MEMS micromirror unit, MEMS micromirror array and manufacturing method

Abstract

The invention discloses an MEMS micromirror unit, an MEMS micromirror array and a manufacturing method, and relates to the technical field of micro electro mechanical systems, the MEMS micromirror unit comprises an outer frame, an inner frame and a driver, the top of the outer frame is used for installing a mirror surface layer; the inner frame is arranged at the bottom of the outer frame, and the vertical projection of the inner frame is located in the vertical projection of the side edge of the outer frame. A driver is connected between the side edge of the outer frame and the side edge, located on the same side, of the inner frame and can drive the mirror surface layers to move relatively. The MEMS micro-mirror array comprises a plurality of MEMS micro-mirror units, the plurality of MEMS micro-mirror units are sequentially arranged in an array mode, and a gap is formed between mirror surface layers of every two adjacent MEMS micro-mirror units. According to the invention, the inner frame and the outer frame are designed, one end of the driver is connected to the inner frame, and the other end of the driver is connected to the outer frame, so that the buried design of the driver is realized, and the filling rate of the MEMS micromirror is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical systems, and in particular to a MEMS micro-mirror unit, a MEMS micro-mirror array and a manufacturing method thereof. Background Art

[0002] A MEMS (Micro-Electro-Mechanical Systems) micromirror is a miniaturized, movable mirror based on MEMS technology. A MEMS micromirror consists of a micro-actuator and a micro-reflective mirror surface, and its size is in the millimeter level. The mirror filling rate of a MEMS micromirror refers to the ratio of the area of ​​the effective reflective surface of the mirror to the area of ​​the MEMS micromirror chip (the surface coplanar with the mirror surface). Currently, the mirror filling rate of a MEMS micromirror is relatively low. Summary of the invention

[0003] The purpose of the present invention is to provide a MEMS micromirror unit, a MEMS micromirror array and a manufacturing method to solve the problems existing in the above-mentioned prior art. An inner frame and an outer frame are designed, one end of the driver is connected to the inner frame, and the other end is connected to the outer frame, thereby realizing a buried design of the driver and greatly improving the filling rate of the MEMS micromirror.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a MEMS micromirror unit, comprising:

[0006] An outer frame, the top of which is used to mount a mirror layer;

[0007] An inner frame, disposed at the bottom of the outer frame, and having a vertical projection located within a vertical projection of a side edge of the outer frame;

[0008] A driver is connected between the side edge of the outer frame and the side edge of the inner frame located on the same side, and the driver can drive the mirror layer to move relative to each other.

[0009] Optionally, the outer frame is a rectangular frame structure, one end of the driver is connected to the inner side of the side of the outer frame, and the other end is connected to the outer side of the side of the inner frame, and the outer frame and the inner frame form a first device layer.

[0010] Optionally, a bonding metal layer is provided on the top of the side of the outer frame, and the mirror layer is fixedly arranged on the bonding metal layer.

[0011] Optionally, it further includes a base layer, wherein the base layer is located below the outer frame, and the inner frame is located inside the base layer; and a through silicon via interconnection structure is provided on the inner frame.

[0012] Optionally, a second device layer is fixedly provided on the bonding metal layer, and the mirror layer is provided on the upper surface of the second device layer.

[0013] Optionally, the driver is electrothermally driven, and its structure includes four S-shaped connecting strips connected end to end in sequence, each of the S-shaped connecting strips includes a metal heating resistor and two dual piezoelectric chip elements stacked in opposite order; the highest points of the two upper S-shaped connecting strips are connected to the side of the outer frame, and the lowest points of the two lower S-shaped connecting strips are connected to the side of the inner frame.

[0014] Optionally, the driver is piezoelectrically driven, and its structure includes four S-shaped connecting strips connected end to end in sequence, each of the S-shaped connecting strips includes two dual piezoelectric chip elements stacked in opposite order, and the dual piezoelectric chip elements are connected to an external power supply; the highest points of the two S-shaped connecting strips located above are connected to the side of the outer frame, and the lowest points of the two S-shaped connecting strips located below are connected to the side of the inner frame.

[0015] Optionally, the driver is electrostatically driven, and its structure includes four S-shaped connecting strips connected end to end in sequence, the highest points of the two S-shaped connecting strips located at the top are connected to the side of the outer frame, and the lowest points of the two S-shaped connecting strips located at the bottom are connected to the side of the inner frame; an upper electrode is provided at the side position of the bottom surface of the outer frame, and a lower electrode corresponding to the upper electrode is provided at the side position of the top surface of the inner frame, and the upper electrode and the lower electrode are respectively connected to external power supplies.

[0016] The present invention provides a MEMS micromirror array, comprising a plurality of the above-mentioned MEMS micromirror units, wherein the plurality of the MEMS micromirror units are arranged in an array in sequence, and a gap is provided between the mirror layers of two adjacent MEMS micromirror units.

[0017] The present invention also provides a method for manufacturing a MEMS micromirror unit, comprising the following steps:

[0018] The first step is to prepare the wafer, which includes the first device layer, buried oxide layer and substrate layer from top to bottom, and clean the wafer to remove metal and organic contaminants;

[0019] The second step is to etch the first device layer using a deep silicon etching method to expose the buried oxide layer, then etch away the buried oxide layer, and continue deep silicon etching to prepare blind holes of a through silicon via interconnect structure;

[0020] The third step is to grow a silicon oxide insulating layer using a thermal oxidation method to insulate the sidewall of the blind hole from the wafer surface.

[0021] The fourth step is to grow a seed layer, perform photolithography, and electroplate copper. After electroplating, remove the photoresist and seed layer, polish the wafer surface, and flatten the wafer so that the filled copper is flush with the wafer surface.

[0022] The fifth step is to grow an insulating layer on the top layer of the wafer;

[0023] The sixth step is to wet-etch the silicon oxide and then grow another layer of silicon oxide as an insulating layer;

[0024] Step 7: grow a metal layer and then grow an insulating layer;

[0025] Step 8: Etch the through silicon via to expose the top copper layer on the through silicon via interconnect structure, then grow an adhesion layer, then grow the heating resistor metal, then grow an oxide layer, and etch the silicon oxide, as shown in the figure;

[0026] The ninth step is photolithography, followed by deep silicon etching of the top silicon layer to remove the photoresist;

[0027] Step 10: Perform temporary bonding using a glass sheet, temporary bonding adhesive and a wafer;

[0028] In the eleventh step, the bottom of the wafer is thinned and polished to expose the TSV interconnect structure layer and make marks for subsequent alignment;

[0029] Step 12: Debond, grow gold on the top layer, prepare another wafer, and then grow a layer of gold on the top layer.

[0030] Step 13: Gold-gold bonding of the new wafer and the sample;

[0031] Step 14: Thin and polish the top wafer, leaving only the second device layer, and then grow a reflective metal on the top layer as a mirror layer;

[0032] Step 15: growing an insulating layer at the bottom, etching an opening, growing a seed layer, then electroplating copper to form a copper column, and electroplating a nickel-chromium alloy;

[0033] Step 16, etching the back cavity, and then etching the silicon oxide of the buried oxide layer;

[0034] In step 17, the device is finally released and the silicon at the bottom of the driver is etched.

[0035] Compared with the prior art, the present invention has achieved the following technical effects:

[0036] The existing known MEMS micromirror drivers are all connected to the outer frame (fixed end) at one end and distributed at the outer edge of the mirror (free end and participating in the movement) at the other end. Therefore, the outer frame and the driver occupy most of the chip area, resulting in a low mirror filling rate. The present invention retains the inner frame structure, the inner frame is located below the outer frame, and the size of the inner frame is smaller than the outer frame, so that one end of the driver is connected to the inner frame (fixed end) and the other end is connected to the outer frame (free end), realizing the buried design of the driver. The driver does not occupy the space of the mirror layer, thereby greatly improving the filling rate of the MEMS micromirror. Compared with the existing MEMS micromirrors, the present invention has a qualitative leap in the filling rate, which can improve the light beam control and processing capabilities of the micromirror. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a schematic diagram of the first step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0039] Figure 2 It is a schematic diagram of the second step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0040] Figure 3 It is a schematic diagram of the third step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0041] Figure 4 It is a schematic diagram of the fourth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0042] Figure 5 It is a schematic diagram of the fifth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0043] Figure 6 It is a schematic diagram of the sixth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0044] Figure 7 It is a schematic diagram of the seventh step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0045] Figure 8 It is a schematic diagram of the eighth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0046] Fig. 9 It is a schematic diagram of the ninth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0047] Fig.10 It is a schematic diagram of the tenth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0048] Fig.11 It is a schematic diagram of the eleventh step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0049] Fig.12 It is a schematic diagram of the twelfth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0050] Fig.13 It is a schematic diagram of the thirteenth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0051] Fig.14 It is a schematic diagram of the fourteenth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0052] Fig.15 It is a schematic diagram of the fifteenth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0053] Fig.16 It is a schematic diagram of the sixteenth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0054] Fig.17 It is a schematic diagram of the seventeenth step of the method for manufacturing a MEMS micromirror unit of the present invention;

[0055] Fig.18 It is a schematic diagram of the structure of the MEMS micromirror unit of the present invention;

[0056] Fig.19 It is a cross-sectional schematic diagram of a MEMS micromirror unit of the present invention;

[0057] Fig. 20 It is a schematic diagram of the local structure of the MEMS micromirror unit near the base layer of the present invention;

[0058] Fig.21 It is a schematic diagram of the local structure of the MEMS micromirror unit near the mirror layer;

[0059] Fig. 22 It is a schematic diagram of the structure of the MEMS micromirror array of the present invention;

[0060] Fig.23 It is a schematic diagram of the structure of the MEMS micromirror array of the present invention after removing a single mirror layer;

[0061] Fig.24 It is a schematic diagram of the back structure of the MEMS micromirror array of the present invention;

[0062] Fig.25 It is a schematic diagram of the back structure of the MEMS micromirror unit of the present invention.

[0063] In the figure: 1-driver, 101-S-shaped connecting strip, 2-bonding metal layer, 3-mirror layer, 4-first device layer, 401-inner frame, 402-outer frame, 5-second device layer, 6-base layer, 7-glass sheet, 8-temporary bonding glue. DETAILED DESCRIPTION

[0064] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] The purpose of the present invention is to provide a MEMS micromirror unit, a MEMS micromirror array and a manufacturing method to solve the problems existing in the above-mentioned prior art. An inner frame and an outer frame are designed, one end of the driver is connected to the inner frame, and the other end is connected to the outer frame, thereby realizing a buried design of the driver and greatly improving the filling rate of the MEMS micromirror.

[0066] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] MEMS (Micro-Electro-Mechanical Systems) micromirror is a miniaturized, movable reflector based on MEMS technology. The MEMS micromirror structure types known to the inventor are divided into four types according to the driver principle: electrostatic, electromagnetic, electrothermal, and piezoelectric. When the electrothermal structure is energized, heat is generated, and the temperature on the driver rises, causing the driver to deform, thereby achieving the purpose of driving the mirror layer. Since the driver of this design is distributed around the outer edge of the mirror, it is inevitable that the driver also occupies a certain space, so the effect of this structure on improving the filling rate is limited. Electrostatic micromirrors, taking electrostatic comb-tooth micromirrors as an example, electrostatic micromirrors usually include driving comb teeth and reflective mirror surfaces. In order to increase the driving ability, the number of comb teeth is often thousands, so it will occupy a large space of the electrostatic micromirror, resulting in a low filling rate of the electrostatic comb-tooth-shaped MEMS micromirror. There are two main types of electromagnetic micromirrors: one is a moving coil micromirror, and the other is a moving magnetic material micromirror. The former is the most widely used, but both require the use of an external magnetic field to generate Lorentz force or electromagnetic force to drive the mirror to move. Therefore, the mirror is often accompanied by a larger frame, and the middle mirror only occupies a small part. The rest is the outer frame and magnetic field coil, so the filling rate is not high. Piezoelectric micromirrors are similar to electrothermal micromirrors. The drivers also mostly support and drive the mirror on the periphery. The area covered by the mirror on the entire chip is limited, and the filling rate is also limited.

[0068] Based on the above reasons, one of the objects of the present invention is to provide a MEMS micromirror unit that can improve the filling rate of the mirror layer, such as Fig.18 , Fig.19 , Fig. 20 , Fig.21 , Fig.25 As shown, the structure includes an outer frame 402 and an inner frame 401 which are arranged up and down, and the top of the outer frame 402 is used to install the mirror layer 3; the inner frame 401 is arranged at the bottom of the outer frame 402, and its vertical projection is located within the vertical projection of the side of the outer frame 402, that is, the area of ​​the outer frame 402 is larger than the area of ​​the inner frame 401; a driver 1 is connected between the side of the outer frame 402 and the side of the inner frame 401 on the same side, thereby realizing the buried design of the driver 1, thereby making the available space of the mirror layer 3 large and improving the filling rate of the mirror layer 3. The inner frame 401 serves as a fixed end and the outer frame 402 serves as a free end. The driver 1 can drive the outer frame 402 to move, thereby driving the mirror layer 3 on the outer frame 402 to move relatively micro-movement.

[0069] In order to realize the buried design of the driver 1 and provide installation space for installing the driver 1, the outer frame 402 of this embodiment is a rectangular frame structure, one end of the driver 1 is connected to the inner side of the side of the outer frame 402, and the other end is connected to the outer side of the side of the inner frame 401, and the outer frame 402 and the inner frame 401 form a first device layer 4; in order to improve the connection stability and safety, a base layer 6 is provided on the outer side of the inner frame 401, and the inner frame 401 is located in the base layer 6, and on the base layer 6, each side of the inner frame 401 is provided with a concave groove space, and a silicon through-hole interconnection structure is provided on the inner frame 401 to facilitate conductive connection. Silicon through-hole interconnection (Through Silicon Via, TSV) is an advanced semiconductor packaging technology for realizing three-dimensional (3D) stacking and interconnection within a chip or between chips. TSV technology establishes electrical connections in the vertical direction by drilling holes in a silicon wafer and filling them with conductive materials (usually copper). This technology has significant advantages in improving chip performance, reducing size and reducing costs.

[0070] In order to arrange the mirror layer 3, a bonding metal layer 2 is provided on the top of the side of the outer frame 402, a second device layer 5 is fixed on the bonding metal layer 2, and a mirror layer 3 is provided on the upper surface of the second device layer 5. The material of the first device layer 4, the second device layer 5 and the base layer 6 is silicon.

[0071] The driver 1, as the supporting structure and driving component of the micromirror, can be the electrothermal driving structure mentioned above, so it is feasible to form an electrothermal MEMS micromirror and an electrothermal array MEMS micromirror. The driver 1 is electrothermal driven, and its structure includes four S-shaped connecting bars 101 connected end to end in sequence, and each S-shaped connecting bar 101 includes a metal heating resistor and two bi-piezoelectric chip elements stacked in opposite order; the highest points of the two S-shaped connecting bars 101 located at the top are connected to the side of the outer frame 402, and the lowest points of the two S-shaped connecting bars 101 located at the bottom are connected to the side of the inner frame 401. In another embodiment, the driver 1 is piezoelectric driven, and its structure includes four S-shaped connecting bars 101 connected end to end in sequence, and each S-shaped connecting bar 101 includes two bi-piezoelectric chip elements stacked in opposite order, and the bi-piezoelectric chip elements are externally connected to a power supply; the highest points of the two S-shaped connecting bars 101 located at the top are connected to the side of the outer frame 402, and the lowest points of the two S-shaped connecting bars 101 located at the bottom are connected to the side of the inner frame 401.

[0072] In other preferred embodiments, the driver 1 can also be an electrostatic drive type, and its structure includes four S-shaped connecting strips 101 connected end to end in sequence, the highest points of the two S-shaped connecting strips 101 located at the top are connected to the side of the outer frame 402, and the lowest points of the two S-shaped connecting strips 101 located at the bottom are connected to the side of the inner frame 401. The driver 1 is a simple supporting structure, which is the same as the structure of the electrothermal driver 1, but there is no heating resistor in the middle; an upper electrode is provided at the side position of the bottom surface of the outer frame 402, and another silicon wafer or glass wafer 7 is bonded to the bottom end of the micromirror and serves as an electrode, which is called a lower electrode. The control of the micromirror surface can be achieved by controlling the power on and off of the electrode. This scheme can form an electrostatic MEMS micromirror and an electrostatic array MEMS micromirror. In addition, like the electrostatic micromirror structure, the driver 1 only plays a supporting role, except that the upper electrode becomes a magnetic material. The driver 1 can also be used as a simple supporting structure, such as the same structure as the electrothermal driver 1, but without a heating resistor in the middle.

[0073] Compared with single-mirror MEMS micromirrors, array MEMS micromirrors can process more light beams and reflect more light energy. People's demand for optical information processing is increasing, and the demand for single-mirror MEMS micromirrors has risen to a more urgent demand for array MEMS micromirrors. For example, array MEMS micromirrors are used in photolithography machines to improve imaging resolution and projection efficiency, making photolithography patterns more accurate and reliable. Based on this, another object of the present invention is to provide a MEMS micromirror array, such as Fig. 22 , Fig.23 , Fig.24As shown, it includes multiple MEMS micromirror units as above, which are arranged in an array in sequence, and there is a gap between the mirror layers 3 of two adjacent MEMS micromirror units. Since the driver 1 is buried at the bottom of the mirror layer 3, the gap spacing of the mirror layer 3 can be very small.

[0074] The present invention also provides a method for manufacturing a MEMS micromirror unit, comprising the following steps:

[0075] The first step is to prepare the SOI wafer. The SOI (Silicon-On-Insulator) wafer is a wafer made using a special semiconductor manufacturing technology. Its core feature is that part of the silicon wafer is isolated by an insulating layer (usually silicon dioxide). This structure can effectively reduce parasitic capacitance and leakage current, thereby significantly improving device performance; the SOI wafer is mainly composed of three layers: Top silicon: This is the silicon layer that ultimately forms the semiconductor device, and its thickness is usually tens of nanometers to several microns, depending on application requirements. The insulating layer is located between the top silicon and the base silicon. It is a thin layer of silicon oxide (SiO2), usually tens to hundreds of nanometers thick. This layer acts as electrical isolation and significantly reduces the parasitic effects of the device. Base silicon: The bottom layer is a thicker silicon base, which mainly serves as mechanical support. From top to bottom are the first device layer 4, the buried oxide layer, and the base layer 6. The RCA standard process cleans the wafer to remove metal and organic contaminants, such as Figure 1 ; RCA standard process usually refers to the RCA wet cleaning process, which is an industrial standard wet cleaning process proposed by the American Radio Corporation (RCA) in the 1960s. This process is mainly used in the semiconductor manufacturing process, especially for cleaning the wafer surface, to remove organic and inorganic pollutants and ensure the cleanliness, consistency and process control of the wafer surface.

[0076] In the second step, the first device layer 4 is etched using a deep silicon etching method to expose the buried oxide layer, the buried oxide layer is etched away, and deep silicon etching is continued to prepare TSV (through silicon via) blind holes, such as Figure 2 Through Silicon Via (TSV) is an advanced semiconductor packaging technology used to achieve three-dimensional (3D) stacking and interconnection within a chip or between chips. TSV technology establishes electrical connections in the vertical direction by drilling holes in a silicon wafer and filling them with conductive materials (usually copper). This technology has significant advantages in improving chip performance, reducing size and reducing costs.

[0077] The third step is to grow a silicon oxide insulating layer using a thermal oxidation method to insulate the sidewalls of the blind hole from the wafer surface. Figure 3 ;

[0078] The fourth step is to grow the seed layer (Cr and Au), perform photolithography, and electroplate copper. After electroplating, remove the photoresist and seed layer, polish the wafer surface, and flatten the wafer so that the filled copper is flush with the wafer surface. Figure 4 ;

[0079] The fifth step is to grow an insulating layer (such as silicon oxide) on the top of the wafer. Figure 5 ;

[0080] The sixth step is to wet etch the silicon oxide and then grow a thin layer of silicon oxide as an insulating layer, such as Figure 6 ;

[0081] The seventh step is to grow a metal layer (such as aluminum) and then grow an insulating layer, such as Figure 7 ;

[0082] The eighth step is to etch the via to expose the top copper layer on the TSV, then grow an adhesion layer (the adhesion layer is not shown), then grow the heating resistor metal, then grow an oxide layer, and etch the silicon oxide, such as Figure 8 ;

[0083] The ninth step is photolithography, and then deep silicon etching of the top layer of silicon to remove the photoresist, such as Fig. 9 ;

[0084] Step 10: Temporary bonding is performed using the glass sheet 7, temporary bonding adhesive 8 and the wafer, such as Fig.10 ;

[0085] In the eleventh step, the bottom of the wafer is thinned and polished to expose the TSV layer and make marks for subsequent alignment, such as Fig.11 ;

[0086] The twelfth step is to debond, grow metal gold on the top layer, prepare another SOI, and then grow a layer of metal gold on the top layer, such as Fig.12 ;

[0087] Step 13: Bond the new SOI wafer and the sample wafer with gold. Fig.13 ;

[0088] In the fourteenth step, the top wafer is thinned and polished, leaving only the second device layer 5, and then a reflective metal (such as aluminum) is grown on the top layer. Fig.14 ;

[0089] In the fifteenth step, an insulating layer is grown at the bottom, and an opening is etched to grow a seed layer (such as Cr / Cu), and then copper is electroplated to form a copper column, and a nickel-chromium alloy is chemically plated to prevent copper from being oxidized. Fig.15 ;

[0090] In the sixteenth step, the back cavity is etched, and then the silicon oxide of the buried oxide layer is etched. Fig.16 ;

[0091] Step 17: Finally, release the device and etch the silicon at the bottom of the driver 1. Fig.17 .

[0092] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A MEMS micromirror unit, characterized in that: include: An outer frame, the top of which is used to mount a mirror layer; An inner frame, disposed at the bottom of the outer frame, and having a vertical projection located within a vertical projection of a side edge of the outer frame; A driver is connected between the side edge of the outer frame and the side edge of the inner frame located on the same side, and the driver can drive the mirror layer to move relative to each other.

2. The MEMS micromirror unit according to claim 1, characterized in that: The outer frame is a rectangular frame structure, one end of the driver is connected to the inner side of the side of the outer frame, and the other end is connected to the outer side of the side of the inner frame. The outer frame and the inner frame form a first device layer.

3. The MEMS micromirror unit according to claim 2, characterized in that: A bonding metal layer is provided on the top of the side of the outer frame, and the mirror layer is fixedly arranged on the bonding metal layer.

4. The MEMS micromirror unit according to claim 1, characterized in that: It also includes a base layer, which is located below the outer frame, and the inner frame is located inside the base layer; a through silicon via interconnection structure is provided on the inner frame.

5. The MEMS micromirror unit according to claim 3, characterized in that: A second device layer is fixedly arranged on the bonding metal layer, and the mirror layer is arranged on the upper surface of the second device layer.

6. The MEMS micromirror unit according to claim 1, characterized in that: The driver is an electrothermal drive, and its structure includes four S-shaped connecting strips connected end to end in sequence, each of the S-shaped connecting strips includes a metal heating resistor and two dual piezoelectric chip elements stacked in opposite order; the highest points of the two S-shaped connecting strips located at the top are connected to the side of the outer frame, and the lowest points of the two S-shaped connecting strips located at the bottom are connected to the side of the inner frame.

7. The MEMS micromirror unit according to claim 1, characterized in that: The driver is piezoelectrically driven, and its structure includes four S-shaped connecting strips connected end to end in sequence, each of the S-shaped connecting strips includes two dual piezoelectric chip elements stacked in opposite order, and the dual piezoelectric chip elements are connected to an external power supply; the highest points of the two S-shaped connecting strips located at the top are connected to the side of the outer frame, and the lowest points of the two S-shaped connecting strips located at the bottom are connected to the side of the inner frame.

8. The MEMS micromirror unit according to claim 1, characterized in that: The driver is electrostatically driven, and its structure includes four S-shaped connecting strips connected end to end in sequence, the highest points of the two S-shaped connecting strips located at the top are connected to the side of the outer frame, and the lowest points of the two S-shaped connecting strips located at the bottom are connected to the side of the inner frame; an upper electrode is provided at the side position of the bottom surface of the outer frame, and a lower electrode corresponding to the upper electrode is provided at the side position of the top surface of the inner frame, and the upper electrode and the lower electrode are respectively connected to an external power supply.

9. A MEMS micromirror array, characterized in that: The method comprises a plurality of MEMS micromirror units as claimed in any one of claims 1 to 8, wherein the plurality of MEMS micromirror units are arranged in an array in sequence, and a gap is provided between the mirror layers of two adjacent MEMS micromirror units.

10. A method for manufacturing a MEMS micromirror unit, characterized in that: The steps include: The first step is to prepare the wafer, which includes the first device layer, buried oxide layer and substrate layer from top to bottom, and clean the wafer to remove metal and organic contaminants; The second step is to etch the first device layer using a deep silicon etching method to expose the buried oxide layer, then etch away the buried oxide layer, and continue deep silicon etching to prepare blind holes of a through silicon via interconnect structure; The third step is to grow a silicon oxide insulating layer using a thermal oxidation method to insulate the sidewall of the blind hole from the wafer surface. The fourth step is to grow a seed layer, perform photolithography, and electroplate copper. After electroplating, remove the photoresist and seed layer, polish the wafer surface, and flatten the wafer so that the filled copper is flush with the wafer surface. The fifth step is to grow an insulating layer on the top layer of the wafer; Step 6: wet-etch the silicon oxide, and then grow another layer of silicon oxide as an insulating layer; Step 7: grow a metal layer and then grow an insulating layer; Step 8: Etch the through silicon via to expose the top copper layer on the through silicon via interconnect structure, then grow an adhesion layer, then grow the heating resistor metal, then grow an oxide layer, and etch the silicon oxide, as shown in the figure; The ninth step is photolithography, followed by deep silicon etching of the top silicon layer to remove the photoresist; Step 10: Perform temporary bonding using a glass sheet, temporary bonding adhesive and a wafer; In the eleventh step, the bottom of the wafer is thinned and polished to expose the TSV interconnect structure layer and make marks for subsequent alignment; Step 12: Debond, grow gold on the top layer, prepare another wafer, and then grow a layer of gold on the top layer. Step 13: Gold-gold bonding of the new wafer and the sample; Step 14: Thin and polish the top wafer, leaving only the second device layer, and then grow a reflective metal on the top layer as a mirror layer; Step 15: growing an insulating layer at the bottom, etching an opening, growing a seed layer, then electroplating copper to form a copper column, and electroplating a nickel-chromium alloy; Step 16, etching the back cavity, and then etching the silicon oxide of the buried oxide layer; In step 17, the device is finally released and the silicon at the bottom of the driver is etched.

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