Method for detecting symmetry of lithography auxiliary pattern based on inversion and related product

Abstract

This invention provides a detection method and related products based on the symmetry of assisted patterns obtained from inversion lithography. The detection method includes: acquiring a target image and determining the symmetry detection range from the target image; combining the main mask pattern and auxiliary pattern within the symmetry detection range into flip units; determining the pattern symmetry transformation type based on the symmetry type of the main mask pattern and the lithography light source; performing a pattern symmetry transformation operation on the flip units according to the pattern symmetry transformation type; comparing the flip units before and after the pattern symmetry transformation operation and marking the areas of difference, thereby obtaining the detection result. This invention achieves automatic identification of asymmetric defects, significantly improving detection efficiency while avoiding the problem of missing minute defects.

Description

Technical Field

[0001] This invention relates to the field of semiconductor computational lithography, and in particular to a detection method and related products based on the symmetry of patterns assisted by inversion lithography. Background Technology

[0002] As semiconductor manufacturing processes advance to 7nm and below advanced process nodes, the feature size of integrated circuits continues to shrink, placing increasingly stringent demands on the precision of photolithography imaging. Inverse Lithography Technology (ILT), also known as reverse lithography or reverse photolithography, is an advanced resolution enhancement technology that significantly improves photolithography imaging quality and process windows by reverse-engineering the mask pattern from the target pattern on the wafer. Inverse lithography uses the desired pattern on the silicon wafer as the target and inversely calculates the required pattern on the mask. It treats the process of optical proximity correction or source-mask optimization (SMO) as a reverse problem, setting the lithographic target pattern as the ideal imaging result, and inversely calculating the mask image based on the transformation model of the imaging system's spatial image. The core of inverse lithography lies in achieving the target contour by optimizing mask / exposure conditions.

[0003] Sub-Resolution Assist Feature (SRAF) is a key component of ILT masks. It adds tiny patterns smaller than the resolution limit of the lithography system around the main pattern, improving the uniformity of the light field distribution of the main pattern through optical proximity effects. This enhances the edge placement accuracy and linewidth uniformity of the lithographic image, improving the imaging quality of the main pattern and increasing process window and yield. In advanced processes, insufficient symmetry of the SRAF can lead to significant local linewidth deviations and contour distortion, reducing process window and chip yield.

[0004] In the ILT (In-Process Technology) workflow, the ridges of the SRAF (Surface Reflection Alignment) are typically extracted from the optimized pixelated image first. Then, a Manhattan-type sub-resolution auxiliary pattern (Manhattan SRAF) is generated based on the ridges. This is followed by pattern merging, Mask Rule Check (MRC), and conflict resolution. When both the main pattern and the light source are symmetrical, insufficient symmetry in the Manhattan SRAF can amplify local errors and reduce the process stability of ILT. A symmetrical SRAF can achieve a more uniform field intensity distribution globally or locally, reducing edge shifts and contour distortion caused by field asymmetry. This helps maintain a stable contour and linewidth distribution within the process window, improving yield robustness.

[0005] Currently, SRAF symmetry detection suffers from problems such as low efficiency, poor accuracy, and easy omission of minute defects. Some existing automated detection methods use polygon transformation and comparison one by one, which is cumbersome, computationally intensive, and prone to errors in detection results due to the shift of the transformation center point. Summary of the Invention

[0006] One objective of this invention is to provide a detection method and related products based on inversion lithography-assisted pattern symmetry that offers high detection efficiency and intuitive display of detection results.

[0007] A further objective of this invention is to reduce contour deviations in multi-layer stacked mask images and reduce lithography yield fluctuations.

[0008] Specifically, this invention provides a detection method based on inversion lithography-assisted pattern symmetry, comprising: Acquire the target image and determine the symmetry detection range from the target image; Combine the main and auxiliary mask patterns within the symmetry detection range into a flip unit; The type of pattern symmetry transformation is determined based on the symmetry type of the main mask pattern and the photolithography light source; Perform a graphic symmetry transformation operation on the flipped unit according to the graphic symmetry transformation type; The flipped units before and after the graphic symmetry transformation operation are compared, and the regions with differences are marked to obtain the detection results.

[0009] Optionally, the steps of acquiring the target image include: Obtain the initial mask pattern obtained through inversion lithography; Auxiliary graphics are generated from the initial mask pattern to obtain the target image.

[0010] Optionally, the step of determining the symmetry detection range from the target image includes: Filter and detect the main mask pattern with geometric symmetry in the target image, as well as the auxiliary patterns generated for the main mask pattern; Obtain the coordinates of the boundary points of the main mask graphic and its auxiliary graphics; The symmetry detection range is defined by the coordinates of the boundary points.

[0011] Optionally, the symmetry types of the mask master pattern and the photolithography light source include: rotational symmetry, bilateral mirror symmetry, and tetrahedral symmetry; and The graphic symmetry transformation type corresponding to rotational symmetry is: rotating the flipped element 180° around its symmetry reference center; The graphic symmetry transformation type corresponding to bilateral mirror symmetry is: to mirror the flipped unit along the X-axis or along the Y-axis; The graphic symmetry transformation type corresponding to square symmetry is: rotating the flipped unit around its symmetry reference center by any angle of 90°, 180°, or 270°, or mirroring it along the coordinate axis.

[0012] Optionally, the step of comparing the flipped units before and after the graphic symmetry transformation operation includes: Perform an XOR operation on the data of each layer of the flipped cell before and after the graphic symmetry transformation operation according to their positions; The set of positions where the XOR operation results in 1 is considered as the region where differences exist.

[0013] Optionally, after obtaining the detection result, the method of the present invention further includes: Output the main mask graphic, auxiliary graphic, and areas with discrepancies to a separate layout data exchange format file.

[0014] Optionally, the auxiliary graphics are sub-resolution auxiliary graphics.

[0015] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the detection method based on inversion lithography-assisted pattern symmetry as described above.

[0016] According to another aspect of the present invention, a computer-readable storage medium is also provided, on which a computer program is stored, wherein the computer program, when executed by a processor, implements the steps of the detection method based on inversion lithography-assisted pattern symmetry described above.

[0017] According to another aspect of the present invention, a computer device is also provided, which includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above-described detection method based on inversion lithography-assisted pattern symmetry.

[0018] This invention presents a detection method based on the symmetry of lithography-assisted patterns. The method combines the main mask pattern and auxiliary pattern within the symmetry detection range into a flip unit. The flip unit undergoes a symmetry transformation operation according to the pattern symmetry transformation type. The flip units before and after the symmetry transformation are compared, avoiding the tedious operation of performing symmetry transformations on each pattern individually. This method also eliminates coordinate offset and center point deviation problems that easily occur during individual transformations, ensuring the consistency of the symmetry detection benchmark. This method matches the corresponding pattern symmetry transformation type based on the symmetry type of the main mask pattern and the lithography light source, providing an accurate reference benchmark for subsequent difference comparison. The overall comparison of the flip units before and after the symmetry transformation and the marking of the difference areas enable automatic identification of asymmetric defects, significantly improving detection efficiency and avoiding the problem of missing minute defects.

[0019] Furthermore, the detection method for pattern symmetry based on inversion lithography of the present invention covers the most mainstream symmetry types in the lithography field, such as rotational symmetry, bilateral mirror symmetry, and tetragonal symmetry. It is compatible with the symmetry characteristics of the main pattern and illumination source in most advanced processes, greatly improving its versatility and applicability.

[0020] Furthermore, the detection method based on inversion lithography-assisted pattern symmetry of the present invention employs layer-by-layer and position-by-position XOR operations for difference comparison, enabling the identification of asymmetric regions with accuracy down to the individual pixel level. This significantly improves detection accuracy and effectively captures minute asymmetric defects. The XOR operation automatically cancels out symmetrical overlapping regions, retaining only the positions with differences, and directly outputs a set of asymmetric regions. This eliminates the need for additional pattern filtering and recognition steps, simplifying the comparison process and enhancing the automation level of detection.

[0021] Furthermore, the detection method based on the symmetry of inversion lithography-assisted patterns of the present invention outputs the main mask pattern, auxiliary pattern, and difference regions to a separate layout data exchange format file. This allows the detection results to adopt a standard format commonly used in the semiconductor industry, enabling them to be directly recognized and processed by subsequent EDA design tools and mask manufacturing equipment, seamlessly integrating into existing mask design and manufacturing processes. The output detection result file contains all key information, allowing engineers to intuitively view the location and morphology of asymmetric defects, providing a clear and direct basis for subsequent SRAF symmetry correction and shortening the defect correction cycle.

[0022] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0023] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of a detection method for pattern symmetry assisted by inversion lithography according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a detection method for a target image based on the symmetry of an inversion lithography-assisted pattern according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the detection result in a detection method based on the symmetry of inversion lithography-assisted patterns according to an embodiment of the present invention; Figure 4This is a flowchart illustrating the comparison of flipped units before and after a pattern symmetry transformation operation in a method for detecting pattern symmetry assisted by inversion lithography according to an embodiment of the present invention. Figure 5 This is a complete detection flowchart of a detection method based on the symmetry of inversion lithography-assisted patterns according to an embodiment of the present invention; Figure 6 This is a schematic diagram of a computer program product according to an embodiment of the present invention; Figure 7 This is a schematic diagram of a computer-readable storage medium according to an embodiment of the present invention; Figure 8 This is a schematic block diagram of a computer device according to an embodiment of the present invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0025] Figure 1 This is a schematic flowchart of a detection method based on inversion lithography-assisted pattern symmetry according to an embodiment of the present invention; the detection method based on inversion lithography-assisted pattern symmetry generally includes: Step S101: Acquire the target image and determine the symmetry detection range from the target image. The target image is a mask pattern with added auxiliary patterns (SRAF), thereby detecting the main mask pattern and auxiliary patterns on the target image. The symmetry detection range refers to the region where both the main mask pattern and the corresponding lithography source have geometric symmetry, such as repeating array regions, gate regions, and other key pattern regions sensitive to imaging quality.

[0026] In some embodiments, the step of acquiring the target image may include: acquiring an initial mask layout obtained by inversion lithography; generating an auxiliary pattern in the initial mask layout to obtain the target image. The initial mask layout contains the main mask pattern to be transferred onto the wafer. Then, based on the initial mask layout and lithography process parameters, a sub-resolution auxiliary pattern (SRAF) is generated using an inversion lithography algorithm, and the layout containing the main mask pattern and the SRAF is used as the target image.

[0027] The steps for determining the symmetry detection range from the target image may include: filtering the target image for a mask master graphic and auxiliary graphics generated for the mask master graphic that have geometric symmetry; obtaining the boundary point coordinates of the mask master graphic and its auxiliary graphics; and defining the symmetry detection range using the boundary point coordinates. In some embodiments, the symmetry detection range can be obtained by analyzing the region of the master graphic area that needs to be SRAF symmetry detection, and the coordinates of the lower left and upper right boundary points of this region can be recorded as boundary point coordinates. The symmetry detection range is generally rectangular or square, and the definition of the symmetry detection range can be achieved using the lower left and upper right boundary points.

[0028] Figure 2 This is a schematic diagram of a target image detection method based on the symmetry of inversion lithography-assisted patterns according to an embodiment of the present invention. The diagram includes three main mask patterns, each surrounded by a series of SRAFs.

[0029] Step S102: Combine the main and auxiliary mask graphics within the symmetry detection range into a flip cell. The flip cell (CELL) uses the geometric center of the symmetry detection range as its unique symmetry reference center, and all subsequent symmetry transformation operations are performed around this reference center. Thus, the flip cell has a uniform size and reference center, facilitating overall rotation, flipping, mirroring, and other operations.

[0030] Step S103: Determine the pattern symmetry transformation type based on the symmetry type of the mask master pattern and the photolithography light source. The symmetry types of the mask master pattern and the photolithography light source include: rotational symmetry (C2), bilateral mirror symmetry (D2), and tetrahedral symmetry (D4).

[0031] Rotational symmetry (C2) refers to a graphic that completely overlaps with the original graphic after being rotated 180° around its geometric center. The corresponding graphic symmetry transformation type is: rotating the flipped element 180° around its symmetry reference center.

[0032] Double-sided mirror symmetry (D2) refers to a graphic that completely overlaps with the original graphic after being mirrored along the X-axis or the Y-axis. The graphic symmetry transformation type corresponding to double-sided mirror symmetry is: mirroring the flipped unit along the X-axis or the Y-axis.

[0033] Four-dimensional symmetry (D4) means that a graphic can be completely superimposed on the original graphic after being rotated 90°, 180°, or 270° around its geometric center, or after being mirrored along the X-axis or Y-axis. The graphic symmetry transformation type corresponding to four-dimensional symmetry is: rotating the flipped unit around its symmetry reference center by any angle of 90°, 180°, or 270°, or mirroring it along the coordinate axes.

[0034] The aforementioned symmetry covers the most mainstream symmetry types in the field of photolithography and is compatible with the symmetry characteristics of the main pattern and illumination source in most advanced processes.

[0035] Step S104: Perform a graphic symmetry transformation operation on the flipped unit according to the graphic symmetry transformation type. This step performs a global symmetry transformation operation on the flipped unit.

[0036] Step S105: Compare the flipped units before and after the graphic symmetry transformation operation, and mark the areas with differences to obtain the detection results.

[0037] Figure 3 This is a schematic diagram of the detection result in a detection method based on inversion lithography-assisted pattern symmetry according to an embodiment of the present invention. The detection target image shown in the figure belongs to the rotationally symmetric (C2) type. After the flip unit is rotated 180°, it is compared with the original state before the rotation to determine the difference area. This difference area is highlighted, which makes it easy for engineers to intuitively view the location and shape of asymmetric defects, providing a clear and direct basis for subsequent SRAF correction.

[0038] The detection method based on the symmetry of lithography-assisted patterns described in the above embodiments combines the main mask pattern and auxiliary pattern within the symmetry detection range into a flip unit. The flip unit undergoes a symmetry transformation operation according to the pattern symmetry transformation type. The flip units before and after the symmetry transformation are compared, avoiding the tedious operation of performing symmetry transformation on each pattern individually. This also eliminates the coordinate offset and center point deviation problems that easily occur during individual transformations, ensuring the consistency of the symmetry detection benchmark. This method matches the corresponding pattern symmetry transformation type based on the symmetry type of the main mask pattern and the lithography light source, providing an accurate reference benchmark for subsequent difference comparison. The overall comparison of the flip units before and after the symmetry transformation and the marking of the difference areas enable automatic identification of asymmetric defects, significantly improving detection efficiency and avoiding the problem of missing minute defects.

[0039] Figure 4 This is a schematic flowchart illustrating the comparison of flipped units before and after a pattern symmetry transformation operation in a method for detecting pattern symmetry based on inversion lithography according to an embodiment of the present invention. The steps for comparing flipped units before and after the pattern symmetry transformation operation may include: Step S401 involves performing a positional XOR operation on the data of each layer of the flipped cell before and after the graphic symmetry transformation. The target image can be a GDS format file (e.g., GraphicData System II, or GDSII for short), which includes multiple layers of data. Each layer of the GDS in the flipped and rotated cell is XORed layer by layer with each layer of the GDS in the cell before the flipped and rotated transformation. XOR processing enables pixel-level data comparison.

[0040] Step S402: The set of positions where the XOR operation result is 1 is taken as the region where there is a difference.

[0041] By performing XOR operations layer by layer and position for difference comparison, asymmetric regions can be identified with precision down to the individual pixel level, significantly improving detection accuracy and effectively capturing minute asymmetric defects. The XOR operation automatically cancels out symmetrical overlapping regions, retaining only the locations with differences, and directly outputs a set of asymmetric regions. This eliminates the need for additional image filtering and recognition steps, simplifying the comparison process and enhancing the automation of detection.

[0042] After obtaining the detection results, the method in this embodiment can also output the main mask pattern, auxiliary patterns, and areas with discrepancies to a separate layout data exchange format file (e.g., GDS format). Using a standard format common in the semiconductor industry, it can be directly recognized and processed by subsequent EDA design tools and mask manufacturing equipment, seamlessly integrating into existing mask design and manufacturing processes.

[0043] Figure 5 This is a complete flowchart of a detection method based on inversion lithography-assisted pattern symmetry according to an embodiment of the present invention. The detection process may include: Step S501: Generate an initial mask layout image based on the ILT-optimized mask layout; Step S502: Extract ridges from the image and generate SRAF; Step S503: Determine the symmetry detection range; Step S504: Convert the symmetry detection range into a flip cell. Step S505: Perform a graphic symmetry transformation operation on the CELL according to the graphic symmetry transformation type; Step S506: Perform XOR processing on the original image GDS and the image GDS generated after the transformation operation. Step S507: Highlight the difference regions identified by the XOR process to generate the detection results.

[0044] This embodiment also provides a computer program product 112, a computer-readable storage medium 113, and a computer device 114. Figure 6 This is a schematic diagram of a computer program product 112 according to an embodiment of the present invention. Figure 7 This is a schematic diagram of a computer-readable storage medium 113 according to an embodiment of the present invention. Figure 8 This is a schematic block diagram of a computer device 114 according to an embodiment of the present invention.

[0045] Computer program product 112 includes computer program 111, which, when executed by processor 310, implements the steps of the detection method based on inversion lithography-assisted pattern symmetry described above. Computer-readable storage medium 113 stores the computer program 111 thereon, which, when executed by processor 310, implements the steps of the detection method based on inversion lithography-assisted pattern symmetry described above. Computer device 114 may include memory 320, processor 310, and computer program 111 stored in memory 320 and running on processor 310.

[0046] The computer program 111 used to perform the operations of this invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, status setting data, integrated circuit configuration data, or source code or object code written in any combination of one or more programming languages ​​and procedural programming languages.

[0047] Computer program 111 may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, to perform aspects of the invention, electronic circuits including, for example, programmable logic circuits, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs) may execute computer-readable program instructions to personalize the electronic circuits by utilizing state information of computer-readable program instructions.

[0048] For the purposes of this embodiment, computer program product 112 is a related product that includes computer program 111.

[0049] For the purposes of this embodiment, a computer-readable storage medium 113 is a tangible device capable of holding and storing a computer program 111. It can be any device capable of containing, storing, communicating, propagating, or transmitting the program 111 for use by or in conjunction with an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of a computer-readable storage medium 113 include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable optical disc read-only memory (CD-ROM), digital versatile disc (DVD), memory stick, floppy disk, mechanical encoding device, and any suitable combination thereof.

[0050] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A detection method based on the symmetry of patterns assisted by inversion lithography, comprising: Acquire a target image and determine the symmetry detection range from the target image; The main and auxiliary patterns of the mask within the symmetry detection range are combined into a flip unit; The pattern symmetry transformation type is determined based on the symmetry type of the main mask pattern and the photolithography light source; Perform a graphic symmetry transformation operation on the flipping unit according to the graphic symmetry transformation type; The flipped units before and after the graphic symmetry transformation operation are compared, and the regions with differences are marked to obtain the detection results.

2. The detection method based on inversion lithography-assisted pattern symmetry according to claim 1, wherein, The steps for acquiring the target image include: Obtain the initial mask pattern obtained through inversion lithography; The auxiliary graphic is generated in the initial mask pattern to obtain the target image.

3. The detection method based on inversion lithography-assisted pattern symmetry according to claim 2, wherein, The step of determining the symmetry detection range from the target image includes: Filter the main mask pattern with geometric symmetry in the target image to obtain the auxiliary pattern generated for the main mask pattern; Obtain the coordinates of the boundary points of the main mask graphic and its auxiliary graphic; The symmetry detection range is defined by the coordinates of the boundary points.

4. The detection method based on inversion lithography-assisted pattern symmetry according to claim 1, wherein, The symmetry types of the mask master pattern and the photolithography light source include: rotational symmetry, bilateral mirror symmetry, and tetrahedral symmetry; and The graphic symmetry transformation type corresponding to the rotational symmetry is: rotating the flip unit 180° around its symmetry reference center; The graphic symmetry transformation type corresponding to the bilateral mirror symmetry is: to mirror the flip unit along the X-axis or along the Y-axis; The graphic symmetry transformation type corresponding to the four-sided symmetry is: rotating the flip unit around its symmetry reference center by any angle of 90°, 180°, or 270° or mirroring it along the coordinate axis.

5. The detection method based on inversion lithography-assisted pattern symmetry according to claim 1, wherein, The step of comparing the flipped units before and after the graphic symmetry transformation operation includes: The data of each layer of the flipped unit before and after the graphic symmetry transformation operation are XORed according to their positions. The set of positions where the XOR operation results in 1 is taken as the region where the difference exists.

6. The detection method based on the symmetry of inversion lithography-assisted patterns according to claim 1, further comprising, after obtaining the detection result: The main mask graphic, the auxiliary graphic, and the regions where the markings differ are output to a separate layout data exchange format file.

7. The detection method based on inversion lithography-assisted pattern symmetry according to claim 1, wherein... The auxiliary graphics are sub-resolution auxiliary graphics.

8. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the detection method based on the symmetry of inversion lithography-assisted patterns as described in any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that... When the computer program is executed by the processor, it implements the steps of the detection method based on the symmetry of inversion lithography-assisted patterns as described in any one of claims 1 to 7.

10. A computer device, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the detection method based on inversion lithography-assisted pattern symmetry as described in any one of claims 1 to 7.

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