Multi-beam drawing method and multi-beam drawing device

Abstract

To reduce a system error caused by the order of shots in a beam pitch cell in an intra-stripe multiple drawing system.SOLUTION: A drawing region of a substrate is divided into a plurality of stripe regions in a drawing progress direction and a vertical direction with a predetermined width and in each stripe region, drawing is performed with intra-stripe multiplicity N (N is an integer equal to or more than 2). Mutually different M kinds (M is an integer equal to or more than 2) of segments defining a plurality of pixels belonging to a plurality of cells, which is obtained by dividing the stripe region, and the order of corresponding shots are generated and the plurality of pixels in the cell is irradiated with first individual beams constituting a multi-beam using (m-1)th segment ((m) is an integer of 2≤m≤M) while deflecting the multi-beam. Thereafter, a plurality of pixels in the cell is irradiated with second individual beams different from the first individual beams using an m-th segment and the irradiation is repeatedly performed successively using the M kinds of segments, thereby drawing all the pixels in each cell with the multiplicity N.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multi-beam writing method and a multi-beam writing apparatus. [Background technology]

[0002] With the increasing integration density of LSIs, the circuit line width required for semiconductor devices is becoming finer year by year. In order to form a desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision original pattern formed as a light-shielding or reflective film on a quartz substrate is reduced and transferred onto a wafer using a reduction projection exposure apparatus. To produce such high-precision original patterns, a so-called electron beam lithography technique is used, in which a resist is exposed to light by an electron beam drawing apparatus to form a pattern.

[0003] A writing apparatus using a multi-beam can irradiate many beams at once compared to writing with a single electron beam, and therefore can greatly improve throughput. In a multi-beam writing apparatus using a blanking aperture array, which is one form of a multi-beam writing apparatus, for example, an electron beam emitted from one electron gun passes through a shaping aperture array with multiple openings to form a multi-beam consisting of multiple beamlets (individual beams). The multi-beam passes through blankers (described later) corresponding to the blanking aperture array. The blanking aperture array has an electrode pair (blanker) for individually deflecting the beams, and an opening for passing the beams is formed between the electrode pair. Blanking deflection of the passing electron beam is performed by controlling the electrode pair to the same potential or to different potentials. The individual beams deflected by the blanker are shielded, and the individual beams not deflected are irradiated onto the substrate.

[0004] In the writing process, for example, the writing area of ​​the substrate is virtually divided into multiple rectangular stripe areas of a predetermined width in the y direction, the beam array is adjusted to be positioned at the left end of the first stripe area, and writing is performed in the +X direction. After writing of the first stripe area is completed, the beam array is adjusted to be positioned at the right end of the second stripe area, and writing is performed in the -X direction.

[0005] A known high-precision writing method is multiple writing, in which the required dose is divided into multiple writing (exposure) steps to average out beam errors. In multiple writing using multiple beams, the position and current errors of each beam are averaged out, reducing errors in the dimensions and position of the written pattern. Methods of multiple writing include stripe multiple writing, in which stripes are shifted and overlapped, and intra-stripe multiple writing, in which multiple exposures are performed within one stripe.

[0006] In intra-stripe multiple writing, for example, a stripe area on a substrate is divided into multiple beam pitch cells at the inter-beam pitch size of the multi-beam. Each beam pitch cell is further divided into multiple pixels. Then, after the beam is shot to all pixels in the shot order assigned to each pixel, the beam is shot again to all pixels in the same shot order. In this example, the same location is shot twice, resulting in multiple writing with a multiplicity of 2.

[0007] For example, consider the case where one beam pitch cell consists of 10 pixels x 10 pixels = 100 pixels, and the 10 pixels in the first row of the beam pitch cell are sequentially exposed while performing stage tracking while continuously moving the stage on which the substrate is placed. 10 shots are performed, and after exposing 10 pixels, an operation is performed to return the beam position to the tracking start position (tracking reset). Repeating the exposure of 10 pixels and tracking reset, 100 pixels are exposed once each, completing the first multiplex exposure. The shot order of the 100 pixels is as shown in Figure 22. Using the same procedure, the 100 pixels of this beam pitch cell are exposed again in the same shot order, completing the second multiplex exposure.

[0008] However, if there is a systematic error according to the shot order, each beam pitch cell is shot in the same shot order in the first and second multiplexes, so there is a problem that the averaging effect of multiple drawing cannot be obtained. For example, if a tracking reset operation generates charging in the column, causing a beam position shift, and this position shift is attenuated during the exposure operation of 10 pixels during tracking, a distribution of shot position shifts will occur as shown in Figure 10. In the above example, each beam pitch cell is shot in the same shot order in the first and second multiplexes, so the averaging effect of multiple drawing cannot be obtained, and a systematic error will occur in the shot position of each pixel, causing errors in the position and line width of the drawing pattern, as shown in Figure 11.

[0009] A method is known that makes systematic errors less likely to appear by dispersing the shot order in the beam pitch cell. For example, by using a dispersed shot order in which the exposure position in the beam pitch cell during one tracking is not biased in either the X or Y direction, as shown in Fig. 23, the error distribution of the shot position can be spatially dispersed. This shot order can be generated by a random number generator. However, even if such a method is used, it is difficult to sufficiently reduce systematic errors according to the shot order, because each beam pitch cell that is exposed simultaneously with multiple beams is shot in the same shot order. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 11-274038 [Patent Document 2] JP 2011-035298 A [Patent Document 3] JP 2014-003180 A Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in consideration of the above-described conventional circumstances, and an object of the present invention is to provide a multi-beam writing method and a multi-beam writing apparatus that reduce systematic errors caused by the shot order in a beam pitch cell in an intra-stripe multiple writing method. [Means for solving the problem]

[0012] A multi-beam writing method according to one embodiment of the present invention divides a writing area of ​​a substrate on a stage onto which a beam array of a multi-beam is irradiated into a plurality of stripe areas of a predetermined width in a direction perpendicular to the writing progress direction, and also divides the area into a plurality of pixels which are irradiation unit areas per individual beam constituting the multi-beam, and writes each stripe area with a predetermined intra-stripe multiplicity N (N is an integer of 2 or more), in which M different types (M is an integer of 2 or more) of segments are generated, which define a shot order corresponding to a plurality of pixels belonging to each of a plurality of cells into which the stripe area is divided, and while deflecting the multi-beam, irradiates a plurality of pixels within the cell using the m-1th segment (m is an integer of 2≦m≦M), and then irradiates a plurality of pixels within the cell using the m-th segment with a second individual beam different from the first individual beam, and repeats the irradiation using the M types of segments in sequence, thereby writing all pixels within each cell with the multiplicity N.

[0013] A multi-beam writing apparatus according to one aspect of the present invention includes a movable stage on which a substrate to be written is placed, a multi-beam forming unit that forms a multi-beam, a memory unit that stores writing data, M types (M is an integer of 2 or more) of different segments that are generated by defining a shot order corresponding to a plurality of pixels that belong to each of a plurality of cells obtained by dividing a writing area of ​​the substrate by a predetermined width in a direction perpendicular to a writing progress direction, and a writing control unit that controls writing using the writing data and the segments, wherein the pixel is an irradiation unit area per individual beam that constitutes the multi-beam, and the writing control unit controls to irradiate a plurality of pixels in the cell with a first individual beam of the multi-beam using the m-1-th segment (m is an integer of 2≦m≦M) while deflecting the multi-beam, and then irradiate a plurality of pixels in the pitch cell with a second individual beam different from the first individual beam using the m-th segment, so as to write each of the plurality of stripe areas with a predetermined intra-stripe multiplicity N (N is an integer of 2 or more). Effect of the Invention

[0014] According to the present invention, in the intra-stripe multiple writing method, systematic errors caused by the shot order in the beam pitch cell can be reduced. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a multi-charged particle beam writing apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a plan view of a shaping aperture member. [Diagram 3] FIG. 11 is a diagram illustrating an example of a drawing operation. [Figure 4] 1A and 1B are diagrams illustrating an example of a multi-beam irradiation area and a pixel to be drawn. [Diagram 5] FIG. 11 is a diagram illustrating an example of a drawing operation. [Figure 6] FIG. 11 is a diagram illustrating an example of a drawing operation. [Figure 7]13(a) to 13(c) are explanatory diagrams of multiple drawing within a stripe. [Figure 8] 13(a) to 13(c) are explanatory diagrams of multiple drawing within a stripe. [Figure 9] 13(a) to 13(c) are explanatory diagrams of multiple drawing within a stripe. [Figure 10] FIG. 13 is a diagram showing a deviation in shot position. [Figure 11] FIG. 13 is a diagram showing an example of systematic errors according to shot order. [Figure 12] FIG. 1 is a diagram illustrating an example of a beam array. [Figure 13] 5(a) to 5(d) are explanatory diagrams of the intra-stripe multiple writing method according to the embodiment. [Figure 14] 5(a) to 5(d) are explanatory diagrams of the intra-stripe multiple writing method according to the embodiment. [Figure 15] FIG. 13 is a diagram showing an example of a segment that defines a shot order and a shot position. [Figure 16] 11(a) to 11(d) are diagrams illustrating the shot order within each pitch cell. [Figure 17] FIG. 1 is a diagram illustrating an example of a beam array. [Figure 18] FIG. 13 is a diagram showing an example of a segment that defines a shot order and a shot position. [Figure 19] 5(a) to 5(c) are explanatory diagrams of the intra-stripe multiple writing method according to the embodiment. [Figure 20] 5(a) to 5(c) are explanatory diagrams of the intra-stripe multiple writing method according to the embodiment. [Figure 21] FIG. 13 is a diagram showing an example of a segment that defines a shot order and a shot position. [Figure 22] FIG. 13 is a diagram for explaining the shot order within a pitch cell. [Diagram 23] FIG. 13 is a diagram for explaining the shot order within a pitch cell. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiment, a configuration using an electron beam as an example of a beam will be described. However, the beam is not limited to an electron beam, and other charged particle beams such as an ion beam may be used.

[0017] FIG. 1 is a schematic diagram of a drawing apparatus according to an embodiment. As shown in FIG. 1, the drawing apparatus 100 includes a drawing unit 100W and a control unit 100C. The drawing apparatus 100 is an example of a multi-charged particle beam drawing apparatus. The drawing unit 100W includes an electron lens barrel 102 and a drawing chamber 103. In the electron lens barrel 102, an electron gun 201, an illumination lens 202, a shaping aperture member 203, a blanking aperture array substrate 204, a reduction lens 205, a limiting aperture member 206, an objective lens 207, and deflectors 208 and 209 are arranged, which constitute a multi-beam generating mechanism. As will be described later, the deflector 208 is used for stage tracking deflection, and the deflector 209 is used for positioning the multi-beam to the pixel. Note that a single deflector having the functions of both the deflector 209 and the deflector 208 may be installed, and both the stage tracking deflection and the positioning of the multi-beam to the pixel may be performed by the single deflector.

[0018] An XY stage 105 is placed in the pattern writing chamber 103. A substrate 101 to be patterned is placed on the XY stage 105. The substrate 101 is, for example, a mask blank or a semiconductor substrate (silicon wafer).

[0019] A mirror 210 for position measurement is disposed on the XY stage 105 .

[0020] The control unit 100C has a control computer 110, a deflection control circuit 130, a stage position detector 139, and a memory unit 140. Drawing data is input from the outside and stored in the memory unit 140. Also, information on segments, which will be described later, is stored in the memory unit 140. The drawing data usually defines information on a plurality of graphic patterns to be drawn. Specifically, a graphic code, coordinates, size, etc. are defined for each graphic pattern.

[0021] The control computer 110 has an area ratio calculation unit 111, an irradiation amount calculation unit 117, and a writing control unit 118. Each unit of the control computer 110 may be configured with hardware such as an electric circuit, or may be configured with software such as a program that executes these functions, or may be configured with a combination of hardware and software.

[0022] The stage position detector 139 irradiates a laser, receives the reflected light from a mirror 210, and detects the position of the XY stage 105 by laser interference.

[0023] Fig. 2 is a conceptual diagram showing the configuration of the shaping aperture member 203. As shown in Fig. 2, the shaping aperture member 203 has m vertical (y direction) rows x n horizontal (x direction) columns (m, n ≥ 2) apertures 22 formed at a predetermined arrangement pitch. Each aperture 22 is formed as a rectangle with the same dimensions. Each aperture 22 may be a circle with the same outer diameter. Multi-beams 20a to 20e are formed by portions of the electron beam 200 passing through each of the multiple apertures 22.

[0024] In the blanking aperture array substrate 204, passage holes are formed in accordance with the arrangement positions of the openings 22 of the shaping aperture member 203. A pair of two electrodes (blankers) is arranged in each passage hole. The electron beams passing through each passage hole are independently controlled to a beam-on or beam-off state by a voltage applied to the blanker. When the beam is on, the opposing electrodes of the blanker are controlled to the same potential, and the blanker does not deflect the beam. When the beam is off, the opposing electrodes of the blanker are controlled to different potentials, and the blanker deflects the beam. In this way, the multiple blankers perform blanking deflection of the corresponding beams among the multi-beams that have passed through the multiple openings 22 of the shaping aperture member 203.

[0025] An electron beam 200 emitted from an electron gun 201 (emitter) illuminates the entire shaping aperture member 203 almost perpendicularly via an illumination lens 202. The electron beam 200 illuminates an area including all of the apertures 22. The electron beam 200 passes through the multiple apertures 22 of the shaping aperture member 203, thereby forming multiple electron beams (multi-beams) 20a to 20e, each having, for example, a rectangular shape.

[0026] The multiple beams 20a to 20e pass through the corresponding blankers of the blanking aperture array substrate 204. Each blanker individually deflects the electron beam passing through. The multiple beams 20a to 20e that have passed through the blanking aperture array substrate 204 are reduced in size by the reduction lens 205, and ideally pass through the same point on the limiting aperture member 206 with all beams in the on state. The beam trajectories are adjusted by an alignment coil (not shown) so that this point is located within the central opening of the limiting aperture member 206.

[0027] Here, the beam controlled to the beam-off state is deflected by the blanker of the blanking aperture array substrate 204, and the beam trajectory passes outside the opening of the limiting aperture member 206, and is therefore blocked by the limiting aperture member 206. On the other hand, the beam controlled to the beam-on state is not deflected by the blanker, and passes through the opening of the limiting aperture member 206. In this way, the beam is turned on and off by the blanking control of the blanking aperture array substrate 204.

[0028] The limiting aperture member 206 blocks each beam deflected by the blankers to be in a beam-off state. Then, a multi-beam for one shot is formed by the beams that pass through the limiting aperture member 206 and are formed from when the beam is turned on until when it is turned off.

[0029] The multi-beams passing through the limiting aperture member 206 are focused by the objective lens 207 and projected onto the substrate 101 at a desired reduction ratio. Deflectors 208 and 209 can each deflect the entire multi-beam. The deflection amounts of the deflectors 208 and 209 are independently controlled. The irradiation positions of the multi-beams on the substrate 101 are controlled by the deflectors 208 and 209.

[0030] During drawing, the XY stage 105 is controlled to move continuously at a constant speed. At this time, the deflector 208 controls the irradiation position of the beam to follow the movement of the XY stage 105. The multiple beams that are simultaneously irradiated are ideally aligned at a pitch that is the arrangement pitch of the multiple openings of the shaping aperture member 203 multiplied by the desired reduction ratio described above. During drawing, the multiple beams perform a raster scan drawing operation by exposing all of the pixels defined on the substrate 101 through position control by deflection. When the beam is on a pixel that does not include a pattern, the beam is controlled to be beam-off through blanking control.

[0031] Fig. 3 is a conceptual diagram for explaining the drawing operation in this embodiment. As shown in Fig. 3, the drawing region 30 on the substrate 101 is virtually divided into a plurality of rectangular stripe regions 32 with a predetermined width in the y direction (first direction), for example, and the longitudinal direction (x direction or second direction) of the stripe regions 32 perpendicular to the y direction becomes the drawing progress direction. When drawing these stripe regions 32, first, the XY stage 105 is moved and adjusted so that an irradiation region (beam array) 34 that can be irradiated by one multi-beam irradiation is positioned at the left end of the first stripe region 32, and drawing is started.

[0032] When drawing the first stripe region 32, the XY stage 105 is continuously moved in the -x direction at a constant speed, thereby drawing on the substrate 101 in the +x direction relatively. After drawing of the first stripe region 32 is completed, the XY stage 105 stops. Next, the stage position is moved in the -y direction by the stripe width, and adjusted so that the beam array 34 is positioned at the right end of the second stripe region 32. Next, the XY stage 105 is continuously moved in the +x direction at a constant speed, thereby drawing on the substrate 101 in the -x direction.

[0033] In the third stripe region 32, drawing is performed in the +x direction, and in the fourth stripe region 32, drawing is performed in the -x direction. It is also possible to draw each stripe region 32 in the same direction, but in this case, an operation of returning the stage position after drawing is added, which increases the drawing time.

[0034] Fig. 4 is a diagram showing an example of a multi-beam irradiation region and a pixel to be written. In Fig. 4, a plurality of control grids 27 are set in the stripe region 32, for example, arranged in a lattice shape with a pitch of the beam size of the multi-beam on the surface of the substrate 101. For example, an arrangement pitch of about 10 nm is preferable.

[0035] The control grids 27 are ideal irradiation positions (ideal positions) where there is no positional deviation of the multi-beam. The arrangement pitch of the control grids 27 is not limited to the same size as the beam size, and may be any size that can be controlled as the deflection position of the deflector 209. Then, a plurality of pixels 36 are set that are virtually divided into a mesh shape with the same size as the arrangement pitch of the control grids 27 and centered on each control grid 27.

[0036] Each pixel 36 is an irradiation unit area per one beam (individual beam) of the multi-beam. The example of Fig. 4 shows a case where the drawing area of ​​the substrate 101 is divided in the y direction into multiple stripe areas 32 with the same width as the size of the beam array 34 (drawing field) that can be irradiated by one irradiation of the multi-beam 20. The size of the beam array 34 in the x direction is a value obtained by multiplying the beam pitch of the multi-beam in the x direction by the number of beams in the x direction. The size of the beam array 34 in the y direction is a value obtained by multiplying the beam pitch of the multi-beam in the y direction by the number of beams in the y direction.

[0037] FIG. 4 shows an example of a multi-beam having 8×8 rows. The multi-beam is not limited to 8×8 rows, and 512×512 rows or the like can be used as appropriate. In addition, in the beam array 34, a plurality of pixels 28 (beam drawing positions) that can be irradiated with one shot of the multi-beam are shown as black pixels. In other words, the pitch between adjacent pixels 28 is the pitch between each beam of the multi-beam in the design. Here, an area having the size of the beam pitch is defined as a pitch cell 29. In the example of FIG. 4, each pitch cell 29 is composed of 4×4 pixels.

[0038] When drawing each stripe region 32, the deflectors 208 and 209 control the beam position in parallel with the continuous movement of the XY stage 105 in the x direction, so that all the pixels on the substrate 101 are exposed the same number of times. At this time, the deflector 208 controls the deflection of the beam position so that the beam during exposure follows the continuous movement of the substrate 101 (stage tracking). The deflector 209 controls the switching of the exposure pixels. When switching the exposure pixels, the deflector 209 deflects the beam array within the range of the pitch cell 29.

[0039] 5 shows an example in which four multibeams are present in the x direction and are arranged at intervals four times the beam size. There may be four or different rows of multibeams in the y direction, but since the multibeams in each row draw an area of ​​the beam pitch width corresponding to the width of the sub-irradiation area 29, it may be considered that FIG. 5 shows a certain row of beam arrays among multiple rows of multibeam arrays and the pixels to be exposed by these.

[0040] In the example of Fig. 5, while the stage moves continuously in the -x direction, each beam exposes one row of four pixels in the y direction, and then the beam moves in the +x direction to expose another row, and this process is repeated. As described above, while each beam exposes one row of four pixels, the deflector 208 performs a stage tracking operation to perform continuous deflection following the movement of the stage so as to fix the position of the beam array on the substrate 101 in the x direction, while the deflector 209 adds a deflection to switch the exposed pixel in the y direction. A large movement of the beam in the +x direction after exposing one row is performed by a tracking reset operation that stops stage tracking and returns the deflection amount of the deflector 208 to the deflection amount at the start of stage tracking.

[0041] In FIG. 5, pixel groups are separated by beam pitch width regions, but when the beam moves to another column, it moves to a region of another pitch width. This movement is performed by controlling the amount of deflection applied in the x direction by the deflector 209. That is, the deflector 208 performs tracking deflection, and the deflector 209 performs deflection within the pitch cell 29 to perform a raster scan operation. In the exposure process shown in FIG. 5, only some of the pixels are exposed in the region of the third pitch width from the left, but all the pixels are exposed in the region of the pitch width to the right of that by repeating the above process. That is, immediately after the start of exposure, the exposure of three beam pitch regions is incomplete, so the drawing operation is started in advance from the region to the left of the drawing region so that the actual drawing region does not enter this portion.

[0042] In this example, during the tracking period, a plurality of pixels are sequentially exposed in the +y direction, but this is not limited to this. For example, as shown in FIG. 6, it is also possible to sequentially expose the pixels in the +x direction.

[0043] In multi-beam writing, in order to average out errors in position and current amount for each beam, it is preferable to perform multiple writing in which the required irradiation amount is divided into multiple writing (exposure) steps.

[0044] A technique known as "multiple drawing within a stripe" is known in which the beam array is divided into multiple regions of the same predetermined width in the x direction (the drawing progress direction), and while drawing one stripe region, the beams in each divided region draw the same location.

[0045] For example, when the shot order assigned to each pixel in the beam pitch region is repeated twice, as shown in Fig. 7(a), the beam array 34 is divided into two regions (sub-beam arrays), a block region R1 and a block region R2, and the pixels in the stripe 32 are written once with the beam belonging to region R1 and once with the beam belonging to region R2. As shown in Fig. 7(b) and Fig. 7(c), the region shown with diagonal lines in the figure is irradiated with the beam of region R1 and then with the beam of region R2. Therefore, one region is written twice, so the multiplicity is 2.

[0046] For example, in Figures 5 and 6, 4x4 pixels in the beam pitch area are exposed once with one of the four multibeams a, b, c, and d, but the right half of the four multibeams in one row, a and b, expose the 4x4 pixels once each. Next, the left half of the multibeams, c and d, expose the pixels once each. In Figures 5 and 6, each of the four multibeams a, b, c, and d exposes four of the 4x4 pixels in the beam pitch area to perform drawing with a multiplicity of 1, but if the four multibeams a, b, c, and d are divided into two block areas, that is, multibeams a, b and c, d, and drawing with a multiplicity of 2 is performed, each of the four multibeams a, b, c, and d exposes eight of the 4x4 pixels in the beam pitch area.

[0047] A specific example of a writing method using intra-stripe multiple writing will be described. For example, as shown in FIG. 8(a), a beam array 34 is divided into two block regions R1 and R2. The beam array has a side of 80 μm, and the width of the stripe region 32 is also 80 μm. The pitch cell 29 obtained by dividing the stripe region by the inter-beam pitch size of the multi-beam has a side of 160 nm. The shot size (size of individual beam) is 16 nm. The pitch cell consists of 10 pixels x 10 pixels = 100 pixels.

[0048] Fig. 8 focuses on pitch cell 29, which is one of the pitch cells, and explains how the 10 x 10 pixels in this pitch cell are exposed by beam array 34. Multiple tracking start positions are set in stripe 32. The position of the right end of the pitch cell where the rightmost beam of the beam array in stripe 32 is located at the start of tracking is indicated by a vertical line in Fig. 8. One or more pitch cells are included between the tracking start point and the next start point. In the example of Fig. 8, multiple pitch cells are included.

[0049] In this case, the inter-beam pitch size does not mean the pitch size between adjacent beams arranged in hardware, but the distance between the beams of the multi-beams used for drawing. For example, in order to limit the total amount of current, if every other beam defined in hardware is used (others are OFF), the inter-beam pitch size becomes twice the pitch defined in hardware.

[0050] While performing stage tracking while continuously moving the XY stage 105, 10 pixels in the first row of the pitch cell are sequentially exposed using one beam in the block region R1. After 10 shots (shot 1 to shot 10), a tracking reset is performed, that is, the beam position in the deflection coordinate system is returned to the tracking start position. At this time, the beam position on the substrate 101 moves to a pitch cell that is to the right of the position at the time of tracking reset. In other words, on the substrate 101, the beam position moves in the +X direction and is positioned within another pitch cell. Since the multiple beams are deflected collectively by the deflector 208, each beam of the multiple beams moves to the right by the same number of pitch cells with the same movement amount by tracking reset.

[0051] As shown in Fig. 8(b), the next stage tracking is started, and 10 pixels in the second row of the pitch cell are sequentially exposed using another beam in the block region R1. After 10 shots, that is, shots 11 to 20, a tracking reset is performed.

[0052] In this way, the exposure of 10 pixels and the drawing operation by tracking reset are repeated for each stage tracking, so that 100 pixels of the target pitch cell 29 are exposed once each by the multiple beams of the block region R1, as shown in Fig. 8(c). In other words, while the block region R1 passes through the target pitch cell 29, the 100 pixels of the pitch cell 29 are exposed once each, and the exposure of the block region R1 with the multiple beams at multiplicity 1 (first multiplex) is completed. The shot order of the 100 pixels is as shown in Fig. 22.

[0053] The drawing operation continues, and the target pitch cell 29 is exposed with the beam in block region R2. Due to a tracking reset after the completion of the exposure with multiplicity 1 by the beam in region R1, the target pitch cell 29 is now positioned with the beam in region R2. Therefore, as shown in FIG. 9(a), one beam in block region R2 is used to sequentially expose 10 pixels in the first row of the pitch cell. After 10 shots, that is, shots 101 to 110, tracking is reset. The 10 pixels in the first row have been exposed for the second time (second pass).

[0054] As shown in Fig. 9(b), the next stage tracking is started, and 10 pixels in the second row of the pitch cell are sequentially exposed using another beam in the block region R2. After 10 shots, that is, shots 111 to 120, the tracking is reset.

[0055] Exposure of 10 pixels and tracking reset while performing stage tracking are repeated, and 100 pixels of the pitch cell are exposed once by the multiple beams of the block region R2, as shown in Fig. 9(c). In other words, while the block region R2 passes through the target pitch cell 29, 100 pixels of the pitch cell 29 are exposed once, and exposure of the block region R2 with multiple beams at multiplicity 1 (second multiplex) is completed.

[0056] With this drawing process, each of the 100 pixels in the pitch cell is exposed twice, resulting in a multiplicity of 2.

[0057] In the examples shown in Figures 8(a) to 8(c) and Figures 9(a) to 9(c), the shot order is monotonous, such as shooting the pixels in the first row of one pitch cell from left to right, and then shooting the pixels in the second row from left to right. If beam drift occurs immediately after tracking reset, a shot position shift occurs as shown in Figure 10. In other words, if charging occurs in the column due to the tracking reset operation, causing a beam position shift, and this position shift is attenuated during the exposure operation of 10 pixels during tracking, a distribution of shot position shifts as shown in Figure 10 occurs.

[0058] In the above example, since each pitch cell is shot in the same shot order in the first and second multiplexes, systematic errors occur in the shot positions of each pixel, as shown in FIG. 11, and errors occur in the position and line width of the drawn pattern.

[0059] By dispersing the shot order in the beam pitch cell in terms of position, systematic errors can be made less likely to appear. For example, by using a dispersed shot order in which the exposure position in the beam pitch cell during one tracking is not biased in either the x or y direction as shown in FIG. 23, the error distribution of the shot position can be spatially dispersed. Hereinafter, such a shot order is called a random shot order. A random shot order can be generated by a random number generator. In multi-beam writing, the positions of the multiple beams are collectively controlled by the deflector 209, so that each pitch cell exposed simultaneously is shot in the same shot order, and systematic errors according to the shot order may appear, which has been an obstacle to improving writing accuracy.

[0060] The inventors have discovered that in the intra-stripe multiple writing method, by assigning different shot orders to multiple pitch cells in a stripe region, systematic errors caused by shot orders can be averaged out and writing accuracy can be improved.

[0061] An example of such a writing method will be described with reference to Fig. 12 to Fig. 14. For convenience of explanation, as shown in Fig. 12, a beam array consisting of 8 × 1 individual beams (beamlets) is used to perform multiple writing within a stripe with a multiplicity of 2. The pitch cell is assumed to consist of 2 pixels × 2 pixels = 4 pixels.

[0062] First, as shown in Fig. 13(a), the beam array is moved in the y direction while performing stage tracking, and two pixels on the left side of the pitch cell are shot. Fig. 13(a) shows the state where individual beams a and b have shot two pixels on the left side of pitch cells P2 and P1. The numbers inside the pixels indicate the number of times the pixel has been shot.

[0063] The tracking is reset and the beam drawing position is aligned with the bottom right pixel of each pitch cell. As shown in Fig. 13(b), while tracking the stage, the beam array is moved in the y direction to shoot the two pixels on the right side of the pitch cell.

[0064] FIG. 13(b) shows a state in which individual beams a and b shoot two pixels on the right side of pitch cells P4 and P3, and individual beams c and d shoot two pixels on the right side of pitch cells P2 and P1.

[0065] The tracking is reset and the beam drawing position is aligned with the upper left pixel of each pitch cell. As shown in Fig. 13(c), while tracking the stage, the beam array is moved in the x direction to shoot the upper two pixels of the pitch cell.

[0066] Figure 13(c) shows a state in which individual beams a and b shoot the upper two pixels of pitch cells P6 and P5, individual beams c and d shoot the upper two pixels of pitch cells P4 and P3, and individual beams A and B shoot the upper two pixels of pitch cells P2 and P1.

[0067] The tracking is reset and the beam drawing position is aligned with the bottom left pixel of each pitch cell. As shown in Fig. 13(d), while tracking the stage, the beam array is moved in the x direction to shoot the lower two pixels of the pitch cell.

[0068] Figure 13(d) shows a state in which individual beams a and b shoot the two pixels below pitch cells P8 and P7, individual beams c and d shoot the two pixels below pitch cells P6 and P5, individual beams A and B shoot the two pixels below pitch cells P4 and P3, and individual beams C and D shoot the two pixels below pitch cells P2 and P1.

[0069] As a result, in each of the pitch cells P1 and P2, four pixels are exposed twice.

[0070] The tracking is reset and the beam drawing position is aligned with the bottom left pixel of each pitch cell. As shown in Fig. 14(a), while tracking the stage, the beam array is moved in the y direction and the two pixels on the left side of the pitch cell are shot.

[0071] Figure 14(a) shows a state in which individual beams a and b shoot the two pixels to the left of pitch cells P10 and P9, individual beams c and d shoot the two pixels to the left of pitch cells P8 and P7, individual beams A and B shoot the two pixels to the left of pitch cells P6 and P5, and individual beams C and D shoot the two pixels to the left of pitch cells P4 and P3.

[0072] As a result, in pitch cells P3 and P4, four pixels are exposed twice each.

[0073] The tracking is reset and the beam drawing position is aligned with the bottom right pixel of each pitch cell. As shown in Fig. 14(b), while tracking the stage, the beam array is moved in the y direction to shoot the two pixels on the right side of the pitch cell.

[0074] Figure 14(b) shows a state in which individual beams a and b shoot the two pixels to the right of pitch cells P12 and P11, individual beams c and d shoot the two pixels to the right of pitch cells P10 and P9, individual beams A and B shoot the two pixels to the right of pitch cells P8 and P7, and individual beams C and D shoot the two pixels to the right of pitch cells P6 and P5.

[0075] As a result, in pitch cells P5 and P6, four pixels are exposed twice each.

[0076] The tracking is reset and the beam drawing position is aligned with the upper left pixel of each pitch cell. As shown in Fig. 14(c), while tracking the stage, the beam array is moved in the x direction to shoot the upper two pixels of the pitch cell.

[0077] Figure 14(c) shows a state in which individual beams a and b shoot the upper two pixels of pitch cells P14 and P13, individual beams c and d shoot the upper two pixels of pitch cells P12 and P11, individual beams A and B shoot the upper two pixels of pitch cells P10 and P9, and individual beams C and D shoot the upper two pixels of pitch cells P8 and P7.

[0078] As a result, in pitch cells P7 and P8, four pixels are exposed twice each.

[0079] The tracking is reset and the beam drawing position is aligned with the bottom left pixel of each pitch cell. As shown in Fig. 14(d), while tracking the stage, the beam array is moved in the x direction to shoot the lower two pixels of the pitch cell.

[0080] Figure 14(d) shows a state in which individual beams a and b shoot the two pixels below pitch cells P16 and P15, individual beams c and d shoot the two pixels below pitch cells P14 and P13, individual beams A and B shoot the two pixels below pitch cells P12 and P11, and individual beams C and D shoot the two pixels below pitch cells P10 and P9.

[0081] As a result, in each of the pitch cells P9 and P10, four pixels are exposed twice.

[0082] When the number of tracking times required for irradiation of one pitch cell is M (M is an integer of 2 or more), M segments each defining a shot order corresponding to a plurality of different pixels in the pitch cell are prepared and stored in the storage unit 140. A segment defines the pixels to be shot in one pitch cell during one tracking and the shot order. In the example shown in Fig. 13 and Fig. 14, the number of tracking times required for irradiation of one pitch cell is four, and four segments 1 to 4 as shown in Fig. 15 are prepared, and different segments are repeatedly assigned in order for each tracking to perform drawing.

[0083] When a segment is regarded as a two-dimensional matrix in which pixels to which a shot is assigned are 1 and other pixels are 0, each element of the sum of the matrices corresponding to segments 1 to 4 coincides with the intra-stripe multiplicity.

[0084] The four pixels of pitch cells P1 and P2 are exposed in the order shown in Fig. 16(a) - that is, drawing based on segment 1, drawing based on segment 2, drawing based on segment 3, and drawing based on segment 4 are performed in that order.

[0085] The four pixels of pitch cells P3 and P4 are exposed in the order shown in Fig. 16(b) - that is, drawing based on segment 2, drawing based on segment 3, drawing based on segment 4, and drawing based on segment 1 are performed in that order.

[0086] The four pixels of pitch cells P5 and P6 are exposed in the order shown in Fig. 16(c) - that is, drawing based on segment 3, drawing based on segment 4, drawing based on segment 1, and drawing based on segment 2 are performed in that order.

[0087] The four pixels of pitch cells P7 and P8 are exposed in the order shown in Fig. 16(d) - that is, drawing based on segment 4, drawing based on segment 1, drawing based on segment 2, and drawing based on segment 3 are performed in that order.

[0088] In this way, by applying different segments to each tracking, different shot orders are assigned to multiple pitch cells in a stripe region, and systematic errors caused by the shot order can be reduced.

[0089] In performing such a drawing process, the area ratio calculation unit 111 reads out drawing data from the storage unit 140, and calculates, for each pixel 36, the pattern area density ρ(x) within the pixel 36 to create an area ratio map. This process is performed, for example, for each stripe region 32.

[0090] Moreover, the area ratio calculation unit 111 virtually divides the drawing region (e.g., stripe region 32) into a plurality of proximity mesh regions (mesh regions for calculating proximity effect correction) in a mesh shape with a predetermined size. The size of the proximity mesh region is preferably set to about 1 / 10 of the range of influence of the proximity effect, for example, about 1 μm. The area ratio calculation unit 111 reads the drawing data from the storage unit 140, and calculates, for each proximity mesh region, the pattern area density ρ' of the pattern arranged in the proximity mesh region.

[0091] Next, the area ratio calculation unit 111 calculates a proximity effect correction coefficient Dp(x) (corrected dose) for correcting the proximity effect for each proximity mesh region. The unknown proximity effect correction dose coefficient Dp(x) can be defined by a threshold model for proximity effect correction similar to the conventional method, using a backscattering coefficient η, a dose threshold Dth of a threshold model, a pattern area density ρ', and a distribution function g(x).

[0092] The irradiation amount calculation unit 117 calculates, for each pixel 36, an incident irradiation amount D(x) (dose amount, exposure amount) for irradiating the 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 a pattern area density ρ(x) and a proximity effect correction coefficient Dp(x). The reference irradiation amount Dbase can be defined, for example, as Dth / (1 / 2+η).

[0093] The dose calculation unit 117 calculates the dose of each beam (individual beam) of the multiple beams for each shot. For example, the dose calculation unit 117 divides the incident dose D(x) of a pixel irradiated with an individual beam by the multiplicity to calculate the dose per pass.

[0094] The writing control unit 118 converts the dose of each beam calculated by the dose calculation unit 117 into irradiation time data and transfers it to the deflection control circuit 130. The deflection control circuit 130 controls the on / off of each blanker of the blanking aperture array substrate 204 based on the irradiation time data. The deflection control circuit 130 also controls the deflection amounts of the deflectors 208 and 209 so as to achieve the shot order shown in Figs. 13 and 14.

[0095] As another example of a writing method for allocating different shot orders to a plurality of pitch cells in a stripe region in the intra-stripe multiple writing method, a case where there are many pixels in a pitch cell will be described with reference to FIGS.

[0096] As shown in Fig. 17, a beam array consisting of 3 × 18 individual beams (beamlets) is used to perform multiple drawing within a stripe with a multiplicity of 2. The pitch cell consists of 3 pixels × 3 pixels = 9 pixels.

[0097] The number of tracking times required for irradiation of one pitch cell is six. Segments 1 to 6 as shown in Fig. 18 are prepared in advance and stored in the storage unit 140. When the segment is regarded as a two-dimensional matrix in which pixels to which a shot is assigned are 1 and other pixels are 0, the value of each element of the sum of segments 1 to 6 is 2 (=intra-stripe multiplicity).

[0098] First, as shown in Fig. 19(a), while performing stage tracking, three pixels of the pitch cell are shot in the shot order by segment 1. Fig. 19(a) shows a state in which individual beams a, b, and c have shot three pixels in pitch cells P3, P2, and P1. After shooting the three pixels, tracking is reset.

[0099] Stage tracking is resumed, and as shown in Fig. 19(b), three pixels of the pitch cell are shot in the shot order of segment 2. Fig. 19(b) shows a state in which individual beams a to f have shot three pixels in pitch cells P6 to P1. After the three pixels have been shot, tracking is reset.

[0100] Stage tracking is resumed, and as shown in Fig. 19(c), three pixels of the pitch cell are shot in the shot order of segment 3. Fig. 19(c) shows a state in which individual beams a to i have shot three pixels in pitch cells P9 to P1. After the three pixels have been shot, tracking is reset.

[0101] Stage tracking is resumed, and three pixels of the pitch cell are shot in the shot order of segment 4, as shown in Fig. 20(a). Fig. 20(a) shows a state in which individual beams a to i and individual beams A to C have shot three pixels in pitch cells P12 to P1. After the three pixels have been shot, tracking is reset.

[0102] Stage tracking is resumed, and three pixels of the pitch cell are shot in the shot order of segment 5, as shown in Fig. 20(b). Fig. 20(b) shows a state in which individual beams a to i and individual beams A to F have shot three pixels in pitch cells P15 to P1. After the three pixels have been shot, tracking is reset.

[0103] Stage tracking is resumed, and as shown in Fig. 20(c), three pixels of the pitch cell are shot in the shot order of segment 6. Fig. 20(c) shows a state in which individual beams a to i and individual beams A to I have shot three pixels in pitch cells P18 to P1.

[0104] As a result, in the pitch cells P1 to P3, nine pixels are exposed twice each. In this example, each segment has a complex shot order that includes both x-direction deflection and y-direction deflection, which can further improve the effect of reducing systematic errors caused by multiple writing.

[0105] If there is systematic drift depending on the shot deflection direction, it is preferable to prepare a segment with a reversed shot order. For example, deflector drift is known in which the shot position drifts in the -x direction from the designed position when the beam is deflected in the +x direction, and the shot position drifts in the +x direction from the designed position when the beam is deflected in the -x direction.

[0106] In this case, as shown in FIG. 21, by using segments in which the same pixels are shot but the shot order is reversed, the error can be cancelled out and the positional accuracy of the writing pattern can be further improved.

[0107] The number of segments is equal to the number of tracking times M required for irradiation of one pitch cell, and when the pixels to which shots are assigned are regarded as a two-dimensional matrix in which the pixels other than the shots are 0, as shown in Fig. 18, the sum of the elements of the M segments should match the intra-stripe multiplicity. As long as this constraint is satisfied, there are no other constraints on the shot order, and the shot order may be random using random numbers.

[0108] In the above embodiment, different segments may be used for each stripe region. For example, in the example shown in Fig. 17 to Fig. 20, segments 1 to 6 are used for writing the first stripe region. Segments 7 to 12, which are different from segments 1 to 6, are used for writing the second stripe region. By using different segments for each stripe region, systematic errors due to shot order can be reduced not only in the x direction but also in the y direction.

[0109] Systematic errors due to the shot order in the y direction can also be reduced by changing the application order of segments for each stripe region. For example, in the examples shown in Figs. 17 to 20, in the first stripe region, writing is performed repeatedly in the order of segment 1, segment 2, segment 3, segment 4, segment 5, and segment 6. In the second stripe region, writing is performed repeatedly in the order of segment 2, segment 4, segment 5, segment 1, segment 6, and segment 3. In the third stripe region, writing is performed repeatedly in the order of segment 5, segment 1, segment 6, segment 3, segment 2, and segment 4.

[0110] In the above embodiment, an example was shown in which the timing of switching the beam irradiating the beam pitch cell and the timing of the tracking reset correspond one-to-one, but the present invention is not limited to this configuration. For example, a tracking reset may be inserted between each shot when an individual beam shoots each pixel in the beam pitch cell. In other words, a tracking reset may be performed for each shot. In this case, the area in which the segment is generated is a cell defined by the maximum area irradiated by one individual beam.

[0111] The present invention is not limited to the above-mentioned embodiment, and the components can be modified without departing from the gist of the present invention. For example, the above-mentioned embodiment describes the case where the multiplicity in the stripe is 2, but the multiplicity is not limited to 2 and may be 4, 8, etc. The above-mentioned embodiment describes a charged particle multi-beam device that controls a charged particle beam with a blanking aperture array, but the present invention can be similarly applied to a multi-charged particle beam drawing device that does not use a blanking aperture and a multi-laser beam drawing device that uses a digital micromirror device (DMD). In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-mentioned embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0112] 100 drawing device 110 Control computer 111 Area ratio calculation part 117 Irradiance calculation section 118 Drawing control section

Claims

1. A method for drawing a pattern on a substrate on a stage onto which a beam array of a multi-beam is irradiated, the method further comprising dividing the pattern into a plurality of stripe regions of a predetermined width in a direction perpendicular to a direction in which the pattern is to be drawn, and dividing the pattern into a plurality of pixels which are irradiation unit regions for individual beams constituting the multi-beam, and drawing each of the stripe regions with a predetermined intra-stripe multiplicity N (N is an integer of 2 or more), the method comprising the steps of: generating M types (M is an integer of 2 or more) of different segments each of which defines a shot order corresponding to a plurality of pixels belonging to each of a plurality of cells obtained by dividing the stripe region; irradiating a plurality of pixels in the cell with a first individual beam using an m-1-th segment (m is an integer of 2≦m≦M) while deflecting the multi-beam, and then irradiating a plurality of pixels in the cell with a second individual beam different from the first individual beam using an m-th segment; A multi-beam writing method in which all pixels in each cell are written with the multiplicity N by repeating irradiation using the M types of segments in sequence.

2. the cells are pitch cells obtained by dividing the stripe region by a beam pitch size of the multi-beams used for drawing, 2. The multi-beam writing method according to claim 1, further comprising: irradiating a plurality of pixels within the pitch cell using the (m-1)-th segment with the first individual beam while performing tracking by deflecting the multi-beam so as to follow the movement of the stage; and irradiating a plurality of pixels within the pitch cell using the (m-1)-th segment with the second individual beam after the tracking reset.

3. 2. The multi-beam writing method according to claim 1, wherein the cells are cells obtained by dividing the stripe region by a maximum area irradiated by one individual beam of the multi-beams.

4. 2. The multi-beam writing method according to claim 1, wherein, when the M types of segments are regarded as two-dimensional matrices in which pixels to which shots are assigned have a value of 1 and pixels to which no shots are assigned have a value of 0, a value of each element of a sum of the two-dimensional matrices corresponding to the M types of segments coincides with the predetermined multiplicity.

5. 2. The multi-beam writing method according to claim 1, wherein two of the M types of segments have the same pixels shot, and the shot order is reversed.

6. 2. The multi-beam writing method according to claim 1, wherein the M types of segments applied when writing the first stripe region are different from the M types of segments applied when writing the second stripe region.

7. a movable stage on which a substrate to be imaged is placed; A multi-beam forming unit that forms multiple beams; a memory unit that stores drawing data and M types (M is an integer of 2 or more) of different segments that are generated by defining a shot sequence corresponding to a plurality of pixels that belong to each of a plurality of cells obtained by dividing a plurality of stripe regions that are obtained by dividing a drawing region of the substrate by a predetermined width in a direction perpendicular to a drawing progress direction; a drawing control unit that controls drawing using the drawing data and the segments; Equipped with the pixel is an irradiation unit area for each individual beam constituting the multi-beam; the drawing control unit controls the multibeam drawing device to irradiate a plurality of pixels within the cell using an m-1-th segment (m is an integer 2≦m≦M) of a first individual beam of the multibeam while deflecting the multibeam, and then irradiate a plurality of pixels within the pitch cell using an m-1-th segment of a second individual beam different from the first individual beam, thereby drawing each of the plurality of stripe regions with a predetermined intra-stripe multiplicity N (N is an integer of 2 or more).

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