WO2023104177A1

WO2023104177A1 - Micro-electro-mechanical system (mems) scanning mirror and preparation method therefor

Info

Publication number: WO2023104177A1
Application number: PCT/CN2022/137822
Authority: WO
Inventors: 何文涛; 张乃川; 石拓
Original assignee: 北京一径科技有限公司
Priority date: 2021-12-10
Filing date: 2022-12-09
Publication date: 2023-06-15
Also published as: CN116256889A

Abstract

A micro-electro-mechanical system (MEMS) scanning mirror and a preparation method therefor. The MEMS scanning mirror comprises: a mirror (107); and a driving module, comprising fixed beams (113, 115, 117) at fixed positions, a rotating beam (109) capable of rotating around an axis, and a connector, wherein the fixed beams (113, 115, 117) are provided with first comb teeth (112); the rotating beam (109) is provided with a second comb tooth (111); the first comb teeth (112) are formed on a first film layer; the second comb tooth (111) is formed on a second film layer; the first comb teeth (112) and the second comb tooth (111) can drive the rotating beam (109) to swing under the action of a driving signal; the connector is connected to the mirror (107) and the rotating beam (109); and the swinging rotating beam (109) can drive the mirror (107) to deflect by means of the connector.

Description

Micro-electromechanical system MEMS scanning mirror and its preparation method

Cross References to Related Applications

This application is based on the application with CN application number 202111504484.X and the application date is December 10, 2021, and claims its priority. The disclosure content of this CN application is hereby incorporated into this application as a whole.

technical field

The present disclosure relates to the technical field of micro-electro-mechanical systems, in particular to a micro-electro-mechanical system (MEMS) scanning mirror and a preparation method thereof.

Background technique

Micro-Electro-Mechanical System (MEMS, Micro-Electro-Mechanical System) scanning mirror is an optical device that integrates a low-light reflector and a MEMS driver based on MEMS technology. The low-light reflector can realize translational movement or pivotal rotation of the low-light reflector in one-dimensional or two-dimensional directions under the action of the MEMS driver.

In the related art, the production process of the MEMS scanning mirror is complicated and the processing efficiency is low, so it is difficult to achieve mass production. Moreover, the dimensional consistency of the produced MEMS is poor.

Contents of the invention

Embodiments of the present disclosure provide a MEMS scanning mirror and a manufacturing method thereof.

The first aspect of the embodiment of the present disclosure provides a MEMS scanning mirror, including:

Mirror;

A drive module, including: a fixed beam with a fixed position, a rotating beam that can rotate around an axis, and a connecting piece;

The fixed beam is provided with first comb teeth; the rotating beam is provided with second comb teeth; the first comb teeth are formed on the first film layer, and the second comb teeth are formed on the second film layer; The first comb and the second comb can drive the rotating beam to swing under the action of a driving signal;

The connecting piece connects the mirror and the rotating beam; the swinging rotating beam can drive the reflector to deflect through the connecting piece; the connecting piece includes a connecting rod and a hinge connected with the connecting rod; At least one of the mirror, the connecting rod and the hinge includes an upper part and a lower part; the upper part is formed on the second film layer; the lower part is formed on the first film layer.

In some embodiments, the material and/or thickness of the first film layer and the second film layer are the same.

In some embodiments, the drive module includes a plurality of stacked film layers; the multiple stacked film layers include: the first film layer, the second film layer, and the and the bonding layer between the second film layer.

In some embodiments, the upper part of the mirror is a mirror surface, and the mirror surface is formed on the second film layer; and/or, the lower part of the mirror is a mirror reinforcement rib, and the mirror reinforcement rib is formed on the first film layer. A film layer and the bonding layer; and/or, the connecting rod and/or the hinge are formed on the first film layer, the second film layer and the bonding layer.

The second aspect of the embodiment of the present disclosure provides a method for preparing a MEMS scanning mirror, including:

At least one of the first comb teeth and the lower part of the connecting rod, the lower part of the hinge and the mirror rib are etched on the first film layer of the first wafer, wherein the first wafer includes the first film layer and a first etch stop layer adjacent to a surface of the first film layer;

Bonding the second wafer and the first wafer on the other surface of the first film layer, wherein the second wafer includes a second film layer, and is the same as the second film layer a second etching barrier layer adjacent to the surface and a bonding layer adjacent to the other surface of the second film layer;

The second comb teeth and at least one of the upper part of the connecting rod, the upper part of the hinge and the mirror surface are etched on the second film layer of the second wafer.

In some embodiments, the method also includes:

After bonding the second wafer and the first wafer on the other surface of the first film layer, the method further includes:

annealing at a first predetermined temperature;

The annealing is stopped after a predetermined period of time, and the temperature is lowered to a second predetermined temperature according to a predetermined cooling rate.

In some embodiments, after bonding the second wafer and the first wafer on the other surface of the first film layer, the method further includes:

removing the substrate layer and/or the second etch barrier layer on the second wafer by a wet etching process;

and / or,

The SiO ₂ located between the first comb teeth and/or the second comb teeth in the bonding layer is removed by using a wet etching process.

In some embodiments, the first wafer includes a substrate layer; the method further includes:

etching a partial area of the substrate layer;

bonding the support sheet to the substrate layer;

Surface treatment of pads and/or mirrored areas;

The support sheet is removed after surface treatment.

In some embodiments, the surface treatment of the pad and/or the mirror area includes:

Sputtering and/or evaporating metal on the area corresponding to the surface pad on the second film layer, wherein the metal includes Ti and/or Al;

and / or,

The surface pad is annealed at a third predetermined temperature in a vacuum environment to form an ohmic contact.

In some embodiments, the surface treatment of the pad and/or the mirror area further includes: sputtering and/or evaporating metal on the mirror area on the surface of the second film layer after annealing, wherein the Metals include Ti and/or Al.

The third aspect of the embodiments of the present disclosure provides a laser radar, and the laser radar includes any of the MEMS scanning mirrors in the embodiments of the present disclosure.

Description of drawings

FIG. 1 is a schematic structural diagram of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 2 is a schematic diagram of a film layer structure of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 3 is a schematic diagram of a film layer structure of a MEMS scanning mirror in the related art.

FIG. 4 is a schematic flowchart of a method for manufacturing a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 5 is a schematic diagram of the film layer structure during the preparation process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 6 is a schematic diagram of the film layer structure during the manufacturing process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 7 is a schematic diagram of a film layer structure during the preparation process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 8 is a schematic diagram of the film layer structure during the manufacturing process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 9 is a schematic diagram of the film layer structure during the manufacturing process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 10 is a schematic diagram of the film layer structure during the manufacturing process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

Fig. 11 is a schematic diagram of the film layer structure during the preparation process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

Fig. 12 is a schematic diagram of the film layer structure during the preparation process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 13 is a schematic diagram of the film layer structure during the preparation process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 14 is a schematic diagram of the film layer structure during the preparation process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

Fig. 15 is a schematic diagram of the film layer structure during the preparation process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

Fig. 16 is a schematic diagram of the film layer structure during the preparation process of a MEMS scanning mirror provided by an embodiment of the present disclosure.

FIG. 17 is a schematic flowchart of a method for manufacturing a MEMS scanning mirror provided by an embodiment of the present disclosure.

Detailed ways

In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and techniques are presented for a thorough understanding of the embodiments of the present disclosure. It will be apparent, however, to one skilled in the art that the present disclosure may be practiced in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present disclosure with unnecessary detail.

Compared with the related art, the technical solution provided by the embodiments of the present disclosure has the following beneficial effects:

In the embodiment of the present disclosure, the fixed beam is provided with a first comb; the rotating beam is provided with a second comb; the first comb is formed on the first film layer, and the second comb is formed on the second film layer. In this way, in the MEMS scanning mirror, since the first comb teeth and the second comb teeth are formed on different film layers, compared to the first comb teeth and the second comb teeth formed on the same film layer, on the one hand, it can be processed with film layers of different thicknesses according to the height requirements of the comb teeth, which improves the dimensional consistency of the comb teeth; There is no need to precisely control the rate and time of etching silicon, which improves the production efficiency of chips and is suitable for mass production.

The connecting piece connects the mirror and the rotating beam; the swinging rotating beam can drive the mirror to deflect through the connecting piece; the connecting piece includes a connecting rod and a hinge connected with the connecting rod; At least one of the mirror, the connecting rod and the hinge includes an upper part and a lower part; the upper part is formed on the second film layer; the lower part is formed on the first film layer. Here, since the connecting piece includes a connecting rod and a hinge connected to the connecting rod, compared with the case where the connecting piece only includes a connecting rod, the hinge can increase the swing range of the connecting piece, thereby driving The free movement of the mirror makes the movement of the mirror more sensitive.

In order to better understand the embodiments of the present disclosure, MEMS is described below through some embodiments:

In some embodiments, the driving methods of the MEMS scanning mirror include electrostatic driving, piezoelectric driving, electromagnetic driving and thermoelectric driving. Among them, the electrostatically driven MEMS scanning mirror has the advantages of small size, low power consumption, high reliability, and quasi-static operation, and is widely used in head-mounted display devices, lidar, augmented reality and other fields. However, compared with other driving methods, electrostatic driving has a smaller driving force. Therefore, most MEMS scanning mirrors have a small deflection angle or can only work in a resonant state, which limits the applicable scenarios of scanning mirrors.

In some embodiments, a frameless electrostatic MEMS scanning mirror is provided. Unlike most electrostatic MEMS scanning mirrors, the rotation direction of the mirror surface of the scanning mirror is perpendicular to the driving shaft, and the connecting rod and flexible hinged connection. The connecting rod and the flexible hinge form a lever-like structure, and the rotation angle of the mirror can be increased by increasing the length of the connecting rod. In the drive structure, the electrostatic comb teeth are designed as high and low comb teeth, so that the mirror can still deflect even under DC drive, thereby realizing the quasi-static operation of the scanning mirror. The advantages of large rotation angle and quasi-static operation greatly improve the applicable scenarios of this type of scanning mirror. However, the MEMS scanning mirror chip has a serious shortage of production capacity. The reason is that in the design of the film layer structure of the scanning mirror chip, the high and low combs, connecting rods, flexible hinges and mirrors of the scanning mirror are designed on the same silicon layer, which requires precise control of silicon and silicon oxide during the chip preparation process. The high etching rate and etching time lead to complex chip preparation process and low processing efficiency, making it difficult to mass produce.

In some embodiments, the height of the comb teeth is controlled by mechanical thinning and/or dry etching process. Due to the inhomogeneity of the above two processes in the chip and between chips, the comb teeth of different chips The height is inconsistent, and the consistency of the key characteristics of the scanning mirror such as resonance frequency and rotation angle is poor. Therefore, the chip needs to be calibrated separately, which will make the development of the back-end user difficult and take a long time.

In order to illustrate the technical solutions described in the present disclosure, specific examples are used below to illustrate.

As shown in Figures 1 and 2, an embodiment of the present disclosure provides a MEMS scanning mirror, including:

mirror 107;

A drive module, comprising: a fixed beam (113, 115 and 117) with a fixed position, a rotating beam 109 that can rotate around an axis and a connecting piece (may include 105 and 122);

The fixed beam (113, 115 and 117) is provided with a first comb tooth 112; the rotating beam 109 is provided with a second comb tooth 111; the first comb tooth 112 is formed on the first film layer (as shown 2 B), the second comb teeth 111 are formed on the second film layer (as shown in Figure 2 A); the first comb teeth 112 and the second comb teeth 111 can drive the The rotating beam 109 swings;

The connecting piece connects the mirror 107 and the turning beam 109; the swinging turning beam 109 can drive the mirror 107 to deflect through the connecting piece; the connecting piece includes a connecting rod (105 and 122) and The hinges (106 and 108) connected by the connecting rods; at least one of the mirror 107, the connecting rods (105 and 122) and the hinges (106 and 108) comprises an upper part and a lower part; the upper part is formed on The second film layer A; the lower part is formed on the first film layer B.

In some embodiments, the first film layer B for processing the first comb teeth 112 and the second film layer A for processing the second comb teeth 111 are not the same film layer.

In some scenario embodiments, the MEMS scanning mirror can be applied to lidar. The laser radar can be based on the MEMS scanning mirror and detect the characteristic quantities such as the position and speed of the target object by emitting a laser beam. Exemplarily, the lidar is composed of a transmitting system, a receiving system, a scanning system, etc., and the MEMS scanning mirror can be applied to the above scanning system.

In some embodiments, the MEMS scanning mirror may be an electrostatic MEMS scanning mirror. Please refer to FIG. 1 again, which is a top view of an electrostatic MEMS scanning mirror. In this disclosure, the MEMS scanning mirror may refer to a MEMS scanning mirror. mirror chip. The MEMS scanning mirror chip may include driving modules (101, 102, 103 and 104), a mirror 107 and connectors. It should be noted that one or more of the driving module, the reflector and the connecting member may be formed by etching a film layer, which is not limited herein. Here, the film layer may be a Si device layer.

In some embodiments, the connecting member may also be a combination including connecting rods (105 and 122) and flexible hinges (106 and 108), which is not limited here.

In some embodiments, the drive module may include comb teeth, rotating beam 109, rotating shaft 110, fixed anchor point 119, fixed beams (113, 115 and 117) and metal pads (114, 116, 118, 120 and 121 ). Wherein, the comb teeth include the first comb teeth 112 and the second comb teeth 111; it should be noted that the first comb teeth 112 and the second comb teeth 111 may appear in pairs. The first comb teeth 112 and the second comb teeth 111 may be arranged parallel and staggered in space. In the embodiment of the present disclosure, the number, shape and/or positional relationship of the first comb teeth 112 and the second comb teeth 111 are not limited.

In some embodiments, the comb teeth formed on the rotating beam 109 are second comb teeth 111 , which may also be called movable teeth. The comb teeth formed on the fixed beams (113, 115 and 117) are first comb teeth 112, which may also be called fixed teeth. Wherein, the rotating beam 109 and the fixed beams (113, 115 and 117) may be arranged in parallel.

In some embodiments, the second comb teeth 111 are attracted by the first comb teeth 112 by respectively applying voltages on the metal pads (114, 116, 118 and 121) (the metal pad 120 may be grounded). It will rotate, thereby driving the rotating beam 109 to swing around the rotating shaft 110, and the swinging of the rotating beam 109 will drive the connecting rod 105 and the flexible hinge (106 and 108) to rotate, thereby driving the mirror surface of the reflecting mirror 107 to rotate. In some embodiments of the present disclosure, the mirror rotation of the mirror may specifically refer to the deflection of the mirror.

In some embodiments, the mirror 107 may be connected to multiple drive modules, for example, four drive modules as shown in FIG. 1 .

In some embodiments, multiple driving modules may have the same structure. The setting positions of the plurality of driving modules may be different. Exemplarily, the driving modules are arranged in pairs in different dimensions of the mirror 107 , for example, the driving modules are arranged in two dimensions of x and y of the mirror 107 .

In some embodiments, the MEMS scanning mirror is a two-dimensional scanning mirror, wherein the driving

modules

101 and 102 form a group and can drive the mirror 107 to rotate in the first dimension; the driving module 103 and the driving module 104 is a group, which can drive the mirror 107 to rotate in the second dimension.

In an embodiment of the present disclosure, the fixed beam is provided with first comb teeth; the rotating beam is provided with second comb teeth; the first comb teeth are formed on the first film layer, and the second comb teeth Formed on the second film layer. In this way, in the MEMS scanning mirror, since the first comb teeth and the second comb teeth are formed on different film layers, compared to the first comb teeth and the second comb teeth formed on the same film layer, on the one hand, it can be processed with film layers of different thicknesses according to the height requirements of the comb teeth, which improves the dimensional consistency of the comb teeth; There is no need to precisely control the rate and time of etching silicon, which improves the production efficiency of chips and is suitable for mass production.

In some embodiments, please refer to FIG. 2 , the material and/or thickness of the first film layer B and the second film layer A are the same.

In some embodiments, the drive module includes a plurality of stacked film layers; the multiple stacked film layers include: the first film layer B, the second film layer A and the A bonding layer between the film layer B and the second film layer A. Here, the bonding layer may be a SiO ₂ bonding layer. The bonding layer may be a film layer obtained after bonding the first film layer B and the second film layer A.

In some embodiments, the upper part of the mirror 107 is a mirror surface, and the mirror surface is formed on the second film layer A; and/or, the lower part of the mirror 107 is a mirror reinforcement rib, and the mirror reinforcement rib is formed on the The first film layer B and the bonding layer. Wherein, the mirror reinforcing rib may be used to support the mirror 107 .

In some embodiments, the link 105 and/or the hinges (106 and 108) are formed on the first film layer B, the second film layer A and the bonding layer.

In some embodiments, the connecting member is jointly processed based on the first film layer B, the second film layer A and the bonding layer. Here, the connection piece may be processed based on a predetermined etching process.

In some embodiments, FIG. 2 is a schematic diagram of a cross-sectional film layer of a multi-film electrostatic MEMS scanning mirror based on silicon on an insulating substrate (SOI, Silicon-On-Insulator) (cut along the II direction in FIG. 1 ) . Along the direction of the arrow in Fig. 2, there are first layer Si device layer 201, SiO ₂ bonding intermediate layer (also called bonding layer) 202, second layer Si device layer 203, SiO ₂ insulating layer 204 and substrate Si layer 205 . Wherein, the second film layer A may be the first Si device layer 201 , and the first film layer B may be the second Si device layer 203 . The bonding layer may be a SiO ₂ bonding interlayer 202 .

In some embodiments, the first Si device layer 201 and the second Si device layer 203 are made of the same material. Exemplarily, all are N-type doped low-resistance silicon.

In some embodiments, the first Si device layer 201 and the second Si device layer 203 have the same thickness. Exemplarily, the thickness is 30 μm.

Exemplarily, the thickness of the SiO ₂ bonding intermediate layer 202 is 1 μm.

Exemplarily, the thickness of the substrate Si layer 205 is 450 μm.

In some embodiments, the electrostatic comb teeth are divided into two types: high teeth 206 (that is, the second comb teeth 111) and low teeth 207 (that is, the first comb teeth 112), and the high teeth 206 are formed on the first layer of Si Device layer 201, the height of the high teeth 206 is consistent with the thickness of the first Si device layer 201; the low teeth are formed on the second Si device layer 203, and the height of the low teeth is consistent with the thickness of the second Si device layer 203 .

In some embodiments, the mirror surface 208 of the MEMS scanning mirror is formed on the first Si device layer 201 , and the mirror surface ribs 212 are jointly formed by bonding the intermediate layer 202 and the second Si device layer 203 . Here, the mirror surface 208 may be the mirror 107 .

In some embodiments, the connecting rod 213 and the flexible hinge 214 are composed of the first Si device layer 201 , the second Si device layer 203 and the bonding intermediate layer 202 .

In some embodiments, metal pads 210 are formed on the upper surface of the first Si device layer 201 , and metal pads 211 are formed on the upper surface of the second Si device layer 202 , respectively serving as access points for driving signals. Wherein, the driving signal may be an electrical signal.

In some embodiments, the material of the metal pad 210 may be Ti and/or Al, for example, may form an ohmic contact with Si of the device layer. In some embodiments, the upper surface of the mirror 208 is also covered with Ti and/or Al (reflection film 209 ), which is used to enhance the reflectivity of the mirror.

In some embodiments, the second Si device layer 203, the SiO ₂ insulating layer 204 and the substrate Si layer 205 are from the same SOI wafer, and the first Si device layer 201 is from another SOI wafer. wafer. Here, the SOI wafer may correspond to one film layer.

In order to better understand the film structure shown in FIG. 2 , the following describes the film structure of the MEMS scanning mirror in the related art through some embodiments:

Please refer to FIG. 3 , which shows a schematic diagram of a cross-sectional film layer of a MEMS scanning mirror product in the related art. It should be noted that the example structure shown in FIG. 3 does not limit the present disclosure, but can be used as an example for understanding purposes.

In FIG. 3 , along the direction of the arrow, there are Si device layer 301 , SiO ₂ insulating layer 302 and Si substrate layer 303 from top to bottom. It can be known that the MEMS scanning mirror has only one layer of silicon as the Si device layer. The functional components of the scanning mirror, including structures such as high teeth 304 , low teeth 305 , connecting rods 309 , reflective film 307 and flexible hinges 310 , are all formed on the same Si device layer 301 . The heights of the high teeth 304 and the low teeth 305 (for example, 21 μm) are not consistent with the thickness of the device layer (for example, 40 μm). Therefore, the Si device layer 301 needs to be etched separately from the upper and lower directions during the preparation of the comb teeth. Since there is no silicon oxide layer in the middle of the Si device layer as an etching barrier layer, it is necessary to precisely control the etching rate and time during the process of etching high-tooth and low-tooth, and even to repeatedly modify the etching program, resulting in chip failure. The production efficiency is low. In addition, the thickness of the Si device layer 301 is achieved by thinning the silicon wafer from about a first thickness (eg, 500 μm) to a second thickness (eg, 40 μm) using a mechanical thinning and chemical mechanical polishing (CMP) process, and Mechanical polishing and CMP will consume a lot of time, further reducing the efficiency of chip preparation. Moreover, both the mechanical thinning of silicon and the dry etching of silicon have certain intra-chip/inter-chip inhomogeneity, resulting in the height of the comb teeth (304, 305) of different chips, the height of the connecting rod 309, the flexible hinge 310 and the mirror surface 306. Inconsistency in thickness causes inconsistency in the rotation angle and resonant frequency of the scanning mirror, which reduces the qualified rate of the scanning mirror. The above two problems make it difficult to mass-produce the electrostatic scanning mirror chip, and the price remains high, which limits its wide application in fields such as lidar. To this end, the present disclosure proposes the MEMS scanning mirror shown in FIG. 2 .

As shown in FIG. 4, an embodiment of the present disclosure provides a method for preparing a MEMS scanning mirror, including:

Step 41. Etch at least one of the first comb teeth, the lower part of the connecting rod, the lower part of the hinge, and the mirror rib on the first film layer of the first wafer, wherein the first wafer includes the a first film layer and a first etch stop layer adjacent to a surface of the first film layer;

Step 42, bonding the second wafer and the first wafer on the other surface of the first film layer, wherein the second wafer includes the second film layer, and the second film layer a second etching barrier layer adjacent to one surface of the film layer and a bonding layer adjacent to the other surface of the second film layer;

Step 43 , etching the second comb teeth and at least one of the upper part of the connecting rod, the upper part of the hinge and the mirror surface on the second film layer of the second wafer.

In some embodiments, the wafer may be an SOI wafer. Here, the first wafer may be a first SOI wafer; the first film layer may be a Si device layer 401; the etch barrier layer may be a SiO ₂ intermediate layer 402; the second wafer It can be a second SOI wafer; the second film layer can be a Si device layer 405; the bonding layer can be a SiO ₂ layer 407; the first comb teeth 112 can be low teeth or lower teeth 404; The second comb teeth 111 may be tall teeth or upper teeth 409 .

Please refer to FIG. 5 , which shows the first SOI wafer used in the preparation process. Exemplarily, the diameter of the first SOI wafer may be 6 inches or 8 inches.

In some embodiments, the first piece of SOI wafer may include Si device layer 401 , SiO ₂ interlayer 402 and Si substrate 403 . Exemplarily, the Si device layer 401 may have a thickness of 30 μm, and may be an N-type low-resistance single crystal silicon layer. Exemplarily, the thickness of the SiO ₂ intermediate layer 402 may be 2 μm. Exemplarily, the Si substrate 403 may be high-resistance single crystal silicon, and its thickness may be 450 μm.

In some embodiments, the method also includes:

The mirror ribs of the MEMS scanning mirror are etched on the first film layer B of the first wafer.

In some embodiments, referring to FIG. 6 , the low teeth 404 (corresponding to the aforementioned first comb teeth 112 ) and the mirror reinforcement are etched on the Si device layer of the first SOI wafer by reactive ion deep etching (DRIE) process. Rib 418 structure, the structure formed at the same time also includes the lower half (half height) of link 419 and flexible hinge 420. In some embodiments, the rate ratio of DRIE etching Si and SiO ₂ is about 100:1, therefore, the SiO ₂ intermediate layer 402 can be used as the first etch barrier layer, and a period of time is allowed to exist during the DRIE etching process. Over-etching, in this way, reduces the control requirements on the etching rate and time, and the height of structures such as the low teeth 404 is determined by the thickness of the Si device layer 401, which is not affected by the DRIE process, and the consistency of the structure is high.

In some embodiments, please refer to FIG. 7 , the second SOI wafer used in the preparation process has the same characteristics as the first SOI wafer. In some embodiments, in order to improve the bonding efficiency, a layer of SiO ₂ (407, corresponding to the aforementioned bonding layer) is deposited on the surface of the Si device layer 405 of the SOI. Exemplarily, the thickness of the SiO ₂ layer may be 1 μm.

Step a, annealing at a first predetermined temperature;

Step b, stop the annealing after a predetermined period of time, and lower the temperature to a second predetermined temperature according to a predetermined cooling rate.

Exemplarily, the first predetermined temperature may be 1100°C±100°C.

Exemplarily, the predetermined duration may be 4h±2h.

Exemplarily, the second predetermined temperature may be 25°C±5°C.

In some embodiments, referring to FIG. 8 , two SOI wafers are bonded together using the SiO ₂ layer 407 as a bonding interlayer. In some embodiments, the pre-bonding process is hydrophilic bonding. After the pre-bonding, annealing is performed in a high-temperature furnace at 1100° C. for 4 hours, and then slowly lowered to room temperature to complete high-strength bonding of wafers.

In some embodiments, after bonding the second wafer and the first wafer on the other surface of the first film layer, the method further includes: using a wet etching process to remove The substrate layer and/or the etch stop layer on the second wafer.

In some embodiments, referring to FIG. 9 , the substrate layer 408 and the SiO ₂ layer 406 of the second SOI wafer are removed by a wet etching process, leaving only the Si device layer 405 .

In some embodiments, referring to FIG. 10 , the upper teeth 409 (corresponding to the second comb teeth 111 ), the mirror surface 410 structure, and the connecting rod 419 and the upper half of the flexible hinge 420 are etched on the device layer 405 by using the DRIE process. . Here, the SiO ₂ layer 407 acts as an etching barrier layer, which requires less control precision of the etching process, and has good dimensional consistency of the etching structure.

In some embodiments, please refer to FIG. 11 , DRIE etches the Si substrate layer 403 until the SiO ₂ insulating layer 402 to prepare a hollow area on the back of the chip. The SiO ₂ insulating layer 402 also acts as an etch stop during the etching process.

In some embodiments, a wet etching process is used to remove SiO ₂ located between the first comb teeth and/or the second comb teeth in the bonding layer.

In some embodiments, referring to FIG. 12 , wet etching is used to remove SiO ₂ between structures such as comb teeth, so as to realize comb teeth release.

It should be noted that, in some embodiments, the solutions of the present disclosure can be executed sequentially according to FIG. 6 , FIG. 8 , FIG. 9 , FIG. 10 , FIG. 11 , and FIG. The public scheme is not limited here.

Step a, etching a part of the substrate layer;

Step b, bonding the support sheet to the substrate layer;

Step c, performing surface treatment on the pad and/or the mirror area;

Step d, removing the supporting sheet after the surface treatment is completed.

Wherein, the surface treatment includes coating treatment.

sequentially sputtering and/or evaporating metal on the area corresponding to the surface pad on the second film layer, wherein the metal includes Ti and/or Al;

and / or,

annealing the surface pad at a third predetermined temperature in a vacuum environment to form an ohmic contact;

and / or,

After annealing, metal is sequentially sputtered and/or evaporated on the mirror area on the upper surface of the second film layer, wherein the metal includes Ti and/or Al.

Exemplarily, the third predetermined temperature may be 450°C±100°C.

In some embodiments, please refer to FIG. 13 , since most areas of the wafer are hollowed out, in order to enhance the strength and operability of the wafer, a piece of glass 411 must be temporarily bonded on the lower surface of the substrate layer 403 as a supporting sheet before coating.

In some embodiments, please refer to FIG. 14 , sputtering/evaporating 10nm Ti (412, 415) and 200nm Al (413, 414) sequentially on the region corresponding to the pad on the upper surface of the device layer 405, and in a vacuum environment 400 °C annealing forms an ohmic contact.

In some embodiments, please refer to FIG. 15 , after annealing, 10nm Ti (416) and 200nm Al (417) are sequentially sputtered/evaporated on the mirror region of the upper surface of the Si device layer 405 to form a reflective film. The reason why the two-step coating process as shown in Figure 14 and Figure 15 is separated is that the annealing process will increase the roughness of the metal film and reduce the reflectivity.

In some embodiments, please refer to FIG. 16 , which shows a schematic view of removing the support sheet in the fabrication method, so that the fabrication of the entire MEMS scanning mirror is completed.

In order to better understand the embodiments of the present disclosure, the following uses an exemplary embodiment to illustrate the embodiments of the present disclosure:

Example 1:

The embodiments of the present disclosure use at least two SOI wafers, namely a first SOI wafer and a second SOI wafer. The first SOI wafer (corresponding to the second film layer in the present disclosure) has a diameter of 6 inches or 8 inches, and the Si device layer is 30 μm, which is an N-type low-resistance single crystal silicon layer. The thickness of the SiO ₂ intermediate layer is 2 μm, and the substrate layer is high-resistance single crystal silicon with a thickness of 450 μm. The second SOI wafer (corresponding to the first film layer in the present disclosure) may be the same as the first SOI wafer, and a layer of SiO ₂ is stacked on the surface of the Si device layer of the second SOI wafer.

Please refer to FIG. 17 , an embodiment of the present disclosure provides a method for manufacturing a MEMS scanning mirror, including:

Step 171. Etch low teeth (corresponding to the first comb teeth) and mirror rib structures on the Si device layer (corresponding to the first film layer) of the first SOI wafer by reactive ion deep etching process, and simultaneously form the structure Also includes the link and the lower half (half the height) of the flexible hinge.

Step 172, using the SiO ₂ layer as an intermediate layer to bond the first SOI wafer and the second SOI wafer together. The pre-bonding process is hydrophilic bonding. After pre-bonding, it is annealed in a high-temperature furnace at 1100°C for 4 hours, and slowly lowered to room temperature to complete high-strength bonding of wafers.

Step 173, using a wet etching process to remove the substrate layer and the SiO ₂ layer of the second SOI wafer, leaving only the Si device layer.

Step 174 , using DRIE process to etch the upper teeth, the mirror surface, and the upper half of the connecting rod and the flexible hinge on the Si device layer of the second SOI wafer.

Step 175, DRIE etching the Si substrate layer until the SiO ₂ insulating layer to prepare a hollow area on the back of the chip. The SiO ₂ insulating layer also acts as an etch stop during the etch process.

Step 176 , using wet etching to remove the SiO ₂ between the comb teeth and other structures, so as to realize the release of the comb teeth. So far, the preparation of the mechanical structure of the rotating mirror chip is completed.

Step 177, temporarily bonding a piece of glass on the lower surface of the substrate layer as a supporting sheet before coating.

Step 178: Sputter or vapor-deposit 10nm Ti and 200nm Al in sequence on the area corresponding to the bonding pad on the upper surface of the Si device layer, and anneal at 400°C in a vacuum environment to form an ohmic contact. After annealing, 10nm Ti and 200nm Al are sequentially sputtered or evaporated on the mirror area of the upper surface of the Si device layer to form a reflective film.

Step 179 , removing the supporting sheet, and completing the preparation of the entire MEMS rotating mirror.

It should be noted that, for the schematic diagrams of the specific structures of the above embodiments, reference may be made to any drawings shown in the present disclosure, that is, descriptions, which are not limited herein.

In some embodiments, the embodiments of the present disclosure further provide a laser radar, which includes the MEMS scanning mirror as described in any one of the present disclosure.

Those skilled in the art can understand that the sequence numbers of the steps in the above embodiments do not mean the order of execution, and the execution order of each process should be determined by its functions and internal logic, rather than the implementation process of the embodiments of the present disclosure. constitute any limitation.

The above-described embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still implement the foregoing embodiments Modifications to the technical solutions described in the examples, or equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present disclosure, and should be included in the within the protection scope of the present disclosure.

Claims

A microelectromechanical system MEMS scanning mirror, comprising:

Mirror;

A drive module, including: a fixed beam with a fixed position, a rotating beam that can rotate around an axis, and a connecting piece;

The fixed beam is provided with first comb teeth; the rotating beam is provided with second comb teeth; the first comb teeth are formed on the first film layer, and the second comb teeth are formed on the second film layer; The first comb and the second comb can drive the rotating beam to swing under the action of a driving signal;

The connecting piece connects the mirror and the rotating beam; the swinging rotating beam can drive the mirror to deflect through the connecting piece; the connecting piece includes a connecting rod and a hinge connected with the connecting rod; At least one of the mirror, the connecting rod and the hinge includes an upper part and a lower part; the upper part is formed on the second film layer; the lower part is formed on the first film layer.
The MEMS scanning mirror according to claim 1, wherein the material and/or thickness of the first film layer and the second film layer are the same.
The MEMS scanning mirror according to claim 1, wherein the driving module comprises a plurality of laminated film layers; the plurality of laminated film layers comprises: the first film layer, the second film layer and a set A bonding layer between the first film layer and the second film layer.
The MEMS scanning mirror according to claim 3, wherein at least one of the following is satisfied:

The upper part of the mirror is a mirror surface, and the mirror surface is formed on the second film layer;

The lower part of the mirror is a mirror reinforcement rib, and the mirror reinforcement rib is formed on the first film layer and the bonding layer; and

At least one of the link and the hinge is formed on the first film layer, the second film layer and the bonding layer.
A preparation method of a microelectromechanical system MEMS scanning mirror, comprising:

At least one of the first comb teeth and the lower part of the connecting rod, the lower part of the hinge and the mirror rib are etched on the first film layer of the first wafer, wherein the first wafer includes the first film layer and a first etch stop layer adjacent to a surface of the first film layer;

Bonding the second wafer and the first wafer on the other surface of the first film layer, wherein the second wafer includes a second film layer, and is the same as the second film layer a second etching barrier layer adjacent to the surface and a bonding layer adjacent to the other surface of the second film layer;

At least one of the second comb teeth and the upper part of the connecting rod, the upper part of the hinge and the mirror surface is etched on the second film layer of the second wafer.
The preparation method according to claim 5, wherein, after bonding the second wafer and the first wafer on the other surface of the first film layer, the method further comprises:

annealing at a first predetermined temperature;

The annealing is stopped after a predetermined period of time, and the temperature is lowered to a second predetermined temperature according to a predetermined cooling rate.
The preparation method according to claim 5, wherein, after bonding the second wafer and the first wafer on the other surface of the first film layer, the method further comprises:

removing the substrate layer and/or the second etch barrier layer on the second wafer by a wet etching process;

and / or,

The SiO 2 located between the first comb teeth and/or the second comb teeth in the bonding layer is removed by using a wet etching process.
The preparation method according to claim 5, wherein the first wafer comprises a substrate layer; the method further comprises:

etching a partial area of the substrate layer;

bonding the support sheet to the substrate layer;

Surface treatment of pads and/or mirrored areas;

The support sheet is removed after surface treatment.
The preparation method according to claim 8, wherein the surface treatment of the pad and/or the mirror area comprises:

Sputtering and/or evaporating metal on the area corresponding to the surface pad on the second film layer, wherein the metal includes Ti and/or Al;

and / or,

The surface pad is annealed at a third predetermined temperature in a vacuum environment to form an ohmic contact.
The preparation method according to claim 9, wherein the surface treatment of the pad and/or the mirror area further comprises:

After the annealing, metal is sputtered and/or evaporated on the mirror area of the upper surface of the second film layer, wherein the metal includes Ti and/or Al.
A laser radar comprising the MEMS scanning mirror according to any one of claims 1 to 4.