A hard x-ray band high-resolution test card and a preparation method thereof

Abstract

The present application belongs to the field of micro-nano processing and X-ray optical testing technology, and particularly relates to a high-resolution test card in hard X-ray band and a preparation method thereof. The test card adopts electron beam lithography combined with proximity effect correction technology to prepare an HSQ template pattern, forms a Siemens star structure with a minimum line width of 10 nm and a height of 500 nm, and then covers a metal working layer on the template surface through atomic layer deposition technology. The HSQ template pattern has a duty cycle less than 1, effectively improving the aspect ratio of the pattern. The covering of the metal working layer doubles the line density of the final pattern. The present application breaks through the resolution limit of the traditional test card, solves the problem of preparation of high-aspect-ratio nano structures, and has simple and reliable process, and is suitable for resolution calibration of absorption contrast and phase contrast imaging systems in hard X-ray band, thereby providing key technical support for performance evaluation of high-end X-ray optical systems.

Description

Technical Field

[0001] This invention belongs to the field of X-ray optical element design and manufacturing technology, specifically relating to a high-resolution test card in the hard X-ray band and its preparation method. Background Technology

[0002] In fields such as hard X-ray microscopy, photolithography, and synchrotron radiation applications, accurate evaluation of the spatial resolution of optical systems is crucial. High-resolution test charts are key tools for this evaluation, and their performance directly determines the accuracy and reliability of resolution measurements.

[0003] Currently, high-resolution test cards used in the hard X-ray band mainly face the following technical bottlenecks:

[0004] (1) Resolution limitation: Traditional optical lithography and electron beam lithography technologies are limited by factors such as proximity effect and development process, making it difficult to stably prepare test patterns with linewidths less than 20 nm. In particular, for complex Siemens star patterns, the continuous variation of their radial linewidth places extremely high demands on process control.

[0005] (2) Aspect Ratio Limitation: As resolution increases, the linewidth of the test pattern decreases continuously. To maintain sufficient mechanical strength and imaging contrast, a large structural height is required. Traditional processes are prone to collapse and deformation when preparing high aspect ratio nanostructures, especially in the hard X-ray band, where sufficiently thick functional materials are needed to provide adequate absorption or phase contrast.

[0006] (3) Material limitations: Existing test cards mostly use a single material system, such as directly etching on a silicon substrate or forming patterns by metal stripping. These methods have limited contrast in the hard X-ray band and it is difficult to balance structural accuracy and mechanical stability.

[0007] (4) Process complexity: Traditional metal test card fabrication requires transferring photoresist patterns to the metal layer through complex etching or stripping processes. These process steps are prone to introducing problems such as dimensional deviation and edge roughness, especially at the 10nm scale, where the process window is extremely narrow.

[0008] Although electron beam lithography theoretically possesses nanoscale processing capabilities, the proximity effect in practical applications severely limits its resolution and pattern fidelity. Existing proximity effect correction methods often struggle to balance correction accuracy and computational complexity, especially for complex patterns like Siemens stars with continuously varying characteristics, where existing correction algorithms have limited effectiveness. Summary of the Invention

[0009] The purpose of this invention is to provide a high-resolution test card in the hard X-ray band and its preparation method. This invention prepares an HSQ template by combining electron beam lithography with proximity effect correction, and then combines atomic layer deposition technology to cover the metal working layer, thereby realizing the preparation of a Siemens star test card with a linewidth of 10 nm and a height of 500 nm.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] This invention provides a method for preparing a high-resolution test card in the hard X-ray band, comprising the following steps:

[0012] (1) A hydrogen silsesquioxane (HSQ) template pattern is prepared on a substrate by electron beam lithography combined with proximity effect correction. The template pattern is a Siemens star pattern with a minimum linewidth of 10 nm and a structural height of 500 nm.

[0013] (2) The surface of the HSQ template pattern obtained in step (1) is covered with a metal working material layer; wherein the duty cycle of the HSQ template pattern is less than 1, and the coverage of the metal working material layer makes the line density of the final test card pattern double relative to the HSQ template pattern.

[0014] In this invention, the metal working material layer in step (2) is any one of platinum, gold or tungsten.

[0015] In this invention, the duty cycle of the HSQ template pattern in step (2) is 0.3-0.7.

[0016] In this invention, the thickness of the metal working material layer in step (2) is 5 nm-50 nm.

[0017] A high-resolution hard X-ray band test card is obtained using the preparation method of the present invention. The test card includes a substrate, an HSQ template pattern layer, and a metal working material layer, wherein: the substrate is provided with an HSQ template pattern layer, and the surface of the HSQ template pattern layer is covered with a metal working material layer; the HSQ template pattern layer contains a Siemens star pattern with a minimum linewidth of 10 nm and a height of 500 nm.

[0018] A high-resolution test card for the hard X-ray band is obtained using the method of this invention. This test card serves as a resolution testing element for an imaging system, which is a hard X-ray microscopy imaging system.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) Breakthrough resolution: By combining electron beam lithography with precise proximity effect correction, Siemens star pattern fabrication with a minimum linewidth of 10nm was achieved, breaking through the resolution limit of traditional test cards.

[0021] (2) Excellent aspect ratio: Using HSQ as template material and combined with optimized process parameters, a structure height of 500nm was achieved, with an aspect ratio of 50:1, providing sufficient contrast for hard X-ray imaging.

[0022] (3) Process innovation: The process route of combining HSQ template with atomic layer deposition avoids the traditional metal etching or stripping steps, greatly simplifies the process flow and improves the preparation success rate.

[0023] (4) Performance improvement: The small duty cycle design of the HSQ template is conducive to achieving a larger aspect ratio graphic, while the metal working material covered by ALD doubles the line density, effectively improving the performance of the test card.

[0024] (5) Wide applicability: This test card is suitable for absorption contrast imaging and phase contrast imaging in the hard X-ray band and can be widely used for resolution calibration of systems such as synchrotron radiation and X-ray microscopes. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the HSQ template in Example 1.

[0026] Figure 2 These are scanning electron microscope images of the HSQ template feature dimensions measured in Example 1.

[0027] Figure 3 This is a scanning electron microscope image of the HSQ template in Example 1 after 10 nm of platinum was deposited using atomic layer deposition.

[0028] Figure 4 This is the imaging result of placing the high-resolution test card as a target under a scanning X-ray microscope in Example 1.

[0029] Figure 5 This is a scanning electron microscope image of the HSQ template when the duty cycle is too high in Example 2.

[0030] Figure 6 This is a scanning electron microscope image of the HSQ template in Example 2 when the duty cycle is too high and the exposure dose is too large.

[0031] Figure 7 This is a scanning electron microscope image of the HSQ template when the duty cycle is too low in Example 2. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the examples. Any simple changes made to the calculation parameters in the embodiments fall within the protection scope of the present invention.

[0033] Example 1: Preparation of the test card and its imaging as a target in an X-ray scanning microscope

[0034] (1) Substrate treatment: Use silicon nitride diaphragm windows with a window size of 1 mm × 1 mm, clean and dry;

[0035] (2) HSQ spin coating: HSQ electron beam photoresist is spin coated on the window surface, and the photoresist thickness is controlled to be 500 nm by optimizing the rotation speed and time;

[0036] (3) Pre-baking: Pre-baking on a hot plate at 150°C for 4 minutes to ensure that the solvent evaporates completely;

[0037] (4) Electron beam lithography: A 100 keV electron beam lithography system was used, combined with a dose-modulated forward scattering proximity effect correction algorithm, to directly write the Siemens star pattern. The outermost diameter of the pattern was 10 μm, and the minimum linewidth was designed to be 10 nm. The exposure dose was adjusted in real time according to the pattern density;

[0038] (5) Development: Develop with 25% tetramethylammonium hydroxide (TMAH) solution for 60 seconds to form the final HSQ template pattern. The electron scanning microscope image is shown below. Figure 1 As shown, the structure is a radial concentric circle, with the line width gradually increasing from the inside to the outside, to facilitate different imaging resolution tests. Feature size measurements are as follows. Figure 2 As shown, the tip of the center line reaches a linewidth of approximately 7 nm.

[0039] (6) Atomic Layer Deposition (ALD): A 10 nm thick platinum layer was deposited on the HSQ template surface using an ALD system. The deposition temperature was 250°C, and the precursors were methylcyclopentadienylplatinum (MeCpPtMe3) and oxygen. After fabrication, the sample was photographed using a scanning electron microscope. The final electron microscope image of the sample is shown below. Figure 3 As shown, a layer of Pt metal can be clearly seen covering the surface.

[0040] (7) The prepared X-ray test card was used as an imaging target and placed in a scanning X-ray microscope for imaging. The imaging results are as follows: Figure 4 As shown, the periodic structure of the image can be clearly seen.

[0041] Example 2: Comparison of different design parameters for HSQ templates

[0042] (1) Substrate treatment: Use silicon nitride diaphragm windows with a window size of 1 mm × 1 mm, clean and dry;

[0043] (2) HSQ spin coating: HSQ electron beam photoresist is spin coated on the window surface, and the photoresist thickness is controlled to be 500 nm by optimizing the rotation speed and time;

[0044] (3) Pre-baking: Pre-baking on a hot plate at 150°C for 4 minutes to ensure that the solvent evaporates completely;

[0045] (4) Electron beam lithography: A 100 keV electron beam lithography system was used, combined with a dose-modulated forward scattering proximity effect correction algorithm, to directly write the Siemens star pattern. The inner ring diameter of the Siemens star pattern was kept constant, while the number of radial lines was varied to achieve pattern exposure for Siemens star test cards with different duty cycles. The outermost diameter of the pattern was 10 μm, and the minimum linewidth was designed to be 10 nm. The exposure dose was adjusted in real time according to the pattern density.

[0046] (5) Development: Develop with 25% tetramethylammonium hydroxide (TMAH) solution for 60 seconds to obtain the HSQ template. Siemens star HSQ templates with different duty cycles were photographed using a scanning electron microscope, such as... Figure 5 , Figure 6 , Figure 7 As shown, where, Figure 5 The exposure and development results when the duty cycle is too high show that there is obvious adhesion between the structures and residual adhesive, which will affect the contrast of the image. Figure 6 For exposure and development results with excessively high duty cycle and excessive exposure dose, more residual adhesive can be seen between structures, which will seriously affect the contrast of the image. Figure 7 The low duty cycle, while resulting in sharp edges on the Siemens star structure and contributing to high imaging contrast, also leads to low signal-to-noise ratios during Fourier spectrum analysis after imaging, posing challenges for subsequent data processing. The results show that the HSQ template exhibits the best self-supporting performance and leaves no residue after development when the duty cycle is at most around 0.2.

Claims

1. A method for preparing a high-resolution test card in the hard X-ray band, characterized in that... Includes the following steps: (1) A hydrogen silsesquioxane (HSQ) template pattern is prepared on a substrate by electron beam lithography combined with proximity effect correction. The template pattern is a Siemens star pattern with a minimum linewidth of 10 nm and a structural height of 500 nm. (2) The surface of the HSQ template pattern obtained in step (1) is covered with a metal working material layer; wherein the duty cycle of the HSQ template pattern is less than 1, and the coverage of the metal working material layer makes the line density of the final test card pattern double relative to the HSQ template pattern.

2. The method for preparing a high-resolution test card in the hard X-ray band according to claim 1, characterized in that... The metal working material layer mentioned in step (2) is any one of platinum, gold or tungsten.

3. The method for preparing a high-resolution test card in the hard X-ray band according to claim 1, characterized in that... The duty cycle of the HSQ template pattern in step (2) is 0.3-0.

7.

4. The method for preparing a high-resolution test card in the hard X-ray band according to claim 1, characterized in that... The thickness of the metal working material layer in step (2) is 5 nm-50 nm.

5. A high-resolution test card for hard X-ray band obtained by the preparation method as described in claim 1, characterized in that... The test card includes a substrate, an HSQ template pattern layer, and a metal working material layer, wherein: the substrate has an HSQ template pattern layer, and the surface of the HSQ template pattern layer is covered with a metal working material layer; the HSQ template pattern layer contains a Siemens star pattern with a minimum linewidth of 10 nm and a height of 500 nm.

6. The application of a high-resolution hard X-ray band test card obtained by the preparation method as described in claim 1 as an imaging system, characterized in that... The test card serves as a resolution testing element.

7. The application according to claim 6, characterized in that, The imaging system is a hard X-ray microscopy imaging system.

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