A photolithography method and an exposure apparatus

Abstract

This invention belongs to the field of semiconductor integrated circuits and provides a photolithography method and exposure apparatus. The photolithography method includes: after forming an anti-reflection layer and a photoresist layer on a wafer, performing an energy-free initial exposure on the photoresist layer to obtain high and low deviation values ​​corresponding to each exposure area, generating a high and low deviation value array; adjusting the exposure energy and exposure focal length according to the high and low deviation values ​​in the high and low deviation array, and performing a second exposure on the photoresist layer to ensure that the distance from the exposure lens to the surface of the photoresist layer is substantially the same; and performing post-baking and development processing on the photoresist layer. By adjusting the exposure focal length of each exposure area according to the high and low deviation array collected during the energy-free initial exposure, the distance from the exposure lens to the surface of the photoresist layer on the wafer is substantially the same, realizing the adjustment and correction of the exposure focal length according to the concavity and convexity of the photoresist layer, adapting to warped wafers, and improving the patterning quality of photolithography.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor integrated circuits, and specifically relates to a photolithography method and an exposure apparatus. Background Technology

[0002] With the rapid development of the semiconductor integrated circuit industry, the process technology of semiconductor devices has entered the nanometer level. At the same time, the semiconductor device manufacturing process has introduced a large number of steps such as thin film deposition, heat treatment and chemical mechanical polishing. Problems such as excessively long heat treatment process, large differences in patterning density, and stress mismatch caused by deposited or filled materials can easily occur. This results in large differences in the internal stress distribution of the manufactured wafers, and the wafers themselves will warp upward or downward.

[0003] During photolithography, the warped wafers cause changes in the distance between the lens and the photoresist surface due to the warped wafer surface, which disrupts the flatness of the wafer and reduces the patterning quality when transferring the pattern from the photomask to the photoresist. Summary of the Invention

[0004] To address the issue of poor patterning quality transferred to the photoresist when exposing warped wafers using uniform exposure energy and focal length during photolithography, this application provides a photolithography method and exposure apparatus.

[0005] This application provides a photolithography method and exposure apparatus, which adopt the following technical solution: A photolithography method, comprising: After forming an anti-reflection layer and a photoresist layer on the wafer, the photoresist layer is subjected to an energy-free first exposure to obtain the high and low deviation values ​​of the photoresist layer in each exposure area, and a high and low deviation value array is generated. The anti-reflection layer is located between the wafer and the photoresist layer. The exposure focal length is adjusted according to the high and low deviation values ​​in the high and low deviation array so that the distance from the exposure lens to the surface of the photoresist layer is basically the same. The photoresist layer is subjected to secondary exposure based on the adjusted exposure focal length and the specified exposure energy. The photoresist layer is subjected to post-baking and development processes.

[0006] By employing the above technical solution, a low-energy initial exposure is performed on the photoresist layer to obtain a high-low deviation value array. Subsequently, based on this array, the exposure focal length corresponding to each exposure area is adjusted to ensure that the distance between the exposure lens and the photoresist layer surface is essentially the same. This guarantees that during the second exposure, the focal length setting for each exposure area conforms to the morphology of the photoresist layer surface. Even if the wafer is warped and the photoresist layer is uneven, the exposure focal length will still be adjusted according to the distance between the photoresist layer and the exposure lens. This solution ensures that the distance between the photoresist layer and the exposure lens is consistent in all exposure areas during the final exposure (i.e., the second exposure with energy), thereby improving patterning quality.

[0007] Optionally, forming the anti-reflective layer and photoresist layer on the wafer includes: An anti-reflective layer of a first preset thickness is formed on the wafer, wherein the adjustment range of the first preset thickness is 200-1500 Å; A photoresist layer of a second preset thickness is formed on the anti-reflective layer, and the adjustment range of the second preset thickness is 500-40000 Å.

[0008] By employing the above technical solution, an anti-reflective layer is formed on the wafer to reduce light reflection during photolithography, preventing image blurring and distortion caused by overexposure of the photoresist layer. The thickness of the anti-reflective layer can be adjusted as needed, ranging from 200 Å to 1500 Å. A photoresist layer is then formed on the anti-reflective layer; the thickness of the photoresist layer can be adjusted according to testing requirements and is typically related to the photoresist material. Various methods can be used to form the anti-reflective layer and photoresist layer (e.g., deposition, spraying), and this solution supports multiple methods for forming both.

[0009] Optionally, the step of performing an energy-free first exposure on the photoresist layer to obtain high and low deviation values ​​of the photoresist layer in each exposure area, and generating a high and low deviation value array, includes: Obtain distance reference value; The exposure energy is set to zero, and the photoresist layer is exposed for the first time at the initial focal length. The distance between the exposure lens and the surface of the photoresist layer in each exposure area is detected as the initial distance value. Based on the distance reference value and the initial distance value of each exposure area, the height deviation value of each exposure area is calculated to obtain an array of height deviation values ​​according to the arrangement of the exposure areas.

[0010] The distance reference value in the above technical solution is a preset value. This value can be set by the wafer manufacturer according to the wafer's factory specifications, or by the photolithography operator according to their own needs. It can also be a value measured during standard part manufacturing, specifically the distance between the exposure lens and the corresponding photoresist layer on the standard part. In this case, the exposure energy is set to 0 to achieve virtual exposure focusing. The distance between the exposure lens and the photoresist layer surface is recorded to obtain the initial distance value for each exposure area. Then, combined with the distribution of the exposure areas, the high / low deviation value for each exposure area is obtained. Based on the distribution of the exposure areas, the corresponding high / low deviation values ​​are arranged to obtain a high / low deviation array.

[0011] Optionally, the exposure focal length is adjusted according to the high and low deviation values ​​in the high and low deviation array to make the distance from the exposure lens to the surface of the photoresist layer substantially the same. A second exposure is then performed on the photoresist layer based on the adjusted exposure focal length and a specified exposure energy, including: When the height deviation value of the exposure area is higher than the first standard deviation value, the exposure focal length is increased; when the height deviation value of the exposure area is lower than the second standard deviation value, the exposure focal length is decreased. Select the corresponding exposure energy based on the exposure focal length corresponding to each exposure area; The photoresist layer is subjected to secondary exposure based on the exposure energy and the exposure focal length corresponding to each exposure area.

[0012] By adopting the above technical solution, when the high-low deviation value is higher than the first standard deviation value xmax, the exposure focal length of the exposure area corresponding to the high-low deviation value is increased, and when the high-low deviation value is lower than the second standard deviation value xmin, the exposure focal length of the exposure area corresponding to the high-low deviation value is decreased. Therefore, as the exposure focal length is adjusted, the high-low deviation value will gradually converge to [xmin, xmax].

[0013] Optionally, the first standard deviation value and the second standard deviation value are set according to the photolithography process conditions.

[0014] By adopting the above scheme, post-baking and development are the conventional basic photolithography processes. Based on the process requirements corresponding to the basic photolithography process, this case integrates the process requirements corresponding to all basic photolithography processes and reads the corresponding first standard deviation value and second standard deviation value from the standard database to ensure that different process requirements can automatically adopt the corresponding first standard deviation value and second standard deviation value to achieve the corresponding focal length adjustment.

[0015] Optionally, the reduction in exposure focal length includes: According to a preset focal length step, the initial focal length of the exposure area is sequentially reduced to obtain a target focal length value until the updated high / low deviation value obtained by exposing the photoresist layer with the target focal length value and zero exposure energy is within the standard deviation range, where the boundary values ​​of the standard deviation range are the first standard deviation value and the second standard deviation value; and / or, the upward adjustment of the exposure focal length includes: According to the preset focal length step, the initial focal length of the exposure area is sequentially increased to obtain the target focal length value, until the updated high and low deviation value obtained by exposing the photoresist layer with the target focal length value and zero exposure energy is within the range of the standard deviation value.

[0016] By adopting the above technical solution, during the adjustment of exposure focal length, each adjustment will be performed in a cyclical manner with the preset focal length as the step size, until the updated high and low deviation values ​​are within the standard deviation range [xmin, xmax] formed by the first standard deviation value xmax and the second standard deviation value xmin.

[0017] Optionally, the reduction in exposure focal length includes: Based on the difference between the high and low deviation values ​​of the exposure area and the first standard deviation value, the corresponding focal length adjustment difference is found from the preset first database; based on the focal length adjustment difference and the initial focal length, the exposure focal length corresponding to the adjusted exposure area is obtained. The aforementioned increase in exposure focal length includes: Based on the deviation difference between the high and low deviation values ​​corresponding to the exposure area and the second standard deviation value, the corresponding focal length adjustment difference is found from the preset first database; based on the focal length adjustment difference and the initial focal length, the exposure focal length corresponding to the adjusted exposure area is obtained; wherein, the first database includes interrelated deviation differences and focal length adjustment differences.

[0018] By adopting the above technical solution, during the adjustment of the exposure focal length upwards and downwards, based on the difference between the high / low deviation value and the first standard deviation value xmax or the second deviation value xmin, the focal length adjustment difference corresponding to the deviation difference is directly found from the first database, and the exposure focal length of the exposure area is adjusted. The interrelated deviation difference-focal length adjustment difference in the first database are either preset by the staff or can be historical deviation difference-focal length adjustment difference values ​​stored in the database.

[0019] Optionally, the upward adjustment of the exposure focal length includes: Based on the high and low deviation values ​​corresponding to the exposure area, the corresponding focal length value is found from the preset second database and used as the exposure focal length corresponding to the adjusted exposure area; wherein, the second database includes interrelated high and low deviation values ​​and focal length values.

[0020] By adopting the above technical solution, during the adjustment of the exposure focal length, the corresponding focal length value is directly retrieved from the second database based on the detected high / low deviation value, and the corresponding exposure focal length is adjusted accordingly. The interconnected high / low deviation value-focal length values ​​in the preset second database are usually pre-set by staff, or historical high / low deviation value-focal length values ​​can be stored for direct retrieval later.

[0021] Optionally, the photoresist includes i-line type, KrF type, ArF type, and iArF type photoresist.

[0022] The present invention also provides an exposure device, characterized in that it includes an exposure lens, a distance sensor, and a lens controller; The exposure lens performs an energy-free first exposure on the photoresist layer, which is formed on an anti-reflective layer on the wafer. The distance sensor is mounted on the exposure lens to detect the distance between the exposure lens and the photoresist layer, so that the lens controller can obtain the high and low deviation values ​​of the photoresist layer in each exposure area and generate a high and low deviation array. The lens controller is connected to the distance sensor and the exposure lens. It adjusts the exposure focal length according to the high and low deviation values ​​in the high and low deviation array so that the distance between the exposure lens and the surface of the photoresist layer is basically the same, so that the exposure lens can perform secondary exposure on the photoresist layer according to the adjusted exposure focal length and the specified exposure energy.

[0023] By employing the above technical solution, a low-energy initial exposure is performed on the photoresist layer to obtain a high-low deviation value array. Subsequently, based on this high-low deviation value array, the exposure focal length corresponding to each exposure area is determined, ensuring that the distance between the exposure lens and the photoresist layer surface is essentially the same. This guarantees that during the second exposure, the focal length setting for each exposure area conforms to the morphology of the photoresist layer surface, even if the wafer is warped, the exposure focal length will still be adjusted according to the photoresist layer. This solution ensures that during the formal exposure (i.e., the second exposure with energy), the distance between the photoresist layer and the exposure lens is consistent in all exposure areas, thereby improving patterning quality.

[0024] In summary, this application includes at least one of the following beneficial technical effects: 1. This method adjusts the exposure focal length of each exposure area based on the first energy-free exposure, thereby ensuring that the focal length setting of each exposure area matches the morphology of the photoresist layer surface during the second exposure. Even if the wafer is a warped wafer, the exposure focal length will still be adjusted according to the photoresist layer, improving the overall patterning quality. The method is simple and has a wide range of applications.

[0025] 2. The lithography system in this case does not require any additional modifications to the overall equipment, does not require the use of other equipment, is low in cost, and is suitable for non-standard processes and high-specification products. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of the photolithography method provided by the present invention; Figure 2 for Figure 1 A schematic diagram of the exposure of the photoresist layer; Figure 3 This is a schematic diagram of the high and low deviation image obtained in step 102; Figure 4 This is a schematic diagram of the elevation deviation image obtained in step 103. Figure 5 A schematic diagram of a finished product generated by an existing photolithography method that directly uses the initial focal length for energetic exposure; Figure 6 This is a schematic diagram of the finished product obtained from step 105. Figure 7 This is a schematic diagram of the exposure apparatus provided by the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, without excluding other elements or objects. In this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "a plurality of" means two or more, unless otherwise expressly defined.

[0028] To address the problems existing in the prior art, this invention provides a photolithography method. (From the reference...) Figure 1As shown, the photolithography method includes: after forming an anti-reflection layer 201 and a photoresist layer 202 on a wafer 200, performing an energy-free first exposure on the photoresist layer 202 to obtain high and low deviation values ​​corresponding to each exposure area, generating a high and low deviation value array; adjusting the exposure focal length according to the high and low deviation values ​​in the high and low deviation array so that the distance from the exposure lens 203 to the surface of the photoresist layer 202 is basically the same; performing a second exposure on the photoresist layer 202 according to the adjusted exposure focal length and the specified exposure energy; and performing post-baking and development processing on the photoresist layer 202.

[0029] This invention performs a low-energy initial exposure on the photoresist layer to obtain a high-low deviation value array. Subsequently, based on this array, the exposure focal length for each exposure area is adjusted to ensure that the distance between the exposure lens 203 and the surface of the photoresist layer 202 is essentially the same. This guarantees that during the second exposure, the focal length setting for each exposure area conforms to the morphology of the photoresist layer 202 surface, even if the wafer 200 is a warped wafer, the exposure focal length will still be adjusted according to the photoresist layer 202. This invention ensures that during the final exposure (i.e., the high-energy second exposure), the distance between the photoresist layer 202 and the exposure lens 203 is consistent across all exposure areas, thereby improving patterning quality.

[0030] The following is a detailed description of the implementation details of a photolithography method according to this embodiment. The following content is only for ease of understanding and is not essential to this embodiment or solution. The specific process of this embodiment is as follows: Figure 1 As shown, it includes the following steps: Step 101: Form an anti-reflective layer and a photoresist layer on the wafer.

[0031] Specifically, the wafer is placed on the wafer stage and its position is fixed. (Reference) Figure 2 As shown, an anti-reflective layer 201 of a first preset thickness is formed on wafer 200 to reduce light reflection during photolithography and prevent overexposure of the photoresist layer, which could lead to image blurring and distortion. The thickness of the anti-reflective layer 200 can be adjusted as needed, with an adjustment range between 200 Å and 1500 Å.

[0032] A photoresist layer 202 of a second preset thickness is formed on the anti-reflective layer 201. The thickness of the photoresist layer 202 can be adjusted according to the testing requirements. The thickness of the photoresist layer 202 is usually related to the material of the photoresist. The adjustment range of the second preset thickness is usually 500-40000A. The photoresist layer uses i-line type, KrF type, ArF type, and iArF type photoresist.

[0033] Step 102: Perform an energy-free first exposure on the photoresist layer to obtain the high and low deviation values ​​of the photoresist layer in each exposure area, and generate a high and low deviation value array.

[0034] Specifically, refer to Figure 2 As shown, the exposure energy E is set to 0, and the parameters of the exposure lens 203 are adjusted with a uniform initial focal length f. The exposure lens 203 is controlled to perform the first energy-free exposure on the photoresist layer 202. Since the first exposure has no energy, the photoresist layer 202 does not react at this time.

[0035] The distance between the exposure lens 203 and the surface of the photoresist layer 202 in each exposure area is detected and used as the initial distance value d. The initial distance values ​​d of all exposure areas in the exposure lens 203 are displayed in image form, which is the initial image.

[0036] Obtain the preset distance reference value d 标 This distance reference value is a preset value. It can be a value set by the wafer manufacturer according to the wafer's factory specifications, a value set by the photolithography operator according to their own needs, or it can be used during standard part manufacturing to measure the distance between the exposure lens and the corresponding photoresist layer of the standard part. This distance reference value d 标 Displayed as an image, it is a standard image.

[0037] Based on the initial distance d corresponding to each exposure area, the elevation deviation D of the exposure area is calculated, where D = dd. 标 The elevation deviation value D is displayed as an image, forming the overall elevation deviation image. In other words, image processing is used to subtract the pixel value of each pixel in the initial image from the pixel value of each pixel in the standard image, and this result is used as the pixel value corresponding to the elevation deviation image. The pixel value of the exposed area corresponding to the initial image is the initial distance value d, the pixel value of the exposed area corresponding to the standard image is the distance reference value d, and the pixel value of the exposed area corresponding to the elevation deviation image is the elevation deviation value D.

[0038] High and low deviation image reference Figure 3 As shown, the circular area represents the region where the photoresist layer 202 is located on wafer 200. This circular area is divided by a grid, where each small square represents an exposure area. The area within each small square is numbered, and the color within each small square represents the high / low deviation value D of that exposure area. According to the distribution of the exposure areas, color boxes corresponding to the high / low deviation values ​​D are arranged to obtain a high / low deviation array of the image shape.

[0039] In one example, a pixel value is defined as "1". The image morphology high / low deviation array is then numerically normalized to obtain a digital high / low deviation array. It's worth noting that the high / low deviation value D in the high / low deviation array can have both positive and negative values.

[0040] In this example, the exposure energy E is set to 0 to achieve virtual exposure focusing. The distance between the exposure lens 203 and the surface of the photoresist layer 202 is recorded to obtain the initial distance value d for each exposure area. Then, combined with the distribution of the exposure areas, the height deviation value D for each exposure area is obtained. This height deviation array represents the flatness of the photoresist layer 202 surface. A positive height deviation value D indicates that the distance d from the exposure lens 203 to the surface of the photoresist layer 202 in the current exposure area is greater than the distance reference value d. 标 If the height deviation value D is negative, it means that the surface of the photoresist layer 202 is recessed, and the focal length of the exposure lens 203 needs to be increased. If the height deviation value D is negative, it means that the distance d from the exposure lens 203 to the surface of the photoresist layer 202 in the current exposure area is less than the distance reference value d. 标 This indicates that the surface of the current photoresist layer 202 is protruding, and at this point, the focal length of the exposure lens 203 needs to be reduced. In the high / low deviation image reference that has not undergone adjustment in step 103... Figure 3 As shown, Figure 3 In the image, the high / low deviation values ​​of the exposure area enclosed by the red box show a strong color difference compared to the high / low deviation values ​​of other exposure areas. This indicates a significant protrusion or depression in the red-boxed area. Exposure based on this will directly lead to abnormal photolithography results in the red-boxed area, resulting in unclear graphic representation. Therefore, it is crucial to ensure that the light focusing position from the exposure lens 203 to the surface of the photoresist layer 202 in the current exposure area is consistent with other exposures.

[0041] Step 103: Adjust the exposure energy and exposure focal length according to the high and low deviation values ​​in the high and low deviation array.

[0042] Specifically, the first standard deviation value xmax and the second standard deviation value xmin are set according to the photolithography process conditions. Post-baking and development are conventional basic photolithography processes. In this case, based on the process requirements corresponding to these basic photolithography processes, the corresponding first standard deviation value xmax and second standard deviation value xmin are read from the standard database to ensure that different process requirements use the corresponding first standard deviation value xmax and second standard deviation value xmin to achieve the corresponding focal length adjustment.

[0043] When the high / low deviation value of the high / low deviation array corresponding to the exposure area is higher than the first standard deviation value xmax, the exposure focal length is increased; when the high / low deviation value of the high / low deviation array corresponding to the exposure area is lower than the second standard deviation value xmin, the exposure focal length is decreased; based on the exposure focal length corresponding to each exposure area, the corresponding exposure energy is selected. By increasing and decreasing the exposure focal length, Figure 3 The exposure areas enclosed by the red frame are modulated to Figure 4The high and low deviation values ​​of the corresponding exposure areas are used to ensure that the light focusing position from the exposure lens 203 to the surface of the photoresist layer 202 in the current exposure area is consistent with that of other exposure areas.

[0044] In one example, the first standard deviation value xmax and the second standard deviation value xmin are both in image form. Using the image processing method described in step 102, the pixel values ​​of the high and low deviation values ​​in the high and low deviation array are compared with the first standard deviation value xmax and the second standard deviation value xmin. This results in the conclusion that "the high and low deviation value of the high and low deviation array corresponding to the exposure area is higher than the first standard deviation value xmax" and "the high and low deviation value of the high and low deviation array corresponding to the exposure area is lower than the second standard deviation value".

[0045] In one example, the first standard deviation value xmax is positive, and the second standard deviation value xmin is negative. Using the pixel value definition proposed in step 102, a pixel value is defined as "1" to standardize the high-low deviation map, i.e., the high-low deviation array becomes a numerical array. Through numerical comparison, it is determined that "the high-low deviation value of the high-low deviation array corresponding to the exposure area is higher than the first standard deviation value xmax" and "the high-low deviation value of the high-low deviation array corresponding to the exposure area is lower than the second standard deviation value".

[0046] As the exposure focal length is adjusted, the high and low deviation values ​​will gradually converge within the range [xmin, xmax]. Furthermore, once the exposure focal length adjustment is complete and all high and low deviation values ​​are within [xmin, xmax], the corresponding exposure energy is selected based on these exposure focal lengths. The exposure energy can be manually selected by the user or obtained directly from a historical database based on the exposure focal length; here, the exposure energy can be set uniformly for all exposure areas or set separately according to the exposure requirements of different exposure areas.

[0047] In some examples, the exposure focal length is reduced, specifically including: according to the preset focal length step Δf, the initial focal length f of the exposure area is cyclically reduced to obtain the target focal length value, until the updated high and low deviation value obtained by exposing the photoresist layer 202 through the exposure lens 203 with the target focal length value and zero exposure energy is within the standard deviation range [xmin, xmax] composed of the first standard deviation value xmax and the second standard deviation value xmin.

[0048] The process of increasing the exposure focal length specifically includes: according to the preset focal length step Δf, the initial focal length f of the exposure area is cyclically increased to obtain the target focal length value, until the updated high and low deviation value obtained by exposing the photoresist layer 202 through the exposure lens 203 with the target focal length value and zero exposure energy is within the standard deviation range [xmin, xmax] composed of the first standard deviation value xmax and the second standard deviation value xmin.

[0049] In this example, the preset focal length step size is used to cyclically decrease until the high and low deviation values ​​fall within the standard deviation range [xmin, xmax]. The smaller the standard deviation range, the more accurate the result. The first standard deviation value xmax and the second deviation value xmin are set based on the average of all high and low deviation values ​​in the high and low deviation array. The difference between the first deviation value xmax, the second deviation value xmin, and the average value is set by the operator; this setting is crucial for accuracy. In other words, this design supports user-defined accuracy performance.

[0050] In some examples, when the high-low deviation value of the high-low deviation array corresponding to the exposure area is higher than the first standard deviation value xmax, the exposure focal length is reduced. Specifically, this includes: finding the corresponding focal length adjustment difference from a preset first database based on the difference between the high-low deviation value corresponding to the exposure area and the first standard deviation value xmax; obtaining the adjusted exposure focal length F corresponding to the exposure area based on the focal length adjustment difference and the initial focal length f; and adjusting the exposure lens 203 based on the exposure focal length F.

[0051] When the high-low deviation value of the high-low deviation array corresponding to the exposure area is lower than the second standard deviation value xmin, the exposure focal length is increased. Specifically, this includes: finding the corresponding focal length adjustment difference from a preset first database based on the deviation difference between the high-low deviation value corresponding to the exposure area and the second standard deviation value xmin; obtaining the exposure focal length F corresponding to the adjusted exposure area based on the focal length adjustment difference and the initial focal length f; and adjusting the exposure lens 203 based on the exposure focal length F.

[0052] In this example, when adjusting the exposure focal length upwards and downwards, the corresponding focal length adjustment difference is directly retrieved from the first database based on the difference between the high / low deviation value and the first labeled deviation value xmax or the second deviation value xmin. This focal length adjustment difference is then superimposed on the current exposure focal length to obtain the exposure focal length corresponding to the adjusted exposure area. The associated deviation differences and focal length adjustment differences in the first database are reusable data, either pre-stored by staff or stored as historical data. Compared to the previous example, which required continuous iteration to obtain results, this method is significantly faster in terms of calculation and execution speed.

[0053] In some examples, when the high-low deviation value of the high-low deviation array corresponding to the exposure area is higher than the first standard deviation value xmax, the exposure focal length is reduced. Specifically, this includes: finding the corresponding focal length value from the preset second database according to the high-low deviation value corresponding to the exposure area, using it as the exposure focal length corresponding to the adjusted exposure area, and adjusting the exposure lens 203 according to the exposure focal length.

[0054] When the high-low deviation value of the high-low deviation array corresponding to the exposure area is lower than the second standard deviation value xmin, the exposure focal length is increased. Specifically, this includes finding the corresponding focal length value from the preset second database based on the high-low deviation value corresponding to the exposure area, using it as the exposure focal length corresponding to the adjusted exposure area, and adjusting the exposure lens 203 according to the exposure focal length.

[0055] In this example, when focus adjustment is needed, the corresponding focus value is directly retrieved from the second database based on the detected elevation deviation value. This focus value is then set as the focus of the exposure lens 203, completing the adjustment of the corresponding exposure focus. The interconnected elevation deviation values ​​and focus values ​​in the second database are typically pre-set by the staff, or they can be historical values ​​stored for later retrieval. This approach is suitable for application environments supporting massive data storage. While it sacrifices some flexibility, the overall application debugging speed is very fast.

[0056] Step 104: Perform a second exposure on the photoresist layer to ensure that the distance between the exposure lens and the surface of the photoresist layer is basically the same.

[0057] Specifically, the exposure lens 203 is adjusted according to the exposure focal length in step 103. Then, using the adjusted exposure lens, the photoresist layer 202 is subjected to a second exposure according to the exposure energy E specified by the user. Since this exposure has a certain amount of energy, this energy causes changes in the photoresist layer 102, completing the exposure step of the traditional photolithography process.

[0058] Furthermore, since the distance between the exposure lens 203 and the surface of the photoresist layer 202 is essentially the same, the energy output by the exposure lens 203 is uniformly absorbed by the photoresist layer 202. Even if the wafer warps, this invention still adjusts the exposure focal length based on the photoresist layer to improve the overall patterning quality.

[0059] Step 105: Perform post-baking and development treatments on the photoresist layer.

[0060] Specifically, after step 104 is performed, the exposed photoresist layer 202 is baked. This is especially beneficial for chemically amplified photoresists, allowing thicker photoresists to be exposed with a lower exposure dose and accelerating the development process. The development process involves dissolving the photoresist layer in the exposed area in the developer solution, causing the photoresist layer to form a three-dimensional pattern.

[0061] Based on traditional photolithography methods, when wafer 200 warps downwards, patterning the photoresist layer 202 using a uniform focal length will result in... Figure 5 The situation shown is that, Figure 5 In the third box of the third row, there is a missing graphic.

[0062] Using this photolithography method, when the wafer 200 warps downwards, the focal length of the exposure lens 203 is adjusted synchronously according to the photoresist layer 202 to ensure that the distance from the exposure lens 203 to all exposure areas on the surface of the photoresist layer 202 is basically the same. The photolithography result is as follows: Figure 6 As shown. In Figure 6 In the third box of the third row, the graphic (black dot) in the exposure area (gray solid box) is displayed. Therefore, this design converts the distance between the exposure lens and the outer surface of the photoresist layer 202 in each exposure area during the first energy-free exposure into a high-low deviation array, and adjusts the exposure focal length corresponding to each exposure area. This ensures that during the second exposure, the focal length setting of each exposure area matches the morphology of the photoresist layer surface. Even if the wafer is a warped wafer, the exposure focal length will still be adjusted according to the photoresist layer, improving the overall patterning quality.

[0063] The steps described above are only for clarity. In practice, they can be combined into one step or some steps can be broken down into multiple steps. As long as they involve the same logical relationship, they are all within the scope of protection of this patent. Adding insignificant modifications or introducing insignificant designs to the algorithm or process, as long as they do not change the core design of the algorithm and process, are also within the scope of protection of this patent.

[0064] The present invention also provides an exposure apparatus 300, for reference Figure 7 As shown, it includes an exposure lens 203, a distance sensor 301, and a lens controller 302; Exposure lens 203 performs energy-free initial exposure on photoresist layer 202; photoresist layer 202 is formed on anti-reflection layer on wafer; Distance sensor 301 is mounted on exposure lens 203 to detect the distance between exposure lens 203 and photoresist layer 202, so that lens controller 302 can obtain the high and low deviation values ​​of photoresist layer 202 in each exposure area and generate high and low deviation array. The lens controller 302 is connected to the distance sensor 301 and the exposure lens 203. It adjusts the exposure focal length according to the high and low deviation values ​​in the high and low deviation array so that the distance between the exposure lens 203 and the surface of the photoresist layer 202 is basically the same, so that the exposure lens 203 can perform secondary exposure on the photoresist layer 202 according to the adjusted exposure focal length and the specified exposure energy.

[0065] This invention ensures that during secondary exposure, the focal length of each exposure area is set to match the morphology of the photoresist layer surface. Even if the wafer is warped, the exposure focal length will still be adjusted according to the photoresist layer. This invention ensures that during formal exposure (i.e., energy-bearing secondary exposure), the distance between the photoresist layer 202 and the exposure lens 203 in all exposure areas is consistent, thereby improving patterning quality.

[0066] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

[0067] The above description of the embodiments is intended to enable those skilled in the art to understand and apply this application. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, this application is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A photolithography method, characterized in that, include: After forming an anti-reflection layer and a photoresist layer on the wafer, the photoresist layer is subjected to an energy-free first exposure to obtain the high and low deviation values ​​of the photoresist layer in each exposure area, and a high and low deviation value array is generated. The anti-reflection layer is located between the wafer and the photoresist layer. The exposure focal length is adjusted according to the high and low deviation values ​​in the high and low deviation array so that the distance from the exposure lens to the surface of the photoresist layer is basically the same. The photoresist layer is subjected to secondary exposure based on the adjusted exposure focal length and the specified exposure energy. The photoresist layer is subjected to post-baking and development processes.

2. The photolithography method according to claim 1, characterized in that, The process of forming an anti-reflective layer and a photoresist layer on a wafer includes: An anti-reflective layer of a first preset thickness is formed on the wafer, wherein the adjustment range of the first preset thickness is 200-1500 Å; A photoresist layer of a second preset thickness is formed on the anti-reflective layer, and the adjustment range of the second preset thickness is 500-40000 Å.

3. The photolithography method according to claim 1, characterized in that, The process of performing an energy-free first exposure on the photoresist layer to obtain high and low deviation values ​​of the photoresist layer in each exposure area, and generating a high and low deviation value array, includes: Obtain distance reference value; The exposure energy is set to zero, and the photoresist layer is exposed for the first time at the initial focal length. The distance between the exposure lens and the surface of the photoresist layer in each exposure area is detected as the initial distance value. Based on the distance reference value and the initial distance value of each exposure area, the height deviation value of each exposure area is calculated to obtain an array of height deviation values ​​according to the arrangement of the exposure areas.

4. The photolithography method according to claim 3, characterized in that, The exposure focal length is adjusted according to the high and low deviation values ​​in the high and low deviation array to make the distance between the exposure lens and the surface of the photoresist layer substantially the same. A second exposure is then performed on the photoresist layer based on the adjusted exposure focal length and the specified exposure energy, including: When the height deviation value corresponding to the exposure area is higher than the first standard deviation value, the exposure focal length is increased; when the height deviation value corresponding to the exposure area is lower than the second standard deviation value, the exposure focal length is decreased. Select the corresponding exposure energy based on the exposure focal length corresponding to each exposure area; The photoresist layer is subjected to secondary exposure based on the exposure energy and the exposure focal length corresponding to each exposure area.

5. The photolithography method according to claim 4, characterized in that, The first standard deviation value and the second standard deviation value are set according to the photolithography process conditions.

6. The photolithography method according to claim 4, characterized in that, The reduction in exposure focal length includes: According to a preset focal length step, the initial focal length of the exposure area is sequentially reduced to obtain a target focal length value until the updated high / low deviation value obtained by exposing the photoresist layer with the target focal length value and zero exposure energy is within the standard deviation range, where the boundary values ​​of the standard deviation range are the first standard deviation value and the second standard deviation value; and / or, the upward adjustment of the exposure focal length includes: According to the preset focal length step, the initial focal length of the exposure area is sequentially increased to obtain the target focal length value, until the updated high and low deviation value obtained by exposing the photoresist layer with the target focal length value and zero exposure energy is within the range of the standard deviation value.

7. The photolithography method according to claim 4, characterized in that, The reduction in exposure focal length includes: Based on the deviation difference between the high and low deviation values ​​corresponding to the exposure area and the first standard deviation value, the corresponding focal length adjustment difference is found from a preset first database; based on the focal length adjustment difference and the initial focal length, the exposure focal length corresponding to the adjusted exposure area is obtained; wherein, the first database includes interrelated deviation differences and focal length adjustment differences; and / or, the upward adjustment of the exposure focal length includes: Based on the difference between the high and low deviation values ​​of the exposure area and the second standard deviation value, the corresponding focal length adjustment difference is found from the preset first database; based on the focal length adjustment difference and the initial focal length, the exposure focal length corresponding to the adjusted exposure area is obtained.

8. The photolithography method according to claim 4, characterized in that, The downward adjustment of the exposure focal length and the upward adjustment of the exposure focal length include: Based on the high and low deviation values ​​corresponding to the exposure area, the corresponding focal length value is found from the preset second database and used as the exposure focal length corresponding to the adjusted exposure area; wherein, the second database includes interrelated high and low deviation values ​​and focal length values.

9. The photolithography method according to claim 1, characterized in that, The photoresist includes i-line type, KrF type, ArF type, and iArF type photoresist.

10. An exposure apparatus, characterized in that, Includes exposure lens, distance sensor, and lens controller; The exposure lens performs an energy-free first exposure on the photoresist layer, which is formed on an anti-reflective layer on the wafer. The distance sensor is mounted on the exposure lens to detect the distance between the exposure lens and the photoresist layer, so that the lens controller can obtain the high and low deviation values ​​of the photoresist layer in each exposure area and generate a high and low deviation array. The distance sensor and the exposure lens are respectively connected to the lens controller. The lens controller adjusts the exposure focal length according to the high and low deviation values ​​in the high and low deviation array so that the distance between the exposure lens and the surface of the photoresist layer is basically the same, so that the exposure lens can perform secondary exposure on the photoresist layer according to the adjusted exposure focal length and the specified exposure energy.

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