Electron beam simulation method based on composite absorption layer and composite absorption layer mask plate

Abstract

The invention relates to the technical field of photoetching, in particular to an electron beam simulation method based on a composite absorption layer and a composite absorption layer mask plate. In order to overcome the technical defect that the direct writing precision of an electron beam is affected due to unexpected exposure of a resist in a peripheral area of a target pattern caused by the proximity effect of back scattering electrons, the mask structure is optimally designed, and the structure of a double-layer absorption film structure of the mask is optimally designed. Compared with a traditional method for designing and verifying through experiments, the method has the advantages that the mask structure optimization efficiency is greatly improved, the material consumption is reduced, the optimal mask model is quickly screened out by reasonably setting the simulation calculation parameters, and the method is suitable for large-scale popularization and application. And experimental effect verification is performed on the optimized mask model in a targeted manner, so that the effect accuracy of the simulation model and the practicability of the simulation method are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photolithography, and in particular to an electron beam simulation method based on a composite absorption layer and a composite absorption layer mask. Background Art

[0002] Electron beam lithography (EBL) is a micro-nanofabrication technology that uses a high-energy electron beam to directly create nanoscale patterns on a resist-coated substrate. Its core principle is to generate an electron beam using an electron gun, focus it to a subnanometer spot using an electromagnetic lens, and then scan it point by point using a computer-controlled deflection system to form a pre-defined pattern. The interaction between the electron beam and the resist triggers a chemical reaction, which, after development, forms a high-precision pattern that is then transferred to the substrate through etching or deposition processes. This technology, with its mask-free operation, extremely high resolution, and strong design flexibility, is widely used in semiconductor mask production, nanodevice development, and cutting-edge scientific research.

[0003] However, in electron beam direct writing (EBW) technology, backscattered electrons (BSE) are a key factor affecting direct writing accuracy. They cause image distortion by inducing the proximity effect, limiting EBL resolution and image fidelity. In the incident electron beam, a portion of the backscattered electrons undergo a series of elastic and inelastic scattering within the sample, causing their direction of motion to deflect by a large angle (typically >90°). These electrons ultimately escape from the incident surface. These electrons retain a significant portion of the incident energy (ranging from near the incident energy E0 to very low energies).

[0004] Backscattered electrons are typically generated when a high-energy electron beam bombards a substrate. Electrons interact with the substrate atoms, causing some electrons to bounce back onto the resist due to elastic scattering (large-angle deflection) or inelastic scattering (energy loss). These electrons have lower energy but are distributed over a wider range, resulting in unintended exposure of the resist around the target pattern. Summary of the Invention

[0005] (1) Technical issues to be solved

[0006] The purpose of the present invention is to overcome the technical defect in the prior art that backscattered electrons induce a proximity effect, resulting in unintended exposure of the resist in the area surrounding the target pattern, thereby affecting the accuracy of electron beam direct writing. In order to overcome this defect, an electron beam simulation method based on a composite absorption layer is provided by adjusting the absorption layer.

[0007] (2) Technical solution

[0008] In a first aspect, the present invention provides an electron beam simulation method based on a composite absorption layer, comprising the following steps:

[0009] S1. Establishing a mask simulation model based on preset initial conditions; wherein the initial conditions include the structure of the mask, the materials and thicknesses of each layer structure, and the structure of the mask from bottom to top includes a base layer, a composite absorption layer, and a resist layer;

[0010] S2. Forming a plurality of mask samples by combining different characteristic parameters of the composite absorption layer; wherein the characteristic parameters include the absorption layer material and the absorption layer thickness;

[0011] S3. Performing electron beam backscattered electron simulation calculations on a plurality of mask samples using the mask simulation model, screening out mask samples with concentrated backscattered electron energy, and using their corresponding characteristic parameters as preferred mask samples.

[0012] Preferably, in step S1, the composite absorption layer comprises a first absorption layer and a second absorption layer from bottom to top, and the thickness of the composite absorption layer is designed to be 40-80 nm.

[0013] Preferably, the material of the base layer is any one of SiO2, soda glass, borosilicate glass or sapphire; the structure of the mask also includes a hard mask layer, which is arranged between the composite absorption layer and the resist layer, and the material of the hard mask layer is any one of SiO2, Si3N4 or TiN; the material of the resist layer is any one of polymethyl methacrylate, ZEP or HSQ.

[0014] Preferably, in step S2, the first absorption layer is a metal film layer, the material of the first absorption layer is selected from any one of Cr, Ta, and Mo, and the thickness of the first absorption layer is in the range of 5-45 nm.

[0015] Preferably, in step S2, the second absorption layer is a metal film layer, the material of the second absorption layer is selected from any one of Cr, Ta, and Mo elements, and the thickness range of the second absorption layer is 5-45 nm; wherein the material of the second absorption layer is different from that of the first absorption layer.

[0016] Preferably, in step S1, the mask simulation model is designed and established using Monte Carlo simulation software.

[0017] Preferably, in step S3, the parameters of the simulation calculation include: thickness of the composite absorption layer, thickness of the electron beam gel, energy of the electron beam, size of the beam spot and number of simulated electron steps.

[0018] Preferably, the electron beam backscattered electron simulation calculation is performed using CASINO software, backscattered electron energy distribution data of different mask samples are obtained by calculation, and a preferred mask sample is obtained by screening based on the backscattered electron energy distribution data.

[0019] Preferably, the method further comprises step S4: subjecting the selected preferred mask samples to electron beam direct writing experiments for verification, determining the optimal composite absorption layer mask structure, and using the optimal composite absorption layer mask structure to prepare the mask.

[0020] In the second aspect, the present invention also provides a composite absorption layer mask, which is prepared by using the preferred mask sample determined by the above-mentioned electron beam simulation method based on the composite absorption layer and the optimal composite absorption layer mask structure determined by electron beam direct writing experiment verification.

[0021] (3) Beneficial effects

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The technical solution of the present invention optimizes the design of the mask structure, mainly optimizing the double-layer absorption film structure of the mask, in order to overcome the technical defect that backscattered electrons induce the proximity effect, resulting in unintended exposure of the resist in the area around the target pattern, thereby affecting the accuracy of electron beam direct writing. Electron backscattering simulation calculations are performed to screen out the composite absorption layer combination types with better results. Compared with the traditional design and verification through experiments, the optimization and verification of the mask structure are performed one by one. This method greatly improves the optimization efficiency of the mask structure and reduces material consumption. By reasonably setting the simulation calculation parameters, the preferred mask model is quickly screened out, and the experimental effect verification of the preferred mask model is carried out in a targeted manner, thereby improving the accuracy of the simulation model effect and the practicality of the simulation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FIG. 4 is a flow chart of a simulation method of an electron beam simulation method based on a composite absorption layer according to an exemplary embodiment of the present invention.

[0025] Figure 2 Schematic diagram of mask modeling for an electron beam simulation method based on a composite absorption layer according to an exemplary embodiment of the present invention.

[0026] Figure 3 FIG. 4 is a diagram of electron scattering trajectories of an electron beam simulation method based on a composite absorption layer according to an exemplary embodiment of the present invention.

[0027] Figure 41 is a short-range electron scattering trajectory of an electron beam simulation method based on a composite absorption layer according to an exemplary embodiment of the present invention.

[0028] Figure 5 1 is a backscattered electron energy distribution diagram when the Ta layer is on the top and the Cr layer is on the bottom in the composite absorption layer of the mask in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0029] Figure 6 1 is a backscattered electron energy distribution diagram when the Cr layer is on the top and the Ta layer is on the bottom in the composite absorption layer of the mask in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0030] Figure 7 1 is a backscattered electron energy distribution diagram when the Mo layer is on the top and the Cr layer is on the bottom in the composite absorption layer of the mask in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0031] Figure 8 1 is a backscattered electron energy distribution diagram when the Cr layer is on the top and the Mo layer is on the bottom in the composite absorption layer of the mask in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0032] Figure 9 1 is a backscattered electron energy distribution diagram when the Mo layer is on the upper side and the Ta layer is on the lower side in the composite absorption layer of the mask in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0033] Figure 10 1 is a backscattered electron energy distribution diagram when the Ta layer is on the top and the Mo layer is on the bottom in the composite absorption layer of the mask in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0034] Figure 11 1 is a SEM image of condition No. 1 in Table 8 in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0035] Figure 12 3 is a SEM image of condition No. 2 in Table 8 in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0036] Figure 13 3 is a SEM image of condition No. 3 in Table 8 in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0037] Figure 14 4 is a SEM image of condition No. 4 in Table 8 in the electron beam simulation method based on the composite absorption layer according to an exemplary embodiment of the present invention.

[0038] Markings in the figure: 1-base layer, 2-first absorption layer, 3-second absorption layer, 4-hard mask layer, 5-resist layer. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments, as all technologies implemented based on the present invention fall within the scope of the present invention.

[0040] In the prior art, backscattered electrons (BSEs) are one of the core factors affecting the direct writing accuracy in electron beam direct writing technology. They cause pattern distortion by inducing the proximity effect, limiting the resolution and pattern fidelity of the EBL. This affects the accuracy of electron beam direct writing. In order to overcome this technical defect, an embodiment of the present invention provides an electron beam simulation method based on a composite absorption layer, which mainly optimizes the structure of the composite absorption layer of the mask. The mask simulation model is established by CASINO software, and the electron beam backscattered electron simulation calculation is performed to screen out the structural type of the composite absorption layer. Compared with the traditional experimental design and the effect verification of the mask structure one by one, this method can greatly shorten the optimization time of the mask structure and improve the optimization efficiency of the mask structure. Experimental verification shows that the simulation results are highly consistent with the experimental verification results, which shows that the simulation calculation method has high accuracy and applicability.

[0041] Please refer to Figure 1 and Figure 2 , Figure 1 The simulation method flow chart of the present invention is shown. Figure 2 Schematic diagram of modeling a mask model; specifically, the following steps are included:

[0042] S1. Establishing a mask simulation model based on preset initial conditions;

[0043] Among them, the mask simulation model is designed and established using Monte Carlo simulation software; the initial conditions include the structure of the mask, the material and thickness of each layer structure, and the structure of the mask from bottom to top includes a base layer 1, a composite absorption layer and a resist layer 5.

[0044] Specifically, in step S1, the material of the base layer can be any one of SiO2, soda glass, borosilicate glass or sapphire; more preferably, in this embodiment, the base layer is made of SiO2.

[0045] The composite absorption layer may include a first absorption layer 2 and a second absorption layer 3. The composite absorption layer has a designed thickness of 40-80 nm. In this embodiment, the composite absorption layer preferably has a thickness of 50 nm. Both the first absorption layer 2 and the second absorption layer 3 are metal film layers. The material of the first absorption layer is selected from any one of Cr, Ta, and Mo. The thickness of the first absorption layer is in the range of 5-45 nm. The material of the second absorption layer is selected from any one of Cr, Ta, and Mo. The thickness of the second absorption layer is in the range of 5-45 nm. The second absorption layer is made of a different material than the first absorption layer.

[0046] The material of the resist layer 5 can be any one of polymethyl methacrylate (PMMA), ZEP brand series electron beam photoresist and HSQ (Hydrogen Silses quioxane).

[0047] PMMA, in particular, has low sensitivity (high dose threshold), high contrast, and excellent development properties (commonly used in MIBK:IPA solutions) in simulations. Among the Zeon Electron Beam Resist (ZEP) series, ZEP520A (and its diluted version, ZEP520A-7) is widely used. Its chemical nature is methyl methacrylate-α-methyl chloroacrylate copolymer, dissolved in organic solvents such as toluene or xylene. HSQ is an inorganic negative-tone electron beam resist. Currently, HSQ offers one of the highest resolutions, achieving line widths <5nm. Its primary component is a caged siloxane structure.

[0048] In this embodiment, the material of the resist layer 5 is preferably polymethyl methacrylate (PMMA). The areas of the resist exposed by the electron beam increase in solubility in the developer and are dissolved away, forming a structure identical to the electron beam scan pattern. The mask structure also includes a hard mask layer 4, which is disposed between the composite absorber layer and the resist layer. Hard mask layer 4 is preferably made of SiO2, Si3N4, or TiN. In this embodiment, hard mask layer 4 is preferably made of SiO2.

[0049] S2. Forming a plurality of mask samples by combining different characteristic parameters of the composite absorption layer; wherein the characteristic parameters include the absorption layer material and the absorption layer thickness.

[0050] In this embodiment, specifically, the design of the composite absorption layer can include: Cr / Ta, Gr / Mo and Ta / Mo according to the combination type of metal elements; each of the above three types includes the following types: in the Cr / Ta combination, there are two combination forms: the Cr film is in the first layer and the Ta layer is in the second layer, and the Ta film is in the first layer and the Cr layer is in the second layer; similarly, in the Gr / Mo combination, there are two combination forms: the Cr film is in the first layer and the Mo film is in the second layer, and in the Ta / Mo combination, there are two combination forms: the Ta film is in the first layer and the Ta layer is in the second layer.

[0051] Furthermore, based on the above classification settings, the thickness ratio is set in a gradient, and the specific settings are shown in the following Table 1-6:

[0052] Table 1 Film thickness combination table of Cr / Ta composite absorption layer (Cr film in the first layer)

[0053]

[0054] Table 2 Film thickness combination table of Cr / Ta composite absorption layer (Cr film in the second layer)

[0055]

[0056] Table 3 Film thickness combination table of Gr / Mo composite absorption layer (Cr film in the first layer)

[0057]

[0058] Table 4 Film thickness combination table of Gr / Mo composite absorption layer (Cr film in the second layer)

[0059]

[0060] Table 5 Film thickness combination table of Ta / Mo composite absorption layer (Ta film in the first layer)

[0061]

[0062] Table 6 Film thickness combination table of Ta / Mo composite absorption layer (Ta film in the second layer)

[0063]

[0064] Several different composite absorption layer combinations were designed according to Tables 1 to 6, and several mask samples were formed while keeping other parameters unchanged.

[0065] S3. Perform electron beam backscattered electron simulation calculations on several mask samples using the mask simulation model, select mask samples with concentrated backscattered electron energy, and use their corresponding characteristic parameters as preferred mask samples.

[0066] In step S3 , the parameters of the electron beam backscattered electron simulation calculation include: the thickness of the composite absorption layer, the thickness of the resist layer, the electron beam energy, the beam spot size and the number of simulated electron steps.

[0067] The electron beam backscattered electron simulation calculation is performed using CASINO software. The backscattered electron energy distribution data of different mask samples are obtained by calculation, and the preferred mask sample is screened based on the backscattered electron energy distribution data.

[0068] Specifically, in this embodiment, the calculation parameters are shown in Table 7: the total height of the composite absorption film layer is set to 50 nm, the electron beam gel thickness is set to 100 nm, the electron beam energy is set to 125 KeV, the beam spot size is set to 3 nm, and the number of simulated electron steps is set to 100,000 steps.

[0069] Table 7 Simulation calculation parameter information

[0070] substrate Composite absorbent layer PMMA Electron beam energy Simulated electronic steps electron beam spot <![CDATA[SiO2]]> 50nm 100nm 125KeV 100000 3nm

[0071] The simulation results of electron scattering are as follows Figure 3 、 Figure 4 shown. Figure 3 is the electron scattering trajectory diagram, Figure 4 is the short-range electron scattering trajectory diagram. Figure 3-Figure 4 The electron scattering motion trajectory shown in the figure can be used to preliminarily determine the distance and distribution of the scattered electrons from the incident center. Among them, the short-range electron scattering trajectory is the electron distribution close to the incident center.

[0072] By analyzing the results and focusing on the energy distribution of backscattered electrons, the energy distribution of backscattered electrons under different combinations of metal composite absorption films is shown as follows: Figures 5 to 10 As shown in Figure 1, the backscattered electron energy distribution diagram mainly describes the statistical distribution of the number of backscattered electrons escaping from the sample surface as their kinetic energy (or energy loss) changes. The horizontal axis is usually the electron energy (E) or normalized energy (E / E0), and the vertical axis is the electron count rate or relative intensity.

[0073] In order to accurately correct the proximity effect, the energy point spread function of the electron beam (including incident electrons, forward scattered electrons, backscattered electrons, and secondary electrons) deposited in the resist must be quantitatively modeled.

[0074] The BSE energy distribution is one of the key inputs for its modeling. It determines the range and shape of the "tail" of the BSE energy deposition in space (usually approximated by a Gaussian function or the superposition of multiple Gaussian functions). The long-range tail contributed by high-energy BSE is particularly important.

[0075] Monte Carlo simulation (such as CASINO, MCSe, etc.) can be used to calculate the BSE energy distribution and spatial distribution under a specific E0 and material (mask structure) combination, thereby constructing a more accurate mask structure model.

[0076] The backscattered electron energy distribution in electron beam direct writing reveals the statistical characteristics of the energy of the incident electrons that escape in the form of BSE after being scattered within the sample. Its core characteristics include:

[0077] High-energy platform close to E0: originates from shallow large-angle elastic scattering, has a long range, and is the main driving force of the long-range proximity effect.

[0078] The peak in the medium energy region (~0.3E0-0.7E0): originates from multiple scattering, has the largest number, medium range, and contributes to the medium-range proximity effect.

[0079] Low-energy tail close to 0eV: originates from deep multiple scattering or near-surface energy depletion, has a short range, and contributes to local exposure.

[0080] From the above backscattered electron energy distribution diagram, we can see that:

[0081] The calculation results of the composite absorption layer mask show that: in the Cr-Ta combination, 45nm Cr film and 5nm Ta film are better;

[0082] In the Ta-Cr combination, 5nm Ta film and 45nm Cr film are better;

[0083] On the one hand, it can be seen that when the Ta layer is on top, the backscattered electron energy is closer to the incident point and the energy is more concentrated; while when the Cr layer is on top, the backscattered electron energy is more dispersed and farther away from the incident point.

[0084] On the other hand, the maximum energy of backscattered electrons when the Cr layer is on top is lower than that when the Ta layer is on top. It can be seen that the Cr-Ta arrangement is more likely to absorb the energy of backscattered electrons.

[0085] In the Cr-Mo combination, a 30nm Cr film and a 20nm Mo film are better; in the Mo-Cr combination, a 10nm Mo film and a 40nm Cr film are better.

[0086] From the energy distribution diagram, it can be seen that the maximum energy of backscattered electrons in the Cr-Mo double-film structure is lower than that in the Cr-Ta and Ta-Mo structures, and the distance to the incident center is closer, which indicates that the combined film structure can better suppress the generation of backscattered electrons and make the energy more concentrated.

[0087] Further preferably, in this embodiment, the method further includes step S4: subjecting the selected preferred mask samples to electron beam direct writing experimental verification respectively to determine the optimal composite absorption layer mask structure, and using the optimal composite absorption layer mask structure to prepare the mask.

[0088] Specifically, by comparing the energy distribution of backscattered electrons near the beam spot, the performance of the masks of the following two groups of composite absorption layer structures with relatively concentrated energy were experimentally verified.

[0089] The following describes the details in conjunction with specific embodiments.

[0090] Example 1:

[0091] This embodiment discloses a composite absorption layer mask, the film layers of which are composed from bottom to top of: a SiO2 base layer, a composite absorption layer (the first absorption layer is a Cr film with a thickness of 30nm, and the second absorption layer is a Mo film with a thickness of 20nm), a SiO2 hard mask layer of 10nm, and a polymethyl methacrylate PMMA resist layer of 100nm.

[0092] Example 2:

[0093] This embodiment discloses a composite absorption layer mask, the film layers of which are composed from bottom to top of: a SiO2 base layer, a composite absorption layer (the first absorption layer is a Mo film with a thickness of 10nm, and the second absorption layer is a Cr film with a thickness of 40nm), a SiO2 hard mask layer of 10nm, and a polymethyl methacrylate PMMA resist layer of 100nm.

[0094] In addition, two control groups were set up, namely Comparative Example 1 and Comparative Example 2.

[0095] Comparative Example 1:

[0096] This comparative example discloses a single-layer absorption layer mask, the film layers of which are composed from bottom to top: SiO2 base layer, single-layer absorption layer (the first absorption layer is Cr film, thickness 50nm), SiO2 material hard mask layer 10nm, polymethyl methacrylate PMMA resist layer 100nm.

[0097] Comparative Example 2:

[0098] This comparative example discloses a single-layer absorption layer mask, the film layers of which are composed from bottom to top: SiO2 base layer, single-layer absorption layer (the first absorption layer is Mo film, with a thickness of 50nm), SiO2 material hard mask layer of 10nm, and polymethyl methacrylate PMMA resist layer of 100nm.

[0099] The four groups of samples of Examples 1-2 and Comparative Examples 1-2 were subjected to the same process for coating, electron beam direct writing, and development. The results are summarized in Table 8:

[0100] Table 8 shows the CD and LER test data of the mask structure of each single-layer film and composite absorption layer based on the electron microscope images.

[0101] Table 8 CD and LER test data of mask structure

[0102]

[0103] from Figures 11 to 14 From the development results, it can be seen that under the fourth group of Cr-40nm-Mo-10nm composite absorption layer structure, the line edge roughness (LER) of each resolution pattern after electron beam direct writing development is lower than that of the single-layer film, indicating that the composite absorption layer structure determined by the electron beam simulation method reduces the generation of short-range backscattered electrons, makes the electron beam energy more concentrated, and the periodic line pattern more uniform, thereby improving the accuracy of electron beam direct writing, which is highly consistent with the simulation results.

[0104] By building a model through simulation experiments, varying the absorption layer structure, performing irradiation, and analyzing the simulation results to identify the optimal absorption layer structure, a mask with better performance can be produced. This solution uses Monte Carlo simulation to design a multilayer metal film structure to reduce backscattered electrons, thereby minimizing the proximity effect and improving the accuracy of electron beam direct writing.

[0105] The above description is only 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 in the scope of protection of the present invention.

Claims

1. An electron beam simulation method based on a composite absorption layer, characterized in that: The steps include: S1. Establishing a mask simulation model based on preset initial conditions; wherein the initial conditions include the structure of the mask, the materials and thicknesses of each layer structure, and the structure of the mask from bottom to top includes a base layer, a composite absorption layer, and a resist layer; S2. Forming a plurality of mask samples by combining different characteristic parameters of the composite absorption layer; wherein the characteristic parameters include the absorption layer material and the absorption layer thickness; S3. Performing electron beam backscattered electron simulation calculations on a plurality of mask samples using the mask simulation model, screening out mask samples with concentrated backscattered electron energy, and using their corresponding characteristic parameters as preferred mask samples.

2. The electron beam simulation method based on the composite absorption layer according to claim 1, characterized in that: In step S1 , the composite absorption layer includes a first absorption layer and a second absorption layer from bottom to top, and the thickness of the composite absorption layer is designed to be 40-80 nm.

3. The electron beam simulation method based on the composite absorption layer according to claim 1, characterized in that: The material of the base layer is any one of SiO2, soda glass, borosilicate glass or sapphire; the structure of the mask also includes a hard mask layer, which is arranged between the composite absorption layer and the resist layer, and the material of the hard mask layer is any one of SiO2, Si3N4 or TiN; the material of the resist layer is any one of polymethyl methacrylate, ZEP or HSQ.

4. The electron beam simulation method based on the composite absorption layer according to claim 2, characterized in that: In step S2, the first absorption layer is a metal film layer, the material of the first absorption layer is selected from any one of Cr, Ta, and Mo, and the thickness of the first absorption layer is in the range of 5-45 nm.

5. The electron beam simulation method based on the composite absorption layer according to claim 4, characterized in that: In step S2, the second absorption layer is a metal film layer, the material of the second absorption layer is selected from any one of Cr, Ta, and Mo, and the thickness of the second absorption layer is in the range of 5-45 nm; wherein the material of the second absorption layer is different from that of the first absorption layer.

6. The electron beam simulation method based on the composite absorption layer according to claim 1, characterized in that: In step S1, the mask simulation model is designed and established using Monte Carlo simulation software.

7. The electron beam simulation method based on the composite absorption layer according to claim 1, characterized in that: In step S3, the parameters of the electron beam backscattered electron simulation calculation include: composite absorption layer thickness, resist layer thickness, electron beam energy, beam spot size and simulated electron step number.

8. The electron beam simulation method based on the composite absorption layer according to claim 7, characterized in that: The electron beam backscattered electron simulation calculation is performed using CASINO software, and backscattered electron energy distribution data of different mask samples are obtained by calculation. The preferred mask sample is screened based on the backscattered electron energy distribution data.

9. The electron beam simulation method based on a composite absorption layer according to any one of claims 1 to 8, characterized in that: The method further includes step S4: performing electron beam direct writing experiments on the selected preferred mask samples to determine the optimal composite absorption layer mask structure, and using the optimal composite absorption layer mask structure to prepare the mask.

10. A composite absorption layer mask, characterized in that: The composite absorption layer mask is prepared by using a preferred mask sample determined by an electron beam simulation method based on a composite absorption layer according to any one of claims 1 to 9 and an optimal composite absorption layer mask structure verified by electron beam direct writing experiments.

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