Superlens and method for manufacturing the same
By setting refractive index-matched anti-reflection structures at the top and bottom of the superlens column structure, an integrated superlens unit is formed, which solves the problems of poor adhesion and stability caused by thin film deposition, and achieves better light energy transmission effect and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YANTAI RAYTRON TECH CO LTD
- Filing Date
- 2023-04-12
- Publication Date
- 2026-07-10
AI Technical Summary
Existing superlenses, which are coated with antireflective and antitransmittance dielectric films, suffer from poor adhesion, easy detachment, film defects, and poor environmental adaptability, thus affecting reliability and stability.
First and second antireflective structures with matching refractive indices are set at the top and bottom of the superlens column structure to reduce the refractive index difference between it, air and the substrate, forming an integrated structure that replaces thin film coating and achieves antireflection and anti-reflection functions.
This improved the reliability and stability of the superlens, reduced production costs, increased production efficiency, and avoided problems such as film detachment and defects.
Smart Images
Figure CN116449468B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of optical technology, and more specifically, to a superlens and its fabrication method. Background Technology
[0002] A superlens is a 2D artificial structure that can flexibly control electromagnetic waves. It is small in size, light in weight, and easy to integrate. It can not only meet conventional imaging needs, but also achieve precise control of parameters such as the amplitude, phase, and polarization of incident light.
[0003] A superlens is composed of cylindrical units arranged in a series. When light strikes these cylindrical units on the surface of the superlens, Fresnel reflection occurs. This reflection significantly hinders the transmission of light energy, resulting in low image quality. To address the problem caused by light reflection, current methods typically involve depositing single or multiple layers of antireflective coatings onto the superlens surface. However, due to the uneven microstructure of the superlens surface, coating thin films results in poor adhesion, easy detachment, and difficulties in ensuring corrosion resistance and thermal stability. This leads to film defects and poor environmental adaptability, ultimately resulting in low reliability and stability of the superlens.
[0004] In conclusion, improving the reliability and stability of superlenses is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0005] In view of this, the purpose of this application is to provide a superlens and a method for its fabrication.
[0006] To achieve the above objectives, this application provides the following technical solution:
[0007] A superlens includes a substrate and a superlens unit array located on the surface of the substrate, the superlens unit array including a plurality of superlens units;
[0008] The superlens unit includes a superlens cylinder structure, a first antireflective structure located at the top of the superlens cylinder structure, and / or a second antireflective structure located at the bottom of the superlens cylinder structure; the refractive index of the first antireflective structure is between the refractive index of air and the refractive index of the superlens cylinder structure, and the refractive index of the second antireflective structure is between the refractive index of the superlens cylinder structure and the refractive index of the substrate; the superlens unit is an integral structure.
[0009] Preferably, the substrate is made of the same material as the superlens unit, the lateral dimension of the first antireflection structure is smaller than the lateral dimension of the superlens column structure, and the lateral dimension of the second antireflection structure is larger than the lateral dimension of the superlens column structure.
[0010] Preferably, the first antireflection structure and / or the second antireflection structure are columnar structures.
[0011] Preferably, the first antireflection structure and the second antireflection structure are non-column structures that are narrower at the top and wider at the bottom.
[0012] Preferably, the first anti-reflection structure is any one of a cone structure, a frustum structure, or a spherical cap structure;
[0013] The second anti-reflection structure is a platform structure.
[0014] Preferably, the heights of the first antireflection structure and the second antireflection structure are both 0.01λ-5λ, where λ is the working center wavelength of the superlens.
[0015] Preferably, the height of the superlens column structure is 0.1λ-10λ, where λ is the working center wavelength of the superlens.
[0016] Preferably, when the superlens is applied in the infrared band, the substrate and the superlens unit are any one of silicon, germanium, sapphire, zinc sulfide, and zinc selenide;
[0017] When the superlens is applied in the visible light band or the terahertz band, the substrate and the superlens unit are made of silicon oxide or quartz glass.
[0018] A method for fabricating a superlens, used to fabricate a superlens as described in any one of the preceding claims, comprising:
[0019] Clean the substrate;
[0020] The pattern on the photomask is transferred onto the photoresist using a photolithography process;
[0021] The flow rate and / or energy of the etching gas are controlled, the substrate is etched using the etching gas, and the sidewalls of the etched surface are protected using a passivation gas.
[0022] The substrate is cleaned to obtain a superlens unit array comprising multiple superlens units; each superlens unit includes a superlens cylinder structure, a first antireflective structure located at the top of the superlens cylinder structure, and / or a second antireflective structure located at the bottom of the superlens cylinder structure, wherein the refractive index of the first antireflective structure is between the refractive index of air and the refractive index of the superlens cylinder structure, and the refractive index of the second antireflective structure is between the refractive index of the superlens cylinder structure and the refractive index of the substrate.
[0023] Preferably, after cleaning the substrate, the process further includes:
[0024] A hard mask is deposited on the surface of the substrate;
[0025] After transferring the pattern on the photomask onto the photoresist using photolithography, the process also includes:
[0026] The hard mask is etched to transfer the pattern in the photoresist onto the hard mask, and the photoresist is then removed.
[0027] This application provides a superlens and a method for fabricating the same. The superlens includes a substrate and a superlens unit array located on the surface of the substrate. The superlens unit array includes multiple superlens units. Each superlens unit includes a superlens cylinder structure and a first antireflective structure located at the top of the superlens cylinder structure, and / or a second antireflective structure located at the bottom of the superlens cylinder structure. The refractive index of the first antireflective structure is between the refractive index of air and the refractive index of the superlens cylinder structure, and the refractive index of the second antireflective structure is between the refractive index of the superlens cylinder structure and the refractive index of the substrate. The superlens unit is a monolithic structure.
[0028] The technical solution disclosed in this application reduces the refractive index difference between the superlens unit and air, and between the superlens unit and the substrate by setting a first anti-reflection structure at the top of the superlens cylinder structure with a refractive index between the refractive index of air and the refractive index of the superlens cylinder structure, and / or setting a second anti-reflection structure at the bottom of the superlens cylinder structure with a refractive index between the refractive index of the superlens cylinder structure and the refractive index of the substrate, thereby reducing reflection and achieving better light energy transmission. Furthermore, the superlens unit is an integrated structure, meaning that the anti-reflection structure and the superlens cylinder structure are manufactured as a single unit. Compared to existing methods that achieve anti-reflection and anti-reflection functions by depositing an anti-reflection and anti-reflection medium film on the surface of the superlens, this application achieves the anti-reflection and anti-reflection function through an integrated anti-reflection structure with the superlens cylinder structure. This effectively solves the problems of poor adhesion, easy peeling, film defects, and poor environmental adaptability associated with depositing anti-reflection and anti-reflection medium films on the surface of the superlens, thereby improving the reliability, stability, and yield of the superlens. Moreover, since it eliminates the need for film deposition, it reduces the production cost and increases the production efficiency of the superlens. Attached Figure Description
[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0030] Figure 1This is a schematic diagram of a superlens provided in an embodiment of this application;
[0031] Figure 2 A top view of a superlens provided in an embodiment of this application;
[0032] Figure 3 This is a schematic diagram of the structure of the first type of superlens unit provided in the embodiments of this application;
[0033] Figure 4 This is a schematic diagram of the structure of the second type of superlens unit provided in the embodiments of this application;
[0034] Figure 5 This is a schematic diagram of the structure of the third type of superlens unit provided in the embodiments of this application;
[0035] Figure 6 This is a schematic diagram of the structure of the fourth type of superlens unit provided in the embodiments of this application;
[0036] Figure 7 This is a schematic diagram of the structure of the fifth type of superlens unit provided in the embodiments of this application;
[0037] Figure 8 This is a schematic diagram of the structure of the sixth type of superlens unit provided in the embodiments of this application;
[0038] Figure 9 This is a schematic diagram of the structure of the seventh type of superlens unit provided in the embodiments of this application;
[0039] Figure 10 This is a schematic diagram of the structure of the eighth type of superlens unit provided in the embodiments of this application;
[0040] Figure 11 This is a schematic diagram of the structure of the ninth type of superlens unit provided in the embodiments of this application;
[0041] Figure 12 This is a schematic diagram of the structure of the tenth type of superlens unit provided in the embodiments of this application;
[0042] Figure 13 This is a schematic diagram of the structure of the eleventh superlens unit provided in the embodiments of this application;
[0043] Figure 14 A flowchart illustrating a method for fabricating a superlens provided in this application embodiment;
[0044] Figures 1-14 The accompanying figure labels are as follows:
[0045] 1-Substrate, 2-Superlens unit, 21-First antireflection structure, 22-Superlens cylinder structure, 23-Second antireflection structure. Detailed Implementation
[0046] The core of this application is to provide a superlens and its fabrication method, which can improve the reliability and stability of the superlens.
[0047] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0048] See Figures 1-13 ,in, Figure 1 This illustration shows a schematic diagram of a superlens provided in an embodiment of this application. Figure 2 This illustration shows a top view of a superlens provided in an embodiment of this application. Figure 3 This illustration shows a schematic diagram of the structure of the first type of superlens unit provided in an embodiment of this application. Figure 4 This paper shows a schematic diagram of the structure of a second type of superlens unit provided in an embodiment of this application. Figure 5 This paper shows a schematic diagram of the structure of the third type of superlens unit provided in an embodiment of this application. Figure 6 This paper shows a schematic diagram of the structure of the fourth type of superlens unit provided in an embodiment of this application. Figure 7 This paper shows a schematic diagram of the structure of the fifth type of superlens unit provided in an embodiment of this application. Figure 8 This paper shows a schematic diagram of the structure of the sixth type of superlens unit provided in an embodiment of this application. Figure 9 This paper shows a schematic diagram of the structure of the seventh type of superlens unit provided in an embodiment of this application. Figure 10 This paper shows a schematic diagram of the structure of the eighth type of superlens unit provided in an embodiment of this application. Figure 11 This paper shows a schematic diagram of the structure of the ninth type of superlens unit provided in an embodiment of this application. Figure 12 This paper shows a schematic diagram of the structure of the tenth superlens unit provided in an embodiment of this application. Figure 13 This illustration shows a schematic diagram of the eleventh type of superlens unit provided in an embodiment of this application. The superlens provided in this embodiment may include a substrate 1 and a superlens unit array located on the surface of the substrate 1. The superlens unit array may include multiple superlens units 2.
[0049] The superlens unit 2 may include a superlens cylinder structure 22, and may also include a first antireflection structure 21 located at the top of the superlens cylinder structure 22, and / or a second antireflection structure 23 located at the bottom of the superlens cylinder structure 22; the refractive index of the first antireflection structure 21 is between the refractive index of air and the refractive index of the superlens cylinder structure 22, and the refractive index of the second antireflection structure 23 is between the refractive index of the superlens cylinder structure 22 and the refractive index of the substrate 1. The superlens unit 2 is an integral structure.
[0050] The superlens provided in this application may include a substrate 1 and a superlens unit array located on the surface of the substrate 1. The superlens unit array includes multiple superlens units 2, which are arranged according to a certain rule to form the superlens unit array, such as... Figure 2 The diagram shows a schematic arrangement of a superlens unit 2. The arrangement of the superlens unit 2 can be the same as that of a traditional cylindrical unit, or it can be rearranged according to the imaging requirements of the superlens. It should be noted that... Figure 1 In this context, H represents the height of the superlens unit 2.
[0051] In this application, the superlens unit 2 is a non-cylindrical structure. Specifically, the superlens unit 2 may include a superlens cylinder structure 22, which is the functional part of the superlens unit 2 and is used to realize the basic functions of the superlens, such as light convergence and polarization. In addition, the superlens unit 2 also includes a first anti-reflection structure 21 located at the top of the superlens cylinder structure 22, and / or a second anti-reflection structure 23 located at the bottom of the superlens cylinder structure 22 (i.e., between the substrate 1 and the superlens cylinder structure 22). That is to say, the superlens unit 2 can be divided into the following three structures: the first structure includes, from top to bottom, a first anti-reflection structure 21, a superlens cylinder structure 22, and a second anti-reflection structure 23 (e.g., ...). Figure 1 , Figure 3 , Figures 6-8 As shown), the second structure, from top to bottom, includes a first anti-reflection structure 21 and a superlens cylinder structure 22 (as shown). Figure 4 , Figures 9-11 As shown), the third structure consists of, from top to bottom, a superlens cylinder structure 22 and a second antireflection structure 23 (as shown). Figure 5 , Figures 12-13 (As shown). The cross-sections of the first anti-reflection structure 21, the superlens cylinder structure 22, and the second anti-reflection structure 23 can be circular, elliptical, quadrilateral (rectangular, square, etc.), or of course, other shapes (regular or irregular).
[0052] The refractive index of the first antireflective structure 21 is greater than that of air and less than that of the superlens cylinder structure 22. This reduces the refractive index difference between the superlens cylinder structure 22 and air, thereby reducing reflection between them and enhancing the optical transmission capability of the superlens unit 2, resulting in better light transmission. The refractive index of the second antireflective structure 23 is greater than that of the superlens cylinder structure 22 and less than that of the substrate 1. This also reduces the refractive index difference between the superlens cylinder structure 22 and the substrate 1, further reducing reflection and enhancing the optical transmission capability of the superlens unit 2, achieving better light transmission. Since all three structures can reduce reflection and enhance light transmission, their optical transmission capabilities are stronger than those of a traditional cylindrical superlens. Furthermore, because the first structure can reduce reflection and enhance light transmission at both the top and bottom, its optical transmission capability is stronger than that of the second and third structures.
[0053] In addition, the superlens unit 2 in this application is an integral structure, that is, the anti-reflection structure (i.e. the first anti-reflection structure 21 and the second anti-reflection structure 23 mentioned above) and the superlens column structure 22 are integrally made. Therefore, the superlens unit 2 with anti-reflection structure provided in this application can not only realize the anti-reflection and anti-reflection function, but also solve the problems existing by depositing anti-reflection and anti-reflection medium film.
[0054] It should be noted that, Figures 1-13 The superlens-related structures are only shown as examples, and it is not required that the superlens array or superlens unit 2 must be the structures shown in the figure.
[0055] The technical solution disclosed in this application reduces the refractive index difference between the superlens unit and air, and between the superlens unit and the substrate by setting a first anti-reflection structure at the top of the superlens cylinder structure with a refractive index between the refractive index of air and the refractive index of the superlens cylinder structure, and / or setting a second anti-reflection structure at the bottom of the superlens cylinder structure with a refractive index between the refractive index of the superlens cylinder structure and the refractive index of the substrate, thereby reducing reflection and achieving better light energy transmission. Furthermore, the superlens unit is an integrated structure, meaning that the anti-reflection structure and the superlens cylinder structure are manufactured as a single unit. Compared to existing methods that achieve anti-reflection and anti-reflection functions by depositing an anti-reflection and anti-reflection medium film on the surface of the superlens, this application achieves the anti-reflection and anti-reflection function through an integrated anti-reflection structure with the superlens cylinder structure. This effectively solves the problems of poor adhesion, easy peeling, film defects, and poor environmental adaptability associated with depositing anti-reflection and anti-reflection medium films on the surface of the superlens, thereby improving the reliability, stability, and yield of the superlens. Moreover, since it eliminates the need for film deposition, it reduces the production cost and increases the production efficiency of the superlens.
[0056] The present application provides a superlens in which the substrate 1 and the superlens unit 2 are made of the same material. The lateral dimension of the first antireflection structure 21 is smaller than the lateral dimension of the superlens column structure 22, and the lateral dimension of the second antireflection structure 23 is larger than the lateral dimension of the superlens column structure 22.
[0057] In this application, the substrate 1 and the superlens unit 2 can be made of the same material. The superlens unit 2 on the surface of the substrate 1 can be fabricated by photolithography etching, thereby reducing the process flow and production cost of the superlens and improving the yield of the superlens. Compared with photoresist hot reflow (difficult to precisely control the shape of non-pillar structures), wet etching (difficult to precisely control the shape of non-pillar structures), and nanoimprinting (although it can precisely control the shape of non-pillar structures, it cannot achieve a high aspect ratio), photolithography etching can precisely control the shape of the superlens unit 2 and achieve the high aspect ratio (i.e., the ratio of etching depth to etching width) required by the superlens.
[0058] With the substrate 1 and the superlens unit 2 made of the same material, the refractive index of the first antireflection structure 21 can be made to be between the refractive index of air and the refractive index of the superlens unit 22 by making the lateral dimension of the first antireflection structure 21 smaller than the lateral dimension of the superlens cylinder structure 22 (wherein, the smaller the size, the smaller the polarization intensity, and the smaller the refractive index, and vice versa). The refractive index of the second antireflection structure 23 can be made to be between the refractive index of the superlens cylinder structure 22 and the refractive index of the substrate 1 by making the lateral dimension of the second antireflection structure 23 larger than the lateral dimension of the superlens cylinder structure 22.
[0059] By setting the lateral dimensions of the first antireflection structure 21, the superlens cylinder structure 22, and the second antireflection structure 23 to satisfy the corresponding refractive index relationship, the structure and fabrication process of the superlens can be simplified, thereby reducing the cost of the superlens.
[0060] Of course, the materials of the substrate 1 and the superlens can also be different. In the case where the materials of the substrate 1 and the superlens are different, the lateral dimensions can be set as described above. Alternatively, the superlens of this application can be formed by preparing a substrate using different materials (the refractive indices of the different materials increase sequentially from top to bottom) and etching the substrate. In this case, the lateral dimensions of the first antireflection structure 21, the superlens cylinder structure 22, and the second antireflection structure 23 can be the same or different. For example, if the superlens unit 2 includes both the first antireflection structure 21 and the second antireflection structure 23, four materials (the refractive indices increase sequentially from top to bottom; of course, more materials can be used, as long as the refractive index relationship mentioned above can be satisfied) can be used to prepare the substrate. Then, etching processes can be used to etch the three materials from top to bottom to form a superlens containing a substrate (the bottommost material can be used as substrate 1) and a superlens unit array. Each superlens unit 2 in the superlens unit array includes a superlens cylinder structure 22, a first antireflection structure 21 located at the top of the superlens cylinder structure 22, and a second antireflection structure 23 located at the bottom of the superlens cylinder structure 22. The other two structures of the superlens unit 2 can be obtained in a similar manner as described above.
[0061] The superlens provided in this application embodiment has a first antireflection structure 21 and / or a second antireflection structure 23 as a cylindrical structure.
[0062] In this application, the first antireflective structure 21 and / or the second antireflective structure 23 can be columnar structures. For example... Figure 6 As shown, the superlens unit 2 includes a first antireflective structure 21 and a second antireflective structure 23, both of which are cylindrical structures. Alternatively, based on the superlens unit 2 including the first antireflective structure 21 and the second antireflective structure 23, either the first antireflective structure 21 or the second antireflective structure 23 can be a cylindrical structure, while the other antireflective structure is a non-cylindrical structure (specifically, it can be a structure that is narrower at the top and wider at the bottom). Figure 9 As shown, the superlens unit 2 includes a first antireflection structure 21, and the first antireflection structure 21 is a cylindrical structure, as... Figure 12 As shown, the superlens unit 2 includes a second antireflection structure 23, and the second antireflection structure 23 is a cylindrical structure.
[0063] The cylindrical structure facilitates etching, thus reducing the complexity and cost of superlens fabrication.
[0064] The superlens provided in this application embodiment has a first antireflection structure 21 and a second antireflection structure 23 that are non-column structures that are narrow at the top and wide at the bottom.
[0065] In this application, both the first antireflection structure 21 and the second antireflection structure 23 can be non-column structures that are narrow at the top and wide at the bottom (e.g., Figures 3-5 , Figure 7 , Figure 8 , Figure 10 , Figure 11 , Figure 13 As shown in the diagram, when the superlens unit 2 includes both the first antireflective structure 21 and the second antireflective structure 23, both the first antireflective structure 21 and the second antireflective structure 23 can be non-cylindrical structures that are narrower at the top and wider at the bottom. When the superlens unit 2 includes only the first antireflective structure 21, the first antireflective structure can be a non-cylindrical structure that is narrower at the top and wider at the bottom. When the superlens unit 2 includes only the second antireflective structure 23, the second antireflective structure 23 can be a non-cylindrical structure that is narrower at the top and wider at the bottom (i.e., the antireflective structures included in the superlens unit 2 of all three structures can be non-cylindrical structures that are narrower at the top and wider at the bottom). In other words, the antireflective structures included in the superlens unit 2 of the three structures mentioned above can all be structures whose horizontal dimensions increase sequentially from top to bottom.
[0066] By setting the antireflection structure included in the superlens unit 2 as a non-cylindrical structure that is narrow at the top and wide at the bottom, the refractive index of the corresponding antireflection structure can be gradually changed (for the first antireflection structure 21 and the second antireflection structure 23, the refractive index gradually increases from top to bottom). This is equivalent to adding a thin film with a gradually changing refractive index gradient distribution to the top and / or bottom of the superlens cylinder structure 22. Therefore, the refractive index difference between the superlens cylinder structure 22 and air and / or between the superlens cylinder structure 22 and the substrate 1 can be better reduced, thereby reducing reflection and achieving better light energy transmission.
[0067] The superlens provided in this application embodiment has a first anti-reflection structure 21 that can be any one of a cone structure, a frustum structure, or a spherical cap structure.
[0068] In this application, the first anti-reflection structure 21 can be a conical structure (specifically, a pyramidal structure or a conical structure, such as...). Figure 8 , Figure 11 (As shown), frustum structure (specifically, it can be any one of the following: truncated pyramid structure, frustum of a cone structure, or frustum of a sphere structure, such as...) Figure 7 , Figure 10 As shown), spherical crown structure (such as...) Figure 3 Any one of the ones shown.
[0069] The second anti-reflection structure 23 can be a frustum structure (specifically, it can be any one of a truncated pyramid structure, a frustum of a cone structure, or a frustum of a sphere structure, such as...). Figure 4 , Figure 7 , Figure 9 (As shown).
[0070] Of course, the first anti-reflection structure 21 and the second anti-reflection structure 23 can also be other non-column structures that are narrower at the top and wider at the bottom (such as a stepped non-column structure that is narrower at the top and wider at the bottom).
[0071] The embodiment of this application provides a superlens in which the heights of the first antireflection structure 21 and the second antireflection structure 23 are both 0.01λ-5λ, where λ is the working center wavelength of the superlens.
[0072] In this application, the height H23 of the first antireflection structure 21 and the height H21 of the second antireflection structure 23 can be 0.01λ-5λ, where λ is the working center wavelength of the superlens, so that the first antireflection structure 21 and the second antireflection structure 23 have high antireflection and anti-reflection effects.
[0073] Considering both the anti-reflection effect and the difficulty of the fabrication process, the heights of the first anti-reflection structure 21 and the second anti-reflection structure 23 can be specifically 0.01λ-2λ, so that the first anti-reflection structure 21 and the second anti-reflection structure 23 have both good anti-reflection effect and relatively low fabrication difficulty.
[0074] The embodiment of this application provides a superlens, wherein the height of the superlens column structure 22 is 0.1λ-10λ, where λ is the working center wavelength of the superlens.
[0075] In this application, the height H22 of the superlens cylinder structure 22 can be 0.1λ-10λ, where λ is the working center wavelength of the superlens, so that the superlens cylinder structure 22 can well realize the basic function of the superlens.
[0076] The present application provides a superlens in which, when the superlens is applied in the infrared band, the substrate 1 and the superlens unit 2 are any one of silicon, germanium, sapphire, zinc sulfide and zinc selenide.
[0077] When the superlens is applied in the visible light band or terahertz band, the substrate 1 and the superlens unit 2 are made of silicon oxide or quartz glass.
[0078] In this application, the substrate 1 and the superlens unit 2 are made of materials with high transmittance in the wavelength band in which the superlens is used. Specifically, when the superlens is used in the infrared band, the substrate 1 and the superlens unit 2 can be silicon, germanium, sapphire, zinc sulfide, or zinc selenide, etc.; when the superlens is used in the visible light band, terahertz band, or other bands, the substrate 1 and the superlens unit 2 can be silicon oxide or quartz glass, etc., so that the superlens has high transmittance in the wavelength band in which it is used, thereby improving the imaging quality of the superlens.
[0079] This application also provides a method for fabricating a superlens, used to fabricate any of the above-mentioned superlenses. See [link to relevant documentation]. Figure 14 It illustrates a flowchart of a method for fabricating a superlens according to an embodiment of this application, which may include:
[0080] S141: Clean the substrate.
[0081] When fabricating a superlens, the substrate can first be cleaned. Specifically, the substrate can be immersed in an acetone solution and ultrasonically cleaned for 15 minutes (the cleaning time can be adjusted according to needs). Then, it can be cleaned with ethanol and deionized water for 15 minutes each (the cleaning time can be adjusted according to needs). After the substrate is clean, it should be allowed to dry, such as by using a nitrogen gun to dry it, in order to shorten the time and improve the efficiency of superlens fabrication.
[0082] S142: The pattern on the photomask is transferred onto the photoresist using a photolithography process.
[0083] After the substrate surface is dried, the pattern on the photomask is transferred onto the photoresist using a photolithography process. Specifically: 1) Coating: A photoresist coating can be spin-coated onto the substrate surface using methods such as spin coating. The coating thickness can be 300nm-100μm (the photoresist thickness can be adjusted according to actual needs). 2) Pre-baking: The substrate is baked using a hot plate. 3) Exposure: The photomask is placed on the substrate (specifically, on top of the photoresist) to expose the photoresist on the substrate, thereby transferring the image from the photomask onto the photoresist. 4) Post-exposure baking: The substrate is baked using a hot plate. 5) Development: After exposure, development is performed using a developer. The development time can be 10s-120s, depending on different image parameters. Then, the substrate is repeatedly rinsed with deionized water to obtain the desired photoresist pattern. 6) Post-baking: The substrate is baked using a hot plate.
[0084] S143: Controlling the flow rate and / or energy of the etching gas, using the etching gas to etch the substrate, and using a passivating gas to protect the etched sidewalls.
[0085] The flow rate and / or energy of the etching gas used to etch the substrate are controlled according to the structure of the superlens unit in the superlens (the energy can be controlled through the etching coil power). The controlled etching gas is used to etch the substrate to transfer the pattern in the photoresist to the substrate surface (i.e., reactive ion etching). During the etching process, etching can be stopped after a certain time, and then the etched sidewalls can be protected with a passivating gas (i.e., passivation protection). Then, the process of etching for a certain time with the etching gas and then protecting the etched sidewalls with passivating gas is repeated until the desired superlens unit array is obtained. The flow rate of the passivating gas can be adjusted during passivation protection.
[0086] Specifically, for the etching of the first antireflection structure, reactive ion etching and passivation protection can be performed alternately to obtain the first antireflection structure. The lateral width of the etching can be adjusted by changing the flow rates of the etching gas and passivation gas, as well as the power of the etching coil (used to adjust the energy of the etching gas). Specifically, a non-cylindrical structure that is narrow at the top and wide at the bottom can be etched by reducing the flow rate of the etching gas and / or the power of the etching coil, while a cylindrical first antireflection structure can be etched by keeping the flow rate of the etching gas and the power of the etching coil constant.
[0087] For etching the cylindrical structure of a superlens, reactive ion etching and passivation protection can be performed alternately until the desired depth is reached, thus obtaining the cylindrical structure of the superlens. During etching, the lateral width of the etching can be adjusted by changing the flow rates of the etching gas and passivation gas, as well as the power of the etching coil. Throughout the process, the flow rate of the etching gas and the power of the etching coil are kept constant to etch the cylindrical structure of the superlens.
[0088] For etching the second antireflection structure, reactive ion etching and passivation protection can be performed alternately to etch the first antireflection structure. The lateral width of the etching can be adjusted by changing the flow rates of the etching gas and passivation gas, as well as the power of the etching coil. Specifically, a non-pillar structure that is narrow at the top and wide at the bottom can be etched by reducing the flow rate of the etching gas and / or the power of the etching coil, while a pillar-like second antireflection structure can be etched by keeping the flow rate of the etching gas and the power of the etching coil constant.
[0089] S144: Clean the substrate to obtain a superlens unit array located on the substrate surface and including multiple superlens units.
[0090] The superlens unit may include a superlens cylinder structure, and may also include a first antireflection structure located at the top of the superlens cylinder structure, and / or a second antireflection structure located at the bottom of the superlens cylinder structure, wherein the refractive index of the first antireflection structure is between the refractive index of air and the refractive index of the superlens cylinder structure, and the refractive index of the second antireflection structure is between the refractive index of the superlens cylinder structure and the refractive index of the substrate.
[0091] After etching, the substrate can be cleaned to remove the photoresist from its surface. Specifically, a photoresist remover can be used to clean the substrate surface to obtain a superlens array containing multiple superlens units located on the substrate surface. Each superlens unit may include a superlens pillar structure, a first antireflective structure at the top of the superlens pillar structure, and / or a second antireflective structure at the bottom of the superlens pillar structure. The refractive index of the first antireflective structure is between the refractive index of air and the refractive index of the superlens pillar structure, and the refractive index of the second antireflective structure is between the refractive index of the superlens pillar structure and the refractive index of the substrate. For a structural description of the superlens, please refer to the description of the relevant parts of a superlens provided in the embodiments of this application; further details will not be repeated here.
[0092] Compared to photoresist reflow (difficult to precisely control the shape of non-pillar structures), wet etching (difficult to precisely control the shape of non-pillar structures), and nanoimprint lithography (which can precisely control the shape of non-pillar structures but cannot achieve a high aspect ratio), photolithography etching can precisely control the shape of the superlens unit and achieve the high aspect ratio (i.e., the ratio of etching depth to etching width) required by the superlens. Compared to depositing an anti-reflection and anti-reflection dielectric film on the superlens surface to achieve anti-reflection and anti-reflection, this application only requires an etching process step, which is simple, has low production costs, and high production efficiency. Furthermore, since no film deposition is required, the superlens provided by this application does not have the risk of material demolding or film defects, resulting in higher yield and better environmental adaptability.
[0093] The method for fabricating a superlens provided in this application embodiment may further include, after cleaning the substrate:
[0094] Deposit a hard mask on the substrate surface;
[0095] After transferring the pattern on the photomask onto the photoresist using photolithography, it may also include:
[0096] The hard mask is etched to transfer the pattern in the photoresist onto the hard mask, and then the photoresist is removed.
[0097] Considering that photoresist may be damaged or even etched away during the etching process, in order to ensure the aspect ratio of the superlens unit and improve the yield of the superlens, after cleaning the substrate (i.e., after the substrate is clean and dry), a hard mask can be deposited on the substrate surface using methods such as chemical vapor deposition. The material of the hard mask can be silicon oxide or silicon nitride, etc. Compared with photoresist, hard masks are not easily etched, thus ensuring the aspect ratio of the superlens unit and improving the yield of the superlens.
[0098] After depositing a hard mask on the substrate surface, a photoresist coating can be spin-coated onto the hard mask surface using methods such as spin coating. The coating thickness can be 300nm-100μm (the photoresist thickness can be adjusted according to actual needs). Then, pre-baking, exposure, post-exposure baking, development, and post-baking are performed to transfer the pattern on the mask onto the photoresist using photolithography. Next, an etching gas is used to etch the hard mask, transferring the image from the photoresist onto the hard mask and removing the photoresist. Specifically, a photoresist remover is used to clean the hard mask surface to remove the photoresist. Then, the flow rate and / or energy of the etching gas are controlled to etch the substrate, and a passivating gas is used to protect the etched sidewalls. The substrate is then cleaned to obtain a superlens array located on the substrate surface, comprising multiple superlens units. At this point, when cleaning the substrate, the substrate is acid-washed. Specifically, the acid solution is used to remove the hard mask on the surface of the substrate in order to obtain the superlens unit array located on the surface of the substrate.
[0099] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that the elements inherent in a process, method, article, or apparatus that includes a list of elements are included. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Additionally, portions of the technical solutions provided in the embodiments of this application that are consistent with the implementation principles of corresponding technical solutions in the prior art have not been described in detail to avoid excessive elaboration.
[0100] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A superlens, characterized in that, It includes a substrate (1) and a superlens unit array located on the surface of the substrate (1), the superlens unit array including a plurality of superlens units (2). The superlens unit (2) includes a superlens cylinder structure (22), a first antireflective structure (21) located at the top of the superlens cylinder structure (22), and / or a second antireflective structure (23) located at the bottom of the superlens cylinder structure (22); the refractive index of the first antireflective structure (21) is between the refractive index of air and the refractive index of the superlens cylinder structure (22), and the refractive index of the second antireflective structure (23) is between the refractive index of the superlens cylinder structure (22) and the refractive index of the substrate (1); the superlens unit (2) is an integral structure; the substrate (1) is made of the same material as the superlens unit (2); the lateral dimension of the first antireflective structure (21) is smaller than the lateral dimension of the superlens cylinder structure (22), and the lateral dimension of the second antireflective structure (23) is larger than the lateral dimension of the superlens cylinder structure (22); The superlens cylinder structure (22) is the functional part of the superlens unit (2) and is used to realize the basic functions of the superlens. The basic functions include at least the convergence and polarization functions of light. The refractive index of the first antireflection structure (21) is greater than that of air and less than that of the superlens cylinder structure (22). The first antireflection structure (21) reduces the difference in refractive index between the superlens cylinder structure (22) and air, thereby reducing the reflection between the superlens cylinder structure (22) and air, enhancing the optical transmission capability of the superlens unit (2), and achieving better light energy transmission effect. The refractive index of the second antireflection structure (23) is greater than that of the superlens cylinder structure (22) and less than that of the substrate (1). The refractive index difference between the superlens cylinder structure (22) and the substrate (1) is reduced by the second antireflection structure (23), thereby reducing the reflection between the superlens cylinder structure (22) and the substrate (1), enhancing the optical transmission capability of the superlens unit (2), and achieving better light energy transmission effect.
2. The superlens according to claim 1, characterized in that, The first antireflection structure (21) and / or the second antireflection structure (23) are columnar structures.
3. The superlens according to claim 1, characterized in that, The first anti-reflection structure (21) and the second anti-reflection structure (23) are non-column structures that are narrow at the top and wide at the bottom.
4. The superlens according to claim 3, characterized in that, The first anti-reflection structure (21) can be any one of the following structures: cone structure, frustum structure, or spherical cap structure; The second anti-reflection structure (23) is a platform structure.
5. The superlens according to claim 1, characterized in that, The heights of the first antireflection structure (21) and the second antireflection structure (23) are both 0.01λ-5λ, where λ is the working center wavelength of the superlens.
6. The superlens according to claim 1, characterized in that, The height of the superlens cylindrical structure (22) is 0.1λ-10λ, where λ is the working center wavelength of the superlens.
7. The superlens according to claim 1, characterized in that, When the superlens is applied in the infrared band, the substrate (1) and the superlens unit (2) are any one of silicon, germanium, sapphire, zinc sulfide, and zinc selenide; When the superlens is applied in the visible light band or the terahertz band, the substrate (1) and the superlens unit (2) are silicon oxide or quartz glass.
8. A method for preparing a superlens, characterized in that, For preparing the superlens as described in any one of claims 1 to 7, comprising: Clean the substrate; The pattern on the photomask is transferred onto the photoresist using a photolithography process; The flow rate and / or energy of the etching gas are controlled, the substrate is etched using the etching gas, and the sidewalls of the etched surface are protected using a passivation gas. The substrate is cleaned to obtain a superlens unit array comprising multiple superlens units; each superlens unit includes a superlens cylinder structure, a first antireflective structure located at the top of the superlens cylinder structure, and / or a second antireflective structure located at the bottom of the superlens cylinder structure, wherein the refractive index of the first antireflective structure is between the refractive index of air and the refractive index of the superlens cylinder structure, and the refractive index of the second antireflective structure is between the refractive index of the superlens cylinder structure and the refractive index of the substrate.
9. The method for preparing a superlens according to claim 8, characterized in that, After cleaning the substrate, the following steps are also included: A hard mask is deposited on the surface of the substrate; After transferring the pattern on the photomask onto the photoresist using photolithography, the process also includes: The hard mask is etched to transfer the pattern in the photoresist onto the hard mask, and the photoresist is then removed.