Mask set and manufacturing method thereof, mask imaging deviation correction method and system

Abstract

Embodiments of the present application provide a mask set and a manufacturing method thereof, a mask imaging deviation correction method and system. The mask set comprises a plurality of masks; in the process of optically imaging the plurality of masks, the theoretical optimal focus values of mask patterns on the plurality of masks are the same; wherein the mask patterns on the plurality of masks comprise the same monitoring patterns; the monitoring patterns are used for optically imaging deviation correction of the mask patterns on the masks, so that in the process of optically imaging the plurality of masks, the offset of the actual optimal focus values of the mask patterns on the plurality of masks relative to the theoretical optimal focus values falls within the specified numerical range of 7.0% to 7.5% of the process node corresponding to the mask set. Through the embodiments of the present application, the offset of the actual optimal focus values of the mask patterns on the plurality of masks relative to the theoretical optimal focus values is reduced, and the consistency of the optical imaging of the plurality of masks in the same mask set is improved.

Description

Technical Field

[0001] The embodiments in this application relate to the field of semiconductor manufacturing technology, specifically to a mask assembly and its manufacturing method, a mask imaging deviation correction method and system. Background Technology

[0002] As a key component in semiconductor photolithography, the optical imaging quality of a photomask significantly impacts the overall performance of semiconductor devices. Specifically, the photomask carries the design pattern of the semiconductor device. Light of a specific wavelength passes through the design pattern on the photomask and onto the photoresist on the wafer surface, thereby transferring the design pattern from the photomask to the wafer surface. Therefore, the optical imaging quality of the photomask directly affects the accuracy of the pattern on the wafer surface.

[0003] Since a single photomask is insufficient to meet the requirements of mass production of semiconductor devices, existing technologies typically utilize multiple photomasks to form a reticle group. This group is used for optical imaging of essentially the same design pattern on different equipment or at different production stages. Therefore, theoretically, the optical imaging of multiple photomasks within a reticle group should be consistent. The consistency of optical imaging among multiple photomasks within a reticle group is commonly measured by the Best-Focus Value (BFV), which indicates that multiple photomasks in the reticle group have the same theoretically optimal focus value during the optical imaging process.

[0004] However, during the optical imaging process of multiple masks in the existing mask set, the researchers found that the actual optimal focus values ​​of multiple masks in the optical imaging process are not the same. The actual optimal focus values ​​of some masks deviate from the theoretical optimal focus values. Therefore, the optical imaging consistency among multiple masks in the existing mask set is poor. Summary of the Invention

[0005] In view of this, several embodiments of this application provide a mask assembly and its manufacturing method, a mask imaging deviation correction method and system, to improve the optical imaging consistency among multiple masks in the mask assembly.

[0006] In one aspect, an embodiment of this application provides a mask set, comprising: a plurality of masks; during optical imaging of the plurality of masks, the theoretical optimal focus values ​​of the mask patterns on the plurality of masks are the same; wherein the mask patterns on the plurality of masks include the same monitoring pattern; the monitoring pattern is used to perform optical imaging deviation correction on the mask patterns on the masks, such that during optical imaging of the plurality of masks, the offset of the actual optimal focus value of the mask patterns on the plurality of masks relative to the theoretical optimal focus value falls within a specified numerical range; wherein the specified numerical range is 7.0% to 7.5% of the process node corresponding to the mask set.

[0007] Optionally, each of the photomasks includes a chip pattern area and a chip cutting area disposed on the periphery of the chip pattern area; wherein, the chip pattern area includes a chip functional pattern area and a chip non-functional pattern area; the monitoring pattern is located in the chip non-functional pattern area.

[0008] Optionally, the monitoring pattern includes multiple sub-monitoring patterns; wherein the multiple sub-monitoring patterns have the same pattern shape and different pattern sizes.

[0009] Optionally, the number of sub-monitoring patterns is 3 to 5.

[0010] Optionally, the sub-monitoring pattern is composed of feature graphics; the number of feature graphics that make up each sub-monitoring pattern is greater than or equal to 60.

[0011] Optionally, the feature pattern includes square holes and rectangles; the feature patterns form a feature pattern combination; each of the sub-monitoring patterns includes one or more of the following feature pattern combinations: arrayed square holes, staggered square holes, linear square holes, isolated square holes, asymmetrical square holes, dense square holes, arrayed rectangles, staggered rectangles, and linear rectangles.

[0012] Optionally, each of the sub-monitoring patterns has two mutually perpendicular arrangement directions.

[0013] Optionally, the plurality of sub-monitoring patterns includes a first sub-monitoring pattern and a second sub-monitoring pattern; wherein, the size of the first sub-monitoring pattern is a reference size; the size of the second sub-monitoring pattern is 1-N1 times to 1+N2 times the reference size; wherein, the value of N1 is greater than or equal to 0.69 and less than 1; the value of N2 is greater than or equal to 0.69 and less than 1.5.

[0014] In another aspect, one embodiment of this application provides a method for manufacturing a mask assembly, the method being used to manufacture a mask assembly as described in the above embodiments.

[0015] In another aspect, one embodiment of this application provides a method for optical imaging deviation correction of a mask. The method is used to correct optical imaging deviations of multiple masks included in a mask group as described in the above embodiments, or the method is used to correct optical imaging deviations of multiple masks included in a mask group manufactured by the manufacturing method of the mask group as described in the above embodiments; the mask group corresponds to a theoretical optimal focus value; the method includes: selecting a reference mask from the multiple masks included in the mask group using an optical proximity correction model; determining a reference monitoring pattern based on the monitoring pattern of the reference mask, such that the actual optimal focus value of the reference mask having the reference monitoring pattern is equal to the theoretical optimal focus value; and applying the reference monitoring pattern to the reference mask. The size of the pattern is measured, and the size of the reference monitoring pattern is used as the first correction reference. Simulated optical imaging is performed on the reference mask to obtain the light intensity distribution data of the image of the reference monitoring pattern, and this data is used as the second correction reference. Based on the first and second correction references, optical imaging deviation correction is performed on the non-reference masks in the mask group (excluding the reference mask), so that during optical imaging of the non-reference masks, the offset between the actual optimal focus value and the theoretical optimal focus value of the mask pattern on the non-reference mask falls within a specified numerical range; wherein the specified numerical range is 7.0% to 7.5% of the corresponding process node of the mask group.

[0016] Optionally, determining the reference monitoring pattern based on the monitoring pattern of the reference mask includes: measuring the size deviation of the monitoring pattern of the reference mask to obtain multiple size deviation statistical features of the monitoring pattern of the reference mask; if all size deviation statistical features of the monitoring pattern of the reference mask meet the correction reference conditions, then using the monitoring pattern of the reference mask as the reference monitoring pattern; or, if any size deviation statistical feature of the monitoring pattern of the reference mask does not meet the correction reference conditions, adjusting the monitoring pattern of the reference mask until all size deviation statistical features of the monitoring pattern of the reference mask meet the correction reference conditions, then using the adjusted monitoring pattern of the reference mask as the reference monitoring pattern.

[0017] Optionally, the plurality of dimensional deviation statistical features include: the dispersion of the dimensional deviation of the monitoring pattern of the reference mask and the trend of the dimensional deviation of the monitoring pattern of the reference mask along a specified direction; the correction reference condition is falling within a specified dimensional deviation range; wherein, the specified dimensional deviation range is 3.4 to 3.6 times the design reference size.

[0018] Optionally, based on the first correction reference and the second correction reference, optical imaging deviation correction is performed on non-reference masks (excluding the reference mask) in the mask group, including: measuring the size of the monitoring pattern of the non-reference mask to obtain the size of the monitoring pattern of the non-reference mask; determining a first correction monitoring pattern of the non-reference mask according to the size of the monitoring pattern of the non-reference mask and the first correction reference; performing simulated optical imaging on the non-reference mask with the first correction monitoring pattern to obtain light intensity distribution data of the first correction monitoring pattern image; determining a second correction monitoring pattern of the non-reference mask according to the light intensity distribution data of the first correction monitoring pattern image and the second correction reference, and using the non-reference mask with the second correction monitoring pattern as the correction mask; wherein, during the optical imaging process of the correction mask, the offset between the actual optimal focus value and the theoretical optimal focus value of the mask pattern on the correction mask falls within the specified numerical range.

[0019] Optionally, the step of determining the first calibration monitoring pattern of the non-reference mask based on the size of the monitoring pattern of the non-reference mask and the first calibration reference includes: comparing the size of the monitoring pattern of the non-reference mask with the first calibration reference; if the size of the monitoring pattern of the non-reference mask is the same as the first calibration reference, directly using the monitoring pattern of the non-reference mask as the first calibration monitoring pattern; or, if the size of the monitoring pattern of the non-reference mask is different from the first calibration reference, performing a first deviation correction on the non-reference mask until the size of the monitoring pattern of the non-reference mask is the same as the first calibration reference, and using the monitoring pattern of the non-reference mask after the first deviation correction as the first calibration monitoring pattern.

[0020] Optionally, determining the second correction monitoring pattern of the non-reference mask based on the light intensity distribution data of the first correction monitoring pattern and the second correction reference includes: comparing the light intensity distribution data of the first correction monitoring pattern with the second correction reference; if the light intensity distribution data of the first correction monitoring pattern is the same as the second correction reference, directly using the first correction monitoring pattern as the second correction monitoring pattern; or, if the light intensity distribution data of the first correction monitoring pattern is different from the second correction reference, performing a second deviation correction on the non-reference mask until the light intensity distribution data of the first correction monitoring pattern after the second deviation correction is the same as the second correction reference, and using the first correction monitoring pattern after the second deviation correction as the second correction monitoring pattern.

[0021] In another aspect, one embodiment of this application provides an optical imaging deviation correction system for a mask, the system being used to perform the optical imaging deviation correction method for a mask as described in the above embodiments.

[0022] In several embodiments of this application, the mask set includes multiple masks, and during the optical imaging process of the multiple masks, the theoretical optimal focus value of the mask patterns on the multiple masks is the same. By setting the same monitoring pattern in the mask patterns of the multiple masks, the optical imaging deviation of the mask patterns on the multiple masks is corrected using the monitoring pattern. This ensures that during the optical imaging process of the multiple masks, the offset of the actual optimal focus value of the mask patterns on the multiple masks relative to the theoretical optimal focus value falls within a specified value range of 7.0% to 7.5% of the corresponding process node of the mask set. The unexpected effects achieved include: since the same monitoring pattern is used as the basis for optical imaging deviation correction of the mask patterns on the multiple masks, the offset of the actual optimal focus value of the mask patterns on the multiple masks relative to the theoretical optimal focus value is reduced during the optical imaging process of the multiple masks, thereby improving the consistency of optical imaging of the multiple masks in the same mask set. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in describing the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A line graph representing the optical imaging differences among multiple masks in an existing mask set, provided for related technologies.

[0025] Figure 2 This is a schematic diagram of the structure of a mask provided for one embodiment of this application.

[0026] Figure 3 This is a schematic diagram illustrating the deformation rules for transferring feature patterns on a mask to a wafer, as provided in one embodiment of this application.

[0027] Figure 4 A schematic diagram of the pattern shape of a sub-monitoring pattern provided for one embodiment of this application.

[0028] Figure 5 This is a schematic diagram of an array of square hole feature patterns provided in one embodiment of this application.

[0029] Figure 6 This is a schematic diagram of an embodiment of the present application showing a combination of staggered square hole feature patterns.

[0030] Figure 7 This is a schematic diagram of a linear square hole feature pattern combination provided in one embodiment of this application.

[0031] Figure 8 This is a schematic diagram of an isolated square hole feature pattern combination provided in one embodiment of this application.

[0032] Figure 9 This is a schematic diagram of an asymmetric square hole feature pattern combination provided in one embodiment of this application.

[0033] Figure 10 This is a schematic diagram of an array of rectangular feature patterns provided in one embodiment of this application.

[0034] Figure 11 This is a schematic diagram of an interlaced rectangular feature graphic combination provided in one embodiment of this application.

[0035] Figure 12 This is a schematic diagram of a linear rectangular feature graphic combination provided in one embodiment of this application.

[0036] Figure 13 This is a schematic flowchart of an optical imaging deviation correction method for a mask provided in one embodiment of this application.

[0037] Figure 14 This is a schematic diagram of the structure of a spatial image measurement system provided in one embodiment of this application.

[0038] Figure 15 An optical imaging result diagram of simulated optical imaging provided for one embodiment of this application.

[0039] Figure 16 An illumination intensity distribution curve for simulated optical imaging provided in one embodiment of this application.

[0040] Figure 17 This is a schematic diagram comparing the wafer printability results before and after correction, provided as an embodiment of this application.

[0041] Figure 18 This is a schematic diagram showing the comparison of the imaging results of the feature patterns before and after correction on the wafer, provided as an embodiment of this application.

[0042] Structural designation explanation

[0043] 100. Photomask; 110. Chip pattern area; 111. Chip functional pattern area; 112. Chip non-functional pattern area; 120. Chip cutting area; 121. Chip cutting mark; 130. Monitoring pattern; 200. Spatial image measurement system; 210. Illumination device; 220. Photomask; 230. Projection lens; 240. CCD camera. Detailed Implementation

[0044] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0045] The accompanying drawings provided in this application are only schematic illustrations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component may be changed, and the layout of the components may also be more complex.

[0046] In the description of the embodiments of this application, it should be understood that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "center," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of the stated features.

[0047] With the continuous development of semiconductor devices towards high integration and miniaturization, semiconductor process technology nodes are shrinking, leading to increasingly higher requirements for the quality of semiconductor device manufacturing processes. In advanced semiconductor processes at 40nm and below, the quality and precision of photolithography have a significant impact on the performance of semiconductor devices. As a crucial component of photolithography, the performance of the photomask is essential for achieving high-quality and high-precision photolithography processes.

[0048] Meanwhile, with the continuous expansion of semiconductor device manufacturing scale, to meet the requirements of high-volume manufacturing (HVM) of the same device, related technologies typically utilize mask groups consisting of multiple masks instead of single masks. Since multiple masks belonging to the same mask group are used to produce the same device, ideally, the optical imaging of multiple masks within the same mask group is consistent; that is, the optical imaging results of multiple masks are completely identical. When using optimal focus values ​​to measure the consistency of optical imaging among multiple masks within the same mask group, the theoretical optimal focus values ​​of multiple masks within the same mask group are the same.

[0049] However, during the actual manufacturing and use of the photomask set, researchers discovered that due to variations in photomask materials and fluctuations in photomask manufacturing technology, differences in imaging patterns occurred during optical imaging among the original, modified, backup, and replacement photomasks belonging to the same photomask set. Using photomasks 1 through 6 belonging to the same photomask set as experimental subjects, researchers performed optical imaging on these photomasks and conducted the following two measurements.

[0050] In the first measurement, researchers measured the mean to target (MTT) deviation between the imaged position and the target position on the wafer for different verification patterns on different masks. Specifically, each mask had six different verification patterns (verification pattern A to verification pattern F), each corresponding to an ideal imaged position on the wafer, i.e., the target position. Ideally, the same verification pattern on each mask should have the same imaged position on the wafer; that is, the imaged position of each verification pattern on each mask should be the target position corresponding to that verification pattern.

[0051] For each verification pattern on each mask, researchers performed multiple measurements on its imaging position on the wafer. Based on the average of these measurements and the target position corresponding to that verification pattern, they calculated the average deviation value. For each mask, a line graph was used to illustrate the trend of the average deviation value for different verification patterns. Ideally, each line graph would be a straight line with a value of 0 and parallel to the horizontal axis. However, please refer to... Figure 1 The changing trends of different broken lines vary considerably. This indicates that the optical imaging results of different masks differ significantly.

[0052] In the second measurement, to eliminate the influence of wafer surface condition on the optimal focus value, researchers measured the optimal focus values ​​of different masks on structured wafers and flat wafers, respectively. Specifically, structured wafers are wafers that have undergone processing and have structures on their surface. Flat wafers are unprocessed raw wafers. Each mask set corresponds to a theoretical optimal focus value (BF), and this value is independent of the wafer surface condition. Therefore, ideally, the actual optimal focus value of different masks on both structured and flat wafers is equal to the theoretical optimal focus value (BF).

[0053] However, please refer to Table 1. As shown in Table 1, on the structured wafer, the actual optimal focus values ​​of masks 2, 3, 4, and 6 all deviated from the theoretical optimal focus value BF, and the amount of deviation varied among the different masks; on the flat wafer, the actual optimal focus values ​​of masks 1, 2, 4, and 5 all deviated from the theoretical optimal focus value BF, and the amount of deviation varied among the different masks.

[0054] Table 1. Differences in actual optimal focus values ​​for different photomasks

[0055]

[0056] The above two measurements show that, in the existing mask set, there are significant differences in the optical imaging results between different masks, and the consistency of optical imaging is poor.

[0057] Further analysis by researchers revealed that the above problems were mainly caused by the following two reasons.

[0058] First, regarding the two-dimensional mask pattern on the mask, due to the limitations of the mask manufacturing precision, there will be slight differences in the mask pattern and critical dimension (CD) on different masks. These differences will be amplified during the optical imaging process, resulting in differences in the optical imaging results.

[0059] Secondly, because photomasks have a certain thickness and are three-dimensional objects, the mask pattern on them is mainly created by removing a portion of the mask material through etching. Due to limitations in etching precision, non-perpendicular sidewalls and critical dimensional deviations between dense and independent lines may occur during etching. Furthermore, during use, oblique incident light illuminating the mask may produce a shadowing effect. The combined effect of these factors approximates spherical aberration, which causes the actual optimal focus value of the mask to be correlated with the size of the mask pattern during optical imaging, thus reducing the consistency of optical imaging between different masks within the same mask group.

[0060] Furthermore, researchers discovered during the actual manufacturing process of the photomask assembly that the aforementioned issues also caused the process window to shrink, leading to a decrease in production yield.

[0061] Therefore, it is necessary to provide a mask set comprising multiple masks. During optical imaging of the multiple masks, the theoretical optimal focus value of the mask patterns on the multiple masks is the same. By setting the same monitoring pattern in the mask patterns on the multiple masks, the optical imaging deviation of the mask patterns on the multiple masks is corrected using the monitoring pattern. This ensures that during optical imaging of the multiple masks, the offset of the actual optimal focus value of the mask patterns on the multiple masks relative to the theoretical optimal focus value falls within a specified range of 7.0% to 7.5% of the corresponding process node of the mask set. This reduces the offset of the actual optimal focus value of the mask patterns on the multiple masks relative to the theoretical optimal focus value, reduces the degree of process window shrinkage, and improves the consistency of optical imaging and production yield of the multiple masks in the same mask set.

[0062] One embodiment of this application provides a mask set. The mask set includes multiple masks that can be used to manufacture the same semiconductor device. For example, the multiple masks can be used to manufacture the same type of chip with the same function for the same model of terminal. Specifically, the multiple masks may include a primary mask, a modified mask, a backup mask, and a replacement mask. The primary mask can be a mask carrying a circuit design pattern for a semiconductor device. The modified mask can be a mask made by slightly modifying the circuit design pattern on the primary mask to correct circuit design defects or optimize the circuit performance of the primary mask. Therefore, the mask pattern on the modified mask differs from the mask pattern on the primary mask, and this difference needs to remain within the allowable variation range in mask manufacturing. Both the backup and replacement photomasks are replicas of the original photomask. Therefore, the mask patterns on both the backup and replacement photomasks are identical to those on the original. Backup photomasks can be used for simultaneous processing on different photolithography machines to improve processing efficiency. Replacement photomasks can be used as alternatives when the original photomask fails or its performance degrades, enabling continuous production.

[0063] In this embodiment, during the optical imaging process of multiple photomasks, the theoretically optimal focus value of the mask patterns on the multiple photomasks is the same. Specifically, since multiple photomasks are used to manufacture the same semiconductor device, in order to improve the production yield of the semiconductor device and maintain the performance stability of the semiconductor device, the optical imaging results of the multiple photomasks should be consistent. The theoretically optimal focus value represents the focus position on which the mask pattern on the photomask can be transferred to the photoresist on the wafer surface most clearly and accurately under theoretical optical imaging conditions. Therefore, the theoretically optimal focus value is used as a representative parameter of the optical imaging results of multiple photomasks.

[0064] The actual optimal focus value represents the focal position where the mask pattern on the mask stencil can be transferred to the photoresist on the wafer surface most clearly and accurately during actual optical imaging. Ideally, during optical imaging of multiple masks, the actual optimal focus values ​​of all masks are the same and equal to the theoretical optimal focus value. However, actual measurements have revealed that the actual optimal focus values ​​of some masks deviate from the theoretical optimal focus value; that is, some masks exhibit optical imaging deviation. To correct for masks with optical imaging deviation and control the degree of deviation, in this embodiment, the mask patterns on multiple masks include the same monitoring pattern. This monitoring pattern can be used to correct the optical imaging deviation of the mask patterns on the masks, ensuring that during optical imaging of multiple masks, the deviation of the actual optimal focus value from the theoretical optimal focus value falls within a specified numerical range. This specified numerical range can be 7.0% to 7.5% of the process node corresponding to the mask group. Specifically, a process node can be the smallest manufacturable feature size in the semiconductor device manufacturing process. For example, the specified numerical range can be 7.0%, 7.14%, 7.28%, or 7.5% of the process node. In the case of a 28nm process node, the specified numerical range can be from 1.96nm to 2.10nm. In the case of a 40nm process node, the specified numerical range can be from 2.80nm to 3.00nm.

[0065] Please see Figure 2 Since each mask 100 may be used to produce a large number of chip cells, after the mask pattern on the mask 100 is transferred to the wafer, the wafer needs to be diced to obtain multiple chip cells. Therefore, in some embodiments, each mask 100 may include a chip patterning area 110 and a chip dicing area 120.

[0066] In this embodiment, the chip patterning region 110 can be used to carry the circuit design pattern of the chip unit, and the chip patterning region 110 can contain all the graphic information related to the function of the chip unit. Specifically, each mask 100 can include multiple chip patterning regions 110, and each chip patterning region 110 can match the chip unit formed on the wafer. For example, the shape of the chip patterning region 110 can be the same as the shape of the chip unit, and the size of the chip patterning region 110 can have a specific proportional relationship with the size of the chip unit. The chip patterning region 110 can be a rectangular region, a circular region, an elliptical region, or an irregular graphic region. This embodiment of the application does not impose specific limitations on the shape of the chip patterning region 110.

[0067] To reduce damage to the chip patterned region 110 during wafer dicing, in this embodiment, the chip dicing region 120 can be disposed on the outer periphery of the chip patterned region 110. Specifically, each mask 100 may include multiple chip dicing regions 120, and the number of chip dicing regions 120 may be the same as the number of chip patterned regions 110. The chip dicing region 120 may match the chip patterned region 110. For example, the shape of the chip dicing region 120 may be the same as the shape of the chip patterned region 110, and the size of the chip dicing region 120 may be larger than the size of the chip patterned region 110. To meet the process requirements of special dicing processes, in some embodiments, the shape of the chip dicing region 120 may also be different from the shape of the chip patterned region 110. The chip dicing region 120 may be a rectangular region, a circular region, an elliptical region, or an irregularly shaped region. This application embodiment does not impose specific limitations on the shape of the chip dicing region 120. The boundary of the chip dicing region 120 can be defined by a chip dicing marker 121, which can be used to provide guiding marks during the wafer dicing process to assist the dicing equipment in identifying the boundaries between different chip units.

[0068] In this embodiment, the chip patterning area 110 may include a chip functional patterning area 111 and a chip non-functional patterning (dummy) area 112. Specifically, the chip functional patterning area 111 can be used to carry design patterns for implementing the functions of the chip unit. For example, the chip functional patterning area 111 can carry design patterns of various working elements such as logic gates, memory cells, and input / output ports, and can include the complete circuit structure of the chip unit, such as transistors, capacitors, resistors, and their connections. In the mask 100, each chip patterning area 110 may include one chip functional patterning area 111. The chip non-functional patterning area 112 can be used for calibration, testing, or alignment. For example, in each chip patterning area 110, areas without design patterns, i.e., areas other than the chip functional patterning area 111, can be designated as chip non-functional patterning areas 112.

[0069] To reduce the interference of the monitoring pattern 130 on the chip's functional graphic area 111, in this embodiment, the monitoring pattern 130 can be located in the chip's non-functional graphic area 112.

[0070] In some embodiments, the monitoring pattern 130 may include multiple sub-monitoring patterns, wherein the multiple sub-monitoring patterns may have the same pattern shape but different pattern sizes. Specifically, the mask pattern on the mask 100 is composed of multiple mask patterns. Since different mask patterns have different functions, different mask patterns may correspond to different critical dimensions. For example, the critical dimension of the auxiliary mask pattern applied to the optical proximity correction model may be smaller, while the critical dimension of the mask pattern used to manufacture signal lines such as power or ground lines may be larger. Therefore, for a mask pattern that includes mask patterns with different critical dimensions, it is necessary to use sub-monitoring patterns of different sizes to achieve its optical imaging deviation correction. In addition, to reduce the process difficulty of using the monitoring pattern 130 for optical imaging deviation correction, the pattern shapes of sub-monitoring patterns of different sizes may be the same.

[0071] To control the process cost of forming the monitoring pattern 130, in some embodiments, the number of sub-monitoring patterns can be 3 to 5. For example, the number of sub-monitoring patterns can be 3, 4, or 5. Multiple sub-monitoring patterns can be evenly distributed in the non-functional patterned area 112 of the chip in the mask 100. For example, one sub-monitoring pattern is distributed in each non-functional patterned area 112 of the chip in the mask 100.

[0072] Please see Figure 3 and Figure 4 During the transfer of the mask pattern from the mask stencil to the wafer, the mask pattern that makes up the mask pattern will be deformed according to a specified deformation rule. That is, if the mask pattern is square, the pattern formed on the wafer will be circular; if the mask pattern is rectangular, the pattern formed on the wafer will be elliptical. To ensure that the pattern formed on the wafer meets design requirements, in some embodiments, the sub-monitoring pattern is composed of feature patterns. Specifically, the feature patterns can be mask patterns that conform to the specified deformation rules. In this embodiment, the feature patterns can include square holes and rectangles.

[0073] When the number of feature patterns constituting a sub-monitoring pattern is small, anomalies in individual feature patterns may lead to significant deviations between the optical imaging information obtained based on the sub-monitoring pattern and the actual optical imaging information. To reduce these deviations and improve the ability to correct optical imaging deviations using monitoring patterns, in some embodiments, the number of feature patterns constituting each sub-monitoring pattern is greater than or equal to 60. For example, the number of feature patterns constituting each sub-monitoring pattern can be 60, 70, or 80.

[0074] Please see Figures 5 to 12 Since the arrangement of feature patterns may affect the correction effect of optical imaging deviation correction using monitoring patterns, one or more feature patterns can be arranged according to various rules to form multiple feature pattern combinations, and one or more feature pattern combinations can be included in the sub-monitoring pattern. In some embodiments, feature patterns can form feature pattern combinations. Each sub-monitoring pattern can include one or more of the following feature pattern combinations: arrayed square holes, staggered square holes, linear square holes, isolated square holes, asymmetrical square holes, arrayed rectangles, staggered rectangles, and linear rectangles. Specifically, arrayed square holes, staggered square holes, and linear square holes are formed by multiple square holes; isolated square holes and asymmetrical square holes are formed by a single square hole; and arrayed rectangles, staggered rectangles, and linear rectangles are formed by multiple rectangles. Specifically, arrayed square holes can be formed by multiple square holes uniformly arranged along two mutually perpendicular directions. Linear square holes can be formed by multiple square holes uniformly arranged along one direction. An interlaced square hole can be formed by first arranging multiple square holes evenly in one direction to create a linear square hole, and then arranging these linear square holes in a direction perpendicular to their extension direction. In an interlaced square hole, adjacent linear square holes are staggered in the direction perpendicular to their extension direction. An isolated square hole is a single square hole. An asymmetrical square hole is an asymmetrical variation of a single square hole. The formation methods of array rectangles, interlaced rectangles, and linear rectangles are similar to those of linear square holes, and will not be elaborated further here.

[0075] During the mask manufacturing process, a mask coordinate system is used to facilitate the positioning of different mask patterns. This coordinate system has its origin at the center point of the mask, from which extend a first and a second direction that are perpendicular to each other. Researchers, through measurements of the finished mask, discovered that due to limitations in the mask manufacturing process precision, the mask patterns on the mask exhibit dimensional deviations along different directions. For example, a square mask pattern may have a designed size of 10 nm along both the first and second directions. Measurements revealed that the actual size along the first direction is 9.8 nm, and the actual size along the second direction is 10.5 nm. To reduce the impact of this phenomenon on the optical imaging quality of the mask, monitoring patterns are needed to correct for optical imaging deviations along different directions. Therefore, in some embodiments, each sub-monitoring pattern can have two mutually perpendicular arrangement directions. Specifically, the two arrangement directions can be aligned with the first and second directions of the mask coordinate system, respectively.

[0076] To ensure that the size of the sub-monitoring pattern covers all critical dimensions of various mask patterns on the mask, in some embodiments, the multiple sub-monitoring patterns may include a first sub-monitoring pattern and a second sub-monitoring pattern. The size of the first sub-monitoring pattern can be a reference size. The reference size can be the smallest critical size achievable at the corresponding process node of the mask. To meet the optical imaging deviation correction requirements for multiple critical dimensions, the second sub-monitoring pattern can be obtained by scaling the first sub-monitoring pattern while maintaining the same pitch. The size range of the second sub-monitoring pattern can be 1-N1 times to 1+N2 times the reference size. Here, N1 can be greater than or equal to 0.69 and less than 1; N2 can be greater than or equal to 0.69 and less than 1.5. For example, the multiple sub-monitoring patterns include one first sub-monitoring pattern and two second sub-monitoring patterns. The sizes of the two second sub-monitoring patterns are 0.31 times and 2.45 times the size of the first sub-monitoring pattern, respectively.

[0077] One embodiment of this application provides a method for manufacturing a mask assembly, which can be used to manufacture mask assemblies as described in the above embodiments.

[0078] In this embodiment, the method for manufacturing the photomask assembly may include the following steps.

[0079] First, based on the design rule requirements of the mask pattern, the generation rules for multiple initial mask patterns used to manufacture multiple mask sets belonging to the same mask group can be determined using the Optical Proximity Correction (OPC) model. These initial mask patterns can include circuit design patterns for chip cells, alignment mark patterns, test patterns, etc.

[0080] Subsequently, based on the Mask Rules Check (MRC) and the process design rules of the mask pattern, the generation rules for the monitoring pattern can be established. The monitoring pattern can include multiple sub-monitoring patterns. The generation rules for the monitoring pattern can include the size, shape, and positional conditions that the monitoring pattern or sub-monitoring patterns must meet. For example, size conditions can include: the minimum critical dimensions and spacing of the process nodes corresponding to the initial mask design pattern, and the ratio between the dimensions of different sub-monitoring patterns. Shape conditions can include: the number of sub-monitoring patterns, the number of feature graphics in each sub-monitoring pattern, and the types of feature graphic combinations in each sub-monitoring pattern. Positional conditions can include the position of each sub-monitoring pattern on the mask and the arrangement direction of the sub-monitoring patterns.

[0081] Next, the generation rules for monitoring patterns can be added to the generation rules for multiple initial mask patterns to obtain the generation rules for multiple mask design patterns. Based on the generation rules for multiple mask design patterns and combined with the code syntax of the specified mask pattern design software, program code for generating multiple mask design patterns can be written and input into the specified mask pattern design software.

[0082] Then, the above program code can be executed using the specified mask pattern design software to output multiple mask design patterns that include the same monitoring pattern.

[0083] Finally, multiple mask design patterns including the same monitoring pattern are formed on the mask material to create a mask set including multiple masks.

[0084] Since the generation rules of multiple mask design patterns include the generation rules of monitoring patterns, the program code written based on the generation rules of mask design patterns can be optimized according to the preset optimization rules when the specified mask design software executes the program code. Therefore, the mask design pattern can make full use of the exposure area of ​​the mask, reduce the blank area on the mask where no pattern is formed, and increase the effective exposure ratio of each exposure area on the mask.

[0085] For other technical effects of the mask assembly manufacturing method described in the above embodiments, please refer to other embodiments of this application for comparison and explanation, and they will not be repeated here.

[0086] One embodiment of this application provides a method for correcting optical imaging deviations of photomasks. This method can be used to correct optical imaging deviations of multiple photomasks included in a photomask group as described in the above embodiments, or it can be used to correct optical imaging deviations of multiple photomasks included in a photomask group manufactured by the manufacturing method of the photomask group as described in the above embodiments. Since the multiple photomasks in the photomask group have the same theoretical optimal focusing value, the photomask group can correspond to a theoretical optimal focusing value.

[0087] Please see Figure 13 The optical imaging deviation correction method for this mask may include steps S110, S120, S130, S140, and S150.

[0088] S110: Select a reference mask from among the multiple masks included in the mask set using an optical proximity correction model.

[0089] To improve the correction effect of optical imaging deviation correction, multiple masks belonging to the same mask group should be corrected for optical imaging deviation based on the same correction reference. At the same time, to reduce the operational complexity of optical imaging deviation correction, one mask can be selected from multiple masks as the reference mask (Golden Reticle).

[0090] The optical proximity correction model can define the process parameters for optical imaging of the mask by combining the mask pattern design rules on the mask, such as the model of the photolithography equipment performing the optical imaging process and the model of the photoresist coated on the wafer surface to receive the mask pattern. To reduce the process cost and complexity of optical imaging deviation correction, in this embodiment, the optical proximity correction model can be used to select the first mask manufactured after all process parameters are defined as the reference mask.

[0091] S120: Determine the reference monitoring pattern based on the monitoring pattern of the reference mask, so that the actual optimal focus value of the reference mask with the reference monitoring pattern is equal to the theoretical optimal focus value.

[0092] Since non-reference masks in the mask group, excluding the reference mask, need to be corrected for optical imaging deviations based on the reference mask, the actual optimal focus value of the reference mask must be equal to the theoretical optimal focus value. Furthermore, the reference monitoring pattern used as the correction reference must meet the process requirements of the process node.

[0093] In some embodiments, determining a reference monitoring pattern based on a monitoring pattern of a reference mask may include: measuring the dimensional deviation of the monitoring pattern of the reference mask to obtain multiple dimensional deviation statistical features of the monitoring pattern of the reference mask; if all dimensional deviation statistical features of the monitoring pattern of the reference mask meet the correction reference conditions, then using the monitoring pattern of the reference mask as the reference monitoring pattern; or, if any dimensional deviation statistical feature of the monitoring pattern of the reference mask does not meet the correction reference conditions, adjusting the monitoring pattern of the reference mask until all dimensional deviation statistical features of the monitoring pattern of the reference mask meet the correction reference conditions, then using the adjusted monitoring pattern of the reference mask as the reference monitoring pattern.

[0094] In this embodiment, dimensional deviation measurement can be performed based on different coordinate systems on a reference mask. Specifically, the reference mask can have a reference mask coordinate system and a feature pattern coordinate system. The reference mask coordinate system uses the center point of the reference mask as its origin, extending into a first reference direction and a second reference direction that are perpendicular to each other. The feature pattern coordinate system uses the center point of each feature pattern that makes up the monitoring pattern on the reference mask as its origin, extending into a first feature direction and a second feature direction that are perpendicular to each other.

[0095] After establishing multiple coordinate systems on the reference mask, the overall size deviation of the monitoring pattern on the reference mask can be measured based on the reference mask coordinate system, and the size deviation of each feature graphic that makes up the monitoring pattern on the reference mask can be measured based on the feature graphic coordinate system.

[0096] The overall dimensional deviation of the monitoring pattern on the reference mask can be measured using the following methods.

[0097] First, for each feature graphic in the monitoring pattern, the actual size of the feature graphic along the first reference direction is measured based on the coordinate system of the reference mask. The dimensional offset of the feature graphic along the first reference direction is calculated based on the difference between the actual size and the design size. The dimensional offset of the feature graphic along the second reference direction is obtained using a similar method.

[0098] Subsequently, the mean of the dimensional offset values ​​of all feature patterns along the first reference direction is calculated as the average dimensional offset value of the monitoring pattern as a whole along the first reference direction. The average dimensional offset value of the monitoring pattern as a whole along the second reference direction is obtained using a similar method. The ratio of the two is taken as the overall dimensional deviation (XY bias) of the monitoring pattern.

[0099] The dimensional deviation of each feature pattern in the monitoring pattern of the reference mask can be measured by the following method.

[0100] First, the various feature pattern combinations that make up the monitoring pattern of the reference mask can be classified according to the shape characteristics of the feature pattern combinations. For example, isolated square holes and asymmetrical square holes can be classified as isolated feature pattern combinations, arrayed square holes, staggered square holes, arrayed rectangles and staggered rectangles can be classified as dense feature pattern combinations, and linear square holes and linear rectangles can be classified as linear feature pattern combinations.

[0101] Subsequently, for each feature graphic in the monitoring pattern, the actual size of the feature graphic along the first feature direction is measured based on its own feature graphic coordinate system. The dimensional offset value of the feature graphic along the first feature direction is calculated based on the difference between the actual size and the designed size. The dimensional offset value of the feature graphic along the second feature direction is obtained using a similar method.

[0102] Next, for each type of feature graphic combination, the mean of the size offset value along the first feature direction and the mean of the size offset value along the second feature direction of the feature graphic belonging to that type of feature graphic combination are calculated, and the ratio of the two is taken as the size deviation of that type of feature graphic combination. This includes: size deviation of isolated feature graphic combination (IsolationVertical-Horizontal bias, ISO VH bias), size deviation of dense feature graphic combination (Dense V-H bias), and size deviation of line feature graphic combination (Line VH bias).

[0103] After obtaining the dimensional deviation measurement data of the monitoring pattern of the reference mask, such as the overall dimensional deviation, the dimensional deviation of isolated feature graphic combination, the dimensional deviation of dense feature graphic combination, and the dimensional deviation of linear feature graphic combination, multiple dimensional deviation statistical characteristics of the monitoring pattern of the reference mask can be obtained through statistical analysis of these dimensional deviation measurement data.

[0104] In some embodiments, multiple dimensional deviation statistical characteristics may include: the dispersion of the dimensional deviation of the monitoring pattern of the reference mask and the trend of the dimensional deviation of the monitoring pattern of the reference mask along a specified direction. Specifically, the dispersion of the dimensional deviation may include the range of the dimensional deviation measurement data and the normal distribution parameter (3 sigma) of the dimensional deviation measurement data. The trend of the dimensional deviation along the specified direction may include: the trend of the dimensional deviation along a first reference direction (X-Trend), the trend of the dimensional deviation along a second reference direction (Y-Trend), and the trend of the dimensional deviation along the direction from the center to the edge (Radial).

[0105] Because the size of the mask pattern on the mask stencil and the size of the pattern formed on the wafer have a specific ratio, typically 4:1, a calibration baseline condition can be determined based on this ratio to improve the production yield of chip cells on the wafer. Therefore, in some embodiments, the calibration baseline condition can be falling within a specified dimensional deviation range. The specified dimensional deviation range can be 3.4 to 3.6 times the design baseline size. The design baseline size can be a size that meets the requirements of After Develop Inspection (ADI) technology.

[0106] S130: Measure the size of the reference monitoring pattern and use the size of the reference monitoring pattern as the first calibration reference.

[0107] In this embodiment, the size of the reference monitoring pattern can be measured using a size measuring device, and the numerical result output by the size measuring device can be used as the first correction reference.

[0108] S140: Perform simulated optical imaging on the reference mask to obtain the light intensity distribution data of the reference monitoring pattern imaging, and use the light intensity distribution data of the reference monitoring pattern imaging as the second correction reference.

[0109] In this embodiment, an Aerial Image Measurement System (AIMS) can be used to perform simulated optical imaging on a reference mask.

[0110] Please see Figure 14 The spatial image measurement system 200 may include an illumination device 210, a mask 220, a projection lens 230, and a CCD (Charge-Coupled Device) camera 240. Specifically, the illumination device 210 may be used to provide a light source, and may have a polarization function, allowing the polarization direction of the incident light to be adjusted. The mask 220 may be used to provide a transfer pattern made of an opaque material. The surface of the mask 220 may be covered with a thin film having semi-transmissive and semi-reflective properties. The projection lens 230 may be a lens group consisting of multiple lenses. Figure 14 Taking the projection lens 230 shown as an example, its magnification is 450x and its numerical aperture (NA) ranges from 0 to 0.35. The numerical aperture determines the resolution of the projection lens 230; a larger numerical aperture results in higher resolution and a smaller minimum key size that can be resolved. The CCD camera 240 can be used to convert the received light into electrical signals to record the transferred pattern on the mask 220.

[0111] In this embodiment, the spatial image measurement system 200 is used to perform simulated optical imaging on the reference mask. The reference mask can be used as a mask 220, so that the light emitted by the illumination device 210 passes through the reference mask. The projection lens 230 magnifies and focuses the reference monitoring pattern on the reference mask onto the CCD camera 240. The information captured by the CCD camera 240 is converted into light intensity distribution data of the reference monitoring pattern imaging, that is, the second correction reference.

[0112] In this embodiment, the light intensity distribution data may include an optical imaging result image and a light intensity distribution curve. The optical imaging result image can be directly recorded by the CCD camera in the spatial imaging measurement system. Specifically, since the CCD camera in the spatial imaging measurement system is used to simulate a wafer, the optical imaging result image can correspond to the pattern transferred to the wafer after actual exposure of the mask. In the optical imaging result image, different colors are used to represent different light intensities received by the CCD camera. The light intensity distribution curve can be generated by the spatial imaging measurement system after analyzing the data recorded by the CCD camera. Specifically, the light intensity distribution curve can represent the light intensity distribution curve of any cross-section of the optical imaging result image, and provide the focus value and specific light intensity value at a specified location within that cross-section.

[0113] Please see Figure 15 and Figure 16 .exist Figure 15 In the image, (a) and (b) represent the optical imaging results of monitoring patterns with the same shape but located at different positions on the mask. Cross-sectional lines are set at corresponding positions in (a) and (b). Figure 16 This is a graph showing the light intensity distribution of the cross section corresponding to the cross section line. Taking the position with a focus value of 0.00 in this cross section as an example, the light intensity value at this position is 0.3742 in (a) and 0.3609 in (b).

[0114] S150: Based on the first and second correction references, optical imaging deviation correction is performed on the non-reference masks in the mask group, excluding the reference mask, so that during the optical imaging process of the non-reference mask, the offset between the actual optimal focus value and the theoretical optimal focus value of the mask pattern on the non-reference mask falls within the specified value range.

[0115] After obtaining the first and second calibration references based on the reference monitoring pattern, non-reference masks with optical imaging deviations can be screened out using the two calibration references. Then, optical imaging deviation corrections can be performed on these non-reference masks based on the two calibration references. Since the process complexity of dimensional measurement is lower than that of simulated optical imaging, the first calibration reference can be used for screening and deviation correction first, and then the second calibration reference can be used for screening and deviation correction.

[0116] In this embodiment, the specified numerical range can be 7.0% to 7.5% of the process node. For example, the specified numerical range can be 7.0%, 7.14%, 7.28%, and 7.5% of the process node. When the process node is 28nm, the specified numerical range can be 1.96nm to 2.10nm. When the process node is 40nm, the specified numerical range can be 2.80nm to 3.00nm.

[0117] In some embodiments, optical imaging deviation correction is performed on non-reference masks (excluding the reference mask) in the mask group based on a first correction reference and a second correction reference. This may include: measuring the size of the monitoring pattern of the non-reference mask to obtain the size of the monitoring pattern of the non-reference mask; determining a first correction monitoring pattern of the non-reference mask based on the size of the monitoring pattern of the non-reference mask and the first correction reference; performing simulated optical imaging on the non-reference mask with the first correction monitoring pattern to obtain light intensity distribution data of the first correction monitoring pattern image; determining a second correction monitoring pattern of the non-reference mask based on the light intensity distribution data of the first correction monitoring pattern image and the second correction reference, and using the non-reference mask with the second correction monitoring pattern as the correction mask; wherein, during the optical imaging process of the correction mask, the offset between the actual optimal focus value and the theoretical optimal focus value of the mask pattern on the correction mask falls within the specified numerical range mentioned above.

[0118] In this embodiment, the method for obtaining the size of the monitoring pattern of the non-reference mask is similar to the method for obtaining the first calibration reference, and will not be described again here.

[0119] In this embodiment, the method for obtaining the light intensity distribution data of the first calibration monitoring pattern image is similar to the method for obtaining the second calibration reference, and will not be described again here.

[0120] In this embodiment, the step of determining the first calibration monitoring pattern of the non-reference mask based on the size of the monitoring pattern of the non-reference mask and the first calibration reference may include: comparing the size of the monitoring pattern of the non-reference mask with the first calibration reference; if the size of the monitoring pattern of the non-reference mask is the same as the first calibration reference, directly using the monitoring pattern of the non-reference mask as the first calibration monitoring pattern; or, if the size of the monitoring pattern of the non-reference mask is different from the first calibration reference, performing a first deviation correction on the non-reference mask until the size of the monitoring pattern of the non-reference mask is the same as the first calibration reference, and using the monitoring pattern of the non-reference mask after the first deviation correction as the first calibration monitoring pattern.

[0121] In this embodiment, the size measurement value of each feature pattern constituting the monitoring pattern of the non-reference mask can be compared with the value of each feature pattern at the corresponding position in the first calibration reference. If the size measurement value of each feature pattern constituting the monitoring pattern of the non-reference mask is equal to the value of each feature pattern at the corresponding position in the first calibration reference, the size of the monitoring pattern of the non-reference mask is determined to be the same as the first calibration reference. If the size measurement value of any feature pattern constituting the monitoring pattern of the non-reference mask is not equal to the value of the feature pattern at the corresponding position in the first calibration reference, the size of the monitoring pattern of the non-reference mask is determined to be different from the first calibration reference.

[0122] In this embodiment, the first deviation correction may include, when it is determined that the size of the monitoring pattern of the non-reference mask is different from the first correction reference, performing operations such as re-etching, defect filling, and pattern size adjustment on the feature patterns in the monitoring pattern of the non-reference mask whose size measurement values ​​are not equal to those in the first correction reference.

[0123] In some embodiments, determining the second correction monitoring pattern of the non-reference mask based on the light intensity distribution data of the first correction monitoring pattern image and the second correction reference may include: comparing the light intensity distribution data of the first correction monitoring pattern image with the second correction reference; if the light intensity distribution data of the first correction monitoring pattern image is the same as the second correction reference, directly using the first correction monitoring pattern as the second correction monitoring pattern; or, if the light intensity distribution data of the first correction monitoring pattern image is different from the second correction reference, performing a second deviation correction on the non-reference mask until the light intensity distribution data of the first correction monitoring pattern image after the second deviation correction is the same as the second correction reference, and using the first correction monitoring pattern after the second deviation correction as the second correction monitoring pattern.

[0124] In this embodiment, the method of comparing the light intensity distribution data of the first calibration monitoring pattern with the second calibration reference is similar to the method of comparing the size of the monitoring pattern of the non-reference mask with the first calibration reference, and will not be described again here.

[0125] In this embodiment, the operation of the second deviation correction is similar to that of the first deviation correction, and will not be described again here.

[0126] Please see Figure 17 and Figure 18 Researchers performed optical imaging on the photomasks before and after optical aberration correction, obtaining the wafer printability results and the imaging results of the feature patterns on the wafer, respectively, corresponding to the photomasks before and after optical aberration correction. Figure 17It can be seen that, compared to the mask before optical deviation correction, the offset between the actual optimal focus value and the theoretical optimal focus value on the wafer is reduced after optical deviation correction, thus correspondingly reducing the degree of process window reduction. Figure 18 It can be seen that, compared with the mask before optical deviation correction, the feature pattern of the mask after optical deviation correction is more refined and clearer on the wafer, and the imaging quality is higher.

[0127] In this embodiment, during optical imaging of multiple masks belonging to the same mask group, the theoretical optimal focus value of the mask patterns on the multiple masks is the same. By setting the same monitoring pattern in the mask patterns on the multiple masks, the optical imaging deviation of the mask patterns on the multiple masks is corrected using the monitoring pattern. This ensures that during optical imaging of the multiple masks, the offset of the actual optimal focus value of the mask patterns on the multiple masks relative to the theoretical optimal focus value falls within a specified range of 7.0% to 7.5% of the corresponding process node of the mask group. The unexpected effects achieved include: reducing the offset of the actual optimal focus value of the mask patterns on the multiple masks relative to the theoretical optimal focus value, reducing the degree of process window shrinkage, and improving the consistency and production yield of optical imaging of multiple masks in the same mask group.

[0128] In some embodiments of this application, after optical imaging of multiple masks belonging to the same mask group, the dimensions of the monitoring pattern formed on the wafer can be measured, and the dimensional measurement data can be fed back to software for Critical Dimension Uniformity Management (CDUM). This software can adjust parameters such as exposure dose and focus depth of the lithography equipment based on the dimensional measurement data, and perform optical imaging of multiple masks based on the adjusted lithography equipment parameters, thereby improving the pattern quality on the wafer.

[0129] One embodiment of this application provides an optical imaging deviation correction system for a mask, which can be used to perform the optical imaging deviation correction method for a mask as described in the above embodiments.

[0130] The technical effects of the optical imaging deviation correction system for the mask described in the above embodiments can be explained by referring to other embodiments of this application, and will not be repeated here.

[0131] It is understood that the specific examples in this application are only intended to help those skilled in the art better understand the embodiments of this application, and are not intended to limit the scope of this application.

[0132] It is understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not limit the implementation process of the embodiments of this application in any way.

[0133] It is understood that the various embodiments described in this application can be implemented individually or in combination, and the embodiments of this application are not limited in this respect.

[0134] Unless otherwise stated, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items. The singular forms "a," "the," and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0135] As should be understood from the several embodiments provided in this application, the disclosed mask assembly and optical imaging deviation correction system can be implemented in other ways. For example, the embodiments of the mask assembly and optical imaging deviation correction system described above are merely illustrative.

[0136] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A mask set, characterized in that The method comprises the following steps: a plurality of mask plates; in the process of optical imaging of the plurality of mask plates, the theoretical optimal focus value of the mask patterns on the plurality of mask plates is the same; wherein the mask patterns on the plurality of mask plates comprise the same monitoring pattern; the monitoring pattern is used for optical imaging deviation correction of the mask patterns on the mask plates, so that in the process of optical imaging of the plurality of mask plates, the actual optimal focus value of the mask patterns on the plurality of mask plates deviates from the theoretical optimal focus value within a specified numerical range; wherein the specified numerical range is 7.0% to 7.5% of the process node corresponding to the mask plate group.

2. The mask set of claim 1, wherein, Each of the mask plates comprises a chip pattern area and a chip cutting area arranged at the periphery of the chip pattern area; wherein the chip pattern area comprises a chip functional pattern area and a chip non-functional pattern area; the monitoring pattern is located in the chip non-functional pattern area.

3. The mask set of claim 1, wherein, The monitoring pattern comprises a plurality of sub-monitoring patterns; wherein the plurality of sub-monitoring patterns have the same pattern shape and different pattern sizes.

4. The mask set of claim 3, wherein, The number of the sub-monitoring patterns is 3 to 5.

5. The mask set of claim 3, wherein, The sub-monitoring pattern is composed of feature patterns; the number of feature patterns constituting each of the sub-monitoring patterns is greater than or equal to 60.

6. The mask set of claim 5, wherein, The feature pattern comprises a square hole and a rectangle; the feature pattern forms a feature pattern combination; each of the sub-monitoring patterns comprises one or more of the following feature pattern combinations: array square hole, staggered square hole, linear square hole, isolated square hole, asymmetric square hole, array rectangle, staggered rectangle and linear rectangle.

7. The mask set of claim 3, wherein, Each of the sub-monitoring patterns has two mutually perpendicular arrangement directions.

8. The mask set of claim 3, wherein, The plurality of sub-monitoring patterns comprises a first sub-monitoring pattern and a second sub-monitoring pattern; wherein the size of the first sub-monitoring pattern is a reference size; the size of the second sub-monitoring pattern ranges from 1-N1 times to 1+N2 times of the reference size; wherein the value of N1 ranges from greater than or equal to 0.69 to less than 1; the value of N2 ranges from greater than or equal to 0.69 to less than 1.

5.

9. A method of manufacturing a mask set, characterized by, The method is used for manufacturing the mask plate group according to any one of claims 1 to 8.

10. A method of optical imaging bias correction for a mask, characterized by, The method is used for optical imaging deviation correction of the plurality of mask plates included in the mask plate group according to any one of claims 1 to 8, or the method is used for optical imaging deviation correction of the plurality of mask plates included in the mask plate group manufactured by the manufacturing method of the mask plate group according to claim 9; the mask plate group corresponds to a theoretical optimal focus value; the method comprises the following steps: selecting a reference mask plate from the plurality of mask plates included in the mask plate group by using an optical proximity correction model; determining a reference monitoring pattern according to the monitoring pattern of the reference mask plate, so that the actual optimal focus value of the reference mask plate with the reference monitoring pattern is equal to the theoretical optimal focus value; measuring the size of the reference monitoring pattern, taking the size of the reference monitoring pattern as a first correction reference; Simulating optical imaging of the reference mask to obtain light intensity distribution data of the reference monitoring pattern imaging, taking the light intensity distribution data of the reference monitoring pattern imaging as a second correction reference; Based on the first correction reference and the second correction reference, optical imaging deviation correction is performed on the non-reference mask in the mask group except the reference mask, so that in the process of optical imaging of the non-reference mask, the offset amount of the actual optimal focus value of the mask pattern on the non-reference mask from the theoretical optimal focus value falls within a specified numerical range; wherein the specified numerical range is 7.0% to 7.5% of the process node corresponding to the mask group.

11. The method of claim 10, wherein, Determine a reference monitoring pattern according to the monitoring pattern of the reference mask, including: Measure the size deviation of the monitoring pattern of the reference mask to obtain a plurality of size deviation statistical characteristics of the monitoring pattern of the reference mask; In the case that all size deviation statistical characteristics of the monitoring pattern of the reference mask meet the correction reference condition, the monitoring pattern of the reference mask is taken as the reference monitoring pattern; or in the case that any size deviation statistical characteristic of the monitoring pattern of the reference mask does not meet the correction reference condition, the monitoring pattern of the reference mask is adjusted until all size deviation statistical characteristics of the monitoring pattern of the reference mask meet the correction reference condition, and the adjusted monitoring pattern of the reference mask is taken as the reference monitoring pattern.

12. The method of claim 11, wherein, The plurality of size deviation statistical characteristics include: the dispersion degree of the size deviation of the monitoring pattern of the reference mask and the variation trend of the size deviation of the monitoring pattern of the reference mask along a specified direction; the correction reference condition is to fall within a specified size deviation range; wherein the specified size deviation range is 3.4 to 3.6 times of the design reference size.

13. The method of claim 10, wherein, Based on the first correction reference and the second correction reference, optical imaging deviation correction is performed on the non-reference mask in the mask group except the reference mask, including: Measure the size of the monitoring pattern of the non-reference mask to obtain the size of the monitoring pattern of the non-reference mask; Determine a first correction monitoring pattern of the non-reference mask according to the size of the monitoring pattern of the non-reference mask and the first correction reference; Simulate optical imaging of the non-reference mask with the first correction monitoring pattern to obtain light intensity distribution data of the first correction monitoring pattern imaging; Determine a second correction monitoring pattern of the non-reference mask according to the light intensity distribution data of the first correction monitoring pattern imaging and a second correction reference, and take the non-reference mask with the second correction monitoring pattern as a correction mask; wherein in the process of optical imaging of the correction mask, the offset amount of the actual optimal focus value of the mask pattern on the correction mask from the theoretical optimal focus value falls within the specified numerical range.

14. The method of claim 13, wherein, Determine a first correction monitoring pattern of the non-reference mask according to the size of the monitoring pattern of the non-reference mask and the first correction reference, including: The size of the monitoring pattern of the non-reference mask is compared with the first correction reference; In the case that the size of the monitoring pattern of the non-reference mask is the same as the first correction reference, the monitoring pattern of the non-reference mask is directly used as the first correction monitoring pattern; or in the case that the size of the monitoring pattern of the non-reference mask is different from the first correction reference, the non-reference mask is subjected to first deviation correction until the size of the monitoring pattern of the non-reference mask is the same as the first correction reference, and the monitoring pattern of the non-reference mask after the first deviation correction is used as the first correction monitoring pattern.

15. The method of claim 13, wherein, The second correction monitoring pattern of the non-reference mask is determined according to the light intensity distribution data of the first correction monitoring pattern and a second correction reference, including: The light intensity distribution data of the first correction monitoring pattern is compared with the second correction reference; In the case that the light intensity distribution data of the first correction monitoring pattern is the same as the second correction reference, the first correction monitoring pattern is directly used as the second correction monitoring pattern; or in the case that the light intensity distribution data of the first correction monitoring pattern is different from the second correction reference, the non-reference mask is subjected to second deviation correction until the light intensity distribution data of the first correction monitoring pattern after the second deviation correction is the same as the second correction reference, and the first correction monitoring pattern after the second deviation correction is used as the second correction monitoring pattern.

16. A system for optical imaging bias correction of a mask, characterized in that, The system is used to perform the optical imaging deviation correction method of the mask as claimed in any one of claims 10 to 15.

Images