Effects of Electron Beam Lithography Process Parameters on the Structure of Nanoscale Devices Across Three Substrate Materials

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript, Liu et al. investigate the effects of EBL process parameters on the structure of nanoscale devices across various substrate materials. The authors conduct a comprehensive experimental analysis to explore the impact of the charging effect and identify the narrow exposure dose windows necessary to achieve optimal pattern fidelity. Based on the results, they analyze the relationship between exposure dose and the width of the structure pattern after development. Additionally, they simulate the charge effect and propose strategies to mitigate its impact on different substrates. I would like to recommend this manuscript be accepted for publication in Photonics after addressing the following comments:

1.       The introduction section could provide more background on the current challenges and limitations of EBL when used on different substrate materials, particularly in terms of charging effects and their impact on pattern fidelity.

2.       While the results on the optimal exposure dose windows for different substrate materials are interesting, more discussion is needed on the implications of these findings for practical applications and future research directions.

3.       In the Abstract, the term “measurement results” is vague. Specify the metrics measured (e.g., linewidth deviation, sidewall steepness).

4.       In Section 3.3, the term “nitride silicon” is unconventional; replace with “silicon nitride” consistently.

 

5.       The figure refers to a “silicon oxide substrate,” but the section discusses silicon nitride. Clarify this discrepancy.

Author Response

Comments 1: The introduction section could provide more background on the current challenges and limitations of EBL when used on different substrate materials, particularly in terms of charging effects and their impact on pattern fidelity.

Response 1: Thanks for your suggestions. We agree that providing a more in-depth discussion of the current challenges and limitations of EBL on various substrate materials would strengthen the introduction. We revised the introduction to include a more comprehensive overview of the charging effects that occur during EBL, especially on insulating and semiconductor substrates, and how these effects impact the accuracy and precision of the lithographic patterns.

We add the following content (highlighted in red font) in the revised manuscript: “The impact of charging effects on pattern fidelity is multifaceted. In addition to beam deflection, charging can cause variations in exposure dose, leading to inconsistent feature sizes and edge roughness. These issues are particularly problematic for applications requiring high precision [18,19], such as the fabrication of photonic crystals, nanoscale sensors, or quantum devices [20,21].” (see the first paragraph in the second page).

Reference

• Kerim, T.A.; Thomas, K.; Aernout, C.Z.; Wilhelmus, S.M.; Carel, T.H.; Cornelis, W.H. Charge-induced Pattern Displacement in E-beam Lithography. Vac. Sci. Technol. B. 2019, 37, 051603.
• Ma, W.T.; Yao, K.P.; Zhong, X.Y.; Liu, J. Efficient Calcilation of Charging Effects in Electron Beam Lithography Using the SA-AMG. IEEE Electr. Device L.2024, 10, 3448504.
• Ding, Z.J.; Li, C.; Da, B.; Liu, J.W. Charging Effect Induced by Electron Beam Irradiation: a Review. Technol. Adv. Mat.2021, 22, 932-971.
• Zykov, V.M.; Neyman, D.A. Modeling of Surface-Volumetric Charging of a Dielectric Irradiated by Electrons with Energy Range from 6 to 30 keV. Phys+. 2024,6, 1857-1869.

Comments 2: While the results on the optimal exposure dose windows for different substrate materials are interesting, more discussion is needed on the implications of these findings for practical applications and future research directions.

Response 2: Thanks for your comments and suggestions. We recognize that discussing the practical implications and future research directions based on our findings would enhance the manuscript. We will expand the discussion section to include a more in-depth analysis of how the identified optimal exposure dose windows can guide the design and optimization of EBL processes. This will provide readers with a broader perspective on the significance and potential impact of our work.

We add the following content (highlighted in red font) in the revised manuscript: “Compare the dose windows of the three materials mentioned above. Insulating materials (e.g., glass, SOI) showed narrow dose windows that demand precise dose control to mitigate edge roughness caused by charge accumulation. Semiconducting materials (e.g., SiN) exhibited wider dose windows that enable the use of a broader range of doses to enhance resolution. In addition, insulating materials (e.g., sapphire, quartz) displayed similar narrow dose windows (e.g., 20–25 μC/cm²) [32] and conductive/semiconducting materials (e.g., Si, GaN) showed wider dose windows (e.g., 20–45 μC/cm²) that allow for higher doses [33]. These findings directly reduce trial-and-error costs in manufacturing processes, improving yield rates for photonic crystals or quantum dot devices. Furthermore, dose sensitivity disparities among materials are useful for the material selection and device design. In the future, leveraging substrate conductivity-dose window correlations will enable real-time feedback systems. Therefore, testing and finding the dose windows are helpful for optimizing EBL processes.” (see the last paragraph in page 9).

Reference

• Arat, K.T.; Zonnevylle, A.C.; Belic, N.; Hofmann, U.; Hagen, C.W. Electron beam lithography on curved or tilted surfaces: Simulations and experiments. Vac. Sci. Technol. B. 2019, 37, 051604.
• Brandt, P.; Belledent, J.; Tranquillin, C.; Figueiro, T.; Icard, B.; Wieland, M. Micro-Nanolith. MEM. 2014, 13, 031306.

Comments 3: In the Abstract, the term “measurement results” is vague. Specify the metrics measured (e.g., linewidth deviation, sidewall steepness).

Response 3:Thank you for pointing this out. The “measurement results” have been replaced with "the measurement results of line width" in the Abstract of the revised manuscript.

Comments 4: In Section 3.3, the term “nitride silicon” is unconventional; replace with “silicon nitride” consistently.

Response 4:Thank you for pointing this out. We have corrected the “nitride silicon” to be “silicon nitride” in the revised manuscript.

Comments 5: The figure refers to a “silicon oxide substrate,” but the section discusses silicon nitride. Clarify this discrepancy.

Response 5:Thank you for pointing this out. The caption errors in Figures 5 and 6 have been corrected to “silicon nitride substrate”.

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review your manuscript, "Effects of electron beam lithography process parameters on the structure of nanoscale devices across various substrate materials". Your study presents an interesting contribution to Photonics. I have provided comments and suggestions that I believe will help strengthen your manuscript. Please find the detailed feedback regarding the methodology, analysis, and presentation of results in the attached file. I suggest that one of the most important part to be improved is comparison of the presented results with other published paper on similar materials and resists.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

English could be improved. Please find my comments in the attached file.

Author Response

Comments 1: Please modify the title since you considered only 3 materials. The word “various” may be confusing for the reader.

Response 1: Thanks for your suggestion. We have revised the manuscript title to: “Effects of electron beam lithography process parameters on the structure of nanoscale devices across three substrate materials”.

Comments 2: Compare your results with others published for the same materials.

Response 2: Thanks for your suggestion. We acknowledge that comparing our results with those published for the same materials would greatly enhance the manuscript. However, we were unable to find published results that used the exact same materials, structures, and resist. Therefore, we enhanced the results section by adding a comparison of dose windows for similar substrate materials, providing readers with a broader perspective and aiding in the contextualization of our findings within the existing literature.

We add the following content (highlighted in red font) in the revised manuscript: “Compare the dose windows of the three materials mentioned above. Insulating materials (e.g., glass, SOI) showed narrow dose windows that demand precise dose control to mitigate edge roughness caused by charge accumulation. Semiconducting materials (e.g., SiN) exhibited wider dose windows that enable the use of a broader range of doses to enhance resolution. In addition, insulating materials (e.g., sapphire, quartz) displayed similar narrow dose windows (e.g., 20–25 μC/cm²) [32] and conductive/semiconducting materials (e.g., Si, GaN) showed wider dose windows (e.g., 20–45 μC/cm²) that allow for higher doses [33]. These findings directly reduce trial-and-error costs in manufacturing processes, improving yield rates for photonic crystals or quantum dot devices. Furthermore, dose sensitivity disparities among materials are useful for the material selection and device design. In the future, leveraging substrate conductivity-dose window correlations will enable real-time feedback systems. Therefore, testing and finding the dose windows are helpful for optimizing EBL processes.” (see the last paragraph in page 9).

Reference

• Arat, K.T.; Zonnevylle, A.C.; Belic, N.; Hofmann, U.; Hagen, C.W. Electron beam lithography on curved or tilted surfaces: Simulations and experiments. Vac. Sci. Technol. B. 2019, 37, 051604.
• Brandt, P.; Belledent, J.; Tranquillin, C.; Figueiro, T.; Icard, B.; Wieland, M. Micro-Nanolith. MEM. 2014, 13, 031306.

Comments 3: “silicon-on-insulator” Clarify which what insulator was used and geometry (layers thickness) of the structure.

Response 3: Thank you for pointing this out. We have clarified the structure of SOI substrates by specifying the layer thicknesses in the revised manuscript. We have added the following details: “The SOI substrates used in our study feature a top layer of 220nm silicon and an insulator layer of 2μm silicon oxide on a silicon substrate. This structural configuration is significant because when the electron beam strikes the photoresist, it causes localized charge accumulation. Although the surface silicon layer can conduct away some of the charge, the intervening insulating layer hinders the prompt dissipation of charge, leading to a potential difference between the photoresist and the substrate.” (see the first paragraph of Section 3.2).

Comments 4: Line 85: Clarify this: “... the sample were placed on a hot plate at 150°C, 150°C and 80°C for 1-2minutes.” Which temperature for which substrate material and which resist? Clarify also for which substrate material did you use the procedures described further in the paragraph.

Response 4: Thank you for pointing this out. We recognize the need for clarity regarding the pre-bake temperatures and the corresponding substrate materials and photoresists used. To address this, we have revised the manuscript to describe the preparation process of each photoresist separately and to specify which temperatures were used for which substrate materials.

We have modified the description of the pre-bake process as follows: “The spin coating speed was 4000 r/min for 60 seconds. Subsequently, the samples were placed on a hot plate for pre-bake. The pre-bake conditions and resulting thicknesses for each substrate and photoresist combination were as follows: the 679.03 layer on silicon oxide was pre-baked at 150°C for 60 seconds (thickness: 150 nm); the 6200.09 layer on silicon oxide was pre-baked at 150°C for 120 seconds (thickness: 400 nm); and the 7520.17 layer on silicon oxide was pre-baked at 80°C for 120 seconds (thickness: 800 nm).” (see Section 2 in the revised manuscript)

Comments 5: Line 93: “In EBL, the processing light source is an electron beam. Electron beam is not the light source in general.

Response 5: Thank you for pointing this out. We agree that the term “light source” is not accurate when referring to an electron beam in EBL. An electron beam is indeed a type of source, but it is distinct from a traditional light source. Therefore, we have revised the manuscript to replace “light source” with “energy source” in the context of EBL. This change ensures the terminology is precise and appropriate for the subject matter.

Comments 6: Lines 93-111: “In EBL, the processing light source is an electron beam... and to optimize their EBL processes for higher quality and more precise nanostructures.” This text is repeating introduction and should be removed from the Results part.

Response 6: Thanks for your suggestion. We agree that the introduction of the charging effect in the Results section was somewhat repetitive. Therefore, we have revised the text by removing the redundant introduction while retaining the essential information about the charging effect.

Comments 7: Lines 122-124: “Our observations revealed that at doses below 300 μC/cm², the structural manifestations exhibited a relatively light color. As the exposure dose increased, the color of these manifestations intensified and ultimately stabilized.” Why darker color is considering as “stabilization”? Could it be overexposure instead? Clarify this in the text.

Response 7: Thank you for raising this point. The use of color under optical microscopy to assess structural dosage is a preliminary method with limited characterization capability. In this context, it helps to exclude structures with insufficient dose, while the precise dose range is determined through SEM measurements. This approach effectively reduces the workload for SEM and speeds up the process of identifying the correct dose.

By “stabilization”, we mean that within the dose range of 300 to 500 μC/cm², the color of the structures observed under optical microscopy remained relatively constant, indicating that a threshold for structural exposure may have been reached. This does not imply that the darker color itself represents stability. Regarding the possibility of overexposure, you are correct that it is a consideration. Within the dose range where color stabilizes, samples exposed to the higher end of this range may indeed be overexposed, while those at the lower end might still be underexposed. Therefore, SEM measurements are essential to evaluate these possibilities and determine the optimal dose.

Comments 8: Lines 134-135: “Only when the exposure dose reaches or exceeds this threshold can the photoresist be fully exposed.” Correct grammar.

Response 8: Thank you for pointing this out. We have reviewed the grammar and corrected the sentence to: “Only when the exposure dose reaches or exceeds this threshold, the photoresist can be fully exposed.”

Comments 9: Line 138: “...quickly determine the optimal exposure dose, we will prioritize...” The sentence is written in future tense. Check the tenses everywhere in the text.

Response 9: Thank you for your suggestion. We have revised the sentence to match the tense: “To boost characterization efficiency and rapidly identify the optimal exposure dose, we prioritized electron microscope measurements and detailed characterizations of structures exposed to a range of suitable doses.” We have also reviewed and corrected the tenses throughout the entire text to ensure consistency.

Comments 10: Figures 1 and 2. The designed pattern is unclear. Why the lines are shifted in Figure 1?

Response 10: Thank you for raising this issue. We acknowledge that the pattern design in Figures 1 and 2 may not be clearly discernible solely from the images. To address this ambiguity, we have added line width specifications to the figure captions: “Figure 1. Optical microscope images of structures with the same design (design width: 200 nm) after exposure” and “Figure 2. Scanning electron microscope images of structures with the same design (design width: 200 nm) after exposure.”

Regarding the “shift” mentioned in your comment, we understand it refers to the inconsistent alignment of line emphasis at the bottom of the structure. This shift is likely caused by substrate charging during the exposure process, which generates an electric field that deflects the electron beam, resulting in structural displacement. As illustrated in the figures, the degree of shift does not show a clear correlation with the dose. Therefore, when determining the appropriate dose window, further adjustments and optimizations can be made to address this shift phenomenon.

Comments 11: Figure 2. What SEM machine and what parameters were used in the experiments? How did you avoid charging during SEM?

Response 11: Thank you for pointing this out. We have included the specific equipment used in our experiments in Section 2: “Finally, an optical microscope (Nikon LV150N) and a scanning electron microscope (Zeiss Gemini 560) were employed.”

Regarding the issue of charging during SEM imaging, especially on insulated substrates, we took several precautions to mitigate these effects. Depending on the sample and instrument setup, the following three measures were implemented: 1. a thin layer of conductive material, such as gold, was applied to the sample surface to effectively dissipate any accumulated charge; 2. the accelerating voltage was reduced (e.g., to ≤5 kV) to minimize electron beam-induced charging, while still maintaining an adequate level of resolution for our analysis; 3. photos were taken quickly to limit the duration of electron beam exposure at the target position, further reducing the risk of charging. We believe these measures helped to ensure accurate and reliable SEM imaging results.

Comments 12: Line 156: “...on structure size in the photolithography...” Your research is related to EBL, not to photolithography. Correct it everywhere in the text.

Response 12: Thank you for pointing this out. We have carefully reviewed the text and corrected all instances where “photolithography” was incorrectly used. The correct term, “EBL” (electron beam lithography), has been substituted throughout the document to accurately reflect the focus of our research.

Comments 13: Table 1. Did you measure values few times? Add error for the measured width.

Response 13: Thank you for your valuable comments. We have measured the values of line width at least three times to ensure accuracy. The measurement process yielded an error of ±2 nm for each measurement. We have been updated Table 1 to include this error margin for the measured widths.

We add the following content (highlighted in red font) in the revised manuscript: “We have included an error margin of ±2 nm for all line width measurements reported in Table 1, which was determined by repeated measurements.” (see the second paragraph in page4).

Comments 14: Line 252: “Nitride silicon substrates are widely employed...” Silicon nitride instead. Correct everywhere.

Response 14: Thank you for pointing this out. We have corrected the “nitride silicon” to be “silicon nitride” in the revised manuscript.

Comments 15: Line 266: “To investigate and analyze the processing issues, a series of structures were designed...” Only one structure is presented in the paper.

Response 15:Thank you for pointing this out. In our research, we found that different structures on the same substrate may require varying exposure doses, which is indeed an important aspect worthy of investigation. However, to maintain focus on the primary objective of this paper, which is to explore the impact of different substrate materials, we limited our experiments to a single line structure. Therefore, we have corrected the phrase “a series of structures” to “a line structure” to accurately reflect the scope of our experimental setup.

Reviewer 3 Report

Comments and Suggestions for Authors

The paper discusses the significance of electron beam lithography (EBL) in producing nanoscale devices. It investigates the effects of EBL process parameters on various substrates, such as silicon dioxide, silicon-on-insulator (SOI), and silicon nitride, focusing on the charging effect and identifying narrow exposure dose windows essential for achieving optimal pattern fidelity. The relationship between exposure dose and structural width after development is analyzed, leading to the identification of optimal exposure doses for each substrate. The findings aim to enhance EBL capabilities in semiconductor and insulator manufacturing and research, contributing to advancements in nanotechnology.

some comments:

- try to use SEM instead of field emission scanning electron microscope

- under the figures: which resist was used

- Figures 1-4 too small. the numbers are too small and the information is really hard to see

- substrates or layers on Si-susbtrates? 

- which silicon nitride and silicon dioxide was used?

- maybe to point out the layouts, they are not described

- further comments direct in the pdf

 

 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

english need just small corrections

Author Response

Comments 1: try to use SEM instead of field emission scanning electron microscope.

Response 1: Thank you for your suggestions on the paper. We agree that the distinction between different types of scanning electron microscopes can be confusing. To clarify, the scanning electron microscope (SEM) used in this study is indeed a field emission type, known for its high characterization ability. Throughout the paper, we have unified the terms “field emission scanning electron microscope” as simply “scanning electron microscope” or “SEM” to avoid any confusion. We believe these changes will enhance the readability and clarity of the paper.

Comments 2: under the figures: which resist was used.

Response 2: We added the information of resist coated on substrate under figures. In addition, we have revised and clarified the description of the substrates and photoresist combinations as follows: “The spin coating speed was 4000 r/min for 60 seconds. Subsequently, the samples were placed on a hot plate for pre-bake. The pre-bake conditions and resulting thicknesses for each substrate and photoresist combination were as follows: the 679.03 layer on silicon oxide was pre-baked at 150℃ for 60 seconds (thickness: 150 nm); the 6200.09 layer on silicon oxide was pre-baked at 150℃ for 120 seconds (thickness: 400 nm); and the 7520.17 layer on silicon oxide was pre-baked at 80℃ for 120 seconds (thickness: 800 nm).” (see Section 2 in the revised manuscript).

Comments 3: Figures 1-4 too small. the numbers are too small and the information is really hard to see.

Response 3: We appreciate the reviewer’s feedback regarding the size and readability of Figures 1-4. We understand that the small size of the figures and the text within them made it difficult to discern the pattern details. To address this issue, we have taken the following steps:

1. We have enlarged Figures 1-4 to improve their overall visibility and readability.
2. In addition to the textual descriptions provided in the main text, we have added the line width specifications directly to the figure captions for clarity. The updated captions now read:

• Figure 1. Optical microscope images of structures of the same design (design width: 200 nm).
• Figure 2. SEM images of structures of the same design (design width: 200 nm).
• Figures 3and 4. SEM images of a set of line structures with widths of 230 nm, 100 nm, and 190 nm.

We believe these changes will enhance the readability and clarity of the figures, making it easier for readers to understand the pattern designs and dimensions presented in the paper.

Comments 4: substrates or layers on Si-substrates? which silicon nitride and silicon dioxide was used? maybe to point out the layouts, they are not described.

Response 4: We appreciate the reviewer's comments regarding the need for more detailed descriptions of the substrates and layers used in our experiments. To address these concerns, we have added specific information about the substrate layers in the relevant sections of the manuscript.

In Section 3.1, we added the layers information of silicon dioxide substrate “experiments on silicon oxide substrates (glass substrates with a thickness of 160 μm)” in the first paragraph.

In Section 3.2, we added the layers information of SOI substrate “The SOI substrates used in our study feature a top layer of 220 nm silicon and an insulator layer of 2 μm silicon oxide on a silicon substrate.” in the first paragraph.

In Section 3.3, we added the layers information of silicon nitride substrate “To investigate and analyze the processing issues, a line structure was designed for exposure on a silicon nitride substrate, which consist with a top layer of 700 nm silicon nitride on silicon substrate.” in the second paragraph.

Comments 5: Line 74: “substrate”, “6” or “8”?

Response 5: We appreciate the reviewer’s attention to detail. To address this, we have added the size information directly into the text as follows: “The experiment utilized substrates (size: 2 cm × 2 cm) made of silicon oxide, silicon-on-insulator, and silicon nitride.”

Comments 6: Line 74: “The processing was carried out using the EBPG 5150 (Raith BV, Netherlands) and the PIONEER Two (Raith, Germany) systems.” Introduce the acceleration voltage here (for both system).

Response 6: Thanks for your suggestions. To address this, we have revised the sentence to read: “The processing was carried out using the EBPG 5150 (Raith BV, Netherlands) with an acceleration voltage of up to 100 kV, and the PIONEER Two (Raith, Germany) with an acceleration voltage of up to 30 kV.” (see the last paragraph in page2).

Comments 7: Line 81: “Poly-methyl methacrylate (PMMA)” which PMMA?

Response 7: To provide this information, we have revised the text to read: “Poly-methyl methacrylate (PMMA, 679.03)”. This clarification should now give readers a clearer understanding of the specific PMMA material utilized in our experiments.

Comments 8: Line 85: Precise parameter would be nice “150℃”.

Response 8: Thank you for pointing this out. To address this, we have revised the text to specify the temperature as “150℃”. Additionally, we will elaborate on the preparation process of the photoresist separately and clarify which substrate material was used in this paragraph for better clarity.

We have modified the description of the pre-bake process and clarify for which substrate as follows: “The spin coating speed was 4000 r/min for 60 seconds. Subsequently, the samples were placed on a hot plate for pre-bake. The pre-bake conditions and resulting thicknesses for each substrate and photoresist combination were as follows: the 679.03 layer on silicon oxide was pre-baked at 150°C for 60 seconds (thickness: 150 nm); the 6200.09 layer on silicon oxide was pre-baked at 150°C for 120 seconds (thickness: 400 nm); and the 7520.17 layer on silicon oxide was pre-baked at 80°C for 120 seconds (thickness: 800 nm).” (see Section 2 in the revised manuscript)

Comments 9: Line 89: If possible describe development time further in a few words (puddle, spray, immersion, how long, temperature) as all these have an impact on the needed exposure dose and contrast.

Response 9: Thank you for your valuable suggestion. We agree that providing detailed information about the development process is crucial, as it directly affects the exposure dose and contrast.

To address this, we have revised Section 2 to include a comprehensive description of the development step for each of the three resists used. Specifically, we now state: “After the EBL process, an immersion development step is carried out at room temperature (21°C). For the 679.03 resist, the developer (600-56) is applied for 30 seconds, followed by a stopper (600-60) for another 30 seconds. For the 6200.09 positive electron beam photoresist, the developer (600-546) is used for 45 seconds, followed by the stopper (600-60) for 45 seconds. Lastly, for the development of the 7520.17 negative electron beam photoresist, the developer (300-47) is employed for 4 minutes, followed by a rinse with DI water as the stopper for 4 minutes.” These details should now provide a clear understanding of the development process and its impact on the exposure dose and contrast.

Comments 10: Line 93: “light source” no light source, we have electrons.

Response 10: Thank you for pointing this out. We agree that the term “light source” is not accurate when referring to an electron beam in EBL. An electron beam is indeed a type of source, but it is distinct from a traditional light source. Therefore, we have revised the manuscript to replace “light source” with “energy source” in the context of EBL. This change ensures the terminology is precise and appropriate for the subject matter.

Comments 11: Line 119: “experiments on silicon oxide substrates...” Si-Wafers with Oxide layer or quarz glass substrate? if only a layer how thick was it?

Response 11: Thank you for pointing this out. We appreciate your feedback and have revised the text accordingly. In Section 3.1, we have now specified the layer information for the silicon dioxide substrate. The revised text now reads: “Subsequently, we carried out exposure experiments on silicon oxide substrates (glass with a thickness of 160 μm) and examined the results using an optical microscope after development.” in the first paragraph.

Comments 12: Line 170: “This charging effect is evident in the field emission SEM images shown in Figure 2, where numerous bright regions indicate charge accumulation.” This is a result of SEM analysis (charging via the SEM beam), is it possible to assume exactly the same charging during EBL?

Response 12: The charging effects observed via SEM and EBL, although similar in nature, occur under different conditions due to the distinct parameters of each technique, such as acceleration voltage, beam current, and beam spot size. In SEM imaging, charging can affect image quality, and reducing the acceleration voltage is one way to mitigate this effect. However, in EBL, charging can impact the quality of the structures being fabricated, and the parameters mentioned cannot be easily adjusted to alleviate charging phenomena because they are intricately linked to the type of photoresist used. Therefore, while the charging processes via the SEM beam and EBL beam share similarities, the methods for addressing and mitigating these effects differ significantly.

Comments 13: Line 179: “SOI” what type of SOI.

Response 13: In Section 3.2, we have now included detailed layer information for the SOI substrate. The revised text now states: “The SOI substrates used in our study feature a top layer of 220 nm silicon and an insulator layer of 2 μm silicon oxide on a silicon substrate.” in the first paragraph.

Comments 14: Line 188: “100 kV acceleration voltage”. Don’t mention this every time, summarize in the beginning when describing the experimental setup.

Response 14: Thank you for pointing this out. To streamline the text, we have removed the repetition of the acceleration voltage information at Line 188. Instead, we have summarized this information at the beginning of Section 2 when describing the experimental setup. The revised text now reads: “The processing was carried out using the EBPG 5150 (Raith BV, Netherlands) with acceleration voltage up to 100 kV and the PIONEER Two (Raith, Germany) with acceleration voltage up to 30 kV systems.” This should make the text more concise and avoid unnecessary repetition.

Comments 15: Line 231: “It is necessary to adjust the dose to find the optimal dose for the entire structure.” On this topic: Was any proximity effect correction used?

Response 15: You are correct that when the charging effect is minimized, the edges of the structure may still receive insufficient dose if a uniform dose is applied. Proximity effect correction is typically employed to address this issue. However, in this paper, we chose not to use proximity effect correction in order to control for variables and focus on other aspects of the process. This decision was made to ensure that our results were not influenced by the corrections applied and to allow for a clearer understanding of the fundamental behavior of the system under study.

Comments 16: Line 253: “Silicon nitride” Full Si₃N₄ or Si-Wafers with a layer of Silicon nitride?

Response 16: Thank you for pointing this out and the descriptions of the substrates should be added. We added the layers information of silicon nitride substrate: “To investigate and analyze the processing issues, a line structure was designed for exposure on a silicon nitride substrate, which consist with a top layer of 700 nm silicon nitride on silicon substrate.” in the second paragraph of Section 3.3.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors,

Thank you for your comments and clarifications!

All my questions were covered properly.

Author Response

Dear Reviewer,

Thank you for your confirmation that our responses have addressed your comments and clarifications thoroughly. We greatly appreciate your effort and time in reviewing our work.

Best regards

Reviewer 3 Report

Comments and Suggestions for Authors

Thynk you for the work! I have some more points:

• it's sill not a Si3N4 susbstrate ;). It's a Si3N4 layer on a Si susbstrate (chip). Which type of Si3N4 is it?
• Fig 3+4 ist still to small for the measurements. adjust the numbers or remove the numbers as in Fig 2. And whats you thinking about the measuring of e.g. 61.34nm, so 0,34nm??
• Fig5. it's larger, but no difference is visible and it's not described in the text or I missed it. so whats the benefit of the 8 images?

Author Response

Comments 1: It's sill not a Si₃N₄ substrate ;). It's a Si₃N₄ layer on a Si substrate (chip). Which type of Si₃N₄ is it?

Response 1: Thank you for pointing this out. In our study, we utilized a silicon nitride (Si₃N₄) layer deposited on a silicon (Si) substrate. Specifically, the Si₃N₄ layer had a thickness of 700 nm. The Si₃N₄ used in our experiments is Si-rich Si₃N₄ which is a standard material commonly used in micro- and nano-fabrication processes. It is not a specific crystalline form of Si₃N₄ (such as α-Si₃N₄, β-Si₃N₄, or γ-Si₃N₄), but rather a non-stoichiometric silicon nitride material. It was deposited by low-pressure chemical vapor deposition (LPCVD) from the manufacturer. We checked the refractive index specifications of the purchased materials to ensure that the compositional properties of the Si-rich Si₃N₄ we used are stable. The choice of Si-rich Si₃N₄ was driven by its excellent optical and electrical properties, which make it suitable for applications such as optical devices and semiconductor devices.

Comments 2: Fig 3+4 is still to small for the measurements. adjust the numbers or remove the numbers as in Fig 2. And whats you thinking about the measuring of e.g. 61.34nm, so 0,34nm?

Response 2: We apologize for any confusion caused by the scale of Figures 3 and 4. To improve clarity, we have revised these two figures to ensure that the measurements are clearly visible. Additionally, we have re-measured the line widths and reported them to two decimal places, following standard practice for precision in measurements. The numbers in the image represent dimensions in nanometers (nm). We believe these changes will enhance the clarity and accuracy of the figures. Please refer to Figures 3 and 4 in the revised manuscript.

Comments 3: Fig5. it's larger, but no difference is visible and it's not described in the text or I missed it. so whats the benefit of the 8 images?

Response 3: We apologize for the lack of clarity regarding Figure 5. The purpose of Figure 5 is to show that the eight structures, when exposed to different doses, are sufficiently similar in appearance under the optical microscope so that their differences are inconspicuous. Further detailed characterization of the structural components within the specified range is required using SEM. Moreover, Figure 5 presents a wider range of exposure doses (500 μC/cm² to 850 μC/cm²) compared to those used in Figure 1. The benefit of this step is to identify the correct dose window range, while demonstrating that different materials exhibit distinct dose window ranges.

Therefore, we have added the following content (highlighted in red font) in the revised manuscript: “Compared with Figure 1 through intensity differentiation, these eight structures, exposed to different doses, exhibited a uniform color, indicating that they have been sufficiently exposed. Moreover, Figure 5 presents a wider range of exposure doses (500 μC/cm² to 850 μC/cm²) than those used in Figures 1 and 2 on the silicon oxide substrate.” (see the second paragraph on page 8).