A method for e-beam lithography proximity effect correction pattern compression

Abstract

The application is a kind of electron beam lithography proximity effect correction layout compression method, which comprises the following steps: S1, normalizing layout boundary; S2, determining the division level of each quadtree grid area; S3, cutting quadtree grid with layout pattern boundary; S4, mapping proximity effect correction dose into non-uniform quadtree grid; and S5, storing quadtree grid and exposure dose into a file. The application adopts a non-uniform quadtree grid compression method, the biggest feature of which is that the grid division is relatively dense at the edge of the layout and relatively sparse in the interior of the layout. This compression method fully conforms to the dose characteristics of electron beam proximity effect correction, and the dose after electron beam proximity effect correction is mapped to the grid, which can greatly reduce the number of grids and thus improve the exposure efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of electron beam lithography proximity effect correction layout compression method, which can carry out grid compression to the layout after proximity effect correction, greatly reduce the number of grid under the premise of ensuring accuracy, effectively improve exposure efficiency. BACKGROUND

[0002] With the minimum size of electron beam lithography (EBL) reaching sub-10 nanometer level, in order to ensure the high resolution of electron beam exposure layout, the grid after electron beam proximity effect correction (PEC) will be further reduced, which increases the storage number of layout grid, thereby greatly reducing the calculation efficiency of electron beam lithography process. In order to compress the number of layout grid, non-uniform grid division mode must be used. At present, triangular grid, quadrilateral grid and other non-rectangular grid patterns are commonly used in two-dimensional non-uniform grid division. However, such non-rectangular grid division is not completely compatible with the horizontal and vertical scanning mode of electron beam lithography in actual electron beam lithography process. When small acute angle grid appears, pixel distortion is easy to occur, thereby affecting the resolution of electron beam lithography.

[0003] Therefore, in order to find a rectangular non-uniform grid layout division method, the present application adopts a non-uniform quadtree grid compression method. The biggest feature of this method is that the grid division is relatively dense at the edge of the layout, and the grid division is relatively sparse in the interior of the layout. This compression method completely conforms to the dose characteristics of electron beam proximity effect correction, that is, the dose correction is relatively obvious at the edge of the layout, and the dose correction is relatively flat in the middle area of the layout. Finally, the dose after electron beam proximity effect correction is mapped to the grid, which can greatly reduce the number of grid, thereby improving the exposure efficiency. SUMMARY

[0004] The present application is an electron beam lithography proximity effect correction layout compression method, which effectively reduces the number of grid of electron beam proximity effect layout and greatly improves the exposure efficiency of electron beam lithography under the premise of ensuring accuracy.

[0005] The technical solution of the present application is to compress the layout after proximity effect correction of electron beam lithography by non-uniform quadtree grid, and the steps of the present application are as follows:

[0006] Step S1, normalize the layout boundary;

[0007] The original layout of e-beam lithography is read, the position coordinates of the outermost boundary of the exposure layout are determined, and a certain distance D is extended outward on the four sides of the rectangular boundary respectively. The extended rectangular grid determines the boundary of the quadtree grid, and then the size in the quadtree grid is normalized to form a 1.0x1.0 floating-point quadtree grid boundary. The grid is defined as the root grid, and the level is 0.

[0008] Step S2, determine the division level of each quadtree grid region;

[0009] Determine the maximum L max and the minimum L min division level of the quadtree grid, and perform non-uniform quadtree grid division. When the lithography layout pattern boundary straight line segment (curve segment is approximated as a multi-segment straight line segment) and any edge of the current quadtree grid exist intersection or overlap relationship, directly perform quadtree division of the current grid.

[0010] Determine the intersection of the straight line segment in the layout and the boundary line segment of the quadtree grid, as shown in Figure 2 (a), line segments AB, CD satisfy formula (1), that is:

[0011]

[0012] In the formula, × represents the vector cross product, and satisfies and are not equal to 0 at the same time, and are not equal to 0 at the same time.

[0013] Determine the overlap of the straight line segment in the layout and the boundary line segment of the quadtree grid, as shown in Figure 2 (b), that is: arrange the four end points of the two line segments in order of size, first compare the horizontal coordinates, the point with larger horizontal coordinate is larger, and the point with larger vertical coordinate is larger when the horizontal coordinates are the same. According to the size order, line segments AB, CD are obtained. When formula (2) is satisfied, that is:

[0014]

[0015] The quadtree division method of the current grid is shown in Figure 3 , that is: take the midpoint S m of the four edges of the current rectangular grid M l , connect the midpoints of the opposite edges, and the two intersection lines and the four edges of M l form four equal-sized sub-grids M l+1 . The newly divided four sub-grids M l+1 replace the current rectangular grid M l , and then take each sub-grid M l+1 as the current grid to continue the quadtree grid division. The minimum division number of each grid is Lmin The maximum number of layers is L max .

[0016] Step S3: The layout pattern boundary is cut off from the quadtree mesh;

[0017] After dividing the quadtree mesh of the layout, the entire quadtree mesh is clipped using the edge segments of the original layout pattern as boundaries, preserving the remaining mesh within the connected domains of the pattern boundaries, such as... Figure 4 As shown, the meshes cut from the pattern boundary region are reconnected end-to-end along the polygon vertices to form new polygon meshes. Meshes within the connected regions of the pattern that are not cut are retained, while those outside the connected regions are discarded. Then, the mesh dimensions are denormalized to obtain the final non-uniform quadtree mesh W of the layout. i (i = 1, 2, ..., N; N is the total number of non-uniform quadtree grids), initialize the corresponding electron beam exposure dose D. i It is 0.

[0018] Step S4: The proximity effect corrected dose is mapped into a non-uniform quadtree mesh;

[0019] The electron beam lithography rectangular pattern is divided into equally spaced uniform grids (i.e., m×n small grids), with each grid representing one pixel p. i The corresponding dose is d i The exposure dose for each pixel was obtained using the electron beam proximity effect dose correction method. The corrected exposure dose d within each pixel was then calculated. i Mapped to a region W of a corresponding non-uniform quadtree mesh i The method is as follows: take the coordinate position p corresponding to the center of each pixel value. i Traverse the entire non-uniform quadtree grid and determine p i In one of the non-uniform quadtree meshes W i Within the region, and the exposure dose D i Updated to:

[0020]

[0021] In the formula, k is each non-uniform quadtree grid W i The number of equally spaced uniform grids contained within.

[0022] Step S5: Save the quadtree mesh and exposure dose into a file;

[0023] W for each non-uniform quadtree grid i The exposure dose D at the boundary vertices, line ends, and within the grid. i They should be standardized and stored as .GDSII or .OASIS file formats. Attached Figure Description

[0024] Figure 1 This is a flowchart of the operation of the present invention;

[0025] Figure 2 It refers to the positional relationship where the ends of the two lines intersect and coincide.

[0026] Figure 3 This is a schematic diagram of quadtree mesh partitioning;

[0027] Figure 4 This is a schematic diagram of connected component shearing;

[0028] Figure 5 It is an electron beam proximity effect corrected dose mapping method. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] This invention relates to a method for compressing electron beam lithography proximity effect correction patterns, the purpose of which is to obtain a non-uniform quadtree mesh with dense mesh division at the edge of the pattern and sparse mesh division at the center. The steps of this invention are as follows: Figure 1 As shown, the process consists of five steps: normalizing the layout boundary; determining the partitioning level of each quadtree mesh region; trimming the quadtree mesh based on the layout pattern boundary; mapping the proximity effect correction dose into the non-uniform quadtree mesh; and saving the quadtree mesh and exposure dose into a file. The technical solution of this invention is: compressing the electron beam lithography layout after proximity correction using a non-uniform quadtree mesh. Taking a polygonal non-uniform quadtree mesh as an example, the specific implementation steps are as follows:

[0031] Step S1, normalize the map boundaries;

[0032] The original electron beam lithography pattern is read in, the coordinates of the rectangular boundary of the exposure pattern are determined, and the rectangular boundary is extended outward by a certain distance D on each of the four sides. The extended rectangular grid determines the boundary of the quadtree grid. Then, the size within the quadtree grid is normalized to form a 1.0×1.0 floating-point quadtree grid boundary, which is defined as the root grid with a level of 0.

[0033] Step S2: Determine the partitioning level of each quadtree grid region;

[0034] Determine the maximum L of the quadtree mesh. max and minimum L min The hierarchical division is performed using a non-uniform quadtree mesh. When a straight line segment (or a curved segment, which is approximately multiple straight line segments) of the lithographic pattern boundary intersects or overlaps with any edge of the current quadtree mesh, the current mesh is directly divided into quadtrees.

[0035] Determine if a straight line segment in the layout intersects with the boundary line segment of the quadtree grid, as shown in Figure 2 (a), that is, line segments AB, CD when satisfying formula (1), that is:

[0036]

[0037] In the formula, × represents the cross product of the vector, and satisfies and are not 0 at the same time, and are not 0 at the same time.

[0038] Determine if a straight line segment in the layout overlaps with the boundary line segment of the quadtree grid, as shown in Figure 2 (b), that is: arrange the four end points of the two line segments in order of size, first compare the horizontal coordinates, the point with larger horizontal coordinate is larger, and the point with larger vertical coordinate is larger when the horizontal coordinates are the same, to get line segments AB, CD in order of size. When satisfying formula (2), that is:

[0039]

[0040] The quadtree partitioning method of the current grid, as shown in Figure 3 , that is: take the midpoint S l of the four edges of the current rectangular grid M m , connect the midpoints of the opposite edges, and the two intersection lines and the four edges of M l form four equally sized sub-grids M l+1 , the newly partitioned four sub-grids M l+1 replace the current rectangular grid M l , then take each sub-grid M l+1 as the current grid, continue to execute the quadtree grid partitioning, and the minimum partitioning level of each grid is L min , and the maximum partitioning level is L max .

[0041] Step S3, the layout pattern boundary is sheared to the quadtree grid;

[0042] After the quadtree grid of the layout is partitioned, the boundary of the entire quadtree grid is sheared with the edge line segment of the original layout pattern as the boundary, and the remaining grid inside the pattern boundary connected domain is retained, as shown in Figure 4 , that is: the grid after the pattern boundary area is cut is reconnected as a new polygon grid according to the polygon vertex head and tail, the grid inside the pattern connected domain that is not cut is retained, and the grid outside the pattern connected domain that is not cut is directly discarded. Then perform a denormalization operation on the size of the grid to obtain the final non-uniform quadtree grid W i(i = 1, 2, ..., N; N is the total number of non-uniform quadtree grids), initialize the corresponding electron beam exposure dose D. i It is 0.

[0043] Step S4: The proximity effect corrected dose is mapped into a non-uniform quadtree mesh;

[0044] The electron beam lithography rectangular pattern is divided into equally spaced uniform grids (i.e., m×n small grids), with each grid representing one pixel p. i The corresponding dose is d i The exposure dose for each pixel was obtained using the electron beam proximity effect dose correction method. The corrected exposure dose d within each pixel was then calculated. i Mapped to a region W of a corresponding non-uniform quadtree mesh i The method is as follows: take the coordinate position p corresponding to the center of each pixel value. i Traverse the entire non-uniform quadtree grid and determine p i In one of the non-uniform quadtree meshes W i Within the region, and the exposure dose D i Updated to:

[0045]

[0046] In the formula, k is each non-uniform quadtree grid W i The number of equally spaced uniform grids contained within.

[0047] Step S5: Save the quadtree mesh and exposure dose into a file;

[0048] W for each non-uniform quadtree grid i The exposure dose D at the boundary vertices, line ends, and within the grid. i They should be standardized and stored as .GDSII or .OASIS file formats.

[0049] like Figure 5 Compared with the layout compression effect shown in Table 1, the electron beam proximity effect layout compression method of the present invention compresses the number of grids in the layout by nearly 10 times while ensuring that the minimum layout accuracy meets the exposure requirements. This effectively reduces the storage size of the layout file and thus greatly improves the exposure efficiency of electron beam lithography.

[0050] Table 1. Layout compression effect after using the present invention.

[0051]

[0052] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the scope of protection of the present application. Based on the description of the examples, those of ordinary skill in the art should be able to understand and make relevant modifications or replacements to the technical solutions of the present application without departing from the essence and scope of the present application.

Claims

1. A method for compressing a layout with proximity effect correction in electron beam lithography, characterized in that, Includes the following steps: Step S1, normalize the layout boundary, characterized in that: the position coordinates of the rectangular boundary of the exposure layout are determined, and the rectangular boundary is extended outward by a certain distance D on each of the four sides. The extended rectangular grid determines the boundary of the quadtree grid. Then the size within the quadtree grid is normalized to form a 1.0×1.0 floating-point quadtree grid boundary. This grid is defined as the root grid with a level of 0. Step S2, determining the partitioning level of each quadtree grid region, characterized in that: determining the maximum L of the quadtree grid. max and minimum L min The hierarchical division is performed, and non-uniform quadtree meshing is carried out. When the straight line segment of the photolithographic pattern boundary intersects or overlaps with any edge of the current quadtree mesh, the current mesh is directly divided into quadtrees. If the photolithographic pattern boundary is a curved segment, it is approximately composed of multiple straight line segments. When satisfied and Not both equal to 0, and When they are not both 0, that is: Then determine whether the straight line segment in the layout intersects with the boundary line segment of the quadtree grid, where × represents the vector cross product; Arrange the four endpoints of the two line segments in order of size. First, compare the x-coordinates; the point with the larger x-coordinate is larger. If the x-coordinates are the same, the point with the larger y-coordinate is larger. Based on this order, we obtain line segments AB and CD, i.e.: Then it is determined that the straight line segment in the layout overlaps with the boundary line segment of the quadtree mesh; The current quadtree partitioning method for the grid is as follows: take the current rectangular grid M. l Midpoint S of the edge m Connect the midpoints of opposite sides; the two intersecting lines intersect at point M. l The four sides form four equal-sized subgrids M. l+1 The four newly divided subgrids M l+1 Replace the current rectangular grid M l Then, for each subgrid M l+1 For the current grid, continue performing quadtree meshing, with a minimum meshing level of L for each grid. min The maximum number of layers is L max ; Step S3: The quadtree mesh is cut along the boundary of the layout pattern. The key feature is that after the quadtree mesh of the layout is divided, the entire quadtree mesh is cut along the boundary using the edge segments of the original layout pattern as the boundary. The remaining mesh within the connected domain of the pattern boundary is retained; that is, the mesh after being cut along the pattern boundary is reconnected to form a new polygon mesh according to the beginning and end of the polygon vertices. The uncut mesh within the connected domain of the pattern is retained, while the uncut mesh outside the connected domain is discarded. Then, the mesh size is denormalized to obtain the final non-uniform quadtree mesh W of the layout. i , where i = 1, 2...n, n is the total number of non-uniform quadtree grids, and the corresponding electron beam exposure dose Di is initialized to 0; Step S4, the proximity effect correction dose is mapped into a non-uniform quadtree grid, characterized in that: the electron beam lithography rectangular pattern is divided into equally spaced uniform grids, dividing the pattern into m×n grids, each grid being a pixel p. i The corresponding dose is d i The exposure dose of each pixel was obtained using the electron beam proximity effect dose correction method, and the corrected exposure dose d within each pixel was calculated. i Mapped to a region W of a corresponding non-uniform quadtree mesh i The method is as follows: take the coordinate position p corresponding to the center of each pixel value. i Traverse the entire non-uniform quadtree grid and determine p i In one of the non-uniform quadtree meshes W i Within the region, and the exposure dose D i Updated to: In the formula, k is each non-uniform quadtree grid W i The number of equally spaced uniform grids contained within; Step S5: Save the quadtree mesh and exposure dose into a file.

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