A temperature-coupled sliding film differential resonant pressure sensor and its preparation method

Abstract

The present invention discloses a temperature-coupled sliding film differential resonant pressure sensor and a preparation method thereof. The sensor includes a pressure-conducting glass layer, a pressure-sensitive film layer and a resonant structure layer connected in sequence from bottom to top, and an aluminum film is arranged on the surface of the detection electrode of the resonant structure layer to form a temperature-sensitive composite detection electrode, which forms a double detection electrode with another detection electrode. The sensor of the present invention can use the detection signals of the double detection electrodes for differential calculation to eliminate the coupling effect of temperature on the sensor, thereby greatly improving the measurement accuracy of the sensor and realizing high-precision, temperature-coupled pressure measurement. It has the advantages of high measurement accuracy, strong anti-interference ability, and easy packaging. It is a new type of pressure sensor with excellent performance, which can be adapted to pressure measurement under different temperature conditions, has high use value, and has good application prospects. The preparation method of the present invention has the advantages of simple preparation, reliable process, low energy consumption, low cost, etc. It is suitable for large-scale preparation and convenient for industrial use.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors and relates to a temperature-coupled sliding film differential resonant pressure sensor and a preparation method thereof. Background Art

[0002] At present, traditional squeeze film resonators have deformation in the direction of force, which will lead to disadvantages such as weakening of excitation and detection signals, complex back-end control circuits, and impaired accuracy. At the same time, squeeze film resonators have very high requirements for the vacuum degree of bonding packaging, which is the key to ensuring a high quality factor. However, the higher the vacuum degree, the higher the process cost and the greater the process difficulty of the resonator. In addition, for sliding film resonators, temperature has a greater impact on the natural frequency of the resonator. Generally speaking, when the temperature changes, it will also cause the output frequency of the resonator to change, which will bring a large measurement error to the resonator, making it difficult to improve the detection accuracy. In response to the above-mentioned defects, existing researchers have proposed a multi-parameter collaboratively sensitive resonant pressure sensor and a preparation method thereof. By making a composite beam temperature sensor on the cantilever beam, not only can the temperature signal be output, but also the pressure signal after temperature compensation can be output through a peripheral compensation circuit, thereby reducing the influence of temperature on the measured pressure and improving the measurement accuracy. However, the composite beam temperature sensor used in it still finds it difficult to eliminate the influence of temperature changes on the natural frequency of the resonator, which is not conducive to effectively improving the measurement accuracy. Moreover, the composite beam temperature sensor used in it requires the addition of four varistors on the cantilever beam, which greatly increases the design and processing difficulty of the resonator, and is therefore not conducive to promotion and application.

[0003] Therefore, developing a synovial differential resonant pressure sensor with high measurement accuracy and strong anti-interference ability and a matching preparation method with simple process, good process compatibility and low processing cost is of great significance for promoting the widespread application of synovial differential resonant pressure sensors. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a temperature-coupled sliding membrane differential resonant pressure sensor with high measurement accuracy and strong anti-interference ability. It also provides a method for preparing a temperature-coupled sliding membrane differential resonant pressure sensor with simple process, good process compatibility and low processing cost.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A temperature-coupled sliding film differential resonant pressure sensor, the sliding film differential resonant pressure sensor comprising a pressure-conducting glass layer, a pressure-sensitive film layer and a resonant structure layer connected in sequence from bottom to top;

[0007] An open cavity is provided on one side of the pressure sensitive film layer corresponding to the resonant structure layer, and four silicon islands are provided at the bottom of the cavity. The four silicon islands are respectively provided on the diagonal lines of the pressure sensitive film of the pressure sensitive film layer;

[0008] The resonance layer includes a main resonance beam and a resonance mechanism located around the main resonance beam; the main resonance beam is composed of four support beams connected to each other and arranged diagonally, and the main resonance beam is connected to the top of the silicon island through the four support beams; the resonance mechanism includes a first comb tooth structure, a second comb tooth structure, a third comb tooth structure, and a fourth comb tooth structure that are arranged between two support beams and connected to the main resonance beam, the first comb tooth structure and the third comb tooth structure are symmetrically arranged, and the second comb tooth structure and the fourth comb tooth structure are symmetrically arranged;

[0009] The first comb-tooth structure comprises a first movable comb-tooth driving electrode and a first fixed comb-tooth driving electrode, and the first movable comb-tooth driving electrode and the first fixed comb-tooth driving electrode are in a comb-tooth matching state to form a comb-tooth capacitor;

[0010] The second comb-tooth structure comprises a first movable comb-tooth detection electrode and a first fixed comb-tooth detection electrode, wherein the first movable comb-tooth detection electrode and the first fixed comb-tooth detection electrode are in a comb-tooth matching state to form a comb-tooth capacitor;

[0011] The third comb-tooth structure comprises a second movable comb-tooth driving electrode and a second fixed comb-tooth driving electrode, wherein the second movable comb-tooth driving electrode and the second fixed comb-tooth driving electrode are in a comb-tooth matching state to form a comb-tooth capacitor;

[0012] The fourth comb-tooth structure comprises a second movable comb-tooth detection electrode and a second fixed comb-tooth detection electrode, wherein the second movable comb-tooth detection electrode and the second fixed comb-tooth detection electrode are in a comb-tooth matching state to form a comb-tooth capacitor;

[0013] An aluminum film is also provided on one side of the second movable comb-tooth detection electrode close to the pressure sensitive film layer to form a temperature-sensitive composite detection electrode.

[0014] As a further improvement of the above technical solution: the thickness of the aluminum film is 100nm to 1000nm.

[0015] As a further improvement of the above technical solution: the resonant structure layer is suspended above the pressure-sensitive membrane through the silicon island and silicon frame of the pressure-sensitive membrane layer; the shape of the silicon island is polygonal or circular; the shape of the silicon frame is polygonal or circular; the shape of the pressure-sensitive membrane is polygonal or circular.

[0016] As a further improvement of the above technical solution: the pressure-conducting glass layer is arranged at the bottom of the silicon frame of the pressure-sensitive film layer.

[0017] As a further improvement of the above technical solution: a pressure-conducting hole is provided at the center of the pressure-conducting glass layer.

[0018] As a further improvement of the above technical solution: a lead electrode is connected to the outer end of the support beam.

[0019] As a general technical concept, the present invention also provides a method for preparing the above-mentioned temperature-coupled sliding film differential resonant pressure sensor, comprising the following steps:

[0020] (1) preparing a pressure-conducting glass layer, a pressure-sensitive film layer, and a resonant structure layer;

[0021] (2) bonding the pressure sensitive film layer and the resonant structure layer by silicon-silicon bonding to form a resonator body;

[0022] (3) The resonator body is bonded to the pressure-conducting glass layer by anodic bonding to obtain a temperature-coupled sliding film differential resonant pressure sensor.

[0023] The above preparation method is further improved, and the preparation method of the pressure-conducting glass layer comprises the following steps:

[0024] (1-a) Cleaning a glass sheet by RCA method; the thickness of the glass sheet is 200 μm to 1000 μm;

[0025] (1-b) A laser is used to punch holes in a glass sheet to form pressure-conducting holes in the glass sheet, thereby obtaining a pressure-conducting glass layer.

[0026] The above preparation method is further improved, and the preparation method of the pressure sensitive film layer comprises the following steps:

[0027] (2-a) Cleaning a silicon wafer using an RCA method; the thickness of the silicon wafer is 300 μm to 700 μm;

[0028] (2-b) depositing a silicon nitride film on the front and back sides of the silicon wafer using an LPCVD method; the thickness of the silicon nitride film is 50 nm to 300 nm;

[0029] (2-c) performing photolithography and dry etching on the silicon nitride film on the back and front sides of the silicon wafer to form opening patterns of silicon islands and pressure-sensitive membranes on the surface of the silicon wafer; the dry etching adopts RIE method or ICP method;

[0030] (2-d) wet etching the dry-etched silicon wafer to form a silicon wafer having a silicon island and a pressure-sensitive membrane; the etching solution used in the wet etching process is a KOH solution or a TMAH solution; the mass content of the etching solution is 20% to 80%; the etching temperature is controlled to be 30° C. to 90° C. during the wet etching process;

[0031] (2-e) The silicon wafer having the silicon island and the pressure-sensitive membrane is immersed in a sulfuric acid solution to remove the silicon nitride film on the surface of the silicon wafer to obtain a pressure-sensitive membrane layer; the mass content of the sulfuric acid solution is 30% to 90%; the system temperature is controlled at 100°C to 200°C during the immersion process; and the immersion time is 1h to 4h.

[0032] The above preparation method is further improved, and the preparation method of the resonant structure layer comprises the following steps:

[0033] (3-a) Cleaning the SOI wafer by RCA method; in the SOI wafer, the thickness of the BOX layer is 200nm-1μm, and the thickness of the top silicon layer is 200nm-2μm;

[0034] (3-b) depositing an aluminum film on the front side of the SOI by a metal lift-off process or a PVD aluminum plating combined with a dry etching process; the thickness of the aluminum film matches the thickness of the top silicon layer and the operating temperature of the resonator;

[0035] (3-c) using an aluminum film as a mask pattern, vertically etching the top silicon layer and the BOX layer of the SOI wafer by dry etching until the bottom silicon layer is etched to form a resonator pattern on the surface of the SOI wafer, wherein the aluminum film is not only a mask pattern for dry etching, but also a mask pattern for subsequent wet etching; the dry etching method adopts an RIE method or an ICP method;

[0036] (3-d) using an aluminum film as a mask pattern, performing self-stop wet etching on a SOI wafer deposited with an aluminum film, and etching to a depth of 3 μm to 100 μm to the underlying silicon; the etching solution used in the self-stop wet etching process is an alkaline solution; the alkaline solution is a KOH solution or a TMAH solution; the mass content of the etching solution is 20% to 80%; the etching temperature is controlled to be 30° C. to 90° C. during the self-stop wet etching process;

[0037] (3-e) using a dry etching method to etch the aluminum film on the surface of the SOI wafer, retaining the aluminum film on the surface of the second movable comb detection electrode, to form a temperature-sensitive composite detection electrode; the dry etching method is an ICP method or a RIE method;

[0038] (3-f) Immersing the SOI wafer prepared with the temperature-sensitive composite detection electrode in a hydrofluoric acid solution to remove the silicon oxide under the resonator, release the resonator, and obtain a resonant structure layer; the mass content of the hydrofluoric acid solution is 1% to 40%; and the immersion time is 10s to 60s.

[0039] The above preparation method is further improved in that in the SOI wafer, the thickness of the BOX layer is 1 μm.

[0040] Compared with the prior art, the advantages of the present invention are:

[0041] (1) Aiming at the defects of low measurement accuracy and weak anti-interference temperature capability of the existing resonant pressure sensor, the present invention creatively proposes a temperature-coupled sliding film differential resonant pressure sensor, which forms a temperature-sensitive composite detection electrode by arranging an aluminum film on the surface of the detection electrode, and together with another conventional detection electrode, forms a dual detection electrode, wherein the temperature-sensitive composite detection electrode composed of aluminum film and silicon material with different thermal expansion coefficients has a significant difference in the vertical direction from the conventional detection electrode, which makes the detection signals of the two detection electrodes have a large difference, and then the coupling effect of temperature on the sensor can be greatly eliminated by differential calculation of the detection signals of the dual detection electrodes, thereby greatly improving the measurement accuracy of the sensor and realizing high-precision, temperature-coupled pressure measurement. In addition, as a sliding film resonator, it is not sensitive to the requirements of vacuum packaging and can obtain a high quality factor under a lower vacuum packaging, so it can meet the device performance requirements and is easy to package and prepare, which is conducive to reducing the process difficulty and preparation cost. Compared with conventional synovial differential resonant pressure sensors, the temperature-coupled synovial differential resonant pressure sensor of the present invention has the advantages of high measurement accuracy, strong anti-interference ability, and easy packaging. It is a new type of synovial differential resonant pressure sensor with excellent performance, which can adapt to pressure measurement under different temperature conditions, has high use value, and good application prospects.

[0042] (2) The present invention also provides a method for preparing a temperature-coupled sliding membrane differential resonant pressure sensor, which can realize the preparation of the sensor through only two bonding processes. Compared with the traditional four-layer structure, the number of bonding processes is less, which is beneficial to reduce the process cost and process difficulty. It has the advantages of simple preparation, reliable process, low energy consumption, low cost, etc. It is suitable for large-scale preparation and convenient for industrial utilization.

[0043] (3) In the preparation method of the present invention, during the preparation of the resonant structure layer, the SOI wafer is used as the substrate, and the anisotropic etching characteristics of wet etching, the self-stopping technology and the resonator wet release technology are used to realize the integrated preparation of the vacuum sealed cavity and the resonator; at the same time, when the SOI wafer is etched using the self-stopping technology, an alkaline solution (such as KOH solution or TMAH solution) is used as the etching solution, which can not only effectively dissolve the silicon oxide and effectively release the resonator, but also will not have an adverse effect on the top silicon of the SOI wafer and the aluminum film deposited on the surface of the SOI wafer, thereby being able to prepare a resonant structure layer that meets the requirements, and is conducive to packaging by bonding twice, with a simpler processing technology and lower processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0045] Figure 1 It is a schematic diagram of the structure of the temperature-coupled sliding film differential resonant pressure sensor of the present invention.

[0046] Figure 2 It is a schematic diagram of the exploded view of the temperature-coupled sliding membrane differential resonant pressure sensor of the present invention.

[0047] Figure 3 The present invention is a flow chart of the preparation process of the temperature-coupled sliding film differential resonant pressure sensor.

[0048] Legend:

[0049] 1. Pressure-conducting glass layer; 11. Pressure-conducting hole; 12. Pressure-conducting glass bonding surface; 2. Pressure-sensitive film layer; 21. Silicon frame; 22. Silicon island; 23. Pressure-sensitive diaphragm; 3. Resonance structure layer; 31. Second fixed comb-tooth detection electrode; 32. First fixed comb-tooth detection electrode; 33. First fixed comb-tooth drive electrode; 34. Second fixed comb-tooth drive electrode; 35. Second movable comb-tooth detection electrode; 36. First movable comb-tooth detection electrode; 37. First movable comb-tooth drive electrode; 38. Second movable comb-tooth drive electrode; 39. Support beam; 310. Lead electrode; 311. Aluminum film. DETAILED DESCRIPTION

[0050] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0051] Example

[0052] In view of the defects of the existing resonant pressure sensor such as low measurement accuracy and weak anti-interference temperature capability, the present invention creatively proposes a temperature-coupled sliding film differential resonant pressure sensor, which forms a temperature-sensitive composite detection electrode by arranging an aluminum film on the surface of the detection electrode, and together with another conventional detection electrode, forms a double detection electrode, wherein the temperature-sensitive composite detection electrode composed of aluminum film and silicon material with different thermal expansion coefficients has a significant difference in the vertical direction from the conventional detection electrode, which makes the detection signals of the two detection electrodes have a large difference, and then the coupling effect of temperature on the sensor can be greatly eliminated by differential calculation of the detection signals of the double detection electrodes, thereby greatly improving the measurement accuracy of the sensor and realizing high-precision, temperature-coupled pressure measurement. In addition, as a sliding film resonator, it is not sensitive to the requirements of vacuum packaging, and can obtain a high quality factor under a lower vacuum packaging, so it can meet the device performance requirements, and is easy to package and prepare, which is conducive to reducing the process difficulty and preparation cost.

[0053] In order to better understand the innovation of the technical solution of the present invention, as one of the examples in the technical solution of the present invention, Figure 1 and Figure 2 As shown, the temperature-coupled sliding film differential resonant pressure sensor involved, the sliding film differential resonant pressure sensor comprises a pressure-conducting glass layer 1, a pressure-sensitive film layer 2 and a resonant structure layer 3 connected in sequence from bottom to top;

[0054] An open cavity is provided on one side of the pressure sensitive film layer 2 corresponding to the resonant structure layer 3, and four silicon islands 22 are provided at the bottom of the cavity. The four silicon islands 22 are respectively provided on the diagonal lines of the pressure sensitive film 23 of the pressure sensitive film layer 2;

[0055] The resonant structure layer includes a main resonant beam and a resonant mechanism located around the main resonant beam; the main resonant beam is composed of four support beams 39 connected to each other and arranged diagonally, and the main resonant beam is connected to the top of the silicon island 22 through the four support beams 39; the resonant mechanism includes a first comb tooth structure, a second comb tooth structure, a third comb tooth structure, and a fourth comb tooth structure that are arranged between two support beams 39 and connected to the main resonant beam, the first comb tooth structure and the third comb tooth structure are symmetrically arranged, and the second comb tooth structure and the fourth comb tooth structure are symmetrically arranged;

[0056] The first comb-tooth structure includes a first movable comb-tooth driving electrode 37 and a first fixed comb-tooth driving electrode 33. The first movable comb-tooth driving electrode 37 and the first fixed comb-tooth driving electrode 33 are in a comb-tooth matching state to form a comb-tooth capacitor.

[0057] The second comb-tooth structure includes a first movable comb-tooth detection electrode 36 and a first fixed comb-tooth detection electrode 32, and the first movable comb-tooth detection electrode 36 and the first fixed comb-tooth detection electrode 32 are in a comb-tooth matching state to form a comb-tooth capacitor;

[0058] The third comb-tooth structure includes a second movable comb-tooth driving electrode 38 and a second fixed comb-tooth driving electrode 34, and the second movable comb-tooth driving electrode 38 and the second fixed comb-tooth driving electrode 34 are in a comb-tooth matching state to form a comb-tooth capacitor;

[0059] The fourth comb-tooth structure includes a second movable comb-tooth detection electrode 35 and a second fixed comb-tooth detection electrode 31, and the second movable comb-tooth detection electrode 35 and the second fixed comb-tooth detection electrode 31 are in a comb-tooth matching state to form a comb-tooth capacitor;

[0060] An aluminum film 311 is also provided on one side of the second movable comb-tooth detection electrode 35 close to the pressure sensitive film layer 2 to form a temperature-sensitive composite detection electrode.

[0061] In this embodiment, the thickness of the aluminum film is 500 nm (the thickness may be 100 nm to 1000 nm).

[0062] In this embodiment, the resonant structure layer 3 is suspended above the pressure-sensitive membrane 23 through the silicon island 22 and the silicon frame 21 of the pressure-sensitive membrane layer 2; the silicon island 22 is in a diamond shape; the silicon frame 21 is in a rectangular shape; and the pressure-sensitive membrane 23 is in a rectangular shape.

[0063] In this embodiment, the pressure-conducting glass layer 1 is disposed at the bottom of the silicon frame 21 of the pressure-sensitive film layer 2 .

[0064] In this embodiment, a pressure-conducting hole 11 is provided at the center of the pressure-conducting glass layer 1 .

[0065] In this embodiment, a lead electrode 310 is connected to the outer end of the support beam 39 .

[0066] In the temperature-coupled sliding membrane differential resonant pressure sensor of the present invention, when the external pressure transmits the pressure to the pressure-sensitive diaphragm 23 of the pressure-sensitive film layer through the pressure-conducting hole 11 of the pressure-conducting glass layer 1, the diaphragm is deformed under the action of pressure, and the four prism-shaped silicon islands 22 are offset. This offset causes internal stress to be generated inside the support beam 39, resulting in a change in the mechanical stiffness of the support beam 39, and ultimately causing the natural frequency of the resonant structure layer 3 to change. At the same time, the movable temperature-sensitive composite detection electrode (the second movable comb-tooth detection electrode 35) deposited with the aluminum film 311 is affected by the temperature and will produce different degrees of downward or upward bending, which is the basis for temperature-coupled differential calculations. Furthermore, in terms of electrical connection, the first fixed comb tooth detection electrode 33 (fixed comb tooth drive electrode), the first fixed comb tooth detection electrode 32 (conventional detection electrode), the second fixed comb tooth detection electrode 31 (fixed temperature-sensitive composite detection electrode), and the lead electrode 310 are respectively connected to four external electrical signals, wherein one drive signal acts on the first fixed comb tooth detection electrode 33 (fixed comb tooth drive electrode), the second detection signal acts on the first fixed comb tooth detection electrode 32 (conventional detection electrode), the third signal acts on the first fixed comb tooth detection electrode 32 (conventional detection electrode), the fourth signal acts on the support beam 39, the first movable comb tooth drive electrode 37 (movable comb tooth drive electrode), the second movable comb tooth drive electrode 38 (movable comb tooth drive electrode), the first movable comb tooth detection electrode 36 (movable conventional detection electrode), and the second The movable comb-tooth detection electrode 35 (movable temperature-sensing composite detection electrode) is electrically connected as a common electrical signal. When the pressure sensor is working, the resonant structure layer 3 performs resonant motion in a circumferential direction around the center of the structure under the action of the driving signal, so that the capacitance between the first movable comb-tooth detection electrode 36 (movable conventional detection electrode) and the first fixed comb-tooth detection electrode 32 (conventional detection electrode) produces a sinusoidal change C1. In addition, the second movable comb-tooth detection electrode 35 (movable temperature-sensing composite detection electrode) is bent downward or upward under the influence of temperature. The sinusoidal change law C2 of the deformed second movable comb-tooth detection electrode 35 (movable temperature-sensing composite detection electrode) and the second fixed comb-tooth detection electrode 31 (fixed temperature-sensing composite detection electrode) is tested, and the influence of temperature coupling is eliminated by differential calculation of C1 and C2, so as to achieve high-precision, temperature-coupled pressure measurement.

[0067] Furthermore, a method for preparing the temperature-coupled sliding film differential resonant pressure sensor in the above embodiment is also provided, such as Figure 3 As shown, the following steps are included:

[0068] (1) Preparation of pressure-conducting glass layer

[0069] 1-a) Cleaning: Take a glass sheet with a thickness of 200 μm to 1000 μm and perform RCA standard cleaning.

[0070] 1-b) Punching: Laser drilling is used to punch a hole in the center of the glass sheet to form a pressure-conducting hole to obtain a pressure-conducting glass layer.

[0071] (2) Preparation of pressure sensitive film layer

[0072] 2-a) Cleaning: Take a silicon wafer of 300 μm to 700 μm and perform RCA standard cleaning.

[0073] 2-b) Silicon nitride deposition: using LPCVD to deposit silicon nitride thin films on the front and back sides of the silicon wafer, with a deposition thickness of 50nm to 300nm;

[0074] 2-c) Dry etching: The silicon wafer with double-sided silicon nitride film is subjected to double-sided photolithography and dry etching. The etching position is the opening position of the silicon island and the pressure sensitive membrane, in preparation for wet etching. The dry etching can be performed by RIE or ICP etching method (specifically, it can be ICP etching method), and the silicon nitride thickness is removed by etching to expose the silicon substrate.

[0075] 2-d) Wet etching: The dry-etched silicon wafer is wet-etched. The wet etching can be performed using a KOH solution (20% wt to 80% wt, such as 60% wt) or a TMAH solution (20% wt to 80% wt, specifically 60% wt). The wet etching temperature can be 30° C. to 90° C., such as controlled at 50° C. Since the aluminum film has a barrier effect on TMAH, it is preferred to use a TMAH etching solution. After wet etching, a sensitive layer having a sensitive membrane and a silicon island is obtained.

[0076] 2-e) Wet etching: Place the silicon wafer with the silicon island and the sensitive layer in concentrated sulfuric acid (30% wt ~ 90% wt, such as 80% wt) and boil it at an etching temperature (100°C ~ 200°C, such as 180°C) for 1h ~ 4h (such as 3 hours) to remove the double-sided silicon nitride and obtain a pressure-sensitive film layer.

[0077] (3) Preparation of resonant structure layer

[0078] 3-a) Cleaning: Take an SOI wafer and perform RCA standard cleaning. The BOX layer thickness of the SOI wafer is 200nm~1μm, and the top silicon is 200nm~2μm. Preferably, the SOI wafer with a BOX layer thickness of more than 1μm is used, and specifically, the SOI wafer with a BOX layer thickness of 1μm is used.

[0079] 3-b) Using a lift-off process (metal stripping process) or a PVD aluminum plating combined with dry etching process, an aluminum film is deposited on the front side of the SOI. Specifically, using a PVD aluminum plating combined with dry etching process, an aluminum film is deposited on the front side of the SOI, so that the thickness of the aluminum film matches the thickness of the top silicon and the operating temperature of the resonator.

[0080] 3-c) Using the aluminum film as a mask pattern, dry etching is used to vertically etch the top silicon and BOX layers of the SOI wafer until the bottom silicon layer is etched, forming a resonator pattern on the surface of the SOI wafer, wherein the aluminum film is not only a dry etching mask pattern, but also a mask pattern for subsequent wet etching. The dry etching method uses the RIE method or the ICP method, specifically the ICP etching method for dry etching, until the etching hole needs to pass through the BOX layer to expose the silicon substrate, in preparation for self-stop wet etching.

[0081] 3-d) Using an aluminum film as a mask pattern, the SOI wafer deposited with an aluminum film is subjected to self-stop wet etching, and the etching depth of the underlying silicon is 3μm to 100μm, specifically; since the resonator is protected by a silicon oxide layer, the etching solution only etches the underlying silicon, and thus the etching is stopped when the etching depth of the underlying silicon is 3μm to 100μm, wherein the etching solution used in the self-stop wet etching process is an alkaline solution, and the alkaline solution is a KOH solution or a TMAH solution, and specifically a TMAH solution is used, and the mass content of the TMAH solution is 50% (the mass content is 20% to 80%, both are acceptable), and at the same time, the etching temperature is controlled to be 50°C (the etching temperature is 30°C to 90°C, both are acceptable) during the self-stop wet etching process.

[0082] 3-e) The aluminum film on the surface of the SOI wafer is etched by dry etching, and the aluminum film on the surface of the second movable comb detection electrode is retained to form a temperature-sensitive composite detection electrode. The dry etching method is an ICP method or a RIE method. Specifically, the ICP etching method is used for dry etching until the etching hole needs to pass through the BOX layer to expose the silicon substrate and form a sealed cavity.

[0083] 3-f) Immerse the SOI wafer prepared with the temperature-sensitive composite detection electrode in a hydrofluoric acid solution to remove the silicon oxide under the resonator, release the resonator, and obtain a resonant structure layer, wherein the mass content of the hydrofluoric acid solution is 20% (the mass content can be 1% to 40%), and the immersion time is 50s (the time can be 10s to 60s).

[0084] (4) Bonding

[0085] 4-a) Silicon-silicon bonding: The resonant structure layer is bonded to the pressure-sensitive film layer by silicon-silicon bonding to obtain the resonator body.

[0086] 4-b) Anodic bonding: Anodic bonding is used to bond the silicon-silicon bonded resonator body to the pressure-conducting glass layer to obtain a temperature-coupled sliding film differential resonant pressure sensor.

[0087] After testing: Compared with conventional synovial differential resonant pressure sensors, the temperature-coupled synovial differential resonant pressure sensor of the present invention has higher measurement accuracy, stronger anti-interference ability, and is easy to package. It is a new type of synovial differential resonant pressure sensor with excellent performance, which can be adapted to pressure measurement under different temperature conditions, has high use value and good application prospects. In addition, the preparation method of the present invention also has the advantages of simple preparation, reliable process, low energy consumption, low cost, etc., and is suitable for large-scale preparation and convenient for industrial use.

[0088] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A temperature-coupled sliding film differential resonant pressure sensor, characterized in that: The sliding film differential resonant pressure sensor comprises a pressure-conducting glass layer, a pressure-sensitive film layer and a resonant structure layer connected in sequence from bottom to top; An open cavity is provided on one side of the pressure sensitive film layer corresponding to the resonant structure layer, and four silicon islands are provided at the bottom of the cavity. The four silicon islands are respectively provided on the diagonal lines of the pressure sensitive film of the pressure sensitive film layer; The resonant structure layer includes a main resonant beam and a resonant mechanism located around the main resonant beam; the main resonant beam is composed of four supporting beams connected to each other and arranged diagonally, and the main resonant beam is connected to the top of the silicon island through the four supporting beams; the resonant mechanism includes a first comb tooth structure, a second comb tooth structure, a third comb tooth structure, and a fourth comb tooth structure, which are arranged between two supporting beams and connected to the main resonant beam, the first comb tooth structure and the third comb tooth structure are symmetrically arranged, and the second comb tooth structure and the fourth comb tooth structure are symmetrically arranged; The first comb-tooth structure comprises a first movable comb-tooth driving electrode and a first fixed comb-tooth driving electrode, and the first movable comb-tooth driving electrode and the first fixed comb-tooth driving electrode are in a comb-tooth matching state to form a comb-tooth capacitor; The second comb-tooth structure comprises a first movable comb-tooth detection electrode and a first fixed comb-tooth detection electrode, wherein the first movable comb-tooth detection electrode and the first fixed comb-tooth detection electrode are in a comb-tooth matching state to form a comb-tooth capacitor; The third comb-tooth structure comprises a second movable comb-tooth driving electrode and a second fixed comb-tooth driving electrode, wherein the second movable comb-tooth driving electrode and the second fixed comb-tooth driving electrode are in a comb-tooth matching state to form a comb-tooth capacitor; The fourth comb-tooth structure comprises a second movable comb-tooth detection electrode and a second fixed comb-tooth detection electrode, wherein the second movable comb-tooth detection electrode and the second fixed comb-tooth detection electrode are in a comb-tooth matching state to form a comb-tooth capacitor; An aluminum film is also provided on one side of the second movable comb-tooth detection electrode close to the pressure sensitive film layer to form a temperature-sensitive composite detection electrode.

2. The temperature-coupled sliding film differential resonant pressure sensor according to claim 1, characterized in that: The thickness of the aluminum film is 100nm-1000nm.

3. The temperature-coupled sliding film differential resonant pressure sensor according to claim 1 or 2, characterized in that: The resonant structure layer is suspended above the pressure-sensitive membrane through the silicon island and silicon frame of the pressure-sensitive membrane layer; the shape of the silicon island is polygonal or circular; the shape of the silicon frame is polygonal or circular; The shape of the pressure sensitive membrane is polygonal or circular.

4. The temperature-coupled sliding film differential resonant pressure sensor according to claim 1 or 2, characterized in that: The pressure-conducting glass layer is arranged at the bottom of the silicon frame of the pressure-sensitive film layer; and a pressure-conducting hole is arranged at the center of the pressure-conducting glass layer.

5. The temperature-coupled sliding film differential resonant pressure sensor according to claim 1 or 2, characterized in that: The outer end of the support beam is connected with a lead electrode.

6. A method for preparing a temperature-coupled sliding film differential resonant pressure sensor according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) preparing a pressure-conducting glass layer, a pressure-sensitive film layer, and a resonant structure layer; (2) bonding the pressure sensitive film layer and the resonant structure layer by silicon-silicon bonding to form a resonator body; (3) The resonator body is bonded to the pressure-conducting glass layer by anodic bonding to obtain a temperature-coupled sliding film differential resonant pressure sensor.

7. The preparation method according to claim 6, characterized in that: The method for preparing the pressure-conducting glass layer comprises the following steps: (1-a) Cleaning a glass sheet by RCA method; the thickness of the glass sheet is 200 μm to 1000 μm; (1-b) A laser is used to punch holes in a glass sheet to form pressure-conducting holes in the glass sheet, thereby obtaining a pressure-conducting glass layer.

8. The preparation method according to claim 7, characterized in that: The method for preparing the pressure sensitive film layer comprises the following steps: (2-a) Cleaning a silicon wafer using an RCA method; the thickness of the silicon wafer is 300 μm to 700 μm; (2-b) depositing a silicon nitride film on the front and back sides of the silicon wafer using an LPCVD method; the thickness of the silicon nitride film is 50 nm to 300 nm; (2-c) performing photolithography and dry etching on the silicon nitride film on the back and front sides of the silicon wafer to form opening patterns of silicon islands and pressure-sensitive membranes on the surface of the silicon wafer; the dry etching adopts RIE method or ICP method; (2-d) wet etching the dry-etched silicon wafer to form a silicon wafer having a silicon island and a pressure-sensitive membrane; the etching solution used in the wet etching process is a KOH solution or a TMAH solution; the mass content of the etching solution is 20% to 80%; the etching temperature is controlled to be 30° C. to 90° C. during the wet etching process; (2-e) The silicon wafer having the silicon island and the pressure-sensitive membrane is immersed in a sulfuric acid solution to remove the silicon nitride film on the surface of the silicon wafer to obtain a pressure-sensitive membrane layer; the mass content of the sulfuric acid solution is 30% to 90%; the system temperature is controlled at 100°C to 200°C during the immersion process; and the immersion time is 1h to 4h.

9. The preparation method according to any one of claims 6 to 8, characterized in that The preparation method of the resonant structure layer comprises the following steps: (3-a) Cleaning the SOI wafer by RCA method; in the SOI wafer, the thickness of the BOX layer is 200nm-1μm, and the thickness of the top silicon layer is 200nm-2μm; (3-b) depositing an aluminum film on the front side of the SOI by a metal lift-off process or a PVD aluminum plating combined with a dry etching process; the thickness of the aluminum film matches the thickness of the top silicon layer and the operating temperature of the resonator; (3-c) using an aluminum film as a mask pattern, vertically etching the top silicon layer and the BOX layer of the SOI wafer by dry etching until the bottom silicon layer is etched to form a resonator pattern on the surface of the SOI wafer, wherein the aluminum film is not only a mask pattern for dry etching, but also a mask pattern for subsequent wet etching; the dry etching method adopts an RIE method or an ICP method; (3-d) using an aluminum film as a mask pattern, performing self-stop wet etching on a SOI wafer deposited with an aluminum film, and etching to a depth of 3 μm to 100 μm to the underlying silicon; the etching solution used in the self-stop wet etching process is an alkaline solution; the alkaline solution is a KOH solution or a TMAH solution; the mass content of the etching solution is 20% to 80%; the etching temperature is controlled to be 30° C. to 90° C. during the self-stop wet etching process; (3-e) using a dry etching method to etch the aluminum film on the surface of the SOI wafer, retaining the aluminum film on the surface of the second movable comb detection electrode, to form a temperature-sensitive composite detection electrode; the dry etching method is an ICP method or a RIE method; (3-f) Immersing the SOI wafer prepared with the temperature-sensitive composite detection electrode in a hydrofluoric acid solution to remove the silicon oxide under the resonator, release the resonator, and obtain a resonant structure layer; the mass content of the hydrofluoric acid solution is 1% to 40%; and the immersion time is 10s to 60s.

10. The preparation method according to claim 9, characterized in that: In the SOI wafer, the thickness of the BOX layer is 1 μm.

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