A high-fidelity three-dimensional two-photon laser direct writing method

Abstract

The application discloses a high-fidelity three-dimensional two-photon laser direct writing method, which comprises the following steps: obtaining processing instruction data of a three-dimensional structure to be processed, performing two-photon laser direct writing on photoresist based on the processing instruction data, and then developing and post-processing to obtain the three-dimensional structure; wherein the method for obtaining the processing instruction data comprises the following steps: constructing a three-dimensional model of the three-dimensional structure, identifying a surface contour area and an internal entity area of the three-dimensional model, generating a scanning path of the surface contour area, performing down-sampling processing on the internal entity area to obtain an internal sparse scanning path, and fusing the scanning path of the surface contour area and the internal sparse scanning path to obtain complete processing instruction data. The method can overcome the proximity effect caused by free radical diffusion, can maintain high fidelity, and can realize high-precision and high-throughput processing on a large-volume three-dimensional structure.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano fabrication technology, specifically relating to a high-fidelity three-dimensional two-photon laser direct writing method. Background Technology

[0002] Two-photon laser direct writing technology is based on the nonlinear two-photon absorption effect of femtosecond lasers and photosensitive materials. It can break through the optical diffraction limit and realize the processing of true three-dimensional micro and nano structures, and has broad application prospects in the fields of photonic crystals, micromechanics, and metamaterials.

[0003] However, existing technologies generally face a severe proximity effect problem when processing high-density, large-volume duty cycle three-dimensional structures. This effect mainly stems from the diffusion of free radicals generated in the photoresist (liquid or semi-solid) during laser exposure. When the laser focus scans point-by-point in a dense area, the active free radicals generated at the previous exposure point have not been completely quenched and will diffuse into the surrounding unexposed areas, resulting in the actual accumulated exposure dose during subsequent exposures being much higher than the preset value. Specifically, when processing solid bulk or high-density grid structures, the central region of the structure is overexposed due to the accumulation of free radicals (resulting in structural bulkiness, decreased resolution, and even carbonization), while the edge regions suffer from insufficient cross-linking density due to the outward escape of free radicals, leading to structural collapse or peeling after development.

[0004] Patent application CN117069867A discloses a photoresist compound and a padding compound for photolithography, a multilayer structure, and a method for manufacturing a semiconductor device. The photoresist compound and the padding compound can improve the resolution and sensitivity of the photoresist pattern and suppress the collapse of the photoresist pattern. The padding compound comprises a cellulose structure having at least one hydroxyl group and at least one vinylsilyl group. The photoresist compound comprises alkylated metal oxide nanoclusters having counter-anion properties.

[0005] Patent application CN117055297A discloses a super-resolution laser direct writing method and apparatus based on optical / chemical three-dimensional dark spots. This invention uses three laser beams, focused onto the photoresist with solid and hollow spots respectively. The three beams are aligned at the center in three-dimensional space. Utilizing the STED properties of the photoinitiator and the restriction of free radical diffusion by the inhibitor, a minimum linewidth of sub-50 nm and a minimum period of sub-100 nm can be obtained in the photoresist.

[0006] Both of the above patents alleviate the overexposure effect caused by free radical accumulation by adding free radical quenchers. However, the structural fidelity is insufficient and the applicability to complex internal morphologies is poor. It can be seen that traditional process optimization methods, such as adjusting laser power, scanning speed or adding free radical quenchers, can partially alleviate the problem, but they often cannot balance processing efficiency and structural fidelity. In particular, they lack universality for structures with complex internal morphologies. Summary of the Invention

[0007] This invention provides a high-fidelity three-dimensional two-photon laser direct writing method, which can overcome the proximity effect caused by free radical diffusion and maintain high fidelity, enabling high-precision and high-throughput processing of large-volume duty cycle three-dimensional structures.

[0008] This invention provides a high-fidelity three-dimensional two-photon laser direct writing method, comprising: The processing instruction data of the periodically arranged three-dimensional structure to be processed is obtained. Based on the processing instruction data, the photoresist is directly written by two-photon laser, and then developed and post-processed to obtain the three-dimensional structure. The method for obtaining the processing instruction data includes: A three-dimensional model of a three-dimensional structure is constructed, the surface contour region and the internal solid region of the three-dimensional model are identified, a scanning path for the surface contour region is generated, the internal solid region is downsampled to obtain an internal sparse scanning path, and the scanning path of the surface contour region and the internal sparse scanning path are fused to obtain complete processing instruction data.

[0009] This invention downsamples the internal solid region to reduce the number of voxel points, thereby lowering the internal crosslinking density. This results in a spatially discontinuous distribution of sparse scanning paths, aiming to form a porous, low-volume-fraction internal support network. This allows free radicals to diffuse and quench freely in non-exposed areas, minimizing overexposure. Meanwhile, by selecting an appropriate thickness for the surface contour region, the exposed structural surface is precisely smoothed. Excess free radicals fill the support network inwards and diffuse freely outwards to blank areas for quenching.

[0010] Preferably, downsampling is used to reduce the number of internal voxel points to 5% to 80% of the original density inside the structure.

[0011] This invention controls the density of the internal sparse scanning path, which not only satisfies the free diffusion and quenching of free radicals, but also provides physical support for the unexposed photoresist monomers.

[0012] Preferably, the downsampling process is uniform random downsampling, and the probability of random sampling is the ratio of the structure density to the original density.

[0013] Preferably, the method for generating a scanning path for a surface contour region includes: obtaining a two-dimensional layer cut image by vertically segmenting the three-dimensional model layer by layer, extracting the edges of the geometric shape using an image processing algorithm, and generating a scanning path for the surface contour region based on the shape distribution of the edges.

[0014] Preferably, while generating the scanning path of the surface contour region, the exposure parameters of the surface contour region are set. The exposure parameters include laser power, scanning speed and thickness. The laser power is 0.1-10 mW, the scanning speed is 0.1-100 mm / s, and the thickness is 0.1-2 μm.

[0015] This invention controls the laser power and scanning speed to control the energy focused on the photoresist, keeping the amount of free radicals within a controllable range. The internal porous structure, through downsampling, allows the controlled amount of free radicals to diffuse and quench better.

[0016] More preferably, the laser power and scanning speed of the internal solid region and the surface contour region are the same.

[0017] Preferably, the photoresist is one of various two-photon photoresists currently on the market, such as IP-Dip and IPS.

[0018] Preferably, the three-dimensional structure is any geometric shape such as a triangular pyramid or a cube.

[0019] More preferably, the height of the triangular pyramid is 1-100 μm, the inclination angle of the three sides is 10°-80°, the side length of the base triangle is 1-100 μm, and the spacing between the triangular pyramids is 0-100 μm.

[0020] More preferably, the laser power in the surface contour region and the internal solid region is 0.5-5mW, the scanning speed is 0.5-10 mm / s, the photoresist is IP-DIP, the number of scanning points or scanning lines in the internal sparse scanning path is reduced to 10%-30% of the original density, and the thickness of the surface contour region is 100-1000 nm.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention ensures that the manufactured three-dimensional structure is highly consistent with the design model in terms of geometry by controlling the appropriate geometric thickness, preserving the complete surface contour, and avoiding edge collapse through internal filling support.

[0022] This invention provides a diffusion channel for free radicals in large-volume processing by designing an internal sparse scanning path, effectively avoiding overexplosion and distortion in the central region of the structure, and significantly improving the processing quality of high-volume duty cycle structures.

[0023] Because of the significant reduction in internal voxel points provided by this invention, the total path length of laser scanning is directly reduced, thereby greatly shortening the processing time and achieving high-throughput manufacturing.

[0024] The method provided by this invention can achieve the diffusion and quenching of free radicals simply by preprocessing the model data, reducing overexposure in the central region of the structure and preventing structural collapse or peeling after development at the edges. It does not require changes to the existing photoresist formulation or frequent switching of light intensity and scanning speed, and is applicable to various existing two-photon laser direct writing systems, possessing strong versatility and industrial application value. Attached Figure Description

[0025] Figure 1 This invention provides a data preprocessing method for a three-dimensional solid model, as described in Embodiment 1 of the present invention. Figure 2 This is an electron microscope image of the processing sample obtained in Comparative Example 1 of the present invention; Figure 3 This is an electron microscope image of the processing sample obtained in Example 1 of the present invention. Detailed Implementation

[0026] To better understand the purpose, technical solution, and advantages of this application, the application is described and explained below in conjunction with the accompanying drawings and embodiments.

[0027] Example 1 This embodiment provides a high-fidelity three-dimensional two-photon laser direct writing method for fabricating a solid cylindrical structure.

[0028] Step 1: Model Building and Loading: A three-dimensional model 101 of a solid triangular pyramid was created in the computer. The base length and height of the pyramid were both 10 μm. This model data was then imported into the data processing software of the two-photon laser direct writing system. For ease of demonstration, Figure 1 A section 102 of the 3D model 101 of the triangular pyramid is used for display.

[0029] Step 2: Data Preprocessing Surface extraction: Using image processing algorithms to identify and extract the surface contours of the model, such as... Figure 1 As shown in Figure 103. The image processing algorithm includes conventional graphics algorithms, such as erosion, dilation, and edge extraction. Parameters for the surface contour region are set, specifically including: thickness 200 nm, light intensity 2 mW, and scanning speed 10 mm / s.

[0030] Internal sparsity reduction: Random downsampling is performed on the internal solid regions of the 3D model 101. Specifically, the voxel points that need to be exposed in the internal regions are randomly removed from their original 100% density to a density of 20%. These retained voxel points will serve as the scanning path for the internal supporting skeleton (e.g., ...). Figure 1 (As shown in Figure 104). The exposure parameters for the internal solid region are: light intensity 2mW, scanning speed 10 mm / s.

[0031] Data fusion: The surface scan path and the internal sparse scan path are merged according to spatial coordinates, such as... Figure 1 As shown in Figure 105, the final machining instruction data is generated.

[0032] Step 3: Two-photon laser direct writing process: Prepare a substrate and deposit a specialized two-photon photoresist onto it. In this embodiment, the photoresist used is IP-DIP. Mount the substrate onto the displacement stage of the two-photon laser direct writing apparatus. Load the processing command data generated in step 2. Use a high-power femtosecond laser and focus the laser beam into the photoresist through a high numerical aperture objective lens.

[0033] As instructed, the laser processes the pyramid starting from the bottom, printing one slice at a time. The surface layer of the slice forms a dense outer shell after being exposed to the laser, while the sparse lattice in the internal region forms a dense support structure. Then, the next slice is scanned, achieving layer-by-layer processing.

[0034] Step 4: Development and Post-processing After processing, the substrate is sequentially immersed in a developer and isopropanol for development to remove unexposed photoresist. Finally, after drying and other treatments, the final three-dimensional structure is obtained.

[0035] Comparative Example 1 Compared to Example 1, the internal entities are not subject to random downsampling; instead, they are sampled in the same way as the surface contour regions.

[0036] Observed under a scanning electron microscope, such as Figure 2 As shown, the control sample pyramid provided in Comparative Example 1 exhibits significant swelling and reduced resolution (overexposure), with the pyramid shape obscured by numerous irrelevant structures. In contrast, the sample processed using the method of this invention, such as... Figure 3 As shown, the pyramid provided in Example 1 has a clear outline and distinct edges. Although the interior has a porous structure, the overall shape remains intact, which proves the effectiveness of the present invention in eliminating proximity effects and improving structural fidelity.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, modifications or equivalent substitutions can be made to the foregoing technical features without departing from the spirit of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-fidelity three-dimensional two-photon laser direct writing method, characterized in that, include: The processing instruction data of the periodically arranged three-dimensional structure to be processed is obtained. Based on the processing instruction data, the photoresist is directly written by two-photon laser, and then developed and post-processed to obtain the three-dimensional structure. The method for obtaining the processing instruction data includes: A three-dimensional solid model with a three-dimensional structure is constructed. The surface contour region and the internal solid region of the three-dimensional solid model are identified. The scanning path of the surface contour region is generated. The internal solid region is downsampled to obtain the internal sparse scanning path. The scanning path of the surface contour region and the internal sparse scanning path are fused to obtain complete processing instruction data. This reduces the number of voxel points inside the three-dimensional structure to 5% to 80% of the original density inside the three-dimensional structure. The laser power and scanning speed are the same for the internal solid region and the surface contour region.

2. The high-fidelity three-dimensional two-photon laser direct writing method according to claim 1, characterized in that, The downsampling process is uniform random downsampling.

3. The high-fidelity three-dimensional two-photon laser direct writing method according to claim 1, characterized in that, A method for generating a scanning path for a surface contour region includes: obtaining a two-dimensional layer cut image by vertically segmenting the three-dimensional model layer by layer, extracting the edges of the geometric shape using an image processing algorithm, and generating a scanning path for the surface contour region based on the shape distribution of the edges.

4. The high-fidelity three-dimensional two-photon laser direct writing method according to claim 1, characterized in that, While generating the scanning path of the surface contour region, the exposure parameters of the surface contour region are set. The exposure parameters include laser power, scanning speed and thickness. The laser power is 0.1-10 mW, the scanning speed is 0.1-100 mm / s, and the thickness is 0.1-2 μm.

5. The high-fidelity three-dimensional two-photon laser direct writing method according to claim 1, characterized in that, The photoresist is a two-photon photoresist.

6. The high-fidelity three-dimensional two-photon laser direct writing method according to claim 1, characterized in that, The three-dimensional structure is a cylinder, a triangular pyramid, or a cube.

7. The high-fidelity three-dimensional two-photon laser direct writing method according to claim 6, characterized in that, The height of the triangular pyramid is 1-100 μm, the inclination angle of the three sides is 10°-80°, the side length of the base triangle is 1-100 μm, and the spacing between the triangular pyramids is 0-100 μm.

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