MEMS micro-mirror device, micro-mirror matrix and preparation method

Abstract

The invention discloses an MEMS micro-mirror device, a micro-mirror matrix and a preparation method, relates to the technical field of micro-electromechanical systems (MEMS), and can improve the yield of micro-mirror products. The invention particularly relates to an MEMS micro-mirror device, a micro-mirror matrix and a preparation method. The MEMS micro-mirror device comprises at least two stacked micro-mirror units, each micro-mirror unit comprises a first substrate, and fixed comb teeth are formed on the first substrate; the second substrate is arranged on one side of the first substrate; a torsion beam and movable comb teeth are formed on the second substrate, teeth of the fixed comb teeth and teeth of the movable comb teeth are arranged in a staggered mode, the mirror surface structure is connected with the torsion beam and connected with the movable comb teeth, and displacement of the movable comb teeth is used for driving the mirror surface structure to rotate in the axial direction of the torsion beam; wherein orthographic projections of the mirror surface structures of the stacked micro-mirror units on the first substrate are overlapped, and the mirror surface structure of the micro-mirror unit close to the light emitting side of the MEMS micro-mirror device is provided with a first hollow structure.

Description

Technical Field

[0001] The present application relates to the field of MEMS (micro-electromechanical systems) technology, and in particular to a MEMS micromirror device, a micromirror matrix, and a preparation method thereof. Background Art

[0002] MEMS micromirrors are chip-scale optical devices fabricated using micromachining techniques. As key components for rapid laser scanning and phase modulation, they are widely used in a variety of fields, including laser confocal scanning microscopes, lidar, laser projection, laser processing, MEMS optical switches, and spatial light modulators. However, existing MEMS micromirrors are all single-layer mirrors. Damage to a single mirror in a micromirror array can easily cause the entire array to fail, resulting in low product yield. Summary of the Invention

[0003] The embodiments of the present application provide a MEMS micromirror device, a micromirror matrix, and a manufacturing method, which can improve the yield of micromirror products.

[0004] According to a first aspect of an embodiment of the present application, a MEMS micromirror device is provided, comprising:

[0005] At least two stacked micromirror units, each micromirror unit comprising:

[0006] a first substrate, wherein the first substrate is formed with fixed comb teeth;

[0007] a second substrate, disposed on one side of the first substrate;

[0008] In the micromirror unit close to the light-emitting side of the MEMS micromirror device, a mirror structure is provided on a side of the second substrate close to the first substrate;

[0009] In the micromirror unit away from the light-emitting side of the MEMS micromirror device, a mirror structure is provided on a side of the second substrate away from the first substrate;

[0010] The second substrate is formed with a torsion beam and movable comb teeth, the teeth of the fixed comb teeth are staggered with the teeth of the movable comb teeth, the mirror structure is connected to the torsion beam, and the mirror structure is connected to the movable comb teeth, and the displacement of the movable comb teeth is used to drive the mirror structure to rotate along the axial direction of the torsion beam;

[0011] The orthographic projections of the mirror structures of the stacked micromirror units on the first substrate overlap, and the mirror structure of the micromirror unit close to the light-emitting side of the MEMS micromirror device is provided with a first hollow structure.

[0012] In some embodiments, in the micromirror unit close to the light-emitting side of the MEMS micromirror device, the first substrate includes a first via hole, and the orthographic projection of the mirror structure on the first substrate falls within the orthographic projection of the first via hole on the first substrate.

[0013] In some embodiments, the fixed comb teeth include first fixed comb teeth and second fixed comb teeth, and an orthographic projection of the first fixed comb teeth on the first substrate and an orthographic projection of the second fixed comb teeth on the first substrate are symmetrical with respect to an orthographic projection of the first via hole on the first substrate;

[0014] An isolation groove is formed between the first fixed comb teeth and the second fixed comb teeth, and a length extension direction of the isolation groove is the same as a length extension direction of the torsion beam.

[0015] In some embodiments, the movable comb teeth include first movable comb teeth and second movable comb teeth, and the first movable comb teeth and the second movable comb teeth are symmetrically arranged with respect to the mirror structure;

[0016] The teeth of the first movable comb teeth are staggered with the teeth of the first fixed comb teeth, and the teeth of the second movable comb teeth are staggered with the teeth of the second fixed comb teeth;

[0017] The torsion beam includes a first torsion beam and a second torsion beam, and the first torsion beam and the second torsion beam are symmetrically arranged with respect to the mirror structure.

[0018] In some embodiments, the second substrate is provided with a second hollow structure;

[0019] The orthographic projection of the first hollow structure on the first substrate overlaps with the orthographic projection of the second hollow structure on the first substrate;

[0020] Wherein, both the first hollow structure and the second hollow structure include a plurality of via holes arranged in an array, and the orthographic projection shape of the via holes on the first substrate includes a polygon and / or a circle.

[0021] In some embodiments, the at least two stacked micromirror units include a first layer of micromirror units and a second layer of micromirror units, and the orthographic projection of the fixed comb teeth in the first layer of micromirror units on the first substrate is the first projection;

[0022] The orthographic projection of the fixed comb teeth in the second layer of micromirror units on the first substrate is the second projection, and the first projection and the second projection coincide with each other; and / or,

[0023] The orthographic projection of the movable comb teeth in the first layer of micromirror units on the first substrate is the third projection;

[0024] The orthographic projection of the movable comb teeth in the second layer of micromirror units on the first substrate is the fourth projection, and the third projection coincides with the fourth projection.

[0025] In some embodiments, the MEMS micromirror device further includes:

[0026] a bonding layer, disposed between the first layer of micromirror units and the second layer of micromirror units;

[0027] The bonding layer includes a third hollow structure, and the orthographic projections of the mirror structure close to the light-emitting side and the mirror structure far from the light-emitting side on the first substrate both fall within the orthographic projection of the third hollow structure on the first substrate.

[0028] In some embodiments, a first insulating layer is provided between the first substrate and the second substrate;

[0029] The first insulating layer includes a fourth hollow structure, and an orthographic projection of the fourth hollow structure on the first substrate coincides with an orthographic projection of the third hollow structure on the first substrate.

[0030] A second aspect of the embodiments of the present application provides a MEMS micromirror matrix, comprising:

[0031] A plurality of MEMS micromirror devices as described in any one of the first aspects.

[0032] A third aspect of the embodiments of the present application provides a method for preparing a MEMS micromirror device, for preparing the MEMS micromirror device according to any one of the first aspects, the method for preparing the MEMS micromirror device comprising:

[0033] preparing a first substrate;

[0034] Etching one side surface of the first substrate to form fixed comb teeth and isolation grooves;

[0035] preparing a second substrate, and bonding the first substrate to the second substrate;

[0036] A mirror structure, a torsion beam, and movable comb teeth are provided on one side of the second substrate. In a micromirror unit close to the light-emitting side of the MEMS micromirror device, a mirror structure is provided on a side of the second substrate close to the first substrate.

[0037] In the micromirror unit away from the light-emitting side of the MEMS micromirror device, a mirror structure is provided on a side of the second substrate away from the first substrate;

[0038] The teeth of the fixed comb teeth are staggered with the teeth of the movable comb teeth, the mirror structure is connected to the torsion beam, and the mirror structure is connected to the movable comb teeth, and the displacement of the movable comb teeth is used to drive the mirror structure to rotate along the axial direction of the torsion beam;

[0039] At least two micromirror units are stacked, wherein the orthographic projections of the two mirror structures of the stacked micromirror units on the first substrate overlap, and the mirror structure of the micromirror unit close to the light-emitting side of the MEMS micromirror device is provided with a first hollow structure.

[0040] The MEMS micromirror device provided in the embodiment of the present application includes at least two stacked micromirror units, and the two layers of micromirror units are independently controlled. By setting a hollow on the micromirror structure close to the light-emitting side, light can be reflected on the mirror structure close to the light-emitting side of the MEMS micromirror device, or pass through the hollow to reach the surface of the mirror structure away from the light-emitting side of the MEMS micromirror device to be reflected, and then be emitted again to the display side through the hollow on the mirror structure of the micromirror unit close to the light-emitting side D. By setting at least two layers of micromirror units and controlling them independently, when a failure occurs in one layer of micromirror units, the other layer of micromirror units can modulate the optical path, thereby preventing damage to a single layer of micromirrors from affecting the entire MEMS micromirror device. Compared with a single-layer micromirror structure, a double-layer micromirror unit greatly reduces the failure probability of the entire MEMS micromirror device and improves the product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic structural diagram of a MEMS micromirror device provided in an embodiment of the present application;

[0042] Figure 2 A schematic cross-sectional view of a MEMS micromirror device along line AA′ provided in an embodiment of the present application;

[0043] Figure 3 A schematic structural diagram of another MEMS micromirror device provided in an embodiment of the present application;

[0044] Figure 4 A schematic structural diagram of another MEMS micromirror device provided in an embodiment of the present application;

[0045] Figure 5 A schematic partial structural diagram of a MEMS micromirror matrix provided in an embodiment of the present application;

[0046] Figure 6 A schematic flow chart of a method for preparing a MEMS micromirror device provided in an embodiment of the present application;

[0047] Figure 7 A process flow chart of a MEMS micromirror device provided in an embodiment of the present application;

[0048] Figure 8 A process flow chart of another MEMS micromirror device provided in an embodiment of the present application;

[0049] Figure 9 A process flow chart of another MEMS micromirror device provided in an embodiment of the present application;

[0050] Figure 10 A process flow chart of another MEMS micromirror device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0051] In order to better understand the technical solutions provided by the embodiments of this specification, the technical solutions of the embodiments of this specification are described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of this specification and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this specification, rather than limitations on the technical solutions of this specification. In the absence of conflict, the embodiments of this specification and the technical features in the embodiments can be combined with each other.

[0052] In this article, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also include elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the statement "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or equipment comprising the elements. The term "two or more" includes two or more than two cases.

[0053] MEMS micromirrors are chip-level optical devices manufactured based on micromachining technology. As one of the key components for rapid laser scanning and phase modulation, they are widely used in various fields such as laser confocal scanning microscopes, lidar, laser projection, laser processing, MEMS optical switches, and spatial light modulators. However, if it is a large-scale micromirror array, if one of the individual micromirrors is damaged, the entire array will fail, resulting in low product yield and high production costs. For example, a micromirror array containing 30 micromirrors has a yield of 95% for each individual micromirror. The yield of a micromirror array containing 30 micromirrors is 0.95 to the power of 30, and the yield of the micromirror array is only 21.5%. For a micromirror device formed by a micromirror array, the product yield is low.

[0054] According to a first aspect of an embodiment of the present application, a MEMS micromirror device is provided. Figure 1 A schematic structural diagram of a MEMS micromirror device provided in an embodiment of the present application. For example, refer to Figure 1 The MEMS micromirror device includes at least two stacked micromirror units, the two stacked micromirror units being a first layer micromirror unit 1000 and a second layer micromirror unit 2000. The first layer micromirror unit 1000 can serve as a micromirror unit close to the light-emitting side D of the MEMS micromirror device, while the second layer micromirror unit 2000 can serve as a micromirror unit away from the light-emitting side D of the MEMS micromirror device. The first layer micromirror unit 1000 and the second layer micromirror unit 2000 can both include a first substrate 100 and a second substrate 200, with the second substrate 200 being located on one side of the first substrate 100. The first substrate 100 is formed with fixed comb teeth 101, wherein the fixed comb teeth on the first substrate in the first layer micromirror unit 1000 are first sub-fixed comb teeth 101-1, and the fixed comb teeth on the first substrate in the second layer micromirror unit 2000 are second sub-fixed comb teeth 101-2. The second substrate 200 is formed with a torsion beam 202 and a movable comb tooth 201. The teeth of the fixed comb tooth 101 are staggered with those of the movable comb tooth 201. The movable comb teeth on the second substrate in the first-layer micromirror unit 1000 are first sub-movable comb teeth 201-1, and the movable comb teeth on the second substrate in the second-layer micromirror unit 2000 are second sub-movable comb teeth 201-2. The torsion beam 202 on the second substrate in the first-layer micromirror unit 1000 and the torsion beam 202 on the second substrate in the second-layer micromirror unit 2000 have their orthographic projections on the first substrate overlapping. In the micromirror unit near the light-emitting side D of the MEMS micromirror device, a mirror structure 300 is provided on the side of the second substrate 200 near the first substrate 100. In the micromirror unit far from the light-emitting side D of the MEMS micromirror device, a mirror structure 300 is provided on the side of the second substrate 200 far from the first substrate 100. The light-emitting side D is the side from which the reflected light of the MEMS micromirror device emerges. The second substrate 200 is provided with an anchor point. One end of the torsion beam 202 is fixed to the second substrate 200 by anchoring, and the other end is connected to the mirror structure 300. The torsion beam 202 can be used to support the mirror structure 300, so that the mirror structure is suspended above the first substrate 100. The mirror structure 300 is connected to the movable comb teeth 201, which can drive the mirror structure to rotate along the axis of the torsion beam 202. By applying a voltage between the fixed comb teeth 101 and the movable comb teeth 201, an electric field is formed between the fixed comb teeth 101 and the movable comb teeth 201, generating an electrostatic force. The electrostatic force generated by the fixed comb teeth 101 and the movable comb teeth 201 can drive the movable comb teeth 201 to move toward the side of the fixed comb teeth 101. The displacement of the movable comb teeth 201 can drive the mirror structure 300 to rotate along the axial direction of the torsion beam 202, so that the light incident on the surface of the micromirror structure from the display side D direction is reflected on the micromirror surface and emitted to the display side at different emission angles, thereby realizing modulation of the light path.

[0055] Exemplary, reference Figure 1 The orthographic projections of the mirror structures 300 of the stacked micromirror units on the first substrate 100 overlap. The orthographic projections of the micromirror structures closer to the light-emitting side D on the first substrate 100 may completely overlap or partially overlap with the orthographic projections of the micromirror structures farther from the light-emitting side D on the first substrate 100. The two stacked layers of micromirror units are independently controlled. Voltages can be applied between the movable comb teeth and the fixed comb teeth on the same side of the mirror structure 300 within a single-layer micromirror unit to form independent electric fields within the two layers of micromirror units, thereby achieving independent driving of the two stacked layers of micromirror units. It is understandable that the two layers of micromirror units are independently controlled. A voltage can be applied between the movable comb teeth and the fixed comb teeth on the left side of the mirror structure 300 in one layer of micromirror units, and a voltage can be applied between the movable comb teeth and the fixed comb teeth on the right side of the mirror structure 300 in the other layer of micromirror units. A voltage can be applied between the movable comb teeth and the fixed comb teeth on the left side of the mirror structure 300 in one layer of micromirror units, and a voltage can be applied between the movable comb teeth and the fixed comb teeth on the left side of the mirror structure 300 in the other layer of micromirror units. Alternatively, a voltage can be applied between the movable comb teeth and the fixed comb teeth on the right side of the mirror structure 300 in one layer of micromirror units, and a voltage can be applied between the movable comb teeth and the fixed comb teeth on the right side of the mirror structure 300 in the other layer of micromirror units. The left side of the micromirror structure 300 is the side of the first fixed comb teeth 101 away from the torsion beam 202, and the right side of the micromirror structure 300 is the side of the second fixed comb teeth 201 away from the torsion beam 202. The mirror structures of the two layers of micromirror units can rotate at the same frequency and in the same direction, at the same frequency and in opposite directions, or at different frequencies and in different directions. Regardless of the rotation method, each layer of micromirror units is independently driven. "Same frequency" refers to the mirror structures vibrating or scanning at the same frequency; "same direction" refers to the mirror structures having the same phase, meaning the same displacement distance or rotation angle. By controlling the vibration frequency and phase of the micromirror units, light emitted by a light source is reflected at different angles from the mirror structure surface to the display side D when passing through the MEMS micromirror device, thereby achieving optical path modulation. A first hollow structure 301 is provided on the mirror structure of the micromirror unit near the light-emitting side D of the MEMS micromirror device. This allows light emitted from the light source to pass through the MEMS micromirror device. The light can either be reflected on the mirror structure 300 near the light-emitting side D of the MEMS micromirror device, or pass through the hollow structure and reflect on the surface of the mirror structure 300 away from the light-emitting side D of the MEMS micromirror device. The light can then be re-emitted to the display side D through the first hollow structure 301 on the mirror structure of the micromirror unit near the light-emitting side D. Since the two layers of micromirror units are independently controlled, if one layer of micromirror units fails, the other layer can continue to modulate the optical path.

[0056] It should be noted that when the mirror structures in the stacked micromirror device rotate at the same frequency and in the same direction, damage to one layer of micromirrors will not affect the function of the entire device. Based on the 95% yield of a conventional single-layer single micromirror, the probability of simultaneous damage to two layers of micromirror units will be reduced to 0.25%. Therefore, the yield of the double-layer micromirror is 99.75%, and the yield of the 30-micromirror array is calculated to be 0.9975 to the 30th power, or 92.8%. The yield of the MEMS micromirror device formed by the double-layer micromirror unit reaches 92.8%, which is far greater than 21.5%.

[0057] The MEMS micromirror device provided in an embodiment of the present application includes at least two stacked micromirror units, and the two layers of micromirror units are independently controlled. A voltage is applied between the fixed comb teeth and the movable comb teeth in the two stacked micromirror units, so that an electrostatic force is generated between the fixed comb teeth and the movable comb teeth to drive the movable comb teeth to move toward the fixed comb teeth. The displacement of the movable comb teeth can drive the mirror structure to rotate along the axial direction of the torsion beam, thereby achieving frequency and phase modulation of the two layers of micromirror units and optical path modulation. By overlapping the orthographic projections of the mirror structures 300 of the two stacked micromirror units on the first substrate 100 and providing a hollow in the micromirror structure near the light-emitting side, light can be reflected on the mirror structure near the light-emitting side of the MEMS micromirror device, or pass through the hollow to reach the surface of the mirror structure away from the light-emitting side of the MEMS micromirror device and be reflected, and then be emitted again to the display side through the hollow in the mirror structure of the micromirror unit near the light-emitting side D. By setting up at least two layers of micromirror units and controlling them independently, when a certain layer of micromirror units fails, the other layer of micromirror units can modulate the optical path to avoid damage to the entire micromirror array by a single layer of micromirrors, thereby avoiding affecting the entire MEMS micromirror device. Compared with a single-layer micromirror structure, the double-layer micromirror unit greatly reduces the failure probability of the entire MEMS micromirror device and improves the product yield.

[0058] Figure 2 A schematic cross-sectional view of a MEMS micromirror device along line AA′ provided in an embodiment of the present application. Figures 1 to 2 In the micromirror unit close to the light-emitting side D of the MEMS micromirror device, the first substrate 100 includes a first via hole 102, and the orthographic projection of the mirror structure 300 on the first substrate 100 falls within the orthographic projection of the first via hole 102 on the first substrate 100. The orthographic projection shape of the first via hole 102 on the first substrate 100 and the orthographic projection shape of the mirror structure 300 on the first substrate 100 may be the same as or different from each other.

[0059] Exemplarily, the orthographic projection shape of the first via hole 102 on the first substrate 100 is the same as the orthographic projection shape of the mirror structure on the first substrate 100, the orthographic projection shape of the first via hole 102 on the first substrate is circular, the orthographic projection shape of the outer contour of the mirror structure 300 on the first substrate 100 is circular, and the orthographic projection shape of the outer contour of the mirror structure 300 on the first substrate 100 is the same as the orthographic projection shape of the first via hole 102 on the first substrate 100. By setting the first via hole, a light path is provided for the mirror structure, avoiding the obstruction of the light input or output path of the mirror structure due to the setting of the fixed comb teeth above the micromirror structure.

[0060] For example, the orthographic projection shape of the first via hole 102 on the first substrate 100 is different from the orthographic projection shape of the mirror structure on the first substrate 100. The orthographic projection shape of the first via hole 102 on the first substrate is a trapezoid or a rectangle, and the orthographic projection shape of the outer contour of the mirror structure 300 on the first substrate 100 is a circle.

[0061] In the embodiment of the present application, the orthographic projection of the mirror structure on the first substrate is arranged to fall within the orthographic projection of the first via hole on the first substrate, thereby providing a light path for the mirror structure and avoiding obstruction of the light input or output path of the mirror structure due to the arrangement of the fixed comb teeth above.

[0062] Figure 3 This is a schematic structural diagram of another MEMS micromirror device provided in an embodiment of the present application. Figures 1 to 3The fixed comb teeth include a first fixed comb tooth 111 and a second fixed comb tooth 112. The first fixed comb tooth 111 and the second fixed comb tooth 112 are symmetrically arranged about the first via hole 102. The orthographic projection of the first fixed comb tooth 111 on the first substrate 100 and the orthographic projection of the second fixed comb tooth 112 on the first substrate 100 are symmetrical about the orthographic projection of the first via hole 102 on the first substrate 102. The first fixed comb tooth on the first substrate of the first layer of micromirror units 1000 is a first sub-fixed comb tooth 111-1, and the second fixed comb tooth on the first substrate of the first layer of micromirror units 1000 is a second sub-fixed comb tooth 112-1. The first fixed comb tooth on the first substrate of the second layer of micromirror units 2000 is a third sub-fixed comb tooth 111-2, and the second fixed comb tooth on the first substrate of the second layer of micromirror units 2000 is a fourth sub-fixed comb tooth 112-2. The movable comb teeth include a first movable comb tooth 211 and a second movable comb tooth 212, which are symmetrically arranged about the mirror structure 300. The first movable comb tooth on the second substrate in the first layer of micromirror units 1000 is a first sub-movable comb tooth 211-1, and the second movable comb tooth on the second substrate in the first layer of micromirror units 1000 is a second sub-movable comb tooth 212-1; the first movable comb tooth on the second substrate in the second layer of micromirror units 2000 is a third sub-movable comb tooth 211-2, and the second movable comb tooth on the second substrate in the second layer of micromirror units 2000 is a fourth sub-movable comb tooth 212-2. The teeth of the first movable comb teeth are staggered with the teeth of the first fixed comb teeth, and the teeth of the second movable comb teeth are staggered with the teeth of the second fixed comb teeth. The symmetrically arranged first and second fixed comb teeth 111, 112 can each be applied with a voltage. This means each fixed comb tooth 111 and each fixed comb tooth 112 are set to a specific potential, while the first and second movable comb teeth 211, 212 share a common potential. The symmetrical arrangement of the fixed comb teeth ensures a more uniform electric field distribution between the fixed and movable comb teeth, preventing uneven driving force caused by unilateral electric field distortion and reducing the risk of warping or fatigue on the mirror surface due to stress concentration.

[0063] Exemplary, reference Figure 4 The torsion beam 202 includes a first torsion beam 205 and a second torsion beam 206. The orthographic projections of the first torsion beam 205 and the second torsion beam 206 on the first substrate 100 are symmetrical with respect to the orthographic projection of the mirror structure 300 on the first substrate. The anchor points include a first anchor point and a second anchor point. The first torsion beam 205 is fixed to the second substrate 200 via the first anchor point, and the second torsion beam 206 is fixed to the second substrate 200 via the second anchor point. The orthographic projections of the first anchor point and the second anchor point on the first substrate 100 are symmetrical with respect to the orthographic projection of the mirror structure 300 on the first substrate 100. When the electrostatic / electromagnetic drive applies a torque, the symmetrically arranged first torsion beam 205 and second torsion beam 206 can ensure that the force on both sides of the mirror structure is uniform, thereby avoiding tilting or distortion caused by unilateral stress concentration.

[0064] Exemplary, reference Figure 1 , the driving power supplies connected to the first fixed comb teeth 111 and the second fixed comb teeth 112 are different, and voltages can be applied to the first fixed comb teeth 111 and the second fixed comb teeth 112 respectively. When voltage is applied to the first fixed comb teeth 111 and no voltage is applied to the second fixed comb teeth 112, the teeth 211 of the first movable comb teeth are attracted into the grooves 123 of the first fixed comb teeth, so that the mirror structure 300 rotates toward one side of the first fixed comb teeth 111. When voltage is applied to the second fixed comb teeth 112 and no voltage is applied to the first fixed comb teeth 111, the teeth 212 of the second movable comb teeth are attracted into the grooves 223 of the second fixed comb teeth, so that the mirror structure 300 rotates toward one side of the second fixed comb teeth 112. By setting the fixed tooth comb symmetry, the electric field distribution between the fixed comb teeth and the movable comb teeth can be made more uniform, avoiding uneven driving force caused by unilateral electric field distortion, and reducing the risk of warping or fatigue of the mirror due to stress concentration.

[0065] Exemplary, reference Figure 1 An isolation groove 103 is formed between the first fixed comb teeth 111 and the second fixed comb teeth 112. The length extension direction of the isolation groove 103 is the same as the length extension direction of the torsion beam 202. The orthographic projection of the torsion beam 202 on the first substrate 100 falls within the orthographic projection on the first substrate 100. The isolation groove 103 is used to provide rotation space for the torsion beam 202 to avoid collision between the torsion beam and adjacent structures, thereby improving the reliability of the MEMS device.

[0066] Figure 4 A schematic structural diagram of another MEMS micromirror device provided in an embodiment of the present application is shown in FIG. Figures 2 to 4 The mirror structure of the micromirror unit near the light-emitting side of the MEMS micromirror device is provided with a first hollow structure 301. That is, the first hollow structure 301 is provided on the mirror structure 300 of the first layer of micromirror units. The second substrate 200 is provided with a second hollow structure 203. The orthographic projection of the first hollow structure 301 on the first substrate 100 overlaps with the orthographic projection of the second hollow structure 203 on the first substrate 100. The orthographic projections of the first hollow structure 301 and the second hollow structure 203 on the first substrate 100 both fall within the orthographic projection of the first via 102 on the first substrate. The first hollow structure 301 is composed of a plurality of via holes 311 arranged in an array, and the second hollow structure is composed of a plurality of via holes 311 arranged in an array. The shapes of the via holes 311 on the first hollow structure 301 correspond one-to-one with the shapes of the via holes on the second hollow structure 203, and the orthographic projections of the via holes 311 on the first hollow structure 301 on the first substrate 100 coincide with the orthographic projections of the via holes on the second hollow structure 203 on the first substrate 100. The orthographic projections of the via holes 311 on the first substrate 100 may be polygonal and / or circular.

[0067] Exemplary, reference Figure 4 , the first hollow structure may include arrayed vias 311 whose orthographic projection on the first substrate 100 is circular, then the orthographic projection of the vias on the second hollow structure 203 on the first substrate 100 is also circular. The orthographic projection of the vias 311 on the first hollow structure 301 on the first substrate 100 is polygonal, then the orthographic projection of the vias on the second hollow structure 203 on the first substrate 100 is also polygonal, wherein the polygon may include a rectangle, a positive direction, a triangle, a trapezoid, etc. By providing arrayed vias on the second substrate and the mirror structure, light can be reflected on the upper micromirror surface, and can also pass through the holes, reach the lower micromirror surface and reflect, and then be emitted again from the upper micromirror holes, thereby improving the light extraction efficiency of the MEMS micromirror device.

[0068] In some embodiments, referring to 3, two stacked micromirror units include a first layer of micromirror units 1000 and a second layer of micromirror units 2000. The micromirror units closer to the light-exiting side are referred to as the first layer of micromirror units 1000, and the micromirror units farther from the light-exiting side D are referred to as the second layer of micromirror units 2000. Taking the application of voltage to a single side of the fixed comb teeth as an example, the voltage applied between the first sub-fixed comb tooth 111-1 and the first sub-movable comb tooth 211-1 and the voltage applied between the third sub-fixed comb tooth 111-2 and the third sub-movable comb tooth 211-2 can be the same or different.

[0069] It should be noted that the voltage applied between the second sub-fixed comb teeth 112-1 and the second sub-movable comb teeth 212-1 and the voltage applied between the fourth sub-fixed comb teeth 112-2 and the fourth sub-movable comb teeth 212-2 can be the same or different. The voltage applied between the first sub-fixed comb teeth 111-1 and the first sub-movable comb teeth 211-1 and the voltage applied between the second sub-fixed comb teeth 112-1 and the second sub-movable comb teeth 212-1 are applied separately, that is, the first sub-fixed comb teeth 111-1 and the second sub-fixed comb teeth 112-1 located on both sides of the isolation slot 103 have separate voltages applied, and the second sub-fixed comb teeth 112-1 and the second sub-movable comb teeth 212-1 each have a potential. The voltages applied on both sides can be the same or different, but the power-up method for the fixed comb teeth on both sides is the same: applying voltage to both the fixed comb teeth and the movable comb teeth causes the movable comb teeth to move toward the fixed comb teeth, thereby causing the fixed comb teeth to drive the mirror structure to rotate about the axial direction of the torsion beam. The voltages applied between the fixed comb teeth and the movable comb teeth on each layer of the double-layer micromirror unit can be the same or different.

[0070] Exemplarily, with reference to 3, a voltage is applied between the first sub-fixed comb tooth 111-1 and the first sub-movable comb tooth 211-1 in the first layer of micromirror unit 1000, and the first sub-movable comb tooth 211-1 in the first layer of micromirror unit 1000 drives the mirror structure 300 to rotate toward the side of the first sub-fixed comb tooth 111-1. At the same time, a voltage is applied between the fourth sub-fixed comb tooth 112-2 and the fourth sub-movable comb tooth 212-2 in the second layer of micromirror unit 2000, and the fourth sub-movable comb tooth 212-2 in the second layer of micromirror unit 2000 drives the mirror structure to rotate toward the side of the fourth sub-fixed comb tooth 112-2, wherein the voltage applied between the first sub-fixed comb tooth 111-1 and the first sub-movable comb tooth 211-1 is used as the third driving voltage, and the voltage applied to the fourth sub-fixed comb tooth 112-2 and the fourth sub-movable comb tooth 212-2 is used as the fourth driving voltage. At this time, if the third driving voltage is the same as the fourth driving voltage, the mirror structure 300 in the first-layer micromirror unit 1000 rotates at the same vibration frequency as the mirror structure 300 in the second-layer micromirror unit 2000, and the mirror structure 300 in the first-layer micromirror unit 1000 rotates in the same direction as the mirror structure 300 in the second-layer micromirror unit 2000. Light incident on the micromirror device via the display side D, after passing through the first-layer micromirror unit 1000 and the second-layer micromirror unit 2000, reflects in the same direction. The micromirror structures in the two stacked micromirror units rotate at the same frequency and in the same direction, and light reflected by the double-layer mirror structure has the same direction of reflection. The reflected light from the double-layer mirror structure is superimposed and emitted to the light-emitting side. Because the double-layer mirror structures rotate in the same direction and the mirror surfaces rotate independently, a failure in one mirror structure will not affect the reflection of the other, thereby increasing the service life of the MEMS micromirror device.

[0071] Exemplarily, a voltage is applied between the first fixed comb tooth 111-1 and the first movable comb tooth 211-1 in the first layer of micromirror units 1000, causing the first movable comb tooth 211-1 to drive the mirror structure 300 to rotate toward the first fixed comb tooth 111-1. Simultaneously, a voltage is applied between the third fixed comb tooth 111-2 and the third movable comb tooth 211-2 in the second layer of micromirror units 2000, causing the third movable comb tooth 211-2 to drive the mirror structure 300 to rotate toward the third fixed comb tooth 111-2. The voltage applied between the first fixed comb tooth 111-1 and the first movable comb tooth 211-1 is used as the third driving voltage, and the voltage applied between the third fixed comb tooth 111-2 and the third movable comb tooth 211-2 is used as the fifth driving voltage. At this time, if the third driving voltage is the same as the fifth driving voltage, the rotation of the mirror structure 300 in the first layer of micromirror units 1000 and the vibration frequency of the mirror structure 300 in the second layer of micromirror units 2000 are the same, and the rotation direction of the mirror structure 300 in the first layer of micromirror units 1000 is opposite to that of the mirror structure 300 in the second layer of micromirror units 2000. As a result, incident light entering the micromirror device via the display side D, after passing through the first layer of micromirror units 1000 and the second layer of micromirror units 2000, has different emission directions. The micromirror structures in the two stacked micromirror units rotate at the same frequency and in opposite directions, and the light reflected by the double-layer mirror structure has different reflection directions. By adjusting the voltage value applied to the first fixed comb teeth 111 in the first layer of micromirror units 1000 and the voltage value applied to the first fixed comb teeth 111 in the second layer of micromirror units 2000, light can be emitted to the display side at a variety of different angles, achieving two scans within a cycle time, thereby improving scanning efficiency.

[0072] For example, when a double-layer micromirror MEMS device is used as a spectroscopic device, the light output angle can be precisely controlled by setting the micromirror structures in the two stacked micromirror units at the same frequency and in opposite directions to quickly achieve spectroscopic coupling.

[0073] Exemplarily, when a voltage is applied between the first fixed sub-comb tooth 111-1 and the first movable sub-comb tooth 211-1 in the first layer of micromirror unit 1000, the plane of the displaced mirror structure forms a first angle with the plane of the second substrate. The first angle ranges from 0° to 20°, and the third driving voltage ranges from 36V to 60V. The third driving voltage is 36V, and the first angle is 5°. The third driving voltage is 45V, and the first angle is 10°. The third driving voltage is 55V, and the first angle is 15°.

[0074] Exemplarily, when a voltage is applied between the fourth fixed sub-comb tooth 112-2 and the fourth movable sub-comb tooth 212-2 in the second-layer micromirror unit 1000, the plane of the displaced mirror structure forms a second angle with the plane of the second substrate, wherein the second angle ranges from 0° to 20°, and the fourth driving voltage ranges from 36V to 60V. The fourth driving voltage is 36V, the second angle is 5°, the fourth driving voltage is 45V, the second angle is 10°, and the fourth driving voltage is 55V, the second angle is 15°.

[0075] Exemplarily, when a voltage is applied between the third fixed sub-comb teeth 111-2 and the third movable sub-comb teeth 211-2 in the second layer of micromirror unit 2000, the plane of the displaced mirror structure forms a third angle with the plane of the second substrate, the third angle ranges from 0° to 20°, and the fifth driving voltage ranges from 36V to 60V. The fifth driving voltage is 36V, the third angle is 5°, the fourth driving voltage is 45V, the third angle is 10°, and the fourth driving voltage is 55V, the third angle is 15°.

[0076] Exemplary, reference Figures 1 to 4 A voltage is applied between the first sub-fixed comb tooth 111-1 and the first sub-movable comb tooth 211-1 in the first layer of micromirror units 1000. Simultaneously, a voltage is applied between the third sub-fixed comb tooth 111-2 and the third sub-movable comb tooth 211-2 in the second layer of micromirror units 2000. The third driving voltage is greater than the fourth driving voltage. At this time, the rotation frequency of the mirror structure 300 in the first layer of micromirror units 1000 is different from that of the mirror structure 300 in the second layer of micromirror units 2000. The rotation direction of the mirror structure 300 in the first layer of micromirror units 1000 is also different from that of the mirror structure 300 in the second layer of micromirror units 2000. The reflected light from the first layer of micromirror units 1000 and the second layer of micromirror units 2000 has different emission directions. The micromirror structures in the two stacked micromirror units rotate at different frequencies and in different directions. As a result, the light reflected from the double-layer mirror structure has different reflection directions and emission frequencies. In the application of laser radar, by applying a large voltage to the first fixed comb teeth 111 in the first layer of micromirror units 1000 and applying a small voltage to the first fixed comb teeth 111 in the second layer of micromirror units 2000, the first layer of micromirror units 1000 can perform low-frequency and large-angle scanning to achieve wide-area detection of the laser radar, and the second layer of micromirror units 2000 can perform high-frequency and small-angle scanning to achieve high-precision tracking of the laser radar.

[0077] In some embodiments, two stacked micromirror units include a first layer of micromirror units 1000 and a second layer of micromirror units 2000. The orthographic projection of the fixed comb teeth in the first layer of micromirror units on the first substrate is a first projection. The orthographic projection of the fixed comb teeth in the second layer of micromirror units on the first substrate is a second projection, and the first projection and the second projection coincide with each other.

[0078] Illustratively, the orthographic projection of the first sub-fixed comb tooth 111 - 1 on the first substrate is the first projection, the orthographic projection of the third sub-fixed comb tooth 111 - 2 on the first substrate is the second projection, and the first projection coincides with the second projection.

[0079] Illustratively, the orthographic projection of the second sub-fixed comb tooth 112 - 1 on the first substrate is the first projection, the orthographic projection of the fourth sub-fixed comb tooth 112 - 2 on the first substrate is the second projection, and the first projection coincides with the second projection.

[0080] In some embodiments, the orthographic projection of the movable comb teeth in the first layer of micromirror units on the first substrate is the third projection, and the orthographic projection of the movable comb teeth in the second layer of micromirror units on the first substrate is the fourth projection, and the third projection coincides with the fourth projection.

[0081] Exemplarily, the orthographic projection of the first movable sub-comb tooth 211 - 1 on the first substrate is the third projection, the orthographic projection of the third movable sub-comb tooth 211 - 2 on the first substrate is the fourth projection, and the third projection coincides with the fourth projection.

[0082] Illustratively, the orthographic projection of the second movable sub-comb tooth 212 - 1 on the first substrate is the third projection, the orthographic projection of the fourth movable sub-comb tooth 212 - 2 on the first substrate is the fourth projection, and the third projection coincides with the fourth projection.

[0083] By overlapping the projections of the fixed comb teeth and the projections of the movable comb teeth in the stacked first-layer micromirror units 1000 and the second-layer micromirror units 2000, the electric field distribution between the fixed comb teeth and the movable comb teeth is made more uniform, avoiding uneven driving force caused by unilateral electric field distortion and reducing the risk of warping or fatigue of the mirror due to stress concentration.

[0084] Exemplary, reference Figure 3, the orthographic projection shape of the first sub-fixed comb tooth 111-1 on the first substrate 100 is the same as the orthographic projection shape of the third sub-fixed comb tooth 111-2 on the first substrate 100, and both can be rectangles, squares or trapezoids. The orthographic projection shape of the first sub-movable comb tooth 211-1 on the first substrate 100 is the same as the orthographic projection shape of the third sub-movable comb tooth 211-2 on the first substrate 100, and both can be rectangles, squares or trapezoids. The spacing between the first sub-fixed comb tooth 111-1 and the first sub-movable comb tooth 211-1 is 3μm to 5μm. Schematically, it can be 3.5μm, 3.8μm, 4μm, 4.5μm or 4.8μm. The spacing between two adjacent first sub-fixed comb teeth 111-1 is 10 to 15μm. Schematically, it can be 11μm, 12μm, 13μm or 14μm.

[0085] In some embodiments, reference Figure 2 The MEMS micromirror device further includes a bonding layer 400, which is disposed between the first-layer micromirror units 1000 and the second-layer micromirror units 2000. The bonding layer 400 can be used to bond the first-layer micromirror units 1000 and the second-layer micromirror units 2000. The bonding layer 400 can also serve as an insulating layer to insulate the first-layer micromirror units 1000 from the second-layer micromirror units 2000, thereby preventing short circuits between the movable comb teeth within the first-layer micromirror units 1000 and the second-layer micromirror units 2000. The bonding layer 400 includes a third hollow structure 405. The orthographic projections of the mirror structure 300 near the light-emitting side and the mirror structure 300 far from the light-emitting side on the first substrate 100 both fall within the orthographic projection of the third hollow structure 405 on the first substrate 100. The bonding layer 400, the second substrate 200 of the first layer of micromirror units, and the second substrate 200 of the second layer of micromirror units are surrounded to form a cavity structure 204. The cavity structure 204 provides sufficient rotation space for the double-layer mirror structure to avoid collision of the mirror structure during rotation, thereby improving the stability of the product.

[0086] Exemplarily, the thickness of the bonding layer 400 ranges from 100 μm to 200 μm, and schematically, may be 110 μm, 130 μm, 150 μm, 170 μm, or 190 μm.

[0087] In some embodiments, a first insulating layer is disposed between the first substrate 100 and the second substrate 200. The first insulating layer includes a fourth hollow structure 161, which is used to provide sufficient rotational space for the mirror structure to prevent collisions during rotation. The orthographic projection of the fourth hollow structure 161 on the first substrate 100 coincides with the orthographic projection of the third hollow structure 405 on the first substrate 100. The third hollow structure 405 and the fourth hollow structure 161 can use the same mask, reducing the processing difficulty and improving the structural consistency of the device.

[0088] A second aspect of the embodiment provides a MEMS micromirror matrix. Figure 5 A schematic partial structural diagram of a MEMS micromirror matrix provided in an embodiment of the present application. For example, refer to Figure 5 The MEMS micromirror matrix 3000 includes a plurality of MEMS micromirror devices 3001 arranged in an array.

[0089] The MEMS micromirror matrix provided in an embodiment of the present application includes at least two stacked micromirror units, and the two layers of micromirror units are independently controlled. A voltage is applied between the fixed comb teeth and the movable comb teeth in the two stacked micromirror units, so that an electrostatic force is generated between the fixed comb teeth and the movable comb teeth to drive the movable comb teeth to move toward the fixed comb teeth. The displacement of the movable comb teeth can drive the mirror structure to rotate along the axial direction of the torsion beam, thereby achieving frequency and phase modulation of the two layers of micromirror units and optical path modulation. By providing a hollow on the micromirror structure near the light-emitting side, light can be reflected on the mirror structure near the light-emitting side of the MEMS micromirror device, or pass through the hollow to reach the surface of the mirror structure away from the light-emitting side of the MEMS micromirror device and be reflected, and then be emitted again to the display side through the hollow on the mirror structure of the micromirror unit near the light-emitting side D. By setting up at least two layers of micromirror units and controlling them independently, when a certain layer of micromirror units fails, the other layer of micromirror units can modulate the optical path, thereby preventing damage to a single layer of micromirrors from affecting the entire MEMS micromirror device. Compared with a single-layer micromirror structure, a double-layer micromirror unit greatly reduces the failure probability of the entire MEMS micromirror device and improves the product yield.

[0090] According to a third aspect of the embodiments of the present application, a method for preparing a MEMS micromirror device is provided. Figure 6 A schematic flow chart of a method for preparing a MEMS micromirror device provided in an embodiment of the present application, Figure 7 A process flow chart of a MEMS micromirror device provided in an embodiment of the present application. For example, refer to Figure 6 and Figure 7 , the preparation method of the MEMS micromirror device includes:

[0091] S101: preparing a first substrate.

[0092] Exemplary, reference Figure 6 and Figure 7 , prepare a first substrate 100, the first substrate includes a first silicon layer 191, a third silicon layer 193 and a second silicon layer 192 arranged between the first silicon layer 191 and the third silicon layer 193, wherein the first silicon layer 191 and the third silicon layer 193 may include silicon, and the second silicon layer 192 may include silicon oxide.

[0093] S102: etching one side surface of the first substrate to form fixed comb teeth and isolation grooves.

[0094] Illustratively, the third silicon layer 193 of the first substrate 100 is dry-etched to form the fixed comb teeth 101 and the isolation grooves 103 . The fixed comb teeth 101 and the isolation grooves 103 are prepared using two masks.

[0095] S103: preparing a second substrate and bonding the first substrate to the second substrate.

[0096] Exemplary, reference Figure 6 and Figure 7 Step S103 includes step S112 and step S113. Step S112: preparing a second substrate 200, the second substrate including a fourth silicon layer 291, a fifth silicon layer 292, a sixth silicon layer 293, and a seventh silicon layer 294, wherein the fourth silicon layer 291 and the sixth silicon layer 293 may both include silicon, and the fifth silicon layer 292 and the seventh silicon layer 294 may both include silicon oxide.

[0097] It should be noted that the first substrate and the second substrate can be prepared separately, and then the two are bonded.

[0098] Step S113 : bonding the seventh silicon layer 294 and the fourth SiO 2 layer 294 of the second substrate toward the third silicon layer 193 and the second SiO layer 193 of the first substrate.

[0099] S104: Disposing a mirror structure, a torsion beam, and movable comb teeth on one side of the second substrate;

[0100] In the micromirror unit close to the light-emitting side of the MEMS micromirror device, a mirror structure is provided on a side of the second substrate close to the first substrate;

[0101] In the micromirror unit away from the light-emitting side of the MEMS micromirror device, a mirror structure is provided on a side of the second substrate away from the first substrate;

[0102] The teeth of the fixed comb teeth and the teeth of the movable comb teeth are staggered, the mirror structure is connected to the torsion beam, and the mirror structure is connected to the movable comb teeth. The displacement of the movable comb teeth is used to drive the mirror structure to rotate along the axial direction of the torsion beam.

[0103] At least two micromirror units are stacked, wherein the orthographic projections of the two mirror structures of the stacked micromirror units on the first substrate overlap, and the mirror structure of the micromirror unit close to the light-emitting side of the MEMS micromirror device is provided with a first hollow structure.

[0104] Exemplary, reference Figure 6 and Figure 7Step S104 includes step S114 and step S115. Step S114: The fourth silicon layer 291 and the second SiO layer 291 are etched away, and via holes are etched in the second SiO layer 292 and the fifth silicon layer 292 of the second substrate, and a metal reflective material is deposited in the via holes to form a mirror structure 300 away from the light-emitting side; then, the second SiO2 layer 292 and the third SiO layer 293 and the sixth silicon layer 293 on the fifth silicon layer 292 are etched to form the movable comb teeth 201 and the torsion beam.

[0105] Step S115 : etching and removing the second SiO layer 292 and the fifth silicon layer 292 to obtain the micromirror unit 600 away from the light-emitting side.

[0106] Figure 8 Another process flow chart of a MEMS micromirror device provided in an embodiment of the present application. For example, refer to Figure 8 The preparation method of the micromirror unit close to the light-emitting side includes: repeating Figure 7 In steps S101, S102, S103 and S113, step S116 is performed after step S113: the fourth silicon layer 291 is removed by etching, and the isolation groove 103 is etched in the fifth silicon layer 292 of the second substrate; after step S116, step S117 is performed: the fifth silicon layer 292 is etched away to obtain the first transition substrate 700.

[0107] Figure 9 A process flow chart of another MEMS micromirror device provided in an embodiment of the present application. For example, refer to Figure 9 The preparation process of the bonding layer 400 and the bonding of the bonding layer to the micromirror unit 600 away from the light-emitting side includes S118 to S120.

[0108] Exemplarily, S118: preparing a bonding layer 400, the bonding layer 400 including an eighth silicon layer 401, a ninth silicon layer 402, a tenth silicon layer 403, and an eleventh silicon layer 404, wherein the eighth silicon layer 401 and the tenth silicon layer 403 may both include silicon, and the ninth silicon layer 402 and the eleventh silicon layer 404 may both include silicon oxide. The bonding layer also includes a third hollow structure 405, which is obtained by etching the eleventh silicon layer 404 and the tenth silicon layer 403.

[0109] Step S119 : bonding the eleventh silicon layer 404 in the bonding layer 400 toward the sixth silicon layer 293 of the micromirror unit 600 away from the light-emitting side.

[0110] Step S120 : etching and removing the eighth silicon layer 401 , and etching and removing the redundant ninth silicon layer 402 , tenth silicon layer 403 and seventh silicon layer 294 to obtain a second transition substrate 800 .

[0111] Figure 10A process flow chart of another MEMS micromirror device provided in an embodiment of the present application. For example, refer to Figure 10 The process of bonding the first transition substrate 700 and the second transition substrate 800 includes: S121 to S123

[0112] Step S121: bonding the sixth silicon layer 293 in the first transition substrate 700 to the ninth silicon layer 402 in the second transition substrate 800;

[0113] Step S122 : etching to remove the first silicon layer 191 and excess second silicon layer 192 in the etched area.

[0114] Step S123: Etching away the excess seventh silicon layer 294, depositing a metal reflective material on the surface of the sixth silicon layer 293, and etching to form a mirror structure 300 near the light-emitting side. Etching a first hollow structure 301 and a second hollow structure 203 on the mirror structure 300 to obtain a stacked micromirror unit. The stacked micromirror structure includes a first layer of micromirror units 1000 and a second layer of micromirror units 2000. The bonding layer 400, the second substrate 200 of the first layer of micromirror units, and the second substrate 200 of the second layer of micromirror units surround a cavity structure 204. A first insulating layer is disposed between the first substrate 100 and the second substrate 200. The first insulating layer includes a fourth hollow structure 161. Both the fourth hollow structure 161 and the cavity structure 204 can be used to provide sufficient rotational space for the mirror structure to prevent collision during rotation. The orthographic projection of the fourth hollow structure 161 on the first substrate 100 coincides with the orthographic projection of the third hollow structure 405 on the first substrate 100 .

[0115] The preparation method of the MEMS micromirror device provided in the embodiment of the present application includes at least two stacked micromirror units, and the two layers of micromirror units are independently controlled. A voltage is applied between the fixed comb teeth and the movable comb teeth in the two stacked micromirror units, so that an electrostatic force is generated between the fixed comb teeth and the movable comb teeth to drive the movable comb teeth to move toward the fixed comb teeth. The displacement of the movable comb teeth can drive the mirror structure to rotate along the axial direction of the torsion beam, thereby achieving frequency and phase modulation of the two layers of micromirror units, and achieving optical path modulation so that the two layers of micromirror units are aligned. By providing a hollow on the micromirror structure near the light-emitting side, light can be reflected on the mirror structure near the light-emitting side of the MEMS micromirror device, or pass through the hollow to reach the surface of the mirror structure away from the light-emitting side of the MEMS micromirror device and be reflected, and then be emitted again to the display side through the hollow on the mirror structure of the micromirror unit near the light-emitting side D. By setting up at least two layers of micromirror units and controlling them independently, when a certain layer of micromirror units fails, the other layer of micromirror units can modulate the optical path, thereby preventing damage to a single layer of micromirrors from affecting the entire MEMS micromirror device. Compared with a single-layer micromirror structure, a double-layer micromirror unit greatly reduces the failure probability of the entire MEMS micromirror device and improves the product yield.

[0116] It should be noted that, in the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0117] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

[0118] Although the preferred embodiments of this specification have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of this specification.

[0119] Obviously, those skilled in the art may make various changes and modifications to this specification without departing from the spirit and scope of this specification. Thus, if such changes and modifications fall within the scope of the claims of this specification and their equivalents, this specification is intended to include such changes and modifications.

Claims

1. A MEMS micromirror device, characterized in that: include: At least two stacked micromirror units, each micromirror unit comprising: a first substrate, wherein the first substrate is formed with fixed comb teeth; a second substrate, disposed on one side of the first substrate; In the micromirror unit close to the light-emitting side of the MEMS micromirror device, a mirror structure is provided on a side of the second substrate close to the first substrate; In the micromirror unit away from the light-emitting side of the MEMS micromirror device, a mirror structure is provided on a side of the second substrate away from the first substrate; The second substrate is formed with a torsion beam and movable comb teeth, the teeth of the fixed comb teeth are staggered with the teeth of the movable comb teeth, the mirror structure is connected to the torsion beam, and the mirror structure is connected to the movable comb teeth, and the displacement of the movable comb teeth is used to drive the mirror structure to rotate along the axial direction of the torsion beam; The orthographic projections of the mirror structures of the stacked micromirror units on the first substrate overlap, and the mirror structure of the micromirror unit close to the light-emitting side of the MEMS micromirror device is provided with a first hollow structure.

2. The MEMS micromirror device according to claim 1, wherein: In the micromirror unit close to the light-emitting side of the MEMS micromirror device, the first substrate includes a first via hole, and the orthographic projection of the mirror structure on the first substrate falls within the orthographic projection of the first via hole on the first substrate.

3. The MEMS micromirror device according to claim 2, wherein: The fixed comb teeth include first fixed comb teeth and second fixed comb teeth, and an orthographic projection of the first fixed comb teeth on the first substrate and an orthographic projection of the second fixed comb teeth on the first substrate are symmetrical with respect to an orthographic projection of the first via hole on the first substrate; An isolation groove is formed between the first fixed comb teeth and the second fixed comb teeth, and a length extension direction of the isolation groove is the same as a length extension direction of the torsion beam.

4. The MEMS micromirror device according to claim 2, wherein: The movable comb teeth include first movable comb teeth and second movable comb teeth, and the first movable comb teeth and the second movable comb teeth are symmetrically arranged with respect to the mirror structure; The teeth of the first movable comb teeth are staggered with the teeth of the first fixed comb teeth, and the teeth of the second movable comb teeth are staggered with the teeth of the second fixed comb teeth; The torsion beam includes a first torsion beam and a second torsion beam, and the first torsion beam and the second torsion beam are symmetrically arranged with respect to the mirror structure.

5. The MEMS micromirror device according to claim 1, wherein: The second substrate is provided with a second hollow structure; The orthographic projection of the first hollow structure on the first substrate overlaps with the orthographic projection of the second hollow structure on the first substrate; Wherein, both the first hollow structure and the second hollow structure include a plurality of via holes arranged in an array, and the orthographic projection shape of the via holes on the first substrate includes a polygon and / or a circle.

6. The MEMS micromirror device according to claim 1, wherein: The at least two stacked micromirror units include a first layer of micromirror units and a second layer of micromirror units, wherein the orthographic projection of the fixed comb teeth in the first layer of micromirror units on the first substrate is a first projection; The orthographic projection of the fixed comb teeth in the second layer of micromirror units on the first substrate is a second projection, and the first projection and the second projection coincide with each other; and / or, The orthographic projection of the movable comb teeth in the first layer of micromirror units on the first substrate is the third projection; The orthographic projection of the movable comb teeth in the second layer of micromirror units on the first substrate is the fourth projection, and the third projection coincides with the fourth projection.

7. The MEMS micromirror device according to claim 6, wherein: Also includes: a bonding layer, disposed between the first layer of micromirror units and the second layer of micromirror units; The bonding layer includes a third hollow structure, and the orthographic projections of the mirror structure close to the light-emitting side and the mirror structure far from the light-emitting side on the first substrate both fall within the orthographic projection of the third hollow structure on the first substrate.

8. The MEMS micromirror unit according to claim 7, characterized in that: A first insulating layer is provided between the first substrate and the second substrate; The first insulating layer includes a fourth hollow structure, and an orthographic projection of the fourth hollow structure on the first substrate coincides with an orthographic projection of the third hollow structure on the first substrate.

9. A MEMS micromirror matrix, characterized in that: include: A plurality of MEMS micromirror devices according to any one of claims 1 to 8.

10. A method for preparing a MEMS micromirror device, for preparing the MEMS micromirror device according to any one of claims 1 to 8, the method comprising: preparing a first substrate; Etching one side surface of the first substrate to form fixed comb teeth and isolation grooves; preparing a second substrate, and bonding the first substrate to the second substrate; A mirror structure, a torsion beam, and movable comb teeth are provided on one side of the second substrate. In the micromirror unit close to the light-emitting side of the MEMS micromirror device, a mirror structure is provided on the side of the second substrate close to the first substrate. In the micromirror unit away from the light-emitting side of the MEMS micromirror device, a mirror structure is provided on a side of the second substrate away from the first substrate; The teeth of the fixed comb teeth are staggered with the teeth of the movable comb teeth, the mirror structure is connected to the torsion beam, and the mirror structure is connected to the movable comb teeth, and the displacement of the movable comb teeth is used to drive the mirror structure to rotate along the axial direction of the torsion beam; At least two micromirror units are stacked, wherein the orthographic projections of the two mirror structures of the stacked micromirror units on the first substrate overlap, and the mirror structure of the micromirror unit close to the light-emitting side of the MEMS micromirror device is provided with a first hollow structure.

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