A process for preparing a piezoelectrically driven MEMS electric field sensor

Abstract

The present invention discloses a process for fabricating a piezoelectrically driven MEMS electric field sensor. The process includes thermally oxidizing a double-sided SOI wafer; fabricating an adhesive layer and a lower drive electrode layer on the insulating layer on the front side of the SOI wafer; fabricating a piezoelectric material layer on the lower drive electrode layer; fabricating an upper drive electrode layer on the piezoelectric material layer, and peeling off the upper drive electrode layer; etching the piezoelectric material layer; etching the lower drive electrode layer and the adhesive layer; etching the insulating layer on the front side of the SOI wafer; fabricating a sensing electrode pad on the top silicon layer on the front side of the SOI wafer; etching the top silicon layer on the front side of the SOI wafer; spin-coating a protective material on the front side of the SOI wafer; removing the insulating layer on the back side of the SOI wafer, etching the bottom silicon layer and buried oxide layer of the SOI wafer; and removing the protective material on the front side of the SOI wafer to obtain a MEMS electric field sensor. The present invention has a simple fabrication process, low cost, and is conducive to large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS electric field sensors, and in particular to a process for preparing a piezoelectrically driven MEMS electric field sensor. Background Art

[0002] Currently, power systems are developing towards intelligent and integrated systems. Online monitoring of equipment requires obtaining valid status information about grid devices, of which the electric field is a crucial state variable. Traditional electric field sensors suffer from limitations such as large size, high power consumption, and limited measurement range. MEMS sensors overcome these limitations and can meet the needs of large-scale deployment and status information sensing for grid equipment. Summary of the Invention

[0003] The purpose of the present invention is to provide a process for preparing a piezoelectrically driven MEMS electric field sensor, which can be used to prepare a piezoelectrically driven MEMS electric field sensor with stable performance and durability. The preparation process is simple, the cost is low, and it is conducive to large-scale production.

[0004] An embodiment of the present invention provides a process for preparing a piezoelectrically driven MEMS electric field sensor, the method comprising:

[0005] S1, thermally oxidizing the double sides of the SOI wafer to form a SiO2 insulating layer on the front and back sides of the SOI wafer respectively;

[0006] S2, preparing an adhesive layer and a lower driving electrode layer on the insulating layer on the front side of the SOI wafer;

[0007] S3, preparing a piezoelectric material layer on the lower driving electrode layer;

[0008] S4, preparing an upper driving electrode layer on the piezoelectric material layer, and peeling off the upper driving electrode layer using a No. 1 photoresist;

[0009] S5, etching the piezoelectric material layer using photoresist No. 2;

[0010] S6, etching the lower driving electrode layer and the bonding layer using a No. 3 photoresist;

[0011] S7, etching the insulating layer on the front side of the SOI wafer using a No. 4 photoresist;

[0012] S8, using a No. 5 photoresist to prepare a sensing electrode pad on the top silicon layer on the front side of the SOI wafer;

[0013] S9, etching the top silicon layer on the front side of the SOI wafer using a No. 6 photoresist;

[0014] S10, spin coating a protective material on the front surface of the SOI wafer;

[0015] S11, removing the insulating layer on the back side of the SOI wafer, and etching the bottom silicon layer and buried oxide layer of the SOI wafer using a No. 7 photoresist;

[0016] S12, removing the protective material on the front surface of the SOI wafer to obtain a MEMS electric field sensor.

[0017] As a further improvement of the present invention, in S1, the thickness of the insulating layer is 500 nm.

[0018] As a further improvement of the present invention, in S2, the bonding layer and the lower driving electrode layer are prepared by magnetron sputtering, wherein the bonding layer is a Ti layer with a thickness of 50 nm, and the lower driving electrode layer is a Pt layer with a thickness of 200 nm.

[0019] As a further improvement of the present invention, in S3, the piezoelectric material layer is prepared by a sol-gel method or a magnetron sputtering method, wherein the piezoelectric material layer is a PZT film or an AlN film with a thickness of 1-2 μm.

[0020] As a further improvement of the present invention, in S4, the upper driving electrode layer is prepared by magnetron sputtering, wherein the driving electrode layer is an Al layer with a thickness of 300 nm.

[0021] As a further improvement of the present invention, in S5, the piezoelectric material layer is etched by reactive ion etching;

[0022] In S6, etching the lower driving electrode layer and the adhesive layer by ion beam etching;

[0023] In S7, the insulating layer on the front side of the SOI wafer is etched by reactive ion etching, and CHF3 gas or a mixed gas of CF4 and H2 is introduced during the etching process;

[0024] In the step S9 , the top silicon layer on the front side of the SOI wafer is etched by reactive ion etching.

[0025] As a further improvement of the present invention, in S8, the sensing electrode pad is prepared by magnetron sputtering and lift-off method, wherein the sensing electrode pad uses Cr and Au, the Cr thickness is 50 nm, and the Au thickness is 300 nm.

[0026] As a further improvement of the present invention, in S10, the protective material is polyimide and / or photoresist.

[0027] As a further improvement of the present invention, in S11, the insulating layer on the back side of the SOI wafer is removed by reactive ion etching, and CHF3 gas is introduced during the removal process; and the bottom silicon layer and buried oxide layer of the SOI wafer are etched by reactive ion etching, and CHF3 gas is introduced during the etching process.

[0028] As a further improvement of the present invention, in S12, the protective material on the front surface of the SOI wafer is removed by reactive ion etching, and O2 gas is introduced during the removal process.

[0029] The present invention has the following beneficial effects: the piezoelectrically driven MEMS electric field sensor prepared using the process of the present invention utilizes an integral cantilever arm structure and support base, ensuring the uniformity of the finished chip and providing the cantilever arm structure with improved stability and durability during operation. The various process steps employed in the process of the present invention do not damage the wafer, the materials of the various membrane layers in the MEMS electric field sensor can be adaptively selected, and the thickness of each membrane layer can be precisely controlled during its preparation. The overall process is simple, low-cost, and conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0031] Figure 1 A design layout of a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0032] FIG2 is a schematic diagram of seven photoresist plates according to an exemplary embodiment of the present invention, wherein FIG2(a) shows photoresist plate No. 1, FIG2(b) shows photoresist plate No. 2, FIG2(c) shows photoresist plate No. 3, FIG2(d) shows photoresist plate No. 4, FIG2(e) shows photoresist plate No. 5, FIG2(f) shows photoresist plate No. 6, and FIG2(g) shows photoresist plate No. 7;

[0033] Figure 3 Schematic diagram of the sensor structure obtained after step S1 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the sensor structure obtained after step S2 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the sensor structure obtained after step S3 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of the sensor structure obtained after step S4 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0037] Figure 7 Schematic diagram of the sensor structure obtained after step S5 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0038] Figure 8 This is a schematic diagram of the sensor structure obtained after step S6 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0039] Figure 9 This is a schematic diagram of the sensor structure obtained after step S7 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0040] Figure 10 This is a schematic diagram of the sensor structure obtained after step S8 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0041] Figure 11 This is a schematic diagram of the sensor structure obtained after step S9 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0042] Figure 12 This is a schematic diagram of the sensor structure obtained after step S10 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0043] Figure 13 This is a schematic diagram of the sensor structure obtained after step S11 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention;

[0044] Figure 14 This is a schematic diagram of the sensor structure obtained after step S12 in a process for preparing a piezoelectrically driven MEMS electric field sensor according to an exemplary embodiment of the present invention.

[0045] In the figure,

[0046] 1. SOI wafer; 2. Insulation layer; 3. Adhesive layer; 4. Lower driving electrode layer; 5. Piezoelectric material layer; 6. Upper driving electrode layer; 7. Sensing electrode pad; 8. Protective material; 9. Piezoelectric driving structure; 10. Shielding electrode; 11. Sensing electrode; 12. L-shaped elastic beam; 13. Damping balance beam; 14. Bottom silicon layer; 15. Buried oxide layer; 16. Top silicon layer. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0048] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0049] In addition, in the description of the present invention, the terms used are for illustrative purposes only and are not intended to limit the scope of the present invention. The terms "comprise" and / or "include" are used to specify the presence of the elements, steps, operations and / or components, but do not exclude the presence or addition of one or more other elements, steps, operations and / or components. The terms "first", "second" and the like may be used to describe various elements, do not represent an order, and do not limit these elements. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more. These terms are only used to distinguish one element from another. These and / or other aspects become apparent in conjunction with the following drawings, and it is easier for a person of ordinary skill in the art to understand the description of the embodiments of the present invention. The accompanying drawings are used to depict the embodiments of the present invention for illustrative purposes only. Those skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods shown in the present invention can be adopted without departing from the principles of the present invention.

[0050] A process for preparing a piezoelectrically driven MEMS electric field sensor according to an embodiment of the present invention, wherein the piezoelectrically driven MEMS electric field sensor is a micro electric field sensor with a cantilever arm structure, comprises:

[0051] S1, thermally oxidizing both sides of the SOI wafer 1 to form a SiO2 insulating layer 2 on the front and back sides of the SOI wafer 1;

[0052] S2, preparing an adhesive layer 3 and a lower driving electrode layer 4 on the insulating layer 2 on the front surface of the SOI wafer 1;

[0053] S3, preparing a piezoelectric material layer 5 on the lower driving electrode layer 4;

[0054] S4, preparing an upper driving electrode layer 6 on the piezoelectric material layer 5, and peeling off the upper driving electrode layer 6 using a No. 1 photoresist;

[0055] S5, etching the piezoelectric material layer 5 using photoresist No. 2;

[0056] S6, etching the lower driving electrode layer 4 and the adhesive layer 3 using a No. 3 photoresist;

[0057] S7, etching the insulating layer 2 on the front surface of the SOI wafer 1 using a No. 4 photoresist;

[0058] S8, using a No. 5 photoresist to prepare a sensing electrode pad 7u on the top silicon layer on the front side of the SOI wafer 1;

[0059] S9, etching the top silicon layer on the front side of the SOI wafer 1 using a No. 6 photoresist;

[0060] S10, spin coating a protective material 8 on the front surface of the SOI wafer 1;

[0061] S11, removing the insulating layer 2 on the back side of the SOI wafer 1, and etching the bottom silicon layer and buried oxide layer of the SOI wafer 1 using a No. 7 photoresist;

[0062] S12, removing the protective material 8 on the front surface of the SOI wafer 1 to obtain a MEMS electric field sensor.

[0063] MEMS sensors, with their small size, low power consumption, and wide measurement range, play a vital role in power grid systems, meeting the needs of large-scale deployment and status information sensing for power grid equipment. They can also obtain valid status information about power grid equipment during the sensing process. The method described in the present invention provides a process for preparing MEMS sensors, resulting in stable and durable MEMS electric field sensors. The preparation process is simple, relying primarily on basic processes such as etching, stripping, and spin coating. This minimizes the complexity of the manufacturing process, reduces costs, and facilitates large-scale production and high-quality fabrication.

[0064] like Figure 1 As shown in FIG. , the design layout of the piezoelectrically driven MEMS electric field sensor of the present invention is shown. The piezoelectrically driven MEMS electric field sensor includes an SOI wafer and a MEME microstructure on the surface, wherein, Figure 3-14As shown, the SOI wafer 1 is a three-layer structure, including a bottom silicon layer 14, a buried oxide layer 15 and a top silicon layer 16. The MEME microstructure includes a piezoelectric drive structure 9, a shielding electrode 10 and a sensing electrode 11. The piezoelectric drive structure 9 adopts a cantilever arm structure. The cantilever arm structure is a three-layer structure, which consists of an upper drive electrode, a piezoelectric film and a lower drive electrode from top to bottom. By applying voltage to the upper and lower drive electrodes, an electric field is formed on the piezoelectric film, thereby controlling the vibration of the piezoelectric drive structure. The shielding electrode 10 is connected to the piezoelectric drive structure 9 through an L-shaped elastic beam 12, which converts the vertical displacement of the piezoelectric drive structure 9 into the vibration of the shielding electrode 10. The torsion of the shielding electrode 10 is provided with a damping balance beam 13 to adjust the vibration damping of the shielding electrode 10.

[0065] As shown in Figure 2, the method of the present invention uses 7 photoresist boards, which are used in different steps of the process method. Among them, photoresist board No. 1 is an upMETAL layer board, photoresist board No. 2 is a PZFILM layer board, photoresist board No. 3 is a bottomMETAL layer board, photoresist board No. 4 is a PADOXIDE layer board, photoresist board No. 5 is a handian layer board, photoresist board No. 6 is a Device Silicon layer board, and photoresist board No. 7 is a Substrate Silicon layer board.

[0066] In one embodiment, in step S1, a four-inch SOI wafer 1 is first prepared and cleaned according to a standard process. After cleaning, the SOI wafer 1 is thermally oxidized on both sides to form a SiO2 layer, for example, 500 nm thick, on the front and back sides of the SOI wafer 1, respectively, as the insulating layer 2. The insulating layer on the front side of the SOI wafer 1 is used to isolate the electrode structure from the top silicon layer 16. The sensor structure after step S1 is completed is as follows: Figure 3 shown.

[0067] Among them, the standard cleaning process is: use sulfuric acid and water in a ratio of 4:1 at a high temperature of 125 degrees, pickling for about 15 minutes, then use deionized water to clean the organic matter of the SOI wafer, then rinse with hydrofluoric acid at room temperature for about 15 minutes, then rinse with deionized water and dry to complete the shedding of oxides on the surface of the SOI wafer, and then complete the oxide cleaning.

[0068] In one embodiment, in step S2, the bonding layer 3 and the lower driving electrode layer 4 are prepared by magnetron sputtering. The sensor structure after step S2 is completed is as follows: Figure 4 The bonding layer 3 is, for example, a Ti layer with a thickness of, for example, 50 nm, and the lower driving electrode layer 4 is, for example, a Pt layer with a thickness of, for example, 200 nm.

[0069] In this embodiment, to achieve good adhesion, two metal layers are magnetron sputtered. A 50nm-thick intermediate layer of rare metal titanium (Ti) is used as the bonding layer, while a 200nm-thick layer of precious metal platinum (Pt) is used for the lower drive electrode. Magnetron sputtering utilizes simple equipment, an easily controllable sputtering process, and a large coating area, resulting in a highly adhesive film.

[0070] In one embodiment, in step S3, the piezoelectric material layer 5 is prepared by a sol-gel method (ie, a sol-gel process) or a magnetron sputtering method. The sensor structure after step S3 is completed is as follows: Figure 5 The piezoelectric material layer 5 is, for example, a PZT film or an AlN film, with a thickness of, for example, 1-2 μm. The Sol-Gel process uses simple equipment and is low-cost. The film produced is highly uniform, and the film thickness can be precisely controlled during the preparation process.

[0071] It is understandable that the piezoelectric material includes but is not limited to lead zirconate titanate PZT, inorganic material aluminum nitride AlN, etc., and any material that can achieve the same function.

[0072] In one embodiment, in step S4, the upper driving electrode layer 6 is prepared by magnetron sputtering. The sensor structure after step S4 is completed is as follows: Figure 6 The driving electrode layer 6 is, for example, an Al layer, and has a thickness of, for example, 300 nm.

[0073] In this embodiment, an upper driving electrode is fabricated on the piezoelectric material layer 5, and a 300 nm thick Al layer is attached to the piezoelectric material layer by magnetron sputtering. Then, the sputtered silicon wafer is placed in a C3H6O solution for peeling using photoresist No. 1 as shown in FIG. 2(a).

[0074] In one embodiment, in step S5, the piezoelectric material layer 5 is etched by reactive ion etching. The sensor structure after step S5 is completed is as follows: Figure 7 shown.

[0075] After completing the above S4, in this embodiment, in order to remove unnecessary films, a general etching method, namely reactive ion etching, is adopted. This etching method can form patterns on any material. The piezoelectric material layer 5 is etched by reactive ion etching using the photomask No. 2 as shown in FIG. 2( b ).

[0076] In one embodiment, in step S6, the lower driving electrode layer 4 and the adhesive layer 3 are etched by ion beam etching. The sensor structure after step S6 is completed is as follows: Figure 8 shown.

[0077] In this embodiment, after completing the above S5, the lower driving electrode layer 4 and the adhesive layer 3 are patterned by etching using an ion beam etching device through the photoresist plate No. 3 as shown in FIG. 2( c ).

[0078] In one embodiment, in step S7, the insulating layer 2 on the front side of the SOI wafer 1 is etched by reactive ion etching, and CHF3 gas or a mixed gas of CF4 and H2 is introduced during the etching process. The sensor structure after step S7 is completed is as follows: Figure 9 shown.

[0079] In this embodiment, the etching gas for SiO2 can be CHF3 gas or a mixture of CF4 and H2 in a suitable ratio. To reduce the variety of gases used and the complexity of fabrication, a reactive ion etching apparatus is preferably used with CHF3 gas to pattern the SiO2 layer on the substrate surface. The photoresist plate No. 4 used in the etching process is shown in Figure 2(d).

[0080] In one embodiment, in step S8, the sensing electrode pad 7 is prepared by magnetron sputtering and peeling-off method. The sensor structure after step S8 is completed is as follows: Figure 10 The sensing electrode pad 7 is made of, for example, Cr and Au, with a thickness of Cr of, for example, 50 nm, and a thickness of Au of, for example, 300 nm.

[0081] In this embodiment, in order to simplify the process steps and reduce the device manufacturing cost, a lift-off process is adopted in the process of manufacturing the sensing electrode pad to eliminate redundant process flows and ensure accurate pattern dimensions. The No. 5 photoresist used in the lift-off process is shown in FIG2(e).

[0082] In one embodiment, in step S9, the top silicon layer 16 on the front side of the SOI wafer 1 is etched by reactive ion etching. The sensor structure after step S9 is completed is as follows: Figure 11 shown.

[0083] In this embodiment, a deep reactive ion etching device is used to etch the top silicon layer 16 on the front side. This method is a dry plasma etching method that can achieve high aspect ratio etching. The No. 6 photoresist used in the etching process is shown in Figure 2(f).

[0084] In one embodiment, in step S10, the protective material 8 is polyimide and / or photoresist. The sensor structure after step S10 is completed is as follows: Figure 12 shown.

[0085] In this embodiment, to prevent subsequent process damage to the sensor structure and ensure the proper etching process, while also enhancing device integrity, a protective material is spin-coated on the structural silicon. This material must be resistant to high temperatures and pressures, easily removable, and minimally impactful. Polyimide (PI) or photoresist is preferred as the protective material. To further enhance the protective effect, a double layer of protective material, such as polyimide and photoresist, can be employed.

[0086] In one embodiment, in step S11, the insulating layer 2 on the back of the SOI wafer 1 is removed by reactive ion etching, and CHF3 gas is introduced during the removal process; and the bottom silicon layer 14 and the buried oxide layer 15 of the SOI wafer 1 are etched by reactive ion etching, and CHF3 gas is introduced during the etching process. The sensor structure after step S11 is completed is as follows: Figure 13 shown.

[0087] In this embodiment, this step is performed in two steps: the first step removes the SiO2 substrate on the back of the SOI wafer 1, and the second step removes the buried oxide layer. A reactive ion etch (RIE) is used with CHF3 gas to remove the SiO2 formed by thermal oxidation on the surface of the bottom silicon layer 14. A deep RIE is then used to pattern the SiO2 substrate. After the SiO2 substrate is released onto the buried oxide layer 15, a RIE is used again with CHF3 gas to remove the buried oxide layer 15 to completely release the sensor structure. The photoresist plate No. 7 used in both steps is shown in Figure 2(g).

[0088] In one embodiment, in step S12, the protective material 8 on the front surface of the SOI wafer 1 is removed by reactive ion etching, and O2 gas is introduced during the removal process. The sensor structure after step S12 is completed is as follows: Figure 14 shown.

[0089] In this embodiment, to obtain a good MEMS electric field sensor, the protective film must be removed to release the movable structure. Dry etching, which eliminates the need for liquids, uses a reactive ion etcher with O2 gas to remove the front protective material, completing the release process without affecting other structures and materials on the MEMS surface.

[0090] The piezoelectrically driven MEMS electric field sensor prepared by the above-described process utilizes a cantilever arm structure and a support base as an integral structure, ensuring the uniformity of the finished chip and providing the cantilever arm structure with improved stability and durability during operation. The various process steps employed in the process of the present invention do not damage the wafer. The materials of the various membrane layers in the MEMS electric field sensor can be adaptively selected, and the thickness of each membrane layer can be precisely controlled during its preparation. The overall process is simple, low-cost, and conducive to large-scale production.

[0091] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0092] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features that are included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of the present invention and to form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.

[0093] It will be understood by those skilled in the art that although the present invention has been described with reference to exemplary embodiments, various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed, but is intended to encompass all embodiments falling within the scope of the appended claims.

Claims

1. A process for preparing a piezoelectrically driven MEMS electric field sensor, characterized in that: The method comprises: S1, thermally oxidizing the double sides of the SOI wafer to form a SiO2 insulating layer on the front and back sides of the SOI wafer respectively; S2, preparing an adhesive layer and a lower driving electrode layer on the insulating layer on the front side of the SOI wafer; S3, preparing a piezoelectric material layer on the lower driving electrode layer; S4, preparing an upper driving electrode layer on the piezoelectric material layer, and peeling off the upper driving electrode layer using a No. 1 photoresist; S5, etching the piezoelectric material layer using photoresist No. 2; S6, etching the lower driving electrode layer and the bonding layer using a No. 3 photoresist; S7, etching the insulating layer on the front side of the SOI wafer using a No. 4 photoresist; S8, using a No. 5 photoresist to prepare a sensing electrode pad on the top silicon layer on the front side of the SOI wafer, by magnetron sputtering and a lift-off method to obtain the sensing electrode pad, wherein the sensing electrode pad is made of Cr and Au, with a Cr thickness of 50 nm and an Au thickness of 300 nm; S9, etching the top silicon layer on the front side of the SOI wafer using a No. 6 photoresist; S10, spin coating a protective material on the front surface of the SOI wafer; S11, removing the insulating layer on the back side of the SOI wafer, and etching the bottom silicon layer and buried oxide layer of the SOI wafer using a No. 7 photoresist, removing the insulating layer on the back side of the SOI wafer by reactive ion etching, and introducing CHF3 gas during the removal process; and etching the bottom silicon layer and buried oxide layer of the SOI wafer by reactive ion etching, and introducing CHF3 gas during the etching process; S12, removing the protective material on the front surface of the SOI wafer to obtain a MEMS electric field sensor, removing the protective material on the front surface of the SOI wafer by reactive ion etching, and introducing O2 gas during the removal process.

2. The method according to claim 1, wherein In S1, the thickness of the insulating layer is 500 nm.

3. The method according to claim 1, wherein In S2, the bonding layer and the lower driving electrode layer are prepared by magnetron sputtering, wherein the bonding layer is a Ti layer with a thickness of 50 nm, and the lower driving electrode layer is a Pt layer with a thickness of 200 nm.

4. The method according to claim 1, wherein In S3, the piezoelectric material layer is prepared by a sol-gel method or a magnetron sputtering method, wherein the piezoelectric material layer is a PZT film or an AlN film with a thickness of 1-2 μm.

5. The method according to claim 1, wherein In S4, the upper driving electrode layer is prepared by magnetron sputtering, wherein the driving electrode layer is an Al layer with a thickness of 300 nm.

6. The method of claim 1, wherein: In S5, etching the piezoelectric material layer by reactive ion etching; In S6, etching the lower driving electrode layer and the adhesive layer by ion beam etching; In S7, the insulating layer on the front side of the SOI wafer is etched by reactive ion etching, and CHF3 gas or a mixed gas of CF4 and H2 is introduced during the etching process; In the step S9 , the top silicon layer on the front side of the SOI wafer is etched by reactive ion etching.

7. The method of claim 1, wherein: In the step S10 , the protective material is polyimide and / or photoresist.

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