CN113900162B

CN113900162B - Super surface of curved substrate and preparation method thereof

Info

Publication number: CN113900162B
Application number: CN202111166670.7A
Authority: CN
Inventors: 郝成龙; 谭凤泽; 朱健
Original assignee: Shenzhen Metalenx Technology Co Ltd
Current assignee: Shenzhen Metalenx Technology Co Ltd
Priority date: 2021-09-30
Filing date: 2021-09-30
Publication date: 2023-08-18
Anticipated expiration: 2041-09-30
Also published as: WO2023050866A1; CN113900162A

Abstract

The embodiment of the application provides a super-surface of a curved substrate and a preparation method thereof, belonging to the technical field of super-surfaces. The super surface comprises a curved substrate and a micro-nano structure; the micro-nano structure is arranged on the surface of the curved substrate; the surface of the curved surface substrate provided with the micro-nano structure is a curved surface; the micro-nano structure is perpendicular to the curved surface. The micro-nano structure of the super surface is vertical to the curved surface substrate, so that the precision of the super surface is improved, and the optical performance of the super surface is improved. According to the preparation method of the super surface of the curved surface substrate, provided by the embodiment of the application, the micro-nano structure vertical to the curved surface substrate is directly processed on the curved surface substrate through a photoetching process, so that the mass production uniformity is realized, and the processing on the free-form surface and the large-curvature curved surface substrate is realized.

Description

Super surface of curved substrate and preparation method thereof

Technical Field

The application relates to the field of super surfaces, in particular to a super surface of a curved substrate and a preparation method thereof.

Background

The super surface is a sub-wavelength artificial layered material, and comprises a substrate and nano structures which are arranged on the surface of the substrate according to a specific rule. The super surface can flexibly and effectively regulate and control the characteristics of electromagnetic wave polarization, amplitude, phase, polarization mode, propagation mode and the like. The supersurface of planar substrates has many applications in the imaging, holographic, display and optical computing fields. The super surface of the curved substrate has significant advantages in terms of miniaturization of the super lens (and the superlens-based optical system) and correction of chromatic aberration, compared to the super surface of the planar substrate.

In the related art, a flexible structure layer transfer method and a curved substrate direct attachment method are mainly adopted to prepare the super surface of the curved substrate. The flexible structure layer transfer method is to prepare a flexible structure layer on a planar substrate and transfer the flexible structure layer to a curved substrate; the direct attachment method of the curved substrate is to attach the processed nanostructure vertically downwards on the curved substrate.

The flexible structure layer transfer method has insufficient mass production uniformity and precision and is difficult to be suitable for free curved surfaces; the super-surface precision of the curved surface substrate direct attachment method is insufficient, and the curved surface substrate direct attachment method is difficult to process when the curvature of the curved surface substrate is overlarge.

Disclosure of Invention

Aiming at the technical problems, the embodiment of the application provides a super surface of a curved substrate and a preparation method thereof, which are used for solving the problems of insufficient mass production uniformity and insufficient precision of the curved substrate in the related art, and the technical scheme is as follows:

in one aspect, an embodiment of the present application provides a hypersurface of a curved substrate, where the hypersurface includes a curved substrate and a micro-nano structure;

the micro-nano structure is arranged on the surface of the curved substrate; the surface of the curved surface substrate provided with the micro-nano structure is a curved surface;

The micro-nano structure is perpendicular to the curved surface.

Optionally, the curved surface comprises a regular curved surface or an irregular curved surface.

Optionally, the shape of the micro-nano structure comprises a polarization dependent shape or a polarization independent shape.

Optionally, the shape of the micro-nano structure comprises a nano cylinder, a nano elliptic cylinder, a nano fin, a nano square cylinder or a nano ring cylinder.

Optionally, the super surface further comprises a reflecting layer, the reflecting layer covers the curved surface, and the micro-nano structure is arranged on the surface of the reflecting layer;

the reflecting layer is conformal with the curved substrate, and the surface is flat; the micro-nano structure is perpendicular to the surface of the reflecting layer; the reflective layer is configured to reflect incident light.

Optionally, the supersurface comprises at least one layer of the micro-nano structure.

Optionally, the super surface further comprises an index matching layer, which is used for improving the transmittance of the light reflected by the reflecting layer through index matching; the refractive index matching layer covers the reflecting layer; the micro-nano structure is arranged on the surface of the reflecting layer;

wherein the refractive index matching layer is conformal with the reflecting layer and has a flat surface; the micro-nano structure is perpendicular to the surface of the refractive index matching layer;

The index matching layer has an index of refraction between the micro-nano structure and air.

In another aspect, an embodiment of the present application further provides a method for preparing a super surface of a curved substrate, where the method at least includes:

step S1, preparing a curved surface substrate;

step S2, uniformly coating a coating layer, such as photoresist/hard mask, on the curved substrate by adopting a coating device;

s3, forming a reference structure on the coated curved substrate by adopting a photoetching and/or electron beam exposure process; the method comprises the steps of keeping the normal line of a to-be-exposed area of a coated curved substrate parallel to the optical axis of an exposure system in the exposure process, wherein the distance between the to-be-exposed area and the exposure system is the focal length of the exposure system;

and S4, depositing a structural layer on the curved substrate with the reference structure until the surface of the structural layer is matched with the surface shape of the curved substrate, so as to obtain the super surface of the curved substrate.

Optionally, the method for preparing the super surface of the curved substrate further comprises the following steps:

step S6, removing the coating, such as photoresist/hard mask, of the super surface of the curved substrate.

Step S5, polishing the structural layer to the same height as the coating layer;

and S6, removing the coating.

Optionally, the preparing the curved substrate includes:

step 101, turning a plane substrate with nanometer precision to obtain the curved substrate; or (b)

And 102, preparing a metal mold with nanometer precision, and adopting the metal mold to perform injection molding to obtain the curved surface substrate.

Optionally, the uniformly coating the curved substrate with the coating device at least includes:

step S201, determining a starting point on the curved substrate, wherein the starting point is the central position of a coverage surface coated for the first time;

step S202, calculating the position of a coating device according to the starting point, so that the coating device is positioned on the curved substrate in the normal direction of the starting point position, and the relative height of the coating device and the curved substrate is larger than the thickness of the coating layer;

and step S203, keeping the relative height of the coating device and the curved substrate unchanged all the time, and moving the coating device according to a reference step length to carry out coating until the whole coating of the curved substrate is completed.

Optionally, forming the reference structure on the coated curved substrate by using photolithography and/or electron beam exposure process at least includes:

Step S301, determining position parameters of the exposure system and the coated curved substrate, including determining the position of the exposure system and the center position and normal vector of the equivalent plane of the coated curved substrate;

step S302, moving the coated curved substrate to enable the center position of an equivalent plane of an area to be exposed to coincide with the focus of the exposure system, and completing focusing;

step S303, after focusing is completed, rotating the coated curved substrate to enable the normal line of the equivalent plane to be parallel to the optical axis of the exposure system, and completing alignment;

step S304, repeating the focusing and the aligning, enabling the center of the next area to be exposed to coincide with the focus of the exposure system, and enabling the normal line of the equivalent plane of the next area to be exposed to be kept parallel to the optical axis of the exposure system until the reference structure is formed on the coated curved substrate;

after one exposure is completed, the coated curved substrate moves along the direction perpendicular to the optical axis of the exposure system by a distance equal to the write field side length of the exposure system.

Optionally, the uniformly coating on the curved substrate by using a coating device comprises scanning type coating; the scanning type coating comprises the step that the coating device scans along a curved substrate with a reference step length until the surface of the curved substrate is uniformly coated.

Optionally, the scanning coating comprises:

the coating device scans along the first direction of the curved substrate, moves one reference step length in the second direction of the curved substrate after scanning the edge of the curved substrate, and continues scanning until the whole curved substrate is coated;

the first direction and the second direction are two directions perpendicular to each other on the equivalent plane of the curved substrate.

Optionally, the uniform coating on the curved substrate by the coating device at least meets the following conditions:

the moving step length of the coating device is the reference step length, and the reference step length is determined by the following formula:

wherein t is _x A functional expression of a one-dimensional gaussian distribution of the thickness of the cladding along the X-axis; sigma is the standard deviation; a is t _x A is equal to the radius of a coverage surface formed by the coating device on the surface of the curved substrate; x is x _H To coat the x-coordinate of the high point, x _L X-coordinates for the coated low points; c is the offset of the coating device along the X axis; t is t _total Thickness of the coating layer along the X-axis direction;d is the reference step length; epsilon is the peak-to-valley difference of the reference; n is a positive integer.

Optionally, the uniform coating on the curved substrate by the coating device at least satisfies the following conditions:

The coating rate of the coating device at least meets the following conditions:

the diameter of the coating area of the coating device is larger than or equal to a reference step length within the time of moving the coating device by one reference step length.

Optionally, the reference step is equal to the diameter of the coverage area formed by the coating device on the surface of the curved substrate.

Optionally, the determining the positional parameters of the exposure system and the coated curved substrate satisfies:

establishing an XYZ coordinate system by taking a focus of the exposure system as an origin, and enabling the exposure system to move and rotate the coated curved surface substrate on a Z axis of the XYZ coordinate system to at least meet the following conditions:

wherein k is a normal vector of the equivalent plane, and θ is a rotation vector of the equivalent plane.

Optionally, the coating device is an ultrasonic spray head or a pneumatic spray head.

Optionally, the method for depositing the structural layer comprises chemical vapor deposition and atomic layer deposition.

Optionally, the material of the structural layer is transparent material of a reference wave band;

the reference bands include at least a visible light band, a near infrared light band, and a far infrared light band.

Optionally, when the reference band is visible light, the material of the structural layer is one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide and hydrogenated amorphous silicon.

Optionally, when the reference band is near infrared light, the material of the structural layer includes one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, hydrogenated amorphous silicon, amorphous silicon and crystalline silicon.

Optionally, when the reference band is far infrared light, the material of the structural layer includes one or more of crystalline silicon, crystalline germanium, zinc sulfide and zinc selenide.

Optionally, when the reference band is ultraviolet, the material of the structural layer includes hafnium oxide.

Optionally, the method moves or rotates the coated curved substrate by a six axis movement system.

Optionally, the method comprises lift-off stripping techniques.

Optionally, the grinding comprises single point diamond turning.

Optionally, the scanning mode of the coating device comprises zigzag scanning.

Optionally, the method further comprises:

and S7, after the step S4 is completed, repeating the steps S2 to S4 on the surface of the structural layer, or repeating the steps S2 to S6 until the super surface of the curved substrate with the target layer number is obtained.

Optionally, the method further comprises:

Step S8, sequentially forming an intermediate layer and a matching medium layer on the super surface of the curved substrate obtained in the step S4 or S6;

step S9, repeating the step S2 to the step S4 on the matching medium layer; or repeating the step S2 to the step S6 on the matching medium layer;

and step S10, repeating the step S8 to the step S9 until the super surface of the curved substrate with the target layer number is obtained. Optionally, the method further comprises:

step S11, forming a reflecting layer on the curved substrate obtained in the step S1;

step S12, uniformly coating the coating layer on the reflecting layer.

The technical scheme provided by the embodiment of the application has the following beneficial effects:

the super surface of the curved surface substrate provided by the embodiment of the application is kept vertical to the curved surface substrate through the micro-nano structure, so that the precision of the super surface of the curved surface substrate is improved, and the optical performance of the super surface of the curved surface substrate is improved. According to the preparation method of the super surface of the curved surface substrate, the coating layer is coated on the curved surface substrate, so that a reference structure is directly processed on the curved surface substrate through photoetching or electron beam exposure technology, the normal line of a region to be exposed is kept perpendicular to the optical axis of an exposure system in the exposure process, and the reference structure is perpendicular to the curved surface substrate, so that a micro-nano structure perpendicular to the curved surface substrate is directly processed on the curved surface substrate, the optical performance and the mass production uniformity of the super surface of the curved surface substrate are improved, and the production cost is reduced; the method also realizes the processing of the micro-nano structure on the free-form surface and the large-curvature surface substrate.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application as claimed.

Drawings

The technical scheme of the embodiment of the application is further described in detail through the drawings and the embodiments.

FIG. 1A is a schematic view of an alternative configuration of a supersurface of a curved substrate according to an embodiment of the application;

FIG. 1B is a flowchart of an alternative method for preparing a supersurface of a curved substrate according to an embodiment of the application;

FIG. 1C is a schematic diagram of another alternative embodiment of a method for preparing a supersurface of a curved substrate according to an embodiment of the application;

FIG. 1D is a schematic diagram of another alternative embodiment of a method for preparing a supersurface of a curved substrate according to an embodiment of the application;

FIG. 1E is a schematic diagram of yet another alternative embodiment of a method for preparing a supersurface of a curved substrate according to an embodiment of the application;

FIG. 2A is an alternative flow chart for uniformly coating a curved substrate surface with a coating in accordance with an embodiment of the present application;

FIG. 2B is a schematic diagram of an alternative photoresist profile provided by an embodiment of the present application;

FIG. 2C is a schematic diagram of a photoresist profile according to an embodiment of the present application;

FIG. 3 is an alternative flow chart of forming a reference structure on a coated curved substrate using a lithography and/or electron beam exposure process according to an embodiment of the present application;

FIG. 4 is a schematic view of an alternative configuration of the supersurface of a non-discrete curved substrate according to an embodiment of the present application.

Reference numerals in the drawings denote:

1-a planar substrate; 11-a curved substrate; 12-micro-nano structure; 13-a curved surface; 2-cladding; 21-a reference structure; 3-structural layer.

Detailed Description

Exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary examples do not represent all implementations consistent with the application. Rather, they are merely examples of apparatus and methods consistent with aspects of the application as detailed in the accompanying claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any or all possible combinations of one or more of the associated listed items.

It should be understood that although the terms first, second, third, etc. may be used herein to describe various information, these information should not be limited by these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the application. The word "if" as used herein may be interpreted as "at … …" or "at … …" or "responsive to a determination", depending on the context. The features of the examples and embodiments described below may be combined with each other without conflict.

The super surface of the curved surface substrate prepared by the flexible structure layer transfer method is insufficient in mass production uniformity and difficult to be suitable for free curved surfaces due to the fact that the flexible structure layer is difficult to align with the curved surface substrate, deformation is generated by adhesion of the flexible structure layer and adhesion is not firm in the transfer process, and the micro-nano structure of the curved surface substrate prepared by the method is influenced by the transfer process, so that the regulation and control precision of the optical phase is insufficient. In the method for directly attaching the curved surface substrate, the micro-nano structure is vertical to the horizontal plane in the attaching process, so that the micro-nano structure cannot be vertical to the curved surface substrate, the regulation and control precision of the micro-nano structure on the optical phase is insufficient, the error of emergent light rays is increased, and the optical performance of the super surface is affected. In addition, the direct attachment method of the curved substrate is not suitable for processing when the curvature of the curved substrate is too large.

The embodiment of the application provides a super surface of a curved substrate, as shown in fig. 1A, the super surface of the curved substrate comprises a curved substrate 11 and a micro-nano structure 12; wherein, the micro-nano structure 12 is arranged on the surface of the curved substrate 11; the surface of the curved substrate 11 provided with the micro-nano structure 12 is a curved surface 13; the micro-nano structure 12 is perpendicular to the curved surface 13. That is, the height axis of any micro-nano structure 12 coincides with (or is parallel to) the normal line of the micro-nano structure 12 at the position on the curved substrate 11; or the height axis of any micro-nano structure 12 is perpendicular to the tangent line of the micro-nano structure 12 at the position on the curved substrate 11.

It should be noted that, the micro-nano structure 12 is a sub-wavelength structure for performing optical phase adjustment on the super surface of the curved substrate. The micro-nano structure 12 is directly processed on the surface of the curved substrate 11, preferably by a photolithography process. The curved substrate 11 may have the micro-nano structure 12 on only one side, or may have the micro-nano structure 12 on both sides. For example, the curved substrate 11 of the super surface of the curved substrate provided in the embodiment of the present application may be a convex lens, and the micro-nano structure 12 is disposed on both convex surfaces of the convex lens. It is understood that the surface of the curved substrate 11 on which the micro-nano structure 12 is not disposed may be curved or non-curved, such as planar, discrete planar or discrete curved.

Alternatively, the curved surface 13 comprises a regular curved surface or an irregular curved surface, such as a parabolic curved surface, a free curved surface, or a non-discrete curved surface. FIG. 4 illustrates an alternative structural schematic of the supersurface of a non-discrete curved substrate.

Alternatively, the shape of the micro-nano structure 12 comprises a polarization dependent shape or a polarization independent shape. For example, a nano-cylinder, a nano-elliptic cylinder, a nano-fin, a nano-square cylinder, or a nano-circular cylinder.

Preferably, the super surface of the curved substrate provided in the embodiment of the present application includes at least one layer of micro-nano structure 12, wherein any layer of micro-nano structure 12 is perpendicular to the curved surface 13. That is, there may be one layer of micro-nano structure 12, or there may be a cascade of layers of micro-nano structure 12. For example, when a single-layer micro-nano structure 12 fails to achieve a particular optical property, a cascade of multiple layers of micro-nano structures 12 may be employed to achieve the particular optical property.

Illustratively, the super surface of the curved substrate provided by the embodiment of the present application further includes a reflective layer, the reflective layer covers the surface of the curved substrate 11, and the micro-nano structure 12 is disposed on the surface of the reflective layer; wherein the reflecting layer is conformal with the curved surface 13 and has a flat surface; the micro-nano structure 12 is perpendicular to the surface of the reflecting layer; the reflective layer is configured to reflect incident light. The reflection layer is conformal to the curved surface 13 and has a flat surface, which means that the curvature of the reflection layer is always the same as that of the curved surface 13 and the surface is neat.

Illustratively, the metasurface provided by the embodiments of the present application further includes an index matching layer; the refractive index matching layer covers the reflecting layer; the micro-nano structure 12 is arranged on the surface of the reflecting layer; the refractive index matching layer is conformal with the reflecting layer, and the surface is flat; the micro-nano structure is perpendicular to the surface of the index matching layer. The refractive index matching layer is used for carrying out refractive index matching, and improves the transmittance of light rays, so that the reflectivity of the reflecting curved surface super surface is improved. Light rays enter a medium (e.g., air) with a mismatched refractive index and are reflected, thus causing reflection losses. Preferably, the index matching layer is made of a material having a refractive index between that of the micro-nano structure 12 and air, so as to increase the transmittance of light reflected by the reflective layer, thereby increasing the reflectivity of the reflective layer.

According to the super-surface of the curved surface substrate, the micro-nano structure is perpendicular to the curved surface substrate, and the included angle between the micro-nano structure and the curved surface substrate is not influenced by the curvature of the curved surface substrate, so that the optical phase adjustment error caused by the curvature of the curved surface substrate is reduced, the precision of the super-surface of the curved surface substrate is increased, and the optical performance of the super-surface of the curved surface substrate is improved.

The embodiment of the application also provides a method for preparing the super surface of the curved substrate, which is used for processing the super surface of the curved substrate, as shown in fig. 1B, and at least comprises the following steps S1 to S4.

Step S1, preparing a curved substrate.

In step S2, a coating apparatus is used to uniformly apply a coating layer, such as a photoresist/hard mask, on the curved substrate.

S3, forming a reference structure on the coated curved substrate by adopting a photoetching and/or electron beam exposure process; the normal line of the area to be exposed of the coated curved substrate is kept parallel to the optical axis of the exposure system in the exposure process, and the distance between the area to be exposed and the exposure system is the focal length of the exposure system.

And S4, depositing a structural layer on the curved surface substrate with the reference structure until the surface of the structural layer is matched with the surface shape of the curved surface substrate, thereby obtaining the super surface of the curved surface substrate.

Preferably, the embodiment of the method for preparing the super surface of the curved substrate provided by the embodiment of the application is as follows:

first, a curved substrate, such as a free-form curved substrate or a large curvature curved substrate, meeting the requirements should be prepared based on the design requirements. In an exemplary embodiment of the present application, the material of the curved substrate is a transparent material in the reference band, for example, a transparent material in the visible band. It should be noted that, the reference band refers to a target band for the super surface design operation of the curved substrate, and includes, but is not limited to, a visible light band, a near infrared light band, and a far infrared light band. It should be understood that photolithographic exposure processes include, but are not limited to, ultraviolet exposure, deep ultraviolet exposure, and extreme ultraviolet exposure.

In an optional implementation manner, in the method for preparing a super surface of a curved substrate provided by the embodiment of the present application, step S1, a process for preparing a curved substrate includes:

step S101, turning the plane substrate with nanometer precision; or alternatively, the first and second heat exchangers may be,

step S102, preparing a metal mold with nanometer precision, and adopting the metal mold for injection molding to obtain a curved surface substrate.

Illustratively, turning a harder material (e.g., glass) is performed by turning a planar substrate, such as with precision single point diamond. Optionally, the material of the substrate comprises one or more of quartz glass, flint glass, crown glass, crystalline silicon and crystalline germanium. Illustratively, a metal mold with nanometer precision is prepared for softer materials, and injection molding is performed by using the prepared metal mold. Optionally, the material of the substrate includes one or more of organic glass (PMMA, polymethyl methacrylate), polycarbonate (PC), polyethylene (PE), polydimethylsiloxane (PDMS). It should be understood that the process of preparing the nano-precision metal mold is not limited to turning.

After the curved substrate is obtained, a coating layer, such as photoresist and/or hard mask, is required to be coated on the curved substrate, see step S2. An alternative implementation manner of step S2, as shown in fig. 2A, the method for uniformly coating a coating layer on a curved substrate by using a coating device according to an embodiment of the present application includes at least:

In step S201, a starting point on the curved substrate is determined, where the starting point is a center position of the coverage surface of the first coating.

Step S202, calculating the position of the coating device based on the starting point, so that the coating device is positioned on the curved substrate in the normal direction of the starting point position, and the relative height of the coating device and the curved substrate is larger than the thickness of the coating layer.

And step S203, the relative height of the coating device and the curved substrate is kept unchanged all the time, and the coating device is moved to carry out coating according to a reference step length until the coating of the whole curved substrate is completed.

Illustratively, the coating applied to the curved substrate in step S2 includes, but is not limited to, photoresist and hard mask.

The following implementation procedure is exemplified by taking the coating material as photoresist, and in the step S2, the coating layer is coated on the surface of the curved substrate by adopting a spraying mode, so that the spraying is favorable for coating on the curved substrate with a large curvature or free curved surface. The coating device is preferably a spray head, such as an ultrasonic spray head or a pneumatic spray head.

The principle of spraying is a process of uniformly coating the surface of a curved substrate after atomizing the photoresist into fine liquid drops. The principle of air pressure atomization is that a high velocity air stream around a nozzle breaks up liquid into fine droplets. Friction between the liquid and the gas breaks the liquid apart to form an atomized, the atomization energy being derived from the gas pressure. The ultrasonic atomization principle is that ultrasonic vibration is conducted to the liquid level to generate reticulate waves, the frequency of the reticulate waves is increased, small liquid drops are split at the wave peaks of the frequency, and the split small liquid drops are further split into smaller liquid drops due to secondary vibration of ultrasonic waves.

The spray nozzle is used for spraying photoresist and is fixed by adopting a curved substrate, and the spray nozzle moves along the curved substrate. When the spray head sprays the photoresist on a plane, the thickness of the photoresist presents Gaussian distribution, one-dimensional Gaussian distribution is formed along a certain direction (for example, the x direction is any direction perpendicular to the height direction of the curved surface substrate), as shown in fig. 2B and 2C, the standard deviation is sigma, and the functional expression isFull width at half maximum a=2.355 σ; c is the offset of the coating device along the X-axis. FIG. 2B shows the distribution of photoresist sprayed by the spray head each time along the x-direction, the thickness of the photoresist sprayed along the x-direction can be expressed asx _i ＝x ₀ And + (i-1) D, D is the step size of the nozzle movement. Fig. 2B shows an alternative distribution of photoresist sprayed by the spray head in the x-direction each time, and fig. 2B shows the displacement of the spray head in the x-direction on the abscissa and the thickness of the photoresist on the ordinate, with each individual peak representing one spray. Fig. 2C is a schematic diagram showing still another alternative photoresist distribution, in which the horizontal axis of fig. 2C is the displacement of the showerhead in the x direction, the vertical axis is the thickness of the photoresist, and the waveform diagram of fig. 2C is the final distribution of the photoresist after the spraying is completed. The peak-to-valley difference of the photoresist thickness sprayed on the curved substrate is the peak-to-valley difference to peak ratio of fig. 2B. Epsilon is the reference peak-valley difference.

The peak-valley difference of the photoresist thickness sprayed on the curved substrate should not be larger than epsilon, and the following expression is given:

in the formula (1), x _H For the x-coordinate of the glue-coated high point, x _L Is the x coordinate of the glue spreading low point. When ε is not more than 10%, t is defined as _total The expression is brought into equation (1) to solve for D.apprxeq.a.

As shown in fig. 2C, the relationship between the moving speed (V) of the spray center position and the spray head discharge rate (V) satisfies the following condition:

the covering surface of the nozzle formed on the surface of the substrate is a round surface, and the diameter is a. The moving speed of the spray head is V, the spraying speed is V, and the glue coating height H after scanning and the single glue coating height H ₀ The thickness of the adhesive after one full scan is obtained by the proportionality coefficient nDesired photoresist thickness t=nt ₀ Wherein N is a positive integer.

In a preferred embodiment of step S2, step S2 is performed as follows:

step S201, determining a starting point O on the curved substrate, the starting point O being the center position of the coverage surface of the first coating, and determining the coordinates of the starting point O as (x) ₀ ，y ₀ ，z ₀ )。

Step S202, calculating the position of the spray head based on the starting point O, so that the spray head is positioned on the normal line of the curved surface substrate at the point O, and the relative height H of the spray head and the curved surface substrate is greater than zero. It should be understood that H is a reference height set according to the processing requirements.

The normal vector of the curved substrate at the O point is (k) _x0 ，k _y0 ，k _z0 ) The spray head should be located at a distance H along the normal direction of the O point, specifically at the S point, the coordinates of the S point (x _s ，y _s ，z _s ) Can be determined according to the following formula (2):

and step S203, keeping the relative height of the spray head and the curved surface substrate unchanged all the time, and moving the spray head according to the step D to glue until the whole curved surface substrate is glued. Alternatively, the coating is performed only once, as long as the coating thickness is measured by the film thickness measuring instrument to reach the standard, i.e., the thickness of the photoresist reaches the standard.

Illustratively, after determining the starting point O and calculating the spray head position S, spraying is started, the speed at which the center position of spraying on the curved substrate moves along the curved substrate is V, and the spray head spray rate is V. At any time point t, the center position of the spraying area is A ₁ (x ₁ ，y ₁ ，z ₁ ) The normal vector is (k) _x1 ，k _y1 ，k _z1 ) The coordinates S of the nozzle at this time _t Derived from equation (3). Equation (3) is as follows:

assuming that the spray is performed along the x direction of the curved substrate along the spray head, the spray center coordinate A2 after the next time t+Δt is A1 plus the projection component of Δtv on the x, y, and z axes, respectively. Calculating the corresponding spray head position S according to different curved surface substrate spraying positions _t 。

Illustratively, the coating apparatus performs coating of the curved substrate in a scan-coating manner, such as a zig-zag scan. The coating rate of the coating device at least meets the following conditions:

The diameter of the coating area of the coating device is greater than or equal to a reference step length during the time that the coating device is moved by the reference step length. The moving mode of the spray head is, for example, z-shaped scanning, after the spray head moves along the X-axis to scan the edge, the spray head moves in the direction of the other axis (Y-axis) by a step length D, and the scanning is continued until the whole curved surface substrate is glued.

The above coating process is illustrated with a coating material as a photoresist, and the movement and coating principle of the coating apparatus are the same as the above example of coating the photoresist when the coating material is a hard mask.

After coating the photoresist/hard mask on the curved substrate, processing the micro-nano structure of the super surface on the curved substrate is started, and the processing technology is as follows.

After the coating is uniformly applied to the curved substrate, reference structures, including but not limited to structures and counter structures, are initially processed on the coated curved substrate. In an alternative embodiment, as shown in fig. 3, forming the reference structure on the coated curved substrate in step S3 by using photolithography and/or electron beam exposure process at least includes:

step S301, determining position parameters of the exposure system and the coated curved substrate, including determining a position of the exposure system and a center position and a normal vector of an equivalent plane of the coated curved substrate.

Step S302, the coated curved substrate is moved, so that the center position of the equivalent plane of the area to be exposed is overlapped with the focus of the exposure system, and focusing is completed.

Step S303, after focusing is completed, the coated curved substrate is rotated, so that the normal line of the equivalent plane is parallel to the optical axis of the exposure system, and alignment is completed.

Step S304, repeatedly moving and rotating the coated curved surface substrate to finish focusing and aligning, enabling the center of the next area to be exposed to coincide with the focus of the exposure system, and enabling the normal line of the equivalent plane of the next area to be exposed to be kept parallel to the optical axis of the exposure system until a reference structure is formed on the coated curved surface substrate;

after one exposure, the coated curved substrate moves along the direction perpendicular to the optical axis of the exposure system by a distance equal to the side length of the writing field of the exposure system. That is, when moving to the next area to be exposed, the moving distance of the moving stage is the side length of the writing field of the exposure system. It is thereby possible to avoid overlapping of the exposed area and the area to be exposed due to an excessively small moving distance and a gap between the exposed area and the area to be exposed due to an excessively large moving distance.

It should be understood that the reference structures in step S3 include, but are not limited to, structures and inverse structures. For example, when the refractive index of the photoresist meets the requirement of the application scene of the super surface of the curved substrate on the refractive index, the nanostructure can be directly exposed on the photoresist. In the step S3, an exposure system with a small writing field range is preferred, and the exposure system is favorable for keeping exposure light or electron beams perpendicular to the curved surface substrate when the curved surface substrate with a large curvature or free curved surface is processed, so that the processed reference structure is perpendicular to the curved surface substrate, the micro-nano structure is perpendicular to the curved surface substrate, and the optical phase regulation precision of the super surface of the curved surface substrate is improved.

In a preferred embodiment of step S3, six axes (x, y, z, θ _x ，θ _y ，θ _z ) The displacement platform is used for placing the curved surface substrate, so that the curved surface substrate can move in a plane and can rotate, and the normal line of the position to be processed of the curved surface substrate is parallel to the optical axis of the exposure system. It should be understood that the coordinate system in step S3 is a different coordinate system from the coordinate system in step S2. An exemplary embodiment of step S3 is as follows:

step S301, determining position parameters of the exposure system and the coated curved substrate, including determining a position of the exposure system and a center position and a normal vector of an equivalent plane of the coated curved substrate. Establishing a coordinate system by taking a focus of an exposure system as an origin (0, 0), wherein the exposure system is positioned at (0, z) ₀ ). Since the exposure area (i.e. write field) is only a square area of a few microns, a curved surface is so smallThe curvature change is negligible over a range of (a). The equivalent method is as follows: the center point (x ₁ ， y ₁ ，z ₁ ) The normal vector of the center point is (k _x ，k _y ，k _z ) The equation for this equivalent plane is then: k (k) _x (x-x ₁ )+ k _y (y-y ₁ )+k _z (z-z ₁ )＝0。

Step S302, moving the coated curved substrate to enable the center position of an equivalent plane of an area to be exposed to coincide with a focus of an exposure system, and completing focusing; for example, when the center position of the equivalent plane is (x ₁ ， y ₁ ，z ₁ ) When the six-axis displacement platform moves, the motion vector of the six-axis displacement platform is (-x) ₁ ，-y ₁ ，-z ₁ )。

illustratively, in steps S302 and S303, the vectors of movement and rotation of the six-axis displacement stage are (x, y, z, θ) _x ，θ _y ，θ _z ) Satisfy equation (4). For example, knowing the focus position of the exposure system as the origin, the exposure system can obtain a motion vector (x, y, z) on the z-axis based on the center position of the equivalent plane and the focus position, and the rotation vector (θ) can be obtained by taking the motion vector (x, y, z) into the formula (4) _x ，θ _y ，θ _z ). Equation (4) is as follows:

step S304, repeating the focusing and aligning in the step S303 and the step S304, enabling the center of the next area to be exposed to coincide with the focus of the exposure system, and enabling the normal line of the equivalent plane of the next area to be exposed to be kept parallel to the optical axis of the exposure system until a reference structure is formed on the coated curved substrate; after one exposure, the coated curved substrate moves along the direction perpendicular to the optical axis of the exposure system by a distance equal to the write field side length of the exposure system.

It is easy to understand that, during the exposure of step S3, keeping the normal of the equivalent plane of the area to be exposed of the coated curved substrate parallel to the optical axis of the exposure system ensures that the uv or e-beam is perpendicular to the surface of the curved substrate when the exposure process is working on the reference structure. Thus, the processed reference structure is perpendicular to the surface of the curved substrate.

The reference structure in step S3 may be a nanostructure or a nano-inverse structure, for example. Preferably, as shown in fig. 1C, nano-inverse structures perpendicular to the curved substrate surface are machined into the photoresist surface.

After the exposure processing is completed, referring to step S4, a structural layer is deposited on the curved substrate until the surface of the structural layer matches the surface shape of the curved substrate. In step S4, embodiments of depositing the structural layer include one or more of chemical vapor Deposition (CVD, chemicalVapor Deposition), atomic layer Deposition (ALD, atomic Layer Deposition), plasma enhanced chemical vapor Deposition (PECVD, plasma Enhanced Chemical Vapor Deposition), and low pressure chemical vapor Deposition (LPCVD, low Pressure ChemicalVapor Deposition). It should be noted that the matching of the surface of the structural layer with the surface shape of the curved substrate means that the upper surface of the structural layer is flat.

In step S4, the material of the structural layer is a transparent material of the reference band, that is, transparent to the radiation of the reference band. For example, when the reference band is the visible light band, the material of the structural layer includes one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, and hydrogenated amorphous silicon; when the reference band is a near infrared band, the material of the structural layer comprises one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, hydrogenated amorphous silicon, amorphous silicon and crystalline silicon; when the reference band is far infrared band, the material of the structural layer comprises one or more of crystalline silicon, crystalline germanium, zinc sulfide and zinc selenide; when the reference band is the ultraviolet band, the material of the structural layer includes hafnium oxide.

In an alternative embodiment, as shown in fig. 1C, the present application provides a method for preparing a super surface of a curved substrate, where the method includes steps S1 to S4, and the specific embodiment is as follows:

in step S1, turning with nanometer precision is directly performed on the planar substrate 1 to prepare the curved substrate 11. Illustratively, the curved substrate 11 is of a harder material, such as one or more of quartz glass, flint glass, crown glass, crystalline silicon, and crystalline germanium.

In step S2, a coating device is used to uniformly apply a coating layer 2 on the curved substrate, and optionally, the coating layer 2 is a photoresist/hard mask. Illustratively, an ultrasonic shower head or an air shower head is used to spray photoresist on the curved substrate 11.

In step S3, the reference structure 21 is formed on the coated curved substrate 11 by photolithography and/or electron beam exposure, and the normal line of the area to be exposed of the coated curved substrate 11 is kept parallel to the optical axis of the exposure system during the exposure process, and the distance between the area to be exposed and the exposure system is the focal length of the exposure system.

Illustratively, the curved substrate 11 is placed on a six-axis moving platform, and the center of an equivalent plane of the area to be exposed on the curved substrate 11 is coincident with the focus of the exposure system by moving and rotating the moving platform, and the equivalent plane is perpendicular to the optical axis of the exposure system; the movement and rotation of the curved substrate 11 is repeated until the exposure on the curved substrate 11 is completed entirely, forming the reference structure 21.

Step S4, depositing the structural layer 3 on the curved substrate with the reference structure 21 until the surface of the structural layer 3 is matched with the surface shape of the curved substrate 11, thereby obtaining the super surface of the curved substrate.

Illustratively, the structural layer 3 is deposited on the curved substrate 11 by an ALD method, the material of the structural layer 3 being selected according to the target band. For example, when the target wavelength band is visible light, the material of the structural layer 3 includes one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, and hydrogenated amorphous silicon; when the target wavelength band is near infrared light, the material of the structural layer 3 includes one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, hydrogenated amorphous silicon, and crystalline silicon; when the target wavelength band is far infrared light, the material of the structural layer 3 includes one or more of crystalline silicon, crystalline germanium, zinc sulfide, and zinc selenide; when the target wavelength band is ultraviolet light, the material of the structural layer 3 includes hafnium oxide.

It will be appreciated that during the exposure of step S3, keeping the normal of the area to be exposed of the coated curved substrate 11 parallel to the optical axis of the exposure system ensures that the light rays are perpendicular to the surface of the curved substrate 11 when the exposure process is working on the reference structure 21. Thereby, the processed reference structure 21 is made perpendicular to the surface of the curved substrate 11.

The reference structure 21 in step S3 may be a nanostructure or a nano-inverse structure, for example. Preferably, as shown in fig. 1C, nano-inverse structures perpendicular to the surface of the curved substrate 11 are processed on the photoresist surface. In step S4, the structural layer 3 is deposited on the curved substrate 11 having the nano-inverse structure. The structural layer 3 is filled with nano-counter structures to form nano-structures, namely micro-nano structures 12 for regulating and controlling the optical phase. The refractive index of the material of the structural layer 3 is different from that of the photoresist. Since the inverse structure formed by the processing in step S3 is perpendicular to the surface of the curved substrate 11, the nanostructure formed by filling the nanostructure of the structural layer 3 is perpendicular to the surface of the curved substrate 11. Thus, step S4 forms a supersurface of the curved substrate with photoresist filling.

In still another alternative embodiment, the present application provides a method for preparing a super surface of a curved substrate, where the method at least includes steps S1 to S4, and the specific embodiments are as follows:

step S1, preparing a metal mold with nanometer precision, and obtaining the curved surface substrate 11 by injection molding of the metal mold. Illustratively, the material of the curved substrate 11 is a softer material such as one or more of a polymethyl methacrylate (PMMA, polymethyl methacrylate), a Polycarbonate (PC), a Polyethylene (PE), a Polydimethylsiloxane (PDMS).

In step S2, the coating device is used to uniformly apply the coating layer 2 on the curved substrate 11. Optionally, the cladding layer 2 is a photoresist/hard mask. Illustratively, a hard mask is sprayed on the curved substrate 11 using an ultrasonic spray head or a pneumatic spray head.

In step S3, a reference structure 21 is formed on the curved substrate 11 coated with the hard mask by using photolithography and/or electron beam exposure process, wherein the normal line of the area to be exposed of the curved substrate 11 coated with the hard mask is kept parallel to the optical axis of the exposure system during the exposure process, and the distance between the area to be exposed and the exposure system is the focal length of the exposure system.

Illustratively, the structural layer 3 is deposited on a curved substrate by a CVD method, the material of the structural layer 3 being selected according to the target band. For example, when the target wavelength band is visible light, the material of the structural layer 3 includes one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, and hydrogenated amorphous silicon; when the target wavelength band is near infrared light, the material of the structural layer 3 includes one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, hydrogenated amorphous silicon, and crystalline silicon; when the target wavelength band is far infrared light, the material of the structural layer 3 includes one or more of crystalline silicon, crystalline germanium, zinc sulfide, and zinc selenide; when the target wavelength band is ultraviolet light, the material of the structural layer 3 includes hafnium oxide.

It will be appreciated that during the exposure of step S3, keeping the normal of the area to be exposed of the curved substrate 11 on which the hard mask has been applied parallel to the optical axis of the exposure system ensures that the light is perpendicular to the surface of the curved substrate 11 when the exposure process is working on the reference structure 21. Thereby, the processed reference structure 21 is made perpendicular to the surface of the curved substrate 11.

The reference structure 21 in step S3 may be a nanostructure or a nano-inverse structure, for example. Preferably, as shown in fig. 1C, nano-inverse structures perpendicular to the surface of the curved substrate 11 are machined on the surface of the spray hard mask. In step S4, the structural layer 3 is deposited on the curved substrate 11 having the nano-inverse structure. The structural layer 3 is filled with nano-counter structures to form nano-structures, namely micro-nano structures 12 for regulating and controlling the optical phase. The refractive index of the material of the structural layer 3 is different from that of the sprayed hard mask. Since the inverse structure formed by the processing in step S3 is perpendicular to the surface of the curved substrate 11, the nanostructure formed by filling the nanostructure of the structural layer 3 is perpendicular to the surface of the curved substrate 11. Thus, step S4 forms a supersurface with the filled curved substrate.

Exemplary, the embodiments of the method for preparing a super surface of a curved substrate provided by the embodiment of the present application are as follows:

and S1, directly turning the crystalline silicon plane substrate with nanometer precision to prepare a curved surface substrate.

And S2, uniformly spraying photoresist on the curved substrate obtained in the step S1 by adopting an ultrasonic nozzle.

And S3, forming a reverse structure on the coated curved substrate by adopting a photoetching process, wherein the normal line of the to-be-exposed area of the glued curved substrate is kept parallel to the optical axis of the exposure system in the exposure process, and the distance between the to-be-exposed area and the exposure system is the focal length of the exposure system.

Illustratively, placing the curved substrate on a six-axis moving platform, and moving and rotating the moving platform to enable the center of an equivalent plane of an area to be exposed on the curved substrate to coincide with a focus of an exposure system and enable the equivalent plane to be perpendicular to an optical axis of the exposure system; and repeatedly moving and rotating the curved substrate until the exposure on the curved substrate is completed, so as to form a reverse structure.

And S4, depositing a structural layer on the curved surface substrate with the reverse structure until the surface of the structural layer is matched with the surface shape of the curved surface substrate, thereby obtaining the super surface of the curved surface substrate.

When the refractive index of the photoresist/hard mask cannot meet the target band of the super surface of the curved substrate, the method for preparing the super surface of the curved substrate provided by the embodiment of the application further comprises the following steps: step S6, removing the coating 2 on the super surface of the curved substrate.

After removal of the coating 2 (e.g., photoresist and/or hard mask), a supersurface of the air-filled curved substrate is obtained. Air filling is adopted among the nano structures of the curved surface substrate, and the refractive index of the material of the nano structures is different from that of air.

In an exemplary embodiment, as shown in fig. 1D, the method for preparing a super surface of a curved substrate according to the embodiment of the present application at least includes steps S1, S2, S3, S4 and S6, and takes a processing of a planar substrate 1 to obtain a curved substrate 11 as an example, where the method is as follows:

in step S1, a curved substrate 11 is prepared.

In step S2, a coating device is used to uniformly apply the coating 2 on the curved substrate 11, optionally the coating 2 comprising a photoresist and/or a hard mask.

In step S3, a reference structure 21 is formed on the coated curved substrate 11 by photolithography and/or electron beam exposure process, and the normal line of the area to be exposed of the coated curved substrate 11 is kept parallel to the optical axis of the exposure system during exposure.

In step S4, the structural layer 3 is deposited on the curved substrate 11 with the reference structure 21 until the surface of the structural layer 3 matches the surface shape of the curved substrate 11, thereby obtaining the super surface of the curved substrate 11.

In step S6, the coating 2, e.g. photoresist and/or hard mask, of the supersurface of the curved substrate is removed, resulting in an air-filled supersurface of the curved substrate. After removal of the coating 2, the structural layer 3 remaining on the curved substrate 11 forms a micro-nano structure 12 for modulating the optical phase. The manner of removing the coating 2 is preferably a lift-off stripping technique.

For example, if the supersurface of the air-filled curved substrate is still unable to meet the target band requirements, a filler material that meets the target band requirements may be filled between the nanostructures of the supersurface of the air-filled curved substrate.

When the stripping effect of the coating 2 of the curved substrate 11 is not good and the coating 2 remains on the curved substrate 11, the method for preparing the super surface of the curved substrate provided by the embodiment of the application further comprises the following steps: and S5, polishing the structural layer to the same height as the coating layer.

In an exemplary embodiment, as shown in fig. 1E, the method for preparing a super surface of a curved substrate according to the embodiment of the present application further includes:

Step S5, polishing the structural layer 3 to be equal to the coating layer 2 in height.

Step S6, removing the coating 2 on the super surface of the curved substrate.

In an exemplary implementation process, the method for preparing the super surface of the curved substrate provided in the embodiment of the present application at least includes steps S1 to S6, as follows:

in step S1, a curved substrate 11 is prepared.

In step S2, a coating device is used to uniformly apply the coating 2 on the curved substrate 11, optionally the coating 2 comprising a photoresist and/or a hard mask. Illustratively, the photoresist is uniformly coated on the curved substrate 11 in a zig-zag scanning manner using an ultrasonic spray head.

In step S6, the coating 2, e.g. photoresist and/or hard mask, of the supersurface of the curved substrate is removed, resulting in an air-filled supersurface of the curved substrate. After removal of the coating 2, the structural layer 3 remaining on the curved substrate 11 forms a micro-nano structure 12 for modulating the optical phase. Illustratively, the manner in which the cover 2 is removed is preferably a lift-off peel technique.

The super surface of the curved substrate can be a single layer or a cascade of the super surfaces of the multi-layer curved substrate. That is, multiple layers of supersurfaces may be formed continuously on the same curved substrate, and may be independent of each other.

In an optional implementation manner, the method for preparing the super surface of the curved substrate provided by the embodiment of the application further comprises the following steps:

and step S7, after the step S4 is completed, repeating the steps S2 to S4 on the surface of the structural layer, or repeating the steps S2 to S6 until the super surface of the curved substrate with the target layer number is obtained.

In still another alternative embodiment, the method for preparing a super surface of a curved substrate provided by the embodiment of the present application further includes:

and S8, sequentially forming an intermediate layer and a matching medium layer on the super surface of the curved substrate obtained in the step S4 or the step S6.

Step S9, repeating the steps S2 to S4 on the matching medium layer; or repeating the steps S2 to S6 on the matching medium layer.

And S10, repeating the steps S8 to S9 until the super surface of the curved substrate with the target layer number is obtained.

step S1, preparing a curved substrate.

And S2, uniformly coating a coating layer on the curved substrate by adopting a coating device.

And S3, forming a reference structure on the coated curved substrate by adopting a photoetching and/or electron beam exposure process, wherein the normal line of the area to be exposed of the coated curved substrate is kept parallel to the optical axis of the exposure system in the exposure process, and the distance between the area to be exposed and the exposure system is the focal length of the exposure system.

Step S9, repeating the steps S2 to S4 on the matching medium layer.

And S9, after the completion of the step S9, obtaining two layers of super-surface cascading, namely the super-surface of the curved substrate with the two layers of nano structures.

And S10, repeating the steps S8 to S9 until the super surface of the curved substrate with the target layer number is obtained. For example, if the number of target layers is 3, after step S9 is completed, step S8 to step S9 are repeated again to form a third layer of the supersurface, so as to obtain the supersurface of the curved substrate with the cascade of three layers of the supersurfaces.

step S1, preparing a curved substrate.

Step S9, repeating the steps S2 to S6 on the matching medium layer. And after the step S8 is completed, obtaining two layers of super-surface cascading, namely the super-surface of the curved substrate with the two layers of nano structures.

step S11, forming a reflecting layer on the curved substrate obtained in the step S1.

Step S12, uniformly coating a coating layer on the reflecting layer.

step S1, preparing a curved substrate.

Step S11, forming a reflecting layer on the curved substrate obtained in the step S1. Optionally, an index matching layer may be further coated on the reflective layer in step S11 to enhance the reflectivity of the reflective layer.

Step S12, uniformly coating the reflective layer with a coating device.

And S4, depositing a structural layer on the curved substrate with the reference structure until the surface of the structural layer is matched with the surface shape of the curved substrate, thereby obtaining the super surface of the curved substrate with the reflecting layer.

According to the preparation method of the super surface of the curved surface substrate, the curved surface substrate is obtained through turning or injection molding, the curved surface substrate is uniformly coated with photoresist or hard mask, and a reference structure can be formed on the curved surface substrate through photoetching or electron beam exposure. During lithography or electron beam exposure, the area to be exposed is kept at the focus of the exposure system, and the normal line of the area to be exposed is parallel to the axis of the exposure system. Therefore, the reference structure formed on the curved surface substrate is perpendicular to the curved surface substrate, the micro-nano structure of the super surface is perpendicular to the curved surface substrate, and the optical performance of the curved surface substrate is improved. The method provided by the embodiment of the application directly processes the nano structure on the curved surface substrate through photoetching and/or electron beam exposure processes, thereby reducing the production cost and improving the mass production uniformity of the super surface of the curved surface substrate. The method also enables the creation of a multi-layer supersurface on a curved substrate to achieve specific optical properties.

In summary, the super surface of the curved substrate provided by the embodiment of the application is kept perpendicular to the curved substrate by the micro-nano structure, so that the precision of the super surface of the curved substrate is improved, and the optical performance of the super surface of the curved substrate is improved. According to the preparation method of the super surface of the curved surface substrate, provided by the embodiment of the application, the photoresist/coating layer is coated on the surface of the curved surface substrate, and the photoetching and the structural layer deposition are carried out on the coating layer, so that the micro-nano structure which is perpendicular to the curved surface substrate is directly processed on the curved surface substrate, the mass production uniformity of the super surface of the curved surface substrate is realized, the precision of the super surface of the curved surface substrate is improved, and the optical performance of the super surface of the curved surface substrate is improved.

Any combination of the above optional solutions may be adopted to form an optional embodiment of the present application, which is not described herein.

The foregoing is illustrative of the present application and is not to be construed as limiting thereof, but rather, the present application is to be construed as limited to the appended claims.

Claims

1. An optical supersurface of a curved substrate, characterized in that it comprises a curved substrate (11) and micro-nano structures (12);

Wherein the micro-nano structure (12) is arranged on the surface of the curved substrate (11); the surface of the curved surface substrate (11) provided with the micro-nano structure (12) is a curved surface (13);

the micro-nano structure (12) is perpendicular to the curved surface so as to improve the regulation precision of the optical super-surface on the optical phase.

2. The optical supersurface of a curved substrate according to claim 1, wherein said curved surface (13) comprises a regular curved surface or an irregular curved surface.

3. The optical supersurface of a curved substrate according to claim 1, wherein the shape of said micro-nano structure (12) comprises a polarization dependent shape or a polarization independent shape.

4. An optical supersurface of a curved substrate according to claim 3, wherein said micro-nano structures (12) comprise nano-cylinders, nano-elliptic cylinders, nano-fins, nano-square cylinders or nano-ring cylinders.

5. The optical supersurface of a curved substrate according to any one of claims 1 to 4, further comprising a reflective layer covering said curved surface (13), said micro-nano structure (12) being provided on the surface of said reflective layer;

wherein the reflecting layer is conformal with the curved substrate (11) and has a flat surface; the micro-nano structure (12) is perpendicular to the reflective layer surface; the reflective layer is configured to reflect incident light.

6. The optical supersurface of the curved substrate according to claim 5, wherein said optical supersurface comprises at least one layer of said micro-nano structures (12).

7. The optical supersurface of the curved substrate of claim 5 further comprising an index matching layer for increasing the transmittance of light reflected by said reflective layer by index matching; the refractive index matching layer covers the reflecting layer; the micro-nano structure (12) is arranged on the surface of the reflecting layer;

wherein the refractive index matching layer is conformal with the reflecting layer and has a flat surface; the micro-nano structure (12) is perpendicular to the surface of the index matching layer;

the index matching layer has an index of refraction between the micro-nano structure (12) and air.

8. A method for preparing an optical supersurface of a curved substrate according to any one of claims 1 to 7, said method comprising at least:

step S1, preparing a curved surface substrate;

step S2, uniformly coating a coating layer on the curved substrate by adopting a coating device;

s3, performing partition exposure on the coated curved substrate by adopting a photoetching and/or electron beam exposure process to form a reference structure; the method comprises the steps of keeping the normal line of a to-be-exposed area of a coated curved substrate parallel to the optical axis of an exposure system in the exposure process, wherein the distance between the to-be-exposed area and the exposure system is the focal length of the exposure system;

And S4, depositing a structural layer on the curved substrate with the reference structure until the surface of the structural layer is matched with the surface shape of the curved substrate, so as to obtain the optical super surface of the curved substrate.

9. The method for preparing an optical super surface of a curved substrate according to claim 8, wherein the method for preparing an optical super surface of a curved substrate further comprises:

and S6, removing the coating of the optical super surface of the curved substrate.

10. The method for preparing an optical super surface of a curved substrate according to claim 8, wherein the method for preparing an optical super surface of a curved substrate further comprises:

and S6, removing the coating.

11. The method for preparing an optical supersurface for a curved substrate according to any one of claims 8 to 10, wherein said preparing a curved substrate comprises:

12. The method for preparing an optical super surface of a curved substrate according to any one of claims 8 to 10, wherein said uniformly coating a coating layer on said curved substrate by using a coating device comprises at least:

step S202, calculating the position of a coating device based on the starting point, so that the coating device is positioned on the curved substrate in the normal direction of the starting point position, and the relative height of the coating device and the curved substrate is larger than the thickness of the coating layer;

13. The method for preparing an optical super surface of a curved substrate according to any one of claims 8 to 10, wherein forming a reference structure on the coated curved substrate by using photolithography and/or electron beam exposure process at least comprises:

step S304, repeating the focusing and the aligning, enabling the center of the next area to be exposed to coincide with the focus of the exposure system, and enabling the normal line of the equivalent plane of the next area to be exposed to be parallel to the optical axis of the exposure system until the reference structure is formed on the coated curved substrate;

14. The method of claim 12, wherein uniformly coating the curved substrate with the coating device comprises a scanning coating; the scanning type coating comprises the step that the coating device scans along a curved substrate with a reference step length until the surface of the curved substrate is uniformly coated.

15. The method of preparing an optical supersurface for a curved substrate according to claim 14, wherein said scanning coating comprises:

16. The method for preparing an optical super surface of a curved substrate according to claim 14, wherein said uniformly coating on said curved substrate by using a coating device at least satisfies:

x _i ＝x ₀ +(i-1)D；

wherein t is _x A functional expression of a one-dimensional gaussian distribution of the thickness of the cladding along the X-axis; sigma is the standard deviation; a is t _x A is equal to the diameter of a coverage surface formed by single coating of the coating device on the surface of the curved substrate; x is x _H To coat the x-coordinate of the high point, x _L X-coordinates for the coated low points; c is the offset of the coating device along the X axis; t is t _total Thickness of the coating layer along the X-axis direction; d is the reference step length; epsilon is the peak-to-valley difference of the reference; n is a positive integer; the X axis is any direction perpendicular to the height direction of the curved substrate.

17. The method for preparing an optical super surface of a curved substrate according to claim 12, wherein said uniformly coating on said curved substrate by a coating device at least satisfies:

the coating rate of the coating device at least meets the following conditions:

18. The method of claim 17, wherein the reference step size is equal to a diameter of a coverage area formed by the coating device on the surface of the curved substrate.

19. The method for preparing an optical super surface of a curved substrate according to claim 13, wherein the forming a reference structure on the coated curved substrate by using photolithography and/or electron beam exposure process satisfies the following conditions:

establishing an XYZ coordinate system by taking a focus of the exposure system as an origin, and enabling the exposure system to move and rotate on a Z axis of the XYZ coordinate system, wherein the movement and rotation of the coated curved surface substrate at least meet the following conditions:

20. The method of preparing an optical supersurface for a curved substrate according to any one of claims 8, 14 to 16, 18 or 19, wherein said coating means is an ultrasonic spray head or a pneumatic spray head.

21. The method for preparing an optical super surface of a curved substrate according to claim 8, wherein said method for depositing a structural layer comprises chemical vapor deposition and atomic layer deposition.

22. The method for preparing an optical super surface of a curved substrate according to claim 20, wherein the material of said structural layer is a transparent material of a reference band;

the reference bands include at least a visible light band, a near infrared band, and a far infrared band.

23. The method of claim 22, wherein the material of the structural layer is one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, and hydrogenated amorphous silicon when the reference wavelength band is visible light.

24. The method of claim 22, wherein the material of the structural layer comprises one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, hydrogenated amorphous silicon, and crystalline silicon when the reference wavelength band is near infrared light.

25. The method of claim 22, wherein the material of the structural layer comprises one or more of crystalline silicon, crystalline germanium, zinc sulfide and zinc selenide when the reference wavelength band is far infrared light.

26. The method of claim 22, wherein the material of the structural layer comprises hafnium oxide when the reference wavelength band is ultraviolet.

27. The method for preparing an optical supersurface of a curved substrate according to claim 8, wherein said method moves or rotates said coated curved substrate by a six axis movement system.

28. The method of preparing an optical supersurface for a curved substrate according to claim 9 or 10, wherein said method comprises lift-off techniques.

29. The method of preparing an optical supersurface for a curved substrate according to claim 10, wherein said lapping comprises single point diamond turning.

30. The method for preparing an optical super surface of a curved substrate according to claim 8, wherein the scanning mode of the coating device comprises a z-scan.

31. The optical supersurface preparation method of claim 10, further comprising:

and S7, after the step S4 is completed, repeating the steps S2 to S4 on the surface of the structural layer, or repeating the steps S2 to S6 until the optical super surface of the curved substrate with the target layer number is obtained.

32. The optical supersurface preparation method of claim 10, further comprising:

step S8, sequentially forming an intermediate layer and a matching medium layer on the optical super surface of the curved substrate obtained in the step S4 or S6;

and step S10, repeating the step S8 to the step S9 until the optical super surface of the curved substrate with the target layer number is obtained.

33. The optical supersurface preparation method of claim 8, further comprising:

step S12, uniformly coating the coating layer on the reflecting layer.

34. The method of claim 8, wherein the coating comprises a photoresist or a hard mask.