Raster beam drawing method and raster beam drawing apparatus

Abstract

This invention provides a drawing method for raster beam drawing that can shorten the drawing time without affecting the drawing accuracy. [Solution] The method includes: a step of calculating a normalized proximity effect correction irradiation dose to correct for the proximity effect when drawing a sample; a step of determining whether the proximity effect correction irradiation dose is greater than a threshold for each of several sub-regions in which the drawing area of ​​the sample is divided into a mesh; a step of calculating a ghost irradiation dose for the sub-regions in which the irradiation dose is greater than the threshold as a result of the determination; and a step of drawing the irradiation unit regions for which the proximity effect correction irradiation dose is greater than the threshold with an incident irradiation dose that is the sum of the irradiation dose based on a limiting correction irradiation dose that is limited from the calculated proximity effect correction irradiation dose and the ghost irradiation dose, for each of several irradiation unit regions for which the beam is irradiated in which the drawing area is divided into a mesh; and drawing the irradiation unit regions in which the proximity effect correction irradiation dose is less than or equal to the threshold with a beam that is the irradiation dose based on the calculated proximity effect correction irradiation dose without ghost exposure.

Description

Technical Field

[0004] , , , ,

[0003]

[0001] The present invention relates to a raster beam drawing method and a raster beam drawing apparatus, and more particularly, to a single / multi-beam drawing apparatus and method using a raster drawing method.

Background Art

[0002] Lithography technology, which is responsible for the progress of semiconductor device miniaturization, is an extremely important process for generating patterns in the semiconductor manufacturing process. In recent years, with the increasing integration of LSIs, the circuit line width required for semiconductor devices has been continuously miniaturized year by year. Here, electron beam (electron beam) lithography technology has inherently excellent resolution, and electron beam lithography is performed on masks for wafer exposure, wafers, and the like.

[0003] For example, there is a drawing apparatus using multi-electron beams. Compared with the case of drawing with a single electron beam, by using multi-electron beams, a large number of beams can be irradiated at one time, so that the throughput can be significantly improved. In such a multi-beam drawing 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. Each unshielded beam is reduced by an optical system and deflected by a deflector to be irradiated to a desired position on the sample.

[0004] In raster beam lithography using a single or multiple electron beam, the shot cycle and lithography speed are typically determined by the maximum irradiation dose within the lithography area or stripe. A larger maximum irradiation dose results in a slower lithography speed and, consequently, a longer lithography time. In electron beam lithography, when the beam is irradiated onto a resist-coated sample, the beam is backscattered within the sample, causing electrons to enter the resist and cause secondary photosensitization of the resist. This secondary photosensitization occurs more strongly in areas with higher pattern density, resulting in a so-called proximity effect. When proximity effect correction is performed by irradiation dose modulation, the irradiation dose is modulated so that it increases as the pattern density decreases. A mask has a main pattern area where the pattern to be transferred to the wafer by the scanner is placed, and a peripheral pattern area outside of it where patterns for mask management are placed. High lithography accuracy is required in the main pattern area, but it is often not required in the peripheral pattern area. If the density of the peripheral pattern area is lower than that of the main pattern area, the maximum irradiation dose in the former will be greater than that in the latter. Therefore, if an attempt is made to draw the main pattern area and the surrounding pattern area simultaneously in order to shorten the drawing time, an unreasonable situation may occur where the drawing speed of the main chip decreases due to the maximum illumination of the surrounding chip, which has a lower drawing accuracy requirement. Therefore, by limiting the illumination amount in the entire area, including both the main chip area and the peripheral chip area, to a range exceeding the illumination amount used in the main chip area where high-precision drawing accuracy is required, the maximum illumination amount in this entire area can be reduced. This allows for a reduction in drawing time without affecting the drawing accuracy of patterns in the main chip area. However, in such cases, the illumination amount in the peripheral chip area, where the illumination amount is limited, becomes insufficient, resulting in problems such as thinner pattern dimensions.

[0005] Here, in addition to irradiating the patterned areas (line pattern areas) with a beam of irradiation dose that resolves the resist to a desired pattern width, a technique has been disclosed in which the irradiation dose at the patterned areas can be reduced and the drawing time shortened by also irradiating the areas without patterns (space areas) with a beam of irradiation dose that does not resolve the pattern (see Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-005729 [Overview of the project] [Problems that the invention aims to solve]

[0007] One aspect of the present invention provides a drawing method and a drawing apparatus that can shorten the drawing time in raster beam drawing while maintaining pattern dimensions in the peripheral chip area without affecting the drawing accuracy of the pattern in the main chip area. [Means for solving the problem]

[0008] One embodiment of the present invention is a raster beam drawing method, A process for calculating a normalized proximity effect correction dose to correct for the proximity effect when drawing a sample with a charged particle beam, A step of determining whether the proximity effect correction irradiation amount for each of the multiple sub-regions in which the drawing area of ​​the sample is divided into a mesh is greater than a threshold, The process involves calculating the ghost exposure dose for small regions where the proximity effect correction dose is greater than the threshold, based on the results of the determination. The process involves dividing the sample's drawing area into a mesh-like structure, and for multiple irradiation unit regions for irradiating with a charged particle beam, drawing the irradiation unit regions with a proximity effect correction dose greater than a threshold using a charged particle beam with an incident irradiation dose that is the sum of a ghost irradiation dose and an irradiation dose based on a limit correction dose that is more restricted than the calculated proximity effect correction dose, and drawing the irradiation unit regions with a proximity effect correction dose not greater than a threshold using a charged particle beam with an incident irradiation dose based on a calculated proximity effect correction dose without ghost exposure. It is equipped with.

[0009] Furthermore, the drawing area consists of multiple processing areas that are virtually divided into processing areas that can be drawn by a single continuous movement of the stage on which the sample is placed in a predetermined direction. In the drawing process of at least one of multiple processing areas, it is preferable to switch between drawing with a charged particle beam with an incident irradiation amount that is the sum of the irradiation amount based on the limiting correction irradiation amount and the ghost irradiation amount, and drawing with a charged particle beam with an incident irradiation amount based on the calculated proximity effect correction irradiation amount without ghost exposure.

[0010] Furthermore, the drawing area of ​​the sample has a main drawing area located in the center of the sample and a secondary drawing area around it. It is preferable to use a threshold value equal to or greater than the proximity effect correction irradiation amount used in the main drawing area.

[0011] Furthermore, it is preferable that the ghost irradiation dose is calculated for each region that is larger in size than the irradiation unit region for irradiating with a charged particle beam.

[0012] Furthermore, it is preferable to further include a step of creating a proximity-effect-corrected irradiation dose map in which proximity-effect-corrected irradiation doses for each small region are defined, in which proximity-effect-corrected irradiation doses that are greater than a threshold dose are changed to limiting-corrected irradiation doses.

[0013] Furthermore, the process includes limiting the incident irradiation amount in an irradiation unit area that exceeds a predetermined maximum irradiation amount used for actual drawing to the maximum irradiation amount, The process involves resizing the graphic pattern according to the insufficient irradiation amount resulting from being limited to the maximum irradiation dose, It is preferable to further include the following:

[0014] One embodiment of the present invention is a raster beam drawing method, A proximity effect correction irradiation dose calculation unit calculates a normalized proximity effect correction irradiation dose to correct for the proximity effect when drawing a sample with a charged particle beam, A determination unit that determines whether the proximity effect correction irradiation amount for each of the multiple sub-regions, in which the drawing area of ​​the sample is divided into a mesh, is greater than a threshold, Based on the results of the determination, a ghost irradiation amount calculation unit calculates the ghost irradiation amount for ghost exposure in small areas where the proximity effect correction irradiation amount is greater than the threshold, A drawing mechanism for a sample, where the drawing area is divided into a mesh-like structure, and multiple irradiation unit regions for irradiating a charged particle beam, is used to draw irradiation unit regions with proximity effect correction doses greater than a threshold using an incident charged particle beam with an irradiation dose based on a limit correction dose that is more restricted than the calculated proximity effect correction dose, plus a ghost irradiation dose. For irradiation unit regions with proximity effect correction doses not greater than a threshold, the drawing mechanism draws them without ghost exposure using an incident charged particle beam with an irradiation dose based on a calculated proximity effect correction dose. It is equipped with. [Effects of the Invention]

[0015] According to one aspect of the present invention, in raster beam drawing, the drawing time can be reduced while maintaining the pattern dimensions in the peripheral chip area without affecting the drawing accuracy of the pattern in the main chip area. [Brief explanation of the drawing]

[0016] [Figure 1] This is a conceptual diagram showing the configuration of the drawing device in Embodiment 1. [Figure 2] This is a conceptual diagram showing the configuration of the molded aperture array substrate in Embodiment 1. [Figure 3]It is a cross-sectional view showing the configuration of the blanking aperture array mechanism in Embodiment 1. [Figure 4] It is a conceptual diagram for explaining an example of the drawing operation in Embodiment 1. [Figure 5] It is a diagram showing an example of the irradiation region of the multi-beam and the drawing target pixel in Embodiment 1. [Figure 6] It is a diagram showing an example of the arrangement of the pattern regions to be drawn in Embodiment 1. [Figure 7] It is a diagram showing an example of the relationship between the proximity effect density and the dose amount incident on the resist on the sample surface in the comparative example of Embodiment 1. [Figure 8] It is a flowchart diagram showing an example of the main process steps of the drawing method in Embodiment 1. [Figure 9] It is a diagram showing an example of the relationship between the proximity effect correction irradiation amount and the proximity effect density in Embodiment 1. [Figure 10] It is a diagram showing an example of the relationship between the proximity effect density and the dose amount in Embodiment 1. [Figure 11] It is a diagram showing an example of the relationship between the irradiation amount and the proximity effect density in Embodiment 1. [Figure 12] It is a diagram for explaining an example of the multi-beam drawing operation in Embodiment 1. [Figure 13] It is a conceptual diagram showing the configuration of the drawing apparatus in Embodiment 2. [Figure 14] It is a flowchart diagram showing an example of the main process steps of the drawing method in Embodiment 2. [Figure 15] It is a diagram showing an example of the relationship between the pattern dimension and the irradiation amount in Embodiment 2.

Embodiments for Carrying Out the Invention

[0017] In the following embodiments, an electron beam configuration will be described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam; it may also be a beam using charged particles such as an ion beam. Furthermore, the charged particle beam may be a single beam or a multi-beam configuration. In the following embodiments, a multi-beam lithography apparatus for raster beam lithography will be described, for example. Alternatively, a single-beam lithography apparatus for raster beam lithography may also be described, for example.

[0018] Embodiment 1. Figure 1 is a conceptual diagram showing the configuration of a lithography apparatus in Embodiment 1. In Figure 1, the lithography apparatus 100 includes a lithography mechanism 150 and a control system circuit 160. The lithography apparatus 100 is an example of a multi-charged particle beam lithography apparatus and an example of a multi-charged particle beam exposure apparatus. Furthermore, the lithography apparatus 100 is an example of a raster beam lithography apparatus. The lithography mechanism 150 includes an electron tube 102 (electron beam column) and a lithography chamber 103. Inside the electron tube 102 are an electron gun 201, an illumination lens 202, a shaping aperture array substrate 203, a blanking aperture array mechanism 204, a reduction lens 205, a limiting aperture substrate 206, an objective lens 207, a main deflector 208, and a sub-deflector 209.

[0019] An XY stage 105 is placed inside the drawing chamber 103. Samples 101, such as masks, which will be the substrates to be drawn on during drawing (exposure), are placed on the XY stage 105. Samples 101 include exposure masks used when manufacturing semiconductor devices, or semiconductor substrates (silicon wafers) on which semiconductor devices are manufactured. Samples 101 also include mask blanks with resist coated on them but with no drawings yet. A mirror 210 for measuring the position of the XY stage 105 is also placed on the XY stage 105.

[0020] The control system circuit 160 includes a control computer 110, memory 112, deflection control circuit 130, digital-to-analog converter (DAC) amplifier units 132 and 134, lens control circuit 136, stage control mechanism 138, stage position measuring instrument 139, and storage devices 140 and 142 such as magnetic disk drives. The control computer 110, memory 112, deflection control circuit 130, lens control circuit 136, stage control mechanism 138, stage position measuring instrument 139, and storage devices 140 and 142 are connected to each other via a bus (not shown). The deflection control circuit 130 is connected to the DAC amplifier units 132 and 134 and the blanking aperture array mechanism 204. The sub-deflector 209 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 130 via the DAC amplifier 132. The main deflector 208 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 130 via the DAC amplifier 134. The lens group, including the illumination lens 202, the reduction lens 205, and the objective lens 207, is controlled by the lens control circuit 136.

[0021] The position of the XY stage 105 is controlled by the drive of motors on each axis (not shown) controlled by the stage control mechanism 138. The stage position measuring instrument 139 measures the position of the XY stage 105 by receiving reflected light from the mirror 210 using the principle of laser interferometry.

[0022] The control computer 110 includes a rasterization processing unit 50, a pattern density calculation unit 51, a proximity effect density calculation unit (U calculation unit) 52, a proximity effect corrected irradiation dose calculation unit (Dp calculation unit) 54, a determination unit 56, a limit correction irradiation dose calculation unit (Dp' calculation unit) 58, a ghost irradiation dose calculation unit 60, an irradiation dose calculation unit 62, an irradiation time calculation unit 64, a drawing control unit 72, and a transfer processing unit 74. Each of these "~ units" has a processing circuit. Such processing circuits include, for example, electrical circuits, computers, processors, circuit boards, quantum circuits, or semiconductor devices. Each "~ section" may use a common processing circuit (the same processing circuit) or different processing circuits (separate processing circuits). Information input to and output to the rasterization processing unit 50, pattern density calculation unit 51, proximity effect density calculation unit 52, proximity effect corrected irradiation amount calculation unit 54, determination unit 56, limit correction irradiation amount calculation unit 58, ghost irradiation amount calculation unit 60, irradiation amount calculation unit 62, irradiation time calculation unit 64, drawing control unit 72, and transfer processing unit 74, as well as information being calculated, is stored in the memory 112 each time.

[0023] The drawing operation of the drawing device 100 is controlled by the drawing control unit 72. Furthermore, the transfer process of the irradiation time data for each shot to the deflection control circuit 130 is controlled by the transfer processing unit 74.

[0024] Furthermore, drawing data (chip data) is input from outside the drawing device 100 and stored in the storage device 140. The chip data defines information about multiple graphic patterns that constitute the chip pattern. Specifically, for each graphic pattern, the coordinates of each vertex are defined in the order in which the graphic is formed. Alternatively, for example, for each graphic pattern, the graphic code, coordinates, and size are defined.

[0025] Here, Figure 1 shows the configuration necessary to explain Embodiment 1. The drawing device 100 may also have other configurations that are normally necessary.

[0026] Figure 2 is a conceptual diagram showing the configuration of a molded aperture array substrate in Embodiment 1. In Figure 2, the molded aperture array substrate 203 has p rows horizontally (x direction) × q rows vertically (y direction) (p,q≧2) holes (openings) 22 formed in a matrix at a predetermined arrangement pitch. In the example of Figure 2, for example, it shows a case where 512 × 512 rows of holes 22 are formed in the vertical and horizontal (x,y directions). The number of holes 22 is not limited to this. For example, 32 × 32 rows of holes 22 may be formed. Each hole 22 is formed as a rectangle of the same dimensions and shape. Alternatively, they may be circles of the same diameter. A portion of the electron beam 200 passes through each of these multiple holes 22 to form a multi-beam 20. In other words, the molded aperture array substrate 203 forms and emits a multi-beam 20. The molded aperture array substrate 203 is an example of a multi-beam emission source or multi-beam formation mechanism.

[0027] Figure 3 is a cross-sectional view showing the configuration of the blanking aperture array mechanism in Embodiment 1. As shown in Figure 3, the blanking aperture array mechanism 204 has a blanking aperture array substrate 31 made of a semiconductor substrate such as silicon placed on a support base 33. In the membrane region 330 in the center of the blanking aperture array substrate 31, through holes 25 (openings) for the passage of each beam of the multi-beam 20 are opened at positions corresponding to each hole 22 of the molded aperture array substrate 203 shown in Figure 2. Then, a set of control electrodes 24 and counter electrodes 26 (blankers: blanking deflectors) are placed at positions opposite each other across the corresponding through holes 25. In addition, a control circuit 41 (logic circuit) that applies a deflection voltage to the control electrode 24 for each through hole 25 is placed inside the blanking aperture array substrate 31 near each through hole 25. The counter electrodes 26 for each beam are connected to ground.

[0028] An amplifier (an example of a switching circuit), not shown in the diagram, is placed inside the control circuit 41. As an example of an amplifier, a CMOS (Complementary MOS) inverter circuit, which acts as a switching circuit, is placed inside. Either an L (low) potential (e.g., ground potential) that is lower than the threshold voltage, or an H (high) potential (e.g., 1.5V) that is higher than the threshold voltage, is applied as a control signal to the input (IN) of the CMOS inverter circuit. In Embodiment 1, when an L potential is applied to the input (IN) of the CMOS inverter circuit, the output (OUT) of the CMOS inverter circuit, which is the output of the control circuit 41, becomes a positive potential (Vdd). The electric field created by the potential difference with the ground potential of the counter electrode 26 deflects the corresponding beam, and the beam is controlled to turn OFF by being shielded by the limiting aperture substrate 206. On the other hand, when a high potential is applied to the input (IN) of the CMOS inverter circuit (active state), the output (OUT) of the CMOS inverter circuit and the control circuit 41 becomes ground potential, eliminating the potential difference with the ground potential of the counter electrode 26. As a result, the corresponding beam is not deflected, and the control is made so that the beam turns ON upon passing through the limiting aperture substrate 206. This deflection is used for blanking control.

[0029] Next, a specific example of the operation of the drawing mechanism 150 will be described. The electron beam 200 emitted from the electron gun 201 (emission source) illuminates the entire molded aperture array substrate 203 almost vertically by the illumination lens 202. Multiple rectangular holes 22 (openings) are formed in the molded aperture array substrate 203, and the electron beam 200 illuminates the area containing all of the multiple holes 22. Each portion of the electron beam 200 irradiated at the location of the multiple holes 22 passes through each of the multiple holes 22 in the molded aperture array substrate 203, thereby forming, for example, a rectangular multi-beam (multiple electron beams) 20. These multi-beams 20 pass through the corresponding blankers of the blanking aperture array mechanism 204. Each of these blankers individually blanks the passing beam so that the beam remains ON for a set drawing time (irradiation time).

[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 limiting aperture substrate 206. Here, the electron beam deflected by the blanker of the blanking aperture array mechanism 204 is moved away from the central hole in the limiting aperture substrate 206 and is shielded by the limiting aperture substrate 206. On the other hand, the electron beam that was not deflected by the blanker of the blanking aperture array mechanism 204 passes through the central hole in the limiting aperture substrate 206 as shown in Figure 1. In this way, the limiting aperture substrate 206 shields each beam that has been deflected by the blanker of the blanking aperture array mechanism 204 to the beam-OFF state. Then, each beam of one shot is formed by the beam that has passed through the limiting aperture substrate 206 from the time the beam is turned ON until it is turned OFF. The multi-beams 20 that have passed through the limiting aperture substrate 206 are focused by the objective lens 207 to form a pattern image with a desired reduction ratio. The main deflector 208 and sub-deflector 209 then deflect the entire multi-beams 20 that have passed through the limiting aperture substrate 206 in the same direction, illuminating each beam at its respective irradiation position on the sample 101. Furthermore, for example, when the XY stage 105 is moving continuously, the main deflector 208 performs tracking control so that the beam irradiation position follows the movement of the XY stage 105. Ideally, the multi-beams 20 irradiated at one time will be arranged at a pitch obtained by multiplying the array pitch of the multiple holes 22 in the molded aperture array substrate 203 by the desired reduction ratio described above.

[0031] Figure 4 is a conceptual diagram illustrating an example of the drawing operation in Embodiment 1. As shown in Figure 4, the drawing area 30 (thick line) of the sample 101 is virtually divided into multiple stripe-shaped areas 32 with a predetermined width in the y direction, for example. The example in Figure 4 shows a case where the drawing area 30 of the sample 101 is divided into multiple stripe areas 32 with a width size substantially the same as the size of the designed irradiation area 34 (drawing field) that can be irradiated with one multi-beam 20 irradiation in the y direction. The size of the irradiation area 34 of the designed multi-beam 20 in the x direction can be defined by the number of beams in the x direction × the beam pitch in the x direction. The size of the rectangular irradiation area 34 in the y direction can be defined by the number of beams in the y direction × the beam pitch in the y direction.

[0032] First, the XY stage 105 is moved to adjust the position of the irradiation area 34 of the multi-beam 20 to the left edge of the first stripe area 32, or even further to the left, and the first stripe area 32 is drawn. When drawing the first stripe area 32, the drawing progresses relatively in the x direction by moving the XY stage 105, for example, in the -x direction. The XY stage 105 is moved continuously at a constant speed, for example. At this time, the speed of the XY stage 105 is determined according to the maximum irradiation amount in the stripe area 32 or drawing area 30. After the drawing of the first stripe area 32 is completed, the stage position is moved in the -y direction by the width of the stripe area 32.

[0033] Next, the illumination area 34 of the multi-beam 20 is adjusted to be located at the left edge of the second stripe area 32, or even further to the left, and the drawing of the second stripe area 32 is performed by moving the XY stage 105, for example, in the -x direction, thereby relatively advancing the drawing in the x direction.

[0034] Furthermore, while the example in Figure 4 shows the case where each stripe region 32 is drawn in the same direction, this is not the only option. For example, for the stripe region 32 to be drawn after the stripe region 32 drawn in the x direction, the XY stage 105 can be moved, for example, in the x direction, so that the drawing is performed in the -x direction. By drawing while alternating directions in this way, the stage movement time can be shortened, and consequently, the drawing time can be shortened. In a single shot, the multi-beam formed by passing through each hole 22 of the molded aperture array substrate 203 forms up to the same number of shot patterns as each hole 22 at once.

[0035] Furthermore, while the example in Figure 4 shows the case where the stage is moved once for the drawing process of each stripe area, this is not the only option. It is also preferable to perform multiple drawing (multiple-path drawing) by moving the stage multiple times over the same position. In that case, for example, it is preferable to perform multiple drawing while shifting in the y direction by an amount equal to 1 / n of the width of the stripe area. Alternatively, it is also preferable to perform multiple drawing (in-path multiple drawing) in which the same position is drawn multiple times with different beams during a single stage movement.

[0036] Figure 5 shows an example of the multi-beam irradiation area and the pixels to be drawn in Embodiment 1. In Figure 5, the stripe area 32 is divided into multiple mesh areas, for example, by the beam size of the multi-beam 20. Each of these mesh areas becomes the pixels 36 to be drawn (beam irradiation unit area, irradiation position). The size of the pixels to be drawn 36 is not limited to the beam size and may be composed of any size regardless of the beam size. For example, it may be composed of a size of 1 / n (where n is an integer of 1 or more) of the beam size. In the example of Figure 5, the drawing area of ​​the sample 101 is shown as being divided into multiple stripe areas 32 in the y direction, for example, with a width size that is substantially the same as the size of the irradiation area 34 (drawing field) that can be irradiated with one irradiation of the multi-beam 20. The size of the rectangular irradiation area 34 in the x direction can be defined by the number of beams in the x direction × the beam pitch in the x direction. The size of the rectangular irradiation area 34 in the y direction can be defined by the number of beams in the y direction × the beam pitch in the y direction. In the example in Figure 5, for example, a 512x512-row multibeam is shown as an 8x8-row multibeam. Within the irradiation area 34, multiple pixels 28 (beam drawing positions) that can be irradiated in one shot of the multibeam 20 are shown. The pitch between adjacent pixels 28 becomes the inter-beam pitch of the multibeam. A rectangular area enclosed by the size of the inter-beam pitch in the x and y directions constitutes one sub-irradiation area 29 (pitch cell area). In the example in Figure 5, each sub-irradiation area 29 is shown as being composed of, for example, 4x4 pixels.

[0037] Figure 6 shows an example of the arrangement of the pattern area to be drawn in Embodiment 1. In the example in Figure 6, a wafer exposure mask is used as the sample 101. In this case, the drawing area of ​​sample 101 consists of a main drawing area located in the center of the sample and a secondary drawing area around it. As shown in Figure 6, the center of sample 101 has a main pattern area where the pattern to be transferred to the wafer by the scanner is placed, and a peripheral pattern area outside of it where the pattern for mask management is placed. The pattern is held as drawing data in units called chips. High drawing accuracy is required for the patterns included in the main pattern area or main chip, but high drawing accuracy is often not required for the patterns included in the peripheral pattern area or peripheral chip. If the main chip and peripheral chip are exposed separately, the number of folding operations of the XY stage 105 increases, so it is preferable to set the drawing stripe to encompass both the main chip and peripheral chip and draw them together, as this minimizes the number of folding operations and the time required for the XY stage 105. The main pattern area (main chip area) corresponds to the main drawing area. The surrounding pattern area (surrounding chip area) corresponds to the sub-drawing area.

[0038] As mentioned above, in raster beam plotting, the plotting speed is usually determined by the maximum illumination amount that illuminates 36 pixels in one pass. The larger the maximum illumination amount, the slower the plotting speed, and as a result, the plotting time increases. Also, when performing proximity effect correction, the illumination amount increases as the pattern density decreases. Peripheral patterns include chips such as alignment marks that have low density and can tolerate low plotting accuracy. In the example in Figure 6, the pattern density (pattern area density) of the geometric patterns placed in the main chip is shown to be, for example, 50% or more. It also shows that one of the two peripheral chips has a pattern density of, for example, 10%. The other of the two peripheral chips has a pattern density of, for example, 60%.

[0039] Here, by limiting the illumination amount in the entire area, including both the main chip and peripheral chip areas, to a range exceeding the illumination amount used in the main chip area where high-precision drawing accuracy is required, the maximum illumination amount in this entire area can be reduced. This allows for a reduction in drawing time without affecting the drawing accuracy of patterns within the main chip. However, in such cases, the illumination amount in the peripheral chip area, where the illumination amount is limited, becomes insufficient, resulting in problems such as thinner pattern dimensions.

[0040] Figure 7 shows an example of the relationship between the proximity effect density and the dose amount incident on the resist on the surface of sample 101 in a comparative example of Embodiment 1. In the example in Figure 7, the proximity effect corrected irradiation amount Dp, when normalized with a reference irradiation amount (base dose) of 1, is shown as the dose amount due to beam irradiation. Also, in the example in Figure 7, examples of the dose amount required to correct for the proximity effect and obtain a uniform pattern dimension are shown for proximity effect density U, for example, 0, 0.3, 0.5, and 1. In electron beam lithography, the irradiation amount of the beam is set so that the dose amount at the position where the height of the dose amount distribution that the beam irradiation gives to the resist becomes 1 / 2 matches the development threshold that develops the resist on the surface of sample 101. When the average density in the area affected by the proximity effect, the proximity effect density U, is not 0, that is, when the proximity effect exists, there is a dose amount due to backscattering, and in the region where the proximity effect density is uniformly U, the dose amount due to backscattering becomes DpηU using the backscattering coefficient η. To determine the beam dose at which proximity effect correction is properly performed, the dose due to backscatter (DpηU) is used as the base dose, and the beam dose is set to twice the dose from this base to the development threshold. The dose due to backscatter changes depending on the proximity effect density U. The larger the proximity effect density U, the larger the base backscatter dose. The resolution threshold (threshold dose in Figure 7) is determined by the masking process and is independent of the proximity effect density U. Therefore, the larger U is, the larger the backscatter dose, and the smaller the irradiation dose needs to be (the incident irradiation dose needs to be reduced to maintain the pattern dimensions). Conversely, if the proximity effect density U is small, the incident irradiation dose needs to be increased (the incident irradiation dose needs to be increased to maintain the pattern dimensions). This adjustment of the incident irradiation dose is performed by the proximity effect correction coefficient Dp. For example, when U=1, Dp=1.0. For example, when U=0.5, Dp=1.3. For example, when U=0.3, Dp=1.5. For example, when U=0, Dp=2.0. In peripheral chip regions, the proximity effect density U may be smaller than in the main chip region. In such cases, a large amount of incident light, unnecessary in the main chip region where high-precision rendering is required, becomes necessary in the peripheral chip region where lower rendering accuracy is acceptable. Consequently, the rendering speed in the peripheral chip region slows down, and the rendering time increases.

[0041] Therefore, in Embodiment 1, the irradiation amount exceeding the range (maximum value) of the incident irradiation amount used in the main chip area is limited across the entire area, including both the main chip area and the peripheral chip area. Ghost exposure is performed in the peripheral chip area to accumulate a dose that does not resolve the resist in order to compensate for the insufficient incident irradiation amount. This will be explained in detail below.

[0042] Figure 8 is a flowchart showing an example of the main steps of the drawing method in Embodiment 1. In Figure 8, the drawing method in Embodiment 1 performs a series of steps: rasterization (S102), pattern density calculation (S110), proximity effect density calculation (S112), proximity effect correction irradiation dose map creation (S114), determination (S116), correction irradiation dose map creation (S118), ghost irradiation dose calculation (S120), dose map creation (S130), and drawing (S140).

[0043] As a rasterization process (S102), the rasterization processing unit 50 reads chip pattern data (drawing data) from the storage device 140 and performs rasterization. Specifically, for each pixel 36, it calculates the pattern density ρ(x) (pattern area density) of the graphic pattern placed within the pixel. For example, it is preferable to perform rasterization for each stripe region 32.

[0044] As a pattern density calculation step (S110), the pattern density calculation unit 51 calculates the pattern density ρ″ (pattern area density) of the geometric patterns placed within each of the multiple adjacent mesh regions (small regions) that are larger in size than the pixels 36 into which the stripe region 32 is divided into a mesh. In other words, the adjacent mesh regions are set with a mesh size coarser than the multiple pixels 36 into which the stripe region 32 is divided into a mesh. The pattern density ρ″ is calculated for each adjacent mesh region with such a coarse mesh size. The vertical and horizontal size of the adjacent mesh region is preferably set to about 1 / 10 of the radius of influence of the proximity effect. For example, it is preferable to set it to about 1 μm. Also, for example, it is preferable to calculate the pattern density ρ″ of multiple adjacent mesh regions within each stripe region 32.

[0045] As a proximity-effect density calculation step (S112), the proximity-effect density calculation unit 52 calculates the proximity-effect density U using the pattern density ρ″(x) and the distribution function g(x). The proximity-effect density U can be defined by the following equation (1), which is a convolution operation between the pattern density ρ″(x) and the distribution function g(x). As the distribution function g(x), it is preferable to use a Gaussian function with a width of 10 μm, for example, which serves as a kernel representing the dose distribution that backscattering imparts to the resist. To make the explanation easier to understand below, the coordinates (x,y) of each position in each equation will be denoted by x. (1) U=∫ρ″(x′)g(xx′)dx′

[0046] As part of the proximity effect correction irradiation dose map creation process (S114), the proximity effect correction irradiation dose calculation unit 54 calculates a normalized proximity effect correction irradiation dose Dp(x) to correct for the proximity effect when drawing the sample 101 with an electron beam. In other words, the proximity effect correction irradiation dose calculation unit 54 calculates a proximity effect correction irradiation dose Dp(x) to correct for the proximity effect for each proximity mesh region (small region). An unknown proximity effect correction irradiation dose Dp(x) can be defined by a threshold model for proximity effect correction similar to conventional methods, using the backscattering coefficient η and the proximity effect density U(x). The proximity effect correction irradiation dose Dp(x) is calculated as a relative value normalized with the reference irradiation dose Dbase set to 1. The proximity effect correction irradiation dose Dp(x) can be defined, for example, by the following equation (2). (2) Dp(x)=(1 / 2+η) / (1 / 2+ηU(x))

[0047] The proximity effect corrected irradiation dose calculation unit 54 creates a proximity effect corrected irradiation dose map (first proximity effect corrected irradiation dose map) using the calculated proximity effect corrected irradiation dose Dp(x) for each proximity mesh region as elements.

[0048] Figure 9 shows an example of the relationship between proximity effect correction irradiation dose and proximity effect density in Embodiment 1. In Figure 9, the vertical axis represents the proximity effect correction irradiation dose Dp, and the horizontal axis represents the proximity effect density U. As shown in Figure 9, the proximity effect correction irradiation dose Dp depends on the proximity effect density U, and becomes larger as the proximity effect density U decreases. If the minimum value of the proximity effect density U of the graphic pattern in the main chip area is, for example, U = 0.5, then the proximity effect correction irradiation dose Dp at this value is used as a threshold, and Dp exceeding this threshold is limited.

[0049] As a determination step (S116), the determination unit 56 determines whether the proximity effect correction irradiation amount Dp(x) for each of the multiple adjacent mesh regions (an example of a small region) into which the target stripe region 32 (an example of a drawing region) of the sample 101 is divided into a mesh is greater than the threshold Dpth. Alternatively, the determination unit 56 may determine whether the proximity effect correction irradiation amount Dp(x) for each of the multiple pixels 36 (another example of a small region) into which the target stripe region 32 (an example of a drawing region) of the sample 101 is divided into a mesh is greater than the threshold Dpth. The threshold Dpth is set to a value greater than or equal to the proximity effect correction irradiation amount used within the main chip area drawn on sample 101. For example, the threshold Dpth is set to the proximity effect correction irradiation amount Dp(x) corresponding to the minimum value of the proximity effect density U of the geometric pattern within the main chip area. For example, the threshold Dpth is set to the proximity effect correction irradiation amount Dp(x) when U=0.5. Alternatively, for example, by referring to the proximity effect correction irradiation amount map, the threshold Dpth is set to the maximum value of the proximity effect correction irradiation amount of the nearby mesh area that overlaps with the main chip area.

[0050] As part of the correction dose map creation process (S118), the limit correction dose calculation unit 58 changes (overwrites) the value of the proximity effect correction dose in the proximity mesh area, which is greater than the threshold Dpth, to a limit correction dose Dp'(x) that is more restricted than the calculated proximity effect correction dose. The limit correction irradiation dose calculation unit 58 then creates a modified correction irradiation dose map (second proximity effect correction irradiation dose map) in which the proximity effect correction irradiation dose for each proximity mesh region is defined, in which the proximity effect correction irradiation dose that is greater than the threshold Dpth is changed to the limit correction irradiation dose Dp'(x).

[0051] However, if left as is, the incident illumination will be insufficient for pixel 36, where the proximity effect correction illumination value is limited, resulting in a thinner line width for the drawn pattern. Therefore, the ghost illumination amount is calculated as follows.

[0052] As a ghost irradiation amount calculation step (S120), the ghost irradiation amount calculation unit 60 calculates the ghost irradiation amount G(x) for ghost exposure for nearby meshes (an example of a small area) where the proximity effect correction irradiation amount is greater than the threshold Dpth as a result of the determination in the determination step (S116). The ghost irradiation amount G(x) is calculated for each area larger than the size of the pixels 36, for example, for each nearby mesh area.

[0053] Figure 10 shows an example of the relationship between proximity effect density and dose amount in Embodiment 1. In the example in Figure 10, the proximity effect corrected irradiation dose Dp is shown as the dose amount when the reference irradiation dose (base dose) is normalized to 1. Also, in the example in Figure 10, examples of the dose amounts required for proximity effect density U in the development threshold model are shown for each case, for example, 0, 0.3, 0.5, and 1. As described above, in the development threshold model in electron beam lithography, the development threshold is set so that 1 / 2 of the irradiation dose resolves the resist on the surface of sample 101. Therefore, if we set the proximity effect-corrected irradiation dose used within the main chip region, for example, the proximity effect-corrected irradiation dose Dp(U) when U=0.5, as the irradiation dose limit value Dpth, and make the backscatter dose amount Dp(U′)ηU′ which forms the base portion at the irradiation dose limit value Dpth the same as the irradiation dose of the base portion at a proximity effect density U smaller than the proximity effect density U′ used at the irradiation dose limit value Dpth, then the dose amount at a proximity effect density U smaller than the proximity effect density U′ used at the irradiation dose limit value Dpth (for example, U<0.5) can be matched in the same way as in the case of U′. Thus, the deficiency in the backscatter dose amount D(U)pηU of the base portion at a proximity effect density U smaller than the proximity effect density U′ used at the irradiation dose limit value Dpth (for example, U<0.5) is compensated for by the ghost irradiation dose G(x). The deficiency in the backscatter dose amount can be defined by the following equation (3) using the proximity effect density U′ used as the threshold. In equation (3), the backscatter dose Dp(U')ηU' at the threshold Dpth is approximated by Dp(U')ηU. (3) ΔD = Dp(U′)ηU - Dp(U)ηU

[0054] Therefore, the ghost radiation dose G(x) can be defined by the following equation (4). (4) G(x)=(Dp(U(x))-Dp(U′(x)))ηU(x) / (1+η) Furthermore, since irradiating with a ghost dose generates a secondary backscatter amount related to the ghost dose, equation (4) takes this into account when calculating the irradiation dose.

[0055] This allows us to limit the proximity effect correction dose Dp(x) to the threshold proximity effect correction dose Dp'(x) in nearby mesh regions where the proximity effect correction dose Dp(x) is greater than the threshold proximity effect correction dose Dp'(x) by taking into account the ghost dose G(x), while maintaining the pattern dimensions.

[0056] In the dose map creation process (S130), the irradiation dose calculation unit 62 calculates the incident irradiation dose by adding the ghost irradiation dose G(x) to the irradiation dose ρ(x)Dp'(x) based on a limiting correction irradiation dose Dp'(x) which is more limited than the calculated proximity effect correction irradiation dose Dp(x) for pixels 36 whose proximity effect correction irradiation dose Dp(x) is greater than the threshold Dpth. Furthermore, for pixels 36 whose proximity effect correction irradiation dose Dp(x) is not greater than the threshold Dpth, the incident irradiation dose is calculated based on the calculated proximity effect correction irradiation dose Dp(x) without ghost exposure. The incident irradiation dose s(x) for pixels without ghost exposure is defined by equation (5-1), which is obtained by multiplying the proximity effect correction irradiation dose Dp(x) by the pattern density ρ(x) of the pixel 36. The incident irradiation amount s(x) for a pixel with ghost exposure is defined by equation (5-2), which is the value obtained by multiplying the proximity effect corrected irradiation amount Dp(x) by the pattern density ρ(x) of the pixel 36 in question, and adding the ghost irradiation amount g(x). (5-1) s(x)=ρ(x)Dp(x) (5-2) s(x)=ρ(x)Dp′(x)+G(x) =ρ(x)Dp′(x) +(Dp(U)-Dp(U′))ηU / (1+η) Note that the incident irradiation dose s(x) here is defined as a relative value normalized with the base dose set to 1.

[0057] The irradiation dose calculation unit 62 then creates a dose map that defines the incident irradiation dose s(x) for each of the calculated pixels 36.

[0058] Figure 11 shows an example of the relationship between irradiation dose and proximity effect density in Embodiment 1. In Figure 11, the vertical axis shows the irradiation dose s [au], and the horizontal axis shows the proximity effect density U. In the example in Figure 11, the case where the pattern density ρ within a pixel is 1 (the so-called solid pattern case) is shown. In the example in Figure 11, the incident irradiation dose s without ghost exposure (Graph A), the incident irradiation dose s with ghost exposure when the proximity effect density at the threshold Dpth is U = 0.3 (Graph B), and the incident irradiation dose s with ghost exposure when the proximity effect density at the threshold Dpth is U = 0.5 (Graph C) are shown. As shown in Figure 11, it can be seen that by performing ghost exposure, the maximum value of the incident irradiation dose s can be significantly reduced in Graph C compared to Graph A. Therefore, it is possible to shorten the drawing time while maintaining the drawing accuracy of the pattern in the main chip area and maintaining the dimensions of the pattern in the peripheral chip area.

[0059] In the drawing process (S140), the irradiation time calculation unit 64 first calculates the irradiation time t for each of the 36 pixels. The actual incident irradiation amount D(x) can be obtained by multiplying the normalized incident irradiation amount s(x) by, for example, a reference irradiation amount Dbase. The irradiation time t can be calculated by dividing D(x) by the current density J. Specifically, it operates as follows: The irradiation time calculation unit 64 refers to the dose map and calculates the irradiation time t for each of the 36 pixels by dividing the value obtained by multiplying the normalized incident irradiation amount s(x) by, for example, a reference irradiation amount Dbase, by the current density J. The drawing control unit 72 then rearranges the obtained irradiation time data for each pixel 36 in shot order and stores it in the storage device 142. The transfer processing unit 74 then transfers the irradiation time data in shot order to the deflection control circuit 130.

[0060] Then, under the control of the drawing control unit 72, the drawing mechanism 150 draws the pixels 36 for which the electron beam is irradiated, which are divided into a mesh-like stripe region 32 (drawing region) of the sample 101, with an incident irradiation amount D(x) which is the sum of the irradiation amount based on the restricted irradiation amount Dp'(x), which is more limited than the calculated proximity effect corrected irradiation amount Dp(x), and the ghost irradiation amount G(x), for pixels 36 whose proximity effect corrected irradiation amount is greater than the irradiation amount limit value Dpth. In addition, pixels 36 whose proximity effect corrected irradiation amount is not greater than the threshold Dpth are drawn without ghost exposure with an incident irradiation amount D(x) which is based on the calculated proximity effect corrected irradiation amount Dp(x).

[0061] Figure 12 is a diagram illustrating an example of multi-beam drawing operation in Embodiment 1. In the example in Figure 12, each sub-irradiation area 29 enclosed by the beam pitch, including one beam irradiation position of each multi-beam 20, is drawn with four different beams. Also in the example in Figure 12, while drawing 1 / 4 (1 / 2 of the number of beams used for irradiation) of each sub-irradiation area 29, the XY stage 105 moves at a speed of 8 beam pitch distance L, showing a continuous drawing operation. In the example in Figure 12, each sub-irradiation area 29 is composed of, for example, 4x4 pixels. In the drawing operation shown in the example in Figure 12, for example, while the XY stage 105 moves a distance L of 8 beam pitch distance, the irradiation position (pixel 36) is sequentially shifted by the sub-deflector 209, and the multi-beam 20 is fired four times in a shot cycle T to draw (expose) four different pixels 36 within the same sub-irradiation area 29. The shot cycle T is set to be longer than the exposure time corresponding to the maximum irradiation amount to be given to each pixel. While the four pixels 36 are being drawn (exposed), the entire multi-beam 20 is deflected collectively by the main deflector 208 to prevent the irradiation area 34 from shifting relative to the sample 101 due to the movement of the XY stage 105, thereby causing the irradiation area 34 to follow the movement of the XY stage 105. In other words, tracking control is performed. After one tracking cycle is completed, the tracking is reset and returned to the previous tracking start position. Since the drawing of the first pixel row from the right in each sub-irradiation area 29 has been completed, after the tracking reset, in the next tracking cycle, the sub-deflector 209 first deflects the beam to adjust (shift) its drawing position so that it can draw, for example, the second pixel row from the right in each sub-irradiation area 29 that has not yet been drawn. By repeating this operation while the stripe area 32 is being drawn, the position of the irradiation area 34 (34a~34o) of the multi-beam 20 moves sequentially, as shown in the lower part of Figure 4, and drawing is performed. In this way, the drawing mechanism 150 illuminates each pixel 36 with a beam of a desired incident irradiation amount D(x) by performing raster beam drawing. By combining each pixel that has been irradiated with the desired incident irradiation amount D(x), the desired pattern is drawn.

[0062] As described above, according to Embodiment 1, in raster beam drawing, the drawing time can be shortened while maintaining the pattern dimensions in the peripheral chip area without affecting the drawing accuracy of the pattern in the main chip area.

[0063] Embodiment 2. Embodiment 1 describes a configuration in which the amount of illumination increased by ghost exposure is not limited, but it is not limited to this. Embodiment 2 describes a configuration in which ghost exposure is taken into consideration, and a maximum illumination amount is set for each pixel, and the amount of illumination exceeding this is limited. In Embodiment 2, the contents are the same as in Embodiment 1, except for the points that are not specifically described below.

[0064] Figure 13 is a conceptual diagram showing the configuration of the drawing device in Embodiment 2. In Figure 13, the configuration is the same as in Figure 1, except that a maximum irradiation dose limiting processing unit 65, a resizing processing unit 66, an area density calculation unit 68, and an irradiation dose calculation unit 70 are added to the control computer 110.

[0065] Each of the "~ section," such as the rasterization processing section 50, pattern density calculation section 51, proximity effect density calculation section 52, proximity effect corrected irradiation dose calculation section 54, determination section 56, limit corrected irradiation dose calculation section 58, ghost irradiation dose calculation section 60, irradiation dose calculation section 62, irradiation time calculation section 64, maximum irradiation dose limit processing section 65, resize processing section 66, area density calculation section 68, irradiation dose calculation section 70, drawing control section 72, and transfer processing section 74, has a processing circuit. Such a processing circuit includes, for example, an electrical circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each of the "~ section" may use a common processing circuit (the same processing circuit) or may use different processing circuits (separate processing circuits). Information input to and output to the rasterization processing unit 50, pattern density calculation unit 51, proximity effect density calculation unit 52, proximity effect corrected irradiation dose calculation unit 54, determination unit 56, limit corrected irradiation dose calculation unit 58, ghost irradiation dose calculation unit 60, irradiation dose calculation unit 62, irradiation time calculation unit 64, maximum irradiation dose limit processing unit 65, resize processing unit 66, area density calculation unit 68, irradiation dose calculation unit 70, drawing control unit 72, and transfer processing unit 74, as well as information being calculated, is stored in the memory 112 each time.

[0066] Figure 14 is a flowchart showing an example of the main steps of the drawing method in Embodiment 2. In Figure 14, it is the same as in Figure 8 except that the maximum irradiation dose limiting step (S132), resizing step (S134), rasterization step (S136), and dose map creation step (S138) are performed between the dose map creation step (S130) and the drawing step (S140).

[0067] The contents of each step from the rasterization process (S102) to the dose map creation process (S130) are the same as in Embodiment 1.

[0068] As a maximum illumination dose limiting step (S132), the maximum illumination dose limiting processing unit 65 limits the illumination dose s(x) of pixels 36 that exceeds a preset maximum illumination dose s0 used for actual drawing to the maximum illumination dose s0. Here, for example, a maximum illumination dose s0 normalized with a reference illumination dose Dbase of 1 is used. It is preferable to set the maximum illumination dose s0 to a value greater than the maximum illumination dose s(x) of pixels in the main chip area. Since it is often difficult to preset the maximum illumination dose s(x) of pixels in the main chip area, it is preferable to set the maximum illumination dose s0 to a value greater than Dp(U'=0.5) (Dp(U'=0.5)+α). For example, it is preferable to set α to a value of 5-20% of Dp(U'=0.5). For example, set it to 10% of Dp(U'=0.5).

[0069] As a resizing step (S134), the resizing processing unit 66 resizes the graphic pattern according to the insufficient irradiation amount ΔE that is lacking due to being limited to the maximum irradiation amount s0.

[0070] Figure 15 shows an example of the relationship between pattern dimensions and irradiation dose in Embodiment 2. In Figure 15, the vertical axis shows the pattern dimension CD, and the horizontal axis shows the irradiation dose. This relationship allows us to determine the tolerance DL(U). The tolerance DL(U) represents the rate of change of CD per unit irradiation dose for each proximity effective density U. The relationship between pattern dimensions CD and irradiation dose is determined in advance by drawing experiments or simulations.

[0071] The insufficient dose ΔE when the maximum dose is limited by s0 is defined by the following equation (6). (6) ΔE=s0-s(x)

[0072] The pattern dimensions become thinner due to the insufficient irradiation dose ΔE, but the amount of pattern resizing ΔCD required to compensate for this is defined by the following equation (7) using the margin DL(U). (7) ΔCD = (-ΔE / s(x))DL(U)

[0073] Then, for each pixel limited to the maximum illumination amount s0, the dimensions of the graphic pattern within that pixel 36 are resized by ΔCD. Specifically, the line width dimension is increased by ΔCD. This allows the pattern dimensions after drawing to be roughly maintained even if the illumination amount is insufficient.

[0074] As part of the rasterization process (S136), the area density calculation unit 68 calculates the pattern density ρ within each pixel 36. Since the area density of the pattern within a pixel changes due to resizing, it is recalculated. Note that the pixels to be calculated here may be all pixels, or only pixels limited to the maximum illumination dose s0.

[0075] As part of the dose map creation process (S138), the irradiation dose calculation unit 70 calculates the incident irradiation dose s(x) using the recalculated pattern density ρ. The incident irradiation dose s(x) for the pixel 36, which is limited to the maximum irradiation dose s0, is defined by equation (8). (8) s(x)=ρ(x)s0

[0076] The incident irradiation dose s(x) for pixel 36, which is not limited to the maximum irradiation dose s0, is defined by equation (5-1) or equation (5-2).

[0077] The irradiation dose calculation unit 70 then creates a dose map that defines the recalculated incident irradiation dose s(x) for each of the 36 pixels.

[0078] The contents of the drawing process (S140) are the same as in Embodiment 1.

[0079] As described above, it is also preferable to pre-set the maximum irradiation dose and limit the maximum value of the incident irradiation dose.

[0080] According to Embodiment 2, the drawing time can be further reduced compared to Embodiment 1.

[0081] The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In the examples described above, only the case of correction for proximity effect was explained, but it is not limited to this. Corrective irradiation amounts to correct dimensional errors due to other causes may be added. Examples include the haze effect, the loading effect, and / or effects specific to the graphic pattern.

[0082] Furthermore, in each of the embodiments described above, the drawing area 30 is divided into a plurality of stripe areas 32 (processing areas) as described above. Each stripe area 32 can be drawn by a single continuous movement of the XY stage 105 on which the sample 101 is placed, for example in the x direction (a predetermined direction), as described above. In other words, all pixels 36 of the target stripe area 32 can be drawn by a single continuous movement of the XY stage 105, for example in the x direction (a predetermined direction). To put it another way, the drawing area 30 consists of a plurality of stripe areas 32 that are virtually divided by stripe areas 32 that can be drawn by a single continuous movement of the XY stage 105 on which the sample 101 is placed, for example in the x direction (a predetermined direction). Here, in at least one of the multiple stripe regions 32, there may be a mixture of pixels 36 drawn with an electron beam whose incident irradiation amount is the amount based on the limiting correction irradiation amount plus the ghost irradiation amount, and pixels 36 drawn with an electron beam whose incident irradiation amount is the amount based on the calculated proximity effect correction irradiation amount, without ghost exposure. In such cases, during the drawing process of at least one of the multiple stripe regions 32, the drawing is switched between drawing with an electron beam whose incident irradiation amount is the amount based on the limiting correction irradiation amount plus the ghost irradiation amount, and drawing with an electron beam whose incident irradiation amount is the amount based on the calculated proximity effect correction irradiation amount, without ghost exposure, depending on the pixel to be drawn.

[0083] Furthermore, while descriptions of the device configuration, control methods, and other parts not directly necessary for explaining the present invention have been omitted, it goes without saying that the necessary device configuration and control methods can be appropriately selected and used. For example, although the control unit configuration for controlling the drawing device 100 has been omitted, it goes without saying that the necessary control unit configuration can be appropriately selected and used.

[0084] Furthermore, all raster beam drawing methods and raster beam drawing apparatus that incorporate elements of the present invention and can be appropriately modified by those skilled in the art are included within the scope of the present invention. [Explanation of Symbols]

[0085] 10 beams 20 Multibeam 22 holes 23 electrodes 24 control electrodes 25 Passing hole 26 Counter electrode 36 pixels 29 Sub-irradiation area 32 Stripe Area 34 Irradiation area 41 Control circuits 50 Rasterization Processing Unit 51 Pattern density calculation unit 52 Proximity Effect Density Calculation Unit 54 Proximity Effect Corrected Irradiation Dose Calculation Unit 56 Judgment section 58 Limitation Correction Irradiation Dose Calculation Unit 60 Ghost Irradiation Dose Calculation Unit 62 Irradiance calculation section 64. Irradiation time calculation unit 65. Maximum irradiation dose limiting processing unit 66 Resizing Processing Unit 68 Area density calculation section 70 Irradiance calculation section 72 Drawing Control Unit 74 Transfer Processing Unit 100 drawing device 101 samples 102 Electronic Microscope Tube 103 Drawing room 105 XY Stages 110 Control Computer 112 memory 130 Deflection control circuit 131 Electrostatic lens control circuit 132,134 DAC Amplifier Unit 135 Air-core coil control circuit 136 Lens control circuit 138 Stage control mechanism 139 Stage position measuring instrument 140,142 Storage device 150 Drawing mechanism 160 Control System Circuits 200 electron beam 201 Electron Gun 202 Illumination Lens 203 Molded aperture array substrate 204 Blanking Aperture Array Mechanism 205 Reduction Lens 206 Limiting Aperture Substrate 207 Objective lens 208 Main deflector 209 Sub deflector 210 Mirror 330 Membrane area

Claims

1. A process for calculating a normalized proximity effect correction dose to correct for the proximity effect when drawing a sample with a charged particle beam, The drawing area of ​​the sample is divided into a mesh-like structure, and for each of the sub-regions, a step is made to determine whether the proximity effect corrected irradiation amount for the irradiation unit area is greater than a threshold. The process involves calculating the ghost exposure dose for small regions where the proximity effect correction irradiation dose is greater than the threshold, based on the results of the determination. The process involves, for multiple irradiation unit regions for irradiating a charged particle beam, in which the drawing area of ​​the sample is divided into a mesh, drawing the irradiation unit regions where the proximity effect corrected irradiation amount is greater than the threshold with a charged particle beam whose incident irradiation amount is the sum of the ghost irradiation amount and the irradiation amount based on a limiting correction irradiation amount that is more limited than the calculated proximity effect corrected irradiation amount, and drawing the irradiation unit regions where the proximity effect corrected irradiation amount is not greater than the threshold with a charged particle beam whose incident irradiation amount is based on the calculated proximity effect corrected irradiation amount without ghost exposure, A raster beam drawing method equipped with [a specific feature / feature].

2. The drawing area consists of a plurality of processing areas that are virtually divided into processing areas that can be drawn by a single continuous movement of the stage on which the sample is placed in a predetermined direction. The raster beam drawing method according to claim 1, wherein in the drawing process of at least one of the plurality of processing areas, the method switches between drawing with a charged particle beam with an incident irradiation amount that is the sum of the irradiation amount based on the limiting correction irradiation amount and the ghost irradiation amount, and drawing with a charged particle beam with an incident irradiation amount based on the calculated proximity effect correction irradiation amount without ghost exposure.

3. The drawing area of ​​the sample has a main drawing area located in the center of the sample and a secondary drawing area located around it. The raster beam drawing method according to claim 1 or 2, wherein the threshold value is greater than or equal to the proximity effect correction irradiation amount used in the main drawing area.

4. The ghost irradiation dose is calculated for each region that is larger than the irradiation unit region for irradiating with the charged particle beam. The raster beam drawing method according to claim 1 or 2.

5. The raster beam drawing method according to claim 1 or 2, further comprising the step of creating a proximity effect correction irradiation amount map in which a proximity effect correction irradiation amount for each small region is defined, wherein the proximity effect correction irradiation amount for each small region is changed to the limiting correction irradiation amount, wherein the proximity effect correction irradiation amount for each small region is changed to a proximity effect correction irradiation amount greater than the threshold.

6. A step of limiting the incident irradiation amount in an irradiation unit area that exceeds a preset maximum irradiation amount used for actual drawing to the said maximum irradiation amount, The process of resizing the graphic pattern according to the insufficient irradiation amount that is lacking due to being limited to the maximum irradiation amount, The raster beam drawing method according to claim 1 or 2, further comprising:

7. A proximity effect correction irradiation dose calculation unit calculates a normalized proximity effect correction irradiation dose to correct for the proximity effect when drawing a sample with a charged particle beam, The drawing area of ​​the sample is divided into a mesh-like structure, and for each of the multiple sub-regions, a determination unit determines whether the proximity effect correction irradiation amount for that sub-region is greater than a threshold. Based on the determination, a ghost irradiation amount calculation unit calculates the ghost irradiation amount for ghost exposure in small regions where the proximity effect correction irradiation amount is greater than the threshold, A drawing mechanism for a plurality of irradiation unit regions for irradiating a charged particle beam, wherein the drawing area of ​​the sample is divided into a mesh, and irradiation unit regions with a proximity effect corrected irradiation dose greater than the threshold are drawn with a charged particle beam whose incident irradiation dose is the sum of the ghost irradiation dose and an irradiation dose based on a limiting correction irradiation dose that is more limited than the calculated proximity effect corrected irradiation dose, and irradiation unit regions with a proximity effect corrected irradiation dose not greater than the threshold are drawn without ghost exposure with a charged particle beam whose incident irradiation dose is based on a calculated proximity effect corrected irradiation dose. A raster beam lithography system equipped with a raster beam.

Images