A system and method for fabricating micro / nano structures based on photoelectrochemical etching

Abstract

This invention belongs to the field of micro-nano optical manufacturing technology, and discloses a system and method for fabricating micro-nano structures based on photoelectrochemical etching. The system includes a laser, a converging lens, a rotating scattering plate, a first collimating lens, a converging objective lens, a filter pinhole, a second collimating lens, a polarizer, a first beam splitter cube, a spatial light modulator, and a Fourier lens arranged along the laser beam path. The converging lens focuses the parallel laser emitted by the laser onto the rotating scattering plate, and the first collimating lens outputs the scattered laser from the rotating scattering plate in parallel. The spatial light modulator modulates the received light, and after passing through the Fourier lens, a target light field pattern is obtained, thereby fabricating the micro-nano structure. The system homogenizes the laser in hardware through the rotating scattering plate, and can generate high-quality arbitrary target light field patterns using the spatial light modulator without complex code, and has higher beam shaping resolution compared to LED light field modulation.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano optical manufacturing technology, and more specifically, relates to a system and method for manufacturing micro-nano structures based on photoelectrochemical etching. Background Technology

[0002] Beam shaping is an important application of spatial light modulators. Given the incident light field and the ideal target light field, the incident light field is subjected to pure phase modulation by loading a corresponding phase grayscale image onto the spatial light modulator. The modulated light field is then subjected to a Fourier transform through a lens, and the reconstructed target light field can be obtained at the back focal plane of the lens, thus achieving intensity shaping of the incident light. Therefore, it is crucial to calculate the corresponding phase modulation image from the incident light field and the ideal target light field. The most basic approach is to use the GS algorithm to continuously perform Fourier iterative transforms to obtain an approximate numerical solution. However, the surface roughness of the target light field reconstructed by this method is relatively large, which is unsuitable for high-quality beam shaping applications. In actual experiments, the quality of the target light field pattern is even worse due to the influence of laser speckle.

[0003] One feasible approach is to improve the optimization algorithm. For example, the MRAF algorithm can obtain a highly uniform reconstructed target light field in the signal region. However, due to the presence of noise regions, this algorithm reduces energy utilization. Furthermore, these algorithms become increasingly complex, yet they still cannot eliminate the interference caused by laser speckle. Using LEDs as the incident light source can avoid speckle noise, but the low coherence of LEDs leads to a significant reduction in the resolution of the reconstructed light field, which cannot meet the requirements of high-precision micro-nano manufacturing. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a system and method for fabricating micro / nano structures based on photoelectrochemical etching. The system improves the beam shaping quality of the spatial light modulator through hardware homogenization, reducing the roughness of maskless etched micro / nano structures. It also uses a rotating scattering sheet to perform hardware decoherence on the incident laser, eliminating speckle and stray light effects on the target light field without significantly reducing the target pattern resolution. This improves the quality and uniformity of beam shaping, thereby solving the technical problem of high roughness in existing maskless photoelectrochemical etched micro / nano structures.

[0005] To achieve the above objectives, according to one aspect of the present invention, the present invention provides a system for fabricating micro-nano structures based on photoelectrochemical etching, the system comprising a laser, a converging lens, a rotating scattering sheet, a first collimating lens, a converging objective lens, a filter pinhole, a second collimating lens, a polarizer, a first beam splitter, a spatial light modulator, and a Fourier lens arranged along a laser optical path;

[0006] The converging lens is used to focus the parallel laser emitted by the laser onto the rotating scattering plate. The first collimating lens outputs the scattered laser from the rotating scattering plate in parallel. The parallel laser is filtered sequentially through the converging objective lens, the filtering pinhole, and the second collimating lens before reaching the polarizer. It then passes sequentially through the polarizer and the first beam splitter before illuminating the spatial light modulator. The spatial light modulator is used to modulate the received light, which passes through a Fourier lens to obtain the target light field pattern, thereby fabricating micro / nano structures.

[0007] Furthermore, the system also includes a first tube mirror, a second beam splitter cube, and a projection objective lens arranged along the projection-type miniaturized optical path.

[0008] Furthermore, the system also includes a camera and a second tube mirror, the second tube mirror being disposed between the camera and the second beam splitter cube for aligning with the sample surface.

[0009] Furthermore, the light field modulated by the spatial light modulator is transmitted to the projection-type miniature optical path to generate the target light field pattern after passing through a Fourier lens, so as to irradiate the sample surface and then perform etching.

[0010] Furthermore, the first collimating lens is an aspherical lens.

[0011] Furthermore, the rotating diffuser is a polished diffuser with a mesh size of 1500 and a rotation speed of ≥3000 rpm.

[0012] Furthermore, the polarization direction of the polarizer should be parallel to the long axis of the spatial light modulator.

[0013] Furthermore, the distance from the rotating diffuser to the converging lens is equal to the focal length of the converging lens; the distance from the rotating diffuser to the first collimating lens is equal to the focal length of the first collimating lens.

[0014] The present invention also provides a method for fabricating micro- and nano-structures based on photoelectrochemical etching, wherein the method uses the system for fabricating micro- and nano-structures based on photoelectrochemical etching as described above.

[0015] In summary, compared with the prior art, the system and method for manufacturing micro and nano structures based on photoelectrochemistry provided by this invention have the following advantages:

[0016] 1. The system homogenizes the laser in hardware by rotating the scattering plate, and can generate high-quality arbitrary target light field patterns using a spatial light modulator without complex code, and has higher beam shaping resolution compared with LED light field modulation.

[0017] 2. This invention generates a high-quality target light field pattern, which is then projected onto the sample surface for maskless photoelectrochemical etching, significantly reducing the surface roughness of the fabricated micro / nano structures. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a system for fabricating micro / nano structures based on photoelectrochemical etching, provided by the present invention.

[0019] Figure 2 It is the target pattern (observed by camera) that is shaped and miniaturized by the spatial light modulator beam after hardware homogenization and projected onto the sample surface.

[0020] Figure 3 It is to utilize Figure 2 Micro-nano structures fabricated in a mid-light field (measured with a white light interferometer);

[0021] Figure 4 yes Figure 3 A cross-sectional schematic diagram of the micro / nano structure in the image;

[0022] Figure 5 yes Figure 3 Another cross-sectional schematic diagram of the micro / nano structure in the image;

[0023] Figure 6 yes Figure 3 Another cross-sectional schematic diagram of the micro / nano structure in the image;

[0024] Figure 7 The target pattern (observed by camera) is projected onto the sample surface without hardware homogenization, spatial light modulator beam shaping, and miniaturization.

[0025] Figure 8 It is to utilize Figure 7 Micro-nano structures fabricated using optical fields (measured with a white light interferometer);

[0026] Figure 9 yes Figure 8 A cross-sectional schematic diagram of the micro / nano structure.

[0027] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-laser, 2-converging lens, 3-rotating diffuser, 4-first collimating lens, 5-converging objective, 6-filter pinhole, 7-second collimating lens, 8-polarizer, 9-first beam splitter cube, 10-spatial light modulator, 11-Fourier lens, 12-first tube mirror, 13-second beam splitter cube, 14-projection objective, 15-sample, 16-second tube mirror, 17-camera. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Please see Figure 1 and Figure 2 This invention provides a system for fabricating micro / nano structures based on photoelectrochemical etching. The system includes a laser 1, a converging lens 2, a rotating scattering sheet 3, a first collimating lens 4, a converging objective lens 5, a filtering pinhole 6, a second collimating lens 7, a polarizer 8, a first beam splitter 9, a spatial light modulator 10, and a Fourier lens 11, all arranged along a laser optical path. The system also includes a first tube mirror 12, a second beam splitter 13, and a projection objective lens 14, all arranged along a projection-type miniaturized optical path. Furthermore, the system includes a camera 17 and a second tube mirror 16, the second tube mirror 16 being positioned between the camera 17 and the second beam splitter 13 for aligning with the surface of a sample 15.

[0030] Please see Figure 3 , Figure 4 , Figure 5 and Figure 6 The converging lens 2 focuses the parallel laser emitted by the laser 1 onto the rotating scattering plate 3. The first collimating lens 4 parallelizes the scattered laser from the rotating scattering plate 3. The parallel-emitted laser is filtered sequentially by the converging objective lens 5, the filtering pinhole 6, and the second collimating lens 7 before reaching the polarizer 8. It then passes sequentially through the polarizer 8 and the first beam splitter 9 before illuminating the spatial light modulator 10. A calculated phase diagram corresponding to the target pattern is loaded onto the spatial light modulator 10 to shape the incident laser beam. The modulated laser beam is then transmitted to the projection-type miniature optical path to generate the target light field pattern via a Fourier lens, and then illuminating the surface of the sample 15 for etching. The projection-type miniature optical path consists of a first tube lens 12, a second beam splitter 13, and a projection objective lens arranged at intervals.

[0031] The first collimating lens 4 is an aspherical lens. The shorter focal length can collect scattered light over a wider range of incident angles, thus improving the energy utilization of the collimated light.

[0032] The rotating diffuser 3 is a polished diffuser with a mesh size of 1500 and a rotation speed of no less than 3000 rpm. It needs to be driven by a corresponding stepper motor.

[0033] The polarization direction of polarizer 8 should be parallel to the long axis of spatial light modulator 10 in order to perform pure phase-type optical field modulation and improve energy utilization.

[0034] The phase diagram loaded on the spatial light modulator 10 is calculated by CGH, where the incident light field is set as the light field illuminating the surface of the spatial light modulator 10, and the target light field can be any pattern. The numerical optimal solution is sought by iterative Fourier transform.

[0035] Please see Figure 7 , Figure 8 and Figure 9 The system effectively improves the uniformity of the generated pattern and reduces the influence of speckle noise without affecting the resolution of the target pattern generated by the spatial light modulator 10, thus greatly reducing the roughness of the micro-nano structure processed by maskless projection photoelectrochemical etching.

[0036] In this embodiment, a converging lens 2 is used to focus the parallel light directly emitted by the laser 1 onto the rotating scattering plate 3. This allows the scattered light to be considered as originating from a single focal point; otherwise, surface scattering would make collimation difficult. An aspherical lens is used to collect and collimate the scattered light because its small focal length allows it to collect scattered light with a larger divergence angle, improving energy utilization. The distances from the rotating scattering plate 3 to the converging lens 2 and the first collimating lens 4 are equal to their respective focal lengths. The collimated laser light after passing through the first collimating lens 4 requires further filtering to improve its intensity stability and uniformity. The hardware-homogenized laser light passes through a linear polarizer 8. The polarization direction of the polarizer 8 should be horizontal with the long axis of the spatial light modulator 10 to perform pure phase-type optical field modulation, further improving energy utilization. A holographic phase image is generated by a simple iterative Fourier transform algorithm based on the incident light illuminating the surface of the spatial light modulator 10. This phase image is then converted into a corresponding grayscale image and loaded onto the surface of the spatial light modulator 10 to modulate the incident light. After being focused by a Fourier lens 11, a high-quality target light field pattern is generated at the front focal plane of the first tube mirror 12. Using a projection-type miniaturized optical path, the target light field pattern generated by the spatial light modulator 10 is proportionally reduced and illuminating the sample surface immersed in a chemical solution. Using the principle of photoelectrochemical etching, a micro / nano structure with the same pattern as the target light field is fabricated.

[0037] To ensure accurate projection of the target light field pattern onto the sample surface without defocusing errors, an auxiliary alignment optical path consisting of a projection lens 14, a second tube lens 16, and a camera 17 is required. First, a reflective sample with a patterned surface is used and illuminated with the target structure light field. The position of the Fourier lens 11 and the distance between the sample and the projection lens 14 are adjusted. When a clear sample surface structure and the target light field can be observed simultaneously on the camera 17, it indicates that the target light field pattern has been accurately projected onto the sample surface. Next, the process is switched to the sample to be processed, and only the distance between the sample and the projection lens 14 is adjusted. When a clear target light field can be observed on the sample surface, it indicates that the target light field pattern has been accurately projected onto the sample surface to be processed, and maskless photoelectrochemical etching can be performed.

[0038] The present invention also provides a method for fabricating micro- and nano-structures based on photoelectrochemical etching, wherein the method uses the system for fabricating micro- and nano-structures based on photoelectrochemical etching as described above.

[0039] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for fabricating micro / nano structures based on photoelectrochemical etching, characterized in that: The system includes a laser, a converging lens, a rotating scattering plate, a first collimating lens, a converging objective lens, a filter pinhole, a second collimating lens, a polarizer, a first beam splitter, a spatial light modulator, and a Fourier lens arranged along the laser optical path. The converging lens is used to focus the parallel laser emitted by the laser onto the rotating scattering plate. The first collimating lens outputs the scattered laser from the rotating scattering plate in parallel. The parallel laser is filtered sequentially through the converging objective lens, the filtering pinhole, and the second collimating lens before reaching the polarizer. It then passes sequentially through the polarizer and the first beam splitter before illuminating the spatial light modulator. The spatial light modulator is used to modulate the received light to obtain a target light field pattern, thereby fabricating micro / nano structures.

2. The system for fabricating micro / nano structures based on photoelectrochemical etching as described in claim 1, characterized in that: The system also includes a first tube mirror, a second beam splitter cube, and a projection objective lens arranged along the projection-type miniature optical path.

3. The system for fabricating micro / nano structures based on photoelectrochemical etching as described in claim 2, characterized in that: The system also includes a camera and a second tube mirror, the second tube mirror being disposed between the camera and the second beam splitter cube for aligning with the sample surface.

4. The system for fabricating micro / nano structures based on photoelectrochemical etching as described in claim 2, characterized in that: The light field modulated by the spatial light modulator is transmitted to the projection-type miniature optical path to generate the target light field pattern after passing through the Fourier lens, so as to illuminate the sample surface and then perform etching.

5. The system for fabricating micro / nano structures based on photoelectrochemical etching as described in any one of claims 1-4, characterized in that: The first collimating lens is an aspherical lens.

6. The system for fabricating micro / nano structures based on photoelectrochemical etching as described in any one of claims 1-4, characterized in that: The rotating diffuser is a polished diffuser with a mesh size of 1500 and a rotation speed of ≥3000 rpm.

7. The system for fabricating micro / nano structures based on photoelectrochemical etching as described in any one of claims 1-4, characterized in that: The polarization direction of the polarizer should be parallel to the long axis of the spatial light modulator.

8. The system for fabricating micro / nano structures based on photoelectrochemical etching as described in any one of claims 1-4, characterized in that: The distance from the rotating diffuser to the converging lens is equal to the focal length of the converging lens; The distance from the rotating diffuser to the first collimating lens is equal to the focal length of the first collimating lens.

9. A method for fabricating micro / nano structures based on photoelectrochemical etching, characterized in that: The method described herein is to fabricate micro-nano structures using the system for fabricating micro-nano structures based on photoelectrochemical etching as described in any one of claims 1-8.

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