Quantitative analysis method and system for electron beam photoresist residue based on edge detection

Abstract

The present invention relates to a method and system for quantitatively analyzing electron beam photoresist residue based on edge detection. The method uses a scanning electron microscope to photograph a photoresist structure after exposure and development. The original image with photoresist structural features obtained by the scanning electron microscope is segmented into a photoresist structure region and a developed region using an edge detection algorithm. The average grayscale of each region is calculated to obtain a quantitative evaluation result of the residual adhesive between the structures. Compared with the prior art, the present invention quantifies the residual adhesive in the electron beam photoresist structure, allowing intuitive comparison of photoresist exposure results obtained with different exposure parameters. This facilitates precise control of electron beam lithography exposure parameters and has the potential to improve the efficiency and yield of electron beam lithography processing.

Description

Technical Field

[0001] The present invention relates to the field of electron beam lithography defect detection, and in particular to an electron beam photoresist residual quantitative analysis method and system based on edge detection. Background Art

[0002] Electron beam lithography is a process that uses electromagnetic lenses to focus the electron beam emitted from an electron gun, forming a high-resolution Gaussian beam spot, which is then used to expose the photoresist on a substrate. It is a flexible, highly automated, maskless exposure technology. Due to its extremely small electron beam spot size, it can produce patterns with feature sizes below 10 nanometers. However, due to collisions and scattering of electrons in the photoresist and substrate, some electrons enter non-exposed areas, resulting in residual photoresist residues in areas that should have been developed cleanly. This can seriously impact subsequent micro-nanofabrication processes and ultimately affect device performance.

[0003] Due to the extremely small scale of electron beam lithography, high-precision and high-sensitivity detection methods are required. Current methods for detecting residual resist in electron beam lithography generally rely on qualitative inspection of the sample surface using a scanning electron microscope to determine the presence of residual resist, allowing for iterative optimization of exposure parameters. However, this method cannot accurately quantify the residual resist results of electron beam lithography, making it difficult to compare residual resist results obtained with different exposure parameters, which reduces the efficiency of iterative optimization of exposure parameters. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for quantitative analysis of electron beam photoresist residues based on edge detection. On the basis of existing residual detection means, a scanning electron microscope and an edge detection algorithm are combined to accurately quantify the electron beam photoresist residues after exposure.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A quantitative analysis method for electron beam photoresist residue based on edge detection is disclosed. The method uses a scanning electron microscope to photograph the exposed and developed photoresist structure, and then divides the original image with photoresist structural features obtained by the scanning electron microscope into the photoresist structure area and the developed area through an edge detection algorithm. The average grayscale of the two areas is calculated respectively to obtain the quantitative evaluation result of the residual between the structures.

[0007] The method comprises the following steps:

[0008] Step 1: Prepare the substrate for electron beam lithography and clean and dry it;

[0009] Step 2: Spin-coat the required electron beam photoresist evenly on the substrate and pre-bake according to the corresponding process time;

[0010] Step 3: Expose the pattern corresponding to the desired photoresist structure using an electron beam lithography device;

[0011] Step 4: Develop and fix the exposed structure according to the corresponding process of the photoresist used;

[0012] Step 5: photographing the exposed photoresist structure under a scanning electron microscope to obtain a scanning electron microscope original image containing the photoresist structure features;

[0013] Step 6: Use the edge segmentation algorithm to segment the photoresist structure area and the developed area of ​​the original image, and calculate the average grayscale of the two areas in the structure respectively. The ratio of the grayscale value of the developed area to the grayscale value of the photoresist structure area is used as the result of quantitative evaluation of the residual glue between the structures.

[0014] The substrate is a silicon wafer.

[0015] The photoresist includes positive photoresist and negative photoresist for electron beam lithography.

[0016] The layout corresponding to the photoresist structure is drawn using L-edit, K-Layout or CAD software.

[0017] When taking multiple photos of the photoresist structure, it should be ensured that the imaging brightness and contrast of the scanning electron microscope are not changed during the shooting.

[0018] The ratio of the grayscale value of the developed area to the grayscale value of the photoresist structure area is used as the quantitative evaluation result of the residual adhesive between the structures:

[0019] Let the gray value of the developed area after edge segmentation be G1, and the gray value of the photoresist structure area be G2. Then the calculation expression of the residual glue amount R in the corresponding area of ​​the image is:

[0020]

[0021] An electron beam photoresist residual quantitative analysis system based on edge detection comprises an electron beam photolithography device, a scanning electron microscope and an image analysis module, and is used to implement the method described above.

[0022] The electron beam lithography apparatus includes a first electron gun, an electron optical system and a first sample stage.

[0023] The scanning electron microscope includes a second electron gun, an electron lens system, a second sample stage, and a detector.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention significantly improves the efficiency of optimizing electron beam exposure parameters in research and development, making it easier to control residual resist in electron beam lithography and improving production efficiency and yield. This method is applicable to most mainstream positive and negative electron beam lithography resists and has potential applications in micro-nano manufacturing, particularly in high-precision device manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart of the method of the present invention;

[0027] Figure 2 Schematic diagram of preparing photoresist structure samples for electron beam lithography;

[0028] Figure 3 Schematic diagram of edge segmentation of electron microscope images of sample structures. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0030] This embodiment provides a quantitative analysis method for electron beam photoresist residues based on edge detection. The method uses a scanning electron microscope to photograph the photoresist structure after exposure and development, and divides the original image with photoresist structure features obtained by the scanning electron microscope into a photoresist structure area and a developed area through an edge detection algorithm, and calculates the average grayscale of the two areas respectively to obtain a quantitative evaluation result of the residual glue between the structures.

[0031] Specifically, such as Figure 1 As shown, the method includes the following steps:

[0032] Step 1: Prepare the silicon wafer substrate for electron beam lithography and clean and dry it.

[0033] Step 2: Spin-coat the required HSQ or PMMA electron beam photoresist evenly on the substrate and pre-bake according to the corresponding process time.

[0034] Step 3: Draw the required photoresist structure layout in software such as L-edit, K-Layout, CAD, etc. and convert it into a gpf format file that can be recognized by the electron beam lithography equipment. Use the electron beam lithography device to expose according to the layout corresponding to the required photoresist structure.

[0035] Step 4: Develop and fix the exposed structure according to the corresponding process of the photoresist used.

[0036] Step 5: Photograph the exposed photoresist structure under a scanning electron microscope to obtain an original scanning electron microscope image containing the photoresist structure features; when taking multiple photos of the photoresist structure, it should be ensured that the imaging brightness and contrast of the scanning electron microscope are not changed during the shooting.

[0037] Step 6: Use the edge segmentation algorithm to segment the photoresist structure area and the developed area of ​​the original image, and calculate the average grayscale of the two areas in the structure respectively. The grayscale value of the developed area (non-exposed area) after edge segmentation is recorded as G1, and the grayscale value of the photoresist structure area (exposed area) is G2. The calculation expression of the residual glue amount R in the corresponding area of ​​the image is:

[0038]

[0039] This embodiment also provides an edge-detection-based quantitative analysis system for electron beam photoresist residues, comprising an electron beam lithography apparatus, a scanning electron microscope, and an image analysis module, for implementing the aforementioned method. The electron beam lithography apparatus comprises a first electron gun, an electron optical system, and a first sample stage; the scanning electron microscope comprises a second electron gun, an electron lens system, a second sample stage, and a detector.

[0040] Based on the above method, combined with Figure 2 This embodiment provides a specific process for preparing an electron beam lithography structure. The detailed steps are as follows:

[0041] Step 1: Obtain a substrate coated with electron beam photoresist; the substrate is a 500 μm thick silicon wafer; the electron beam photoresist is HSQ with a concentration of 2%. Figure 2 As shown in step ①, the substrate is placed on a spin coater, the substrate is fixed by vacuum adsorption, 0.5 ml of photoresist is sucked up with a pipette and transferred to the substrate, and the photoresist is spin-coated at a speed of 3 kr / min for 1 minute. The photoresist thickness is about 40 nm. After spin coating, it is placed on a hot plate at 180°C and baked for 3 minutes.

[0042] Step 2: Use AutoCAD software to draw the required photoresist structure layout. The structure layout used in this embodiment is a ring grating structure with a diameter of 200 μm, a duty cycle of 0.5, and a line width of 30 nm.

[0043] Step 3: Convert the drawn layout file into a gpf file and import it into the control computer of the electron beam lithography machine, and use the electron beam for exposure, such as Figure 2 The high voltage is 100kV and the exposure dose is 2000μC / cm 2 , the exposure beam current is 1nA. After the exposure is completed, the substrate is taken out for development-fixing work, such as Figure 2The developer is a 2.38% TMAH solution, developed in a 45°C waterbath, and fixed at 20°C with deionized water. The developing time is 4 minutes, and the fixing time is 30 seconds. Finally, the sample is dried with a nitrogen gun to obtain a photoresist structure sample.

[0044] Based on the photoresist structure obtained above, the following residual photoresist quantitative analysis and detection are performed:

[0045] Step 4: Photograph the exposed HSQ photoresist structure under a scanning electron microscope. Use a high voltage of 2kV and a magnification of 60kX when photographing the photoresist structure. Adjust the focal length and aberration and astigmatism during shooting, and align the photoresist structure under the field of view to obtain a scanning electron microscope photograph of the photoresist containing structural features.

[0046] Step 5: Figure 3 As shown in the figure, the edge segmentation algorithm is used to segment the photoresist structure area and the developed area. The grayscale value of the developed area after edge segmentation is G1, and the grayscale value of the photoresist structure area is G2. Then, the residual glue amount R in the corresponding area of ​​the image can be calculated:

[0047]

[0048] in, Figure 3 In the figure, ① is the original image obtained by SEM, ② is the photoresist structure area obtained by algorithm segmentation, and ③ is the developed area.

[0049] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A quantitative analysis method for electron beam photoresist residue based on edge detection, characterized in that: The method uses a scanning electron microscope to photograph the exposed and developed photoresist structure, and then uses an edge detection algorithm to segment the original image with photoresist structural features obtained by the scanning electron microscope into a photoresist structure area and a developed area. The average grayscale of the two areas is calculated to obtain a quantitative evaluation result of the residual photoresist between the structures. The method comprises the following steps: Step 1: Prepare the substrate for electron beam lithography and clean and dry it; Step 2: Spin-coat the required electron beam photoresist evenly on the substrate and pre-bake according to the corresponding process time; Step 3: Expose the pattern corresponding to the desired photoresist structure using an electron beam lithography device; Step 4: Develop and fix the exposed structure according to the corresponding process of the photoresist used; Step 5: photographing the exposed photoresist structure under a scanning electron microscope to obtain a scanning electron microscope original image containing the photoresist structure features; Step 6: Use the edge segmentation algorithm to segment the photoresist structure area and the developed area of ​​the original image, and calculate the average grayscale of the two areas in the structure respectively. The ratio of the grayscale value of the developed area to the grayscale value of the photoresist structure area is used as the result of quantitative evaluation of the residual glue between the structures: Let the gray value of the developed area after edge segmentation be G1, and the gray value of the photoresist structure area be G2. Then the calculation expression of the residual glue amount R in the corresponding area of ​​the image is:

2. The method for quantitatively analyzing residual electron beam photoresist based on edge detection according to claim 1, wherein: The substrate is a silicon wafer.

3. The method for quantitatively analyzing electron beam photoresist residue based on edge detection according to claim 1, wherein: The photoresist includes positive photoresist and negative photoresist for electron beam lithography.

4. The method for quantitatively analyzing electron beam photoresist residue based on edge detection according to claim 1, wherein: The layout corresponding to the photoresist structure is drawn using L-edit, K-Layout or CAD software.

5. The method for quantitatively analyzing electron beam photoresist residue based on edge detection according to claim 1, wherein: When taking multiple photos of the photoresist structure, ensure that the imaging brightness and contrast of the scanning electron microscope are not changed during the shooting.

6. An electron beam photoresist residual quantitative analysis system based on edge detection, characterized in that: The method comprises an electron beam lithography device, a scanning electron microscope and an image analysis module, and is used to implement the method according to any one of claims 1 to 5.

7. The electron beam photoresist residue quantitative analysis system based on edge detection according to claim 6, characterized in that: The electron beam lithography apparatus includes a first electron gun, an electron optical system and a first sample stage.

8. The electron beam photoresist residue quantitative analysis system based on edge detection according to claim 6, characterized in that: The scanning electron microscope includes a second electron gun, an electron lens system, a second sample stage, and a detector.

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