Charged particle beam lithography method, charged particle beam lithography apparatus, and program

Abstract

A method is provided that can correct the focal position even when the height position distribution has changed due to irreversible deformation of a sample caused by irradiation with a charged particle beam. [Configuration] A charged particle beam writing method according to one aspect of the present invention is characterized by comprising the steps of: determining a height change distribution, which defines the height change from the height position of the sample before irradiation caused by irreversible deformation of the sample at each position on the sample at the time of irradiating the sample with a charged particle beam, the sample being irreversibly deformed depending on the irradiation dose distribution of the charged particle beam; correcting the focal position of the charged particle beam when irradiating the sample with the charged particle beam based on the height change distribution; and writing a pattern on the sample with the charged particle beam having the corrected focal position.

Description

[Technical Field]

[0001] One aspect of the present invention relates to a charged particle beam lithography method, a charged particle beam lithography apparatus, and a program, and relates to, for example, a technique for lithography a pattern on a substrate that is irreversibly deformed by irradiation with an electron beam. [Background technology]

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

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

[0004] Here, the positional accuracy of the pattern is important for the mask substrate, and one of the factors that deteriorates the global positional accuracy of the pattern is that the glass substrate used as the sample undergoes reversible deformation due to thermal expansion caused by heating of the glass substrate in association with irradiation of the electron beam and subsequent contraction. The deformation of the glass substrate causes a problem of misalignment of the beam irradiation position or the pattern formation position (see, for example, Patent Document 1).

[0005] On the other hand, in response to these problems, blank manufacturers that produce glass substrates have developed low-thermal expansion material (LTEM) substrates that suppress the thermal expansion of the substrate itself. In such LTEM substrates, thermal expansion due to the temperature rise caused by electron beam irradiation is small, and the deformation of the substrate caused by this can be suppressed. This has solved problems such as positional displacement due to reversible deformation caused by thermal expansion. However, it has become clear that electron beam irradiation causes irreversible shrinkage of the glass substrate. This is due to the fact that the amount of beam irradiation has increased by lowering the resist sensitivity in order to improve local dimensional accuracy, and that the shrinkage phenomenon of the glass substrate has become relatively more apparent as thermal expansion has become negligible with the spread of LTEM substrates.

[0006] As a result, even if the height distribution of the sample surface is measured before writing, the sample warps during writing, causing the height position of the sample surface to change.If the height position of the sample surface shifts before writing, there is a problem in that the accuracy of the focal position of the electron beam deteriorates. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2004-128196 Summary of the Invention [Problem to be solved by the invention]

[0008] One aspect of the present invention provides a method, an apparatus, etc. that can correct the focal position even when the height position distribution has changed due to irreversible deformation of the sample caused by irradiation with a charged particle beam. [Means for solving the problem]

[0009] A charged particle beam lithography method according to one aspect of the present invention is: A step of determining a defined height change distribution for a sample that deforms irreversibly depending on the irradiation dose distribution of a charged particle beam, where the height change from the height position before irradiation, caused by the irreversible deformation of the sample at each position of the sample at the time of irradiation with the charged particle beam, A step of correcting the focal position of the charged particle beam when irradiating a sample with a charged particle beam based on the height change distribution, writing a pattern on a sample with a charged particle beam whose focal position has been corrected; The present invention is characterized by the following features.

[0010] Preferably, the method further comprises the step of correcting the magnification and rotation of the irradiation area of ​​the charged particle beam in synchronization with the correction of the focal position of the charged particle beam.

[0011] Also, a step of determining a dose distribution of the charged particle beam irradiated onto a plurality of processing regions obtained by dividing the writing region of the sample into a mesh pattern; determining a strain distribution that defines the strain at each location of the sample caused by irreversible deformation of the sample using the dose distribution; It is preferable to further include the following:

[0012] Furthermore, the process involves measuring the height distribution of the sample before irradiating it with a charged particle beam, The process involves using the height change distribution at the time of beam irradiation to each position to determine the effective height position distribution for each position in the height position distribution by adding the height change at the time of beam irradiation to the height of that position, Furthermore, The focal position is preferably corrected using the effective height position distribution.

[0013] A charged particle beam lithography apparatus according to one aspect of the present invention comprises: A height change distribution calculation unit determines a defined height change distribution for a sample that deforms irreversibly depending on the irradiation dose distribution of a charged particle beam, where the height change amount from the height position before irradiation, caused by the irreversible deformation of the sample at each position of the sample at the time of irradiation with the charged particle beam, a correction unit that corrects a focal position of the charged particle beam when irradiating the sample with the charged particle beam based on the height change distribution; a drawing mechanism that draws a pattern on a sample using a charged particle beam whose focal position has been corrected; The present invention is characterized by the following features.

[0014] A program according to one aspect of the present invention is: A process to determine the distribution of the irradiation dose of a charged particle beam irradiated onto multiple processing regions, each of which the sample drawing area is divided into a mesh, and which deforms irreversibly depending on the irradiation dose distribution of the charged particle beam. A process of determining a strain distribution that defines the strain amount at each position of the sample at the time of beam irradiation caused by irreversible deformation of the sample using the dose distribution; A process of storing the strain distribution in a storage device; The process involves reading the strain distribution from the storage device, calculating and outputting a height change distribution based on the strain distribution, which defines the height change from the design height position of the sample at each position of the sample at the time of beam irradiation. to be executed by the computer. [Effects of the Invention]

[0015] According to one aspect of the present invention, the focal position can be corrected even when the height position distribution changes due to irreversible deformation of the sample caused by irradiation with a charged particle beam. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a conceptual diagram showing a configuration of a drawing device according to a first embodiment. [Figure 2] FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate according to the first embodiment. [Figure 3] 2 is a cross-sectional view showing the configuration of a blanking aperture array mechanism in the first embodiment. FIG. [Figure 4] FIG. 2 is a diagram showing an example of an evaluation board according to the first embodiment. [Figure 5]This figure shows an example of the relationship between the amount of displacement of the evaluation substrate and an example of substrate deformation in Embodiment 1. [Figure 6] This figure shows an example of the state when the evaluation substrate is irradiated with a beam in Embodiment 1. [Figure 7] 5A and 5B are diagrams showing an example of a stress state caused by beam irradiation on an evaluation substrate in the first embodiment. [Figure 8] 5A and 5B are diagrams showing an example of height position distribution of a sample surface before and after writing in the first embodiment. [Figure 9] FIG. 2 is a flowchart showing an example of main steps of the writing method according to the first embodiment. [Figure 10] 3A to 3C are conceptual diagrams for explaining an example of each region on a sample and an example of a writing operation in the first embodiment. [Figure 11] 3 is a diagram showing an example of a multi-beam irradiation area and a pixel to be written in the first embodiment. FIG. [Figure 12] FIG. 4 is a diagram showing an example of the relationship between the reduction rate of the substrate and the dose amount in the first embodiment. [Figure 13] This figure shows an example of a model using the finite element method in Embodiment 1. [Figure 14] FIG. 10 is a diagram showing an example of a change in height during drawing in the first embodiment. [Figure 15] FIG. 3 is a diagram showing an example of a correction table according to the first embodiment. [Figure 16] This figure illustrates an example of multibeam lithography operation in Embodiment 1. [Figure 17] FIG. 2 is a diagram showing an example of a beam array shape after rotation and magnification correction according to the first embodiment. [Figure 18] This is a conceptual diagram showing an example of the configuration of the drawing device in Embodiment 2. [Figure 19] FIG. 10 is a conceptual diagram for explaining each region in the second embodiment. [Figure 20] FIG. 10 is a diagram for explaining an example of a method for acquiring parameters of deflection sensitivity according to the second embodiment. DETAILED DESCRIPTION OF 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, Embodiment 1 will describe the case where a multi-beam configuration consisting of multiple electron beams is used. However, the correction method described below is not limited to multi-beam configurations and can also be applied to single-beam configurations. Embodiment 2 will describe the case where a single-beam configuration is used.

[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 comprises 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. The lithography mechanism 150 comprises 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 deflector 208, a deflector 209, a detector 212, and at least one correction lens 214, 216, 218.

[0019] It is preferable to use three or more correction lenses as at least one of the correction lenses 214, 216, 218. In the example in Figure 1, three correction lenses 214, 216, 218 are shown. Furthermore, it is preferable to use electrostatic lenses as correction lenses 214, 216, 218, for example. However, it is not limited to this. Electromagnetic lenses may also be used as correction lenses 214, 216, 218. When using electrostatic lenses, for example, one electrostatic lens is constructed by a combination of three electrode substrates: a first electrode substrate to which ground potential is applied, a second electrode substrate to which a control voltage is applied, and a third electrode substrate to which ground potential is applied. Therefore, for example, in the case of a three-stage electrostatic lens, three such combinations are arranged. Note that for adjacent electrostatic lenses, it is also preferable to share one electrode substrate for the upper third electrode substrate and the lower first electrode substrate.

[0020] An XY stage 105 is placed inside the drawing chamber 103. A sample 101, such as a mask, which will be the substrate to be drawn on during drawing (exposure), is placed on the XY stage 105. For example, the back surface of the sample 101 is supported by three rod-shaped support members (not shown) at three points. The sample 101 also includes a mask blank with resist coated on it, but with no drawing yet. A low thermal expansion (LTEM) substrate is used for the glass substrate of the sample 101.

[0021] Furthermore, a mark 106 is placed on the XY stage 105. A cross pattern is preferably used as the mark pattern for the mark 106. The mark pattern may consist of a single cross pattern, or it may consist of multiple cross patterns arranged in an array, for example. The surface of the mark 106 is adjustable to the same height as the surface of the sample 101.

[0022] Furthermore, a mirror 210 for measuring the position of the XY stage 105 is placed on the XY stage 105.

[0023] Furthermore, a z-sensor 220 is positioned in the drawing chamber 103, which measures the height position of the sample surface. This z-sensor is composed of a light emitter 211 that obliquely incidents inspection light onto the surface of the sample 101, and a light receiver 213 that receives the reflected light reflected from the surface of the sample 101.

[0024] The control system circuit 160 includes a control computer 110, memory 112, deflection control circuit 130, correction lens control circuit 131, digital-to-analog converter (DAC) amplifier units 132 and 134, lens control circuit 136, detection circuit 137, 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, correction lens control circuit 131, lens control circuit 136, detection circuit 137, 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 DAC amplifier units 132 and 134 and a blanking aperture array mechanism 204. The 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 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. Electromagnetic lens groups, such as the illumination lens 202, reduction lens 205, and objective lens 207, are controlled by the lens control circuit 136.

[0025] The plurality of correction lenses 214 , 216 , and 218 are controlled by a correction lens control circuit 131 .

[0026] 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.

[0027] The detector 212 detects secondary electrons emitted from the sample surface as a result of the electron beam being irradiated onto the sample surface for mark measurement. The detected signal is output to the detection circuit 137, where it is amplified and converted into digital data before being output to the control computer 110.

[0028] The control computer 110 includes an irradiation dose distribution creation unit 50, a strain amount distribution creation unit 52, a deformation amount distribution creation unit 54, a height change amount distribution calculation unit 56, a height position distribution creation unit 58, an effective height position distribution creation unit 60, a focus correction unit 62, a rotation / magnification correction unit 64, a shot data generation unit 70, a data processing unit 72, a transfer processing unit 74, and a drawing control unit 76. Each of these "~ unit" units, such as the irradiation dose distribution creation unit 50, strain amount distribution creation unit 52, deformation amount distribution creation unit 54, height change amount distribution calculation unit 56, height position distribution creation unit 58, an effective height position distribution creation unit 60, a focus correction unit 62, a rotation / magnification correction unit 64, a shot data generation unit 70, a data processing unit 72, a transfer processing unit 74, and a drawing control unit 76, 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 "~ 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 irradiation amount distribution creation unit 50, strain amount distribution creation unit 52, deformation amount distribution creation unit 54, height change amount distribution calculation unit 56, height position distribution creation unit 58, effective height position distribution creation unit 60, focus correction unit 62, rotation / magnification correction unit 64, shot data generation unit 70, data processing unit 72, transfer processing unit 74, and drawing control unit 76, as well as information being calculated, is stored in the memory 112 each time.

[0029] The drawing operation of the drawing device 100 is controlled by the drawing control unit 76. 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.

[0030] Furthermore, drawing data (chip data) is input from outside the drawing device 100 and stored in the storage device 140. The chip data defines information on a plurality of graphic patterns that make up the chip pattern. Specifically, for example, a coordinate sequence of each vertex coordinate is defined for each graphic pattern. It is also preferable that other data such as a graphic code be defined. Alternatively, the graphic code, coordinates, and size may be defined.

[0031] 1 shows the configuration necessary for explaining the first embodiment. The drawing device 100 may also include other configurations that are normally required.

[0032] FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate in the first embodiment. In FIG. 2, holes (openings) 22 are formed in a matrix of p columns (y direction) by q columns (x direction) (p, q≧2) at a predetermined arrangement pitch in the shaping aperture array substrate 203. The example in FIG. 2 shows a case where, for example, 512×512 columns of holes 22 are formed in the vertical and horizontal directions (x, y directions). The number of holes 22 is not limited to this. For example, 32×32 columns of holes 22 may be formed. Each hole 22 is formed as a rectangle of the same size and shape. Alternatively, it may be a circle of the same diameter. A portion of the electron beam 200 passes through each of the plurality of holes 22, thereby forming a multibeam 20. In other words, the shaping aperture array substrate 203 forms and emits the multibeam 20. The shaping aperture array substrate 203 is an example of an emission source of the multibeam 20.

[0033] FIG. 3 is a cross-sectional view showing the configuration of the blanking aperture array mechanism according to the first embodiment. As shown in FIG. 3, the blanking aperture array mechanism 204 includes a blanking aperture array substrate 31, which is formed on a support substrate 33 and uses a semiconductor substrate made of silicon or the like. In a central membrane region 330 of the blanking aperture array substrate 31, passage holes 25 (openings) for passing through each beam of the multi-beams 20 are formed at positions corresponding to the holes 22 of the shaping aperture array substrate 203 shown in FIG. 2. Pairs of control electrodes 24 and counter electrodes 26 (blankers: blanking deflectors) are disposed at positions facing each other across the corresponding passage holes 25 among the plurality of passage holes 25. Furthermore, a control circuit 41 (logic circuit) is disposed inside the blanking aperture array substrate 31 near each passage hole 25, which applies a deflection voltage to the control electrode 24 for each passage hole 25. The counter electrodes 26 for each beam are connected to ground.

[0034] An amplifier (an example of a switching circuit), not shown, is disposed within the control circuit 41. As an example of the amplifier, a CMOS (Complementary MOS) inverter circuit serving as a switching circuit is disposed. To the input (IN) of the CMOS inverter circuit, either an L (low) potential (e.g., ground potential) that is lower than the threshold voltage or an H (high) potential (e.g., 1.5 V) that is equal to or higher than the threshold voltage is applied as a control signal. In the first embodiment, when an L potential is applied to the input (IN) of the CMOS inverter circuit, the output (OUT) of the CMOS inverter circuit applied to the control circuit 41 becomes a positive potential (Vdd), and the corresponding beam is deflected by an electric field due to the potential difference with the ground potential of the counter electrode 26, and is controlled so that the beam is turned OFF by being shielded by the limiting aperture substrate 206. On the other hand, when an H potential is applied to the input (IN) of the CMOS inverter circuit (active state), the output (OUT) of the CMOS inverter circuit becomes the ground potential, and there is no potential difference with the ground potential of the opposing electrode 26, so the corresponding beam is not deflected, and the beam is controlled to be ON by passing through the limiting aperture substrate 206. Blanking control is performed by this deflection.

[0035] 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).

[0036] The multi-beams 20 that pass through the blanking aperture array mechanism 204 are reduced by the reduction lens 205 and travel toward a central hole formed in the limiting aperture substrate 206. Here, the electron beams deflected by the blankers of the blanking aperture array mechanism 204 are shifted from the central hole of the limiting aperture substrate 206 and are blocked by the limiting aperture substrate 206. On the other hand, the electron beams that are not deflected by the blankers of the blanking aperture array mechanism 204 pass through the central hole of the limiting aperture substrate 206 as shown in FIG. 1. In this way, the limiting aperture substrate 206 blocks each beam that is deflected by the blankers of the blanking aperture array mechanism 204 to be in a beam-off state. Then, each beam of one shot is formed by the beams that pass through the limiting aperture substrate 206 from when the beams are turned on until when they are turned off. The multibeams 20 that have passed through the limiting aperture substrate 206 are focused by the objective lens 207 to form a pattern image with the desired reduction ratio, and the entire multibeams 20 that have passed through the limiting aperture substrate 206 are deflected in the same direction by the deflectors 208 and 209, and each beam is irradiated onto its respective irradiation position on the sample 101. Furthermore, for example, when the XY stage 105 is moving continuously, the deflector 208 performs tracking control so that the beam irradiation position follows the movement of the XY stage 105. Ideally, the multibeams 20 that are irradiated at one time are arranged at a pitch obtained by multiplying the arrangement pitch of the plurality of holes 22 in the shaping aperture array substrate 203 by the desired reduction ratio described above.

[0037] By using an LTEM substrate as the main substrate portion of the sample to be written, thermal expansion due to irradiation with a single or multiple electron beams is virtually eliminated. Therefore, the problem of misalignment of the writing position due to thermal expansion is greatly improved to the point that it can be ignored. However, it has been discovered that the accumulation of dose due to multiple electron beam irradiations can cause irreversible shrinkage of the glass substrate that forms the main substrate of the sample 101.

[0038] Figure 4 shows an example of an evaluation substrate in Embodiment 1. An LTEM substrate is used as the evaluation substrate. Specifically, a mask blank is used in which, for example, a chromium (Cr) film is formed on the LTEM substrate, and a resist film is formed on the Cr film. Figure 4 shows an example of a pattern after three drawing processes. Each drawing process proceeds in the y-direction from the bottom to the top of the evaluation substrate. In the first drawing process (1S), multiple cross patterns are drawn in a grid pattern across the entire evaluation substrate. In the second drawing process (2S), L-shaped patterns are drawn near each cross pattern, for example, in the upper right and lower left corners, and rectangular patterns with different pattern densities in the lower and upper halves of the evaluation substrate are drawn as backgrounds for the multiple cross patterns. For example, the background of the lower half drawn in the first half has a pattern density of, for example, 3%. The background of the upper half drawn in the second half has a pattern density of, for example, 75%. In the third drawing process (3S), L-shaped patterns are drawn near each cross pattern, for example, in the upper left and lower right corners. After each drawing process, the position of each drawn pattern is measured. The pattern's position is measured using a position measuring instrument (not shown).

[0039] Figure 5 shows an example of the relationship between the amount of displacement of the evaluation substrate and an example of substrate deformation in Embodiment 1. Figure 5 shows an example of a graph of the amount of displacement Δx in the x direction in the state (2S-1S), which is obtained by subtracting the position of each pattern after drawing process 1S from the position of each pattern after drawing process 2S. As shown in the (2S-1S) graph, the amount of displacement Δx is small at a pattern density of 3% background, whereas at a pattern density of 75% background, the amount of displacement Δx increases with increasing area of ​​drawing. This indicates that the deformation due to shrinkage of the glass substrate increases depending on the amount of irradiation. Figure 5 also shows an example graph of the x-direction misalignment Δx and the y-direction misalignment Δy for the (3S-1S) state, which is the difference between the position of each pattern after 3S and the position of each pattern after 1S. As shown in the (3S-1S) graph, the misalignment Δx at 2S remains even after 3S. It can also be seen that the lower half of the substrate deforms in response to the shrinkage of the upper half, and by 3S, the substrate position shifts, increasing the misalignment Δx. It can also be seen that the misalignment ΔY in the y-direction gradually increases in the upper half of the substrate. This is due to the fact that the upper half of the substrate is irradiated with a relatively large beam dose, causing significant deformation due to shrinkage, as shown in the lower right diagram of Figure 5. As shown in the diagram, the upper half of the substrate is deformed due to significant shrinkage caused by 2S.

[0040] Figure 6 shows an example of the state when the evaluation substrate is irradiated with a beam in Embodiment 1. Figure 7 shows an example of the stress state caused by beam irradiation to the evaluation substrate in Embodiment 1. As described above, the evaluation substrate shown in FIG. 6 is a mask blank in which, for example, a chromium (Cr) film 13 is formed on an LTEM substrate 12 and a resist film 16 is formed on the Cr film 13. When an electron beam is irradiated onto this evaluation substrate, the electron beam reaches the LTEM substrate 12 and penetrates several tens of micrometers into the surface of the LTEM substrate 12. This causes irreversible localized contraction of the LTEM substrate 12 at the irradiated position. Because the beam is irradiated at multiple locations, localized contraction occurs throughout the entire beam-irradiated region, generating tensile stress near the substrate surface as shown in FIG. 7. This causes irreversible deformation near the surface of the LTEM substrate 12 due to the contraction phenomenon. Note that a deformation of, for example, a depth of 20 μm is small compared to the thickness of the LTEM substrate 12 (e.g., 6.35 mm), and therefore the nature of thermal deformation of the entire substrate remains unchanged. Therefore, reversible deformation due to thermal expansion can be ignored.

[0041] FIG. 8 is a diagram showing an example of the height position distribution of the sample surface before and after writing in the first embodiment. In FIG. 8, the vertical axis represents the height position z, and the horizontal axis represents the position. It is assumed that the sample is supported at three points. As described above, the sample warps due to irreversible deformation caused by irradiation with the electron beam. Therefore, as shown in FIG. 8, the height position changes at each position on the sample. Due to the warping of the sample, the height position changes in the -z direction, particularly on the inside of the three-point support, and the height position changes in the +z direction on the outside of the three-point support.

[0042] If the height position of the surface of the sample 101 changes during writing, the focal position of the multi-beam 20 will shift. As a result, the beam will become blurred. Generally, the height position of the sample surface is measured before writing, and the focal position is dynamically corrected according to the measured height position distribution, assuming that the height position will not change. However, if the height position distribution continues to change gradually due to irreversible deformation caused by the irradiation of the electron beam during writing, the focus correction accuracy will deteriorate.

[0043] Therefore, in Embodiment 1, the amount of height position change due to irreversible deformation associated with the irradiation of the electron beam during drawing is calculated, and the focus correction deviation is corrected. This will be explained in detail below.

[0044] Fig. 9 is a flowchart showing an example of main steps of the writing method according to Embodiment 1. In Fig. 9, the writing method according to Embodiment 1 carries out a series of steps including a height position distribution measuring step (S102), a dose map creating step (S108), a writing schedule creating step (S110), an irradiation dose distribution creating step (S112), a distortion amount distribution creating step (S114), a deformation amount distribution creating step (S116), a height change amount distribution creating step (S118), a determination step (S120), an effective height position distribution creating step (S130), and a writing step (S140). Within the drawing process (S140), the dynamic correction process (S142) and the shot process (S144) are repeated. Furthermore, the height-position distribution measurement process (S102) may be performed after the determination process (S120). Alternatively, the height-position distribution measurement process (S102) may be performed in parallel with the series of processes from the dose map creation process (S108) to the determination process (S120).

[0045] Figure 10 is a conceptual diagram illustrating an example of each region on the sample and an example of the drawing operation in Embodiment 1. As shown in Figure 10, the drawing region 30 (thick line) of the sample 101 is defined based on the position of the reference mark 14. The drawing area 30 (thick line) is virtually divided into multiple stripe-shaped areas 32 with a predetermined width in the y direction, for example. In the example in Figure 10, the drawing area 30 of the sample 101 is shown as being divided into multiple stripe areas 32 with a width size that is substantially the same as the size of the designed irradiation area 34 (beam array area) that can be irradiated with a single multi-beam 20 irradiation, for example 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.

[0046] 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. 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.

[0047] Next, the irradiation area 34 of the multibeam 20 is adjusted to be located at the left end of the second stripe area 32 or at a position further to the left, and the XY stage 105 is moved, for example, in the -x direction, thereby relatively progressing the drawing in the x direction, thereby drawing the second stripe area 32. Thereafter, drawing is similarly performed in order from the lower stripe area 32 toward the upper side (y direction).

[0048] 10 shows the case where each stripe region 32 is written in the same direction, but this is not limiting. For example, the stripe region 32 to be written next to the stripe region 32 written in the x direction may be written in the -x direction by moving the XY stage 105 in the x direction, for example. By writing while alternating directions in this way, the stage movement time can be shortened, and ultimately the writing time can be shortened. In one shot, the multi-beam 20 formed by passing through each hole 22 in the shaping aperture array substrate 203 simultaneously forms multiple shot patterns, up to the same number as the holes 22.

[0049] FIG. 11 shows an example of a multibeam irradiation area and a target pixel for drawing in the first embodiment. In FIG. 11, a stripe area 32 is divided into a plurality of mesh areas, for example, based on the beam size of the multibeam 20. Each mesh area corresponds to a target pixel 36 (unit irradiation area, irradiation position, or drawing position). The size of the target pixel 36 is not limited to the beam size and may be any size regardless of the beam size. For example, the size may be 1 / n (n is an integer greater than or equal to 1) of the beam size. The example of FIG. 11 shows a case where the target region for drawing on the sample 101 is divided, for example, in the y direction, into a plurality of stripe areas 32, each having a width substantially equal to the size of an irradiation region 34 (drawing field) that can be irradiated with a single irradiation of the multibeam 20. The size of the rectangular irradiation region 34 in the x direction can be defined by the number of beams in the x direction multiplied by the beam pitch in the x direction. The size of the rectangular irradiation region 34 in the y direction can be defined by the number of beams in the y direction multiplied by the beam pitch in the y direction. In the example of FIG. 11, for example, a 512×512 array of multi-beams is shown as an 8×8 array of multi-beams. A plurality of pixels 28 (beam drawing positions) that can be irradiated with one shot of the multi-beam 20 are shown within the irradiation area 34. The pitch between adjacent pixels 28 is the pitch between each beam of the multi-beam. A rectangular area surrounded by the size of the beam pitch in the x and y directions constitutes one sub-irradiation area 29 (pitch cell). In the example of FIG. 11, each sub-irradiation area 29 is shown as being composed of, for example, 4×4 pixels.

[0050] The drawing method of the first embodiment will be described below with reference to the flowchart shown in FIG.

[0051] In the height position distribution measurement step (S102), the height position distribution creation unit 58 measures the height position distribution of the sample 101 before irradiating the sample 101 with the multibeam 20. Specifically, the operation is as follows. First, the XY stage 105 is moved to a position where the inspection light from the z sensor 220 is irradiated onto the left end of the first stripe region 32. Then, the inspection light is scanned over each stripe region 32, starting from the first stripe region 32. As a result, the reflected light at each position is measured by the photodetector 213, and the height position at each position is measured using the optical lever principle. The measured height position information is output to the control computer 110. The height position distribution creation unit 58 creates a height position distribution of the sample 101 using the input height position information for each position. The height position distribution is defined, for example, as the amount of change from the designed height position. The created height position distribution data is stored in the storage device 142.

[0052] In the dose map creation step (S108), the shot data generation unit 70 creates a dose map in which a dose amount is defined for each pixel, which will be described later. Specifically, the shot data generation unit 70 operates as follows: First, as a rasterization process, the shot data generation unit 70 calculates, for each pixel 36, a pattern area density ρ′ of the pattern to be placed in the neighboring mesh region.

[0053] Next, the shot data generation unit 70 virtually divides the writing region (for example, a stripe region) into a plurality of proximity mesh regions (mesh regions for calculating proximity effect correction) in a mesh shape of 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 dose map creation unit 50 reads out the writing data from the storage device 140, and calculates, for each proximity mesh region, the pattern area density ρ″ of the pattern to be placed in that proximity mesh region.

[0054] Next, the shot data generation unit 70 calculates a proximity effect corrected dose Dp(x) for correcting the proximity effect for each proximity mesh region. The unknown proximity effect corrected dose Dp(x) can be defined by a threshold model for proximity effect correction similar to conventional methods, using a backscattering coefficient η, a dose threshold Dth of a threshold model, a pattern area density ρ", and a distribution function g(x). The proximity effect corrected dose Dp(x) is calculated as a relative value normalized with the base dose Dbase set to 1.

[0055] Next, the shot data generation unit 70 calculates, for each pixel, an incident irradiation dose D(x) (dose) for irradiating the pixel. The incident irradiation dose D(x) may be calculated, for example, as the value obtained by multiplying the base irradiation dose Dbase by the proximity effect-corrected irradiation dose Dp and the pattern area density ρ'. The base irradiation dose Dbase may be defined, for example, as Dth / (1 / 2 + η). As a result, the proximity effect-corrected incident irradiation dose D(x) for each pixel can be obtained based on the layout of multiple graphic patterns defined in the drawing data. Alternatively, the shot data generation unit 70 may preferably define the incident irradiation dose D(x) for each pixel as an incident irradiation dose D(x) normalized by setting the base irradiation dose Dbase to 1. In this case, the incident irradiation dose D(x) may be calculated, for example, as the value obtained by multiplying the proximity effect-corrected irradiation dose Dp by the pattern area density ρ'.

[0056] Next, the shot data generation unit 70 creates a dose map whose elements are the incident irradiation dose D(x) of each pixel 36. In other words, each pixel (position) (x, y) is defined in association with the incident irradiation dose D(x) of that pixel. The created dose map is stored in the storage device 142. The shot data generation unit 70 creates a dose map for the entire drawing region 30 where drawing processing is performed in accordance with the drawing data (chip data).

[0057] In the writing schedule creation step (S110), the writing control unit 76 creates a writing schedule that defines the shot order for each pixel defined in the dose map. This allows the position and dose of irradiation that have been performed up until the time of the shot (writing) to be known for each shot.

[0058] Here, the influence range of the global displacement is in the range of several hundred μm to several millimeters. Therefore, the influence range of the global displacement is larger than the beam array size (x and y directions) of the multi-beam 20, for example, several tens of μm. So, the drawing control unit 76 first virtually divides the area of ​​the sample 101 surface into multiple global mesh regions 11 in a mesh-like manner of a predetermined size, as shown in Figure 10. The size of the global mesh region 11 is preferably set to about 1 / 10 of the influence range of the global displacement, which is several tens of μm to several hundred μm. For example, if the beam array size is about 80 μm, it is preferable to set it to about half of that, about 40 μm. However, this is not limited to cases smaller than the beam array size. It may be a size larger than the beam array size.

[0059] In the dose distribution creation step (S112), the dose distribution creation unit 50 calculates the dose distribution of the electron beam irradiated onto a plurality of global mesh regions 11(xi, yi) (processing regions) obtained by dividing the writing region 30 of the sample 101 into a mesh. In other words, the dose distribution creation unit 50 creates the dose distribution of the electron beam irradiated onto a plurality of global mesh regions 11(xi, yi) (processing regions) obtained by dividing the writing region 30 of the sample 101 into a mesh. Specifically, the operation is as follows. The dose distribution creation unit 50 creates, from the writing schedule, a dose distribution indicating the dose of each global mesh region 11 at the time of beam irradiation onto each global mesh region 11(xi, yi) (an example of a position) of the sample 101 when the multibeam 20 is irradiated to write a pattern. For example, for each of the multiple shots of the multibeam 20, a dose distribution is created indicating the dose of each global mesh region 11 irradiated up to that point when the shot at the coordinate (xj, yj) of the sample 101 is completed. i indicates the index of the global mesh region 11. j indicates the index of the shot number. Coordinates (xj, yj) indicate the reference position in the shot. For example, they indicate the coordinates irradiated by the central beam of the multi-beam 20. The dose to each global mesh region 11 is calculated by referring to the dose map and calculating the total incident dose irradiated to each global mesh region 11 (xi, yi).

[0060] In the strain distribution creation step (S114), the strain distribution creation unit 52 uses the irradiation dose distribution to determine a strain distribution that defines the amount of strain at each position on the sample 101 caused by irreversible deformation of the sample 101. In other words, the strain distribution creation unit 52 uses the irradiation dose distribution to determine a strain distribution that defines the amount of strain at each position on the sample 101 caused by irreversible deformation of the sample 101 at the time of beam irradiation to each position on the sample 101. In further words, the strain distribution creation unit 52 uses the irradiation dose distribution to create a strain distribution that defines the amount of strain generated in the sample 101. Specifically, the operation is as follows. The strain distribution creation unit 52 calculates the amount of strain generated in each global mesh region 11(xi, yi) at each time a beam is irradiated onto each global mesh region 11 (an example of a position) of the sample 101, and creates a strain distribution. For example, for each shot, the strain distribution is calculated to create a strain distribution by calculating the amount of strain generated in each global mesh region 11(xi, yi) at the time the shot at coordinates (xj, yj) is completed. Irreversible compressive deformation occurs on the surface of the global mesh region 11 irradiated with the multibeam 20 and in the vicinity thereof (hereinafter referred to as the surface) due to the beam irradiation, and other surfaces of the global mesh region 11 are stretched by stress caused by compressive strain on the surface of the beam-irradiated global mesh region 11. As a result, distortion occurs on the surface of each global mesh region 11 (xi, yi).

[0061] FIG. 12 is a diagram showing an example of the relationship between the reduction ratio of a substrate and the dose amount in the first embodiment. In FIG. 12, the vertical axis represents the reduction ratio, and the horizontal axis represents the dose amount. In the example of FIG. 12, dies a to d were written with variable pattern area density ρ and variable irradiation dose amount D. Then, the amount of distortion (reduction ratio: ΔL / L) in each die was calculated, and the relationship between the amount of distortion (reduction ratio) and ρD (total dose amount per unit area) was calculated. L represents the size of the substrate, and ΔL represents the amount of misalignment. As shown in the example of FIG. 12, it can be seen that the distortion (reduction ratio) increases in proportion to ρD. Therefore, the amount of distortion (reduction ratio) can be obtained using the irradiation amount defined in the irradiation dose distribution. In other words, the sample 101 is irreversibly deformed depending on the irradiation dose distribution of the electron beam.

[0062] Fig. 13 is a diagram showing an example of a model based on the finite element method according to Embodiment 1. In the example of Fig. 13, a 6-inch mask, which is an example of the sample 101, is divided into triangular pyramidal elements. Each triangular pyramid element has four vertices, each of which is connected to a displacement vector u = (u x ,u y ,u z ) three-dimensional displacement information. In other words, one unit element has a total of 4 × 3 = 12 variables. In the relational expression ε = Bu between this displacement vector u (12 × 1) and the strain vector ε (6 × 1), the strain-displacement matrix M1 (6 × 12) of the unit element is expressed as the following equation (1), for example.

[0063]

number

[0064] On the other hand, in the relational expression σ = Dε between the stress vector σ (6 × 1) and the strain vector ε (6 × 1), the material property matrix M2 (6 × 6) of the unit element is expressed as the following equation (2) using the Young's modulus E and Poisson's ratio ν of the quartz substrate.

[0065]

number

[0066] Here, the distortion e of the substrate surface caused by the charged particle beam irradiation dose Q (=ρD) is defined by the following equation (3) using coefficients c0 and c1.

[0067]

number

[0068] If we assume that the shear strain caused by the charged particle beam irradiation is zero, the strain vector ε of the unit element can be defined by the following equation (4).

[0069]

number

[0070] The stiffness matrix per unit element is then described by the following equation (5).

[0071]

number

[0072] However, t represents the transpose matrix. By combining the above equations for all elements, the displacement vectors U at all vertices, the overall stiffness matrix K, and the equivalent nodal forces f are defined as shown in the following equations (6-1), (6-2), and (6-3).

[0073]

number

[0074] As a result, it can be expressed as equation (7) below.

[0075]

number

[0076] Finally, the total displacement vector U can be calculated using the following equation (8).

[0077]

number

[0078] By substituting the values ​​of the elements of the irradiation dose distribution into Q in equation (3), the strain e of each element and the strain vector ε in equation (4) are obtained. This allows the amount of strain in each global mesh region 11 at the time of the beam shot to coordinate (xi, yi) to be determined, and a strain distribution is created. The strain distribution is stored in the memory device 142.

[0079] As part of the deformation distribution creation process (S116), the deformation distribution creation unit 54 uses the strain distribution to calculate the irreversible deformation amounts (Δxi, Δyi, Δzi) occurring in each global mesh region 11 (xi,yi) at each beam irradiation point and creates a deformation distribution. For example, for each shot, the irreversible deformation amounts occurring in each global mesh region 11 at the time the shot to coordinate (xj,yj) is completed are calculated and a deformation distribution is created. For example, by finding f in equation (6-3) under the obtained strain vector ε of each element and solving equation (8), the total displacement vector U, including the displacement vector u of each element at the time the shot to coordinate (xj,yj) is completed, is calculated. This makes it possible to determine the irreversible deformation amounts (Δxi, Δyi, Δzi) occurring in each global mesh region 11 (xi,yi) at the time the shot to coordinate (xj,yj) is completed. The deformation distribution is stored in the memory device 142.

[0080] As a height change distribution creation step (S118), the height change distribution calculation unit 56 determines a height change distribution that defines the height change amount from the height position of the sample 101 before irradiation, which occurs at the time of beam irradiation of the sample 101 at each position of the sample 101, due to the irreversible deformation of the sample 101 at the time of beam irradiation, for the sample 101 which deforms irreversibly depending on the irradiation dose distribution of the multi-beam 20. In other words, the height change distribution calculation unit 56 reads the strain distribution from the storage device 142 and calculates and outputs a height change distribution that defines the height change amount from the design height position of the sample 101 at each position of the sample 101 at the time of beam irradiation, based on the strain distribution. To put it another way, the height change distribution calculation unit 56 creates a height change distribution that defines the height change amount from the design height position of the sample 101, which occurs at the time of beam irradiation of the sample 101 at each position of the sample 101, due to the irreversible deformation of the sample 101, when drawing a pattern by irradiating the sample 101 with the multi-beam 20, which deforms irreversibly depending on the irradiation dose distribution of the multi-beam 20. A height variation distribution is created for each point (xj, yj) at which the beam is irradiated. For example, the height change dzi at a representative position, such as the center position, of each global mesh region 11 is calculated to create a height change distribution. The height change dzi due to the Nth shot at a representative position (xi, yi) of each global mesh region 11 is calculated from the dose distribution due to the (N-1)th shot of that global mesh region. The strain e of each element and the strain vector ε of equation (4) are calculated from the dose distribution and equation (3). Then, f of equation (6-3) is calculated using the obtained strain vector ε of each element, and equation (8) is solved to calculate the total displacement vector U, including the displacement vector u of each element when the shot at coordinate (xj, yj) is completed. This allows the positional deviation (dxi, dyi, dzi), including the height change, that occurs in each global mesh region 11 (xi, yi) when the shot at coordinate (xj, yj) is completed. As the surface of the substrate body of the sample 101 shrinks in the compression direction, the sample 101 deforms and warps downward, as shown in Figure 5.

[0081] FIG. 14 is a diagram showing an example of the progression of height change during writing in embodiment 1. In FIG. 14, the vertical axis represents the height change amount, and the horizontal axis represents the x-coordinate. Although the example in FIG. 14 shows the x-direction, the height position also changes in the y-direction. In the middle of the first half of the writing process, as shown in graph A, the sample 101 is warped, but the height change amount is small. In the middle of the writing process, as shown in graph B, the warp of the sample 101 progresses, and the height change amount at each position also increases. At the end of writing, as shown in graph C, the warp progresses further, and the height change amount at each position also increases.

[0082] In the determination step (S120), the writing control unit 76 (an example of a determination unit) determines whether height change amount distributions have been created for all shots. If height change amount distributions have not yet been created for all shots, the process returns to the dose distribution creation step (S112), and the steps from the dose distribution creation step (S112) to the determination step (S120) are repeated while incrementing the shot number to the next number until height change amount distributions have been created for all shots. The calculated height change amount distributions for each shot are output and stored in the storage device 142.

[0083] The height distribution created in the height distribution creation step (S102) does not take into account height changes due to irreversible deformation caused by electron beam irradiation. Therefore, if left as is, the height of each position on the actual sample 101 during beam irradiation will differ. Therefore, in the first embodiment, an effective height distribution is created so as to match the height of each position on the actual sample 101.

[0084] In the effective height position distribution creation step (S130), the effective height position distribution creation unit 60 uses the height change distribution at the time of irradiating each position with the multibeam 20 to calculate an effective height position distribution by adding the height change at the time of irradiating the position with the beam to the height position of that position for each position in the height position distribution. In other words, the effective height position distribution creation unit 60 uses the height change distribution at the time of irradiating each position with the beam to create an effective height position distribution by adding the height change at the time of irradiating the position with the beam to the height position of that position for each position in the height position distribution. The effective height position is defined, for example, by the effective height change from the designed height position. Here, since the height at the time of beam irradiation is required, it is preferable to add, for example, the height change at the stage immediately before beam irradiation at that position as the height change at the time of beam irradiation. However, this is not limited to this. The global height change between immediately before and immediately after beam irradiation at that position is small. Therefore, for example, the height change at the time of beam irradiation may be added as the height change at the time of beam irradiation. Furthermore, the height change amount is the height change amount in the global mesh region 11 that includes the location in question.

[0085] After the above pre-processing is completed, the actual drawing process is carried out.

[0086] In the writing step (S140), first, the shot data generation unit 70 calculates the irradiation time for each pixel 36 using the incident irradiation amount D(x) (dose amount) defined in the dose map. The irradiation time for each pixel 36 can be calculated by dividing the incident irradiation amount D(x) for that pixel by the current density J. When the incident irradiation amount D(x) defined in the dose map is normalized with the reference irradiation amount Dbase set to 1, the irradiation time for each pixel 36 can be calculated by multiplying the incident irradiation amount D(x) by the reference irradiation amount Dbase and dividing the result by the current density J.

[0087] Then, the data processing unit 72 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 transfers the irradiation time data to the deflection control circuit 130 in shot order.

[0088] Then, under the control of the writing control unit 76, the writing mechanism 150 writes a pattern on the sample 101 with the multi-beam 20 (electron beam) whose focal position has been dynamically corrected, while dynamically correcting the focal position of the multi-beam 20 with at least one correcting lens 214, 216, 218. This will be specifically described below.

[0089] As a dynamic correction step (S142), the focus correction unit 62 corrects the focal position of the multi-beam 20 when irradiating the sample 101 with the multi-beam 20, based on the height change distribution. Here, for example, the correction is performed dynamically. The focus correction unit 62 dynamically corrects the focal position of the multi-beam 20 for each shot. Specifically, the focal position is corrected using the effective height position distribution. In other words, the focus correction unit 62 dynamically corrects the focal position of the multi-beam 20 when irradiating the sample 101 with the multi-beam 20 using the effective height position distribution. The dynamic correction of the focal position is performed by multiple correction lenses 214, 216, and 218. Here, when the focal position of the multi-beam 20 is shifted, the rotation and magnification of the multi-beam 20 image also change accordingly. When the rotation and magnification of the multi-beam 20 image change, the beam array shape on the sample surface shifts. Therefore, in Embodiment 1, it is preferable to correct the magnification and rotation of the irradiation area of ​​the multi-beam 20 in synchronization with the correction of the focal position of the multi-beam 20.

[0090] Figure 15 shows an example of a correction table in Embodiment 1. In Figure 15, the correction table defines the correction amounts Δ for three correction lenses 1, 2, and 3 that correct the focal position, rotation, and magnification for each height change Δz from the design height position. Since there are three correction parameters—focal position, rotation, and magnification—three correction lenses are required. Here, the correction amounts for the lens values ​​of the three correction lenses are determined in advance by experiment or simulation so that no rotational or magnification changes occur on the sample surface of the multi-beam 20 image when the focal position is corrected according to the height change. These values ​​are then defined as a correction table.

[0091] The multi-beam 20 scans the mark 106 with at least four corner beams, and the secondary electrons emitted from the mark 106 are detected by the detector 212, converted into digital data by the detection circuit 137, and output to the control computer 110. The drawing control unit 76 calculates the beam array shape from the measured mark positions at at least four corners. More precisely, this can be obtained by similarly measuring the mark positions on beams at even more positions. This provides the beam array shape for each height change Δz. Once the beam array shape is obtained, correction amounts for rotation and magnification are obtained by measuring the rotation and magnification changes from the design beam array shape.

[0092] The correction table is stored in the storage device 142.

[0093] The correction lens control circuit 131 refers to the correction table and, for each shot, adds the correction amount of each correction lens 214, 216, and 218 to the lens value according to the height change corresponding to the shot position. As a result, the multiple correction lenses 214, 216, and 218 dynamically correct the focal position of the multi-beam 20. In addition, it corrects the rotational and magnification changes of the multi-beam 20.

[0094] Furthermore, if only the focal position of the multi-beam 20 is corrected, and the rotational and magnification changes of the multi-beam 20 are ignored, there is only one correction parameter, and therefore only one correction lens is needed. Thus, at least one correction lens is sufficient.

[0095] As a shot process (S144), the drawing mechanism 150 draws a pattern on the sample 101 with a multi-beam 20 whose focal position has been corrected. Specifically, the drawing mechanism 150 shots the sample 101 with at least a multi-beam 20 whose focal position has been corrected for each shot. By repeating this dynamic correction process (S142) and the shot process (S144), the drawing mechanism 150 draws a drawing pattern on the sample by combining the shot patterns.

[0096] Figure 16 is a diagram illustrating an example of multi-beam drawing operation in Embodiment 1. The example in Figure 16 shows a case where each sub-irradiation region 29, enclosed by the beam pitch and including one beam irradiation position of each of the multi-beams 20, is drawn with four different beams. The example in Figure 16 also shows a drawing operation in which the XY stage 105 moves continuously at a speed that moves, for example, by the distance of two beam pitches, while drawing 1 / 4 (1 of the number of beams used for irradiation) of the area within each sub-irradiation region 29. The example in Figure 16 shows a case where each sub-irradiation region 29 is composed of, for example, 4 × 4 pixels.

[0097] In the drawing operation shown in the example in Figure 16, for example, while the XY stage 105 moves a distance of 2 beam pitches in the x direction, the deflector 209 sequentially shifts the irradiation position (pixel 36), and four shots of the multi-beam 20 are taken in a shot cycle T, thereby drawing (exposing) four different pixels 36 within the same sub-irradiation area 29. While these four pixels 36 are being drawn (exposed), the deflector 208 deflects the entire multi-beam 20 collectively so that the irradiation area 34 does not shift 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. In the example in Figure 16, the tracking cycle is given as an example of the time it takes for the XY stage 105 to move a distance of 2 beam pitches in the x direction, but it is not limited to this. It may also be the time it takes to move a distance greater than 2 beam pitches, for example, 8 beam pitches or 16 beam pitches.

[0098] Once a tracking cycle is completed, the tracking is reset and returned to the previous tracking start position. Since the first pixel row from the left of each sub-irradiation area 29 has already been drawn, after the tracking reset, in the next tracking cycle, the deflector 209 first deflects (shifts) the beam so that it can draw a different beam from the first pixel row, for example, the second pixel row from the left of each sub-irradiation area 29, which has not yet been drawn. By repeating this operation while drawing the stripe area 32, the position of the irradiation area 34 (34a~34o) of the multi-beam 20 moves sequentially, as shown in the middle diagram of Figure 10, and drawing is performed.

[0099] Figure 17 shows an example of a beam array shape after rotation and magnification correction in Embodiment 1. As shown in Figure 17, the beam array shape of the multi-beam 20, whose rotation and magnification have changed on the sample surface by correcting the focus shift, can be corrected to a rectangle, for example, in synchronization with the focus correction. For example, it can be returned to the shape before focus correction.

[0100] As described above, according to Embodiment 1, the focal position can be corrected even when the height position distribution changes due to irreversible deformation of the sample 101 caused by irradiation with the multi-beam 20. In addition, the beam array shape can also be corrected.

[0101] Embodiment 2 Embodiment 1 describes a case in which focus correction and corresponding beam array shape correction are performed in response to changes in height position due to irreversible deformation caused by multi-beam irradiation, but it is not limited to this. Embodiment 2 describes a case in which focus correction and corresponding deflection sensitivity correction are performed in response to changes in height position due to irreversible deformation caused by single-beam irradiation of a variable molding die (VSB type).

[0102] The main steps of the writing method in the second embodiment are the same as those in Fig. 9. The contents other than those specifically explained below are the same as those in the first embodiment.

[0103] FIG. 18 is a conceptual diagram showing an example of the configuration of a drawing apparatus according to the second embodiment. In FIG. 18, the drawing apparatus 400 includes a drawing mechanism 450 and a control circuit 460. The drawing apparatus 400 is an example of a charged particle beam drawing apparatus. In particular, it is an example of a variable shaping type (VSB type) drawing apparatus. The drawing mechanism 450 includes an electron lens barrel 402 and a drawing chamber 403. Inside the electron lens barrel 402, an electron gun 501, an illumination lens 502, a blanking deflector (blanker) 512, a blanking aperture 514, a first shaping aperture 503, a projection lens 504, a deflector 505, a second shaping aperture 506, an objective lens 507, a main deflector 508, a sub-deflector 509, a detector 212, and at least one of correction lenses 214, 216, and 218 are arranged.

[0104] An XY stage 405 movable in at least the X and Y directions is placed in the patterning chamber 403. A resist-coated sample 101 (substrate) to be patterned is placed on the XY stage 405. For example, the backside of the sample 101 is supported at three points by three rod-shaped support members (not shown). The sample 101 also includes a mask blank coated with resist but on which nothing has yet been patterned. A low thermal expansion (LTEM) substrate is used as the glass substrate for the sample 101.

[0105] Furthermore, a mark 106 is placed on the XY stage 405. The mark 106 is the same as that in the first embodiment.

[0106] Also, illustration of the drive mechanism and position measurement mechanism of the XY stage 405 is omitted, and therefore illustration of mirrors for measuring the position of the XY stage 405 is omitted.

[0107] Moreover, above the writing chamber 403, the z sensor 220 similar to that in the first embodiment is disposed.

[0108] The control system circuit 460 includes a control computer unit 410, a memory 412, a deflection control circuit 420, DAC (digital-analog converter) amplifier units 430, 432, and 434 (deflection amplifiers), a correction lens control circuit 431, and storage devices 440 and 442 such as magnetic disk drives. The control computer unit 410, the deflection control circuit 420, and the storage devices 440 and 442 such as magnetic disk drives are connected to one another via a bus (not shown). The DAC amplifier units 430, 432, and 434 are connected to the deflection control circuit 420. The DAC amplifier unit 430 is connected to a blanking deflector 512. The DAC amplifier unit 432 is connected to a sub-deflector 509. The DAC amplifier unit 434 is connected to a main deflector 508.

[0109] The plurality of correction lenses 214 , 216 , and 218 are controlled by a correction lens control circuit 431 .

[0110] The detector 212 detects secondary electrons emitted from the sample surface when the sample surface is irradiated with an electron beam for mark measurement. The detected signal is output to a detection circuit (not shown), amplified, converted into digital data, and then output to the control computer 410.

[0111] Furthermore, the control computer unit 410 includes an irradiation dose distribution creation unit 50, a strain amount distribution creation unit 552, a deformation amount distribution creation unit 54, a height change amount distribution calculation unit 56, a height position distribution creation unit 58, an effective height position distribution creation unit 60, a focus correction unit 62, a deflection sensitivity correction unit 63, a shot data generation unit 70, a transfer processing unit 74, and a drawing control unit 76. Each of these "~ unit" components, such as the irradiation dose distribution creation unit 50, strain amount distribution creation unit 52, deformation amount distribution creation unit 54, height change amount distribution calculation unit 56, height position distribution creation unit 58, an effective height position distribution creation unit 60, a focus correction unit 62, a deflection sensitivity correction unit 63, a shot data generation unit 70, a transfer processing unit 74, and a drawing control unit 76, 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 "~ 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 irradiation dose distribution creation unit 50, strain amount distribution creation unit 52, deformation amount distribution creation unit 54, height change amount distribution calculation unit 56, height position distribution creation unit 58, effective height position distribution creation unit 60, focus correction unit 62, deflection sensitivity correction unit 63, shot data generation unit 70, transfer processing unit 74, and drawing control unit 76, as well as information being calculated, is stored in the memory 112 each time.

[0112] The drawing operation of the drawing apparatus 100 is controlled by a drawing control unit 76. Furthermore, the transfer process of the shot data of each shot to the deflection control circuit 430 is controlled by a transfer processing unit 74.

[0113] Furthermore, drawing data (chip data) is input from outside the drawing device 400 and stored in the storage device 440. The chip data defines information about multiple graphic patterns that constitute the chip pattern. Specifically, for each graphic pattern, for example, a coordinate sequence of each vertex coordinate is defined. In addition, graphic codes and the like may also be defined. Alternatively, graphic codes, coordinates, and size may be defined.

[0114] Figure 19 is a conceptual diagram illustrating each region in Embodiment 2. In Figure 19, the drawing region 30 of the sample 101 is virtually divided into multiple stripe regions 32 in a stripe-like shape in the y-direction, for example, by the deflection width of the main deflector 508. Each stripe region 32 is also virtually divided into multiple subfields (SFs) 530 (small regions) in a mesh-like shape by the deflection size of the sub-deflector 509. Shot figures 542 are then drawn at each shot position in each SF 530. The sample 101 is also divided into multiple global mesh regions 11, similar to Embodiment 1. The global mesh regions 11 are preferably set to about 1 / 10 of the influence range of the global positional displacement, or to about several tens of micrometers to several hundred micrometers. For example, they are formed to the same size as the SF 530. However, they are not limited to this. The global mesh regions 11 may be larger or smaller than the SF 530.

[0115] A digital signal for blanking control is output from the deflection control circuit 420 to the DAC amplifier unit 430. The DAC amplifier unit 430 then converts the digital signal to an analog signal, amplifies it, and applies it as a deflection voltage to the blanking deflector 512. This deflection voltage deflects the electron beam 500, forming the beam for each shot.

[0116] A digital signal for main deflection control is output from the deflection control circuit 420 to the DAC amplifier unit 434. The DAC amplifier unit 434 then converts the digital signal to an analog signal, amplifies it, and applies it as a deflection voltage to the main deflector 508. This deflection voltage deflects the electron beam 500, causing the beam of each shot to be deflected to a reference position in a predetermined subfield (SF) that is virtually divided into a mesh.

[0117] The deflection control circuit 420 outputs a digital signal for sub-deflection control to the DAC amplifier unit 432. The DAC amplifier unit 432 then converts the digital signal into an analog signal, amplifies it, and applies it as a deflection voltage to the sub-deflector 509. The electron beam 500 is deflected by this deflection voltage, and each shot of the beam is deflected to each shot position within a predetermined sub-field (SF) that is virtually divided into a mesh shape.

[0118] The drawing apparatus 400 uses multiple stages of deflectors to perform the drawing process for each stripe region 32. Here, as an example, a two-stage deflector, consisting of a main deflector 508 and a sub-deflector 509, is used. While the XY stage 405 continuously moves, for example, in the -x direction, drawing of the first stripe region 32 proceeds in the x direction. After drawing of the first stripe region 32 is completed, drawing of the second stripe region 32 proceeds in the same manner or in the opposite direction. Subsequently, drawing of the third and subsequent stripe regions 32 proceeds in the same manner. The main deflector 208 (first deflector) sequentially deflects the electron beam 500 to the reference position of the SF 530 so as to follow the movement of the XY stage 105. The sub-deflector 509 (second deflector) deflects the electron beam 500 from the reference position of each SF 530 to a shot position 542 of the beam to be irradiated within that SF 530. Thus, the main deflector 508 and the sub-deflector 509 have deflection regions of different sizes.

[0119] The electron beam 500 emitted from the electron gun 501 (emission unit) is controlled by the blanking deflector 512 as it passes through it. When the beam is ON, it passes through the blanking aperture 514, and when the beam is OFF, the entire beam is deflected by the blanking aperture 514. One electron beam shot consists of the electron beam 500 passing through the blanking aperture 514 from the beam OFF state to the beam ON state and then to the beam OFF state. The blanking deflector 512 controls the direction of the passing electron beam 500 to alternately generate the beam ON state and the beam OFF state. For example, no voltage can be applied when the beam is ON, and a voltage can be applied to the blanking deflector 212 when the beam is OFF. The irradiation time of each shot adjusts the amount of electron beam 500 irradiated onto the sample 101 per shot.

[0120] As described above, the electron beam 500 of each shot, generated by passing through the blanking deflector 512 and the blanking aperture 514, is illuminated by the illumination lens 502, which illuminates the entire first shaping aperture 503, which has a rectangular, for example, hole. Here, the electron beam 500 is first shaped into a rectangle, for example. Then, the electron beam 500 of the first aperture image, which has passed through the first shaping aperture 503, is projected onto the second shaping aperture 506 by the projection lens 504. The deflector 505 controls the deflection of the first aperture image on the second shaping aperture 506, allowing the beam shape and dimensions to be changed (variable shaping). Such variable shaping is performed for each shot, and usually each shot is shaped into a different beam shape and dimensions. Then, the electron beam 500 of the second aperture image, having passed through the second shaping aperture 506, is focused by the objective lens 507, deflected by the main deflector 508 and the sub-deflector 509, and irradiated to a desired position on the sample 101 placed on the continuously moving XY stage 405. In this way, multiple shots of the electron beam 200 are sequentially deflected onto the sample 101, which serves as the substrate, by each deflector.

[0121] The contents of each step from the height position distribution measuring step (S102) to the effective height position distribution creating step (S130) in the second embodiment are the same as those in the first embodiment. Therefore, a height change amount distribution is created for each time point when a beam is irradiated to each position (xj, yj). For example, the height change amount dzi of a representative position of each global mesh region 11, for example, the center position, is calculated to create a height change amount distribution. The height change amount distribution for each time point when a beam is irradiated to each position (xj, yj) is stored in the storage device 442.

[0122] In the dose map creation step (S108), the shot data generation unit 70 reads out pattern data from the drawing data stored in the storage device 440, for example, for each stripe region 32, and performs multiple stages of data conversion processing to generate shot data for each shot. In each shot data, a figure code, coordinates, and size of the shot figure are defined. The shot data generation unit 70 calculates the proximity effect correction amount Dp(x) for each shot based on this shot diagram. The method for calculating the proximity effect correction amount Dp(x) is the same as in the first embodiment. The incident irradiation amount D(x) may be calculated, for example, as the value obtained by multiplying the proximity effect correction irradiation amount Dp at each shot position by the reference irradiation amount. Alternatively, the shot data generation unit 70 may suitably define the incident irradiation amount D(x) for each pixel as an incident irradiation amount D(x) normalized with the reference irradiation amount Dbase set to 1. In this case, the incident irradiation amount D(x) becomes, for example, the proximity effect correction irradiation amount Dp.

[0123] Next, the shot data generation unit 70 creates a dose map whose elements are the incident irradiation amount D(x) at each shot position (x,y). In a VSB type drawing device, vector scanning is performed, so a dose map that defines the dose amount for each shot position is sufficient, and it does not need to be a dose map for each pixel.

[0124] As part of the drawing process (S140), the shot data generation unit 70 first calculates the irradiation time for each shot position using the incident irradiation amount D(x) (dose amount) defined in the dose map. The irradiation time for each shot position can be calculated by dividing the incident irradiation amount D(x) at that shot position by the current density J. If the incident irradiation amount D(x) defined in the dose map is normalized with a reference irradiation amount Dbase of 1, the irradiation time for each shot position can be calculated by multiplying the incident irradiation amount D(x) by the reference irradiation amount Dbase and dividing the result by the current density J. The irradiation time data is additionally defined in the shot data.

[0125] The transfer processing unit 74 transfers the shot data to the deflection control circuit 430 in shot order.

[0126] Then, under the control of the writing control unit 76, the writing mechanism 450 writes a pattern on the sample 101 with the electron beam 500 whose focal position has been dynamically corrected, while dynamically correcting the focal position of the electron beam 500 with at least one of the correction lenses 214, 216, and 218. This will be specifically described below.

[0127] As a dynamic correction step (S142), the focus correction unit 62 dynamically corrects the focal position of the electron beam 500 when irradiating the sample 101 with the electron beam 500, based on the height change distribution. The focus correction unit 62 dynamically corrects the focal position of the electron beam 500 for each shot. Specifically, the focus correction unit 62 dynamically corrects the focal position of the electron beam 500 when irradiating the sample 101 with the electron beam 500 using the effective height position distribution. The dynamic correction of the focal position is corrected by at least one correction lens 214, 216, 218. Here, if the height position of the sample 101 at the irradiation position changes, for example, the deflection sensitivity of the main deflector 508 changes. Therefore, in Embodiment 2, it is preferable to correct the deflection sensitivity of the main deflector 508 in synchronization with the correction of the focal position of the electron beam 500.

[0128] Figure 20 illustrates an example of a method for obtaining the deflection sensitivity parameters in Embodiment 2. In Figure 20, the XY stage 105 is moved to a position where the mark 106 can be irradiated. Then, the mark 106 is moved sequentially from a reference position of multiple points obtained by dividing a rectangular main deflection region of size 2L into a mesh, to each position. Each time, the electron beam is scanned over the mark 106, for example, a cross pattern, and the emitted secondary electrons are detected by the detector 212 to measure the mark position at each location. The deflection sensitivity of the deflector is then measured from the stage movement amount and the beam deflection amount (deflection distance). Here, if the height position of the sample surface changes, this deflection sensitivity will shift.

[0129] The correction lens control circuit 131 adds the correction amount of at least one of the correction lenses 214, 216, 218 to the lens value for each shot in accordance with the height change amount corresponding to the shot position. As a result, the at least one of the correction lenses 214, 216, 218 dynamically corrects the focal position of the electron beam 500.

[0130] In addition to the focal position correction, the deflection control circuit 420 dynamically corrects the deflection sensitivity for each shot in accordance with the amount of height change corresponding to the shot position.

[0131] As a shot process (S144), the lithography mechanism 150 draws a pattern on the sample 101 with a multi-beam 20 whose focal position has been corrected. Specifically, the lithography mechanism 150 shots the sample 101 with at least one electron beam 500 whose focal position has been corrected for each shot. By repeating this dynamic correction process (S142) and shot process (S144), the lithography mechanism 150 draws a lithography pattern on the sample by combining the shot patterns.

[0132] As described above, according to the second embodiment, the focal position can be corrected even when the height position distribution changes due to irreversible deformation of the sample 101 caused by irradiation with a single beam. In addition, the deflection sensitivity of the deflector can be corrected.

[0133] Although the embodiments have been described above with reference to specific examples, the present invention is not limited to these specific examples. The processes described in each embodiment may be executed by a computer, and a program for causing a computer to execute such processes may be stored in a non-transitory, tangible readable recording medium such as a magnetic disk device.

[0134] Although the description of the device configuration, control method, and other parts not directly necessary for the explanation of the present invention have been omitted, the required device configuration and control method can be appropriately selected and used. For example, the description of the control unit configuration that controls the drawing device 100 has been omitted, but it goes without saying that the required control unit configuration can be appropriately selected and used.

[0135] In addition, all electron beam writing methods, electron beam writing apparatuses, and programs that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included within the scope of the present invention. [Explanation of symbols]

[0136] 11 Global Mesh Area 12 LTEM board 13Cr membrane 14. Standard Mark 16. Resist film 20 Multibeam 22 holes 24 control electrode 25 Passing hole 26 Counter electrode 29 Sub-irradiation area 30 drawing area 31. Blanking aperture array substrate 32 Stripe Area 33 Support substrate 34 Irradiation area 36 pixels 41 Control circuit 50. Irradiation dose distribution creation unit 52. Distortion Distribution Creation Section 54. Deformation Amount Distribution Creation Unit 56 Height change distribution creation section 58 Height position distribution creation unit 60 Effective Height Position Distribution Creation Unit 62 Focus correction section 63 Deflection sensitivity correction section 64 Rotation / Magnification Correction Section 70 Shot data generation unit 72 Data Processing Department 74 Transfer Processing Unit 76 Drawing Control Unit 100 drawing device 101 Sample 102 Electron Telescope 103 Drawing room 105 XY stage 106 Mark 110 Control computer 112 memory 130 Deflection control circuit 131 Correction lens control circuit 132,134 DAC amplifier unit 136 Lens control circuit 137 Detection Circuit 138 Stage Control Mechanism 139 Stage position measuring instrument 140,142,144 Storage device 150 Drawing mechanism 160 Control Circuits 200 electron beam 201 Electron Gun 202 Lighting lens 203 Shaped Aperture Array Substrate 204 Blanking Aperture Array Mechanism 205 Reduction Lens 206 Limiting Aperture Substrate 207 Objective Lens 208 Deflector 209 Deflector 210 Mirror 211 Floodlight 212 detector 213 Receiver 214,216,218 Corrective lenses 220 z sensor 330 Membrane Region 400 Drawing device 450 Drawing mechanism 460 Control Circuits 402 Electron Telescope 403 Drawing room 405 XY stage 410 Control Computer Unit 412 memory 420 Deflection control circuit 430, 432, 434 DAC amplifier unit 431 Correction lens control circuit 440,442 Storage device 501 Electron Gun 502 Lighting lens 512 Blanking Deflector 514 Blanking Aperture 503 First shaping aperture 504 Projection Lens 505 Deflector 506 Second Shaping Aperture 507 Objective Lens 508 Main deflector 509 Sub deflector 530 SF 542 Shot Shape

Claims

1. a step of determining a height change distribution, which defines a height change amount from a height position of the sample before irradiation caused by irreversible deformation of the sample at each position of the sample at the time of irradiating the sample with the charged particle beam, the height change amount being determined depending on the irradiation dose distribution of the charged particle beam; A step of correcting the focal position of the charged particle beam when irradiating the sample with the charged particle beam based on the height change distribution, A step of drawing a pattern on the sample with a charged particle beam whose focal position has been corrected, A charged particle beam lithography method characterized by comprising the following:

2. A charged particle beam writing method, further comprising the step of correcting the magnification and rotation of an irradiation area of ​​the charged particle beam in synchronization with the correction of the focal position of the charged particle beam.

3. A step of determining the irradiation dose distribution of a charged particle beam irradiated onto multiple processing regions in which the drawing area of ​​the sample is divided into a mesh-like structure, A step of determining a strain distribution that defines the amount of strain at each position of the sample caused by irreversible deformation of the sample using the irradiation dose distribution, 3. The charged particle beam writing method according to claim 1, further comprising:

4. A step of measuring the height position distribution of the sample before irradiating the sample with the charged particle beam, using a height change distribution at the time of irradiating each position with the charged particle beam, to calculate an effective height position distribution by adding a height change amount at the time of irradiating the position with the beam to the height position of the height position distribution; Furthermore, 3. The charged particle beam writing method according to claim 1, wherein the focal position is corrected using the effective height position distribution.

5. a height change distribution calculation unit that calculates a height change distribution that defines height changes from a height position before irradiation of a sample that occurs due to irreversible deformation of the sample at each position of the sample at the time of irradiating the sample with the charged particle beam, the height change distribution being determined based on the irreversible deformation of the sample depending on the irradiation dose distribution of the charged particle beam; A correction unit that corrects the focal position of the charged particle beam when irradiating the sample with the charged particle beam based on the height change distribution, A drawing mechanism for drawing a pattern on the sample with a charged particle beam whose focal position has been corrected, A charged particle beam lithography apparatus characterized by comprising the following features.

6. A process to determine the distribution of the irradiation dose of a charged particle beam irradiated onto multiple processing regions, each of which the sample drawing area is divided into a mesh, and which deforms irreversibly depending on the irradiation dose distribution of the charged particle beam. A process of using the irradiation dose distribution to obtain a strain amount distribution that defines the amount of strain at each position of the sample at the time of beam irradiation caused by irreversible deformation of the sample; a process of storing the strain distribution in a storage device; a process of reading out the strain distribution from the storage device, calculating a height change distribution based on the strain distribution, in which a height change amount from a design height position of the sample at each position of the sample at the time of beam irradiation is defined, and outputting the calculated height change distribution; A program that causes a computer to execute the following.

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