Capacitance film vacuum gauge and preparation method thereof

Abstract

The invention aims to provide a capacitance thin film vacuum gauge and a preparation method thereof, and belongs to the technical field of semiconductor manufacturing, the capacitance thin film vacuum gauge is resistant to high temperature and corrosion, in the process manufacturing stage, a room temperature laser bonding technology and a direct bonding technology for materials such as single crystal silicon carbide under vacuum high temperature and high pressure conditions are combined, and the capacitance thin film vacuum gauge is obtained. The connection problem of three layers of structures of high-temperature-resistant and corrosion-resistant transparent single crystal materials such as silicon carbide is completed, the problem of failure of metal under the high-temperature bonding condition of the single crystal materials is avoided, and meanwhile the vacuum degree and the bonding strength of a vacuum cavity and the stability of a vacuum gauge are guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor manufacturing, and in particular relates to a capacitance film vacuum gauge and a preparation method thereof. Background Art

[0002] Capacitance diaphragm gauge (CDG) has been studied since the 1980s. The measurement range of common capacitance diaphragm gauges can reach 10 -2 ~10 5 Pa, with its small size, light weight, high measurement accuracy, good linearity, fast dynamic response, good output stability and long-term stability, it can measure the total pressure of gas, and the measurement result is independent of the type of gas, and can achieve long-distance measurement and control. It is corrosion-resistant and resistant to air pressure shock, and is widely used in nuclear physics, semiconductor industry, aerospace, high-end equipment manufacturing and other fields. High-precision capacitance film vacuum gauge can be used as a low vacuum reference standard and a transfer standard for the value transfer process, which can meet the needs of deep space exploration, etc.

[0003] Existing MEMS capacitive thin film vacuum gauges are generally made of silicon wafers, silicon wafer glass and metal films. Due to the limitations of materials, they have great restrictions on the use environment and cannot be used in high temperature and complex gas environments. At the same time, the key technology of the capacitive thin film vacuum gauge sensor lies in the connection and sealing between the diaphragm and the shell on the sensor. In the prior art, the commonly used connection and sealing process is to apply sealing materials such as glass slurry or by welding. During the welding process, pressure needs to be applied to correct the membrane spacing. Therefore, the welding of sealing materials may bring undue stress and affect the performance of the capacitive thin film vacuum gauge sensor. In addition, some thin film vacuum gauges made by connecting heterogeneous materials have problems such as poor stability due to stress and thermal mismatch between different materials.

[0004] Materials such as silicon carbide, quartz, and sapphire have excellent high-temperature stability and can withstand higher temperatures without affecting performance. They are chemically stable, highly resistant to corrosion, and can work in complex gas environments. However, these materials are difficult to manufacture and process, especially the etching and bonding processes of the materials. Common bonding processes now are carried out under high temperature and high pressure, but the bonding of materials such as silicon carbide and sapphire does not meet the conditions suitable for MEMS sensors. At the same time, many previous manufacturing processes are not resistant to high-temperature environments, and there is a great incompatibility in the choice of processes.

[0005] Capacitance film vacuum gauges use the pressure change in the environment to displace the pressure-sensitive film, causing the distance between the upper substrate and the pressure-sensitive film to change, thereby changing the capacitance between the pressure-sensitive film electrode and the upper substrate reference electrode and the measuring electrode. The vacuum degree of the environment to be measured can be obtained by measuring the capacitance value. However, in high-temperature and complex gas environments, common capacitance film vacuum gauges are affected by temperature and other external interferences, resulting in large errors in the vacuum gauges.

[0006] The common connection and sealing process used in the current capacitance film vacuum gauge is to apply sealing materials such as glass slurry or by welding. The welding of sealing materials may bring undue stress and affect the performance of the capacitance film vacuum gauge sensor. The bonding of single crystal materials such as silicon carbide generally needs to be carried out under high temperature and high pressure conditions, and metal electrodes cannot withstand the temperature under bonding conditions.

[0007] Common capacitance thin film vacuum gauges generally use materials such as silicon, but these materials are limited by temperature conditions and cannot be adapted to the detection of complex gases at high temperatures. At the same time, common vacuum gauges use materials such as getters to make vacuum reference cavities, which may cause chemical reactions in high temperature and complex gas environments, damaging the sensor. Summary of the invention

[0008] In view of the above problems, the present invention provides a capacitance thin film vacuum gauge and a preparation method thereof. The present invention uses silicon carbide, quartz, sapphire and other high temperature and corrosion resistant single crystal transparent materials, and utilizes room temperature laser bonding technology and high temperature and high pressure bonding technology to complete the high strength connection of transparent high temperature and corrosion resistant materials such as silicon carbide, quartz, sapphire, etc., and reduces the unnecessary stress and stress and thermal mismatch problems between different materials caused by the welding of sealing materials. The differential capacitance structure is adopted to reduce the influence of errors and improve accuracy.

[0009] Under vacuum conditions, the vacuum sealing chamber is made using high temperature and high pressure conditions, ensuring the bonding strength and airtightness of the vacuum sealing chamber without the need for getter materials to ensure the vacuum degree. After that, the metal electrode is sputtered, and at room temperature, the upper shell and the capacitor film are connected using laser bonding technology, avoiding the conflict between the metal electrode and the seal at high temperature due to its inability to withstand high temperatures. At the same time, the materials are all homogeneous single crystal materials, without introducing intermediate layers, avoiding the generation of multiple complex stresses and ensuring the performance of the sensor.

[0010] The present invention adopts the following technical solution: A capacitance film vacuum gauge comprises a substrate, an upper shell and a pressure-sensitive film made of homogeneous single crystal material, wherein the upper shell is located above the substrate, the pressure-sensitive film is located between the substrate and the upper shell, a first cavity is provided on the inner side of the substrate, a second cavity is provided on the inner side of the upper shell, the width of the second cavity is greater than the width of the first cavity, a metal electrode is provided on one side surface of the pressure-sensitive film located in the second cavity as the pressure-sensitive electrode, a metal electrode is provided on the inner side of the upper surface of the second cavity as the measuring electrode and the reference electrode, a vent hole is provided at one end of the upper shell, a lead-out hole 1 for the pressure-sensitive electrode is provided at the other end, and a lead-out hole 2 and a lead-out hole 3 are provided on the side of the upper shell close to the measuring electrode and the reference electrode, respectively.

[0011] Furthermore, the single crystal material is a transparent material that is resistant to high temperatures and corrosion, including any one of silicon carbide, sapphire and quartz.

[0012] Furthermore, the reference electrode is in a circular ring shape, the inner diameter of the reference electrode is larger than the outer diameter of the measuring electrode, and the outer diameter of the reference electrode is smaller than the inner diameter of the sensing electrode.

[0013] Furthermore, the thickness of the connection end of the pressure-sensitive film with the substrate and the upper shell is greater than the thickness of the middle part of the pressure-sensitive film.

[0014] A method for preparing a capacitance film vacuum gauge comprises the following steps: The first step is to perform RCA standard cleaning on the substrate, upper shell and pressure-sensitive film; The second step is to etch the substrate using a dry etching process: spin-coat photoresist on the substrate surface, then sputter metal nickel as a mask layer, open an etching window through a stripping process, etch the substrate using ICP, and finally use dilute nitric acid to corrode the excess mask layer to obtain the first cavity as a vacuum cavity; The third step is to treat the pressure-sensitive film before bonding: rinse with BOE solution to remove oxides on the substrate surface; clean the substrate and the unthinned pressure-sensitive film through a standard cleaning process, and treat the substrate and the unthinned pressure-sensitive film with oxygen plasma to increase the particle activity on the surface and increase hydrophilicity; Pre-bonding is performed under hydroxide-rich conditions, and direct bonding is performed in a vacuum one-way hot press furnace; The fourth step is to thin and polish the pressure-sensitive film, and then perform standard cleaning on the thinned and polished pressure-sensitive film; Step 5: Use the first metal film pattern mask to perform photolithography on the thinned pressure-sensitive film to prepare a pressure-sensitive electrode. The pressure-sensitive electrode is located directly above the first cavity and its center is located directly at the center of the pressure-sensitive film. The alignment is completed using the alignment technology of the photolithography machine. After the development, a metal layer is deposited on the pressure-sensitive film surface using a magnetron sputtering system. The first metal layer is niobium, which is used as an adhesion layer with a thickness of 50nm. The second metal layer is platinum, which is used as a metal plate with a thickness of 400nm. After the deposition is completed, it is placed in acetone for stripping to obtain a patterned plate and a pressure-sensitive electrode. Step 6: Use dry etching process to etch the upper shell, and use sputtering and electroplating process to prepare a thicker metal mask layer: first, sputter 50nm Ti as an adhesion layer and 50nm Au as a seed layer, then electroplate 5µm metal nickel as a mask layer, and use ICP to etch the upper shell to form the second cavity; Step 7: Photolithography, exposure and development are performed on the upper surface of the second cavity by using the spraying process to prepare the measuring electrode and the reference electrode: the first layer of metal niobium is sputtered as an adhesion layer, and the second layer of metal platinum is used as a metal electrode, with the same thickness as the metal layer of the piezoelectric electrode. The upper shell of the sputtered metal is placed in acetone to complete the stripping by using the stripping process, and the patterning of the measuring electrode and the reference is completed; Step 8: Use the upper shell mask to make lead-out hole 1, lead-out hole 2, lead-out hole 3 and vent hole: use TSV technology to lead out the measuring electrode and reference electrode in the second cavity, and use a metal rod to lead out the pressure-sensing electrode in the second cavity; use laser drilling to drill lead-out hole 1, lead-out hole 2, lead-out hole 3 and vent hole; In the ninth step, the upper shell and the polished and thinned pressure-sensitive film are bonded at room temperature using laser bonding technology to obtain a capacitive film vacuum gauge.

[0015] Furthermore, the direct bonding conditions are 1300° C., 4.5 MPA, and 3 h.

[0016] Furthermore, the thickness of the thinned pressure-sensitive film is less than 0.5 mm.

[0017] Furthermore, the diameter of the vent hole is 2 mm, and the diameters of the first outlet hole, the second outlet hole, and the third outlet hole are all 500 μm.

[0018] Furthermore, the preparation method further comprises the following steps: a tenth step, providing a silver layer as an electromagnetic shielding layer on the outer surface of the capacitance film vacuum gauge; In the eleventh step, after setting the electromagnetic shielding layer, the capacitance film vacuum gauge is bonded to the ceramic substrate. The adhesive used is glass slurry. The sensing electrode, measuring electrode and reference electrode are connected to the pads of the ceramic substrate through metal leads, and the signal is then led out through wires.

[0019] The beneficial effects of the present invention are as follows: 1. The present invention combines room temperature laser bonding technology with direct bonding technology of single crystal silicon carbide and other materials under high temperature and high pressure conditions in vacuum during the manufacturing process, thereby solving the connection problem of three-layer structures of transparent single crystal materials such as silicon carbide, avoiding the failure problem of metal under high temperature bonding conditions of single crystal materials, and at the same time ensuring the vacuum degree of the vacuum chamber, bonding strength and stability of the vacuum gauge.

[0020] 2. In the structure of the capacitance film vacuum gauge of the present invention, the preparation of the capacitance pressure-sensitive film is completed by using wafer thinning and polishing technology, which reduces the difficulty of the direct bonding process under high temperature and high pressure. The thickness of the capacitance pressure-sensitive film is determined by the thinning and polishing thickness, making the thickness of the capacitance pressure-sensitive film easier to control and more accurate.

[0021] 3. The capacitance thin film vacuum gauge structure of the present invention adopts a differential capacitance structure. When the diaphragm is deformed, the measuring capacitance and the reference capacitance increase at the same time. The output capacitance is the difference between the measuring capacitance and the reference capacitance. This can effectively suppress common mode noise, improve signal integrity, and make the performance more stable under temperature changes, reduce the influence of errors, and improve accuracy. The area of ​​the pressure sensing electrode is much larger than the area of ​​the reference electrode and the measuring electrode. Since the size of the capacitance is determined by the effective area of ​​the two electrodes, the requirements for alignment accuracy are reduced.

[0022] 4. The present invention adopts numerical control machine tool (CNC) technology to reduce the process difficulty and cost of making through holes in materials such as silicon carbide and sapphire using etching technology.

[0023] 5. The present invention adopts a high temperature resistant electrode. Common metal electrodes are not resistant to high temperatures. By controlling the manufacturing method and thickness ratio of niobium and platinum electrodes, an electrode with a thickness of hundreds of nanometers is obtained, which can prevent failure under working conditions of 1000°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of the preparation method of the present invention; Figure 2 It is a structural schematic diagram of a capacitance film vacuum gauge of the present invention; Figure 3 is a schematic structural diagram of the first cavity; Figure 4 It is a schematic diagram of the connection between the pressure-sensitive film and the substrate; Figure 5 Schematic diagram of the planar structure of the pressure-sensing electrode; Figure 6 is a schematic cross-sectional view of a pressure-sensing electrode; Figure 7 It is a schematic diagram of the planar structure of the metal electrode of the upper shell; Figure 8 It is a schematic diagram of the upper shell structure; Fig. 9 A schematic diagram of a structure in which a silver layer is provided as an electromagnetic shielding layer for a capacitance film vacuum gauge; Fig.10 It is a schematic diagram of the connection between the capacitance film vacuum gauge and the ceramic substrate; Among them: 1-substrate; 11-first cavity; 2-pressure-sensitive film; 21-pressure-sensitive electrode; 3-upper shell; 31-second cavity; 32-measuring electrode; 33-reference electrode; 34-lead-out hole 1; 35-lead-out hole 2; 36-lead-out hole 3; 37-vent; 4-electromagnetic shielding layer; 5-ceramic substrate; 51-wire hole; 52-glass slurry. DETAILED DESCRIPTION

[0025] The present invention will be further described with reference to the accompanying drawings.

[0026] 1. Capacitance film vacuum gauge (1) Capacitance film vacuum gauge materials Suitable for transparent materials that are resistant to high temperature and corrosion, such as silicon carbide, sapphire and quartz.

[0027] (2) Capacitance film vacuum gauge structure The capacitance film vacuum gauge comprises a substrate, an upper shell and a pressure-sensitive film made of homogeneous single crystal material, wherein the upper shell is located above the substrate, the pressure-sensitive film is located between the substrate and the upper shell, a first cavity is provided on the inner side of the substrate, a second cavity is provided on the inner side of the upper shell, the width of the second cavity is greater than the width of the first cavity, a metal electrode is provided on one side surface of the pressure-sensitive film located in the second cavity as a pressure-sensitive electrode, a metal electrode is provided on the inner side of the upper surface of the second cavity as a measuring electrode and a reference electrode, a vent hole is provided at one end of the upper shell, and a lead-out hole 1 for the pressure-sensitive electrode is provided at the other end, and a second lead-out hole and a third lead-out hole are provided on one side of the upper shell close to the measuring electrode and the reference electrode, respectively.

[0028] A three-layer structure is adopted. The substrate and the pressure-sensitive film are directly bonded to complete a high-bonding strength connection, while ensuring the vacuum degree in the sealed cavity; the pressure-sensitive film and the upper shell are connected at high strength at room temperature through laser bonding technology, avoiding the denaturation and shedding of the metal electrode during high-temperature bonding. A wider range of electrode materials and electrode preparation processes can be used. Through TSV (through silicon via technology), metal is filled in the lead-out hole to complete the lead-out of the capacitor electrode; the upper electrode, i.e., the pressure-sensitive electrode, is led out by inserting a metal rod or the like; the test cavity is connected through the upper vent hole, so that the gas can flow into the cavity and the vacuum degree can be measured. The upper electrode is designed to be divided into a measuring electrode and a reference electrode, so that it is located on the lower surface of the concave ring of the second cavity. The lower electrode is designed to cover the sensitive film above the vacuum cavity, so that high-precision electrode alignment is not required during the bonding connection, reducing the process difficulty. The preparation flow chart is as follows Figure 1 , the structure is as follows Figure 2 shown.

[0029] (3) Capacitance film vacuum gauge connection relationship The substrate and the pressure-sensitive film adopt direct bonding technology to complete high-strength wafer bonding, ensure the vacuum degree of the sealed cavity, and meet the requirements for manufacturing absolute pressure thin-film vacuum gauges. The substrate and the pressure-sensitive film are made of single crystal homogeneous materials at the same time, avoiding problems such as thermal stress incompatibility caused by bonding of heterogeneous materials.

[0030] The pressure-sensitive film and the upper shell adopt laser bonding technology, which can complete high-strength wafer connection at room temperature, avoiding the problems of metal layer degeneration and shedding caused by high temperature during the bonding process. The pressure-sensitive film and the upper shell are made of single crystal materials at the same time, solving the problems of thermal stress incompatibility of heterogeneous materials.

[0031] (4) Working principle and process of capacitance film vacuum gauge Working principle: The elastic detection diaphragm (pressure-sensitive film) deforms under the pressure difference of different vacuum environments on both sides, causing the capacitance to change. The conversion circuit converts the capacitance change signal into a voltage or current signal output. The current air pressure value of the cavity to be tested can be obtained through signal processing.

[0032] Working process: The gas in the cavity to be tested enters the second cavity through the vent, causing the pressure difference between the first and second cavities, which causes the pressure-sensitive film in the middle of the two cavities to deform, causing the metal film sputtered on the pressure-sensitive film to deform, and causing the distance between the metal film and the upper electrode to change, resulting in a change in capacitance. The capacitance change signal is led out through the electrode, and the capacitance change is converted into a voltage or capacitance signal output through a conversion circuit. The current air pressure value of the cavity to be tested can be obtained through signal processing.

[0033] (5) Preparation process Preparation steps: 1. Prepare the first cavity mask, the second cavity mask, the upper shell mask (electrode lead hole, vent hole), the first metal film pattern mask, the pattern is a circle of a certain size, the second metal film pattern mask, the pattern is a circle of a certain size, and the third metal film pattern mask, the pattern is a ring with an inner diameter larger than the outer diameter of the second metal film and an outer diameter smaller than the inner diameter of the second cavity pattern. Different diameters and widths can be designed according to different vacuum meter ranges.

[0034] 2. Perform RCA routine cleaning on the wafer substrate, middle layer, and upper shell. (hereinafter collectively referred to as standard cleaning) 3. Use dry etching process to etch the substrate and deposit nickel as mask layer. Spin-coat photoresist. Here, AZ 5214 photoresist is used with a thickness of 2 µm. Sputter metal nickel as mask layer. Open the etching window through stripping process. Etch silicon carbide using ICP. Use dilute nitric acid to corrode the excess nickel mask to obtain the first cavity vacuum chamber. The etching results are shown in Figure 1. Figure 3 The size and depth of the first etching cavity are determined according to the design range of the vacuum gauge.

[0035] 4. Treat the wafer before bonding. Different treatment methods, steps and process parameters are adopted for different materials. The chemical activity and number of functional groups on the wafer bonding surface are improved by pre-treatment of the wafer. Under specific bonding conditions, a vacuum reference cavity with high bonding strength and high airtightness is obtained, and impurities such as voids that appear during the bonding process are reduced to obtain high-quality wafer bonding. Here are the treatment methods, steps and parameters for silicon carbide materials: rinse with BOE solution to remove oxides on the wafer surface; clean the wafer substrate and the unthinned intermediate layer film through a standard cleaning process, and treat the wafer substrate and the unthinned intermediate layer film with oxygen plasma to increase the surface particle activity and hydrophilicity. Pre-bonding is performed under hydroxide-rich conditions, and direct bonding is performed in a vacuum unidirectional hot pressing furnace. The bonding conditions are 1300℃, 4.5 MPA, and 3 h. The above treatment methods, steps and parameters work together to obtain a vacuum reference cavity with low defects, high bonding strength and good airtightness. Different method parameters and different materials will result in different direct bonding conditions. During the direct bonding process, the vacuum level in the bonding chamber needs to be maintained.

[0036] 5. Thin and polish the intermediate film bonding sheet. The thinning thickness is processed according to the film thickness designed according to the vacuum meter range requirements. Perform standard cleaning on the thinned and polished sheet. The schematic diagram after thinning and polishing is as follows Figure 4 . The thickness after thinning is less than 0.5mm.

[0037] 6. Use the first metal film pattern mask to perform photolithography on the thinned film to prepare the lower plate metal electrode. The metal electrode is located directly above the first cavity and its center is located in the center of the pressure-sensitive film. The alignment is completed using the alignment technology of the photolithography machine. After the development is completed, the metal layer is deposited on the surface of the intermediate film using a magnetron sputtering system. The first metal layer is niobium, which is used as an adhesion layer with a thickness of 50 nm. The second metal layer is platinum, which is used as a metal plate with a thickness of 400 nm. After the deposition is completed, it is placed in acetone to complete the peeling, and the plate is patterned to obtain a metal electrode, such as Figure 5 , 6 shown.

[0038] 7. The upper shell is etched using a dry etching process. The etching depth is determined by the designed range size. Since the second cavity is deeply etched, a thicker metal mask layer is prepared by sputtering and electroplating. First, 50 nm of Ti is sputtered as an adhesion layer and 50 nm of Au is used as a seed layer. Then, 5 µm of metal nickel is electroplated as a mask layer. The upper shell is etched using ICP. The width of the second cavity is greater than that of the first cavity.

[0039] 8. Using the spray process, photolithography, exposure, and development are performed on the upper surface of the second cavity to prepare the upper plate metal electrode. The first layer of metal niobium is sputtered as an adhesion layer, and the second layer of metal platinum is used as a metal electrode. The thickness is the same as the thickness of the metal layer of the film upper electrode. Using the stripping process, the shell with the sputtered metal is placed in acetone to complete the stripping and complete the patterning of the metal electrode. The graphic structure is as follows Figure 7 shown.

[0040] 9. Use the upper shell mask to make electrode lead-out holes and vents. Use TSV technology to lead out the upper electrode in the second cavity, and use a metal rod to lead out the lower electrode in the second cavity. The upper electrode lead-out hole is located at the edge of the upper electrode metal layer, and the lower electrode lead-out hole is located at the edge of the second cavity, away from the upper electrode metal layer. The diameter of the electrode lead-out hole is 500 µm, and the diameter of the vent is 2 mm. The electrode lead-out hole and the vent are drilled by laser. The result is shown in the figure below. Figure 8 shown.

[0041] 10. The upper shell and the polished and thinned pressure-sensitive film are bonded at room temperature using laser bonding technology, which avoids damage to the metal layer caused by high-temperature bonding. At the same time, laser bonding technology does not require high bonding surface roughness and has high bonding strength.

[0042] 11. Laser bonding uses femtosecond laser technology to finely process the bonding interface, control the laser energy and laser beam, and effectively manage the heat generated during the bonding process, so that the wafer becomes molten on the bonding interface without damaging the material. The chemical properties of the bonding area are changed to achieve effective bonding between the wafers.

[0043] 12. A silver layer is provided on the outer surface of the capacitance film vacuum gauge as an electromagnetic shielding layer. Fig. 9 shown.

[0044] 13. The capacitance film vacuum gauge is bonded to the ceramic substrate, and the adhesive used is glass paste. The electrode leads are connected to the ceramic substrate through metal leads, and then the signal is led out through wires. Fig.10 shown.

[0045] The connection pad metal on the ceramic substrate is gold.

[0046] The present invention uses a method combining direct bonding technology and laser bonding technology to complete the production of a vacuum sealed cavity and a capacitor electrode cavity, and makes the metal electrode outside the vacuum sealed cavity to avoid the high temperature and high pressure conditions of direct wafer bonding causing the metal electrode to fail. Direct bonding technology is used to complete the connection of layers 1 and 2 (substrate and middle layer pressure-sensitive film), with high air tightness and high bonding strength. Laser bonding technology is used to complete the connection of layers 2 and 3 (upper shell and pressure-sensitive film) at room temperature, avoiding the damage of the metal electrode caused by direct bonding high temperature conditions.

[0047] The substrate and the middle layer are directly bonded under high temperature and high pressure to obtain a vacuum sealed cavity as a reference cavity. After the bonding is completed, the middle layer is thinned and polished to obtain a pressure-sensitive film, and the thickness of the sensitive film relative to the designed range vacuum gauge is completed.

[0048] The capacitance change is the change of relative area capacitance. The lower electrode is designed to be a large electrode and the upper electrode is designed to be two arc electrodes, which reduces the alignment accuracy of the upper and lower electrodes and facilitates the lead-out of the electrodes. Differential capacitance is used to ensure the stability of the capacitance film vacuum gauge.

[0049] The design of the vacuum reference cavity can ensure the vacuum degree in the reference cavity directly during the bonding process, without the need to fill getter, thus avoiding interference under high temperature and complex gases.

[0050] The metal electrode uses a high-temperature resistant metal electrode, niobium-platinum electrode, and controls the electrode manufacturing method, electrode thickness and niobium-platinum thickness ratio, and can withstand high temperatures of 1000°C.

Claims

1. A capacitance film vacuum gauge, characterized in that: The invention comprises a substrate (1), an upper shell (3) and a pressure-sensitive film (2) made of homogeneous single crystal material, wherein the upper shell (3) is located above the substrate (1), and the pressure-sensitive film (2) is located between the substrate (1) and the upper shell (3); a first cavity (11) is provided on the inner side of the substrate (1), and a second cavity (31) is provided on the inner side of the upper shell (3); the width of the second cavity (31) is greater than the width of the first cavity (11); a metal electrode as a pressure-sensitive electrode (21) is provided on a surface of the pressure-sensitive film (2) located in the second cavity (31); metal electrodes as a measuring electrode (32) and a reference electrode (33) are provided on the inner side of the upper surface of the second cavity (31); a vent hole (37) is provided at one end of the upper shell (3), and a first lead-out hole (34) for the pressure-sensitive electrode (21) is provided at the other end; and a second lead-out hole (35) and a third lead-out hole (36) are provided on one side of the upper shell (3) close to the measuring electrode (32) and the reference electrode (33), respectively.

2. A capacitance film vacuum gauge according to claim 1, characterized in that: The single crystal material is a transparent material that is resistant to high temperatures and corrosion, including any one of silicon carbide, sapphire and quartz.

3. A capacitance film vacuum gauge according to claim 1, characterized in that: The reference electrode (33) is in the shape of a ring, the inner diameter of the reference electrode (33) is larger than the outer diameter of the measuring electrode (32), and the outer diameter of the reference electrode (33) is smaller than the inner diameter of the sensing electrode (21).

4. A capacitance film vacuum gauge according to claim 1, characterized in that: The thickness of the connection end of the pressure-sensitive film (2) with the substrate (1) and the upper shell (3) is greater than the thickness of the middle part of the pressure-sensitive film (2).

5. A method for preparing a capacitance film vacuum gauge according to claim 1, characterized in that: The steps include: The first step is to perform RCA standard cleaning on the substrate, upper shell and pressure-sensitive film; The second step is to etch the substrate using a dry etching process: spin-coat photoresist on the surface of the substrate, then sputter metal nickel as a mask layer, open an etching window through a stripping process, etch the substrate using ICP, and finally use dilute nitric acid to corrode the excess mask layer to obtain the first cavity as a vacuum cavity; The third step is to treat the pressure-sensitive film before bonding: rinse with BOE solution to remove oxides on the substrate surface; clean the substrate and the unthinned pressure-sensitive film through a standard cleaning process, and treat the substrate and the unthinned pressure-sensitive film with oxygen plasma to increase the particle activity on the surface and increase hydrophilicity; Pre-bonding is performed under hydroxide-rich conditions, and direct bonding is performed in a vacuum one-way hot press furnace; The fourth step is to thin and polish the pressure-sensitive film, and then perform standard cleaning on the thinned and polished pressure-sensitive film; Step 5: Use the first metal film pattern mask to perform photolithography on the thinned pressure-sensitive film to prepare a pressure-sensitive electrode. The pressure-sensitive electrode is located directly above the first cavity and its center is located directly at the center of the pressure-sensitive film. The alignment is completed using the alignment technology of the photolithography machine. After the development, a metal layer is deposited on the pressure-sensitive film surface using a magnetron sputtering system. The first metal layer is niobium, which is used as an adhesion layer with a thickness of 50nm. The second metal layer is platinum, which is used as a metal plate with a thickness of 400nm. After the deposition is completed, it is placed in acetone for stripping to obtain a patterned plate and a pressure-sensitive electrode. Step 6: Use dry etching process to etch the upper shell, and use sputtering and electroplating process to prepare a thicker metal mask layer: first, sputter 50nm Ti as an adhesion layer and 50nm Au as a seed layer, then electroplate 5µm metal nickel as a mask layer, and use ICP to etch the upper shell to form the second cavity; Step 7: Photolithography, exposure and development are performed on the upper surface of the second cavity by using the spraying process to prepare the measuring electrode and the reference electrode: the first layer of metal niobium is sputtered as an adhesion layer, and the second layer of metal platinum is used as a metal electrode, with the same thickness as the metal layer of the piezoelectric electrode. The upper shell of the sputtered metal is placed in acetone to complete the stripping by using the stripping process, and the patterning of the measuring electrode and the reference is completed; Step 8: Use the upper shell mask to make lead-out hole 1, lead-out hole 2, lead-out hole 3 and vent hole: use TSV technology to lead out the measuring electrode and reference electrode in the second cavity, and use a metal rod to lead out the pressure-sensing electrode in the second cavity; use laser drilling to drill lead-out hole 1, lead-out hole 2, lead-out hole 3 and vent hole; In the ninth step, the upper shell and the polished and thinned pressure-sensitive film are bonded at room temperature using laser bonding technology to obtain a capacitive film vacuum gauge.

6. The method for preparing a capacitance film vacuum gauge according to claim 5, characterized in that: The direct bonding conditions are 1300° C., 4.5 MPA, and 3 h.

7. The method for preparing a capacitance film vacuum gauge according to claim 5, characterized in that: The thickness of the thinned pressure-sensitive film is less than 0.5 mm.

8. The method for preparing a capacitance film vacuum gauge according to claim 5, characterized in that: The diameter of the vent hole is 2 mm, and the diameters of the first, second and third outlet holes are all 500 μm.

9. The method for preparing a capacitance film vacuum gauge according to claim 5, characterized in that: The preparation method further comprises the following steps: a tenth step, providing a silver layer as an electromagnetic shielding layer on the outer surface of the capacitance film vacuum gauge; In the eleventh step, after setting the electromagnetic shielding layer, the capacitance film vacuum gauge is bonded to the ceramic substrate. The adhesive used is glass slurry. The sensing electrode, measuring electrode and reference electrode are connected to the pads of the ceramic substrate through metal leads, and the signal is then led out through wires.

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