CN113031252A - Micro mirror with micro-nano structure, micro mirror manufacturing method and laser display system - Google Patents

Micro mirror with micro-nano structure, micro mirror manufacturing method and laser display system Download PDF

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CN113031252A
CN113031252A CN201911255766.3A CN201911255766A CN113031252A CN 113031252 A CN113031252 A CN 113031252A CN 201911255766 A CN201911255766 A CN 201911255766A CN 113031252 A CN113031252 A CN 113031252A
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layer
micro
nano structure
micromirror
wafer
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CN113031252B (en
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马宏
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Juexin Electronics Wuxi Co ltd
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Juexin Electronics Wuxi Co ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
    • G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/0009—Structural features, others than packages, for protecting a device against environmental influences
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
    • B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
    • B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
    • B81C1/00134—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems comprising flexible or deformable structures
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0905—Dividing and/or superposing multiple light beams
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0002—Lithographic processes using patterning methods other than those involving the exposure to radiation, e.g. by stamping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B2201/00—Specific applications of microelectromechanical systems
    • B81B2201/04—Optical MEMS
    • B81B2201/042—Micromirrors, not used as optical switches

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Computer Hardware Design (AREA)
  • Manufacturing & Machinery (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Mechanical Light Control Or Optical Switches (AREA)
  • Micromachines (AREA)

Abstract

A micro mirror with a micro-nano structure, a micro mirror manufacturing method and a laser display system are provided. The invention provides a micro mirror with a micro-nano structure, which comprises a base material layer, a micro-nano structure layer and a reflection layer, wherein the micro-nano structure layer is positioned above the base material layer, the micro-nano structure layer is arranged in a specific area on the surface of the base material layer, the micro-nano structure layer is a micro-lens array or a Fresnel lens array, and the reflection layer is positioned above the micro-nano structure layer. The preparation of the micro mirror is based on a nano-imprinting technology, a nano-printing technology or a photoresist hot melting technology, integrates a curved surface reflection micro-nano structure, has high precision and small size, can realize more uniform distribution of the micro-nano structure, enables the energy of each reflected sub-beam to be more uniform, and enables the speckle suppression effect to be better.

Description

Micro mirror with micro-nano structure, micro mirror manufacturing method and laser display system
Technical Field
The invention relates to the field of optical display, in particular to a micro mirror with a micro-nano structure, a micro mirror preparation method and a laser display system.
Background
Speckle is a granular speckle of random intensity distribution that occurs when a coherent light source, such as a laser light source, illuminates an optically rough surface or passes through an inhomogeneous medium. Coherent light beams, such as laser light, are diffusely reflected off the optically rough surface to form randomly distributed light with phase differences in space. The light generated by diffuse reflection has the same frequency as the incident light, and is interfered after meeting in space, so that the light intensity is randomly distributed in the space to form speckles.
Speckle has different meanings in different applications and fields. In coherent light display systems, such as laser display systems, speckle can cause a lack of a portion of the image information displayed, reducing the resolution of the display, and thus can be detrimental to coherent light display systems. In laser projection display systems, the primary parameter measuring speckle is speckle contrast, which is defined as the ratio of the standard deviation of the intensity of light on a uniformly illuminated screen to the mean. When the speckle phenomenon is obvious, the C value is large; otherwise, C will go to zero. To make the speckle in the image imperceptible to the human eye, the speckle contrast value should be less than 4%. According to related studies, when the speckle contrast is suppressed below 4%, the human visual system cannot identify the speckle in the projected image.
From the cause analysis of the speckle, the root cause of the speckle is that the illuminating beam has excellent coherence. Therefore, the fundamental method of speckle suppression is to reduce the coherence of the illuminating beam. The existing speckle suppression technologies can be broadly divided into three categories: the optical properties of the laser beam are influenced temporally and/or spatially by driving the multi-laser to form a low-coherence laser light source or to average the resulting speckle brightness, by compensating for the human vision by means of an oscillating projection screen, by adding optical elements with specific functions in the beam path. The total output light power is constant due to the light emitting characteristics of the lasers, and the power consumption for driving the multiple lasers is larger than that for driving a single laser. Meanwhile, the number of lasers is increased, and the production cost is increased. The technique of realizing speckle suppression by vibrating the projection screen has many limitations in practical use. Therefore, when speckle suppression is performed, an optical element with a specific function is added to an optical path, so that the speckle suppression device has the widest application prospect at the present stage.
In speckle suppression technology, optical elements mainly used in the prior art include various types of scattering sheets, diffractive optical elements, microlens arrays, and MEMS micromirrors with roughened surfaces.
The scattering sheet has quite limited speckle suppression effect in a static state, and needs to be driven by a driving system, and the light beams form sub-beams with time-varying random phases after penetrating through the rotating and/or vibrating scattering sheet. The speckle effect formed by the sub-beams is small and the overall effect is reduced after the sub-beams are overlapped with each other. However, the addition of an additional driving system in the laser display system may not only adversely affect the reliability of the precision optical system, but also may generate negative effects such as noise, and is also not conducive to the integration and miniaturization of the system module, thereby limiting the commercial application value of the system module.
The diffractive optical element can split the transmitted light beam in a static state, and the diffractive optical element has a micro-nano structure, so that the split sub-beams have random phases, and the speckle effect formed by the sub-beams is small and the overall effect is reduced after the sub-beams are overlapped with each other. However, since a specific diffractive optical element can split only a coherent light beam having a specific wavelength, there is a certain limitation in use.
The micro lens array refers to the arrangement and combination of a certain number of micro-nano scale spherical or free-form surface lenses. The periodic size of the microlens array is typically 500nm-50 μm. The micro lens array can also split the light beam in a static state, and has better beam splitting and beam homogenizing effects compared with a diffraction optical element. Typically, microlens arrays typically require two arrays to be used in combination. Because the beam homogenizing effect of a single micro-lens array is not as good as that of a micro-lens array group, the brightness distribution in the light spot is uneven after beam homogenizing, and the speckle suppression effect is poor. The use of multiple microlens arrays increases the module size. Meanwhile, when the micro-lens array pair is used, two micro-lens arrays need to be mutually corresponding, and the requirements on the precision of the size and the position are high. In addition, due to the manufacturing process, when a lens array (not only a micro lens array) is used, a scattering phenomenon inevitably occurs, which causes energy loss and reduction of spot brightness, and is disadvantageous to laser display.
The surface roughened MEMS micro-mirror causes the reflected beam to acquire a phase with time-variability by vibrating in one or more dimensions. However, the prior art still has certain disadvantages, such as complex process, poor stability of the finished product, high cost, low yield, etc. Meanwhile, according to several documents, the height or depth of the protrusions formed by roughening needs to be 1/4-2 times of the incident wavelength. Therefore, the requirement for the precision of the micro/nano structure on the surface of the roughened MEMS micro-mirror is high, so that a certain limit exists in practical use.
Disclosure of Invention
In order to solve the technical problem, the invention discloses a micro mirror with a micro-nano structure, a micro mirror preparation method and a laser display system.
In a first aspect of the present invention, a method for manufacturing a micromirror is provided, which includes the following steps:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer on the surface of the wafer device layer;
heating the polymer layer in a vacuum environment until the temperature of the polymer layer is higher than the glass transition temperature of the polymer layer, stamping the liquid polymer layer to a certain depth by using a stamp, and keeping for a period of time to enable the liquid polymer to fill the gaps of the stamp graph;
step four, reducing the temperature to solidify the polymer and demoulding to form a micro-nano structure layer;
evaporating and plating a reflecting layer on the surface of the micro-nano structure layer;
removing the redundant polymer layer on the device layer, and then etching the device layer to the oxygen burying layer to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer of the wafer, and etching the back cavity to the buried oxide layer to expose the buried oxide layer within the range of the back cavity;
and step eight, corroding the oxygen burying layer exposed in the range of the back cavity to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
Further, the polymer layer is a thermoplastic polymer.
Further, the material of the thermoplastic polymer is polypropylene ethylene or polymethyl methacrylate.
Further, the vacuum degree of the vacuum environment in the third step is less than or equal to 1 mbar.
Further, the heating temperature in the third step is 250-320 ℃.
Further, the pressure of the stamping in the step three is 5bar-70 bar.
Furthermore, the size of the stamp is not larger than 150mm, and the stamp is made of quartz (Silicon) or Nickel (Nickel).
Further, the lowering of the temperature in the fourth step is such that the temperature of the thermoplastic polymer is below its glass transition temperature.
In a second aspect of the present invention, a method for manufacturing a micromirror is provided, which includes the following steps:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer on the surface of the wafer device layer;
third, stamping the liquid polymer layer to a certain depth by using a stamp in a vacuum environment, keeping for a period of time, filling the gaps of the stamp pattern with the liquid polymer, and irradiating by using ultraviolet light through the stamp;
solidifying a polymer layer filled in the seal and demolding to form a micro-nano structure layer;
evaporating and plating a reflecting layer on the surface of the micro-nano structure layer;
removing the redundant polymer layer on the device layer, and then etching the device layer to the oxygen burying layer to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer of the wafer, and etching the back cavity to the buried oxide layer to expose the buried oxide layer within the range of the back cavity;
and step eight, corroding the oxygen burying layer exposed in the range of the back cavity to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
Further, the polymer layer is an ultraviolet light curing material.
Further, the vacuum degree of the vacuum environment in the third step is less than or equal to 1 mbar.
Further, the pressure of the stamping in the step three is 5bar-70 bar.
Further, the stamp is made of quartz glass (Fused Silica).
In a third aspect of the present invention, a method for manufacturing a micromirror is provided, which includes the following steps:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer on the surface of the wafer device layer;
scanning the surface of the device layer of the substrate layer by layer to form a micro-nano structure layer with a designed pattern by utilizing a two-photon polymerization technology;
after the pattern of the micro-nano structure layer is completely formed by a two-photon polymerization technology, removing the redundant polymer layer;
evaporating and plating a reflecting layer on the surface of the micro-nano structure layer;
removing the redundant polymer layer on the device layer, and then etching the device layer to the oxygen burying layer to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer of the wafer, and etching the back cavity to the buried oxide layer to expose the buried oxide layer within the range of the back cavity;
and step eight, corroding the oxygen burying layer exposed in the range of the back cavity to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
Further, the polymer layer is a negative photoresist.
Further, according to the complexity of the patterns to be processed, for more complex patterns such as Fresnel lens arrays, a Sol-gel state (Sol-gel) photoresist is selected; other patterns, such as microlens arrays with slightly larger apertures, use liquid photoresist.
In the third step, the two-photon polymerization technology is utilized to scan layer by layer under the control of the piezoelectric technology and the galvanometer technology.
And in the fourth step, the residual negative photoresist is directly removed, and the micro-nano structure layer is remained.
The fourth aspect of the present invention provides a method for manufacturing a micromirror, comprising the steps of:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer on the surface of the device layer of the wafer;
etching the polymer layer into a plurality of fine cylindrical polymer layers by photoetching and developing;
heating and baking the small cylindrical polymer layers to be in a lens shape under the action of tension, and cooling to form a micro-nano structure with a micro-lens array;
evaporating and plating a reflecting layer on the surface of the micro-nano structure layer;
removing the redundant polymer layer on the device layer, and then etching the device layer to the oxygen burying layer to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer of the wafer, and etching the back cavity to the buried oxide layer to expose the buried oxide layer within the range of the back cavity;
and step eight, corroding the oxygen burying layer exposed in the range of the back cavity to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
Further, the polymer layer is photoresist.
According to a sixth aspect of the invention, the micro mirror with the micro-nano structure is provided, and the micro mirror prepared by the micro mirror preparation method comprises a base material layer, a micro-nano structure layer and a reflection layer, wherein the micro-nano structure layer is positioned above the base material layer, the micro-nano structure layer is arranged in a specific area on the surface of the base material layer, the micro-nano structure layer is a micro-lens array or a Fresnel lens array, and the reflection layer is positioned above the micro-nano structure layer.
The seventh aspect of the present invention provides a laser display system, comprising a laser light source, a collimating unit, a beam combiner, a speckle suppressing device and a first micro-mirror device arranged in sequence,
the laser light source receives the driving signal and emits laser beams with at least one color;
the collimation unit respectively collimates the laser beams into collimated laser beams meeting the size requirement of scanning beams;
the beam combiner forms the collimated laser beams into combined beams;
the speckle suppression device is used for expanding, splitting, homogenizing and converging the combined beam to generate an emergent beam consisting of a plurality of sub-beams;
the first micro-mirror device is used for reflecting the emergent light beam into a scanning light beam and projecting the scanning light beam to a projection surface for scanning display;
the speckle suppression device at least comprises a second micromirror device and a condensing lens, the second micromirror device comprises a second micromirror and a second micromirror driving device, the second micromirror adopts the micromirror, the second micromirror driving device drives the second micromirror to do periodic translation or deflection motion in at least one dimension, the incident angle and the position of the expanded beam are periodically changed, and a reflected beam formed by a plurality of sub-beams is formed; the condensing lens converges and collimates the reflected light beam to form the emergent light beam.
Further, the first micromirror device comprises a first micromirror and a first micromirror driving device, and the first micromirror driving device drives the first micromirror to make a periodic translational motion or a deflection motion in at least one dimension.
In one embodiment, the speckle reduction apparatus further comprises a beam expander.
In an eighth aspect of the present invention, there is provided a laser display system, comprising a laser light source, a collimating unit, a beam combiner and a speckle suppressing device arranged in sequence,
the laser light source receives the driving signal and emits laser beams with at least one color;
the collimation unit respectively collimates the laser beams into collimated laser beams meeting the size requirement of scanning beams;
the beam combiner forms the collimated laser beams into combined beams;
the speckle suppression device is used for expanding, splitting, homogenizing and converging the combined beam light, generating a scanning beam consisting of a plurality of sub-beams and projecting the scanning beam to a projection surface for scanning and displaying;
the speckle suppression device at least comprises a micromirror device and a condensing lens, the micromirror device comprises the micromirror and a micromirror driving device, the micromirror driving device drives the micromirror to do periodic translation or deflection motion in at least one dimension, and the incident angle and the position of the expanded beam are periodically changed to form a reflected beam consisting of a plurality of sub-beams; the condensing lens converges and collimates the reflected light beam to form the scanning light beam.
In one embodiment, the speckle reduction apparatus further comprises a beam expander.
By adopting the technical scheme, the invention has the following beneficial effects:
1) the preparation of the micro-mirror is based on a nano-imprinting technology and a nano-printing technology, a curved surface reflection micro-nano structure is integrated, the micro-nano structure is high in precision and small in size, more uniform distribution of the micro-nano structure can be realized, the energy of each reflected sub-beam is more uniform, and the speckle suppression effect is better;
2) the preparation of the micro-mirror is based on the nano-imprinting technology and the nano-printing technology, the micro-nano structure based on the self-defined pattern can be easily designed and manufactured, the micro-nano structure comprises the micro-nano structure which cannot be manufactured or is difficult to manufacture by the traditional photoetching technology, such as a micro-lens array pattern, a Fresnel lens array pattern, a lamellar grating and the like, and the micro-nano structure is integrated on the surface of a galvanometer of the MEMS micro-mirror, so that the composition of sub-beams of a reflected beam is more flexibly controlled, and the optimal beam splitting and homogenizing effects on the beam at the present stage, which are the same as the micro-lens array, are realized in a curved;
3) according to the micro-mirror, the beam splitting and the beam homogenizing of all visible light can be realized by a single micro-mirror by controlling the size and the arrangement mode of a special micro-nano structure;
4) the preparation of the micro-mirror is based on the nano-imprinting technology and the nano-printing technology, multiple photoetching is not needed, the process flow is simple, the process stability is good, integrated manufacturing can be realized by using the nano-printing technology, even a seal and a mask are not needed to be manufactured, and the process flow is simple;
5) the micro mirror does not need to be matched with a vibrating projection screen for use, the designed speckle suppression effect can be realized on a static screen, and the convenience and the practicability of the system are improved;
6) the micro-mirror does not need to introduce additional precise optical elements such as a micro-lens array, a diffractive optical element or a rotating scattering sheet for speckle suppression, so that the module has higher reliability, higher integration degree and smaller size;
7) the micro mirror is driven by the micro mirror driving device, has low power consumption and basically no noise when in work, and can avoid the damage to other components in the module caused by factors such as vibration and the like possibly caused by using other driving modes, thereby improving the reliability of equipment and the module;
8) the micro mirror has weaker repulsion to the prior art and good applicability, and can be matched with part of the prior art for use, such as a vibrating screen technology, a speckle suppression technology based on special optical components and the like, so that further speckle suppression is carried out, and the defect of the part of the prior art in the speckle suppression degree is overcome;
9) when the invention is applied to the HUD system, the MEMS micro-mirror device can directly replace the MEMS micro-mirror device in the original laser display system, namely only one micro-mirror device is needed in the system, the speckle suppression and scanning display functions can be realized simultaneously, and the speckle suppression function is realized without adding extra parts, so that the complexity of system integration is not increased, and the power consumption of the system is not increased.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIGS. 1(a) -1(g) are flow charts of the method for fabricating a micromirror according to embodiment 1 of the invention;
FIGS. 2(a) -2(g) are flow charts of the method for fabricating a micromirror device according to embodiment 2 of the invention;
FIGS. 3(a) -3(g) are flowcharts illustrating a method for fabricating a micro mirror according to embodiment 3 of the present invention;
FIGS. 4(a) -4(g) are flow charts of the method for fabricating the micromirror of the embodiment 4 of the invention;
FIG. 5 is a schematic diagram of a micromirror of embodiment 5 of the invention;
FIG. 6 is a schematic diagram of a micromirror of embodiment 6 according to the invention;
FIG. 7 is a schematic view of a laser display system according to embodiment 7 of the present invention;
fig. 8 is a schematic view of a laser display system according to embodiment 8 of the present invention.
The following is a supplementary description of the drawings:
101-a substrate layer; 101 a-a device layer; 101 b-buried oxide layer; 101 c-a support layer; 102-a polymer layer; 103-seal; 104-micro-nano structure layer; 105-a reflective layer;
201-a substrate layer; 201 a-device layer; 201 b-buried oxide layer; 201 c-a support layer; 202-a polymer layer; 203-a seal; 204-ultraviolet light; 205-micro-nano structure layer; 206-a reflective layer;
301-a substrate layer; 301 a-device layer; 301 b-buried oxide layer; 301 c-support layer; 302-a polymer layer; 303-micro-nano structure layer; 304-a reflective layer;
401-a substrate layer; 401 a-device layer; 401 b-buried oxide layer; 401 c-a support layer; 402-a polymer layer; 403-a fine cylindrical polymer layer; 404, micro-nano structure layer; 405-a reflective layer;
501-a substrate layer; 501 a-device layer; 501 b-buried oxide layer; 501 c-a support layer; 502-micro nano structure layer; 503-a reflective layer;
601-a substrate layer; 601 a-device layer; 601 b-buried oxide layer; 601 c-a support layer; 602-a micro-nano structure layer; 603-a reflective layer;
71-a laser light source; 72-a collimating unit; 73-a combiner; 74-speckle reduction means; 741-a beam expander; 741 a-a first lens; 741 b-a second lens; 742-a second micromirror device; 742 a-a second micromirror; 742 b-a second micromirror driving device; 75-a first micro-mirror device; 751-a first micromirror; 752-first micromirror drive means;
81-laser light source; 82-a collimating unit; 83-a combiner; 84-speckle suppression means; 841-a beam expander; 841 a-first lens; 841 b-second lens; 842-a second micro-mirror device; 842 a-micro mirror; 842 b-micromirror drive means.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic may be included in at least one implementation of the invention. In the description of the present invention, it is to be understood that the terms "upper", "lower", "top", "bottom", and the like, as used herein, refer to an orientation or positional relationship based on that shown in the drawings, which is for convenience and simplicity of description, and does not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein.
Example 1: (thermal nanoimprint technology)
As shown in fig. 1(a) -1(g), a method for fabricating a micromirror comprises:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer 102 on the surface of the wafer device layer 101 a;
thirdly, heating the polymer layer 102 to a temperature higher than the glass transition temperature of the polymer layer 102 in a vacuum environment, stamping the liquid polymer layer 102 to a certain depth by using a stamp 103, and keeping for a period of time to enable the liquid polymer to fill the pattern gaps of the stamp 103;
step four, reducing the temperature to solidify the polymer and demolding to form the micro-nano structure layer 104;
evaporating on the surface of the micro-nano structure layer 104 to form a reflecting layer 105;
sixthly, removing the redundant polymer layer 102 on the device layer 101a, and then etching the device layer to the buried oxide layer 101b to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer 101c of the wafer, and etching the back cavity to the buried oxide layer 101b to expose the buried oxide layer 101b within the range of the back cavity;
and step eight, corroding the oxygen burying layer 101b exposed in the range of the back cavity to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
In said first step the profile of the micromirror is defined by photolithography and shallow etching.
As shown in fig. 1(a), the wafer is a substrate layer 101, and includes a device layer 101a, a buried oxide layer 101b and a support layer 101c, where the device layer 101a is a surface layer, and the buried oxide layer 101b is an intermediate layer; the support layer 101c is a bottom layer.
The device layer 101a is made of monocrystalline silicon, the buried oxide layer 101b is made of silicon dioxide, and the support layer 101c is made of monocrystalline silicon.
The polymer layer 102 is a thermoplastic polymer.
The thermoplastic polymer has a glass transition temperature (glass transition temperature) about 100-C higher than the temperature of the wafer at which the metal is evaporated.
The thermoplastic polymer is polypropylene (Polystyrene, abbreviated as PS) or Polymethyl methacrylate (PMMA).
The vacuum degree of the vacuum environment in the third step is less than or equal to 1 mbar.
The heating temperature in the third step is 250-320 ℃.
The pressure of the embossing in the third step is 5-70 bar.
The size of the stamp 103 is not larger than 150mm, and the stamp 103 is made of quartz (Silicon) or Nickel (Nickel).
The characteristic size of the pattern of the seal 103 is 20nm-300nm, and the seal 103 is manufactured by Electron Beam Lithography (EBL); the characteristic size of the pattern of the seal 103 is 300nm-2 μm, and deep ultraviolet lithography (DUV) is selected to manufacture the seal 103; the characteristic dimension of the pattern of the stamp 103 is more than 2 μm, and the stamp 103 is manufactured by selecting conventional photoetching (UVL).
The pattern of the stamp 103 is a micro-lens array with a caliber of 300nm-400 μm and arranged in a hexagonal close arrangement or other arrangement modes.
The fourth step of reducing the temperature is such that the temperature of the thermoplastic polymer is below its glass transition temperature.
In the fifth step, a metal is evaporated in vacuum by Physical Vapor Deposition (PVD) to form the reflective layer 105, and the reflective layer 105 is a metal thin film.
The reflective layer 105 is made of aluminum or gold.
The thickness of the reflective layer 105 is 50nm to 500 nm.
In the sixth step, the excessive polymer layer 102 is removed by photolithography and etching, and the device layer is etched to the buried oxide layer 101b by photolithography and etching back to form the main structures of the electrically isolated trench and the micromirror, such as the comb structure.
And seventhly, preparing a back cavity in a defined range through photoetching and etching.
In the eighth step, the buried oxide layer 101b exposed in the back cavity area is etched by hydrofluoric acid.
Example 2: (ultraviolet nanoimprint)
As shown in fig. 2(a) -2(g), a method for fabricating a micromirror comprises:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer 202 on the surface of the wafer device layer 201 a;
thirdly, stamping the liquid polymer layer 202 to a certain depth by using the stamp 203 in a vacuum environment, keeping for a period of time, filling pattern gaps of the stamp 203 with the liquid polymer, and irradiating by using ultraviolet light 204 through the stamp 203;
step four, solidifying the polymer layer 202 filled in the seal 203 and demolding to form a micro-nano structure layer 205;
step five, evaporating and plating a reflective layer 206 on the surface of the micro-nano structure layer 205;
sixthly, removing the redundant polymer layer 202 on the device layer 201a, and then etching the device layer to the buried oxide layer 201b to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer 201c of the wafer, wherein the back cavity is etched to the buried oxide layer 201b, so that the buried oxide layer 201b in the range of the back cavity is exposed;
and step eight, corroding the oxygen burying layer 201b exposed in the back cavity range to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
In said first step the profile of the micromirror is defined by photolithography and shallow etching.
The wafer is a substrate layer 201 and comprises a device layer 201a, a buried oxide layer 201b and a supporting layer 201c, wherein the device layer 201a is a surface layer, and the buried oxide layer 201b is an intermediate layer; the support layer 201c is a bottom layer.
The device layer 201a is made of monocrystalline silicon, the buried oxide layer 201b is made of silicon dioxide, and the support layer 201c is made of monocrystalline silicon.
The polymer layer 202 is an ultraviolet light 204 curable material.
The glass transition temperature (glass transition temperature) of the uv light 204 curable material is about 100 ° C higher than the temperature of the wafer when the metal is evaporated.
The vacuum degree of the vacuum environment in the third step is less than or equal to 1 mbar.
The pressure of the embossing in the third step is 5-70 bar.
The stamp 203 is made of quartz glass (Fused Silica).
The characteristic size of the pattern of the seal 203 is 20nm-300nm, and Electron Beam Lithography (EBL) is selected to manufacture the seal 203; the characteristic size of the pattern of the seal 203 is 300nm-2 μm, and deep ultraviolet light 204 etching (DUV) is selected to manufacture the seal 203; the characteristic dimension of the pattern of the stamp 203 is more than 2 μm, and the stamp 203 is manufactured by selecting conventional photoetching (UVL).
The pattern of the stamp 203 is a micro-lens array with the aperture of 300nm-400 μm and arranged in a hexagonal close arrangement or other arrangement modes.
In the fifth step, a metal is vacuum-evaporated by Physical Vapor Deposition (PVD) to form the reflective layer 206, and the reflective layer 206 is a metal thin film.
The reflective layer 206 is made of aluminum or gold.
The thickness of the reflective layer 206 is 50nm to 500 nm.
In the sixth step, the excessive polymer layer 202 is removed by photolithography and etching, and the device layer is etched to the buried oxide layer 201b by photolithography and etching back to form the main structures of the electrically isolated trench and the micromirror, such as comb tooth structure, etc.
And seventhly, preparing a back cavity in a defined range through photoetching and etching.
In the eighth step, the buried oxide layer 201b exposed in the back cavity area is etched by hydrofluoric acid.
Example 3: (Nano printing process)
As shown in fig. 3(a) -3(g), a method for fabricating a micromirror comprises:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer 302 on the surface of the wafer device layer 301 a;
step three, scanning the surface of the device layer 301a of the substrate layer 301 layer by layer to form a micro-nano structure layer 303 with a designed pattern by using a two-photon polymerization technology;
step four, after the pattern of the micro-nano structure layer 303 is completely formed by a two-photon polymerization technology, removing the redundant polymer layer 302;
evaporating and plating a reflective layer 304 on the surface of the micro-nano structure layer 303;
sixthly, removing the redundant polymer layer 302 on the device layer 301a, and then etching the device layer to the buried oxide layer 301b to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer 301c of the wafer, and etching the back cavity to the buried oxide layer 301b to expose the buried oxide layer 301b within the range of the back cavity;
step eight, the buried oxide layer 301b exposed in the back cavity range is etched to release the movable part of the micromirror, and the micromirror fabrication is completed.
In said first step the profile of the micromirror is defined by photolithography and shallow etching.
The wafer is a substrate layer 301 and comprises a device layer 301a, a buried oxide layer 301b and a supporting layer 301c, wherein the device layer 301a is a surface layer, and the buried oxide layer 301b is an intermediate layer; the support layer 301c is a bottom layer.
The device layer 301a is made of monocrystalline silicon, the buried oxide layer 301b is made of silicon dioxide, and the support layer 301c is made of monocrystalline silicon.
The polymer layer 302 is a negative photoresist.
The negative photoresist has a glass transition temperature (glass transition temperature) about 100-C higher than the wafer temperature at which metal is evaporated.
Selecting a Sol-gel state (Sol-gel) photoresist for more complicated patterns such as a Fresnel lens array according to the complexity of the patterns to be processed; other patterns, such as microlens arrays with slightly larger apertures, use liquid photoresist.
In the third step, the scanning layer by layer is carried out by utilizing a two-photon polymerization technology under the control of a piezoelectric technology (piezo technology) and a galvanometer technology (galvo technology).
And in the fourth step, the residual negative photoresist is directly removed, and the micro-nano structure layer 303 is remained.
In the fifth step, a metal is vacuum-evaporated by Physical Vapor Deposition (PVD) to form the reflective layer 304, and the reflective layer 304 is a metal thin film.
The reflective layer 304 is made of aluminum or gold.
The thickness of the reflective layer 304 is 50nm to 500 nm.
In the sixth step, the excessive polymer layer 302 is removed by photolithography and etching, and the device layer is etched to the buried oxide layer 301b by photolithography and etching back to form the main structures of the electrically isolated trench and the micromirror, such as the comb structure.
And seventhly, preparing a back cavity in a defined range through photoetching and etching.
In the eighth step, the buried oxide layer 301b exposed in the back cavity region is etched by hydrofluoric acid.
Example 4: (Photoresist Hot melt Process)
As shown in fig. 4(a) -4(g), a method for fabricating a micromirror comprises:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer 402 on the surface of the device layer 401a of the wafer;
step three, etching the polymer layer 402 into a plurality of fine cylindrical polymer layers 403 through photoetching and development;
heating and baking the small cylindrical polymer layers 403 to be in a lens shape under the action of tension, and cooling to form a micro-nano structure with a micro-lens array;
evaporating and plating a reflective layer 405 on the surface of the micro-nano structure layer 404;
sixthly, removing the redundant polymer layer 402 on the device layer 401a, and then etching the device layer to the buried oxide layer 401b to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer 401c of the wafer, and etching the back cavity to the buried oxide layer 401b to expose the buried oxide layer 401b within the range of the back cavity;
and step eight, corroding the oxygen burying layer 401b exposed in the range of the back cavity to release the movable part of the micro mirror, thereby completing the manufacture of the micro mirror.
In said first step the profile of the micromirror is defined by photolithography and shallow etching.
The wafer is a substrate layer 401 and comprises a device layer 401a, an oxygen burying layer 401b and a supporting layer 401c, wherein the device layer 401a is a surface layer, and the oxygen burying layer 401b is an intermediate layer; the support layer 401c is a bottom layer.
The device layer 401a is made of monocrystalline silicon, the buried oxide layer 401b is made of silicon dioxide, and the support layer 401c is made of monocrystalline silicon.
The polymer layer 402 is a photoresist. Negative photoresist can be selected as the material for forming the polymer layer 402 according to actual requirements.
In the fifth step, a metal is evaporated in vacuum by Physical Vapor Deposition (PVD) to form the reflective layer 405, and the reflective layer 405 is a metal thin film.
The reflective layer 405 is made of aluminum or gold.
The thickness of the reflective layer 405 is 50nm to 500 nm.
In the sixth step, the excessive polymer layer 402 is removed by photolithography and etching, and the device layer is etched to the buried oxide layer 401b by photolithography and etching back to form the main structures of the electrically isolated trench and the micromirror, such as the comb structure.
And seventhly, preparing a back cavity in a defined range through photoetching and etching.
In the eighth step, the buried oxide layer 401b exposed in the back cavity area is etched by hydrofluoric acid.
Example 5:
as shown in fig. 5, a micro mirror with micro-nano structure comprises a substrate layer 501, a micro-nano structure layer 502 and a reflective layer 503,
the micro-nano structure layer 502 is located above the substrate layer 501, the micro-nano structure layer 502 is manufactured by performing nano-imprinting or nano-printing in a specific area on the surface of the substrate layer 501, and the reflecting layer 503 is located above the micro-nano structure layer 502.
The substrate layer 501 is a wafer, the wafer comprises a device layer 501a, an oxygen burying layer 501b and a supporting layer 501c, the device layer 501a is a surface layer, and the oxygen burying layer 501b is an intermediate layer; the support layer 501c is a bottom layer.
The device layer 501a is made of monocrystalline silicon, the buried oxide layer 501b is made of silicon dioxide, and the support layer 501c is made of monocrystalline silicon.
The thickness of the single crystal silicon device layer 501a is between 10 μm and 100 μm.
The buried oxide layer 501b is made of silicon dioxide.
The material of the micro-nano structure layer 502 is a polymer, and the material and the thickness of the micro-nano structure layer 502 are different according to different processing technologies.
The micro-nano structure layer 502 is a micro-lens array.
When the micro-nano structure layer 502 is prepared by adopting a nano-imprinting technology, the thickness t of the micro-nano structure layer 5021Slightly larger than the aperture d of the unit lens, so as to avoid direct contact between the stamp and the substrate layer 501 during stamping;
when the micro-nano structure layer 502 is prepared by adopting a nano printing technology, the thickness t of the micro-nano structure layer 5021Typically the same as the cell lens aperture d.
When the nano-imprinting processing is carried out, the thickness of the processed lens layer can be controlled by different means for different nano-imprinting processing technologies. For example, for a partial thermal nanoimprint process, the thickness of the resulting lens layer after imprinting can be controlled by controlling the polymer thickness before imprinting and the depth of imprinting at the time of imprinting; for another part of the thermal nano-imprinting process, the thickness of the lens layer obtained after imprinting can be directly controlled by controlling the pattern of the stamp or the mask used for imprinting.
The reflecting layer 503 is a metal film formed by evaporating metal on the micro-nano structure layer 502.
The reflective layer 503 is made of aluminum or gold.
Thickness t of the reflective layer 5032Is 50nm-500 nm.
Example 6:
as shown in fig. 6, a micro mirror with micro-nano structure comprises a substrate layer 601, a micro-nano structure layer 602 and a reflective layer 603,
the micro-nano structure layer 602 is located above the substrate layer 601, the micro-nano structure layer 602 is manufactured by performing nano-imprinting or nano-printing in a specific area on the surface of the substrate layer 601, and the reflection layer 603 is located above the micro-nano structure layer 602.
The substrate layer 601 is a wafer, the wafer comprises a device layer 601a, an oxygen buried layer 601b and a support layer 601c, the device layer 601a is a surface layer, and the oxygen buried layer 601b is an intermediate layer; the support layer 601c is a bottom layer.
The device layer 601a is made of monocrystalline silicon, the buried oxide layer 601b is made of silicon dioxide, and the support layer 601c is made of monocrystalline silicon.
The thickness of the monocrystalline silicon device layer 601a is between 10 μm and 100 μm.
The material of the buried oxide layer 601b is silicon dioxide.
The material of the micro-nano structure layer 602 is a polymer, and the material and the thickness t of the micro-nano structure layer 602 are different according to the adopted processing technology1And also different.
When the nano-imprinting processing is carried out, the thickness of the processed lens layer can be controlled by different means for different nano-imprinting processing technologies. For example, for a partial thermal nanoimprint process, the thickness of the resulting lens layer after imprinting can be controlled by controlling the polymer thickness before imprinting and the depth of imprinting at the time of imprinting; for another part of the thermal nano-imprinting process, the thickness of the lens layer obtained after imprinting can be directly controlled by controlling the pattern of the stamp or the mask used for imprinting.
The reflecting layer 603 is a metal film formed by evaporating metal on the micro-nano structure layer 602.
The reflective layer 603 is made of aluminum or gold.
Thickness t of the reflective layer 6032Is 50nm-500 nm.
Example 7:
a laser display system comprises a laser light source 71, a beam combiner 73, a speckle suppression device 74 and a first micro-mirror device 75 which are arranged in sequence,
the laser light source 71 receives the driving signal and emits three-color laser beams;
the collimating unit 72 collimates the laser beams into collimated laser beams meeting the size requirement of the scanning beams respectively;
the beam combiner 73 combines the collimated laser beams into combined beams;
the speckle suppression device 74 is configured to expand, split, homogenize, and converge the combined beam to generate an outgoing beam composed of a plurality of sub-beams;
the first micro-mirror device 75 is configured to reflect the outgoing light beam into a scanning light beam, and project the scanning light beam to a projection surface for scanning display;
the speckle reduction device 74 includes a second micromirror device 742 and a condensing lens (not shown in the figure), the second micromirror device 742 includes a second micromirror 742a and a second micromirror driving device 742b, the second micromirror driving device 742b drives the second micromirror 742a to make a periodic translational motion or a deflection motion in at least one dimension, an incident angle and a position of the expanded beam are periodically changed, a reflected beam composed of a plurality of sub-beams is formed, and optical properties such as phases of the sub-beams have time variability; the condensing lens converges and collimates the reflected light beam to form the emergent light beam.
The first micromirror device 75 includes a first micromirror 751 and a first micromirror driver 752, and the first micromirror driver 752 drives the first micromirror 751 to make a periodic translational or deflecting motion in at least one dimension. As shown in fig. 7, the first micromirror 751 is driven by the first micromirror driving device 752 to make a periodic out-of-plane translation in the vertical direction.
In addition, the first micromirror 751 can be driven by the first micromirror driving device 752 to periodically translate in-plane in the horizontal direction, or periodically translate or deflect in both the horizontal and vertical directions.
In this embodiment, the second micromirror has a micromirror structure of embodiment 5, and the micro-nano structure layer of the second micromirror is a microlens array.
The second micromirror may also be the micromirror structure of embodiment 6, and the micro-nano structure layer of the second micromirror is a fresnel lens array.
Under the condition that the vibrating mirror structure of the second micro mirror and the surface profile of the vibrating mirror are fixed, the larger the area of the vibrating mirror irradiated by the beam expanding light beam is, the better the speckle suppression effect is.
The speckle reduction device 74 further includes a beam expander 741, where the beam expander 741 is a lens group including a first lens 741a and a second lens 741 b. The lens group may be omitted.
Example 8:
as shown in fig. 8, a laser display system includes a laser light source 81, a collimating unit 82, a beam combiner 83 and a speckle reduction device 84 arranged in sequence,
the laser light source 81 receives the driving signal and emits three-color laser beams;
the collimating unit 82 collimates the laser beams into collimated laser beams meeting the size requirement of the scanning beams;
the beam combiner 83 combines the collimated laser beams into combined beams;
the speckle suppression device 84 is used for expanding, splitting, homogenizing and converging the combined beam light, generating a scanning beam composed of a plurality of sub-beams and projecting the scanning beam to a projection surface for scanning and displaying;
the speckle reduction device 84 at least includes a micromirror device 842 and a condenser lens (not shown in the figure), the micromirror device 842 includes the aforementioned micromirror 842a and a micromirror driving device 842b, the micromirror driving device 842b drives the micromirror 842a to make a periodic translational motion or a deflection motion in at least one dimension, and periodically changes the incident angle and the position of the expanded light beam to form a reflected light beam composed of a plurality of sub-light beams; the condensing lens converges and collimates the reflected light beam to form the scanning light beam.
The speckle reduction device 84 also includes a beam expander 841. The beam expander 841 is a lens group including a first lens 841a and a second lens 841 b. The lens group may be omitted.
In this embodiment, the micromirror 842a is a micromirror structure of embodiment 5, and the micro-nano structure layer of the micromirror 842a is a fresnel lens array.
The micromirror 842a can also be a micromirror structure of embodiment 6, and the micro-nano structure layer of the micromirror 842a is a microlens array.
Under the condition that the galvanometer structure of the micromirror 842a and the surface profile of the galvanometer are fixed, the larger the area of the galvanometer irradiated by the expanded beam is, the better the speckle suppression effect is.
Specifically, the laser display system can be applied to a HUD system.
According to the invention, a micro-nano structure formed by special patterns is integrated on a micro mirror surface of the MEMS micro mirror device through a nano imprinting technology and a nano printing technology. Compared with the traditional roughening method such as photoetching, the manufacturing method based on the nanoimprint technology and the nano printing technology can integrate the micro-nano structure which is smaller in size and higher in precision and is formed by special patterns and can perform curved surface reflection on the surface of the micro-mirror galvanometer.
According to the manufacturing method, patterns and distribution of the micro-nano structure can be designed simply and conveniently according to actual requirements, even the micro-nano structure which cannot be realized or is difficult to realize by the traditional method, such as a Fresnel lens array and the like, can be realized, so that the optimal beam homogenizing and splitting effect at the current stage which is the same as that of the micro-lens array is realized in a curved surface reflection mode, and the speckle suppression effect and the applicability of the micro mirror integrated with the curved surface reflection micro-nano structure are far superior to those of the traditional roughened micro mirror. In addition, for a part of simple micro-nano structures such as a micro lens array, direct processing can be carried out through a hot melting process of photoresist and the like.
The micro-mirror device of the invention is independent of the MEMS micro-mirror device for scanning imaging in the scanning laser display system. The MEMS micro-mirror device is characterized in that a laser beam generated by a laser is incident to the MEMS micro-mirror device, and the mirror surface of the micro-mirror device is provided with a micro-nano structure formed by special patterns. The sub-beams forming the scanning beam respectively form speckle patterns with smaller energy when the projection surface is imaged, and the speckle pattern effects with smaller energy are mutually overlapped, so that the overall speckle effect is homogenized, the brightness is weakened, and the speckles appearing during imaging are restrained. Meanwhile, the MEMS micro-mirror device can move in at least one dimension under the driving of an MEMS system, so that the incident angle/position of an incident laser beam is changed periodically, and a reflected beam formed by the MEMS micro-mirror device also has time variation, thereby further realizing speckle suppression.
The micro-mirror device can be manufactured with low cost and high yield by combining the traditional MEMS micro-mirror manufacturing process with the nano-imprinting technology and the nano-printing technology.
By adopting the technical scheme, the invention has the following beneficial effects:
the preparation of the micro mirror is based on a nano-imprinting technology and a nano-printing technology, integrates a curved surface reflection micro-nano structure, has high precision and small size, can realize more uniform distribution of the micro-nano structure, enables the energy of each reflected sub-beam to be more uniform, and enables the speckle suppression effect to be better.
The preparation of the micro-mirror is based on the nano-imprinting technology and the nano-printing technology, the micro-nano structure based on the self-defined pattern can be easily designed and manufactured, the micro-nano structure comprises micro-nano structures which cannot be manufactured or are difficult to manufacture by the traditional photoetching technology, such as a micro-lens array pattern, a Fresnel lens array pattern, a lamellar grating and the like, and the micro-nano structure is integrated on the surface of a vibrating mirror of the MEMS micro-mirror, so that the composition of sub-beams of a reflected beam is more flexibly controlled, and the optimal beam splitting and homogenizing effects on the beam at the present stage, which are the same as the micro-lens array, are realized in a curved surface.
The micro mirror can realize beam splitting and beam homogenizing of all visible light by using a single micro mirror by controlling the size and the arrangement mode of the special micro-nano structure.
The preparation of the micro-mirror is based on the nano-imprinting technology and the nano-printing technology, does not need to be subjected to photoetching for many times, has simple process flow and good process stability, can realize integrated manufacturing by utilizing the nano-printing technology, and even does not need to manufacture a seal and a mask, and has simple process flow.
The micro mirror does not need to be matched with a vibrating projection screen for use, the designed speckle suppression effect can be realized on a static screen, and the convenience and the practicability of the system are improved.
The micro-mirror does not need to introduce additional precise optical elements such as a micro-lens array, a diffractive optical element or a rotating scattering sheet for speckle suppression, and the module has higher reliability, higher integration degree and smaller size.
The micro mirror is driven by the micro mirror driving device, has low power consumption and basically no noise when in work, and can avoid the damage to other components in the module caused by factors such as vibration and the like possibly caused by using other driving modes, thereby improving the reliability of equipment and the module.
The micro mirror has weak rejection to the prior art and good applicability, and can be matched with part of the prior art for use, such as a vibrating screen technology, a speckle suppression technology based on special optical components and the like, so as to further suppress speckles and make up for the defect of the part of the prior art in the degree of speckle suppression.
When the invention is applied to the HUD system, the MEMS micro-mirror device can directly replace the MEMS micro-mirror device in the original laser display system, namely only one micro-mirror device is needed in the system, the speckle suppression and scanning display functions can be realized simultaneously, and the speckle suppression function is realized without adding extra parts, so that the complexity of system integration is not increased, and the power consumption of the system is not increased.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. A method for manufacturing a micromirror, comprising the steps of:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer on the surface of the wafer device layer;
heating the polymer layer in a vacuum environment until the temperature of the polymer layer is higher than the glass transition temperature of the polymer layer, stamping the liquid polymer layer to a certain depth by using a stamp, and keeping for a period of time to enable the liquid polymer to fill the gaps of the stamp graph;
step four, reducing the temperature to solidify the polymer and demoulding to form a micro-nano structure layer;
evaporating and plating a reflecting layer on the surface of the micro-nano structure layer;
removing the redundant polymer layer on the device layer, and then etching the device layer to the oxygen burying layer to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer of the wafer, and etching the back cavity to the buried oxide layer to expose the buried oxide layer within the range of the back cavity;
and step eight, corroding the oxygen burying layer exposed in the range of the back cavity to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
2. The method of claim 1, wherein: the polymer layer is a thermoplastic polymer, and the thermoplastic polymer is made of polypropylene ethylene or polymethyl methacrylate.
3. A method for manufacturing a micromirror, comprising the steps of:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer on the surface of the wafer device layer;
third, stamping the liquid polymer layer to a certain depth by using a stamp in a vacuum environment, keeping for a period of time, filling the gaps of the stamp pattern with the liquid polymer, and irradiating by using ultraviolet light through the stamp;
solidifying a polymer layer filled in the seal and demolding to form a micro-nano structure layer;
evaporating and plating a reflecting layer on the surface of the micro-nano structure layer;
removing the redundant polymer layer on the device layer, and then etching the device layer to the oxygen burying layer to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer of the wafer, and etching the back cavity to the buried oxide layer to expose the buried oxide layer within the range of the back cavity;
and step eight, corroding the oxygen burying layer exposed in the range of the back cavity to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
4. The method of claim 3, wherein: the polymer layer is made of ultraviolet curing materials.
5. A method for manufacturing a micromirror, comprising the steps of:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer on the surface of the wafer device layer;
scanning the surface of the device layer of the substrate layer by layer to form a micro-nano structure layer with a designed pattern by utilizing a two-photon polymerization technology;
after the pattern of the micro-nano structure layer is completely formed by a two-photon polymerization technology, removing the redundant polymer layer;
evaporating and plating a reflecting layer on the surface of the micro-nano structure layer;
removing the redundant polymer layer on the device layer, and then etching the device layer to the oxygen burying layer to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer of the wafer, and etching the back cavity to the buried oxide layer to expose the buried oxide layer within the range of the back cavity;
and step eight, corroding the oxygen burying layer exposed in the range of the back cavity to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
6. The method of claim 5, wherein: the polymer layer is a negative photoresist.
7. A method for manufacturing a micromirror, comprising the steps of:
firstly, preparing a wafer, and defining the outline of a micro mirror on the surface of the wafer;
step two, uniformly coating a polymer layer on the surface of the device layer of the wafer, wherein the polymer layer is photoresist;
etching the polymer layer into a plurality of fine cylindrical polymer layers by photoetching and developing;
heating and baking the small cylindrical polymer layers to be in a lens shape under the action of tension, and cooling to form a micro-nano structure with a micro-lens array;
evaporating and plating a reflecting layer on the surface of the micro-nano structure layer;
removing the redundant polymer layer on the device layer, and then etching the device layer to the oxygen burying layer to form the main structures of the electric isolation groove and the micro mirror;
preparing a back cavity on the supporting layer of the wafer, and etching the back cavity to the buried oxide layer to expose the buried oxide layer within the range of the back cavity;
and step eight, corroding the oxygen burying layer exposed in the range of the back cavity to release the movable part of the micro mirror, thereby finishing the manufacture of the micro mirror.
8. A micro mirror with a micro-nano structure, which is characterized in that the micro mirror is prepared according to the micro mirror preparation method of claim 1 or 3 or 5 or 7, and comprises a substrate layer, a micro-nano structure layer and a reflection layer, wherein the micro-nano structure layer is positioned above the substrate layer, the micro-nano structure layer is arranged in a specific area on the surface of the substrate layer, the micro-nano structure layer is a micro lens array or a Fresnel lens array, and the reflection layer is positioned above the micro-nano structure layer.
9. A laser display system is characterized by comprising a laser light source, a collimation unit, a beam combiner, a speckle suppression device and a first micro-mirror device which are sequentially arranged,
the laser light source receives the driving signal and emits laser beams with at least one color;
the collimation unit respectively collimates the laser beams into collimated laser beams meeting the size requirement of scanning beams;
the beam combiner forms the collimated laser beams into combined beams; the speckle suppression device is used for expanding, splitting, homogenizing and converging the combined beam to generate an emergent beam consisting of a plurality of sub-beams;
the first micro-mirror device is used for reflecting the emergent light beam into a scanning light beam and projecting the scanning light beam to a projection surface for scanning display;
the speckle suppression device at least comprises a second micromirror device and a condensing lens, wherein the second micromirror device comprises a second micromirror and a second micromirror driving device, the second micromirror adopts the micromirror of claim 8, and the second micromirror driving device drives the second micromirror to make periodic translation or deflection motion in at least one dimension, so that the incident angle and the position of the expanded beam are periodically changed, and a reflected beam consisting of a plurality of sub-beams is formed; the condensing lens converges and collimates the reflected light beam to form the emergent light beam.
10. A laser display system is characterized by comprising a laser light source, a collimation unit, a beam combiner and a speckle suppression device which are sequentially arranged,
the laser light source receives the driving signal and emits laser beams with at least one color;
the collimation unit respectively collimates the laser beams into collimated laser beams meeting the size requirement of scanning beams;
the beam combiner forms the collimated laser beams into combined beams; the speckle suppression device is used for expanding, splitting, homogenizing and converging the combined beam light, generating a scanning beam consisting of a plurality of sub-beams and projecting the scanning beam to a projection surface for scanning and displaying;
the speckle suppression device at least comprises a micromirror device and a condensing lens, wherein the micromirror device comprises the micromirror of claim 8 and a micromirror driving device, and the micromirror driving device drives the micromirror to make periodic translation or deflection motion in at least one dimension, so as to periodically change the incident angle and position of the expanded beam and form a reflected beam consisting of a plurality of sub-beams; the condensing lens converges and collimates the reflected light beam to form the scanning light beam.
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