阅读说明：本技术 一种宽带宽角度抗反射复合微纳结构表面及其制备方法 (Wide-bandwidth angle anti-reflection composite micro-nano structure surface and preparation method thereof ) 是由 欧阳名钊 张自强 付跃刚 任航 张凯 刘智颖 张磊 胡源 王加科 于 2021-09-06 设计创作，主要内容包括：一种宽带宽角度复合微纳结构抗反射表面,属于光学技术和微纳加工技术领域,为了克服上述仿生蛾眼微纳结构表面技术中结构高度和深宽比对微纳加工工艺的制约,以及光学减反射薄膜技术中的减反射性能受到入射角度的限制,其为在光学材料基底表面形成单层薄膜,在薄膜层上形成一定深度的蛾眼微纳结构,并留出残余膜层,其由三层基本结构组成,依次包括：微纳结构层、中间残余层和基底层。所述微纳结构层由微纳结构单元阵列组成,微纳结构单元周期满足设计入射角度条件下的亚波长传输要求即：其中λ-(min)表示最小入射波长,n-(sub)表示基底折射率,n-(0)表示空气折射率,θ-(max)表示最大入射角度,p表示微纳结构单元周期。本发明在保证高透过率的同时对成像质量无影响。(A wide-bandwidth angle composite micro-nano structure anti-reflection surface belongs to the technical field of optical technology and micro-nano processing, and aims to overcome the restriction of the structure height and depth-width ratio on the micro-nano processing technology in the bionic moth eye micro-nano structure surface technologyAnd the antireflection performance in the optical antireflection film technology is limited by the incident angle, a single-layer film is formed on the surface of the optical material substrate, a moth eye micro-nano structure with a certain depth is formed on the film layer, and a residual film layer is reserved, and the optical antireflection film consists of three layers of basic structures and sequentially comprises: the micro-nano structure layer, the middle residual layer and the substrate layer. The micro-nano structure layer is composed of a micro-nano structure unit array, the period of the micro-nano structure unit meets the sub-wavelength transmission requirement under the condition of a designed incident angle, namely: wherein λ min Denotes the minimum incident wavelength, n sub Denotes the refractive index of the substrate, n 0 Denotes the refractive index of air, theta max Represents the maximum incident angle, and p represents the unit period of the micro-nano structure. The invention ensures high transmittance and has no influence on imaging quality.)

1. The utility model provides a compound micro-nano structure anti-reflection surface of wide bandwidth angle, characterized by, it is for forming the individual layer film on optical material substrate surface, forms the moth eye micro-nano structure of certain depth on the film layer to reserve residual film layer, it comprises three-layer basic structure, includes in proper order: the micro-nano structure layer comprises a micro-nano structure layer (1), a middle residual layer (2) and a substrate layer (3).

2. The optical antireflection surface with the wide bandwidth angle and the composite micro-nano structure according to claim 1, is characterized in that:

the micro-nano structure layer (1) is composed of a micro-nano structure unit array, and the period of the micro-nano structure unit meets the sub-wavelength transmission requirement under the condition of a designed incident angle, namely:wherein λ_minDenotes the minimum incident wavelength, n_subDenotes the refractive index of the substrate, n₀Denotes the refractive index of air, theta_maxRepresenting the maximum incident angle, and p represents the unit period of the micro-nano structure;

the micro-nano structure unit is of a cylinder, a round table, a cone, a Gaussian face type or a paraboloid type, the appearance of the micro-nano structure unit is optimized according to an incident spectrum section and bandwidth and an incident angle range, and the appearance of the cylinder, the round table or the cone is determined by the height h of the micro-nano structure unit₁Diameter of tip d₁Diameter of bottom end d₂Describing that the equation of the micro-nano structure unit under the three-dimensional Cartesian coordinate system is as follows:wherein x, y and z represent the three-dimensional coordinates of a certain point on the surface of the micro-nano structure unit, d_zThe distance between a point (x, y, z) on the surface of the micro-nano structure unit and the central axis of the micro-nano structure unit is twice; the Gaussian surface type and the paraboloid type consist of the height h of the micro-nano structure unit₁Describing the diameter d of the bottom end of the micro-nano structure, wherein the equation of the Gaussian face type in the three-dimensional Cartesian coordinate system is as follows:the equation for a parabolic profile in a three-dimensional cartesian coordinate system is:

the arrangement form of the micro-nano structure units comprises: the square or hexagonal is periodically arranged;

the medium material of the middle residual layer (2) is the same as that of the micro-nano structure layer (1), and the refractive indexes of the medium material and the micro-nano structure layer are all n₁Represents; its thickness h₂＜h₁；

The optical material of the substrate layer (3) comprises visible light optical material and infrared optical material, and the refractive index of the optical material is n₂And satisfies n₂＞n₁。

3. An etching processing method of an optical anti-reflection surface of a wide-bandwidth angle composite micro-nano structure is characterized by comprising the following steps:

forming a dielectric film layer with the refractive index lower than that of the original substrate on the surface of the substrate by using a film coating technology or a thermal growth technology, and then manufacturing a patterned template meeting the periodic condition on the surface of the dielectric film layer by using a photoetching pattern method, wherein the patterned template comprises a nanosphere photoetching template and a direct-writing mask template method; and finally, partially etching the medium thin layer by an etching technology to form a final composite micro-nano structure anti-reflection surface.

4. The etching processing method of the optical anti-reflection surface with the wide bandwidth angle composite micro-nano structure according to claim 3,

SiO with Si as substrate₂The etching processing method of the optical antireflection surface of the composite micro-nano structure as the film layer comprises the following steps:

step 1, silicon surface thermal oxidation treatment:

silicon thermal oxidation process for silicon to oxidize silicon atoms on silicon surface to generate SiO₂So that the surface of the Si substrate is covered with dense SiO₂Film formation:

(1) respectively putting the double-sided polished Si sample wafer into acetone, ethanol and deionized water solution for ultrasonic cleaning for 10 min;

(2) putting the cleaned silicon sample into a muffle furnace, and introducing N₂After 5min, adding O₂By detachment by heating to 95 ℃The water is then introduced into the furnace, O₂The flow rate is 200cc/min, the heating temperature in the furnace is set to be 1200 ℃, and the heating time is 1000 min;

step 2, etching by inductively coupled ion beams:

coating PS polyethylene balls on a Si wafer subjected to thermal oxidation treatment, etching a SiO2 film by using an inductively coupled ion etching (ICP) method, and finally removing the PS polyethylene balls to form a micro-nano structure:

(1) preparing a piranha solution, and pouring 70ml of concentrated sulfuric acid into 30ml of 30% hydrogen peroxide solution; soaking the Si slices subjected to thermal oxidation treatment in the piranha solution for 120min, and then performing ultrasonic oscillation on the Si slices with deionized water for 5 min;

(2) taking an evaporation dish with the caliber of 20cm, injecting deionized water with a proper height into the evaporation dish, placing a sample wafer with surface hydrophilicity, obliquely placing a glass plate which is also subjected to hydrophilic treatment, and enabling one edge of the glass plate to lean against the wall of the evaporation dish;

(3) taking 10ml of PS microsphere solution (50% of PS globules and 50% of ethanol), uniformly and slowly dripping the PS microsphere solution on a glass inclined plate by using a rubber head dropper to ensure that the PS microsphere is fully paved on the whole liquid surface, and finally slowly dripping SDS surfactant along the side wall of a vessel far away from the position of a sample wafer to push the microsphere to form a film;

(4) slowly extracting deionized water from the liquid level by using a needle cylinder until PS microspheres on the surface are settled on the surface of the sample wafer;

(5) drying the sample at room temperature;

(6) etching the surface of the sample wafer by adopting inductively coupled ion beam etching (ICP), wherein the etching parameters are as follows: SF₆Flow rate of 30sccm, CHF₄The flow is 10sccm, the ICP power is 300W, the RF power is 20W, the temperature is 10 ℃, and the etching time is 800 s;

(7) taking out the sample wafer, ultrasonically cleaning with ethanol for 10min, and removing the surface globules.

5. A nanoimprint processing method for an optical antireflection surface of a wide-bandwidth angle composite micro-nano structure is characterized by comprising the following steps:

firstly, an imprinting master plate which meets the shape requirement of the wide-band wide-angle anti-reflection composite micro-nano structure is manufactured, namely the imprinting master plate is designedThe surface of the micro-nano structure layer (1) is of a reverse structure; secondly, selecting usable stamping materials to form the micro-nano structure layer (1) and the intermediate residual layer (2), wherein the usable stamping materials include but are not limited to high molecular polymer PMMA for realizing the antireflection effect with the wavelength of 380nm-780nm, and chalcogenide glass material As₂S₃Realizing the antireflection effect with the wavelength of 8-12 mu m; and finally, controlling the pressure and temperature change in the imprinting process to press the imprinting material to the surface of the substrate layer (3) through a nano-imprinting technology to form the final anti-reflection surface of the composite micro-nano structure.

6. The nanoimprint processing method for the optical antireflection surface of the composite micro-nano structure according to claim 5, characterized in that,

the nanoimprint machining method of the optical anti-reflection surface of the composite micro-nano structure with ZF6 as a substrate and PMMA as a film layer comprises the following steps:

(1) preparing an imprinting mother board, and manufacturing a periodic cylindrical array Si mask plate by using a laser interference lithography technology, wherein the diameter of a cylinder is 120nm, and the height of the cylinder is 200 nm;

(2) preparing a working template, preparing the working template, gluing the surface of an original Si mold, stamping the original Si mold on a soft film for forming, and finally demolding;

(3) spin-coating a 3 wt% PMMA toluene solution on the polished surface of ZF6 at a speed of 4000r/m for 1min, and then baking the sample wafer at a temperature of 90 ℃ for 5 min;

(4) nanoimprinting is carried out in a commercial hydraulic hot press with a heating aluminum plate; the mold was initially contacted with the coupon, and then the mold and substrate were heated to 180 ℃ and a pressure of 2500psi was applied; annealing the sample for 20 minutes while keeping the temperature and pressure constant;

(5) after the annealing time, the sample was cooled below its glass transition temperature and then the mold was released from the patterned substrate.

7. The nanoimprint processing method for the optical antireflection surface of the composite micro-nano structure according to claim 5, characterized in that,

as with Ge As substrate₂S₃The nano-imprint processing method of the optical anti-reflection surface of the composite micro-nano structure as the film layer comprises the following steps:

(1) preparing an imprinting mother board, and manufacturing a periodic circular truncated cone type array Si mask by using a laser interference lithography technology, wherein the diameter of the bottom end of a circular truncated cone is 140nm, the diameter of the top end of the circular truncated cone is 80nm, and the height of the circular truncated cone is 140 nm;

(2) preparing a working template, plating an NiV alloy with the thickness of 85nm on the surface of a mother board by using a magnetron sputtering technology, then depositing Ni with the thickness of 300 mu m by electroforming, dissolving a Si mother board in 30% KOH solution, and obtaining the working template at the temperature of 80 ℃; depositing Al with the thickness of 20nm on the surface of the working template by using an atomic layer deposition technology₂O₃Finally, depositing FDTS on the surface by using a gas phase deposition method to serve as an anti-adhesion coating;

(3) respectively putting the double-sided polished Ge sample wafer into acetone, ethanol and deionized water solution for ultrasonic cleaning for 10 min;

(4) plating 3 μm As on Ge surface by evaporation method₂S₃A film;

(5) putting the sample wafer into an imprinting device, wherein the imprinting temperature is 210 ℃, and the pressure is 120N/cm²(ii) a And after the imprinting is finished, cooling and taking out the sample wafer.

Technical Field

The invention relates to a wide-bandwidth wide-angle anti-reflection composite micro-nano structure surface and a preparation process method thereof, belonging to the technical field of optical technology and micro-nano processing.

Background

The optical reflection resistance is an important interface characteristic for improving the energy utilization rate of the optical element and reducing stray light. In a common anti-reflection window, a single layer or multiple layers of dielectric films with different refractive indexes are plated on the surface of a substrate, and light rays are reflected in the films for multiple times to generate an interference phenomenon. When the wavelength of incident light, the thickness of the film layer and the refractive index of the film meet the destructive interference condition, the transmittance of light energy is maximum, and the aim of antireflection is achieved. In the traditional infrared band anti-reflection optical window, because the wavelength of an infrared band is longer than that of visible light, the thickness of a film is required to be thicker, and if the bonding force between the film and a substrate is not enough, demolding is easy to occur. And the anti-reflection range of the infrared anti-reflection film is limited by the wavelength and the angle. In CN 112596132A, SiO and Ge are used as coating materials, Si is used as a substrate for double-sided coating, and the average transmittance of a 3.7-4.8 mu m wave band is more than 98%. The antireflection film structure has good antireflection effect only when approaching a normal incidence angle, and has thicker film thickness and more film layers.

The moth eye micro-nano structure is a novel antireflection technology, is a sub-wavelength micro-nano structure, and has a size smaller than the wavelength. The anti-reflection mechanism of the moth-eye micro-nano structure is that the refractive index gradual transition from air to a substrate medium is constructed, and Fresnel reflection generated by the refractive index sudden change is reduced. Compared with an infrared coating window, the infrared coating window has the advantages of wide adaptability to the incident angle and the wavelength range, no need of coating and capability of being directly formed on the surface of a substrate. The ZnS material is used in broad spectrum wide angle moth eye anti-reflection super surface structure design analysis by Linhe, university of Changchun science, and the like, and the transmittance of more than 98.5 percent in the wavelength range of 0-60 degrees and 0.41-5 mu m is realized. The moth eye micro-nano structure can achieve an ideal broadband antireflection effect, but with the requirement on the angle being larger, such as 70-80 degrees, the transmittance of the moth eye structure is greatly reduced, and the excellent antireflection effect cannot be maintained. In order to maintain a large-angle transmittance of 70-80 degrees, the structure height and the depth-to-width ratio of the moth-eye micro-nano structure need to be improved, which provides a serious challenge for a micro-nano processing technology.

Disclosure of Invention

In order to overcome the restriction of the structure height and the depth-to-width ratio on the micro-nano processing technology in the bionic moth eye micro-nano structure surface technology and the limitation of the antireflection performance in the optical antireflection film technology by the incident angle, the invention provides the wide-band wide-angle composite micro-nano structure optical antireflection surface and the preparation method thereof, and the antireflection of the infrared band with wide angle and wide wavelength can be realized.

The technical scheme for solving the technical problem is as follows:

the utility model provides a compound micro-nano structure anti-reflection surface of wide bandwidth angle, it is for forming the individual layer film on optical material substrate surface, forms the moth eye micro-nano structure of certain depth on the film layer to reserve residual film layer, it comprises three-layer basic structure, includes in proper order: the micro-nano structure layer, the middle residual layer and the substrate layer.

The micro-nano structure layer is composed of a micro-nano structure unit array, the period of the micro-nano structure unit meets the sub-wavelength transmission requirement under the condition of a designed incident angle, namely:wherein λ_minDenotes the minimum incident wavelength, n_subDenotes the refractive index of the substrate, n₀Denotes the refractive index of air, theta_maxRepresenting the maximum incident angle, and p represents the unit period of the micro-nano structure;

the micro-nano structure unit is of a cylinder, a round table, a cone, a Gaussian face type or a paraboloid type, the appearance of the micro-nano structure unit is optimized according to an incident spectrum section and bandwidth and an incident angle range, and the appearance of the cylinder, the round table or the cone is determined by the height h of the micro-nano structure unit₁Diameter of tip d₁Diameter of bottom end d₂Describing that the equation of the micro-nano structure unit under the three-dimensional Cartesian coordinate system is as follows:wherein x, y and z represent the three-dimensional coordinates of a certain point on the surface of the micro-nano structure unit, d_zThe distance between a point (x, y, z) on the surface of the micro-nano structure unit and the central axis of the micro-nano structure unit is twice; the Gaussian surface type and the paraboloid type consist of the height h of the micro-nano structure unit₁Describing the diameter d of the bottom end of the micro-nano structure, wherein the equation of the Gaussian face type in the three-dimensional Cartesian coordinate system is as follows:the equation for a parabolic profile in a three-dimensional cartesian coordinate system is:

the arrangement form of the micro-nano structure units comprises: the square or hexagonal is periodically arranged;

the medium material of the middle residual layer is the same as the micro-nano structure layer, and the refractive indexes of the medium material and the micro-nano structure layer are all n₁Represents; its thickness h₂＜h₁；

The optical material of the substrate layer comprises visible light optical material and infrared optical material, and the refractive index of the optical material is n₂And satisfies n₂＞n₁。

An etching processing method of an optical anti-reflection surface of a wide-bandwidth angle composite micro-nano structure is characterized by comprising the following steps:

forming a dielectric film layer with the refractive index lower than that of the original substrate on the surface of the substrate by using a film coating technology or a thermal growth technology, and then manufacturing a patterned template meeting the periodic condition on the surface of the dielectric film layer by using a photoetching pattern method, wherein the patterned template comprises a nanosphere photoetching template and a direct-writing mask template method; and finally, partially etching the medium thin layer by an etching technology to form a final composite micro-nano structure anti-reflection surface.

SiO with Si as substrate₂The etching processing method of the optical antireflection surface of the composite micro-nano structure as the film layer comprises the following steps:

step 1, silicon surface thermal oxidation treatment:

silicon thermal oxidation process for silicon to oxidize silicon atoms on silicon surface to generate SiO₂So that the surface of the Si substrate is covered with dense SiO₂Film formation:

(1) respectively putting the double-sided polished Si sample wafer into acetone, ethanol and deionized water solution for ultrasonic cleaning for 10 min;

(2) putting the cleaned silicon sample into a muffle furnace, and introducing N₂After 5min, adding O₂Heating to 95 deg.C deionized water, and introducing into a furnace₂The flow rate is 200cc/min, the heating temperature in the furnace is set to be 1200 ℃, and the heating time is 1000 min;

step 2, etching by inductively coupled ion beams:

coating PS polyethylene balls on a Si wafer subjected to thermal oxidation treatment, etching a SiO2 film by using an inductively coupled ion etching (ICP) method, and finally removing the PS polyethylene balls to form a micro-nano structure:

(1) preparing a piranha solution, and pouring 70ml of concentrated sulfuric acid into 30ml of 30% hydrogen peroxide solution; will be subjected to thermal oxidation treatment

Soaking the Si slices in the piranha solution for 120min, and then performing ultrasonic oscillation for 5min by using deionized water;

(2) taking an evaporation dish with the caliber of 20cm, injecting deionized water with a proper height into the evaporation dish, placing a sample wafer with surface hydrophilicity, obliquely placing a glass plate which is also subjected to hydrophilic treatment, and enabling one edge of the glass plate to lean against the wall of the evaporation dish;

(3) taking 10ml of PS microsphere solution (50% PS globules and 50% ethanol), and uniformly and slowly dripping the solution on a glass inclined plate by using a rubber head dropper

Spreading PS microspheres on the whole liquid level, and finally slowly dripping SDS (sodium dodecyl sulfate) surfactant along the side wall of the vessel far away from the sample wafer to push the microspheres to form a film;

(4) slowly extracting deionized water from the liquid level by using a needle cylinder until PS microspheres on the surface are settled on the surface of the sample wafer;

(5) drying the sample at room temperature;

(6) etching the surface of the sample wafer by adopting inductively coupled ion beam etching (ICP), wherein the etching parameters are as follows: SF₆Flow rate of 30sccm, CHF₄The flow is 10sccm, the ICP power is 300W, the RF power is 20W, the temperature is 10 ℃, and the etching time is 800 s;

(7) taking out the sample wafer, ultrasonically cleaning with ethanol for 10min, and removing the surface globules.

A nanoimprint processing method for an optical antireflection surface of a wide-bandwidth angle composite micro-nano structure is characterized by comprising the following steps:

firstly, manufacturing an impression master plate which meets the requirement of the wide-bandwidth wide-angle anti-reflection composite micro-nano structure appearance, namely designing a reverse structure of the surface of the micro-nano structure layer (1); secondly, selecting usable stamping materials for forming the micro-nano structure layer (1) and the intermediate residual layer (2), wherein the usable stamping materials include but are not limited to the useThe high molecular polymer PMMA realizes the antireflection effect with the wavelength of 380nm-780nm, and the chalcogenide glass material As is used₂S₃Realizing the antireflection effect with the wavelength of 8-12 mu m; and finally, controlling the pressure and temperature change in the imprinting process to press the imprinting material to the surface of the substrate layer (3) through a nano-imprinting technology to form the final anti-reflection surface of the composite micro-nano structure.

The nanoimprint machining method of the optical anti-reflection surface of the composite micro-nano structure with ZF6 as a substrate and PMMA as a film layer comprises the following steps:

(1) preparing an imprinting mother board, and manufacturing a periodic cylindrical array Si mask plate by using a laser interference lithography technology, wherein the diameter of a cylinder is 120nm, and the height of the cylinder is 200 nm;

(2) preparing a working template, preparing the working template, gluing the surface of an original Si mold, stamping the original Si mold on a soft film for forming, and finally demolding;

(3) spin-coating a 3 wt% PMMA toluene solution on the polished surface of ZF6 at a speed of 4000r/m for 1min, and then baking the sample wafer at a temperature of 90 ℃ for 5 min;

(4) nanoimprinting is carried out in a commercial hydraulic hot press with a heating aluminum plate; the mold is initially brought into contact with the coupon and the mold is then placed

Heating the substrate to 180 ℃ and applying a pressure of 2500 psi; annealing the sample for 20 minutes while keeping the temperature and pressure constant;

(5) after the annealing time, the sample was cooled below its glass transition temperature and then the mold was released from the patterned substrate.

As with Ge As substrate₂S₃The nano-imprint processing method of the optical anti-reflection surface of the composite micro-nano structure as the film layer comprises the following steps:

(1) preparing an imprinting mother board, and manufacturing a periodic circular truncated cone type array Si mask by using a laser interference lithography technology, wherein the diameter of the bottom end of a circular truncated cone is 140nm, the diameter of the top end of the circular truncated cone is 80nm, and the height of the circular truncated cone is 140 nm;

(2) preparing a working template, plating an NiV alloy with the thickness of 85nm on the surface of a mother plate by a magnetron sputtering technology, then depositing Ni with the thickness of 300 mu m by electroforming, and dissolving a Si mother plate in a KOH solution with the concentration of 30 percentAnd the temperature is 80 ℃, so that a working template is obtained; depositing Al with the thickness of 20nm on the surface of the working template by using an atomic layer deposition technology₂O₃Finally, depositing FDTS on the surface by using a gas phase deposition method to serve as an anti-adhesion coating;

(3) respectively putting the double-sided polished Ge sample wafer into acetone, ethanol and deionized water solution for ultrasonic cleaning for 10 min;

(4) plating 3 μm As on Ge surface by evaporation method₂S₃A film;

(5) putting the sample wafer into an imprinting device, wherein the imprinting temperature is 210 ℃, and the pressure is 120N/cm²(ii) a And after the imprinting is finished, cooling and taking out the sample wafer.

The invention has the beneficial effects that:

the optical anti-reflection surface of the composite micro-nano structure can meet the requirement of high transmittance of a wide spectrum and a wide angle, does not generate high diffraction order, has no influence on imaging quality while ensuring high transmittance, can reduce the structure height and the depth-width ratio of the micro-nano structure with a large-angle anti-reflection effect of 70-80 degrees, and simultaneously keeps the anti-reflection effect during normal incidence and low-angle incidence. For example, with Al₂O₃SiO as a substrate₂The structure of the film has a transmission rate of more than 90% in a range of 0-80 degrees to an incident angle and a wavelength of 3-5 mu m; the preparation method of the composite micro-nano structure comprises the steps of plating an optical film on the surface of an optical substrate, and then further manufacturing the micro-nano structure on the surface of the film. The first preparation method uses the existing silicon thermal oxidation process and electric induction coupling plasma etching process, wherein the silicon thermal oxidation process is to oxidize the surface of a Si sheet and grow a layer of SiO with compact structure₂Thin films are commonly used for semiconductor integrated circuits and silicon-based solar cells. For SiO₂The film can be used for etching a micro-nano structure by using an inductively coupled plasma etching method. Preparation methodAnd secondly, combining a surface coating with a nano-imprinting technology, wherein nano-imprinting is a low-cost large-area micro-nano structure processing method, a high-precision mask needs to be manufactured by using a photoetching technology and an etching technology, and the surface of the micro-nano structure to be processed is formed at one time under the action of pressure and a certain temperature adjusting piece. When the optical substrate is Ge material, the surface film is As₂S₃When the material is made, due to the thermal plasticity of chalcogenide glass, As can be imprinted by a nano-imprinting method₂S₃And (5) stamping the film into a required micro-nano structure shape.

Drawings

Fig. 1 is a schematic diagram of a single period of an anti-reflection composite micro-nano structure surface with a wide bandwidth angle. The corresponding reference numerals mean: 1. micro-nano structure unit 2, middle residual layer 3, and basal layer.

Fig. 2 is a schematic diagram of an optical anti-reflection surface of a three-dimensional composite micro-nano structure.

FIG. 3 shows that SiO2, which is an Al2O 3-based substrate, has a transmittance in a wavelength band of 3-5 μm in a range of 0-50 DEG of an incident angle of the thin film, and the transmittance at any wavelength and incident angle in the range of the incident angle and the wavelength band reaches more than 94%.

FIG. 4 shows that SiO2, which is an Al2O 3-based substrate, has a transmittance in a wavelength band of 3-5 μm in a range of 60-80 DEG incident angle of the thin film, and the transmittance at any wavelength and incident angle in the range of the incident angle and the wavelength band is more than 90%.

Fig. 5 is a flow chart of an etching processing method of the optical antireflection surface of the composite micro-nano structure with the substrate of Si, i.e., SiO2, as a thin film. The corresponding reference numerals mean: 1. thermal oxidation treatment 2 of silicon, polyethylene ball deposition 3 and electric induction ion etching.

Fig. 6 is a nanoimprint processing method of a composite micro-nano structure optical antireflection surface with Ge As a substrate As2S3 As a thin film. The corresponding reference numerals mean: 1. plating an As2S3 film 2, a nano-imprint mask 3 and a nano-imprint transfer micro-nano structure on the surface of the Ge substrate.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

As shown in fig. 1-2, a broad bandwidth angle anti-reflection composite micro-nano structure surface is formed by forming a single-layer optical film on the surface of an optical material substrate and forming a micro-nano structure with a certain depth on the film layer; the structure includes: the micro-nano structure layer comprises a micro-nano structure layer 1, a middle residual layer 2 and a substrate layer 3.

The micro-nano structure unit is of a cylinder, a round table, a cone or a Gaussian face type or a paraboloid type, and the like, the unit morphology is optimized according to an incident spectrum segment, bandwidth and an incident angle range, and the cylinder, the round table and the cone morphology can be determined by the height h of the micro-nano structure unit₁Diameter of tip d₁Diameter of bottom end d₂To describe. The equation of the micro-nano structure unit under the three-dimensional Cartesian coordinate system is as follows:wherein x, y and z represent the three-dimensional coordinates of a certain point on the surface of the micro-nano structure unit, d_zRepresents the distance from the (x, y, z) point on the surface of the micro-nano structure unit to the central axis of the micro-nano structure unit twice. The Gaussian surface type and the parabolic surface type can be formed by the height h of the micro-nano structure unit₁And the diameter d of the bottom end of the micro-nano structure. The equation of the Gaussian profile under the three-dimensional Cartesian coordinate system is as follows:the equation for a parabolic profile in a three-dimensional cartesian coordinate system is:the arrangement form of the micro-nano structure units comprises: square or hexagonal periodic arrangement.

The medium material of the middle residual layer 2 is the same as that of the micro-nano structure layer 1, and the refractive indexes are all n₁And (4) showing. Its thickness h₂＜h₁；

The optical material of the substrate layer 3 comprises visible light optical material and infrared optical material, and has refractive index n₂Given by the design task and satisfying n₂＞n₁。

The following provides design examples of the micro-nano structure units in the middle infrared spectrum with an incident angle of 0-80 DEG and in the cylindrical and truncated cone shapes. The design parameters are as follows: when the micro-nano structure unit is cylindrical, the period p is 1p_max～1.3p_maxThickness h of the intermediate residual layer₂Is 0.2 lambda_min～0.3λ_minHeight h of micro-nano structural unit₁Is 0.5 lambda_min～0.7λ_minDiameter of tip d₁Is 0.44p_max～1p_maxDiameter of bottom end d₂The diameter of the tip is the same; when the micro-nano structure unit is in a truncated cone shape, the period p is p_max～1.3p_maxThickness h of the intermediate residual layer₂Is 0.2 lambda_min～0.3λ_minHeight h of micro-nano structural unit₁Is 0.5 lambda_min～0.8λ_minDiameter of tip d₁Is 0.3p_max～0.6p_maxDiameter of bottom end d₂Is 0.5p_max～1p_max。

Incident light enters the optical anti-reflection surface of the composite micro-nano structure, interference enhancement is generated between the incident light and the surface micro-nano structure and the film layer, matching of the refractive index and the thickness can be achieved through optimization of geometric parameters including the top end diameter and the bottom end diameter of the micro-nano structure, the height of a micro-nano structure unit and the thickness of a residual film part, and therefore the best anti-reflection effect is obtained.

FIG. 3 shows that SiO2, which is an Al2O 3-based film, has a transmittance in a wavelength band of 3-5 μm within a range of 0-50 degrees of an incident angle, and the transmittance of any wavelength and incident angle within the range of the incident angle and the wavelength band reaches more than 94%, which shows that the high transmittance of the invention at normal incidence and low angles is high.

FIG. 4 shows that SiO2, which is an Al2O 3-based film, has a transmittance in a wavelength band of 3-5 μm within a range of 60-80 degrees of incident angle, and the transmittance of any wavelength and incident angle within the range of incident angle and wavelength band reaches over 90%, which shows that the high transmittance of the invention at normal incidence and low angle is achieved.

The etching processing method of the anti-reflection surface of the composite micro-nano structure is characterized by comprising the following steps:

a dielectric film layer with the refractive index lower than that of the original substrate is formed on the surface of the substrate by using a film coating technology or a thermal growth technology, and then a patterned template meeting the periodic condition, including a nanosphere photoetching template, a direct-writing mask template and the like, is manufactured on the surface of the dielectric film layer by using a photoetching pattern method. And finally, partially etching the medium thin layer by an etching technology to form a final composite micro-nano structure anti-reflection surface.

As shown in fig. 5, an example of an etching method for an optical anti-reflective surface of a composite micro-nano structure with Si as a substrate and SiO2 as a film layer includes the following steps:

firstly, silicon surface thermal oxidation treatment:

oxidizing silicon atoms on the surface of the silicon by using a silicon thermal oxidation process to generate SiO2, so that the surface of the Si substrate is covered with a dense SiO2 thin film:

(1) and respectively putting the double-sided polished Si sample wafer into acetone, ethanol and deionized water solution for ultrasonic cleaning for 10 min.

(2) And (3) putting the cleaned silicon sample into a muffle furnace, introducing N for 25min, then introducing O2 into the furnace after passing through deionized water heated to 95 ℃, wherein the flow rate of O2 is 200cc/min, the heating temperature in the furnace is set to be 1200 ℃, and the heating time is 1000 min.

Secondly, etching by using an inductively coupled ion beam:

coating PS polyethylene balls on a Si wafer subjected to thermal oxidation treatment, etching a SiO2 film by using an inductively coupled ion etching (ICP) method, and finally removing the PS polyethylene balls to form a micro-nano structure:

(1) a piranha solution was prepared by pouring 70ml of concentrated sulfuric acid into 30ml of 30% hydrogen peroxide solution. Soaking the Si slices subjected to thermal oxidation treatment in the piranha solution for 120min, and then performing ultrasonic oscillation with deionized water for 5 min.

(2) An evaporation dish with the caliber of 20cm is taken, deionized water with a proper height is injected into the evaporation dish, a sample wafer with surface hydrophilicity is placed, a glass plate which is also subjected to hydrophilic treatment is obliquely placed, and one edge of the glass plate is leaned against the wall of the evaporation dish.

(3) Taking 10ml of PS microsphere solution (50% PS globules and 50% ethanol), and uniformly and slowly dripping the solution on a glass inclined plate by using a rubber head dropper

And (3) spreading the PS microspheres on the whole liquid level, and finally slowly dripping SDS (sodium dodecyl sulfate) surfactant along the side wall of the vessel far away from the sample wafer to push the microspheres to form a film.

(4) And slowly extracting the deionized water from the liquid level by using a syringe until the PS microspheres on the surface are settled on the surface of the sample wafer.

(5) The coupons were dried at room temperature.

(6) Etching the surface of the sample wafer by adopting inductively coupled ion beam etching (ICP), wherein the etching parameters are as follows: SF6 at 30sccm, CHF4 at 10sccm, ICP power of 300W, RF power of 20W, temperature of 10 deg.C, and etching time of 800 s.

(7) Taking out the sample wafer, ultrasonically cleaning with ethanol for 10min, and removing the surface globules.

The nanoimprint machining method for the antireflection surface of the composite micro-nano structure is characterized by comprising the following steps of:

firstly, an imprinting master plate which meets the requirement of the wide-bandwidth wide-angle anti-reflection composite micro-nano structure appearance is manufactured, namely a reverse structure of the surface of the micro-nano structure layer 1 is designed. And secondly, selecting a usable imprinting material to form the structure micro-nano structure layer 1 and the middle residual layer 2, wherein the usable imprinting material comprises but is not limited to a material which uses a high molecular polymer PMMA to realize an antireflection effect with the wavelength of 380nm-780nm, and a chalcogenide glass material As2S3 to realize an antireflection effect with the wavelength of 8-12 mu m. And finally, controlling the pressure and temperature change in the imprinting process to press the imprinting material to the surface of the substrate layer 3 through a nano-imprinting technology to form the final anti-reflection surface of the composite micro-nano structure. Different from the nanoimprint technology that the residual layer needs to be removed by using the etching technology after other micro-nano structures are manufactured, the composite micro-nano structure in the invention needs to retain the residual layer and has the thickness h₂The thickness is controlled to be designed to meet the anti-reflection effect, and the preferable thickness range is 0.2 lambda_min～0.3λ_min。

As shown in fig. 6, an example of a nanoimprint processing method for a composite micro-nano structure optical anti-reflection surface with ZF6 as a substrate and PMMA as a film layer includes the following steps:

preparing an imprinting mother board, and manufacturing a periodic cylindrical array Si mask plate by using a laser interference lithography technology, wherein the diameter of a cylinder is 120nm, and the height of the cylinder is 200 nm.

Preparing a working template, preparing the working template, gluing the surface of an original Si mold, impressing the original Si mold on a soft film for forming, and finally demolding.

Spin-coating a 3 wt% PMMA solution in toluene on the polished ZF6 surface at 4000r/m for 1min, and then baking the sample at 90 ℃ for 5 min.

Nanoimprinting was performed in a commercial hydraulic hot press with a heated aluminum plate. The mold was initially contacted with the coupon, and then the mold and substrate were heated to 180 ℃ and a pressure of 2500psi was applied. The samples were annealed for 20 minutes while keeping the temperature and pressure constant.

After the annealing time, the sample was cooled below its glass transition temperature and then the mold was released from the patterned substrate.

An example of a nanoimprint processing method of an optical antireflection surface of a composite micro-nano structure with Ge As a substrate As2S3 As a film layer comprises the following steps:

(1) preparing an imprinting mother board, and manufacturing a periodic cylindrical array Si mask plate by using a laser interference lithography technology, wherein the diameter of a cylinder is 1 mu m, and the height of the cylinder is 2 mu m.

(2) Preparing a working template, plating an NiV alloy with the thickness of 85nm on the surface of a mother plate by using a magnetron sputtering technology, then depositing Ni with the thickness of 300 mu m by electroforming, dissolving a Si mother plate in 30% KOH solution, and obtaining the working template at the temperature of 80 ℃. Depositing Al2O3 with the thickness of 20nm on the surface of the working template by using an atomic layer deposition technology, and finally depositing FDTS on the surface by using a gas phase deposition method to serve as an anti-adhesion coating.

(3) And respectively putting the double-sided polished Ge sample wafer into acetone, ethanol and deionized water solution for ultrasonic cleaning for 10 min.

(4) A3 μm As2S3 thin film was deposited on the Ge surface by evaporation.

(5) The coupons were placed in an imprint apparatus at a temperature of 210 ℃ and a pressure of 120N/cm 2. And after the imprinting is finished, cooling and taking out the sample wafer.