Irradiation dose calculation method, charged particle beam lithography method, charged particle beam lithography apparatus and program

Abstract

This approach improves the resolution of charged particle beam plotting while suppressing the increase in computational load. [Solution] An irradiation dose calculation method according to one aspect of the present invention calculates the irradiation dose of a charged particle beam for drawing a graphic pattern on a drawing area on a substrate with a target mesh size based on design data. In this method, the drawing area on which the graphic pattern is drawn is virtually divided into a plurality of first mesh areas by a predetermined mesh size larger than the target mesh size, the area density of the graphic pattern placed in each first mesh area is calculated, the first irradiation dose of an individual beam with the grid intersection of a control grid provided in the drawing area as the irradiation position is calculated using the area density, and the second irradiation dose of the individual beam when the drawing area is virtually divided by the target mesh size is determined using the first irradiation dose and a conversion formula that includes a reduction ratio of the target mesh size to the predetermined mesh size.

Description

[Technical Field]

[0001] This invention relates to a method for calculating irradiation dose, a charged particle beam lithography method, a charged particle beam lithography apparatus, and a program. [Background technology]

[0002] With the increasing integration of LSIs, the circuit line widths required for semiconductor devices are becoming smaller year by year. To form the desired circuit patterns on semiconductor devices, a method is employed in which a high-precision original pattern formed on silica is reduced and transferred onto a wafer using a reduction projection exposure system. The high-precision original pattern is drawn using an electron beam lithography system, and so-called electron beam lithography technology is employed.

[0003] For example, there are lithography systems that use multiple beams. Compared to lithography with a single electron beam, using multiple beams allows for the irradiation of many beams at once, significantly improving throughput. In a multi-beam lithography system, for example, an electron beam emitted from an electron source is passed through a molded aperture array substrate with multiple apertures to form multiple beams. Each beam is then blanked, and the unshielded beams are reduced by an optical system, deflected by a deflector, and irradiated to the desired position on the sample.

[0004] In a multibeam lithography system, the sample surface is virtually divided into a mesh to generate multiple mesh regions, and the area density of the geometric patterns placed within each mesh region is calculated. Then, the irradiation dose of each beam of the multibeam system is calculated based on the area density.

[0005] Resolution can be improved by reducing the size of the mesh region (mesh size) used to calculate area density. However, reducing the mesh size increases the computational load and processing time, and also increases the amount of data from the calculation results, making it difficult to transfer and store the data in memory. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-004596 [Patent Document 2] Japanese Patent Publication No. 2021-044352 [Patent Document 3] Special Publication No. 2023-547622 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention has been made in view of the above-mentioned conventional circumstances, and aims to provide an irradiation dose calculation method, a charged particle beam lithography method, a charged particle beam lithography apparatus, and a program that can improve the resolution of charged particle beam lithography while suppressing an increase in computational load. [Means for solving the problem]

[0008] A method for calculating irradiation dose according to one aspect of the present invention is a method for calculating the irradiation dose of a charged particle beam for drawing a graphic pattern on a drawing area on a substrate with a target mesh size based on design data, comprising: generating a plurality of first mesh areas by virtually dividing the drawing area on which the graphic pattern is drawn with a predetermined mesh size larger than the target mesh size; calculating the area density of the graphic pattern placed in each first mesh area; calculating a first irradiation dose of an individual beam with the grid intersection of a control grid provided in the drawing area as the irradiation position using the area density; and determining a second irradiation dose of the individual beam when the drawing area is virtually divided with the target mesh size using the first irradiation dose and a conversion formula that includes a reduction ratio of the target mesh size to the predetermined mesh size.

[0009] A multi-charged particle beam drawing method according to one aspect of the present invention involves irradiating the substrate with the charged particle beam based on the second irradiation dose calculated by the above irradiation dose calculation method, and drawing the graphic pattern on the substrate.

[0010] A multi-charged particle beam drawing apparatus according to one aspect of the present invention is a charged particle beam drawing apparatus that calculates the irradiation amount of a charged particle beam for drawing a graphic pattern on a drawing area on a substrate with a target mesh size based on design data, and draws the graphic pattern with the target mesh size, comprising: a rasterization unit that irradiates a substrate with a charged particle beam to draw the graphic pattern, virtually divides the drawing area with a predetermined mesh size larger than the target mesh size to generate a plurality of first mesh areas, and calculates the area density of the graphic pattern arranged in each first mesh area; a calculation unit that uses the area density to calculate a first irradiation amount of an individual beam with the grid intersection of a control grid provided in the drawing area as the irradiation position; a conversion unit that uses the first irradiation amount and a conversion formula including a reduction ratio of the target mesh size with respect to the predetermined mesh size to determine a second irradiation amount of the individual beam when the drawing area is virtually divided with the target mesh size; and a drawing unit that irradiates the charged particle beam based on the second irradiation amount and draws the graphic pattern on the substrate.

[0011] A program according to one aspect of the present invention is a program for calculating the irradiation amount of a charged particle beam for drawing a graphic pattern on a drawing area on a substrate with a target mesh size based on design data, and causes a computer to perform the following steps: generating a plurality of first mesh areas by virtually dividing the drawing area on which a pattern is drawn by irradiating the substrate with a charged particle beam into a predetermined mesh size larger than the target mesh size; calculating the area density of the graphic pattern arranged in each first mesh area; calculating a first irradiation amount of an individual beam using the area density, with the grid intersection of a control grid provided in the drawing area as the irradiation position; and determining a second irradiation amount of the individual beam when the drawing area is virtually divided into the target mesh size, using the first irradiation amount and a conversion formula that includes a reduction ratio of the target mesh size to the predetermined mesh size. [Effects of the Invention]

[0012] According to the present invention, it is possible to improve the resolution of charged particle beam lithography while suppressing an increase in the amount of calculation.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic diagram of a multi-charged particle beam lithography apparatus according to an embodiment of the present invention. [Figure 2] It is a plan view of a shaping aperture member. [Figure 3] It is a diagram for explaining an example of a drawing operation. [Figure 4] It is a diagram for explaining rasterization processing. [Figure 5] It is a diagram showing an example of a control grid. [Figure 6] It is a diagram showing the relationship between the mesh size and the pattern area density. [Figure 7] It is a graph showing an irradiation amount conversion formula. [Figure 8] It is a flowchart for explaining a drawing method according to the embodiment. [Figure 9] (a) is a diagram showing a simulation result of a pattern drawn without performing irradiation amount conversion, and (b) is a diagram showing a simulation result of a pattern drawn with irradiation amount conversion. [Figure 10] It is a graph showing an irradiation amount conversion formula according to a modification example. [Figure 11] It is a graph showing an irradiation amount conversion formula according to a modification example. [Figure 12] (a) to (c) are diagrams showing simulation results of a pattern drawn with irradiation amount conversion.

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described based on the drawings. In the embodiments, as an example of the beam, a configuration using an electron beam will be described. However, the beam is not limited to an electron beam, and other charged particle beams such as an ion beam may also be used.

[0015] Figure 1 is a schematic diagram of a lithography apparatus according to an embodiment. As shown in Figure 1, the lithography apparatus 100 comprises a lithography unit W and a control unit C. The lithography apparatus 100 is an example of a multi-charged particle beam lithography apparatus. The lithography unit W comprises an electron-optical lens barrel 102 and a lithography chamber 103. Inside the electron-optical lens barrel 102 are arranged an electron source 201, an illumination lens 202, a shaped aperture array substrate 203, a blanking aperture array substrate 204, a reduction lens 205, a limiting aperture member 206, an objective lens 207, and deflectors 208 and 209, which constitute a multi-beam generation mechanism.

[0016] An XY stage 105 is placed inside the drawing chamber 103. The substrate 101 to be drawn is placed on the XY stage 105. The substrate 101 is, for example, a mask blank or a semiconductor substrate (silicon wafer). A mirror 210 for position measurement is also placed on the XY stage 105.

[0017] The control unit 160 includes a control computer 110, a deflection control circuit 130, a stage position detector 139, and memory units 140 and 142. The memory unit 140 receives and stores drawing data from an external source. The drawing data typically defines information for multiple graphic patterns to be drawn. Specifically, each graphic pattern has a defined graphic code, coordinates, and size.

[0018] The control computer 110 includes a rasterization unit 111, an irradiation dose calculation unit 112, an irradiation dose conversion unit 113, an irradiation time calculation unit 114, and a drawing control unit 115. Each part of the control computer 110 may be composed of hardware such as electrical circuits, or it may be composed of software such as programs that perform these functions. If it is composed of software, a program that realizes at least some of the functions of the control computer 110 may be stored on a recording medium such as a flexible disk or CD-ROM, loaded into a computer, and executed.

[0019] The stage position detector 139 emits a laser, receives the reflected light from the mirror 210, and detects the position of the XY stage 105 using laser interferometry.

[0020] Figure 2 is a conceptual diagram showing the configuration of the molded aperture array substrate 203. As shown in Figure 2, the molded aperture array substrate 203 has openings 22 formed in a configuration of m rows (y direction) x n columns (x direction) (m, n ≥ 2) at a predetermined arrangement pitch. Each opening 22 is formed as a rectangle or circle of the same dimensions and shape.

[0021] The electron beam 200 emitted from the electron source 201 illuminates the entire molded aperture array substrate 203 almost vertically through the illumination lens 202. The electron beam 200 illuminates a region containing multiple apertures 22. As the electron beam 200 passes through the multiple apertures 22 of the molded aperture array substrate 203, a multi-beam 20 is formed, for example, having a rectangular beam array.

[0022] The blanking aperture array substrate 204 has through holes formed in it to match the positions of each opening 22 of the molded aperture array substrate 203. Each through hole is fitted with a pair of electrodes (blankers). The multibeam 20 passes through each corresponding through hole in the blanking aperture array substrate 204.

[0023] The electron beam passing through each aperture is independently controlled for each beam to either a beam-on or beam-off state by the voltage applied to the blanker. When the beam is on, the opposing electrodes of the blanker are controlled to the same potential, and the blanker does not deflect the beam. When the beam is off, the opposing electrodes of the blanker are controlled to different potentials, and the blanker deflects the beam. In this way, multiple blankers perform blanking deflection of their respective beams from among the multi-beams that have passed through the multiple apertures 22 of the molded aperture array substrate 203.

[0024] The multi-beams 20 that have passed through the blanking aperture array substrate 204 are reduced by the reduction lens 205, and with all beams turned on, they ideally pass through the same point on the limiting aperture member 206. The beam trajectories are adjusted using an alignment coil (not shown) so that this point is located within the central opening of the limiting aperture member 206.

[0025] Here, the beam controlled to the beam-off state is deflected by the blanker of the blanking aperture array substrate 204 and follows a trajectory that passes outside the opening of the limiting aperture member 206, and is therefore shielded by the limiting aperture member 206. On the other hand, the beam controlled to the beam-on state is not deflected by the blanker and passes through the opening of the limiting aperture member 206. In this way, the on / off state of the beam is controlled by the blanking control of the blanking plate 204.

[0026] The limiting aperture member 206 shields each beam that has been deflected by multiple blankers to the beam-off state. Then, the beam that has passed through the limiting aperture member 206, formed from the time the beam is turned on until it is turned off, forms a multi-beam for one shot.

[0027] The multi-beam 20, having passed through the limiting aperture member 206, is focused by the objective lens 207 and projected onto the substrate 101 at a desired reduction ratio. The deflectors 208 and 209 each deflect the entire multi-beam by the same direction and distance. The amount of deflection of the deflectors 208 and 209 is controlled independently. The irradiation position of the multi-beam on the substrate 101 is controlled by the deflectors 208 and 209.

[0028] During drawing, the XY stage 105 is controlled to move continuously at a constant speed. At this time, the beam irradiation position is controlled by the deflector 208 so that it follows the movement of the XY stage 105. The simultaneously irradiated multi-beams are ideally aligned at a pitch obtained by multiplying the array pitch of the multiple apertures 22 of the molded aperture array substrate 203 by the desired reduction ratio described above. During drawing, the multi-beam 20 performs a raster scan drawing operation in which the position control by deflection exposes all pixels defined on the substrate 101. If the beam is on a pixel that does not contain a pattern, the beam is controlled to be off by blanking control.

[0029] Figure 3 is a conceptual diagram illustrating the drawing operation. As shown in Figure 3, the drawing area 30 on the substrate 101 is virtually divided into multiple stripe-shaped areas 32 with a predetermined width in the y-direction (first direction), for example. When drawing these stripe areas, first, the XY stage 105 is moved to adjust the position of the irradiation area (beam array) 34 that can be irradiated with a single multi-beam irradiation at the left end of the first stripe area 32, and then drawing is started.

[0030] When drawing the first stripe region 32, the XY stage 105 is continuously moved at a constant speed in the -x direction, thereby drawing the substrate 101 relatively in the +x direction. After the drawing of the first stripe region 32 is completed, the XY stage 105 stops. Next, the stage position is moved in the -y direction by the stripe width to adjust the beam array 34 so that it is positioned at the right edge of the second stripe region 32. Subsequently, the XY stage 105 is continuously moved at a constant speed in the +x direction, thereby drawing the substrate 101 toward the -x direction.

[0031] In the third stripe region 32, drawing is performed in the +x direction, and in the fourth stripe region 32, drawing is performed in the -x direction. It would also be possible to draw each stripe region 32 in the same direction, but in this case, an additional operation to return the stage position after drawing is required, which increases the drawing time.

[0032] In multibeam lithography, rasterization is performed, and as shown in Figure 4, the substrate 101 surface is virtually divided into a mesh to generate multiple mesh regions R1, and the area density of the geometric pattern P placed inside each mesh region R1 is calculated. Hereafter, the size of the mesh region (length of one side) will be referred to as the mesh size.

[0033] Furthermore, in multi-beam lithography, as shown in Figure 5, a grid-like control grid is set on the surface of the substrate 101, and the grid intersections 27 become the irradiation positions for each beam (individual beam) of the multi-beam system. The irradiation position is the reference position where each beam is irradiated, and the grid intersections do not necessarily have to be at the center of each beam being irradiated. The spacing of the control grid is hereinafter referred to as the grid size L. The grid size L is any size that can be controlled as the deflection position of the deflector 209. A smaller grid size L is preferable for accuracy, and can be 1 / N of the mesh size (where N is a natural number).

[0034] Each beam is assigned an irradiation dose to grid intersection 27. The irradiation dose is calculated from the area density of the mesh region R1.

[0035] For example, the mesh size is less than or equal to the beam size of the individual beam (the size of one side of the individual beam on the substrate 101 surface). Figure 4 shows an example where the mesh size is half the beam size B.

[0036] Figure 5 shows an example where the grid size L is 1 / 4 of the beam size B. When the grid size L is B / 4, 16 grid intersections 27 are arranged within the region of one individual beam. That is, when the beam is irradiated at each grid intersection 27, the same region on the substrate 101 surface is irradiated 16 times, resulting in multiplexing with a multiplicity of 16. Note that it is not necessarily required to irradiate all grid intersections with the beam; a method of irradiating only some intersections can also be considered.

[0037] The irradiation dose to be assigned to grid intersection 27 is calculated based on the area density of the mesh region R1 where the grid intersection 27 is located.

[0038] Reducing the mesh size improves rendering resolution, but increases computational complexity. For example, reducing the mesh size by half quadruples the number of mesh regions R1, increasing the computational cost of area density calculations. Furthermore, the amount of data from the calculation results increases, making it difficult to transfer and store the results.

[0039] In this embodiment, the resolution is achieved at a level comparable to that obtained when calculating area density with a small mesh size, while suppressing an increase in computational load.

[0040] In this embodiment, first, rasterization is performed with a large mesh size to calculate the area density for each mesh region, and the first irradiation dose of the beam corresponding to each grid intersection 27 is calculated using the calculated area density. Then, the first irradiation dose is substituted into a predetermined conversion formula to convert it into a second irradiation dose that is equivalent to the irradiation dose based on the area density calculated with a small mesh size (target mesh size).

[0041] Since the first and second irradiation doses are values ​​proportional to the area density, they can be treated by normalizing them to a range of 0 to 1.

[0042] Figure 6 shows the relationship between pattern area density when the mesh size is B / 2 and when it is B / 4.

[0043] When the pattern area density is between 0 and 0.25 with a mesh size of B / 2, the pattern area density can be considered to be 0 with a mesh size of B / 4.

[0044] For a mesh size B / 2 with a pattern area density in the range of 0.25 to 0.75, the pattern area density of mesh size B / 4 increases proportionally to the increase in the pattern area density of mesh size B / 2. When the pattern area density of mesh size B / 2 is 0.5, the pattern area density of mesh size B / 4 can also be considered to be 0.5. When the pattern area density of mesh size B / 2 is 0.75, the pattern area density of mesh size B / 4 can be considered to be 1.

[0045] When the pattern area density is 0.75 to 1 with a mesh size of B / 2, the pattern area density can be considered to be 1 with a mesh size of B / 4.

[0046] In other words, by using the conversion formula Y=F(X) shown in Figure 7, the first irradiation dose X based on the area density at mesh size B / 2 can be converted to a second irradiation dose Y equivalent to the irradiation dose based on the area density at mesh size B / 4 (target mesh size).

[0047] 0 ≤ X ≤ X min Within this range, Y=0 (slope is 0), X max In the range ≤X ≤ 1, Y = 1 (slope is 0). Here, if A is the reduction ratio of the mesh size due to the transformation, then X min =0.5(1-A), X max = 0.5(1+A). For example, when reducing a mesh size from B / 2 to B / 4, the reduction ratio A = 1 / 2.

[0048] X min <X<X max Within the range, the transformation formula becomes Y=(X-0.5) / A+0.5. min <X<X max The slope of the graph within this range is the reciprocal of the reduction factor A.

[0049] By substituting the first irradiation dose X, calculated using the area density of a mesh region with a large mesh size, into this conversion formula, a second irradiation dose Y equivalent to the irradiation dose based on the area density calculated with a small mesh size can be obtained. Since this only involves converting the irradiation dose using a conversion formula, the increase in computational load can be kept low compared to calculating the area density for each mesh region with a small mesh size.

[0050] The memory unit 142 stores data for such conversion formulas.

[0051] Next, the drawing method according to this embodiment will be explained with reference to the flowchart shown in Figure 8.

[0052] The rasterization unit 111 reads drawing data from the storage unit 140 and performs rasterization processing (step S1). Specifically, the drawing area 30 of the substrate 101 is divided into a mesh with a predetermined first mesh size to generate mesh areas R1, and the area density of the geometric patterns placed within each mesh area R1 is calculated. The first mesh size is less than or equal to the beam size B of the individual beams of the multi-beam 20, for example, B / 2 (1 / 2 of the beam size). The beam size B is the length of one side if the shape of the individual beam is square, and the diameter if it is circular.

[0053] The irradiation dose calculation unit 112 sets a control grid with a predetermined grid size in the drawing area 30 of the substrate 101, and calculates the first irradiation dose of an individual beam with the grid intersection 27 as the irradiation position for each grid intersection 27 (step S2). The grid size is smaller than the first mesh size of the mesh division in step S1, for example, B / 4 (1 / 4 of the beam size).

[0054] For example, the irradiation dose calculation unit 112 calculates the first irradiation dose by multiplying the area density of the mesh region R1 where the grid intersection point 27 is located by a preset reference irradiation dose.

[0055] The irradiation dose conversion unit 113 reads the conversion formula from the storage unit 142, substitutes the first irradiation dose X (a value in the range of 0 to 1 obtained by dividing the first irradiation dose by the reference irradiation dose) calculated in step S2 into the conversion formula, and converts it to the second irradiation dose Y (step S3). The second irradiation dose Y is a value equivalent to the irradiation dose calculated when rasterization processing is performed with a second mesh size smaller than the first mesh size.

[0056] The exposure time calculation unit 114 multiplies the second exposure Y (the value obtained by multiplying the converted second exposure by the reference exposure) by the proximity effect correction factor to obtain the incident exposure of the beam at each grid intersection 27, divides the incident exposure by the beam current to generate exposure time data, and transfers it to the deflection control circuit 130 (step S4). The deflection control circuit 130 controls the on / off of each blanker of the blanking aperture array substrate 204 based on the exposure time data to draw a pattern on the substrate 101 (step S5).

[0057] FIG. 9(a) shows the simulation result of the pattern drawn when rasterization processing is performed at a mesh size of B / 2 for a sine wave-shaped pattern, the exposure of each beam is obtained at a grid size of B / 4, and no exposure conversion is performed.

[0058] FIG. 9(b) shows the simulation result of the pattern drawn when rasterization processing is performed at a mesh size of B / 2 for the same sine wave-shaped pattern, the exposure of each beam is obtained at a grid size of B / 4, and the exposure is converted using a conversion formula with a reduction ratio of 1 / 2.

[0059] It can be seen that by performing rasterization processing at a mesh size of B / 2 and converting the exposure using a conversion formula with a reduction ratio of 1 / 2, better resolution can be achieved compared to the case where rasterization processing is performed at a mesh size of B / 2 and no exposure conversion is performed.

[0060] The conversion formula shown in FIG. 7 passes through the points where X = 0.5 and Y = 0.5. However, as shown in FIG. 10, by making X min and X max smaller, that is, by offsetting the range of X min < X < X max in the negative direction, a resize process for enlarging the pattern can be added.

[0061] As shown in FIG. 11, X min ​​By increasing it, that is, offsetting the range of Xmin < X < Xmax in the positive direction, a resizing process for reducing the pattern can be added.

[0062] When performing the resizing process as well, if the resizing amount is Resize and the mesh size for the rasterization process is Mesh, then X min and X max can be expressed by the following formula. Note that the resizing amount that can be set is a value smaller than the mesh size, that is, |Resize| < Mesh.

[0063]

Equation

[0064] Also, the conversion formula is as follows.

[0065]

Equation

[0066] Figure 12(a) shows the simulation result of the pattern drawn when performing rasterization processing on a circular pattern with a mesh size of B / 2, obtaining the irradiation amount of each beam with a grid size of B / 4, and converting the irradiation amount using a conversion formula including a reduction rate of 1 / 2 and a resizing process for enlarging the pattern.

[0067] Figure 12(b) shows the simulation result of the pattern drawn when performing rasterization processing on the same circular pattern with a mesh size of B / 2, obtaining the irradiation amount of each beam with a grid size of B / 4, and converting the irradiation amount using a conversion formula with a reduction rate of 1 / 2.

[0068] Figure 12(c) shows the simulation result of the pattern drawn when performing rasterization processing on a circular pattern with a mesh size of B / 2, obtaining the irradiation amount of each beam with a grid size of B / 4, and converting the irradiation amount using a conversion formula including a reduction rate of 1 / 2 and a resizing process for reducing the pattern.

[0069] By including a resizing process term (offset amount) in the conversion formula, it can be seen that the resizing process of the drawing pattern can be performed.

[0070] The conversion formula Y = F(X) shown in FIG. 7 includes a region with a slope of 0 and a region with a slope greater than 1, and when displayed on a graph, it is a combination of straight lines, but it may include a curve in at least a part of the range of 0 < X < 1 as long as Y = F(0) = 0 and Y = F(1) = 1 are satisfied.

[0071] Note that the present invention is not limited to the above-described embodiments as they are, and at the implementation stage, the components can be modified and embodied without departing from the gist thereof. For example, in the above-described embodiments, a multi-charged particle beam is used, but a raster beam can also be applied. Further, various inventions can be formed by appropriately combining a plurality of components disclosed in the above-described embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined.

Explanation of Reference Numerals

[0072] 100 Drawing apparatus 110 Control computer 111 Rasterization unit 112 Irradiation amount calculation unit 113 Irradiation amount conversion unit 114 Irradiation time calculation unit 115 Drawing control unit

Claims

1. A method for calculating the irradiation dose of a charged particle beam for drawing a geometric pattern on a substrate in a drawing area with a target mesh size based on design data, The drawing area on which the geometric pattern is drawn is virtually divided into a predetermined mesh size larger than the target mesh size to generate a plurality of first mesh areas. The area density of the geometric patterns arranged in each first mesh region is calculated. Using the area density, the first irradiation dose of an individual beam is calculated, with the grid intersection of the control grid provided in the drawing area as the irradiation position. A method for calculating irradiation dose, which determines the second irradiation dose of the individual beams when the drawing area is virtually divided by the target mesh size, using the first irradiation dose and a conversion formula that includes a reduction ratio of the target mesh size to the predetermined mesh size.

2. The method for calculating irradiation dose according to claim 1, wherein the conversion formula further includes the resizing amount of the graphic pattern, and the second irradiation dose is the irradiation dose of the individual beams for resizing the graphic pattern.

3. The irradiation dose calculation method according to claim 1 or 2, wherein the predetermined mesh size is less than or equal to the size of the individual beams.

4. The method for calculating irradiation dose according to claim 1 or 2, wherein the conversion formula is expressed as a function Y = F(X), where X is the first irradiation dose and Y is the second irradiation dose, and the function Y = F(X) includes a region where the slope is 0 and a region where the slope is a predetermined value greater than 1, depending on the first irradiation dose.

5. The method for calculating irradiation dose according to claim 1 or 2, wherein the conversion formula is expressed as a function Y = F(X), where X is the first irradiation dose and Y is the second irradiation dose, and when X and Y in the function Y = F(X) are normalized to the range of 0 to 1, Y = F(0) = 0 and Y = F(1) = 1.

6. A charged particle beam drawing method comprising irradiating the substrate with the charged particle beam based on the second irradiation dose calculated by the irradiation dose calculation method according to claim 1 or 2, and drawing the graphic pattern on the substrate.

7. A charged particle beam lithography apparatus that calculates the irradiation amount of a charged particle beam to draw a geometric pattern on a drawing area on a substrate with a target mesh size based on design data, and draws the pattern with the target mesh size, A rasterization unit that irradiates a substrate with a charged particle beam to draw the graphic pattern, virtually divides the drawing area with a predetermined mesh size larger than the target mesh size to generate a plurality of first mesh areas, and calculates the area density of the graphic pattern placed in each first mesh area. A calculation unit that uses the area density to calculate a first irradiation dose for individual beams whose irradiation position is the grid intersection of the control grid provided in the drawing area, A conversion unit that determines the second irradiation dose of the individual beams when the drawing area is virtually divided by the target mesh size, using the first irradiation dose and a conversion formula that includes the reduction ratio of the target mesh size to the predetermined mesh size, A drawing unit that irradiates the charged particle beam based on the second irradiation dose and draws the graphic pattern on the substrate, A charged particle beam lithography apparatus equipped with the following features.

8. A program for calculating the irradiation amount of a charged particle beam to draw a geometric pattern on a drawing area on a substrate with a target mesh size based on design data, The process involves generating multiple first mesh regions by virtually dividing the drawing area, where a pattern is drawn by irradiating a substrate with a charged particle beam, into a predetermined mesh size larger than the target mesh size, and A step of calculating the area density of the geometric pattern arranged in each first mesh region, Using the area density, the first irradiation dose of an individual beam is calculated, with the grid intersection of the control grid provided in the drawing area as the irradiation position. A step of determining the second irradiation dose of the individual beams when the drawing area is virtually divided by the target mesh size, using the first irradiation dose and a conversion formula that includes a reduction ratio of the target mesh size to the predetermined mesh size; A program that causes a computer to execute something.

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