Method for improving line edge roughness of side wall of line of photoresist

Abstract

The invention discloses a method for improving the line edge roughness of the side wall of a line of photoresist. The method comprises the following steps: S1, providing two product sheets before a photoetching process; s2, gluing is carried out, two gluing sheets are obtained, and photoresist for gluing is I line glue; s3, exposure is carried out, two exposure sheets are obtained, two PEB (post-exposure baking) temperatures are set for the two exposure sheets, the two PEB temperatures are different, and other exposure parameters are the same; s4, developing, namely developing the two exposed sheets under the same developing condition to obtain two developing sheets; and S5, performing SEM slicing on each developing sheet, observing the line edge roughness of the side wall, determining the influence of the PEB temperature on the line edge roughness of the side wall, and determining the optimized parameters and the optimized process of batch production of the photoetching process. Therefore, the line edge roughness of the side wall of the line of the photoresist can be improved.

Description

Technical Field

[0001] This disclosure relates to the semiconductor field, and more specifically to a method for improving the line edge roughness of the sidewalls of a photoresist line. Background Technology

[0002] In semiconductor device fabrication, photolithography is a crucial step, involving the formation of patterns using photoresist, followed by subsequent etching. In photolithographic patterns, the sidewalls of the lines must be smooth, meaning low line edge roughness (LER). If the sidewalls are uneven, exhibiting poor perpendicularity (i.e., jagged edges perpendicular to the bottom surface of the line), this unevenness not only affects the effective measurement of linewidth but also the linewidth quality of the etching layer beneath the photolithographic pattern. Since the line edge roughness of the sidewalls in photolithographic patterns is influenced by many factors, further in-depth research is needed to continuously broaden optimization directions for improving the line edge roughness of photolithographic lines, providing optimized parameters and processes for mass production in the photolithography process. Summary of the Invention

[0003] In view of the problems existing in the background art, one object of this disclosure is to provide a method for improving the line edge roughness of the sidewalls of photoresist lines, which can improve the line edge roughness of the sidewalls of photoresist lines, can provide an optimization direction for improving the line edge roughness of the sidewalls of photoresist lines, and can provide optimized parameters and optimized processes for mass production of photolithography processes.

[0004] Another object of this disclosure is to provide a method for improving the line edge roughness of the sidewalls of photoresist lines, which can ensure effective measurement of line width dimensions and ensure the line width quality of the etching of the film layer under the photolithographic pattern.

[0005] Therefore, a method for improving the line edge roughness of the sidewalls of photoresist lines includes the following steps: S1, providing two product wafers before the photolithography process; S2, coating with photoresist to obtain two coated wafers, wherein the photoresist used for coating is I-line photoresist; S3, exposure to obtain two exposed wafers, wherein two PEB (post-exposure baking) temperatures are set for the two exposed wafers, the two PEB temperatures are different, and the other exposure parameters are the same; S4, development, the two exposed wafers are developed under the same development conditions to obtain two developed wafers; S5, each developed wafer is sectioned by SEM to observe the line edge roughness of the sidewalls, determine the influence of PEB temperature on the line edge roughness of the sidewalls, and determine the optimized parameters and optimized process for mass production of the photolithography process.

[0006] The beneficial effects of this disclosure are as follows.

[0007] According to the method for improving the edge roughness of the sidewalls of photoresist lines disclosed herein, for an I-line photoresist, by using two different PEB temperatures in step S3, as verified by the testing process, the effect of PEB temperature on the edge roughness of the sidewalls of the lines can be observed. This provides an optimization direction for improving the edge roughness of the sidewalls of the photoresist lines (i.e., improving the perpendicularity of the line sidewalls; in other words, making the line sidewalls smoother in the direction perpendicular to the bottom surface of the line), and provides optimized parameters and processes for mass production in the photolithography process. In other words, the method for improving the edge roughness of the sidewalls of photoresist lines disclosed herein can improve the edge roughness of the sidewalls of photoresist lines, provide an optimization direction for improving the edge roughness of the sidewalls of photoresist lines, and provide optimized parameters and processes for mass production in the photolithography process.

[0008] Furthermore, the method disclosed herein for improving the line edge roughness of the sidewalls of the photoresist lines can ensure effective measurement of the line width dimension and ensure the line width quality of the etching of the film layer beneath the photolithographic pattern. Attached Figure Description

[0009] Figure 1 This is the sidewall morphology of the lines of a SEM slice of one of the two product slices in Example 1 after photolithography at a PEB temperature of 110°C.

[0010] Figure 2 The image shows the sidewall morphology of the lines on a SEM slice of another product sheet from Example 1, after photolithography at a PEB temperature of 130°C. Detailed Implementation

[0011] It will be understood that the disclosed embodiments are merely examples of this disclosure, which can be implemented in various forms. Therefore, the specific details disclosed herein should not be construed as limiting, but are intended only as the basis for the claims and as an illustrative basis to teach those skilled in the art how to implement this disclosure in various ways.

[0012] [Methods to improve the edge roughness of the sidewalls of photoresist lines] The method for improving the line edge roughness of the sidewalls of photoresist lines according to this disclosure includes the following steps: S1 provides two product wafers before the photolithography process; S2, applying photoresist to obtain two coated films, wherein the photoresist used for coating is I-line photoresist; S3, Exposure, to obtain two exposure films. For the two exposure films, two PEB (post-exposure baking) temperatures are set. The two PEB temperatures are different, and the other exposure parameters are the same. S4, Development: The two exposed films are developed under the same development conditions to obtain two developed films. S5. Perform SEM slices on each display film to observe the line edge roughness of the sidewalls of the lines, determine the effect of PEB temperature on the line edge roughness of the sidewalls of the lines, and determine the optimization parameters and optimization process for mass production of the photolithography process.

[0013] According to the method for improving the edge roughness of the sidewalls of photoresist lines disclosed herein, for an I-line photoresist, by using two different PEB temperatures in step S3, as verified by the testing process, the effect of PEB temperature on the edge roughness of the sidewalls of the lines can be observed. This provides an optimization direction for improving the edge roughness of the sidewalls of the photoresist lines (i.e., improving the perpendicularity of the line sidewalls; in other words, making the line sidewalls smoother in the direction perpendicular to the bottom surface of the line), and provides optimized parameters and processes for mass production in the photolithography process. In other words, the method for improving the edge roughness of the sidewalls of photoresist lines disclosed herein can improve the edge roughness of the sidewalls of photoresist lines, provide an optimization direction for improving the edge roughness of the sidewalls of photoresist lines, and provide optimized parameters and processes for mass production in the photolithography process.

[0014] Furthermore, the method disclosed herein for improving the line edge roughness of the sidewalls of the photoresist lines can ensure effective measurement of the line width dimension and ensure the line width quality of the etching of the film layer beneath the photolithographic pattern.

[0015] In the method for improving the edge roughness of the sidewalls of photoresist lines according to this disclosure, the PEB temperature affects the edge roughness of the sidewalls. The inventors believe that one characteristic of I-line photoresist is the standing wave effect, caused by the interference between the reflected light beam and the original incident light beam during exposure. This causes a noticeable wavy structure to form on the sidewall morphology of the photoresist lines during exposure. The PEB (post-exposure baking) temperature directly affects this wavy structure. Under the heat of the PEB, the mobility of the polymer chains in the I-line photoresist changes, and the acid diffusion within the photoresist changes during development. This change in diffusion alters the uniformity of the longitudinal acid concentration within the photoresist, thus affecting the smoothness of the sidewalls. In other words, the PEB temperature has a substantial impact on reducing the standing wave reaction and thus reducing LER (Left Edge Reduction). Furthermore, the heat energy provided by the PEB affects the sufficiency and completeness of the photochemical reaction in all exposed areas. The thermal process of the PEB affects polymer chain relaxation, releasing internal stress, and causing residual solution to evaporate. All of these factors substantially affect the sidewall morphology of the wavy structure of the photoresist lines.

[0016] In step S1, in one example, each product wafer is an 8-inch diameter wafer with a 150 Å thick SIN film coating on its surface. However, this is not the only possibility; the surface condition and size of the product wafers can vary depending on actual production conditions.

[0017] In one example, step S2, the coating process, includes the following sub-steps: S21, HMDS film formation, where an HMDS film is formed on the surface of each product sheet using a vapor phase method; S22, pre-cooling before spin coating, where each product sheet with the HMDS film on its surface is cooled in a cooling bath to the temperature required for spin coating; S23, coating, where each product sheet is spin-coated in a spin coating process tank; and S24, pre-baking, where each product sheet after spin coating is pre-baked in a pre-baking process tank. More specifically, in one example, in sub-step S21, the operation of forming the HMDS film using a vapor phase method is as follows: each product sheet is placed on a stage in a vacuum chamber and the stage is heated to 110°C. Nitrogen is used as the carrier gas at a pressure of 25 kPa. HMDS vapor carried by nitrogen is introduced, the pressure of the vacuum chamber is maintained at 20 Pa, the HMDS vapor carried by nitrogen is introduced for 60 s, and the thickness of the formed HMDS film is 6 Å. More specifically, in one example, the temperature required for spin coating in sub-step S22 is 23°C. More specifically, in one example, in sub-step S23, the spin coating process is as follows: 1.5 mL of adhesive solution is dropped onto the center of each product sheet at a dynamic speed of 2050 rpm. After the adhesive solution is dropped completely in 1.5 s, each product sheet is rotated at 3180 rpm for 30 s, resulting in a final coating thickness of 5350 Å. More specifically, in one example, in sub-step S23, the adhesive type is AR80-3.3CP. More specifically, in one example, in sub-step S24, the pre-baking temperature is 90°C, and the time is 60 s.

[0018] In one example, step S3, exposure, includes the following sub-steps: S31, pre-exposure cooling, where the two coated films, after pre-baking, are cooled in a cooling bath to the required exposure temperature of 23°C; S32, exposure, using a photomask and a Nikon SF120 exposure unit with stepping in the X direction at 12949 μm and in the Y direction at 250389 μm, and an exposure dose of 268 mJ / cm² for each step. 2 The imaging focal length is -0.4μm and the NA value is 0.62; S33, post-exposure baking, the post-exposure baking is performed in the post-exposure baking process tank using the PEB (post-exposure baking) temperature set in step S3, the PEB (post-exposure baking) temperatures of the two exposure films are 110℃ and 130℃ respectively, and the time is 120s for both.

[0019] In one example, the development step S4 includes the following sub-steps: S41, pre-development cooling, where the two exposed films baked after exposure are cooled in a cooling tank to the temperature of 23°C required for development; S42, development, where the pre-development cooled films are placed on the turntable of the developing machine, and while rotating, developer is dripped onto the center of each film, followed by rinsing with water while rotating. The rotation is unidirectional, the rotation speed is 2000 rpm, positive photoresist developer is used, the developer type is ZX-238, the development time is 60s, and the rinsing time is 30s; S43, post-baking in a post-baking process tank, the post-baking temperature is 110°C, and the time is 90s.

[0020] [test] Example 1 Example 1 uses the following steps: S1 provides two product wafers before the photolithography process, each of which is an 8-inch diameter wafer with a 150Å thick SIN film coating on its surface. S2, applying photoresist, obtaining two coated films, wherein the photoresist used for coating is I-line photoresist. The adhesive application in step S2 is performed using the following sub-steps: S21, HMDS film formation: HMDS film is formed on the surface of each product sheet using a vapor phase method. The operation of forming HMDS film using a vapor phase method is as follows: each product sheet is placed on the stage of the vacuum chamber and the stage is heated to 110°C. Nitrogen is used as the carrier gas and the pressure of the nitrogen is 25 kPa. HMDS vapor carried by nitrogen is introduced. The pressure of the vacuum chamber is maintained at 20 Pa. The time for introducing HMDS vapor carried by nitrogen is 60 s. The thickness of the formed HMDS film is 6 Å. S22, Cooling before spin coating: Each product sheet with an HMDS film formed on its surface is cooled in a cooling bath to the temperature required for spin coating, wherein the temperature required for spin coating is 23°C. S23, Coating: Each product sheet is spin-coated in a spin coating process tank. The spin coating process is as follows: 1.5 mL of adhesive solution is dropped onto the center of each product sheet at a dynamic speed of 2050 rpm. After the adhesive solution is dropped for 1.5 seconds, each product sheet is rotated at 3180 rpm for 30 seconds. The final coating thickness is 5350 Å. The adhesive type is AR80-3.3CP. S24, Pre-baking: After spin coating and uniform application, each product sheet is pre-baked in the pre-baking process tank, where the pre-baking temperature is 90℃ and the time is 60s. S3, Exposure, resulting in two exposed films. Two different PEB (post-exposure baking) temperatures are set for the two films; all other exposure parameters are the same. The exposure in step S3 is performed using the following sub-steps: S31, pre-exposure cooling: the two coated sheets, after pre-baking, are cooled in a cooling bath to the temperature of 23°C required for exposure. S32, exposure, using a photomask and Nikon SF120 machine for step exposure, with a step size of 12949 μm in the X direction and 250389 μm in the Y direction. The exposure dose per step exposure is 268 mJ / cm². 2 The imaging focal length is -0.4μm and the NA value is 0.62; S33, Post-exposure baking: Post-exposure baking is performed in the post-exposure baking process tank using the PEB (post-exposure baking) temperature set in step S3. The PEB (post-exposure baking) temperatures of the two exposed films are 110℃ and 130℃, respectively, and the time is 120s for each film. S4, Development: The two exposed films are developed under the same conditions to obtain two developed films. The development step S4 comprises the following sub-steps: S41, pre-development cooling: Cool the two exposed films that have been baked after exposure in a cooling bath to the temperature required for development, 23°C. S42, Development: Place the cooled film on the turntable of the developing machine. While rotating, drip developer onto the center of each film. Then, while rotating, rinse with water. The rotation is unidirectional and the rotation speed is 2000 rpm. Positive photoresist developer is used. The developer type is ZX-238. The development time is 60 seconds and the rinsing time is 30 seconds. S43, post-drying in the post-drying process tank, the post-drying temperature is 110℃ and the time is 90s; S5. Perform SEM slices on each display film to observe the line edge roughness of the sidewalls of the lines, determine the effect of PEB temperature on the line edge roughness of the sidewalls of the lines, and determine the optimization parameters and optimization process for mass production of the photolithography process.

[0021] Figure 1 This is the sidewall morphology of the lines of a SEM slice of one of the two product slices in Example 1 after photolithography at a PEB temperature of 110°C. Figure 2 The image shows the sidewall morphology of the lines on a SEM slice of another product sheet from Example 1, after photolithography at a PEB temperature of 130°C.

[0022] Comparison Figure 1 and Figure 2It can be seen that using a PEB temperature of 130℃ significantly improves the sidewall morphology (i.e., line edge roughness) of the lines compared to using a PEB temperature of 110℃. Compared to the 110℃ PEB temperature, the increased heat from the PEB at 130℃ enhances the mobility of the polymer chains in the I-line photoresist, promoting acid diffusion within the photoresist during development. This enhanced diffusion improves the uniformity of longitudinal acid concentration within the photoresist, resulting in smoother sidewalls. In other words, the 130℃ PEB temperature reduces standing wave reaction and thus reduces LER (Low Efficiency Ratio). Furthermore, compared to the 110℃ PEB temperature, the increased heat provided by the PEB at 130℃ ensures that the photochemical reactions in all exposed areas are fully and thoroughly completed. The enhanced thermal process of the PEB relaxes the polymer chains, releasing internal stress and allowing residual solution to further evaporate.

[0023] Several exemplary embodiments have been described in detail above, but this document is not intended to limit itself to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined to form several other combinations, which are not shown for simplicity.

Claims

1. A method for improving the edge roughness of the sidewalls of photoresist lines, characterized in that, Including the following steps: S1 provides two product wafers before the photolithography process; S2, applying photoresist to obtain two coated films, wherein the photoresist used for coating is I-line photoresist; S3, Exposure, to obtain two exposure films. For the two exposure films, two PEB (post-exposure baking) temperatures are set. The two PEB temperatures are different, and the other exposure parameters are the same. S4, Development: The two exposed films are developed under the same development conditions to obtain two developed films. S5. Perform SEM slices on each display film to observe the line edge roughness of the sidewalls, determine the effect of PEB temperature on the line edge roughness of the sidewalls, and determine the optimized parameters and optimized process for mass production of the photolithography process.

2. The method for improving the edge roughness of the sidewalls of photoresist lines according to claim 1, characterized in that, In step S1, each product wafer is an 8-inch diameter wafer with a 150Å thick SIN film coating on its surface.

3. The method for improving the edge roughness of the sidewalls of photoresist lines according to claim 2, characterized in that, Step S2, applying adhesive, includes the following sub-steps: S21, HMDS film formation, using a vapor phase method to form an HMDS film on the surface of each product sheet; S22, Cooling before spin coating: Each product sheet with an HMDS film formed on its surface is cooled in a cooling bath to the temperature required for spin coating. S23, Coating: Each product sheet is coated with adhesive in a spin coating process tank. S24, Pre-baking: After spin coating and uniform application, each product sheet is pre-baked in the pre-baking process tank.

4. The method for improving the edge roughness of the sidewalls of photoresist lines according to claim 3, characterized in that, In sub-step S21, The operation of forming HMDS film by gas phase is as follows: each product sheet is placed on the stage of the vacuum chamber and the stage is heated to 110°C. Nitrogen is used as the carrier gas and the pressure of nitrogen is 25 kPa. HMDS vapor carried by nitrogen is introduced. The pressure of the vacuum chamber is maintained at 20 Pa and the time for introducing HMDS vapor carried by nitrogen is 60 s. The thickness of the formed HMDS film is 6 Å.

5. The method for improving the edge roughness of the sidewalls of photoresist lines according to claim 3, characterized in that, In sub-step S22, the temperature required for homogenization is 23°C.

6. The method for improving the edge roughness of the sidewalls of photoresist lines according to claim 3, characterized in that, In sub-step S23, the spin coating process is as follows: 1.5 mL of adhesive solution is dropped onto the center of each product sheet at 2050 rpm. After the adhesive solution is dropped in 1.5 s, each product sheet is rotated at 3180 rpm for 30 s. The final coating thickness is 5350 Å. In sub-step S23, the adhesive type is AR80-3.3CP.

7. The method for improving the edge roughness of the sidewalls of photoresist lines according to claim 3, characterized in that, In sub-step S24, the pre-baking temperature is 90°C and the time is 60 seconds.

8. The method for improving the edge roughness of the sidewalls of photoresist lines according to claim 2, characterized in that, The exposure in step S3 includes the following sub-steps: S31, pre-exposure cooling: the two coated sheets, after pre-baking, are cooled in a cooling bath to the temperature of 23°C required for exposure. S32, exposure, using a photomask and Nikon SF120 machine for step exposure, with a step size of 12949 μm in the X direction and 250389 μm in the Y direction. The exposure dose per step exposure is 268 mJ / cm². 2 The imaging focal length is -0.4μm and the NA value is 0.62; S33, Post-exposure baking: Post-exposure baking is performed in the post-exposure baking process tank using the PEB (post-exposure baking) temperature set in step S3. The PEB (post-exposure baking) temperatures of the two exposed films are 110℃ and 130℃, respectively, and the time is 120s for each.

9. The method for improving the line edge roughness of the sidewalls of a photoresist line according to claim 8, characterized in that, The development step S4 includes the following sub-steps: S41, pre-development cooling: Cool the two exposed films baked after exposure in a cooling bath to the temperature required for development, 23°C. S42, Development: Place the cooled film on the turntable of the developing machine. While rotating, drip developer onto the center of each film. Then, while rotating, rinse with water. The rotation is unidirectional and the rotation speed is 2000 rpm. Positive photoresist developer is used. The developer type is ZX-238. The development time is 60 seconds and the rinsing time is 30 seconds. S43, post-drying in the post-drying process tank, the post-drying temperature is 110℃ and the time is 90s.

Images