WO2025218062A1 - 一种超表面透镜及制造方法、红外折超混合量子点相机 - Google Patents

一种超表面透镜及制造方法、红外折超混合量子点相机

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Publication number
WO2025218062A1
WO2025218062A1 PCT/CN2024/111614 CN2024111614W WO2025218062A1 WO 2025218062 A1 WO2025218062 A1 WO 2025218062A1 CN 2024111614 W CN2024111614 W CN 2024111614W WO 2025218062 A1 WO2025218062 A1 WO 2025218062A1
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WIPO (PCT)
Prior art keywords
lens
metasurface
infrared
quantum dot
wafer
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PCT/CN2024/111614
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English (en)
French (fr)
Inventor
易飞
陈岩
刘斯坦
李林翰
林永超
何炀
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Optics Valley Laboratory
Huazhong University of Science and Technology
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Optics Valley Laboratory
Huazhong University of Science and Technology
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Publication of WO2025218062A1 publication Critical patent/WO2025218062A1/zh
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Anticipated expiration legal-status Critical

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/02—Simple or compound lenses with non-spherical faces
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/002—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of materials engineered to provide properties not available in nature, e.g. metamaterials
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/14—Optical objectives specially designed for the purposes specified below for use with infrared or ultraviolet radiation
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
    • 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
    • G02B27/0012—Optical design, e.g. procedures, algorithms, optimisation routines
    • 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
    • G03F7/0005—Production of optical devices or components in so far as characterised by the lithographic processes or materials used therefor

Definitions

  • the present invention belongs to the field of infrared imaging and micro-nano photonics technology, and more specifically, relates to a metasurface lens and a manufacturing method, and an infrared refractive-metasurface hybrid quantum dot camera.
  • Infrared imaging technology aims to capture the thermal radiation of a target object using an infrared detector and convert it into a visible image.
  • This technology has been widely used in military applications such as nighttime reconnaissance, infrared guidance, and missile early warning. It also holds broad application prospects in civilian areas such as security monitoring, vehicle-mounted night vision, and industrial inspection.
  • quantum dot detectors offer advantages such as long effective carrier lifetime, low dark current, high operating temperature, and response to vertically incident light, enabling better identification and detection of target objects.
  • infrared imaging technology In recent years, with the increasing application of infrared imaging technology in various mobile devices, such as those mounted on aircraft and vehicles, the demand for lightweight, simplified structures, miniaturized size, and cost-effective devices has become increasingly stringent. Lightweight, compact, simple, and affordable infrared optical systems have become an increasing research focus. Overall, the current development trend of infrared imaging technology can be summarized as simpler system structures and stronger sensing capabilities.
  • metasurfaces as an emerging research direction in the field of nanophotonics, are expected to replace traditional lenses, thereby achieving the goal of simplifying infrared optical systems.
  • the structure of the metasurface is a two-dimensional periodic array of electromagnetic resonance units with subwavelength or wavelength scales, which can control the intensity, phase, polarization and other parameters of electromagnetic waves throughout the entire electromagnetic spectrum.
  • metasurface-based imaging technology especially metasurface lenses, has the advantages of simple overall structure, economical mass production cost, and better adaptability to planar processing technology. Therefore, it has a great significance in infrared imaging.
  • the introduction of metasurface lenses is expected to further reduce the weight, volume and cost of infrared cameras.
  • Chinese patent CN113917578A discloses a large-aperture chromatic aberration-corrected metalens, a metalens system, and an optical system.
  • the metalens has a large aperture but is insufficiently thick, less than 2 mm. This will lead to a weakened optical system structure, reduced impact resistance, and prone to deformation and distortion.
  • the present invention provides a metasurface lens and a manufacturing method, as well as an infrared refractive-metasurface hybrid quantum dot camera, thereby achieving lightweight equipment, simplified structure, miniaturization, and cost-effectiveness of current infrared quantum dot cameras, and solving the technical problem of insufficient lens thickness of large-aperture metasurface lenses in practical applications.
  • a method for manufacturing a metasurface lens which uses a bonding process to increase the thickness of the metasurface lens and reduce the diameter-to-thickness ratio, thereby improving the mechanical stress that the metasurface lens can withstand.
  • the method comprises the following steps:
  • a micro-nanostructure array and a bonding alignment mark are prepared on the front side of the first wafer, and a film is applied on the front side to protect the micro-nanostructure array;
  • a bonding alignment mark is prepared on the front side of the second wafer, and a micro-nanostructure array is prepared on the back side, and a film is applied on the back side to protect the micro-nanostructure array;
  • the first to third wafers are cleaned and heated, the back of the first wafer and the front of the second wafer are respectively aligned with the third wafer by photolithography and heated for pre-bonding and high-temperature annealing, and finally the bonded wafers are cleaned to remove the surface masks.
  • the wafer is shaken and cleaned with organic cleaning agents such as acetone and ethanol in sequence, and then the wafer is cleaned with corrosive cleaning agents such as hydrofluoric acid to remove the surface oxide layer, and then the wafer is heated and treated with alkaline oxidizing solutions such as ammonia and hydrogen peroxide to increase the number of hydroxyl groups adsorbed on the silicon wafer, which is beneficial to improve the bonding effect, and then the photolithography alignment and wafer bonding are carried out.
  • organic cleaning agents such as acetone and ethanol
  • corrosive cleaning agents such as hydrofluoric acid
  • alkaline oxidizing solutions such as ammonia and hydrogen peroxide
  • a second aspect of the present invention provides a metasurface lens, which is obtained using the above-mentioned manufacturing method.
  • a third aspect of the present invention provides an infrared refractive-metasurface hybrid quantum dot camera, comprising a lens, a metasurface lens, a quantum dot infrared detector, and an optical lens assembly sequentially arranged along an optical axis;
  • the lens and the metasurface lens form an optical lens group.
  • the lens is used to converge the incident light.
  • the converged incident light is corrected for aberration by the metasurface lens and then focused on the focal plane of the quantum dot infrared detector.
  • Quantum dot infrared detectors are used to eliminate stray light and incident light in non-target bands and perform infrared detection imaging;
  • the lens and the metasurface lens are placed in an optical lens assembly, which is used to fix and protect the lens and the metasurface lens.
  • the lens is an aspheric lens, comprising: a first aspheric surface and a second aspheric surface; the surface coordinates Z 1 and Z 2 of the first aspheric surface and the second aspheric surface respectively satisfy:
  • r is the distance from any point on the aspheric lens to the optical axis of the optical imaging system; C 1 and C 2 are the curvatures of the corresponding two spherical surfaces, respectively; k 1 and k 2 are the conic coefficients of the corresponding two spherical profiles, respectively; X 1 , Y 1 , M 1 , and N 1 are the fourth-order, sixth-order, eighth-order, and tenth-order coefficients of the surface coordinates of the first aspheric surface, respectively; and X 2 , Y 2 , M 2 , and N 2 are the fourth-order, sixth-order, eighth-order, and tenth-order coefficients of the surface coordinates of the second aspheric surface, respectively.
  • the lens is a meniscus refractive lens with positive optical power.
  • the metasurface lens includes a dielectric substrate layer and a columnar microstructure array, wherein the columnar microstructure array is composed of a plurality of columnar microstructure units arranged in a hexagonal lattice or a tetragonal lattice periodic array;
  • the heights of the columnar microstructure units are all the same and are on the order of wavelength of the thermal radiation of the target object, and the diameters of the columnar microstructure units are on the order of sub-wavelength.
  • the quantum dot infrared detector includes a detector window, a filter and an infrared photosensitive surface, and the detector window and infrared photosensitive surface are arranged in sequence along the optical axis; the detector window and filter are used to eliminate stray light and incident light in non-target bands; the infrared photosensitive surface is used to detect and image the focused light.
  • the lens and the metasurface lens are placed in the optical lens assembly, and the optical lens assembly uses a thread and groove structure to fix and protect the lens and the metasurface lens, and facilitates structural adjustment of the optical system.
  • the optical lens assembly comprises a lens barrel body and a lens barrel outer wall.
  • the groove structure built into the lens barrel body is provided with a buffer rubber material for shock-absorbing and protecting the optical system.
  • the lens barrel outer wall is provided with a heat-insulating material coating.
  • ⁇ is the radial coordinate of the metasurface
  • R is the normalized radius
  • n is the maximum number of terms in the phase distribution
  • the radius and height of the columnar microstructure unit at each position on the metasurface lens are determined according to the phase distribution of the hexagonal lattice or tetragonal lattice periodic array.
  • both the front and back surfaces of the metasurface lens are coated with anti-reflection and anti-transmission coating layers for increasing the transmittance of incident light and filtering incident light in non-target bands.
  • the metasurface lens is a double-sided metasurface lens or a single-sided metasurface lens.
  • the material of the columnar microstructure unit includes but is not limited to silicon, germanium or titanium dioxide; the material of the dielectric substrate layer includes but is not limited to silicon, silicon dioxide or barium fluoride.
  • the metasurface lens is prepared using a semiconductor process, and the metasurface preparation method includes but is not limited to ICP etching, photolithography, and nanoimprinting.
  • the metasurface lens adopts a bonding process to increase the thickness of the metasurface lens and reduce the diameter-to-thickness ratio, thereby increasing the mechanical stress that the metasurface lens can withstand.
  • the wafer bonding process, wherein the silicon-silicon bonding process includes:
  • the present invention proposes a method for manufacturing a metasurface lens, wherein the metasurface lens can be manufactured through a multi-wafer bonding process, wherein the thickness of the third wafer can be selected according to actual requirements, thereby increasing the thickness of the lens and reducing the diameter-to-thickness ratio to below 10, thereby improving the mechanical stress that the metasurface lens can withstand, as well as the structural strength and impact resistance of the metasurface lens, thereby improving the overall stability of the optical system without affecting the optical performance of the system; at the same time, the metasurface lens is manufactured using a semiconductor process, which can achieve mass production, improve the optical processing accuracy and reliability, and reduce the mass production cost of the optical system.
  • the existing technology that can provide chromatic aberration correction metalenses has a large diameter but insufficient thickness, which will lead to problems such as weakening of the optical system structure, reduced impact resistance, and easy deformation and distortion.
  • the present invention uses a bonding process to achieve the combination of multiple metastructure element wafers without modifying existing equipment, thereby increasing the thickness of the metasurface lens, thereby solving the technical problem of insufficient lens thickness of large-aperture metasurface lenses in practical applications.
  • the present invention proposes an infrared refractive index hybrid quantum dot camera, in which the optical lens part adopts only a two-piece structure, the system structure is simple, easy to assemble, and the number of pieces is reduced compared to traditional optical systems; at the same time, the system has excellent optical performance, and the modulation transfer function (MTF) is close to the diffraction limit.
  • the simple lens structure is used to realize the combination with a small-pixel, large-array quantum dot infrared detector to achieve high-resolution infrared detection imaging with good imaging quality; the optical lens assembly uses a thread and groove structure to fix and protect the lens and metasurface lens, and facilitates the structural adjustment of the optical system.
  • FIG1 is a schematic structural diagram of an infrared refractive index hybrid quantum dot camera according to an embodiment of the present invention.
  • FIG2 is a schematic diagram of the structure of a metasurface lens proposed in an embodiment of the present invention.
  • FIG3 is an MTF curve diagram of the first optical system simulated in the first embodiment of the present invention.
  • FIG4 is a diagram of light spots at the photosensitive surface of a mid-infrared quantum dot detector simulated in Example 1 of the present invention.
  • FIG. 5 is an MTF curve diagram of the second optical system simulated in the first embodiment of the present invention.
  • FIG6 is a diagram of light spots at the photosensitive surface of a near-infrared quantum dot detector simulated in Example 1 of the present invention.
  • FIG7 is a schematic flow chart of the metasurface lens bonding process proposed in an embodiment of the present invention.
  • the structure of an electromagnetic metasurface is a two-dimensional periodic array of electromagnetic resonant units at subwavelength or wavelength scales. Its function is to control the intensity, frequency, phase, polarization, and other parameters of electromagnetic waves across the entire electromagnetic spectrum.
  • imaging technology based on electromagnetic metasurfaces, especially metasurface lenses has advantages such as simple overall structure, low-cost mass production, and greater adaptability to planar processing. Therefore, it shows broad application prospects in infrared imaging.
  • the introduction of metasurface lenses is expected to further reduce the weight, volume, and cost of infrared cameras. Combining them with traditional refractive lenses provides a new solution for the design of infrared detection systems.
  • the present invention provides an infrared refractive-metasurface hybrid quantum dot camera, comprising a lens 1, a metasurface lens 2, an infrared quantum dot detector 3, and an optical lens assembly 4, which are sequentially placed along the direction of incident light.
  • the metasurface lens 2 adopts a bonding process to increase the thickness of the metasurface and its mechanical stress
  • the quantum dot infrared detector 3 is used to eliminate stray light and incident light in non-target bands and perform infrared detection imaging;
  • the lens 1 and the metasurface lens 2 form an optical lens group for converging the thermal radiation of the target object and focusing it on the surface of the quantum dot infrared detector 3;
  • the refractive lens 1 and the metasurface lens 2 are placed in the optical lens assembly 4, and the optical lens assembly 4 uses a thread and groove structure to fix and protect the lens and the metasurface lens, and facilitates the structural adjustment of the optical system.
  • the metasurface lens 2 includes a dielectric substrate layer and a columnar microstructure array.
  • the columnar microstructure array is composed of a plurality of columnar microstructure units arranged in a hexagonal lattice or a tetragonal lattice periodic array.
  • the heights of the columnar microstructure units are all the same and are on the order of the wavelength of the thermal radiation of the target object.
  • the diameters of the columnar microstructure units are on the sub-wavelength order.
  • ⁇ is the radial coordinate of the metasurface
  • R is the normalized radius
  • n is the maximum number of terms in the phase distribution
  • the diameter, period, height and arrangement of the columnar microstructure units are determined according to the corresponding phase distribution.
  • the infrared refractive index hybrid quantum dot camera realizes focused imaging in the mid-infrared band of 3.7-4.8 ⁇ m with a center wavelength of 4.25 ⁇ m.
  • the entrance pupil diameter of the optical system is 32.4mm
  • the field of view angle is 5.4°
  • the system focal length is 63.2mm
  • the aperture number is 2
  • the total length of the optical system does not exceed 64mm
  • the focal length variation is less than 0.1%.
  • Table 3 Conic coefficients and polynomial coefficients of the aspheric lens of the first optical system
  • the MTF curve of the first optical system of the infrared refractive index hybrid quantum dot camera in the mid-infrared band provided by an embodiment of the present invention is shown in Figure 3.
  • the MTF values in all fields of view are higher than 0.5, and the MTF curve is close to the diffraction limit.
  • the system point diagram is shown in Figure 4.
  • the RMS radius is less than 6 ⁇ m, and the maximum chromatic focus shift is less than 0.1%, achieving near-diffraction-limited imaging.
  • the infrared refractive index hybrid quantum dot camera realized by the present invention realizes focused imaging in the mid-infrared band of 1.3-1.8 ⁇ m with a center wavelength of 1.55 ⁇ m.
  • the entrance pupil diameter of the optical system is 12 mm
  • the field of view angle is 5.4°
  • the system focal length is 46.1 mm
  • the aperture number is 4, the total length of the optical system does not exceed 42 mm
  • the focal length variation is less than 0.12%.
  • the MTF curve of the second optical system of the near-infrared hybrid quantum dot camera provided by an embodiment of the present invention is shown in Figure 5.
  • the MTF values in all fields of view are higher than 0.6, and the MTF curve is close to the diffraction limit.
  • the system point diagram is shown in Figure 6.
  • the RMS radius is less than 4.2 microns, and the maximum chromatic focus shift is less than 0.12%, achieving near-diffraction-limited imaging.
  • An embodiment of the present invention provides an infrared refractive-metasurface hybrid quantum dot camera, which adopts the form of a hybrid of a refractive lens and a metasurface lens.
  • the metasurface lens by virtue of its ability to finely control the incident light, modulates the incident light together with the refractive lens.
  • the optical system has excellent performance, the MTF curve is close to the diffraction limit, and the aperture number matches the target detector, thereby realizing integration with the infrared quantum dot detector.
  • the metasurface lens manufactured by this design adopts a bonding process to increase the thickness of the metasurface lens, thereby increasing the mechanical stress that the metasurface lens can withstand as well as the structural strength and impact resistance of the metasurface lens, thereby improving the overall stability of the optical system without affecting the optical performance of the system.
  • the present invention also provides a method for manufacturing a metasurface lens, comprising:
  • the metasurface lens is prepared by semiconductor technology, and the metasurface preparation method includes but is not limited to ICP etching, photolithography, and nanoimprinting;
  • the metasurface lens adopts a bonding process, the process diagram of which is shown in FIG7 , to increase the thickness of the metasurface lens and reduce the diameter-to-thickness ratio, thereby increasing the mechanical stress that the metasurface lens can withstand.
  • the wafer bonding process, wherein the silicon-silicon bonding process includes:
  • a mark position is reserved.
  • a micro-nanostructure array and alignment marks are prepared on the front side of the first meta-element wafer using processes such as step-and-step photolithography and deep silicon etching.
  • a double-sided photolithography process is used to prepare bonding alignment marks on the front side of the second meta-element wafer, and a micro-nanostructure array is prepared on the back side of the wafer.
  • the meta-element is then surface-coated to protect the microstructure array on its surface.
  • a surface-polished high-purity silicon wafer is used.
  • the silicon wafer is vibrated and cleaned in an ultrasonic cleaner using acetone and ethanol in that order.
  • the silicon wafer is then cleaned with hydrofluoric acid to remove the oxide layer on the surface of the silicon wafer.
  • the silicon wafer is then placed in a solution of concentrated sulfuric acid and hydrogen peroxide for heat treatment.
  • the silicon wafer is treated with ammonia and hydrogen peroxide.
  • a photolithography machine is used for photolithography alignment and pre-bonding and high-temperature annealing are performed in a wafer bonder.
  • a buffered oxide etchant is used to clean the bonded silicon wafer to remove the surface mask.
  • the specific number of bonding wafers depends on the absorption coefficient of the substrate material in the target band and the system transmittance index. The requirements and the diameter-to-thickness ratio required for metasurface lens assembly are determined.
  • the metasurface lens manufactured according to the manufacturing method of the metasurface lens provided in this embodiment is used in an infrared refractive-metasurface hybrid quantum dot camera, and has the corresponding beneficial effects as in the above embodiments.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Lenses (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Abstract

本发明公开了一种超表面透镜及制造方法、红外折超混合量子点相机，属于红外成像与微纳光子学技术领域，包括沿光轴依次设置的透镜、超表面透镜、量子点红外探测器以及光学镜头组装件；超表面透镜采用键合工艺，提升超表面厚度以及其能承受的机械应力。本发明仅采用双片式简单光学结构，实现了光学系统的简单化，使用范围广泛，同时保证了光学系统在红外波段的成像质量，并将光学系统与量子点红外探测器结合，组成红外量子点相机。

Description

一种超表面透镜及制造方法、红外折超混合量子点相机 【技术领域】
本发明属于红外成像与微纳光子学技术领域，更具体地，涉及一种超表面透镜及制造方法、红外折超混合量子点相机。
【背景技术】
红外成像技术旨在通过红外探测器捕捉目标物体的热辐射信息，并将其转化为可见图像。该技术在军事领域的夜间侦查、红外制导、导弹预警等任务中得到广泛应用，同时在民用领域的安防监控、车载夜视、工业检测等领域也表现出了广泛的应用前景。相比于传统红外探测器，量子点探测器具有有效载流子寿命长、暗电流低、工作温度高、对垂直入射光响应等优势，可以更好地对目标物体进行识别探测。
近年来，随着红外成像技术在机载、车载等各类移动设备上应用的逐步增多，对于设备轻量化、结构简单化、体积小型化、成本经济化的要求越来越高，轻便、紧凑、简单、实惠的红外光学系统越来越成为研究的重点。总体而言，红外成像技术当前的发展趋势可概括为系统结构更为简化、感知能力更强。
然而，传统透镜由于其依赖于元件曲面形状和材料光学特性来实现对光波前的调控，因而在进一步减小红外相机的重量、体积和成本方面面临一定的困难。在这一背景下，超表面作为纳米光子学领域中的新兴研究方向，有望替代传统透镜，从而实现红外光学系统更为简化的目标。超表面的结构为具有亚波长或波长尺度的电磁谐振单元的二维周期阵列，其能够在整个电磁波谱范围内调控电磁波的强度、相位、偏振等参数。基于超表面的成像技术，尤其是超表面透镜，相较于传统光学元件，具有整体结构简单、大批量生产成本经济、更适应平面加工工艺等优势，因此在红外成 像中展现出广泛的应用前景。超表面透镜的引入有望进一步减小红外相机的重量、体积和成本。
但是目前大口径超表面透镜在实际应用中存在透镜厚度不足的问题，例如，中国专利CN113917578A公布了一种大口径色差校正超透镜、超透镜系统和光学系统，其中超透镜口径较大，但是厚度不足，小于2mm，这将导致光学系统结构弱化、抗冲击性能降低、容易出现变型和扭曲等问题。
【发明内容】
针对现有技术的以上缺陷或改进需求，本发明提供了一种超表面透镜及制造方法、红外折超混合量子点相机，由此实现目前红外量子点相机的设备轻量化、结构简单化、体积小型化、成本经济化以及解决大口径超表面透镜在实际应用中存在透镜厚度不足的技术问题。
为实现上述目的，按照本发明的一个方面，提供了一种超表面透镜的制造方法，采用键合工艺，以增加超表面透镜厚度，降低直径-厚度比例，从而提高超表面透镜能够承受的机械应力，包括以下步骤：
在第一晶圆正面制备微纳结构阵列和键合对准标记，并在正面镀膜以保护微纳结构阵列；在第二晶圆正面制备键合对准标记，反面制备微纳结构阵列，并在反面镀膜以保护微纳结构阵列；
根据所述超表面透镜的口径、透过率要求确定第三晶圆厚度，对第三晶圆的正面和反面进行抛光；
对所述第一至第三晶圆进行清洗和加热处理，将第一晶圆的反面和第二晶圆的正面分别与第三晶圆光刻对准并进行加热预键合以及高温退火处理，最后清洗键合后的晶圆片去除表面掩膜。
可选的，按先后顺序使用丙酮、乙醇等有机清洗剂对晶圆进行震荡清洗，随后利用氢氟酸等腐蚀性清洗剂清洗晶圆以去除表面氧化层，然后对晶圆进行加热处理，再用氨水、双氧水等碱性氧化溶液处理晶圆，提高硅晶圆上吸附的羟基数量，有利于提升键合效果，再进行光刻对准、晶圆键 合。
本发明第二方面提供了一种超表面透镜，所述超表面透镜采用上述的制造方法得到。
本发明第三方面提供了一种红外折超混合量子点相机，包括沿光轴依次设置的透镜、超表面透镜、量子点红外探测器和光学镜头组装件；
所述透镜和超表面透镜组成光学镜头组，透镜用于对入射光进行汇聚，汇聚后的入射光经过超表面透镜进行像差矫正后，聚焦于量子点红外探测器的焦平面上；
量子点红外探测器用于消除杂散光和非目标波段的入射光并且进行红外探测成像；
透镜和超表面透镜置于光学镜头组装件中，光学镜头组装件用于对透镜和超表面透镜进行固定和保护。
可选的，所述透镜为非球面透镜，包括：第一非球面和第二非球面；所述第一非球面和所述第二非球面的面型坐标Z1、Z2分别满足：

其中，r为非球面透镜上任意点到所述光学成像系统光轴的距离；C1、C2分别为对应的两个球面的曲率；k1、k2分别为对应的两个球面轮廓的圆锥系数，X1、Y1、M1、N1分别为第一非球面面型坐标的四次项、六次项、八次项、十次项系数，X2、Y2、M2、N2分别为第二非球面面型坐标的四次项、六次项、八次项、十次项系数。
可选的，所述透镜为具有正光焦度的弯月形折射透镜。
所述超表面透镜包括介质衬底层和柱状微结构阵列，所述柱状微结构阵列由多个柱状微结构单元按照六方晶格或者四方晶格周期阵列排列而成； 所述柱状微结构单元的高度全部相同且介于所述目标物体热辐射的波长量级，所述柱状微结构单元的直径介于亚波长量级。
所述量子点红外探测器包括探测器窗口片、滤波片和红外光敏面，所述探测器窗口和红外光敏面沿光轴方向依次设置；所述探测器窗口片和滤波片用于消除杂散光及非目标波段的入射光；所述红外光敏面用于对聚焦后的光线进行探测成像。
所述透镜和超表面透镜置于所述光学镜头组装件，所述光学镜头组装件采用螺纹和凹槽结构对透镜和超表面透镜进行固定和保护，并便于进行光学系统的结构调节。
所述光学镜头组装件包括镜筒主体和镜筒外壁，镜筒主体内置的凹槽结构处具有缓冲橡胶材料用以对光学系统进行减震保护，镜筒外壁具有隔热材料涂层。
所述柱状微结构单元周期阵列的相位分布满足如下表达式：
其中，ρ为超表面径向坐标，R为归一化半径，n为相位分布的最大项数，Ai(i＝1,2,3,…n)均为多项式系数。
可选的，所述超表面透镜上每个位置的柱状微结构单元的半径和高度根据六方晶格或四方晶格周期阵列的相位分布确定。
可选的，所述超表面透镜正反两面均镀有增透减反膜层，用于对入射光的增透以及非目标波段入射光的过滤。
可选的，所述超表面透镜为双面超表面透镜、单面超表面透镜。
可选的，所述柱状微结构单元的材料包括但不限于硅、锗或二氧化钛；所述介质衬底层的材料包括但不限于硅、二氧化硅或氟化钡。
可选的，所述超表面透镜采用半导体工艺制备，所述超表面制备方法包括但不限于ICP刻蚀、光刻、纳米压印。
可选的，所述超表面透镜采用键合工艺，以增加超表面透镜厚度，降低直径-厚度比例，从而提高超表面透镜能够承受的机械应力，所述晶圆键合工艺，其中硅-硅键合流程包括：
通过本发明所构思的以上技术方案，与现有技术相比，能够取得以下有益效果：
1、本发明提出一种超表面透镜的制造方法，其中超表面透镜可以通过多片键合工艺，其中第三晶圆的厚度可根据实际要求进行选择，增加镜片的厚度，将径厚比降至10以下，从而提升超表面透镜能够承受的机械应力以及超表面透镜的结构强度、抗冲击性能，在不影响系统光学性能的前提下提升了光学系统的整体稳定性；同时超表面透镜采用半导体工艺制备，可以实现大批量生产，提高了光学加工精度和可靠性，降低了光学系统批量生产成本。
2、现有技术中能够提供色差校正超透镜存在超透镜口径较大，但是厚度不足，这将导致光学系统结构弱化、抗冲击性能降低、容易出现变型和扭曲等问题，本发明通过键合工艺，在不改造现有设备的前提下，实现多片超构元件晶圆的结合，提升了超表面透镜的厚度，从而解决大口径超表面透镜在实际应用中存在透镜厚度不足的技术问题。
3、本发明提出的一种红外折超混合量子点相机，其中光学镜头部分仅采用双片式结构，系统结构简单，易于装配，相比传统光学系统减少片数；同时系统光学性能优异，调制传递函数(MTF)接近衍射极限，利用简单的镜头结构实现了与小像元、大阵列量子点红外探测器的结合，实现高分辨红外探测成像，成像质量良好；光学镜头组装件采用螺纹和凹槽结构对透镜和超表面透镜进行固定和保护，并便于进行光学系统的结构调节。
【附图说明】
图1是本发明实施例提出的红外折超混合量子点相机的结构示意图。
图2是本发明实施例提出的超表面透镜的结构示意图。
图3是本发明实施例一模拟的第一光学系统的MTF曲线图。
图4是本发明实施例一模拟的中红外波段量子点探测器光敏面处的光斑点列图。
图5是本发明实施例一模拟的第二光学系统的MTF曲线图。
图6是本发明实施例一模拟的近红外波段量子点探测器光敏面处的光斑点列图。
图7是本发明实施例提出的超表面透镜键合工艺的流程示意图。
在所有附图中，相同的附图标记用来表示相同的元件或结构，其中：1-透镜；2-超表面透镜；3-量子点红外探测器；4-光学镜头组装件。
【具体实施方式】
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。此外，下面所描述的本发明各个实施方式中所涉及到的技术特征只要彼此之间未构成冲突就可以相互组合。
电磁超表面的结构为具有亚波长或波长尺度的电磁谐振单元的二维周期阵列，其功能在于能够在整个电磁波谱范围内调控电磁波的强度、频率、相位、偏振等参数。基于电磁超表面的成像技术，尤其是超表面透镜，相较于传统光学元件，具有整体结构简单、大批量生产成本经济、更适应平面加工工艺等优势，因此在红外成像中展现出广泛的应用前景。超表面透镜的引入有望进一步减小红外相机的重量、体积和成本，将其与传统的折射透镜相结合，为红外探测系统的设计提供了新方案。
下面结合一个优选实施例，对上述实施例中涉及的内容进行说明。
实施例一
如图1所示，本发明提供了一种红外折超混合量子点相机，包括沿入射光方向依次放置的透镜1、超表面透镜2、红外量子点探测器3以及光学镜头组装件4；
所述超表面透镜2采用键合工艺，提升超表面厚度以及其机械应力；
所述量子点红外探测器3用于消除杂散光和非目标波段的入射光并且进行红外探测成像；
所述透镜1和超表面透镜2组成光学镜头组，用于对目标物体的热辐射进行汇聚并且聚焦于所述量子点红外探测器3的表面；
所述折射透镜1和超表面透镜2置于所述光学镜头组装件4，所述光学镜头组装件4采用螺纹和凹槽结构对透镜和超表面透镜进行固定和保护，并便于进行光学系统的结构调节。
所述超表面透镜2包括介质衬底层和柱状微结构阵列，如图2所示，所述柱状微结构阵列由多个柱状微结构单元按照六方晶格或者四方晶格周期阵列排列而成；所述柱状微结构单元的高度全部相同且介于所述目标物体热辐射的波长量级，所述柱状微结构单元的直径介于亚波长量级；
所述柱状微结构单元周期阵列的相位分布满足如下表达式：
其中，ρ为超表面径向坐标，R为归一化半径，n为相位分布的最大项数，Ai(i＝1,2,3,…n)均为多项式系数。
可选的，所述柱状微结构单元的直径、周期、高度以及排布方式根据对应的相位分布确定。
本实施例中采用的红外量子点探测器用于对聚焦后的红外光进行成像， 其像元尺寸为15μm，像元数量或分辨率为640×512。当光学系统的MTF曲线接近衍射极限且截止频率与探测器像元间距满足公式：截止频率＝1/(2*像元尺寸)时，表示此光学系统与探测器匹配并且光学性能良好。
示例性的，在一具体实施例中，本发明提供的红外折超混合量子点相机面向以4.25μm为中心波长、3.7-4.8μm的中红外波段实现聚焦成像，光学系统的入瞳直径为32.4mm，视场角为5.4°，系统焦距为63.2mm，光圈数为2，光学系统总长不超过64mm，在3.7-4.8μm波段，焦距变化小于0.1％。
更详细地，在本发明实施例所提供的第一光学系统中具体参数数值见表一、表二、表三。
表一：第一光学系统的超表面透镜参数表
表二：第一光学系统结构参数

表三：第一光学系统的非球面透镜圆锥系数与多项式系数
本发明实施例提供的中红外波段的红外折超混合量子点相机第一光学系统的MTF曲线图如图3所示，在截止频率34lp/mm下，所有视场下的MTF值均高于0.5，MTF曲线接近衍射极限，系统点列图如图4所示，RMS半径小于6μm，最大色焦移小于0.1％，实现近衍射极限成像。
在另一具体实施例中，本发明提供的红外折超混合量子点相机面向以1.55μm为中心波长、1.3-1.8μm的中红外波段实现聚焦成像，光学系统的入瞳直径为12mm，视场角为5.4°，系统焦距为46.1mm，光圈数为4，光学系统总长不超过42mm，在1.3-1.8μm波段，焦距变化小于0.12％。
更详细地，在本发明实施例所提供的第二光学系统中具体参数数值见表四、表五、表六。
表四：第二光学系统的超表面透镜参数表

表五：第二光学系统结构参数
表六：第二光学系统的非球面透镜圆锥系数与多项式系数
本发明实施例提供的近红外波段的红外折超混合量子点相机第二光学系统的MTF曲线图如图5所示，在截止频率34lp/mm下，所有视场下的MTF值均高于0.6，MTF曲线接近衍射极限，系统点列图如图6所示，RMS半径小于4.2微米，最大色焦移小于0.12％，实现近衍射极限成像。
本发明实施例提供一种红外折超混合量子点相机，采用折射透镜与超表面透镜混合的形式，超表面透镜凭借其对入射光的精细调控能力，与折射透镜共同对入射光进行调制，光学系统性能优异，MTF曲线接近衍射极限，光圈数与目标探测器匹配，从而实现了与红外量子点探测器的结合；本设计所制造的超表面透镜采用键合工艺，提升了超表面透镜的厚度，从而提升了超表面透镜能够承受的机械应力以及超表面透镜的结构强度、抗冲击性能，在不影响系统光学性能的前提下提升了光学系统的整体稳定性。
实施例二
本发明还提供了一种超表面透镜的制造方法，包括：
所述超表面透镜采用半导体工艺制备，所述超表面制备方法包括但不限于ICP刻蚀、光刻、纳米压印；
可选的，所述超表面透镜采用键合工艺，流程示意图如图7所示，以增加超表面透镜厚度，降低直径-厚度比例，从而提高超表面透镜能够承受的机械应力，所述晶圆键合工艺，其中硅-硅键合流程包括：
首先在光刻版图绘制时预留标记位置，利用步进式光刻、深硅刻蚀等工艺在第一片超构元件晶圆正面制备微纳结构阵列和对准标记，并使用双面光刻工艺，在第二片超构元件晶圆正面制备键合对准标记，晶圆反面制备微纳结构阵列；随后对超构元件进行表面镀膜处理，以保护其表面的微结构阵列，并采用表面抛光高纯度硅晶圆，根据所述超表面透镜口径、透过率要求确定晶圆厚度后，按先后顺序使用丙酮、乙醇在超声波清洗机中对上述硅晶圆进行震荡清洗，随后利用氢氟酸清洗硅晶圆以去除硅片表面氧化层，然后将硅晶圆放入浓硫酸和双氧水组成的溶液中进行加热处理，清洗后用氨水和双氧水处理硅晶圆，清洗后使用光刻机进行光刻对准并在晶圆键合机中进行加热预键合以及高温退火处理，最后使用缓冲氧化物刻蚀液清洗键合后的硅片去除表面掩膜。
具体键合片数根据衬底材料在目标波段的吸收系数、系统透过率指标 要求以及超表面透镜装配所需径厚比决定。
根据本实施例提供的超表面透镜的制造方法所制造出的超表面透镜应用在红外折超混合量子点相机中，具有如上述实施例中相应的有益效果。
本领域的技术人员容易理解，以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种超表面透镜的制造方法，其特征在于，包括以下步骤：
    在第一晶圆正面制备微纳结构阵列和键合对准标记，并在正面镀膜；在第二晶圆正面制备键合对准标记，反面制备微纳结构阵列，并在反面镀膜；
    根据所述超表面透镜的口径、透过率要求确定第三晶圆厚度，对第三晶圆的正面和反面进行抛光；
    对所述第一至第三晶圆进行清洗和加热处理，将第一晶圆的反面和第二晶圆的正面分别与第三晶圆光刻对准并进行加热预键合以及高温退火处理，最后清洗键合后的晶圆片去除表面掩膜。
  2. 一种超表面透镜，其特征在于，所述超表面透镜采用权利要求1所述的制造方法得到。
  3. 一种红外折超混合量子点相机，其特征在于，包括沿光轴依次设置的透镜(1)、权利要求2所述的超表面透镜(2)、量子点红外探测器(3)以及光学镜头组装件(4)；
    所述透镜(1)用于对入射光进行汇聚，所述汇聚后的入射光经过超表面透镜(2)进行像差矫正后，聚焦于所述量子点红外探测器(3)的焦平面上；
    所述量子点红外探测器(3)用于消除杂散光和非目标波段的入射光并且进行红外探测成像；
    所述透镜(1)和超表面透镜(2)置于所述光学镜头组装件(4)中，所述光学镜头组装件(4)用于对透镜(1)和超表面透镜(2)进行固定和保护。
  4. 根据权利要求1所述的一种红外折超混合量子点相机，其特征在于，所述透镜(1)为非球面透镜或者具有正光焦度的弯月形折射透镜。
  5. 根据权利要求1所述的一种红外折超混合量子点相机，其特征在于，所述超表面透镜(2)包括介质衬底层和位于介质衬底层两侧的柱状微结构阵列，所述柱状微结构阵列包括按照六方晶格或者四方晶格周期阵列排列的多个柱状微结构单元；所述每个柱状微结构单元的高度全部相同且介于所述目标物体热辐射的波长量级，所述每个柱状微结构单元的直径和周期介于亚波长量级；
    所述柱状微结构单元周期阵列的相位分布满足如下表达式：
    其中，ρ为超表面径向坐标，R为归一化半径，n为相位分布的最大项数，Ai均为多项式系数，i＝1,2,3,…n。
  6. 根据权利要求5所述的一种红外折超混合量子点相机，其特征在于，所述超表面透镜(2)通过以下方法设计：
    仿真获取所述超表面透镜中柱状微结构单元的尺寸与相位分布和透过率之间的对应关系，包括：
    根据时域有限差分算法和严格耦合波分析方法，对超表面透镜的柱状微结构单元的尺寸参数进行仿真，确定柱状微结构单元的高度、周期和直径与相位分布和透过率之间的对应关系。
  7. 如权利要求3所述的一种红外折超混合量子点相机，其特征在于，所述超表面透镜(2)的正反两面均镀有目标波段的增透减反膜层。
  8. 根据权利要求5所述的一种红外折超混合量子点相机，其特征在于，所述超表面透镜(2)的柱状微结构单元的材料为硅、锗或二氧化钛；所述介质衬底层的材料为硅、二氧化硅或氟化钡。
  9. 根据权利要求3所述的一种红外折超混合量子点相机，其特征在于， 所述量子点红外探测器(3)包括沿光轴方向依次设置的探测器窗口片、滤光片、光阑和红外光敏面，所述探测器窗口片、滤光片和光阑用于消除杂散光及非目标波段的入射光；所述红外光敏面用于对聚焦后的光线进行探测成像。
  10. 根据权利要求3所述的一种红外折超混合量子点相机，其特征在于，所述光学镜头组装件(4)包括镜筒主体和镜筒外壁，所述镜筒主体内置凹槽结构，用于固定透镜(1)和超表面透镜(2)，所述凹槽结构处具有减震材料，用以对透镜(1)和超表面透镜(2)进行减震保护；所述镜筒外壁具有隔热材料涂层。
PCT/CN2024/111614 2024-04-19 2024-08-13 一种超表面透镜及制造方法、红外折超混合量子点相机 Pending WO2025218062A1 (zh)

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