A self-sealing capacitive diaphragm vacuum gauge based on MEMS and a manufacturing method thereof

Abstract

The application discloses a self-closing capacitive diaphragm vacuum gauge based on MEMS and a manufacturing method thereof. The vacuum gauge comprises, from top to bottom, a vacuum locking diaphragm, a first insulating layer, a first bottom silicon layer, a pressure sensing diaphragm, a second insulating layer and a second bottom silicon layer. The first bottom silicon layer and the pressure sensing diaphragm are bonded together through an edge support layer and an adhesive layer. A test cavity is formed between the first bottom silicon layer and the pressure sensing diaphragm. Metal electrodes are arranged on opposite sides of the first bottom silicon layer and the pressure sensing diaphragm. An air inlet hole is formed in the right side of the vacuum locking diaphragm, the first insulating layer and the first bottom silicon layer. A through hole is formed in the left side of the first bottom silicon layer and the pressure sensing diaphragm, thereby forming a reference cavity. A self-locking hole is formed in the left or right center of the first bottom silicon layer, which is connected with the reference cavity and the test cavity. The disclosed vacuum gauge can realize self-closing of the reference cavity, and improve the measurement range, the measurement accuracy under high vacuum, the working stability and the reliability of the capacitive diaphragm vacuum gauge.

Description

Technical Field

[0001] This invention belongs to the field of vacuum measurement technology, and specifically relates to a MEMS-based self-sealing capacitive thin-film vacuum gauge and its fabrication method. Background Technology

[0002] Vacuum measurement is of great significance to the development of deep space exploration, national defense, and other fields. There are many types of vacuum gauges, among which capacitive vacuum gauges are widely used due to their high accuracy, wide measurement range, and insensitivity to different gas types. Capacitive vacuum gauges obtain the real-time pressure of the measured environment by detecting changes in the sensitive capacitance between a pressure-sensitive diaphragm and metal electrodes, thus achieving pressure detection.

[0003] The pressure-sensing diaphragm is the core component of a capacitive thin-film vacuum gauge. It serves as both the movable electrode of the sensitive capacitor and the flexible structure of the vacuum reference cavity, thus significantly impacting the gauge's performance. When not in operation, capacitive thin-film vacuum gauges are often stored at atmospheric pressure. Under extreme pressure differential loads, the pressure-sensing diaphragm undergoes significant deformation. Over time, this can lead to plastic damage such as creep, or even brittle fracture, causing the gauge to fail. This severely affects the gauge's operational stability and reliability. During operation, the sensitive capacitor of the capacitive thin-film vacuum gauge is based on the vacuum reference cavity (<10). -2 The pressure difference between the pressure sensor and the measured environment changes, and is affected by the vacuum level of the vacuum reference chamber. When the vacuum level of the measured environment is less than 1 Torr, the displacement of the pressure-sensing diaphragm of the capacitive thin-film vacuum gauge is extremely small, resulting in a very weak change in the sensitive capacitance. Consequently, the capacitive thin-film vacuum gauge has low measurement accuracy for high vacuum environment pressure and a high lower limit of its effective measurement range.

[0004] To address the issues of plastic failure and brittle fracture of pressure-sensitive diaphragms, two main technical solutions have been researched: one solution involves placing a baffle in the vacuum chamber, which contacts the pressure-sensitive diaphragm when subjected to a large pressure load, thus preventing diaphragm fracture. However, this solution cannot solve the problem of plastic failure of the pressure-sensitive diaphragm, and it also causes a decrease in the measurement range and output linearity of the capacitive film vacuum gauge. The other solution involves reducing the aspect ratio of the pressure-sensitive diaphragm of the capacitive film vacuum gauge, sacrificing the measurement range and accuracy of the gauge to improve its reliability.

[0005] To address the issues of low measurement accuracy and insufficient measurement range under high vacuum conditions, two main technical solutions have been researched: one employing a differential structure with dual electrodes; and the other using an electrostatic force balance structure with force balance feedback. The measurement accuracy of vacuum gauges in both of these solutions remains highly dependent on the high-vacuum reference cavity. Therefore, their improvement in measurement accuracy and range under high vacuum conditions is extremely limited, and they increase the design difficulty of external circuits, thus increasing the complexity of the vacuum gauge system. However, with the continuous promotion and deepening of applications, higher demands are being placed on the measurement accuracy, measurement range, operational stability, and reliability of vacuum gauges under high vacuum conditions. The above solutions clearly cannot meet these increasingly higher requirements for vacuum gauges. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a MEMS-based self-sealing capacitive thin-film vacuum gauge and its fabrication method. By designing a vacuum-locking thin film, the reference cavity of the capacitive thin-film vacuum gauge is self-sealed, effectively solving problems such as plastic damage and brittle fracture of the pressure-sensitive thin film, and significantly improving the measurement accuracy and range of the capacitive thin-film vacuum gauge under high vacuum conditions.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A MEMS-based self-sealing capacitive thin-film vacuum gauge includes, from top to bottom, a vacuum-locking thin film, a first insulating layer, a first bottom silicon layer, a pressure-sensitive thin film, a second insulating layer, and a second bottom silicon layer. A first support layer and a second support layer are respectively disposed on the edge regions of the opposite sides of the first bottom silicon layer and the pressure-sensitive thin film. The first support layer and the second support layer are bonded together by a first adhesive layer and a second adhesive layer.

[0009] A test cavity is formed between the first bottom silicon layer and the pressure-sensitive film, and a first metal electrode and a second metal electrode are respectively disposed in the central region of the opposite side of the first bottom silicon layer and the pressure-sensitive film.

[0010] Electrode lead-out holes for leading out the first metal electrode and the second metal electrode are respectively opened on the upper and lower sides of the vacuum locking film, the first insulating layer and the first bottom silicon layer. An air inlet hole communicating with the test chamber is opened on the right side of the vacuum locking film, the first insulating layer and the first bottom silicon layer.

[0011] A through-hole is formed on the left side of the first bottom silicon layer and the pressure-sensitive film, and the through-hole passes through the first support layer, the second support layer, the first adhesive layer and the second adhesive layer; the first insulating layer and the second insulating layer located on the upper and lower sides of the test cavity are etched away, thereby forming a connected reference cavity between the vacuum locking film, the first bottom silicon layer, the pressure-sensitive film and the second bottom silicon layer.

[0012] A self-locking hole connecting the reference cavity and the test cavity is opened at a position slightly to the left or right of the center of the first bottom silicon layer.

[0013] In the above scheme, the first and second bottom silicon layers are made of monocrystalline silicon, the first and second insulating layers are made of silicon dioxide, and the vacuum locking film and pressure sensing film are made of monocrystalline silicon.

[0014] In the above scheme, the materials of the first metal electrode and the second metal electrode are one or more combinations of molybdenum, platinum, aluminum, silver and gold.

[0015] In the above scheme, the materials of the first support layer and the second support layer are one or a combination of silicon dioxide and silicon nitride.

[0016] In the above scheme, the materials of the first adhesive layer and the second adhesive layer are both metals or both polymers.

[0017] In a further technical solution, the metal material is one or a combination of two of gold and indium.

[0018] In a further technical solution, the polymer is made of either epoxy resin or benzocyclobutene.

[0019] In the above scheme, the cross-sectional shape of the air inlet, electrode lead-out hole, and self-locking hole includes one of the following: circle, rectangle, and polygon.

[0020] A method for fabricating a MEMS-based self-sealing capacitive thin-film vacuum gauge as described above includes the following steps:

[0021] S1. Two SOI substrates are provided, namely a first SOI substrate and a second SOI substrate. The first SOI substrate includes a first bottom silicon layer, a first insulating layer and a first top silicon layer. The second SOI substrate includes a second bottom silicon layer, a second insulating layer and a second top silicon layer. The first top silicon layer and the second top silicon layer are thinned by chemical mechanical polishing to obtain a vacuum-locking film and a pressure-sensitive film, respectively.

[0022] S2. The vacuum locking film, the first bottom silicon layer and the pressure-sensitive film are locally etched to form through holes; the pressure-sensitive film is etched to form one through hole near the left boundary; the vacuum locking film is etched to form three through holes, located at the upper, lower and right boundary positions respectively; the first bottom silicon layer is etched to form five through holes, one of which is located slightly to the left or right of the center and is a self-locking hole, and the other four through holes are evenly distributed at the boundary positions, wherein the first through hole at the left boundary position is aligned with the second through hole on the pressure-sensitive film, and the through holes at the upper, lower and right boundaries are aligned with the through holes at the upper, lower and right boundaries of the vacuum locking film respectively;

[0023] S3. The first insulating layer and the second insulating layer are partially etched through the through hole to release the vacuum locking film and the pressure sensing film. After release, the through hole on the right side serves as the air inlet, and the through holes on the upper and lower sides serve as the electrode lead-out holes.

[0024] S4. Deposit a first metal electrode and a second metal electrode in the central region of the first bottom silicon layer and the pressure-sensitive film, respectively.

[0025] S5. Deposit a first support layer and a second support layer at the edges of the first bottom silicon layer and the pressure-sensitive film, respectively.

[0026] S6. Deposit a first adhesive layer and a second adhesive layer on the first support layer and the second support layer, respectively;

[0027] S7. The pressure-sensitive film is calibrated and bonded to the first bottom silicon layer through the first adhesive layer and the second adhesive layer, and the first metal electrode and the second metal electrode are led out through the through holes on the upper and lower sides respectively. After the electrodes are led out, polyvinyl chloride resin is filled for sealing. After bonding, a test cavity is formed between the first metal electrode and the second metal electrode. The air inlet is connected to the test cavity. After the through hole on the left boundary of the pressure-sensitive film and the through hole on the left boundary of the first bottom silicon layer are connected, they together with the second bottom silicon layer and the vacuum locking film form a reference cavity. The test cavity and the reference cavity are connected through the locking hole, thereby forming a complete vacuum gauge.

[0028] Through the above technical solution, the self-sealing capacitive thin-film vacuum gauge based on MEMS and its fabrication method provided by the present invention have the following beneficial effects:

[0029] 1. The present invention is a self-sealing high-reliability capacitive thin-film vacuum gauge based on MEMS technology. It has the advantages of small size, low power consumption, stable working performance and excellent reliability. It also has low production cost, simple preparation process and compatibility with existing mature integrated circuit technology.

[0030] 2. Compared with existing pressure-sensing film protection technologies for capacitive thin-film vacuum gauges, this invention's MEMS-based vacuum-locking film design enables the self-sealing of the reference cavity, effectively solving problems such as plastic damage and brittle fracture of the pressure-sensing film during atmospheric pressure storage. This significantly improves the operational stability and reliability of the capacitive thin-film vacuum gauge. The reason is that the vacuum-locking film only seals the reference cavity during operation, maintaining a constant pressure vacuum. The pressure-sensing film then deforms under the pressure difference between the reference and test chambers, causing a change in the sensitive capacitance. During non-operation, the vacuum-locking film releases, and the reference cavity connects to the atmosphere through a self-locking hole. At this point, the upper and lower surfaces of the pressure-sensing film are in equilibrium, and the film remains undeformed. Therefore, the capacitive thin-film vacuum gauge with a vacuum-locking film structure effectively improves its operational stability and reliability.

[0031] 3. Compared with existing capacitive thin-film vacuum gauge pressure measurement technology, this invention's MEMS-based vacuum-locking thin-film design enables the self-sealing of the reference cavity of the capacitive thin-film vacuum gauge. This effectively solves the problems of small displacement of the pressure-sensing diaphragm and weak change in sensitive capacitance when measuring high vacuum environments, greatly improving the measurement accuracy and range of the capacitive thin-film vacuum gauge in high vacuum environments. The reason is that during operation, the vacuum gauge is connected to the environment under test through an air inlet. Over time, the vacuum-locking diaphragm first seals the reference cavity under the pressure difference between the working environment and the environment under test, at which point the pressure in the reference cavity is constant. Subsequently, the pressure in the environment under test and the pressure in the test cavity gradually converge. The pressure-sensing diaphragm deforms upwards under the pressure difference between the reference cavity and the test cavity, causing a change in the sensitive capacitance. It is worth noting that in this design, the pressure in the reference cavity is greater than the pressure in the environment under test. Therefore, the lower the pressure in the environment under test, the greater the deformation of the pressure-sensing diaphragm, resulting in a higher change in capacitance. This solves the problem of low accuracy and high lower limit of measurement for capacitive vacuum gauges when measuring high vacuum environments. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0033] Figure 1 This is a schematic cross-sectional view of a MEMS-based self-sealing capacitive thin-film vacuum gauge disclosed in an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of a method for fabricating a MEMS-based self-sealing capacitive thin-film vacuum gauge, as disclosed in an embodiment of the present invention.

[0035] Figure 3 This is a schematic cross-sectional view of the structure obtained in step S1 of the preparation method disclosed in the embodiment of the present invention; (a) first SOI substrate; (b) second SOI substrate;

[0036] Figure 4 These are top and bottom views of the structure obtained in step S2 of the preparation method disclosed in the embodiments of the present invention; (a) top view of the first SOI substrate; (b) bottom view of the first SOI substrate; (c) top view of the second SOI substrate;

[0037] Figure 5 This is a cross-sectional schematic diagram of the structure obtained in step S2 of the preparation method disclosed in the embodiments of the present invention; (a) first SOI substrate; (b) second SOI substrate;

[0038] Figure 6These are schematic diagrams of the structure obtained in step S3 of the preparation method disclosed in the embodiments of the present invention, showing top and bottom views: (a) Top view of the first SOI substrate; (b) Bottom view of the first SOI substrate; (c) Top view of the second SOI substrate;

[0039] Figure 7 This is a cross-sectional schematic diagram of the structure obtained in step S3 of the preparation method disclosed in the embodiments of the present invention; (a) first SOI substrate; (b) second SOI substrate;

[0040] Figure 8 These are top and bottom views of the structure obtained in step S4 of the preparation method disclosed in the embodiments of the present invention; (a) top view of the first SOI substrate; (b) bottom view of the first SOI substrate; (c) top view of the second SOI substrate;

[0041] Figure 9 This is a cross-sectional schematic diagram of the structure obtained in step S4 of the preparation method disclosed in the embodiment of the present invention; (a) first SOI substrate; (b) second SOI substrate;

[0042] Figure 10 This is a top view schematic diagram of the structure obtained in step S5 of the preparation method disclosed in the embodiment of the present invention; (a) first SOI substrate; (b) second SOI substrate;

[0043] Figure 11 This is a cross-sectional schematic diagram of the structure obtained in step S5 of the preparation method disclosed in the embodiments of the present invention; (a) first SOI substrate; (b) second SOI substrate;

[0044] Figure 12 This is a top view schematic diagram of the structure obtained in step S6 of the preparation method disclosed in the embodiment of the present invention; (a) first SOI substrate; (b) second SOI substrate;

[0045] Figure 13 This is a cross-sectional schematic diagram of the structure obtained in step S6 of the preparation method disclosed in the embodiment of the present invention; (a) first SOI substrate; (b) second SOI substrate;

[0046] Figure 14 This is a top view schematic diagram of the structure obtained in step S7 of the preparation method disclosed in the embodiment of the present invention.

[0047] In the figure, 10 is the vacuum locking film; 11 is the air inlet; 12 is the electrode lead-out hole; 13 is the self-locking hole; 20 is the first insulating layer; 30 is the first bottom silicon layer; 40 is the first metal electrode; 50 is the first support layer; 51 is the test chamber; 60 is the first adhesive layer; 70 is the second adhesive layer; 80 is the second support layer; 90 is the second metal electrode; 100 is the pressure-sensitive film; 110 is the second insulating layer; 111 is the reference chamber; and 120 is the second bottom silicon layer. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0049] This invention provides a MEMS-based self-sealing capacitive thin-film vacuum gauge, comprising, from top to bottom, a vacuum-locking thin film 10, a first insulating layer 20, a first bottom silicon layer 30, a pressure-sensitive thin film 100, a second insulating layer 110, and a second bottom silicon layer 120. A first support layer 50 and a second support layer 80 are respectively disposed on the edge regions of the opposite sides of the first bottom silicon layer 30 and the pressure-sensitive thin film 100. The first support layer 50 and the second support layer 80 are bonded together by a first adhesive layer 60 and a second adhesive layer 70.

[0050] A test cavity 51 is formed between the first bottom silicon layer 30 and the pressure-sensitive film 100, and the first support layer 50 and the second support layer 80 constitute the framework of the test cavity 51. A first metal electrode 40 and a second metal electrode 90 are respectively disposed in the central region of the opposite side of the first bottom silicon layer 30 and the pressure-sensitive film 100.

[0051] Electrode lead-out holes 12 for leading out the first metal electrode 40 and the second metal electrode 90 are respectively opened on the upper and lower sides of the vacuum locking film 10, the first insulating layer 20 and the first bottom silicon layer 30. An air inlet hole 11 communicating with the test chamber 51 is opened on the right side of the vacuum locking film 10, the first insulating layer 20 and the first bottom silicon layer 30.

[0052] A through-hole is formed on the left side of the first bottom silicon layer 30 and the pressure-sensitive film 100, and the through-hole passes through the first support layer 50, the second support layer 80, the first adhesive layer 60 and the second adhesive layer 70; the first insulating layer 20 and the second insulating layer 110 located on the upper and lower sides of the test cavity 51 are etched away, thereby forming a connected reference cavity 111 between the vacuum locking film 10, the first bottom silicon layer 30, the pressure-sensitive film 100 and the second bottom silicon layer 120.

[0053] A self-locking hole 13 is formed at a position slightly to the left or right of the center of the first bottom silicon layer 30, connecting the reference cavity 111 and the test cavity 51.

[0054] It should be noted that the principle of forming the reference cavity 111 is as follows: when the vacuum gauge is connected to the external environment to be measured through the air inlet 11, over time, the pressure on the lower surface of the vacuum locking film 10 becomes the pressure of the external environment to be measured. It is easy to see that under the action of internal and external pressure loads, the vacuum locking film 10 deforms and covers the self-locking hole 13 on the first bottom silicon layer 30. At this time, the internal cavity structure is completely sealed, forming the reference cavity 111, and the vacuum degree of the reference cavity 111 is controlled by the adjustment of the vacuum locking film 10.

[0055] Specifically, the first bottom silicon layer 30 and the second bottom silicon layer 120 are made of monocrystalline silicon, the first insulating layer 20 and the second insulating layer 110 are made of silicon dioxide, and the vacuum locking film 10 and the pressure sensing film 100 are made of monocrystalline silicon.

[0056] Specifically, the first metal electrode 40 and the second metal electrode 90 are made of one or more combinations of molybdenum, platinum, aluminum, silver, and gold. In an embodiment of the present invention, both the first metal electrode 40 and the second metal electrode 90 are made of aluminum.

[0057] Specifically, the first support layer 50 and the second support layer 80 are made of one or a combination of silicon dioxide and silicon nitride. In an embodiment of the present invention, the first support layer 50 and the second support layer 80 are made of silicon dioxide.

[0058] Specifically, the materials of the first adhesive layer 60 and the second adhesive layer 70 are either metals or polymers. The metal material is one or a combination of gold and indium, and the polymer material is one of epoxy resin and benzocyclobutene.

[0059] The cross-sectional shape of the air inlet 11, electrode lead-out hole 12, and self-locking hole 13 includes one of the following: circular, rectangular, and polygonal. In the embodiment of the present invention, the cross-sectional shape of the air inlet 11, electrode lead-out hole 12, and self-locking hole 13 is circular.

[0060] This invention also provides a method for fabricating the aforementioned MEMS-based self-sealing capacitive thin-film vacuum gauge, such as... Figure 2 As shown, it includes the following steps:

[0061] S1. Two SOI substrates are provided, namely a first SOI substrate and a second SOI substrate. The first SOI substrate includes a first bottom silicon layer 30, a first insulating layer 20, and a first top silicon layer. The second SOI substrate includes a second bottom silicon layer 120, a second insulating layer 110, and a second top silicon layer. The first and second top silicon layers are thinned by chemical mechanical polishing to obtain a vacuum locking film 10 and a pressure-sensitive film 100, respectively. Figure 3 As shown;

[0062] S2. Local etching is performed on the vacuum locking film 10, the first bottom silicon layer 30, and the pressure-sensitive film 100 to form vias. The pressure-sensitive film 100 forms one via near its left boundary through etching. The vacuum locking film 10 forms three vias through etching, located at the upper, lower, and right boundaries, respectively. The first bottom silicon layer 30 forms five vias through etching, one of which is a self-locking via 13 located slightly to the left or right of the center. The other four vias are evenly distributed at the boundaries. The first via at the left boundary is aligned with the second via on the pressure-sensitive film 100, and the vias at the upper, lower, and right boundaries are aligned with the vias at the upper, lower, and right boundaries of the vacuum locking film 10, respectively. Figure 4 , Figure 5 As shown;

[0063] Specifically, the vacuum locking film 10, the first bottom silicon layer 30, and the pressure-sensitive film 100 can be locally etched using methods such as wet etching or dry etching. Wet etching can employ methods such as EDP wet etching, KOH wet etching, and TMAH wet etching; dry etching can employ methods such as plasma etching, reactive ion etching, and deep reactive ion etching. The etched shape includes, but is not limited to, a circle, a rectangle, and a polygon. In the embodiments of this invention, the vacuum locking film 10, the first bottom silicon layer 30, and the pressure-sensitive film 100 are all locally etched using a self-stopping EDP wet etching method. The resulting vias have a circular cross-sectional shape with a diameter of 5 μm.

[0064] It should be noted that the vacuum locking film 10, the first bottom silicon layer 30 and the pressure-sensitive film 100 are subjected to self-stop etching treatment, that is, the vacuum locking film 10, the first bottom silicon layer 30 and the pressure-sensitive film 100 with the photolithographic pattern are placed into the EDP wet etching apparatus respectively, and the etching stops when the silicon dioxide layer is etched.

[0065] S3. Local etching is performed on the first insulating layer 20 and the second insulating layer 110 through the through-holes to release the vacuum locking film 10 and the pressure sensing film 100. After release, the through-hole on the right side serves as the air inlet 11, and the through-holes on the upper and lower sides serve as electrode lead-out holes 12. Figure 6 , Figure 7 As shown;

[0066] Specifically, local etching can be performed using methods such as plasma etching, ion beam etching, and reactive ion etching. The etched shape includes, but is not limited to, one of circles, rectangles, and polygons. In the embodiments of the present invention, the first insulating layer 20 and the second insulating layer 110 are both formed into circular through holes by gaseous HF etching.

[0067] S4. A first metal electrode 40 and a second metal electrode 90 are deposited in the central regions of the first bottom silicon layer 30 and the pressure-sensitive thin film 100, respectively. Figure 8 , Figure 9 As shown;

[0068] Specifically, the materials of the first metal electrode 40 and the second metal electrode 90 are one or more combinations of molybdenum, platinum, aluminum, silver, and gold. Molybdenum, platinum, aluminum, silver, and gold can all be formed by a stripping process or by a method of sputtering followed by etching. In the embodiments of the present invention, the materials of the first metal electrode 40 and the second metal electrode 90 are both aluminum and are formed by a stripping process.

[0069] S5. A first support layer 50 and a second support layer 80 are deposited at the edges of the first bottom silicon layer 30 and the pressure-sensitive film 100, respectively. Figure 10 , Figure 11 As shown;

[0070] Specifically, the material of the first support layer 50 includes, but is not limited to, one or a combination of silicon dioxide and silicon nitride; wherein, silicon dioxide can be formed by methods such as dry oxidation, wet oxidation, plasma-enhanced chemical vapor deposition, and low-pressure chemical vapor deposition, and silicon nitride can be formed by methods such as plasma-enhanced chemical vapor deposition and low-pressure chemical vapor deposition; in the embodiments of the present invention, the material of the first support layer 50 is silicon dioxide formed by low-pressure chemical vapor deposition.

[0071] Specifically, the materials of the first support layer 50 and the second support layer 80 include, but are not limited to, silicon dioxide and silicon nitride, or a combination of both. Silicon dioxide can be formed by methods such as dry oxidation, wet oxidation, plasma-enhanced chemical vapor deposition, and low-pressure chemical vapor deposition, while silicon nitride can be formed by methods such as plasma-enhanced chemical vapor deposition and low-pressure chemical vapor deposition. In the embodiments of the present invention, the materials of the first support layer 50 and the second support layer 80 are both silicon dioxide formed by low-pressure chemical vapor deposition.

[0072] S6. A first adhesive layer 60 and a second adhesive layer 70 are deposited on the first support layer 50 and the second support layer 80, respectively. Figure 12 , Figure 13 As shown;

[0073] Specifically, the materials of the first adhesive layer 60 and the second adhesive layer 70 are both metals (the material is one or a combination of gold and indium) or polymers (the material is not limited to epoxy resin and benzocyclobutene); wherein, the metal can be formed by a peeling process or by a method of sputtering followed by etching; the polymer can be coated by methods such as spraying, electrodeposition, or printing; in the embodiments of the present invention, the materials of the first adhesive layer 60 and the second adhesive layer 70 are both gold and are formed by a peeling process.

[0074] S7. The pressure-sensitive film 100 is calibrated and bonded to the first bottom silicon layer 30 through the first adhesive layer 60 and the second adhesive layer 70. The first metal electrode 40 and the second metal electrode 90 are led out through the through holes on the upper and lower sides, respectively. After the electrodes are led out, they are sealed with polyvinyl chloride resin. After bonding, a test cavity 51 is formed between the first metal electrode 40 and the second metal electrode 90. The air inlet 11 is connected to the test cavity 51. After the through hole on the left edge of the pressure-sensitive film 100 is connected to the through hole on the upper left edge of the first bottom silicon layer 30, it forms a reference cavity 111 together with the second bottom silicon layer 120 and the vacuum locking film 10. The test cavity 51 and the reference cavity 111 are connected through the locking hole 13, thereby forming a complete vacuum gauge. Figure 1 , Figure 14 As shown;

[0075] Specifically, the pressure-sensitive film 100 and the first bottom silicon layer 30 can be bonded using methods such as direct bonding or intermediate layer bonding. In the embodiments of the present invention, the pressure-sensitive film 100 and the first bottom silicon layer 30 are bonded using a thermo-press bonding method.

[0076] It should be noted that, in order to ensure that the electrode lead-out hole 12 is sealed, after the first metal electrode 40 and the second metal electrode 90 are led out, polyvinyl chloride resin needs to be filled into the electrode lead-out hole 12. The polyvinyl chloride resin can fully fill the pores of the through hole and prevent air leakage from the vacuum gauge test chamber 51.

[0077] It should be noted that the principle for forming the complete structure of the vacuum gauge is as follows: under high-temperature vacuum conditions of approximately 300°C, thermo-press bonding is performed between the pressure-sensitive film 100 and the first bottom silicon layer 30. On one hand, both the first adhesive layer 60 and the second adhesive layer 70 are made of gold, which has a low melting point, is corrosion-resistant, and can achieve hermetically sealed bonding. Therefore, the high-temperature environment of 300°C provides good bonding conditions for thermo-press bonding, enabling good bonding strength between adjacent substrates. On the other hand, under the action of the high temperature of 300°C, the polyvinyl chloride resin is in a viscous flow state, which can fully seal the voids in the through holes.

[0078] As described above, the MEMS-based self-sealing high-reliability capacitive thin-film vacuum gauge of the present invention has advantages such as small size, low power consumption, stable working performance and excellent reliability. It also has low production cost, simple preparation process and compatibility with existing mature integrated circuit technology. Compared with the existing capacitive thin-film vacuum gauge pressure-sensing film 100 protection technology, the MEMS-based vacuum locking film 10 design of the present invention can realize the self-sealing of the reference cavity 111 of the capacitive thin-film vacuum gauge, effectively solving the problems of plastic damage and brittle fracture of the pressure-sensing film 100 when stored in an atmospheric pressure environment, and greatly improving the working stability and reliability of the capacitive thin-film vacuum gauge.

[0079] The reason is that: when the capacitive thin film vacuum gauge is in working condition, the vacuum locking film 10 seals the reference cavity 111 under the action of internal and external pressure loads. At this time, the reference cavity 111 is in a vacuum state, and the pressure sensing film 100 deforms under the action of internal and external pressure difference, and the sensitive capacitance also changes accordingly. When not in working condition, the vacuum locking film 10 is released, and the pressure of the reference cavity 111 is atmospheric pressure. At this time, the upper and lower surfaces of the pressure sensing film 100 are in equilibrium, and the pressure sensing film 100 does not deform.

[0080] Therefore, the capacitive thin-film vacuum gauge with a vacuum-locking diaphragm 10 of the present invention can effectively improve the reliability of the vacuum gauge and ensure stable operation. Compared with existing capacitive thin-film vacuum gauge pressure measurement technology, the self-sealing technology of the vacuum gauge reference cavity 111 based on the vacuum-locking diaphragm 10 structure can effectively solve the problems of small displacement of the pressure-sensing diaphragm 100 and weak change of sensitive capacitance when measuring high vacuum environments (less than 1 Torr), greatly improving the measurement accuracy and measurement range of the capacitive thin-film vacuum gauge under high vacuum. The reason is that when the vacuum gauge is working, it is connected to the environment to be measured through the air inlet 11. As time goes by, the pressure of the environment to be measured and the pressure of the test chamber 51 gradually become consistent. During this process, the vacuum locking diaphragm 10 first deforms under the load of the pressure difference between the working environment and the environment to be measured, sealing the reference chamber 111. Therefore, this design allows the reference chamber 111 to maintain a high pressure. Subsequently, the pressure sensing diaphragm 100 deforms under the load of the pressure difference between the reference chamber 111 and the test chamber 51, thereby causing the sensitive capacitance to change. It is worth noting that the lower the pressure value of the environment to be measured, the greater the deformation of the pressure sensing diaphragm 100, and the higher the capacitance change. This solves the problem of low accuracy and high measurement lower limit of capacitive vacuum gauges when measuring high vacuum environments.

[0081] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0082] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A MEMS-based self-closing capacitance diaphragm gauge, characterized by, The lock vacuum film, the first insulating layer, the first bottom silicon layer, the pressure sensing film, the second insulating layer and the second bottom silicon layer are sequentially arranged from top to bottom, the edge area of the opposite surface of the first bottom silicon layer and the pressure sensing film is respectively provided with the first support layer and the second support layer, and the first support layer and the second support layer are bonded together through the first adhesive layer and the second adhesive layer; The first bottom silicon layer and the pressure sensing film form a test cavity, and the center area of the opposite surface of the first bottom silicon layer and the pressure sensing film is respectively provided with the first metal electrode and the second metal electrode; The upper side and the lower side of the lock vacuum film, the first insulating layer and the first bottom silicon layer are respectively provided with electrode lead-out holes for leading out the first metal electrode and the second metal electrode, and the right side of the lock vacuum film, the first insulating layer and the first bottom silicon layer is provided with a gas inlet hole in communication with the test cavity; The left side of the first bottom silicon layer and the pressure sensing film is provided with a through hole in communication, and the through hole passes through the first support layer, the second support layer, the first adhesive layer and the second adhesive layer; the first insulating layer and the second insulating layer located on the upper and lower sides of the test cavity are etched, so as to form a reference cavity in communication between the lock vacuum film, the first bottom silicon layer, the pressure sensing film and the second bottom silicon layer; The first bottom silicon layer is provided with a self-locking hole in communication with the reference cavity and the test cavity at a position deviated to the left or right of the center.

2. A self-closing capacitance diaphragm gauge based on MEMS according to claim 1, characterized in that, The materials of the first bottom silicon layer and the second bottom silicon layer are monocrystalline silicon, the materials of the first insulating layer and the second insulating layer are silicon dioxide, and the materials of the lock vacuum film and the pressure sensing film are monocrystalline silicon.

3. The self-closing capacitance diaphragm gauge based on MEMS according to claim 1, characterized in that, The materials of the first metal electrode and the second metal electrode are one or a combination of molybdenum, platinum, aluminum, silver and gold.

4. The self-closing capacitance diaphragm gauge based on MEMS according to claim 1, characterized in that, The materials of the first support layer and the second support layer are one or a combination of silicon dioxide and silicon nitride.

5. The self-closing capacitance diaphragm gauge based on MEMS according to claim 1, characterized in that, The materials of the first adhesive layer and the second adhesive layer are both metal or both polymer.

6. A self-closing capacitance diaphragm gauge based on MEMS according to claim 5, characterized in that, The metal material is one or a combination of gold and indium.

7. A self-closing capacitance diaphragm gauge based on MEMS according to claim 5, characterized in that, The polymer material is one of epoxy resin and benzocyclobutene.

8. The self-closing capacitance diaphragm gauge based on MEMS according to claim 1, characterized in that, The cross-sectional shape of the gas inlet hole, the electrode lead-out hole and the self-locking hole includes one of a circle, a rectangle and a polygon.

9. A method of fabricating a MEMS-based self-closing capacitance diaphragm gauge as claimed in claim 1, characterized in that, The method comprises the following steps: S1, providing two SOI substrates, namely a first SOI substrate and a second SOI substrate, the first SOI substrate comprising a first bottom silicon layer, a first insulating layer and a first top silicon layer, and the second SOI substrate comprising a second bottom silicon layer, a second insulating layer and a second top silicon layer; thinning the first top silicon layer and the second top silicon layer by a chemical mechanical polishing method to obtain a lock vacuum film and a pressure sensing film, respectively; S2, the lock vacuum film, the first bottom silicon layer and the pressure sensitive film are respectively locally etched to form through holes; the pressure sensitive film forms one through hole by etching, which is close to the left boundary; the lock vacuum film forms three through holes by etching, which are respectively located at the upper, lower and right boundary positions; the first bottom silicon layer forms five through holes by etching, one of which is located at the center left or right position as a self-locking hole, and the other four are uniformly distributed at the boundary position, wherein the first through hole at the left boundary position is aligned with the second through hole on the pressure sensitive film, and the through holes at the upper, lower and right boundary positions are respectively aligned with the through holes at the upper, lower and right boundary positions of the lock vacuum film; S3, the first insulating layer and the second insulating layer are locally etched by the through holes to release the lock vacuum film and the pressure sensitive film, and the through hole at the right side is used as an air inlet hole, and the through holes at the upper and lower sides are used as electrode lead-out holes; S4, a first metal electrode and a second metal electrode are respectively deposited in the center area of the first bottom silicon layer and the pressure sensitive film; S5, a first support layer and a second support layer are respectively deposited at the edges of the first bottom silicon layer and the pressure sensitive film; S6, a first adhesive layer and a second adhesive layer are respectively deposited on the first support layer and the second support layer; S7, the pressure sensitive film and the first bottom silicon layer are aligned and bonded through the first adhesive layer and the second adhesive layer, and the first metal electrode and the second metal electrode are respectively led out through the through holes at the upper and lower sides, and then filled with polyvinyl chloride resin for sealing after leading out the electrodes; after bonding, a test cavity is formed between the first metal electrode and the second metal electrode, the air inlet hole is communicated with the test cavity, the through hole at the left boundary of the pressure sensitive film and the through hole at the left boundary of the first bottom silicon layer are communicated, and then, together with the second bottom silicon layer and the lock vacuum film, a reference cavity is formed, the self-locking hole is communicated with the test cavity and the reference cavity, thereby forming a complete vacuum gauge.

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