Multi-charged particle beam lithography apparatus and charged particle beam lithography method

Abstract

PURPOSE: To provide a device capable of suppressing an increase in a dose modulation rate when positional deviation correction of each beam is performed by dose modulation in multi-beam writing.CONSTITUTION: A multi-charged particle beam writing device according to an embodiment of the present invention includes an identification unit 52 that identifies a first beam that has the closest actual irradiation position to a design grid of a target beam among the multi-charged particle beams, for each of a plurality of design grids serving as the design irradiation positions of the multi-charged particle beams, a setting unit 56 that sets a plurality of combinations composed of two or more beams including the first beam from the multi-charged particle beam for each of the design grids, a dose distribution ratio calculation unit 58 that calculates, for each of the design grids and for each of the plurality of combinations, a dose distribution ratio for each of the two or more beams that make up the combination, and a combination selection unit 62 that selects a combination in which the dose distribution ratio of the first beam is greater than the dose distribution ratio of the remaining one or more beams of the two or more beams constituting the combination, for each of the design grids.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One aspect of the present invention relates to a multi-charged particle beam lithography apparatus and a multi-charged particle beam lithography method, and relates to a technique for reducing pattern dimensional deviation in multi-beam lithography, for example.

Background Art

[0002] Lithography technology, which is responsible for the progress of semiconductor device miniaturization, is an extremely important process for generating patterns, which is unique among semiconductor manufacturing processes. In recent years, with the high integration of LSIs, the circuit line widths required for semiconductor devices have been miniaturized year by year. Here, electron beam (electron beam) lithography technology has inherently excellent resolution, and mask patterns are drawn on mask blanks using electron beams.

[0003] For example, there is a lithography apparatus using a multi-beam. Compared with the case of drawing with a single electron beam, by using a multi-beam, a large number of beams can be irradiated at once, so the throughput can be significantly improved. In such a multi-beam type lithography apparatus, for example, an electron beam emitted from an electron gun is passed through a mask having a plurality of holes to form a multi-beam, and each beam is blanking-controlled, and the mask image is reduced by reducing each unshielded beam by an optical system, and is deflected by a deflector and irradiated to a desired position on the sample.

[0004] In the case of multi-beam, due to the characteristics of the optical system, distortion occurs in the exposure field, and due to such distortion or the like, the irradiation positions of the individual beams deviate from the ideal grid. However, in the case of multi-beam, it is difficult to deflect the individual beams separately, so it is difficult to individually control the positions of the individual beams on the sample surface. Therefore, the positional deviation of each beam is corrected by dose modulation (see, for example, Patent Document 1). However, when correcting the positional deviation by dose modulation, there has been a problem that the maximum modulation rate among the dose modulation rates of the individual beams after dose modulation may increase. As the maximum modulation rate increases, the maximum irradiation time becomes longer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] One aspect of the present invention provides an apparatus and method capable of suppressing an increase in the dose modulation rate when correcting the positional deviation of each beam by dose modulation in multi-beam lithography.

Means for Solving the Problems

[0007] A multi-charged particle beam lithography apparatus according to one aspect of the present invention includes: a beam forming mechanism for forming a multi-charged particle beam; a specifying unit that specifies a first beam among the multi-charged particle beams for which the actual irradiation position is closest to the design grid of the target beam for each design grid of a plurality of design grids that are the design irradiation positions of the multi-charged particle beam; a combination setting unit that sets a plurality of combinations each composed of two or more beams including the first beam from the multi-charged particle beam for each design grid; For each design grid and for each combination of a plurality of combinations, a dose distribution rate to each of two or more beams constituting the combination is calculated so that the sum of the distributed dose amounts after distribution is equal to the dose amount planned to be irradiated to the design grid, and the dose amount planned to be irradiated to the design grid is distributed to the two or more beams constituting the combination. A distribution rate calculation unit; For each design grid, a combination selection unit that selects a combination in which the dose distribution rate of the first beam is greater than the dose distribution rates of the remaining one or more beams of the two or more beams constituting the combination; According to the dose distribution rates to the two or more beams constituting the combination selected for each design grid in the entire beam array of the multi-charged particle beam, the dose amount distributed to each irradiation position in the design of the beam is added to the dose amount at the irradiation position for correction, and a dose correction unit that outputs the corrected dose amount; A drawing mechanism that draws a pattern on a sample using the multi-charged particle beam of the corrected dose amount; Comprising 、 For each combination of the plurality of combinations, the combination setting unit selects a second beam from among the two or more beams from within the beam group in the restricted restricted region Characterized by this.

[0008] A multi-charged particle beam drawing method according to an aspect of the present invention is A step of forming a multi-charged particle beam; For each design grid of a plurality of design grids that are the design irradiation positions of the multi-charged particle beam, a step of identifying a first beam whose actual irradiation position is closest to the design grid of the target beam among the multi-charged particle beams; For each design grid, a step of setting a plurality of combinations composed of two or more beams including the first beam from the multi-charged particle beam; For each design grid and for each combination of a plurality of combinations, calculating a dose distribution rate for each of two or more beams constituting the combination such that the sum of the dose amounts after distribution for each of the two or more beams is equal to the dose amount planned to be irradiated to the design grid. For each design grid, selecting a combination in which the dose distribution rate of the first beam is greater than the dose distribution rates of the remaining one or more beams of the two or more beams constituting the combination. Correcting the dose amount distributed to each irradiation position in the design of the beam by adding it to the dose amount at the irradiation position according to the dose distribution rates to the two or more beams constituting the combination selected for each design grid in the entire beam array of the multi-charged particle beam, and outputting the corrected dose amount. Drawing a pattern on a sample using the multi-charged particle beam with the corrected dose amount. Comprising 、 For each combination of the plurality of combinations, the second beam among the two or more beams is selected from within the beam group in the restricted restricted region Characterized in that.

Effect of the Invention

[0009] According to one aspect of the present invention, in multi-beam drawing, an increase in the dose modulation rate can be suppressed when correcting the misalignment of each beam by dose modulation.

Brief Description of the Drawings

[0010]

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, 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 a beam using charged particles such as an ion beam may also be used.

[0012] Embodiment 1. FIG. 1 is a conceptual diagram showing the configuration of the drawing apparatus according to Embodiment 1. In FIG. 1, the drawing apparatus 100 includes a drawing mechanism 150 and a control system circuit 160. The drawing apparatus 100 is an example of a multi-charged particle beam drawing apparatus. The drawing mechanism 150 includes an electron lens barrel 102 (multi-electron beam column) and a drawing chamber 103. In 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 deflector 208, and a deflector 209 are arranged. An XY stage 105 is arranged in the drawing chamber 103. On the XY stage 105, a sample 101 such as a mask blank coated with a resist that becomes a drawing target substrate during drawing is arranged. The sample 101 includes an exposure mask for manufacturing a semiconductor device, or a semiconductor substrate (silicon wafer) on which a semiconductor device is manufactured. On the XY stage 105, a mirror 210 for measuring the position of the XY stage 105 is further arranged. On the XY stage 105, a Faraday cup 106 is further arranged.

[0013] 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, 134, a stage position detector 139, and storage devices 140, 142, 144 such as magnetic disk devices. The control computer 110, the memory 112, the deflection control circuit 130, the DAC amplifier units 132, 134, the stage position detector 139, and the storage devices 140, 142, 144 are connected to each other via a bus (not shown). The deflection control circuit 130 is connected to the DAC amplifier units 132, 134 and a blanking aperture array mechanism 204. The output of the DAC amplifier unit 132 is connected to a deflector 209. The output of the DAC amplifier unit 134 is connected to a deflector 208. The deflector 208 is composed of four or more electrodes and is controlled by the deflection control circuit 130 via the DAC amplifier 134 for each electrode. The deflector 209 is composed of four or more electrodes and is controlled by the deflection control circuit 130 via the DAC amplifier 132 for each electrode. The stage position detector 139 irradiates a mirror 210 on the XY stage 105 with laser light and receives the reflected light from the mirror 210. Then, the position of the XY stage 105 is measured using the principle of laser interference using the information of such reflected light.

[0014] Inside the control computer 110, a beam position deviation map creation unit 50, a specifying unit 52, a region limiting unit 54, a setting unit 56, a dose distribution rate calculation unit 58, a current density correction unit 60, a combination selection unit 62, an iterative calculation processing unit 64, a rasterization unit 66, a dose map creation unit 68, a dose correction unit 70, an irradiation time calculation unit 72, and a drawing control unit 74 are arranged. Each “~ unit” such as the beam position deviation map creation unit 50, the specifying unit 52, the region limiting unit 54, the setting unit 56, the dose distribution rate calculation unit 58, the current density correction unit 60, the combination selection unit 62, the iterative calculation processing unit 64, the rasterization unit 66, the dose map creation unit 68, the dose correction unit 70, the irradiation time calculation unit 72, and the drawing control unit 74 has a processing circuit. Such a processing circuit includes, for example, an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each “~ unit” may use a common processing circuit (the same processing circuit), or may use different processing circuits (separate processing circuits). Information input to and output from the beam position deviation map creation unit 50, the specifying unit 52, the region limiting unit 54, the setting unit 56, the dose distribution rate calculation unit 58, the current density correction unit 60, the combination selection unit 62, the iterative calculation processing unit 64, the rasterization unit 66, the dose map creation unit 68, the dose correction unit 70, the irradiation time calculation unit 72, and the drawing control unit 74, as well as information during calculation, is stored in the memory 112 each time.

[0015] Also, drawing data is input from outside the drawing device 100 and stored in the storage device 140. The drawing data usually defines information on a plurality of graphic patterns for drawing. Specifically, for each graphic pattern, a graphic code, coordinates, size, etc. are defined.

[0016] Here, in FIG. 1, the configurations necessary for explaining Embodiment 1 are described. The drawing device 100 may usually be provided with other necessary configurations.

[0017] FIG. 2 is a conceptual diagram showing the configuration of the shaping aperture array substrate in Embodiment 1. In FIG. 2, in the shaping aperture array substrate 203, holes (openings) 22 arranged in a matrix at a predetermined array pitch are formed in p columns in the vertical (y direction) × q columns in the horizontal (x direction) (p, q ≧ 2). In FIG. 2, for example, holes 22 of 512 × 512 columns are formed in the vertical and horizontal (x, y directions). Each of the holes 22 is formed in a rectangular shape with the same dimensional shape. Alternatively, they may be circular with the same diameter. The shaping aperture array substrate 203 (beam forming mechanism) forms a multi-beam 20. Specifically, a multi-beam 20 is formed by a part of the plurality of these holes 22 being passed through by the electron beam 200 respectively. Also, the arrangement of the holes 22 is not limited to the case where they are arranged in a grid pattern vertically and horizontally as shown in FIG. 2. For example, the holes in the k-th row in the vertical (y direction) and the (k + 1)-th row may be arranged with a deviation of dimension a in the horizontal (x direction). Similarly, the holes in the (k + 1)-th row and the (k + 2)-th row in the vertical (y direction) may be arranged with a deviation of dimension b in the horizontal (x direction).

[0018] FIG. 3 is a cross-sectional view showing the configuration of the blanking aperture array mechanism in Embodiment 1. As shown in FIG. 3, in the blanking aperture array mechanism 204, a semiconductor substrate 31 made of silicon or the like is arranged on a support base 33. The central portion of the substrate 31 is processed, for example, by being cut from the back side to form a membrane region 330 (first region) with a thin film thickness h. The periphery surrounding the membrane region 330 becomes an outer peripheral region 332 (second region) with a thick film thickness H. The upper surface of the membrane region 330 and the upper surface of the outer peripheral region 332 are formed to be at the same height position or substantially the same height position. The substrate 31 is held on the support base 33 at the back surface of the outer peripheral region 332. The central portion of the support base 33 is open, and the position of the membrane region 330 is located in the open region of the support base 33.

[0019] In the membrane region 330, through-holes 25 (openings) for passage of respective beams of the multi-beam 20 are formed at positions corresponding to the respective holes 22 of the shaped aperture array substrate 203 shown in FIG. 2. In other words, a plurality of through-holes 25 through which the respective corresponding beams of the multi-beam 20 using an electron beam pass are formed in an array in the membrane region 330 of the substrate 31. And, on the membrane region 330 of the substrate 31, a plurality of electrode pairs each having two electrodes are arranged at positions facing each other with the corresponding through-hole 25 interposed therebetween among the plurality of through-holes 25. Specifically, on the membrane region 330, as shown in FIG. 3, a pair of a control electrode 24 and a counter electrode 26 for blanking deflection (blanker: blanking deflector) are arranged at positions facing each other with the corresponding through-hole 25 interposed therebetween in the vicinity of each through-hole 25. Also, inside the substrate 31 and in the vicinity of each through-hole 25 on the membrane region 330, a control circuit 41 (logic circuit) for applying a deflection voltage to the control electrode 24 for each through-hole 25 is arranged. The counter electrode 26 for each beam is grounded.

[0020] An amplifier (an example of a switching circuit) (not shown) is arranged in the control circuit 41. As an example of the amplifier, a CMOS (Complementary MOS) inverter circuit is arranged. And, the CMOS inverter circuit is connected to a positive potential (Vdd: blanking potential: first potential) (for example, 5V) (first potential) and a ground potential (GND: second potential). The output line (OUT) of the CMOS inverter circuit is connected to the control electrode 24. On the other hand, a ground potential is applied to the counter electrode 26. And, a plurality of control electrodes 24 to which the blanking potential and the ground potential can be switchably applied are arranged on the substrate 31 at positions facing the respective corresponding counter electrodes 26 of the plurality of counter electrodes 26 with the respective corresponding through-holes 25 of the plurality of through-holes 25 interposed therebetween.

[0021] Either an L (low) potential (e.g., ground potential) lower than the threshold voltage or an H (high) potential (e.g., 1.5 V) equal to or higher than the threshold voltage is applied as a control signal to the input (IN) of the CMOS inverter circuit. In Embodiment 1, when the L potential is applied to the input (IN) of the CMOS inverter circuit, the output (OUT) of the CMOS inverter circuit becomes the positive potential (Vdd), and one corresponding electron beam in the multi-beam 20 is deflected by the electric field due to the potential difference from the ground potential of the counter electrode 26, and is controlled to be beam OFF by shielding with the limiting aperture substrate 206. On the other hand, when the 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 since there is no potential difference from the ground potential of the counter electrode 26 and one corresponding electron beam in the multi-beam 20 is not deflected, it is controlled to be beam ON by passing through the limiting aperture substrate 206.

[0022] Each corresponding electron beam in the multi-beam 20 passing through each via hole is deflected independently by the voltages applied to the two control electrodes 24 and the counter electrode 26 that form a pair. Blanking control is performed by such deflection. Specifically, the pair of the control electrode 24 and the counter electrode 26 blanking deflects the corresponding beam of the multi-beam 20 individually by the potential switched by the CMOS inverter circuit serving as the corresponding switching circuit. Thus, a plurality of blankers perform blanking deflection of the corresponding beams among the multi-beams 20 that have passed through the plurality of holes 22 (openings) of the shaping aperture array substrate 203.

[0023] FIG. 4 is a conceptual diagram for explaining an example of a drawing operation in Embodiment 1. As shown in FIG. 4, the drawing area 30 of the sample 101 is virtually divided, for example, into a plurality of strip areas 32 in the shape of strips with a predetermined width in the y direction. First, the XY stage 105 is moved so that the irradiation area 34 that can be irradiated with a single shot of the multi-beam 20 is positioned at the left end of the first strip area 32 or a position further to the left, and the drawing is started. When drawing the first strip area 32, the XY stage 105 is moved, for example, in the -x direction, so that the drawing progresses relatively in the x direction. The XY stage 105 is moved continuously, for example, at a constant speed. After the drawing of the first strip area 32 is completed, the stage position is moved in the -y direction so that the irradiation area 34 is positioned relatively in the y direction at the right end of the second strip area 32 or a position further to the right. Then, the XY stage 105 is moved, for example, in the x direction to perform the drawing similarly in the -x direction. In the third strip area 32, the drawing is performed in the x direction, and in the fourth strip area 32, the drawing is performed in the -x direction. By drawing while alternating the directions in this way, the drawing time can be shortened. However, not limited to the case of drawing while alternating the directions in this way, when drawing each strip area 32, the drawing may proceed in the same direction. In a single shot, a maximum of the same number of shot patterns as the plurality of holes 22 formed in the shaping aperture array substrate 203 are formed at once by the multi-beam formed by passing through each hole 22 of the shaping aperture array substrate 203. Also, in the example of FIG. 4, the case where each strip area 32 is drawn once is shown, but it is not limited to this. Multiple drawing in which the same area is drawn multiple times is also suitable. When performing multiple drawing, it is preferable to set the strip area 32 of each pass while shifting the position.

[0024] FIG. 5 is a diagram showing an example of an irradiation region of a multi-beam and a pixel to be drawn in Embodiment 1. In FIG. 5, in stripe region 32, for example, a plurality of control grids 27 (design grids) arranged in a lattice pattern at the beam size pitch of multi-beam 20 on the surface of sample 101 are set. It is preferable that this control grid 27 has an arrangement pitch of about 10 nm, for example. Such a plurality of control grids 27 become the irradiation positions in the design of multi-beam 20. The arrangement pitch of control grid 27 is not limited to the beam size, and may be configured with any size that can be controlled as the deflection position of deflector 209 regardless of the beam size. And a plurality of pixels 36 virtually divided in a mesh pattern with the same size as the arrangement pitch of control grid 27 centered on each control grid 27 are set. Each pixel 36 is an irradiation unit region per one beam of the multi-beam. In the example of FIG. 5, the drawing region of sample 101 is shown as being divided into a plurality of stripe regions 32 with substantially the same width size as the size of irradiation region 34 (drawing field) that can be irradiated by one irradiation of multi-beam 20 (beam array) in the y direction, for example. The x-direction size of irradiation region 34 can be defined by a value obtained by multiplying the beam pitch in the x direction of multi-beam 20 by the number of beams in the x direction. The y-direction size of irradiation region 34 can be defined by a value obtained by multiplying the beam pitch in the y direction of multi-beam 20 by the number of beams in the y direction. Note that the width of stripe region 32 is not limited to this. It is preferable that it is n times (n is an integer of 1 or more) the size of irradiation region 34. In the example of FIG. 5, for example, the illustration of a multi-beam of 512×512 columns is shown by omitting it to a multi-beam of 8×8 columns. And a plurality of pixels 28 (drawing positions of the beam) that can be irradiated by one shot of multi-beam 20 are shown in irradiation region 34. In other words, the pitch between adjacent pixels 28 becomes the pitch between each beam of the multi-beam in the design. In the example of FIG. 5, one sub-irradiation region 29 is configured by a region surrounded by the beam pitch. In the example of FIG. 5, each sub-irradiation region 29 is shown as being composed of 4×4 pixels.

[0025] FIG. 6 is a diagram for explaining an example of a multi-beam drawing method according to Embodiment 1. In FIG. 6, among the multi-beams for drawing the stripe region 32 shown in FIG. 5, a part of the sub-irradiation region 29 drawn by each beam at the coordinates (1, 3), (2, 3), (3, 3), ···, (512, 3) in the k-th row in the y direction is shown. In the example of FIG. 6, for example, a case is shown where 4 pixels are drawn (exposed) while the XY stage 105 moves a distance of 8 beam pitches. While such 4 pixels are being drawn (exposed), the entire multi-beam 20 is deflected collectively by the deflector 208 so that the relative position with respect to the sample 101 does not shift due to the movement of the XY stage 105 in the irradiation region 34. Thereby, the irradiation region 34 is made to follow the movement of the XY stage 105. In other words, tracking control is performed. The example of FIG. 6 shows a case where one tracking cycle is implemented by drawing (exposing) 4 pixels while moving a distance of 8 beam pitches.

[0026] Specifically, in each shot, a beam with an irradiation time (drawing time, or exposure time) corresponding to each control grid 27 within the set maximum irradiation time is irradiated. Specifically, each control grid 27 is irradiated with a beam corresponding to each of the ON beams among the multi-beams 20. Then, for each shot cycle time Ttr obtained by adding the settling time of the DAC amplifier to the maximum irradiation time, the irradiation position of each beam is moved to the next shot position by collective deflection by the deflector 209.

[0027] And in the example of FIG. 6, when 4 shots are completed, the DAC amplifier unit 134 resets the beam deflection for tracking control. Thereby, the tracking position is returned to the tracking start position where the tracking control was started.

[0028] Note that the drawing of the first pixel column from the right in each sub-irradiation area 29 has been completed. Therefore, after the tracking reset, in the next tracking cycle, first, the deflector 209 deflects so as to align (shift) the irradiation positions of the beams corresponding to the control grids 27 of the first pixel from the bottom and the second pixel from the right in each sub-irradiation area 29. By repeating such an operation, the drawing of all pixels is performed. When the sub-irradiation area 29 is composed of n×n pixels, n pixels are drawn by different beams in n tracking operations respectively. As a result, all the pixels within one n×n pixel area are drawn. Similar operations are simultaneously performed on other n×n pixel areas within the multi-beam irradiation area, and they are drawn in the same way.

[0029] Next, the operation of the drawing mechanism 150 in the drawing apparatus 100 will be described. The electron beam 200 emitted from the electron gun 201 (emission source) illuminates the entire shaping aperture array substrate 203 by the illumination lens 202. A plurality of rectangular holes 22 (openings) are formed in the shaping aperture array substrate 203. Then, the electron beam 200 illuminates the area including all the plurality of holes 22. Each part of the electron beam 200 irradiated at the positions of the plurality of holes 22 passes through the plurality of holes 22 of the shaping aperture array substrate 203 respectively. Thereby, for example, a plurality of electron beams (multi-beam 20) having a rectangular shape are formed. Such a multi-beam 20 passes through the corresponding blanker (first deflector: individual blanking mechanism) of the blanking aperture array mechanism 204. Such a blanker deflects (performs blanking deflection) the electron beam passing through individually.

[0030] The multi-beam 20 that has passed through the blanking aperture array mechanism 204 is reduced by the reduction lens 205 and travels toward the central hole formed in the restriction aperture substrate 206. Here, among the multi-beam 20, the electron beam deflected by the blanker of the blanking aperture array mechanism 204 is displaced from the central hole of the restriction aperture substrate 206 and is shielded by the restriction aperture substrate 206. On the other hand, the electron beam not deflected by the blanker of the blanking aperture array mechanism 204 passes through the central hole of the restriction aperture substrate 206 as shown in FIG. 1. By turning ON / OFF such an individual blanking mechanism 47, blanking control is performed and the ON / OFF of the beam is controlled. In this way, the restriction aperture substrate 206 shields each beam deflected to the OFF state of the beam by the individual blanking mechanism 47. Then, for each beam, a beam for one shot is formed by the beam that has passed through the restriction aperture substrate 206 and is formed from when the beam is turned ON until it is turned OFF. The multi-beam 20 that has passed through the restriction aperture substrate 206 is focused by the objective lens 207 to form a pattern image with a desired reduction ratio, and each beam (the entire multi-beam 20 that has passed through) that has passed through the restriction aperture substrate 206 is deflected collectively in the same direction by the deflectors 208 and 209 and irradiated to each irradiation position on the sample 101 of each beam. The multi-beam 20 irradiated at one time will ideally be arranged at a pitch obtained by multiplying the arrangement pitch of the plurality of holes 22 of the shaping aperture array substrate 203 by the above-described desired reduction ratio.

[0031] As described above, in multi-beam lithography, due to the characteristics of the optical system, distortion occurs in the exposure field, and due to such distortion or the like, the irradiation positions of the individual beams of the multi-beam 20 deviate from the ideal grid. However, since it is difficult to individually deflect the individual beams of the multi-beam 20, it is difficult to individually control the positions of the individual beams on the sample 101 surface. Therefore, the positional deviation of each beam is corrected by dose modulation. However, there are cases where the maximum modulation rate among the dose modulation rates of each beam after dose modulation becomes large. As the maximum modulation rate increases, the maximum irradiation time becomes long. Therefore, in Embodiment 1, attention is paid to the nearest beam that is irradiated closest to the control grid 27, and by increasing the dose distribution amount to such a nearest beam, the maximum modulation rate is reduced. This will be specifically described below.

[0032] FIG. 7 is a flowchart showing the main process steps of the lithography method in Embodiment 1. In FIG. 7, the lithography method in Embodiment 1 includes a beam position deviation measurement step (S102), a first nearest beam identification step (S104), a region limitation step (S106), a combination setting step (S108), a dose distribution rate calculation step (S110), a current density correction step (S112), a combination selection step (S114), an iterative calculation processing step (S118), a dose amount calculation step (S130), a dose correction step (S134), an irradiation time calculation step (S140), and a lithography step (S142).

[0033] Each of the steps of the beam position deviation measurement step (S102), the first nearest beam identification step (S104), the region limitation step (S106), the combination setting step (S108), the dose distribution rate calculation step (S110), the current density correction step (S112), the combination selection step (S114), and the iterative calculation processing step (S118) is performed as preprocessing before starting the lithography process.

[0034] In addition, in the drawing method according to the first embodiment, it is preferable to perform the iterative calculation process step (S118), but it may be omitted. When omitting the iterative calculation process step (S118), the iterative calculation processing unit 64 disposed in the control computer 110 in FIG. 1 may be omitted. Conversely, when performing the iterative calculation process step (S118), as its internal steps, a series of steps including a composite map creation step (S120), a determination step (S122), a combination update step (S124), a combination change step (S125), and a determination step (S126) are performed.

[0035] Also, in the drawing method according to the first embodiment, it is preferable to perform the current density correction step (S112), but it may be omitted. When omitting the current density correction step (S112), the current density correction unit 60 disposed in the control computer 110 in FIG. 1 may be omitted.

[0036] As the beam position deviation measurement step (S102), the drawing apparatus 100 measures the amount of position deviation by which the irradiation position of each beam of the multi-beam 20 on the sample 101 surface deviates from the corresponding control grid 27.

[0037] FIG. 8 is a diagram for explaining the beam misalignment and misalignment periodicity in the first embodiment. In the multi-beam 20, as shown in FIG. 8(a), due to the characteristics of the optical system, distortion occurs in the exposure field, and due to such distortion or the like, the actual irradiation position 39 of each beam is displaced from the control grid 27 which is the ideal grid. Therefore, in the first embodiment, the amount of displacement of the actual irradiation position 39 of each such beam is measured. Specifically, the multi-beam 20 is irradiated onto an evaluation substrate coated with a resist, and the position of the resist pattern generated by developing the evaluation substrate is measured with a position measuring device. Thereby, the amount of displacement for each beam is measured. In the shot size of each beam, if it is difficult to measure the size of the resist pattern at the irradiation position of each beam with the position measuring device, a graphic pattern (for example, a rectangular pattern) of a size measurable with the position measuring device is drawn for each beam. Then, the edge positions on both sides of the graphic pattern (resist pattern) are measured, and the amount of displacement of the target beam may be measured from the difference between the intermediate position between both edges and the intermediate position of the designed graphic pattern. Then, the displacement amount data of the irradiation position of each obtained beam is input to the drawing apparatus 100 and stored in the storage device 144. Further, in multi-beam drawing, since drawing is advanced while shifting the irradiation area 34 within the stripe area 32, for example, in the drawing sequence described in FIG. 6, as shown in the lower part of FIG. 4, during the drawing of the stripe area 32, the position of the irradiation area 34 sequentially moves as in the irradiation areas 34a to 34o. Then, periodicity occurs in the misalignment of each beam every time the irradiation area 34 moves. Or, in the case of a drawing sequence in which each beam irradiates all the pixels 36 within the corresponding sub-irradiation area 29, as shown in FIG. 8(b), periodicity occurs in the misalignment of each beam for each unit area 35 (35a, 35b, ···) having at least the same size as the irradiation area 34. Therefore, if the amount of displacement of each beam corresponding to the irradiation area 34 of the beam array is measured, the measurement result can be diverted. In other words, for each beam, it is sufficient to measure the amount of displacement at each pixel 36 within the corresponding sub-irradiation area 29.

[0038] Then, the beam position deviation map creation unit 50 first creates a beam position deviation map that defines the amount of beam position deviation for each beam of each pixel 36 within one rectangular unit area 35 on the sample surface corresponding to the irradiation area 34, in other words, for each beam array. Specifically, the beam position deviation map creation unit 5 0 may read the position deviation amount data of the irradiation position of each beam from the storage device 144 and create a beam position deviation map using such data as map values. Which beam irradiates the control grid 27 of each pixel 36 within one rectangular unit area 35 on the sample surface corresponding to the entire irradiation area 34 of the multi-beam 20 is determined by the drawing sequence, as described in FIG. 6, for example. Therefore, the beam position deviation map creation unit 50 specifies the beam responsible for irradiating each control grid 27 for each pixel 36 within one unit area 35 according to the drawing sequence, and calculates the amount of position deviation of the beam. The created beam position deviation map is stored in the storage device 144.

[0039] FIG. 9 is a diagram showing an example of the dose distribution ratio when performing beam irradiation position and position deviation correction in the comparative example of Embodiment 1. FIG. 10 is a diagram showing another example of the dose distribution ratio when performing position shift correction for the beam irradiation position in the comparative example of Embodiment 1. In FIGS. 9 and 10, for example, a region where 5×5 pixels 36 are arranged is shown. Which beam irradiates each pixel 36 is determined by the drawing sequence. The actual irradiation position 39 of each beam often deviates from the control grid 27 arranged in a grid pattern. In the example of FIG. 9, when it is desired to irradiate the control grid 27a of the pixel located at the center with a desired dose amount, in the comparative example, the dose amount planned to be irradiated to the control grid 27a is distributed to three beams surrounding the control grid 27a. In the example of FIG. 9, for example, the dose is distributed to the beam at the irradiation position 39a, the beam at the irradiation position 39b, and the beam at the irradiation position 39c. The dose distribution ratio is calculated so that the center of gravity of the dose distribution amount becomes the position of the control grid 27a. As a result, the beam at the irradiation position 39a has a dose distribution ratio of 0.03 despite the small deviation amount from the control grid 27a. As a result, the dose distribution ratio to the beam at the irradiation position 39b away from the control grid 27a becomes 0.64. Similarly, the dose distribution ratio to the beam at the irradiation position 39c further away from the beam at the irradiation position 39b becomes 0.33. In this way, for each control grid 27, similarly, the dose distribution ratio for distributing the dose to the surrounding beams is calculated.

[0040] In the example of FIG. 10, an example of the case of distributing the dose to the control grid 27b of the pixel adjacent to the control grid 27a in the y direction is shown. In the example of FIG. 10, the dose is distributed to, for example, the beam at the irradiation position 39b, the beam at the irradiation position 39d, and the beam at the irradiation position 39e surrounding the control grid 27b. Similar to the case of the control grid 27a, the dose distribution ratio is calculated so that the center of gravity of the dose distribution amount becomes the position of the control grid 27b. As a result, the beam at the irradiation position 39b closest to the control grid 27b has a dose distribution ratio of 0.82. The dose distribution ratio to the beam at the irradiation position 39d becomes 0.15. Similarly, the dose distribution ratio to the beam at the irradiation position 39e becomes 0.03. For the two control grids 27a and 27b of the doorWith only the dose distribution of the

[0041] zeroth grid, the dose distribution rate to the beam at the irradiation position 39b becomes 1.46 (= 0.64 + 0.82). It is highly likely that the dose distribution rates from the other control grids 27 to the beam at the irradiation position 39b are also added. Thus, in the comparative example, there is a beam for which the total dose distribution rate greatly exceeds 1. As a cause of this, it can be cited that the dose distribution rate from the control grid 27a to the beam at the irradiation position 39a where the deviation amount from the control grid 27a is small is as small as 0.03. Therefore, in Embodiment 1, the dose distribution rate to the nearest beam irradiated closest to each control grid 27 is increased. To that end, the following steps are implemented.

[0041] As the first nearest beam specifying step (S104), for each control grid 27 of the plurality of control grids 27 that are the designed irradiation positions of the multi-beam 20, the specifying unit 52 specifies the nearest beam (first beam) for which the actual irradiation position 39 is closest to the target control grid 27 among the multi-beams 20.

[0042] FIG. 11 is a diagram showing an example of the control grid and the actual beam irradiation position in Embodiment 1. In the example of FIG. 11, for example, a region where 5×5 pixels 36 are arranged is shown. Which beam irradiates each pixel 36 is determined by the drawing sequence. For the control grids 27 arranged in a grid pattern, the actual irradiation positions 39 of the respective beams often deviate. In the example of FIG. 11, an example of the control grid 27 and the actual beam irradiation position 39 having the same positional relationship as FIGS. 9 and 10 is shown. In FIG. 11, it can be seen that the nearest beam closest to the control grid 27a of the pixel 36 located at the center is the beam at the irradiation position 39a. Thus, the specifying unit 52 specifies the beam at the irradiation position 39a as the nearest beam for the control grid 27a. Similarly, for the other control grids 27, the nearest beam is specified.

[0043] As the area limitation step (S106), the area limitation unit 54 limits, for each control grid 27, an area (limitation area) for selecting a second beam (second beam) for setting a plurality of combinations each composed of two or more beams including the nearest beam from the multi-beam 20.

[0044] FIG. 12 is a diagram showing an example of a limitation area in Embodiment 1. In FIG. 12, the limitation area 17 is an area on the opposite side of the irradiation position 39a of the nearest beam with respect to a straight line 13 passing through the control grid 27a and orthogonal to a straight line 11 connecting the target control grid 27a and the irradiation position 39a of the nearest beam.

[0045] As the combination setting step (S108), the setting unit 56 (combination setting unit) sets, for each control grid 27, a plurality of combinations each composed of two or more beams including the nearest beam from the multi-beam 20, for example, three beams.

[0046] FIG. 13 is a diagram showing an example of a control grid, an actual beam irradiation position, and a beam combination in Embodiment 1. As described above, the setting unit 56 selects, for each combination of the plurality of combinations, a second beam from among two or more beams in the beam group within the limited limitation area 17. In the example of FIG. 13, the second beam is selected from the limitation area 17 on the opposite side of the irradiation position 39a with respect to the straight line 13. In the example of FIG. 13, for example, the beam at the irradiation position 39f is selected as the second beam (second beam). By positioning the second beam on the opposite side of the straight line 13 with respect to the nearest beam, the dose distribution rate of the nearest beam can be increased.

[0047] The setting unit 56 selects the third and subsequent beams among the two or more beams constituting the combination. For the third and subsequent beams, any position may be used as long as the control grid 27 of interest can be surrounded by three or more beams constituting the combination. In the example of FIG. 13, the beam at the irradiation position 39g is selected as the third beam (the third beam). Thus, FIG. 13 shows a case where one of the plurality of combinations set for the control grid 27a is constituted by the beam at the irradiation position 39a, the beam at the irradiation position 39f, and the beam at the irradiation position 39g. Illustrations of other combinations are omitted here. Here, a case where a combination is constituted by three beams is described, but three or more beams may be used.

[0048] As the dose distribution ratio calculation step (S110), the dose distribution ratio calculation unit 58 (distribution ratio calculation unit) calculates, for each control grid 27 and for each combination of a plurality of combinations, the sum of the distributed dose amounts after distribution to two or more beams constituting the combination is equal to the dose amount scheduled to be irradiated to the control grid 27, for example, the dose amount scheduled to be irradiated to the control grid 27 so as to be equal, for example, to match, the dose distribution ratio of each beam of the two or more beams constituting the combination is calculated. The dose distribution ratio calculation unit 58 calculates the dose distribution ratio of each beam of the two or more beams so that the deviation between the center of gravity of each distributed dose amount after distribution to the two or more beams and the corresponding control grid 27 is within the allowable range Th. In Embodiment 1, it is desirable that the center of gravity completely coincides with the control grid 27, but it is not limited thereto. It is sufficient that the deviation between the center of gravity and the control grid 27 is within the allowable range Th. For example, it is suitable if it is within 1 / 5 of the pixel size. More preferably, it is within 1 / 10 of the pixel size. When the normalized dose amount d(i) of the target control grid 27 is set to d(i)=1, the dose distribution ratios d1, d2, and d3 to the nearest beam, the second beam, and the third beam can be obtained as values that satisfy the following equations (1-1) and (1-2) using the vector r from an arbitrary reference position to the target control grid 27 and the vectors r1, r2, and r3 to each beam. i indicates an index.

[0049]

Number

[0050] In addition to the dose distribution ratios d1, d2, and d3 when Th = 0, the dose distribution ratios d1, d2, and d3 when Th ≠ 0 can be calculated. Among these, it is desirable to adopt the value that makes the dose distribution ratio d1 of the nearest beam as large as possible.

[0051] As the current density correction step (S112), the current density correction unit 60 (weighting processing unit) calculates a weighted dose distribution ratio by using a current density correction value that corrects the deviation of the current density for each control grid 27 and for each combination of a plurality of combinations for the dose distribution ratios to two or more beams.

[0052] FIG. 14 is a diagram showing an example of the current density distribution in the first embodiment. In the example of FIG. 14, for example, the case of using 5 × 5 multi-beams 20 is shown. As shown in the example of FIG. 14, the current density generally forms a distribution in which the central beam is the highest and decreases toward the outer peripheral direction. Therefore, even when the irradiation time is the same, the incident dose amount is different between the case of being irradiated with the central beam and the case of being irradiated with the outer peripheral beam. Therefore, the current density correction unit 60 calculates a weighted dose distribution ratio by using a current density correction value that corrects the deviation of the current density of the corresponding beam. The weighted dose distribution ratio di′ can be defined by the following formula (2). Specifically, the ratio of the ideal current density J divided by the actual current density J(i) of the i-th beam is multiplied by the dose distribution ratio di to the i-th beam. Thereby, the weighted dose distribution ratio di′ to the i-th beam can be obtained. The ratio (J / J(i)) of the ideal current density J divided by the actual current density J(i) of the i-th beam is an example of the current density correction value.

[0053]

Number

[0054] Here, when performing n - time multiple drawing, the beams dose - distributed to each control grid 27 will be different. When evenly dividing the irradiation time planned for irradiating each control grid 27 in each pass, the irradiation time of each pass can be weighted by the ratio obtained by dividing the current density n·J for n times by the sum of the current densities J(i) of the beams of each pass. On the other hand, for each pass, two or more beams dose - distributed from each control grid 27 are different. Therefore, among the second or / and third beams of each pass, there may be cases where the irradiation positions are completely different from those of other passes. On the other hand, the nearest - neighbor beam irradiates the vicinity of the target control grid 27. Thus, for each control grid 27, using the current density J(i) of the nearest - neighbor beam of each pass, the dose distribution rate di of two or more beams of each pass is weighted by the ratio obtained by dividing the current density n·J for n times by the sum of the current densities J(i) of the nearest - neighbor beams of each pass. The weighted dose distribution rate di′ can be defined by the following formula (3). The ratio obtained by dividing the current density n·J for n times by the sum of the current densities J(i) of the nearest - neighbor beams of each pass is another example of the current density correction value.

[0055]

Number

[0056] Here, when the ideal current density J is normalized to 1, assume that the current densities of the nearest - neighbor beams in each pass of 4 - time multiple drawing are, for example, 1.0, 0.9, 0.95, and 0.85. The current density correction values using formula (2) are, for each pass, (1.0 / 1.0), (1.0 / 0.9), (1.0 / 0.95), (1.0 / 0.85). Therefore, the maximum value among these is 1.18 (=1.0 / 0.85). In contrast, in the calculation of the current density correction value using formula (3), the sum of the actual current densities of the 4 - time passes is 3.7 (=1.0 + 0.9+0.95 + 0.85). The sum n·J of the ideal current densities of the 4 - time passes is 4 (=4×1.0). Therefore, the current density correction value of each pass is 1.08 (=4 / 3.7), which can be made smaller than the case of using formula (2).

[0057] As the combination selection step (S114), for each control grid 27, the combination selection unit 62 selects a combination in which the dose distribution rate of the nearest beam is greater than the dose distribution rates of one or more of the remaining beams among the two or more beams constituting the combination. When there are two or more combinations in which the dose distribution rate of the nearest beam is greater than the dose distribution rates of one or more of the remaining beams among the two or more beams constituting the combination, it is preferable to select the combination in which the dose distribution rate of the nearest beam is the largest.

[0058] Note that when the current density correction step (S112) is omitted, the dose distribution rate targeted in the combination selection step (S114) uses the dose distribution rate before being weighted by the current density correction value. When the current density correction step (S112) is performed, the combination selection unit 62 selects a combination in which the weighted dose distribution rate of the nearest beam is greater than the weighted dose distribution rates of one or more of the remaining beams among the two or more beams constituting the combination.

[0059] FIG. 15 is a diagram showing an example of a simulation result of the relationship between the maximum modulation rate and the maximum misalignment amount associated with misalignment correction in Embodiment 1. In FIG. 15, the vertical axis represents the maximum modulation rate. The horizontal axis represents the maximum misalignment amount of the multi-beam 20. The maximum modulation rate is defined as the maximum value among the total dose distribution rates obtained by summing up the dose distribution rates assigned to each control grid 27 for each beam. The data indicated by ◇ shows the case where the dose distribution rate of the nearest beam is not considered to be larger than the dose distribution rates of the remaining beams. In the example of FIG. 15, it can be seen that in any case, the maximum modulation rate becomes 1 or more if the consideration of increasing the dose distribution rate of the nearest beam is not implemented. Also, it can be seen that as the misalignment amount increases, the maximum modulation rate also increases. On the other hand, in Embodiment 1, by selecting a combination such that the dose distribution rate of the nearest beam is larger than the dose distribution rates of the remaining beams, the maximum modulation rate can be reduced (data indicated by □). Also, as the misalignment amount increases, the tendency for the maximum modulation rate to increase is the same. Further, the maximum modulation rate can be further reduced by selecting a combination after weighting the dose distribution rate with the current density correction value (data indicated by △). The current density correction value in the example of FIG. 15 shows the case where the ratio of Equation (3) is used.

[0060] Next, the case of implementing the iterative calculation processing step (S118) will be described.

[0061] As the iterative calculation processing step (S118), the iterative calculation processing unit 64 calculates the total dose distribution rate summed for each designed irradiation position of the beams in the entire beam array each time while changing the combination selected for each control grid. Specifically, it operates as follows.

[0062] FIG. 16 is a block diagram showing an example of the internal configuration of the iterative operation processing unit in Embodiment 1. In FIG. 16, a composite map creation unit 80, a determination unit 82, a determination unit 86, and a combination change unit 88 are arranged in the iterative operation processing unit 64. Each "~ unit" such as the composite map creation unit 80, the determination unit 82, the determination unit 86, and the combination change unit 88 has a processing circuit. Such a processing circuit includes, for example, an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each "~ unit" may use a common processing circuit (the same processing circuit), or may use different processing circuits (separate processing circuits). Information input to and output from the composite map creation unit 80, the determination unit 82, the determination unit 86, and the combination change unit 88 and information during calculation are stored in the memory 112 each time.

[0063] As the composite map creation step (S120), the composite map creation unit 80 (total calculation unit) calculates the total dose distribution rate obtained by summing (compositing) the dose distribution rates to two or more beams that constitute the combination selected for each control grid 27 in the entire beam array of the multi-beam 20 for each designed irradiation position of the beam. Then, a composite map having the total dose distribution rate of each designed irradiation position of each beam as an element is created. The composite map is preferably created in the same array as the beam array arrangement of the multi-beam 20. There may be a case where dose is distributed from a plurality of control grids 27 to one beam. Therefore, each dose distribution rate distributed from the plurality of control grids 27 is composited for each designed irradiation position of the beam. Here, simply calculating the total value may be sufficient.

[0064] As the determination step (S122), the determination unit 82 determines whether the maximum value (maximum modulation amount) of the total dose distribution rate of the designed irradiation positions of each beam in the combination selected for each k-th control grid 27 is smaller than the maximum value (maximum modulation amount) of the total dose distribution rate of the designed irradiation positions of each beam in the combination selected for each control grid 27 before the (k - 1)-th time. In the first time, since it is impossible to compare with the maximum value of the total dose distribution rate before the previous time, it may be determined that it does not become smaller. After the second time, since there is the maximum modulation amount before the previous time, the magnitude relationship may be determined each time. When the maximum modulation amount becomes smaller, the process proceeds to the combination update step (S124). When the maximum modulation amount does not become smaller, the process proceeds to the combination change step (S125). Also, in this step, temporarily, the total dose distribution rate may be updated. In that case, the update is performed only on the part related to the control grid 27 being focused on.

[0065] As the combination update step (S124), when the maximum value of the total dose distribution rate of the designed irradiation positions of each beam in the entire k-th (k is an integer of 2 or more) beam array is smaller than the maximum value of the total dose distribution rate of the designed irradiation positions of each beam in the entire beam array before the (k - 1)-th time, the combination selection unit 62 re-selects the combination for each control grid 27 that is the basis of the total dose distribution rate of the designed irradiation positions of each beam in the entire k-th beam array. In other words, the combination for each currently selected control grid 27 is updated. At the same time, the total dose distribution rate is updated. This update is performed only on the part related to the control grid 27 for which the combination has been updated.

[0066] As the combination change step (S125), the combination change unit 88 changes the combination selected for each control grid 27. The nearest beam is specified for each control grid 27. The second beam is limited to the beam that irradiates the irradiation position 39 within the restriction area 17. Under such conditions, change to other combinations. For each control grid 27, if there are two or more combinations in which the dose distribution rate of the nearest beam is greater than the dose distribution rates of the remaining one or more beams that make up the combination, it is also preferable to change the combination from among them. Then, return to the composite map creation step (S120), and repeat the composite map creation step (S120) to the combination change step (S125) until the specified number of times is reached in the next determination step (S126). Note that in the composite map creation step (S120) when repeating, it is not limited to recalculating the total dose distribution rate of the designed irradiation positions of each beam in the entire beam array, and it is also possible to calculate only the total dose distribution rate at the irradiation positions that are the combination targets of the control grids for which the combination has been changed.

[0067] As the determination step (S126), the determination unit 86 determines whether the number of times k of the iterative calculation process in which the combination has been updated has reached the preset number of times m. When the number of times k of the iterative calculation process in which the combination has been updated has reached the preset number of times m, maintain the combination for each currently selected control grid 27 and end the iterative calculation process. When the number of times k of the iterative calculation process in which the combination has been updated has not reached the preset number of times m, proceed to the combination change step (S125). Even if the number of times k of the iterative calculation process in which the combination has been updated has not reached m times, it is also preferable to end the iterative calculation process when the difference from the maximum value at the (k - 1) - th time is smaller than the preset value. Also, even if the combination is not updated as a result of performing the iterative calculation process, if the number of times of the iterative calculation process for each control grid reaches the preset number of times q for that control grid, the iterative calculation process for that control grid may be ended.

[0068] Then, return to the composite map creation step (S120), and repeat each step from the composite map creation step (S120) to the combination change step (S125) until the number of times k of the iterative calculation process reaches a preset number of times m.

[0069] The composite map creation unit 80 calculates the total dose distribution rate summed for each design irradiation position of the beam in the entire beam array each time while changing the combination selected for each control grid 27. The dose distribution rate for each of the two or more beams constituting each combination after changing the combination may use the result already calculated in the dose distribution rate calculation step (S110).

[0070] By changing the combination for each control grid 27, the total dose distribution rate for each design irradiation position of the beam changes. As a result, the maximum modulation rate after synthesis changes. Therefore, the maximum modulation rate can be further reduced by performing iterative calculation processing (iteration).

[0071] Then, the modulation rate of the beam to the two or more beams constituting the combination selected for each control grid 27 is stored in the storage device 144 as position shift correction data. The position shift correction data may be created for one rectangular unit area 35 on the sample surface corresponding to the irradiation area 34.

[0072] As the dose amount calculation step (S130), the dose map creation unit 68 (dose amount calculation unit) calculates the individual dose amount of each pixel 36 on the sample 101 corresponding to the drawing pattern for each drawing pattern. Specifically, it operates as follows. First, the rasterization unit 66 reads the drawing data from the storage device 140 and calculates the pattern area density ρ' within each pixel 36 for each pixel 36. Such processing is executed, for example, for each stripe area 32.

[0073] Next, the dose map creation unit 68 first virtually divides a drawing area (here, for example, the stripe area 32) into a plurality of proximity mesh areas (proximity effect correction calculation mesh areas) in a mesh form with a predetermined size. The size of the proximity mesh area is preferably set to about 1 / 10 of the influence range of the proximity effect, for example, about 1 μm. The dose map creation unit 68 reads the drawing data from the storage device 140 and calculates the pattern area density ρ of the patterns arranged in each proximity mesh area for each proximity mesh area.

[0074] Next, the dose map creation unit 68 calculates a proximity effect correction irradiation coefficient Dp(x) (correction irradiation amount) for correcting the proximity effect for each proximity mesh area. The unknown proximity effect correction irradiation coefficient Dp(x) can be defined by a threshold model for proximity effect correction similar to the conventional method using the backscattering coefficient η, the irradiation amount threshold Dth of the threshold model, the pattern area density ρ, and the distribution function g(x).

[0075] Next, the dose map creation unit 68 calculates an incident irradiation amount D(x) (dose amount) for irradiating each pixel 36. The incident irradiation amount D(x) may be calculated, for example, as a value obtained by multiplying a preset reference irradiation amount Dbase by the proximity effect correction irradiation coefficient Dp and the pattern area density ρ'. The reference irradiation amount Dbase can be defined, for example, by Dth / (1 / 2 + η). As described above, it is possible to obtain the original desired incident irradiation amount D(x) with the proximity effect corrected based on the layout of the plurality of graphic patterns defined in the drawing data.

[0076] Then, the dose map creation unit 68 creates a dose map that defines the incident irradiation amount D(x) for each pixel 36 in stripe units. The incident irradiation amount D(x) for each such pixel 36 is, by design, the incident irradiation amount D(x) scheduled to be irradiated to the control grid 27 of the pixel 36. In other words, the dose map creation unit 68 creates a dose map that defines the incident irradiation amount D(x) for each control grid 27 in stripe units. The created dose map is stored, for example, in the storage device 144.

[0077] As a dose correction process (S134), the dose correction unit 70 reads out the misregistration correction data from the storage device 144 for each drawing pattern, applies the misregistration correction data to the individual dose amounts of the respective pixels according to the drawing pattern, and corrects the dose amount. Specifically, for each control grid 27, the dose correction unit 70 distributes the incident irradiation amount D(x) scheduled to be irradiated to the target control grid 27 to the pixels at the design irradiation positions irradiated by two or more beams that form a combination according to the dose distribution ratio. Then, the dose amounts distributed to each pixel at the design irradiation position of the beam are added up. In other words, the dose correction unit 70 corrects by adding the dose amount distributed to each pixel to the dose amount of that pixel, and outputs the corrected corrected dose amount. The dose amount of the pixel to be added corresponds to the dose amount remaining after being distributed to other pixels when there is distribution to other pixels.

[0078] As an irradiation time calculation process (S140), the irradiation time calculation unit 72 calculates the irradiation time t corresponding to the dose amount of each pixel whose beam misregistration has been corrected. The irradiation time t can be calculated by dividing the dose amount D by the current density J. The irradiation time t of each pixel 36 (control grid 27) is calculated as a value within the maximum irradiation time Ttr that can be irradiated in one shot of the multi-beam 20. The irradiation time t of each pixel 36 (control grid 27) is converted into gradation value data of 0 to 1023 gradations with the maximum irradiation time Ttr being, for example, 1023 gradations (10 bits). The gradated irradiation time data is stored in the storage device 142.

[0079] As the drawing process (S142), first, the drawing control unit 74 rearranges the irradiation time data in shot order along the drawing sequence. Then, the irradiation time data is transferred to the deflection control circuit 130 in shot order. The deflection control circuit 130 outputs a blanking control signal to the blanking aperture array mechanism 204 in shot order and outputs a deflection control signal to the DAC amplifier units 132 and 134 in shot order. Then, the drawing mechanism 150 uses the multi-beam 20 in which the dose amounts to be irradiated to the respective control grids 27 are distributed to two or more beams that constitute a selected combination to draw a pattern on the sample 101. In other words, a pattern is drawn on the sample 101 using the multi-beam 20 with the corrected dose amount corrected by the addition of the dose amount in the dose correction process (S134).

[0080] As described above, according to the first embodiment, in multi-beam drawing, an increase in the dose modulation rate in the case where the positional deviation correction of each beam is performed by dose modulation can be suppressed. Therefore, an increase in the maximum irradiation time can be suppressed, and thus an increase in the drawing time can be suppressed.

[0081] As described above, the embodiments have been described with reference to specific examples. However, the present invention is not limited to these specific examples. In the above-described example, the case where each beam of the multi-beam 20 individually controls the irradiation time for each beam within the maximum irradiation time Ttr for one shot has been described. However, the present invention is not limited to this. For example, the maximum irradiation time Ttr for one shot is divided into a plurality of sub-shots with different irradiation times. Then, for each beam, a combination of sub-shots is selected so that the irradiation time for one shot is obtained from among the plurality of sub-shots. Then, by irradiating the same pixel with the combination of sub-shots selected by the same beam continuously, it is also suitable to control the irradiation time for one shot for each beam.

[0082] In addition, descriptions of parts that are not directly necessary for the description of the present invention, such as the device configuration and control method, etc., are omitted, but the required device configuration and control method can be appropriately selected and used. For example, although the description of the control unit configuration for controlling the drawing device 100 is omitted, it goes without saying that the required control unit configuration can be appropriately selected and used.

[0083] In addition, all multi-charged particle beam drawing devices and multi-charged particle beam drawing methods that include the elements of the present invention and can be appropriately designed and modified by those skilled in the art are included in the scope of the present invention.

Explanation of Reference Numerals

[0084] 20 Multi-beam 22 Hole 24 Control electrode 25 Through hole 26 Opposing electrode 27 Control grid 28 Pixel 29 Sub-irradiation region 30 Drawing region 32 Strip region 31 Substrate 33 Support base 34 Irradiation region 35 Rectangular unit region 36 Pixel 39 Irradiation position 41 Control circuit 50 Beam position deviation map creation unit 52 Specifying unit 54 Region limiting unit 56 Setting unit 58 Dose distribution rate calculation unit 60 Current density correction unit 62 Combination selection unit 64 Iterative arithmetic processing unit 66 Rasterization unit 68 Dose map creation unit 70 Dose correction unit 72 Irradiation time calculation unit 74 Drawing control unit 80 Composite map creation unit 82,86 Decision Unit 88 Combination Change Unit 100 Drawing Device 101 Specimen 102 Electron Gun Barrel 103 Drawing Chamber 105 XY Stage 110 Control Computer 112 Memory 130 Deflection Control Circuit 132,134 DAC Amplifier Unit 139 Stage Position Detector 140,142,144 Storage Device 150 Drawing Mechanism 160 Control System Circuit 200 Electron Beam 201 Electron Gun 202 Illumination Lens 203 Shaping Aperture Array Substrate 204 Blanking Aperture Array Mechanism 205 Reduction Lens 206 Limiting Aperture Substrate 207 Objective Lens 208,209 Deflector 210 Mirror 330 Membrane Region 332 Peripheral Region

Claims

1. a beam forming mechanism for forming a multi-charged particle beam; for each design grid of a plurality of design grids that are the designed irradiation positions of the multi-charged particle beam, a specifying unit that specifies a first beam in the multi-charged particle beam whose actual irradiation position is closest to the design grid of the target beam; a combination setting unit that sets a plurality of combinations each composed of two or more beams including the first beam from the multi-charged particle beam for each design grid; for each design grid and for each combination of the plurality of combinations, a dose distribution rate calculation unit that calculates a dose distribution rate for each of the two or more beams constituting the combination so that the sum of the distributed dose amounts after distribution is equal to the dose amount planned to be irradiated to the design grid; a combination selection unit that selects, for each design grid, a combination in which the dose distribution rate of the first beam is greater than the dose distribution rates of the remaining one or more beams of the two or more beams constituting the combination; a dose correction unit that corrects the dose amount distributed for each designed irradiation position of the beam by adding it to the dose amount at the irradiation position according to the dose distribution rates to the two or more beams constituting the combination selected for each design grid in the entire beam array of the multi-charged particle beam, and outputs the corrected dose amount; a drawing mechanism that draws a pattern on a sample using the multi-charged particle beam of the corrected dose amount; comprising; wherein the combination setting unit selects a second beam among the two or more beams from among a group of beams within a restricted restricted region for each combination of the plurality of combinations, a multi-charged particle beam drawing apparatus.

2. The multi-charged particle beam drawing apparatus according to claim 1, wherein the restricted region is orthogonal to a straight line connecting the design grid of the target of the first beam and the irradiation position of the first beam, and is on the side opposite to the irradiation position of the first beam with respect to a straight line passing through the design grid of the target of the first beam.

3. The multi-charged particle beam lithography apparatus according to claim 1 or 2, wherein the dose distribution rate calculation unit calculates the dose distribution rate for each of the two or more beams so that the deviation between the center of gravity based on each dose amount after distribution to the two or more beams and the corresponding design grid is within an allowable range.

4. The multi-charged particle beam lithography apparatus according to any one of claims 1 to 3, further comprising a weighting processing unit that calculates a weighted dose distribution rate by using a current density correction value for correcting the deviation of the current density for the dose distribution rate to the two or more beams for each design grid and for each combination of the plurality of combinations.

5. The multi-charged particle beam lithography apparatus further comprises a total calculation unit that calculates a total dose distribution rate obtained by summing the dose distribution rates to the two or more beams constituting the combination selected for each design grid over the entire beam array of the multi-charged particle beam for each design grid and for each irradiation position in the design of the beam, The total calculation unit calculates the total dose distribution rate obtained by summing for each irradiation position in the design of the beam over the entire beam array each time while changing the combination selected for each design grid, The combination selection unit re-selects the combination for each design grid that is the basis of the total dose distribution rate for each irradiation position in the design of the beam in the k-th (k is an integer of 2 or more) beam array when the maximum value of the total dose distribution rate for each irradiation position in the design of the beam in the k-th beam array is smaller than the maximum value of the total dose distribution rate for each irradiation position in the design of the beam in the beam arrays before the (k - 1)-th time. The multi-charged particle beam lithography apparatus according to any one of claims 1 to 4.

6. A step of forming a multi-charged particle beam; For each design grid of a plurality of design grids that are the design irradiation positions of the multi-charged particle beam, a step of identifying a first beam whose actual irradiation position is closest to the design grid of the target beam among the multi-charged particle beams; For each design grid, a step of setting a plurality of combinations composed of two or more beams including the first beam from the multi-charged particle beam; For each design grid and for each combination of the plurality of combinations, the total sum of the allocated dose amounts after allocation to each of the two or more beams constituting the combination is equal to the dose amount planned to be irradiated to the design grid. A step of calculating a dose distribution ratio to each beam of the two or more beams constituting the combination for allocating the planned dose amount to be irradiated to the design grid; For each design grid, a step of selecting a combination in which the dose distribution ratio of the first beam is greater than the dose distribution ratios of the remaining one or more beams of the two or more beams constituting the combination; According to the dose distribution ratios to the two or more beams constituting the combination selected for each design grid in the entire beam array of the multi-charged particle beam, correct by adding the dose amount allocated to each irradiation position in the design of the beam to the dose amount at the irradiation position, and output the corrected dose amount; A step of drawing a pattern on a sample using the multi-charged particle beam of the corrected dose amount; Comprising; A multi-charged particle beam drawing method of selecting a second beam out of the two or more beams from among a group of beams within a limited restricted region for each combination of the plurality of combinations.

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