A method of determining contact hole lithography process conditions
By optimizing the contact hole photolithography process conditions through measurement and photolithography simulation, the adaptability problem of contact hole photolithography process was solved, the imaging quality and photolithography process window were improved, and it is suitable for 55nm-65nm technology nodes. The formed contact holes have small deformation, uniform linewidth and excellent etching effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GTA SEMICON CO LTD
- Filing Date
- 2023-10-17
- Publication Date
- 2026-05-19
AI Technical Summary
In integrated circuit manufacturing, the contact hole lithography process is difficult to adapt to changes in the previous thin film, resulting in defects such as standing wave effect, collapse, and bottom pin. In addition, the non-immersion lithography process has low imaging quality and insufficient lithography process window.
By measuring and obtaining the parameters of the substrate thin film, performing photolithography simulation, selecting the target film thickness and extinction coefficient, and combining multiple sets of illumination parameters and exposure anchor point simulation, the photolithography process conditions are optimized, the energy margin and focus depth are verified, and the optimal exposure anchor point is determined.
It improves the photolithography imaging quality of contact holes, expands the photolithography process window, reduces deformation and defects, improves the roughness after etching, adapts to different ILD process variations, and saves new product development costs and time.
Smart Images
Figure CN117389116B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of integrated circuit manufacturing technology, and in particular to a method for determining the photolithography process conditions for contact holes. Background Technology
[0002] In integrated circuit manufacturing, contact hole defects at advanced process nodes can directly cause failures in the connection between front-end and back-end circuits. The photolithography process for contact holes requires not only precise pattern definition but also consideration of improving uniformity and providing greater process tolerance for etching. Therefore, the requirements for the photolithography process are extremely stringent.
[0003] Contact hole deformation defects are mainly related to the contact hole forming process, which is directly related to process steps such as inter-layer dielectric (ILD) planarization, contact hole photolithography, and etching. The feature size of the contact hole is usually determined by the photolithography process, and the energy margin and focus depth will affect the photoresist morphology and size after contact hole exposure. In the research and development and introduction stage of new products, the thickness of the inter-layer dielectric layer and inorganic anti-reflection coating often needs to be continuously changed according to the process design. The resulting change in the extinction coefficient (the reflectivity value is represented by the letter n and the refractive index by k, and n and k are collectively referred to as the extinction coefficient) can cause defects such as intensified standing wave effect, collapse, bottom pinning, and T-shaped tops in the photolithography pattern. How to quickly adapt to changes in the preceding thin film to explore photolithography process conditions is a difficult problem in contact hole technology.
[0004] Contact hole lithography at the 55nm-65nm technology node often requires the use of an immersion argon fluoride (ArF) lithography machine. However, the imaging quality is affected by the intermediate exposure medium (water), which can introduce residual water defects. Current technologies partially employ dry argon fluoride (ArF) lithography for contact holes, but due to limitations imposed by the optical proximity effect and the characteristics of 193nm photoresist, it is often difficult to obtain high-quality lithographic patterns and sufficient lithography process windows.
[0005] Photolithography simulation models optical imaging and the process, using computer calculations to predict and characterize various parameters of the photolithography process. However, a single simulation depends on the accuracy of the model, and its predictive ability is limited by the number of data points and computing power. Summary of the Invention
[0006] The purpose of this invention is to provide a method for determining the photolithography process conditions for contact holes, which can efficiently establish and determine the photolithography process conditions for contact holes, improve imaging quality, and enhance the photolithography process window.
[0007] To achieve the above objectives, the present invention provides a method for determining the photolithography process conditions for contact holes, comprising the following steps: measuring and obtaining the parameters of the front thin film of the substrate to be coated with an anti-reflective coating; performing photolithography simulation to obtain the relationship curve between the simulated film thickness and extinction coefficient of the anti-reflective coating to be coated; and then selecting the target film thickness of the anti-reflective coating to be coated. The substrate includes a substrate and multiple thin films deposited on the substrate. The parameters of the front thin film include the film thickness and corresponding extinction coefficient of each of the N thin films starting from the topmost film of the substrate; performing photolithography simulation based on the parameters of the front thin film and the target film thickness and extinction coefficient of the anti-reflective coating to obtain the target film thickness of the photoresist; and using multiple sets of illumination parameters to adjust the photoresist... The process involves simulating exposure at a preset exposure anchor point to obtain target illumination parameters; selecting candidate exposure anchor points and fixing the parameters to be optimized for lithography simulation to obtain at least one target exposure anchor point; verifying the lithography process conditions obtained in the preceding steps by changing the energy margin and focus depth on a pre-fabricated substrate; selecting the target exposure anchor point with the largest lithography process window as the selected exposure anchor point; and obtaining the corresponding target energy margin and target focus depth to determine the contact hole lithography process conditions. The lithography process window includes energy margin and focus depth. The lithography process conditions obtained in the preceding steps include: the target film thickness of the anti-reflective coating to be applied, the target film thickness of the photoresist, the target illumination parameters, and the at least one target exposure anchor point.
[0008] The above technical solution, by combining computational lithography with design experiments, provides a method for determining the lithography process conditions for contact holes. It is applicable to the development of non-immersion lithography processes at the 55nm-65nm technology node, saving time and economic costs for new product development and introduction at this node, and effectively improving product yield. It is adaptable to different ILD processes and can quickly respond to changes in lithography process conditions caused by variations in ILD processes. The target exposure anchor point selected in this invention is suitable for the 55nm-65nm process node, providing high imaging quality and meeting design requirements within the process window. Contact holes formed using the lithography process conditions determined by this invention have advantages such as small deformation, good linewidth uniformity, no T-shaped tops, no bottom pins, and no or minimal standing wave effect. When the aspect ratio of the contact holes formed using the lithography process conditions determined by this invention is ≥2.8:1, the surface roughness after etching is significantly improved. Attached Figure Description
[0009] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0010] Figure 1 A flowchart of a method for determining photolithography process conditions for contact holes provided in an embodiment of the present invention;
[0011] Figure 2 A schematic diagram of a feature pattern provided in an embodiment of the present invention;
[0012] Figure 3 This is a schematic diagram of a contact hole formed using the photolithography process conditions determined by the present invention. Detailed Implementation
[0013] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0014] Please refer to the following: Figures 1-2 ,in, Figure 1 This is a flowchart of a method for determining photolithography process conditions for contact holes according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a feature pattern provided in an embodiment of the present invention.
[0015] like Figure 1 As shown, the method for determining the contact hole photolithography process conditions described in this embodiment includes the following steps: S11, measuring and obtaining the parameters of the front thin film of the substrate to be coated with the anti-reflective coating, performing photolithography simulation to obtain the relationship curve between the simulated film thickness and extinction coefficient of the anti-reflective coating to be coated, and then selecting the target film thickness of the anti-reflective coating to be coated; S12, performing photolithography simulation based on the parameters of the front thin film and the target film thickness and extinction coefficient of the anti-reflective coating to be coated, and obtaining the target film thickness of the photoresist; S13, simulating exposure of the photoresist at a preset exposure anchor point using multiple sets of illumination parameters, and obtaining the target illumination parameters; S14, selecting candidate exposure anchor points, fixing the parameters to be optimized, and performing photolithography simulation to obtain at least one target exposure anchor point; and S15, verifying the photolithography process conditions obtained in the aforementioned steps on a pre-fabricated substrate by changing the energy margin and focus depth, selecting the target exposure anchor point with the largest photolithography process window as the selected exposure anchor point, and obtaining the corresponding target energy margin and target focus depth, thereby determining the contact hole photolithography process conditions.
[0016] Regarding step S11, the parameters of the front thin film of the substrate to be coated with the anti-reflective coating are measured and obtained, and the relationship curve between the simulated film thickness and extinction coefficient of the anti-reflective coating to be coated is obtained by photolithography simulation, and then the target film thickness of the anti-reflective coating to be coated is selected; wherein, the substrate includes a substrate and multiple thin films deposited on the substrate, and the parameters of the front thin film include the film thickness and corresponding extinction coefficient of each of the N thin films from the topmost thin film of the substrate.
[0017] By measuring the N layers of films with corresponding thicknesses deposited on the substrate, the thickness and extinction coefficient of each film in the N layers starting from the top layer of the substrate are obtained. The bottom anti-reflective coating (BARC) is to be applied on the top layer of the substrate. The thickness of the anti-reflective coating is based on the thickness and extinction coefficient of the previous N layers of films.
[0018] In some embodiments, the N-layer thin films are all inter-layer dielectrics (ILDs).
[0019] In some embodiments, N is greater than or equal to 3. For example, the film thickness and corresponding extinction coefficient of each of the three films starting from the top layer of the substrate can be measured. Alternatively, the film thickness and corresponding extinction coefficient of each of the four films starting from the top layer of the substrate can be measured to improve the accuracy of the simulation results.
[0020] In some embodiments, step S11 further includes: comparing the theoretical film thickness versus extinction coefficient curve of the antireflective coating to be coated with the simulated film thickness versus extinction coefficient curve, and selecting the target film thickness of the antireflective coating to be coated. The simulated film thickness versus extinction coefficient curve of the antireflective coating to be coated can be obtained using industry-standard photolithography simulation software (specifically S-Litho, Pro-Litho, etc.), by inputting the film thickness and extinction coefficient into the software model. The theoretical film thickness versus extinction coefficient curve of the antireflective coating to be coated can be obtained by consulting the product manual based on the product model of the antireflective coating to be coated. Each antireflective coating has its corresponding film thickness versus extinction coefficient curve, which can be considered as a product manual and can be looked up based on its product model.
[0021] In some embodiments, step S11, selecting the target film thickness of the antireflective coating to be applied, further includes: obtaining the first slope of the first minimum point of the simulated film thickness versus extinction coefficient curve of the antireflective coating to be applied; obtaining the second slope of the second minimum point of the theoretical film thickness versus extinction coefficient curve of the antireflective coating to be applied; and selecting the film thickness corresponding to the position of the slope with the smaller absolute value between the first slope and the second slope as the target film thickness of the antireflective coating. That is, both curves will have corresponding minimum points, but the slopes near the minimum points are different. In this embodiment, the film thickness corresponding to the position with the smaller absolute value of the slope is preferentially selected as the target film thickness of the antireflective coating.
[0022] In some embodiments, step S11, which involves selecting the target film thickness of the antireflective coating to be applied, further includes: selecting a target film thickness range for the antireflective coating to be applied based on the theoretical film thickness versus extinction coefficient curve and the simulated film thickness versus extinction coefficient curve; and selecting the film thickness corresponding to the slope position with the smaller absolute value within the target film thickness range as the target film thickness of the antireflective coating to be applied based on the thickness versus rotation speed curve of the antireflective coating to be applied. That is, the target film thickness range of the antireflective coating to be applied is selected based on the aforementioned two curves (theoretical and simulated film thickness versus extinction coefficient curves), and further, by combining the thickness versus rotation speed curve of the antireflective coating to be applied, the film thickness corresponding to the slope position with the smaller absolute value is selected as the target film thickness of the antireflective coating to be applied, to achieve a more precise selection and ensure process stability.
[0023] Regarding step S12, photolithography simulation is performed based on the parameters of the previous thin film and the target film thickness and extinction coefficient of the antireflective coating to be applied to obtain the target film thickness of the photoresist.
[0024] In some embodiments, step S12 includes at least: (1) inputting the parameters of the previous thin film and the target film thickness and extinction coefficient of the anti-reflection coating into photolithography simulation software for simulation, obtaining the key dimension swing curve of the photoresist (the curve of the key linewidth changing with the photoresist thickness), and selecting at least one photoresist film thickness whose absolute value of the curve slope is close to zero; (2) selecting one of the at least one photoresist film thicknesses as the target film thickness of the photoresist according to the photolithography process requirements. That is, the determination of the photoresist thickness should meet (but is not limited to) the above two conditions, and the above two conditions must be met simultaneously. The photolithography simulation software can be industry-standard photolithography simulation software (specifically S-Litho, Pro-Litho, etc.), which includes a process window analysis (PWA) function, which can simulate and obtain the optimal film thickness of the current layer based on the previous film thickness and extinction coefficient.
[0025] Regarding step S13, the photoresist is simulated to be exposed at a preset exposure anchor point using multiple sets of illumination parameters to obtain the target illumination parameters. Illumination parameters refer to the illumination mode of the exposure light source, specifically categorized as conventional illumination, annular illumination, and quadar illumination. By simulating exposure at the exposure anchor point, the photoresist imaging resolution under different illumination parameter conditions is compared, and then the illumination parameters are optimized to obtain the target illumination parameters.
[0026] In some embodiments, the step of obtaining the target illumination parameters further includes: comparing the photoresist imaging resolution under different illumination parameter conditions based on the simulated exposure results, and selecting the illumination parameters of the simulated two-dimensional and three-dimensional graphics of the contact hole that meet the design conditions of the photolithography process window as the target illumination parameters. Specifically, the simulated two-dimensional graphics of the contact hole are burr-free, have high roundness, and good uniformity of key linewidth; the simulated three-dimensional graphics of the contact hole have small deformation, no standing wave effect or an insignificant standing wave effect, no bottom foot, and no T-shaped top.
[0027] In some embodiments, the multiple sets of illumination parameters further employ optical coherence (σ). outer , σ inter The optimization involves one or more combinations of single and synergistic variations in numerical aperture (NA). Optionally, the industry standard for the 55nm-65nm node is annular illumination. By optimizing multiple sets of illumination parameters using the above optimization method, the target illumination parameters that meet the design requirements of the lithography process window can be better obtained.
[0028] Regarding step S14, selecting candidate exposure anchor points and fixing the parameters to be optimized, performing photolithography simulation, and obtaining at least one target exposure anchor point. Specifically, the mask error enhancement factor of the target exposure anchor point satisfies the photolithography process window design conditions, and the photolithography process window includes energy margin and focus depth.
[0029] In some embodiments, the step of obtaining at least one target exposure anchor point further includes: (1) selecting a series of feature patterns as candidate exposure anchor points, the candidate exposure anchor points including the preset exposure anchor points; (2) performing photolithography simulation with fixed parameters to be optimized, and obtaining the key linewidth changes corresponding to the candidate exposure anchor points; (3) obtaining the ratio of the key linewidth difference of the candidate exposure anchor points to the actual key linewidth difference on the wafer as a mask error enhancement factor; (4) obtaining at least one candidate exposure anchor point among the candidate exposure anchor points whose mask error enhancement factor satisfies the photolithography process window design conditions as the target exposure anchor point. The simulation result is the key linewidth change corresponding to the exposure anchor point. The mask error enhancement factor is calculated with reference to the simulation result, and then the candidate exposure anchor point corresponding to the mask error enhancement factor that satisfies the photolithography process window design conditions is selected as the target exposure anchor point.
[0030] In some embodiments, the parameters to be optimized include the temperature and time of pre-baking, post-baking, and hard baking, as well as the developing method and time.
[0031] In some embodiments, the parameters to be optimized can be fixed by using the parameters recommended by the photoresist technology data. Simulation results show that the exposure anchor points with periods of 120 / 80 and 130 / 70 both meet the design conditions of the photolithography process window.
[0032] Following the above embodiments, as Figure 2 As shown, the series of feature graphics includes: (1) a preset periodic dense graphic (e.g. Figure 2 As shown in part (a), a preset periodic semi-dense pattern (e.g., Figure 2 As shown in section (b), isolated figures within sparse regions (e.g.) Figure 2 (as shown in part (c)); and / or, (2) a preset periodic dense graphic with auxiliary graphics added based on preset rules (e.g. Figure 2 As shown in section (a'), a preset periodic semi-dense graphic with auxiliary graphics added based on preset rules (e.g., Figure 2 As shown in section (b'), isolated graphics within sparse regions (e.g., those with auxiliary graphics added based on preset rules) Figure 2 (as shown in part (c')).
[0033] The line width of the graphic in the dense and semi-dense areas can vary with gradients or be a specific periodic graphic. Auxiliary graphics can be added to the graphic in the dense, semi-dense, and sparse areas based on different rules.
[0034] Regarding step S15, the photolithography process conditions obtained in the preceding steps are verified on the pre-fabricated substrate by changing the energy margin and focus depth. The target exposure anchor point with the largest photolithography process window is selected as the chosen exposure anchor point, and the corresponding target energy margin and target focus depth are obtained to determine the contact hole photolithography process conditions. Specifically, the photolithography process window includes the energy margin and focus depth, and the photolithography process conditions obtained in the preceding steps include: the target film thickness of the anti-reflective coating to be applied, the target film thickness of the photoresist, the target illumination parameters, and the at least one target exposure anchor point. Specifically, the photolithography process conditions obtained in the preceding steps are applied sequentially to the target exposure anchor point, changing the energy margin and focus depth, to perform a complete photolithography process verification on the pre-fabricated substrate.
[0035] In some embodiments, the pre-fabricated substrate includes different thin film structures and thicknesses. The complete photolithography process includes, but is not limited to, spin-coating of a tackifier, spin-coating of an anti-reflective coating, spin-coating of a photoresist, soft baking, exposure, post-baking, development, and hard baking.
[0036] In some embodiments, the step of selecting the target exposure anchor point with the largest photolithography process window as the selected exposure anchor point and obtaining the corresponding target energy margin and target focus depth further includes: (1) measuring the contact hole formed by the photolithography process verification using a linewidth scanning electron microscope to obtain the key linewidth value and planar two-dimensional image of the corresponding contact hole, and then obtaining the corresponding energy margin and focus depth; (2) selecting the target exposure anchor point with the largest photolithography process window as the selected exposure anchor point based on the obtained corresponding energy margin and focus depth, and defining the energy margin and focus depth of the selected photolithography process window as the target energy margin and target focus depth. The measurement results of the linewidth scanning electron microscope can obtain the key linewidth value and planar two-dimensional image of the contact hole from the sparse area to the dense area. By analyzing and calculating the energy margin and focus depth under the exposure condition based on the key linewidth value and planar two-dimensional image, the target exposure anchor point with the largest process window is selected, and the corresponding energy margin and focus depth under the exposure condition are defined. In a narrow sense, the process window mainly includes the energy margin and focus depth.
[0037] In some embodiments, the method further includes step S16: determining whether there is room for improvement in the obtained lithography process window; if there is room for improvement, adjusting the parameters to be optimized and re-executing steps S14 and S15. Specifically, step S16 includes: (1) inputting the target energy margin and different focus depths into the lithography simulation software to simulate and obtain the theoretical energy margin; (2) inputting the target focus depth and different energy margins into the lithography simulation software to simulate and obtain the theoretical focus depth; (3) determining whether the theoretical energy margin and theoretical focus depth are within the reference threshold range; (4) if the theoretical energy margin and theoretical focus depth are outside the reference threshold range, adjusting the parameters to be optimized and re-performing the lithography simulation to obtain a new target exposure anchor point, and performing lithography process verification. Input the target energy margin and target focus depth obtained in step S15 into the lithography simulation software (specifically, industry-standard lithography simulation software such as S-Litho, Pro-Litho, etc.). Perform two simulations to obtain the theoretical energy margin and theoretical focus depth under the lithography process conditions obtained in the aforementioned steps. This will help determine if there is room for improvement in the lithography process window obtained in step S15. The process window generally has reference values within the industry; it must be within the reference range. If the process window is not met, improvement is needed. If there is room for improvement, the parameters to be optimized in step S14 can be adjusted to design an experiment, and steps S14 and S15 can be re-executed.
[0038] In some embodiments, the method further includes step S17: performing etching, defect inspection, and failure analysis to further verify the contact hole photolithography process conditions. Step S17 can be performed after step S15; if step S16 exists, step S17 can be performed after step S16. After obtaining sufficient contact hole photolithography process conditions, further verification is performed using etching, failure analysis slicing, and defect inspection equipment to obtain optimal contact hole photolithography process conditions.
[0039] The above embodiments of the present invention provide a method for determining contact hole lithography process conditions by combining computational lithography with design experiments. This method is applicable to the development of non-immersion lithography processes at 55nm-65nm technology nodes; it is adaptable to different ILD processes and can quickly respond to changes in lithography process conditions caused by variations in ILD processes. The exposure anchor points selected in this invention (periods of 120 / 80 and 130 / 70) are suitable for 55nm-65nm process nodes, offering high imaging quality and meeting design requirements within the process window. Specifically, the exposure anchor point with a period of 130 / 70 is applicable to 65nm / 55nm technical nodes; the exposure anchor point with a period of 120 / 80 is applicable to 55nm technical nodes. Contact holes formed using the lithography process conditions determined by this invention have advantages such as small deformation, good linewidth uniformity, no T-shaped tops, no bottom pins, and no or minimal standing wave effect. When the aspect ratio of the contact holes formed using the lithography process conditions determined by this invention is ≥2.8:1, the surface roughness after etching is significantly improved.
[0040] Please see Figure 3 This is a schematic diagram of a contact hole formed using the photolithography process conditions determined by the present invention, wherein... Figure 3 Part (a) is a two-dimensional image of the top of the photolithographic contact hole, and part (b) is a three-dimensional image of the cross-section of the photolithographic contact hole. Figure 3 It can be seen that the contact holes formed by the photolithography process conditions determined by the present invention have advantages such as small deformation, good linewidth uniformity, no T-shaped top, no bottom foot, no standing wave effect or no standing wave effect.
[0041] Generally, terms can be understood at least partially from their usage in context. For example, the term "one or more" as used herein depends at least in part on the context and can be used to describe a feature, structure, or characteristic in a singular sense, or in a plural sense to describe a combination of features, structures, or characteristics. Additionally, the term "based on" can be understood not necessarily to express an exclusive set of factors, but rather, alternatively, also depends at least in part on the context, allowing for the presence of other factors that are not necessarily explicitly described.
[0042] It should be noted that the terms "comprising" and "having," and their variations, used in this invention document are intended to cover non-exclusive inclusion. The terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence, unless explicitly indicated by the context. It should be understood that such data used interchangeably where appropriate. Furthermore, embodiments and features within embodiments of this invention can be combined with each other unless otherwise specified. In addition, descriptions of well-known components and technologies have been omitted in the above description to avoid unnecessarily obscuring the concepts of this invention. In the various embodiments described above, each embodiment focuses on its differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.
[0043] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for determining photolithography process conditions for contact holes, characterized in that, Includes the following steps: The parameters of the front thin film of the substrate to be coated with the anti-reflective coating are measured and obtained. The relationship curve between the simulated film thickness and the extinction coefficient of the anti-reflective coating to be coated is obtained by photolithography simulation. Then, the target film thickness of the anti-reflective coating to be coated is selected. The substrate includes a substrate and multiple thin films deposited on the substrate. The parameters of the front thin film include the film thickness and the corresponding extinction coefficient of each of the N thin films from the topmost film of the substrate. Photolithography simulation is performed based on the parameters of the previous thin film and the target film thickness and extinction coefficient of the anti-reflection coating to be applied to obtain the target film thickness of the photoresist. Multiple sets of illumination parameters are used to simulate exposure at the preset exposure anchor point of the photoresist to obtain the target illumination parameters; Select candidate exposure anchor points, fix the parameters to be optimized, and perform photolithography simulation to obtain at least one target exposure anchor point; The photolithography process conditions obtained in the preceding steps are verified by changing the energy margin and focus depth on the pre-fabricated substrate. The target exposure anchor point with the largest photolithography process window is selected as the selected exposure anchor point, and the corresponding target energy margin and target focus depth are obtained to determine the contact hole photolithography process conditions. The photolithography process window includes the energy margin and focus depth. The photolithography process conditions obtained in the preceding steps include: the target film thickness of the anti-reflective coating to be applied, the target film thickness of the photoresist, the target illumination parameters, and the at least one target exposure anchor point.
2. The method according to claim 1, characterized in that, All N thin films are interlayer dielectric layers. N is greater than or equal to 3.
3. The method according to claim 1, characterized in that, The step of selecting the target film thickness of the antireflective coating to be applied further includes: Obtain the first slope of the first minimum point of the simulated film thickness versus extinction coefficient curve of the antireflective coating to be applied; Obtain the second slope of the second minimum point of the curve relating the theoretical film thickness to the extinction coefficient of the antireflective coating to be applied; The film thickness corresponding to the position of the slope with the smaller absolute value between the first slope and the second slope is selected as the target film thickness of the anti-reflective coating.
4. The method according to claim 1, characterized in that, The step of selecting the target film thickness of the antireflective coating to be applied further includes: Based on the theoretical film thickness and extinction coefficient relationship curve of the anti-reflective coating to be applied and the simulated film thickness and extinction coefficient relationship curve, the target film thickness range of the anti-reflective coating to be applied is selected. Based on the thickness versus rotation speed curve of the antireflective coating to be applied, the film thickness corresponding to the slope position with the smaller absolute value of the slope within the target film thickness range is selected as the target film thickness of the antireflective coating to be applied.
5. The method according to claim 1, characterized in that, The step of obtaining the target film thickness of the photoresist includes at least the following: The parameters of the front thin film and the target film thickness and extinction coefficient of the anti-reflection coating are input into the photolithography simulation software for simulation to obtain the key dimension swing curve of the photoresist, and at least one photoresist film thickness with an absolute value of the curve slope close to zero is selected. According to the requirements of the photolithography process, one of the at least one photoresist film thicknesses is selected as the target film thickness of the photoresist.
6. The method according to claim 1, characterized in that, The step of obtaining target illumination parameters further includes: Based on the comparison of photoresist imaging resolution under different illumination parameters according to the simulated exposure results, the illumination parameters that meet the design conditions of the photolithography process window for the two-dimensional and three-dimensional graphics of the contact hole simulation are selected as the target illumination parameters.
7. The method according to claim 1, characterized in that, The multiple sets of illumination parameters are further optimized using one or more combinations of optical coherence, single variation and synergistic variation of numerical aperture.
8. The method according to claim 1, characterized in that, The step of obtaining at least one target exposure anchor point further includes: A series of feature images are selected as candidate exposure anchor points, including the preset exposure anchor points; Photolithography simulation was performed with the parameters to be optimized fixed to obtain the key linewidth changes corresponding to the candidate exposure anchor points; The ratio of the critical linewidth difference of the candidate exposure anchor point to the actual critical linewidth difference on the wafer is obtained as the mask error enhancement factor; At least one candidate exposure anchor point among the candidate exposure anchor points whose mask error enhancement factor satisfies the lithography process window design conditions is selected as the target exposure anchor point.
9. The method according to claim 8, characterized in that, The series of feature graphics includes: Preset periodic dense graphics, preset periodic semi-dense graphics, isolated graphics in sparse regions; and / or, preset periodic dense graphics with auxiliary graphics added based on preset rules, preset periodic semi-dense graphics with auxiliary graphics added based on preset rules, isolated graphics in sparse regions with auxiliary graphics added based on preset rules.
10. The method according to claim 1, characterized in that, The step of selecting the target exposure anchor point with the largest photolithography process window as the selected exposure anchor point and obtaining the corresponding target energy margin and target focus depth further includes: The contact holes formed by the photolithography process were measured using a linewidth scanning electron microscope to obtain the key linewidth values and two-dimensional planar images of the corresponding contact holes, and then the corresponding energy margin and focus depth were obtained. Based on the obtained energy margin and focus depth, the target exposure anchor point with the largest photolithography process window is selected as the selected exposure anchor point, and the energy margin and focus depth of the selected photolithography process window are defined as the target energy margin and target focus depth.
11. The method according to claim 1, characterized in that, The method further includes: The target energy margin and different focus depths are input into the lithography simulation software to simulate and obtain the theoretical energy margin. The target focus depth and different energy margins are input into the lithography simulation software to simulate and obtain the theoretical focus depth. Determine whether the theoretical energy margin and theoretical depth of focus are within the reference threshold range; If the theoretical energy margin and theoretical focus depth are outside the reference threshold range, the parameters to be optimized are adjusted, and a new photolithography simulation is performed again to obtain a new target exposure anchor point, and the photolithography process is verified.
12. The method according to claim 1, characterized in that, The method further includes: The etching process, defect inspection, and failure analysis were carried out, and the contact hole photolithography process conditions were further verified.