating, i.e. realization cold end and hot end is quickly converted, into
And the temperature for controlling gas sensitive structure improves the environmental suitability and environment of MEMS gas sensor around preset temperature
Stable type.MEMS design is used, so that heat transfer process is short, balancing speed is fast, it is low in cost to produce in enormous quantities.
Embodiment 2
As shown in Fig. 2, optimizing on the basis of the above embodiments, MEMS gas sensor further includes that thermal conductivity is preferable
Gluey silicone grease, the bottom surface phase that the upper surface of temperature control unit passes through thermal conductivity preferably gluey silicone grease and sensitive structure substrate
Even, the thickness of gluey silicone grease layer is no more than 50 μm.Thermal conductivity preferably refers to that the thermal coefficient of heat-conducting silicone grease reaches 2.0W/ (m*K)
More than, for operating ambient temperature range at -40 DEG C to 200 DEG C, thickness is generally 1-5mm, can control thickness by smearing process
Degree.Existing CPU heat transmission heat-conducting silicone grease can generally meet above-mentioned requirements.
Preferably, may there are one or more gas sensitization units and temperature sensing unit above sensitive structure substrate,
As the sensitive structure of MEMS gas sensor, only one sensitive structure substrate of entire sensitive structure.Gas sensitization unit and
The distance of temperature sensing unit is 100 μm or so.
Gas sensitization unit is a kind of own physical characteristic micron scale structures relevant to specific gas concentration, by metal
Electrode and gas-sensitive film two parts composition, gas-sensitive film are covered on surface of metal electrode.Gas sensitization unit can
The concentration variation of specific gas ingredient in ambiance is converted to the variation of self-conductive characteristic (resistance).
Since different gas sensitive materials has sensibility to different gas, such as metal phthalocyanine compound is to NO2
Gas sensibility with higher, and SnO2To H2S gas sensibility with higher, it is multiple based on gas with various by preparing
Gas-sensitive film (include sensitive material), form multiple gas sensitization units, may be implemented to gas with various and its concentration
Detection.
Gas sensitization unit detects most typical principle (principle used in the present embodiment) in the principle of certain gas：Gas
Suction-operated can occur between sensitive thin film and specific gas (i.e. object gas) molecule, in this process gas-sensitive film
There are electric charge transfers between material molecule and target gas molecules, therefore have been correspondingly formed inside gas-sensitive film higher or more
The electrons of low concentration.This charge transfer process is gradually deep into inside gas sensitive material with target gas molecules
And gradually become more significant, after a period of time, the electric conductivity of gas-sensitive film can produce significant and quantitative variation,
By the variation of detection gas sensitive thin film electric conductivity, the measurement to target gas levels can be realized.
The following relationship of target gas levels general satisfaction in gas-sensitive film resistance and environment：
In formula, R (t) indicates the resistance value of t moment, R0Gas-sensitive film when indicating that object gas is not present in environment
Resistance value, KTIndicate that temperature coefficient, K indicate sensitivity of the gas-sensitive film to object gas, K is bigger, indicates gas sensitization
Film is more sensitive to target gas levels variation, and T indicates the time constant of gas-sensitive film, and usual T is several seconds or bigger
Value, CgasIndicate target gas levels.
When time long enough, i.e. t>>When T：
R (t)=KTR0(1+KCgas) (2)
Preferably, the interdigitated electrode structure structure of two groups of mutual symmetries of metal electrode A, B, as shown in figure 3, every group includes multiple forks
Refer to, interdigital width w is 5-30 μm, and interdigital spacing d is 5-30 μm, and metal electrode is with a thickness of 1000-2000A.Entire gas sensitization
The length L and width D range of structure are 2000-8000 μm.The metal electrode metal material good by electric conductivity and environmental stability
It is made, such as gold.Gas-sensitive film is covered on surface of metal electrode and is deep into interdigital gap, thickness and metal
The thickness of electrode layer is close.Gas-sensitive film material is the self-conductive substance and chloroform etc. sensitive to specific gas
The mixture formed after organic solvent mixing.
Temperature sensing unit is a kind of own physical characteristic micron scale structures relevant to the temperature of its local environment, by
One or more groups of metal broken line type structure compositions, as shown in figure 4, for the variation of local environment temperature to be converted to self-resistance
Variation.Preferably, temperature sensing unit is made of the good platinum metal material of resistivity temperature character constancy, resistance with
The broken line length of metal broken line type structure is directly proportional, is inversely proportional with fold line cross-section width and thickness.Therefore, by changing broken line
Dimensional parameters can adjust the resistance value of temperature sensing unit in a certain range.
Sensitive structure substrate be by the semiconductor materials such as monocrystalline silicon wafer by oxidation and be thinned etc. techniques is formed put down
Surface structure is that gas sensitization unit and temperature are quick for providing the machining starting point of gas sensitization unit and temperature sensing unit
Feel unit and mechanical support and structure interconnection are provided, and provides necessary electric insulating quality for entire sensitive structure.Preferably, quick
Feel structured substrate with a thickness of 200 μm or so.
Temperature control unit is one kind by Bi2Te3Based on Peltier (Peltier) effect made of equal semiconductor materials
Flat structure, as shown in figure 5, including N-type semiconductor, P-type semiconductor and ceramic shell.N-type semiconductor material is partly led with p-type
Body material is made of doping process, and the two is directly connected to, and forms thermocouple structure, the outer surface of the thermocouple structure is by ceramics
Shell carries out overall package.Preferably, length and width is greater than the length and width of sensitive structure substrate, with a thickness of 1000
μm or so.When electric current flow through its it is internal when, the heat of its cold end can be transferred to hot end, therefore can realize the refrigeration function to cold end
Energy.Switching can correspondingly switch corresponding cold and hot end by the sense of current of temperature control unit, that is, pass through control stream
Sense of current and size through temperature control unit change the surface, it can be achieved that refrigeration and heating to its a certain surface
Temperature.Preferably, in the present embodiment, temperature control unit selects the MPC-D404 of Miropelt company.
When implementation, temperature control unit is for maintaining the temperature of MEMS gas sensor chip to be in preset temperature, i.e., in fact
Existing constant temperature is eliminated or is weakened influence of the environment temperature to MEMS gas sensor chip, improves MEMS gas sensor to environment
The adaptability of temperature.
Embodiment 3
As shown in fig. 6, present embodiments providing a kind of MEMS gas sensor, including MEMS gas sensor chip and control
Circuit processed.Control circuit includes microcontroller, N-type MOSFET, p-type MOSFET, power supply.
The input terminal of microcontroller receives two-way input signal, is all the way the measurement temperature of temperature sensing unit output, separately
All the way it is preset temperature, is arranged by user according to working sensor demand.The output end of microcontroller respectively with N-type MOSFET and
The grid of p-type MOSFET is connected.
The source electrode of N-type MOSFET is connected with the source electrode of p-type MOSFET；The drain electrode of N-type MOSFET connects positive supply, p-type
The drain electrode of MOSFET connects negative electricity.
One electric interfaces of temperature control unit by lead respectively with the source electrode of N-type MOSFET and p-type MOSFET
Drain electrode is connected, another electric interfaces is directly grounded.
Preferably, microcontroller is compared two-way input signal, exports control signal according to comparison result.Control letter
Number by the on-off of control N-type MOSFET and p-type MOSFET, and then control the sense of current for flowing through temperature control unit and big
It is small, change the temperature of sensitive structure substrate surface.
The temperature of MEMS gas sensor controls realization process：The micro-control that temperature control unit passes through interface M and periphery
Device processed is connected with ambipolar DC power supply (V+, V-), and interface N is directly grounded, and M1 is N-type MOSFET, and M2 is p-type MOSFET.When
When M1 is connected in the control signal of microcontroller output, since M1 and M2 is complementary, M2 ends at this time, and electric current connects from interface M flow direction
Mouth N, the heat of the upper surface of temperature control unit is transferred to lower surface at this time, therefore can reduce the temperature of upper surface.And when micro-
When M2 is connected in the control signal of controller output, M1 ends at this time, and electric current flows to interface M from interface N, and temperature control at this time is single
The heat of first lower surface is transferred to upper surface, therefore can increase the temperature of upper surface.Make since the voltage signal of MOSFET amplifies
With the control signal that flowing through the size of current between interface M and interface N can be exported by microcontroller controls, and therefore, microcontroller was both
The temperature of temperature control unit upper surface can be made to increase, and the temperature of temperature control unit upper surface can be made to reduce.
Further, since being connected between the upper surface and sensitive structure substrate of temperature control unit by the preferable silicone grease of thermal conductivity
It is connected together, therefore temperature control unit upper surface is to the heat transfer process between gas sensitization unit and temperature sensing unit
Thermal resistance it is smaller, i.e., the temperature difference between gas sensitization unit and temperature sensing unit and temperature control unit upper surface is smaller.It will
The temperature (actual temperature) that temperature sensing unit measurement obtains is input to microcontroller as feedback signal, and microcontroller can should
Actual temperature is compared with preset temperature, and when actual temperature is higher than preset temperature, M1 is connected in the control signal of output, drop
The temperature of low temperature control unit upper surface.And when actual temperature is lower than preset temperature, the control signal of microcontroller output
M2 is connected, improves the temperature of temperature control unit upper surface.Therefore, by the above method, the temperature of sensitive structure can finally be made
Degree is stablized in preset temperature, reduces influence of the environment temperature to sensitive structure, improves the environmental suitability of sensitive structure.
Compared with prior art, MEMS gas sensor provided in this embodiment can make gas sensitization by microcontroller
The temperature of unit is with faster velocity-stabilization around preset temperature (preset temperature).Pass through the quick of gas sensitization cell temperature
Control, can reduce influence of the variation of ambient temperature to gas sensitization unit autosensitization, MEMS gas sensor can be improved
Environmental suitability and environmental stability.
Embodiment 4
As shown in fig. 7, present embodiments providing a kind of process for preparing MEMS gas sensor in embodiment 3, wrap
Include following steps：
1. being cleaned to semiconductor crystal wafer the semiconductor crystal wafer made of the single crystal silicon material, then, passing through hot oxygen
Chemical industry skill grows the oxide layer of a layer thickness 500A in semiconductor wafer surface；
2. preparing gas sensitization unit in oxidation layer surface；
3. in oxidation layer surface preparation temperature sensing unit；
4. pair semiconductor crystal wafer carries out thinned, its thickness is made to reach 200 μm；
5. pair semiconductor crystal wafer carries out scribing, sensitive structure substrate is formed, includes gas sensitization list on sensitive structure substrate
The complete structure of member and temperature sensing unit；
6. preparing the temperature control unit of plate morphology；
7. sensitive structure substrate and temperature control unit are engaged by heat-conducting silicone grease, needle is completed after cured
To the preparation process of the MEMS gas sensitive structure of the multiple gases such as nitrogen oxides；
8. building control circuit, MEMS gas sensor chip is accessed into control circuit, obtains MEMS gas sensor.
2-3 step is repeated, multiple gas sensitization units for gas with various and multiple temperature can be made on the same substrate
Spend sensing unit.
Further, as shown in figure 8, including aoxidizing the step of layer surface prepares gas sensitization unit：
1. the nickel simple substance layer of a layer thickness 50A is grown in oxidation layer surface using PVD process such as sputterings；
2. the golden simple substance layer of thickness 1000-2000A is formed on nickel simple substance layer using PVD process such as sputterings；
3. the metal electrode X-Y scheme in gas sensitization unit is transferred to golden simple substance layer surface using photoetching process；
4. removing extra metal material and photoresist by etching process, metal electrode is formed；
5. after for the sensitive material of specific gas and organic solvent dissolution, through spin coating proceeding on metal electrode
Gas-sensitive film is prepared, the preparation of gas sensitization unit is just completed by this step.
3-5 step is repeated, and in step 5 using the sensitive material for being directed to gas with various, it can be in sensitive structure substrate
On multiple gas sensitization units for different specific gas are made.
Further, as shown in figure 9, including the step of aoxidizing layer surface preparation temperature sensing unit：
1. generating the platinum simple substance layer with a thickness of 1000A by PVD process such as sputterings in oxide layer；
2. the two-dimensional structure of temperature sensing unit is transferred to platinum simple substance layer surface by photoetching process；
3. removing extra metal material and photoresist by etching process, the platinum structure of broken line type is formed, is passed through
This step completes the preparation of temperature sensing unit.
2-3 step is repeated, multiple temperature sensing units can be made on sensitive structure substrate.
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto,
In the technical scope disclosed by the present invention, any changes or substitutions that can be easily thought of by anyone skilled in the art,
It should be covered by the protection scope of the present invention.
Claims (10)
1. a kind of MEMS gas sensor chip, which is characterized in that including gas sensitization unit, temperature sensing unit, sensitive knot
Structure substrate and temperature control unit；
The gas sensitization unit and temperature sensing unit are in same layer, and the two is respectively arranged at the upper of the sensitive structure substrate
Side, and the two bottom surface is directly contacted with the upper surface of the sensitive structure substrate；
The temperature control unit is set to the lower section of the sensitive structure substrate, for controlling the temperature of sensitive structure substrate surface
Degree.
2. MEMS gas sensor chip according to claim 1, which is characterized in that the gas sensitization unit, including
Metal electrode and gas-sensitive film；The gas-sensitive film is covered on the surface of metal electrode；
The gas sensitization unit, for the concentration variation of specific gas ingredient in local environment atmosphere to be converted into self-resistance
Variation；
The temperature sensing unit, including at least one set of metal broken line type structure, for converting the variation of local environment temperature
At the variation of self-resistance.
3. MEMS gas sensor chip according to claim 2, which is characterized in that the metal electrode is mutual symmetry
Interdigitated electrode structure structure, the interdigital width of the interdigitated electrode structure structure is 5-30 μm, and interdigital spacing is 5-30 μm, metal electrode with a thickness of
1000-2000A；
The temperature sensing unit uses alloy platinum material, and resistance is directly proportional to the broken line length of metal broken line type structure, with broken line
Cross-sectional width and thickness are inversely proportional.
4. MEMS gas sensor chip described in one of -3 according to claim 1, which is characterized in that the temperature control unit
Partly to be led made of semiconductor material based on the flat structure of paltie effect, including upper layer N-type semiconductor and lower layer's p-type
Body, the upper layer N-type semiconductor and lower layer's P-type semiconductor are directly connected to；The length and width of the temperature control unit is greater than
The length and width of the sensitive structure substrate, with a thickness of 1000 μm or so；
The upper surface of the upper layer N-type semiconductor is attached by the bottom surface of gluey silicone grease and sensitive structure substrate.
5. MEMS gas sensor chip according to claim 4, which is characterized in that the thickness of the sensitive structure substrate
It is 200 μm or so, the distance of the gas sensitization unit and temperature sensing unit is 100 μm or so.
6. a kind of MEMS gas sensor, which is characterized in that including MEMS gas sensor core described in one of claim 1-5
Piece and control circuit；
The input terminal of the control circuit receives two-way input signal, is all the way the measurement temperature of temperature sensing unit output, separately
It is all the way preset temperature；The control circuit is compared the two-way input signal, exports control letter according to comparison result
Number；The control signal flows through the current direction and size of the temperature control unit by control, changes sensitive structure substrate
The temperature on surface.
7. MEMS gas sensor according to claim 6, which is characterized in that the control circuit includes microcontroller, N
Type MOSFET, p-type MOSFET, positive-negative power；
The input terminal of the microcontroller receives the two-way input signal, the output end of the microcontroller respectively with the N
Type MOSFET is connected with the grid of p-type MOSFET, controls the N-type using the temperature deviation result of the two-way input signal
The on-off of MOSFET and p-type MOSFET；
The source electrode of the N-type MOSFET is connected with the source electrode of the p-type MOSFET；The drain electrode of the N-type MOSFET connects positive supply,
The drain electrode of the p-type MOSFET connects negative supply；
One electric interfaces of the temperature control unit respectively with the source electrode of the N-type MOSFET and the p-type MOSFET
Drain electrode is connected, another electric interfaces is directly grounded.
8. a kind of method for preparing MEMS gas sensor described in claim 6 or 7, which is characterized in that include the following steps：
After cleaning to semiconductor crystal wafer, layer of oxide layer is grown in semiconductor wafer surface by thermal oxidation technology；
Gas sensitization unit is prepared in the oxidation layer surface；
In the oxidation layer surface preparation temperature sensing unit；
The semiconductor crystal wafer is carried out thinned；
Scribing is carried out to the semiconductor crystal wafer, forms sensitive structure substrate, includes gas sensitization on the sensitive structure substrate
The complete structure of unit and temperature sensing unit；
Prepare the temperature control unit of plate morphology；
The sensitive structure substrate and the temperature control unit are engaged by heat-conducting silicone grease, obtain MEMS gas sensing
Device chip；
Control circuit is built, the MEMS gas sensor chip is accessed into the control circuit, the MEMS gas is obtained and passes
Sensor.
9. the preparation method of MEMS gas sensor according to claim 8, which is characterized in that in the oxidation layer surface
The step of preparing gas sensitization unit include,
Using sputtering technology in oxide layer Surface Creation nickel simple substance layer；
Golden simple substance layer is generated on the nickel simple substance layer using sputtering technology；
Metal electrode X-Y scheme in gas sensitization unit is transferred to by the golden simple substance layer surface using photoetching process；
Extra metal material and photoresist are removed by etching process, form metal electrode；
After for the sensitive material of specific gas and organic solvent dissolution, gas is prepared on metal electrode by spin coating proceeding
Body sensitive thin film.
10. the preparation method of MEMS gas sensor according to claim 8 or claim 9, which is characterized in that in the oxide layer
The step of surface preparation temperature sensing unit includes,
Platinum simple substance layer is generated by sputtering technology in the oxide layer；
The two-dimensional structure of temperature sensing unit is transferred to the platinum simple substance layer surface by photoetching process；
Extra metal material and photoresist are removed by etching process, form the platinum structure of broken line type.
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| CN112255272A (en) * | 2020-09-14 | 2021-01-22 | 重庆大学 | Gas sensor and preparation method thereof |
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