Method for splitting mask layout
By first splitting the mask pattern into mandatory graphics and then classifying the free graphics, the problem of uneven distribution of target graphics was solved, thus improving the pattern quality of the photolithography process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SEMICON MFG INT TIANJIN
- Filing Date
- 2022-01-25
- Publication Date
- 2026-05-19
AI Technical Summary
In existing technologies, splitting dense target patterns onto multiple mask patterns results in uneven pattern distribution and large density differences, which affects the lithography process.
By first splitting the mandatory graphics, then classifying and splitting the free graphics separately, and combining the results of the mandatory graphics splitting with fine adjustments, the total area and density of the target graphics in each mask layout are balanced within a preset range, thus improving the graphic outline effect after exposure.
This achieves a balanced distribution of target pattern area and density in each mask pattern, improving the pattern quality of the photolithography process.
Smart Images
Figure CN116540490B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a method for splitting a mask pattern. Background Technology
[0002] Patterning is an essential process in semiconductor manufacturing. This involves designing a mask pattern based on the semiconductor device, which includes the target pattern. These target patterns are then transferred from the mask pattern onto photoresist using photolithography, followed by exposure and development of the photoresist.
[0003] However, with the development of semiconductor technology, the integration density of integrated circuits is increasing, and the feature size of semiconductor devices is becoming smaller. Correspondingly, the requirements for manufacturing processes are becoming more precise, and the number and density of target patterns on the mask layout are increasing dramatically. It is becoming increasingly impossible to expose all target patterns onto the wafer at once during photolithography. Therefore, MP (Multi-Patterning) technology has become a necessary means to ensure that the exposed patterns meet the process requirements of each node. MP technology splits the densely packed target patterns originally placed on a single mask layout into multiple mask layouts, exposing each one separately to complete the transfer of the target patterns.
[0004] However, there are still many problems with the existing technology of splitting dense target patterns onto multiple mask layouts. Summary of the Invention
[0005] The technical problem solved by this invention is to provide a method for splitting a mask pattern, which can better balance the area, number and density of graphics on each mask pattern at the level of the whole mask pattern and each unit area of the mask pattern, so as to improve the effect of the graphic outline after exposure.
[0006] To address the aforementioned problems, the present invention provides a method for splitting a mask layout, comprising: providing an initial layout having a plurality of target graphics, the target graphics including a plurality of mandatory split graphics and a plurality of free graphics; performing a first splitting process on the initial layout, such that the plurality of mandatory split graphics are formed on different initial mask layouts; classifying the plurality of free graphics to form a plurality of graphic groups, each graphic group including at least one free graphic; and performing a second splitting process on the initial layout based on the first splitting process, such that the plurality of free graphics are formed on different initial mask layouts to obtain mask layouts, wherein the difference in the total area of the target graphics in the different mask layouts and / or the difference in the graphic density in the different mask layouts satisfy a preset condition.
[0007] Optionally, before performing the first splitting process on the initial layout, the splitting method further includes: obtaining the spacing size between adjacent target graphics in the initial layout; providing a minimum exposure size; dividing the target graphics with spacing sizes smaller than the minimum exposure size into the mandatory splitting graphics, and dividing the remaining target graphics into the free graphics.
[0008] Optionally, the target graphic is a rectangle; when there is no overlapping projection between adjacent target graphics along the arrangement direction, the spacing dimension is the spacing dimension between the nearest vertices of adjacent target graphics; when there is overlapping projection between adjacent target graphics along the arrangement direction, the spacing dimension is the spacing dimension between the nearest side lengths of adjacent target graphics.
[0009] Optionally, several graphic groups include: small-area graphic groups and large-area graphic groups.
[0010] Optionally, the method for classifying several free graphics to form several graphic groups includes: providing an area threshold; classifying free graphics with an area smaller than the area threshold into the small area graphic group, and classifying free graphics with an area larger than the area threshold into the large area graphic group.
[0011] Optionally, the large-area graphic group includes: a long graphic group and a short graphic group.
[0012] Optionally, the method of classifying several free graphics to form several graphic groups further includes: providing a length threshold; classifying the free graphics in the large-area graphic group whose graphic length is greater than the length threshold into the long graphic group, and classifying the free graphics in the large-area graphic group whose graphic length is less than the length threshold into the short graphic group.
[0013] Optionally, the length threshold is the median of the lengths of all the target graphics in the large-area graphic group.
[0014] Optionally, the area threshold is the median of the area of all the target graphics in the initial layout.
[0015] Optionally, the difference in the total area of the target graphic in different mask layouts and / or the difference in the graphic density in different mask layouts satisfying preset conditions include: the difference in the total area of the target graphic in different mask layouts is within a first preset range; and the difference in the graphic density in different mask layouts is within a second preset range.
[0016] Optionally, the theoretical area value of the total area of the target graphic in each of the mask layouts is obtained, wherein the theoretical area value is the total area of all the target graphics in the initial layout divided by the number of mask layouts formed after splitting; the first preset range is less than 5% of the theoretical area value.
[0017] Optionally, the second preset range is less than 5% of the target graphic density in the initial layout.
[0018] Optionally, each of the mask layouts has several unit regions, and the difference between the graphic density in each unit region and the graphic density of the corresponding mask layout is within a third threshold range.
[0019] Optionally, the third preset range is less than 5% of the target graphic density in the initial layout.
[0020] Compared with the prior art, the technical solution of the present invention has the following advantages:
[0021] In the mask pattern splitting method of the present invention, several mandatory splitting graphics are first split, and several free graphics are classified and split separately. At the same time, fine adjustments are made based on the splitting results of the mandatory splitting graphics, so that the difference in the total area of the target graphics in the different mask patterns is within a first preset range, and the difference in the graphic density in the different mask patterns is within a second preset range. This not only ensures that the graphic area in each mask pattern is well balanced, but also ensures that the number and distribution of graphics in each mask pattern are well balanced, thereby improving the effect of the graphic outline after exposure.
[0022] Furthermore, each of the mask layouts has several unit regions, and the difference between the pattern density in each unit region and the pattern density of the corresponding mask layout is within a third threshold range. Since the mask layout has a large area, if the target patterns formed in the mask layout are concentrated in a certain area, the pattern quality exposed on the wafer will be poor. Therefore, in order to make the distribution of the target patterns formed on the mask layout more uniform, it is necessary to ensure that the difference between the pattern density in each unit region and the pattern density of the corresponding mask layout is within the third threshold range. Attached Figure Description
[0023] Figure 1 It is a schematic diagram of the structure of the target graphic split into multiple mask layouts;
[0024] Figure 2 This is a flowchart of the mask layout splitting method according to an embodiment of the present invention;
[0025] Figures 3 to 8This is a schematic diagram of the steps in the mask pattern splitting method in an embodiment of the present invention. Detailed Implementation
[0026] As described in the background section, existing techniques for splitting dense target patterns onto multiple mask layouts still present numerous problems. These will be explained in detail below with reference to the accompanying drawings.
[0027] Please refer to Figure 1 In the existing technology, during the target graphic decomposition process, while ensuring that the feature size between the target graphics meets the exposure limit, the multiple mask layouts after decomposition are balanced according to the graphic area, so that the target graphic area ratio of each mask layout is at the same level.
[0028] However, when there are large differences in the size of the target patterns, balancing based solely on area may result in uneven distribution of the target patterns. The density of the target patterns on each mask pattern may vary greatly in the unit region, which will have a significant impact on the morphology of the pattern formed on the photoresist layer in subsequent photolithography processes.
[0029] Based on this, the present invention provides a method for splitting a mask pattern. First, several mandatory split graphics are split, and then several free graphics are classified and split separately. At the same time, fine adjustments are made based on the splitting results of the mandatory split graphics, so that the difference in the total area of the target graphics in the different mask patterns is within a first preset range, and the difference in the graphic density in the different mask patterns is within a second preset range. This not only ensures that the graphic area in each mask pattern is well balanced, but also ensures that the number and distribution of graphics in each mask pattern are well balanced, thereby improving the effect of the graphic outline after exposure.
[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0031] Figure 2 This is a flowchart of a mask layout splitting method according to an embodiment of the present invention, including:
[0032] Step S101: Provide an initial layout, which has several target graphics, including several mandatory split graphics and several free graphics;
[0033] Step S102: Perform a first splitting process on the initial layout, so that several of the splittable graphics are formed on different initial mask layouts;
[0034] Step S103: Classify the free graphics to form several graphic groups, each graphic group including at least one free graphic.
[0035] Step S104: Based on the first splitting process, the initial layout is split into a second splitting process, forming several free graphics on different initial mask layouts to obtain mask layouts. The difference in the total area of the target graphics in the different mask layouts and / or the difference in the graphic density in the different mask layouts meet preset conditions.
[0036] The steps of the mask layout splitting method are described in detail below with reference to the accompanying drawings.
[0037] Figures 3 to 8 This is a schematic diagram of the steps in the mask pattern splitting method in an embodiment of the present invention.
[0038] Please refer to Figure 3 An initial layout 100 is provided, on which a plurality of target graphics 101 are provided, the target graphics 101 including a plurality of mandatory split graphics and a plurality of free graphics.
[0039] It should be noted that, in this embodiment, the initial layout 100 is a pattern of all device structures designed on a certain layer of the wafer in the semiconductor manufacturing process. The number and density of the target patterns 101 on the initial layout 100 are large. If all the target patterns 101 are exposed onto the wafer at once during the photolithography process, the large number and density of the target patterns 101 on the initial layout 100 will lead to significant mutual influence between the target patterns 101 during exposure, resulting in poor pattern quality on the wafer. Therefore, it is necessary to subsequently split several of the target patterns 101 in the initial layout 100 onto different mask layouts to reduce the number and density of target patterns on each mask layout, thereby improving the quality of the pattern outline displayed on the wafer after exposure.
[0040] In this embodiment, before performing the first splitting process on the initial layout 100, the splitting method further includes: obtaining the spacing size between adjacent target graphics 101 in the initial layout 100; providing a minimum exposure size; dividing the target graphics 101 with a spacing size smaller than the minimum exposure size into the mandatory splitting graphics, and dividing the remaining target graphics 101 into the free graphics.
[0041] Please refer to Figure 4 In this embodiment, the target graphic 101 is a rectangle; when there is no overlapping projection between adjacent target graphics 101 along the arrangement direction X, the spacing size is the spacing size d1 between the nearest vertices of adjacent target graphics 101.
[0042] Please refer to Figure 5When there is an overlapping projection between adjacent target graphics 101 along the arrangement direction X, the spacing dimension is the spacing dimension d2 between the nearest side lengths of adjacent target graphics 101.
[0043] It should be noted that, in this embodiment, the mandatory split patterns are the target patterns 101 with very small spacing and adjacent dimensions. Because of their small spacing, these target patterns 101 significantly influence each other during exposure. Therefore, to reduce this mutual influence, these target patterns 101 need to be split onto different mask patterns. In contrast, the free patterns, due to their larger spacing, have less mutual influence during exposure; therefore, several free patterns can be formed on any single mask pattern.
[0044] Please refer to Figure 6 The initial layout 100 is subjected to a first splitting process, so that several of the split graphics are formed on different initial mask layouts.
[0045] It should be noted that in this embodiment, the first splitting process of the several mandatory split graphics does not involve directly extracting and processing these mandatory split graphics and then forming them on the corresponding initial mask layout. Instead, these mandatory split graphics are first distinguished using different identifier elements. Subsequently, after the several free graphics are uniformly split, the mandatory split graphics and the free graphics with the same identifier elements are extracted and formed on the same mask layout.
[0046] In this embodiment, an initial mask layout has one mandatory split pattern; in other embodiments, an initial mask layout may have multiple mandatory split patterns.
[0047] In this embodiment, the identification element is a color; in other embodiments, the identification element may also be a number.
[0048] Please continue to refer to this. Figure 6 The free graphics are classified and processed to form several graphic groups, and each graphic group includes at least one free graphic.
[0049] In this embodiment, the plurality of graphic groups include: small-area graphic groups and large-area graphic groups.
[0050] In this embodiment, the method for classifying several free graphics to form several graphic groups includes: providing an area threshold; classifying free graphics with an area smaller than the area threshold into the small area graphic group, and classifying free graphics with an area larger than the area threshold into the large area graphic group.
[0051] In this embodiment, the area threshold is the median of the area of all the target graphics 101 in the initial layout 100.
[0052] In this embodiment, the large-area graphic group includes: a long graphic group and a short graphic group.
[0053] In this embodiment, the method of classifying and processing several free graphics to form several graphic groups further includes: providing a length threshold; classifying the free graphics in the large-area graphic group whose graphic length is greater than the length threshold into the long graphic group, and classifying the free graphics in the large-area graphic group whose graphic length is less than the length threshold into the short graphic group.
[0054] In this embodiment, the length threshold is the median of the lengths of all the target graphics 101 in the large area graphic group.
[0055] After forming several graphic groups, the method further includes: based on the first splitting process, performing a second splitting process on the free graphic in each graphic group, forming several free graphic on different initial mask layouts, such that the initial mask layouts form mask layouts 200, the difference in the total area of the target graphic 101 in the different mask layouts 200 is within a first preset range, and the difference in graphic density in the different mask layouts 200 is within a second preset range.
[0056] In this embodiment, by first splitting several mandatory graphics, then classifying and splitting several free graphics individually, and making minor adjustments based on the splitting results of the mandatory graphics, the difference in the total area of the target graphics in the different mask layouts is within a first preset range, and the difference in the graphic density in the different mask layouts 200 is within a second preset range. This not only ensures a good balance in the area of the graphics in each mask layout 200, but also ensures a good balance in the number and distribution of graphics in each mask layout 200, thereby improving the effect of the graphic outline after exposure.
[0057] Please refer to Figure 7 In this embodiment, the second splitting process for the free graphics in each graphic group is not performed by directly extracting and processing these free graphics and then forming them on the corresponding mask layout 200. Instead, based on the already assigned identifier elements of several graphics that must be split, the free graphics are redistributed using these existing identifier element types, thereby achieving the splitting of the several free graphics.
[0058] Please refer to Figure 8After splitting several free graphics, the mandatory split graphics and the free graphics with the same identifier element are extracted and formed on the same mask layout 200.
[0059] During the process of splitting the free graphic, it is necessary to ensure that the difference in the total area of the target graphic in different mask layouts 200 and / or the difference in the graphic density in different mask layouts 200 meet the preset conditions.
[0060] Specifically, the difference in the total area of the target pattern in different mask layouts 200 is within a first preset range, and the difference in the pattern density in different mask layouts 200 is within a second preset range.
[0061] In this embodiment, the theoretical area value of the total area of the target graphic 201 in each of the mask layouts 200 is obtained. The theoretical area value is the total area of all the target graphics 101 in the initial layout 100 divided by the number of mask layouts 200 formed after splitting. The first preset range is less than 5% of the theoretical area value.
[0062] In this embodiment, the second preset range is less than 5% of the density of the target graphic 101 in the initial layout 100.
[0063] In this embodiment, each of the mask layouts 200 has a plurality of unit regions, and the difference between the graphic density in each unit region and the graphic density of the corresponding mask layout 200 is within a third threshold range.
[0064] Since the mask layout 200 has a large area, if the target patterns 101 formed in the mask layout 200 are all concentrated in a certain area, the quality of the pattern exposed on the wafer will be poor. Therefore, in order to make the distribution of the target patterns 101 formed on the mask layout 200 more uniform, it is necessary to ensure that the difference between the pattern density in each unit region and the corresponding pattern density of the mask layout 200 is within a third threshold range.
[0065] It should be noted that for some target graphics 101 that span several unit regions, the graphic density needs to be considered over a larger area. Generally, the graphic density is calculated by the sum of the areas of the several unit regions that the target graphics 101 spans.
[0066] In this embodiment, the third preset range is less than 5% of the density of the target graphic 101 in the initial layout 100.
[0067] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A method for splitting a mask layout, characterized in that, include: An initial layout is provided, which has several target graphics, including several mandatory split graphics and several free graphics; The initial layout is subjected to a first splitting process, so that several of the necessarily split graphics are formed on different initial mask layouts; The free graphics are classified and processed to form several graphic groups, and each graphic group includes at least one free graphic. Based on the first splitting process, the initial layout is subjected to a second splitting process, and several free graphics are formed on different initial mask layouts to obtain mask layouts. The difference in the total area of the target graphics in different mask layouts and / or the difference in the graphic density in different mask layouts meet preset conditions. Each of the mask layouts has several unit regions, and the difference between the graphic density in each unit region and the graphic density of the corresponding mask layout is within a third preset range.
2. The method for splitting a mask layout as described in claim 1, characterized in that, Before performing the first splitting process on the initial layout, the splitting method further includes: obtaining the spacing size between adjacent target graphics in the initial layout; providing a minimum exposure size; dividing the target graphics with spacing sizes smaller than the minimum exposure size into the mandatory splitting graphics, and dividing the remaining target graphics into the free graphics.
3. The method for splitting a mask layout as described in claim 2, characterized in that, The target graphic is a rectangle; when there is no overlapping projection between adjacent target graphics along the arrangement direction, the spacing dimension is the spacing dimension between the nearest vertices of adjacent target graphics; when there is overlapping projection between adjacent target graphics along the arrangement direction, the spacing dimension is the spacing dimension between the nearest side lengths of adjacent target graphics.
4. The method for splitting a mask layout as described in claim 1, characterized in that, Several graphic groups include: small-area graphic groups and large-area graphic groups.
5. The method for splitting a mask layout as described in claim 4, characterized in that, A method for classifying a number of free graphics to form a number of graphic groups includes: providing an area threshold; classifying free graphics with an area smaller than the area threshold into the small area graphic group, and classifying free graphics with an area larger than the area threshold into the large area graphic group.
6. The method for splitting a mask layout as described in claim 5, characterized in that, The large-area graphic group includes: long graphic group and short graphic group.
7. The method for splitting a mask layout as described in claim 6, characterized in that, The method of classifying and processing several free graphics to form several graphic groups further includes: providing a length threshold; classifying the free graphics in the large-area graphic group whose graphic length is greater than the length threshold into the long graphic group, and classifying the free graphics in the large-area graphic group whose graphic length is less than the length threshold into the short graphic group.
8. The method for splitting a mask layout as described in claim 7, characterized in that, The length threshold is the median of the lengths of all target graphics in the large-area graphic group.
9. The method for splitting a mask layout as described in claim 5, characterized in that, The area threshold is the median of the areas of all the target graphics in the initial layout.
10. The method for splitting a mask layout as described in claim 1, characterized in that, The difference in the total area of the target graphic in different mask layouts and / or the difference in the graphic density in different mask layouts satisfying preset conditions include: the difference in the total area of the target graphic in different mask layouts is within a first preset range; and the difference in the graphic density in different mask layouts is within a second preset range.
11. The method for splitting a mask layout as described in claim 10, characterized in that, Obtain the theoretical area value of the total area of the target graphic in each of the mask layouts, wherein the theoretical area value is the total area of all the target graphics in the initial layout divided by the number of mask layouts formed after splitting; The first preset range is less than 5% of the theoretical area value.
12. The method for splitting a mask layout as described in claim 10, characterized in that, The second preset range is less than 5% of the target graphic density in the initial layout.
13. The method for splitting a mask layout as described in claim 1, characterized in that, The third preset range is less than 5% of the target graphic density in the initial layout.