Omnidirectional dynamic heat source pendulum type three-axis micro-machined accelerometer and its processing method

Abstract

The present application discloses an all-round dynamic heat source pendulum type three-axis micromechanical accelerometer and a processing method thereof. The accelerometer includes an upper sensitive layer, a lower sensitive layer and a cover plate. A heater is arranged at the center of the sensitive layer, which is suspended at the center of the sensitive layer by six completely symmetrical semicircular support beams, and below is a circular middle heating cavity; the lower sensitive layer contains four thermistors distributed orthogonally, and below is a rectangular middle detection cavity; the heater and the thermistor are powered by constant current; a groove is etched on the cover plate, and is tightly connected to the upper surface of the sensitive layer. The present invention can realize the detection of three-axis acceleration, with a wide measurement range, high sensitivity and fast response speed. At the same time, it has simple processing technology, compact structure, low structural stress, high reliability, easy intelligence and integration, which is in line with the development direction of sensors towards micro-miniature, comprehensive and intelligent types.

Description

Technical Field

[0001] The present invention relates to a technical field of utilizing an omnidirectional dynamic heat source pendulum to swing under the action of linear acceleration to detect acceleration attitude parameters of a moving carrier, and in particular to an omnidirectional dynamic heat source pendulum type three-axis micro-mechanical accelerometer and a processing method thereof, belonging to the field of inertial measurement. Background Art

[0002] Due to the application demand of carrier attitude measurement in various fields such as civil vehicles, railway construction, industrial production, bridge construction, earthquake research, geodetic mapping, geological and mineral exploration, marine survey, satellite communication, robotics engineering, etc., in recent years, the organic combination of sensor technology and emerging science and technology will make attitude sensors develop in the direction of miniature, comprehensive and intelligent. Micro inertial sensors made by MEMS (Micro-Electro-Mechanical-System) technology have many advantages such as mass production, low cost, small size and low power consumption. They are ideal products for medium and low precision micro inertial sensors in the future. Accelerometers are the core inertial sensors for carrier motion attitude measurement and control.

[0003] The most commonly used accelerometer is the pendulum accelerometer. Currently, there are three types of pendulum inclination sensors: liquid pendulum, solid pendulum and heat flow. The solid pendulum inclination sensor has a complex structure and high cost. The solid pendulum has a large movement amplitude and is difficult to withstand high overload or impact. The main problems of the liquid pendulum inclination sensor are that it has many structural components, long response time, and large performance changes with temperature. The heat flow accelerometer has a small sensitive mass, a simple structure, and has the characteristics of withstanding high overload, short response time, good temperature performance and low cost, and can be used in harsh environments. At present, the market has higher and higher requirements for the ability of micro accelerometers to adapt to harsh and harsh environments. Therefore, among micro accelerometers, micromechanical (MEMS) heat flow accelerometers are unique in MEMS sensors with their ultra-high impact resistance and ultra-low manufacturing cost, which is unmatched by other MEMS sensors.

[0004] The working principle of the micro-machined (MEMS) heat flow accelerometer is: a resistive heater is set in a closed cavity, and symmetrically distributed parallel detection thermistors are set around it. The heater is powered on to heat up to form a heat source that emits heat flow to the surrounding area. Since the temperature field is symmetrically distributed, the influence on the thermistors is consistent. When external wired acceleration is input, the flow direction of the hot air flow is the same as the acceleration direction, and it changes in the direction of the input acceleration, causing the temperature field of the air flow to be asymmetrically distributed, so that the temperature changes of two adjacent detection thermistors in the same direction are opposite, and the two detection thermistors produce a temperature difference. Acceleration detection can be achieved by detecting the temperature difference through a Wheatstone bridge. China Patent: Micro Silicon Bridge Thermal Convection Accelerometer (Patent Application No. 02116842.3) uses the heat flow generated by the heater to move under the action of the input wire acceleration, resulting in an asymmetric temperature field, and the asymmetric distribution of the temperature field is detected by setting symmetrical thermistors. Since the speed of the thermal airflow is very small, the asymmetric temperature field gradient caused by the airflow deflection is very small, so the unbalanced voltage output by the Wheatstone bridge composed of thermistors is small and the sensitivity of the sensor is low. In the existing solutions, although the sensitivity can be improved by increasing the power of the heater, it is limited by power consumption and there is no substantial change or improvement in sensitivity, making it difficult to break through this practical bottleneck. Summary of the invention

[0005] The purpose of the present invention is to provide an omnidirectional dynamic heat source pendulum type three-axis micro-mechanical accelerometer to solve the technical problems existing in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides an omnidirectional dynamic heat source pendulum type three-axis micromechanical accelerometer, characterized in that it comprises an upper sensitive layer, a lower sensitive layer and a cover plate, wherein:

[0008] An omnidirectional dynamic heat source swing heater is arranged at the center of the upper sensitive layer, four thermistors are arranged on the upper surface of the lower sensitive layer, and the upper sensitive layer and the lower sensitive layer are bonded together to form a sensitive layer;

[0009] The length and width directions of the accelerometer are defined as the X and Y directions respectively, and the height direction of the accelerometer is defined as the Z direction; the thermistors are orthogonally distributed in the X and Y directions with the omnidirectional dynamic heat source pendulum heater as the center; four thermistors are arranged opposite to each other in pairs, and are used to detect the acceleration of the XYZ three axes;

[0010] The omnidirectional dynamic heat source pendulum heater adopts a Hot Wheels-type sensitive structure, the center of which contains a central wheel hub with a circular mass block, which is suspended at the center of the sensitive layer through six completely symmetrical semicircular support beams; below it is a circular intermediate heating cavity;

[0011] The heater and thermistor are powered by constant current.

[0012] The cover plate is etched with a groove and is tightly connected to the upper surface of the upper sensitive layer;

[0013] The cover plate and the lower sensitive layer isolate the gas medium of the middle heating cavity and the middle detection cavity from the outside world to form a sealed working system; the height of the middle heating cavity and the middle detection cavity and the depth of the groove in the cover plate are the total cavity height z, 300μm≤z≤1000μm.

[0014] As a further technical solution, the depth of the groove of the cover plate is 2 / 3 of the height of the cover plate.

[0015] As a further technical solution, the height of the heater and the thermistor is 100 nm to 1000 nm.

[0016] As a further technical solution, the length of the thermistor is 1 / 6 to 1 / 5 of the width of the entire sensitive layer.

[0017] As a further technical solution, the heater and the thermistor are formed of a metal layer consisting of a chromium adhesion layer and a platinum layer.

[0018] A method for machining an omnidirectional dynamic heat source pendulum-type three-axis micromechanical accelerometer, the specific process flow is as follows:

[0019] Step 1: thermally oxidize a 0.5 μm thick silicon dioxide film on an N-type (100) single crystal silicon wafer;

[0020] Step 2: Photolithography to form a thermistor structure pattern on the silicon dioxide film;

[0021] Step 3: sputtering a metal layer consisting of a chromium adhesion layer and a platinum layer on the photoresist and silicon dioxide in sequence by using a magnetron sputtering process;

[0022] Step 4: Use ultrasonic stripping process to strip off the metal layer outside the thermistor structure pattern to form the thermistor structure;

[0023] Step 5: Use photolithography and wet etching process to etch away a portion of silicon dioxide;

[0024] Step 6: Use silicon etching process to form a groove with a depth of 300 μm, so that the thermistor is suspended and fixed on the lower sensitive layer through the silicon dioxide film, and the processing of the lower sensitive layer is completed;

[0025] Step 7: thermally oxidize a 0.5 μm thick silicon dioxide film on another N-type (100) single crystal silicon wafer;

[0026] Step 8: Photolithography to form a omnidirectional oscillator heater structure pattern on the silicon dioxide film;

[0027] Step nine: sputtering a metal layer consisting of a chromium adhesion layer and a platinum layer on the photoresist and silicon dioxide in sequence by using a magnetron sputtering process;

[0028] Step 10: Use an ultrasonic stripping process to strip off the metal layer outside the omnidirectional vibrator heater structure pattern to form an omnidirectional vibrator heater structure;

[0029] Step 11: Use photolithography and wet etching process to etch away a portion of silicon dioxide;

[0030] Step 12: Use silicon etching process to etch through and form a middle heating cavity, so that the omnidirectional oscillator heater is suspended and fixed on the upper sensitive layer through the silicon dioxide film, and the processing of the upper sensitive layer is completed;

[0031] Step 13: Bonding the lower sensitive layer and the upper sensitive layer through a bonding process;

[0032] Step 14: Bond the cover plate and the upper sensitive layer through a bonding process so that the upper surface of the sensitive layer is in a closed cavity, completing the processing of the sensitive element.

[0033] By adopting the above technical solution, the present invention has the following beneficial effects:

[0034] 1. This omnidirectional dynamic heat source pendulum three-axis micromechanical accelerometer inherits the advantages of MEMS thermal flow accelerometer, with small size, light weight, and easy intelligence and integration.

[0035] 2. The sensitive structure of this accelerometer is an omnidirectional dynamic heat source pendulum heater. In addition to being able to swing up and down along the Z axis perpendicular to the plane of the sensitive layer, the omnidirectional dynamic heat source pendulum sensitive structure has the freedom of inertial force (swing) at any azimuth angle on the XOY plane of the sensitive layer, and can be sensitive to input acceleration in three axes. The omnidirectional dynamic heat source pendulum heater is suspended at the center of the sensitive layer through six completely symmetrical semicircular support beams to achieve three-axis measurement of acceleration, with a wide measurement range, high sensitivity and fast response speed.

[0036] 3. The omnidirectional dynamic heat source pendulum adopts a Hot Wheels-style sensitive structure. The central wheel hub is a mass block and also a heater. The Hot Wheels-style sensitive structure adopts a sensitive structure center support, and the structural stress is small.

[0037] 4. This accelerometer adopts a hot wheel sensitive structure. The flexible structure allows the heat source with a high temperature gradient to vibrate in all directions, thereby forming a large temperature gradient at the thermistor and achieving a high sensitivity output. 5. It has a very simple structure and processing technology, extremely low cost, high reliability, and excellent anti-vibration and shock characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 A schematic diagram of a three-dimensional structure of an accelerometer provided in an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of a three-dimensional double-layer structure of a sensitive layer provided in an embodiment of the present invention;

[0041] Figure 3 A schematic diagram of a three-dimensional structure of a cover plate provided in an embodiment of the present invention;

[0042] Figure 4 A top view of an accelerometer provided by an embodiment of the present invention;

[0043] Figure 5 A top view of a lower sensitive layer provided by an embodiment of the present invention;

[0044] Figure 6 for Figure 4 AA section view;

[0045] Figure 7 A working principle diagram provided for an embodiment of the present invention;

[0046] Figure 8 A schematic diagram of an output circuit provided by an embodiment of the present invention;

[0047] Fig. 9 A flow chart of the manufacturing process of the omnidirectional dynamic heat source pendulum-type three-axis micromechanical accelerometer provided by an embodiment of the present invention;

[0048] Icon: 1-upper sensitive layer, 2-lower sensitive layer, 3-electrode, 4-middle heating cavity, 5-middle detection cavity, 6-cover plate, 7-groove, 8-all-round dynamic heat source swing heater, 9-thermistor, 10-thermistor, 11-thermistor, 12-thermistor. DETAILED DESCRIPTION

[0049] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0051] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0053] Combination Figure 1-6 As shown, this embodiment provides an omnidirectional dynamic heat source pendulum type three-axis micromechanical accelerometer, comprising an upper sensitive layer 1, a lower sensitive layer 2 and a cover plate 6, wherein:

[0054] An omnidirectional dynamic heat source swing heater 8 is arranged at the center of the upper sensitive layer 1, and four thermistors are arranged on the upper surface of the lower sensitive layer 2. The upper sensitive layer and the lower sensitive layer are bonded together to form a sensitive layer;

[0055] Define the length and width directions of the accelerometer as X and Y directions respectively, and the height direction of the sensitive layer as Z direction;

[0056] The omnidirectional dynamic heat source swing heater 8 is suspended at the center of the upper sensitive layer 1 through six completely symmetrical semicircular spokes, and below it is a circular intermediate heating chamber 4; the heater 8 can swing along the Z axis perpendicular to the sensitive layer, and can also swing along any azimuth angle in the XOY plane where the upper sensitive layer 1 is located;

[0057] The four thermistors are arranged opposite to each other in pairs, thermistor 9 and thermistor 10 are symmetrically arranged in the left-right direction perpendicular to the X-axis, and thermistor 11 and thermistor 12 are symmetrically arranged in the up-down direction perpendicular to the Y-axis;

[0058] The heater and thermistor are powered by constant current.

[0059] The cover plate 6 is etched with a groove 7 and is tightly connected to the upper surface of the upper sensitive layer 1 .

[0060] Combination Figure 7 and Figure 8 As shown, in this embodiment, as a further technical solution, a constant current is passed through the resistive omnidirectional dynamic heat source pendulum heater 8, and the resistive heater generates Joule heat when it is energized, releases heat to the surrounding gas, and performs heat diffusion, forming a heat flow around the omnidirectional dynamic heat source pendulum heater. x1 (thermistor 9) and T x2 (thermistor 10) or T x3 (thermistor 11) and T x4 (Thermistor 12) constitutes the two bridge arms of the Wheatstone bridge and participates in the deflection of the sensitive airflow. When the linear acceleration along the X-axis or Y-axis is input, the dynamic heat source pendulum moves in the same direction as the acceleration under the action of the acceleration, resulting in an asymmetric distribution of the thermal airflow. Two relative thermistors T in the same direction x1 (thermistor 9) and T x2 (thermistor 10) or T y1 (thermistor 11) and T y2 The temperature of thermistor 12 changes in the opposite direction. The temperature of the thermistor in the direction of the moving heat source is higher than that of the thermistor parallel to it, and a temperature difference is generated between the two thermistors. x1 and T x2 (thermistor 9 and thermistor 10) or T y1 and T y2 Thermistors 11 and 12 are two arms of the Wisden bridge. The temperature difference caused by the input line acceleration is converted into a change in the resistance of the bridge arm, thereby causing an unbalanced bridge voltage V proportional to the input acceleration. X or V Y . According to the output voltage V X or V Y The linear acceleration of the X-axis or Y-axis can be calculated, thereby being sensitive to the acceleration in the X or Y direction.

[0061] When there is a linear acceleration input perpendicular to the Z-axis, the omnidirectional dynamic heat source pendulum moves in the same direction as the acceleration under the action of the acceleration. The heat flux emitted by the omnidirectional dynamic heat source pendulum heater will be offset along the Z-axis. When the acceleration points to the thermistor input along the Z-axis, the dynamic heat source pendulum heater approaches the four thermistors, and the resistance of the four thermistors increases. The sum of the voltages across the four thermistors is V ZWhen the acceleration is input along the Z axis away from the thermistor, the heat source moves away from the four thermistors, the resistance of the four thermistors decreases, and the sum of the voltages across the four thermistors V Z Therefore, V Z The magnitude of the acceleration is detected by V Z The direction of acceleration is detected by the increase or decrease of the acceleration, thereby being sensitive to the acceleration in the Z-axis direction.

[0062] In this embodiment, as a further technical solution, the cover plate 6 and the lower sensitive layer 2 isolate the gas medium of the intermediate heating chamber 4 and the intermediate detection chamber 5 from the outside world to form a sealed working system; the height of the intermediate heating chamber 4 and the intermediate detection chamber 5 and the depth of the groove 7 in the upper sealing layer are the total cavity height z, 300μm≤z≤1000μm, and the total cavity height in this embodiment is on the order of hundreds of microns, which can effectively suppress the natural convection movement of the gas flow in the cavity.

[0063] In this embodiment, as a further technical solution, the depth of the groove 7 is 2 / 3 of the height of the cover plate 6 .

[0064] In this embodiment, as a further technical solution, in order to increase the depth of the cover plate groove to increase the space for gas flow, the height of the heater on the upper sensitive layer and the thermistor on the surface of the lower sensitive layer is 100nm to 1000nm.

[0065] In this embodiment, as a further technical solution, in order to form a thin film resistor with a small change in resistance with temperature and a more stable and reliable resistance, the length of the thermistor is 1 / 6 to 1 / 5 of the width of the entire sensitive layer.

[0066] In this embodiment, as a further technical solution, the heater and the thermistor are both composed of a metal layer consisting of a chromium adhesion layer and a platinum layer.

[0067] Combination Fig. 9 As shown, the specific process flow of the dynamic heat source pendulum type three-axis micromechanical accelerometer disclosed in the present invention is as follows:

[0068] Step (a): thermally oxidize a 0.5 μm thick silicon dioxide film on an N-type (100) single crystal silicon wafer.

[0069] Step (b): Photolithography is performed on the silicon dioxide film to form a full-range oscillator heater and a thermistor structure pattern.

[0070] Step (c): sputtering a metal layer consisting of a chromium adhesion layer and a platinum layer on the photoresist and silicon dioxide in sequence by using a magnetron sputtering process.

[0071] Step (d): using an ultrasonic stripping process to strip off the metal layer outside the omnidirectional vibrator heater and thermistor structure pattern to form an omnidirectional vibrator heater and thermistor structure.

[0072] Step (e): using photolithography and wet etching processes to etch away a portion of the silicon dioxide.

[0073] Step (f): A silicon etching process is used to form a groove with a depth of 300 μm, so that the omnidirectional oscillator heater and thermistor are suspended and fixed on the sensitive layer through the silicon dioxide film, thereby completing the processing of the sensitive layer.

[0074] Step (g): thermally oxidize a 0.5 μm thick silicon dioxide film on another N-type (100) single crystal silicon wafer.

[0075] Step (h): Photolithography is performed on the silicon dioxide film to form an omni-directional oscillator heater structure.

[0076] Step (i): sputtering a metal layer consisting of a chromium adhesion layer and a platinum layer on the photoresist and silicon dioxide in sequence by a magnetron sputtering process.

[0077] Step (j): using an ultrasonic stripping process to strip off the metal layer outside the omnidirectional vibrator heater structure pattern to form an omnidirectional vibrator heater structure.

[0078] Step (k): using photolithography and wet etching processes to etch away a portion of the silicon dioxide.

[0079] Step (1): using a silicon etching process to etch through and form an intermediate heating cavity, so that the omnidirectional oscillator heater is suspended and fixed on the upper sensitive layer through the silicon dioxide film, thereby completing the processing of the upper sensitive layer.

[0080] Step (m): bonding the lower sensitive layer and the upper sensitive layer by a bonding process.

[0081] Step (n): The cover plate and the upper sensitive layer are bonded together by a bonding process so that the upper surface of the sensitive layer is in a closed cavity, thereby completing the processing of the sensitive element.

[0082] In summary, the present invention breaks the inherent pattern of previous research on heat flow accelerometers, and proposes an omnidirectional dynamic heat source pendulum type three-axis micromechanical accelerometer, which allows the heater with a high temperature gradient to move, so that it is deflected by the inertial force to form a large temperature gradient at the thermistor, thereby achieving a high sensitivity output. The sensitive structure of this accelerometer is an omnidirectional dynamic heat source pendulum heater. In addition to being able to swing up and down along the Z axis perpendicular to the plane of the sensitive layer, the omnidirectional dynamic heat source pendulum sensitive structure has the degree of freedom of inertial force at any azimuth angle on the XOY plane of the sensitive layer, and can be sensitive to the input acceleration of the three axes. The omnidirectional dynamic heat source pendulum heater is suspended at the center of the sensitive layer through six completely symmetrical semicircular support beams to achieve three-axis measurement of acceleration, with a wide measurement range, high sensitivity and fast response speed. The present invention inherits the advantages of MEMS sensors, and has the characteristics of compact structure, small size, light weight, low cost, easy intelligence and integration, etc., which is in line with the development direction of sensors towards micro-miniature, comprehensive and intelligent types. At the same time, it has simple processing technology, extremely low cost, high reliability, and excellent anti-vibration and impact properties.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An omnidirectional dynamic heat source pendulum three-axis micromechanical accelerometer, characterized in that: It includes an upper sensitive layer, a lower sensitive layer and a cover plate, wherein: An omnidirectional dynamic heat source swing heater is arranged at the center of the upper sensitive layer, four thermistors are arranged on the upper surface of the lower sensitive layer, and the upper sensitive layer and the lower sensitive layer are bonded together to form a sensitive layer; The length and width directions of the accelerometer are defined as the X and Y directions respectively, and the height direction of the accelerometer is defined as the Z direction; the thermistors are orthogonally distributed in the X and Y directions with the omnidirectional dynamic heat source pendulum heater as the center; four thermistors are arranged opposite to each other in pairs to detect the acceleration of three axes; The omnidirectional dynamic heat source pendulum heater adopts a Hot Wheels-type sensitive structure, the center of which contains a central wheel hub with a circular mass block, which is suspended at the center of the sensitive layer through six completely symmetrical semicircular support beams; below it is a circular intermediate heating cavity; The omnidirectional dynamic heat source swing heater can swing along the Z axis perpendicular to the sensitive layer, and can also swing along any azimuth angle in the XOY plane where the sensitive layer is located; The heater and thermistor are powered by constant current. The cover plate is etched with a groove and is tightly connected to the upper surface of the upper sensitive layer; The cover plate and the lower sensitive layer isolate the gas medium in the middle heating cavity and the middle detection cavity from the outside world to form a sealed working system; the height of the middle heating cavity and the middle detection cavity and the depth of the groove in the cover plate are the total cavity height z, 300μm≤z≤1000μm; The depth of the groove of the cover plate is 2 / 3 of the height of the cover plate; The height of the omnidirectional dynamic heat source pendulum heater and the thermistor is 100nm to 1000nm.

2. The omnidirectional dynamic heat source pendulum three-axis micromechanical accelerometer according to claim 1 is characterized in that: The length of the thermistor is consistent, being 1 / 6 to 1 / 5 of the width of the entire lower sensitive layer.

3. The omnidirectional dynamic heat source pendulum three-axis micromechanical accelerometer according to claim 1, characterized in that: The omnidirectional dynamic heat source swing heater and the thermistor are both composed of a metal layer consisting of a chromium adhesion layer and a platinum layer.

4. A method for processing the omnidirectional dynamic heat source pendulum type three-axis micromechanical accelerometer according to any one of claims 1 to 3, characterized in that: The specific process is as follows: Step 1: Thermally oxidize a 0.5µm thick silicon dioxide film on an N-type (100) single crystal silicon wafer; Step 2: Photolithography to form a thermistor structure pattern on the silicon dioxide film; Step 3: sputtering a metal layer consisting of a chromium adhesion layer and a platinum layer on the photoresist and silicon dioxide in sequence by using a magnetron sputtering process; Step 4: Use ultrasonic stripping process to strip off the metal layer outside the thermistor structure pattern to form the thermistor structure; Step 5: Use photolithography and wet etching process to etch away a portion of silicon dioxide; Step 6: Use silicon etching process to form a groove with a depth of 300µm, so that the thermistor is suspended and fixed on the lower sensitive layer through the silicon dioxide film, and the processing of the lower sensitive layer is completed; Step 7: Thermally oxidize a 0.5µm thick silicon dioxide film on another N-type (100) single crystal silicon wafer; Step 8: Photolithography to form a omnidirectional oscillator heater structure pattern on the silicon dioxide film; Step nine: sputtering a metal layer consisting of a chromium adhesion layer and a platinum layer on the photoresist and silicon dioxide in sequence by using a magnetron sputtering process; Step 10: Use an ultrasonic stripping process to strip off the metal layer outside the omnidirectional vibrator heater structure pattern to form an omnidirectional vibrator heater structure; Step 11: Use photolithography and wet etching process to etch away a portion of silicon dioxide; Step 12: Use silicon etching process to etch through and form a middle heating cavity, so that the omnidirectional oscillator heater is suspended and fixed on the upper sensitive layer through the silicon dioxide film, and the processing of the upper sensitive layer is completed; Step 13: Bonding the lower sensitive layer and the upper sensitive layer through a bonding process; Step 14: Bond the cover plate and the upper sensitive layer through a bonding process so that the upper surface of the sensitive layer is in a closed cavity, completing the processing of the sensitive element.

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