Electrostatic MEMS micromirror with independent electrode structure and manufacturing method thereof

Abstract

The invention discloses an electrostatic comb tooth driving MEMS micromirror with an independent electrode structure and a manufacturing method, and belongs to the field of micro-optical electro-mechanical systems, and the electrostatic comb tooth driving MEMS micromirror comprises a mirror surface, comb tooth electrodes, a comb tooth supporting structure, a torsion beam, a bonding pad, a cavity and a fixed frame. And the driving movable comb tooth electrode and the detection movable comb tooth electrode are connected with the bonding pad through the torsion beam. According to the micro-mirror, comb electrodes are divided into detection comb electrodes and driving comb electrodes by filling isolation channels, and parasitic capacitance is reduced by removing silicon substrates at the bottoms of the comb electrodes, so that feed-through interference of driving signals on detection signals is avoided, and the capacitance detection precision of the electrostatic MEMS micro-mirror is improved. According to the back cavity etching priority sequence, the invention further discloses two manufacturing methods of the electrostatic MEMS micromirror with the independent electrode structure, and according to the manufacturing methods of the electrostatic MEMS micromirror, the isolation and interconnection of different comb teeth electrodes are realized by filling a channel, an insulating layer and a metal wire with a polymer.

Description

Technical Field

[0001] The invention belongs to the field of micro-opto-electromechanical systems (MOEMS), and relates to an electrostatic MEMS micromirror with an independent electrode structure and a manufacturing method thereof. Background Art

[0002] Electrostatic MEMS micromirrors have the advantages of high frequency, large angle, small size and low power consumption, and are widely used in industrial and consumer electronics fields, such as laser radar, AR display devices, 3D cameras, etc. However, the scanning stability of micromirrors is easily affected by ambient temperature, humidity and atmospheric pressure, which limits the application of micromirrors in these fields. Therefore, position detection is required to provide real-time and accurate angle and phase information for micromirrors, thereby improving the scanning stability and scanning accuracy of micromirrors.

[0003] For electrostatic MEMS micromirrors, the main position detection methods are currently optical detection, capacitive sensing, piezoresistive sensing, and piezoelectric sensing. Among them, capacitive detection directly uses an electrostatic comb driver as a detection structure. Compared with other detection methods, it does not require additional assembly and sensors, and has become the preferred detection solution for electrostatic micromirrors. At present, the capacitance detection method mainly adopts the method of sharing comb electrodes, that is, a group of comb drivers are used as driving electrodes and detection electrodes at the same time. In the specific implementation process, a driving signal is applied to the moving comb electrode, and the driving signal is converted into a detection signal with capacitance change information through the variable capacitor between the moving and static comb teeth, and the detection signal is extracted through the fixed comb electrode. Since the driving electrode and the detection electrode are shared, the driving signal will be directly introduced into the detection signal through the variable capacitor, thereby generating serious feedthrough interference, resulting in waveform distortion and low signal-to-noise ratio, seriously reducing the capacitance detection accuracy, and increasing the difficulty of extracting the sensing signal. Therefore, in order to improve the capacitance detection accuracy of the micromirror, it is necessary to eliminate the feedthrough interference of the driving signal to the sensing signal. Summary of the invention

[0004] In order to eliminate the feedthrough interference in the capacitance detection process, the purpose of the present invention is to provide an electrostatic comb-tooth driven MEMS micromirror with an independent electrode structure and a manufacturing method. The micromirror divides the comb-tooth electrode into a detection comb-tooth electrode and a driving comb-tooth electrode by filling an isolation trench, and removes the silicon substrate at the bottom of the comb-tooth electrode to reduce the parasitic capacitance, thereby avoiding the feedthrough interference of the driving signal on the detection signal and improving the capacitance detection accuracy of the electrostatic MEMS micromirror.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The invention discloses an electrostatic MEMS micromirror with an independent electrode structure, comprising a mirror surface, a comb-tooth electrode, a comb-tooth support structure, a torsion beam, a pad, a cavity and a fixed frame. The movable comb-tooth electrode is separated into a driving movable comb-tooth electrode and a detecting movable comb-tooth electrode by a filling groove. The driving movable comb-tooth electrode and the detecting movable comb-tooth electrode are connected to the pad through a torsion beam. The fixed comb-tooth electrode is located on the fixed frame and separated into a driving fixed comb-tooth electrode, a ground electrode and a detecting fixed comb-tooth electrode by a filling groove. The ground electrode is located between the driving fixed comb-tooth electrode and the detecting fixed comb-tooth electrode to avoid feedthrough interference of the driving signal on the detection signal. The bottom silicon substrate of the area connected to the fixed comb-tooth electrode is removed and connected to the fixed frame through the filling groove to eliminate the parasitic capacitance introduced by the buried oxide layer and the substrate layer in the SOI wafer, and further reduce the feedthrough interference of the driving signal on the detection signal. The pad is located on the fixed frame, and insulation between different pads is achieved by filling the groove, and connected to different electrodes through metal wires. The comb-tooth electrode is divided into a detection comb-tooth electrode and a driving comb-tooth electrode by filling the isolation trench, and the parasitic capacitance is reduced by removing the silicon substrate at the bottom of the comb-tooth electrode, thereby avoiding the feedthrough interference of the driving signal on the detection signal and improving the capacitance detection accuracy of the electrostatic MEMS micromirror.

[0007] The comb tooth support structure is connected to the mirror plate, the detection movable comb teeth are located at the end of the comb tooth support structure, and the shape of the comb tooth support structure includes a trapezoid or a rectangle. Preferably, the shape of the comb tooth support structure is a trapezoid, and the detection movable comb teeth are located on one side of the short side of the trapezoid, and the strength of the capacitive sensing signal is improved by increasing the overlapping area of ​​the comb teeth.

[0008] The movable comb teeth electrodes are separated into driving movable comb teeth electrodes and detecting movable comb teeth electrodes by filling trenches, and connected to the pads through metal wires and torsion beams. Preferably, the total ratio of detecting movable comb teeth to driving movable comb teeth is between 1:1 and 2:5.

[0009] There are three ways to arrange the positions of the moving comb teeth electrodes: Way 1: the driving moving comb teeth and the detecting moving comb teeth are all located on the mirror plate, which can reduce the chip size and thus reduce the production cost; Way 2: the driving moving comb teeth and the detecting moving comb teeth are all located on the comb teeth supporting structure, which can avoid the interference effect of the comb teeth on the mirror plate on the light; Way 3: the driving moving comb teeth are located on the mirror plate and the detecting moving comb teeth are all located on the comb teeth supporting structure, which increases the driving force to reduce the driving voltage and increases the overlapping area of ​​the detecting moving comb teeth and the detecting fixed comb teeth to increase the capacitance sensing signal strength, thereby further improving the capacitance sensing accuracy.

[0010] The driving movable comb tooth electrode and the detecting movable comb tooth electrode are connected to the pad via a torsion beam. The torsion beam structure is a single torsion beam or a double torsion beam. When a single torsion beam structure is adopted, the driving movable comb tooth electrode and the detecting movable comb tooth electrode are respectively connected to two pads via the single torsion beam and the metal wire above the single torsion beam; when a double torsion beam structure is adopted, the driving movable comb tooth electrode and the detecting movable comb tooth electrode are respectively connected to two pads via two torsion beams in the double torsion beam.

[0011] The fixed comb-tooth electrode is isolated from the fixed frame by the filling channel and connected to the pad by the metal wire. The pad is surrounded by the filling channel to achieve electrical isolation between different pads. The number of circles of the filling channel around the pad is between 1 and 4. Preferably, the number of circles of the filling channel is 2, and multiple openings are opened around the filling channel around the pad to release the stress inside the filling channel and reduce the parasitic capacitance introduced by the filling channel.

[0012] The present invention also discloses two methods for manufacturing an electrostatic MEMS micromirror with an independent electrode structure, which are used to manufacture the electrostatic MEMS micromirror with an independent electrode structure. The present invention also discloses two methods for manufacturing an electrostatic MEMS micromirror with an independent electrode structure, which are divided into two methods according to the priority of back cavity etching:

[0013] Regarding the method for manufacturing a post-etched back cavity, the method for manufacturing an electrostatic MEMS micromirror with an independent electrode structure disclosed in the present invention comprises the following steps:

[0014] Step (a): The electrostatic MEMS micromirror with independent electrode structure is made of SOI wafer, each SOI wafer is composed of device layer, buried oxide layer and substrate layer. Photoresist is coated on the surface of SOI wafer device layer and electrical isolation channel is patterned, and then deep silicon etching process is used to etch the SOI wafer device layer to the SOI wafer insulation layer to form a deep groove for filling insulation material.

[0015] Step (b): the insulating material is a polymer, preferably, the polymer is PI, BCB, SOG, LCP or a combination of the above polymer materials; the polymer is filled into the channel by spin coating, and the bubbles in the channel are removed by vacuum treatment, and then placed in a nitrogen oven for high-temperature curing.

[0016] Step (c): using chemical mechanical polishing (CMP) to remove excess filler material from the surface to obtain a smooth surface for subsequent processes;

[0017] Step (d): using enhanced plasma chemical vapor deposition (PECVD) to grow a layer of SiO2 for insulation between the metal wire and the device layer, and using a wet etching process to remove excess SiO2;

[0018] Step (e): depositing a metal film on the front side of the device layer and patterning it to form metal wires, metal pads and a mirror reflection layer for interconnection.

[0019] Step (f): The surface of the SOI device layer is coated with glue and patterned, and deep silicon is etched to the insulating layer to form a micromirror device structure.

[0020] Step (g): The surface of the SOI substrate layer is coated with photoresist and patterned, and deep silicon is etched to the insulating layer to form a cavity structure.

[0021] Step (h): removing the SOI buried oxide layer by dry or wet method, and then removing the photoresist on the surface to form an electrostatic micromirror with independent detection electrodes.

[0022] For the manufacturing method of etching the back cavity first, the electrostatic MEMS micromirror manufacturing method with an independent electrode structure disclosed in the present invention includes the following steps:

[0023] Step (a): The electrostatic MEMS micromirror with independent electrode structure is made of SOI wafer, each SOI wafer is composed of device layer, buried oxide layer and substrate layer. Photoresist is coated on the surface of SOI wafer device layer and electrical isolation channel is patterned, and then deep silicon etching process is used to etch the SOI wafer device layer to the SOI wafer insulation layer to form a deep groove for filling insulation material.

[0024] Step (b): the insulating material is a polymer, preferably, the polymer is PI, BCB, SOG, LCP or a combination of the above polymer materials; the polymer is filled into the channel by spin coating, and the bubbles in the channel are removed by vacuum treatment, and then placed in a nitrogen oven for high-temperature curing.

[0025] Step (c): Use CMP process to remove excess filling material on the surface to obtain a flat surface to facilitate subsequent processes.

[0026] Step (d): The surface of the SOI substrate layer is coated with photoresist and patterned, and deep silicon is etched to the insulating layer to form a cavity structure.

[0027] Step (e): Spin-coat a layer of photoresist on the surface of the SOI device layer to protect the front structure, and then use a wet etching process to remove SiO2 in the buried oxide layer.

[0028] Step (f): bonding the glass and the SOI substrate layer together using an anodic bonding process.

[0029] Step (g): using a PECVD process to grow a layer of SiO2 on the surface of the SOI device layer for insulation between the metal wire and the device layer, and using a wet etching process to remove excess SiO2.

[0030] Step (h): depositing a metal film on the front side of the device layer and patterning it to form metal wires, metal pads and a mirror reflection layer for interconnection.

[0031] Step (i): The surface of the SOI device layer is coated with glue and patterned, and deep silicon is etched to the buried oxide layer to form a micromirror device structure.

[0032] Beneficial effects:

[0033] 1. The present invention discloses an electrostatic micromirror with an independent detection comb structure, which isolates the driving comb electrode and the detection comb electrode by filling the trench, eliminates the feedthrough interference of the driving signal on the detection signal, and significantly improves the capacitance detection accuracy of the electrostatic MEMS micromirror.

[0034] 2. The present invention discloses an electrostatic micromirror with an independent detection comb tooth structure, which reduces parasitic capacitance by removing the silicon substrate at the bottom of the comb tooth electrode and placing a ground electrode between the driving fixed comb tooth electrode and the detection fixed comb tooth electrode, thereby further improving the capacitance detection accuracy of the electrostatic MEMS micromirror.

[0035] 3. The present invention discloses an electrostatic micromirror with an independent detection comb tooth structure, which realizes a low-voltage, small-volume electrostatic MEMS micromirror with an independent detection comb tooth structure through a variety of comb tooth layouts, and improves the capacitance sensing accuracy by increasing the overlapping area between the detection comb teeth.

[0036] 4. The present invention discloses an electrostatic micromirror with an independent detection comb structure, which uses a double torsion beam to electrically interconnect different comb electrodes, thereby avoiding deformation of the torsion beam caused by metal wires covering the top of the torsion beam and improving the reliability of the torsion beam.

[0037] 5. The present invention discloses a method for manufacturing an electrostatic micromirror with an independent detection comb structure, which realizes isolation and interconnection of different comb-tooth electrodes by filling channels, insulating layers and metal wires with polymers.

[0038] 6. The present invention discloses a method for manufacturing an electrostatic micromirror with an independent detection comb structure. The post-etching back cavity process adopts a single-chip SOI wafer processing, does not require a multi-wafer bonding process, and the process is simple and easy to implement with good repeatability.

[0039] 7. The present invention discloses a method for manufacturing an electrostatic micromirror with an independent detection comb structure. The back cavity etching process adopts a SOI wafer and a glass anode bonding to avoid photoresist residue inside the comb teeth. The process has a high yield rate and is easy for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of embodiment 1 of an electrostatic micromirror with an independent detection electrode structure;

[0041] Figure 2 Schematic diagram of pads with different structures, where: Figure 2 (a) is a pad with a single-circle filled trench. Figure 2 (b) is a pad with a double-circle filled trench. Figure 2 (c) is a pad having a filled trench opening;

[0042] Figure 3 Schematic diagram of a second embodiment of an electrostatic micromirror with an independent detection electrode structure;

[0043] Figure 4 Schematic diagram of a third embodiment of an electrostatic micromirror with an independent detection electrode structure;

[0044] Figure 5 Schematic diagram of different comb tooth support structures, where: Figure 5 (a) is a rectangular comb tooth support structure. Figure 5 (b) is a trapezoidal comb tooth support structure;

[0045] Figure 6 Schematic diagram of a fourth embodiment of an electrostatic micromirror with an independent detection electrode structure;

[0046] Figure 7 (a)~ Figure 7 (j) is a schematic diagram of the post-etching back cavity process steps based on a single SOI wafer;

[0047] Figure 8 (a)~ Figure 8 (j) is a schematic diagram of the process steps of etching the back cavity first based on silicon glass anodic bonding;

[0048] Among them, 100-fixed frame, 101-detection of moving comb teeth, 102-detection of fixed comb teeth, 103-driving moving comb teeth, 104-driving fixed comb teeth, 105-comb tooth support structure, 106-mirror plate, 107-single torsion beam, 108-metal wire, 109-first filling channel, 110-second filling channel, 111-third filling channel, 112-fourth filling channel, 113-driving negative electrode pad, 114-detection of positive electrode pad, 115-ground electrode pad, 116-driving positive electrode pad, 117-detection of negative electrode pad Disk, 118-double torsion beam, 119-first torsion beam, 120-second torsion beam, 121-fifth filled channel, 122-sixth filled channel, 123-seventh filled channel, 124-eighth filled channel, 125-ninth filled channel, 201-filled channel opening, 701-device layer, 701-buried oxide layer, 703-substrate layer, 704-groove, 705-channel filling, 706-silicon dioxide, 707-metal, 708-micromirror structure, 709-cavity, 710-photoresist, 801-glass. DETAILED DESCRIPTION

[0049] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0050] Embodiment 1

[0051] like Figure 1 As shown, an electrostatic micromirror with an independent electrode detection structure disclosed in this embodiment is made of SOI wafer, including a driving comb tooth structure, a detection comb tooth structure, a mirror plate 106, a single torsion beam 107, a pad, a metal wire 108 and a filling channel. The driving comb tooth structure includes a driving movable comb tooth 103 and a driving fixed comb tooth 104, which are used to drive the mirror plate 106 to rotate, wherein the driving movable comb tooth 103 is connected to the mirror plate 106, and the driving fixed comb tooth 104 is connected to the fixed frame 100. The driving movable comb tooth 103 is electrically isolated from the comb tooth support structure through the second filling channel 110 to form an independent electrical isolation area, and is connected to the driving negative electrode pad 113 through the metal wire 108 above the single torsion beam 107. The driving fixed comb tooth 104 is electrically isolated from the fixed frame 100 through the third filling channel 111, forming an independent electrical isolation interval and connected to the driving positive electrode pad 116 through the metal wire 108.

[0052] The detection comb structure includes a detection movable comb 101 and a detection fixed comb 102, which are used for capacitive sensing of the micromirror, wherein the detection movable comb 101 is connected to the comb support structure 105, and the detection fixed comb 102 is connected to the fixed frame 100. The detection movable comb 101 is electrically isolated from the mirror plate 106 and the fixed frame 100 through the first filling channel 109 and the second filling channel 110 to form an independent electrical isolation interval, and is connected to the detection negative electrode pad 117 through the single torsion beam 107 and the metal wire 108. The detection fixed comb 102 is electrically isolated from the fixed frame 100 through the third filling channel 111 to form an independent electrical isolation interval, and is connected to the detection positive electrode pad 114 through the metal wire 108.

[0053] The third filling trench 111 isolates an independent isolation area connected to the ground electrode pad 115 between the driving fixed comb tooth area and the detection fixed comb tooth area to avoid feedthrough interference of the driving positive electrode signal on the detection positive electrode signal. At the same time, the substrate silicon at the bottom of the independent electrical isolation area connected to the third filling trench 111 is completely hollowed out to avoid feedthrough interference caused by parasitic capacitance introduced by the substrate silicon.

[0054] The pads are surrounded by the fourth filling trench 112, which electrically isolates different pads for applying corresponding voltages. The fourth filling trench 112 may surround the pads in a circle, such as Figure 2 (a); the fourth filling trench 112 may also surround the pad multiple times, for example, 2 times, in order to reduce parasitic capacitance. Figure 2(b) As shown; a plurality of filling channel openings 201 may be opened around the fourth filling channel 112, and the silicon at the opening is etched away to release the stress inside the filling channel and further reduce the parasitic capacitance, such as Figure 2 (c) as shown.

[0055] The electrical signal is input through the pad, the driving signal is applied to the driving positive pad 116, the signal to be detected is applied to the detection positive pad 114, the driving negative pad 113 and the ground electrode pad 115 are grounded, and the detection negative pad 117 is connected to the detection circuit to obtain the capacitance detection signal of the micromirror movement.

[0056] Embodiment 2

[0057] This embodiment discloses another electrostatic micromirror with an independent electrode detection structure, such as Figure 3 As shown. In this embodiment, the double torsion beam 118 is used to support the mirror surface and the electrical connection. The double torsion beam is composed of a first torsion beam 119 and a second torsion beam 120. The two torsion beams can transmit different electrical signals respectively. The first torsion beam 119 forms an independent electrical isolation area through the fifth filling channel 121 and the sixth filling channel 122, and is connected to the mirror plate 106 and the driving negative electrode pad 113 through the metal wire 108. The second torsion beam 120 forms an independent electrical isolation area through the fifth filling channel 121 and the second filling channel 110, and is connected to the detection negative electrode pad 117 through the metal wire 108. The double torsion beam 118 on the other side is directly connected to the comb support structure 105, forms an independent electrical isolation area through the first filling channel 109 and the second filling channel 110, and then is connected to the detection negative electrode pad 117 through the metal wire 108.

[0058] Embodiment 3

[0059] Another electrostatic micromirror with an independent electrode detection structure disclosed in this embodiment is Figure 4 As shown. In this embodiment, the driving movable comb teeth 103 and the detecting movable comb teeth 101 are both located on the comb tooth support structure 105, and the driving movable comb teeth 103 and the detecting movable comb teeth 101 are divided into two independent electrically isolated areas by the seventh filling trench 123, and are electrically interconnected by a double torsion beam. The double torsion beam electrical interconnection layout in this embodiment can also be replaced by the single torsion beam electrical interconnection layout in the first embodiment.

[0060] At the same time, the comb support structure 105 has two layouts, such as Figure 5 One structure is a rectangle, such as Figure 5 As shown in (a), the detection movable comb teeth 101 are fixed to one end connected to the torsion beam, and the driving movable comb teeth 103 are fixed to one end connected to the mirror plate 106. The width of the structure is preferably 30μm to 100μm; another structure is a trapezoidal shape, such as Figure 5As shown in (b), the detection movable comb teeth 101 are located on the short bottom side of the trapezoidal structure, the short bottom side of the trapezoidal structure is connected to the torsion beam, and the driving movable comb teeth 103 are located on the long bottom side of the trapezoidal structure, and the long bottom side of the trapezoidal structure is connected to the mirror plate 106. This structure is conducive to improving the amplitude of the capacitive sensing signal and increasing the accuracy of capacitive sensing.

[0061] Embodiment 4

[0062] This embodiment discloses another electrostatic micromirror with an independent electrode detection structure, such as Figure 6 As shown. In this embodiment, the driving movable comb teeth 103 and the detecting movable comb teeth 101 are both located on the mirror plate 105, and the driving movable comb teeth 103 and the detecting movable comb teeth 101 are divided into two independent electrically isolated areas through the eighth filling trench 124, and are respectively connected to the driving negative electrode pad 113 and the detecting negative electrode pad 117 through the single torsion beam 107 and the metal wire 108. The third filling trench 111 isolates an independent isolation area connected to the ground electrode pad 115 between the driving fixed comb tooth area and the detecting fixed comb tooth area to avoid feed-through interference of the driving positive electrode signal on the detecting positive electrode signal.

[0063] In order to realize the manufacturing of an electrostatic micromirror with an independent electrode detection structure, in one embodiment, the present invention proposes a post-etching back cavity manufacturing method based on a single SOI wafer, such as Figure 7 Shown

[0064] (a) The electrostatic MEMS micromirror with independent electrode structure is made of SOI wafer, and each SOI wafer is composed of a device layer 701, a buried oxide layer 702 and a substrate layer 703. Photoresist is coated on the surface of the SOI wafer device layer and the electrical isolation channel is patterned, and then the SOI wafer device layer is etched to the SOI wafer insulation layer by a deep silicon etching process to form a groove 704 for filling the insulation material.

[0065] (b) The channel filler 705 is a polymer. Preferably, the polymer is PI, BCB, SOG, LCP or a combination of the above polymer materials. The polymer is filled into the channel by spin coating, and the bubbles in the channel are removed by vacuum treatment, and then placed in a nitrogen oven for high-temperature curing.

[0066] (c) using a CMP process to remove the excess trench filler 705 on the surface to obtain a flat surface for subsequent processes;

[0067] (d) using PECVD to grow a layer of silicon dioxide 706 for insulation between the metal wire and the device layer, the thickness of the silicon dioxide is preferably 300nm to 1000nm;

[0068] (e) removing excess silicon dioxide by wet etching;

[0069] (f) depositing a layer of metal 707 on the front side of the device layer, and forming metal wires, metal pads and a mirror reflection layer for interconnection by stripping or dry etching, wherein the metal is preferably Au or Al;

[0070] (g) The surface of the SOI device layer is coated with glue and patterned, and deep silicon is etched to the buried oxide layer to form a micromirror structure 708;

[0071] (h) The surface of the SOI substrate layer is coated with photoresist and patterned, and deep silicon is etched to the buried oxide layer to form a cavity 709;

[0072] (i) spraying photoresist 710 on the surface of the SOI device layer to protect the front structure;

[0073] (j) The SOI buried oxide layer is removed by a dry method or a wet method, and then the photoresist on the surface is removed to form an electrostatic micromirror with an independent detection electrode.

[0074] In order to realize the manufacturing of electrostatic micromirrors with independent electrode detection structures, in another embodiment, the present invention proposes a back cavity first etching manufacturing process based on silicon glass anodic bonding, such as Figure 8 Shown

[0075] (a) The electrostatic MEMS micromirror with independent electrode structure is made of SOI wafer, and each SOI wafer is composed of a device layer 701, a buried oxide layer 702 and a substrate layer 703. Photoresist is coated on the surface of the SOI wafer device layer and the electrical isolation channel is patterned, and then the SOI wafer device layer is etched to the SOI wafer insulation layer by a deep silicon etching process to form a groove 704 for filling the insulation material.

[0076] (b) The channel filler 705 is a polymer. Preferably, the polymer is PI, BCB, SOG, LCP or a combination of the above polymer materials. The polymer is filled into the channel by spin coating, and the bubbles in the channel are removed by vacuum treatment, and then placed in a nitrogen oven for high-temperature curing.

[0077] (c) using a CMP process to remove the excess trench filler 705 on the surface to obtain a flat surface for subsequent processes;

[0078] (d) The surface of the SOI substrate layer is coated with photoresist 710 and patterned, and deep silicon is etched to the buried oxide layer to form a cavity 709;

[0079] (e) removing the SOI buried oxide layer by dry or wet method;

[0080] (f) Anodically bonding the SOI substrate layer to the glass 801;

[0081] (g) using PECVD to grow a layer of silicon dioxide 706 for insulation between the metal wire and the device layer, the thickness of the silicon dioxide is preferably 300nm to 1000nm;

[0082] (h) removing excess silicon dioxide by wet etching;

[0083] (i) depositing a layer of metal 707 on the front side of the device layer, and using stripping or dry etching to form metal wires, metal pads and a mirror reflection layer for interconnection, wherein the metal is preferably Au or Al;

[0084] (j) The surface of the SOI device layer is coated with glue and patterned, and deep silicon is etched to the buried oxide layer to form a micromirror structure 708, completing the processing of the electrostatic micromirror with independent detection electrodes.

[0085] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An electrostatic MEMS micromirror with an independent electrode structure, characterized in that: It includes a mirror, a comb tooth electrode, a comb tooth support structure, a torsion beam, a pad, a cavity and a fixed frame; the movable comb tooth electrode is separated into a driving movable comb tooth electrode and a detecting movable comb tooth electrode by a filling groove; the driving movable comb tooth electrode and the detecting movable comb tooth electrode are connected to the pad through the torsion beam; the fixed comb tooth electrode is located on the fixed frame and separated into a driving fixed comb tooth electrode, a ground electrode and a detecting fixed comb tooth electrode by a filling groove; the ground electrode is located between the driving fixed comb tooth electrode and the detecting fixed comb tooth electrode to avoid feed-through interference of the driving signal on the detection signal; The bottom silicon substrate in the area connected to the fixed comb-tooth electrode is removed and connected to the fixed frame by filling the trench, so as to eliminate the parasitic capacitance introduced by the buried oxide layer and the substrate layer in the SOI wafer, and further reduce the feedthrough interference of the driving signal on the detection signal; the pad is located on the fixed frame, and the insulation between different pads is achieved by filling the trench, and connected to different electrodes through metal wires; the comb-tooth electrode is divided into a detection comb-tooth electrode and a driving comb-tooth electrode by filling the isolation trench, and the silicon substrate at the bottom of the comb-tooth electrode is removed to reduce the parasitic capacitance, avoid the feedthrough interference of the driving signal on the detection signal, and improve the capacitance detection accuracy of the electrostatic MEMS micromirror.

2. An electrostatic MEMS micromirror with an independent electrode structure as claimed in claim 1, characterized in that: The shape of the comb teeth support structure is trapezoidal, and the detection moving comb teeth are located on the short side of the trapezoid. The strength of the capacitive sensing signal is improved by increasing the overlapping area of ​​the comb teeth. The total ratio of the detection movable comb teeth to the driving movable comb teeth is between 1:1 and 2:

5.

3. The electrostatic MEMS micromirror with an independent electrode structure as claimed in claim 1, characterized in that: There are three ways to arrange the positions of the moving comb teeth electrodes: Way 1: the driving moving comb teeth and the detecting moving comb teeth are all located on the mirror plate, thereby reducing the chip size and thus reducing the production cost; Way 2: the driving moving comb teeth and the detecting moving comb teeth are all located on the comb teeth supporting structure, thereby avoiding the interference effect of the comb teeth on the mirror plate on the light; Way 3: the driving moving comb teeth are all located on the mirror plate and the detecting moving comb teeth are all located on the comb teeth supporting structure, thereby increasing the driving force and thus reducing the driving voltage, while increasing the overlapping area of ​​the detecting moving comb teeth and the detecting fixed comb teeth, thereby increasing the capacitance sensing signal strength and further improving the capacitance sensing accuracy.

4. The electrostatic MEMS micromirror with an independent electrode structure as claimed in claim 1, characterized in that: The driving movable comb tooth electrode and the detecting movable comb tooth electrode are connected to the pad via a torsion beam; the torsion beam structure is a single torsion beam or a double torsion beam; when a single torsion beam structure is adopted, the driving movable comb tooth electrode and the detecting movable comb tooth electrode are respectively connected to two pads via the single torsion beam and the metal wire above the single torsion beam; when a double torsion beam structure is adopted, the driving movable comb tooth electrode and the detecting movable comb tooth electrode are respectively connected to two pads via the two torsion beams in the double torsion beam.

5. The electrostatic MEMS micromirror with an independent electrode structure as claimed in claim 1, characterized in that: The fixed comb-tooth electrodes are isolated from the fixed frame by filling channels and connected to the pads through metal wires; the pads are surrounded by filling channels to achieve electrical isolation between different pads; the number of filling channel circles surrounding the pads is between 1 and 4.

6. The electrostatic MEMS micromirror with an independent electrode structure as claimed in claim 5, characterized in that: The number of circles of the filled trench is 2, and a plurality of openings are opened around the filled trench of the pad to release stress inside the filled trench and reduce parasitic capacitance introduced by the filled trench.

7. An electrostatic MEMS micromirror with an independent electrode structure as claimed in claim 1, 2, 3, 4, 5 or 6, characterized in that: The preparation method comprises the following steps: Step (a): an electrostatic MEMS micromirror with an independent electrode structure is manufactured using an SOI wafer, each SOI wafer consisting of a device layer, a buried oxide layer and a substrate layer; a photoresist is coated on the surface of the SOI wafer device layer and an electrical isolation channel is patterned, and then a deep silicon etching process is used to etch the SOI wafer device layer to the SOI wafer insulation layer to form a deep groove for filling an insulating material; Step (b): the insulating material is a polymer; the polymer is filled into the channel by spin coating, and the bubbles in the channel are removed by vacuum treatment, and then placed in a nitrogen oven for high-temperature curing; Step (c): using chemical mechanical polishing (CMP) to remove excess filler material from the surface to obtain a smooth surface for subsequent processes; Step (d): using enhanced plasma chemical vapor deposition (PECVD) to grow a layer of SiO2 for insulation between the metal wire and the device layer, and using a wet etching process to remove excess SiO2; Step (e): depositing a metal film on the front side of the device layer and patterning to form metal wires, metal pads and a mirror reflection layer for interconnection; Step (f): coating and patterning the surface of the SOI device layer, and deep silicon etching to the insulating layer to form a micromirror device structure; Step (g): coating the surface of the SOI substrate layer with photoresist and patterning it, and deep silicon etching to the insulating layer to form a cavity structure; Step (h): removing the SOI buried oxide layer by dry or wet method, and then removing the photoresist on the surface to form an electrostatic micromirror with independent detection electrodes.

8. An electrostatic MEMS micromirror with an independent electrode structure as claimed in claim 1, 2, 3, 4, 5 or 6, characterized in that: The preparation method comprises the following steps: Step (a): an electrostatic MEMS micromirror with an independent electrode structure is manufactured using an SOI wafer, each SOI wafer consisting of a device layer, a buried oxide layer and a substrate layer; a photoresist is coated on the surface of the SOI wafer device layer and an electrical isolation channel is patterned, and then a deep silicon etching process is used to etch the SOI wafer device layer to the SOI wafer insulation layer to form a deep groove for filling an insulating material; Step (b): the insulating material is a polymer; the polymer is filled into the channel by spin coating, and the bubbles in the channel are removed by vacuum treatment, and then placed in a nitrogen oven for high-temperature curing; Step (c): using a CMP process to remove excess filler material from the surface to obtain a flat surface for easy subsequent processing; Step (d): coating the surface of the SOI substrate layer with photoresist and patterning it, and deep silicon etching to the insulating layer to form a cavity structure; Step (e): Spin-coating a layer of photoresist on the surface of the SOI device layer to protect the front structure, and then using a wet etching process to remove SiO2 in the buried oxide layer; Step (f): bonding the glass and the SOI substrate layer together using an anodic bonding process; Step (g): using a PECVD process to grow a layer of SiO2 on the surface of the SOI device layer for insulation between the metal wire and the device layer, and using a wet etching process to remove excess SiO2; Step (h): depositing a metal film on the front side of the device layer and patterning to form metal wires, metal pads and a mirror reflection layer for interconnection; Step (i): The surface of the SOI device layer is coated with glue and patterned, and deep silicon is etched to the buried oxide layer to form a micromirror device structure.

9. The electrostatic MEMS micromirror with an independent electrode structure as claimed in claim 7, characterized in that: The polymer is selected from PI, BCB, SOG, LCP or a combination of the above polymer materials.

10. The electrostatic MEMS micromirror with an independent electrode structure as claimed in claim 8, characterized in that: The polymer is selected from PI, BCB, SOG, LCP or a combination of the above polymer materials.

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