Membrane mirror and method for manufacturing a membrane mirror

Abstract

This application discloses a MEMS micromirror and its manufacturing method. The micromirror includes a substrate, a mirror surface, a drive comb pair, and an isolation component. A cavity is formed on the substrate, and the two ends of the mirror surface are fixed to the substrate by a support beam assembly arranged along the cross-sectional direction of the cavity. The mirror surface deflects around the support beam assembly under the drive of the drive comb pair. The surface of the drive comb pair is uniformly covered with an insulating layer deposited by low-temperature IBD ion beam. The isolation component includes a protrusion array disposed in the cavity. The protrusion array includes at least two protrusions arranged in a regular pattern. The protrusions support the mirror surface when it deflects to its lowest point and block the airflow caused by the mirror surface deflection. This can prevent contact discharge between the fixed and moving comb teeth when the micromirror is working, improve the service life and reliability of the product, effectively block the small airflow generated when the micromirror vibrates during operation, increase the wind resistance of the mirror surface, and significantly improve the stability of the micromirror.

Description

Technical Field

[0001] This application relates to the field of semiconductor MEMS device technology, and in particular to a MEMS micromirror and its manufacturing method. Background Technology

[0002] MEMS (Micro-Electro-Mechanical Systems) micromirrors, with their advantages of miniaturization, low power consumption, high-speed scanning, and high precision, have become core optical devices in fields such as lidar, AR / VR, optical communication, medical, industrial inspection, and automotive, covering multiple sectors including consumer, automotive, medical, industrial, communication, and aerospace. A MEMS micromirror mainly consists of a substrate, a mirror, a pair of driving comb teeth, and a support beam assembly. The driving comb teeth pair includes interdigitated moving and fixed comb teeth. The moving comb teeth are connected to the mirror or a movable frame, while the fixed comb teeth are fixed to the substrate. When a voltage is applied between the fixed and moving comb teeth, an electrostatic force is generated, driving the moving comb teeth to deflect the mirror around the support beam, thereby changing the light reflection path.

[0003] Traditional drive comb pairs, when subjected to impacts or process defects, may experience physical contact between the moving and stationary comb teeth, leading to a direct short circuit between the positive and negative electrodes, generating large currents or even sparks, and damaging the device. Furthermore, when the mirror oscillates at high speeds, the gas flow between the mirror and the substrate cavity generates pressure film damping, affecting system stability. Simultaneously, at the microscopic scale, if the mirror deflection angle is too large, it may adhere to the substrate (due to capillary action, etc.) and become irrecoverable, leading to failure.

[0004] To address the aforementioned issues, the current solution involves covering at least one surface of the moving and fixed comb teeth with an insulating layer. This insulating layer provides electrical isolation in case of accidental contact between the moving and fixed comb teeth, preventing short circuits and thus avoiding discharge damage. Additionally, an isolation beam fixed to the bottom is added to the center of the base cavity below the mirror, and several tiny protrusions are incorporated. When the mirror deflects, the gas flow below is blocked by the isolation beam, forcing the gas to pass through the narrow gap between the mirror and the beam. This significantly increases gas flow resistance, effectively suppressing unexpected vibrations of the mirror and improving the stability and accuracy of the scanning trajectory. When the mirror swings to its maximum angle due to accident or excessive driving voltage, it first contacts the tiny protrusions rather than adhering extensively to the bottom of the base cavity. Because the contact area is extremely small, the resulting adhesive force is very weak, allowing the mirror to easily detach and return to its original position, preventing "sticking" failure.

[0005] However, the insulating layer on the surface of the comb teeth currently mainly adopts plasma-enhanced chemical vapor deposition (PECVD) or stepwise heterogeneous deposition methods. In reality, for the ultra-high aspect ratio structure of comb teeth, traditional PECVD or stepwise heterogeneous deposition methods cannot meet the step coverage requirements, and the deposition methods are too complex to implement. While adding an isolation beam under the mirror cavity can increase the pressure damping during mirror movement, the effect of an isolation beam in improving the pressure damping to enhance the performance and stability of the micromirror system is limited. Summary of the Invention

[0006] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a MEMS micromirror and its manufacturing method to solve the problems of short circuit in the drive comb tooth pair and poor mirror stability in current MEMS micromirrors.

[0007] In a first aspect, this application provides a MEMS micromirror, comprising: a substrate, a mirror surface, a pair of driving comb teeth, and an isolation component; A cavity is formed on the substrate, and the two ends of the mirror are fixed to the substrate by a support beam assembly arranged along the cross-sectional direction of the cavity. The mirror deflects around the support beam assembly under the drive of the drive comb pair. The surface of the drive comb pair is uniformly covered with an insulating layer deposited by low-temperature IBD ion beam. The isolation component includes an array of protrusions disposed within the cavity. The array of protrusions includes at least two protrusions arranged in a regular pattern. The protrusions support the mirror surface when it is deflected to its lowest point and block the airflow caused by the deflection of the mirror surface.

[0008] In some embodiments, the drive comb pair includes staggered fixed comb teeth and movable comb teeth, the movable comb teeth being connected to the edge of the mirror, the fixed comb teeth being fixed to the side region of the cavity, and the surface of the fixed comb teeth being completely covered with an insulating layer deposited by a low-temperature IBD ion beam. The insulating layer includes a silicon dioxide layer, or a stacked structure of a silicon dioxide layer and a silicon nitride layer.

[0009] In some embodiments, the protrusion array covers the effective range of the arc-shaped deflection of the mirror, and the arrangement direction of the protrusion array is perpendicular to the flow direction of the airflow generated by the deflection of the mirror.

[0010] In some embodiments, the length of the protrusion in the axial direction of the cavity and / or the length of the protrusion in the radial direction of the cavity gradually decreases as the distance from the axis of the cavity moves away from the cavity.

[0011] In some embodiments, the distance between two adjacent protrusions gradually decreases as the axis moves away from the cavity.

[0012] In some embodiments, the mirror surface is covered with a reflective layer, the thickness of which is 20nm-50nm.

[0013] In some embodiments, the raised surfaces are all covered with the insulating layer.

[0014] Secondly, this application also provides a method for manufacturing a MEMS micromirror, used to prepare a MEMS micromirror as described in any one of the first aspects, the method comprising: A comb tooth and bump array are fabricated on the first wafer; An insulating layer was deposited on the fixed comb teeth and the protrusion array using ion beam deposition technology to obtain a film. After fabricating a mirror surface on a second wafer to obtain a top wafer, the top wafer and the bottom wafer are bonded together. A MEMS micromirror is obtained by fabricating moving comb teeth on the top plate.

[0015] In some embodiments, the method further includes: Electrode pads are prepared using at least one of sputtering, photolithography, and etching processes; After the electrode pads are prepared, a reflective layer is prepared on the mirror surface using a stripping process.

[0016] In some embodiments, the method further includes: The mirror area of ​​the top sheet is thinned.

[0017] The above-described one or more embodiments of this application have at least one or more of the following beneficial effects: This application provides a MEMS micromirror and its manufacturing method. An insulating layer is uniformly covered on the surface of the driving comb teeth by ion beam deposition, which can prevent contact discharge between the upper and lower comb teeth during the operation of the micromirror, thereby improving the service life and reliability of the product. A protrusion array is set in the cavity, including at least two protrusions arranged in a regular pattern. The protrusions support the mirror surface when it is deflected to the lowest point and block the airflow caused by the deflection of the mirror surface. This can effectively improve the effect of blocking the small airflow generated when the micromirror vibrates during operation, increase the wind resistance of the mirror surface, and greatly improve the stability of the micromirror.

[0018] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0019] The disclosure of this application will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this application. Furthermore, similar numbers in the drawings are used to denote similar components, wherein: Figure 1 This is a perspective view of a MEMS micromirror provided in one embodiment of this application; Figure 2 This is a cross-sectional view of a MEMS micromirror provided in one embodiment of this application; Figure 3 This is a cross-sectional view of the protrusion array in a MEMS micromirror provided in one embodiment of this application; Figure 4 This is a cross-sectional view of the protrusion array in a MEMS micromirror provided in another embodiment of this application; Figure 5 This is a cross-sectional view of the composite substrate in the MEMS micromirror manufacturing method provided in one embodiment of this application; Figure 6 This is a cross-sectional view of the MEMS micromirror manufacturing method provided in one embodiment of this application after depositing a second silicon dioxide layer on a composite substrate; Figure 7 This is a cross-sectional view of the composite substrate after one photolithography and etching of alignment marks in the MEMS micromirror manufacturing method provided in one embodiment of this application; Figure 8 This is a cross-sectional view of the first wafer after photolithographic etching of isolation trenches in the MEMS micromirror manufacturing method provided in one embodiment of this application; Figure 9 This is a cross-sectional view of the MEMS micromirror manufacturing method provided in one embodiment of this application after using nanoimprinting to manufacture the fixed comb teeth and protrusion array; Figure 10 This is a cross-sectional view of the MEMS micromirror manufacturing method provided in one embodiment of this application after photolithography etching is used to manufacture the fixed comb teeth and the protrusion array; Figure 11 This is a cross-sectional view of the top surface after bonding with the substrate in the manufacturing method of a MEMS micromirror provided in one embodiment of this application; Figure 12 This is a partially enlarged view of the comb array fabricated in the MEMS micromirror manufacturing method provided in one embodiment of this application; Figure 13 This is a cross-sectional view of the mirror surface after the reflective layer is prepared in the manufacturing method of a MEMS micromirror provided in one embodiment of this application.

[0020] The components are: 1. Substrate; 11. Low-resistivity silicon substrate; 12. First silicon dioxide layer; 13. SOI silicon layer; 14. Second silicon dioxide layer; 15. Third silicon dioxide layer; 16. Electrode pad; 2. Mirror surface; 3. Drive comb tooth pair; 31. Fixed comb tooth; 32. Moving comb tooth; 4. Isolation component; 5. Cavity; 7. Protrusion; 8. Reflective layer; 9. Isolation groove; 10. Cover epitaxial silicon wafer. Detailed Implementation

[0021] Some embodiments of this application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this application and are not intended to limit the scope of protection of this application.

[0022] As mentioned in the background section, CN202210508327.4 discusses how electrostatically driven comb structures in MEMS micromirrors are easily damaged by adsorption discharge and short circuits when the comb structures come into contact with each other, leading to high instantaneous currents and potential micro-explosions. It describes using plasma-enhanced chemical vapor deposition (PECVD) or stepwise heterogeneous deposition methods to add insulating layers to the surfaces of the driving comb teeth and grounding comb to maintain an open circuit and prevent short circuits. However, this section only emphasizes the deposition method of the insulating layer. In reality, for comb teeth, which are ultra-high aspect ratio structures, traditional PECVD or stepwise heterogeneous deposition methods cannot meet the step coverage requirements and are therefore unusable.

[0023] CN114594594B describes a manufacturing process where the solder pads (PADs) and the mirror (Mirror) use the same metal and thickness. Especially when using gold, maintaining consistency with the PAD thickness results in an excessively thick gold mirror, even though the PADs could be made without gold. While adding an isolation beam under the mirror cavity increases the pressure damping during mirror movement, improving the performance and stability of the micromirror system, a single isolation beam is not ideal. A more complex isolation structure is needed to significantly enhance pressure damping and improve the overall performance and stability of the micromirror system.

[0024] To address the aforementioned issues, this application creatively proposes a MEMS micromirror and its manufacturing method. An insulating layer is uniformly deposited onto the surface of the driving comb teeth by ion beam deposition, preventing contact discharge between the upper and lower comb teeth during micromirror operation and improving product lifespan and reliability. A protrusion array is arranged within the cavity, comprising at least two regularly arranged protrusions. These protrusions support the mirror surface when it deflects to its lowest point and block airflow caused by mirror deflection. This effectively enhances the blocking of minute airflow generated during micromirror operation vibrations, increases the mirror surface's wind resistance, and significantly improves the micromirror's stability.

[0025] The present application will be specifically described below through specific embodiments.

[0026] This application provides a MEMS micromirror, as shown in the reference. Figure 1 and Figure 2 As shown, the system includes: a base 1, a mirror 2, a drive comb pair 3, and an isolation component 4; a cavity 5 is formed on the base 1, and the two ends of the mirror 2 are fixed to the base 1 by a support beam assembly arranged along the cross-sectional direction of the cavity 5. The mirror 2 deflects around the support beam assembly under the drive of the drive comb pair 3; the surface of the drive comb pair 3 is uniformly covered with an insulating layer (not shown) deposited by low-temperature IBD ion beam; the isolation component 4 includes an array of protrusions disposed in the cavity 5, the array of protrusions including at least two protrusions 7 arranged in a regular pattern, the protrusions 7 supporting the mirror 2 when it deflects to its lowest point, and blocking the airflow caused by the deflection of the mirror 2.

[0027] In some embodiments, the drive comb pair 3 includes staggered fixed comb teeth 31 and movable comb teeth 32, the movable comb teeth 32 being connected to the edge of the mirror surface 2, the fixed comb teeth 31 being fixed to the side region of the cavity, and the surface of the fixed comb teeth 31 being completely covered with an insulating layer deposited by a low-temperature IBD ion beam; the insulating layer includes a silicon dioxide layer, or a stacked structure of a silicon dioxide layer and a silicon nitride layer.

[0028] Specifically, the moving comb teeth 32 are etched and formed on the upper SOI epitaxial silicon layer and connected to the edge of the mirror 2. They rotate synchronously with the mirror 2. The fixed comb teeth 31 are formed on the upper SOI epitaxial silicon layer and are located in the side area of ​​the cavity under the mirror 2, and are integrally fixed with the substrate 1.

[0029] An insulating layer is covered on at least one of the fixed comb teeth 31 and the moving comb teeth 32 to prevent accidental contact and short circuit between the fixed comb teeth 31 and the moving comb teeth 32. Considering that the moving comb teeth 32 are formed after the fixed comb teeth 31, as well as the process difficulty and cost, it is preferable that the surface of the fixed comb teeth 31 is completely covered with an insulating layer deposited by low-temperature IBD ion beam.

[0030] Silicon dioxide and silicon nitride have high process compatibility with silicon substrates and can form a uniform thin film on the silicon wafer surface by low-temperature IBD ion beam deposition. They have extremely strong adhesion to silicon, are not easy to delaminate and fall off, and are compatible with all MEMS manufacturing processes such as photolithography, etching, bonding, and metal deposition.

[0031] When the insulating layer adopts a laminated structure of silicon dioxide layer and silicon nitride layer, the silicon dioxide layer covers the surface of the fixed comb tooth 31, and the silicon nitride layer covers the surface of the highly insulating silicon dioxide layer. The silicon nitride layer forms a dense water vapor impurity barrier layer and wear-resistant layer on the outermost layer, which avoids the silicon dioxide layer from oxidation and corrosion due to water vapor, and avoids the silicon dioxide layer from being scratched by the contact between the fixed comb tooth 31 and the moving comb tooth 32, thus ensuring the long-term integrity of the insulating layer.

[0032] The bump 7 can be a silicon-based material, a tiny dot-like or island-like bump, or a columnar, ring-shaped, stepped, or strip-shaped bump structure. As long as it is a silicon-based material, it can be integrated with the substrate without adding complex process steps, ensuring mass production feasibility and cost control.

[0033] In some embodiments, the protrusion array covers the effective range of the arc-shaped deflection of the mirror 2, and the arrangement direction of the protrusion array is perpendicular to the flow direction of the airflow generated by the deflection of the mirror 2.

[0034] Specifically, the protrusion array is positioned directly below the mirror 2 within the cavity 5 below the mirror 2. It supports the mirror 2 when it deflects to its lowest point, preventing it from rotating too much and sticking to the bottom of the cavity 5. The protrusion array covers the effective arc-shaped deflection range of the mirror 2, ensuring that the mirror 2 is supported by the protrusions 7 regardless of its direction of deflection to its lowest point, without any blind spots. The arrangement direction of the protrusion array is perpendicular to the airflow direction generated by the deflection of the mirror 2, optimizing the protrusions' effect in blocking the airflow generated by the mirror 2's deflection.

[0035] In some examples, the height of the protrusion 7 is 2μm-20μm, and the height of the protrusion 7 gradually decreases as it moves away from the axis perpendicular to the cavity 5. Optionally, the height of the protrusion 7 can be 2μm, 5μm, 8μm, 10μm, 13μm, 15μm, 18μm, 20μm, or any value within the above height range. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0036] Specifically, as the protrusions 7 move further away from the axis of the cavity 6, they gradually approach the edge of the mirror 2. The height of the protrusions 7 near the edge of the mirror 2 is lower than that of the protrusions 7 near the center of the mirror 2. This facilitates the high-frequency free deflection of the mirror 2 at a certain angle and optimizes the effect of the protrusions 7 in blocking the airflow generated by the deflection of the mirror 2. It should be noted that the height of the protrusions 7 refers to the length of the protrusions 7 in the direction perpendicular to the arrangement surface of the protrusions 7.

[0037] In some embodiments, the protrusion array includes protrusions 7 of uniform size and equal spacing, which facilitates manufacturing 2.

[0038] In some embodiments, refer to Figure 3 and Figure 4 As shown, as the distance from the axis of the cavity 5 is increased, the length of the protrusion 7 in the axial direction of the cavity 5 and / or the length of the protrusion 7 in the radial direction of the cavity 5 gradually decreases.

[0039] When mirror 2 deflects around the support beam assembly, the edge region furthest from the axis experiences the largest deflection amplitude and a longer trajectory. The protrusions 7 in the region furthest from the axis of cavity 5 only need to be small to prevent adhesion, while the protrusions closer to the axis are slightly larger to improve support stability. Furthermore, the minute airflow generated by the deflection of mirror 2 gradually increases in velocity and becomes more turbulent as it diffuses from the axis to the edge. The small protrusions 7 furthest from the axis form dense airflow blocking nodes, gradually weakening the disturbance of high-speed airflow and preventing the increased turbulence caused by the large protrusions 7. The slightly larger protrusions 7 closer to the axis provide basic blocking for low-speed airflow, balancing damping effect and structural strength. Additionally, the region within cavity 5 furthest from the axis is the main motion space for the mirror 2's oscillation. Gradually decreasing the size of the protrusions 7 reduces their occupation of this motion space, preventing interference between the protrusions 7 and mirror 2 or moving comb teeth 32. The region closer to the axis has less motion space, so the larger protrusions 7 do not affect the normal oscillation of mirror 2.

[0040] In some embodiments, the distance between two adjacent protrusions 7 gradually decreases as the axis moves away from the cavity 5.

[0041] The edge of mirror 2 furthest from the axis is the area with the largest deflection amplitude, the fastest movement speed, and the highest risk of adhesion to the bottom of cavity 5. It is also the area with the fastest flow rate and strongest disturbance of the tiny airflow generated by the swing of mirror 2. The spacing of the protrusions 7 decreases as they move away from the axis of cavity 5. The densely packed protrusions 7 in the edge area form multiple layers of fine, progressively dense obstructions to the high-speed, strongly disturbed airflow. This allows the airflow to repeatedly collide and decelerate in the gaps between the protrusions 7, forming turbulence and significantly increasing the pressure film damping. This fundamentally suppresses the disturbance of the edge airflow to mirror 2 and improves rotational stability. The protrusions 7 closer to the axis have a larger spacing, which avoids wind resistance redundancy caused by excessive packing. This prevents excessive wind resistance during the swing of mirror 2 from increasing the driving voltage and power consumption, achieving a balance between stability and low power consumption.

[0042] The support beam assembly includes a support beam and connecting members. The support beam is arranged along the cross-sectional direction of the cavity 5, and its two ends are movably connected to the inner walls of both sides of the cavity 5 via connecting members. The support beam is directly connected to the mirror 2 as a rotation axis for the deflection of the mirror 2. Preferably, the support beam is arranged radially along the cavity 5, and the radial direction of the support beam coincides with that of the mirror 2, resulting in a symmetrical structure and greater stability. This application does not impose specific limitations on the shape and size of the support beam and connecting members, as long as they can stably support the mirror 2 and support its deflection.

[0043] It should be noted that the length of the protrusion 7 in the axial direction of the cavity 5 gradually decreases, the length of the protrusion 7 in the radial direction of the cavity 5 gradually decreases, and the distance between two adjacent protrusions 7 gradually decreases as they move away from the axis of the cavity 5. These protrusions can be arbitrarily combined in the protrusion array.

[0044] In some embodiments, the mirror 2 is covered with a reflective layer 8, the thickness of which is 20nm-50nm. Optionally, the thickness of the reflective layer can be 20nm, 23nm, 25nm, 30nm, 35nm, 40nm, 42nm, 45nm, 48nm, 50nm, or any value within the above thickness range. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0045] This application also provides a method for manufacturing a MEMS micromirror, used to prepare a MEMS micromirror as described in any of the above embodiments, the method comprising: S1. Fabricate a comb tooth and bump array on the first wafer.

[0046] S2. An insulating layer is deposited on the fixed comb teeth and the protrusion array using ion beam deposition technology to obtain a film.

[0047] S3. After fabricating a mirror surface on the second wafer to obtain a top wafer, bond the top wafer to the bottom wafer.

[0048] S4. A moving comb tooth is fabricated on the top plate to obtain a MEMS micromirror.

[0049] In some embodiments, step S1 specifically includes: The first wafer is prepared, and isolation trenches are etched on the first wafer to create a comb tooth and bump array.

[0050] In some embodiments, fabricating the first wafer includes: Reference Figure 5As shown, a composite substrate is obtained by sequentially stacking a low-resistivity silicon substrate 11, a first silicon dioxide layer 12, and an SOI silicon layer 13. The thickness of the low-resistivity silicon substrate is 300μm-600μm. Optionally, the thickness of the low-resistivity silicon substrate, i.e., its length in the stacking direction with the first silicon dioxide layer and the SOI silicon layer, can be 300μm, 330μm, 400μm, 453μm, 500μm, 536μm, 600μm, or any mass ratio within the above thickness range. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. The thickness of the first silicon dioxide layer, i.e., its length in the stacking direction, is 0.8 μm-1.1 μm. Optionally, the thickness of the first silicon dioxide layer can be 0.8 μm, 0.85 μm, 0.9 μm, 1 μm, 1.1 μm, or any value within the above thickness range. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Preferably, the thickness of the first silicon dioxide layer is 1 μm, which achieves electrical and physical isolation between the bottom and top layers and prevents interlayer short circuits. The thickness of the SOI silicon layer is 30 μm-70 μm. Optionally, the thickness of the SOI silicon layer, i.e., its length in the stacking direction, can be 30 μm, 35 μm, 40 μm, 47 μm, 50 μm, 54 μm, 60 μm, 66 μm, 70 μm, or any value within the above thickness range. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. The thickness of the SOI silicon layer is determined based on the design height of the fixed and moving comb teeth of the MEMS micromirror. The fixed comb teeth 31 and the isolation component 4 in the driving comb tooth pair 3 are both formed in the SOI silicon layer.

[0051] Reference Figure 6 As shown, a second silicon dioxide layer 14 is deposited on the SOI silicon layer 13 in the composite substrate to serve as alignment marks for a single photolithography and etching process. After the alignment marks are formed, as shown... Figure 7 As shown. The thickness of the second silicon dioxide layer 14, i.e., its length in the stacking direction of each layer of the composite substrate, is 50nm-500nm. Optionally, the thickness of the second silicon dioxide layer 14, i.e., its length in the stacking direction of each layer of the composite substrate, can be 50nm, 100nm, 155nm, 200nm, 243nm, 300nm, 357nm, 400nm, 465nm, 500nm, or any value within the above thickness range. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. This satisfies the requirements for clear marking and lithography machine recognition without interfering with subsequent processes.

[0052] A third silicon dioxide layer 15 is deposited for subsequent etching of the comb teeth 31, etc., to obtain the first wafer.

[0053] In some embodiments, the process of etching isolation trenches on the first wafer to create a comb tooth and bump array includes: Reference Figure 8 As shown, isolation trenches 9 of a certain depth are photolithographically etched on the SOI silicon layer 13. The depth of the isolation trenches 9, i.e., the length of the isolation trenches 9 in the stacking direction of each layer of the composite substrate, is 40%-70% of the thickness of the SOI silicon layer 13. Optionally, the depth of the isolation trenches 9 can be 40%, 43%, 45%, 50%, 55%, 60%, 65%, 70% of the thickness of the SOI silicon layer 13, or any value within the above range. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0054] Specifically, photolithography is performed first, followed by etching. First, silicon dioxide is etched, and then the SOI silicon layer is etched through a deep etching process (BOSCH process).

[0055] After etching isolation trench 9 is completed, refer to Figure 9 The comb teeth 31 and the protrusion array are fabricated using nanoimprinting, or refer to... Figure 10 The fixed comb teeth 31 and the protrusion array are fabricated by photolithography etching.

[0056] In some embodiments, step S2 includes: An insulating layer is deposited on the surface of the fixed comb teeth 31 and the protrusion array using low-temperature IBD ion beam deposition technology. Specifically, silicon dioxide is deposited on the surface of the fixed comb teeth 31 and the protrusion array using low-temperature IBD ion beam deposition technology, or silicon dioxide and silicon nitride are deposited sequentially on the surface of the fixed comb teeth 31 and the protrusion array using low-temperature IBD ion beam deposition technology.

[0057] In subsequent processes, especially when etching the mirror 2 and the moving comb teeth 32, it plays an important role in protecting the completed fixed comb teeth 31 and the protrusion array, and in preventing electrical short circuits between the upper and lower comb teeth during operation, thus avoiding discharge explosions that could damage the comb teeth.

[0058] In some embodiments, step S3 includes: Reference Figure 11 As shown, a cap epitaxial silicon wafer 10 is used as the second wafer for alignment marking etching. Then, the mirror surface 2 is photolithographically etched on the cap epitaxial silicon wafer 10. The top and bottom wafers are then bonded using Si-Si bonding. Alternatively, the micromirror chip can be treated with a metal ring and then precision alignment bonding such as Au-Au or Au-Sn can be performed. If Si-Si bonding is used, high-temperature annealing is required to eliminate stress and make the interface stronger and better bonded.

[0059] After bonding, the silicon substrate 11 is thinned to remove part of the layer, forming a cavity 5 under the mirror 2.

[0060] Using photolithography, movable comb teeth 32 are etched onto the top wafer. A partial magnified view of the comb tooth array formed by the etched movable comb teeth 32 and fixed comb teeth 31 is shown below. Figure 12 As shown.

[0061] In some embodiments, the method further includes: Electrode pads are prepared using at least one of sputtering, photolithography, and etching processes; after the electrode pads are prepared, a reflective layer is prepared on the mirror surface using a stripping process.

[0062] Specifically, the electrode pads 16 of the MEMS micromirror are fabricated using conventional methods such as sputtering / photolithography / etching, and then fabricated using life-off processes. Figure 13 The reflective layer 8 on the mirror 2 shown, in one example, includes a gold plating. This reduces the thickness of the reflective layer 8 to 200-500 Å or even less, significantly reducing the amount of gold used and manufacturing costs. If fabricated together with the electrode pads 16, the thickness of the reflective layer 8 typically exceeds 2000 Å.

[0063] In some embodiments, the method further includes: The mirror area of ​​the top sheet is thinned.

[0064] Specifically, after the mirror 2 is fabricated on the second wafer, the mirror 2 area on the top wafer is etched and thinned before the top wafer and the bottom wafer are bonded.

[0065] In the description of this specification, the references to "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0067] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A MEMS micromirror, characterized in that, include: Substrate, mirror, drive comb teeth pair, and isolation components; A cavity is formed on the substrate, and the two ends of the mirror are fixed to the substrate by a support beam assembly arranged along the cross-sectional direction of the cavity. The mirror deflects around the support beam assembly under the drive of the drive comb pair. The surface of the drive comb teeth is uniformly covered with an insulating layer deposited by low-temperature IBD ion beam. The isolation component includes an array of protrusions disposed within the cavity. The array of protrusions includes at least two protrusions arranged in a regular pattern. The protrusions support the mirror surface when it is deflected to its lowest point and block the airflow caused by the deflection of the mirror surface.

2. The MEMS micromirror according to claim 1, characterized in that, The drive comb pair includes staggered fixed comb teeth and movable comb teeth. The movable comb teeth are connected to the edge of the mirror surface, and the fixed comb teeth are fixed to the side area of ​​the cavity. The surface of the fixed comb teeth is completely covered with the insulating layer deposited by the ion beam. The insulating layer includes a silicon dioxide layer, or a stacked structure of a silicon dioxide layer and a silicon nitride layer.

3. The MEMS micromirror according to claim 1, characterized in that, The array of protrusions covers the effective range of the arc-shaped deflection of the mirror, and the arrangement direction of the array of protrusions is perpendicular to the flow direction of the airflow generated by the deflection of the mirror.

4. The MEMS micromirror according to claim 1 or 3, characterized in that, As the distance from the axis of the cavity moves away from its center, the length of the protrusion in the axial direction of the cavity and / or the length of the protrusion in the radial direction of the cavity gradually decreases.

5. The MEMS micromirror according to claim 1 or 3, characterized in that, As the axis moves away from the cavity, the distance between two adjacent protrusions gradually decreases.

6. The MEMS micromirror according to claim 1, characterized in that, The raised surfaces are all covered with the insulating layer.

7. The MEMS micromirror according to claim 1, characterized in that, The mirror surface is covered with a reflective layer, the thickness of which is 20nm-50nm.

8. A method for manufacturing a MEMS micromirror, characterized in that, The method for fabricating a MEMS micromirror as described in any one of claims 1-7 comprises: A comb tooth and bump array are fabricated on the first wafer; An insulating layer was deposited on the fixed comb teeth and the protrusion array using ion beam deposition technology to obtain a film. After fabricating a mirror surface on a second wafer to obtain a top wafer, the top wafer and the bottom wafer are bonded together. A MEMS micromirror is obtained by fabricating moving comb teeth on the top plate.

9. The method for manufacturing a MEMS micromirror according to claim 8, characterized in that, The method further includes: Electrode pads are prepared using at least one of sputtering, photolithography, and etching processes; After the electrode pads are prepared, a reflective layer is prepared on the mirror surface using a stripping process.

10. The method for manufacturing a MEMS micromirror according to claim 8, characterized in that, The method further includes: The mirror area of ​​the top sheet is thinned.

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