Covering rate calculation method, charged particle beam drawing method, covering rate calculation device and charged particle beam drawing device

Abstract

To reduce a calculation amount and a memory use amount of a pixel covering rate in rasterization processing.SOLUTION: A covering rate calculation method emits a charged particle beam, calculates a covering rate of a pattern for each pixel region obtained by dividing a drawing region for drawing a pattern by a prescribed size, generates a plurality of first pixel regions by virtually dividing the drawing region by the first size, calculates a covering rate of a pattern of the first pixel region, generates a plurality of second pixel regions corresponding to the pixel region by virtually dividing the first pixel region by the second size smaller than the first size, selects the second pixel region that approximates the pattern shape in the first pixel region, and calculates the covering rate of the selected second pixel region on the basis of the covering rate of the pattern of the first pixel region, the number of the second pixel regions in the first pixel region, and the number of the selected second pixel regions.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a coverage rate calculation method, a charged particle beam drawing method, a coverage rate calculation device, and a charged particle beam drawing device.

Background Art

[0002] With the high integration of LSIs, the circuit line width required for semiconductor devices has been gradually miniaturized year by year. In order to form a desired circuit pattern on a semiconductor device, a method of reducing and transferring a high-precision original pattern formed on quartz onto a wafer using a reduction projection exposure apparatus has been adopted. For the production of a high-precision original pattern, a so-called electron beam lithography technique, in which a resist is exposed by an electron beam drawing apparatus to form a pattern, is used.

[0003] As an electron beam drawing apparatus, for example, a multi-beam drawing apparatus that irradiates many beams at once using multi-beams to improve throughput is known. In this multi-beam drawing apparatus, for example, an electron beam emitted from an electron gun forms multi-beams by passing through an aperture member having a plurality of openings, and each beam is blanking-controlled at a blanking plate. The unshielded beam is reduced by an optical system and irradiated to a desired position on a mask to be drawn.

[0004] The multi-beam drawing apparatus obtains the coverage rate (area density) of a pattern for each pixel (picture element) obtained by dividing a drawing area into a mesh shape, and adjusts the irradiation amount of each beam of the multi-beams according to the coverage rate. The smaller the pixel size, the more accurately the pattern shape is reflected, and the resolution and drawing accuracy are improved. However, with the reduction of the pixel size, there has been a problem that the time required for coverage rate calculation increases, and the memory usage amount for storing the calculation result of the coverage rate increases.

[0005] ]For example, as shown in Figures 9(a) and 9(b), when the pixel size (length of one side of a pixel) is reduced from 16 nm to 4 nm, the number of calculations for coverage increases from 1 to 4. Also, the memory used to store the calculation results for coverage increases from 2 bytes to 32 bytes. By reducing the pixel size to 1 / n times (where n is an integer greater than or equal to 2), the number of calculations increases by n times, and the memory usage increases by n. 2 It had doubled in size. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2005-340438 [Patent Document 2] Japanese Patent Publication No. 2012-230689 [Patent Document 3] International Publication No. 2008 / 084543 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to provide a method for calculating pixel coverage, a charged particle beam lithography method, a coverage calculation apparatus, and a charged particle beam lithography apparatus that can reduce the amount of calculation and memory usage required for pixel coverage. [Means for solving the problem]

[0008] A method for calculating coverage according to one aspect of the present invention is a method for calculating the coverage of a pattern for each pixel region obtained by dividing a drawing area into predetermined sizes by irradiating it with a charged particle beam. The method involves virtually dividing the drawing area into a first size to generate a plurality of first pixel regions, calculating the coverage of the pattern in the first pixel regions, virtually dividing the first pixel regions into a second size smaller than the first size to generate a plurality of second pixel regions corresponding to the pixel regions, selecting the second pixel regions that approximate the pattern shape within the first pixel regions, and calculating the coverage of the selected second pixel regions based on the coverage of the pattern in the first pixel regions, the number of the second pixel regions within the first pixel regions, and the number of the selected second pixel regions.

[0009] A charged particle beam drawing method according to one aspect of the present invention involves calculating the irradiation amount for each pixel region using the coverage rate of the second pixel region calculated by the above coverage rate calculation method, controlling the charged particle beam based on the calculated irradiation amount, and drawing a pattern on a substrate.

[0010] A coverage rate calculation device according to one aspect of the present invention is a coverage rate calculation device that irradiates a charged particle beam and calculates the coverage rate of a pattern for each pixel region obtained by dividing a drawing area into predetermined sizes, and has a rasterization unit that virtually divides the drawing area into a first size to generate a plurality of first pixel regions, calculates the coverage rate of the pattern in the first pixel regions, virtually divides the first pixel regions into a second size smaller than the first size to generate a plurality of second pixel regions corresponding to the pixel regions, and selects the second pixels that approximate the pattern shape in the first pixel region, and calculates the coverage rate of the selected second pixel regions based on the coverage rate of the pattern in the first pixel region, the number of the second pixel regions in the first pixel region, and the number of the selected second pixel regions.

[0011] A charged particle beam lithography apparatus according to an aspect of the present invention calculates the irradiation dose for each pixel region using the coverage rate of the second pixel region calculated by the above-mentioned coverage rate calculation apparatus, and creates a dose map defining the irradiation dose for each pixel region. It includes a dose map creation unit, an irradiation time calculation unit that calculates the irradiation time for each pixel region based on the dose map, and a drawing control unit that controls the irradiation dose of the charged particle beam based on the calculated irradiation time.

Effects of the Invention

[0012] According to the present invention, the calculation amount of pixel coverage rate and the memory usage amount can be reduced.

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 diagram showing a configuration example of an aperture member. [Figure 3] It is a diagram for explaining an example of a drawing operation. [Figure 4] It is a diagram showing an example of an irradiation region of a multi-beam and a pixel to be drawn. [Figure 5] It is a flowchart for explaining a drawing method according to the same embodiment. [Figure 6] (a) is a diagram showing the coverage rate of the first pixel, (b) is a diagram showing the second pixel obtained by dividing the first pixel, and (c) is a diagram showing the inside / outside determination information of the second pixel. [Figure 7] It is a diagram showing the coverage rate of the second pixel. [Figure 8] (a) is a diagram showing the centroid position of the pattern in the first pixel, and (b) to (d) are diagrams for explaining the method of selecting the second pixel. [Figure 9] (a) and (b) are diagrams for explaining the number of calculation times of the coverage rate according to a comparative example.

Embodiments 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 a charged particle beam, a configuration using an electron beam will be described. However, the charged particle beam is not limited to an electron beam, and an ion beam or the like may also be used.

[0015] FIG. 1 is a schematic configuration diagram of a drawing apparatus using a coverage rate calculation apparatus according to an embodiment. As shown in FIG. 1, the drawing apparatus 100 includes a drawing unit 150 and a control unit 160. The drawing apparatus 100 is an example of a multi-charged particle beam drawing apparatus.

[0016] The drawing unit 150 includes an electron column 102 and a drawing chamber 103. Inside the electron column 102, an electron gun 201, an illumination lens 202, an aperture member 203, a blanking plate 204, a reduction lens 205, a limiting aperture member 206, an objective lens 207, and a deflector 208 are arranged.

[0017] Inside the drawing chamber 103, an XY stage 105 capable of continuous movement is arranged. On the XY stage 105, a substrate 101 to be drawn during drawing is arranged. The substrate 101 includes an exposure mask when manufacturing a semiconductor device, or a semiconductor substrate (silicon wafer) on which a semiconductor device is manufactured, etc. Further, the substrate 101 includes mask blanks on which a resist is applied and nothing has been drawn yet. On the XY stage 105, a mirror 210 for measuring the position of the XY stage 105 is further arranged.

[0018] The control unit 160 has a control computer 110, a memory 112, a deflection control circuit 130, a stage position detector 139, and storage devices 140, 142 such as a magnetic disk device. These are connected to each other via a bus. Drawing data is input from the outside and stored in the storage device 140.

[0019] The control computer 110 includes a rasterization unit 50, a dose map creation unit 52, an irradiation time calculation unit 54, and a drawing control unit 60. These functions may be configured as hardware such as electrical circuits, or as software. If configured as software, a program that implements at least some of the functions may be stored on a recording medium and loaded and executed by a computer having a CPU. The recording medium for storing the program is not limited to removable ones such as magnetic disks or optical disks, but may also be a fixed recording medium such as a hard disk drive or memory. Information such as calculation results in the control computer 110 is stored in the memory 112 each time. The rasterization unit 50 and the dose map creation unit 52 execute the processing of the coverage rate calculation device according to this embodiment.

[0020] Figure 2 is a conceptual diagram showing an example configuration of the aperture member 203. In Figure 2, the aperture member 203 has multiple openings 22 formed in a matrix at a predetermined arrangement pitch in the vertical and horizontal directions. For example, 512 × 512 rows of openings 22 are formed in the vertical and horizontal (x,y directions). Each opening 22 is formed as a rectangle of the same dimensions. The openings 22 may also be circular.

[0021] A portion of the electron beam 200 passes through each of these multiple openings 22, thereby forming a multi-beam 20a to e. Here, an example is shown in which there are two or more rows of openings 22 in both the vertical and horizontal (x,y directions), but this is not the only example. For example, one direction (vertical or horizontal) may have multiple rows, while the other has only one row.

[0022] The blanking plate 204 has through holes (openings) for the passage of each beam of the multibeam at positions corresponding to each opening 22 of the aperture member 203 shown in Figure 2. Then, a set of electrodes for blanking deflection (blankers: blanking deflectors) is placed on either side of each through hole. A deflection voltage based on a control signal from the deflection control circuit 130 is applied to one of the two electrodes, and the other is grounded.

[0023] Each electron beam 20a to e passing through each through-hole is independently deflected by a blanker, and blanking control is performed. In this way, multiple blankers perform blanking deflection of the corresponding beam from among the multi-beams that have passed through the multiple openings 22 of the aperture member 203.

[0024] Figure 3 is a conceptual diagram illustrating an example of a drawing operation. As shown in Figure 3, the drawing area 30 of the substrate 101 is virtually divided into multiple stripe-shaped areas 32 with a predetermined width in the y-direction, for example.

[0025] First, the XY stage 105 is moved to adjust the position of the irradiation area 34 that can be irradiated with a single multi-beam 20 irradiation to the left edge of the first stripe area 32, or even further to the left, and then drawing begins. When drawing the first stripe area 32, the drawing progresses relatively in the x direction by moving the XY stage 105, for example, in the -x direction. The XY stage 105 is moved, for example, continuously at a predetermined speed.

[0026] After the first stripe area 32 has been drawn, the stage position is moved in the -y direction to adjust the illumination area 34 so that it is positioned relatively in the y direction at the right edge of the second stripe area 32, or even further to the right. Then, the XY stage 105 is moved, for example, in the x direction, to perform drawing in the same manner in the -x direction.

[0027] Drawing time can be shortened by alternating directions while drawing, such as drawing in the x-direction in the third stripe region 32 and in the -x-direction in the fourth stripe region 32. However, drawing is not limited to alternating directions; drawing may also be done in the same direction when drawing each stripe region 32. In a single shot, multiple shot patterns, up to the same number as the openings 22, are formed at once by the multi-beams formed by passing through each opening 22 of the aperture member 203.

[0028] Figure 4 shows an example of a multi-beam irradiation area and a pixel to be drawn. In Figure 4, the stripe area 32 is divided into multiple mesh areas 40, for example, by the beam size of the multi-beam. Each mesh area 40 becomes a drawing pixel area (drawing position). In the example in Figure 4, the drawing area of ​​the substrate 101 is shown as being divided into multiple stripe areas 32 with a width size smaller than the size (shot size) of the irradiation area 34 that can be irradiated with one multi-beam 20a to e in the y direction. Note that the width of the stripe area 32 is not limited to this, and may be, for example, n times the size of the irradiation area 34 (where n is an integer of 1 or more).

[0029] Within the irradiation area 34, multiple pixels 24 (beam drawing positions) that can be irradiated with a single multi-beam 20a to e are shown. In other words, the pitch between adjacent pixels 24 becomes the pitch between each beam of the multi-beam. In the example in Figure 4, one sub-pitch area 26 is formed by a square area surrounded by four adjacent pixels 24 and containing one of the four pixels 24. Figure 4 shows the case where each sub-pitch area 26 consists of 4x4 pixels.

[0030] Figure 4 shows that the beam size is defined as the size of the drawing pixel area. The smaller the size of the drawing pixel area, the more accurately the pattern shape is reflected, resulting in improved resolution and drawing accuracy.

[0031] Next, the operation of the drawing unit 150 will be described. The electron beam 200 emitted from the electron gun 201 (emitting unit) illuminates the entire aperture member 203 almost vertically by the illumination lens 202. As the electron beam 200 passes through each of the multiple openings 22 of the aperture member 203, multiple electron beams (multibeams) 20a to e, for example, rectangular in shape, are formed. The multibeams 20a to e pass through their respective corresponding blankers in the blanking plate 204. Each blanker individually deflects the electron beam 20 passing through it so that the beam is ON only for the calculated drawing time (irradiation time), and OFF otherwise (performs blanking deflection).

[0032] The multi-beams 20a to e that have passed through the blanking plate 204 are reduced by the reduction lens 205 and proceed toward the central opening formed in the limiting aperture member 206. The electron beams deflected by the blanking plate 204 to be beam-off are moved away from the central opening of the limiting aperture member 206 (blanking aperture member) and are shielded by the limiting aperture member 206. On the other hand, the electron beams that were not deflected by the blanking plate 204 (blinded to be beam-on) pass through the central opening of the limiting aperture member 206.

[0033] 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 the beam for one shot. The multi-beam that has passed through the limiting aperture member 206 is focused by the objective lens 207 to form a pattern image with the desired reduction ratio, and each beam (the entire multi-beam 20) is deflected in the same direction by the deflector 208 and irradiated onto the respective drawing positions (irradiation positions) on the substrate 101.

[0034] When the XY stage 105 is moving continuously, the beam drawing position (irradiation position) is tracked and controlled by the deflector 208 so that it follows the movement of the XY stage 105. A laser is shone from the stage position detector 139 toward the mirror 210 on the XY stage 105, and the position of the XY stage 105 is measured using the reflected light. Ideally, the multi-beams irradiated at one time will be aligned at a pitch obtained by multiplying the arrangement pitch of the multiple openings of the aperture member 203 by the desired reduction ratio described above.

[0035] The drawing device 100, during each tracking operation, irradiates a multi-beam, which becomes a shot beam, while sequentially shifting the drawing position, following the movement of the XY stage 105.

[0036] Figure 5 is a flowchart illustrating the drawing method according to the embodiment.

[0037] The rasterization unit 50 reads drawing data from the storage device 140 and calculates the pattern coverage rate (hereinafter referred to as coverage rate) within each first pixel area (step S1). The first pixel area is a virtual division of the drawing area (for example, the stripe area 32) into a mesh shape with a first size M1. The first size M1 is, for example, the size of one beam (individual beam) of a multi-beam system. The coverage rate of the first pixel area is stored in the memory 112.

[0038] Next, the rasterization unit 50 virtually divides each first pixel region into multiple second pixel regions in a mesh-like manner using a second size M2 smaller than the first size M1. The second pixel regions correspond to the drawing pixel regions. Hereinafter, the first pixel region, second pixel region, and drawing pixel region will be referred to as the first pixel, second pixel, and drawing pixel, respectively. For each second pixel, the rasterization unit 50 checks whether the center of the second pixel is included in the pattern, and determines that the second pixel whose center is included in the pattern is a second pixel located inside the pattern (step S2). The center of a second pixel being included in the pattern means that the center of the second pixel is located on the pattern. The group of second pixels located inside the pattern approximates the pattern shape.

[0039] The second pixel whose center is not included in the pattern is determined to be the second pixel located outside the pattern. For each second pixel, the inside / outside determination information, indicating whether it is located inside or outside the pattern, is stored in memory 112.

[0040] For example, in step S1, the coverage rate for each first pixel is calculated as shown in Figure 6(a). The coverage rate A of the first pixel is stored in memory 112 with, for example, 16-bit precision.

[0041] As shown in Figure 6(b), in step S2, the first pixel of the first size M1 is virtually divided into the second pixel of the second size M2. In this example, the second size M2 is set to 1 / 4 the length of one side of the first size M1 (M1 / M2=4), and the first pixel is virtually divided into 16 second pixels.

[0042] Next, we check whether the center of the second pixel is included in the pattern. In the example shown in Figure 6(b), the centers of the four second pixels in the bottom row of the figure, and the centers of the three second pixels in the second row from the bottom, from the first to the third from the right, are included in the pattern, so these seven second pixels are determined to be located inside the pattern. The one second pixel in the second row from the bottom, the first from the left, the four second pixels in the first row from the top, and the four second pixels in the second row from the top have centers that are not included in the pattern, so these nine second pixels are determined to be located outside the pattern.

[0043] For each second pixel, a 1-bit inside / outside determination information is stored in memory 112, where "1" is set if it is located inside the pattern and "0" is set if it is located outside. For example, as shown in Figure 6(c), 16 bits of inside / outside determination information are stored in memory 112 for 16 second pixels obtained by virtually dividing the first pixel.

[0044] Next, the dose map creation unit 52 virtually divides the drawing area (e.g., the stripe area 32) into a mesh of a predetermined size into multiple adjacent mesh areas (mesh areas for calculating proximity effect correction). The size of the adjacent mesh area is preferably set to about 1 / 10 of the area affected by the proximity effect, for example, about 1 μm. The dose map creation unit 52 reads the drawing data from the storage device 140 and calculates the coverage rate ρ of the pattern placed within each adjacent mesh area.

[0045] Next, the dose map creation unit 52 calculates a proximity effect correction irradiation coefficient Dp(x) for each adjacent mesh region to correct for the proximity effect. The proximity effect correction irradiation coefficient Dp(x) can be defined by a threshold model for proximity effect correction similar to conventional methods, using the backscattering coefficient η, the irradiation dose threshold Dth of the threshold model, the coverage ρ, and the distribution function g(x).

[0046] Next, the dose map creation unit 52 calculates the incident irradiation amount D (dose amount) to irradiate each drawing pixel (second pixel). The incident irradiation amount D can be calculated, for example, by multiplying a preset reference irradiation amount Dbase by a proximity effect correction irradiation coefficient Dp and the coverage rate ρ' of the drawing pixel.

[0047] The reference dose Dbase can be defined, for example, as Dth / (1 / 2+η).

[0048] In calculating the coverage rate ρ' of the drawing pixels, the dose map creation unit 52 reads the coverage rate A of the first pixel, which includes the drawing pixels, and the inside / outside determination information from the memory 112. The dose map creation unit 52 reads the coverage rate A of the first pixel and the number N of drawing pixels in the first pixel for which the inside / outside determination information is "1". IN Using the size M1 of the first pixel and the size M2 of the drawing pixel, the coverage rate ρ´ of the drawing pixel with an inside / outside determination information of "1" is calculated from the following equation (1). (M1 / M2) 2 This represents the number of drawing pixels within the first pixel.

[0049] ρ'=(A / N) IN )×(M1 / M2) 2 ...(1)

[0050] The dose map creation unit 52 sets the coverage ρ' of the drawing pixel (second pixel) for which the inside / outside determination information is "0" to 0.

[0051] In the example shown in Figures 6(a) to (c), if the coverage A of the first pixel is set to 0.4, the coverage ρ' of the 16 drawing pixels within the first pixel will be as shown in Figure 7.

[0052] In this way, the dose map creation unit 52 calculates the incident irradiation amount D(x) for each drawing pixel, corrected for proximity effects, based on the layout of multiple geometric patterns defined in the drawing data.

[0053] Then, the dose map creation unit 52 creates a dose map that defines the incident irradiation amount D for each drawing pixel on a stripe-by-strand basis (step S3). The created dose map is stored, for example, in the storage device 142.

[0054] The irradiation time calculation unit 54 calculates the irradiation time t corresponding to the irradiation dose D for each drawing pixel by referring to the latest dose map (step S4). The irradiation time t is calculated by dividing the irradiation dose D by the current density. The irradiation time t for each drawing pixel is calculated as a value within the maximum irradiation time that can be irradiated in one shot of the multi-beam 20. The irradiation time data is stored in the storage device 142.

[0055] In the drawing process (step S5), the drawing control unit 60 rearranges the irradiation time data in shot order according to the drawing sequence. Then, it transfers the irradiation time data in shot order to the deflection control circuit 130. The deflection control circuit 130 outputs blanking control signals to the blanking plate 204 in shot order and also outputs deflection control signals to the deflector 208 in shot order. The drawing unit 150 draws a pattern on the substrate 101 using a multi-beam irradiation amount calculated for each drawing pixel.

[0056] In the rasterization process, the example shown in Figure 9(b) required 32 bytes of memory to store the calculation results of the coverage percentage of 16 pixels. However, in this embodiment, it is sufficient to store the coverage percentage of the first pixel (16 bits) and the inside / outside determination information (16 bits) of 16 second pixels, reducing memory usage to 4 bytes. Furthermore, the number of coverage percentage calculations is reduced, thereby lowering the computational load.

[0057] In the above embodiment, the center of the second pixel obtained by virtually dividing the first pixel is checked to see if it is inside or outside the pattern, and the second pixel whose center is inside the pattern is selected as the second pixel that approximates the pattern shape. However, the second pixel that approximates the pattern shape may also be selected by considering the centroid position of the pattern in the first pixel.

[0058] For example, as shown in Figure 8(a), the rasterization unit 50 calculates the coverage A of the first pixel and also determines the centroid CG of the pattern at the first pixel.

[0059] Next, as shown in Figure 8(b), the rasterization unit 50 selects the edge closest to the centroid CG from among the four edges H1 to H4 of the first pixel of the rectangle. In the example shown in Figure 8(b), the lower edge H1 in the figure is closest to the centroid CG.

[0060] Next, the rasterization unit 50 selects a plurality of second pixels (second pixel groups) that approximate the pattern shape within the first pixel. For example, starting from the edge H1 closest to the centroid CG of the pattern, k rows of second pixel groups parallel to edge H1 are selected, moving toward the edge H3 opposite to edge H1. k is calculated from the following equation (2) using the coverage A of the first pixel, the size M1 of the first pixel, and the size M2 of the second pixel.

[0061] k = ceil(A × (M1 / M2)) ... (2)

[0062] For example, if we set A=0.4 and virtually divide the first pixel into 16 second pixels (M1 / M2=4), then k=2, and as shown in Figure 8(c), we select two columns from edge H1 toward edge H3, i.e., the lower two columns of the second pixel group.

[0063] As shown in Figure 8(d), for each second pixel, a 1-bit selection information is stored in memory 112, along with the coverage A of the first pixel, where "1" is set if selected and "0" is set if not selected.

[0064] The dose map creation unit 52 determines the coverage A of the first pixel and the number N of drawing pixels (second pixels) with selection information of "1". SEL Using the size M1 of the first pixel and the size M2 of the drawing pixel, the coverage ρ' of the drawing pixels with selection information of "1" is calculated from the following equation (3).

[0065] ρ'=(A / N) SEL )×(M1 / M2) 2 ...(3)

[0066] The dose map creation unit 52 sets the coverage ρ' of the drawing pixel (second pixel) for which the selection information is "0" to 0.

[0067] Thus, by selecting a second group of pixels that approximate the pattern shape based on the centroid position of the pattern in the first pixel, and assigning a coverage rate to these selected second pixels, the computational amount and memory usage for the pixel coverage rate can be reduced, similar to the embodiment described above.

[0068] In the above embodiment, a multi-beam lithography apparatus was described as an example of a charged particle beam apparatus to which the coverage rate calculation device is applied, but it is also applicable to a single-beam lithography apparatus. Furthermore, the coverage rate calculation device is applicable not only to lithography apparatuses but also to inspection apparatuses. The inspection apparatus compares the coverage rate of the second pixel calculated from the lithography data using the coverage rate calculation method according to the above embodiment with the coverage rate of the second pixel based on the measurement results of the pattern actually drawn on the substrate using this lithography data, and checks whether they match or not.

[0069] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Moreover, components from different embodiments may be appropriately combined. [Explanation of Symbols]

[0070] 50 Rasterized section 52 Dose Map Creation Department 54 Irradiation time calculation unit 60 Drawing Control Unit 100 Drawing device 110 Control Computer

Claims

1. A method for calculating a pattern coverage rate for each pixel region obtained by dividing a pattern drawing region into a predetermined size by irradiating a charged particle beam, the method comprising the steps of: virtually dividing the drawing area by a first size to generate a plurality of first pixel areas; Calculating a coverage of the pattern in the first pixel region; virtually dividing the first pixel region by a second size smaller than the first size to generate a plurality of second pixel regions corresponding to the pixel region; selecting the second pixel area that approximates a pattern shape in the first pixel area; A coverage calculation method for calculating a coverage of the selected second pixel region based on a coverage of a pattern of the first pixel region, the number of the second pixel regions in the first pixel region, and the number of the selected second pixel regions.

2. 2. The method according to claim 1, further comprising the step of selecting, from among the plurality of second pixel regions, a second pixel region whose center is inside the pattern as the second pixel region that approximates the pattern shape.

3. Detecting a centroid of a pattern within the first pixel region; selecting a first side of the four sides of the rectangular first pixel region that is closest to the center of gravity; selecting k columns (k is an integer equal to or greater than 1) of second pixel regions parallel to the first side from the first side toward a second side opposite the first side as second pixel regions approximating the pattern shape; The method of claim 1 , wherein k is a value based on the coverage of the first pixel region, the first size, and the second size.

4. 4. A method for calculating a dose of irradiation for each of the pixel regions, the dose being calculated by using the coverage of the second pixel region calculated by the coverage calculation method according to claim 1 ; A charged particle beam writing method for writing a pattern on a substrate by controlling a charged particle beam based on the calculated dose.

5. A coverage calculation device that calculates a coverage of a pattern for each pixel region obtained by dividing a drawing region in which a pattern is drawn by irradiating a charged particle beam, the pixel region being divided by a predetermined size, the device comprising: a rasterization unit that virtually divides the drawing area by a first size to generate a plurality of first pixel areas, calculates a pattern coverage rate of the first pixel areas, virtually divides the first pixel area by a second size smaller than the first size to generate a plurality of second pixel areas corresponding to the pixel areas, and selects the second pixels that approximate a pattern shape in the first pixel area; A coverage calculation device that calculates the coverage of the selected second pixel region based on the coverage of the pattern of the first pixel region, the number of the second pixel regions in the first pixel region, and the number of the selected second pixel regions.

6. The coverage calculation device according to claim 5 , wherein the rasterization unit selects, from among the plurality of second pixel regions, a second pixel region whose center is inside the pattern as a second pixel region that approximates the pattern shape.

7. A dose map creation unit that calculates an irradiation amount for each pixel region using the coverage of the second pixel region calculated by the coverage calculation device according to claim 5, and creates a dose map that defines the irradiation amount for each pixel region; and an irradiation time calculation unit that calculates an irradiation time for each pixel region based on the dose map; a writing control unit that controls an irradiation amount of the charged particle beam based on the calculated irradiation time; A charged particle beam writing apparatus comprising:

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