Preparation method of double-sided single-layer and double-sided multi-layer micro-nano structure of super lens and prepared super lens

Abstract

The application provides a preparation method of double-sided single-layer and double-sided multi-layer micro-nano structures of a superlens and the prepared superlens, and belongs to the technical field of micro-nano optics. The preparation method of double-sided single-layer and double-sided multi-layer micro-nano structures of the superlens comprises the following steps: preparing a convex metal chromium alignment mark through double-sided alignment lithography and etching, which has better edge sharpness than the alignment mark of a glue structure; compared with the downward etched alignment mark, the alignment mark is easier to be observed when being covered in the subsequent process, so that the alignment accuracy of the subsequent photolithography process is less than or equal to 4 microns; after the preparation of the focusing superlens micro-nano structure, a metal chromium film protective layer is prepared through a coating process, so that the focusing superlens micro-nano structure is protected from being damaged in the process of correcting the superlens micro-nano structure; a chromium removal liquid is used, the chromium removal liquid is usually acidic, does not react with the material of the double-sided micro-nano structure of the superlens, and can better remove the metal chromium protective film layer and the convex metal chromium alignment mark without damaging the micro-nano structure.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano optics technology, and particularly relates to a method for fabricating double-sided single-layer and double-sided multilayer micro-nano structures of a superlens, and the fabricated superlens. Background Technology

[0002] Metalenses, as a cutting-edge micro-nano optical device, use subwavelength nanostructure arrays to control light waves, achieving high-resolution imaging and subwavelength focusing. They have significant advantages such as thinness, light weight, small size, and high integration.

[0003] In the design of superlenses, single-layer planar superlenses struggle to achieve near-diffraction-limited focusing at different incident angles. Therefore, inspired by the traditional method of correcting aberrations through lens groups in refractive optical lenses, a double-sided superlens combining a focusing superlens and a correcting superlens on both sides of a substrate has been developed. This addresses the problem that single-layer planar superlenses lack sufficient degrees of freedom to correct off-axis aberrations such as coma, astigmatism, and field curvature. However, existing technologies for fabricating double-sided superlenses present two challenges: 1) the alignment of the micro / nano structures on both sides of the substrate; and 2) the potential damage to the micro / nano structures of the focusing superlens during the fabrication of the correcting superlens after the focusing superlens has been completed. Summary of the Invention

[0004] Therefore, to solve the above-mentioned technical problems, this invention proposes a method for fabricating double-sided single-layer and double-sided multi-layer micro / nano structures of a superlens, as well as the fabricated superlens. High-precision alignment of the double-sided micro / nano structure is achieved by preparing metal chromium alignment marks that are easier to observe through double-sided alignment photolithography and etching. After protecting the fabricated focusing superlens micro / nano structure with a wear-resistant hard metal chromium film, the superlens micro / nano structure is processed for correction, and finally the metal film is removed without damaging the micro / nano structure.

[0005] To achieve the above objectives, this invention provides a method for fabricating a double-sided single-layer micro / nano structure of a superlens. The double-sided micro / nano structure comprises a focusing superlens micro / nano structure and a correcting superlens micro / nano structure, located on opposite sides of the superlens substrate, respectively. The method includes the following steps:

[0006] A chromium layer was deposited on the micro-nano structure material film of the focusing superlens and the micro-nano structure material film of the correction superlens using a coating process.

[0007] Alignment mark masks are prepared on the chromium metal layers on both sides using a double-sided alignment photolithography process;

[0008] Raised chromium alignment marks were fabricated on the micro / nano structure material film of the focusing superlens and the micro / nano structure material film of the correcting superlens using an etching process.

[0009] Based on the raised chromium alignment marks on the micro / nano structure material film of the focusing superlens, the micro / nano structure of the focusing superlens is first prepared by photolithography and etching process, and then a chromium film protective layer is prepared on the micro / nano structure of the focusing superlens by coating process.

[0010] The corrective superlens micro-nano structure is fabricated using photolithography and etching processes based on the raised chromium alignment marks on the micro-nano structure material film.

[0011] The chromium film protective layer and the raised chromium alignment marks are removed using a chromium removal solution.

[0012] Preferably, when the substrate material of the superlens is inconsistent with the micro / nanostructure material of the focusing superlens and the micro / nanostructure material of the correcting superlens, the method further includes the steps of preparing the micro / nanostructure material film layer of the superlens and the micro / nanostructure material film layer of the correcting superlens, as follows:

[0013] Focusing superlens micro / nano structure material films and correcting superlens micro / nano structure material films are respectively prepared on the front and back sides of the superlens substrate using a coating process.

[0014] Preferably, the focusing superlens micro / nano structure material and the correcting superlens micro / nano structure material are independently selected from any one of TiO2, HfO2, ZrO2, GaN, Si2N3, Si, SiO2, GaAs, ZnS, and AlN.

[0015] Preferably, the coating process is selected from any one of vacuum evaporation, magnetron sputtering, ion beam evaporation, physical vapor deposition, chemical vapor deposition, and atomic layer deposition, depending on the material and application of the film.

[0016] Preferably, the photolithography process is selected from any one of electron beam lithography, two-photon lithography, stepper lithography, and ultraviolet lithography.

[0017] Preferably, the etching process is selected from any one of wet etching, reactive ion etching, inductively coupled plasma etching, ion beam etching, and laser etching.

[0018] This invention also provides a method for fabricating a double-sided multilayer micro / nano structure of a superlens, wherein the double-sided micro / nano structure comprises a focusing superlens micro / nano structure and a correcting superlens micro / nano structure, located on opposite sides of the superlens substrate, and includes the following steps:

[0019] A chromium layer was deposited on the micro-nano structure material film of the focusing superlens and the micro-nano structure material film of the correction superlens using a coating process.

[0020] Alignment mark masks are prepared on the chromium metal layers on both sides using a double-sided alignment photolithography process;

[0021] Raised chromium alignment marks were fabricated on the micro / nano structure material film of the focusing superlens and the micro / nano structure material film of the correcting superlens using an etching process.

[0022] Based on the raised chromium alignment marks on the micro-nano structure material film of the focusing superlens, the first layer, the second layer, ... and the Nth layer of the focusing superlens micro-nano structure are sequentially prepared by photolithography and etching processes, and then a chromium film protective layer is prepared on the Nth layer of the focusing superlens micro-nano structure by a coating process.

[0023] Based on the raised chromium alignment marks on the film of the corrective superlens micro / nano structure material, the first layer, the second layer, ... and the Nth layer of the corrective superlens micro / nano structure are sequentially prepared using photolithography and etching processes;

[0024] The chromium film protective layer and the raised chromium alignment marks are removed using a chromium removal solution.

[0025] Preferably, N is a natural number, and N≥2.

[0026] The present invention also provides a superlens, which is prepared by the above-described preparation method.

[0027] The advantages of the above technical solution adopted in this invention are:

[0028] The present invention discloses a method for fabricating double-sided single-layer and double-sided multilayer micro / nano structures of a superlens. This method utilizes double-sided alignment photolithography combined with etching to prepare raised chromium alignment marks, which exhibit better edge sharpness compared to alignment marks on a photoresist structure. Compared to alignment marks etched downwards, these marks are easier to observe when covered in subsequent processes, effectively improving alignment accuracy to ≤4μm for subsequent photolithography. After fabrication of the focusing superlens micro / nano structure, a chromium film protective layer is prepared using a coating process to protect the focusing superlens micro / nano structure from damage during the calibration process. A chromium removal solution, typically acidic, is used, which does not react with the double-sided micro / nano structure materials of the superlens, allowing for effective removal of the chromium protective film and raised chromium alignment marks without damaging the micro / nano structure. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic flowchart of the fabrication method of the double-sided single-layer micro / nano structure of the superlens of the present invention;

[0031] Figure 2 This is a schematic diagram of the fabrication process of the superlens micro / nano structure material film and the correction superlens micro / nano structure material film;

[0032] Figure 3 This is a schematic diagram of the fabrication process of the superlens micro / nano structure and the correction superlens micro / nano structure in the fabrication method of the double-sided multilayer micro / nano structure of the superlens of the present invention;

[0033] Figure 4 This is a diagram illustrating the analysis and demonstration results of the aberration change trend when alignment errors exist. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, this invention provides a method for fabricating a double-sided single-layer micro / nano structure of a superlens. The double-sided micro / nano structure comprises a focusing superlens micro / nano structure and a correcting superlens micro / nano structure, located on opposite sides of the superlens substrate 1-1, and includes the following steps:

[0036] A chromium layer 1-4 was deposited on the micro-nano structure material film layer 1-2 of the focusing superlens and the micro-nano structure material film layer 1-3 of the correction superlens using a coating process.

[0037] Alignment mark masks 1-5 are prepared on the chromium metal layers on both sides using a double-sided alignment photolithography process;

[0038] Raised metallic chromium alignment marks 1-6 are prepared on the focusing superlens micro-nano structure material film layer 1-2 and the correcting superlens micro-nano structure material film layer 1-3 respectively using an etching process;

[0039] Based on the raised chromium alignment marks 1-6 on the micro-nano structure material film of the focusing superlens, the micro-nano structure 1-7 of the focusing superlens is first prepared by photolithography and etching process, and then the chromium protective film 1-8 is prepared on the micro-nano structure of the focusing superlens by coating process.

[0040] Based on the raised chromium alignment marks 1-6 on the film layer of the corrective superlens micro / nano structure material, the corrective superlens micro / nano structure 1-9 is prepared by photolithography combined with etching process;

[0041] The chromium film protective layer 1-8 and the raised chromium alignment marks 1-6 are removed using a chromium removal solution.

[0042] When the substrate material of the superlens is inconsistent with the micro / nanostructure material of the focusing superlens and the micro / nanostructure material of the correcting superlens, the process also includes the steps of preparing the superlens micro / nanostructure material film 1-2 and the correcting superlens micro / nanostructure material film 1-3, as follows: Figure 2 As shown, the details are as follows:

[0043] A focusing superlens micro / nano structure material film layer 1-2 and a correcting superlens micro / nano structure material film layer 1-3 are respectively prepared on the front and back sides of the superlens substrate 1-1 using a coating process.

[0044] Among them, the micro-nano structure materials of the focusing superlens and the correction superlens are independently selected from any one of TiO2, HfO2, ZrO2, GaN, Si2N3, Si, SiO2, GaAs, ZnS, AlN, etc., and appropriate micro-nano structure materials of the focusing superlens and the correction superlens can be selected according to the performance and process requirements of the focusing superlens and the correction superlens.

[0045] The coating process is selected from any one of vacuum evaporation, magnetron sputtering, ion beam evaporation, physical vapor deposition, chemical vapor deposition, atomic layer deposition, etc., depending on the material and application of the film. The photolithography process is selected from any one of electron beam lithography, two-photon lithography, stepper lithography, ultraviolet lithography, etc. The etching process is selected from any one of wet etching, reactive ion etching, inductively coupled plasma etching, ion beam etching, laser etching, etc.

[0046] The alignment marks prepared by this invention are raised metallic chromium, which have better edge sharpness than alignment marks with adhesive structure; compared with alignment marks etched downwards, they are easier to observe when covered in subsequent processes, which can effectively improve alignment accuracy.

[0047] Chromium removal solutions are typically acidic and do not react with the micro / nanostructure materials of focusing and correcting superlenses. Therefore, metallic chromium can be used as a protective film to protect the fabricated focusing superlens micro / nanostructure before removing the protective film and raised chromium alignment marks without damaging the micro / nanostructure.

[0048] This invention also provides a method for fabricating a double-sided multilayer micro / nano structure of a superlens, wherein the double-sided micro / nano structure comprises a focusing superlens micro / nano structure and a correcting superlens micro / nano structure, located on opposite sides of the superlens substrate 1-1, and includes the following steps:

[0049] A chromium layer 1-4 was deposited on the micro-nano structure material film layer 1-2 of the focusing superlens and the micro-nano structure material film layer 1-3 of the correction superlens using a coating process.

[0050] Alignment mark masks 1-5 are prepared on the metal chromium layers 1-4 on both sides using a double-sided alignment photolithography process;

[0051] Raised metallic chromium alignment marks 1-6 are prepared on the focusing superlens micro-nano structure material film layer 1-2 and the correcting superlens micro-nano structure material film layer 1-3 respectively using an etching process;

[0052] like Figure 3 As shown, based on the raised chromium alignment marks 1-6 on the micro-nano structure material film of the focusing superlens, the first layer, the second layer, ... and the Nth layer of the focusing superlens micro-nano structure (shown as two layers 1-7 in the figure) are sequentially prepared by photolithography and etching process. Then, a chromium film protective layer 1-8 is prepared on the Nth layer of the focusing superlens micro-nano structure by coating process.

[0053] Based on the raised chromium alignment marks on the film of the corrective superlens micro / nano structure material, the first layer, the second layer, ... and the Nth layer of the corrective superlens micro / nano structure are sequentially prepared by photolithography and etching processes (shown as two layers 1-9 in the figure);

[0054] The chromium film protective layer 1-8 and the raised chromium alignment marks 1-6 are removed using a chromium removal solution.

[0055] Where N is a natural number, N≥2.

[0056] The present invention also provides a superlens, which is prepared by the above-described preparation method.

[0057] In the fabrication method of the double-sided single-layer and double-sided multilayer micro / nano structures of the superlens of this invention, the preparation of raised chromium alignment marks ensures that the alignment accuracy of the subsequent photolithography process is ≤4μm. Therefore, we used ray tracing to analyze and demonstrate the aberration variation trend when alignment errors exist. For example... Figure 4 The figure shows the ray tracing diagrams of two typical double-sided metalenses and the relationship between aberrations and offset. Figure 4 (a) is a ray tracing diagram of a double-sided meta-lens with an entrance pupil diameter: thickness: back working distance ratio of 1:2:2 after indefocusing optimization. Figure 4 (b) is a ray tracing diagram of a double-sided meta-lens with an entrance pupil diameter: thickness: back working distance ratio of 1:2:1 after indefocusing optimization. Figure 4(c) shows the aberration variation range when alignment errors exist in the two typical structures described above. The relative offset is the ratio of the absolute offset to the entrance pupil diameter; the aberration magnitude is described by the average of the coordinate variances of the ray tracing points at each field of view on the focal plane. It can be seen that the aberration magnitude is more sensitive to the offset at higher numerical apertures, but overall remains within 1% of the entrance pupil diameter. For metalenses with an entrance pupil diameter greater than 1 mm, the aberration increase is less than 50% at large numerical apertures, and negligible at small numerical apertures; for centimeter-level metalenses, the relative offset can be controlled below 0.05%, and no significant aberration increase occurs for metalenses of any numerical aperture. Therefore, an alignment accuracy of 4 μm fully meets the design requirements.

[0058] The advantages of the above technical solution adopted in this invention are:

[0059] The present invention discloses a method for fabricating double-sided single-layer and double-sided multilayer micro / nano structures of a superlens. This method utilizes double-sided alignment photolithography combined with etching to prepare raised chromium alignment marks, which exhibit better edge sharpness compared to alignment marks on a photoresist structure. Compared to alignment marks etched downwards, these marks are easier to observe when covered in subsequent processes, effectively improving alignment accuracy to ≤4μm for subsequent photolithography. After fabrication of the focusing superlens micro / nano structure, a chromium film protective layer is prepared using a coating process to protect the focusing superlens micro / nano structure from damage during the calibration process. A chromium removal solution, typically acidic, is used, which does not react with the double-sided micro / nano structure materials of the superlens, allowing for effective removal of the chromium protective film and raised chromium alignment marks without damaging the micro / nano structure.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a double-sided single-layer micro / nano structure of a superlens, wherein the double-sided micro / nano structure comprises a focusing superlens micro / nano structure and a correcting superlens micro / nano structure, located on opposite sides of the superlens substrate, characterized in that, Includes the following steps: A chromium layer was deposited on the micro-nano structure material film of the focusing superlens and the micro-nano structure material film of the correction superlens using a coating process. Alignment mark masks were fabricated on the metal chromium layers on both sides of the fabrication area of ​​the micro / nano structure using a double-sided alignment photolithography process. Raised chromium alignment marks were fabricated on the micro / nano structure material film of the focusing superlens and the micro / nano structure material film of the correcting superlens using an etching process. Based on the raised chromium alignment marks on the micro / nano structure material film of the focusing superlens, the micro / nano structure of the focusing superlens is first prepared by photolithography and etching process, and then a chromium film protective layer is prepared on the micro / nano structure of the focusing superlens by coating process. The corrective superlens micro-nano structure is fabricated using photolithography and etching processes based on the raised chromium alignment marks on the micro-nano structure material film. The chromium film protective layer and the raised chromium alignment marks are removed using a chromium removal solution.

2. The method for fabricating the double-sided micro / nano structure of the superlens according to claim 1, characterized in that, When the substrate material of the superlens is inconsistent with the micro / nanostructure material of the focusing superlens and the micro / nanostructure material of the correcting superlens, the process also includes the steps of preparing the micro / nanostructure material film and the correcting superlens micro / nanostructure material film, as follows: Focusing superlens micro / nano structure material films and correcting superlens micro / nano structure material films are respectively prepared on the front and back sides of the superlens substrate using a coating process.

3. The method for fabricating the double-sided micro / nano structure of the superlens according to claim 2, characterized in that, The focusing superlens micro / nano structure material and the correcting superlens micro / nano structure material are independently selected from any one of TiO2, HfO2, ZrO2, GaN, Si2N3, Si, SiO2, GaAs, ZnS, and AlN.

4. The method for fabricating the double-sided micro / nano structure of the superlens according to claim 1, characterized in that, The coating process can be selected from any one of vacuum evaporation, magnetron sputtering, ion beam evaporation, physical vapor deposition, chemical vapor deposition, or atomic layer deposition, depending on the material and application of the film.

5. The method for fabricating the double-sided micro / nano structure of the superlens according to claim 1, characterized in that, The photolithography process can be selected from any one of electron beam lithography, two-photon lithography, stepper lithography, and ultraviolet lithography.

6. The method for fabricating the double-sided micro / nano structure of the superlens according to claim 1, characterized in that, The etching process can be selected from any one of wet etching, reactive ion etching, inductively coupled plasma etching, ion beam etching, and laser etching.

7. A method for fabricating a double-sided multilayer micro / nano structure of a superlens, wherein the double-sided micro / nano structure comprises a focusing superlens micro / nano structure and a correcting superlens micro / nano structure, located on opposite sides of the superlens substrate, respectively, characterized in that... Includes the following steps: A chromium layer was deposited on the micro-nano structure material film of the focusing superlens and the micro-nano structure material film of the correction superlens using a coating process. Alignment mark masks were fabricated on the metal chromium layers on both sides of the fabrication area of ​​the micro / nano structure using a double-sided alignment photolithography process. Raised chromium alignment marks were fabricated on the micro / nano structure material film of the focusing superlens and the micro / nano structure material film of the correcting superlens using an etching process. Based on the raised chromium alignment marks on the micro-nano structure material film of the focusing superlens, the first layer, the second layer, ... and the Nth layer of the focusing superlens micro-nano structure are sequentially prepared by photolithography and etching processes, and then a chromium film protective layer is prepared on the Nth layer of the focusing superlens micro-nano structure by a coating process. Based on the raised chromium alignment marks on the film of the corrective superlens micro / nano structure material, the first layer, the second layer, ... and the Nth layer of the corrective superlens micro / nano structure are sequentially prepared using photolithography and etching processes; The chromium film protective layer and the raised chromium alignment marks are removed using a chromium removal solution.

8. The method for fabricating a double-sided multilayer micro / nano structure of a superlens according to claim 7, characterized in that, N is a natural number, N≥2.

9. A superlens, characterized in that, It is prepared by the method described in any one of claims 1-8.

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