CN113031127B

CN113031127B - Wafer-level optical system and laser micro projection equipment applying same

Info

Publication number: CN113031127B
Application number: CN201911256481.1A
Authority: CN
Inventors: 马宏
Original assignee: Juexin Electronics Wuxi Co ltd
Current assignee: Juexin Electronics Wuxi Co ltd
Priority date: 2019-12-09
Filing date: 2019-12-09
Publication date: 2022-11-11
Anticipated expiration: 2039-12-09
Also published as: CN113031127A

Abstract

The invention provides a wafer-level optical system and laser micro-projection equipment using the same, wherein the optical system comprises an optical frame structure and an optical wafer structure which are formed by space wafers; the optical frame structure formed by the space wafers is a supporting structure formed by stacking a plurality of semiconductor wafers through a semiconductor processing technology and used for supporting the optical wafer structure; the optical wafer structure is bonded with an optical frame structure formed by the space wafer; the optical wafer structure comprises an optical wafer body bonded with the space wafer and an optical structure formed on the surface of the optical wafer.

Description

Wafer-level optical system and laser micro projection equipment applying same

Technical Field

The invention relates to the technical field of micro-nano manufacturing and processing, in particular to a wafer-level optical system and laser micro-projection equipment using the same.

Background

Speckle is a granular speckle of random intensity 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. According to the related research, when the speckle contrast is suppressed below 4% for the image projected by the laser display system, the human visual system cannot recognize 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 brightness of the low-coherence laser light source or the speckle formed by averaging is formed by driving multiple lasers, is compensated for in human vision by an oscillating projection screen, and the optical properties of the laser beam are influenced temporally and/or spatially by adding optical elements with specific functions in the beam path. The total output light power is constant due to the light emitting characteristic of the laser, 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 at present include various scattering sheets, diffractive optical elements, micro-lens arrays and MEMS micro-mirrors 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. 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 due to the micro/nano structure of the diffractive optical element, 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. However, since a specific diffractive optical element can only split a coherent light beam having a specific wavelength, there is a certain limitation in use. 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. However, using 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 some documents, the height or depth of the protrusions formed by roughening needs to be 1/4 to 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.

The terahertz imaging technology is a technology that an object to be measured is irradiated by terahertz light, and transmission or reflection information of the object is collected on a focal plane so as to form an image. Terahertz imaging is widely applied to the fields of nondestructive testing, security inspection and biomedicine at present.

The selection of a suitable terahertz light source is a key technology of the imaging system. Compared with point light source scanning imaging, the terahertz area array imaging method has the advantages of more pixels, high imaging speed, real-time imaging and the like. The surface light source required by the area array imaging system and the response degree calibration of the area array detector both require the use of large-area terahertz light beams with uniform energy distribution. The existing terahertz source mainly utilizes a gas laser to pump methanol, difluoromethane or methane chloride to generate terahertz light with different wave bands or utilizes a Quantum Cascade Laser (QCL) to realize all-solid-state terahertz laser. The terahertz light output generated by the two methods has power fluctuation, the diameter of a light spot is very small (in millimeter level), the energy is in Gaussian distribution, and the requirements of an area array real-time imaging system cannot be met. In order to obtain a large-area uniform terahertz light beam, a device for expanding and homogenizing terahertz laser is needed.

Although the prior art can basically meet the requirement of obtaining large-area uniform terahertz beams, more uniform flat-top energy distribution still cannot be achieved, and the calibration of a focal plane detector is not facilitated.

Optical integrators are commonly used in illumination apparatuses and exposure apparatuses, and achieve uniform illumination or exposure through their own optical characteristics. Fly-eye optical integrators are also widely used in the field of laser speckle suppression. Fly-eye optical integrators are typically composed of several lenses and a set of microlens array pairs. The characteristic that the light beam can form a light beam consisting of a plurality of sub-light beams after penetrating through the compound eye optical integrator is utilized, the sub-light beams forming the light beam respectively form speckles with weak energy when in projection display, and the formed speckle effects are mutually overlapped in the human eye visual persistence time, so that the integral speckle phenomenon is suppressed while the integral brightness of the light spot is maintained.

Disclosure of Invention

In order to solve the technical problems, the invention provides a multifunctional wafer-level optical system which can be applied to optical systems such as laser display and terahertz imaging, and aims to solve the corresponding technical problems such as speckle suppression and light energy homogenization and maintain the integratability of a module. Meanwhile, the multifunctional wafer-level lens set provided by the invention is used for carrying out semiconductor processing and optical process processing by taking wafers as units, and after the processing is finished, a plurality of aligned wafers are stacked and bonded into a whole through a wafer bonding process, so that the multifunctional wafer-level lens set is produced and manufactured in a large batch manner with low cost, high yield and high process controllability.

In a first aspect of the present invention, a wafer-level optical system is provided, where the optical system includes an optical frame structure formed by a space wafer and an optical lens structure formed by an optical wafer; the optical frame structure formed by the space wafers is a supporting structure formed by stacking a plurality of semiconductor wafers through a semiconductor processing technology and used for supporting the optical lens structure formed by the optical wafers; an optical lens structure formed by the optical wafer is bonded with an optical frame structure formed by the space wafer; the optical lens structure formed by the optical wafer comprises an optical wafer body bonded with the space wafer and an optical structure formed on the surface of the optical wafer.

Further, a variable focus lens is integrated in the wafer level optical system.

In a second aspect of the invention, a laser microprojection apparatus is provided, the apparatus comprising a wafer-level optical system.

In a third aspect of the present invention, a terahertz imaging system is provided, which includes a wafer-level optical system.

The multifunctional wafer-level lens group has at least one of the following characteristics:

firstly, the lens assembly is stacked by a plurality of space wafers to form an optical frame structure of the lens assembly, and the optical frame structure is used for fixing and aligning various lens structures forming the lens assembly and determining the distance between the lens structures.

And secondly, the lens group is stacked through various lenses to form a complete multifunctional optical system which comprises a compound eye optical integrator system and realizes operations of collimation, beam expansion, beam splitting, condensation and the like on incident beams.

Third, a lens constituting the lens group includes: a planar lens for controlling the amount of incident light, at least one cylindrical lens for controlling the beam shape, at least one collimating lens for collimation, a group of lens groups for expanding the beam (telecentric lens group), at least one lens array for forming a fly-eye optical integrator, and at least one condenser lens for collecting the beam. The lens array includes, but is not limited to, a spherical microlens array, a lenticular lens array, a fresnel lens array, etc.

Fourthly, the various lenses and lens arrays may be single-sided wafer-level lenses integrated on one main surface of the optical wafer, double-sided wafer-level lenses integrated on both main surfaces of the optical wafer, or integrated wafer-level lenses manufactured by processes such as imprinting and the like and containing no other substrate material.

Fifth, in general, each lens constituting the lens group operates in a stationary state. However, when the lenses are integrated on a MEMS device based on an SOI wafer, the lenses can be moved under the drive of the MEMS system to achieve more functions.

Sixthly, the processing process of the lens group is always carried out by taking a wafer as a unit, and the processing technology belongs to the wafer-level processing technology. The method comprises the steps of stacking, bonding, thinning and the like a plurality of semiconductor wafers which are independently processed to form a complete wafer with the lens groups arranged, and finally separating the independent lens groups from the wafer through cutting, scribing and other processes.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic diagram of an optical path structure of a laser micro-projection device according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a wafer level optical system according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a wafer level optical system according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a wafer level optical system according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a wafer level optical system with a variable focus structure according to an embodiment of the present invention;

FIG. 6 (a) is a schematic diagram of a wafer level optical system with a variable focus structure according to an embodiment of the present invention;

FIG. 6 (b) is a schematic diagram of a wafer level optical system with a variable focus structure according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a wafer level optical system with a variable focus structure according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of an embodiment of a wafer level optical system according to the present invention;

FIG. 9 is a schematic diagram of a wafer level optical system with a variable focus structure according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of a wafer level optical system with a variable focus structure according to an embodiment of the present invention;

FIG. 11 is a top view of a wafer level optical system with a variable focus structure according to an embodiment of the present invention;

FIGS. 12 (a) - (b) are schematic diagrams of wafer level dicing of a lens assembly with a variable focus lens structure according to the invention;

fig. 13 (a) -fig. 13 (h) are schematic diagrams illustrating a manufacturing process of a wafer-level variable focus lens according to an embodiment of the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the 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, are used in an orientation or positional relationship indicated on the basis of the orientation or positional relationship shown in the drawings, which is for convenience of description and simplicity of description only, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated in a particular manner, and therefore, are not to 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 to implicitly indicate 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.

The first embodiment is as follows:

in an alternative embodiment, as shown in fig. 1, a schematic diagram of the optical path structure of the optical module of the most basic laser micro-projection device is shown.

The laser driving signal drives the three-color laser group 101 to emit corresponding laser beams of three colors RGB, which are collimated by the collimating lens disposed in the lens group 102 at a close distance. Each laser corresponds to a collimating lens in the emitting direction. The collimated three-color laser beams are combined into a combined beam 111 via the beam combiner 103.

The synthesized light beam 111 is reflected by the MEMS micro-mirror 121 under the control of the micro-mirror driving system 122 to be a scanning light beam 123, and is projected to a projection surface for scanning display, thereby forming a scanning image 124.

The second embodiment:

in an alternative embodiment, as shown in FIG. 2, a schematic diagram of a wafer level lens assembly is shown. The wafer level lens assembly may be placed at the position of the lens assembly 102 in the optical system shown in fig. 1 in place of the collimating lenses in the lens assembly 102.

The wafer level lens group consists of 17 layers of wafers, including 10 layers of space wafers and 7 layers of optical wafers. The space wafer is used as a supporting structure of the wafer-level lens group and is manufactured by a semiconductor wafer through a semiconductor processing technology. According to actual requirements and design, semiconductor wafers with different materials and sizes can be selected from the same wafer-level lens group for processing, space wafers with different thicknesses are generated, and the distance between the lenses is controlled by changing the number of the space wafers and the size of a single wafer.

The optical wafer integrates various lens structures on the surface of the wafer, and the optical wafer and the various lens structures integrated on the surface jointly form a lens part of the wafer-level lens group. According to different manufacturing modes, the materials of various lenses integrated on the surface of the optical wafer are ultraviolet light curing materials or hot melting curing materials or the optical wafer. The various lens structures can be integrated through the traditional wafer-level optical processing technology, such as mould pressing, photoetching, etching technology and the like, or integrated through the nano-imprinting and nano-printing technology.

And processing each layer of space wafer and each layer of optical wafer separately, and processing the space wafer and the optical wafer by using a bonding process after processing and forming. The space wafer and the optical wafer are directly or indirectly bonded, so that the wafer structures of all layers are coupled into a whole.

The embodiment of the wafer-level lens assembly shown in fig. 2 is characterized in that the optical path structure formed by the lens portion can form a complete optical system with multiple functions. The

lens portions

218, 210, 212, 214, 216, 217, 219 are all formed by an optical wafer as a substrate, and lenses of various functional structures or coatings for changing reflectivity are integrated on the surface of the wafer.

The light beam enters the wafer-level lens group through the lens portion 218 and exits the lens portion 219. The lens portion 218 is a flat lens, and is formed by integrating a mirror surface or a coating layer having a specific transmittance on the principal surface of an optical wafer as a substrate, thereby forming a flat lens portion which can completely or incompletely transmit a light beam. The optical transparency of the lens portion 218 can be predetermined at design time according to the function of the lens assembly 200 shown. In some embodiments, the lens portion can only pass a portion of the light, which is related to the transmittance of the lens portion 218, for example, if the transmittance of the lens portion is 90%, the lens portion 218 can only pass 90% of the light beam, and the remaining 10% of the light beam is reflected by the lens portion 218 and returns to the laser along the original optical path, so that the laser enters a coherence collapse state, thereby reducing the coherence of the laser beam generated by the laser.

The lens unit 210 is a convex lens, collimates an incident light beam, and has the same function as the lens group 102 shown in fig. 1.

Lens portion 212 is a concave lens and lens portion 214 is a convex lens. The concave lens 212 and the convex lens 214 together form a telecentric lens structure, and expand the small-sized light beams collimated by the lens portion 210 to form large-sized collimated light beams.

The

lens portions

216 and 217 integrate a microlens array on the principal surface of the optical wafer to form a fly-eye optical integrator. The single light beam can form a light beam consisting of a plurality of sub-light beams after passing through the compound eye type optical integrator.

The lens part 219 is a convex lens and functions as a condenser lens. The light beam composed of a plurality of sub-beams formed after passing through the fly-eye integrator is focused and converged by the lens part 219 to form a light beam having a size in accordance with the design requirement.

In the wafer-level lens group 200, the

lens portions

212, 214, 216, 217 and 219 together form a sub-optical system capable of suppressing the laser speckle phenomenon, and the sub-optical system is matched with a laser coherence collapse state caused by the lens portion 218, so that the most perfect speckle suppression at the present stage is realized. Therefore, when the wafer-level lens assembly 200 is applied to a laser display system, the optical system formed by the lens assembly 200 has two functions of laser beam collimation and speckle suppression.

Example three:

in an alternative embodiment, as shown in fig. 3, a wafer level lens assembly is proposed, which consists of 24 layers of wafers, including 15 layers of space wafers and 9 layers of optics wafers. The wafer level lens assembly shown in FIG. 3 has exactly the same function as the embodiment shown in FIG. 2, and can be placed at the position of the lens assembly 102 shown in FIG. 1 instead of the collimating lenses in the lens assembly 102.

The space wafer is used as a supporting structure of the wafer-level lens group and is manufactured by a semiconductor wafer through a semiconductor processing technology. According to actual requirements and design, semiconductor wafers with different materials and sizes can be selected from the same wafer-level lens group for processing, space wafers with different thicknesses are generated, and the distance between the lenses is controlled by changing the number of the space wafers and the size of a single wafer.

The space wafer and the optical wafer of each layer are separately processed. After processing and forming, direct or indirect bonding is carried out between the space wafers and the optical wafers by utilizing a wafer-level optical processing technology, so that the wafer structures of all layers are coupled into a whole.

The embodiment shown in fig. 3 differs from the embodiment shown in fig. 2 in that the embodiment shown in fig. 3 uses a rod lens array-based optical integrator instead of the micro-lens array-based fly-eye optical integrator used in the embodiment shown in fig. 2.

Example four:

in an alternative embodiment, as shown in fig. 4, a wafer level lens assembly is proposed, which consists of 24 layers of wafers, including 15 layers of space wafers and 9 layers of optics wafers. The wafer level lens assembly shown in fig. 4 has exactly the same function as the embodiment shown in fig. 2, and can also be placed at the position of the lens assembly 102 shown in fig. 1, instead of the collimating lenses in the lens assembly 102.

The embodiment shown in fig. 4 is different from the embodiment shown in fig. 2 in that the embodiment shown in fig. 4 uses a double-layer wafer level lens, and integrates microlens arrays on two main surfaces of the same optical wafer at the same time, instead of the fly-eye optical integrator based on two single-layer wafer level lenses used in the embodiment shown in fig. 2.

Example five:

FIG. 5 is a schematic diagram of one embodiment of the wafer level lens assembly.

As shown in fig. 5, the wafer level lens assembly is composed of 15 layers of wafers, including 8 layers of space wafers, 1 layer of MEMS structure, and 6 layers of optical wafers. The wafer level lens assembly shown in fig. 5 has almost the same function as the embodiment shown in fig. 2, and can be placed at the position of the lens assembly 102 shown in fig. 1, instead of each collimating lens in the lens assembly 102, and has the function of speckle suppression.

The embodiment shown in fig. 5 contains only one microlens array and integrates the microlens array on a MEMS structure with a vertical comb structure. MEMS structure 521 is fabricated from an SOI wafer by a semiconductor processing process with a vertical comb structure. In further embodiments, the MEMS structure has a horizontal comb tooth structure, or both a horizontal comb tooth structure and a vertical comb tooth structure.

When the MEMS structure is driven, the MEMS structure drives the micro-lens array integrated with the surface device layer to move in at least one dimension. According to different designed comb tooth structures, the MEMS structure has different translation modes. For MEMS structures with only horizontal comb fingers, the MEMS structure can only resonate at a certain frequency. For MEMS structures with vertical comb teeth, the MEMS structure can move both in resonance and quasi-static, even remaining stationary at a certain spatial location. The MEMS structure is driven in an electrostatic mode. Through the operation, the sub-beams formed after transmission have time-varying property, and the speckle suppression effect is improved.

In the embodiment shown in fig. 5, the lens assembly contains a movable MEMS structure. To transmit the driving signals to the MEMS structure, the partial space wafer constituting the embodiment shown in FIG. 5 includes through-silicon vias (not shown). The driving signals generated by the ASIC (not shown) are transmitted to the MEMS structure through the through-silicon vias. The ASIC can be directly bonded on the upper/lower surfaces of the lens group and directly transmits a driving signal through a silicon through hole; or the MEMS structure can be subjected to system-in-package with the lens group, and the driving signal is transmitted to the lens group through lead bonding and then transmitted to the MEMS structure through the through silicon via; the lens group can also be connected with an independently packaged lens group and transmits a driving signal through lead bonding.

In certain embodiments, the non-movable portion of the MEMS structure is also lined with through silicon vias.

As shown in fig. 5, the laser diode generates a first laser beam 501 at a certain divergence angle. The laser beam 501 passes mostly through the planar lens 511 and a small portion is reflected by 511 to the laser diode, causing it to enter a coherence collapsed state. The passed laser beam is collimated into a collimated beam after entering the collimating lens 512. The collimated light beam passes through a telecentric lens group consisting of a plurality of lenses in sequence, expands the beam and is re-collimated into a collimated light beam with larger size. The telecentric lens group is shown at 513, 514 in fig. 5, but may contain more lenses in actual design. The collimated beam having a large size after the re-collimation is incident on the microlens array 515 integrated in the MEMS portion, and a beam composed of a plurality of sub-beams is formed. The beam composed of several sub-beams is further converged by the condenser lens 516 into the second laser beam 502 conforming to the laser scanning display size. The laser beam 502 is then incident on a beam combiner (not shown) that combines the two other laser beams of different wavelengths (colors) into a single laser beam and directed to a scanner (not shown).

Example six:

fig. 6 (a) and 6 (b) are schematic structural diagrams of one embodiment of the wafer level lens assembly. As shown in fig. 6 (a) and 6 (b), the wafer level lens assembly is composed of 17 layers of wafers, including 9 layers of space wafers, 1 layer of MEMS structure, and 7 layers of optical wafers. The wafer level lens assembly shown in fig. 6 (a) and 6 (b) has almost the same function as the embodiment shown in fig. 2, and can be placed at the position of the lens assembly 102 shown in fig. 1, instead of each collimating lens in the lens assembly 102, and has the function of speckle suppression.

The embodiment shown in fig. 6 (a), 6 (b) contains two microlens arrays, and the second microlens array is integrated on the MEMS structure having comb structure. The MEMS structure 621 is fabricated from an SOI wafer by a semiconductor processing process, having a vertical comb structure, as shown in fig. 6 (a). In other embodiments, the MEMS structure has a horizontal comb structure, as in FIG. 6 (b), or both a horizontal and vertical comb structure.

When the MEMS structure is driven, the MEMS structure drives the micro-lens array integrated with the surface device layer to move in one dimension. According to different designed comb tooth structures, the MEMS structure has different translation modes. For MEMS structures with only horizontal comb fingers, the MEMS structure can only resonate at a certain frequency. For MEMS structures with vertical combs, the MEMS structure can move either in resonance or quasi-static, even remaining stationary at a spatial location. The MEMS structure is driven in an electrostatic mode.

Through the operation, the sub-beam formed after transmission has time-varying property, and the speckle suppression effect is improved. Compared with the embodiment shown in fig. 2, the embodiment shown in fig. 6 (a) and 6 (b) adds an MEMS structure, increases the process complexity, and increases the manufacturing cost. However, compared with the embodiment shown in fig. 2, the sub-beams generated by the embodiment shown in fig. 6 (a) and 6 (b) have time-varying characteristics, and the speckle reduction effect is better. Compared with the embodiment shown in fig. 5, the embodiment shown in fig. 6 (a) and 6 (b) has a compound eye structure formed by a double micro lens array, and the speckle suppression effect is better.

Like the fifth embodiment, the sixth embodiment is also provided with a through silicon via structure (not shown).

Example seven:

FIG. 7 is a schematic diagram of one embodiment of the wafer level lens assembly. As shown in fig. 7, the wafer level lens assembly is composed of 18 layers of wafers, including 9 layers of space wafers, 2 layers of MEMS structures, and 7 layers of optical wafers. The wafer level lens assembly shown in fig. 7 has almost the same function as the embodiment shown in fig. 2, and can be placed at the position of the lens assembly 102 shown in fig. 1, instead of each collimating lens in the lens assembly 102, and has the function of speckle suppression.

The embodiment shown in fig. 7 contains two microlens arrays and integrates the two microlens arrays on the MEMS structure having the vertical comb tooth structure, respectively. MEMS structures 721, 722 are fabricated from SOI wafers by semiconductor processing, with vertical comb tooth structures. In other embodiments, there is both a horizontal and a vertical comb tooth configuration.

When the MEMS structure is driven, the MEMS structure drives the micro-lens array integrated with the surface device layer to move in one dimension. Compared with the embodiments shown in fig. 6 (a) and 6 (b), the embodiment shown in fig. 7 has a unique motion pattern. In operation, the MEMS structure is actuated to move the two microlens arrays to a position and remain stationary, respectively, such that the second microlens array 712 is located at the focal plane of the first microlens array 711, the focal length of the first microlens array being f. By further driving the MEMS structure, the distance between the second microlens array and the condenser lens can be changed, thereby changing the size of the light beam incident on the condenser lens to some extent. It should be noted that, in this process, the first microlens array is also driven by the corresponding MEMS structure to remain relatively stationary with the second microlens array, so that the second microlens array is always located on the focal plane of the first microlens array.

The embodiment shown in fig. 7 can also realize the motion modes of the embodiments shown in fig. 6 (a) and 6 (b) through the MEMS structure. The MEMS structure is driven in an electrostatic mode.

Through the operation, the sub-beams formed after transmission can have time-varying property, the speckle suppression effect is improved, and the size of the beams entering the condensing lens can be controlled to a certain degree.

Like the fifth embodiment, the seventh embodiment is also provided with a through silicon via structure (not shown).

Example eight:

FIG. 8 is a schematic structural diagram of one embodiment of the wafer level lens assembly.

As shown in FIG. 8, the wafer level lens set is actually composed of two sub-wafer level lenses. The two sets of wafer level lenses may be fabricated by wafer level optical processing to form the embodiment of the wafer level lens set shown in fig. 8. The collimating function and the speckle suppression/beam homogenizing function of the wafer-level lens group shown in the figures 2-7 are separated. The collimation function and the speckle suppression/homogenization function of the embodiment shown in fig. 7 are respectively composed of a first sub-lens group 810 and a second sub-lens group 820. A first sub-lens group 810 is disposed near the exit surface of each laser. When applied to the laser display module shown in fig. 1, there are 3 first

sub-lens groups

810 and 1 second sub-lens group 820 constituting the optical system. A beam combiner 804 is disposed between the two sub-lens groups, and the beam combiner 804 may be formed by known devices such as dichroic filters. A laser beam 801 having a divergence angle generated by a laser is collimated into a collimated beam by a first sub-lens group 810 placed at a close distance. The collimated light beam is combined with the other two

laser beams

802 and 803 by the beam combiner, enters the second sub-lens group 820, and forms a laser beam consisting of a plurality of sub-beams after passing through 820. The

laser beams

802, 803 are generated by further lasers and are likewise collimated by the same first sub-lens groups 810 as 810, respectively placed closer to the lasers (not shown in the figure). The first sub-lens group 810 and the second sub-lens group 820 are both bottom-sealed by an optical wafer, so that wafer-level vacuum packaging is realized. Meanwhile, the optical wafer bottom cover of the first sub-lens group 810 is plated with a coating capable of changing reflectivity, and the optical wafer bottom cover of the second sub-lens group 820 is plated with an anti-reflection film.

Compared to the embodiments shown in fig. 2-7, the collimation and speckle suppression/beam homogenization functions of the embodiment shown in fig. 8 are respectively realized by two independent sub-lens groups. The method has the advantages of reducing the number of wafer layers required by the system and reducing the cost.

Meanwhile, the second sub-lens group of the embodiment shown in fig. 8 may be replaced with the corresponding portion of the embodiment shown in fig. 2 to 7, constituting a new embodiment.

Example nine:

in one embodiment of the present description, the variable focus lens arrangement contained in the lens group is as shown in fig. 9, and the micro-scale continuously variable focus lens 900 is composed of a MEMS driving part 910 and a lens part 920. The MEMS driving part 910 is manufactured from an SOI wafer through a semiconductor process, and the lens part 920 is manufactured from an optical wafer through a wafer-level optical process. The MEMS driving part 910 and the lens part 920 are first manufactured separately, then wafer-level bonding is performed through a bonding process to form a composite integral wafer, and then the lens part 920 is separated from the optical wafer through a cutting or etching process to release the movable structure, thereby completing the wafer-level variable focus lens apparatus. And finally, carrying out wafer-level bonding with other wafers forming the lens group, and separating the lens group containing the continuous variable-focus lens from the whole wafer through a cutting process.

The micro-size in the present invention means that the overall size of the lens is in the order of hundreds of micrometers to millimeters, for example, the lens has a length and a width of 0.5-1mm, or the lens has a length and a width of several millimeters.

The lens portion 920 is composed of an optical wafer whose lower bottom surface (second main surface) is formed into a grid cavity structure (frame structure) by dry etching, and a surface-integrated lens structure, so as to facilitate later dicing. The lens structure may be integrated on the upper surface (first main surface) of the optical wafer by a photolithography and etching process, a molding process, an ultraviolet nanoimprint process, or the like. The integrated lens has different structures and different precision requirements, and different manufacturing processes are required. For the embodiment shown in fig. 1, the integrated lens structure is a simple spherical lens with the aperture of 2mm-3mm, and the precision requirement is not high, so that the integrated lens structure can be realized by adopting a simple photoetching and etching or mould pressing process. The MEMS driving part 910 and the lens part 920 are separately manufactured in a wafer unit, and then coupling of the wafer wafers is achieved through an anodic bonding process or the like. The process flows are all wafer level, i.e. wafers of various types of wafers are taken as operation objects. Finally, the lens portion 920 is separated from the optical wafer by a dicing process, releasing the movable structure, and the wafer-level zoom lens apparatus is completed. The transverse dimensions of a single said variable focus lens arrangement are substantially dependent on the dimensions of the MEMS drive section, and are approximately: the length is 5mm-6mm, the width is 3mm-4mm, and the whole size of the device is millimeter level. In some scenarios the size of the variable focus device may be made smaller, for example in the range of 0.5-1mm in length and width.

The SOI wafer used to fabricate the MEMS driver 910 is comprised of one or more layers of a single crystal silicon device layer 911, one or more buried silicon dioxide layers 912, and a bottom single crystal silicon substrate layer 913. Wherein the single crystal silicon device layer 911 is between 10 μm and 100 μm thick.

The MEMS driver 910 contains a window structure formed by etching through a SOI wafer. The silicon frame structure of the window structure is coupled to the bottom surface (second main surface) of the optical wafer by anodic bonding. The upper surface (first main surface) of the optical wafer is integrated with a spherical lens, the spherical lens is aligned with the light-transmitting window structure below, and the alignment error range is 1-10 μm. The optical wafer and the spherical lens together form a lens portion 920 of the device.

The MEMS driving part 910 includes a comb structure, and is driven by an electrostatic driving method, so that the movable structure of the MEMS driving part 910 drives the lens part 920 to periodically perform a resonant motion in at least one dimension. In the embodiment shown in fig. 9, the MEMS driving part 910 drives the lens part 920 to perform a periodic resonant motion in the vertical direction (Z direction), and the motion stroke is within 0-200 μm. Thus, the embodiment of FIG. 9 has a continuously variable focus in the range of 0-200 μm.

In some embodiments, the fixed structure of the MEMS driver 910 is also lined with through silicon vias.

In summary, the overall size of the device is very small, the whole device is in the millimeter order, and the zooming range is also small, which results in that the traditional driving method cannot realize driving, such as motor driving, piezoelectric driving and the like are ineffective. The embodiment solves the structural design of the small-size variable-focus lens on one hand and also solves the problem of driving the lens under the small size on the other hand.

Example ten:

in the system shown in fig. 10, lens set 1030 is comprised of several different types of lenses. The lens 1021, the lens 1023, the lens 1024 and the lens 1025 are integrated on an optical wafer through wafer-level optical processing, and jointly form a lens part in the lens group. The whole size of each lens part is millimeter-sized and about 1mm-2mm, and the aperture size of the unit lens of the micro lens array is micron-sized and about 300nm-400 μm.

In the embodiment shown in fig. 10, the lens 1021, the lens 1023, the lens 1024 and the lens 1025 are sequentially a convex lens, a concave lens, a convex lens and a convex lens. The aperture sizes of the two convex lenses are different, and the lens 1023 and the lens 1024 are fixed lenses, and the lens 1021 and the lens 1025 are movable lenses based on the MEMS technology described in the specification.

Specifically, the lens 1021 is a non-variable focal length convex lens, the lens 1023 is a variable focal length concave lens, the lens 1024 is a variable focal length convex lens, and the lens 1025 is a variable focal length convex lens. The lens 1021, the lens 1023, the lens 1024 and the lens 1025 form an optical system similar to a conventional camera lens, but different from a conventional camera lens in which a lens structure is driven by a mechanical device to move for focusing, in the embodiment shown in fig. 10, the overall focal length of the optical system is adjusted by the variable-focus lens 1021 and the lens 1025 which are driven by MEMS, so that a function similar to that of the conventional camera lens is realized, and fine focusing is realized.

Fig. 10 is a diagram schematically illustrating that the variable focus lens based on MEMS technology according to the present specification can be used in an optical path system of a multi-lens, and the type, size, number, arrangement order, mobility, etc. of the lens portions constituting the lens group 1030 can be designed according to practical situations, and is not limited to the embodiment shown in fig. 10.

The lens group 1030 of fig. 10 further includes a plurality of supports and MEMS actuators fabricated from a semiconductor wafer by semiconductor processing. The MEMS driving unit 1011 and the driving unit 1015 are coupled to the lens unit 1021 and the lens unit 1025 by direct bonding, and together constitute the movable lens based on the MEMS technology described herein. The

support portions

1012, 1013, and 1014 are fabricated from a semiconductor wafer by semiconductor processing (etching). The MEMS driving unit 1011 and the driving unit 1015 are formed from an SOI wafer, and the lens 1021 and the lens 1025 are integrated in a device layer of the SOI wafer.

In the initial state, the distance between the lens 1025 and the components of the photosensitive chip in the system is D. When the MEMS driving device works, the MEMS driving part is driven as required, the lens part integrated on the device layer is driven to perform quasi-static translation in the vertical direction (Z-axis direction) through the vertical comb structure of the MEMS driving part, and the translation distance is

The distance is typically no more than the thickness of the device layer of the SOI wafer used to fabricate the MEMS actuators, and ranges from 0-50 μm.

And is also the focusing range of the camera automatic focusing system. The thickness of the semiconductor wafer and the size of the window structure can be designed according to the actual situation, and is not limited to the embodiment shown in fig. 10.

Example eleven:

in fig. 11,

regions

1122, 1123, and 1124 represent lens portions of the variable focus lens device. 1122 denotes an optical wafer, the lower surface of which is bonded to the movable stage 1113, and the upper surface (in the region indicated by 1123, 1124) of which is integrated with a lens portion. The lens part is a spherical lens with the aperture of 1mm-2mm. The size of the aperture of the lens part is larger than that of the optical window, and the lens part can be divided into 1123 and 1124 areas according to whether the lens part is positioned right above the optical window, namely 1123 is not transparent and 1124 is transparent. The lower surface of the optics wafer 1122 is anodically coupled to the movable platform 1113 of the MEMS actuator 1110 during processing. The silicon frame of the movable stage 1113 (without the extended comb structures) is the same size, about 2-2.5mm, as the surface-coupled optics wafer 1122. The MEMS drive is about: the length is 5-6mm, and the width is 3-4mm. Movable platform 1113 has comb-teeth structures 1115, and the region 1121 above comb-teeth structures 1115 is not covered by the optical wafer, as shown in fig. 11, i.e., the silicon frame of movable platform 1113 (without the extended comb-teeth structures) is the same size as the optical wafer 1122 coupled to the surface, which is about 2-2.5mm.

1122. 1123, 1124 together constitute the lens portion of the variable focus lens arrangement, wherein 1123 and 1124 are the lens structure of the lens portion, here a ball lens.

1122 is anodically coupled to the movable platform 1113 of the MEMS actuator 1110 during processing. As shown in fig. 11, the fixed platform 1114 of the MEMS actuator 1110 has a comb tooth structure 1111, a torsion axis 1112 with a meandering cantilever structure capable of providing a restoring force in an unbalanced position, and a movable platform 1113 coupled to the optical wafer of the lens section at the range marked by

torsion axes

1122 and 1123, the movable platform 1113 having a comb tooth structure 1115. The

comb tooth structures

1111 and 1115 of the two platforms form a comb tooth pair structure, and when the system does not work (in an initial state), the

comb tooth structures

1111 and 1115 are not in the same horizontal plane and are always arranged in a staggered manner.

The MEMS driving part 1110 is manufactured by processing an SOI wafer through a semiconductor process. The center of the movable platform 1113 is completely etched through to form a through circular window-like structure. The lens of the lens section above the movable stage 1113 is divided into 1123 and 1124 regions depending on whether or not it is located right above the circular window.

The realization shape and arrangement mode of the vertical comb teeth, the torsion shaft, the spring and other structures of the MEMS driving part can also adopt other modes, and the MEMS driving part is not limited to the structure shown in the attached figure 11 of the application.

Example twelve:

fig. 12 (a) - (b) are schematic diagrams of wafer level dicing of the variable focus lens provided by the present invention. Fig. 12 (a) - (b) illustrate the embodiment shown in fig. 10 as an example. To complete the lens stack with the variable focus lens arrangement shown in fig. 10, at least two cuts are required. The first cut is made after the completion of the variable focus lens arrangement at the wafer level. And the second cutting is carried out after all wafers forming the wafer-level lens group are bonded. So that the individual complete lens groups with variable focus lens arrangement are separated from each other.

As shown in fig. 12 (a), the first cutting is performed after the completion of the wafer-level variable focus lens device, i.e., after the MEMS structure is bonded to the optical wafer, and only the optical wafer is cut along the cutting lines 1201, i.e., along the grid frame structure on the lower bottom surface of the optical wafer. The first cut is intended to separate the lens portions of the lens devices from each other, exposing a portion of the MEMS structure of each lens device on the SOI wafer, such as a bond pad 1210, for subsequent processing, such as through-silicon-via space wafer bonding, wire bonding, packaging, etc. After the first cutting is finished, the wafer can be bonded with other wafers to form the wafer-level lens set. And after the wafer-level lens group is formed in a wafer form through a bonding process, performing secondary cutting. The second dicing, dicing only the SOI wafer according to the dicing lines 1202, is performed to separate the complete lens groups from each other, thereby forming an independent lens group having a variable focus lens apparatus according to the present invention. The scribe lines 1202 divide the SOI wafer into regions of equal size according to the size of the lens group. The other spacer wafers bonded to the MEMS structure while the second cut is made are not shown in fig. 12 (a).

In addition, as shown in fig. 12 (b), the lens apparatus of the present invention has low requirement on the precision of the cutting process, and when the first cutting is performed, the range divided by the cutting line 1201 is slightly larger than the range of the actual optical window frame 1203, but the optical wafer remaining after the cutting may not cover the structure, such as the pad, which needs to be exposed on the SOI wafer.

Example thirteen:

the process flow for manufacturing the variable focus lens device is cumbersome, and when the optical wafer is cut right above the comb structure, the comb structure may be damaged. If more spaces are reserved, namely the optical wafer is cut away from the comb tooth structure, the load of the MEMS driving part can be increased, and the performance of the system is reduced.

The process flow diagrams shown in fig. 13 (a) -13 (h) can solve the above problems.

As shown in fig. 13 (a), an SOI wafer 1310 and an optical wafer 1320 are prepared. The preparation work of the SOI wafer means that the whole manufacture of the MEMS part on the SOI device layer is completed, and the preparation work specifically comprises the following steps: defining a basic structure outline of the MEMS part on the SOI wafer device layer 1311 through photoetching and shallow etching; a metal layer is evaporated in a specific area of the SOI wafer device layer through an evaporation process, and the metal layer is made of gold to form a bonding pad 1314 of the MEMS structure; etching to the silicon dioxide buried layer 1312 through photolithography and deep etching, and forming main MEMS structures including an optical window structure, a comb structure, a torsion axis structure, an electrical isolation trench, and the like in the device layer 1311. The preparation work for the optical wafer specifically comprises the following steps: grinding and polishing two main surfaces of the optical wafer 1320; a number of first cavities 1323 are etched in the lower surface (second main surface) 1322 of the optics wafer by photolithography and deep etching. When the optics wafer 1320 and the SOI wafer 1310 are aligned, all of the first cavities 1323 arranged on the optics wafer are located directly above all of the bonding pads 1314 arranged on the SOI wafer, one to one.

In another embodiment, the device layer structure of the MEMS micro-mirror is manufactured through photoetching and deep etching processes, then a silicon through hole is formed on the SOI wafer through a TSV process, and finally a metal layer is formed above the silicon through hole through an evaporation process to serve as a bonding pad.

As shown in fig. 13 (b), the prepared SOI wafer 1310 and the optical wafer 1320 are wafer-level bonded by anodic bonding or the like. After bonding, the cavity 1323 of the optics wafer 1320 completely covers the corresponding pad 1314, and only the pad 1314 corresponding to the cavity 1323 is included.

As shown in fig. 13 (c), after the wafer level bonding is completed, a photoresist layer, such as a positive photoresist or a negative photoresist, is spin-coated or spray-coated on the first main surface 1321 (the upper surface of the optical wafer 1320) of the bonded whole wafer, and the photoresist layer 1324 is stamped by using a previously prepared stamp 1330 and exposed. The positive photoresist is used as an example for illustration.

As shown in fig. 13 (d), after exposure, a resist pattern layer 1325 is formed through post-baking, development, resist stripping, film hardening, and the like.

As shown in fig. 13 (e), the optical wafer is etched by a dry etching or wet etching process, so that the structure of the photoresist pattern layer 1325 is transferred into the optical wafer, and a lens portion 1326 and a mesa structure 1327 are formed. Wherein, each lens part is an island structure and is not contacted with other parts of the optical wafer.

As shown in fig. 13 (f), when the remaining fabrication of the MEMS portion is continued, the entire wafer is inverted, the mesa structure 1327 of the optical wafer is in contact with the etching tool, and the device layer 1311 and the lens portion 1326 are prevented from being in direct contact with the etching tool, thereby protecting the completed MEMS structure and lens structure.

As shown in fig. 13 (g), the bottom single-crystal silicon substrate layer 1313 of the SOI wafer is etched and etched (back cavity etch) to form a second cavity (back cavity) 1315 within the defined area, exposing the buried silicon dioxide layer 1312 within the second cavity 1315.

As shown in fig. 13 (h), the buried layer 1312 exposed in the back cavity region is etched by hydrofluoric acid, the movable structure of the MEMS part is released, and the optical window is opened, thereby completing the MEMS part fabrication. The continuously variable focus lens arrangement based on MEMS technology is also substantially complete.

The application of the process flow at least has the following advantages:

first, a complicated additional protection device is omitted, the cost is reduced, and the flow is simplified. The high platform structure can prevent the lens part and the device layer from directly contacting with the platform, thereby protecting the finished MEMS structure and the lens structure

Secondly, damage to the precision MEMS structure, such as comb teeth, caused when the lens structure is separated is avoided. The lens structure is separated from the rest of the optical wafers by using an etching process to form an island structure, so that the damage of the precise MEMS structure caused by using a cutting process is avoided.

Thirdly, by utilizing the etching process, redundant optical wafers bonded on the MEMS driving part can be reduced to the maximum extent, and the ground load of the MEMS driving part is reduced, so that the performance of the device is improved.

If the process flow shown in fig. 13 (a) to 13 (h) is adopted, the first cutting shown in fig. 12 (a) - (b) is not required.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.

Claims

1. A wafer level optical system, comprising an optical frame structure formed by a space wafer and an optical lens structure formed by an optical wafer;

the optical frame structure formed by the space wafers is a supporting structure formed by stacking a plurality of semiconductor wafers through a semiconductor processing technology and is used for supporting an optical lens structure formed by the optical wafers;

an optical lens structure formed by the optical wafer is bonded with an optical frame structure formed by the space wafer;

the optical lens structure formed by the optical wafer comprises an optical wafer body bonded with the space wafer and an optical structure formed on the surface of the optical wafer;

the optical lens structure further includes:

a wafer level continuous variable focus lens and a variable focus driving structure; the variable-focus driving structure is used for moving under the action of a driving force so as to enable the focal position of the variable-focus lens to be continuously changed;

the movement comprises a first direction movement and a second direction movement; the first direction is perpendicular to the second direction.

2. The wafer-level optical system of claim 1, wherein the space wafers are bonded to each other, and the spacing between the optical lens structures formed by the optical wafers is changed by changing the thickness of the space wafers.

3. The wafer-level optical system of claim 1,

the optical frame structure formed by the space wafer comprises various semiconductor wafers;

and/or the presence of a gas in the gas,

through silicon holes and metal wiring are distributed on an optical frame structure formed by the space wafer to provide driving force for an optical system;

and/or the presence of a gas in the gas,

the optical frame structure formed by the space wafers is a supporting structure formed by stacking a plurality of the wafers through a semiconductor processing technology and used for supporting and aligning each optical lens structure formed by the optical wafers.

4. The wafer-level optical system of claim 1, wherein the optical structure formed on the surface of the optical wafer comprises at least one of:

a cylindrical lens for controlling a beam shape;

a collimating lens for collimating;

a lens group for performing beam expansion;

a lens array for constituting a fly-eye optical integrator;

a condenser lens for converging;

a mirror surface having a specific transmittance or a coating having a specific transmittance.

5. The wafer-level optical system of claim 4, wherein the lens array for forming the fly-eye optical integrator includes, but is not limited to, a spherical microlens array, a cylindrical lens array, and a Fresnel lens array.

6. The wafer-level optical system of claim 1, wherein the optical structure formed on the surface of the optical wafer comprises:

a first lens for controlling an amount of incident light;

and/or a second lens for controlling the outgoing light beam.

7. The wafer-level optical system of claim 6, wherein the first lens is a flat mirror with a specific transmittance mirror surface or a flat mirror with a specific transmittance coating;

and/or the second lens is a convex lens for controlling the width of the emergent light beam.

8. The wafer-level optical system of claim 1, wherein the wafer-level continuously variable focus lens comprises:

a lens section and an MEMS driving section;

the lens part comprises a lens structure and a bonding structure;

the MEMS driving part comprises a fixing part and the variable-focus driving structure;

the bonding structure is bonded with the variable-focus driving structure;

the variable-focus driving structure and the fixed part generate continuous relative displacement under the action of driving force, so that the focal position of the variable-focus lens is continuously changed.

9. The wafer-level optical system of claim 8, wherein the fixed portion is formed from an SOI wafer comprising:

a device layer (911);

a buried layer of silicon dioxide (912);

a bottom monocrystalline silicon substrate layer (913);

the device layer is used for defining and forming an optical window, a torsion shaft and a comb tooth structure; and the bonding structure of the lens part is bonded with the device layer.

10. A laser microprojection apparatus, wherein said apparatus comprises:

the laser driving signal drives the three-color laser group to emit laser beams with corresponding wavelengths, and the laser beams are RGB three colors; the wafer level optical system of any of claims 1-8 collimated with the three color laser placed in close proximity;

each laser corresponds to one wafer-level optical system of the emergent direction of the laser;

the collimated three-color laser beams are combined into a combined beam through a beam combiner.