Method for solving photoetching morphology abnormity
By employing a two-dimensional array of distributed grain photomasks and FEM data exposure during the photolithography process, combined with imaging focal length adjustment, the problem of abnormal photolithography morphology is accurately determined, improving the three-dimensional contour accuracy and yield of the photolithography pattern, and reducing the solution cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI JINGWEI TECHNOLOGY CO LTD
- Filing Date
- 2026-03-13
- Publication Date
- 2026-05-12
AI Technical Summary
In existing technologies, the problem of abnormal lithographic morphology, especially the large white edges of lines, has not been effectively solved, resulting in a decrease in the three-dimensional contour accuracy and yield of lithographic patterns.
By employing a two-dimensional array of distributed grain photomasks and FEM data exposure during the photolithography process, combined with the adjustment and testing of the imaging focal length, the normal imaging focal length fluctuation value is accurately determined, and the abnormal photolithography morphology caused by the imaging focal length fluctuation is addressed primarily from the perspective of equipment parameters.
It effectively reduces the complexity of lithographic anomalies, lowers the cost of solving them, and improves the accuracy and yield of the three-dimensional contour of the lithographic pattern.
Smart Images
Figure CN122018247A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the semiconductor field, and more specifically to a method for resolving lithographic anomalies. Background Technology
[0002] In semiconductor manufacturing, photolithography is one of the key technologies for integrated circuits. Photolithography generally includes resist coating, exposure, and development. After development, the results of the photolithography are typically observed under a scanning electron microscope, especially the lithographic morphology. The lithographic morphology refers to the three-dimensional contour features of the pattern formed by photolithography. The white edges of the lines in the three-dimensional contour are one such morphological feature. These white edges reflect the verticality of the sidewalls or the flatness of the sidewalls in the vertical direction. Reducing the white edges is crucial for improving the accuracy and yield of the three-dimensional contour of the photolithographic pattern.
[0003] In production, excessive white edges on lines are considered abnormal photolithography morphology, which stems from several main factors, including environment, equipment, materials, and process parameters. Therefore, further in-depth research is needed to provide solutions for production. Summary of the Invention
[0004] In view of the problems existing in the background art, one object of this disclosure is to provide a method for solving lithographic anomalies, which can provide a solution for the lithographic anomaly of excessive white edges on lines.
[0005] Another objective of this disclosure is to provide a method for resolving lithographic anomalies that can do so more effectively and at a lower cost.
[0006] Therefore, a method for solving photolithographic anomalies includes the following steps: S1, the product wafer on the production line is coated with resist, exposed, and developed. During exposure, a photomask of the product wafer is constructed using a two-dimensional array of grains distributed along the X and Y directions, and exposure is performed using FEM data. In the FEM data, the exposure dose is constant, and the imaging focal length along the X or Y direction is taken as the normal imaging focal length F of the grain at the center of the product wafer and changes with a fixed step size ΔF. When the imaging focal length changes in the X direction, it increases from left to right; when the imaging focal length changes in the Y direction, it increases from top to bottom. S2, the product wafer on the production line is observed. If the observed white edges of the lines exceed a specified value, it indicates an abnormal photolithography morphology, and the subsequent step S3 is executed. Otherwise, if the photolithography morphology is normal, the process parameters for coating, exposure, and development in step S1 are used for subsequent production, and steps after step S2 are not required. S3: If an abnormal photolithography morphology is determined in step S2, a product wafer before photolithography is provided as the first offline test wafer. S4: Coating, exposure, and development are performed on the first offline test wafer, wherein the exposure mask is a mask with a different optimal focal point than the photomask of the online product wafer, and the normal imaging focal length F' of the exposure is zero. Except for the fixed step size ΔF´, which is no greater than the fixed step size ΔF on the production line in step S1, the other parameters are the same as the photolithography parameters of the products on the production line; S5, the first offline test piece after development is sent back to the exposure machine in step S4 for optimal focus testing and the average value of the optimal focus is obtained. If the average value of the optimal focus is less than or equal to the range of ±ΔF´ fixed step size in step S4, it indicates that the abnormal morphology of the online product is not caused by the normal imaging focal length fluctuation of the exposure machine on the online product, and needs to be solved from other aspects of the photolithography process. There is no need to perform the steps after step S5. If the average value of the optimal focus is... If the range is greater than the ±ΔF´ fixed step size in step S4, proceed to step S6; S6, the average value of the optimal focus in step S5 is added to the exposure equipment in step S4 as a compensation value, so that the actual normal imaging focal length of the equipment after compensation is the sum of the normal imaging focal length F´ in step S4 and the compensation value; S7, another product wafer before photolithography is provided as the second offline test wafer; S8, the second offline test wafer is coated with adhesive, exposed and developed, wherein the exposure equipment has been compensated based on the normal imaging focal length in step S6 and the die located at the center of the second offline test wafer is the actual normal imaging focal length of the equipment after compensation.S9: The developed second offline test piece is sent back to the exposure equipment in step S8 for optimal focus testing, and the average value of the optimal focus is obtained. If the average value of the optimal focus is less than or equal to the ±ΔF' fixed step size in step S4, the complement value of the normal imaging focal length is used as the complement value of the exposure equipment for the online product piece, and step S10 is performed. If the average value of the optimal focus is greater than the ±ΔF' fixed step size in step S4, the complement value of the normal imaging focal length cannot be used as the complement value of the exposure equipment for the online product piece, and a solution needs to be found in other aspects of the photolithography process. Step S10 is not performed. The steps are as follows: S10, the product wafers on the production line are coated with resist, exposed, and developed. The exposure machine is based on the normal imaging focal length supplemented in step S9, and the die at the center of the product wafer is the actual normal imaging focal length of the machine after the supplementation. S11, the morphology of the product wafers on the production line is observed. If the observed white edges of the lines are less than the specified value, it indicates that the photolithography morphology has recovered to normal and the process parameters for coating, exposure, and development in step S10 are used for subsequent production on the production line. If the observed white edges of the lines are still greater than the specified value, the solution to the abnormal photolithography morphology has failed, and solutions need to be found in other aspects of the photolithography process.
[0007] The beneficial effects of this disclosure are as follows: In the method for resolving lithographic anomalies according to this disclosure, through steps S3 to S9, the value of normal imaging focal length fluctuation can be accurately determined. Combined with the observation of excessive white edges (i.e., exceeding a specified value) on the production line products in steps S1 to S2 and the changes in white edges on the production line products after adjusting the value at the normal imaging focal length in steps S10 to S11, it can be determined that the excessive white edges are caused by fluctuations in the normal imaging focal length. This provides a solution for this lithographic anomaly. Furthermore, if the determination of excessive white edges as caused by fluctuations in the normal imaging focal length is based on the equipment parameters of the exposure equipment, the complexity of resolving this lithographic anomaly from a process perspective can be reduced. In other words, prioritizing a solution from an equipment perspective is more effective and less costly than a process perspective. Therefore, the method for resolving lithographic anomalies according to this disclosure can resolve lithographic anomalies more effectively and at a lower cost. Attached Figure Description
[0008] Figure 1 It is a schematic diagram of the structural relationship between the mask, the product wafer, and the grain.
[0009] Figure 2 These are photographs of production line wafers with abnormal lithographic morphology observed under a wide-area scanning electron microscope.
[0010] Figure 3 It is the control interface of the machine for the exposure of the normal imaging focal length before the compensation value during offline testing.
[0011] Figure 4 It is the curve of the best focus obtained by testing the normal imaging focal length before the compensation value during offline testing, as well as the average value of the best focus.
[0012] Figure 5 It is the control interface of the machine for the exposure of the normal imaging focal length after the compensation value during offline testing.
[0013] Figure 6 It is the curve of the best focus obtained after the normal imaging focal length is compensated during offline testing, as well as the average value of the best focus.
[0014] Figure 7 These are photographs of production line wafers whose lithographic morphology has been restored to normal, as observed under an online wide-area scanning electron microscope. Detailed Implementation
[0015] 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.
[0016] [Methods for resolving photolithographic anomalies] Reference Figures 1 to 7 The method for resolving photolithographic anomalies according to this disclosure includes the following steps: S1, on the production line, the product wafer undergoes coating, exposure, and development. During exposure, a photomask (mask plate) is constructed using a two-dimensional array of grains distributed along the X and Y directions, and exposure is performed using FEM (Focus Energy Matrix) data. In the FEM data, the exposure dose is constant, and the imaging focal length along the X or Y direction is based on the grain at the center of the product wafer as the normal imaging focal length F, changing with a fixed step size ΔF. When the imaging focal length changes in the X direction, it increases from left to right; when the imaging focal length changes in the Y direction, it increases from top to bottom (e.g., ...). Figure 1 (as shown) S2, observe the morphology of the product pieces on the production line (e.g., Figure 2 As shown in the figure, if the white edge of the observed line is greater than the specified value, it indicates that the photolithography is abnormal and the subsequent step S3 is executed. Otherwise, the photolithography is normal and the process parameters of coating, exposure and development in step S1 are used for subsequent production, and there is no need to execute the steps after step S2. S3, if the photolithography morphology is found to be abnormal in step S2, a product wafer before photolithography is provided as the first offline test wafer; S4, the first offline test piece is coated with adhesive, exposed and developed. Except that the exposed mask is a mask with the best test focus that is different from the photomask of the online product piece, and the normal imaging focal length F´ of the exposure is zero and the fixed step size ΔF´ is no greater than the fixed step size ΔF on the production line in step S1, the rest are the same as the photolithography parameters of the product on the production line. S5, the first offline test film after development is sent back to the exposure machine of step S4 for optimal focus testing and the average value of the optimal focus is obtained (e.g., Figure 4 (As shown), if the average value of the best focus is less than or equal to the range of ±ΔF´ fixed step size in step S4, it indicates that the abnormal shape of the online product is not caused by the normal imaging focal length fluctuation of the exposure machine of the online product, and needs to be solved from other aspects of the photolithography process. There is no need to execute the steps after step S5. If the average value of the best focus is greater than the range of ±ΔF´ fixed step size in step S4, then proceed to step S6. S6, the average value of the optimal focus from step S5 is added as a supplementary value to the exposure equipment from step S4 (e.g., Figure 3 and Figure 5 As shown), so that the actual normal imaging focal length of the machine after the compensation is the sum of the normal imaging focal length F´ in step S4 and the compensation; S7 provides another product wafer before photolithography as a second offline test wafer; S8, apply adhesive, expose and develop the second offline test piece, wherein the exposure machine has been compensated for the normal imaging focal length based on step S6, and the grain at the center of the second offline test piece is the actual normal imaging focal length of the machine after compensation. S9, the developed second offline test film is sent back to the exposure machine of step S8 for optimal focus testing and the average value of the optimal focus is obtained (e.g., Figure 6 As shown), if the average value of the optimal focus is less than or equal to the range of ±ΔF´ fixed step size in step S4, then the complement value of the normal imaging focal length is used as the complement value of the exposure machine for the online product wafer, and step S10 is performed. If the average value of the optimal focus is greater than the range of ±ΔF´ fixed step size in step S4, then the complement value of the normal imaging focal length cannot be used as the complement value of the exposure machine for the online product wafer, and it needs to be solved from other aspects of the photolithography process. Steps after step S10 are not executed. S10, the product sheet on the production line is coated with adhesive, exposed and developed. The exposure machine is based on step S9 to supplement the normal imaging focal length, and the grain at the center of the product sheet is the actual normal imaging focal length of the machine after supplementation. S11, observe the morphology of the product pieces on the production line (e.g., Figure 7As shown in the figure, if the observed white edge of the line is less than the specified value, it means that the photolithography morphology has been restored to normal and the process parameters of coating, exposure and development in step S10 are used for subsequent production on the production line. If the observed white edge of the line is still greater than the specified value, the solution to the abnormal photolithography morphology has failed and needs to be solved from other aspects of the photolithography process.
[0017] In the method for resolving lithographic anomalies according to this disclosure, steps S3 to S9 accurately determine the value of normal imaging focal length fluctuation. Combined with the observation of excessive white edges (i.e., exceeding a specified value) on the production line products in steps S1 to S2 and the changes in white edges on the production line products after adjusting the normal imaging focal length in steps S10 to S11, it can be determined that the excessive white edges are caused by fluctuations in the normal imaging focal length. This provides a solution for this lithographic anomaly. Furthermore, if the excessive white edges are determined to be caused by fluctuations in the normal imaging focal length from the perspective of the exposure equipment parameters, the complexity of resolving this lithographic anomaly from a process perspective can be reduced. In other words, addressing it from an equipment perspective is more effective and less costly than addressing it from a process perspective. Therefore, the method for resolving lithographic anomalies according to this disclosure can resolve lithographic anomalies more effectively and at a lower cost.
[0018] In steps S1, S3, S7, and S10, in one example, the 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 wafer can vary depending on actual production requirements. Furthermore, various functional layers may be present beneath the SIN film, depending on the product requirements.
[0019] In steps S1, S4, S8, and S10, in one example, the coating process includes the following sub-steps: Sa, HMDS film formation, where an HMDS film is formed on the surface of the product sheet using a vapor phase method; Sb, pre-coating cooling, where the product sheet with the HMDS film on its surface is cooled in a cooling bath to the temperature required for coagulation; Sc, coating, where the product sheet is spin-coated in a coagulation process tank; and Sd, pre-baking, where the spin-coated product sheet is pre-baked in a pre-baking process tank. More specifically, in one example, in sub-step Sa, the operation of forming the HMDS film using a vapor phase method is as follows: the 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 required temperature for spin coating in sub-step Sb is 23°C. More specifically, in one example, in sub-step Sc, the spin coating process is as follows: 1.5 mL of adhesive solution is dropped onto the center of the product sheet at a dynamic speed of 2500 rpm. After the adhesive solution has been dropped for 2 seconds, the product sheet is rotated at 2400 rpm for 35 seconds, resulting in a final coating thickness of 4800 Å. In sub-step Sc, the adhesive type is DHK-BF511. More specifically, in one example, in sub-step Sd, the pre-baking temperature is 110°C, and the time is 60 seconds.
[0020] In steps S5 and S9, refer to Figure 4 and Figure 6 During the optimal focus test, two separate curves are generated in the X and Y directions. The curves in the X and Y directions are defined as follows: because the lens of the exposure equipment has inherent astigmatism, the curves in different directions achieve the best image quality at different Z-axis positions. The "optimal focus" to be aligned for exposure is a plane, and the average value of the "optimal focus" of the two separate curves in the X and Y directions is taken as the "optimal focus" to be aligned for exposure.
[0021] In steps S6 and S10, in one example, refer to Figure 3 and Figure 5 The normal imaging focal length and its complement are determined through the offset and offset calibration (calib.offset(AIS)) input fields under Wafer Focusing in the ADJUST machineparameters control interface. Offset corresponds to the normal imaging focal length F, and offset calibration (calib.offset(AIS)) corresponds to the complement of the normal imaging focal length.
[0022] In steps S1, S4, S8, and S10, in one example, the exposure includes the following sub-steps: Si, pre-exposure cooling, where the pre-baked product sheet coated with adhesive is cooled in a cooling bath to the required exposure temperature of 23°C; Si, exposure, using a photomask and a Nikon S205C step-scan exposure machine, with a stepping X-axis of 12949 μm and a stepping Y-axis of 250389 μm, and an exposure dose of 20 mJ / cm² for each step-scan exposure. 2 The NA value is 0.68; Siii, post-exposure baking, is performed in a post-exposure baking process bath at a temperature of 110℃ and a time of 120℃; wherein, the photomask (i.e., the mask plate) in steps S1 and S10 is VOT612-010-BE, F is zero, and ΔF is 0.05μm; the photomask (i.e., the mask plate) in steps S4 and S8 is Nikon R2504HMF, and ΔF´ is 0.05μm. Note that ΔF and ΔF´ can be selected according to the actual situation, but F is always zero.
[0023] In one example, in steps S1, S4, S8, and S10, development includes the following sub-steps: S1, pre-development cooling, where the exposed and baked product sheet is cooled in a cooling bath to the temperature required for development, 23°C; SII, development, where the pre-development cooled product sheet is placed on the turntable of the developing machine, and while rotating, developer is dripped onto the center of the product sheet, 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; SIII, post-baking in a post-baking process tank, the post-baking temperature is 110°C, and the time is 90s.
[0024] In steps S2 and S11, in one example, the morphology is observed using a linewidth scanning electron microscope.
[0025] The specified values for steps S2 and S11 are determined based on actual production requirements. For example, the ratio of the white edge of the line to the corresponding line width is greater than a certain value (e.g., but not limited to 5%).
[0026] [test] Example 1 Example 1 uses the following steps: S1, on the production line, the product wafer undergoes coating, exposure, and development. During exposure, a photomask is constructed using a two-dimensional array of grains distributed along the X and Y directions, and exposure is performed using FEM data. In the FEM data, the exposure dose is constant, and the imaging focal length along the Y direction is set to the grain at the center of the product wafer as the normal imaging focal length F (F = 0 μm), which varies with the grain in a fixed step size ΔF (ΔF = 0.05 μm). The imaging focal length along the Y direction increases from top to bottom. Figure 1As shown, the product wafer is an 8-inch diameter wafer with a 150Å thick SIN film coating on its surface. S2, observe the morphology of the product pieces on the production line, such as... Figure 2 As shown, the morphology is observed under a line width scanning electron microscope. If the white edge of the line is greater than the specified value (the ratio of the white edge of the line to the corresponding line width is 5%), it indicates that the lithographic morphology is abnormal. S3, if the photolithography morphology is found to be abnormal in step S2, a product wafer before photolithography is provided as the first offline test wafer. Similarly, the product wafer is an 8-inch diameter wafer with a 150Å thick SIN film layer deposited on its surface. S4, the first offline test piece is coated with adhesive, exposed and developed. Except that the exposure mask is a test optimal focus mask that is different from the photomask of the online product piece, and the normal imaging focal length F´ of the exposure is zero, and the fixed step size ΔF´ is equal to the fixed step size ΔF on the production line in step S1 (i.e. ΔF´ is 0.05μm), the rest are the same as the photolithography parameters of the product on the production line. S5, the first offline test film after development is sent back to the exposure machine from step S4 for optimal focus testing (e.g., Figure 4 (as shown) and the average value of the optimal focus (-0.228 μm) is obtained. The average value of the optimal focus is greater than the range of ±ΔF´ fixed step size in step S4 (i.e. -0.05 μm to 0.05 μm). S6, the average value of the optimal focus in step S5 (i.e., -0.228μm) is used as a compensation value to supplement the exposure equipment in step S4 (refer to...). Figure 5 And compare Figure 3 In this process, the actual normal imaging focal length of the machine after the compensation value is the sum of the normal imaging focal length F´ in step S4 and the compensation value (i.e., 0μm + (-0.228μm) = -0.228μm). S7 provides another product wafer before photolithography as a second offline test wafer. Similarly, the product wafer is an 8-inch diameter wafer with a 150Å thick SIN film layer deposited on its surface. S8, the second offline test piece is coated with adhesive, exposed and developed. The exposure equipment has been compensated for in step S6 on the normal imaging focal length and the grain at the center of the second offline test piece is the actual normal imaging focal length of the equipment after compensation (that is, the exposure equipment will use -0.228μm as the normal imaging focal length for exposure). S9, the developed second offline test film is sent back to the exposure machine from step S8 for optimal focus testing (e.g., Figure 6(As shown) and obtain the average value of the optimal focus (i.e. -0.009μm). If the average value of the optimal focus is less than the range of ±ΔF´ fixed step size in step S4 (i.e. -0.05μm~0.05μm), then the complementary value of the normal imaging focal length (i.e. -0.228μm) is used as the complementary value of the machine for the exposure of the online product film, and step S10 is performed. S10, the product wafers on the production line are coated with adhesive, exposed and developed. The exposure machine is based on the normal imaging focal length of step S9, and the die at the center of the product wafer is the actual normal imaging focal length of the machine after the compensation (i.e. the actual normal imaging focal length is -0.228μm). Similarly, the product wafers are 8-inch diameter wafers with a 150Å thick SIN film layer on the surface. S11, observe the morphology of the product pieces on the production line. The morphology observation is performed under a line-width scanning electron microscope, such as... Figure 7 As shown, it was observed that the white edge of the line was less than the specified value (the ratio of the white edge of the line to the corresponding line width was 5%), indicating that the photolithographic morphology was restored to normal and the process parameters of coating, exposure and development in step S10 were used for subsequent production on the production line. in, In steps S1, S4, S8, and S10, the adhesive application is performed using the following sub-steps: Sa, HMDS film formation: HMDS film is formed on the surface of the product sheet using a vapor phase method. The operation of forming HMDS film using a vapor phase method is as follows: the 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 and the time for introducing HMDS vapor carried by nitrogen is 60 s. The thickness of the formed HMDS film is 6 Å. Sb, Cooling before spin coating: The product sheet with HMDS film formed on the surface is cooled in a cooling bath to the temperature required for spin coating, wherein the temperature required for spin coating is 23°C. Sc, Coating, The 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 the product sheet at a dynamic speed of 2500 rpm. After the adhesive solution is dropped completely in 2 seconds, the product sheet is rotated at 2400 rpm for 35 seconds. The final coating thickness is 4800 Å. The adhesive type is DHK-BF511. Sd, pre-baking, the product sheet after spin coating is pre-baked in the pre-baking process tank, wherein the pre-baking temperature is 110℃ and the time is 60s; In step S5 (refer to) Figure 4 ) and step S9 (refer to Figure 6In the optimal focus test, two separate curves are generated in the X and Y directions. The curves in the X and Y directions are defined as follows: because the lens of the exposure machine has inherent astigmatism, the curves in different directions achieve the best image quality at different Z-axis positions. The "optimal focus" to be aligned for exposure is a plane, and the average value of the "optimal focus" of the two separate curves in the X and Y directions is taken as the "optimal focus" to be aligned for exposure. In step S6 (refer to) Figure 3 ) and step S10 (refer to Figure 5 In the exposure machine's control interface, the normal imaging focal length and its complement are obtained through the offset and calib.offset(AIS) input fields under Wafer Focusing in the Adjust machine parameters window of the exposure machine's control interface. In steps S1, S4, S8, and S10, the exposure employs the following sub-steps: Si, cooling before exposure: the pre-baking product sheet coated with adhesive is cooled in a cooling bath to the temperature required for exposure, 23°C. Sii exposure was performed using a photomask and a Nikon S205C step-scan exposure system. The step size was 12949 μm in the X direction and 250389 μm in the Y direction. The exposure dose for each step-scan exposure was 20 mJ / cm². 2 And the NA value is 0.68; Siii, Post-exposure baking: Post-exposure baking is carried out in a post-exposure baking process tank at a temperature of 110°C and a time of 120°C. In step S1 and step S10, the photomask is VOT612-010-BE, F is zero, and ΔF is 0.05μm; in step S4 and step S8, the photomask is Nikon R2504HMF, and ΔF´ is 0.05μm. In steps S1, S4, S8, and S10, the development process employs the following sub-steps: SI, pre-development cooling, involves cooling the exposed and baked product sheet in a cooling bath to the temperature required for development, 23°C. SII, Development: The product sheet, cooled before development, is placed on the turntable of the developing machine. While rotating, developer is dripped onto the center of the product sheet. Then, while rotating, water is rinsed. The rotation is unidirectional and the rotation speed is 2000 rpm. Positive cortical developer is used. The developer type is ZX-238. The development time is 60 seconds and the rinsing time is 30 seconds. SIII, post-drying in the post-drying process tank, the post-drying temperature is 110℃ and the time is 90s.
[0027] 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 solving photolithographic morphology anomalies, characterized in that, Including the following steps: S1, on the production line, the product sheet is coated with adhesive, exposed and developed. During exposure, the product sheet is made of a two-dimensional array of grains distributed along the X and Y directions and exposed using FEM data. In the FEM data, the exposure dose is constant. The imaging focal length along the X or Y direction is the normal imaging focal length F with the grain at the center of the product sheet and changes with the grain by a fixed step size ΔF. When the imaging focal length changes in the X direction, the imaging focal length increases from left to right. When the imaging focal length changes in the Y direction, the imaging focal length increases from top to bottom. S2. Observe the morphology of the product wafer on the production line. If the white edge of the observed line is greater than the specified value, it indicates that the photolithography morphology is abnormal, and the subsequent step S3 is executed. Otherwise, the photolithography morphology is normal and the process parameters of coating, exposure and development in step S1 are used for subsequent production. There is no need to execute the steps after step S2. S3, if the photolithography morphology is found to be abnormal in step S2, a product wafer before photolithography is provided as the first offline test wafer; S4, the first offline test piece is coated with adhesive, exposed and developed. Except that the exposed mask is a mask with the best test focus that is different from the photomask of the online product piece, and the normal imaging focal length F´ of the exposure is zero and the fixed step size ΔF´ is no greater than the fixed step size ΔF on the production line in step S1, the rest are the same as the photolithography parameters of the product on the production line. S5, after development, the first offline test piece is sent back to the exposure machine in step S4 to perform the best focus test and obtain the average value of the best focus. If the average value of the best focus is less than or equal to the range of ±ΔF´ fixed step size in step S4, it means that the abnormal shape of the online product is not caused by the normal imaging focal length fluctuation of the exposure machine of the online product, and needs to be solved from other aspects of the photolithography process. There is no need to perform the steps after step S5. If the average value of the best focus is greater than the range of ±ΔF´ fixed step size in step S4, then proceed to step S6. S6, the average value of the best focus in step S5 is added to the exposure of the machine in step S4 as a supplementary value, so that the actual normal imaging focal length of the machine after the supplementary value is the sum of the normal imaging focal length F´ in step S4 and the supplementary value. S7 provides another product wafer before photolithography as a second offline test wafer; S8, apply adhesive, expose and develop the second offline test piece, wherein the exposure machine has been compensated for the normal imaging focal length based on step S6, and the grain at the center of the second offline test piece is the actual normal imaging focal length of the machine after compensation. S9, the developed second offline test piece is sent back to the exposure machine in step S8 to perform the best focus test and obtain the average value of the best focus. If the average value of the best focus is less than or equal to the range of ±ΔF´ fixed step size in step S4, the complement value of the normal imaging focal length is used as the complement value of the exposure machine for the online product piece, and step S10 is performed. If the average value of the best focus is greater than the range of ±ΔF´ fixed step size in step S4, the complement value of the normal imaging focal length cannot be used as the complement value of the exposure machine for the online product piece, and it needs to be solved from other aspects of the photolithography process. Steps after step S10 are not performed. S10, the product sheet on the production line is coated with adhesive, exposed and developed. The exposure machine is based on step S9 to supplement the normal imaging focal length, and the grain at the center of the product sheet is the actual normal imaging focal length of the machine after supplementation. S11. Observe the morphology of the product wafer on the production line. If the white edge of the observed lines is less than the specified value, it means that the photolithography morphology has returned to normal and the process parameters of coating, exposure and development in step S10 are used for subsequent production on the production line. If the white edge of the observed lines is still greater than the specified value, the solution to the abnormal photolithography morphology has failed and it is necessary to solve the problem from other aspects of the photolithography process.
2. The method for solving photolithographic morphology anomalies according to claim 1, characterized in that, In steps S1, S3, S7, and S10, The product is an 8-inch diameter wafer with a 150Å thick SIN film coating on its surface.
3. The method for solving photolithographic morphology anomalies according to claim 1, characterized in that, In steps S1, S4, S8, and S10, Applying adhesive includes the following sub-steps: Sa, HMDS film formation: HMDS film is formed on the surface of the product sheet using a vapor phase method; Sb, pre-coating cooling: The product sheet with an HMDS film formed on its surface is cooled in a cooling bath to the temperature required for coagulation. Sc, coating, refers to the process of spin coating a product sheet onto a coating tank. Sd, pre-baking, the product sheet after spin coating and uniform coating is pre-baked in the pre-baking process tank.
4. The method for solving photolithographic morphology anomalies according to claim 3, characterized in that, In substep Sa, The operation of forming HMDS film by gas phase is as follows: the 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. In sub-step Sb, the temperature required for homogenization is 23°C.
5. The method for solving photolithographic morphology anomalies according to claim 3, characterized in that, In sub-step Sc, the spin coating process is as follows: 1.5 mL of adhesive solution is dropped onto the center of the product sheet at a dynamic speed of 2500 rpm. After the adhesive solution is dropped for 2 seconds, the product sheet is rotated at 2400 rpm for 35 seconds, and the final coating thickness is 4800 Å. In sub-step Sc, the adhesive type is DHK-BF511; In sub-step Sd, the pre-baking temperature is 110℃ and the time is 60s.
6. The method for solving photolithographic morphology anomalies according to claim 1, characterized in that, In steps S5 and S9, During the optimal focus test, two separate curves are generated in the X and Y directions. The curves in the X and Y directions are defined as follows: because the lens of the exposure equipment has inherent astigmatism, the curves in different directions achieve the best image quality at different Z-axis positions. The "optimal focus" to be aligned for exposure is a plane, and the average value of the "optimal focus" of the two separate curves in the X and Y directions is taken as the "optimal focus" to be aligned for exposure.
7. The method for solving photolithographic morphology anomalies according to claim 6, characterized in that, In steps S6 and S10, The normal imaging focal length and its complement are determined through the offset and calib.offset(AIS) input fields under Wafer Focusing in the ADJUST machine parameters window of the exposure machine's control interface.
8. The method for solving photolithographic morphology anomalies according to claim 3, characterized in that, In steps S1, S4, S8, and S10, Exposure includes the following sub-steps: Si, cooling before exposure: the pre-baking product sheet coated with adhesive is cooled in a cooling bath to the temperature required for exposure, 23°C. Sii exposure was performed using a photomask and a Nikon S205C step-scan exposure system. The step size was 12949 μm in the X direction and 250389 μm in the Y direction. The exposure dose for each step-scan exposure was 20 mJ / cm². 2 And the NA value is 0.68; Siii, Post-exposure baking: Post-exposure baking is performed in a post-exposure baking process tank at a temperature of 110°C and a time of 120°C. in, The photomask used in steps S1 and S10 is VOT612-010-BE, with F being zero and ΔF being 0.05μm; The photomask used in steps S4 and S8 is Nikon's R2504HMF with a ΔF' of 0.05 μm.
9. The method for solving photolithographic morphology anomalies according to claim 8, characterized in that, In steps S1, S4, S8, and S10, Development includes the following sub-steps: SI, pre-development cooling, involves cooling the exposed and baked product sheet in a cooling bath to the temperature required for development, 23°C. SII, Development: The product sheet, cooled before development, is placed on the turntable of the developing machine. While rotating, developer is dripped onto the center of the product sheet. Then, while rotating, water is rinsed. The rotation is unidirectional and the rotation speed is 2000 rpm. Positive cortical developer is used. The developer type is ZX-238. The development time is 60 seconds and the rinsing time is 30 seconds. SIII, post-drying in the post-drying process tank, the post-drying temperature is 110℃ and the time is 90s.
10. The method for solving photolithographic morphology anomalies according to claim 1, characterized in that, In steps S2 and S11, the morphology is observed under a linewidth scanning electron microscope.