CN217033791U

CN217033791U - Micro-heating chip of MEMS (micro-electromechanical systems) catalytic combustion sensor and sensor

Info

Publication number: CN217033791U
Application number: CN202122652368.4U
Authority: CN
Inventors: 杨正; 薛峰; 荣钱; 陈栋梁; 吴秋菊; 张伟; 高陈; 项小婷
Original assignee: Micro Nano Perception Hefei Technology Co ltd
Current assignee: Micro Nano Perception Hefei Technology Co ltd
Priority date: 2021-10-29
Filing date: 2021-10-29
Publication date: 2022-07-22
Anticipated expiration: 2031-10-29

Abstract

The utility model discloses a micro-heating chip of an MEMS (micro-electromechanical systems) catalytic combustion sensor, which comprises a heating measurement layer, wherein the heating measurement layer comprises a heating element and a thermopile; the thermopile comprises a thermopile cold junction material and a thermopile hot junction material; the heating elements, the thermopile cold junction material and the thermopile hot junction material are arranged in a staggered way on the same layer. The utility model separates heating from measurement, can eliminate signal inhibition in the catalytic combustion process when the traditional heating and measurement are integrated, and improves the response of the catalytic combustion sensor.

Description

Micro-heating chip of MEMS (micro-electromechanical systems) catalytic combustion sensor and sensor

Technical Field

The utility model relates to the technical field of catalytic combustion gas sensing, catalytic combustion micro-heating chips and heat conduction sensing, in particular to an MEMS (micro-electromechanical system) catalytic combustion sensor micro-heating chip and a sensor.

Background

With the continuous development of the concept of internet of things, the demand of a gas sensor for sensing smell through a simulated nose is also increasing. As an important branch in the field of gas sensors, the catalytic combustion type gas sensor is widely applied to household natural gas leakage detection, mine gas monitoring, gas monitoring of a hydrogenation station and the like due to the advantages of simple structure, temperature and humidity interference resistance, no response to non-combustible gas and the like. In addition, as the new energy automobile is vigorously developed in China, the electric automobile is gradually started up, and huge development space is brought to the gas sensor. At present, electric automobiles are powered by batteries, and lithium batteries are used by a plurality of automobile manufacturers on the market due to the advantages of high energy density, high output voltage and the like. However, the lithium battery is prone to cause internal short circuit heating due to swelling, cracking, breakage and the like, and even to cause ignition and explosion of the automobile. Therefore, the battery needs to be monitored in the using process, and early warning is given when the battery fails.

Generally, a lithium battery can generate a large amount of hydrogen when being damaged, and the hydrogen can be detected through a gas sensor. Electrochemical gas sensors cannot be used due to their slow reaction rate, short service life, and other disadvantages. The semiconductor gas sensor performs the sensor through the oxidation-reduction reaction between the sensitive material and the gas, however, the current sensor is easily affected by environmental factors such as temperature and humidity, polluted gas and the like and is difficult to use. And the catalytic combustion sensor can effectively avoid the interference of the environment through the mutual matching of black and white elements. When the combustible gas is in a certain concentration range, a catalytic element in the catalytic combustion sensor is heated to about 400 ℃ by a platinum wire, so that the combustible gas is flameless combusted to cause temperature rise, and the sensing is realized by sensing temperature change through the platinum wire. The traditional catalytic combustion sensor is heated by a wire-wound platinum wire, and has the defects of high power consumption, large volume, difficult wire winding of the platinum wire, high production cost, easy volatilization of the platinum wire at high temperature and the like, so that the traditional catalytic combustion sensor is gradually replaced by a Micro-Electro-Mechanical System (MEMS) based heater. The MEMS-based micro-heater can realize high temperature of more than 500 ℃ by constructing a heating platform on a micrometer scale through a semiconductor process. The MEMS-based catalytic combustion microheaters currently on the market deposit platinum onto silicon wafers by sputtering to form platinum wires, loading the catalytic material on the plane, so heating and measurement is still performed simultaneously by the platinum. It is known that when combustible gases are present in the environment, they undergo flameless combustion on the catalytic material, causing the temperature of the material to rise, with a consequent rise in the temperature of the platinum wire. However, this results in an increase in the resistance of the platinum wire, which reduces the efficiency of the heating of the platinum wire, i.e. a signal suppression occurs, and an increase in the resistance of the platinum wire prevents the temperature from rising further. In addition, the resistance change of the platinum wire is not large along with the temperature change when the platinum wire is used for sensing, and by taking a traditional bright catalytic combustion methane sensor as an example, according to the detection standard that the bridge voltage is not less than 12mV when the national standard is 1% methane concentration, the resistance change of the platinum wire of a black element of the sensor is also less than 1 omega under the optimal bridge matching, and the sensitivity of the sensor is limited by the poor temperature sensing capability of the platinum wire.

On the other hand, when the gas to be measured in the environment exceeds a certain concentration, the catalytic combustion sensor has a "double value effect", i.e., the same signal as that generated by a certain low concentration, due to insufficient combustion caused by a decrease in the oxygen content of the environment. The thermal conductivity sensor can realize target gas detection in a high concentration range. The thermal conductivity gas sensor is manufactured according to the principle that the total thermal conductivity of mixed gas changes along with the content of gas to be measured. Generally, a detection element and a compensation element are paired to form a bridge, and when the gas is subjected to a gas having a thermal conductivity coefficient larger than that of air, the resistance of the detection element becomes smaller, and conversely, the resistance becomes larger. When the thermal conductivity sensor is used, the thermocouple can be connected in series to compensate the offset caused by the change of the environmental temperature, so that the test circuit can adopt a bridge circuit. The output voltage changes the reaction gas concentration of the bridge circuit. At present, the chip based on the thermal conductivity principle also adopts a platinum wire to heat and measure simultaneously, and the thermal conductivity sensor cannot detect gas with lower concentration because the gas concentration needs to reach a certain degree and then can change the environmental thermal conductivity.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide the micro-heating chip of the MEMS catalytic combustion sensor, which has high detection precision and is suitable for various gas concentrations.

The utility model solves the technical problems through the following technical means:

the MEMS catalytic combustion sensor micro-heating chip sequentially comprises a substrate (1), an insulating support film layer (2), a heating measuring layer and a protective layer (10) from bottom to top; a hollow-out area (1') is etched on the substrate (1); the insulating support film layer (2) is positioned in the hollow area (1 ') and is etched with a suspension beam (2'); the heating measurement layer is positioned on the suspension beam (2'); the protective layer (10) covers the heating measurement layer;

the heating measurement layer comprises a heating element (3), a thermopile (100); the thermopile (100) comprises a thermopile cold junction material (8) and a thermopile hot junction material (9); the heating elements (3), the thermopile cold junction material (8) and the thermopile hot junction material (9) are arranged in a staggered mode on the same layer.

The utility model separates heating and measurement, can eliminate signal inhibition in the catalytic combustion process when the traditional heating and measurement are integrated, and correspondingly improves the response of the catalytic combustion sensor. The thermopile and the heater are arranged in the same layer, so that the processing technology is simplified, and the size of the sensor is reduced.

Furthermore, the thermopile cold junction material (8) and the thermopile hot junction material (9) are coiled on the insulating support film layer (2), and the thermopile cold junction material (8) is coiled along a gap of the thermopile hot junction material (9).

Furthermore, the thermopile cold junction material (8), the thermopile hot junction material (9) and the heating element (3) are arranged in an S-shaped trend disc.

Further, the thermopile cold junction material (8) and the thermopile hot junction material (9) are arranged on at least 3 sides of the heating element (3) in a coiling mode.

Further, the thermopile cold junction material (8), the thermopile hot junction material (9) and the heating element (3) are led to the areas of the insulating support film layer except the cantilever beam structure through leads and are electrically connected with external equipment.

The utility model also provides an MEMS sensor, which comprises two micro heating chips, wherein the two micro heating chips are electrically connected; one of the micro heating chips is loaded with catalytic sensitive materials.

Furthermore, the two micro-heating chips are electrically connected in a bridge mode.

Further, the circuit of the MEMS sensor includes a catalytic combustion sensor S1, where RS1 and RH1 are respectively a thermopile (100) and a heating element (3) of the catalytic combustion sensor S1, a thermal conductivity sensor S2, RS2 and RH2 are respectively a thermopile (100) and a heating element (3) of the thermal conductivity sensor S2, bridge matching resistors R1 and R2, an amplifier U1, MOS transistors Q1, Q2 and Q3, and a single chip microcomputer U2;

after the R1 and the R2 are connected in series, the non-series end of R1 is connected with a VCC power supply, the non-series end of R2 is grounded, and the series common point of R1 and R2 is connected with the non-inverting input end of U1; after RS1 and RS2 are connected in series, the non-series end of RS2 is connected with a VCC power supply, the non-series end of RS1 is grounded through Q2, the series common point of RS1 and RS2 is connected with the inverting input end of U1, and the output end of U1 is connected with the AD sampling port of the singlechip U2; after RH1 and RH2 are connected in series, wherein the non-series end of RH2 is connected with a VCC power supply, the non-series end of RH1 is grounded through Q3, and the common point of RH1 and RH2 in series is grounded through Q1; the grid electrodes of the Q1, the Q2 and the Q3 are respectively connected with the GPIO end of the single chip microcomputer U2.

The utility model has the advantages that:

(1) the utility model separates heating from measurement, can eliminate signal inhibition in the catalytic combustion process when the traditional heating and measurement are integrated, and correspondingly improves the response of the catalytic combustion sensor;

(2) the thermopile manufactured by the MEMS technology is used as a measuring element, and the advantages of low detection limit and high sensitivity of thermopile temperature measurement are utilized, so that the heat released by catalytic combustion can be accurately detected, the requirement on a catalyst material is reduced, and the power consumption of the sensor is reduced.

(3) The catalytic combustion sensor and the thermopile sensor are combined, so that the overall sensitivity of the sensor is improved, the sensing precision is increased, and the sensing concentration range is enlarged.

Drawings

FIG. 1 is a schematic top view of a basic structure of a chip in example 1 of the present invention;

FIG. 2 is an exploded view of a chip structure in example 1 of the present invention;

fig. 3 is a schematic diagram of the chip combination in embodiment 2 of the present invention, in which a catalytic combustion sensitive material is loaded on the left side to become a catalytic combustion sensor and a bare chip on the right side serves as a thermal conductivity sensor;

fig. 4 is a schematic diagram of a sensor usage circuit control in embodiment 2 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The present embodiment provides a chip for measuring the thermal change of a catalytic element and the temperature change in thermal conductivity sensing in a catalytic combustion process by using a thermopile, the structure of which is shown in fig. 1 and fig. 2, the chip structure mainly includes a substrate 1, an insulating support film layer 2, a heating element 3, a heating lead 4, a heating pin 5, a thermopile lead 6, a thermopile lead 7, a thermopile cold junction material 8, a thermopile hot junction material 9, and a protective layer 10. The middle position of the substrate 1 is etched with a hollow area 1', and an insulating material layer 2 is arranged on the upper surface of the substrate 1 and used for insulating and supporting the devices above. The insulating support film layer 2 is positioned in the hollow area 1 ' and is etched with a suspension beam 2 ', and the heating element 3 and the thermopile are positioned on the suspension beam 2 '. The heater element 3 can provide necessary temperature for gas combustion and thermal conductivity sensing, and can be made of materials (such as gold and tungsten) with high thermal efficiency and reduced resistance temperature; the components 3-9 are distributed around the heating element in a staggered manner, the thermopile cold junction material 8 and the thermopile hot junction material 9 are arranged on the same layer in a crossed manner, and the thermopile space arrangement forms one end (a near end) which is closer to the heating element and one end (a far end) which is farther away from the heating element; the uppermost isolation protection layer is fabricated on the micro heater element and the thermopile to isolate the thermocouple material from air contact, prevent oxidation, and prevent long-term resistance drift due to sublimation of the heating element metal at high temperature.

In this embodiment, the thermopile cold junction material and the thermopile hot junction material are both coiled on the insulating support film layer, wherein the thermopile cold junction material is coiled along the gap of the thermopile hot junction material. In this embodiment, an S-shaped disc arrangement mode is adopted, and other disc arrangement modes such as a square-back shape mode can also be adopted.

In this embodiment, the thermopile cold junction material, the thermopile hot junction material disk is provided on at least 3 sides of the heating element. The thermopile cold junction material, the thermopile hot junction material and the heating element are led to the areas of the insulating support film layer except the cantilever beam structure through lead wires and are electrically connected with external equipment.

The MEMS sensing chip designed in this embodiment provides the proper temperature by applying a voltage to the heating element. The near-end carriers in the thermocouple integrated around the heating element flow to the far end and concentrate at the far end, thereby generating a thermoelectric potential. The potential value is relatively stable when the environment is unchanged. The chip designed by the utility model needs to load a catalytic combustion element above the heating element area to be used as a catalytic combustion sensor. When the target gas exists outside, the catalytic combustion element loaded on the catalytic combustion sensor catalyzes the gas to generate flameless combustion, and the temperature rises. The temperature of the near end is increased relatively fast to that of the far end, so that the thermoelectric potential is increased, and the gas sensing of the catalytic combustion sensor can be realized according to the potential change. On the contrary, in the case of the thermal conductivity sensor, since the thermal conductivity of the target gas (e.g., hydrogen gas, etc.) is high, the temperature of the heating element is lowered, the thermoelectric force is lowered, and the gas concentration can be measured according to the degree of the reduction of the thermoelectric force.

Example 2

Based on the chip provided in embodiment 1, two chips can be used in combination to form a gas sensor, which specifically comprises the following steps:

as shown in fig. 3, one of them is used as a catalytic combustion sensor (the black part on the left side in the figure is a sensitive material), and the catalytic sensitive material needs to be loaded in use. The other one acts as a thermal conductivity sensor. The two sensors are connected in a bridge mode, are matched with proper resistors to acquire signals, and can acquire signals of a single sensor. When no target gas exists in the environment, the thermal conductivity sensor chip can be used as a white element of the catalytic combustion sensor at the same time to compensate the signal drift of the catalytic combustion sensor caused by the change of the environmental temperature. The compensation specifically corrects data by measuring the response drift of the sensor when no target gas is present at different temperatures. When the target gas in the environment reaches a certain concentration (such as 0.1% -8% of combustible gas hydrogen or methane), the temperature of the catalytic combustion sensor can be raised, the thermopile generates an electric signal, at the moment, the gas can take away the heat on the surface of the thermal conductivity sensor to lower the temperature of the thermal conductivity sensor, so that an opposite electric signal is generated, and the overall output signal of the sensor can be increased due to the opposite change of the two electric signals of the bridge circuit, so that the sensitivity is improved. When the target gas in the environment reaches a high concentration (for example, the combustible gas hydrogen or methane is more than 8%), the catalytic combustion sensor may have a "double value effect", and the detection error is contrary to the former, and the thermopile of the catalytic combustion sensor can be used as a compensation element of the thermal conductivity sensor. The compensation is performed by measuring the response drift of the heat conduction sensor working at different temperatures when no target gas exists, so as to correct the data. The designed circuit is shown in fig. 4, and comprises a catalytic combustion sensor S1, wherein RS1 and RH1 are respectively a thermopile and a heating element of the catalytic combustion sensor S1, a thermal conductivity sensor S2, RS2 and RH2 are respectively a thermopile and a heating element of the thermal conductivity sensor S2, bridge matching resistors R1 and R2, an amplifier U1, MOS transistors Q1, Q2 and Q3, and a single chip microcomputer U2;

The bridge is composed of R1, R2, RS1 and RS2, the U1 amplifies bridge signals, and AD pins of the single chip microcomputer acquire the amplified bridge signals. And the GPIO pin of the singlechip controls the on and off of the Q1, the Q2 and the Q3. When the Q2 is conducted, the sensor sensitive resistors RS1 and RS2 are in a working state; when the Q2 is switched off, the sensor sensitive resistors RS1 and RS2 are in an off state, and are in an on state in a normal state. When the external concentration is low, Q1 is off, Q3 is on, and both sensors RH1 and RH2 are in an operating state. When the external combustible gas concentration is high, Q1 is conducted and Q3 is disconnected, and the sensor RH2 works independently.

The utility model combines the characteristics of the catalytic combustion and the thermal conductivity gas sensor, separates the heating and the measurement of the sensor, simultaneously meets the use requirements of the two sensors, eliminates the signal inhibition of the catalytic combustion sensor and improves the sensitivity. The utility model innovatively adopts the thermopile to detect the temperature change in the sensing process, the thermopile has very high temperature-sensitive characteristic based on the Seebeck effect (in a temperature field, the temperature of two materials is different due to different temperature sensing capacities, the hot end is called a hot junction, and the cold section is called a cold junction, and current carriers in the materials can move along the direction of reducing the temperature gradient to cause the accumulation of charges on the cold junction and generate thermoelectric force in a loop), the temperature change of 0.1 ℃ can be sensed, and the sensitivity of the sensor can be improved by adopting the thermopile for measurement. Meanwhile, the heating and the measurement are separated, so that more choices are provided for heating materials and measuring modes, for example, a tungsten wire with higher heat efficiency can be used for heating, and a thermopile is used for measuring.

Example 3

Example 1 a process for manufacturing a micro-heating chip designed for catalytic combustion or thermal conductivity sensors is as follows:

a: depositing a silicon nitride film with the thickness of 1um on a silicon substrate with a polished single surface as a supporting film layer 1 by utilizing a PECVD (plasma enhanced chemical vapor deposition) technology;

b: depositing 20nm metal titanium on the deposited silicon nitride film as a metal adhesion layer by using a magnetron sputtering technology, and then depositing 100nm metal gold, tungsten or nickel-chromium alloy and the like on the same position to serve as leads of a heater and a thermocouple;

d: using magnetron sputtering technique, 100nm thick metallic nickel is deposited, serving as the hot junction material of the thermopile. Depositing metal chromium with the thickness of 100nm by using a magnetron sputtering technology to serve as a cold junction material of the thermopile, and finishing the manufacturing of the thermocouple;

e: depositing a silicon nitride film with the thickness of 200nm on the heater and thermocouple materials as a protective layer 6 by utilizing a PECVD (plasma enhanced chemical vapor deposition) technology;

etching the silicon nitride film with the thickness of 2350nm by using RIE etching technology to form a wet etching silicon window;

and g, placing the silicon wafer into KOH solution for etching by utilizing a wet etching technology to form a cavity (namely a hollow-out area 1').

Example 4

Example 1 a process for manufacturing a micro-heating chip designed for use in a catalytic combustion or thermal conductivity sensor is as follows:

a: depositing a silicon nitride film with the thickness of 1um on a silicon substrate with a single-side polished surface by using a PECVD (plasma enhanced chemical vapor deposition) technology to be used as a supporting film layer 1;

b: depositing 20nm metal titanium as a metal adhesion layer on the deposited silicon nitride film by using a magnetron sputtering technology, and then depositing 200nm metal gold, tungsten or nickel-chromium alloy and the like on the same position to serve as leads of a heater and a thermocouple;

d: metallic nickel was deposited with a thickness of 200nm using magnetron sputtering technique to act as the hot bonding material for the thermopile. Depositing metal chromium with the thickness of 200nm by utilizing a magnetron sputtering technology to serve as a cold junction material of the thermopile, and finishing the manufacture of the thermocouple, except for the two thermocouple materials;

e: depositing a silicon nitride film with the thickness of 500nm on the heater and thermocouple materials by utilizing a PECVD technology to be used as a protective layer 6;

Example 5

a: depositing a silicon nitride film with the thickness of 2um on a silicon substrate with a polished single surface as a supporting film layer 1 by utilizing a PECVD (plasma enhanced chemical vapor deposition) technology;

b: depositing 10nm metal titanium as a metal adhesion layer on the deposited silicon nitride film by using a magnetron sputtering technology, and then depositing 100nm metal gold, tungsten or nickel-chromium alloy and the like on the same position to serve as leads of a heater and a thermocouple;

d: metal gold with a thickness of 200nm is deposited by using a magnetron sputtering technology and serves as a hot junction material of the thermopile. Depositing P-type polycrystalline silicon with the thickness of 200nm by utilizing a magnetron sputtering technology to serve as a cold junction material of the thermopile, and finishing the manufacture of the thermocouple except for the two thermocouple materials;

e: depositing a silicon nitride film with the thickness of 500nm on the heater and thermocouple materials as a protective layer 6 by utilizing a PECVD (plasma enhanced chemical vapor deposition) technology;

etching the silicon nitride film with the thickness of 2350nm by using RIE etching technology to form a window for etching silicon by a wet method;

and g, placing the silicon wafer into a KOH solution for etching by utilizing a wet etching technology to form a cavity (namely a hollow area 1').

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

The micro-heating chip of the MEMS catalytic combustion sensor is characterized by sequentially comprising a substrate (1), an insulating support film layer (2), a heating measurement layer and a protective layer (10) from bottom to top; a hollow-out area (1') is etched on the substrate (1); the insulating support film layer (2) is positioned in the hollow area (1 ') and is etched with a cantilever beam (2'); the heating measurement layer is positioned on the suspension beam (2'); the protective layer (10) covers the heating measurement layer;

the heating measurement layer comprises a heating element (3), a thermopile (100); the thermopile (100) comprises a thermopile cold junction material (8) and a thermopile hot junction material (9); the heating elements (3), the thermopile cold junction material (8) and the thermopile hot junction material (9) are arranged in a staggered mode on the same layer.
2. The MEMS catalytic combustion sensor micro-heating chip of claim 1, wherein the thermopile cold junction material (8) and the thermopile hot junction material (9) are coiled on the insulating support film layer (2), and the thermopile cold junction material (8) is coiled along the gap of the thermopile hot junction material (9).
3. The MEMS catalytic combustion sensor micro-heating chip as claimed in claim 2, wherein the thermopile cold junction material (8), the thermopile hot junction material (9) and the heating element (3) are coiled in an S-shaped trend.
4. The MEMS catalytic combustion sensor micro-heating chip according to any of claims 1 to 3, characterized in that the thermopile cold junction material (8), thermopile hot junction material (9) disk is provided on at least 3 sides of the heating element (3).
5. The MEMS catalytic combustion sensor micro-heating chip of any one of claims 1 to 3, characterized in that the thermopile cold junction material (8), the thermopile hot junction material (9), the heating element (3) are led to the insulating support film layer except the cantilever beam structure through lead wires to be electrically connected with external equipment.
6. An MEMS sensor, comprising two micro heater chips according to any one of claims 1 to 5, wherein the two micro heater chips are electrically connected; one of the micro heating chips is loaded with catalytic sensitive materials.
7. The MEMS sensor of claim 6, wherein two of the micro-heater chips are electrically connected in a bridge pattern.
8. The MEMS sensor according to claim 7, wherein the circuit of the MEMS sensor comprises a catalytic combustion sensor S1, wherein RS1 and RH1 are respectively a thermopile (100) and a heating element (3) of the catalytic combustion sensor S1, wherein the thermal conductivity sensors S2, RS2 and RH2 are respectively a thermopile (100) and a heating element (3) of the thermal conductivity sensor S2, wherein bridge matching resistors R1, R2, an amplifier U1, MOS transistors Q1, Q2, Q3, a single chip microcomputer U2;

after the R1 and the R2 are connected in series, the non-series end of R1 is connected with a VCC power supply, the non-series end of R2 is grounded, and the series common point of R1 and R2 is connected with the non-inverting input end of U1; after RS1 and RS2 are connected in series, the non-series end of RS2 is connected with a VCC power supply, the non-series end of RS1 is grounded through Q2, the series common point of RS1 and RS2 is connected with the inverting input end of U1, and the output end of U1 is connected with the AD sampling port of the singlechip U2; after RH1 and RH2 are connected in series, wherein the non-series end of RH2 is connected with a VCC power supply, the non-series end of RH1 is grounded through Q3, and the series common point of RH1 and RH2 is grounded through Q1; the grid electrodes of the Q1, the Q2 and the Q3 are respectively connected with the GPIO end of the single chip microcomputer U2.