A MEMS electrostatic actuator and a preparation method and application thereof

Abstract

The application provides a MEMS electrostatic actuator and a preparation method and application thereof, and comprises the following steps: providing an SOI wafer, wherein the SOI wafer comprises a device silicon layer, an oxide buried layer and a bottom silicon layer which are sequentially arranged; processing the SOI wafer to remove at least part of the bottom silicon layer and expose the oxide buried layer, and further removing the oxide buried layer, so that the device silicon layer forms an independent movable structure layer; manufacturing an upper electrode structure on a bonding surface of the movable structure layer; providing a silicon substrate, and forming a groove structure or a boss structure for defining an electrostatic driving gap on the silicon substrate; manufacturing a lower electrode structure on the silicon substrate, wherein the lower electrode structure comprises a lower electrode plate, a connecting wire and an external contact electrode; aligning and bonding the movable structure layer with the silicon substrate, so that an electrostatic driving gap is formed between the upper electrode structure and the lower electrode structure, and a MEMS electrostatic actuator is obtained.

Description

Technical Field

[0001] This invention relates to the field of microelectromechanical systems (MEMS), and particularly to a MEMS electrostatic actuator, its fabrication method, and its application. Background Technology

[0002] Microelectromechanical systems (MEMS) devices are widely used in fields such as microactuators, microsensors, optical modulators, radio frequency devices, and microfluidic systems due to their small size, fast response speed, low power consumption, and ease of mass production. Among them, MEMS electrostatic actuators based on the electrostatic drive principle have become an important device type in the MEMS field due to their advantages such as low driving voltage, simple structure, and ease of integration.

[0003] Currently, the manufacturing methods for MEMS electrostatic actuators mainly include two categories: surface micromachining methods based on sacrificial layer release and bulk micromachining methods based on wafer bonding. For example, CN103395741B discloses a typical surface micromachining method based on sacrificial layer release, the main process of which includes: (1) providing a silicon substrate with a silicon dioxide insulating layer formed on its surface; (2) depositing phosphosilicate glass (PSG) or silicon dioxide material on the surface of the silicon substrate by chemical vapor deposition (CVD) to form a sacrificial layer; (3) patterning the sacrificial layer by photolithography and etching to form anchor point windows, so that... Partial areas expose the bottom substrate; (4) a movable electrode layer is formed by depositing polycrystalline silicon material using low-pressure chemical vapor deposition (LPCVD) process, and the movable electrode layer is filled with anchor point windows to achieve connection with the substrate; (5) the polycrystalline silicon movable electrode layer is planarized using chemical mechanical polishing (CMP) process; (6) a release hole array penetrating to the sacrificial layer is formed in the polycrystalline silicon movable electrode layer by photolithography and reactive ion etching (RIE) or deep reactive ion etching (DRIE) process; (7) the sacrificial layer is removed by hydrofluoric acid (HF) wet etching process, so that the polycrystalline silicon movable electrode layer is released to form a suspended structure. This type of technology realizes the manufacturing of the suspended structure of MEMS electrostatic actuator through the temporary support of the sacrificial layer and the subsequent release process. It is a relatively mature manufacturing method in the MEMS field. However, the above-mentioned technology based on sacrificial layer release still has the following shortcomings: (1) there is a risk of structural adhesion during the release process: after the sacrificial layer is removed by HF wet etching, a micron-level gap is formed between the movable electrode and the substrate. During the subsequent drying process, the capillary force generated by the surface tension of the liquid can easily cause the flexible movable electrode structure to shift towards the substrate and eventually adhere permanently to the substrate, resulting in the movable structure being unable to move normally and reducing the device manufacturing yield. (2) The manufacturing process is complex and the process cost is high: The above process usually requires multiple steps such as sacrificial layer deposition, sacrificial layer patterning, polysilicon deposition, planarization, release hole processing and wet release. Among them, the CMP process equipment is expensive, and the sacrificial layer release process has high requirements for etching time, material selection and structural size, which increases the manufacturing cycle and process control difficulty. (3) Release holes affect device structural performance: In order to improve the sacrificial layer release efficiency, a release hole array needs to be set in the movable electrode layer. However, the release holes will reduce the structural integrity of the movable electrode, cause stress concentration in local areas, reduce the effective electrode area, thereby reducing the electrostatic driving force and increasing the complexity of device structural design. (4) The release process can easily cause damage to the underlying structure: When using HF etching to release the sacrificial layer, the etchant may enter the device through the release hole, causing excessive etching of the oxide layer or other insulating structures below the cavity area.For example, some existing technologies point out that the HF release process can easily cause damage to the bottom insulating layer, thereby affecting the device reliability and insulation performance. (5) Residual stress in polycrystalline silicon is difficult to control: The residual stress of polycrystalline silicon thin films formed by LPCVD is easily affected by process parameters such as deposition temperature, pressure and gas ratio. When there is a large residual stress or uneven stress distribution inside the film, the movable structure after release is prone to warping, buckling or even breakage, and the subsequent CMP process cannot fundamentally eliminate this problem.

[0004] Another type of method is the MEMS manufacturing method without sacrificial layer release proposed in CN105712290A. Its main steps include: (1) providing a first substrate, forming a first metal layer on the front side of the first substrate, and forming a lower electrode plate through patterning; (2) providing a second substrate, and etching a recessed structure corresponding to the lower electrode plate on the back side of the second substrate; (3) aligning and bonding the front side of the first substrate with the back side of the second substrate, so that the lower electrode plate enters the recessed area, thereby forming a gap between the upper and lower electrodes; (4) thinning the front side of the bonded second substrate to control the thickness of the upper electrode structure; (5) forming a metal layer on the surface of the second substrate, and forming an upper electrode plate and a cantilever beam structure through patterning and etching, while exposing the corresponding contact electrodes. This scheme directly forms the electrode gap through wafer bonding, avoiding sacrificial layer deposition and HF wet release process from the process principle, thus reducing the risk of release adhesion. However, this type of technology has the following problems: (1) the thinning process after bonding is difficult. Since the inside of the bonded wafer forms a hollow region, there is no effective support below the hollow region during mechanical grinding or chemical mechanical polishing. The grinding pressure can easily cause local depression and deformation of the structure above the cavity. When the thinning thickness is further reduced, the structure is prone to springback and warping, making it impossible to accurately control the final upper electrode thickness. (2) Poor film thickness uniformity. Since the thinning process occurs on the bonded structure that has formed a cavity, the mechanical support conditions of different regions in the wafer are different, resulting in differences in the film thickness after thinning, which affects the consistency of MEMS devices. (3) Risk of wafer breakage. The overall thinning after bonding usually requires a large mechanical force, while the internal cavity structure reduces the overall mechanical strength of the wafer, which can easily lead to wafer breakage and reduce manufacturing yield. (4) Increased process steps and material costs. In order to achieve thin film transfer, some solutions require the introduction of temporary support wafers, multiple bonding and subsequent removal steps, which increases manufacturing complexity and material consumption.

[0005] In summary, among the existing MEMS electrostatic actuator manufacturing methods, on the one hand, although the traditional sacrificial layer release technology can form a suspended structure, it has problems such as release adhesion, release holes affecting performance, and complex processes; on the other hand, although the sacrificial layer-free bonding technology avoids the release process, it still relies on mechanical thinning after bonding, and the cavity structure after bonding causes problems such as depressions, warping, and uncontrolled thickness during the thinning process. Summary of the Invention

[0006] The purpose of this invention is to provide a MEMS electrostatic actuator, its fabrication method, and its application. By pre-forming a movable structure layer and completing the movable structure thickness control and electrode processing before bonding, this invention solves the problems of uncontrolled movable structure thickness and hollow area depression and warping caused by mechanical thinning after bonding in existing dual-substrate bonding processes. At the same time, it avoids the risks of adhesion failure and over-corrosion in traditional sacrificial layer wet release processes, achieving high-precision control of movable structure thickness and a significant improvement in process yield.

[0007] To achieve the above objectives, this technical solution provides a method for fabricating a MEMS electrostatic actuator, comprising: S1. Provide an SOI wafer, wherein the SOI wafer includes a device silicon layer, a buried oxide layer and a bottom silicon layer stacked sequentially; S2. Process the SOI wafer to remove at least part of the bottom silicon layer and expose the buried oxide layer, and further remove the buried oxide layer to form an independent movable structure layer of the device silicon layer. S3. Fabricate an electrode structure on the bonding surface of the movable structural layer; S4. Provide a silicon substrate and form a groove structure or boss structure on the silicon substrate to define an electrostatic drive gap; S5. Fabricate a lower electrode structure on a silicon substrate, wherein the lower electrode structure includes a lower electrode plate, connecting wires, and an external contact electrode. S6. Align and bond the movable structure layer to the silicon substrate to form an electrostatic drive gap between the upper electrode structure and the lower electrode structure, thereby obtaining a MEMS electrostatic actuator.

[0008] Compared with existing technologies, this invention has the following outstanding advantages over existing sacrificial layer release processes and double substrate bonding post-thinning processes: 1. High-precision controllable movable layer thickness with excellent intra-wafer consistency. This solution moves all thin-film processing steps to before the bonding step, directly using the top silicon layer of the SOI wafer to predefine the movable electrode thickness. No substrate grinding or thinning is performed after bonding. The movable layer thickness is guaranteed by the manufacturing precision of the SOI wafer manufacturer, and the thickness uniformity is far superior to the traditional mechanical grinding process after bonding, fundamentally solving the defects of uncontrolled movable structure thickness and warping and springback in hollow areas.

[0009] 2. Simplified process flow, wider process window, and significantly improved mass production yield. Core processing steps such as movable thin film patterning and substrate etching are completed independently on a single wafer. After bonding, only electrode patterning is required, eliminating the complex CMP polishing process. The overall process steps are streamlined, and the process tolerance range is wide, which greatly reduces the risk of processing debris and structural damage, and effectively improves the mass production yield of devices.

[0010] 3. Eliminates the wet release process with a sacrificial layer, thus removing the risks of adhesion and insulation corrosion. The electrostatic gap between electrodes is directly defined by DRIE etching recesses on the substrate, and the gap size can be flexibly adjusted according to device requirements. No sacrificial layer needs to be deposited throughout the process, completely avoiding the problem of permanent adhesion to the structure caused by capillary forces in the micron gap, while also eliminating the risk of device insulation failure caused by excessive corrosion of the underlying insulating oxide layer by the release solution.

[0011] 4. The movable electrode has no release hole, significantly optimizing structural stiffness and driving performance. This solution eliminates the need for release holes in the movable structural layer, ensuring a complete and continuous movable electrode plate surface. This avoids stress concentration and reduced structural stiffness caused by release holes, suppressing warping and breakage after device release. Furthermore, it maximizes the effective facing area of ​​the electrodes, eliminating the weakening effect of release holes on electrostatic driving force and improving actuator driving efficiency and output performance. Attached Figure Description

[0012] Figure 1 This is the process flow diagram of Example 3.

[0013] Figure 2 This is a schematic diagram of the movable electrode structure in Embodiment 3.

[0014] Figure 3 This is a schematic diagram of the substrate structure in Example 3.

[0015] Figure 4 This is a schematic diagram of the bonding process in Example 3.

[0016] Figure 5 This is the process flow diagram of Example 4.

[0017] Figure 6 This is a schematic diagram of the substrate structure in Example 4.

[0018] Figure 7 This is a schematic diagram of the bonding process in Example 4. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0020] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0021] Example 1 This solution provides a method for fabricating a MEMS electrostatic actuator, including the following steps: The method for fabricating a MEMS electrostatic actuator includes the following steps: S1. Provide an SOI wafer, wherein the SOI wafer includes a device silicon layer, a buried oxide layer and a bottom silicon layer stacked sequentially; S2. Process the SOI wafer to remove at least part of the bottom silicon layer and expose the buried oxide layer, and further remove the buried oxide layer to form an independent movable structure layer of the device silicon layer. S3. Fabricate an electrode structure on the bonding surface of the movable structural layer; S4. Provide a silicon substrate and form a groove structure or boss structure on the silicon substrate to define an electrostatic drive gap; S5. Fabricate a lower electrode structure on a silicon substrate, wherein the lower electrode structure includes a lower electrode plate, connecting wires, and an external contact electrode. S6. Align and bond the movable structure layer to the silicon substrate to form an electrostatic drive gap between the upper electrode structure and the lower electrode structure, thereby obtaining a MEMS electrostatic actuator.

[0022] It should be noted that this solution uses the SOI device layer as the final movable structure thickness reference. That is, the device silicon layer thickness of the SOI wafer is pre-selected according to the target movable structure thickness of the MEMS electrostatic actuator. The advantage of this is that the thickness of the movable structure layer can be determined by the device silicon layer thickness of the SOI wafer before the movable structure layer is aligned and bonded to the silicon substrate, and there is no need to perform mechanical thinning of the movable structure layer after alignment and bonding.

[0023] In traditional bonding processes, after two wafers are bonded to form a cavity, the upper wafer is typically thinned using methods such as grinding and CMP to obtain the desired movable structure thickness. However, because the bonded cavity region lacks bottom support, problems such as localized depressions, wafer warping, uneven thickness, and increased intra-wafer thickness deviations can easily occur during the thinning process. This solution, on the other hand, directly selects an SOI wafer with a device silicon layer of the target thickness. The device silicon layer itself serves as the final movable structure layer, eliminating the need for subsequent thinning. This improves the accuracy of movable structure thickness control, avoids thickness runaway caused by post-bonding thinning, reduces residual stress changes due to material deposition, and enhances the mechanical performance stability of the MEMS electrostatic actuator.

[0024] In step S1, the bottom silicon layer of the SOI wafer can be selected as either highly doped silicon or undoped silicon, depending on the device design.

[0025] In step S2, the bottom silicon layer is etched using a deep reactive ion etching (DRIE) process, causing the etching to stop at the buried oxide layer.

[0026] In some embodiments, deep reactive ion etching is used to dry etch the bottom silicon layer using photoresist as a mask to expose the buried oxide layer.

[0027] In some embodiments, the bottom silicon layer is patterned and etched on the back side using DRIE to form a ring support structure. The central area of ​​the ring support structure is completely hollowed out, and a single notch is formed on the ring support structure.

[0028] In some embodiments, the buried oxide layer is removed by a wet etching process, so that the silicon layer of the device forms an independent movable structural layer.

[0029] In some embodiments, the wet etching process uses hydrofluoric acid solution or buffered oxide etching solution.

[0030] In some embodiments, the buried oxide layer is etched into the same shape as the underlying silicon layer.

[0031] In step S3, a metal layer is formed on the contact surface where the original oxide buried layer of the movable structural layer is located as the upper electrode structure, wherein the upper electrode structure includes an upper electrode plate, connecting lines and an upper contact electrode.

[0032] In some embodiments, the upper electrode structure is formed within the space surrounded by the bottom silicon layer.

[0033] In step S4, the silicon substrate is etched using a deep reactive ion etching process to form a groove structure or a boss structure, wherein the depth of the groove structure or boss structure is used to define the electrostatic drive gap between the upper electrode structure and the lower electrode structure.

[0034] In some embodiments, at least one spaced groove or an upwardly protruding boss structure is etched on the silicon substrate.

[0035] In some embodiments, dry etching is performed on the periphery of the silicon substrate using photoresist as a mask to form a boss structure in the middle of the silicon substrate. After etching, the photoresist mask is removed. At this point, the boss structure is located at the geometric center of the silicon substrate. The boss has a trapezoidal cross-section, with the top surface dimension smaller than the bottom surface dimension, and the overall structure is a stepped platform-like structure that is narrower at the top and wider at the bottom.

[0036] In some embodiments, photoresist is spin-coated onto the insulating layer on the surface of a silicon substrate using thermal oxidation, and a pattern is defined by photolithography. DRIE first etches the insulating layer, then etches the silicon substrate, etching a certain depth in the middle portion and etching circuit channels on one side to form a groove structure.

[0037] In step S4, the electrostatic drive gap is controlled by detecting the etching depth of the groove structure or boss structure; wherein, the etching depth is monitored by laser interferometry, profilometry or other depth detection methods.

[0038] In step S5, electrode connection channels are etched in the corresponding area of ​​the boss structure or groove structure, and a metal layer is formed in the boss structure or groove structure as the lower electrode plate. A metal layer is deposited on the inner wall of the electrode connection channel as a connection line, and a metal layer is formed on the back side of the silicon substrate as the external contact electrode.

[0039] In some embodiments, a through-hole structure is formed inside the boss structure or the groove. The through-hole structure serves as an electrode connection channel, and a metal conductive layer is formed on the inner wall of the through-hole structure as a connection line to realize the electrical connection between the lower electrode plate and the external circuit.

[0040] In some embodiments, deep reactive ion etching (DRIE) technology is used to etch through-hole structures in the center of the boss structure or the groove structure using photoresist as a mask, which are then used as electrode connection channels. After etching is completed, the photoresist mask is removed.

[0041] In some embodiments, a metal layer is formed on the front side of the boss structure or groove structure of the silicon substrate using a hard mask as a lower electrode plate; and a metal layer is formed on the back side of the silicon substrate using a hard mask as an outer contact electrode.

[0042] In step S6, the bonding method includes at least one of the following: adhesive bonding, silicon-silicon direct bonding, anodic bonding, and metal eutectic bonding.

[0043] It is particularly important to note that this solution does not include a sacrificial layer during the formation of the MEMS electrostatic actuator, and the movable structure layer does not include a release hole for releasing the sacrificial layer.

[0044] In some embodiments, the electrode pattern region of the movable electrode layer is suspended above the groove structure or boss structure of the silicon substrate to form a MEMS electrostatic actuator.

[0045] In some embodiments, the metal plate of the upper electrode structure falls directly above the boss structure or the groove structure, and the bottom silicon layer is stacked on the silicon substrate.

[0046] Example 2 This solution provides a MEMS electrostatic actuator, including: Movable structure layer, wherein the movable structure layer is formed from the device silicon layer of the SOI wafer; An upper electrode structure formed on a movable structural layer; Silicon substrates with groove or boss structures; The lower electrode structure formed on a silicon substrate; The movable structure layer is connected to the silicon substrate by bonding; the upper electrode structure is suspended above the lower electrode structure and forms an electrostatic drive gap through a groove structure or a boss structure; the movable structure layer does not have a sacrificial layer release hole.

[0047] In some embodiments, the thickness of the movable structural layer is determined by the silicon layer thickness of the SOI wafer device, so that the movable structural layer does not need to undergo mechanical thinning after bonding during the formation process.

[0048] In some embodiments, the MEMS electrostatic actuator includes a buried oxide layer and a bottom silicon layer of the same shape disposed sequentially under the device silicon layer, wherein notches are formed on the buried oxide layer and the bottom silicon layer, and the bottom silicon layer is bonded to a groove structure or a boss structure.

[0049] The MEMS electrostatic actuators provided in this solution can be applied in fields such as optical communication and optoelectronic imaging, RF microwave communication MEMS devices, consumer electronics acoustic devices, biomedicine, and microfluidic chips. Specifically, they can be applied to MEMS micromirror arrays / LiDAR scanning mirrors, optical communication optical switches, optical phase shifters, micro-projectors, infrared thermal imaging optical modulation units, and electrostatic MEMS micro-speakers.

[0050] Example 3 like Figures 1 to 4 As shown, this third embodiment provides a specific method for fabricating a MEMS electrostatic actuator with a boss structure formed on a silicon substrate, including the following steps: (1) Prepare SOI wafers and perform top silicon processing: SOI wafer 100 (4 inches) is selected, which includes device silicon layer 01, buried oxide layer 02 and bottom silicon layer 03 from top to bottom. Photolithography is performed on the top surface of device silicon, and alignment marks are etched by DRIE for subsequent double-sided alignment. Then, photoresist is spin-coated on the back side of the substrate silicon layer, and photolithography is performed to form a mask pattern to define the area to be removed.

[0051] (2) Etching the underlying silicon: DRIE (Bosch process) uses photoresist as a mask, dry etching through the substrate silicon layer and stopping at the buried oxide layer. The endpoint is determined by the abrupt change in the etching rate of the buried oxide layer, with 10% over-etching. Acetone is used to remove the photoresist, followed by rinsing and drying.

[0052] (3) Etching the buried oxide layer: The buried oxide layer was removed by wet etching with BHF-buffered hydrofluoric acid (NH4F:HF = 7:1, 25°C) for approximately 11 minutes. The layer was then rinsed with deionized water, dehydrated with isopropanol, and dried with nitrogen. This yielded a separate, intact, crack-free thin layer containing only the silicon of the device.

[0053] (4) Fabrication of the upper electrode: The hard mask of the bonding surface (original buried oxide contact surface) of the silicon thin layer of the obtained device is aligned and fixed with the target area. Then, a metal layer is deposited in the designated area by sputtering to form the upper electrode plate 04, the connecting line and the upper contact electrode, thus forming the upper electrode structure 101.

[0054] (5) Etching substrate grooves: A separate silicon wafer 200 is used as a substrate, and an insulating layer is thermally oxidized on its surface. Photoresist is spin-coated, and the perimeter pattern is defined by photolithography. DRIE first etches the insulating layer, then etches the silicon substrate, etching the perimeter to a depth of 5μm (defining the electrode gap) to form a boss structure. After confirming the trench depth with a profilometer, the photoresist is removed, and the substrate is cleaned.

[0055] (6) Etching substrate vias: Photoresist is spin-coated onto the back of the silicon substrate, and the pattern is defined by photolithography. DRIE first etches the insulating layer, then etches the silicon substrate, and etches through-holes (to introduce electrodes) in the middle section before removing the photoresist and cleaning.

[0056] (7) Fabricating the metal layer: A lower electrode plate (located on top of the boss) is formed by sputtering a metal layer using a hard mask on the front side of the substrate with the boss structure, and a metal layer is formed on the inner wall of the central through hole to connect 14.

[0057] (8) Forming external electrodes: A metal layer is sputtered on the back side of a silicon substrate using a hard mask to form an external contact electrode 15, thus fabricating a substrate 201.

[0058] (9) Integrated assembly: Align the bonding surface (with electrode pattern) of the movable structural thin layer obtained in step (4) with the front side of the lower electrode substrate obtained in step (8), and place the upper electrode metal plate directly above the boss. Use adhesive 16 to bond them together to form an electrostatic actuator 301. Alternatively, the upper and lower parts can be bonded by direct bonding.

[0059] In this embodiment, the air gap between the metal layer of the upper electrode structure and the metal layer of the lower motor structure is determined by the thickness and etching depth of the bottom silicon and buried oxide layer of the SOI wafer; the thickness of the top silicon layer is guaranteed by SOI accuracy (deviation < ±0.5μm), serving as the structural support for the metal layer of the upper electrode structure, and the device is warped.

[0060] Example 4 like Figures 5 to 7 Unlike Embodiment 3, in Embodiment 4, a groove structure is formed on the silicon substrate, including the following steps: (5) Fabrication of the lower electrode structure Take a silicon substrate and thermally oxidize the insulating layer on the surface. Spin-coat photoresist and use photolithography to define the pattern. DRIE first etches the insulating layer, then etches the silicon substrate, etching the middle part to a depth of 2μm (defining the electrode gap), and etches the circuit channel (introducing the electrode) on one side to form a groove structure. Then remove the photoresist and clean the substrate.

[0061] (6) Fabrication of the lower electrode metal layer An aluminum layer (approximately 1 μm) is sputtered on the front side of the groove, and the lower electrode plate 24, connecting lines, and lower contact electrode 25 are formed by photolithography and wet etching to create the substrate portion 202.

[0062] The remaining steps are the same as in Example 3, and the electrostatic actuator 302 is formed by bonding with adhesive or direct bonding.

[0063] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for fabricating a MEMS electrostatic actuator, characterized in that, Includes the following steps: S1. Provide an SOI wafer, wherein the SOI wafer includes a device silicon layer, a buried oxide layer and a bottom silicon layer stacked sequentially; S2. Process the SOI wafer to remove at least part of the bottom silicon layer and expose the buried oxide layer, and further remove the buried oxide layer to form an independent movable structure layer of the device silicon layer. S3. Fabricate an electrode structure on the bonding surface of the movable structural layer; S4. Provide a silicon substrate and form a groove structure or boss structure on the silicon substrate to define an electrostatic drive gap; S5. Fabricate a lower electrode structure on a silicon substrate, wherein the lower electrode structure includes a lower electrode plate, connecting wires, and an external contact electrode. S6. Align and bond the movable structure layer to the silicon substrate to form an electrostatic drive gap between the upper electrode structure and the lower electrode structure, thereby obtaining a MEMS electrostatic actuator.

2. The method for fabricating a MEMS electrostatic actuator according to claim 1, characterized in that, In step S2, the bottom silicon layer is etched using a deep reactive ion etching process, and the etching stops at the buried oxide layer. The buried oxide layer is then removed using a wet etching process.

3. The method for fabricating a MEMS electrostatic actuator according to claim 1, characterized in that, In step S3, a metal layer is formed on the contact surface where the original oxide buried layer of the movable structural layer is located as the upper electrode structure, wherein the upper electrode structure includes an upper electrode plate, connecting lines and an upper contact electrode.

4. The method for fabricating a MEMS electrostatic actuator according to claim 1, characterized in that, In step S4, the silicon substrate is etched using a deep reactive ion etching process to form a groove structure or a boss structure, wherein the depth of the groove structure or boss structure is used to define the electrostatic drive gap between the upper electrode structure and the lower electrode structure.

5. The method for fabricating a MEMS electrostatic actuator according to claim 1, characterized in that, The electrostatic drive gap is controlled by detecting the etching depth of the groove or boss structure; the etching depth is monitored by laser interferometry or a step gauge.

6. The method for fabricating a MEMS electrostatic actuator according to claim 1, characterized in that, Electrode connection channels are etched in the corresponding areas of the boss or groove structure, and a metal layer is formed in the boss or groove structure as the lower electrode plate. A metal layer is deposited on the inner wall of the electrode connection channel as the connection line, and a metal layer is formed on the back side of the silicon substrate as the external contact electrode.

7. The method for fabricating a MEMS electrostatic actuator according to claim 1, characterized in that, The bonding methods include at least one of the following: adhesive bonding, silicon-silicon direct bonding, anodic bonding, and metal eutectic bonding.

8. The method for fabricating a MEMS electrostatic actuator according to claim 1, characterized in that, The electrode pattern area of ​​the movable electrode layer is suspended above the groove structure or protrusion structure of the silicon substrate.

9. A MEMS electrostatic actuator, prepared according to the method for preparing a MEMS electrostatic actuator according to any one of claims 1 to 8, characterized in that, include: Movable structure layer, wherein the movable structure layer is formed from the device silicon layer of the SOI wafer; An upper electrode structure formed on a movable structural layer; Silicon substrates with groove or boss structures; The lower electrode structure formed on a silicon substrate; The movable structure layer is connected to the silicon substrate by bonding; the upper electrode structure is suspended above the lower electrode structure and forms an electrostatic drive gap through a groove structure or a boss structure; the movable structure layer does not have a sacrificial layer release hole.

10. The MEMS electrostatic actuator according to claim 9, characterized in that, It is applied in the fields of optical communication and optoelectronic imaging, RF microwave communication MEMS devices, consumer electronics acoustic devices, and biomedical and microfluidic chip fields.

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