Method for manufacturing three-dimensional gray scale structure and three-dimensional micro-nano hollow structure based on low-voltage frozen gel electron beam exposure

Abstract

The invention discloses a manufacturing method of a three-dimensional gray scale structure and a three-dimensional micro-nano structure based on low-voltage ice gel electron beam exposure. The manufacturing method comprises the following steps: depositing an ice layer on a processing surface; then, low-energy electron beam layered exposure is utilized, the ice layer of the specific part of each layer is removed, and finally a three-dimensional gray scale ice sculpture structure with a specific gray scale pattern is formed; selectively depositing a material on the three-dimensional ice sculpture structure by adopting physical vapor deposition to form a three-dimensional micro-nano structure; the ice layer is water ice; and the energy of the low-voltage electron beam is lower than 5keV. According to the method, a three-dimensional ice sculpture structure without a supporting structure can be obtained by utilizing the characteristics of iEBL and low-energy exposure in water ice, and gray scale ice sculpture can be successfully converted into a high-purity three-dimensional metal structure. The breakthrough provides potential for improving nano device manufacturing by adopting a water ice resist, and establishes a key technical position of the iEBL in construction of a fine and pollution-free three-dimensional metal nano structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanostructure manufacturing or processing, and specifically relates to a three-dimensional grayscale structure and a three-dimensional micro-nano structure manufacturing method based on low-voltage cryogel electron beam exposure. Background Art

[0002] Due to the advantages of reduced forward scattering and smaller beam spot, high-energy electrons (above 30 keV) are widely used in conventional electron beam lithography (EBL) to fabricate high-resolution dense patterns. However, high-voltage EBL also has some limitations, such as low throughput, significant proximity effect, and high cost. In addition, the depth and profile of the exposed pattern are not controlled, which may cause radiation damage and complicate the direct fabrication of three-dimensional patterns. Compared with high-energy electron exposure processes, low-energy electrons (below 3 keV) show unique advantages in patterning, especially the fabrication of three-dimensional structures, with characteristics including lower critical dose and shorter backscattering range. Step-like three-dimensional nanostructures have been successfully fabricated on cured electronic resist using 3 keV. However, the potential of low-voltage EBL is still poorly explored and still faces some challenges that need to be addressed for wider application. First, when applying very low initial beam energy, the depth of the electron action volume will be less than the thickness of the resist, resulting in incomplete exposure. Therefore, in order to achieve the desired nanopattern depth, subsequent deposition or etching steps usually require additional processes. In addition, as the accelerating voltage decreases, the forward scattering of electrons increases significantly, which is widely considered to be the main factor limiting the resolution. Therefore, solutions combining linewidth control and direct grayscale patterning require further investigation.

[0003] Unlike traditional resists, ice layers / ice films show higher applicability in low-energy electron exposure. Studies have shown that the use of 1keV electrons to protect the ice layer can significantly reduce radiation damage to sensitive materials. Ice-assisted electron beam lithography (iEBL) also achieves layered 3D printing through organic ice and water ice, with advantages such as in-situ alignment, pollution-free processing, free development, and time saving, which is more competitive than focused electron beam induced deposition (FEBID) and scanning probe lithography (SPL). Although water ice can fabricate nanostructures as a positive resist, its ability to fabricate 3D grayscale structures has not been fully developed. In addition, additional deposition processes are required to maintain the ice structure, so it is still challenging to achieve high-resolution self-supporting 3D structures. FEBID can be used to fabricate small and delicate 3D metal structures (typically 20 to 60 nm), but FEBID has difficulties in fabricating high-purity metal 3D structures due to the inevitable incorporation of impurities such as carbon. These impurities may weaken or mask the properties of the target material. Since many applications are closely related to the properties of deposited materials, research targeting high-purity structures is crucial to ensure device performance. Summary of the invention

[0004] The present invention provides a method for manufacturing a three-dimensional grayscale structure and a three-dimensional micro-nano hollow structure based on low-voltage ice gel electron beam exposure. The method changes the idea of ​​three-dimensional printing that requires supporting materials when processing traditional three-dimensional nanostructures, and combines multiple exposures with low-energy electron beams to achieve the processing of three-dimensional grayscale structures on ice layers / ice films without the need for additional supporting structures. At the same time, the resolution of the three-dimensional grayscale structure is improved, and there is no problem of impurity contamination.

[0005] A method for manufacturing a three-dimensional grayscale structure based on low-voltage ice gel electron beam exposure, comprising: depositing a layer of ice on a processing surface; then using a low-energy electron beam for layered exposure to remove a specific portion of each layer of ice, and finally forming a three-dimensional ice sculpture structure with a specific grayscale pattern, i.e., a three-dimensional grayscale structure; the ice layer is water ice; and the low-voltage electron beam energy is less than 5keV.

[0006] Furthermore, the number of layers of the electron beam layered exposure and the area to be exposed in each layer are determined by the grayscale value corresponding to the three-dimensional grayscale structure.

[0007] Furthermore, before processing, the grayscale image corresponding to the three-dimensional ice sculpture structure is divided into multiple black and white sub-images; when using low-energy electron beam layered exposure, each layer corresponds to a black and white sub-image, the black area corresponds to the exposure area, and the white area is not exposed.

[0008] A method for processing a three-dimensional micro-nano hollow structure by low-voltage electron beam exposure based on ice carving comprises: using the above-mentioned three-dimensional grayscale structure manufacturing method to process a three-dimensional ice sculpture structure of the specific pattern; then depositing a material film on the three-dimensional ice sculpture structure; heating the three-dimensional ice sculpture structure to sublimate, and obtaining a three-dimensional micro-nano hollow structure corresponding to the ice sculpture structure.

[0009] It should be noted that the "grayscale" structure described in this article does not refer to a two-dimensional grayscale plane image, but a three-dimensional structure composed of "pixel points" with different depths. The three-dimensional structure is a three-dimensional ice sculpture structure composed of ice points of different heights (different depths). Of course, there is an inherent corresponding relationship between the three-dimensional ice sculpture structure and its corresponding two-dimensional image. Further, before the three-dimensional grayscale structure is manufactured, for its corresponding two-dimensional grayscale image or depth image, the image is divided into multiple black and white sub-images according to the grayscale value of the image (for example, the grayscale of the image can be divided into custom steps through MATLAB software (or other software that can recognize the grayscale value of the image), and the images of different grayscale intervals are exported separately to form "sub-images"). The black area in the sub-image corresponds to the exposure area, while the white area is not exposed. The number of sub-images can be set according to the selected image. For images with high accuracy requirements or a wide range of grayscale values, multiple sub-images can be set.

[0010] Furthermore, a method for processing a three-dimensional grayscale structure / three-dimensional micro-nano hollow structure by low-voltage electron beam exposure based on ice engraving comprises the following steps:

[0011] (1) Ice deposition: a layer of ice is deposited on the processing surface;

[0012] (2) Ice patterning: Using a low-voltage electron beam to remove specific parts of the ice layer multiple times in layers, ultimately forming a three-dimensional ice sculpture with a specific grayscale pattern;

[0013] (3) Material deposition (optional): depositing a material film on the surface of the sample to be processed, including a portion of the material film deposited on the ice mask and a portion of the material film directly deposited on the surface of the sample to be processed;

[0014] (4) Dry stripping (optional): The temperature is raised to sublime the ice mask, and the remaining material film (i.e., the portion of the material film directly deposited on the surface of the sample to be processed) forms a micro-nano structure corresponding to the ice sculpture on the surface of the sample to be processed.

[0015] Furthermore, in the step of removing the ice layer of a specific part by multiple layers using a low-voltage electron beam, the number of layers (or the corresponding number of sub-images) can be set to 2-50 sub-images, preferably 5-30. The number of sub-images corresponds to the number of electron beam exposure layers. The thickness of each layer is preferably less than 150nm; more preferably 5-150nm; more preferably 5-100nm; more preferably 5-60nm; more specifically preferably 5-30nm.

[0016] By adopting the method of the present invention, after each layer of electron beam exposure process, the line width is less than 50nm, further less than 30nm; more preferably: the line width is 5-30nm.

[0017] Furthermore, preferably, the total dose of the electron beam exposure area is in the range of 0.1C / cm 2 -10C / cm 2 For example, it can be 0.2C / cm 2 , 0.5C / cm 2 , 1C / cm 2 , 2C / cm 2 、3C / cm 2 , 4C / cm 2 , 5C / cm 2 , 6C / cm 2 , 7C / cm 2 , 8C / cm 2 , 9C / cm 2 , 10C / cm 2 , and specific point values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer exhaustively list the specific point values ​​included in the range. Preferably 1C / cm 2 -4C / cm 2 The single layer dose can be determined by the total dose / number of layers, and is generally preferably 0.05-0.5 C / cm 2 .

[0018] Furthermore, the energy of the low-voltage electron beam is below 4.5 keV; more preferably below 3.5 keV; specifically, the energy of the low-voltage electron beam is 0.3 keV-1 keV.

[0019] In the present invention, the total thickness of the ice film is 20 to 500 nm, further limited to 25 to 500 nm, and more preferably 50 to 300 nm.

[0020] The present invention can form an ice film on a planar substrate or a sample surface to be processed (planar or non-planar), and has no requirements on the substrate material, which can be a conductive substrate or a non-conductive substrate. The main components of the planar substrate material are any one or more combinations of Au, Ag, Cu, Al, Pt, Pd, Mn, Fe, Co, Ni, Zn, Cd, Ge, Sn, Pb, Sb, Bi, Si, Ge, GaN, GaAs, GaP, ITO, InP, InAs, ZnS, ZnSe, CdS, CdSe, ZnO, TiO2, MgO, CdO, Al2O3, SiO2 or Si3N4. For example, an Al2O3 substrate, a Si wafer substrate, a Si substrate with a 200-300nm thick SiO2 layer on the surface, etc. can be selected.

[0021] In step (3), the material is a metal, and the thickness of the metal can be selected from 20-500 nm, preferably 30-100 nm. The type of the metal is selected from one or more materials that can be physically vapor deposited, such as gold, silver, copper, and chromium.

[0022] The present invention can be carried out in a scanning electron microscope. The scanning electron microscope is selected from a thermal field emission scanning electron microscope, a cold field emission scanning electron microscope, and an environmental scanning electron microscope. In the present invention, the electron beam exposure time can be determined according to the size requirements of the pattern that needs to be etched or processed. The specific shape of the pattern that needs to be processed is controlled by inputting data information into the scanning electron microscope.

[0023] In the present invention, the ice layer is obtained at low temperature, and the low temperature range is the desublimation temperature of the amorphous crystalline state of water vapor at the corresponding pressure or lower than the desublimation temperature of the amorphous crystalline state. Preferably, the low temperature range is 100K-140K. For example, 100K, 110K, 120K, 130K, 140K, and specific point values ​​between the above values. Due to space limitations and for simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range. Preferably, the low temperature range is 120K-140K.

[0024] This technology is based on low-voltage ice gel electron beam lithography (iEBL) and uses water ice as a resist to achieve high-resolution, pollution-free three-dimensional grayscale patterns and three-dimensional micro-nano hollow structures, showing broad application prospects. It is suitable for fields such as nano-optical devices, quantum devices, and biosensors; it can generate complex grayscale patterns without support, which can be used in optical components such as microlens arrays; and the ability to convert ice sculptures into high-purity three-dimensional metal structures provides a new solution for the manufacture of micromechanical systems (MEMS) and advanced storage devices. In addition, this technology is green and environmentally friendly, has low energy consumption, is in line with the development trend of sustainable manufacturing, and has important research and industrialization value.

[0025] Compared with the existing technology, we propose an extremely low-energy electron beam nanofabrication strategy based on ice-assisted electron beam lithography (iEBL). This method specifically focuses on the fabrication of grayscale patterns and three-dimensional metal nanostructures. By using a low-energy electron beam, this strategy overcomes the limitation imposed by the electron action volume and achieves more precise control of pattern depth ( Figure 1 ). In addition, low-energy electron beams based on ice-assisted electron beam lithography (iEBL) can be used to create linear patterns with resolutions below 30nm, as well as grayscale patterns with up to 30 layers, with a single layer thickness as low as 10nm, which is much higher than what can be achieved with conventional techniques. More importantly, by leveraging the properties of iEBL and low-energy exposure in water ice, we successfully transformed grayscale ice sculptures into high-purity three-dimensional metal structures. This breakthrough provides the potential for improved nanodevice manufacturing using water ice resists and establishes iEBL as a key technology in constructing fine, contamination-free three-dimensional metal nanostructures. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Comparison of the step exposure mechanism of electrons at high voltage 10keV and low energy 1keV.

[0027] Figure 2 SEM images of the critical size study results of electron beam exposure at different voltages (the inset in the circle is the local enlarged SEM image corresponding to 0.3 keV).

[0028] Figure 3 SEM images of the grayscale koi structure processing and the research results on the influence of electron beam energy and exposure strategy on grayscale lithography.

[0029] Figure 4 SEM images of continuous grayscale and step ice structure based on a checkerboard pattern.

[0030] Figure 5 Continuous grayscale and step ice structure SEM images of different slope structures.

[0031] Figure 6 Schematic diagram of the process of manufacturing three-dimensional hollow gold structure using continuous grayscale and stepped ice sculpture, where 1: ice layer; 2: metal layer. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings:

[0033] A method for manufacturing a three-dimensional grayscale structure or a three-dimensional micro-nano hollow structure based on low-voltage cryogel electron beam exposure can be referred to Figure 6 As shown, the following steps are included:

[0034] (1) A layer of ice is deposited on the processing surface;

[0035] (2) Then, a low-voltage electron beam exposure is used to remove specific parts of the ice layer in layers multiple times, ultimately forming a three-dimensional ice sculpture structure with a specific pattern ( Figure 3 (a)), i.e., a three-dimensional grayscale structure; the ice layer is water ice;

[0036] (3) Material deposition (optional): depositing a material film on the surface of the sample to be processed, including a portion of the material film deposited on the ice mask and a portion of the material film directly deposited on the surface of the sample to be processed ( Figure 3 (b));

[0037] (4) Dry stripping (optional): The temperature is raised to sublime the ice mask, and the remaining material film (i.e., the part of the material film directly deposited on the surface of the sample to be processed) forms a micro-nano hollow structure corresponding to the ice sculpture on the surface of the sample to be processed ( Figure 3 (c) and (d)).

[0038] For the manufacture of complex three-dimensional patterns. Before electron beam exposure, the image is divided into multiple black and white sub-images according to the grayscale value of the image. Specifically, before step (1) processing, the image is first divided into multiple black and white sub-images according to the grayscale value of the depth image or grayscale image of the target three-dimensional structure (for example, the grayscale of the image can be divided into custom steps through MATLAB, and the images of different grayscale intervals can be exported separately to form "sub-images"). The black area in the sub-image corresponds to the exposure area, while the white area is not exposed. The number of sub-images can be set according to the selected image, and the number of sub-images can range from 2 to 50.

[0039] In actual processing, the number of sub-images is determined according to the characteristics of the pattern; the total ice layer thickness and the total number of layers are determined by comprehensively considering the three-dimensional structure characteristics and precision requirements, and then the thickness of each layer is determined. Each sub-image corresponds to a layer of exposure operation. The layer thickness can be determined according to the actual precision requirements. As a general choice, the layer thickness is 5-30nm. The electron beam voltage is selected to be 1keV and below. Other parameters are selected from the conventional scheme.

[0040] The ice layer deposited in step (1) can be completed at low temperature. That is, at low temperature, the ice layer is formed by water vapor deposition. In actual operation, the substrate is placed in a scanning electron microscope, the sample stage temperature is reduced to 135K by a refrigeration device, and water vapor is vapor-deposited on the sample surface to form a water ice film of the desired thickness. The electronic book exposure operation can select a scanning electron microscope, and the scanning electron microscope is selected from a thermal field emission scanning electron microscope, a cold field emission scanning electron microscope, and an environmental scanning electron microscope. In this embodiment, we use a cold field emission scanning electron microscope for processing.

[0041] Figure 2 to Figure 6 For the actual research conducted on the method of the present invention:

[0042] Figure 2 As shown, the overall thickness of the ice layer is about 250nm. The three figures correspond to beam energies of 300eV, 600eV, and 1keV, respectively. In each figure, the measurement increases gradually from left to right, with a step size of 0.12C / cm 2 , the total dose is 1.2C / cm 2 The inset of the circular part corresponds to the enlarged SEM image of the sample stage after tilting at 300 eV. The scale bar is 2 μm.

[0043] Critical dimension and critical dose are important parameters in EBL nanofabrication. Figure 2 In the figure, the critical dimension is shown at different accelerating voltages, while keeping the ice thickness, beam current and working distance constant. A gradually increasing dose is applied to the array of lines from left to right. By tilting the sample stage by 15° and observing the depth of the crack at the end of the line, the dose that just completely removes the ice can be determined. As shown in the inset, the bottom of the two lines on the left are lighter in color, indicating the presence of residual ice. The line within the dotted circle on the far right has been fully exposed, and its width is defined as the critical dimension, and its corresponding dose is the critical dose. Figure 2 The results show that in ice layers / films, 1keV electrons can still create structures with line widths less than 30nm, which is better than other resists such as PMMA, HSQ or ZEP-520, whose resolution at 1keV exceeds 50nm. The pattern resolution can be further improved by reducing the thickness of the ice resist.

[0044] Figure 3 (a) is a schematic diagram of making a continuous grayscale Koi structure, and (b)-(e) are the results of the effect of electron beam energy and exposure strategy on grayscale lithography. (b) uses 5keV electrons for a single exposure for each small sector, and the dose changes according to the grayscale change (the sector block with a high grayscale value corresponds to a dose of 1.3C / cm 2 The dose corresponding to the lowest sector block is 1.3 / 12=0.108C / cm 2 ). (c) Single exposure using 1keV electrons, the dose remains unchanged. (d) 12 exposures using 5keV electrons, the total dose corresponding to each sector remains unchanged, the layer dose and the number of exposures are determined according to the number of black sub-images at the corresponding position. (e) 12 exposures using 1keV electrons, same as above. The scale bars in (b)-(e) are all 1μm. The ice layer thickness is 300nm, and the total dose at the highest grayscale value is 1.3C / cm 2 .

[0045] Before actual processing, MATLAB software was used to Figure 3The koi image shown in (a) is divided into 15 sub-images to achieve a continuous grayscale structure in the ice, as shown in Figure 3 As shown in the right figure of (a). During the specific processing, electron beam exposure was performed on different layers of the 15 black and white sub-images, where the black area corresponds to the exposure area, and the white area is not exposed. Finally, we obtained the micrometer-scale ice koi, and its SEM image is shown in the lower left corner.

[0046] At the same time, to verify the advantages of our exposure strategy, we compared the 12-layer grayscale fan-shaped patterns manufactured with different beam energies, i.e., voltages (1 keV and 5 keV) and exposure times (1 and 12 times). Figure 3 In (b) and (d), an inhomogeneous interface is observed in the partially exposed ice layer regardless of the exposure method. In contrast, when a 1 keV electron beam is used ( Figure 3 In (c) and (e), at low area doses, the two exposure methods behave similarly. However, as the dose increases (corresponding to an increase in the grayscale of the pattern), the pattern ( Figure 3 c) The boundary becomes blurred, affecting the preparation of 3D multilayer nanostructures. In contrast, the multiple exposure strategy ( Figure 3 e) It can effectively alleviate charge accumulation and generate a step structure with clear boundaries.

[0047] Figure 4 (a)-(d) show the resolution limit of the grayscale ice pattern. Figure 4 In the figure, (a) and (b) are grid arrays, where (a) is a checkerboard pattern with a side length of 600nm made on a 300nm thick ice layer, containing 6 different heights (6 black and white sub-images, 6 exposures, using a 1keV electron beam exposure). The structure in (b) is the same as (a), but the side length of each square is 500nm. (c) is a 30-layer inverted pyramid structure made on a 300nm thick ice layer (30 black and white sub-images, 30 exposures, using a 1keV electron beam exposure). (d) is a positive pyramid structure of the same size as (c). The scale bars in (a) and (b) are 1μm, and the scale bars in (c) and (d) are 2μm. The total dose is 1.3C / cm 2 . Figure 4 (c)-(d) show a 30-layer multilayer structure with a step width of 300 nm. The boundaries of each layer are clearly visible under SEM.

[0048] Our exposure strategy also supports the fabrication of slope nanostructures. Figure 5 (a) and (b) show the stepped slope structure with a trapezoidal cross section. Figure 5(a) Grayscale structural SEM image of a trapezoidal cross section, with a slope of 500 nm in lateral dimension. (b) Slope with a width of 1 μm. (c) Slant grating with five periods, each with a slope of 1 μm in width. (d) Structure consisting of two slopes, each with a lateral dimension of 500 nm. (e) Double slope structure, with the widths of the slopes on both sides being 1000 nm and 500 nm respectively. (f) Tilt grating composed of the elements in (e). Ice layer thickness 300 nm, electron beam energy 1 keV, total dose 1.3 C / cm 2 When the step width is set to 100 nm or less, the boundary becomes indistinguishable under SEM observation, and the step structure gradually evolves into an inclined plane. Figure 5 (c) shows a grating structure including continuous slopes. In addition, Figure 5 (d)-(f) show double slope structures with lateral dimension ratios of 1:1 and 1:2. Figure 5 (f) shows the preparation of a slope structure array with slopes on both sides, with 20 layers.

[0049] Taking advantage of the superior slope structure generated by low-energy iEBL, we successfully fabricated three-dimensional hollow gold structures, including hemispheres and roof structures. Figure 6 shown. Figure 6 Schematic diagram of the process of fabricating 3D hollow gold structures using continuous grayscale and step ice sculpture. (a) Continuous grayscale exposure on an ice substrate with an ice layer thickness of 500 nm and a total dose of 1.6 C / cm 2 , 15 layers. (b) Evaporating metallic gold (Au) onto the exposed ice structure, (c) heating the entire sample, and (d) completing the structure fabrication through a one-step lift-off process. The illustrations of each step show SEM micrographs of the hemispherical and roof structures. (e) to (f) Focused ion beam (FIB) cutting shows the internal cavity of the hollow gold structure. (g) to (h) Atomic force microscopy (AFM) images and their corresponding height distribution maps of the hollow gold structure. Scale bar: 500nm. After generating the structure through grayscale iEBL ( Figure 6 ), the sample was thermally evaporated to deposit a 40nm thick layer of gold (Au) on the ice structure ( Figure 6 (b)). Further expansion, the metal thickness can be selected from 20-500nm, preferably 30-100nm. After metallization, the sample is returned to room temperature and a simple one-step stripping process ( Figure 6 d) The final three-dimensional hollow gold structure is easily obtained. Since the metal is directly evaporated by physical vapor deposition, the purity of the structure is theoretically equal to that of the evaporation source. In addition, this strategy has no restrictions on the choice of metal. In order to show the hollow structure in detail, the hemisphere and roof structure were cut using focused ion beam technology ( Figure 6ef), revealing clear internal cavity outlines. In addition, the fabrication was extended to generate arrays of these hollow structures and their morphology was analyzed using AFM ( Figure 6 gh).

[0050] In summary, we proposed a novel nanofabrication strategy based on ice-assisted electron beam lithography (iEBL), with a special focus on the fabrication of grayscale patterns and three-dimensional metal nanostructures. The application of low-energy electron beams in iEBL breaks through the limitation of the electron interaction volume on the pattern depth. The experimental results fully demonstrate that the 1keV electron beam exhibits higher exposure efficiency despite a slight increase in the critical size. We proposed a revolutionary method to fabricate grayscale nanopatterns, successfully realizing continuous grayscale and stepped ice structures (e.g., koi, pyramid, ramp-shaped ice sculptures) with a maximum number of up to 30 layers, which exceeds the number of layers achieved by PMMA-based grayscale patterns in the literature. Furthermore, through the optimized low-energy iEBL strategy, we successfully fabricated complex three-dimensional hollow metal structures by converting grayscale ice sculptures. This highlights the potential of low-energy grayscale water ice iEBL in the field of complex three-dimensional nanofabrication.

Claims

1. A method for manufacturing a three-dimensional grayscale structure based on low-voltage cryogel electron beam exposure, characterized in that: include: A layer of ice is deposited on the processing surface; then a low-energy electron beam is used for layered exposure to remove a specific portion of each layer of ice, ultimately forming a three-dimensional ice sculpture structure with a specific grayscale pattern; the ice layer is water ice; and the energy of the low-voltage electron beam is less than 5keV.

2. The method for manufacturing a three-dimensional grayscale structure based on low-voltage cryogel electron beam exposure according to claim 1, characterized in that: The number of layers of the electron beam layered exposure and the area to be exposed in each layer are determined by the grayscale value corresponding to the three-dimensional grayscale structure.

3. The method for manufacturing a three-dimensional grayscale structure based on low-voltage cryogel electron beam exposure according to claim 1, characterized in that: Before processing, the grayscale image corresponding to the three-dimensional ice sculpture structure is divided into multiple black and white sub-images; when using low-energy electron beam layered exposure, each layer corresponds to a black and white sub-image, the black area corresponds to the exposure area, and the white area is not exposed.

4. The method for manufacturing a three-dimensional grayscale structure based on low-voltage cryogel electron beam exposure according to claim 1, characterized in that: The number of layers is 2-50.

5. The method for manufacturing a three-dimensional grayscale structure based on low-voltage cryogel electron beam exposure according to claim 1, characterized in that: The thickness of each layer is 5-150nm.

6. The method for manufacturing a three-dimensional grayscale structure based on low-voltage cryogel electron beam exposure according to claim 1, characterized in that: The low voltage electron beam energy is 0.3keV-1keV.

7. The method for manufacturing a three-dimensional grayscale structure based on low-voltage cryogel electron beam exposure according to claim 1, characterized in that: When using low voltage electron beam for layered exposure, the single layer exposure dose is 0.05~0.5C / cm 2 .

8. A method for processing three-dimensional micro-nano hollow structures by low-voltage electron beam exposure based on ice engraving, characterized in that: include: A three-dimensional ice sculpture structure is obtained by processing using the three-dimensional grayscale structure manufacturing method according to any one of claims 1 to 7; Then depositing a thin film of material on the three-dimensional ice sculpture structure; The three-dimensional ice sculpture structure is heated to cause sublimation, thereby obtaining a three-dimensional micro-nano hollow structure corresponding to the deposited material.

9. The method for processing three-dimensional micro-nano hollow structures by low-voltage electron beam exposure based on ice engraving according to claim 8, characterized in that: The material is selected from one or more of gold, silver, copper and chromium, and a thin film of the material can be obtained by physical vapor deposition.

10. The method for processing three-dimensional micro-nano hollow structures by low-voltage electron beam exposure based on ice engraving according to claim 8, characterized in that: The material film thickness is 20-500nm.

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