Multi-charged particle beam drawing method, multi-charged particle beam drawing apparatus, and program

Abstract

PURPOSE: To provide a drawing method capable of reducing a quantization error while suppressing a throughput regardless of the presence or absence of a beam having a specific current density when multiple drawing is performed on a sample using a multiple beam.CONSTITUTION: A multi-charged particle beam drawing method of an embodiment of the present invention includes the steps of: setting one of a plurality of weighting factors in each beam of the multi-charged particle beam according to an arrangement position of the multi-charged particle beam; correcting an irradiation amount of a plurality of beams obtained in advance by using two or more kinds of weighting coefficients of the plurality of beams for drawing the position for each of the plurality of beams for irradiating the position in a case where the same position of a sample to be drawn is multi-drawn by the plurality of beams having different arrangement positions in which two or more kinds of weighting coefficients are set among the multi-charged particle beams; and drawing a pattern on the sample using the multi-charged particle beam so that the position is multi-drawn by the plurality of beams with the irradiation amount of each beam of the plurality of beams corrected for each position of the sample.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] One aspect of the present invention relates to a multi-charged particle beam writing method, a multi-charged particle beam writing apparatus, and a program, and relates to, for example, a technique for correcting irradiation time in multiple writing using multiple beams with a current density distribution. [Background technology]

[0002] Lithography technology, which is responsible for the advancement of miniaturization of semiconductor devices, is the only extremely important process in semiconductor manufacturing that generates patterns. In recent years, with the increasing integration density of LSIs, the circuit line width required for semiconductor devices has been getting finer year by year. Here, electron beam (EB) lithography technology has inherently excellent resolution, and lithography is carried out using an electron beam to draw on wafers, etc.

[0003] For example, there is a lithography system that uses multiple beams. Compared to lithography using a single electron beam, using multiple beams allows for the irradiation of many beams at once, thereby significantly improving throughput. In such a lithography system, for example, an electron beam emitted from an electron gun is passed through a mask with multiple holes to form multiple beams, each of which is blanked, and the unblocked beams are reduced in size by an optical system, deflected by a deflector, and irradiated onto the desired position on the sample.

[0004] However, the current density of each beam is not uniform in the multiple beams used in multi-beam lithography, resulting in a current density distribution. Therefore, even if lithography is performed without correction, the required dose cannot be obtained, resulting in poor lithography accuracy. To address this issue, a conventional method involves correcting the designed dose when irradiating a sample with each beam by using a correction coefficient calculated by dividing the current density of the beam by the ideal current density. In such a case, correction is performed shot by shot, so if a beam has an unusual current density, it may require an irradiation time that is different from that of other shots. In multi-beam lithography, the shot cycle is set to match the overall maximum irradiation time. Therefore, if a shot has an unusual irradiation time, the overall lithography time increases, resulting in poor throughput.

[0005] Therefore, when performing multiple writing on a sample, a method has been devised in which the current density of the beam used in each pass is averaged, and the ratio of the ideal current density divided by the averaged current density is used as a correction coefficient to correct the designed dose amount for each pass (see Patent Document 1). This makes it possible to average out the anomalous current density, thereby suppressing the anomalous irradiation time.

[0006] In such cases, the same correction coefficient is used for multiple beams irradiating the same position, which can result in the same irradiation time for each pass, resulting in a similar accumulation of quantization errors and resulting in errors in the actual dose. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2023-056384 Summary of the Invention [Problem to be solved by the invention]

[0008] One aspect of the present invention provides a writing method and apparatus that can reduce quantization errors while suppressing a decrease in throughput when multiple beams are used to write to a sample, regardless of whether or not a beam with a specific current density is present. [Means for solving the problem]

[0009] A multi-charged particle beam writing method according to one aspect of the present invention includes: setting one of a plurality of weight coefficients for each beam of the multi-charged particle beam according to an arrangement position of the multi-charged particle beam; When the same position of a sample to be written is written by a plurality of beams of the multi-charged particle beams having different arrangement positions and having two or more weighting factors set thereto, a step of correcting, for each of the plurality of beams irradiating the position, the irradiation doses of the plurality of beams determined in advance for the plurality of beams using the two or more weighting factors of the plurality of beams writing the position; writing a pattern on the sample using multiple charged particle beams such that, for each location on the sample, the multiple beams write the location multiple times with the corrected dose of each of the multiple beams; The present invention is characterized by the following.

[0010] Furthermore, the irradiation amount of each beam is obtained by multiplying the current amount of each beam by the irradiation time, and it is preferable to correct the irradiation time of each beam for each of the multiple beams using two or more weighting coefficients and the current amount of each of the multiple beams, and irradiate each beam for the corrected irradiation time.

[0011] Furthermore, it is preferable that the weighting coefficients set for each beam are set independently, regardless of the amount of current of the beam.

[0012] It is also preferable to set a weighting coefficient for each beam so that the total value of the irradiation amount of the plurality of beams irradiated at each position on the sample is equal to the design value.

[0013] It is also preferable that different weighting coefficients are set for a plurality of beams irradiating the same position on the sample.

[0014] Furthermore, it is preferable that the product of a first weighting factor and a second weighting factor that are independent of each other be used as the weighting factor set for each beam.

[0015] A multi-charged particle beam writing apparatus according to one aspect of the present invention comprises: a setting unit that sets one of a plurality of weighting factors for each beam of the multi-charged particle beam in accordance with an arrangement position of the multi-charged particle beam; a correction unit that corrects, for each of the multiple beams irradiating the position, a previously determined irradiation amount of each of the multiple beams using two or more weighting factors of the multiple beams that write to the position, when the same position of a sample to be written is multiple-written with a plurality of beams that have different arrangement positions and for which two or more weighting factors are set among the multiple charged particle beams; a writing mechanism for writing a pattern on the sample using multiple charged particle beams such that multiple beams write multiple patterns on each position of the sample with the corrected irradiation dose of each of the multiple beams; The present invention is characterized by the following.

[0016] A program to be executed by a computer according to one aspect of the present invention comprises: a function of setting one of a plurality of weighting factors for each beam of the multi-charged particle beam according to the arrangement position of the multi-charged particle beam; a function of storing weighting coefficients set for each beam in a storage device; a function of reading out weighting coefficients from the storage device, and when performing multiple drawing on the same position of a sample to be drawn using a plurality of beams of the multi-charged particle beams with different arrangement positions and having two or more weighting coefficients set thereon, correcting the irradiation amount of each of the plurality of beams that irradiates the position using the two or more weighting coefficients of the plurality of beams that draw the position, and outputting the corrected amount; to be executed by the computer. [Effects of the Invention]

[0017] According to one aspect of the present invention, when multiple beams are used to perform multiple writing on a sample, it is possible to reduce quantization errors while suppressing throughput, regardless of whether or not a beam with a specific current density exists. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a conceptual diagram showing a configuration of a drawing device according to a first embodiment. [Figure 2] FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate according to the first embodiment. [Figure 3] 2 is a cross-sectional view showing the configuration of a blanking aperture array mechanism in the first embodiment. FIG. [Figure 4] FIG. 2 is a conceptual diagram for explaining an example of a drawing operation in the first embodiment. [Figure 5] 3 is a diagram showing an example of a multi-beam irradiation area and a pixel to be written in the first embodiment. FIG. [Figure 6] FIG. 2 is a diagram for explaining an example of a multi-beam writing operation according to the first embodiment. [Figure 7] FIG. 3 is a diagram showing an example of a current density distribution in the first embodiment. [Figure 8] FIG. 10 is a diagram for explaining a method for correcting deviation in irradiation time due to difference in current density in Comparative Example 1 of Embodiment 1. [Figure 9] FIG. 10 is a diagram for explaining a method for correcting deviation in irradiation time due to difference in current density in Comparative Example 2 of Embodiment 1. [Figure 10] FIG. 10 is a diagram for explaining an example of multiple drawing with a multiplicity of 2 in the first embodiment. [Figure 11] 1 is an example of a flowchart illustrating main steps of a writing method according to the first embodiment. [Figure 12] FIG. 10 is a diagram for explaining an example of multiple drawing with a multiplicity of 4 in the first embodiment. [Figure 13] FIG. 3 is a diagram showing an example of a group region of a weighting factor according to the first embodiment. [Figure 14]FIG. 2 is a diagram showing an example of a block configuration within a beam array according to the first embodiment. [Figure 15] FIG. 10 is a diagram showing another example of group regions of weighting factors according to the first embodiment. [Figure 16] FIG. 10 is a diagram for explaining a method of multiple drawing in a modification of the first embodiment. [Figure 17] 10A and 10B are diagrams illustrating an example of a correction coefficient distribution and a quantization error in a first comparative example of the first embodiment. [Figure 18] 10 is a diagram showing an example of a correction coefficient distribution and a quantization error in a second comparative example of the first embodiment. FIG. [Figure 19] 5A and 5B are diagrams illustrating an example of a correction coefficient distribution and a quantization error according to the first embodiment. [Figure 20] FIG. 10 is a diagram illustrating a first modification of weighting coefficients according to the first embodiment. [Figure 21] FIG. 10 is a diagram illustrating a second modification of the weighting coefficients in the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] In the following embodiments, a configuration using an electron beam will be described as an example of a charged particle beam, but the charged particle beam is not limited to an electron beam and may be a beam using charged particles such as an ion beam.

[0020] Embodiment 1 FIG. 1 is a conceptual diagram showing the configuration of a lithography apparatus according to the first embodiment. In FIG. 1, the lithography apparatus 100 includes a lithography mechanism 150 and a control circuit 160. The lithography apparatus 100 is an example of a multi-charged particle beam lithography apparatus and also an example of a multi-charged particle beam exposure apparatus. The lithography mechanism 150 includes an electron lens barrel 102 (electron beam column) and a lithography chamber 103. Inside the electron lens barrel 102, an electron gun 201, an illumination lens 202, a shaping aperture array substrate 203, a blanking aperture array mechanism 204, a reduction lens 205, a limiting aperture substrate 206, an objective lens 207, a main deflector 208, and a sub-deflector 209 are arranged.

[0021] An XY stage 105 is disposed within the patterning chamber 103. A sample 101, such as a mask, which will be the patterned substrate during patterning (exposure) is disposed on the XY stage 105. The sample 101 includes an exposure mask used in manufacturing a semiconductor device, or a semiconductor substrate (silicon wafer) on which a semiconductor device is manufactured. The sample 101 also includes a mask blank coated with resist and on which nothing has yet been patterned. A mirror 210 for measuring the position of the XY stage 105 is also disposed on the XY stage 105.

[0022] In addition, a Faraday cup 106 is placed on the XY stage 105 .

[0023] The control system circuit 160 includes a control computer 110, a memory 112, a deflection control circuit 130, digital-to-analog conversion (DAC) amplifier units 132 and 134, a lens control circuit 136, a stage control mechanism 138, a stage position measurement device 139, and storage devices 140 and 142 such as magnetic disk drives. The control computer 110, the memory 112, the deflection control circuit 130, the lens control circuit 136, the stage control mechanism 138, the stage position measurement device 139, and storage devices 140 and 142 are connected to one another via a bus (not shown). The deflection control circuit 130 is connected to the DAC amplifier units 132 and 134 and a blanking aperture array mechanism 204. The sub-deflector 209 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 130 via the DAC amplifier 132. The main deflector 208 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 130 via the DAC amplifier 134. The lens group including the illumination lens 202 , the reduction lens 205 , and the objective lens 207 is controlled by a lens control circuit 136 .

[0024] The position of the XY stage 105 is controlled by driving motors (not shown) for each axis controlled by a stage control mechanism 138. A stage position measuring device 139 receives light reflected from a mirror 210 and measures the position of the XY stage 105 based on the principle of laser interferometry.

[0025] The control computer 110 includes a rice processing unit 50, a shot data generation unit 52, a current density distribution creation unit 56, a weighting coefficient setting unit 58, a correction coefficient calculation unit 60, a correction unit 62, a writing control unit 72, and a transfer processing unit 74. Each of the "~" units, such as the rice-rice processing unit 50, the shot data generation unit 52, the current density distribution creation unit 56, the weighting coefficient setting unit 58, the correction coefficient calculation unit 60, the correction unit 62, the writing control unit 72, and the transfer processing unit 74, has a processing circuit. Such a processing circuit may include, for example, an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each of the "~" units may use a common processing circuit (the same processing circuit) or different processing circuits (separate processing circuits). Information input to and output from the rice-rice processing unit 50, the shot data generation unit 52, the current density distribution creation unit 56, the weighting coefficient setting unit 58, the correction coefficient calculation unit 60, the correction unit 62, the writing control unit 72, and the transfer processing unit 74, as well as information being calculated, is stored in memory 112 each time.

[0026] The drawing operation of the drawing apparatus 100 is controlled by a drawing control unit 72. In other words, the drawing control unit 72 (an example of a control circuit) controls the drawing mechanism 150. In addition, a transfer process of the irradiation time data of each shot to the deflection control circuit 130 is controlled by a transfer processing unit 74.

[0027] Furthermore, drawing data (chip data) is input from outside the drawing device 100 and stored in the storage device 140. The chip data defines information on a plurality of figure patterns that constitute the chip pattern. Specifically, for each figure pattern, for example, the coordinates of each vertex are defined in the order in which the figure is formed. Alternatively, for each figure pattern, for example, a figure code, coordinates, size, etc. are defined.

[0028] 1 shows the configuration necessary for explaining the first embodiment. The drawing device 100 may also include other configurations that are normally required.

[0029] FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate in the first embodiment. In FIG. 2, holes (openings) 22 are formed in a matrix of p horizontal (x direction) columns by q vertical (y direction) columns (p, q≧2) at a predetermined arrangement pitch in shaping aperture array substrate 203. The example in FIG. 2 shows, for example, a case where 512×512 horizontal and vertical (x, y direction) columns of holes 22 are formed. The number of holes 22 is not limited to this. For example, 32×32 columns of holes 22 may be formed. Each hole 22 is formed as a rectangle of the same size and shape. Alternatively, each hole 22 may be a circle of the same diameter. A portion of electron beam 200 passes through each of these multiple holes 22, thereby forming multiple beams 20. In other words, shaping aperture array substrate 203 forms multiple beams 20.

[0030] FIG. 3 is a cross-sectional view showing the configuration of the blanking aperture array mechanism according to the first embodiment. As shown in FIG. 3, the blanking aperture array mechanism 204 includes a blanking aperture array substrate 31, which is made of a semiconductor substrate such as silicon, and is disposed on a support base 33. In a central membrane region 330 of the blanking aperture array substrate 31, passage holes 25 (openings) for passing through each beam of the multi-beams 20 are formed at positions corresponding to the holes 22 of the shaping aperture array substrate 203 shown in FIG. 2. Pairs of control electrodes 24 and counter electrodes 26 (blankers: blanking deflectors) are disposed at positions facing each other across the corresponding passage holes 25 among the plurality of passage holes 25. Furthermore, a control circuit 41 (logic circuit) is disposed inside the blanking aperture array substrate 31 near each passage hole 25, which applies a deflection voltage to the control electrode 24 for each passage hole 25. The counter electrodes 26 for each beam are connected to ground.

[0031] An amplifier (an example of a switching circuit), not shown, is disposed within the control circuit 41. As an example of the amplifier, a CMOS (Complementary MOS) inverter circuit serving as a switching circuit is disposed. To the input (IN) of the CMOS inverter circuit, either an L (low) potential (e.g., ground potential) that is lower than the threshold voltage or an H (high) potential (e.g., 1.5 V) that is equal to or higher than the threshold voltage is applied as a control signal. In the first embodiment, when an L potential is applied to the input (IN) of the CMOS inverter circuit, the output (OUT) of the CMOS inverter circuit applied to the control circuit 41 becomes a positive potential (Vdd), and the corresponding beam is deflected by an electric field due to the potential difference with the ground potential of the counter electrode 26, and is controlled so that the beam is turned OFF by being shielded by the limiting aperture substrate 206. On the other hand, when an H potential is applied to the input (IN) of the CMOS inverter circuit (active state), the output (OUT) of the CMOS inverter circuit becomes the ground potential, and there is no potential difference with the ground potential of the opposing electrode 26, so the corresponding beam is not deflected, and the beam is controlled to be ON by passing through the limiting aperture substrate 206. Blanking control is performed by this deflection.

[0032] Next, a specific example of the operation of the drawing mechanism 150 will be described. An electron beam 200 emitted from an electron gun 201 (emission source) is illuminated almost perpendicularly by an illumination lens 202 onto the entire shaping aperture array substrate 203. A plurality of rectangular holes 22 (openings) are formed in the shaping aperture array substrate 203, and the electron beam 200 illuminates an area including all of the holes 22. Portions of the electron beam 200 irradiated onto the positions of the holes 22 pass through the holes 22 of the shaping aperture array substrate 203, thereby forming, for example, a rectangular multibeam (multiple electron beams) 20 (beam array). The multibeam 20 passes through corresponding blankers of a blanking aperture array mechanism 204. Each blanker performs blanking control on the beams passing through it so that the beams are turned on for a set drawing time (irradiation time).

[0033] The multi-beams 20 that pass through the blanking aperture array mechanism 204 are reduced by the reduction lens 205 and travel toward a central hole formed in the limiting aperture substrate 206. Here, the electron beams deflected by the blankers of the blanking aperture array mechanism 204 are shifted from the central hole of the limiting aperture substrate 206 and are blocked by the limiting aperture substrate 206. On the other hand, the electron beams that are not deflected by the blankers of the blanking aperture array mechanism 204 pass through the central hole of the limiting aperture substrate 206 as shown in FIG. 1. In this way, the limiting aperture substrate 206 blocks each beam that is deflected by the blankers of the blanking aperture array mechanism 204 to be in a beam-off state. Then, each beam of one shot is formed by the beams that pass through the limiting aperture substrate 206 from when the beams are turned on until when they are turned off. The multibeams 20 that have passed through the limiting aperture substrate 206 are focused by the objective lens 207 to form a pattern image with the desired reduction ratio, and the entire multibeams 20 that have passed through the limiting aperture substrate 206 are deflected in the same direction by the main deflector 208 and the sub-deflector 209, and each beam is irradiated onto its respective irradiation position on the sample 101. Furthermore, for example, when the XY stage 105 is moving continuously, tracking control is performed by the main deflector 208 so that the beam irradiation position follows the movement of the XY stage 105. Ideally, the multibeams 20 that are irradiated at one time are arranged at a pitch obtained by multiplying the arrangement pitch of the plurality of holes 22 in the shaping aperture array substrate 203 by the desired reduction ratio described above.

[0034] Fig. 4 is a conceptual diagram for explaining an example of the writing operation in embodiment 1. As shown in Fig. 4, the writing region 30 (bold line) on the sample 101 is virtually divided, for example, in the y direction into a plurality of rectangular stripe regions 32 each having a predetermined width. The example in Fig. 4 shows a case in which the writing region 30 on the sample 101 is divided, for example, in the y direction, into a plurality of stripe regions 32 each having a width that is substantially the same as the size of the designed irradiation region 34 (writing field, beam array region) that can be irradiated by a single irradiation of the multibeam 20.

[0035] The example of FIG. 4 illustrates a case where multiple writing is performed with a multiplicity of 2. For the first writing process, a first stripe layer is set, which is composed of multiple stripe regions 32 obtained by dividing the writing region 30. For the second writing process, a second stripe layer is set, which is composed of multiple stripe regions 32 shifted in the y direction relative to the first stripe layer. The amount of shift in the x and y directions between passes when performing multiple writing is set depending on, for example, the multiplicity. For example, for a multiplicity of N, it is preferable to shift the positions between passes by 1 / N of the width of the stripe regions 32. The multiplicity is not limited to 2 and may be 3 or more. A pass of multiple writing refers to the movement of each stage when multiple writing is performed by repeatedly moving stripe regions 32 with the same number between stages. Furthermore, multiple drawing may be performed by drawing the same pixel multiple times within the same path, in other words, during one stage run.

[0036] In addition, although the example in Figure 4 shows a case where the positions are shifted in both the x and y directions, this is not limited to this. The positions may be shifted between passes of multiple drawing only in the x direction. Alternatively, the positions may be shifted between passes of multiple drawing only in the y direction. Next, an example of a drawing operation will be described.

[0037] First, the XY stage 105 is moved and adjusted so that the irradiation area 34 of the multibeam 20 is positioned at the left end of the first stripe region 32 of the first stripe layer, or at a position further to the left. Then, when writing the first stripe region 32, the XY stage 105 is moved, for example, in the -x direction, thereby relatively progressing writing in the x direction. The XY stage 105 is moved continuously at a constant speed, for example.

[0038] After writing of the first stripe region 32 of the first stripe layer is completed, the stage position is moved in the -y direction by, for example, 1 / N of the width of the stripe region 32. As a result, the written stripe region 32 is shifted in the y direction by, for example, 1 / N of the width of the stripe region 32. The example in Figure 4 shows a case where multiple writing is performed using two passes, so the shift is made in the y direction by, for example, 1 / 2 of the width of the stripe region 32.

[0039] Next, the irradiation area 34 of the multibeam 20 is adjusted to be located at the left end of the first stripe area 32 of the second stripe layer, or at a position further to the left. Then, by moving the XY stage 105, for example, in the -x direction, writing proceeds relatively in the x direction. In this way, writing is performed on the first stripe area 32 of the second stripe layer. After writing the first stripe area 32 of the second stripe layer is completed, writing is performed on the second stripe area 32 of the first stripe layer. In this way, corresponding stripe areas 32 of each stripe layer are written in order. By repeating the same process thereafter, writing is performed on all stripe areas 32 of each stripe layer.

[0040] 4 shows the case where each stripe region 32 is written in the same direction, but this is not limiting. For example, the stripe region 32 to be written next to the stripe region 32 written in the x direction may be written in the -x direction by moving the XY stage 105 in the x direction, for example. By writing while alternating directions in this way, the stage movement time can be shortened, and ultimately the writing time can be shortened. In one shot, multiple shot patterns, up to the same number as the holes 22, are formed at once by the multi-beams formed by passing through each hole 22 in the shaping aperture array substrate 203.

[0041] FIG. 5 shows an example of a multibeam irradiation area and a target pixel for drawing in the first embodiment. In FIG. 5, the stripe area 32 is divided into a plurality of mesh areas, for example, based on the beam size of the multibeam 20. Each mesh area corresponds to a target pixel 36 (beam irradiation unit area, irradiation position, position). The size of the target pixel 36 is not limited to the beam size and may be any size regardless of the beam size. For example, the size may be 1 / n (n is an integer greater than or equal to 1) of the beam size. The example of FIG. 5 shows a case where the target region for drawing on the sample 101 is divided, for example, in the y direction, into a plurality of stripe areas 32, each having a width substantially equal to the size of the irradiation region 34 (drawing field) that can be irradiated with one irradiation of the multibeam 20. The size of the rectangular irradiation region 34 in the x direction can be defined by the number of beams in the x direction multiplied by the beam pitch in the x direction. The size of the rectangular irradiation region 34 in the y direction can be defined by the number of beams in the y direction multiplied by the beam pitch in the y direction. In the example of Figure 5, for example, a 512 x 512 array of multi-beams is shown as an 8 x 8 array of multi-beams. A plurality of pixels 28 (beam drawing positions) that can be irradiated with one shot of the multi-beams 20 are shown within the irradiation area 34. The pitch between adjacent pixels 28 is the inter-beam pitch of each of the multi-beams. A rectangular area surrounded by the size of the inter-beam pitch in the x and y directions constitutes one sub-irradiation area 29 (pitch cell area). In the example of Figure 5, each sub-irradiation area 29 is shown as being composed of, for example, 4 x 4 pixels.

[0042] FIG. 6 is a diagram illustrating an example of a multi-beam writing operation in the first embodiment. The example of FIG. 6 illustrates a case where writing is performed in each sub-irradiation region 29 with four different beams. The example of FIG. 6 also illustrates a writing operation in which the XY stage 105 continuously moves at a speed of a distance L corresponding to eight beam pitches while writing one-quarter of each sub-irradiation region 29 (one corresponding to the number of beams used for irradiation). In the writing operation illustrated in the example of FIG. 6, for example, while the XY stage 105 moves the distance L corresponding to eight beam pitches, the sub-deflector 209 sequentially shifts the irradiation position (pixel 36) to write (expose) four different pixels in the same sub-irradiation region 29, thereby firing four shots of the multi-beam 20 in a shot cycle T. While writing (exposing) these four pixels, the main deflector 20 collectively deflects the entire multi-beam 20, causing the irradiation region 34 to follow the movement of the XY stage 105 so that the relative position of the irradiation region 34 to the sample 101 does not shift due to the movement of the XY stage 105. In other words, tracking control is performed. When one tracking cycle is completed, tracking is reset and the system returns to the previous tracking start position. Note that since the drawing of the first pixel row from the right in each sub-irradiation area 29 has been completed, after tracking reset, the sub-deflector 209 first deflects the beam in the next tracking cycle to align (shift) the drawing position of the beam so that the drawing of an undrawn pixel row in each sub-irradiation area 29, for example, the second pixel row from the right, is drawn. By repeating this operation during drawing of the stripe area 32, the position of the irradiation area 34 of the multi-beam 20 sequentially moves as shown in the irradiation areas 34a, 34b, 34c, ... 34o shown in the lower diagram of Figure 4, and drawing is performed.

[0043] For example, in the example of FIG. 6, when performing a drawing process using a 32×32 multi-beam 20, each pixel 36 is drawn once during one stage run. When performing the same operation using a 512×512 array of multi-beams 20, each sub-irradiation area 29 is configured with 16×16 pixels. Then, while the XY stage 105 moves a distance L equivalent to 32 beam pitches, the sub-deflector 209 sequentially shifts the irradiation position (pixel 36), and 16 shots of the multi-beam 20 are fired in a shot cycle T to draw (expose) 16 different pixels within the same sub-irradiation area 29. After a tracking reset, the irradiation position is aligned with the column adjacent to the column in each sub-irradiation area 29 where drawing has been completed. By repeating this operation, each pixel 36 is drawn once during one stage run (per pass).

[0044] FIG. 7 is a diagram showing an example of a current density distribution in the first embodiment. The current density of each beam of the multi-beams 20 constituting the beam array is not uniform. For example, as shown in FIG. 7, the current density decreases radially outward compared to the central beam group. In the example of FIG. 7, the current density of the central beam group is 100%, whereas the current density outside is 97%, the current density further outside is 95%, and the current density decreases even further outside. For this reason, even if the sample surface is irradiated with beams having the same irradiation time, the dose incident on the sample will differ.

[0045] FIG. 8 is a diagram illustrating a method for correcting deviations in irradiation time due to differences in current density in Comparative Example 1 of Embodiment 1. In Comparative Example 1, for beams with low current density, the error in current density is corrected using a correction coefficient so that the current density becomes the ideal one. Specifically, the irradiation time t(i,j) is corrected using the ratio (J0 / J(i,j)) of the current density J(i,j) of each beam to, for example, the ideal current density J0 of 100%, as the correction coefficient. (i,j) is an index indicating the arrangement position of each beam in the beam array. The dose (i,j) can be defined by the following equation (1):

[0046]

number

[0047] As shown in equation (1), the dose (i, j) is calculated by multiplying the product of the current density J(i, j) and the irradiation time by the correction coefficient (J0 / J(i, j)), and the product of the uncorrected irradiation time t(i, j) calculated using the ideal current density and the current density J(i, j) is multiplied by the correction coefficient (J0 / J(i, j)). Since the writing process is controlled by the irradiation time, the corrected irradiation time t'(i, j) obtained by multiplying the uncorrected irradiation time t(i, j) by the correction coefficient (J0 / J(i, j)) can be used. However, in Comparative Example 1, if a beam with an unusually low current density occurs in the beam array, the correction coefficient for that beam becomes unusually large. In multi-beam writing, the shot cycle is set to match the longest irradiation time. Therefore, if an unusual correction coefficient exists, the shot cycle for all shots becomes longer, which in turn lengthens the writing time. As a result, throughput deteriorates.

[0048] FIG. 9 is a diagram illustrating a method for correcting deviations in irradiation time due to differences in current density in Comparative Example 2 of Embodiment 1. As shown in FIG. 9, multiple writing is performed while shifting the position of the beam array. The example in FIG. 9 shows a case where multiple writing is performed while shifting the beam array by half in the x direction. In this case, each pixel on the sample surface is irradiated by multiple beams at different array positions. In Comparative Example 2, the current densities J(i, j) of multiple beams at different array positions used for the same pixel in each pass of multiple writing are averaged. The dose (i, j) in Comparative Example 2 can be defined by the following equation (2):

[0049]

number

[0050] As shown in equation (2), the designed dose of each pass is corrected using the ratio of the ideal current density J0 divided by the averaged current density (ΣJ(i,j) / n) as a correction coefficient. n indicates the number of current densities to be averaged. In other words, n indicates the multiplicity N. This allows the anomalous current densities to be averaged, thereby suppressing the anomalous irradiation time.

[0051] FIG. 10 is a diagram illustrating an example of multiple writing with a multiplicity of 2 in the first embodiment. The example in FIG. 10 shows a case where the multiplicity N=2. Writing is performed in the second pass by shifting the beams in the x and y directions from the first pass by half the width of the stripe region 32. Each stripe region 32 is divided into multiple rectangular regions 35 in the x direction, each of which has the same size as the irradiation region 34 of the beam array. Writing is repeated under the same beam conditions in each of the rectangular regions 35. Therefore, when multiple writing is performed by shifting the beams in the x and y directions by half the width of the stripe region 32, two beam groups with the same symbol in four blocks obtained by dividing the irradiation region of the beam array into 2×2 blocks write the same region of the stripe region 32 in different passes of multiple writing. In the two blocks A, the lower left and upper right, the region written by the beam group in the upper right block A in the first pass is written by the beam group in the lower left block A in the second pass. In other words, the pixels irradiated by each beam in the upper right block A are irradiated by the beams in the lower left block A at the corresponding array positions.

[0052] In Comparative Example 2, the correction coefficients of the two beams irradiating the same pixel are the same due to the averaging shown in Equation (2). The designed irradiation time for each pass in multiple writing is generally set to the same value. Therefore, the corrected irradiation time is likely to be the same as well. As a result, the dose error controlled by the irradiation time also acts in the same direction due to the quantization error that occurs when quantifying the irradiation time in a predetermined quantization unit. When the reference irradiation time is normalized to 1, the irradiation time for each pass of a certain pixel is, for example, 1.5. Suppose a quantization error of, for example, +0.1 exists. In such a case, repeated multiple writing is performed using the same irradiation time, and the quantization error accumulates. For example, a quantization error of +0.2 occurs with a multiplicity of 2, and a quantization error of +0.4 occurs with a multiplicity of 4. Therefore, with a multiplicity of 4, a dose error of 0.4 × current density occurs in the direction of an excessive increase in the dose. Conversely, suppose a quantization error of, for example, -0.1 exists. Repeated multiple writing is performed using the same irradiation time, and the quantization error accumulates. For example, a quantization error of -0.2 occurs when the multiplicity is 2, and -0.4 occurs when the multiplicity is 4. Therefore, when the multiplicity is 4, a dose error of 0.4 × current density occurs in the direction of a dose deficiency.

[0053] Therefore, in the first embodiment, in multiple writing, two or more types of weighting are applied to the multiple beams that irradiate each pixel, and the irradiation time in each pass is shifted. This will be specifically described below.

[0054] Fig. 11 is an example of a flowchart illustrating the main steps of the writing method according to Embodiment 1. In Fig. 11, the writing method according to Embodiment 1 carries out a series of steps including a current density distribution creation step (S102), a weighting coefficient setting step (S104), a correction coefficient calculation step (S110), an irradiation time data generation step (S120), an irradiation time correction step (S130), and a writing step (S140).

[0055] In the current density distribution creation step (S102), first, under the control of the writing control unit 72, the current density is measured for each beam of the multi-beam 20. For example, the beams other than the target beam are controlled to be turned off, and the target beam is incident on the Faraday cup 106. This allows the current value of the beam to be measured. The measurement results for each beam are output to the control computer 110 via a detection circuit (not shown). The current density distribution creation unit 56 creates a current density distribution in which the current density of each beam is defined as an element. For example, a current density map is created. The current density can be calculated by dividing the measured current value by the cross-sectional area of the beam. Note that if there is variation in the diameter of the holes (openings) 22 in the shaping aperture array substrate 203, the current amount for each beam may be defined as an element, taking into account the variation in hole diameter. The created current density distribution (current amount distribution) is stored in the storage device 142. Here, the current density of each beam will be described as an example of the current amount of each beam.

[0056] In the weighting coefficient setting step (S104), the weighting coefficient setting unit 58 sets one of a plurality of weighting coefficients α for each beam of the multibeam 20 according to the arrangement position (i, j) of the multibeam 20.

[0057] 12 is a diagram illustrating an example of multiple writing with a multiplicity of 4 in the first embodiment. The example in FIG. 12 shows a case where the multiplicity N=4. Each pass is shifted in the x and y directions from the previous pass to perform writing by ¼ of the width of the stripe region 32. Writing is repeated in each stripe region 32 under the same beam conditions in a plurality of rectangular regions 35 obtained by dividing the stripe region 32 in the x direction and having the same size as the irradiation region 34 of the beam array. Therefore, when multiple writing is performed by shifting in the x and y directions by ¼ of the width of the stripe region 32, beams in blocks with the same symbol among 16 blocks A to D obtained by dividing the beam array into 4×4 blocks write the same region of the stripe region 32.

[0058] Therefore, among the multiple blocks in the beam array, the beam groups in the four blocks of symbol A write the same area of the stripe region 32 using different passes for each block. In other words, beams at corresponding array positions in blocks of the same symbol (e.g., A) irradiate the same pixel. If the correction coefficients of the four beams irradiating the same pixel are averaged to the same value as in Comparative Example 2, the above-mentioned quantization error occurs. Therefore, the weighting coefficient setting unit 58 sets weighting coefficients for each beam so that at least two of the passes have different correction coefficients.

[0059] In the first embodiment, the same pixel 36 on the sample 101 is subjected to multiple writing using multiple beams 20 at different array positions, each of which has two or more weighting coefficients α(i,j) set. In this case, the dose (i,j) of the beam in each pass can be defined for each of the multiple beams irradiating the pixel 36 using two or more weighting coefficients α(i,j) of the multiple beams writing the pixel 36 and the current amount, for example, current density J(i,j) of each of the multiple beams. The dose (i,j) of the beam in each pass can be defined by the following equation (3). Although the current density J(i,j) of each beam is used in equation (3), the current amount I(i,j) of each beam may be used instead of the current density J(i,j).

[0060]

number

[0061] The weighting coefficient α(i,j) set for each beam irradiating the same pixel in equation (3) is set independently, regardless of the current amount of the beam, for example, the current density J(i,j). Furthermore, the weighting coefficient α(i,j) is set for each beam so that the total value of the dose (irradiation amount) of the multiple beams irradiating each pixel 36 of the sample 101 is equal to the design value. Note that a deviation of the total value from the design value is permitted to the extent that it does not affect the writing accuracy.

[0062] In addition, in equation (3), when averaging the current density J between paths, the values obtained by multiplying the beam current density J of each path by the weighting coefficient of that beam are summed. Then, the sum is divided by the weighting coefficient of that beam. Simply multiplying the averaged correction coefficient shown in Comparative Example 2 by the weighting coefficient will result in a deviation from the designed dose. Therefore, when correcting using a weighting coefficient as in equation (3), the designed dose can be achieved by correcting in relation to the current density J. A specific example will be described below.

[0063] FIG. 13 is a diagram showing an example of a group region of weighting factors in the first embodiment. The example of FIG. 13 shows a case of multiple writing with a multiplicity of 4, in which positions are shifted in the x and y directions by ¼ the width of the stripe region 32. The example of FIG. 13 shows a case in which different weighting factors are set for multiple beams irradiating the same position on the sample 101. A specific explanation will be given below. Note that "the same position" does not necessarily mean the exact same position; there may be a positional shift of the beam or a shift in the designed writing (irradiation) position, and it is sufficient that at least a portion of the beams overlap.

[0064] In the example of Fig. 13, the beam array is divided into four group areas in the y direction. For example, from the bottom, the beam groups within that area are group areas G1, G2, G3, and G4. In the case of a 512 x 512 array of multi-beams 20, the array position (i, j) of each beam is defined as 0 to 511 for both i and j.

[0065] It is preferable to prepare the same number of weighting coefficients α as the multiplicity N of multiple drawing. The multiple weighting coefficients may include 1. Furthermore, the multiple weighting coefficients may include two or more different values. For example, in the case of a multiplicity of 4, four weighting coefficients, e.g., 0.98, 0.99, 1.01, and 1.02, are used as α. In this way, it is preferable that all four values are different. However, this is not limited to this. α may include 1, e.g., 0.97, 1.00, 1.01, and 1.02. Alternatively, if there are two or more values, e.g., 0.99, 1.01, 0.99, and 1.01, the same values may be used for some of them. In the case of a multiplicity of 2, two weighting coefficients, e.g., 0.99 and 1.01, are used as α. Furthermore, although the range of the weighting coefficients is not particularly limited, considering quantization error, it is preferable that the difference between the multiple weighting coefficients is on the order of 1 / M (M is the number of gradations of the exposure dose). For example, it can be divided in 1 / 100 units, and it is preferable to set it in the range of 0.95 to 1.05.

[0066] In either case, the sum of the weighting factors of the passes applied to the same pixel is set to match the multiplicity value. In the above example, if α is set to, for example, 0.98, 0.99, 1.01, or 1.02, the sum is 4, which matches the multiplicity of 4. This allows the sum of the doses (irradiation amounts) of the multiple beams irradiated to each pixel 36 to be set as the design value.

[0067] It is preferable that a plurality of weighting factors α are determined in advance for each load level, and data of the weighting factor sets for each load level is stored in the storage device 140.

[0068] In the example of FIG. 13, the weighting coefficient setting unit 58 sets the beam group with arrangement positions (0 to 511, 0 to 127) (beams in the first region from the bottom) as group region G1, and sets a weighting coefficient α0=0.99 for each beam in group region G1.

[0069] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (0 to 511, 128 to 255) (beams in the second area from the bottom) as group area G2, and sets a weighting coefficient α1=1.01 for each beam in group area G2.

[0070] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (0 to 511, 256 to 383) (beams in the third region from the bottom) as group region G3, and sets a weighting coefficient α2=0.98 for each beam in group region G3.

[0071] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (0 to 511, 384 to 511) (beams in the fourth region from the bottom) as group region G4, and sets a weighting coefficient α3=1.02 for each beam in group region G4.

[0072] As described above, in multiple beam lithography, the same region is repeatedly lithographed for each block of the beam array. Therefore, by setting different weighting factors between blocks of the same symbol, the weighting factors of multiple beams irradiating the same position in each pass can be set to different values. In the example of FIG. 12, the position is shifted in the x direction for each pass, so the beam is divided into four blocks A to D in the x direction. However, it is sufficient to change the weighting factors for each of the four group regions divided in the y direction. In this way, by setting weighting factors for each group region containing multiple beams, the number of weighting factors can be reduced compared to setting weighting factors individually for each beam. Alternatively, weighting factors may be set for each beam so that each block, which is greater in number than the number of group regions, has a different correction coefficient. Alternatively, weighting factors may be set for each beam so that each subblock, which is obtained by further dividing each block, has a different correction coefficient. For example, it is preferable to divide each block into 4 × 4 subblocks. Alternatively, weighting factors may be set for each beam so that each beam has a different correction coefficient.

[0073] In the example of FIG. 12, in the first pass, for example, a sub-region of the stripe region 32 is irradiated with the beam group of the topmost block A among the four blocks A, so α3=1.02 is applied to the beam group of the topmost block A. In the second pass, the same sub-region is irradiated with the beam group of the second-highest block A, so α2=0.98 is applied to the beam group of the second-highest block A. In the third pass, α1=1.01 is applied. And in the fourth pass, α0=0.99 is applied. Thus, in the four blocks A, the same region is irradiated with different passes of multiple writing, but the weighting coefficient changes for each pass. Alternatively, at least two types of weighting coefficients are applied to the four passes.

[0074] In the correction coefficient calculation step (S110), when the same pixel 36 (position) of the sample 101 to be written is written multiple times with multiple beams of the multi-beam 20 at different array positions to which two or more weighting factors α are set, the correction coefficient calculation unit 60 calculates a correction coefficient K for each of the multiple beams irradiating the pixel 36, using two or more weighting factors α of the multiple beams writing the pixel 36 and the current density J(i, j) of each of the multiple beams.

[0075] As shown in Figure 13, the correction coefficient K can be defined by the following equation (4) using the weighting coefficient α(i, j) of the beam used in each path, the ideal current density J0, and the current density J(i, j) of the beam used in each path, as can be seen from equation (3).

[0076]

number

[0077] The calculated data of the correction coefficients for each beam is stored in the storage device 142 .

[0078] FIG. 14 is a diagram showing an example of a block configuration in a beam array in the first embodiment. The example in FIG. 14 shows a case where the multiplicity N=4. Each pass is shifted in the x and y directions from the previous pass to perform writing by ¼ of the width of the stripe region 32. Writing is repeated in each stripe region 32 under the same beam conditions in a plurality of rectangular regions 35 obtained by dividing the stripe region 32 in the x direction and having the same size as the irradiation region 34 of the beam array. Therefore, when multiple writing is performed by shifting in the x and y directions by ¼ of the width of the stripe region 32, beam groups in blocks with the same symbol among 16 blocks A to D obtained by dividing the beam array into 4×4 blocks will write the same region of the stripe region 32.

[0079] Therefore, among the multiple blocks in the beam array, the beam groups in the four blocks with symbol A (A1 to A4) write the same area of the stripe region 32 using different paths for each block. In other words, beams at corresponding array positions in blocks with the same symbol (for example, A) irradiate the same pixel. Up to this point, it is the same as in the case of FIG. 12.

[0080] In the example of FIG. 14 , since the weighting coefficients are changed for each group region, even among blocks of the same symbol A, different correction coefficients can be used for blocks A1, A2, A3, and A4. Therefore, even if quantization errors occur, multiple drawing can average them out rather than simply accumulating them in one direction. Similarly, even among blocks of the same symbol B, different correction coefficients can be used for blocks B1, B2, B3, and B4. Therefore, even if quantization errors occur, multiple drawing can average them out rather than simply accumulating them in one direction. Similarly, even among blocks of the same symbol C, different correction coefficients can be used for blocks C1, C2, C3, and C4. Therefore, even if quantization errors occur, multiple drawing can average them out rather than simply accumulating them in one direction. Similarly, even among blocks of the same symbol D, different correction coefficients can be used for blocks D1, D2, D3, and D4. Therefore, even if quantization errors occur, multiple drawing can average them out rather than simply accumulating them in one direction.

[0081] In the example of FIG. 13 described above, a case where a beam array is divided in the y direction and a plurality of group regions are set is shown, but the present invention is not limited to this.

[0082] FIG. 15 is a diagram showing another example of group regions of weighting coefficients in the first embodiment. In FIG. 15, in addition to the case of FIG. 13, division is also performed in the x direction. In the example of FIG. 15, division is performed into four group regions in the x direction, and the beam array is divided into 16 group regions G11 to G44 in a 4×4 array. Weighting coefficients are then set for each group region. At this time, weighting coefficients are adjusted between groups that draw the same region in different passes in multiple drawing. In other words, weighting coefficients are adjusted for group regions G11, G22, G33, and G44 (corresponding to blocks A1, A2, A3, and A4) that draw the same region. Similarly, weighting coefficients are adjusted for group regions G41, G12, G23, and G34 (corresponding to blocks B1, B2, B3, and B4) that draw the same region. Similarly, weighting coefficients are adjusted for group regions G21, G32, G43, and G14 (corresponding to blocks C1, C2, C3, and C4) that draw the same region. Similarly, the weighting coefficients are adjusted for group areas G31, G42, G13, and G24 (corresponding to blocks D1, D2, D3, and D4) that depict the same area.

[0083] In the example of FIG. 15, the weighting coefficient setting unit 58 sets a group of beams with arrangement positions (0 to 127, 0 to 127) as a group region G11, and sets a weighting coefficient α11=0.99 for each beam in the group region G11.

[0084] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (128 to 255, 0 to 127) as a group region G21, and sets a weighting coefficient α21=0.99 for each beam in the group region G21.

[0085] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (256 to 383, 0 to 127) as a group region G31, and sets a weighting coefficient α31=1.02 for each beam in the group region G31.

[0086] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (384 to 511, 0 to 127) as a group region G41, and sets a weighting coefficient α41=0.99 for each beam in the group region G41.

[0087] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (0 to 127, 128 to 255) as a group region G12, and sets a weighting coefficient α12=1.02 for each beam in the group region G12.

[0088] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (128 to 255, 128 to 255) as a group region G22, and sets a weighting coefficient α22=1.01 for each beam in the group region G22.

[0089] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (256 to 383, 128 to 255) as a group region G32, and sets a weighting coefficient α32=1.01 for each beam in the group region G32.

[0090] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (384 to 511, 128 to 255) as a group region G42, and sets a weighting coefficient α42=0.98 for each beam in the group region G42.

[0091] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (0 to 127, 256 to 383) as a group region G13, and sets a weighting coefficient α13=1.01 for each beam in the group region G13.

[0092] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (128 to 255, 256 to 383) as a group region G23, and sets a weighting coefficient α23=0.98 for each beam in the group region G23.

[0093] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (256 to 383, 256 to 383) as a group region G33, and sets a weighting coefficient α33=0.98 for each beam in the group region G33.

[0094] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (384 to 511, 256 to 383) as a group region G43, and sets a weighting coefficient α43=0.98 for each beam in the group region G43.

[0095] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (0 to 127, 384 to 511) as a group region G14, and sets a weighting coefficient α14=1.02 for each beam in the group region G14.

[0096] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (128 to 255, 384 to 511) as a group region G24, and sets a weighting coefficient α24=0.99 for each beam in the group region G24.

[0097] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (256 to 383, 384 to 511) as a group region G34, and sets a weighting coefficient α34=1.01 for each beam in the group region G34.

[0098] The weighting coefficient setting unit 58 sets the beam group with arrangement positions (384 to 511, 384 to 511) as a group region G44, and sets a weighting coefficient α44=1.02 for each beam in the group region G44.

[0099] FIG. 16 is a diagram illustrating a method of multiple writing in a modification of the first embodiment. The example of FIG. 16 illustrates a case where multiple writing is performed within the same pass. The example of FIG. 16 illustrates a case where multiple writing is performed using the left and right halves of the beam array. For example, when writing is performed using 512 × 512 arrays of multibeams 20, each sub-irradiation area 29 is configured with, for example, 16 × 16 pixels. In this case, while the XY stage 105 moves a distance L equivalent to 16 beam pitches, the sub-deflector 20 sequentially shifts the irradiation position (pixel 36), and 16 shots of the multibeams 20 are performed in a shot cycle T to write (expose) 16 different pixels within the same sub-irradiation area 29. This allows multiple writing of an area written using the right half of the beam array using the left half of the beam array.

[0100] The example in Figure 16 shows a case where the multiplicity N = 8. A total of eight multiple drawing passes are performed, with four passes and two passes within each pass. Each pass is performed by shifting the drawing from the previous pass by 1 / 4 of the width of the stripe region 32 in the y direction and 1 / 8 of that in the x direction. Each stripe region 32 is divided in the x direction into multiple rectangular regions 35 that have the same size as the irradiation region 34 of the beam array, and drawing is repeated under the same beam conditions. Furthermore, in Figure 16, drawing is repeated in the left and right halves of each rectangular region 35 under the same beam conditions. Therefore, when multiple drawing is performed by shifting the beams in the y direction by 1 / 4 of the width of the stripe region 32 and in the x direction by 1 / 8 of the width, the beam groups in the blocks with the same symbol out of the 32 blocks A to D obtained by dividing the beam array into 8 x 4 will draw the same area of the stripe region 32.

[0101] Therefore, among the multiple blocks in the beam array, beams in eight blocks designated by symbol A write the same region of the stripe region 32 in different passes for each block or in the same pass. In other words, beams at corresponding array positions in blocks designated by the same symbol (e.g., A) irradiate the same pixel. Regarding the correction coefficients of the eight beams irradiating the same pixel, the weighting coefficient setting unit 58 sets weighting coefficients for each beam so that at least two of the passes have different correction coefficients. Alternatively, weighting coefficients may be set for each beam so that different correction coefficients are used for each pass. Alternatively, weighting coefficients may be set for each beam so that different correction coefficients are used for each block. Alternatively, weighting coefficients may be set for each beam so that different correction coefficients are used for each beam.

[0102] In the irradiation time data generation step (S120), first, the rasterization processing unit 50 reads chip pattern data (drawing data) for each stripe region 32 from the storage device 140 and performs rasterization processing. Specifically, the pattern density (pattern area density) is calculated for each pixel 36.

[0103] Next, the shot data generation unit 52 calculates, for each pixel 36, an irradiation dose D to be applied to that pixel 36. The irradiation dose D may be calculated, for example, by multiplying a preset reference irradiation dose Dbase by a proximity effect correction irradiation coefficient Dp and a pattern area density ρ. In this way, the irradiation dose D is preferably calculated in proportion to the pattern area density calculated for each pixel 36. Regarding the proximity effect correction irradiation coefficient Dp, the drawing region (e.g., the stripe region 32) is virtually divided into a plurality of proximity mesh regions (mesh regions for calculating proximity effect correction) of a predetermined size in a mesh pattern. The size of the proximity mesh region is preferably set to approximately 1 / 10 of the range of influence of the proximity effect, for example, approximately 1 μm. Then, the drawing data is read from the storage device 140, and for each proximity mesh region, a pattern density ρ' (pattern area density) of the pattern to be arranged within the proximity mesh region is calculated.

[0104] Next, a proximity effect correction exposure coefficient Dp for correcting the proximity effect is calculated for each proximity mesh region. Here, the size of the mesh region for calculating the proximity effect correction exposure coefficient Dp does not need to be the same as the size of the mesh region for calculating the pattern density ρ'. Furthermore, the correction model for the proximity effect correction exposure coefficient Dp and its calculation method may be the same as the method used in the conventional single-beam writing method.

[0105] Then, the shot data generation unit 52 calculates, for each pixel 36, the irradiation time t of the electron beam for making the calculated irradiation dose D incident on that pixel 36. The irradiation time t can be calculated by dividing the irradiation dose D by the current density J. In this way, a dose map (actually, an irradiation time map with irradiation time data as an element) is created in which irradiation time data (shot data) for each pixel 36 is defined.

[0106] When multiple writing is performed, a dose map (actually, an irradiation time map) is created for each writing process of each pass. In other words, a dose map (actually, an irradiation time map) is created for each stripe layer. The created irradiation time data is stored in the storage device 142.

[0107] In the irradiation time correction step (S130), when the same position on the sample 101 is multiplexed by a plurality of beams of the multibeams 20 that are arranged at different positions and for which two or more weighting factors are set, the correction unit 62 (an example of an irradiation time calculation unit) corrects the previously determined irradiation doses of the plurality of beams for each of the plurality of beams that irradiate the position, using two or more weighting factors for the plurality of beams that write to the position. As described above, the irradiation dose of each beam is obtained by multiplying the current amount of each beam by the irradiation time, and here, for example, the irradiation time of each beam is corrected. In other words, when the same pixel 36 (position) on the sample 101 is subjected to multiple writing using multiple beams of the multibeam 20 at different array positions, each beam having two or more weighting coefficients, the correction unit 62 (an example of an irradiation time calculation unit) calculates, for each of the multiple beams irradiating the pixel 36, an individual irradiation time t′(i,j) of the beam corrected using two or more weighting coefficients α(i,j) of the multiple beams writing the pixel 36 and the current density J(i,j) of each of the multiple beams. Specifically, the correction unit 62 reads the correction coefficient K and the pre-correction irradiation time t(i,j) of the target beam from the storage device 142, and calculates the corrected irradiation time t′(i,j) by multiplying the pre-correction irradiation time t(i,j) by the correction coefficient K for the beam. The created corrected irradiation time data is stored in the storage device 142 in shot order.

[0108] In the above example, an individual correction coefficient K is first calculated for each beam at each array position and stored in the storage device 142, and the correction coefficient K is then read from the storage device 142 to correct the pre-correction irradiation time t(i,j). However, this is not limiting. Instead of calculating the correction coefficient K in advance, the post-correction irradiation time t'(i,j) may be directly calculated using two or more weighting coefficients α(i,j) of the multiple beams that draw the pixel 36 and the current density J(i,j) of each of the multiple beams according to the following equation (5):

[0109]

number

[0110] Furthermore, it is not necessary to correct the irradiation amount by correcting the irradiation time, but the current density (amount of current) may be corrected. In this case, the correction may be performed by multiplying the current density (amount of current) or a coefficient by which the reference amount of the current density (amount of current) is multiplied by the correction coefficient K.

[0111] In the writing step (S140), the writing mechanism 150 writes a pattern on the sample 101 using the multibeam 20 so that the multiple beams write multiple times at each pixel 36 of the sample 101 with the corrected irradiation dose of each of the multiple beams. In other words, the writing mechanism 150 writes a pattern on the sample 101 using the multibeam 20 so that the multiple beams write multiple times at each pixel 36 of the sample 101 with the calculated individual irradiation times t'(i,j).

[0112] As described above, the irradiation amount of each beam is obtained by multiplying the current amount of each beam by the irradiation time, and for each of the multiple beams, the irradiation time of each beam is corrected using two or more weighting coefficients and the current amount of each of the multiple beams, and each beam is irradiated for the corrected irradiation time.

[0113] FIG. 17 is a diagram illustrating an example of a correction coefficient distribution and a quantization error in Comparative Example 1 of the first embodiment. FIG. 18 is a diagram illustrating an example of a correction coefficient distribution and a quantization error in Comparative Example 2 of the first embodiment. FIG. 19 is a diagram showing an example of a correction coefficient distribution and a quantization error according to the first embodiment. 17, 18, and 19, the upper part shows an example of an in-plane distribution diagram of the correction coefficient, the middle part shows an example of a graph showing the variation of the correction coefficient for each block, and the lower part shows an example of the quantization error for each design dose.

[0114] In Comparative Example 1, as shown in the upper diagram of FIG. 17, the correction coefficient value of the peripheral beam with low current density becomes large, and the irradiation time becomes long. The irradiation dose becomes uniform. However, as shown in part A of the middle diagram of FIG. 17, an unusually large correction coefficient may occur. As a result, the irradiation time at the singular point becomes long, and the overall shot cycle becomes long. As a result, the writing time becomes long, and throughput deteriorates. Furthermore, as shown in the lower diagram of FIG. 17, the quantization error is large in pixels with low dose. Therefore, the controllability of the pattern edge position tends to deteriorate.

[0115] In Comparative Example 2, as shown in the upper diagram of FIG. 18, the correction coefficient values are averaged, so they become almost uniform. Therefore, the irradiation time is also uniform. Furthermore, as shown in the middle diagram of FIG. 18, the maximum irradiation time is shortened because the correction coefficients are almost uniform. As a result, the writing time is shortened. However, as shown in the lower diagram of FIG. 18, since the irradiation time of each beam tends to be the same value, quantization errors accumulate in the same direction, and the total quantization error becomes large.

[0116] In contrast to these, in the first embodiment, as shown in the upper and middle diagrams of FIG. 19, the correction coefficients do not become singularly large values and can be made uniform. This makes it possible to prevent the shot cycle from becoming long. Furthermore, as shown in the lower diagram of FIG. 19, since the correction coefficients are not uniform, the quantization errors of each beam can be averaged. As a result, the magnitude of the total quantization error can be improved.

[0117] FIG. 20 is a diagram illustrating a first variation of the weighting coefficient in the first embodiment. In electron beam writing, blurring due to Coulomb force is likely to occur. To reduce the effects of Coulomb force, it is effective to vary the dose between adjacent beams irradiated simultaneously. Therefore, as shown in FIG. 20, it is effective to set the dose of each beam of the multi-beam 20 so that it varies in intensity, for example, in a checkerboard pattern. Therefore, the weighting coefficient α(i,j) is defined as the product of multiple independent weighting coefficient elements. In the example of FIG. 20, it is preferable to use the product of the above-described weighting coefficient α(i,j) (first weighting coefficient) and the weighting coefficient β(i,j) (second weighting coefficient) for suppressing the Coulomb effect, which are independent of each other, as the weighting coefficient α(i,j) set for each beam. Note that, in the case of a multiplicity of 2, the weighting coefficient β(i,j) for suppressing the Coulomb effect is set to, for example, 1.5 for one of the adjacent beams and 0.5 for the other beam in the first pass. Then, for example, in the second pass, one of the adjacent beams is set to 0.5 and the other to 1.5, which can reduce the Coulomb effect.

[0118] FIG. 21 is a diagram illustrating a second modification of the weighting coefficients in the first embodiment. Among the multi-beams 20, there may be defective beams whose dose cannot be controlled or whose beams are always OFF. Therefore, for these defective beams, the weighting coefficients are set to zero so that the post-correction irradiation time is zero. Therefore, as shown in FIG. 21, it is preferable to use the product of the above-described weighting coefficient α(i,j) (first weighting coefficient) and the weighting coefficient β(i,j) (second weighting coefficient) for defect beam determination, which are independent of each other, as the weighting coefficient α(i,j) set for each beam. The weighting coefficient β(i,j) for defect beam determination should be set to 1 for normal beams and to 0 for defective beams. Note that constantly ON beams are excluded from this defect determination because they cannot be controlled. The designed dose required for a beam with β(i,j)=0 can be allocated to beams of other paths.

[0119] As described above, according to the first embodiment, when multiple writing is performed on the sample 101 using the multiple beams 20, it is possible to suppress the throughput and reduce the quantization error regardless of whether or not a beam with a specific current density exists.

[0120] The processing functions described in the above embodiments may be executed by a computer, and a program for causing a computer to execute such processing functions may be stored in a non-transitory, tangible readable recording medium such as a magnetic disk device.

[0121] Although the description of the device configuration, control method, and other parts not directly necessary for the explanation of the present invention have been omitted, the required device configuration and control method can be appropriately selected and used. For example, the description of the control unit configuration that controls the drawing device 100 has been omitted, but it goes without saying that the required control unit configuration can be appropriately selected and used. In the above-described embodiment, a drawing apparatus, a drawing method, and a program using a charged particle beam are described, but the present invention is not limited to charged particles, and can also be applied to a drawing apparatus, a drawing method, and a program using a laser.

[0122] In addition, all other multi-charged particle beam writing methods, multi-charged particle beam writing apparatuses, and programs that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included within the scope of the present invention. [Explanation of symbols]

[0123] 20 Multibeam 22 holes 24 control electrode 25 Passing hole 26 Counter electrode 29 Sub-irradiation area 30 drawing area 32 stripe area 34 Irradiation area 35 rectangular area 36 pixels 41 Control circuit 42 patterns 50 Rice Rise Processing Unit 52 Shot data generation unit 56 Current density distribution creation section 58 Weighting coefficient setting unit 60 Correction coefficient calculation unit 62 Correction unit 72 Drawing control unit 74 Transfer Processing Unit 100 drawing device 101 Sample 102 Electron Telescope 103 Drawing room 105 XY stage 106 Faraday Cup 110 Control computer 112 memory 130 Deflection control circuit 132,134 DAC amplifier unit 136 Lens control circuit 138 Stage Control Mechanism 139 Stage Position Measuring Instrument 140,142 Storage device 150 Drawing mechanism 160 Control Circuits 200 electron beam 201 Electron Gun 202 Lighting lens 203 Shaped Aperture Array Substrate 204 Blanking Aperture Array Mechanism 205 Reduction Lens 206 Limiting Aperture Substrate 207 Objective Lens 208 Main deflector 209 Sub deflector 210 Mirror 330 Membrane Region

Claims

1. setting one of a plurality of weighting coefficients for each beam of the multi-charged particle beam according to an arrangement position of the multi-charged particle beam; When the same position of a sample to be written is written by a plurality of beams of the multi-charged particle beams having different arrangement positions and having two or more weighting factors set thereto, a step of correcting, for each of the plurality of beams irradiating the position, the irradiation amount of the plurality of beams determined in advance by using two or more weighting factors of the plurality of beams writing the position; writing a pattern on the sample using the multi-charged particle beams such that the multiple beams write multiple patterns at each position on the sample with the corrected irradiation dose of each of the multiple beams; A multi-charged particle beam writing method comprising:

2. 2. The multi-charged particle beam writing method according to claim 1, wherein the irradiation amount of each of the beams is obtained by multiplying the current amount of each of the beams by the irradiation time, and the irradiation time of each of the beams is corrected for each of the plurality of beams using the two or more weighting coefficients and the current amount of each of the plurality of beams, and each of the beams is irradiated for the corrected irradiation time.

3. 3. A multi-charged particle beam writing method according to claim 2, wherein the weighting coefficients set for the respective beams are set independently of the current amounts of the beams.

4. 3. A multi-charged particle beam writing method according to claim 1, wherein a weighting coefficient is set for each of the beams so that the total value of the irradiation dose of the plurality of beams irradiated at each position of the sample becomes a design value.

5. 3. A multi-charged particle beam writing method according to claim 1, wherein different weighting coefficients are set for the plurality of beams irradiating the same position on the sample.

6. 3. A multi-charged particle beam writing method according to claim 1, wherein the weighting coefficient set for each beam is a product of a first weighting coefficient and a second weighting coefficient which are independent of each other.

7. a setting unit that sets one of a plurality of weighting factors for each beam of the multi-charged particle beam in accordance with an arrangement position of the multi-charged particle beam; a correction unit that corrects, for each of the plurality of beams irradiating the position, a previously determined irradiation amount of each of the plurality of beams using two or more weighting factors of the plurality of beams that draw the position, when the same position of a sample to be drawn is multiple-written with a plurality of beams of the multi-charged particle beams that have different arrangement positions and to which two or more weighting factors are set; a drawing mechanism that draws a pattern on the sample using the multi-charged particle beams so that the multiple beams perform multiple drawing on each position of the sample with the corrected irradiation amount of each of the multiple beams; A multi-charged particle beam drawing apparatus comprising:

8. a function of setting one of a plurality of weighting factors for each beam of the multi-charged particle beam in accordance with an arrangement position of the multi-charged particle beam; a function of storing weighting coefficients set for each beam in a storage device; a function of reading out the weighting coefficients from the storage device, and when performing multiple drawing on the same position of a sample to be drawn using a plurality of beams of the multi-charged particle beams having different arrangement positions and having two or more weighting coefficients set thereto, correcting the irradiation amount of each of the plurality of beams that irradiates the position using the two or more weighting coefficients of the plurality of beams that draw the position, and outputting the corrected amount; A program that causes a computer to execute the following.

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