A low-temperature-drift MEMS resonant pressure sensor sensitive chip and a preparation method thereof

Abstract

The application belongs to the field of microcomputer electromechanical sensors, and particularly relates to a low-temperature-drift MEMS resonant pressure sensor sensitive chip and a preparation method thereof; comprising: a cap layer, a resonant layer, a pressure sensing layer and an isolation base which are sequentially bonded from top to bottom; the cap layer is provided with electrode through holes and a vacuum cavity groove, and a getter is sputtered in the vacuum cavity groove; the resonant layer is provided with two Si-SiO2 composite resonators and multiple lead frames, and each lead frame is provided with a metal electrode; the metal electrodes are equal in number to the electrode through holes of the cap layer, and the metal electrodes are located directly below the electrode through holes; the pressure sensing layer is provided with two groups of silicon islands on the front surface and three rectangular sensitive membranes of the same size on the back surface; and the isolation base is a glass table; the application greatly improves the output sensitivity of the sensor, reduces the complexity of chip processing, and reduces the introduction of additional stress and materials.

Description

Technical Field

[0001] The present invention belongs to the field of micro-electromechanical sensors, and in particular relates to a low-temperature drift MEMS resonant pressure sensor sensitive chip and a preparation method thereof. Background Art

[0002] With the development of microelectromechanical systems (MEMS) technology, MEMS silicon resonant pressure sensors, based on the working principle of mechanical vibration, have the characteristics of high precision and high stability. At the same time, the output is a resonant frequency signal, which does not require analog-to-digital conversion and has a high signal-to-noise ratio and excellent anti-interference capabilities. They are widely used in precision measurement fields such as aerospace, industrial control, and meteorological measurement. The temperature drift of MEMS silicon resonant pressure sensors is a major factor restricting the accuracy of the sensor. The current mainstream temperature compensation structure uses stress isolation, multi-resonator differential output, and all-silicon process methods to effectively reduce the temperature drift caused by thermal stress. However, less attention has been paid to the sensitivity temperature drift caused by the Young's modulus of silicon material. In addition, most resonant pressure sensors using a multi-resonator differential output structure have multiple resonators arranged on the same sensitive membrane, which has the problem of large sensitive membrane area and low sensitivity.

[0003] To address the temperature drift mechanism of silicon resonant pressure sensors, a new resonant pressure sensor sensitive chip is urgently needed. This chip can compensate for and optimize the sensor temperature drift caused by thermal stress and Young's modulus drift. At the same time, an improved piezoresistive output detection structure can reduce the stress caused by the additional materials and steps introduced in the complex process. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention proposes a low-temperature drift MEMS resonant pressure sensor sensitive chip and a preparation method thereof, comprising:

[0005] The cap layer, the resonant layer, the pressure-sensing layer and the isolation base are bonded and connected in sequence from top to bottom;

[0006] The cap layer is provided with an electrode through hole and a vacuum cavity groove, and a getter is sputtered in the vacuum cavity groove;

[0007] The resonant layer is provided with two Si-SiO2 composite resonators and a plurality of lead plates, each lead plate is provided with a metal electrode; the number of the metal electrodes is equal to the number of the electrode through holes in the cap layer and the metal electrodes are located directly below the electrode through holes;

[0008] The front side of the pressure-sensitive layer is provided with two groups of silicon islands, and the back side is provided with three rectangular sensitive films of the same size;

[0009] The isolation base is a glass table.

[0010] Preferably, the Si-SiO2 composite resonator is formed after the resonator thermally oxidizes and grows an oxide layer, and the resonator includes a symmetrical X-shaped torsional piezoresistive structure, a resonant beam, a vibration pickup beam, hollow comb teeth, fixed comb teeth, a connecting beam and a movable anchor point; all the resonant beams, vibration pickup beams and the middle parts of the hollow comb teeth are connected by a connecting beam, and the two ends of each resonant beam are respectively connected to the suspended torsion structure on the movable anchor point, and the two ends of each vibration pickup beam are respectively connected to two symmetrical X-shaped torsional piezoresistive structures; the hollow comb teeth cooperate with the fixed comb teeth on both sides of the resonator to form a driving capacitor.

[0011] Furthermore, two groups of silicon islands are arranged in the area where the horizontal displacement of the sensitive membrane is the largest under pressure. The center of one rectangular sensitive membrane is located directly below one Si-SiO2 composite resonator, and the centers of the other two rectangular sensitive membranes are located directly below another Si-SiO2 composite resonator.

[0012] Preferably, the lead pads on the resonant layer are divided into a DC bias lead pad, an AC drive lead pad and an output detection lead pad.

[0013] Preferably, a groove is provided on the glass platform, and the groove is in the shape of a cross, so that four rectangular glass protrusions are formed on the glass platform.

[0014] A method for preparing a low-temperature drift MEMS resonant pressure sensor sensitive chip, comprising:

[0015] S1: A clean double-sided polished SOI silicon wafer is used to prepare the silicon island of the pressure-sensitive layer;

[0016] S2: Prepare a clean double-sided polished SOI silicon wafer as the resonance layer substrate, and bond the silicon island surface of the pressure-sensitive layer to the resonance layer substrate;

[0017] S3: preparing a Si-SiO2 composite resonator and a lead plate of the resonance layer on the resonance layer substrate to obtain the resonance layer;

[0018] S4: using a double-polished single-crystal silicon wafer to prepare a capping layer, and bonding the capping layer to the resonant layer by silicon-silicon low-temperature vacuum bonding;

[0019] S5: preparing a rectangular sensitive film on the reverse side of the pressure-sensitive layer;

[0020] S6: preparing an isolation base, and anodically bonding the isolation base to the reverse side of the pressure-sensitive layer;

[0021] S7: Etching silicon oxide on the resonance layer through the electrode through-hole of the cap layer, and sputtering metal through the electrode through-hole of the cap layer to form an ohmic contact on the resonance layer, thereby completing the preparation of the metal electrode.

[0022] Furthermore, the process of preparing the silicon island includes:

[0023] S11: Prepare a clean double-sided polished SOI silicon wafer;

[0024] S12: thermally oxidizing and growing silicon oxide on a double-sided polished SOI silicon wafer as an etching mask;

[0025] S13: Photolithographically etching silicon oxide on the surface of the SOI silicon wafer device layer to form a silicon island pattern etching mask;

[0026] S14: performing DRIE etching on the device layer to form a silicon island.

[0027] Furthermore, the process of preparing the Si-SiO2 composite resonator and the lead plate includes:

[0028] S31: Using a CMP process to thin the substrate layer of the SOI silicon wafer to 50 μm, and then using KOH or TMAH wet etching to etch the remaining silicon to expose the oxide layer of the SOI silicon wafer;

[0029] S32: Photolithographically etching silicon oxide to obtain a resonant layer device pattern etching mask;

[0030] S33: DRIE etches the device layer of the SOI silicon wafer to obtain the resonator and lead pad structure;

[0031] S34: Dry etching to remove the oxide layer on the surface of the resonator layer, completing the preparation of the resonator-silicon island integrated structure;

[0032] S35: thermally oxidizing and growing an oxide layer on the surface of the resonator to form a Si-SiO2 composite resonator.

[0033] Furthermore, the process of preparing the capping layer includes:

[0034] S41: performing laser drilling on the single crystal silicon double polished wafer to obtain electrode through holes;

[0035] S42: thermally oxidizing and growing silicon oxide on a single crystal silicon double-polished wafer, and photolithographically etching the silicon oxide to obtain a vacuum cavity groove pattern etching mask;

[0036] S43: RIE etching of vacuum cavity grooves;

[0037] S44: magnetron sputtering of Ti getter in the vacuum chamber groove.

[0038] The beneficial effects of the present invention are:

[0039] (1) The present invention grows silicon oxide on the surface of a single-crystal silicon resonator to form a Si-SiO2 composite resonant beam. The positive frequency temperature coefficient of silicon oxide offsets the negative frequency temperature coefficient of single-crystal silicon, thereby compensating for the temperature drift of the Young's modulus of the silicon material and significantly reducing the temperature drift of the sensor sensitivity.

[0040] (2) The design of an X-shaped torsional piezoresistive structure eliminates the need for additional piezoresistors and corresponding metal wiring, reducing chip processing complexity and the introduction of additional stress and materials.

[0041] (3) The dual resonator anchor points in the present invention are both located in the area where the horizontal displacement of the sensitive film is maximum under the action of pressure, differentially offsetting the drift caused by thermal stress while maximizing the stress transfer effect of the sensitive film-silicon island. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the overall structure of the low-temperature drift MEMS resonant pressure sensor sensitive chip of the present invention;

[0043] Figure 2 Schematic diagram of the front and back structures of the capping layer in the present invention;

[0044] Figure 3 Schematic diagram of the resonance layer structure in the present invention;

[0045] Figure 4 Schematic diagram of the front and back structures of the pressure-sensitive layer in the present invention;

[0046] Figure 5 Schematic diagram of the isolation base structure of the present invention;

[0047] Figure 6 This is a schematic diagram of the silicon island process flow in the present invention;

[0048] Figure 7 Schematic diagram of the resonance layer process flow in the present invention;

[0049] Figure 8 This is a schematic diagram of the process flow of the capping layer and the sensitive membrane in the present invention;

[0050] Figure 9 It is a schematic diagram of the isolation base process flow in the present invention. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention 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 making creative efforts are within the scope of protection of the present invention.

[0052] The present invention proposes a low-temperature drift MEMS resonant pressure sensor sensitive chip and a preparation method thereof, such as Figure 1 As shown, the chip includes: a cap layer (Layer 1), a resonance layer (Layer 2), a pressure-sensing layer (Layer 3) and an isolation base (Layer 4) bonded together in sequence from top to bottom.

[0053] like Figure 2 As shown, the cap layer is provided with an electrode through-hole (1) and a vacuum cavity groove (2), and a getter (3) is sputtered in the vacuum cavity groove. The cap layer (Layer 1) uses a single crystal silicon wafer laser to process the electrode through-hole (1) and RIE to etch the vacuum cavity groove (2), and the getter (3) is sputtered in the groove. After bonding with the resonant layer (Layer 2), a vacuum cavity is formed.

[0054] like Figure 3 As shown, two Si-SiO2 composite resonators (4) and a plurality of lead disks (5, 6, 7) are provided on the resonance layer, and each lead disk is provided with a metal electrode (8); the number of the metal electrodes is equal to the number of the electrode through holes in the cap layer, and the metal electrodes are located directly below the electrode through holes.

[0055] The Si-SiO2 composite resonator is formed after the resonator is thermally oxidized to grow an oxide layer. The resonator comprises a symmetrical X-shaped torsional piezoresistive structure (10), a resonant beam (11), a vibration pickup beam (12), hollow comb teeth (13), fixed comb teeth (22), a connecting beam (14) and a movable anchor point (9); all the resonant beams, vibration pickup beams and the middle parts of the hollow comb teeth are connected by a connecting beam, the two ends of each resonant beam are respectively connected to the suspended torsional structure (21) on the movable anchor point, and the two ends of each vibration pickup beam are respectively connected to two symmetrical X-shaped torsional piezoresistive structures; the hollow comb teeth cooperate with the fixed comb teeth on both sides of the resonator to form a driving capacitor.

[0056] The resonator is the core structure of the sensitive chip of the MEMS resonant pressure sensor. Based on the principle of electrostatic excitation / piezoresistive detection, the present invention designs a double-ended fixed-support resonant beam structure. The structure mainly consists of two groups of beams, namely the resonant beam and the vibration pickup beam. The two groups of beams are connected together by a connecting beam in the middle. The two ends of the resonant beam are connected to the suspended torsion structure on the movable anchor point, and the two ends of the vibration pickup beam are connected to the X-shaped torsion piezoresistive structure in the fixed area of ​​the chip. On the outside of the beam is a driving comb structure. The driving comb teeth (hollow comb teeth) cooperate with the fixed comb teeth to form a driving capacitor. A layer of silicon oxide grows on the surface of the single crystal silicon of the resonator to form a Si-SiO2 composite resonant beam. The positive frequency temperature coefficient of silicon oxide offsets the negative frequency temperature coefficient of single crystal silicon, thereby compensating for the temperature drift of the Young's modulus of the silicon material, which can greatly reduce the temperature drift of the sensor sensitivity.

[0057] Conventional piezoresistive detection methods use ion implantation to prepare diffused piezoresistors on the resonant beam or the pickup beam, and output resistance changes through metal wiring. The present invention directly uses heavily doped wafers to etch out long strip structures as piezoresistors to form an X-shaped torsional piezoresistive structure. When the pickup beam vibrates with the resonant beam, the end connected to the X-shaped piezoresistive structure drives the X-shaped piezoresistive structure to torsion, and the total resistance of the series-parallel network composed of the X-shaped piezoresistive structure produces alternations of the same frequency with vibration. In addition, the X-shaped torsional piezoresistive structure is located in the fixed area of ​​the chip, and the connection of the pickup beam to it effectively reduces the out-of-plane displacement of the drive comb teeth under pressure, thereby improving the stability of the drive.

[0058] When the width of the drive comb connection block is insufficient, the low lateral stiffness can easily cause the movable comb teeth to vibrate synchronously during resonator vibration, affecting drive stability. Therefore, the present invention designs a hollow comb structure, increasing the width of the comb connection block to improve vibration stiffness and prevent the comb teeth from deforming with the vibration of the resonant beam. Furthermore, an overly large comb connection block results in an excessively large effective mass of the resonator's vibration, significantly reducing the natural frequency and causing a decrease in sensor sensitivity. Therefore, designing it as a hollow structure can reduce the effective mass while ensuring vibration stiffness, increasing the resonant frequency of the resonator and improving sensor sensitivity.

[0059] The lead pads on the resonant layer are divided into a DC bias lead pad, an AC drive lead pad, and an output detection lead pad. The lead pads are formed by etching.

[0060] like Figure 4 As shown, two groups of silicon islands (15, 16) are provided on the front side of the pressure-sensing layer, and three rectangular sensitive films (17, 18, 19) of the same size are etched on the back side by DRIE; the two groups of silicon islands are arranged in the area where the horizontal displacement of the sensitive film is the largest under the action of pressure, the center of one rectangular sensitive film is located directly below one Si-SiO2 composite resonator, and the centers of the other two rectangular sensitive films are located directly below another Si-SiO2 composite resonator.

[0061] The present invention's three-membrane, dual-resonator differential output structure employs two resonators made of identical materials and structural parameters: one placed in the center of a sensitive membrane and the other between two outer ones. Under pressure, the two resonant beams generate tensile and compressive stresses, respectively, increasing and decreasing the resonant frequency. While the temperature-induced drift is identical, the difference in output frequency offsets the drift caused by thermal stress, simultaneously improving sensor sensitivity. The anchor points of both resonators are located in the area of ​​maximum horizontal displacement of the sensitive membrane, maximizing the stress transfer effect between the sensitive membrane and the silicon island. The rectangular design of the sensitive membrane significantly increases the horizontal displacement of the sensitive membrane compared to a square membrane.

[0062] Preferably, Figure 5As shown, the isolation base (20) is a glass table. Specifically, the isolation base (Layer 4) is borosilicate glass that is grinded and grooved by a thick glass grinding wheel to form four rectangular glass protrusions (20), which are anodically bonded to the pressure-sensitive layer to isolate assembly stress.

[0063] The working principle of the low-temperature drift MEMS resonant pressure sensor sensitive chip designed by the present invention is:

[0064] The present invention employs an electrostatic drive / piezoresistive detection method. Antiphase AC voltages are applied to the comb capacitors on either side of the resonator, generating alternating electrostatic forces that drive the resonator to vibrate in the same direction within the plane. The vibration of the resonant beam causes the pickup beam to twist around the center of the X-shaped torsional piezoresistive detection structure, causing the resistance of the piezoresistive detection structure to change at the same frequency. When pressure acts on the sensitive membrane, the silicon island converts the membrane's deformation into axial stress on the resonant beam, thereby altering the beam's stiffness and causing its natural frequency to change linearly. Pressure measurement is achieved by measuring the alternating frequency of the output resistance during resonance.

[0065] The present invention adopts an electrostatic drive / piezoresistive detection method during operation, applies a DC bias voltage to a DC bias lead disk (5), connects an external resistor to an output detection lead disk (7) and then to ground, and the potential of the hollow comb teeth (13) is suspended, so there is no voltage drop on each comb tooth and the potential is the same. Two AC drive lead disks (6) are applied with reversed-phase AC voltages, so that the comb tooth capacitors on both sides of the resonator generate alternating electrostatic forces to drive the resonator to vibrate in the same direction in the plane. The vibration of the resonant beam (11) drives the vibration pickup beam to twist around the center point of the X-shaped torsion type piezoresistive structure (10), so that the resistance value of the piezoresistive detection structure changes at the same frequency. The pressure acting on the sensitive film (17) converts the deformation of the sensitive film into tensile stress on the resonant beam through the silicon island, thereby increasing the resonator frequency. The pressure acting on the sensitive films (18, 19) converts the deformation of the sensitive film into compressive stress on the resonant beam through the silicon island, thereby reducing the resonator frequency. Two completely identical resonators are completely affected by thermal stress. The difference in the frequencies of the two resonators offsets the influence of the thermal stress and increases the output sensitivity.

[0066] The present invention also provides a method for preparing a low-temperature drift MEMS resonant pressure sensor sensitive chip, comprising:

[0067] S1: A clean double-sided polished SOI silicon wafer is used to prepare the silicon island of the pressure-sensitive layer.

[0068] like Figure 6 As shown, the process of preparing silicon islands includes:

[0069] S11: Prepare a clean double-sided polished SOI silicon wafer.

[0070] Prepare double-sided polished SOI silicon wafers and perform standard RCA cleaning. The SOI silicon wafer is divided into three layers: device layer, oxide layer, and substrate layer.

[0071] S12: thermally oxidizing and growing silicon oxide on a double-sided polished SOI silicon wafer as an etching mask;

[0072] S13: Photolithographically etching silicon oxide on the surface of the device layer to obtain a silicon island pattern etching mask;

[0073] S14: performing DRIE etching on the device layer to form a silicon island.

[0074] S2: Prepare a clean double-sided polished SOI silicon wafer as the resonance layer substrate, and bond the silicon island surface of the pressure-sensitive layer to the resonance layer substrate.

[0075] like Figure 7 As shown, the resonant layer is prepared using a double-sided polished SOI silicon wafer. The thickness of the device layer of the SOI silicon wafer used is the designed thickness of the resonant layer device. Standard RCA cleaning is performed to serve as the resonant layer substrate. The silicon island surface of the pressure-sensitive layer and the resonant layer substrate are silicon-silicon bonded.

[0076] S3: preparing a Si-SiO2 composite resonator and a lead plate of the resonance layer on the resonance layer substrate to obtain the resonance layer.

[0077] like Figure 7 As shown, the process of preparing Si-SiO2 composite resonator and lead disk includes:

[0078] S31: Use CMP process to thin the substrate layer of the SOI silicon wafer to 50μm, and then use KOH or TMAH wet etching to etch the remaining silicon to expose the oxide layer of the SOI silicon wafer.

[0079] S32: Photolithographically etching silicon oxide to obtain a resonant layer device pattern etching mask;

[0080] S33: DRIE etches the device layer of the SOI silicon wafer to obtain the resonator and lead pad structure;

[0081] The lead pads etched around the resonator include a DC bias lead pad, an AC drive lead pad, and an output detection lead pad.

[0082] S34: Dry etching to remove the oxide layer on the surface of the resonator layer, completing the preparation of the resonator-silicon island integrated structure;

[0083] S35: thermally oxidizing and growing an oxide layer on the surface of the resonator to form a Si-SiO2 composite resonator.

[0084] S4: Use a double-polished single-crystal silicon wafer to prepare a capping layer, and bond the capping layer to the resonant layer silicon-silicon low-temperature vacuum bonding.

[0085] like Figure 8 As shown, the process of preparing the capping layer includes:

[0086] S41: performing laser drilling on the single crystal silicon double polished wafer to obtain electrode through holes;

[0087] S42: thermally oxidizing and growing silicon oxide on a single crystal silicon double-polished wafer, and photolithographically etching the silicon oxide to obtain a vacuum cavity groove pattern etching mask;

[0088] S43: RIE etching of vacuum cavity grooves;

[0089] S44: magnetron sputtering of Ti getter in the vacuum chamber groove.

[0090] S5: preparing a rectangular sensitive film on the reverse side of the pressure-sensitive layer.

[0091] like Figure 8 As shown, in the pressure-sensitive layer, the bottom silicon oxide is etched to obtain a sensitive film pattern etching mask. Then, the silicon of the pressure-sensitive layer is dry-etched to the silicon oxide self-stop layer. Finally, dry etching is used to remove the silicon oxide at the bottom of the pressure-sensitive layer.

[0092] S6: preparing an isolation base, and anodically bonding the isolation base to the reverse side of the pressure-sensitive layer.

[0093] like Figure 9 As shown, the process of preparing the isolation base includes: preparing a thick glass table, and using a grinding wheel to grind and groove it, the groove is in the shape of a cross, and four rectangular bosses are prepared on the glass table.

[0094] S7: Etching silicon oxide on the resonance layer through the electrode through-hole of the cap layer, and sputtering metal through the electrode through-hole of the cap layer to form an ohmic contact on the resonance layer, thereby completing the preparation of the metal electrode.

[0095] like Figure 9 As shown, the silicon oxide on the resonance layer in the electrode through hole of the cap layer is etched, and a metal is evaporated or sputtered on the resonance layer using a hard mask to form an ohmic contact, thereby completing the preparation of the metal electrode.

[0096] After the metal electrode is prepared, a prepared low-temperature drift MEMS resonant pressure sensor sensitive chip is obtained.

[0097] In summary, the present invention addresses the temperature drift caused by the Young's modulus and thermal stress of the MEMS resonant pressure sensor, as well as the low sensitivity of existing thermal stress compensation methods, and designs a low-temperature drift resonant pressure sensor sensitive chip based on a Si-SiO2 composite resonator and a three-membrane-dual resonator structure. Compared with existing MEMS resonant pressure sensors, the present invention uses a Si-SiO2 composite resonator to compensate for the temperature drift of the Young's modulus of silicon materials, which can significantly reduce the sensitivity temperature drift of the sensor. At the same time, the three-membrane-dual resonator structure is designed to separate two identical resonators and place them on the maximum displacement area of ​​different sensitive diaphragms, maximizing the deformation of the sensitive membrane and greatly improving the sensor output sensitivity under the same size conditions. At the same time, the present invention designs an X-shaped torsional piezoresistive structure, which does not require additional piezoresistors and corresponding metal wiring, reduces the complexity of chip processing, and reduces the introduction of additional stress and materials. In addition, the present invention uses a silicon cap layer to bond with the resonant layer to form a vacuum cavity, seals the resonator in a vacuum environment, improves the resonator quality factor, and bonds an isolation base to reduce assembly stress.

[0098] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation plans of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A low-temperature drift MEMS resonant pressure sensor sensitive chip, characterized in that: include: The cap layer, the resonant layer, the pressure-sensing layer and the isolation base are bonded and connected in sequence from top to bottom; The cap layer is provided with an electrode through hole and a vacuum cavity groove, and a getter is sputtered in the vacuum cavity groove; The resonant layer is provided with two Si-SiO2 composite resonators and a plurality of lead disks, and each lead disk is provided with a metal electrode; the number of the metal electrodes is equal to the number of the electrode through-holes in the cap layer, and the metal electrodes are located directly below the electrode through-holes; the Si-SiO2 composite resonator is formed after the resonator is thermally oxidized to grow an oxide layer, and the resonator includes a symmetrical X-shaped torsional piezoresistive structure, a resonant beam, a vibration pickup beam, hollow comb teeth, fixed comb teeth, a connecting beam and a movable anchor point; all the resonant beams, vibration pickup beams and the middle parts of the hollow comb teeth are connected by a connecting beam, and the two ends of each resonant beam are respectively connected to the suspended torsion structure on the movable anchor point, and the two ends of each vibration pickup beam are respectively connected to the two symmetrical X-shaped torsional piezoresistive structures; the hollow comb teeth cooperate with the fixed comb teeth on both sides of the resonator to form a driving capacitor; The front side of the pressure-sensitive layer is provided with two groups of silicon islands, and the back side is provided with three rectangular sensitive films of the same size; The isolation base is a glass table.

2. The low-temperature drift MEMS resonant pressure sensor sensitive chip according to claim 1, characterized in that: Two groups of silicon islands are set in the area where the horizontal displacement of the sensitive membrane is the largest under pressure. The center of one rectangular sensitive membrane is located directly below one Si-SiO2 composite resonator, and the centers of the other two rectangular sensitive membranes are located directly below another Si-SiO2 composite resonator.

3. The low-temperature drift MEMS resonant pressure sensor sensitive chip according to claim 1, characterized in that: The lead pads on the resonant layer are divided into a DC bias lead pad, an AC drive lead pad and an output detection lead pad.

4. The low-temperature drift MEMS resonant pressure sensor sensitive chip according to claim 1, characterized in that: The glass platform is provided with a groove in a cross shape, so that four rectangular glass protrusions are formed on the glass platform.

5. A method for preparing a low-temperature drift MEMS resonant pressure sensor sensitive chip according to any one of claims 1 to 4, characterized in that: include: S1: A clean double-sided polished SOI silicon wafer is used to prepare the silicon island of the pressure-sensitive layer; S2: Prepare a clean double-sided polished SOI silicon wafer as the resonance layer substrate, and bond the silicon island surface of the pressure-sensitive layer to the resonance layer substrate; S3: preparing a Si-SiO2 composite resonator and a lead plate of the resonance layer on the resonance layer substrate to obtain the resonance layer; S4: using a double-polished single-crystal silicon wafer to prepare a capping layer, and bonding the capping layer to the resonant layer by silicon-silicon low-temperature vacuum bonding; S5: preparing a rectangular sensitive film on the reverse side of the pressure-sensitive layer; S6: preparing an isolation base, and anodically bonding the isolation base to the reverse side of the pressure-sensitive layer; S7: Etching silicon oxide on the resonance layer through the electrode through-hole of the cap layer, and sputtering metal through the electrode through-hole of the cap layer to form an ohmic contact on the resonance layer, thereby completing the preparation of the metal electrode.

6. The method for preparing a low-temperature drift MEMS resonant pressure sensor sensitive chip according to claim 5, characterized in that: The process of preparing silicon islands includes: S11: Prepare a clean double-sided polished SOI silicon wafer; S12: thermally oxidizing and growing silicon oxide on a double-sided polished SOI silicon wafer as an etching mask; S13: Photolithographically etching silicon oxide on the surface of the SOI silicon wafer device layer to form a silicon island pattern etching mask; S14: performing DRIE etching on the device layer to form a silicon island.

7. The method for preparing a low-temperature drift MEMS resonant pressure sensor sensitive chip according to claim 5, characterized in that: The process of preparing Si-SiO2 composite resonators and lead disks includes: S31: Using a CMP process to thin the substrate layer of the SOI silicon wafer to 50 μm, and then using KOH or TMAH wet etching to etch the remaining silicon to expose the oxide layer of the SOI silicon wafer; S32: Photolithographically etching silicon oxide to obtain a resonant layer device pattern etching mask; S33: DRIE etches the device layer of the SOI silicon wafer to obtain the resonator and lead pad structure; S34: Dry etching to remove the oxide layer on the surface of the resonator layer, completing the preparation of the resonator-silicon island integrated structure; S35: thermally oxidizing and growing an oxide layer on the surface of the resonator to form a Si-SiO2 composite resonator.

8. The method for preparing a low-temperature drift MEMS resonant pressure sensor sensitive chip according to claim 5, characterized in that: The process of preparing the capping layer includes: S41: performing laser drilling on the single crystal silicon double polished wafer to obtain electrode through holes; S42: thermally oxidizing and growing silicon oxide on a single crystal silicon double-polished wafer, and photolithographically etching the silicon oxide to obtain a vacuum cavity groove pattern etching mask; S43: RIE etching of vacuum cavity grooves; S44: magnetron sputtering of Ti getter in the vacuum chamber groove.

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