CN114035253A

CN114035253A - MEMS (micro-electromechanical system) micro-mirror with stray light elimination function, laser scanning equipment and manufacturing method of micro-mirror

Info

Publication number: CN114035253A
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: 2022-02-11

Abstract

The invention provides an MEMS (micro-electromechanical system) micro-mirror with a stray light elimination function, laser scanning equipment and a manufacturing method of the micro-mirror. A MEMS micro-mirror with stray light elimination, comprising: the surface of the frame structure is provided with a light extinction layer, and the frame structure is provided with a hole structure; the torsional structure is arranged at the hole structure and is connected with the hole wall of the hole structure; a mirror, the torsional structure supporting the mirror. The invention solves the problem of stray light of the MEMS micro-mirror in the prior art.

Description

MEMS (micro-electromechanical system) micro-mirror with stray light elimination function, laser scanning equipment and manufacturing method of micro-mirror

Technical Field

The invention relates to the field of micro-opto-electromechanics, in particular to an MEMS (micro-electromechanical system) micro-mirror with a stray light elimination function, laser scanning equipment and a manufacturing method of the micro-mirror.

Background

With the development and progress of technology, it is desirable that the light manipulation device has 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 of the relevant personnel. At present, the MEMS micro-mirror is already 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 the MEMS micro-mirror often determines the performance of the whole device.

When the existing MEMS micro-mirror works, light beams generated by a light source irradiate on a reflecting mirror surface of the micro-mirror, are reflected by the reflecting mirror surface and then are emitted, and the light beams can be projected to different positions of a target area by rotating the reflecting mirror surface, so that the aim of light beam manipulation is fulfilled. In the MEMS micro-mirror, except the reflecting mirror surface, the mirror surface torsion structure and the driver for driving the mirror surface to rotate around the mirror surface torsion structure, a frame structure is also arranged for supporting and fixing the above structures, so that the firmness is increased, and simultaneously, the clamping of a micro-mirror chip is facilitated. When the MEMS micro-mirror chip is designed, in order to ensure the size of the critical micro-structure (torsion beam and driver), the frame structure needs to surround other structures, and the distance between the frame structure and the other structures cannot be too large, so that the process size with larger difference is prevented from occurring, and the precision of the critical size is not influenced. Therefore, 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 light beam is directed to the reflective mirror surface, because the light beam is not an ideal parallel light beam, a portion of the light beam at the periphery of the light beam is directed to the frame structure located around the reflective mirror surface, and the surface of the frame structure is a polished surface, after the light beam is reflected by the polished surface, the light beam forms stray light in the projection range, which affects the use of the micromirror.

Fig. 24 shows a biaxial electrostatic comb-tooth driven MEMS micro-mirror (from the article "High-Q MEMS detectors for laser beam scanning displays"), in which 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 a torsion beam thereof rotate together with the movable frame to implement 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 projected pattern of the biaxial MEMS micro-mirrors in a projected line display application. When the MEMS micro-mirror works, a light beam projected on the reflecting mirror surface forms a visible two-dimensional image in a field range through the reflection of the two-dimensional scanning mirror surface, a light beam projected on the movable frame forms a vertical bright line in the field range through the reflection of the vertically scanning movable frame, and a light beam projected on the fixed frame forms a static bright spot in the field range through the reflection of the fixed frame. The movable frame and the fixed frame reflect vertical bright lines and bright spots formed in the visual field range, which deteriorate the display quality and seriously affect the image quality. In addition, in the projection display, besides the stray light formed by reflection of the frame structure, the bright spot formed by reflection of the incident light beam by the window glass used for packaging the MEMS micro-mirror is also an important factor influencing the imaging quality, and the oblique window glass disclosed in the U.S. patent (US2009/0097087a1) reflects the light spot generated by the window glass out of the visual field range, thereby solving the interference of the window glass on the image display. However, the influence of stray light generated by the frame structure is difficult to be effectively eliminated.

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

In laser printing application, laser beams containing text and image information are projected on a reflecting mirror surface of a single-axis electromagnetic drive MEMS (micro-electromechanical systems) micro-mirror, an external drive magnetic circuit (composed of a drive coil, an iron core and an iron yoke) drives an electromagnetic drive permanent magnet to drive the reflecting mirror surface to rotate around a torsion structure of the reflecting mirror surface, so that the reflecting mirror surface reflects the beams to different positions of a photosensitive selenium drum to form a shallow image on the selenium 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 a static bright spot on the toner cartridge, and the static bright spot is always irradiated by the laser beam when the laser is turned on, and finally the static bright spot is always printed, so that a vertical black line is formed on printing paper.

In order to eliminate stray light generated by the frame structure, the MEMS micromirror disclosed in US patent (US7072089B2) (as shown in fig. 26 and 27) greatly reduces the area of the frame structure, and reduces it to the anchor point of the twisted structure of the two reflective mirror surfaces, so that it is far away from the reflective mirror surfaces, and avoids the irradiation of the periphery of the light beam. Although the stray light generated by the frame structure is eliminated, the stray light generated by the light beam irradiating on other structures such as a driving magnetic circuit positioned behind the MEMS micro-mirror is still avoided. In addition, the critical dimension is difficult to guarantee due to large-area etching, the frame structure becomes fragile due to the reduction of the dimension, the supporting and fixing effects are greatly weakened, force application points can only be two anchor points of the chip in the clamping, transferring and installing processes of the chip, the reflector surface torsion structure with the tiny dimension (from micron level to submicron level) can bear more gravity from the chip and the adhesion force between the chip and a placing plane, the acting force caused by incomplete synchronization of the acting forces of the two anchor points in the clamping, transferring and installing processes of the chip increases the damage risk of the reflector surface torsion structure.

In the application of laser radar, the sensitivity of a laser receiving detector is very high, the laser receiving detector can respond to stray light formed by an MEMS micro-mirror frame structure, and a near return light signal is easily submerged in the stray light, so that an effective signal cannot be received, and a visual field blind area is generated near. In the laser radar disclosed in the invention patent (CN110045498A), a light-absorbing member (as shown in fig. 28) coated with a light-absorbing or light-reflecting material is disposed in front of a reflector substrate (frame structure), so as to reduce stray light generated on the reflector substrate, eliminate interference of the stray light on near signals, and improve the receiving and detecting range of the radar. However, as shown in fig. 29, the extinction member is mounted on the front surface of the reflector, the height h of the extinction member needs to be determined according to the incident light angle α and the radius difference d between the diaphragm and the reflector and mounted at an accurate position, the mounting difficulty is high, and in order not to affect the main light spot, a margin is inevitably left for the processing error of each structural member, the incident angle error of the laser, and the mounting error. In addition, in order to not block the light path, the incident light is generally emitted from the side direction, the extinction member cannot block the incident light directly irradiating on the reflection mirror surface, the radius of the diaphragm is larger than that of the reflection mirror (radius difference d), the peripheral light beam may 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 generated by the frame structure irradiated by the light beam from the periphery of the light beam seriously affects the usage of the MEMS micro-mirror. Related technicians realize the elimination of stray light by a method of greatly reducing the area of a frame structure and arranging an extinction piece, but also introduce the problems of increased risk of chip damage, increased assembly difficulty and the like. Therefore, it is desirable to realize a MEMS micromirror with stray light elimination that avoids the problems associated with the above method while eliminating stray light.

Disclosure of Invention

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

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

Furthermore, 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 reflector is located at 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 reflector, 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 reflector 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 rough, and the roughness Ra of the concave-convex structure is more than or equal to 1 mu m.

Furthermore, the matte layer is a matte surface, and the roughness Ra of the matte surface is more than or equal to 1 mu m.

Further, the extinction layer is an extinction 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 micromirror having the stray light elimination function described above.

According to another aspect of the present invention, there is provided a method for processing a micro mirror, which is used for processing the MEMS micro mirror with the stray light elimination function, the method for processing the micro mirror includes: step S110: selecting an SOI silicon wafer comprising 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 region corresponding to the device layer to form a suede surface which is used as an 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 area 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 elimination 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 region by adopting a photoetching process to serve 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 as to expose the upper surface of the frame structure area corresponding to the device layer; step S123: etching the SOI silicon wafer to form a textured surface on the upper surface of the exposed frame structure region, and removing the first mask.

Further, step S123 includes: step S1231: pre-cleaning an SOI silicon wafer in a first liquid medicine; step S1232: etching the pre-cleaned SOI silicon wafer in a second liquid medicine; step S1233: alkali washing the textured SOI silicon wafer in a third liquid medicine; step S1234: pickling the alkali-washed SOI silicon wafer in a fourth liquid medicine; so as to form a suede surface with the roughness Ra of more than or equal to 1 mu m on 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 to serve 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 in the area uncovered by the second mask; step S133: and carrying out 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 in 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 remaining 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 to serve as a fourth mask; step S152: etching the silicon oxide in the area, which is not covered by the fourth mask, on the upper surface of the device layer to expose the part of the device layer, and performing dry deep silicon etching on the exposed part of the device layer to etch out a movable structure; step S153: and removing the fourth mask, removing the exposed silicon oxide film and the buried oxide layer on the back of the movable structure, releasing the movable structure, and forming the MEMS micro-mirror with the stray light elimination function.

According to another aspect of the present invention, there is provided a method for processing a micro mirror, which is used for processing the MEMS micro mirror with the stray light elimination function, the method for processing the micro mirror 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 multilayer film structure on the upper surface of the frame structure area corresponding to the device layer, wherein the light absorption film is used as a light extinction layer; step S230: etching the substrate layer to form a cavity which meets the motion 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 elimination 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 region by adopting a photoetching process as a first mask; step S222: forming a light absorption film with a multi-layer film structure on the upper surface of the SOI silicon chip 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 light 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 to serve as a second mask; step S231: and carrying out dry deep silicon etching on the exposed substrate layer to form a cavity meeting the motion 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 remaining 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 to serve as a fourth mask; step S252: performing dry deep silicon etching on the device layer in the region not covered by the fourth mask to etch a movable structure; step S253: and removing the fourth mask, removing the buried oxide layer on the back of the movable structure, releasing the movable structure and forming the MEMS micro-mirror with the stray light elimination function.

According to another aspect of the present invention, there is provided a method for processing a micro mirror, which is used for processing the MEMS micro mirror with the stray light elimination function, the method for processing the micro mirror 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 area of the intermediate structure to form a light eliminating 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 substrate layer to form a cavity meeting the motion 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 remaining 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: performing dry deep silicon etching on the device layer which is not covered by the third mask 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, releasing the movable structure and forming the intermediate structure.

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

Further, in the process that the surface of the frame structure area of the intermediate structure is etched by adopting laser to form a concave-convex structure, and 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 being more than or equal to 1 μm and the depth being more than or equal to 2 μm.

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

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

The extinction layer is arranged on the frame structure, has a certain absorption effect on light beams, reduces the reflection of the extinction layer on light rays, and effectively reduces the generation of stray light. At least a part of the torsional structure is connected with the wall of the hole structure, and the torsional structure is connected with the reflector and/or the movable frame, supports the reflector and/or the movable frame, and rotates around the torsional 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 elimination function can completely cover the frame structure, and the exposed polished surface is not irradiated by incident 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 in order to eliminate the stray light, and the design flexibility of the MEMS micro-mirror is increased.

(2) The extinction layer formed by laser etching has strong selectivity, the non-etching surface does not need to be covered and protected, the extinction layer can be formed after other manufacturing processes of the MEMS micro-mirror are finished, the manufacturing of the MEMS micro-mirror is not influenced, the surface roughness is obviously increased due to the filamentous slag formed on the surface, and the extinction effect is improved.

(3) The texture surface making process and the light absorption film forming extinction layer are completely compatible with the MEMS micro-mirror manufacturing process, can be integrated into the MEMS micro-mirror manufacturing process, and do not increase the process difficulty.

(4) The extinction effect is good, the reflectivity of the rough microstructure surface and the pyramid texture surface can be less than 14%, the light absorption film is diffuse reflection, 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 incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 illustrates a schematic structural diagram of a MEMS micro-mirror in accordance with an alternative embodiment of the present invention;

FIG. 2 is a schematic diagram showing the path of reflection of light by the MEMS micro-mirror of FIG. 1;

FIG. 3 illustrates a schematic structural diagram of a MEMS micro-mirror in accordance with another alternative embodiment of the present invention;

FIG. 4 is a schematic diagram showing the reflected path of light from the MEMS micro-mirror of FIG. 3;

FIG. 5 illustrates a schematic structural diagram of a MEMS micro-mirror in accordance with another alternative embodiment of the present invention;

FIG. 6 is a schematic diagram showing the path of reflection of light by the MEMS micro-mirror 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 micro mirror according to a first embodiment of the present invention;

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

FIG. 10 shows a surface topography of an extinction layer of 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 view showing a process of fabricating a micromirror according to a second embodiment of the invention;

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

fig. 14 shows an SEM image of the front surface of the extinction layer in example three of the present invention;

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

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

FIG. 17 shows a moving path of a continuous laser in a 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 the positional relationship of the first micro-pits and the second micro-pits in FIG. 19;

fig. 21 is a schematic view showing another overlapping manner of spots of the pulsed laser according to the third embodiment of the present invention;

fig. 22 is a schematic view showing another overlapping manner of spots of the pulsed laser according to the third embodiment of the present invention;

FIG. 23 is a schematic diagram showing the reflection of light by a MEMS micro-mirror in the prior art;

FIG. 24 is a schematic structural diagram of a two-axis MEMS micro-mirror in the prior art;

FIG. 25 is a schematic diagram illustrating stray light generated by the two-axis MEMS micro-mirror of FIG. 24;

FIG. 26 is a schematic view showing another MEMS micro-mirror in the prior art;

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

FIG. 28 is a schematic diagram of a MEMS micro-mirror in the prior art;

fig. 29 is a schematic diagram showing the reflection of light by the MEMS micro-mirror of fig. 28.

Wherein the figures include the following reference numerals:

10. a frame structure; 11. a pore structure; 12. a matte layer; 13. a fixed frame; 14. a movable frame; 20. a torsion structure; 30. a mirror; 40. a relief structure; 50. a first micro-pit; 60. a second micro-pit; 70. and a third micro-pit.

Detailed Description

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

In order to solve the problem of stray light of 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 the stray light elimination function includes: the device comprises a frame structure 10, a torsion structure 20 and a reflector 30, wherein the upper surface of the frame structure 10 is provided with an extinction layer 12, 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 torsional 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 light rays is reduced, and the generation of stray light is effectively reduced. The torsional structure 20 is connected to the wall of the hole structure 11, while the torsional structure 20 is connected to the mirror 30 to support the mirror 30, and the mirror 30 rotates around the torsional structure 20.

It should be noted that the hole structure 11 may be a through hole or a blind hole.

In the particular embodiment shown in fig. 1 to 4, the frame structure 10 is fixed 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 rotates the mirror 30. It should be noted that, 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, the movable frame 14 moves around the frame torsion structure, and then the mirror 30 is moved. 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.

Note that the fixed frame 13 is stationary.

Fig. 6 is a schematic diagram of the operation of the dual-axis MEMS micro-mirror with stray light elimination, in which the central part of the incident light beam irradiates on the reflector 30, and is reflected by the reflector 30 and then emitted, the reflector 30 rotates around the mirror surface torsion structure, the movable frame 14 rotates around the frame torsion structure, and the emission angles of the emitted light beams respectively deviate toward the rotation directions of the reflector 30 and the movable frame 14, thereby implementing two-dimensional manipulation of the light beam. The peripheral part of the incident beam irradiates on the extinction layer 12 around the reflector 30 and the extinction layer 12 around the movable frame 14, the extinction layer 12 has an absorption effect on the incident beam, most of the incident beam is absorbed by the extinction layer 12, the rest part of the incident beam is reflected by the extinction layer 12, the reflection directions are different, and diffuse reflection is formed on the extinction layer 12, so that the purpose of eliminating stray light is achieved. Specifically, the surface of the matte layer 12 on the side away from the frame structure 10 is a rough surface, and the roughness Ra of the rough surface is greater than or equal to 1 μm. 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 strike 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 at various positions on the rough surface, diffuse reflection is formed on the rough surface, and the light rays reflected by the reflector 30 are not influenced due to different reflection angles of the reflector 30.

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 relatively smooth and easily reflects light to form stray light. The roughness Ra is limited within the range of more than 1 mu m, the stray light effect of the extinction layer 12 is reduced, the manufacturing difficulty is reduced, and the manufacturing cost is saved.

As shown in fig. 7, the matte layer 12 has a relief structure 40. By arranging the concave-convex structure 40 on the surface of the frame structure, when light beams irradiate the extinction layer 12, the light beams enter the concave part of the concave-convex structure 40 and are reflected back and forth at the concave part to absorb the light beams, so that the reflection of the extinction layer 12 to the light beams 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 the light beams are reflected multiple times in the concave-convex structure 40, and the rest is reflected in different directions to form diffuse reflection, so that stray light is eliminated.

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

Specifically, the depth of the concave-convex structure 40 is greater than or equal to 2 μm, 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 not less than 4 μm and not more than 12 μm. If the depth of the concave-convex structure 40 is less than 4 μm, the depth of the concave-convex structure 40 is too small, and when the light enters the concave portion, the light is easily reflected 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, which increases the manufacturing cost. The depth of the concave-convex structure 40 is limited within the range of 4-12 μm, so that the manufacturing difficulty and the manufacturing cost are reduced while stray light is reduced.

As shown in fig. 7, the convex structure in the concave-convex structure 40 is a cone-shaped structure, and the convex structure is pointed, so that light that strikes the front surface of the convex structure is less, direct reflection of the concave-convex structure 40 to light is reduced, absorption of the concave-convex structure 40 to light is increased, and generation of 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 light extinction layer 12 is a light absorption film having a multilayer film structure. The extinction layer 12 is a light absorption film which can absorb light to reduce the reflection of light, so as to achieve the extinction effect and further reduce the generation of 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 textured surface, and the textured surface is a rough pyramid textured surface, which can absorb light. The roughness Ra of the suede is more than or equal to 1 mu m, so that the absorption effect of the suede to light can be ensured.

Preferably, the roughness Ra of the suede is greater than or equal to 2 μm.

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

Optionally, the laser scanning apparatus comprises the MEMS micro-mirror with stray light elimination 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 the miniaturization of the laser scanning equipment.

In the specific embodiment shown in fig. 2, 4 and 6, when the MEMS micro-mirror operates, a part of the incident light beam (the reflected light beam is a solid line) irradiated on the outer side of the incident light beam (the reflected light beam is a dashed line) irradiated on the extinction layer 12 on the surface of the frame structure 10, the extinction layer 12 has an absorption effect on the incident light beam, most of the incident light beam is absorbed by the extinction layer 12, and the rest of the incident light beam is reflected by the extinction layer 12, and the reflection directions are not the same, so as to form a diffuse reflection, thereby achieving the purpose of eliminating the stray light.

Example one

In this embodiment, the matte layer 12 is made by a texturing process.

As shown in fig. 8 to 9, the method for processing a micromirror is used to process the MEMS micromirror with stray light elimination function, and the method for processing a micromirror comprises: step S110: selecting an SOI silicon wafer comprising 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 region corresponding to the device layer to form a suede surface, wherein the suede surface is used as an 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 area 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 elimination function.

The silicon oxide film is formed on the surface of the SOI silicon wafer, so that the region which is not subjected to texturing etching can be protected, and the function of the part of structure is not influenced by the texturing process. And a suede surface can be formed on the upper surface of the frame structure region through a texturing process so as to achieve the purpose of light absorption and reduce the generation of stray light. And etching the substrate layer 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 reflector region to achieve the purpose of reflecting light, and the reflector region is distinguished from the frame structure region, so that the generation of stray light is reduced.

It should be noted that, the matte is firstly manufactured through a matte manufacturing process, and then the process steps of etching and releasing the movable structure of the device layer are performed, the area for manufacturing the matte is slightly larger than the area of the frame structure, and the extra matte area is etched again when the movable structure is etched, so as to ensure that the matte completely covers the surface of the frame structure.

It should be noted that the frame structure region is a region where the frame structure 10 is subsequently formed.

In the uniaxial MEMS micromirror, the movable structure includes a structure requiring rotation, such as the torsion structure 20 and the mirror 30. In the biaxial MEMS micro-mirror, the movable structure includes the torsion structure 20, the mirror 30, and the movable frame 14, which need to be rotated. After the structure to be rotated is etched, the cavity connects the upper and lower surfaces of the SOI silicon wafer to form 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 region by adopting a photoetching process to serve 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 as to expose the upper surface of the frame structure area corresponding to the device layer; step S123: etching the SOI silicon wafer to form a textured surface on the upper surface of the exposed frame structure region, and removing the first mask. And forming a photoresist layer on the upper surface of the device layer to protect the region except the frame structure region, and then removing the silicon oxide film at the frame structure region. The upper surface of the whole SOI silicon chip is required to be put into liquid medicine for etching in the texturing etching process, and due to the fact that the first mask and the silicon oxide film are arranged in the region except the frame structure region for protection, when the texturing is formed in the frame structure region, other positions of the device layer cannot be damaged, and other structures can be formed conveniently in the follow-up process. Step S120 corresponds to a, b, c in fig. 9.

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

Specifically, the first liquid medicine comprises HDI and H₂O₂And KOH. HDI and H in the first liquid medicine₂O₂The ratio of KOH and HDI is in various cases, and HDI and H are required to be ensured₂O₂And KOH and can pre-clean the SOI silicon wafer if HDI and H₂O₂When the concentration of KOH and KOH is low, the residence time in the first chemical solution can be prolonged to achieve the corresponding object. If HDI, H₂O₂When the concentration of KOH and KOH is high, the residence time in the first chemical solution can be shortened to achieve the corresponding object.

The second medicinal liquid comprises HDI, ADD, and TMAH. The proportion of HDI, ADD and TMAH in the second liquid medicine is various, the HDI, ADD and TMAH are required to be ensured, and the suede can be formed on the SOI silicon wafer. If the concentrations of HDI, ADD and TMAH are high, the corresponding purpose can be achieved by shortening the retention time in the second liquid medicine.

The third liquid medicine comprises KOH and H₂O₂And KOH. KOH and H in the third liquid medicine₂O₂The proportion of KOH and KOH is various, and KOH and H are required to be ensured in the liquid medicine₂O₂And KOH and can carry out alkali washing on the SOI silicon chip if KOH and H₂O₂When the concentration of KOH and KOH is low, the residence time in the third chemical solution can be prolonged to achieve the corresponding object. If KOH, H₂O₂When the concentration of KOH and KOH is high, the residence time in the third chemical solution can be shortened to achieve the corresponding object.

The fourth liquid medicine includes HDI and HF. The ratio of HDI to HF in the fourth liquid medicine is in various conditions, HDI and HF are required to be ensured in the liquid medicine, and the SOI silicon wafer can be subjected to acid cleaning.

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 to serve 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 in the area uncovered by the second mask; step S133: and carrying out 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 the moveable structure to move within the cavity. Meanwhile, the second mask can protect the region which does not need to be etched, and the integrity of the structure 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 in 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 remaining metal film as a reflecting layer. The mirror region may be exposed by providing a third mask, a metal film may be formed on the entire upper surface, and then the metal film and the third mask having the third mask may be removed, and finally only the metal film at the mirror region may be left. Step S140 corresponds to f to h.

Preferably, the metal thin film is an Au film.

The third predetermined shape may be designed according to the shape of the reflecting mirror 30, and it is only necessary that the third predetermined shape can expose the reflecting 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 to serve as a fourth mask; step S152: etching the silicon oxide in the area, which is not covered by the fourth mask, on the upper surface of the device layer to expose the part of the device layer, and performing dry deep silicon etching on the exposed part of the device layer to etch out a movable structure; step S153: and removing the fourth mask, removing the exposed silicon oxide film and the buried oxide layer on the back of the movable structure, releasing the movable structure, and forming the MEMS micro-mirror with the stray light elimination function. The arrangement of the fourth mask protects the region which does not need the dry deep silicon etching so as to ensure the integrity of the structure. The movable structure can be released by etching silicon oxide with HF 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 the stray light is effectively reduced. Corresponding to i through k in fig. 9.

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

The surface of the texture is a pyramid texture as shown in fig. 10, and the size of the pyramid base of the pyramid texture is within 2-4 μm.

It should be noted that the steps described above correspond to those in fig. 9 only in a schematic diagram, and do not correspond to one another.

Example two

The difference from the first embodiment is that, in the present embodiment, the extinction layer 12 is manufactured by a plating process.

As shown in fig. 11 and 12, the method for processing a micromirror is used to process the MEMS micromirror with the stray light elimination function, and the method for processing a micromirror comprises: 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 multilayer 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 light extinction layer 12; step S230: etching the substrate layer to form a cavity which meets the motion 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 elimination function.

The light absorption film is manufactured firstly, and then the movable structure of the device layer is etched and released, the area for manufacturing the light absorption film is slightly larger than the area of the frame structure, and the extra area of the light absorption film is etched when the movable structure is etched, so that the light absorption film is ensured to completely cover the surface of the frame structure.

The light absorption film is formed in a film coating mode, so that the purpose of light absorption can be achieved, and the generation of stray light is reduced. And etching the substrate layer to form a cavity, wherein the movable structure can move in the cavity, and enough movement space of the movable structure is ensured. And a reflecting layer is formed in the reflector region to achieve the purpose of reflecting light, and the reflector region is distinguished from the frame structure region, so that the generation of 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 micromirror, the movable structure includes a structure requiring rotation, such as the torsion structure 20 and the mirror 30. In the biaxial MEMS micro-mirror, the movable structure includes the torsion structure 20, the mirror 30, and the movable frame 14, which need to be rotated. After the structure to be rotated is etched, the cavity connects the upper and lower surfaces of the SOI silicon wafer to form the hole structure 11. The frame structure area is the area where the frame structure 10 is finally formed, and the mirror area is the area where the mirror 30 is finally 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 the frame structure region by adopting a photoetching process to serve as a first mask; step S222: forming a light absorption film with a multi-layer 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 light extinction layer. Forming the photoresist layer on the upper surface of device layer in order to form the protection to the region except that frame structure region, then depositing in order to form the membrane of inhaling of the upper surface of whole SOI silicon chip, frame structure region is different with the height in the region except that frame structure region, and then be convenient for follow-up first mask and the membrane of inhaling on the first mask of region department except that frame structure region get rid of, only remain the membrane of inhaling of frame structure region to as extinction layer 12. Corresponding to a to c in fig. 12.

In step S222, a multilayer film structure in which high refractive index film layers and low refractive index film layers are alternated 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 index difference between two adjacent layers in the multilayer film structure needs to be ensured.

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 thickness of each layer of film is determined by the wavelength of incident light beams, and 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 to serve as a second mask; step S231: and carrying out dry deep silicon etching on the exposed substrate layer to form a cavity meeting the motion requirement of the movable structure. Meanwhile, the second mask can protect the region which does not need to be etched, and the integrity of the structure 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 remaining metal film as a reflecting layer. The reflecting mirror region can be exposed by arranging the third mask, then a metal film is formed on the whole upper surface, finally the metal film and the third mask at the position of the third mask are removed, and finally only the metal film at the position of the reflecting mirror region is reserved. The third predetermined shape may be designed according to the shape of the reflecting mirror 30, and it is only necessary that the third predetermined shape can expose the reflecting 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 to serve as a fourth mask; step S252: performing dry deep silicon etching on the device layer in the region not covered by the fourth mask to etch a movable structure; step S253: and removing the fourth mask, removing the buried oxide layer on the back of the movable structure, releasing the movable structure and forming the MEMS micro-mirror with the stray light elimination function. The arrangement of the fourth mask protects the region which does not need the dry deep silicon etching so as to ensure the integrity of the structure. The silicon oxide is corroded by HF to release the movable structure to form a complete MEMS micro-mirror, and the MEMS micro-mirror has the function of eliminating stray light, so that the generation of the stray light is effectively reduced. Steps S240 and S250 correspond to f to j.

It should be noted that the steps described above correspond to those in fig. 12 only in a schematic diagram, and do not correspond to one another.

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

In this embodiment, stray light is eliminated by forming a light-absorbing film having a multilayer film structure, and absorbing incident light that has irradiated on the frame structure by multiple reflection interference of light within the light-absorbing film.

Similarly, the process ensures that the light absorption film is formed on the upper surface of the whole MEMS micro-mirror frame structure, because the light absorption film is very thin, the whole thickness is dozens of nanometers to hundreds of nanometers, the processes of photoetching, etching, film coating and the like in the MEMS process cannot be influenced, and the light absorption film can also be arranged in reasonable process steps according to the actual process 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 formed by laser etching.

As shown in fig. 13 to 22, the processing method of the MEMS micro-mirror with the stray light elimination 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 area of the intermediate structure to form a light eliminating 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 light absorption is achieved, and the generation of stray light is reduced. The base layer is etched to form a cavity within which the moveable structure is capable of moving. A reflecting layer is formed in the reflecting mirror area to achieve the purpose of reflecting light, and meanwhile, the reflecting mirror area is distinguished from the frame structure area, so that the generation of stray light is reduced. The frame structure area is subjected to laser etching to form the extinction layer 12, so that the purpose of light absorption 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 substrate layer to form a cavity meeting the motion requirement of the movable structure. Under the action of the first mask, the region which does not need to be etched is protected, and the integrity of the structure is prevented from being damaged.

Meanwhile, the second mask can protect the region which does not need to be etched, and the integrity of the structure 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 remaining metal film as a reflecting layer. The mirror region may be exposed by providing a second mask, then forming a metal film on the entire upper surface, then removing the metal film and the second mask having the second mask, and finally leaving only the metal film at the mirror region.

The second predetermined shape may be designed according to the shape of the reflecting mirror 30, and it is only necessary that the second predetermined shape can expose the reflecting 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: performing dry deep silicon etching on the device layer which is not covered by the third mask 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, releasing the movable structure and forming the intermediate structure. The third mask is arranged to protect the region which does not need the dry deep silicon etching so as to ensure the integrity of the structure. The movable structure can be released by HF etching of the silicon oxide on the back side to form an intermediate structure.

The third predetermined shape may be designed according to the shape of the movable structure.

Specifically, in step S350, 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 the 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 by the laser beam at one time on the intermediate structure is 6 μm or more and 15 μm or less.

In the process that the concave-convex structure 40 is formed by etching the frame structure area of the intermediate structure by adopting laser, and the concave-convex structure 40 is used as the 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 that the concave-convex structure 40 is formed by etching the frame structure region of the intermediate structure by adopting laser, and the concave-convex structure 40 is used as the extinction layer, the etching time of the laser is controlled to obtain the roughness Ra of more than or equal to 1 μm and the depth of more than or equal to 2 μm. Thus, the light absorption effect of the extinction layer 12 can be effectively ensured.

Preferably, the uneven 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, the laser beam being swept over the entire surface of the frame structure 10, forming the relief structure 40. The surface of the concave-convex structure 40 processed on the monocrystalline silicon by the laser is full of silica filamentous slag generated by silicon in the processing process, as shown in fig. 16, the irregular and porous slag 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 the light beam in the concave-convex structure 40, and uniformly reflects the emergent light beam to the surrounding space to form diffuse reflection, thereby eliminating stray light.

In the specific embodiment shown in fig. 17, the concave-convex structure 40 is formed by etching the frame structure region of the intermediate structure with laser, and the concave-convex structure 40 is used as the extinction layer, and the frame structure region is continuously etched along the serpentine shape with laser. Therefore, the whole frame structure area can be etched, and the power of the laser is controlled to ensure the size of the concave-convex structure 40 formed on the frame structure area, so that the extinction effect of the extinction layer 12 is ensured.

As shown in fig. 17, when the concave-convex structure 40 is processed by the continuous laser, the etching track of the continuous laser has a serpentine shape, 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 machining is performed in order to make the path of the laser snake along the surface of the frame structure 10, so that the continuous laser can etch the whole surface of the extinction layer 12 to form the concave-convex structure 40 on the whole surface.

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

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

In the embodiment shown in fig. 18, the laser is used to continuously etch the frame structure region from one side along the serpentine shape and then from the adjacent side along the serpentine shape. In this embodiment, the frame structure region is etched from two different directions to ensure that the frame structure region can be formed with the concave-convex structure 40, thereby ensuring 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 (dotted 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 whole frame structure 10 is processed.

In the embodiment shown in fig. 21 and 22, the laser forms a first etching pit consisting of a layer of tangent micro pits by means of spot etching, and forms a second etching pit by performing spot etching on a plurality of non-etched areas surrounded by the plurality of first etching pits. The arrangement can also ensure that the frame structure area is etched by laser, and effectively reduces the generation of stray light.

The first etch pit is formed by a plurality of micro pits when the laser is used to etch the first layer, and the second etch pit is formed by a plurality of micro pits when the laser is used to etch the second layer. Or, when the point etching is adopted, one layer of etching is adopted, the first layer structure formed during the first etching is a first etching pit, and the second layer structure formed during the second etching is a second etching pit.

In the embodiment shown in fig. 19 and 20, the laser forms a first etching pit consisting of tangent micro pits by means of spot etching, and forms a second etching pit by taking the tangent point of two adjacent micro pits in the first etching pit as an etching center. The arrangement can also ensure that the frame structure area is etched by laser, and effectively reduces the generation of stray light.

Specifically, the concave-convex structure 40 is formed by stacking micro pits formed on the extinction layer 12 each time by a pulse laser when the pulse laser is processed.

In the embodiment shown in fig. 19 and 20, the relief structure 40 is formed by stacking micron-sized circular micro-pits processed by pulsed laser, the circular micro-pits can be stacked to form a nested pattern, and four second micro-pits 60 are nested around one first micro-pit 50, and the edges of the four micro-pits coincide with the center of the first micro-pit 50.

In the embodiment shown in fig. 21, the rugged structure 40 is formed by stacking micro-scale circular micro-pits processed by a pulsed laser, as shown in fig. 21, the circular micro-pits are stacked to form a sequentially arranged pattern, the pattern is divided into two layers, the first micro-pits 50 are sequentially arranged in one layer, the second micro-pits 60 are also sequentially arranged in one layer, and the center of the second micro-pits 60 is located at the center of the first micro-pits 50 where the gap is left.

In the embodiment shown in fig. 22, the relief structure 40 is formed by stacking micro-scale circular micro-pits processed by pulsed laser, the circular micro-pits are stacked to form a close-packed pattern, the pattern is divided into three layers, the first micro-pits 50 are arranged in one layer as a first layer, and six circular first micro-pits 50 are arranged around one circular first micro-pit 50. Second micro-pits 60 are arranged in a second layer, with second micro-pits 60 being most densely arranged, and the center of second micro-pit 60 being located at the center of the void left by a portion of first micro-pit 50. The third micro-pits 70 are arranged in 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 the gap left by the rest of the micro-pits of the first layer.

It should be noted that during laser processing, part of the slag splashes out of the frame structure area and falls on the reflector area to cause the pollution of the mirror surface, and during the processing, the flowing gas is used to blow off the pollutants on the mirror surface, and the ultrasonic/megasonic cleaning is performed on the chip after processing, so as 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 micromirror frame structure 10 by using a laser etching method. Fig. 14 is a front view of the entire frame structure 10 having its upper surface laser etched without an exposed polished surface. FIG. 15 is a cross-sectional picture with a maximum height difference of 8-9 μm for laser etching. Fig. 16 is an enlarged front view, the surface of the microstructure etched by laser is covered with silica filamentous slag generated by silicon during the processing, the irregular and porous slag increases the surface roughness of the extinction layer 12, greatly improves the light absorption capability of the extinction layer, increases the reflection times of the light beam inside the concave-convex structure 40, and uniformly reflects the outgoing light beam to the surrounding space to form diffuse reflection, thereby eliminating stray light.

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

The laser-etched matte layer 12 should have a surface roughness Ra value greater than 1 μm, and preferably a surface roughness Ra value greater than 1.5 μm.

In the laser etching process, it is required to ensure that the upper surface of the frame structure is completely etched, and a laser beam is required to sweep the whole surface to be etched.

Claims

1. A MEMS micro-mirror with stray light elimination, 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 an aperture structure (11);

a torsional structure (20), the torsional structure (20) being arranged at the pore structure (11), and at least a part of the torsional structure (20) being connected with a pore wall of the pore structure (11);

a mirror (30), the torsional structure (20) supporting the mirror (30).

2. The MEMS micro-mirror with stray light elimination function according to claim 1, wherein 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 received at the hole structure (11), and the movable frame (14) has a central through hole, the mirror (30) is located 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 a 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. The MEMS micro-mirror with stray light canceling function according to claim 1, wherein the canceling layer (12) is a concave-convex structure (40).

4. The MEMS micro-mirror with stray light elimination according to claim 3,

the depth of the concave-convex structure (40) is more than or equal to 2 mu m;

the surface of the concave-convex structure (40) is rough, and the roughness Ra of the concave-convex structure (40) is larger than or equal to 1 mu m.

5. The MEMS micromirror with stray light elimination function as claimed in claim 1, wherein the extinction layer (12) is a textured surface with roughness Ra equal to or greater than 1 μm.

6. The MEMS micromirror having a stray light canceling function according to claim 1, wherein the canceling layer (12) is a light absorbing film having a multilayer film structure in which the refractive indices of the film structures of adjacent two layers are different.

7. A laser scanning apparatus comprising the MEMS micro-mirror with stray light elimination function according to any one of claims 1 to 6.

8. A method for manufacturing a micro-mirror, which is used to manufacture the MEMS micro-mirror with stray light elimination function of claim 1, 2 or 5, the method for manufacturing the micro-mirror comprising:

step S110: selecting an SOI silicon wafer comprising 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 region corresponding to the device layer to form a suede surface, wherein the suede surface is used as an 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 area 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 elimination function.

9. The method for processing a micromirror according to claim 8, wherein the step S120 comprises:

step S121: forming a photoresist layer with a first preset shape on the upper surface of the device layer except the frame structure region by adopting a photoetching process to serve 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 as to expose the upper surface of the frame structure area corresponding to the device layer;

step S123: etching the SOI silicon wafer in a texturing mode, forming a textured surface on the upper surface of the exposed frame structure area, and removing the first mask.

10. The method for processing a micromirror according to claim 9, wherein the step S123 comprises:

step S1231: the SOI silicon chip is pre-cleaned in a first liquid medicine;

step S1232: etching the pre-cleaned SOI silicon wafer in a second liquid medicine;

step S1233: carrying out alkali washing on the textured SOI silicon wafer in a third liquid medicine;

step S1234: pickling the SOI silicon wafer subjected to alkali washing in a fourth liquid medicine;

so as to form a suede surface with the roughness Ra of more than or equal to 1 mu m on the exposed device layer.

11. The method for processing a micromirror according to claim 8, wherein the step S130 comprises:

step S131: forming a photoresist layer with a second preset shape on the lower surface of the substrate layer by adopting a photoetching process to serve as a second mask;

step S132: etching the silicon oxide film exposed on the lower surface of the substrate layer to remove the exposed silicon oxide film so as to expose the substrate layer in the area uncovered by the second mask;

step S133: and carrying out dry deep silicon etching on the exposed substrate layer to form a cavity meeting the motion requirement of the movable structure.

12. The method for processing a micromirror according to claim 11, wherein the step S140 comprises:

step S141: removing the second mask, and forming a photoresist layer in 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 remaining metal film as a reflecting layer.

13. The method for processing a micromirror according to claim 8, wherein the step S150 comprises:

step S151: forming a photoresist layer with a fourth preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a fourth mask;

step S152: etching the silicon oxide in the area, which is not covered by the fourth mask, on the upper surface of the device layer to expose the 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 of the movable structure, releasing the movable structure, and forming the MEMS micro-mirror with the stray light elimination function.

14. A method for manufacturing a MEMS micro-mirror having a stray light elimination function as claimed in claim 1, 2 or 6, 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 the frame structure region corresponding to the device layer, wherein the light absorption film is used as a light extinction layer (12);

step S230: etching the substrate layer to form a cavity meeting 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 elimination function.

15. The method for processing a micromirror according to claim 14, wherein the step S220 comprises:

step S221: forming a photoresist layer with a first preset shape on the upper surface of the device layer except the frame structure region by adopting a photoetching process to serve as a first mask;

step S222: forming a light absorption film with a multi-layer 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 light extinction layer.

16. The method for processing a micromirror according to claim 14, wherein the step S230 comprises

Step S231: forming a photoresist layer with a second preset shape on the lower surface of the substrate layer by adopting a photoetching process to serve as a second mask;

step S231: and carrying out dry deep silicon etching on the exposed substrate layer to form a cavity meeting the motion requirement of the movable structure.

17. The method for processing a micromirror according to claim 16, wherein the step S240 comprises:

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 remaining metal film as a reflecting layer.

18. The method for processing a micromirror according to claim 14, wherein the step S250 comprises:

step S251: forming a photoresist layer with a fourth preset shape on the upper surface of the device layer by adopting a photoetching process to serve as a fourth mask;

step S252: performing dry deep silicon etching on the device layer in the region uncovered by the fourth mask to etch a movable structure;

step S253: and removing the fourth mask, removing the buried oxide layer on the back of the movable structure, releasing the movable structure and forming the MEMS micro-mirror with the stray light elimination function.

19. A method for manufacturing a micro mirror, for manufacturing the MEMS micro mirror with a stray light elimination function according to any one of claims 1 to 4, 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 upper surface of the frame structure area of the intermediate structure to form a light eliminating layer, thereby obtaining the MEMS micro-mirror with the stray light eliminating function.

20. The method for processing a micromirror according to claim 19, 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 to serve as a first mask;

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

21. The method for processing a micromirror according to claim 20, 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, and taking the remaining metal film as a reflecting layer.

22. The method for processing a micromirror according to claim 21, wherein the step S340 comprises:

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: performing dry deep silicon etching on the device layer uncovered by the third mask to etch a movable structure;

step S343: and removing the third mask, removing the buried oxide layer on the back of the movable structure, releasing the movable structure and forming the intermediate structure.

23. The method for processing a micromirror according to claim 19, 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.

24. The method of claim 23, wherein during the etching of the upper surface of the frame structure region of the intermediate structure with the laser to form the relief structure as the matte layer,

and controlling the power, spot size and scanning speed of the laser to obtain the concave-convex structure with the roughness Ra of more than or equal to 1 mu m and the depth of more than or equal to 2 mu m.

25. The method of processing a micromirror according to claim 23, wherein the entire upper surface of the frame structure (10) is scanned during the etching of the frame structure region of the intermediate structure with laser to form the relief structure as the extinction layer.