MOEMS acceleration sensing unit based on adjustable Fabry-Perot resonant cavity and preparation method thereof

Abstract

The invention relates to the field of micro-electro-mechanical systems, and provides an MOEMS acceleration sensing unit based on an adjustable Fabry-Perot resonant cavity and a preparation method thereof in order to improve process applicability and reduce cost, the preparation method is carried out based on a surface sacrificial layer process, and comprises the following steps: depositing a lower Bragg layer, a sacrificial layer, an upper Bragg layer, a mass block layer and an electrode layer on a substrate, an insulating groove, a movable mirror, an elastic beam, a supporting frame, a mass block, an upper electrode and a lower electrode are prepared by adopting photoetching and etching processes, a sacrificial layer is removed by adopting a wet etching or gaseous hydrogen fluoride etching process, the whole structure is released, and the adjustable Fabry-Perot resonant cavity is formed. The above mode is compatible with a widely used CMOS technology, the technology applicability is higher, and the cost is lower.

Description

Technical Field

[0001] The invention relates to the technical field of micro-electromechanical systems, in particular to a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity and a preparation method thereof. Background Art

[0002] The Fabry-Perot resonant cavity is composed of two parallel lenses and a cavity between the lenses. Based on the principle of multi-beam interference, the incident light undergoes multiple reflections and transmissions after entering the resonant cavity. In the end, only the incident light of a specific wavelength can interfere constructively and transmit out of the resonant cavity, forming a sharp transmission peak. When the incident light is incident normally and the cavity is vacuum or air, the relationship between the transmission peak wavelength and the cavity length can be expressed by the formula In other words, m is the interference order, λ m is the peak transmission wavelength at the corresponding interference order, and d is the cavity length of the Fabry-Perot resonant cavity. The two mirrors of the Fabry-Perot resonant cavity are manufactured so that one mirror is fixed and the other mirror is movable, forming a movable Fabry-Perot resonant cavity. When a collimated laser of a specific wavelength is used for incident, the length of the Fabry-Perot resonant cavity is changed to satisfy the formula The maximum transmitted light intensity appears at the cavity length of λ, and the transmitted light intensity deviates from λ as the cavity length of the Fabry-Perot resonant cavity deviates from λ. m And sharply decrease or increase.

[0003] The acceleration sensitive unit based on the movable Fabry-Perot resonant cavity is realized by using MOEMS (micro-opto-electro-mechanical system) technology, manufacturing the mass block on the movable mirror, and setting the initial cavity length to satisfy the formula when manufacturing the movable Fabry-Perot resonant cavity. When the mass block is subjected to acceleration, it can drive the movable mirror to displace, causing the length of the movable Fabry-Perot resonant cavity to change. At this time, the change in cavity length will cause a sharp change in the intensity of the emitted light. The intensity of the emitted light is detected using a photodetector, and the acceleration information can be obtained after processing the light intensity data. Compared with the currently widely used capacitive acceleration sensitive units, piezoelectric acceleration sensitive units, and piezoresistive acceleration sensitive units, it has the advantages of high sensitivity and fast response speed.

[0004] In the process of using MOEMS technology to manufacture the movable Fabry-Perot resonant cavity, process errors are unavoidable, such as the thickness of the sacrificial layer deposition deviating from the designed thickness, and the inconsistent etching of the elastic beam leading to inconsistent stress, etc. These will cause the initial cavity length of the movable Fabry-Perot resonant cavity to deviate from the originally designed cavity length, and cause the movable mirror and the fixed mirror to be non-parallel. At the same time, temperature changes during use will also cause the cavity length of the movable Fabry-Perot resonant cavity to change. The above process errors and temperature changes will cause the transmitted light intensity of the acceleration sensitive unit to deviate from the original set range, resulting in reduced sensitivity or increased measurement errors.

[0005] Conductive layers can be set inside the fixed mirror and the movable mirror, and the conductive layers in the fixed mirror and the movable mirror are connected by electrodes and voltage is applied. At this time, the movable Fabry-Perot resonant cavity becomes a parallel plate capacitor. Changing the magnitude of the applied voltage will change the magnitude of the electrostatic attraction between the movable mirror and the fixed mirror, thereby changing the cavity length of the movable Fabry-Perot resonant cavity. At the same time, the electrostatic attraction between the fixed mirror and the movable mirror can also balance the stress difference between the elastic beams and reduce structural deformation. Therefore, the movable Fabry-Perot resonant cavity can be made into an adjustable Fabry-Perot resonant cavity by setting a conductive layer inside the fixed mirror and the movable mirror. The acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity can solve the above-mentioned problems of reduced sensitivity and increased measurement error caused by process errors and temperature changes, and also provide a basis for the closed-loop control of the acceleration sensitive unit.

[0006] Currently, the manufacturing of MOEMS acceleration sensitive units based on adjustable Fabry-Perot resonant cavity is mainly based on bulk silicon process. Bulk silicon process requires the use of special equipment, is incompatible with the widely used CMOS process, and has poor process applicability. At the same time, the MOEMS acceleration sensitive units based on adjustable Fabry-Perot resonant cavity manufactured using bulk silicon process also have the problems of complex structure and high cost. Summary of the invention

[0007] In order to solve the problem that the bulk silicon process requires the use of special equipment, is incompatible with the widely used CMOS process, and has poor process applicability, and the MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity manufactured using the bulk silicon process also has the problems of complex structure and high cost, the present application provides a MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity and a preparation method thereof.

[0008] The technical solution adopted by the present invention to solve the above problems is:

[0009] The method for preparing a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity includes:

[0010] Step 1, alternately depositing multiple layers of silicon nitride and polysilicon on the upper surface of the substrate to form a lower Bragg layer, with the uppermost film layer being polysilicon;

[0011] Step 2, ion implantation and diffusion are performed on the uppermost layer of polysilicon in the lower Bragg layer to increase the conductivity of the polysilicon layer and form a lower conductive layer;

[0012] Step 3, depositing a sacrificial layer on the upper surface of the lower Bragg layer;

[0013] Step 4, depositing a layer of polysilicon on the upper surface of the sacrificial layer;

[0014] Step 5, ion implantation and diffusion of polysilicon are performed to increase the conductivity of the polysilicon layer to form an upper conductive layer;

[0015] Step 6: Use a photolithography process to define a pattern, and then use an etching process to pattern the upper conductive layer to form an insulating groove;

[0016] Step 7, alternately depositing multiple layers of silicon nitride and polysilicon on the upper surface of the upper conductive layer, and the film layer in contact with the upper conductive layer is silicon nitride, and the deposited multiple layers of silicon nitride, polysilicon and the upper conductive layer together constitute an upper Bragg layer;

[0017] Step 8, depositing a layer of silicon nitride on the upper surface of the upper Bragg layer to form a mass block;

[0018] Step 9: Use a photolithography process to define a pattern, and then use an etching process to pattern the uppermost silicon nitride layer to form a mass block, and expose the upper Bragg layer that is not covered by the mass block;

[0019] Step 10: Use a photolithography process to define a pattern, and then use an etching process to pattern the film layer other than the upper conductive layer in the upper Bragg layer not covered by the mass block to form an upper electrode hole;

[0020] Step 11: Use a photolithography process to define a pattern, and then use an etching process to pattern the upper Bragg layer and the sacrificial layer that are not covered by the mass block to form a lower electrode hole, and the lower electrode hole passes through the insulating groove;

[0021] Step 12: deposit a layer of metal to fill the upper electrode hole and the lower electrode hole;

[0022] Step 13: Use a photolithography process to define the patterns of the upper electrode and the lower electrode, and then use an etching process or a wet etching process to pattern the metal to form the upper electrode and the lower electrode;

[0023] Step 14: define a pattern using a photolithography process, and then pattern the upper Bragg layer using an etching process, removing a portion between a middle portion and an edge portion of the upper Bragg layer to form an elastic beam and a movable mirror;

[0024] Step 15: Use a wet etching process or a gaseous hydrogen fluoride etching process to remove the sacrificial layer, release the entire structure, and form a cavity.

[0025] Furthermore, the steps for determining the cavity thickness are:

[0026] Determine the initial range of mass thickness and cavity thickness;

[0027] Taking values ​​of the mass block thickness and the cavity thickness at preset intervals within the initial range to form a combination of the cavity thickness and the mass block thickness;

[0028] Calculate the transmittance of all combinations of cavity thickness and mass block thickness under incident light of a preset wavelength;

[0029] Determine the specific thickness of the mass block according to design requirements;

[0030] The specific thickness of the cavity is determined according to the specific thickness of the mass block and the transmittance requirement, and the thickness of the cavity is the thickness of the sacrificial layer.

[0031] Furthermore, the thickness of each film layer in the upper Bragg layer and the lower Bragg layer is given by the formula Determine, where h is the thickness of each film layer, λ is the wavelength of incident light, and n is the refractive index of each film layer.

[0032] Furthermore, the substrate is a silicon wafer, a gallium nitride wafer, a gallium arsenide wafer or a silicon carbide wafer.

[0033] Furthermore, the material of the sacrificial layer is phosphate glass, borophosphosilicate glass or silicon oxide.

[0034] Furthermore, the metal deposited in step 12 is aluminum, gold, silver or copper.

[0035] The MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity is prepared by using the MOEMS acceleration sensitive unit preparation method based on the adjustable Fabry-Perot resonant cavity, including:

[0036] substrate;

[0037] a fixed mirror, located on the upper surface of the substrate, and having a lower conductive layer disposed therein;

[0038] A sacrificial layer, located on the upper surface of the fixed mirror, wherein the middle portion is removed to form a cavity, and the edge portion is retained to support the upper structure;

[0039] A support frame is located on the upper surface of the sacrificial layer and has an upper conductive layer disposed therein;

[0040] an elastic beam, located above the cavity, connecting the movable mirror and the support frame, and having an upper conductive layer disposed therein;

[0041] The movable mirror is connected to the support frame through an elastic beam, is located above the cavity, and has an upper conductive layer disposed therein;

[0042] A mass block is located on the upper surface of the movable mirror;

[0043] an upper electrode in contact with the upper conductive layer in the support frame;

[0044] The lower electrode contacts the lower conductive layer in the fixed mirror.

[0045] Furthermore, the elastic beam has a straight shape, an L shape or a U shape.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The preparation method provided by the present invention is based on a surface sacrificial layer process, is compatible with the widely used CMOS process, has stronger process applicability, and has the advantages of low cost, simple process, and short preparation cycle. The MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity manufactured by the method of the present invention has the advantages of simple structure and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1-Figure 15 It is a structural schematic diagram of the preparation process;

[0049] Fig.16 is the transmittance distribution diagram;

[0050] Fig.17 is the transmittance curve changing with the cavity thickness at the incident light wavelength of 1550nm;

[0051] Fig.18 Schematic diagram of the MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0053] A method for preparing a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity is based on a surface sacrificial layer process and includes:

[0054] Step 1: alternately deposit multiple layers of silicon nitride and polysilicon on the upper surface of the substrate to form a lower Bragg layer, and the uppermost film layer is polysilicon; Figure 1 As shown, in the present embodiment, five layers of silicon nitride and polysilicon are alternately deposited on the upper surface of the substrate 10, which are, from bottom to top, the first layer of polysilicon 11a, the second layer of silicon nitride 11b, the third layer of polysilicon 11c, the fourth layer of silicon nitride 11d, and the fifth layer of polysilicon 11e; the substrate includes but is not limited to a silicon wafer, a gallium nitride wafer, a gallium arsenide wafer or a silicon carbide wafer; the specific number of layers of silicon nitride and polysilicon can be set according to actual needs.

[0055] Step 2: Ion implantation and diffusion are performed on the topmost polysilicon layer in the lower Bragg layer to increase the conductivity of the polysilicon layer and form a lower conductive layer, such as boron doping to make it a P-type semiconductor. Figure 2 shown.

[0056] Step 3: Figure 3 As shown, a sacrificial layer 12 is deposited on the upper surface of the lower Bragg layer. The material of the sacrificial layer includes but is not limited to PSG (phosphate glass), BPSG (borophosphosilicate glass) or silicon oxide.

[0057] Step 4: Figure 4 As shown, a layer of polysilicon 13a is deposited on the upper surface of the sacrificial layer;

[0058] Step 5: Figure 5 As shown, ion implantation and diffusion are performed on the polysilicon 13a to increase the conductivity of the polysilicon layer and form an upper conductive layer;

[0059] Step 6: Figure 6 As shown, a photolithography process is used to define a pattern, and then an etching process is used to pattern the conductive layer to form an insulating groove 13a1;

[0060] Step 7: Figure 7 As shown, four layers of silicon nitride and polysilicon are alternately deposited on the upper surface of the upper conductive layer, and the film layer in contact with the upper conductive layer is silicon nitride. The deposited multiple layers of silicon nitride and polysilicon together with the upper conductive layer constitute an upper Bragg layer; the upper Bragg layer is, from bottom to top, the first layer of polysilicon 13a, the second layer of silicon nitride 13b, the third layer of polysilicon 13c, the fourth layer of silicon nitride 13d, and the fifth layer of polysilicon 13e; the specific number of layers of silicon nitride and polysilicon can be set according to actual needs.

[0061] Step 8: Figure 8 As shown, a layer of silicon nitride 14a is deposited on the upper surface of the upper Bragg layer to form a quality block.

[0062] Step 9: Fig. 9As shown, a pattern is defined by using a photolithography process, and then an etching process is used to pattern the uppermost silicon nitride layer to form a mass block 14b, and to expose the upper Bragg layer that is not covered by the mass block.

[0063] Step 10: Fig.10 As shown, a photolithography process is used to define a pattern, and then an etching process is used to pattern the film layer except the upper conductive layer in the upper Bragg layer not covered by the mass block to form an upper electrode hole 15a.

[0064] Step 11: Fig.11 As shown, a photolithography process is used to define a pattern, and then an etching process is used to pattern the upper Bragg layer and the sacrificial layer that are not covered by the mass block to form a lower electrode hole 15b, and the lower electrode hole passes through the insulating groove.

[0065] Step 12: Fig.12 As shown, a layer of metal aluminum 16a is deposited to fill the upper electrode hole and the lower electrode hole; in addition to aluminum, the deposited metal may also be gold, silver or copper.

[0066] Step 13: Fig.13 As shown, the upper electrode and the lower electrode patterns are defined by using a photolithography process, and then the metal is patterned by using an etching process or a wet etching process to form an upper electrode 16b and a lower electrode 16c;

[0067] Step 14: Fig.14 As shown, a pattern is defined by a photolithography process, and then an etching process is used to pattern the upper Bragg layer, and a portion 17 between the middle portion and the edge portion of the upper Bragg layer is removed to form a movable mirror 17a, a support frame 17b, and an elastic beam 17c connecting the movable mirror 17a and the support frame 17b, wherein the elastic beam 17c is not shown in the figure;

[0068] Step 15: Fig.15 As shown, the sacrificial layer is removed by a wet etching process or a gaseous hydrogen fluoride etching process, the overall structure is released, and the cavity 18 is formed, thereby completing the manufacture of the MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity.

[0069] In this embodiment, the thickness of each film layer in the upper Bragg layer and the lower Bragg layer is given by the formula: Determine, where h is the thickness of each film layer, λ is the wavelength of the incident light, and n is the refractive index of each film layer. In this embodiment, a laser with a wavelength of 1550nm is used as the incident light when the MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity works. The refractive index of polysilicon is 3.46, and the refractive index of silicon nitride is 1.98. The thickness of polysilicon is calculated to be 112nm, and the thickness of silicon nitride is 195.7nm.

[0070] The thickness of the cavity and the thickness of the mass block are determined by the transmittance results of the MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity under the incident light of 1550nm wavelength calculated by using COMSOL Multiphysics finite element simulation software. Specifically, the cavity thickness is changed at intervals of 2nm between 1300-1800nm, and the mass block thickness is changed at intervals of 2nm between 60-784nm. The transmittance of all combinations of cavity thickness and mass block thickness under the incident light of 1550nm is calculated, and the transmittance distribution diagram with the change of mass block thickness and cavity thickness is obtained, as shown in the figure. Fig.16 As shown. According to the transmittance distribution diagram, the thickness of the mass block can be arbitrarily selected. Considering the design requirements of the range and sensitivity of the MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity, the thickness of the mass block is taken as 600nm. After determining the thickness of the mass block, the transmittance data obtained by the above simulation that varies with the thickness of the mass block and the thickness of the cavity can be used to obtain the transmittance curve when the thickness of the mass block is 600nm and the cavity thickness varies between 1300-1800nm, as shown in Fig.17 The cavity thickness when the transmittance is 0.5 is taken as the cavity thickness of the MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity, which is given by Fig.17 It can be obtained that the cavity thickness is 1539 nm or 1561 nm when the transmittance is 0.5, and the thickness of the cavity is determined to be 1561 nm.

[0071] It can be seen from the transmittance curve that when the MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity is subjected to an upward acceleration, the cavity length of the resonant cavity becomes smaller and the transmittance will increase. When the MOEMS acceleration sensitive unit based on the adjustable Fabry-Perot resonant cavity is subjected to a downward acceleration, the cavity length of the resonant cavity becomes larger and the transmittance will decrease.

[0072] like Fig.18As shown, this embodiment also provides a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity, which is prepared by a preparation method of a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity, including: a substrate 10, a fixed mirror 11, which is located on the upper surface of the substrate and has a lower conductive layer disposed therein; a sacrificial layer 12, which is located on the upper surface of the fixed mirror, wherein the middle portion thereof is removed to form a cavity, and the edge portion thereof is reserved for supporting the upper structure; a cavity 18, which is located between the fixed mirror 11 and the movable mirror 17a and is formed by removing the middle portion of the sacrificial layer 12; a support frame 17b, which is located on the upper surface of the sacrificial layer 12 and has an upper conductive layer disposed therein; an elastic beam 17c, which is located above the cavity 18 and connects the movable mirror 17a and the support frame 17b and has an upper conductive layer disposed therein. The embodiment is provided with a total of 4 identical straight-line elastic beams, namely, a first elastic beam 17c1, a second elastic beam 17c2, a third elastic beam 17c3, and a fourth elastic beam 17c4; the shape of the elastic beam can also be L-shaped or U-shaped, etc., and the number and shape can be selected according to actual conditions; the movable mirror 17a is connected to the support frame 17b through the elastic beam 17c, is located above the cavity 18, and is provided with an upper conductive layer inside; the mass block 14b is located on the upper surface of the movable mirror 17a; the upper electrode is in contact with the upper conductive layer in the support frame through the upper electrode hole, and a total of 2 identical upper electrodes are provided, namely, a first upper electrode 16b1 and a second upper electrode 16b2; the lower electrode is in contact with the lower conductive layer in the fixed mirror through the lower electrode hole, and a total of 2 identical lower electrodes are provided, namely, a first lower electrode 16c1 and a second lower electrode 16c2.

[0073] The fixed mirror 11, the movable mirror 17a, and the cavity 18 between the fixed mirror and the movable mirror together constitute an adjustable Fabry-Perot resonant cavity. When the movable mirror 17a is acted upon by electrostatic force, it can move up and down, causing the thickness of the cavity 18 to change; when the mass block is acted upon by acceleration, it can drive the movable mirror 17a to move up and down, causing the thickness of the cavity 18 to change.

Claims

1. A method for preparing a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity, characterized in that: include: Step 1, alternately depositing multiple layers of silicon nitride and polysilicon on the upper surface of the substrate to form a lower Bragg layer, with the uppermost film layer being polysilicon; Step 2, ion implantation and diffusion are performed on the uppermost layer of polysilicon in the lower Bragg layer to increase the conductivity of the polysilicon layer and form a lower conductive layer; Step 3, depositing a sacrificial layer on the upper surface of the lower Bragg layer; Step 4, depositing a layer of polysilicon on the upper surface of the sacrificial layer; Step 5, ion implantation and diffusion of polysilicon are performed to increase the conductivity of the polysilicon layer to form an upper conductive layer; Step 6: Use a photolithography process to define a pattern, and then use an etching process to pattern the upper conductive layer to form an insulating groove; Step 7, alternately depositing multiple layers of silicon nitride and polysilicon on the upper surface of the upper conductive layer, and the film layer in contact with the upper conductive layer is silicon nitride, and the deposited multiple layers of silicon nitride, polysilicon and the upper conductive layer together constitute an upper Bragg layer; Step 8, depositing a layer of silicon nitride on the upper surface of the upper Bragg layer to form a mass block; Step 9: Use a photolithography process to define a pattern, and then use an etching process to pattern the uppermost silicon nitride layer to form a mass block, and expose the upper Bragg layer that is not covered by the mass block; Step 10: Use a photolithography process to define a pattern, and then use an etching process to pattern the film layer other than the upper conductive layer in the upper Bragg layer not covered by the mass block to form an upper electrode hole; Step 11: Use a photolithography process to define a pattern, and then use an etching process to pattern the upper Bragg layer and the sacrificial layer that are not covered by the mass block to form a lower electrode hole, and the lower electrode hole passes through the insulating groove; Step 12: deposit a layer of metal to fill the upper electrode hole and the lower electrode hole; Step 13: Use a photolithography process to define the patterns of the upper electrode and the lower electrode, and then use an etching process or a wet etching process to pattern the metal to form the upper electrode and the lower electrode; Step 14: define a pattern using a photolithography process, and then pattern the upper Bragg layer using an etching process, removing a portion between a middle portion and an edge portion of the upper Bragg layer to form an elastic beam and a movable mirror; Step 15: Use a wet etching process or a gaseous hydrogen fluoride etching process to remove the sacrificial layer, release the entire structure, and form a cavity.

2. The method for preparing a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity according to claim 1, characterized in that: The steps to determine the cavity thickness are: Determine the initial range of mass thickness and cavity thickness; Taking values ​​of the mass block thickness and the cavity thickness at preset intervals within the initial range to form a combination of the cavity thickness and the mass block thickness; Calculate the transmittance of all combinations of cavity thickness and mass block thickness under incident light of a preset wavelength; Determine the specific thickness of the mass block according to design requirements; The specific thickness of the cavity is determined according to the specific thickness of the mass block and the transmittance requirement, and the thickness of the cavity is the thickness of the sacrificial layer.

3. The method for preparing a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity according to claim 2, characterized in that: The thickness of each film layer in the upper Bragg layer and the lower Bragg layer is given by the formula Determine, where h is the thickness of each film layer, λ is the wavelength of incident light, and n is the refractive index of each film layer.

4. The method for preparing a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity according to claim 1, characterized in that: The substrate is a silicon wafer, a gallium nitride wafer, a gallium arsenide wafer or a silicon carbide wafer.

5. The method for preparing a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity according to claim 1, characterized in that: The material of the sacrificial layer is phosphate glass, borophosphosilicate glass or silicon oxide.

6. The method for preparing a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity according to any one of claims 1 to 5, characterized in that: The metal deposited in step 12 is aluminum, gold, silver or copper.

7. A MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity, prepared by the method for preparing a MOEMS acceleration sensitive unit based on an adjustable Fabry-Perot resonant cavity according to any one of claims 1 to 6, characterized in that: include: substrate; a fixed mirror, located on the upper surface of the substrate, and having a lower conductive layer disposed therein; A sacrificial layer, located on the upper surface of the fixed mirror, wherein the middle portion is removed to form a cavity, and the edge portion is retained to support the upper structure; A support frame is located on the upper surface of the sacrificial layer and has an upper conductive layer disposed therein; an elastic beam, located above the cavity, connecting the movable mirror and the support frame, and having an upper conductive layer disposed therein; The movable mirror is connected to the support frame through an elastic beam, is located above the cavity, and has an upper conductive layer disposed therein; A mass block is located on the upper surface of the movable mirror; an upper electrode in contact with the upper conductive layer in the support frame; The lower electrode contacts the lower conductive layer in the fixed mirror.

8. The MOEMS acceleration sensing unit based on the adjustable Fabry-Perot resonant cavity according to claim 7 is characterized in that: The elastic beam has a straight shape, an L shape or a U shape.

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