Reverse angle vertical comb-micro mirror driving structure, driving micro mirror and preparation method thereof

Abstract

This invention discloses a reverse-angle vertical comb-tooth micromirror driving structure, a driving micromirror, and its fabrication method. The reverse-angle vertical comb-tooth micromirror driving structure includes a main body and a cover plate fitted onto the main body. The cover plate includes a cover plate base, and a misalignment activation boss and an angle activation boss are fixed on the lower surface of the cover plate base. The main body includes a stator anchor, fixed comb teeth, moving comb teeth, and a main body base. The fixed comb teeth extend from the stator anchor, and the stator anchor is connected to the main body base through a serpentine beam. The moving comb teeth and the fixed comb teeth are interleaved, forming a reverse-angle vertical comb-tooth micromirror driving structure together. When the cover plate and the main body are assembled, the misalignment activation boss presses down on the component connected to the fixed comb teeth, creating a vertical height difference between the fixed comb teeth and the moving comb teeth. The stator anchor is pressed down by the angle activation boss, causing the fixed comb teeth to tilt. Compared with the AVC structure, its fixed comb teeth and moving comb teeth have a larger overlap area, providing a greater attraction force, and the advantages become more obvious as the micromirror rotation angle increases.

Description

Technical Field

[0001] This invention belongs to the field of microelectromechanical systems (MEMS) technology, specifically relating to a reverse-angle vertical comb-tooth micromirror driving structure, the driving micromirror, and its fabrication method. Background Technology

[0002] Microelectromechanical systems (MEMS) technology is a technology that integrates electronic, mechanical, and optical functional modules into a micrometer-scale system based on microelectronics. MEMS technology integrates mechanical components, optical systems, drive components, and electronic control systems into a single unit, enabling not only the acquisition, processing, and transmission of information or commands, but also the execution of actions based on that information. Compared to traditional mechanical systems, systems employing MEMS technology offer advantages such as miniaturization, integration, low power consumption, low cost, high precision, long lifespan, and good dynamic performance.

[0003] MEMS micromirrors are important optical devices in microelectromechanical systems (MEMS) and have been widely used in optical switches, projection displays, and fiber optic sensing systems. Furthermore, with the further improvement of MEMS fabrication technology, MEMS micromirrors are increasingly being adopted as core scanning devices in emerging application areas such as lidar systems, novel laser confocal microscopy systems, and high-performance optical communication systems.

[0004] Based on different driving methods, MEMS micromirrors can be divided into four categories: electrostatic driving, electromagnetic driving, piezoelectric driving, and electrothermal driving. Compared with the other three driving types, electrostatic driving has advantages such as simple structure, low power consumption, high resonant frequency, and complete compatibility of fabrication technology with integrated circuit processes, making it a research hotspot for many research institutions both domestically and internationally. Currently, electrostatic driving methods include three structures: parallel plate driving, transverse comb driving, and vertical comb driving, each with its own advantages and disadvantages. The parallel plate structure is the earliest and simplest driving method, but the nonlinear driving force and pull-down phenomenon severely limit the working range and application scenarios of the micromirror. The transverse comb structure has the characteristic of generating linear displacement in the plane that is proportional to the driving voltage, making it suitable for generating in-plane translation or rotation; although this structure can also be used to achieve torsion of the micromirror, the actuator structure is relatively complex, and its resonant frequency is not high. Vertical comb drives consist of one or more pairs of moving and stationary combs with a height difference in the vertical direction. They are well-suited for generating torsional plasma surface motion. Although the height difference between the moving and stationary combs increases the manufacturing process of the driver to some extent, its excellent motion characteristics still make it the choice for most electrostatic driven micro-scanning mirror drive structures.

[0005] There are two main structures for vertical comb drives: one is the staggered vertical comb-drive actuator (SVC), and the other is the angular vertical comb-drive actuator (AVC).

[0006] Because the larger the overlap area between the stationary and moving comb teeth in an electrostatic comb actuator, the stronger the electrostatic attraction, AVC (Automatic Valve Cylinder) exhibits better performance than SVC (Solid Valve Cylinder). However, current common AVC fabrication methods generally utilize polymer tension. First, planar comb teeth are fabricated on an SOI wafer using a deep etching process, with the moving comb teeth having a hinge structure. Then, a polymer, such as benzocyclobutene (BCB) or a negative adhesive, is processed onto the hinge structure. Heating causes the polymer to reflow, and after cooling, the polymer tension is used to tilt the moving comb teeth, thus achieving a tilted vertical comb tooth drive. However, this method is not suitable for mass production and has poor reliability.

[0007] Therefore, how to improve the performance of the vertical comb structure while maximizing process stability, thereby enhancing the performance of electrostatic MEMS micromirrors, is a pressing technical problem that needs to be solved. Summary of the Invention

[0008] In order to improve the performance of the vertical comb tooth structure while maximizing the stability of the process, this application proposes a reverse angle vertical comb tooth micromirror driving structure, a driving micromirror and its preparation method, which are manufactured using a boss activation structure.

[0009] To achieve the above objectives, the present invention provides a reverse-angle vertical comb micromirror driving structure, comprising a main body and a cover plate fitted onto the main body; the cover plate includes a cover plate base, and a misalignment activation boss and an angle activation boss are fixed on the lower surface of the cover plate base; the height of the angle activation boss is greater than the height of the misalignment activation boss; the main body includes a stator anchor, fixed comb teeth, movable comb teeth, and a main body base, the fixed comb teeth extending from the stator anchor, and the stator anchor being connected to the main body base via a serpentine beam; the movable comb teeth and the fixed comb teeth are interleaved; when the cover plate and the main body are assembled, the misalignment activation boss presses down on the component connected to the fixed comb teeth, causing a vertical height difference between the fixed comb teeth and the movable comb teeth; the stator anchor is pressed down by the angle activation boss, causing the fixed comb teeth to tilt upwards.

[0010] Furthermore, a misaligned platform is connected between the serpentine beam and the stator anchor, and the stator anchor is connected to the misaligned platform through a fulcrum beam; when the cover plate and the main body are assembled, the misaligned platform is pressed down by the misaligned activation boss, so that there is a vertical height difference between the fixed comb teeth and the moving comb teeth.

[0011] Furthermore, three misaligned activation protrusions are fixed on the lower surface of the cover plate base; the three misaligned activation protrusions are located above the misaligned platform, with two of them located above the two ends of the misaligned platform and the other misaligned activation platform located at the bottom end of the misaligned platform.

[0012] Furthermore, the cover plate and the main body are bonded together.

[0013] A driving micromirror includes a mirror platform, electrodes, and two opposing reverse-angle vertical comb-tooth micromirror driving structures as described in claim 1; the two sides of the mirror platform are respectively connected to a main body substrate via two torsion beams; each end of the mirror platform is connected to a reverse-angle vertical comb-tooth micromirror driving structure, the torsion beams are separated from the main body substrate by an isolation channel, and the electrodes are fixed above the main body substrate enclosed by the isolation channel.

[0014] Furthermore, a positioning boss is fixed on the lower surface of the cover plate base, and a positioning groove is provided on the main body base, into which the positioning boss is inserted.

[0015] Furthermore, an optical reflective film layer may be provided on the mirror platform.

[0016] The above-mentioned method for preparing a driven micromirror includes the following steps:

[0017] S1. Prepare the micromirror body and the micromirror cover plate;

[0018] The preparation of the micromirror body includes the following steps:

[0019] SA1, Remove the oxide layer on the surface of the SOI wafer;

[0020] SA2. An insulating trench is etched on the front side of the SOI wafer.

[0021] SA3. Deposit oxide layers on both sides of the insulating channel groove, and fill the insulating channel groove with polycrystalline silicon to obtain the insulating channel.

[0022] SA4. Remove excess material from the surface of the structure obtained in step SA3;

[0023] SA5. A silicon dioxide insulating layer is deposited on the front side of the structure obtained in step SA4, and the electrode area is etched out.

[0024] SA6. A metal layer is deposited on the front side of the structure obtained in step SA5, and the metal layer is etched to obtain the electrode.

[0025] SA7. The structure obtained in step SA6 is etched with various components such as serpentine beam, misaligned platform, fulcrum beam, stator anchor, fixed comb tooth, moving comb tooth, torsion beam, mirror platform and positioning groove on the front side.

[0026] SA8. The back space etching window of the structure obtained in step G is etched, and the etching is carried out from the back space etching window to the buried oxide layer. Then the buried oxide layer is etched to release the serpentine beam, the misaligned platform, the fulcrum beam, the stator anchor, the fixed comb tooth, the moving comb tooth, the torsion beam and the mirror platform.

[0027] The preparation of the micromirror cover plate includes the following steps:

[0028] SB1. Remove the oxide layer from the silicon wafer surface to obtain the cover plate substrate;

[0029] SB2. A boss structure is manufactured on the cover plate substrate, the boss structure including a positioning boss, a misalignment activation boss and an angle activation boss;

[0030] SB3. Machine through holes in the cover plate base;

[0031] S2. Assemble the micromirror body and the micromirror cover plate together. Press down the stator anchor by activating the tilting boss. Use the fulcrum beam as the pivot to make the fixed comb teeth lift up. At the same time, press down the misalignment platform by activating the misalignment boss. The stator anchor will generate a vertical displacement, which will further generate a vertical height difference between the fixed comb teeth and the moving comb teeth, thus creating a MEMS micromirror with a reverse angle vertical comb tooth micromirror driving structure.

[0032] Furthermore, step SB2 includes the following steps:

[0033] SB2.1 Spin-coat a layer of photoresist on the front side of the silicon wafer;

[0034] SB2.2. Perform grayscale photolithography on the photoresist to create a boss structure.

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

[0036] The reverse-angle vertical comb-tooth micromirror driving structure of this invention differs from conventional methods that tilt the moving comb teeth; instead, it alters the position of the fixed comb teeth, thereby improving process stability and device operational stability. First, during the assembly of the cover plate and the main body, the tilting activation boss structure on the cover plate presses down the stator anchor extending from the main body, causing the fixed comb teeth to tilt upwards using the fulcrum beam as a pivot. Second, during the assembly of the cover plate and the main body, the misalignment activation boss on the cover plate presses down the misalignment platform connected to the stator anchor via the fulcrum beam, causing the stator anchor to undergo vertical displacement. This further creates a vertical height difference between the fixed and moving comb teeth, resulting in the reverse-angle vertical comb-tooth micromirror driving structure.

[0037] In electrostatic comb actuators, the larger the overlap area between the stationary and moving comb teeth, the stronger the electrostatic attraction. In MEMS micromirrors driven by a vertical comb structure, the micromirror reaches its maximum rotation angle when the overlap angle between the stationary and moving comb teeth is at its maximum. With essentially the same parameters, at the maximum angle, the overlap area between the stationary and moving comb teeth in the AVC structure is larger than that in the SVC structure, and the advantage becomes more pronounced as the angle increases. Therefore, the AVC structure has better performance than the SVC structure. However, currently common AVCs are usually fabricated using polymer tension processing, which is not conducive to mass production and has poor reliability. Compared to existing AVC fabrication methods, the reverse-angle vertical comb micromirror driving structure proposed in this application, fabricated using a boss activation structure, is prepared using a standardized method, making it more suitable for mass production and with higher reliability. The maximum rotation angle of the micromirror can be easily changed by selecting different activation boss heights. Moreover, compared to the AVC structure, its larger overlap area between the stationary and moving comb teeth provides a greater attraction, and the advantage becomes more pronounced as the micromirror rotation angle increases. Furthermore, existing vertical comb structures often involve machining the moving and fixed comb teeth on different layers, making it difficult to reduce the gap between them and align them. In the structure proposed in this application, the comb teeth, which serve as the driving components, can be machined simultaneously on the same layer for self-alignment. This allows the gap between the fixed and moving comb teeth to be smaller than that achievable with conventional processes, thereby accommodating more comb teeth within the same area and further improving the electrostatic driving force of the structure. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the existing vertical comb tooth structure.

[0039] Figure 2 A schematic diagram of the reverse angle vertical comb tooth micromirror driving structure provided in this application;

[0040] Figure 3 A schematic cross-sectional view of the reverse-angle vertical comb-tooth micromirror driving structure provided in this application;

[0041] Figure 4 An exploded view of the reverse-angle vertical comb-tooth micromirror driving structure provided in this application;

[0042] Figure 5 A schematic diagram of the main body of the reverse angle vertical comb-tooth micromirror driving structure provided in this application;

[0043] Figure 6 A schematic diagram of the cover plate for the reverse angle vertical comb micromirror driving structure provided in this application;

[0044] Figure 7 Schematic diagram of the reverse-angle vertical comb tooth micromirror driven variant structure;

[0045] Figure 8 A schematic diagram of the micromirror body of an electrostatic MEMS micromirror provided in this application;

[0046] Figure 9 A schematic diagram of a micromirror cover plate for an electrostatic MEMS micromirror provided in this application;

[0047] Figure 10 A cross-sectional schematic diagram of an electrostatic MEMS micromirror provided for this application;

[0048] Figure 11 A schematic diagram of an electrostatic MEMS micromirror provided in this application;

[0049] Figure 12 A schematic diagram of the fabrication process of an electrostatic MEMS micromirror provided in this application;

[0050] Figure 13 A schematic diagram of the fabrication process of a cover plate for an electrostatic MEMS micromirror provided in this application;

[0051] Figure 14 A schematic diagram of the assembly process of the body and cover plate of an electrostatic MEMS micromirror provided in this application;

[0052] Reference numerals: 11. Cover plate substrate; 12. Positioning boss; 13. Misalignment activation boss; 14. Tilt activation boss; 15. Through hole; 21. Main body substrate; 22. Serpentine beam; 23. Misalignment platform; 24. Support beam; 25. Stator anchor; 26. Fixed comb tooth; 27. Moving comb tooth; 28. Positioning groove; 29. ​​Mirror platform; 30. Torsion beam; 31. Insulating channel; 32. Electrode; 42. New serpentine beam; 50. Insulating channel groove; 51. Oxide layer; 52. Polycrystalline silicon; 53. Silicon dioxide insulating layer; 54. Electrode area; 55. Backside space etching window; 56. Buried oxide layer; 57. Photoresist. Detailed Implementation

[0053] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0054] In the description of this invention, unless otherwise stated, "a plurality of" means two or more. It should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0055] See Figure 1 , Figure 1 This is a schematic diagram of an existing vertical comb structure. With essentially the same parameters, at the maximum angle, the overlap area between the stationary and moving comb teeth in the AVC structure is greater than that in the SVC structure, and this advantage becomes more pronounced as the angle increases. Therefore, the AVC structure offers better performance than the SVC structure. (See also...) Figure 2 , Figure 2 The diagram shows the structural principle of this application. Compared with the AVC structure, the overlap area between the fixed and moving comb teeth is larger, which can provide a greater attraction. The greater the rotation angle of the micromirror, the more obvious the advantage.

[0056] Example 1

[0057] See Figures 3 to 6 A reverse-angle vertical comb micromirror driving structure manufactured using a boss activation structure is divided into two parts: a cover plate and a main body.

[0058] The cover plate includes a cover plate base 11, a positioning boss 12, a misalignment activation boss 13, and a tilt activation boss 14. The positioning boss 12, the misalignment activation boss 13, and the tilt activation boss 14 are all fixedly connected to the lower surface of the cover plate base 11.

[0059] It should be understood that the height of the tilt activation boss 14 is greater than that of the misalignment activation boss 13, so that the stator anchor can be further pressed down relative to the misalignment platform.

[0060] It should be understood that the vertical orientation here is only for the purpose of illustrating the displacement direction of the misaligned platform and the fixed comb teeth. In actual production, some deviations may occur due to manufacturing processes or manufacturing precision.

[0061] It should be understood that the misalignment activation boss 13 is used to stably control the displacement of the misalignment platform and enhance its stability after movement. The misalignment activation boss 13 can be one, two, or more. If there are three misalignment activation bosses 13, they are located above the U-shaped misalignment platform 23. Two of these bosses are located above both ends of the misalignment platform 23, with the center of their contact surface closer to the ends than the connection point between the misalignment platform 23 and the support beam 24. The third boss is located above the center of the bottom end of the U-shaped misalignment platform. The purpose of setting the misalignment activation bosses 13 is to provide vertical displacement for the stator anchor 25. This invention does not impose specific limitations on the specific shape and number of the misalignment activation bosses 13.

[0062] The main body includes a main base 21, a serpentine beam 22, a misaligned platform 23, a support beam 24, a stator anchor 25, fixed comb teeth 26, moving comb teeth 27, and a positioning groove 28.

[0063] Among them, the serpentine beam 22, the misaligned platform 23, the fulcrum beam 24, the stator anchor 25, the fixed comb tooth 26 and the moving comb tooth 27 are processed in the same layer and are connected to each other. They are all located inside the main body base 21, and the positioning grooves 28 are distributed around the main body base 21.

[0064] The misaligned platform 23 is U-shaped, and its two sides are connected to the main base 21 by two serpentine beams 22. The stator anchor 25 is located inside the misaligned platform 23, and its two sides are connected to the inner wall of the misaligned platform 23 by two support beams 24. One end of the stator anchor 25 extends outward with a fixed comb tooth 26. The main base 21 extends with a movable comb tooth 27. The fixed comb tooth 26 and the movable comb tooth 27 are processed in the same layer and interlocked with each other.

[0065] The height of the tilt activation boss 14 is greater than the height of the misalignment activation boss 13; the misalignment platform 23 is connected to the main body base 21 through the serpentine beam 22; the stator anchor 25 is connected to the misalignment platform 23 through the fulcrum beam 24; the fixed comb tooth 26 extends from the stator anchor 25; the movable comb tooth 27 extends from the main body base 21 and is used to intersect with the fixed comb tooth 26, forming a reverse angle vertical comb tooth micromirror driving structure with the fixed comb tooth after the cover plate and the main body are assembled. A positioning groove 28 is provided on the main body base 21. When the cover plate and the main body are assembled, the positioning boss 12 is inserted into the positioning groove 28 for positioning. The tilt activation boss 14 is located above the stator anchor 25. The tilt activation boss 14 presses down on the stator anchor 25, using the fulcrum beam 24 as the pivot, causing the fixed comb tooth 26 to tilt up. The misalignment activation boss 13 is located above the misalignment platform 23. The misalignment activation boss 13 presses down on the misalignment platform 23, causing the serpentine beam 22 to deform in the Z direction. The stator anchor generates a vertical displacement, thereby creating a vertical height difference between the fixed comb tooth 26 and the moving comb tooth 27, ultimately resulting in a reverse angle vertical comb tooth micromirror driving structure. When the main body and the cover plate are assembled, the fixed comb tooth will tilt up and move in the vertical direction, thus creating a reverse angle vertical comb tooth micromirror driving structure.

[0066] Optionally, the moving comb teeth 27 and the fixed comb teeth 26 can be conventional rectangular or trapezoidal.

[0067] Optionally, the misaligned platform 23 and the main base 21 can be connected by a serpentine beam or other beams with greater stiffness in the X and Y directions and less stiffness in the z direction. This application does not impose any restrictions on this.

[0068] Optionally, the stator anchor 25 and the misaligned platform 23 can be connected by the fulcrum beam 24, or other beams with low torsional stiffness, which is not limited in this application.

[0069] Optionally, the cover plate and the main body can be bonded or not. In specific embodiments, bonding is preferred, which can make the displacement of the fixed comb teeth more stable, thereby improving the performance stability of the micromirror.

[0070] Example 2

[0071] See Figure 7 , Figure 7This is a variation of the aforementioned structure. It removes the misalignment platform 23 and the fulcrum beam 24. The new serpentine beam 42 combines the functions of the original serpentine beam 22 and the fulcrum beam 24. Compared to the original serpentine beam, its structure extends the beam portion at the end of the serpentine beam parallel to the x-axis, allowing it to connect directly to the stator anchor 25 and reducing torsional stiffness. The stator anchor 25 is divided into two ends by the axis of rotation determined by the beam portion at the end of the new serpentine beam 42 parallel to the x-axis. The end of the stator anchor 25 located near the moving comb tooth 27 has a lower misalignment activation boss 13, while the end located away from the moving comb tooth 27 has a higher tilt angle activation boss 14. This variant structure also achieves the effect of the fixed comb tooth tilting upwards and having a certain vertical displacement, and therefore falls within the scope of protection of this patent.

[0072] Example 3

[0073] The following describes an electrostatic MEMS micromirror according to a specific embodiment of this application. This electrostatic MEMS micromirror includes the aforementioned reverse-angle vertical comb micromirror driving structure. It is also divided into two parts: a main body and a cover plate covering the main body. The main body further includes a mirror platform 29, a torsion beam 30, an isolation trench 31, and an electrode 32. The mirror platform 29 is connected to the main body substrate 21 on both sides in the X direction via two torsion beams 30. Each end of the mirror platform 29 in the Y direction is connected to a reverse-angle vertical comb micromirror driving structure. The isolation trench 31 is located on the outer periphery of the connection between the torsion beam 30 and the main body substrate 21, used to achieve electrical isolation between the fixed comb teeth 26 and the moving comb teeth 27. The electrode 32 is fixed above the main body substrate 21 enclosed by the isolation trench 31 and used for welding wires.

[0074] See Figure 8 , Figure 8 This is a schematic diagram of the main body of an electrostatic MEMS micromirror provided in this application. Four positioning grooves 28 are distributed at the four corners of the substrate; an isolation channel 31 is located on the outer periphery of the connection between the torsion beam 30 and the main substrate 21; an electrode 32 is fixed above the main substrate 21 enclosed by the isolation channel 31; a mirror platform 29 and the main substrate 21 are connected by two torsion beams 30; two serpentine beams 22 connect the two sides of the misaligned platform 23 to the main substrate 21; a stator anchor 25 is connected to the misaligned platform 23 via a fulcrum beam 24; fixed comb teeth 26 extend from the stator anchor 25; movable comb teeth 27 extend from the mirror platform 29 and are perpendicular to the rotation axis determined by the torsion beams 30; the fixed comb teeth 26 and the movable comb teeth 27 are processed in the same layer and interlock; the shape of the comb teeth is typically designed as a simple rectangle or trapezoid.

[0075] Optionally, the mirror platform 29 may be provided with an optical reflective film layer. In specific embodiments, an optical reflective film layer should be provided first, as it can greatly enhance the reflectivity of the mirror platform and improve the performance of the micromirrors.

[0076] Optionally, one end of the movable comb tooth 27 can be fixed on the mirror platform 29, on the torsion beam 30, or on a cantilever beam extending from the micromirror and parallel to the torsion beam. This application does not make specific limitations in this regard.

[0077] Optionally, this application does not limit the shape of the micromirror. For example, the micromirror surface can be circular, rectangular, elliptical, etc.

[0078] Optionally, the cover plate and the main body can be bonded or not. In specific embodiments, bonding is preferred, which can make the displacement of the fixed comb teeth more stable, thereby improving the performance stability of the micromirror.

[0079] It should be understood that the moving comb teeth 27 are not necessarily perpendicular to the rotation axis determined by the torsion beam 30. For example, in an embodiment where the mirror surface is circular, the moving comb teeth may also be distributed circumferentially along the edge of the mirror surface, and the fixed comb teeth 26 may be adjusted accordingly. This application does not impose any limitations on this.

[0080] It should be understood that the positioning groove 28 may or may not be through, and the angle between its inner wall and the z-axis can be set as needed. This application does not impose any restrictions on this.

[0081] It should be understood that the positioning grooves 28 can be located in corners or on edges, and their relative positions only need to be the same as the relative positions of the positioning bosses of the cover plate. This application does not require their specific positions.

[0082] See Figure 9 , Figure 9 This is a schematic diagram of a cover plate for an electrostatic MEMS micromirror provided in this application. A through hole 15 is provided in the middle to provide space for the micromirror to rotate around a rotation axis defined by a torsion beam 30, while ensuring that light directly hits the micromirror and that reflections are not obstructed. The cover plate is fixed with positioning bosses 12, misalignment activation bosses 13, and tilt activation bosses 14. The relative positions of the positioning bosses 12 are the same as the relative positions of the positioning grooves 28 on the base of the main body, and correspond one-to-one. The relative position of the misalignment activation bosses 13 on the cover plate is the same as the relative position of the misalignment platform 23 on the main body. The relative position of the tilt activation bosses 14 on the cover plate is the same as the relative position of the stator anchor 25 on the main body.

[0083] It should be understood that the angle between the outer wall of the misaligned activation boss 13 and the tilt activation boss 14 and the z-axis can be set according to actual needs, and this application does not impose any restrictions on this.

[0084] See Figure 10 and Figure 11The main body and cover plate are assembled together after their relative positions are determined by the positioning boss 12 and positioning groove 28. The tilt activation boss 14 matches the stator anchor 25 and presses down the stator anchor 25, causing the fixed comb tooth 26 to lift up with the fulcrum beam 24 as the pivot. The misalignment activation boss 13 matches the misalignment platform 23 and presses down the misalignment platform 23, causing the serpentine beam 22 to deform in the Z direction. The stator anchor produces a vertical displacement, thereby creating a vertical height difference between the fixed comb tooth 26 and the moving comb tooth 27, and finally obtaining the reverse angle vertical comb tooth micromirror drive structure.

[0085] It should be understood that the height of the tilt activation boss 14 is greater than the height of the misalignment activation boss 13. In a specific embodiment, the preferred height difference between the tilt activation boss 14 and the misalignment activation boss 13 is such that the fixed comb teeth can be tilted up and point towards the rotation axis determined by the torsion beam 30. This maximizes the overlap area between the fixed comb teeth 26 and the moving comb teeth 27, thereby achieving optimal performance of the micromirror.

[0086] For the sake of consistency, in this application, height refers to the distance in the z-direction, and perpendicularity refers to the z-direction.

[0087] It should be noted that the reverse angle vertical comb micromirror driving structure with boss activation structure provided in this application can be applied not only to electrostatic MEMS micromirrors, but also to any other MEMS device.

[0088] Example 4

[0089] A method for fabricating an electrostatic MEMS micromirror includes the following steps:

[0090] The structure and principle of the driven micromirror have been explained in detail above. Because a new comb tooth structure has been proposed, a new fabrication process is needed to prepare the driven micromirror. See below for details. Figures 12 to 14 A brief explanation of the relevant manufacturing process is provided.

[0091] See Figure 12 A method for preparing a micromirror body includes the following steps:

[0092] (A) SOI wafers are treated with diluted buffered hydrofluoric acid solution to remove the oxide layer on the surface of SOI wafers;

[0093] (B) Photolithography is performed on the front side of the SOI wafer, and an insulating channel groove 50 is etched by combining anisotropic inductively coupled plasma etching and isotropic dry etching.

[0094] (C) An oxide layer 51 is deposited on both sides of the insulating channel groove 50 using a wet oxidation process, and then polysilicon 52 is used to fill the insulating channel groove 50 by a low-pressure chemical vapor deposition process to obtain the insulating channel 31.

[0095] (D) Remove excess material from the surface of the structure obtained in step C using a chemical mechanical polishing process;

[0096] (E) A silicon dioxide insulating layer 53 is deposited on the front side of the structure obtained in step D, and then the electrode region 54 is etched out by photolithography and dry etching processes.

[0097] (F) A metal layer is deposited on the front side of the structure obtained in step E, and then the metal layer is etched by photolithography and dry etching to obtain electrode 32;

[0098] (G) The front-side photolithography of the structure obtained in step F is used to etch the serpentine beam 22, the misaligned platform 23, the fulcrum beam 24, the stator anchor 25, the fixed comb tooth 26, the moving comb tooth 27, the torsion beam 30, the mirror platform 29 and the positioning groove 28 and other device structures using anisotropic inductively coupled plasma etching process.

[0099] (H) A silicon dioxide layer is deposited on the back side of the structure obtained in step G, and then the back space etching window 55 is etched out by photolithography and dry etching processes.

[0100] (I) Anisotropic inductively coupled plasma etching process is used to etch from the back space etching window 54 to the buried oxide layer 55, and then the buried oxide layer 56 is etched by dry etching process to release the serpentine beam 22, the misaligned platform 23, the fulcrum beam 24, the stator anchor 25, the fixed comb tooth 26, the moving comb tooth 27, the torsion beam 30 and the mirror platform 29.

[0101] See Figure 13 The method for preparing the cover plate of the microscope includes the following steps:

[0102] (J) The silicon wafer was treated with a diluted buffered hydrofluoric acid solution to remove the surface oxide layer and obtain the cover plate substrate 11;

[0103] (K) A layer of photoresist 57 is spin-coated on the front side of the cover plate substrate 11. The photoresist 57 is SU-8 photoresist.

[0104] (L) Grayscale photolithography is performed on photoresist 57 to create a boss structure with different heights; the boss structure includes positioning boss 12, misaligned activation boss 13 and tilt activation boss 14.

[0105] (M) Through holes 15 are manufactured using laser processing.

[0106] This method directly utilizes photoresist as the boss structure, which reduces the subsequent etching process and lowers the processing cost compared to conventional processes.

[0107] See Figure 14 The method for preparing a driven micromirror includes the following steps:

[0108] (M) After aligning the cover plate and the main body, they are assembled using a bonding process. The tilting activation boss 13 on the cover plate presses down the stator anchor 25, which extends from the fixed comb teeth 26 on the main body. Using the fulcrum beam 24 as the pivot, the fixed comb teeth 26 are raised. Next, during the assembly of the cover plate and the main body, the misalignment activation boss 14 on the cover plate presses down the misalignment platform 23, which is connected to the stator anchor 25 through the fulcrum beam 24. The stator anchor 25 generates a vertical displacement, which further creates a vertical height difference between the fixed comb teeth 26 and the moving comb teeth 27, thereby manufacturing a MEMS micromirror with a reverse angle vertical comb tooth micromirror driving structure.

[0109] The foregoing provides a detailed description of a reverse-angle vertical comb-tooth micromirror driving structure and an electrostatic MEMS micromirror manufactured using a boss activation structure. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the methods and central ideas of this application. The directional terms mentioned, such as up, down, left, right, front, or back, are only for reference to the accompanying drawings and are used for explanation, not to limit this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0110] Note that the above description is merely a preferred embodiment of this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of this application, the scope of which is determined by the scope of the appended claims.

Claims

1. A reverse-angle vertical comb-tooth micromirror driving structure, characterized in that, It includes a main body and a cover plate that covers the main body; the cover plate includes a cover plate base (11), and a misalignment activation boss (13) and an angle activation boss (14) are fixed on the lower surface of the cover plate base (11); the height of the angle activation boss (14) is greater than the height of the misalignment activation boss (13); The main body includes a stator anchor (25), fixed comb teeth (26), movable comb teeth (27), and a main body base (21). The fixed comb teeth (26) extend from the stator anchor (25), and the stator anchor (25) is connected to the main body base (21) through a serpentine beam (42). The movable comb teeth (27) and the fixed comb teeth (26) are interlocked. When the cover plate and the main body are assembled, the misalignment activation boss (13) presses down on the component connected to the fixed comb tooth (26), causing a vertical height difference between the fixed comb tooth (26) and the moving comb tooth (27); the stator anchor (25) is pressed down by the tilt activation boss (14), causing the fixed comb tooth (26) to lift up.

2. The reverse angle vertical comb-tooth micromirror driving structure according to claim 1, characterized in that, The serpentine beam (42) is connected to the stator anchor (25) by a misaligned platform (23), and the stator anchor (25) is connected to the misaligned platform (23) through the fulcrum beam (24). When the cover plate and the main body are assembled, the misaligned platform (23) is pressed down by the misaligned activation boss (13), so that the fixed comb tooth (26) and the moving comb tooth (27) have a vertical height difference.

3. The reverse angle vertical comb-tooth micromirror driving structure and its driving micromirror according to claim 2, characterized in that, Three misaligned activation protrusions (13) are fixed on the lower surface of the cover plate base (11); the three misaligned activation protrusions (13) are located above the misaligned platform (23), of which two misaligned activation protrusions (13) are located above the two ends of the misaligned platform (23), and the other misaligned activation platform (13) is located at the bottom end of the misaligned platform (23).

4. The reverse angle vertical comb-tooth micromirror driving structure according to claim 1, characterized in that, The cover plate and the main body are bonded together.

5. A driving micromirror, characterized in that, The micromirror driving structure of claim 1 includes a mirror platform (29), electrodes (32), and two oppositely arranged reverse-angle vertical comb teeth. The mirror platform (29) is connected to the main body base (21) on both sides by two torsion beams (30); each end of the mirror platform (29) is connected to a reverse angle vertical comb micromirror drive structure, the torsion beams (30) and the main body base (21) are separated by an isolation channel (31), and the electrode (32) is fixed above the main body base (21) surrounded by the isolation channel (31).

6. A driving micromirror according to claim 5, characterized in that, A positioning boss (12) is fixed on the lower surface of the cover plate base (11), and a positioning groove (28) is provided on the main body base. The positioning boss (12) is inserted into the positioning groove (28).

7. A driving micromirror according to claim 5, characterized in that, An optical reflective film layer may be provided on the mirror platform (29).

8. The method for preparing a driven micromirror according to claim 5, characterized in that, Includes the following steps: S1. Prepare the micromirror body and the micromirror cover plate; The preparation of the micromirror body includes the following steps: SA1, Remove the oxide layer from the surface of the SOI wafer; SA2, an insulating channel groove (50) is etched on the front side of the SOI wafer; SA3. Deposit oxide layers (51) on both sides of the insulating channel groove (50), and fill the insulating channel groove (50) with polycrystalline silicon (52) to obtain the insulating channel (31). SA4. Remove excess material from the surface of the structure obtained in step SA3; SA5. A silicon dioxide insulating layer (53) is deposited on the front side of the structure obtained in step SA4, and the electrode area (54) is etched out. SA6. A metal layer is deposited on the front side of the structure obtained in step SA5, and the metal layer is etched to obtain the electrode (32); SA7. The structure obtained in step SA6 is etched with various components such as serpentine beam (22), misaligned platform (23), fulcrum beam (24), stator anchor (25), fixed comb tooth (26), moving comb tooth (27), torsion beam (30), mirror platform (29) and positioning groove (28) on the front side. SA8. The back space etching window (55) of the structure obtained in step G is etched from the back space etching window (55) to the buried oxide layer (56), and then the buried oxide layer (56) is etched to release the serpentine beam (22), the misaligned platform (23), the fulcrum beam (24), the stator anchor (25), the fixed comb tooth (26), the moving comb tooth (27), the torsion beam (30) and the mirror platform (29). The preparation of the micromirror cover plate includes the following steps: SB1. Remove the oxide layer on the surface of the silicon wafer to obtain the cover plate substrate (11); SB2. A boss structure is manufactured on the cover plate base (11), the boss structure including a positioning boss (12), a misalignment activation boss (13) and an angle activation boss (14); SB3. A through hole (15) is machined on the cover plate base (11); S2, the micromirror body and the micromirror cover are assembled together. The stator anchor (25) is pressed down by the tilt activation boss (13). The fixed comb tooth (26) is raised by using the fulcrum beam (24) as the pivot. At the same time, the misalignment activation boss (14) presses down the misalignment platform (23). The stator anchor (25) generates a vertical displacement, which further generates a vertical height difference between the fixed comb tooth (26) and the moving comb tooth (27), thus creating a MEMS micromirror with a reverse angle vertical comb tooth micromirror driving structure.

9. The method for preparing a driven micromirror according to claim 8, characterized in that, Step SB2 includes the following steps: SB2.1 Spin-coat a layer of photoresist on the front side of the silicon wafer; SB2.

2. Perform grayscale photolithography on the photoresist to create a boss structure.

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