MEMS (Micro Electro Mechanical System) chip, preparation method thereof, MEMS gas sensor and gas detection device

Abstract

The invention discloses an MEMS (Micro Electro Mechanical System) chip, a preparation method of the MEMS chip, a micro electro mechanical system gas sensor and a gas detection device. The MEMS chip comprises a first pole plate and a second pole plate, a cavity is formed between the first pole plate and the second pole plate, a dielectric substance in the cavity is gas, the first pole plate is provided with a first vent hole, the cavity is communicated with the outside through the first vent hole, and the second pole plate is provided with a second vent hole. The mechanical resonant frequency of the first polar plate is far greater than the frequency of sending voltage excitation to the MEMS chip by an ASIC (Application Specific Integrated Circuit) chip, or both the mechanical resonant frequency of the first polar plate and the frequency of sending voltage excitation to the MEMS chip by the ASIC chip are 60 kHz to 100 kHz; the first pole plate and the second pole plate form a variable capacitor, and the dielectric substance of the variable capacitor is gas, so that the sensitivity of the MEMS gas sensor using the MEMS chip can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection devices, and more specifically, to a MEMS chip, a preparation method thereof, a micro-electromechanical gas sensor, and a gas detection device. Background Art

[0002] In related technologies, gas leakage from equipment can have an impact on our health, quality of life, life safety, and the operation of industrial processes. For example, some refrigerant gases are flammable and explosive, so real-time detection of such refrigerant leakage becomes extremely important.

[0003] The capacitive gas sensors currently in general use are mostly sensitive to the environment (humidity, temperature, pressure). Traditional capacitive gas sensors mostly use dielectric materials with selective gas adsorption properties (for example, high molecular polymers or metal oxides, etc.), and these dielectric materials easily adsorb water vapor in the air and cause the capacitance to change, resulting in large detection errors.

[0004] Therefore, it is necessary to provide a new technical solution to solve the above technical problems. Summary of the invention

[0005] An object of the present invention is to provide a new technical solution for a MEMS chip.

[0006] According to a first aspect of the present invention, a MEMS chip is provided. The MEMS chip comprises a first electrode plate and a second electrode plate, a cavity is formed between the first electrode plate and the second electrode plate, the dielectric in the cavity is a gas, the first electrode plate is provided with a first vent hole, and the cavity is connected to the outside through the first vent hole;

[0007] The mechanical resonance frequency of the first electrode is much greater than the frequency at which the ASIC chip sends voltage excitation to the MEMS chip, or the mechanical resonance frequency of the first electrode and the frequency at which the ASIC chip sends voltage excitation to the MEMS chip are both 60kHz to 100kHz.

[0008] Optionally, a distance between the first electrode plate and the second electrode plate is 100 nm to 300 nm.

[0009] Optionally, the size of the opposing portions of the first electrode plate and the second electrode plate is less than or equal to 200 μm.

[0010] Optionally, the thickness of the first electrode plate is 0.5 um to 1 um, and the first electrode plate is provided with the first vent hole along the thickness direction.

[0011] Optionally, the first ventilation hole has a diameter of 0.2 um to 0.6 um.

[0012] Optionally, an insulating layer is deposited on the inner wall of the cavity, and the thickness of the insulating layer is 50 nm to 100 nm.

[0013] Optionally, the MEMS chip further includes a substrate, the thickness of the substrate is 200 nm to 500 nm, and the first electrode plate and the second electrode plate are respectively connected to two opposite sides of the substrate.

[0014] Optionally, a temperature sensor and / or a heater is also provided on the substrate.

[0015] According to a second aspect of the present application, a method for preparing a MEMS chip is provided, the method comprising:

[0016] Providing a substrate, the substrate comprising a base plate, a first electrode plate and a second electrode plate are respectively provided on opposite sides of the base plate, and the first electrode plate is provided with a first vent hole;

[0017] Etching the substrate between the first electrode plate and the second electrode plate to form a cavity between the first electrode plate and the second electrode plate;

[0018] Depositing a sealing layer on the surface of the first electrode plate to seal the first vent hole;

[0019] Etching a relief hole on the substrate, wherein the relief hole is suitable for depositing a pad;

[0020] Depositing a passivation layer on the surface of the substrate and / or the first electrode plate;

[0021] The redundant sealing layer on the surface of the first electrode plate is etched so that the cavity is connected to the outside through the first vent hole.

[0022] According to a third aspect of the present invention, a micro-electromechanical gas sensor is provided, which comprises an ASIC chip and the MEMS chip of the above embodiment, wherein the ASIC chip is electrically connected to the MEMS chip.

[0023] According to a fourth aspect of the present invention, a gas detection method is provided, which is performed by using the micro-electromechanical gas sensor of the above embodiment. The gas detection method comprises:

[0024] The gas to be detected enters the cavity of the MEMS chip, and the dielectric constant of the gas in the cavity changes, so that the capacitance of the MEMS chip changes;

[0025] The MEMS chip converts the capacitance change into an analog signal and transmits it to the ASIC chip;

[0026] The ASIC chip receives the analog signal and processes it;

[0027] The ASCI chip sends a voltage excitation to the MEMS chip to vibrate the first electrode of the MEMS chip, thereby changing the capacitance of the MEMS chip.

[0028] According to a fifth aspect of the present invention, a gas detection device is provided, which includes the micro-electromechanical gas sensor of the above embodiment.

[0029] Optionally, the gas detection device further comprises a shell, the shell is provided with a second vent hole, and the micro-electromechanical gas sensor is arranged in the shell.

[0030] Optionally, the gas detection device further includes a pressure sensor and / or a humidity sensor, and the pressure sensor and / or the humidity sensor are arranged in the housing.

[0031] One of the technical effects of the present application is that the first electrode plate and the second electrode plate of the MEMS chip form a variable capacitor, and the dielectric in the cavity of the variable capacitor is gas. When the gas to be detected enters the cavity from the first vent, the capacitance of the variable capacitor changes, and the detection error is small, so as to improve the detection sensitivity of the micro-electromechanical gas sensor using the MEMS chip of the present invention.

[0032] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0034] Figure 1 It is a schematic diagram of the structure of a micro-electromechanical gas sensor according to an embodiment of the present application.

[0035] Figure 2 It is a schematic diagram of the partial structure of a micro-electromechanical gas sensor according to an embodiment of the present application.

[0036] Figure 3 It is a frequency response curve diagram of a micro-electromechanical gas sensor according to an embodiment of the present application.

[0037] Figure 4 It is a schematic diagram of a full-bridge detection circuit of a micro-electromechanical gas sensor according to an embodiment of the present application.

[0038] Figure 5 It is a schematic structural diagram of a gas detection device according to an embodiment of the present application.

[0039] Reference numerals:

[0040] 1. MEMS chip; 11. first electrode; 111. first vent; 12. second electrode; 13. cavity; 14. pad; 15. substrate; 16. passivation layer; 2. ASIC chip; 3. insulating layer; 7. base plate; 4. shell; 41. cover; 42. PCB board; 43. second vent; 5. pressure sensor; 6. humidity sensor. DETAILED DESCRIPTION

[0041] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0042] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0043] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0044] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0045] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0046] According to one embodiment of the present application, a MEMS chip 1 is provided. Figures 1 to 5 As shown, the MEMS chip 1 includes a first plate 11 and a second plate 12, a cavity 13 is formed between the first plate 11 and the second plate 12, the dielectric in the cavity 13 is gas, the first plate 11 is provided with a first vent 111, and the cavity 13 is connected to the outside through the first vent 111. An ASIC chip 2 is electrically connected to the MEMS chip 1. The mechanical resonance frequency of the first plate 11 is much greater than the frequency at which the ASIC chip 2 sends voltage excitation to the MEMS chip 1, or the mechanical resonance frequency of the first plate 11 and the frequency at which the ASIC chip 2 sends voltage excitation to the MEMS chip 1 are both 60kHz to 100kHz.

[0047] In this example, a cavity 13 is formed between the first electrode plate 11 and the second electrode plate 12, and the first electrode plate 11 and the second electrode plate 12 form a variable capacitor. The dielectric in the cavity 13 of the variable capacitor is gas. When the gas to be detected enters the cavity 13 from the first vent 111, the capacitance of the variable capacitor changes, and the detection error is small, so as to improve the detection sensitivity of the micro-electromechanical gas sensor using the MEMS chip of the present invention.

[0048] In this example, the MEMS chip 1 of the present application can be used for micro-electromechanical sensors to detect gas. For example, it can be used to detect toxic and harmful gases leaking from certain equipment. For example, third-generation refrigerants (R32, R134a) and fourth-generation refrigerants (R290, R1234yf, R1234ze) generally have the characteristics of being flammable and explosive. When there is no gas leakage, the dielectric in the cavity 13 is air. When the gas leaks, the gas can enter the cavity 13 from the first vent 111 on the first plate 11, thereby causing the dielectric in the cavity 13 to change. The dielectric constant of the dielectric of the variable capacitor changes, so that the capacitance of the variable capacitor changes, and the MEMS chip 1 can transmit the signal to the ASIC chip 2 for further processing, and transmit it to the control unit. Among them, the effective capacitance of the variable capacitor can be 2pF~4pF.

[0049] Of course, the micro-electromechanical gas sensor of the present application can also be used to detect other gases, and those skilled in the art may determine the method based on actual conditions, and no specific limitation is made here.

[0050] In this example, the MEMS chip 1 of the present application uses air as the dielectric of the variable capacitor, so that it can maximally accurately measure and compensate for interference and cross-sensitivity caused by environmental changes, so as to realize a high-precision, miniaturized, low-power, fast-response, low-cost refrigerant leakage gas detection sensor.

[0051] In this example, the mechanical resonance frequency of the first plate 11 is much greater than the frequency at which the ASIC chip 2 sends voltage excitation to the MEMS chip 1. That is, assuming that the mechanical resonance frequency of the first plate 11 is f1, and the frequency at which the ASIC chip 2 sends voltage excitation to the MEMS chip 1 is f0, it satisfies that f1 is much greater than f0. For example, f1 can be one or two orders of magnitude greater than f0, for example, f0 is 30kHz, f1 is 300kHz, or f0 is 30kHz, f1 is 2MHz, etc. As for the specific values ​​of f1 and f0, those skilled in the art can determine according to the actual situation, and no specific limitation is made here.

[0052] In this example, the mechanical resonance frequency of the first plate 11 is assumed to be f1, and the ASIC chip 2 can apply polarization voltage to the MEMS chip 1. Assuming that the frequency at which the ASIC chip 2 sends voltage excitation to the MEMS chip 1 is f0, and f1 is much greater than f0, at this time, the first plate 11 can be considered not to vibrate, and the capacitance of the variable capacitor is changed only by the change of the dielectric constant, and this design does not need to consider acoustic or gas flow damping.

[0053] Alternatively, the mechanical resonance frequency of the first plate 11 and the frequency at which the ASIC chip 2 sends voltage excitation to the MEMS chip 1 are both 60kHz to 100kHz. That is, the mechanical resonance frequency of the first plate 11 is 60kHz to 100kHz, the voltage excitation frequency sent by the ASIC chip 2 to the MEMS chip 1 is 60kHz to 100kHz, and the mechanical resonance frequency f1 of the first plate 11 matches the voltage excitation frequency f0 sent by the ASIC chip 2 to the MEMS chip 1. For example, f1 can be equal to f0, or f1 is close to f0. At this time, the ASIC chip 2 sends a voltage excitation to the MEMS chip 1, which can cause the first plate 11 to mechanically resonate, and the vibration of the first plate 11 can change the distance from the second plate 12, thereby further increasing the change in capacitance, so as to further improve the sensitivity of the micro-electromechanical gas sensor.

[0054] In this example, the structural design of the MEMS chip 1 can reduce the acoustic damping as much as possible to improve Q (quality factor), and the first plate 11 can resonate more stably. Among them, reducing the acoustic damping, that is, reducing the acoustic resistance, for example, can reduce the low acoustic damping by increasing the opening rate of the first plate 11, increasing the aperture of the first vent 111, reducing the hole spacing of the plurality of first vents 111, and increasing the gap height of the cavity 13 to improve Q.

[0055] In this example, f1 may be greater than f0, or f1 may be less than f0. Those skilled in the art may determine this based on actual conditions, and no specific limitation is given here.

[0056] like Figure 3 As shown, when the mechanical resonance frequency of the first electrode 11 is equal to the voltage excitation frequency, that is, f1=f0, the response amplitude is the largest and the generated signal is the largest, that is, when there is gas leakage and when there is no gas leakage, the difference in response is the largest, which is more conducive to detecting weak gas leakage signals when the leaked gas is small. Among them, the response can be a signal such as capacitance, pressure or current generated.

[0057] like Figure 4As shown, the MEMS chip 1 is provided with two variable capacitors Cs, and the MEMS chip 1 is also provided with two fixed capacitors Cr. And the two variable capacitors Cs and the two fixed capacitors Cr constitute a Wheatstone full-bridge detection circuit. The ASIC chip 2 sends VB and VS voltage excitations to the MEMS chip 1, and the ASIC chip can receive signals from the OUT+ and OUT- terminals of the MEMS chip 1. Among them, VB can be a high-frequency voltage pulse / or a sine wave excitation, and VS can be a zero potential.

[0058] In one example, the distance between the first electrode plate 11 and the second electrode plate 12 is 100 nm to 300 nm.

[0059] In this example, the distance between the first electrode plate 11 and the second electrode plate 12 is 100nm to 300nm, which can ensure the capacitance value of the capacitor and reduce the influence of the edge effect on the capacitor. For example, the distance between the first electrode plate 11 and the second electrode plate 12 can be 100nm, 120nm, 130nm, 180nm, 240nm, 270nm or 300nm, etc., and those skilled in the art can determine it according to actual conditions, and it is not specifically limited here.

[0060] In one example, the size of the opposing portions of the first electrode plate 11 and the second electrode plate 12 is less than or equal to 200 μm.

[0061] In this example, the size of the relative portion of the first electrode plate 11 and the second electrode plate 12 is less than or equal to 200 μm. That is, the size of the capacitor cavity 13 is less than or equal to 200 μm, for example, when the cavity 13 is cylindrical, the diameter of the cavity 13 is less than or equal to 200 μm, or when the cross section of the cavity 13 is rectangular, the side length of the cavity 13 is less than or equal to 200 μm. By setting the size of the relative portion of the first electrode plate 11 and the second electrode plate 12, the area of ​​the capacitor electrode plate can be adjusted, so that the capacitance value of the capacitor can be guaranteed, and the influence of the edge effect on the capacitor can be further reduced.

[0062] For example, the size of the opposing parts of the first electrode plate 11 and the second electrode plate 12 may be 200 μm, 180 μm, 170 μm or 150 μm, etc. Those skilled in the art may determine the size according to actual conditions, and no specific limitation is made here.

[0063] In an example, the thickness of the first electrode plate 11 is 0.5 um to 1 um, and the first electrode plate 11 is provided with the first vent holes 111 along the thickness direction.

[0064] In this example, the first electrode plate 11 is provided with a first vent hole 111 along the thickness direction. By setting the thickness of the first electrode plate 11 along the thickness direction to 0.5um to 1um, the capacitance value of the capacitor can be guaranteed, and the influence of the edge effect on the capacitor can be further reduced. For example, the thickness of the first electrode plate 11 is 0.5um, 0.6μm, 0.7μm, 0.8μm, 0.9μm or 1um, etc. Those skilled in the art can determine according to the actual situation, and no specific limitation is made here.

[0065] In an example, Figure 2 As shown, an insulating layer 3 is deposited on the inner wall of the cavity 13 , and the thickness of the insulating layer 3 is 50 nm to 100 nm.

[0066] like Figure 2 As shown, in this example, the first electrode plate 11 and the second electrode plate 12 are spaced apart, and the first electrode plate 11 and the second electrode plate 12 form a cavity 13, and an insulating layer 3 is provided on the inner wall of the cavity 13 to play a role in insulation protection. The thickness of the insulating layer 3 can be 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, etc., which can be determined by those skilled in the art according to actual conditions, and is not specifically limited here.

[0067] like Figure 2 As shown, in this example, the outer surface of the first electrode 11 can be provided with an insulating layer 3. The insulating layer 3 can be formed by atomic layer deposition ALD or molecular vapor deposition MVD with good conformal coverage, and the material can be silicon-rich silicon nitride SiNx (atomic ratio x = 0.9 to 1.1), SAM (i.e., self-assembled monolayer polymer Self-Assembled-Monolayer), and the hydrophobic property of SAM can also prevent water vapor condensation in the cavity 13, broadening the application range of the gas sensor, such as low temperature, high humidity, etc.

[0068] It should be noted that an insulating layer 3 is provided on the inner wall of the cavity 13 , and along the direction from the first electrode plate 11 to the second electrode plate 12 , the gap of the cavity 13 has a value of 100 nm to 300 nm.

[0069] In an example, Figure 2 As shown, the MEMS chip 1 further includes a substrate 7 , the thickness of the substrate 7 is 200 nm to 500 nm, and the first electrode plate 11 and the second electrode plate 12 are respectively connected to two opposite sides of the substrate 7 .

[0070] like Figure 2As shown, in this example, the MEMS chip 1 also includes a substrate 7, and the first electrode plate 11 and the second electrode plate 12 are respectively installed on both sides of the substrate 7 along the thickness direction. That is, a through hole is provided in the middle of the substrate 7, and the first electrode plate 11 and the second electrode plate 12 are installed on the opposite sides of the substrate 7, and the first electrode plate 11 and the second electrode plate 12 are partially opposite to the through hole, so that the first electrode plate 11, the second electrode plate 12 and the inner wall of the through hole can form a cavity 13. Among them, the thickness of the substrate 7 is 200nm to 500nm. By setting the thickness of the substrate 7, it is beneficial to adjust the value of the gap of the cavity 13 along the direction from the first electrode plate 11 to the second electrode plate 12 to a suitable value, which is beneficial to ensure the capacitance value of the capacitor and can further reduce the influence of the edge effect on the capacitor. For example, the thickness of the substrate 7 can be 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm, etc., and those skilled in the art can determine it according to actual conditions, and no specific limitation is made here.

[0071] like Figure 2 As shown, in this example, the surface of the substrate 7 may be covered with an insulating layer 3 .

[0072] In this example, the substrate 7 may be made of materials such as silicon dioxide, and those skilled in the art may determine the material based on actual conditions, and no specific limitation is made here.

[0073] In one example, the aperture of the first vent 111 is 0.2um to 0.6um. Among them, the first vent 111 can be a cylindrical hole, a prismatic hole, or can also be a vent of other irregular shapes. The aperture of the first vent 111 can be 0.2μm, 0.3μm, 0.4μm, 0.5μm or 0.6μm, etc. Those skilled in the art can determine according to the actual situation, and no specific limitation is made here. By setting the aperture to 0.2um to 0.6um, external gas can smoothly enter the cavity 13, which is also conducive to reducing acoustic damping.

[0074] like Figure 2 As shown, in this example, a plurality of first vent holes 111 may be arranged at intervals, for example, two, three, four, five or more vent holes may be arranged at intervals. Those skilled in the art may determine the number based on actual conditions, and no specific limitation is made here.

[0075] In one example, a temperature sensor and / or a heater is also provided on the substrate 7 .

[0076] In this example, a temperature sensor may be provided on the substrate 7 so as to detect the temperature of the gas environment. The temperature sensor may be a resistance temperature detector, such as RTD (Resistance Temperature Detector) or PT100 (temperature sensor based on platinum resistance). Alternatively, Figure 2 As shown, the second electrode 12 is N++ (N-type semiconductor with high doping concentration), and P+ (P-type semiconductor with high doping concentration) is also provided on the substrate 7 to form a PN junction temperature sensor. Of course, the specific structure of the temperature sensor can be determined by those skilled in the art according to actual conditions, and is not specifically limited here.

[0077] Alternatively, a heater may be provided on the substrate 7 to achieve a heating function. By providing a heater, it is possible to help prevent the adverse effects caused by water vapor condensation. The heater may be a metal film or a high resistance material, etc. Those skilled in the art may determine the method according to actual conditions, and no specific limitation is made here.

[0078] Of course, the temperature sensor and the heater can also be integrated on the substrate 7 at the same time.

[0079] In an example, Figure 2 As shown, the MEMS chip 1 further includes a plurality of pads 14. The second electrode 12, P+ (a P-type semiconductor with a high doping concentration) and the first electrode 11 are all provided with pads 14, which can be electrically connected to other structures.

[0080] like Figure 2 As shown, in this example, the second electrode 12 and P+ (P-type semiconductor with a high doping concentration) are arranged on one side of the substrate 7, and the substrate 7 is provided with an avoidance hole at the corresponding position. The welding pad 14 can be deposited in the avoidance hole from the side of the substrate 7 away from the first electrode 11 and P+, and welded to the first electrode 11 and P+ respectively.

[0081] In an example, Figure 2 As shown, the MEMS chip 1 further includes a substrate 15, and the substrate 15 is connected to one side of the substrate 7. For example, the substrate 15 can be connected to the side of the substrate 7 where the second electrode plate 12 and P+ are provided, and the second electrode plate 12 and P+ are embedded in the substrate 15. The MEMS chip 1 can be bonded to the PCB board 42 through the substrate 15. Among them, the substrate 15 can be made of silicon, etc., and those skilled in the art can determine it according to the actual situation, and it is not specifically limited here.

[0082] In an example, Figure 2As shown, a passivation layer 16 is further provided on the side of the substrate 7 facing away from the substrate 15, and the passivation layer 16 is provided on the surface of the substrate 7 and the surface of the first electrode 11, and the passivation layer 16 avoids the pad 14 and the first vent hole 111. By providing the passivation layer 16, the first electrode 11 can be mechanically protected and anti-corrosion. Among them, the passivation layer 16 can be made of silicon nitride or the like.

[0083] In this example, the surfaces of the first electrode plate 11 and the substrate 7 are provided with an insulating layer 3 , and the passivation layer 16 may be provided on the surface of the insulating layer 3 .

[0084] According to another aspect of the present application, a method for preparing a micro-electromechanical gas sensor is provided, which is used to prepare the micro-electromechanical gas sensor of the above embodiment, and the preparation method comprises:

[0085] A substrate is provided, wherein the substrate includes a base plate 7, and a first electrode plate 11 and a second electrode plate 12 are respectively provided on opposite sides of the base plate 7, and the first electrode plate 11 is provided with a first vent hole 111;

[0086] In this example, a first electrode plate 11 and a second electrode plate 12 are respectively disposed on both sides of the substrate 7 in the thickness direction, and a first vent hole 111 is disposed on the first electrode plate 11 in the thickness direction. A substrate 15 is also disposed on the side of the substrate 7 away from the first electrode plate 11, and the second electrode plate 12 is embedded in the substrate 15.

[0087] Etching the substrate 7 between the first electrode plate 11 and the second electrode plate 12 to form a cavity 13 between the first electrode plate 11 and the second electrode plate 12;

[0088] In this example, the substrate 7 is etched through the first vent hole 111 on the first electrode plate 11. That is, the portion between the first electrode plate 11 and the second electrode plate 12 of the substrate 7 is etched away and then released through the first vent hole 111. Thus, a cavity 13 can be formed between the first electrode plate 11 and the second electrode plate 12.

[0089] Depositing a sealing layer on the surface of the first electrode plate 11 to seal the first vent hole 111;

[0090] In this example, a sealing layer is deposited on the surface of the first electrode plate 11 to seal the first vent hole 111 , so as to prevent particles and residues from entering the cavity 13 through the first vent hole 111 when other operations are performed on the substrate later.

[0091] The sealing layer may be made of silicon nitride. When depositing the sealing layer, silicon nitride may be deposited on the surface of the first electrode plate 11 and the surface of the substrate 7 as the insulating layer 3 .

[0092] A avoidance hole is etched on the substrate 7, wherein the avoidance hole is suitable for depositing the pad 14;

[0093] In this example, after the first vent hole 111 is sealed, an escape hole is etched on the substrate 7 for subsequently depositing a pad 14 in the escape hole. The pad 14 is used to be electrically connected to the second electrode plate 12.

[0094] Depositing a passivation layer 16 on the surface of the substrate 7 and / or the first electrode plate 11;

[0095] In this example, the passivation layer 16 is deposited on the surface of the substrate 7, or on the surface of the substrate 7 away from the second electrode plate 12, or on the surfaces of the substrate 7 and the first electrode plate 11. Those skilled in the art may determine the method according to actual conditions, and no specific limitation is made here.

[0096] The redundant sealing layer on the surface of the first electrode plate 11 is etched so that the cavity 13 is connected to the outside through the first vent hole 111 .

[0097] In this example, the excess sealing layer on the surface of the first electrode plate 11 is etched, that is, the sealing layer sealing the first vent hole 111 is etched so that the cavity 13 can communicate with the outside through the first vent hole 111 .

[0098] According to another embodiment of the present application, a micro-electromechanical gas sensor is provided. The micro-electromechanical gas sensor comprises an ASIC chip 2 and the MEMS chip 1 of the above embodiment. The ASIC chip 2 is electrically connected to the MEMS chip 1 .

[0099] A cavity 13 is formed between the first electrode plate 11 and the second electrode plate 12 of the MEMS chip, and the first electrode plate 11 and the second electrode plate 12 form a variable capacitor. The dielectric in the cavity 13 of the variable capacitor is gas. When the gas to be detected enters the cavity 13 from the first vent 111, the capacitance of the variable capacitor changes, and the detection error is small, so as to improve the detection sensitivity of the micro-electromechanical gas sensor using the MEMS chip of the present invention.

[0100] According to another embodiment of the present application, a gas detection method is provided, which is detected by the micro-electromechanical gas sensor of the above embodiment, and the gas detection method includes:

[0101] S1. The gas to be detected enters the cavity of the MEMS chip 1, and the dielectric constant of the gas in the cavity 13 changes, so that the capacitance of the MEMS chip 1 changes. After the refrigerant or other gas leaks, it enters the cavity 13 of the MEMS chip through the first through hole 111 on the first electrode plate 11, so that the dielectric constant of the dielectric in the cavity 13 changes, thereby causing the capacitance of the MEMS chip 1 to change.

[0102] S2. The MEMS chip converts the capacitance change into an analog signal and transmits it to the ASIC chip. After the capacitance of the MEMS chip 1 changes, the MEMS chip 1 can convert the capacitance change signal into an analog signal and transmit the analog signal to the ASIC chip 2 for further processing.

[0103] S3, the ASIC chip receives and processes the analog signal. After receiving the analog signal, the ASIC chip 2 can amplify and filter the analog signal, and then output the processed signal to an external device.

[0104] S4, the ASCI chip sends a voltage excitation to the MEMS chip to vibrate the first electrode plate 11 of the MEMS chip, thereby changing the capacitance of the MEMS chip. The ASIC chip 2 receives the analog signal of the MEMS chip, and the ASCI chip 2 can send a voltage excitation to the MEMS chip 1. The mechanical resonance frequency of the first electrode plate 11 matches the frequency of the voltage excitation, so that the first electrode plate 11 undergoes mechanical resonance, thereby further increasing the capacitance change of the MEMS chip 1, thereby increasing the signal, which is beneficial for detecting a weak gas leakage signal when the gas leakage is small.

[0105] According to another embodiment of the present application, a gas detection device is provided. Figure 5 As shown, the gas detection device includes the micro-electromechanical gas sensor of the above embodiment.

[0106] In this example, the micro-electromechanical gas sensor includes a MEMS chip 1, including a first plate 11 and a second plate 12, a cavity 13 is formed between the first plate 11 and the second plate 12, the dielectric in the cavity 13 is gas, the first plate 11 is provided with a first vent 111, and the cavity 13 is connected to the outside through the first vent 111. An ASIC chip 2 is electrically connected to the MEMS chip 1. A cavity 13 is formed between the first plate 11 and the second plate 12, the first plate 11 and the second plate 12 form a variable capacitor, the dielectric in the cavity 13 of the variable capacitor is gas, when the gas to be detected enters the cavity 13 from the first vent 111, the capacitance of the variable capacitor changes, the detection error is small, so as to improve the detection sensitivity of the micro-electromechanical gas sensor.

[0107] In an example, Figure 5 As shown, the gas detection device further comprises a shell 4 , the shell 4 is provided with a second vent hole 43 , and the micro-electromechanical gas sensor is arranged in the shell 4 .

[0108] In this example, the MEMS gas sensor is disposed in the housing 4, for example, bonded to the inner wall of the housing 4. The housing 4 is provided with a second vent hole 43, through which external air can enter the housing 4, and then enter the cavity 13 through the first vent hole 111.

[0109] In this example, the housing 4 includes a PCB board 42 and a cover 41, and the cover 41 is disposed on one side of the PCB board 42. The cover 41 can be bonded to the PCB board 42, and a second vent 43 is further disposed on the cover 41. The MEMS chip 1 and the ASIC chip 2 are both bonded to the PCB board 42, and the ASIC chip 2 is electrically connected to the PCB board 42 through a wire.

[0110] In one example, the gas detection device further includes a pressure sensor 5 and / or a humidity sensor 6 , and the pressure sensor 5 and / or the humidity sensor 6 are disposed in the housing 4 .

[0111] like Figure 5 As shown, in this example, the gas detection device also includes a pressure sensor 5 and a humidity sensor 6, and the pressure sensor 5 and the humidity sensor 6 are both integrated in the housing 4, for example, bonded to the surface of the PCB board 42. The pressure sensor 5 is used to detect the gas pressure, and the humidity sensor 6 is used to detect the humidity in the air. The micro-electromechanical gas sensor, the pressure sensor 5 and the humidity sensor 6 share a second vent 43. Among them, the pressure sensor 5 and the humidity sensor 6 are both configured as micro-electromechanical sensors, and multiple sensors can share an ASCI chip, or each sensor is correspondingly provided with an ASCI chip.

[0112] Alternatively, one of the pressure sensor 5 and the humidity sensor 6 may be disposed in the housing 4, and the other may be packaged separately. Alternatively, only the micro-electromechanical gas sensor may be disposed in the housing 4, and the pressure sensor 5 and the humidity sensor 6 may be packaged separately. The specific structure of the gas detection device may be determined by those skilled in the art according to actual conditions, and is not specifically limited here.

[0113] The above embodiments focus on the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, they will not be repeated here.

[0114] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A MEMS chip, characterized in that: include: a first electrode plate and a second electrode plate, wherein a cavity is formed between the first electrode plate and the second electrode plate, the dielectric in the cavity is gas, the first electrode plate is provided with a first vent hole, and the cavity is connected to the outside through the first vent hole; The mechanical resonance frequency of the first electrode is much greater than the frequency at which the ASIC chip sends voltage excitation to the MEMS chip, or the mechanical resonance frequency of the first electrode and the frequency at which the ASIC chip sends voltage excitation to the MEMS chip are both 60kHz to 100kHz.

2. The MEMS chip according to claim 1, characterized in that: The distance between the first electrode plate and the second electrode plate is 100 nm to 300 nm.

3. The MEMS chip according to claim 1, characterized in that: The size of the opposing portions of the first electrode plate and the second electrode plate is less than or equal to 200 μm.

4. The MEMS chip according to claim 1, characterized in that: The thickness of the first electrode plate is 0.5 um to 1 um, and the first electrode plate is provided with the first vent hole along the thickness direction.

5. The MEMS chip according to claim 1, characterized in that: The first vent hole has a diameter of 0.2 um to 0.6 um.

6. The MEMS chip according to claim 1, characterized in that: An insulating layer is deposited on the inner wall of the cavity, and the thickness of the insulating layer is 50nm-100nm.

7. The MEMS chip according to claim 1, characterized in that: The MEMS chip further includes a substrate, the thickness of the substrate is 200nm-500nm, and the first electrode plate and the second electrode plate are respectively connected to two opposite sides of the substrate.

8. The MEMS chip according to claim 7, characterized in that: The substrate is also provided with a temperature sensor and / or a heater.

9. A method for preparing a MEMS chip, characterized in that: include: Providing a substrate, the substrate comprising a base plate, a first electrode plate and a second electrode plate are respectively provided on opposite sides of the base plate, and the first electrode plate is provided with a first vent hole; Etching the substrate between the first electrode plate and the second electrode plate to form a cavity between the first electrode plate and the second electrode plate; Depositing a sealing layer on the surface of the first electrode plate to seal the first vent hole; Etching a relief hole on the substrate, wherein the relief hole is suitable for depositing a pad; Depositing a passivation layer on the surface of the substrate and / or the first electrode plate; The redundant sealing layer on the surface of the first electrode plate is etched so that the cavity is connected to the outside through the first vent hole.

10. A micro-electromechanical gas sensor, characterized in that: The invention comprises an ASIC chip and a MEMS chip as claimed in any one of claims 1 to 8, wherein the ASIC chip is electrically connected to the MEMS chip.

11. A gas detection method, characterized in that: The gas detection method comprises: The gas to be detected enters the cavity of the MEMS chip, and the dielectric constant of the gas in the cavity changes, so that the capacitance of the MEMS chip changes; The MEMS chip converts the capacitance change into an analog signal and transmits it to the ASIC chip; The ASIC chip receives the analog signal and processes it; The ASCI chip sends a voltage excitation to the MEMS chip to vibrate the first electrode of the MEMS chip, thereby changing the capacitance of the MEMS chip.

12. A gas detection device, characterized in that: Comprising the micro-electromechanical gas sensor as claimed in claim 10.

13. The gas detection device according to claim 12, characterized in that: The device also includes a shell, wherein the shell is provided with a second vent hole, and the micro-electromechanical gas sensor is arranged in the shell.

14. The gas detection device according to claim 13, characterized in that: It also includes a pressure sensor and / or a humidity sensor, and the pressure sensor and / or the humidity sensor are arranged in the housing.

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