CN114035253B

CN114035253B - MEMS micro-mirror with stray light eliminating function, laser scanning equipment and manufacturing method of micro-mirror

Info

Publication number: CN114035253B
Application number: CN202111398312.9A
Authority: CN
Inventors: 宋旭东; 宋秀敏; 夏长锋; 游桥明
Original assignee: Xi An Zhisensor Technologies Co ltd
Current assignee: Xi An Zhisensor Technologies Co ltd
Priority date: 2021-11-23
Filing date: 2021-11-23
Publication date: 2024-06-07
Anticipated expiration: 2041-11-23
Also published as: CN114035253A

Abstract

The invention provides a MEMS micro-mirror with stray light eliminating function, laser scanning equipment and a manufacturing method of the micro-mirror. MEMS micro-mirror with stray light elimination function, characterized by comprising: the surface of the frame structure is provided with a extinction layer, and the frame structure is provided with a hole structure; the torsion structure is arranged at the hole structure and is connected with the hole wall of the hole structure; a mirror, the torsion structure supporting the mirror. The invention solves the problem of stray light existing in MEMS micromirrors in the prior art.

Description

MEMS micro-mirror with stray light eliminating function, laser scanning equipment and manufacturing method of micro-mirror

Technical Field

The invention relates to the field of micro-optics and electromechanics, in particular to a MEMS micro-mirror with stray light eliminating function, laser scanning equipment and a manufacturing method of the micro-mirror.

Background

With the development and advancement of technology, it is desirable for the light management device to have a smaller volume and weight and lower cost and power consumption. Therefore, replacing the conventional mechanical scanning mirror with a miniaturized, lightweight, low cost, low power consumption MEMS micro mirror is a common goal for related personnel. At present, the MEMS micro-mirror has been applied to the fields of laser printing, 3D imaging, projection display, laser radar and the like, and has wide development prospect. In practical applications, the performance of MEMS micromirrors often determines the performance of the entire device.

When the existing MEMS micro-mirror works, the light beam generated by the light source irradiates on the reflecting mirror surface of the micro-mirror, is reflected by the reflecting mirror surface and then is emitted, and the light beam can be projected to different positions of a target area by rotating the reflecting mirror surface, so that the purpose of light beam manipulation is realized. In the MEMS micro-mirror, besides the reflecting mirror surface, the mirror surface torsion structure and a driver for driving the mirror surface to rotate around the mirror surface torsion structure, a frame structure is used for supporting and fixing the structure, so that the firmness is improved, and the micro-mirror chip is convenient to clamp. When designing the MEMS micro-mirror chip, in order to ensure the dimensions of the critical micro-structures (torsion beams and drivers), the frame structures need to surround other structures, and the distance between the frame structures cannot be too large, so that the process dimensions with larger phase difference cannot occur, and the precision of the critical dimensions is not affected. Thus, the frame structure is very close to the mirror surface and has a larger area than other structures. As shown in fig. 23, when the incident beam irradiates the reflecting mirror, since the beam is not ideal parallel, part of the beam at the periphery of the beam irradiates the frame structure around the reflecting mirror, and the surface of the frame structure is a polished surface, and after being reflected, the beam forms stray light in the projection range, which affects the use of the micromirror.

FIG. 24 shows a dual-axis electrostatic comb-driven MEMS micromirror (from High-Q MEMS resonators for laser beam SCANNING DISPLAYS, paper), wherein a movable frame torsion comb-tooth driver drives a movable frame to rotate around a movable frame torsion structure (i.e., vertical scanning), a mirror surface torsion comb-tooth driver drives a mirror surface to rotate around a mirror surface torsion structure (i.e., horizontal scanning), and the mirror surface and torsion beams thereof rotate together with the movable frame to realize two-dimensional scanning of the mirror surface, and a fixed frame provides support and fixation for the whole movable structure and is a stationary structure. FIG. 25 is a pattern projected by the dual-axis MEMS micromirror in a projection line display application. When the MEMS micro-mirror works, a light beam projected on the reflecting mirror surface is reflected by the two-dimensional scanning mirror surface, a visible two-dimensional image is formed in the field of view, a light beam projected on the movable frame is reflected by the vertically scanning movable frame, a vertical bright line is formed in the field of view, and a static bright spot is formed in the field of view by the reflection of the fixed frame. The movable frame and the fixed frame reflect vertical bright lines and bright spots formed in the field of view to deteriorate the display quality, severely affecting the image quality. In addition, in projection display, besides stray light formed by reflection of a frame structure, bright spots formed by reflection of incident light beams by window glass adopted by the packaging MEMS micro mirror are also important factors influencing imaging quality, and the inclined plane window glass disclosed in U.S. patent (US 2009/0097087A 1) reflects light spots generated by the window glass to the outside of a visual field range, so that interference of the inclined plane window glass on image display is solved. However, the influence of stray light formed by the frame structure is difficult to be effectively eliminated.

However, in the prior art, many means are adopted to solve the above-mentioned problem of stray light, and the result is still not ideal.

In laser printing applications, a laser beam containing text and image information is projected onto a single-axis electromagnetic drive MEMS micro-mirror surface, and an external drive magnetic circuit (consisting of a drive coil, an iron core, and an iron yoke) drives an electromagnetic drive permanent magnet to drive the mirror surface to rotate around a mirror surface torsion structure, so that the mirror surface reflects the beam to different positions of a photosensitive drum, and a shallow image is formed on the drum. If the periphery of the laser beam is projected on the fixed frame around the reflecting mirror surface, stray light formed by reflection of the fixed frame can form static bright spots on the selenium drum, the static bright spots are always irradiated by the laser beam when the laser is lightened, and finally the laser beam is always printed, so that a vertical black line is formed on printing paper.

The MEMS micro-mirror disclosed in US7072089B2 (as shown in fig. 26 and 27) eliminates stray light formed by the frame structure, greatly reduces the area of the frame structure, reduces the area of the frame structure to be an anchor point of the torsion structure of the two reflecting mirror surfaces, and makes the anchor point far away from the reflecting mirror surfaces, so as to avoid the irradiation of the periphery of the light beam. Although this eliminates stray light generated by the frame structure, it is still necessary to avoid stray light from being generated by light beam peripheral irradiation on other structures such as a driving magnetic circuit located behind the MEMS micro mirror. In addition, the large-area etching makes critical dimensions difficult to ensure, the frame structure becomes fragile due to the reduction of the dimensions, the supporting and fixing effects are greatly weakened, the force application points of the chip can only be two anchor points of the chip in the process of clamping, transferring and installing, the reflection mirror surface torsion structure with the tiny dimensions (from micron level to submicron level) can bear more gravity from the chip and adhesion force between the chip and a placing plane, and the acting force caused by incomplete synchronization of acting forces of the two anchor points of the chip in the process of clamping, transferring and installing increases the damage risk of the reflection mirror surface torsion structure.

In laser radar application, the sensitivity of the laser receiving detector is very high, and the laser receiving detector can respond to stray light formed by the MEMS micro-mirror frame structure, a near return light signal is easy to submerge in the stray light, so that an effective signal cannot be received, and a visual field blind area is generated near the laser receiving detector. The laser radar disclosed in the patent (CN 110045498A) is provided with the extinction piece (shown in figure 28) coated with the light absorption or reflection material in front of the reflector substrate (frame structure), so that stray light is reduced on the reflector substrate, interference of the stray light on a near signal is eliminated, and the receiving and detecting range of the radar is improved. However (as shown in fig. 29), the extinction element is assembled on the front surface of the reflector, the height h of the extinction element is required to be determined according to the angle alpha of the incident light and the radius difference d between the diaphragm and the reflector, and the extinction element is assembled at an accurate position, so that the assembly difficulty is high, and in order not to affect the main light spot, the allowance is inevitably reserved for the machining error of each structural member, the incident angle error of the laser and the assembly error. In addition, in order not to block the light path, the incident light is usually injected from the side direction, the extinction piece cannot block the incident light directly on the reflecting mirror surface, the radius of the diaphragm is larger than that of the reflecting mirror (radius difference d), peripheral light beams can still irradiate on the frame structure to form partial stray light, and the stray light cannot be completely eliminated.

In summary, in the practical application of the MEMS micro-mirror, the stray light formed by the irradiation of the beam periphery to the frame structure seriously affects the use of the MEMS micro-mirror. The related technicians realize stray light elimination by greatly reducing the area of the frame structure and arranging the extinction piece, but simultaneously the problems of increased risk of chip damage, increased assembly difficulty and the like are also introduced. Accordingly, it is desirable to achieve a MEMS micro-mirror that eliminates stray light while avoiding the problems associated with the above-described methods.

Disclosure of Invention

The invention mainly aims to provide an MEMS micro-mirror with a stray light eliminating function, laser scanning equipment and a manufacturing method of the micro-mirror, so as to solve the problem that the MEMS micro-mirror has stray light in the prior art.

In order to achieve the above object, according to an aspect of the present invention, there is provided a MEMS micro mirror having a stray light eliminating function, comprising: the upper surface of the frame structure is provided with a extinction layer, and the frame structure is provided with a hole structure; the torsion structure is arranged at the hole structure, and at least one part of the torsion structure is connected with the hole wall of the hole structure; a mirror, the torsion structure supporting the mirror.

Further, the frame structure comprises a fixed frame and a movable frame, the fixed frame is provided with a hole structure, the movable frame is accommodated in the hole structure, the movable frame is provided with a central through hole, the reflecting mirror is positioned in the central through hole, the torsion structure comprises a mirror surface torsion structure and a frame torsion structure, the mirror surface torsion structure is connected with the movable frame and the reflecting mirror, and the frame torsion structure is connected with the hole wall of the hole structure and the movable frame so that the movable frame drives the reflecting mirror to rotate.

Further, the extinction layer is of a concave-convex structure.

Further, the depth of the concave-convex structure is more than or equal to 2 μm; the surface of the concave-convex structure is a rough surface, and the roughness Ra of the concave-convex structure is more than or equal to 1 mu m.

Further, the extinction layer is a suede, and the roughness Ra of the suede is more than or equal to 1 mu m.

Further, the extinction layer is a light absorption film with a multilayer film structure, and the refractive indexes of the film structures of two adjacent layers in the multilayer film structure are different.

According to another aspect of the present invention, there is provided a laser scanning apparatus including the MEMS micro mirror having the stray light eliminating function described above.

According to another aspect of the present invention, there is provided a method for processing a micro mirror for processing the MEMS micro mirror having the stray light eliminating function, the method comprising: step S110: selecting an SOI silicon wafer which comprises a device layer, an oxygen burying layer and a substrate layer from top to bottom, and forming a silicon oxide film on the surface of the SOI silicon wafer; step S120: etching the upper surface of the frame structure area corresponding to the device layer to form a suede, wherein the suede is used as a extinction layer; step S130: etching the substrate layer to obtain a cavity meeting the movement requirement of the movable structure; step S140: depositing a metal film on the upper surface of the reflector region corresponding to the device layer to obtain a reflecting layer; step S150: and etching the device layer to obtain a movable structure and releasing the movable structure, thereby obtaining the MEMS micro mirror with the stray light eliminating function.

Further, step S120 includes: step S121: forming a photoresist layer with a first preset shape on the upper surface of the device layer except the frame structure area by adopting a photoetching process as a first mask; step S122: etching the upper surface of the device layer to remove the silicon oxide film in the area uncovered by the first mask, so that the upper surface of the frame structure area corresponding to the device layer is exposed; step S123: and performing texturing etching on the SOI silicon wafer, forming a textured surface on the upper surface of the exposed frame structure area, and removing the first mask.

Further, step S123 includes: step S1231: pre-cleaning the SOI silicon wafer in the first liquid medicine; step S1232: the SOI silicon wafer after the pre-cleaning is subjected to texturing in the second liquid medicine; step S1233: alkali washing the textured SOI silicon wafer in the third liquid medicine; step S1234: acid washing is carried out on the alkali-washed SOI silicon wafer in the fourth liquid medicine; to form a textured surface with a roughness Ra of 1 μm or more at the exposed device layer.

Further, step S130 includes: step S131: forming a photoresist layer with a second preset shape on the lower surface of the substrate layer by adopting a photoetching process as a second mask; step S132: etching the exposed silicon oxide film on the lower surface of the substrate layer to remove the exposed silicon oxide film so as to expose the substrate layer at the uncovered area of the second mask; step S133: and performing dry deep silicon etching on the exposed substrate layer to form a cavity meeting the motion requirement of the movable structure.

Further, step S140 includes: step S141: removing the second mask, and forming a photoresist layer with a third preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a third mask; step S142: depositing a layer of metal film on the upper surface of the device layer by adopting a magnetron sputtering process; step S143: and removing the third mask and the metal film on the third mask by adopting an organic solvent and matching with ultrasonic waves, and taking the remained metal film as a reflecting layer.

Further, step S150 includes: step S151: forming a photoresist layer with a fourth preset shape on the upper surface of the device layer by adopting a photoetching process as a fourth mask; step S152: etching silicon oxide of a region of the upper surface of the device layer, which is not covered by the fourth mask, so as to expose part of the device layer, and performing dry deep silicon etching on the exposed part of the device layer to etch a movable structure; step S153: and removing the fourth mask, removing the exposed silicon oxide film and the buried oxide layer on the back surface of the movable structure, and releasing the movable structure to form the MEMS micro mirror with the stray light eliminating function.

According to another aspect of the present invention, there is provided a method for processing a micro mirror for processing the MEMS micro mirror having the stray light eliminating function, the method comprising: step S210: selecting an SOI silicon chip with a three-layer structure comprising a device layer, an oxygen burying layer and a substrate layer from top to bottom; step S220: forming a light absorption film with a multi-layer film structure on the upper surface of a frame structure area corresponding to the device layer, wherein the light absorption film is used as a extinction layer; step S230: etching the substrate layer to form a cavity which meets the movement of the movable structure; step S240: depositing a metal film on the upper surface of the reflector region corresponding to the device layer to form a reflecting layer; step S250: and etching the device layer to obtain a movable structure and releasing the movable structure, thereby obtaining the MEMS micro mirror with the stray light eliminating function.

Further, step S220 includes: step S221: forming a photoresist layer with a first preset shape on the upper surface of the device layer except the frame structure area by adopting a photoetching process as a first mask; step S222: forming a light absorption film with a multilayer film structure on the upper surface of the SOI silicon wafer by adopting a low-temperature deposition process; step S223: and removing the first mask and the light-absorbing film on the first mask by adopting an organic solvent and matching with ultrasonic waves, and only leaving the light-absorbing film in the frame structure area as a extinction layer.

Further, step S230 includes: step S231: forming a photoresist layer with a second preset shape on the lower surface of the substrate layer by adopting a photoetching process as a second mask; step S231: and carrying out dry deep silicon etching on the exposed basal layer to form a cavity meeting the movement requirement of the movable structure.

Further, step S240 includes: step S241: removing the second mask, and forming a photoresist layer with a third preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a third mask; step S242: depositing a layer of metal film on the upper surface of the device layer by adopting a magnetron sputtering process; step S243: and removing the third mask and the metal film on the third mask by adopting an organic solvent and matching with ultrasonic waves, and taking the remained metal film as a reflecting layer.

Further, step S250 includes: step S251: forming a photoresist layer with a fourth preset shape on the upper surface of the device layer by adopting a photoetching process as a fourth mask; step S252: carrying out dry deep silicon etching on the device layer at the area which is not covered by the fourth mask so as to etch the movable structure; step S253: and removing the fourth mask, removing the oxygen buried layer on the back surface of the movable structure, and releasing the movable structure to form the MEMS micro mirror with the stray light eliminating function.

According to another aspect of the present invention, there is provided a method for processing a micro mirror for processing the MEMS micro mirror having the stray light eliminating function, the method comprising: step S310: selecting an SOI silicon chip with a three-layer structure comprising a device layer, an oxygen burying layer and a substrate layer from top to bottom; step S320: etching the substrate layer to form a cavity meeting the movement requirement of the movable structure; step S330: depositing a metal film on the upper surface of the reflector region corresponding to the device layer to form a reflecting layer; step S340: etching the device layer to obtain a movable structure and releasing the movable structure to obtain an intermediate structure; step S350: and carrying out laser etching on the frame structure region of the intermediate structure to form an extinction layer, thereby obtaining the MEMS micro mirror with the stray light eliminating function.

Further, step S320 includes: step S321: forming a photoresist layer with a first preset shape on the lower surface of the substrate layer by adopting a photoetching process as a first mask; step S322: and carrying out dry deep silicon etching on the exposed basal layer to form a cavity meeting the movement requirement of the movable structure.

Further, step S330 includes: step S331: removing the first mask, and forming a photoresist layer with a second preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a second mask; step S332: depositing a layer of metal film on the upper surface of the SOI silicon wafer by adopting a magnetron sputtering process; step S333: and removing the second mask and the metal film on the second mask by adopting an organic solvent and matching with ultrasonic waves, and taking the remained metal film as a reflecting layer.

Further, step S340 includes: step S341: removing the second mask, and forming a photoresist layer with a third preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a third mask; step S342: carrying out dry deep silicon etching on the device layer which is not covered by the third mask so as to etch the movable structure; step S343: and removing the third mask, removing the buried oxide layer on the back surface of the movable structure, and releasing the movable structure to form an intermediate structure.

Further, in step S350, the upper surface of the frame structure region of the intermediate structure is etched by using laser to form a concave-convex structure, and the concave-convex structure is used as a extinction layer.

Further, in the process of etching the surface of the frame structure region of the intermediate structure by using laser to form a concave-convex structure, the concave-convex structure is used as an extinction layer, the power, the spot size and the scanning speed of the laser are controlled to obtain the concave-convex structure with the roughness Ra of 1 μm or more and the depth of 2 μm or more.

Further, in the process of etching the upper surface of the frame structure region of the intermediate structure by laser to form a concave-convex structure, the concave-convex structure is used as a extinction layer, the whole upper surface of the frame structure is scanned.

By applying the technical scheme of the invention, the MEMS micro-mirror with the stray light eliminating function comprises: the device comprises a frame structure, a torsion structure and a reflecting mirror, wherein a extinction layer is arranged on the surface of the frame structure, and the frame structure is provided with a hole structure; the torsion structure is arranged at the hole structure, and at least one part of the torsion structure is connected with the wall of the hole structure; the torsion structure supports the mirror and/or the movable frame.

By arranging the extinction layer on the frame structure, the extinction layer has a certain absorption effect on light beams, so that the reflection of the extinction layer on light rays is reduced, and the generation of stray light is effectively reduced. At least a portion of the torsion structure is connected to the wall of the hole structure while the torsion structure is connected to the mirror and/or the movable frame supporting the mirror and/or the movable frame, the mirror and/or the movable frame rotating about the torsion structure.

The invention has the following beneficial effects: (1) The extinction layer directly formed on the surface of the frame structure by the MEMS micro mirror with the stray light eliminating function can completely cover the frame structure, and the exposed polished surface is not irradiated by incident light beams, so that the stray light is effectively eliminated; the design of the MEMS micro-mirror is not required to be changed or the assembly difficulty of the MEMS micro-mirror is not required to be increased for eliminating stray light, and the flexibility of the MEMS micro-mirror design is improved.

(2) The laser etching forming extinction layer has strong selectivity, does not need to cover and protect the non-etched surface, can be carried out after other manufacturing processes of the MEMS micro-mirror are finished, does not influence the manufacturing of the MEMS micro-mirror, and the filiform slag formed on the surface obviously increases the surface roughness, thereby improving the extinction effect.

(3) The texturing process and the extinction layer formed by the light absorption film are completely compatible with the MEMS micro-mirror manufacturing process, can be integrated into the MEMS micro-mirror manufacturing process, and does not increase the process difficulty.

(4) The extinction effect is good, the reflectivity of the rough microstructure surface and the pyramid suede can be less than 14%, diffuse reflection is adopted, and the energy absorption rate of the light absorption film can reach 85% -99.99%.

(5) The manufacturing method of the extinction layer is simple and reliable, high in efficiency and low in cost.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

FIG. 1 shows a schematic structure of a MEMS micromirror in an alternative embodiment of the invention;

FIG. 2 shows a schematic path diagram of the reflection of light by the MEMS micromirror of FIG. 1;

FIG. 3 shows a schematic structure of a MEMS micromirror in accordance with another alternative embodiment of the invention;

FIG. 4 is a schematic diagram showing the path of reflection of light by the MEMS micromirror of FIG. 3;

FIG. 5 shows a schematic structural diagram of a MEMS micromirror in accordance with another alternative embodiment of the invention;

FIG. 6 shows a schematic path diagram of the reflection of light by the MEMS micromirror of FIG. 5;

FIG. 7 shows an angled view of the frame structure of FIG. 1;

FIG. 8 is a process flow diagram of a method for fabricating a micromirror according to a first embodiment of the invention;

FIG. 9 is a schematic diagram showing a process of fabricating a micromirror according to the first embodiment of the invention;

FIG. 10 shows a surface topography of a matting layer according to a first embodiment of the invention;

FIG. 11 is a process flow diagram of a method for fabricating a micromirror according to a second embodiment of the invention;

FIG. 12 is a schematic diagram showing a process of fabricating a micromirror according to a second embodiment of the invention;

FIG. 13 is a process flow diagram of a method of fabricating a micromirror according to a third embodiment of the invention;

FIG. 14 shows an SEM image of the front of a matting layer in a third embodiment of the invention;

FIG. 15 shows a cross-sectional view of an SEM of the front side of the matting layer of FIG. 14;

FIG. 16 shows an enlarged view of an SEM of the front side of the matting layer of FIG. 14;

fig. 17 shows a moving path of the continuous laser in the third embodiment of the present invention;

fig. 18 shows another moving path of the continuous laser in the third embodiment of the present invention;

FIG. 19 is a schematic diagram showing a superposition of the spots of the pulsed laser in the third embodiment of the present invention;

Fig. 20 is a schematic diagram showing a positional relationship between the first pit and the second pit in fig. 19;

FIG. 21 is a schematic diagram showing another mode of stacking the spots of the pulsed laser according to the third embodiment of the present invention;

FIG. 22 is a schematic diagram showing another mode of stacking the spots of the pulsed laser according to the third embodiment of the present invention;

FIG. 23 shows a schematic reflection of light by a MEMS micromirror in the prior art;

FIG. 24 shows a schematic structural diagram of a dual-axis MEMS micromirror of the prior art;

FIG. 25 shows a schematic diagram of stray light generated by the dual-axis MEMS micromirror of FIG. 24;

FIG. 26 shows a schematic structural diagram of another MEMS micromirror in the prior art;

FIG. 27 shows another angled view of FIG. 26;

FIG. 28 shows a schematic structural diagram of a MEMS micromirror in the prior art;

Fig. 29 shows a schematic reflection of light by the MEMS micro-mirror of fig. 28.

Wherein the above figures include the following reference numerals:

10. A frame structure; 11. a pore structure; 12. a matting layer; 13. a fixed frame; 14. a movable frame; 20. a torsion structure; 30. a reflecting mirror; 40. a concave-convex structure; 50. a first dimple; 60. a second dimple; 70. and a third dimple.

Detailed Description

It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.

In order to solve the problem of stray light in the MEMS micro-mirror in the prior art, the invention provides the MEMS micro-mirror with the stray light eliminating function, laser scanning equipment and a manufacturing method of the micro-mirror.

As shown in fig. 1 to 22, the MEMS micro mirror having a stray light eliminating function includes: the structure comprises a frame structure 10, a torsion structure 20 and a reflecting mirror 30, wherein a extinction layer 12 is arranged on the upper surface of the frame structure 10, and the frame structure 10 is provided with a hole structure 11; the torsion structure 20 is arranged at the hole structure 11, and the torsion structure 20 is connected with the hole wall of the hole structure 11; the torsion structure 20 supports the mirror 30.

By arranging the extinction layer 12 on the frame structure 10, the extinction layer 12 has a certain absorption effect on light beams, so that the reflection of the extinction layer 12 on the light beams is reduced, and the generation of stray light is effectively reduced. The torsion structure 20 is connected to the hole wall of the hole structure 11, while the torsion structure 20 is connected to the mirror 30 to support the mirror 30, the mirror 30 being rotated around the torsion structure 20.

The hole structure 11 may be a through hole or a blind hole.

In the particular embodiment shown in fig. 1-4, the frame structure 10 is stationary and the torsion structure 20 is connected to the aperture structure 11 and the mirror 30 such that the mirror 30 moves about the torsion structure 20.

As shown in fig. 5 and 6, the frame structure 10 includes a fixed frame 13 and a movable frame 14, the movable frame 14 is connected to the mirror 30, and the movable frame 14 drives the mirror 30 to rotate. In the case of the movable frame 14, the torsion structure 20 includes a mirror torsion structure and a frame torsion structure, the mirror torsion structure is connected to the mirror 30, the mirror 30 moves around the mirror torsion structure, and the frame torsion structure is connected to the movable frame 14, and the movable frame 14 moves around the frame torsion structure, thereby driving the mirror 30 to move. The direction of the mirror surface torsion structure driving the mirror 30 to move is the same as or different from the direction of the movable frame 14 driving the mirror 30 to move.

The fixed frame 13 is fixed.

Fig. 6 is a schematic diagram of the operation of the dual-axis MEMS micro-mirror with stray light eliminated, where the center portion of the incident beam irradiates the mirror 30, is reflected by the mirror 30, and is emitted, the mirror 30 rotates around the mirror torsion structure, the movable frame 14 rotates around the frame torsion structure, and the emission angles of the emitted beam are respectively shifted to the rotation directions of the mirror 30 and the movable frame 14, so as to realize two-dimensional manipulation of the beam. The outer periphery of the incident beam irradiates the extinction layer 12 around the reflector 30 and the extinction layer 12 around the movable frame 14, the extinction layer 12 has absorption effect on the incident beam, most of the incident beam is absorbed by the extinction layer 12, the rest of the incident beam is reflected by the extinction layer 12, the reflection directions are inconsistent, diffuse reflection is formed on the extinction layer 12, and the purpose of eliminating stray light is achieved. Specifically, the surface of the matting layer 12 on the side far from the frame structure 10 is a rough surface, and the roughness Ra of the rough surface is 1 μm or more. The rough surface can increase the light absorption effect of the extinction layer 12, and effectively reduce the generation of stray light. After the light rays are incident on the rough surface, most of the light rays are absorbed by the extinction layer 12, and a small part of the light rays are reflected by the extinction layer 12, but due to different reflection effects on the rough surface, diffuse reflection is formed on the rough surface, and the reflection angle of the diffuse reflection is different from that of the reflection mirror 30, so that the light rays reflected by the reflection mirror 30 are not influenced.

The preferred surface roughness Ra value should be greater than 1.5 μm.

If the roughness Ra of the rough surface is less than 1 μm, the rough surface is smoother, and stray light is easily formed by reflection of light rays. The roughness Ra is limited to be more than 1 mu m, so that the manufacturing difficulty is reduced and the manufacturing cost is saved while the stray light effect of the extinction layer 12 is reduced.

As shown in fig. 7, the matting layer 12 has a concave-convex structure 40. By arranging the concave-convex structure 40 on the surface of the frame structure, when the light beam is incident on the extinction layer 12, the light enters into the concave part of the concave-convex structure 40, and the light is absorbed by back and forth reflection at the concave part, so that the reflection of the extinction layer 12 to the light is reduced, and the generation of stray light is greatly reduced.

In the embodiment shown in fig. 1 to 7, the extinction layer 12 is a concave-convex structure 40 processed on the frame structure 10, the concave-convex structure 40 has a rough surface, when incident light irradiates on the concave-convex structure 40, most of light beams are absorbed by multiple reflections inside the concave-convex structure 40, the rest of light beams are reflected in different directions to form diffuse reflection, and stray light is eliminated.

Alternatively, the relief structure 40 is processed by at least one of a continuous laser and a pulsed laser. While the relief structure 40 may be regular or irregular.

Specifically, the depth of the concave-convex structure 40 is 2 μm or more, so that the absorption efficiency of the concave-convex structure 40 to light can be ensured.

Preferably, the depth of the concave-convex structure 40 is 4 μm or more and 12 μm or less. If the depth of the concave-convex structure 40 is smaller than 4 μm, the depth of the concave-convex structure 40 is too small, and when light enters the concave portion, the light is easily reflected out to form stray light, and the effect of reducing the stray light is not ideal. If the depth of the concave-convex structure 40 is greater than 12 μm, the structural strength of the frame structure 10 is weakened, and the manufacturing of the concave-convex structure 40 is not facilitated, and the manufacturing cost is increased. The depth of the concave-convex structure 40 is limited to a range of 4 μm to 12 μm, and the manufacturing difficulty and the manufacturing cost are reduced while reducing stray light.

As shown in fig. 7, the protruding structures in the concave-convex structure 40 are cone-shaped structures, the protruding structures are pointed, so that light emitted to the front surface of the protruding structures is less, direct reflection of light by the concave-convex structure 40 is reduced, absorption of light by the concave-convex structure 40 is increased, and stray light is reduced.

Specifically, the surface of the concave-convex structure 40 is a rough surface. The surface of the concave-convex structure 40 is set to be a rough surface, so that the absorption of the concave-convex structure 40 to light is increased, and the generation of stray light is reduced.

Alternatively, the extinction layer 12 is a light absorbing film having a multilayer film structure. The extinction layer 12 is arranged as a light absorption film to absorb light so as to reduce reflection of the light and extinction, thereby reducing stray light. The refractive indexes of two adjacent film structures in the multilayer film structure are different, so that the light absorption effect of the light absorption film is ensured.

Preferably, the multilayer film structure is formed by alternately stacking high refractive index film layers and low refractive index film layers.

Optionally, the extinction layer 12 is a matte surface, and the matte surface is a rough pyramid matte surface, so that the light absorption effect can be achieved. The roughness Ra of the pile surface is more than or equal to 1 mu m, so that the light absorption effect of the pile surface can be ensured.

Preferably, the roughness Ra of the pile surface is 2 μm or more.

The surface morphology of the pile is shown in fig. 10.

Optionally, the laser scanning device includes the MEMS micro mirror with the stray light eliminating function described above. The laser scanning equipment with the MEMS micro-mirror does not need to be provided with an independent extinction piece, has the function of convenient installation, and is beneficial to miniaturization of the laser scanning equipment.

In the embodiment shown in fig. 2,4 and 6, when the MEMS micro-mirror described above is operated, the incident beam (the reflected light is a solid line) irradiated on the reflecting mirror 30 is partially irradiated on the extinction layer 12 positioned on the surface of the frame structure 10, the extinction layer 12 absorbs the incident beam, most of the incident beam is absorbed by the extinction layer 12, and the rest of the incident beam is reflected by the extinction layer 12, and the reflection directions are inconsistent, so as to form diffuse reflection, thereby achieving the purpose of eliminating stray light.

Example 1

In this embodiment, the matting layer 12 is produced by a texturing process.

As shown in fig. 8 to 9, a method for processing a micro mirror for processing the MEMS micro mirror having the stray light eliminating function includes: step S110: selecting an SOI silicon wafer which comprises a device layer, an oxygen burying layer and a substrate layer from top to bottom, and forming a silicon oxide film on the surface of the SOI silicon wafer; step S120: etching the upper surface of the frame structure area corresponding to the device layer to form a suede, wherein the suede is used as the extinction layer 12; step S130: etching the substrate layer to obtain a cavity meeting the movement requirement of the movable structure; step S140: depositing a metal film on the upper surface of the reflector region corresponding to the device layer to obtain a reflecting layer; step S150: and etching the device layer to obtain a movable structure and releasing the movable structure, thereby obtaining the MEMS micro mirror with the stray light eliminating function.

The silicon oxide film is formed on the surface of the SOI silicon wafer, so that the area which is not subjected to texturing etching can be protected, and the function of the structure is not influenced by the texturing process. And the upper surface of the frame structure area can be textured by a texturing process, so that the purpose of light absorption is achieved, and the generation of stray light is reduced. The substrate layer is etched to form a cavity, so that the movable structure can move in the cavity, and the movable structure is ensured to have enough movement space. And a reflecting layer is formed in the reflecting mirror region to achieve the purpose of reflecting light rays, and meanwhile, the reflecting mirror region is distinguished from the frame structure region, so that stray light is reduced.

It should be noted that, firstly, the suede is manufactured through the texturing process, then, the process steps of etching and releasing the movable structure of the device layer are performed, the area for manufacturing the suede is slightly larger than the area of the frame structure, and when the movable structure is etched, the excessive suede area is etched again, so that the whole surface of the frame structure is covered by the suede.

The frame structure region is a region where the frame structure 10 is formed later.

In the uniaxial MEMS micro mirror, the movable structure includes a structure requiring rotation such as the torsion structure 20 and the mirror 30. In contrast, in the biaxial MEMS micro-mirror, the movable structure includes a torsion structure 20, a mirror 30, a movable frame 14, and the like, which need to be rotated. After the structure to be rotated is etched, the cavity connects the upper and lower surfaces of the SOI wafer, and thus serves as the hole structure 11.

As shown in fig. 8, step S120 includes: step S121: forming a photoresist layer with a first preset shape on the upper surface of the device layer except the frame structure area by adopting a photoetching process as a first mask; step S122: etching the upper surface of the device layer to remove the silicon oxide film in the area uncovered by the first mask, so that the upper surface of the frame structure area corresponding to the device layer is exposed; step S123: and performing texturing etching on the SOI silicon wafer, forming a textured surface on the upper surface of the exposed frame structure area, and removing the first mask. A photoresist layer is formed on the upper surface of the device layer to protect the region other than the frame structure region, and then the silicon oxide film at the frame structure region is removed. The etching process needs to etch the upper surface of the whole SOI silicon wafer in the liquid medicine, and as the areas except the frame structure area are protected by the first mask and the silicon oxide film, other positions of the device layer can not be damaged when the suede is formed at the frame structure area, so that other structures can be formed later. Step S120 corresponds to a, b, c in fig. 9.

Specifically, step S123 includes: step S1231: pre-cleaning the SOI silicon wafer in the first liquid medicine; step S1232: the SOI silicon wafer after the pre-cleaning is subjected to texturing in the second liquid medicine; step S1233: alkali washing the textured SOI silicon wafer in the third liquid medicine; step S1234: and (3) pickling the alkali-washed SOI silicon wafer in the fourth liquid medicine to form a suede with the roughness Ra of more than or equal to 1 mu m at the exposed device layer. The first, second, third and fourth liquid medicines are washed to form a suede with a roughness Ra of 1 μm or more, so that the extinction efficiency of the extinction layer 12 is ensured, and the generation of stray light is reduced. The pile surface is obtained by pre-cleaning, pile making, alkali cleaning and acid cleaning.

Specifically, the first medical fluid comprises HDI, H ₂O₂ and KOH. The ratio of HDI, H ₂O₂ and KOH in the first liquid medicine is various, it is necessary to ensure that HDI, H ₂O₂ and KOH are present and that the SOI wafer can be pre-cleaned, and if the concentration of HDI, H ₂O₂ and KOH is low, the corresponding objective can be achieved by extending the residence time in the first liquid medicine. If the concentration of HDI, H ₂O₂ and KOH is high, the corresponding objective can be achieved by shortening the residence time in the first liquid medicine.

The second medical fluid comprises HDI, ADD, TMAH. The HDI, ADD, TMAH ratio in the second solution is various, HDI, ADD, TMAH needs to be ensured and a suede can be formed on the SOI silicon wafer, and if the concentration of HDI, ADD, TMAH is low, the corresponding purpose can be achieved by prolonging the residence time in the second solution. If HDI, ADD, TMAH is high, the corresponding object can be achieved by shortening the residence time in the second liquid medicine.

The third liquid medicine comprises KOH, H ₂O₂ and KOH. The ratios of KOH, H ₂O₂ and KOH in the third solution are various, and it is necessary to ensure that KOH, H ₂O₂ and KOH are present in the solution and that the SOI wafer can be alkali washed, and if the concentrations of KOH, H ₂O₂ and KOH are low, the corresponding objective can be achieved by extending the residence time in the third solution. If the concentrations of KOH, H ₂O₂ and KOH are high, the corresponding object can be achieved by shortening the residence time in the third liquid medicine.

The fourth medical fluid comprises HDI and HF. The ratio of the HDI to the HF in the fourth liquid medicine is various, the HDI and the HF in the liquid medicine are required to be ensured, the SOI silicon chip can be pickled, the corresponding purpose can be achieved by prolonging the residence time in the fourth liquid medicine under the condition that the concentration of the HDI and the HF is low, and the corresponding purpose can be achieved by shortening the residence time in the fourth liquid medicine under the condition that the concentration of the HDI and the HF is high.

As shown in fig. 9, step S130 includes: step S131: forming a photoresist layer with a second preset shape on the lower surface of the substrate layer by adopting a photoetching process as a second mask; step S132: etching the exposed silicon oxide film on the lower surface of the substrate layer to remove the exposed silicon oxide film so as to expose the substrate layer at the uncovered area of the second mask; step S133: and performing dry deep silicon etching on the exposed substrate layer to form a cavity meeting the motion requirement of the movable structure. This arrangement may form a cavity in the lower surface of the substrate layer to enable movement of the movable structure within the cavity. Meanwhile, the second mask can protect the area which does not need etching, and structural integrity is prevented from being damaged. Step S130 corresponds to d and e in fig. 9.

The second preset shape can be designed according to the shape and the position of the cavity, and the cavity can be exposed only by the second preset shape.

As shown in fig. 9, step S140 includes: step S141: removing the second mask, and forming a photoresist layer with a third preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a third mask; step S142: depositing a layer of metal film on the upper surface of the device layer by adopting a magnetron sputtering process; step S143: and removing the third mask and the metal film on the third mask by adopting an organic solvent and matching with ultrasonic waves, and taking the remained metal film as a reflecting layer. The mirror region can be exposed by providing the third mask, forming a metal film on the entire upper surface, then removing the metal film and the third mask with the third mask, and finally leaving only the metal film at the mirror region. Step S140 corresponds to f to h.

Preferably, the metal thin film is an Au film.

The third preset shape may be designed according to the shape of the mirror 30, and only the third preset shape is required to expose the mirror region.

As shown in fig. 9, step S150 includes: step S151: forming a photoresist layer with a fourth preset shape on the upper surface of the device layer by adopting a photoetching process as a fourth mask; step S152: etching silicon oxide of a region of the upper surface of the device layer, which is not covered by the fourth mask, so as to expose part of the device layer, and performing dry deep silicon etching on the exposed part of the device layer to etch a movable structure; step S153: and removing the fourth mask, removing the exposed silicon oxide film and the buried oxide layer on the back surface of the movable structure, and releasing the movable structure to form the MEMS micro mirror with the stray light eliminating function. The arrangement of the fourth mask protects the area which does not need dry deep silicon etching so as to ensure the structural integrity. The movable structure can be released through HF corrosion of silicon oxide to form a complete MEMS micro-mirror, and the MEMS micro-mirror also has the function of eliminating stray light, so that the stray light is effectively reduced. Corresponding to i through k in fig. 9.

The fourth preset shape may be designed according to the shape of the movable structure. In this embodiment, the extinction layer 12 is a textured surface, and the textured surface is a rough surface, and after light is reflected in the textured surface for multiple times, the light is absorbed by the textured surface, so that stray light is eliminated.

The surface morphology of the pile is a pyramid pile as shown in fig. 10, and the tower base size of the pyramid pile is within 2-4 mu m.

It should be noted that the steps described above correspond to those shown in fig. 9 only in a schematic view, and are not in a one-to-one correspondence.

Example two

In the present embodiment, the matting layer 12 is produced by a plating process, unlike the first embodiment.

As shown in fig. 11 and 12, the processing method of the micromirror is used for processing the MEMS micromirror with the stray light eliminating function, and includes: step S210: selecting an SOI silicon chip with a three-layer structure comprising a device layer, an oxygen burying layer and a substrate layer from top to bottom; step S220: forming a light absorption film with a multi-layer film structure on the upper surface of the frame structure region corresponding to the device layer, wherein the light absorption film is used as a extinction layer 12; step S230: etching the substrate layer to form a cavity which meets the movement of the movable structure; step S240: depositing a metal film on the upper surface of the reflector region corresponding to the device layer to form a reflecting layer; step S250: and etching the device layer to obtain a movable structure and releasing the movable structure, thereby obtaining the MEMS micro mirror with the stray light eliminating function.

It should be noted that, the light-absorbing film is first manufactured, then the process steps of etching and releasing the movable structure of the device layer are carried out, the area for manufacturing the light-absorbing film is slightly larger than the area of the frame structure, and when the movable structure is etched, the excessive light-absorbing film area is etched again, so that the light-absorbing film is ensured to cover the surface of the frame structure entirely.

The light absorption film is formed in a film plating mode, so that the purpose of absorbing light can be achieved, and stray light is reduced. The substrate layer is etched to form a cavity, and the movable structure can move in the cavity, so that the movable structure is ensured to have enough movement space. And a reflecting layer is formed in the reflecting mirror region to achieve the purpose of reflecting light rays, and meanwhile, the reflecting mirror region is distinguished from the frame structure region, so that stray light is reduced. The refractive indexes of the film structures of two adjacent layers in the multilayer film structure are different so as to ensure the light absorption efficiency of the light absorption film.

In the uniaxial MEMS micro mirror, the movable structure includes a structure requiring rotation such as the torsion structure 20 and the mirror 30. In contrast, in the biaxial MEMS micro-mirror, the movable structure includes a torsion structure 20, a mirror 30, a movable frame 14, and the like, which need to be rotated. After the structure to be rotated is etched, the cavity connects the upper and lower surfaces of the SOI wafer, and thus serves as the hole structure 11. The frame structure region is the region where the frame structure 10 is last formed, and the mirror region is the region where the mirror 30 is last formed.

As shown in fig. 12, the step S220 includes: step S221: forming a photoresist layer with a first preset shape on the upper surface of the device layer except for the frame structure area by adopting a photoetching process as a first mask; step S222: forming a light absorption film with a multilayer film structure on the upper surface of the SOI silicon wafer by adopting a low-temperature deposition process; step S223: and removing the first mask and the light absorption film on the first mask by adopting an organic solvent and matching with ultrasonic waves, and only leaving the light absorption film in the frame structure area as a extinction layer. A photoresist layer is formed on the upper surface of the device layer to form a protection for the region other than the frame structure region, and then the upper surface of the whole SOI wafer is deposited to form a light absorbing film, wherein the heights of the frame structure region and the region other than the frame structure region are different, so that the subsequent removal of the first mask and the light absorbing film on the first mask at the region other than the frame structure region is facilitated, and only the light absorbing film of the frame structure region is reserved as the light extinction layer 12. Corresponding to a to c in fig. 12.

In step S222, a multilayer film structure in which high refractive index layers and low refractive index layers are alternately deposited is formed by alternately depositing a high refractive index material and a low refractive index material.

It should be noted that the high refractive index material and the low refractive index material are opposite, and only the refractive indexes of two adjacent layers in the multilayer film structure are required to be different.

And then carrying out low-temperature deposition on the frame structure area to form a light absorption film with a multi-layer film structure, wherein the film thickness of each layer is determined by the wavelength of an incident light beam, so that the light absorption effect of the light absorption film is ensured.

As shown in fig. 12, step S230 includes step S231: forming a photoresist layer with a second preset shape on the lower surface of the substrate layer by adopting a photoetching process as a second mask; step S231: and carrying out dry deep silicon etching on the exposed basal layer to form a cavity meeting the movement requirement of the movable structure. Meanwhile, the second mask can protect the area which does not need etching, and structural integrity is prevented from being damaged. Step S230 corresponds to d to e in fig. 12.

As shown in fig. 12, step S240 includes: step S241: removing the second mask, and forming a photoresist layer with a third preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a third mask; step S242: depositing a layer of metal film on the upper surface of the device layer by adopting a magnetron sputtering process; step S243: and removing the third mask and the metal film on the third mask by adopting an organic solvent and matching with ultrasonic waves, and taking the remained metal film as a reflecting layer. The mirror region can be exposed by providing the third mask, then a metal film is formed on the entire upper surface, and finally the metal film and the third mask at the third mask are removed, and finally only the metal film at the mirror region is remained. The third preset shape may be designed according to the shape of the mirror 30, and only the third preset shape is required to expose the mirror region.

Preferably, the metal thin film is an Au film.

As shown in fig. 12, step S250 includes: step S251: forming a photoresist layer with a fourth preset shape on the upper surface of the device layer by adopting a photoetching process as a fourth mask; step S252: carrying out dry deep silicon etching on the device layer at the area which is not covered by the fourth mask so as to etch the movable structure; step S253: and removing the fourth mask, removing the oxygen buried layer on the back surface of the movable structure, and releasing the movable structure to form the MEMS micro mirror with the stray light eliminating function. The arrangement of the fourth mask protects the area which does not need dry deep silicon etching so as to ensure the structural integrity. The movable structure is released through HF corrosion of silicon oxide to form a complete MEMS micro-mirror, and the MEMS micro-mirror also has the function of eliminating stray light, so that the generation of stray light is effectively reduced. Step S240 and step S250 correspond to f to j.

It should be noted that the steps described above correspond to those shown in fig. 12 only in a schematic view, and are not in a one-to-one correspondence.

The fourth preset shape may be designed according to the shape of the movable structure.

In this embodiment, by forming the light absorbing film having a multilayer film structure, incident light irradiated on the frame structure is absorbed by utilizing multiple reflection interference of light within the light absorbing film, eliminating stray light.

In the same way, the process ensures that the light absorption film is formed on the upper surface of the whole MEMS micro mirror frame structure, and the whole thickness is tens of nanometers to hundreds of nanometers because the light absorption film is very thin, the photoetching, etching, coating and other processes in the MEMS process are not affected, and the light absorption film can be arranged in reasonable process steps according to the actual process procedures and process requirements of the MEMS micro mirror device.

Example III

The difference from the first embodiment is that in the present embodiment, the extinction layer 12 is made by laser etching.

As shown in fig. 13 to 22, the processing method for processing the MEMS micro-mirror with the stray light eliminating function includes: step S310: selecting an SOI silicon chip with a three-layer structure comprising a device layer, an oxygen burying layer and a substrate layer from top to bottom; step S320: etching the substrate layer to form a cavity meeting the movement requirement of the movable structure; step S330: depositing a metal film on the upper surface of the reflector region corresponding to the device layer to form a reflecting layer; step S340: etching the device layer to obtain a movable structure and releasing the movable structure to obtain an intermediate structure; step S350: and carrying out laser etching on the frame structure region of the intermediate structure to form an extinction layer, thereby obtaining the MEMS micro mirror with the stray light eliminating function.

The concave-convex structure is formed on the surface of the frame structure through laser etching, so that the purpose of absorbing light is achieved, and stray light is reduced. The base layer is etched to form a cavity within which the movable structure is capable of moving. A reflecting layer is formed in the reflecting mirror area to achieve the purpose of reflecting light rays, and meanwhile the reflecting mirror area is distinguished from the frame structure area, so that stray light is reduced. The extinction layer 12 is formed by laser etching the frame structure region, so that the purpose of absorbing light can be achieved, and stray light is eliminated.

Specifically, step S320 includes: step S321: forming a photoresist layer with a first preset shape on the lower surface of the substrate layer by adopting a photoetching process as a first mask; step S322: and carrying out dry deep silicon etching on the exposed basal layer to form a cavity meeting the movement requirement of the movable structure. Under the action of the first mask, the area which does not need etching is protected, and the structural integrity is prevented from being damaged.

Meanwhile, the second mask can protect the area which does not need etching, and structural integrity is prevented from being damaged.

Specifically, step S330 includes: step S331: removing the first mask, and forming a photoresist layer with a second preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a second mask; step S332: depositing a layer of metal film on the upper surface of the SOI silicon wafer by adopting a magnetron sputtering process; step S333: and removing the second mask and the metal film on the second mask by adopting an organic solvent and matching with ultrasonic waves, and taking the remained metal film as a reflecting layer. The mirror region can be exposed by providing the second mask, then forming a metal film on the entire upper surface, then removing the metal film and the second mask with the second mask, and finally leaving only the metal film at the mirror region.

The second preset shape may be designed according to the shape of the mirror 30, and only the second preset shape is required to expose the mirror region.

Preferably, the metal thin film is an Au film.

Specifically, step S340 includes: step S341: removing the second mask, and forming a photoresist layer with a third preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a third mask; step S342: carrying out dry deep silicon etching on the device layer which is not covered by the third mask so as to etch the movable structure; step S343: and removing the third mask, removing the buried oxide layer on the back surface of the movable structure, and releasing the movable structure to form an intermediate structure. The arrangement of the third mask protects the area which does not need dry deep silicon etching so as to ensure the structural integrity. The movable structure can be released by HF etching of the back side silicon oxide to form an intermediate structure.

It should be noted that the third preset shape may be designed according to the shape of the movable structure.

Specifically, in step S350, a frame structure region of the intermediate structure is etched by using laser to form an uneven structure, and the uneven structure is used as a extinction layer. The surface of the concave-convex structure is provided with a rough surface, so that the light absorption effect of the frame structure area is improved.

The diameter of the micro pits formed on the intermediate structure by the laser is 6 μm or more and 15 μm or less.

In the process of etching the frame structure region of the intermediate structure by laser to form the concave-convex structure 40, the concave-convex structure 40 is used as a extinction layer, the whole surface of the frame structure 10 is etched to ensure that the concave-convex structure 40 is formed on the whole surface.

Specifically, in the process of etching the frame structure region of the intermediate structure by laser to form the concave-convex structure 40, the concave-convex structure 40 is used as a matting layer, the etching time of the laser is controlled to obtain a roughness Ra of 1 μm or more and a depth of 2 μm or more. This effectively ensures the absorption of light by the matting layer 12.

Preferably, the concave-convex structure 40 having a roughness Ra of 1 μm or more and a depth of 4 μm or more and 12 μm or less is obtained.

The relief structure 40 is realized by laser machining, wherein a laser beam is scanned across the surface of the frame structure 10 to form the relief structure 40. The surface of the concave-convex structure 40 processed by laser on monocrystalline silicon is covered with silicon dioxide filiform slag generated in the processing process of silicon, as shown in fig. 16, the irregular slag which is porous increases the surface roughness of the extinction layer 12, greatly improves the light absorption capacity of the extinction layer 12, increases the reflection times of light beams in the concave-convex structure 40, and uniformly reflects outgoing light beams to surrounding space to form diffuse reflection, thereby eliminating stray light.

In the specific embodiment shown in fig. 17, in the process of etching the frame structure region of the intermediate structure with laser to form the concave-convex structure 40, the frame structure region is continuously etched with laser along a serpentine shape in the course of using the concave-convex structure 40 as the extinction layer. This ensures that the entire frame structure region is etched while controlling the power of the laser to ensure the size of the relief structure 40 formed on the frame structure region, thereby ensuring the extinction effect of the extinction layer 12.

As shown in fig. 17, when the concave-convex structure 40 is processed by the continuous laser, the etching track of the continuous laser is serpentine, and the distance g between two adjacent etching tracks is smaller than the profile diameter d of the beam of the continuous laser. The continuous laser processing is performed in order to have the path of the laser follow a serpentine motion along the surface of the frame structure 10 so that the continuous laser can etch the entire surface of the matting layer 12 to form the relief structure 40 over the entire surface.

Of course, the continuous laser may be etched directly on the surface of the frame structure 10 to form a surface having the relief structure 40, the relief structure 40 acting as the matting layer 12.

The relief structure 40 is machined by continuous laser beam etching of the surface of the frame structure 10.

In the particular embodiment shown in fig. 18, a laser is used to first continuously etch the frame structure area from one side along the serpentine and then to continuously etch the frame structure area from an adjacent side along the serpentine. In this embodiment, the frame structure region is etched from two different directions to ensure that the concave-convex structure 40 can be formed on the frame structure region, and ensure the extinction effect at the frame structure region.

As shown in fig. 18, the etching track of the continuous laser beam may be a double-layer serpentine track, the second layer etching track (dashed line) is perpendicular to the first layer etching track, and the distance g between two adjacent tracks is smaller than the diameter d of the profile of the laser beam processing profile, so as to ensure that the surface of the entire frame structure 10 is processed.

In the specific embodiment shown in fig. 21 and 22, a first etching pit formed by a layer of tangent micro pits is formed by laser in a point etching mode, and a second etching pit is formed by performing point etching on a plurality of unetched areas surrounded by a plurality of first etching pits. The arrangement can also ensure that the frame structure areas are etched by laser, and effectively reduce the generation of stray light.

The first etching pit is formed by a plurality of micro pits when the laser etches the first layer, and the second etching pit is formed by a plurality of micro pits when the laser etches the second layer. Or, the point etching is performed layer by layer, the first layer structure formed in the first etching is a first etching pit, and the second layer structure formed in the second etching is a second etching pit.

In the specific embodiment shown in fig. 19 and 20, a first etching pit formed by tangential micro pits is formed by laser in a spot etching manner, and a second etching pit is formed by taking the tangential point of two adjacent micro pits in the first etching pit as the etching center. The arrangement can also ensure that the frame structure areas are etched by laser, and effectively reduce the generation of stray light.

Specifically, the relief structure 40 is formed by stacking micro pits formed on the extinction layer 12 each time by pulse laser light during pulse laser processing.

In the embodiment shown in fig. 19 and 20, the concave-convex structure 40 is formed by overlapping micron-sized circular micro-pits processed by pulse laser, the circular micro-pits can be overlapped with each other to form a nested pattern, four second micro-pits 60 are nested around one first micro-pit 50, and four pit edges are coincident with the circle centers of the first micro-pits 50.

In the embodiment shown in fig. 21, the concave-convex structure 40 is formed by overlapping micro-scale circular micro-pits processed by pulse laser, as shown in fig. 21, the circular micro-pits are overlapped to form a sequential arrangement pattern, the pattern is divided into two layers, the first micro-pits 50 are sequentially arranged into one layer, the second micro-pits 60 are also sequentially arranged into one layer, and the center of the second micro-pit 60 is positioned at the center of the left gap of the first micro-pits 50.

In the specific embodiment shown in fig. 22, the concave-convex structure 40 is formed by overlapping micron-sized circular micro pits processed by pulse laser, the circular micro pits are overlapped to form a close-packed pattern, the pattern is divided into three layers, the first micro pits 50 are arranged into a first layer, and six circular first micro pits 50 are arranged around one circular first micro pit 50. The second micro pits 60 are arranged in a layer of the second layer, the second micro pits 60 are most densely arranged, and the center of the second micro pits 60 is located at the center of the void left by a part of the first micro pits 50. The third micro pits 70 are arranged in a layer of a third layer, the third micro pits 70 are arranged most densely, and the center of the third micro pit 70 is positioned at the center of a gap left by the micro pits of the remaining first layer.

During laser processing, part of slag splashes out of the frame structure area and falls on the reflector area to cause mirror surface pollution, and in the processing process, flowing gas is adopted to blow off pollutants on the mirror surface, and after processing, ultrasonic/megasonic cleaning is performed on the chip to ensure the smoothness of the reflector 30.

Fig. 14 to 16 are SEM pictures of the extinction layer 12 formed on the upper surface of the MEMS micro-mirror frame structure 10 using a laser etching method. Fig. 14 is a front view of the entire upper surface of the frame structure 10 being laser etched without exposed polished surfaces. FIG. 15 is a cross-sectional view showing that the maximum height difference of laser etching is 8-9 μm. Fig. 16 is an enlarged front view, the surface of the microstructure etched by laser is covered with silicon dioxide filiform slag generated in the processing process of silicon, the irregular slag with porous shape increases the surface roughness of the extinction layer 12, greatly improves the light absorption capacity of the extinction layer, increases the reflection times of light beams in the concave-convex structure 40, and uniformly reflects the emergent light beams to the surrounding space to form diffuse reflection, thereby eliminating stray light.

The diameter d of the round micro-pit structure formed by the single micro-pit on the surface of the intermediate structure is between 6 and 15 mu m, and the depth is between 4 and 12 mu m. The preferred circular micro-pits should have a diameter d between 10-12 μm and a depth between 8-10 μm. The pit diameter d is too small, the processing efficiency is reduced, batch processing is not facilitated, the pit diameter d is too large, the etching selectivity is poor, when the edge of a frame structure area is etched, other structures such as a reflecting mirror, a torsion structure and a torsion driver nearby are easily damaged, the distance between the frame structure 10 and the other structures is usually 30 mu m, the maximum alignment error of laser etching is not more than 20 mu m,20+d/2 mu m is less than 30 mu m, and other structures cannot be damaged. The micro-pit depth h is too small, the extinction effect becomes poor, and too large influences the strength of the frame structure 10.

The surface roughness Ra value of the matting layer 12 formed by laser etching should be greater than 1 μm, and a preferable surface roughness Ra value should be greater than 1.5 μm.

In the laser etching process, it is required to ensure that the upper surface of the frame structure is entirely etched, requiring the laser beam to sweep across the entire surface to be etched.

Claims

1. A MEMS micro-mirror having a stray light eliminating function, comprising:

a frame structure (10), the upper surface of the frame structure (10) being provided with a matting layer (12), the frame structure (10) having a hole structure (11);

-a torsion structure (20), the torsion structure (20) being arranged at the hole structure (11), and at least a portion of the torsion structure (20) being connected with the hole wall of the hole structure (11);

-a mirror (30), the torsion structure (20) supporting the mirror (30);

The extinction layer (12) is a concave-convex structure (40), the depth of the concave-convex structure (40) is more than or equal to 2 mu m and less than or equal to 12 mu m, the surface of the concave-convex structure (40) is a rough surface, and the roughness Ra of the concave-convex structure (40) is more than or equal to 1 mu m;

the extinction layer (12) is manufactured by laser etching, and the upper surface of the frame structure (10) is etched completely.

2. MEMS micro-mirror with stray light cancellation function according to claim 1, characterized in that the frame structure (10) comprises a fixed frame (13) and a movable frame (14), the fixed frame (13) has the hole structure (11), the movable frame (14) is accommodated at the hole structure (11), and the movable frame (14) has a central through hole, the mirror (30) is positioned at the central through hole, the torsion structure (20) comprises a mirror torsion structure and a frame torsion structure, the mirror torsion structure is connected with the movable frame (14) and the mirror (30), the frame torsion structure is connected with the hole wall of the hole structure (11) and the movable frame (14), so that the movable frame (14) drives the mirror (30) to rotate.

3. A laser scanning apparatus characterized by comprising the MEMS micro-mirror with a stray light eliminating function as claimed in any one of claims 1 to 2.

4. A method for processing the micro-mirror, characterized in that it is used for processing the MEMS micro-mirror with stray light eliminating function according to any one of claims 1 to 2, the method for processing the micro-mirror comprising:

Step S310: selecting an SOI silicon chip with a three-layer structure comprising a device layer, an oxygen burying layer and a substrate layer from top to bottom;

step S320: etching the substrate layer to form a cavity meeting the movement requirement of the movable structure;

Step S330: depositing a metal film on the upper surface of the reflector region corresponding to the device layer to form a reflecting layer;

step S340: etching the device layer to obtain a movable structure and releasing the movable structure to obtain an intermediate structure;

Step S350: and performing laser etching on the upper surface of the frame structure area of the intermediate structure to form an extinction layer, thereby obtaining the MEMS micro-mirror with the stray light eliminating function.

5. The method of claim 4, wherein the step S320 comprises:

Step S321: forming a photoresist layer with a first preset shape on the lower surface of the substrate layer by adopting a photoetching process as a first mask;

Step S322: and carrying out dry deep silicon etching on the exposed substrate layer to form a cavity meeting the movement requirement of the movable structure.

6. The method of fabricating a micromirror according to claim 5, wherein the step S330 comprises:

step S331: removing the first mask, and forming a photoresist layer with a second preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a second mask;

Step S332: depositing a layer of metal film on the upper surface of the SOI silicon wafer by adopting a magnetron sputtering process;

step S333: and removing the second mask and the metal film on the second mask by adopting an organic solvent and matching with ultrasonic waves, wherein the remained metal film is used as a reflecting layer.

7. The method of claim 6, wherein the step S340 includes:

Step S341: removing the second mask, and forming a photoresist layer with a third preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a third mask;

Step S342: carrying out dry deep silicon etching on the device layer which is not covered by the third mask so as to etch a movable structure;

Step S343: and removing the third mask, removing the buried oxide layer on the back surface of the movable structure, and releasing the movable structure to form the intermediate structure.

8. The method according to claim 4, wherein in the step S350, the upper surface of the frame structure region of the intermediate structure is etched by laser to form a concave-convex structure, and the concave-convex structure is used as the extinction layer.

9. The method of fabricating a micromirror as defined in claim 8, wherein, in the etching of the upper surface of the frame structure region of the intermediate structure with laser to form the concave-convex structure, the concave-convex structure is used as the extinction layer,

The power, spot size and scanning speed of the laser are controlled to obtain a concave-convex structure with a roughness Ra of 1 μm or more and a depth of 2 μm or more and 12 μm or less.

10. A method of fabricating a micromirror according to claim 8, wherein the frame structure region of the intermediate structure is etched with a laser to form a relief structure, which is scanned over the entire upper surface of the frame structure (10) during the process of functioning as the extinction layer.