Background waveform acquisition method, mark position detection method, electron beam writing method, and electron beam writing apparatus

Abstract

PURPOSE: To provide a method that enables highly accurate acquisition of a background waveform near a mark using a simple technique.CONSTITUTION: A method for acquiring a background waveform according to an embodiment of the present invention includes the steps of scanning a sample with an electron beam in a plurality of areas near a line pattern on which a mark using the line pattern is formed and arranged in a direction that is not parallel to the direction in which the line pattern extends, and determining and outputting a waveform of a background that is not a mark from among a plurality of measurement waveforms measured by scanning the plurality of areas.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] One aspect of the present invention relates to a background waveform acquisition method, a mark position detection method, an electron beam writing method, and an electron beam writing apparatus, and relates to, for example, a technique for measuring the position of a mark formed on a substrate to be written. [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] In electron beam lithography including multi-beam lithography, when the substrate to be lithographed is placed on the stage, marks (alignment marks) formed on the substrate are detected by the electron beam, and the lithography area is aligned based on the detected alignment marks.

[0005] Modern alignment marks are formed with finer line widths than conventional alignment marks. The electron yield when the mark is irradiated with an electron beam is low, making it difficult to obtain contrast. This results in a poor signal-to-noise ratio, making it difficult to find the alignment mark on the substrate. To address this issue, increasing the electron beam dose to obtain contrast has been considered. However, this method poses the problem of resist scattering and contaminating the chamber when a high-dose electron beam is irradiated over a wide area.

[0006] Therefore, in order to obtain contrast, a technique has been proposed in which background components obtained by scanning a position without a mark are removed from a waveform obtained by scanning a mark (see, for example, Patent Document 1). However, the scanned waveform is easily affected by factors such as the tilt of the substrate. Therefore, it is desirable to obtain a waveform that serves as background near the target mark. However, when attempting to obtain a waveform at a position without a mark near the mark, there is a possibility that the mark position may be shifted due to misalignment of the substrate, etc., and a waveform including the mark may be obtained, making it difficult to determine whether it is a background component. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2001-085300 Summary of the Invention [Problem to be solved by the invention]

[0008] One aspect of the present invention provides a method that can acquire a background waveform near a mark with high accuracy using a simple technique. [Means for solving the problem]

[0009] A method for acquiring a background waveform according to one aspect of the present invention includes: a step of scanning the sample with an electron beam in a plurality of areas arranged in a direction not parallel to the extending direction of the line pattern, the area being in the vicinity of the line pattern of the sample on which a mark using the line pattern is formed; a step of determining and outputting a waveform of a background other than a mark from among a plurality of measurement waveforms measured by scanning a plurality of regions; The present invention is characterized by the following.

[0010] The method further includes a step of calculating, for at least one combination of two measurement waveforms from a plurality of measurement waveforms obtained in a plurality of regions, a first difference obtained by subtracting a second measurement waveform from a first measurement waveform constituting the combination, and a second difference obtained by subtracting the first measurement waveform from the second measurement waveform, A background waveform is determined based on the first difference waveform and the second difference waveform. This is preferable.

[0011] Alternatively, the method may further include a step of calculating a first difference for each combination of two measurement waveforms from a plurality of measurement waveforms obtained in a plurality of regions, the first difference being calculated by subtracting a second measurement waveform from a first measurement waveform constituting the combination; It is also preferable to configure the apparatus so that the background waveform is determined based on the first difference waveform.

[0012] Alternatively, the method may further include a step of calculating, for each of a plurality of measurement waveforms obtained in a plurality of regions, a parameter using a difference between the measurement waveform and a template waveform for determining a background waveform, The measured waveform with the smaller parameter is determined as the background waveform. This is preferable.

[0013] A mark position detection method according to one aspect of the present invention includes: a step of scanning the sample with an electron beam in a plurality of areas arranged in a direction not parallel to the extending direction of the line pattern, the area being in the vicinity of the line pattern of the sample on which a mark using the line pattern is formed; a step of determining a background waveform that is not a mark from among a plurality of measurement waveforms measured by scanning a plurality of regions; scanning the specimen with an electron beam in an area including a line pattern; a step of removing a background waveform obtained by judgment from a measured waveform measured by scanning an area including the line pattern; calculating and outputting the mark position from the measured waveform from which the background waveform has been removed; The present invention is characterized by the following.

[0014] An electron beam writing method according to one aspect of the present invention includes: a step of scanning the sample with an electron beam in a plurality of areas that are adjacent to the line pattern and aligned in a direction that is not parallel to the extending direction of the line pattern, for each mark of the sample on which a plurality of marks using a line pattern are formed; a step of determining a background waveform that is not a mark from among a plurality of measurement waveforms measured by scanning a plurality of regions for each mark; scanning the specimen with an electron beam in an area including the line pattern for each mark; a step of removing a background waveform obtained by judgment from a measurement waveform measured by scanning an area including the line pattern for each mark; calculating, for each mark, the mark position from the measured waveform from which the background waveform has been removed; correcting the position of a pattern to be written using the calculated positions of the marks; writing a position-corrected pattern onto a specimen using an electron beam; The present invention is characterized by the following.

[0015] An electron beam lithography apparatus according to one aspect of the present invention comprises: a stage on which a sample having a plurality of marks formed using a line pattern is placed; a scanning mechanism for scanning the sample with an electron beam in a plurality of areas adjacent to the line pattern and arranged in a direction not parallel to the direction in which the line pattern extends, for each mark on the sample; a determination unit that determines a background waveform that is not a mark from among a plurality of measurement waveforms measured by scanning a plurality of regions for each mark; a background waveform removing unit that removes a background waveform obtained by judgment from a measurement waveform measured by scanning the sample with an electron beam in an area including the line pattern for each mark; a mark position calculation unit that calculates the mark position for each mark from the measured waveform from which the background waveform has been removed; a correction unit that corrects the position of a pattern to be written using the calculated positions of the plurality of marks; a drawing mechanism having a stage and a scanning mechanism, and using an electron beam to draw a position-corrected pattern on a sample; The present invention is characterized by the following. [Effects of the Invention]

[0016] According to one aspect of the present invention, a background waveform near a mark can be obtained with high accuracy using a simple method. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a conceptual diagram showing a configuration of a drawing device according to a first embodiment. [Figure 2] FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate according to the first embodiment. [Figure 3] 2 is a cross-sectional view showing the configuration of a blanking aperture array mechanism in the first embodiment. FIG. [Figure 4] FIG. 2 is a conceptual diagram for explaining an example of a drawing operation in the first embodiment. [Figure 5] 3 is a diagram showing an example of a multi-beam irradiation area and a pixel to be written in the first embodiment. FIG. [Figure 6]FIG. 2 is a diagram for explaining an example of a multi-beam writing operation according to the first embodiment. [Figure 7] FIG. 2 is a diagram showing an example of the positional relationship between a stage and a sample in the first embodiment. [Figure 8] 2 is a cross-sectional view showing an example of the configuration of an alignment mark in the first embodiment. FIG. [Figure 9] FIG. 4 is a cross-sectional view showing another example of the configuration of the alignment mark in the first embodiment. [Figure 10] FIG. 10 is a diagram showing an example of the positional relationship between an off-mark area and an alignment mark in a comparative example of the first embodiment. [Figure 11] FIG. 10 is a diagram showing another example of the positional relationship between the off-mark area and the alignment mark in the comparative example of the first embodiment. [Figure 12] FIG. 2 is a flowchart showing an example of main steps of the writing method according to the first embodiment. [Figure 13] 4 is a diagram showing an example of the positional relationship between an alignment mark, an on-mark area, and a plurality of off-mark areas in the first embodiment. FIG. [Figure 14] FIG. 10 is a diagram showing another example of the positional relationship between the alignment mark and a plurality of off-mark areas according to the first embodiment. [Figure 15] FIG. 10 is a diagram showing another example of the positional relationship between the alignment mark, the on-mark area, and the plurality of off-mark areas in the first embodiment. [Figure 16] FIG. 10 is a diagram showing another example of the positional relationship between the alignment mark and a plurality of off-mark areas according to the first embodiment. [Figure 17] FIG. 4 is a diagram for explaining an example of a method for scanning an off-mark area in the first embodiment. [Figure 18] FIG. 10 is a diagram for explaining another example of a method for scanning an off-mark area in the first embodiment. [Figure 19] FIG. 3 is a diagram showing an example of a measured waveform A in the first embodiment. [Figure 20] FIG. 4 is a diagram showing an example of a measured waveform B in the first embodiment. [Figure 21] FIG. 3 is a diagram showing an example of a differential waveform (AB) according to the first embodiment. [Figure 22] FIG. 4 is a diagram showing an example of a differential waveform (BA) according to the first embodiment. [Figure 23] FIG. 10 is a diagram showing another example of the measured waveform A in the first embodiment. [Figure 24] FIG. 10 is a diagram showing another example of the measured waveform B in the first embodiment. [Figure 25] FIG. 10 is a diagram showing another example of the differential waveform (AB) according to the first embodiment. [Figure 26] FIG. 10 is a diagram showing another example of the differential waveform (BA) according to the first embodiment. [Figure 27] FIG. 10 is a diagram showing an example of the results of differential waveforms for each combination when there are three off-mark areas according to the first embodiment. [Figure 28] FIG. 10 is a diagram showing another example of the results of the differential waveforms for each combination when there are three off-mark areas according to the first embodiment. [Figure 29] FIG. 4 is a diagram for explaining an example of a method for determining a background waveform using a template according to the first embodiment. [Figure 30] FIG. 4 is a diagram showing an example of a measured waveform in which a peak exists in a differential waveform according to the first embodiment. [Figure 31] FIG. 10 is a diagram for explaining how to shift an on-mark area in the first embodiment. [Figure 32] FIG. 3 is a diagram showing an example of a mark position in the first embodiment. [Figure 33] FIG. 4 is a diagram showing an example of a method of correcting data in the first embodiment. [Figure 34] FIG. 10 is a diagram showing an example of the positional relationship between an alignment mark, an on-mark area, and a plurality of off-mark areas in a modification of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the following embodiments, a configuration using an electron beam will be described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam, and a beam using charged particles such as an ion beam may also be used. Furthermore, a configuration using multiple electron beams will be described below, but the present invention is not limited to this. A configuration using a single beam may also be used.

[0019] Embodiment 1 FIG. 1 is a conceptual diagram showing the configuration of a lithography apparatus according to the first embodiment. In FIG. 1, the lithography apparatus 100 includes a lithography mechanism 150 and a control circuit 160. The lithography apparatus 100 is an example of a multi-charged particle beam lithography apparatus and also an example of a multi-charged particle beam exposure apparatus. The lithography mechanism 150 includes an electron lens barrel 102 (electron beam column) and a lithography chamber 103. Inside the electron lens barrel 102, an electron gun 201, an illumination lens 202, a shaping aperture array substrate 203, a blanking aperture array mechanism 204, a reduction lens 205, a limiting aperture substrate 206, an objective lens 207, a main deflector 208, a sub-deflector 209, and a detector 212 are arranged.

[0020] An XY stage 105 is disposed within the patterning chamber 103. A sample 101, such as a mask, which will be the patterned substrate during patterning (exposure) is disposed on the XY stage 105. The sample 101 includes an exposure mask used in manufacturing a semiconductor device, or a semiconductor substrate (silicon wafer) on which a semiconductor device is manufactured. The sample 101 also includes a mask blank coated with resist and on which nothing has yet been patterned. A mirror 210 for measuring the position of the XY stage 105 is also disposed on the XY stage 105.

[0021] The control system circuit 160 includes a control computer 110, a memory 112, a deflection control circuit 130, digital-to-analog conversion (DAC) amplifier units 132 and 134, a lens control circuit 136, a detection circuit 137, a stage control mechanism 138, a stage position measurement device 139, and storage devices 140 and 142 such as magnetic disk drives. The control computer 110, the memory 112, the deflection control circuit 130, the lens control circuit 136, the detection circuit 137, the stage control mechanism 138, the stage position measurement device 139, and storage devices 140 and 142 are connected to one another via a bus (not shown). The deflection control circuit 130 is connected to the DAC amplifier units 132 and 134 and a blanking aperture array mechanism 204. The sub-deflector 209 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 130 via the DAC amplifier 132. The main deflector 208 is composed of four or more electrodes, and each electrode is controlled by a deflection control circuit 130 via a DAC amplifier 134. A group of lenses, including an illumination lens 202, a reduction lens 205, and an objective lens 207, is controlled by a lens control circuit 136. The group of lenses may be electromagnetic lenses or electrostatic lenses.

[0022] The position of the XY stage 105 is controlled by driving motors (not shown) for each axis controlled by a stage control mechanism 138. A stage position measuring device 139 receives light reflected from a mirror 210 and measures the position of the XY stage 105 based on the principle of laser interferometry.

[0023] Secondary electrons emitted from the sample 101 when the sample 101 is irradiated with the electron beam are detected by the detector 212. The detection data of the detector 212 is output to the detection circuit 137, converted into digital data in the detection circuit 137, and then output to the control computer 110.

[0024] The control computer 110 includes a rasterization processing unit 50, a shot data generation unit 52, a coordinate setting unit 54, an area setting unit 56, a scanning processing unit 58, a judgment unit 60, a difference calculation unit 62, a judgment unit 64, a removal unit 65, a judgment unit 66, a mark position calculation unit 68, a judgment unit 69, a correction unit 70, a drawing control unit 72, and a transfer processing unit 74. Each of the "~ units" such as the rasterization processing unit 50, shot data generation unit 52, coordinate setting unit 54, area setting unit 56, scan processing unit 58, determination unit 60, difference calculation unit 62, determination unit 64, removal unit 65, determination unit 66, mark position calculation unit 68, determination unit 69, correction unit 70, drawing control unit 72, and transfer processing unit 74 has a processing circuit. Such a processing circuit includes, for example, an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each of the "~ units" may use a common processing circuit (the same processing circuit) or different processing circuits (separate processing circuits). Information input and output to and from the rasterization processing unit 50, shot data generation unit 52, coordinate setting unit 54, area setting unit 56, scanning processing unit 58, judgment unit 60, difference calculation unit 62, judgment unit 64, removal unit 65, judgment unit 66, mark position calculation unit 68, judgment unit 69, correction unit 70, drawing control unit 72, and transfer processing unit 74, as well as information being calculated, are stored in memory 112 each time.

[0025] The drawing operation of the drawing apparatus 100 is controlled by a drawing control unit 72. In other words, the drawing control unit 72 (an example of a control circuit) controls the drawing mechanism 150. In addition, a transfer process of the irradiation time data of each shot to the deflection control circuit 130 is controlled by a transfer processing unit 74.

[0026] Furthermore, drawing data (chip data) is input from outside the drawing device 100 and stored in the storage device 140. The chip data defines information on a plurality of figure patterns that constitute the chip pattern. Specifically, for each figure pattern, for example, the coordinates of each vertex are defined in the order in which the figure is formed. Alternatively, for each figure pattern, for example, a figure code, coordinates, size, etc. are defined.

[0027] 1 shows the configuration necessary for explaining the first embodiment. The drawing device 100 may also include other configurations that are normally required.

[0028] 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 shaping aperture array substrate 203. The example in FIG. 2 shows a case where, for example, 1024×1024 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, 512×512 columns or 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 electron beam 200 passes through each of these multiple holes 22, thereby forming multiple beams 20. In other words, shaping aperture array substrate 203 forms multiple beams 20.

[0029] FIG. 3 is a cross-sectional view showing the configuration of the blanking aperture array mechanism according to the first embodiment. As shown in FIG. 3, the blanking aperture array mechanism 204 includes a blanking aperture array substrate 31, which is made of a semiconductor substrate such as silicon, and is disposed on a support base 33. In a central membrane region 330 of the blanking aperture array substrate 31, passage holes 25 (openings) for passing through each beam of the multi-beams 20 are formed at positions corresponding to the holes 22 of the shaping aperture array substrate 203 shown in FIG. 2. Pairs of control electrodes 24 and counter electrodes 26 (blankers: blanking deflectors) are disposed at positions facing each other across the corresponding passage holes 25 among the plurality of passage holes 25. Furthermore, a control circuit 41 (logic circuit) is disposed inside the blanking aperture array substrate 31 near each passage hole 25, which applies a deflection voltage to the control electrode 24 for each passage hole 25. The counter electrodes 26 for each beam are connected to ground.

[0030] 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.

[0031] Next, a specific example of the operation of the drawing mechanism 150 will be described. An electron beam 200 emitted from an electron gun 201 (emission source) is illuminated by an illumination lens 202 almost perpendicularly onto the entire shaping aperture array substrate 203. A plurality of rectangular holes 22 (openings) are formed in the shaping aperture array substrate 203, and the electron beam 200 illuminates an area including all of the holes 22. Portions of the electron beam 200 irradiated onto the positions of the holes 22 pass through the holes 22 of the shaping aperture array substrate 203, thereby forming, for example, a rectangular multibeam (multiple electron beams) 20. The multibeam 20 passes through corresponding blankers of a blanking aperture array mechanism 204. Each blanker performs blanking control on the beams passing through it so that the beams are turned on for a set drawing time (irradiation time).

[0032] The multi-beams 20 that pass through the blanking aperture array mechanism 204 are reduced by the reduction lens 205 and travel toward a central hole formed in the limiting aperture substrate 206. Here, the electron beams deflected by the blankers of the blanking aperture array mechanism 204 are shifted from the central hole of the limiting aperture substrate 206 and are blocked by the limiting aperture substrate 206. On the other hand, the electron beams that are not deflected by the blankers of the blanking aperture array mechanism 204 pass through the central hole of the limiting aperture substrate 206 as shown in FIG. 1. In this way, the limiting aperture substrate 206 blocks each beam that is deflected by the blankers of the blanking aperture array mechanism 204 to be in a beam-off state. Then, each beam of one shot is formed by the beams that pass through the limiting aperture substrate 206 from when the beams are turned on until when they are turned off. The multibeams 20 that have passed through the limiting aperture substrate 206 are focused by the objective lens 207 to form a pattern image with the desired reduction ratio, and the entire multibeams 20 that have passed through the limiting aperture substrate 206 are deflected in the same direction by the main deflector 208 and the sub-deflector 209, and each beam is irradiated onto its respective irradiation position on the sample 101. Furthermore, for example, when the XY stage 105 is moving continuously, tracking control is performed by the main deflector 208 so that the beam irradiation position follows the movement of the XY stage 105. Ideally, the multibeams 20 that are irradiated at one time are arranged at a pitch obtained by multiplying the arrangement pitch of the plurality of holes 22 in the shaping aperture array substrate 203 by the desired reduction ratio described above.

[0033] Fig. 4 is a conceptual diagram for explaining an example of the writing operation in embodiment 1. As shown in Fig. 4, the writing region 30 (chip region) (bold frame) of the sample 101 is virtually divided, for example, in the y direction into a plurality of rectangular stripe regions 32 with a predetermined width. The example of Fig. 4 shows a case where the writing region 30 of the sample 101 is divided, for example, in the y direction, into a plurality of stripe regions 32 with a width that is substantially the same as the size of the designed irradiation region 34 (writing field) that can be irradiated with a single irradiation of the multibeam 20.

[0034] Furthermore, a plurality of alignment marks 14 are arranged around the writing area 30 (chip area). For example, a cross pattern is preferably used as the alignment mark 14. Note that the example in FIG. 4 shows a case where one cross pattern is arranged as each alignment mark 14, but this is not limiting. For example, each alignment mark 14 may preferably be configured as a set of a large cross pattern and a small cross pattern with the same line width. The large cross pattern is configured with a pattern in which the line patterns forming the cross are long, and the small cross pattern is configured with a pattern in which the line patterns forming the cross are short.

[0035] Also, the example in FIG. 4 shows a case where writing is performed with a multiplicity of 1. Multiple writing (N-pass writing) may be performed in which each stripe region 32 is repeatedly written by moving the XY stage multiple times (N times) in the x direction. In this case, it is preferable to shift the stripe region 32 for each pass. For example, in N-pass writing, it is preferable to shift the position by 1 / N of the width of the stripe region 32. The multiplicity is not limited to 2, and may be 3 or more.

[0036] Furthermore, the above-described position shift is not limited to the y direction, but may be applied to the x direction as well. Next, an example of the drawing operation will be described.

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

[0038] After the writing of the first stripe region 32 is completed, the stage position is moved in the -y direction by the width size of the stripe region 32.

[0039] Next, the irradiation area 34 of the multi-beam 20 is adjusted to be located at the left end of the second stripe area 32, or at a position further to the left. Then, by moving the XY stage 105, for example, in the -x direction, writing proceeds relatively in the x direction. In this way, writing of the second stripe area 32 is completed. By repeating this process thereafter, writing of each stripe area 32 is completed.

[0040] 4 shows the case where each stripe region 32 is written in the same direction, but this is not limiting. For example, the stripe region 32 to be written next to the stripe region 32 written in the x direction may be written in the -x direction by moving the XY stage 105 in the x direction, for example. By writing while alternating directions in this way, the stage movement time can be shortened, and ultimately the writing time can be shortened. In one shot, 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.

[0041] FIG. 5 shows an example of a multibeam irradiation area and a target pixel for drawing in the first embodiment. In FIG. 5, the stripe area 32 is divided into a plurality of mesh areas, for example, based on the beam size of the multibeam 20. Each mesh area corresponds to a target pixel 36 (beam irradiation unit area, irradiation position). The size of the target pixel 36 is not limited to the beam size and may be any size regardless of the beam size. For example, the size may be 1 / n (n is an integer greater than or equal to 1) of the beam size. The example of FIG. 5 shows a case where the target region for drawing on the sample 101 is divided, for example, in the y direction, into a plurality of stripe areas 32, each having a width substantially equal to the size of the irradiation region 34 (drawing field) that can be irradiated with one irradiation of the multibeam 20. The size of the rectangular irradiation region 34 in the x direction can be defined by the number of beams in the x direction multiplied by the beam pitch in the x direction. The size of the rectangular irradiation region 34 in the y direction can be defined by the number of beams in the y direction multiplied by the beam pitch in the y direction. In the example of FIG. 5, for example, a 1024×1024 array of multi-beams is shown, but is abbreviated to 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 inter-beam pitch of each of the multi-beams. A rectangular area surrounded by the size of the inter-beam pitch in the x and y directions constitutes one sub-irradiation area 29 (pitch cell area). In the example of FIG. 5, each sub-irradiation area 29 is shown as being composed of, for example, 4×4 pixels.

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

[0043] Here, as described above, before drawing on the sample, the alignment marks of the sample 101 placed on the XY stage 105 are measured.

[0044] FIG. 7 is a diagram showing an example of the positional relationship between the stage and the sample in the first embodiment. As shown in FIG. 7, when the transported sample 101 is placed on the XY stage 105, it is difficult to perfectly align the orientation of the sample 101 with the drawing coordinate system. The example in FIG. 7 shows a case where the sample 101 is rotated obliquely. Meanwhile, each pattern defined in the drawing data is aligned with the drawing coordinate system. Therefore, if the pattern is drawn as is, it will be drawn at a misaligned position. Therefore, multiple alignment marks 14 are measured, and the positions of the patterns defined in the drawing data are corrected based on the multiple alignment marks 14.

[0045] FIG. 8 is a cross-sectional view showing an example of the configuration of an alignment mark in the first embodiment. The example of FIG. 8 shows a case where an exposure mask is used as the sample 101. In the sample 101, as shown in FIG. 8, a light-shielding film 82 made of chromium (Cr) or the like is formed on a glass substrate 80. Then, a recess is formed in the light-shielding film 82, and the recessed portion is used as the line width of the alignment mark 14. Therefore, the surface of the recessed portion and the surface of the protruding portion become the same light-shielding film 82. In this way, the alignment mark 14 is formed with a concave-convex structure made of the same material. Then, the sample 101 (mask) on which such a mark is formed is coated with a resist and transported into the writing apparatus 100, where mark measurement is performed.

[0046] FIG. 9 is a cross-sectional view showing another example of the configuration of the alignment mark according to the first embodiment. The example of FIG. 9 shows a case where the sample 101 is an EUV exposure mask. In the sample 101, a multilayer film 86, for example, made of molybdenum (Mo) and silicon (Si) stacked in multiple layers, is formed on a low-thermal expansion glass substrate 84. A recess is formed in a portion of the multilayer film 86, and an absorber film 88 (anti-reflection film) mainly composed of, for example, Cr or tantalum (Ta) is formed on the multilayer film 86 including the recess. The recessed portion of the absorber film 88 formed on the recessed portion of the multilayer film 86 is used as the line width of the alignment mark 14. Therefore, the surface of the recessed portion and the surface of the protruding portion are made of the same absorber film 88. In this way, the alignment mark 14 is formed with a concave-convex structure made of the same material. The line width of the recess is 0.2 to 200 μm, for example, 4 to 5 μm. Then, a resist is applied to the sample 101 (mask) on which such a mark is formed, and the sample is transported into the drawing apparatus 100, where mark measurement is performed.

[0047] 8 and 9, marks in which the concave and convex portions are made of the same material have a low electron yield when the mark is irradiated with an electron beam, making it difficult to obtain contrast. As a result, there is a problem that the S / N ratio is poor and it is difficult to find the alignment mark on the substrate.

[0048] Therefore, in order to obtain contrast, the background waveform obtained by scanning a position where there is no mark is removed from the mark waveform obtained by scanning the mark.

[0049] FIG. 10 is a diagram showing an example of the positional relationship between the off-mark area and the alignment mark in a comparative example of the first embodiment. FIG. 11 is a diagram showing another example of the positional relationship between the off-mark area and the alignment mark in a comparative example to the first embodiment. As described above, it is desirable to obtain a background waveform near the target mark. Ideally, as shown in Figure 10, it is desirable to obtain a waveform in an off-mark region 12 where no mark is present near the line patterns 16 and 18 that make up the cross pattern to be measured as the background waveform. However, there are cases where the mark position is shifted due to misalignment of the substrate, and part of the mark overlaps with the off-mark region 12, as shown in Figure 11. Therefore, even if measurement is performed in the off-mark region 12, it is difficult to determine whether the obtained waveform is actually that of an off-mark region.

[0050] Therefore, in the first embodiment, a plurality of off-mark areas 12 are scanned to obtain measured waveforms of the plurality of off-mark areas 12. This will be specifically described below.

[0051] Fig. 12 is a flowchart showing an example of main steps of the writing method according to Embodiment 1. In Fig. 12, the writing method according to Embodiment 1 carries out a series of steps including an on-mark coordinate setting step (S102), an off-mark area setting step (S104), an off-mark area scanning step (S106), a determination step (S108), a difference calculation step (S110), a determination step (S120), an on-mark scanning step (S130), a background removal step (S140), a determination step (S142), a mark position calculation step (S144), a determination step (S146), a data correction step (S150), and a writing step (S152).

[0052] Among these steps, the on-mark coordinate setting step (S102), the off-mark area setting step (S104), the off-mark area scanning step (S106), the judgment step (S108), the difference calculation step (S110), and the judgment step (S120) are the main steps of the background waveform acquisition method.

[0053] The main steps of the mark position detection method are the on-mark coordinate setting step (S102), the off-mark area setting step (S104), the off-mark area scanning step (S106), the determination step (S108), the difference calculation step (S110), the determination step (S120), the on-mark scanning step (S130), the background removal step (S140), the determination step (S142), and the mark position calculation step (S144).

[0054] In the on-mark coordinate setting step (S102), the coordinate setting unit 54 sets the coordinates of an on-mark area including a line pattern constituting the alignment mark 14 from the design coordinates of one of the multiple alignment marks 14 on the sample 101. The coordinates of the on-mark area are set, for example, to a position moved a predetermined distance from the coordinates of the center of the cross pattern of the alignment mark 14 in the direction in which the target line pattern extends, within the range in which the line pattern exists. It is preferable that the on-mark area be set to a rectangular area of ​​the same size as the irradiation area 34, which is the beam array area of ​​the multi-beam 20. However, this is not a limitation. The on-mark area may be smaller than the irradiation area 34. Alternatively, the on-mark area may be larger than the irradiation area 34.

[0055] In the off-mark area setting step (S104), the area setting unit 56 sets, outside the drawing area, a plurality of off-mark areas 12 that are near a target line pattern among the plurality of line patterns that make up the selected alignment mark 14 but do not include the target line pattern. The off-mark areas 12 are preferably set to the same size as the on-mark area. Specifically, they are preferably set to rectangular areas the same size as the irradiation area 34, which is the beam array area of ​​the multi-beam 20. However, this is not a limitation. Like the on-mark areas, the off-mark areas 12 may be smaller than the irradiation area 34. Alternatively, they may be larger than the irradiation area 34.

[0056] 13 is a diagram showing an example of the positional relationship between the alignment mark, the on-mark area, and multiple off-mark areas in the first embodiment. To measure the position of the alignment mark 14, the position in the x direction and the position in the y direction are required. For the position in the x direction, the x coordinate of the line pattern 16 extending in the y direction out of the two line patterns 16, 18 that make up the alignment mark 14 is measured. For the position in the y direction, the y coordinate of the line pattern 18 extending in the x direction out of the two line patterns 16, 18 that make up the alignment mark 14 is measured.

[0057] The example of FIG. 13 shows a case where, of the two line patterns 16, 18 constituting the alignment mark 14, the line pattern 16 extending in the y direction is the target line pattern, and multiple off-mark areas 12 are set. In the case of a line pattern 16 extending in the y direction, scanning is performed in the x direction so as to straddle the line pattern 16 in the width direction of the line pattern 16. Therefore, it is preferable to arrange the multiple off-mark areas 12 side by side in the x direction. Furthermore, it is even more preferable to arrange them on both sides of the line pattern 16. The example of FIG. 13 shows a case where an off-mark area 12-1 is set on the x-direction side of an on-mark area 19 of the line pattern 16, and an off-mark area 12-2 is set on the -x-direction side. N off-mark areas 12 (N is an integer equal to or greater than 2) are set. The number of off-mark areas 12 needs to be two or more, and may be two, three, or more. The direction in which the off-mark areas 12 are arranged is not limited to this. It is sufficient to set a plurality of off-mark areas 12 arranged in the vicinity of the line pattern 16 in a direction that is not parallel to the y direction in which the line pattern 16 extends.

[0058] 14 is a diagram showing another example of the positional relationship between the alignment mark and multiple off-mark areas in embodiment 1. For example, when multiple off-mark areas 12-1 and 12-2 are set parallel to the y direction with respect to a line pattern 16 extending in the y direction, as shown in FIG. 14, there is a possibility that multiple off-mark areas 12-1 and 12-2 will both be arranged on the line pattern 16. In this case, it is not possible to determine whether or not they are off-mark areas, and therefore such an arrangement configuration is not acceptable.

[0059] FIG. 15 is a diagram showing another example of the positional relationship between the alignment mark, the on-mark area, and multiple off-mark areas in the first embodiment. The example in FIG. 15 illustrates a case where multiple off-mark areas 12 are set using the line pattern 18 extending in the x-direction as the target line pattern among the two line patterns 16, 18 constituting the alignment mark 14. For the line pattern 18 extending in the x-direction, scanning is performed in the y-direction across the line pattern 18 in the width direction. Therefore, it is preferable to arrange the multiple off-mark areas 12 side by side in the y-direction. Furthermore, it is even more preferable to arrange them on both sides of the line pattern 18. The example in FIG. 15 illustrates a case where an off-mark area 12-1 is set on the +y-direction side of the on-mark area 19 of the line pattern 18, and an off-mark area 12-2 is set on the -y-direction side. N (N is an integer equal to or greater than 2) off-mark areas 12 are set. The number of off-mark areas 12 may be two or more, and may be two, three, or more. The direction in which the off-mark areas 12 are arranged is not limited to this. It is sufficient to set a plurality of off-mark areas 12 arranged in the vicinity of the line pattern 18 in a direction that is not parallel to the x direction in which the line pattern 18 extends.

[0060] 16 is a diagram showing another example of the positional relationship between the alignment mark and multiple off-mark areas in embodiment 1. For example, when multiple off-mark areas 12-1 and 12-2 are set parallel to the y direction with respect to a line pattern 18 extending in the x direction, as shown in Fig. 16, there is a possibility that multiple off-mark areas 12-1 and 12-2 will both be arranged on the line pattern 18. In this case, it is not possible to determine whether or not they are off-mark areas, and therefore such an arrangement configuration is not acceptable.

[0061] In the off-mark area scanning step (S106), the scanning mechanism scans the sample 101 with an electron beam at multiple off-mark areas 12 that are arranged near the line pattern 16 (18) and in a direction that is not parallel to the extension direction of the line pattern 16 (18) for each alignment mark 14 on the sample 101. Specifically, for each off-mark area 12, the target off-mark area 12 is scanned with the electron beam. First, the sample 101 is moved by moving the XY stage 105 to a position where the target off-mark area 12 can be irradiated with the electron beam. For example, it is preferable to move the irradiation area 34 of the multi-beam 20 and the off-mark area 12 to a position where they overlap without beam deflection during irradiation with the multi-beam 20.

[0062] FIG. 17 is a diagram illustrating an example of how the off-mark area 12 is scanned in the first embodiment. In FIG. 17, the off-mark area 12 is scanned by sequentially moving the beam rows that are ON among the multi-beams 20 in the scanning direction. The example in FIG. 17 shows an example of scanning the off-mark area 12 set near a line pattern 16 extending in the y direction in the x direction. Specifically, using a blanking aperture array mechanism 204, which is an example of a scanning mechanism, the first beam group 21 of the multi-beams 20 aligned in the y direction in the x direction is first turned ON. The remaining beams are turned OFF. Next, the second beam group 21 aligned in the y direction in the x direction is turned ON. The remaining beams are turned OFF. Next, the third beam group 21 aligned in the y direction in the x direction is turned ON. The remaining beams are turned OFF. Subsequently, the same operation is performed up to the final beam group 21 aligned in the y direction in the x direction, thereby scanning the off-mark area 12 in the x direction with the beam groups 21. In other words, the blanking aperture array mechanism 204 switches and moves (switches) the ON beam group 21 arranged in the y direction among the multi-beams 20 in order from the first column to the last column in the x direction.

[0063] When scanning the off-mark area 12 set near the line pattern 18 extending in the x direction in the y direction, the blanking aperture array mechanism 204 simply switches and moves (switches) the ON beam group 21 of the multi-beam 20 arranged in the x direction in the y direction in order from the first column to the last column.

[0064] In the above example, the beam group 21 is not limited to a single row of beams, but may be a group of multiple adjacent rows of beams. For example, every two rows of beams may be ON.

[0065] The beam scanning method is not limited to this.

[0066] 18 is a diagram illustrating another example of a method for scanning the off-mark area 12 in the first embodiment. In the example of FIG. 18, the blanking aperture array mechanism 204 turns on, for example, one row of beam group 21 arranged in a direction perpendicular to the scanning direction among the multi-beams 20, and turns off the remaining beams. For example, the beam group including the central beam is turned on, and the remaining beams are turned off. Then, the off-mark area 12 may be scanned with the beam group 21 by collectively deflecting the beam group 21 in the scanning direction using the main deflector 208 (or the sub-deflector 209), which is another example of a scanning mechanism.

[0067] In the above example, the beam group 21 is not limited to a single row of beams, but may be a group of adjacent rows of beams. For example, two rows of beam groups may be ON beams.

[0068] By scanning the off-mark area 12 as described above, the off-mark area 12 is irradiated with the electron beam, and secondary electrons and reflected electrons are emitted from the off-mark area 12. The emitted secondary electrons and reflected electrons are detected by the detector 212 and output to the control computer 110 via the detection circuit 137.

[0069] In the determination step (S108), the determination unit 60 determines whether scanning of the specified N off-mark areas 12 has been completed for each line pattern constituting the alignment mark 14. If scanning of the N off-mark areas 12 has not yet been completed, the process returns to the off-mark area scanning step (S106) and repeats the off-mark area scanning step (S106) until scanning of the N off-mark areas 12 is completed. If scanning of the N off-mark areas 12 has been completed, the process proceeds to the difference calculation step (S110).

[0070] As a result of the above, measured waveforms of a plurality of off-mark regions 12 are obtained for each line pattern that constitutes the alignment mark 14. These measured waveforms are stored in the storage device 142, for example.

[0071] In the difference calculation step (S110), the difference calculation unit 62 calculates, for at least one combination of two measurement waveforms from the multiple measurement waveforms obtained in the multiple off-mark areas 12, a difference (AB) (first difference) obtained by subtracting measurement waveform B (second measurement waveform) from measurement waveform A (first measurement waveform) constituting the combination, and a difference (BA) (second difference) obtained by subtracting measurement waveform A from measurement waveform B.

[0072] FIG. 19 is a diagram showing an example of the measured waveform A according to the first embodiment. FIG. 20 is a diagram showing an example of the measured waveform B according to the first embodiment. 19 and 20, the vertical axis represents the detected intensity, and the horizontal axis represents the position. The examples in Fig. 19 and 20 show a case where the number of multi-beams 20 in the x direction is 1024. As a result, each of the measurement waveforms A and B shows 1024 detected values ​​in the x direction.

[0073] FIG. 21 is a diagram showing an example of a differential waveform (AB) according to the first embodiment. FIG. 22 is a diagram showing an example of a differential waveform (BA) according to the first embodiment. The example of Figure 21 shows an example of a differential waveform (AB) obtained by subtracting the measured waveform B shown in Figure 20 from the measured waveform A shown in Figure 19. On the other hand, the example of Figure 22 shows an example of a differential waveform (BA) obtained by subtracting the measured waveform A shown in Figure 19 from the measured waveform B shown in Figure 20. If the measured waveform B contains a positive peak (convex upward) indicating a line pattern or the like, subtracting the measured waveform B from the measured waveform A will invert the sign of each intensity value of the measured waveform B, resulting in a negative peak (convex downward) appearing in the differential waveform. Conversely, subtracting the measured waveform A from the measured waveform B will not invert the sign of each intensity value of the measured waveform B, resulting in a positive peak (convex upward) appearing in the differential waveform.

[0074] FIG. 23 is a diagram showing another example of the measured waveform A according to the first embodiment. FIG. 24 is a diagram showing another example of the measured waveform B according to the first embodiment. FIG. 25 is a diagram showing another example of the differential waveform (AB) according to the first embodiment. FIG. 26 is a diagram showing another example of the differential waveform (BA) according to the first embodiment. The example of Figure 25 shows an example of a differential waveform (AB) obtained by subtracting the measured waveform B shown in Figure 24 from the measured waveform A shown in Figure 23. On the other hand, the example of Figure 26 shows an example of a differential waveform (BA) obtained by subtracting the measured waveform A shown in Figure 23 from the measured waveform B shown in Figure 24. If neither measured waveform A nor B has any peaks indicating a line pattern or the like, no peak will appear in the differential waveform (AB) obtained by subtracting the measured waveform B from the measured waveform A. Similarly, no peak will appear in the differential waveform (BA) obtained by subtracting the measured waveform A from the measured waveform B.

[0075] In the determination step (S120), the determination unit 64 determines a background waveform that is not a mark from among a plurality of measurement waveforms measured by scanning a plurality of off-mark areas 12 for each alignment mark 14. Here, the determination unit 64 determines a background waveform that is not a target line pattern from among a plurality of measurement waveforms measured by scanning a plurality of off-mark areas 12 for each line pattern that constitutes part of the alignment mark 14. Specifically, the determination unit 64 determines the background waveform based on the differential waveform (AB) and the differential waveform (BA). More specifically, the operation is as follows.

[0076] The determination unit 64 first determines whether or not an upwardly convex peak exists in the differential waveform (AB). If an upwardly convex peak exists in the differential waveform (AB), the determination unit 64 determines that the measured waveform B is the background waveform G. If an upwardly convex peak does not exist in the differential waveform (AB), the determination unit 64 determines whether or not an upwardly convex peak exists in the differential waveform (BA). If an upwardly convex peak exists in the differential waveform (BA), the determination unit 64 determines that the measured waveform A is the background waveform G. If there is no upward convex peak in the differential waveform (BA), in other words, if there is no upward convex peak in both the differential waveform (AB) and the differential waveform (BA), both measurement waveforms A and B may be determined to be background waveform G, or either one may be determined to be background waveform G.

[0077] 21 and 22, there is no upward convex peak in the differential waveform (AB). Furthermore, there is an upward convex peak in the differential waveform (BA). Therefore, the measured waveform A is determined to be the background waveform G.

[0078] 25 and 26, there are no upwardly convex peaks in either the differential waveform (AB) or the differential waveform (BA). Therefore, both measurement waveforms A and B may be determined to be background waveform G, or either one of them may be determined to be background waveform G.

[0079] The measured waveform determined to be the background waveform G is output to the storage device 142 and stored together with the position of the off-mark region 12.

[0080] 8 and 9, the alignment mark 14 has a line pattern formed in a recessed portion. If the recessed portion can be formed sharply, the peak can be detected as a downwardly convex negative peak. However, when the line width of the recess is small, the recess is not formed sharply but with a gentle slope from the perspective of processing accuracy. In fact, the recess of the alignment mark 14 with a small line width on the order of a few microns is formed with a gentle slope. When the recess is formed with a gentle slope, the peak is detected as a positive peak that is convex upward. This occurs because, when the recess is sharp, the intensity of the reflected electrons emitted from the bottom in the opposite direction (upward) to the incident direction of the electron beam is detected along the sharp shape of the recess, compared to the isotropically emitted secondary electrons. On the other hand, when the recess is not formed sharply but with a gentle slope, there are few bottom surfaces perpendicular to the incident direction of the electron beam and many slopes, so the intensity of the secondary electrons emitted isotropically from the slopes becomes dominant over the reflected electrons emitted upward. When the intensity of the secondary electrons becomes dominant, the peak is detected as a positive peak that is convex upward when the line width of the recess is small. Therefore, the determining section 64 only needs to determine whether or not there is an upwardly projecting peak in the differential waveform.

[0081] FIG. 27 shows an example of the results of differential waveforms for each combination when there are three off-mark areas according to the first embodiment. FIG. 28 shows another example of the results of the differential waveforms for each combination when there are three off-mark areas according to the first embodiment. For example, as shown in Figure 13, if three off-mark areas 12-1, 12-2, and 12-3 are set for the line pattern 16, multiple combinations of two are set. Here, three combinations are established: a combination of off-mark areas 12-1 and 12-2, a combination of off-mark areas 12-2 and 12-3, and a combination of off-mark areas 12-1 and 12-3. In Figures 27 and 28, the measured waveform of off-mark area 12-1 is indicated by 1, the measured waveform of off-mark area 12-2 by 2, and the measured waveform of off-mark area 12-3 by 3. The vertical axis represents the waveform to be drawn, and the horizontal axis represents the waveform to be drawn.

[0082] In the example of Figure 27, the differential waveform (1-2) has no upwardly convex peaks. The differential waveform (2-1) has no upwardly convex peaks. Therefore, the judgment unit 64 judges that both measured waveforms 1 and 2 could be background waveforms G (OK). The differential waveform (1-3) has no upwardly convex peaks. The differential waveform (3-1) has no upwardly convex peaks. Therefore, the judgment unit 64 judges that both measured waveforms 1 and 3 could be background waveforms G (OK). The differential waveform (2-3) has no upwardly convex peaks. The differential waveform (3-2) has no upwardly convex peaks. Therefore, the judgment unit 64 judges that both measured waveforms 2 and 3 could be background waveforms G (OK). Therefore, the measured waveforms 1, 2, and 3 could both be background waveforms G (OK).

[0083] In the example of Figure 28, the differential waveform (1-2) has no upwardly convex peaks. The differential waveform (2-1) has an upwardly convex peak. Therefore, the judgment unit 64 judges that the measured waveform 1 can be the background waveform G (OK). The differential waveform (1-3) has no upwardly convex peaks. The differential waveform (3-1) has no upwardly convex peaks. Therefore, the judgment unit 64 judges that both the measured waveforms 1 and 3 can be the background waveform G (OK). The differential waveform (2-3) has an upwardly convex peak. The differential waveform (3-2) has an upwardly convex peak. Therefore, the judgment unit 64 judges that the measured waveform 3 can be the background waveform G (OK). Therefore, the measured waveforms 1 and 3 can be the background waveform G (OK). However, the measured waveform 2 is judged to be unusable as the background waveform G (NG).

[0084] In the above example, the background waveform is determined from the difference between two measured waveforms, but the method for determining the background waveform is not limited to this.

[0085] The difference calculation unit 62 calculates a parameter Rssd for each of the multiple measurement waveforms Wi obtained in the multiple off-mark areas 12 using the difference (Ti-Wi) between the template waveform Ti used to determine the background waveform and the measurement waveform Wi.

[0086] FIG. 29 is a diagram illustrating an example of a method for determining a background waveform using a template according to the first embodiment. First, a template waveform Ti for determining the background waveform is prepared in advance. For example, the template waveform Ti can be a measured waveform obtained as a result of scanning at a position sufficiently distant from the alignment mark 14. Alternatively, the template waveform Ti may be created as a waveform having characteristics of a past background waveform. The template waveform Ti is stored, for example, in the storage device 142. Then, as shown in FIG. 29, the sum of squared differences between the template waveform Ti and the measured waveform Wi is calculated for each measured waveform. In the example of FIG. 29, since there are 1,024 measurement points on the waveform, the sum of squared differences is divided by a coefficient k to align the digits of the sum of squared differences with the digits of the intensity at each measurement point on the waveform, and the value calculated as the parameter Rssd is the sum of squared differences divided by a coefficient k. The coefficient k is set to, for example, 10,000. In the example of FIG. 29, the calculation result for measured waveform A, which is candidate 1, is parameter Rssd=356, and the calculation result for measured waveform B, which is candidate 2, is parameter Rssd=170.

[0087] The determination unit 64 determines, from among the multiple candidate measured waveforms, the measured waveform that has a high similarity to the template waveform Ti as the background waveform. Specifically, from among the multiple candidate measured waveforms, the determination unit 64 determines, as the background waveform, the measured waveform with the smaller parameter Rssd. In the example of Figure 29, the determined measured waveform B, which is candidate 2 and has a small parameter Rssd, is determined to be the background waveform G.

[0088] The measured waveform determined to be a background waveform is output to the storage device 142 and stored together with the position of the off-mark region 12.

[0089] As described above, by using the measured waveforms obtained in a plurality of off-mark areas 12 in the vicinity of the alignment mark 14, a highly accurate background waveform can be obtained.

[0090] FIG. 30 shows an example of a measured waveform in which a peak exists in the differential waveform in the first embodiment. As described above, if a peak exists in the differential waveform (AB), a peak exists in the measured waveform A. Alternatively, if a peak exists in the differential waveform (BA), a peak exists in the measured waveform B. Therefore, it may seem appropriate to use the measured waveform in which a peak exists as the measured waveform C in the on-mark area 19 in which a mark exists. However, as shown in the example of FIG. 30, the peak may be caused by a foreign substance on the sample 101. Therefore, in the first embodiment, even if a peak exists in the measured waveform in the off-mark area 12 used to determine the background waveform G, an on-mark area containing part of the mark is searched for again.

[0091] In the on-mark scanning step (S130), the scanning mechanism scans the sample 101 with an electron beam in the on-mark area 19 including the target line pattern 16 (18). The method for scanning the on-mark area 19 is the same as the method for scanning the off-mark area 12.

[0092] In the background removal step (S140), the removal unit 65 removes the background waveform G obtained by the judgment from the measurement waveform C measured by scanning the on-mark area 19 including the line pattern. Specifically, a differential waveform (CG) is calculated by subtracting the background waveform from the measurement waveform C of the on-mark area.

[0093] In the determination step (S142), the determination unit 66 determines whether or not an upwardly projecting peak exists in the differential waveform (CG) obtained by removing the background waveform G from the measured waveform C of the on-mark area 19. If an upwardly projecting peak exists in the differential waveform (CG) obtained by removing the background waveform G from the measured waveform C of the on-mark area, the process proceeds to the mark position calculation step (S144). If an upwardly projecting peak does not exist in the differential waveform (CG), the process returns to the on-mark coordinate setting step (S102), and while shifting the coordinates of the on-mark area 19, the on-mark coordinate setting step (S102) to the determination step (S142) are repeated until an upwardly projecting peak exists in the differential waveform (CG) obtained by removing the background waveform G from the measured waveform C of the on-mark area 19.

[0094] FIG. 31 is a diagram illustrating a method for shifting the on-mark area in the first embodiment. The example in FIG. 31 illustrates a case where an on-mark area 19 including the line pattern 16 extending in the y direction, out of two line patterns 16 and 18 constituting the alignment mark 14, is searched for. If the placement position of the sample 101 on the XY stage 105 is shifted, the line pattern 16 (18) may not necessarily be included in the on-mark area 19 at the set coordinates. In this case, no peak appears in the measurement waveform obtained in the on-mark scanning step (S130). Therefore, if no peak exists even after removing the background waveform G, the on-mark area 19 including the line pattern is searched for while shifting the on-mark area 19. In this case, as shown in FIG. 31, the second on-mark area 19-2 is set so that it partially overlaps with the first on-mark area 19-1 in the 45° direction, which is midway between the x and y directions. If there is no peak in the on-marked area 19-2, the third on-marked area 19-3 is set in the opposite direction (225°) from the on-marked area 19-2 so that it partially overlaps with the on-marked area 19-1. If there is no peak in the on-marked area 19-3, the fourth on-marked area 19-4 is set at a 45° angle from the on-marked area 19-2 so that it partially overlaps with the on-marked area 19-2. This is repeated while alternating directions and shifting positions until a peak appears. Then, each time an on-marked area 19 is set, multiple off-marked areas 12 are set nearby. By shifting the positions of the on-marked areas 19 so that they partially overlap, it is possible to prevent missed detection of line patterns.

[0095] In the mark position calculation step (S144), the mark position calculation unit 68 calculates the mark position from the measured waveform from which the background waveform G has been removed.

[0096] 32 is a diagram showing an example of a mark position in the first embodiment. The position of an upward convex peak that appears in the differential waveform (CG) is the position of the target line pattern. Since the position of the on-mark area 19 is known, the position of the target line pattern can also be calculated.

[0097] After determining the x-position (y-position) of one of the line patterns 16 (18) that make up the alignment mark 14, the steps from the on-mark coordinate setting step (S102) to the mark position calculation step (S144) are performed for the other paired line pattern 18 (16), thereby calculating the y-position (x-position) of the line pattern 18 (16).

[0098] If the x position of line pattern 16 extending in the y direction and the y position of line pattern 18 extending in the x direction are known, the center coordinates (x, y) of the target alignment mark 14 can be calculated. To obtain even higher accuracy, for example, the x positions of line pattern 16 are measured at positions in the y direction and the -y direction across line pattern 18. Similarly, for example, the y positions of line pattern 18 are measured at positions in the x direction and the -x direction across line pattern 16. Then, the average position of the two x positions and the average position of the two y positions are calculated as the center coordinates (x, y) of the target alignment mark 14.

[0099] In this way, the position of the target alignment mark 14 can be detected.

[0100] In the determination step (S146), the determination unit 69 determines whether or not the positions of all alignment marks 14 have been calculated. If the positions of all alignment marks 14 have not yet been calculated, the process returns to the on-mark coordinate setting step (S102), and the steps from the on-mark coordinate setting step (S102) to the mark position calculation step (S144) are repeated until the positions of all alignment marks 14 have been calculated. In other words, the above-mentioned steps are performed for each alignment mark 14.

[0101] This allows the position of each alignment mark 14 to be detected.

[0102] In the data correction step (S150), the correction unit 70 corrects the position of the pattern to be written using the calculated positions of the plurality of alignment marks 14.

[0103] 33 is a diagram showing an example of a method of data correction in the first embodiment. Each pattern data defined in the writing data is defined based on each alignment mark 14 when the sample 101 is placed at the designed position. Therefore, each pattern data is defined along the writing coordinate system. However, the sample 101 actually placed on the XY stage 105 has positional and rotational deviations from the designed position. Therefore, the position of each pattern data is corrected to match the positional and rotational deviations, based on the actually measured positions of each alignment mark 14.

[0104] In the drawing step (S152), first, the rasterization processing unit 50 reads out chip pattern data (drawing data) from the storage device 140 and performs rasterization processing. Specifically, the pattern density (pattern area density) is calculated for each pixel 36.

[0105] Next, the shot data generation unit 52 calculates, for each pixel 36, an irradiation dose D to be applied to that pixel 36. The irradiation dose D may be calculated, for example, by multiplying a preset reference irradiation dose Dbase by a proximity effect-corrected irradiation dose Dp and a pattern area density ρ. The proximity effect-corrected irradiation dose Dp is defined as a relative value normalized with the reference irradiation dose Dbase set to 1. In this way, the irradiation dose D is preferably calculated in proportion to the pattern area density calculated for each pixel 36. For the proximity effect-corrected irradiation dose Dp, the drawing region (e.g., the stripe region 32) is virtually divided into a plurality of proximity mesh regions (mesh regions for calculating proximity effect correction) of a predetermined size in a mesh pattern. The size of the proximity mesh region is preferably set to approximately 1 / 10 of the range of influence of the proximity effect, for example, approximately 1 μm. Then, the drawing data is read from the storage device 140, and for each proximity mesh region, a pattern density ρ' (pattern area density) of the pattern to be arranged within the proximity mesh region is calculated.

[0106] Next, a proximity effect correction dose Dp for correcting the proximity effect is calculated for each proximity mesh region. The correction model and calculation method for the proximity effect correction dose Dp may be the same as those used in the conventional single-beam writing method.

[0107] Then, the shot data generation unit 52 calculates, for each pixel 36, the irradiation time t of the electron beam for making the calculated irradiation dose D incident on that pixel 36. The irradiation time t can be calculated by dividing the irradiation dose D by the current density J. In this way, a dose map (actually an irradiation time map) is created in which irradiation time data (shot data) for each pixel 36 is defined.

[0108] Then, under the control of the writing control unit 72, the writing mechanism 150 uses the multi-beam 20 to write the pattern, the position of which has been corrected, onto the workpiece 101.

[0109] As described above, according to the first embodiment, the background waveform near the mark can be acquired with high accuracy using a simple method.

[0110] FIG. 34 is a diagram showing an example of the positional relationship between an alignment mark, an on-mark area, and multiple off-mark areas in a modification of the first embodiment. The example of FIG. 34 illustrates a case in which multiple off-mark areas 12 are set using the line pattern 16 extending in the y direction, of the two line patterns 16, 18 constituting the alignment mark 14, as the target line pattern. The example of FIG. 34 illustrates a case in which an off-mark area 12-1 is set on the x-direction side of the on-mark area 19 of the line pattern 16, and an off-mark area 12-2 is set on the -x-direction side. In this case, the mark position may be shifted due to a misalignment of the substrate, etc., and, for example, as shown in FIG. 34, a part of the mark may overlap the off-mark area 12-2. Even in such a case, the difference calculation step (S110) described above calculates a difference (AB) (first difference) obtained by subtracting measured waveform B (second measured waveform) from measured waveform A (first measured waveform) and a difference (BA) (second difference) obtained by subtracting measured waveform A from measured waveform B. In this way, the case where the difference calculation is performed twice for two measured waveforms has been described. In a modification of the first embodiment, a case where the determination can be made based on one of the differences will be described.

[0111] For example, in the first differential calculation, if a differential waveform (BA) is obtained by subtracting measured waveform A from measured waveform B, as shown in Figure 22, it can be seen that there is an upward convex peak in the differential waveform (BA).Therefore, in a modified example of embodiment 1, in the judgment step (S120), the judgment unit 64 judges measured waveform A to be background waveform G.

[0112] In this way, if a differential waveform is obtained only once and an upward convex peak is present in the obtained differential waveform, the background waveform G can be determined from the subtracted measured waveform A from that single differential waveform.

[0113] Conversely, for example, in the first differential calculation, when a differential waveform (AB) is obtained by subtracting measured waveform B from measured waveform A as shown in FIG. 21, if there is no upward convex peak in the differential waveform (AB), in the modification of embodiment 1, the judgment unit 64 judges measured waveform A to be background waveform G in the judgment step (S120).

[0114] In this way, if the differential waveform is calculated only once and there is no upward convex peak in the calculated differential waveform, the background waveform G can be determined from the subtracted measured waveform A from that single differential waveform.

[0115] Furthermore, in the above example, a case where an alignment mark (line pattern) appears in the measured waveform as a peak that is convex upward has been described, but this is not limited to this. The background waveform acquisition method and mark position detection method in the above embodiment can also be applied to a case where an alignment mark (line pattern) appears in the measured waveform as a peak that is convex downward. In such a case, the "peak that is convex upward" can be read as a "peak that is convex downward" and applied. Furthermore, the line patterns 16, 18 of the alignment mark 14 may be formed not only as continuous lines, but also as dots, broken lines, or segments.

[0116] Furthermore, the processing functions described in each of the above-mentioned embodiments may be executed by a computer, and a program for causing a computer to execute such processing functions may be stored in a non-transitory, tangible readable recording medium such as a magnetic disk device.

[0117] 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.

[0118] In addition, all background waveform acquisition methods, mark position detection methods, electron beam writing methods, and electron beam writing apparatuses that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention. [Explanation of symbols]

[0119] 12 Off-mark area 14 Alignment marks 16,18 line pattern 19 On-mark area 20 Multibeam 21 beam group 22 holes 24 control electrode 25 Passing hole 26 Counter electrode 28 pixels 29 Sub-irradiation area 30 drawing area 32 stripe area 34 Irradiation area 36 pixels 40 areas 41 Control circuit 50 Rice Rise Processing Unit 52 Shot data generation unit 54 Coordinate setting section 56 Area setting section 58 Scanning Processing Unit 60 Judgment section 62 Difference calculation part 64 Judgment section 65 Removal part 66 Judgment section 68 Mark position calculation unit 69 Judgment section 70 Correction unit 72 Drawing control unit 74 Transfer Processing Unit 80 Glass substrate 82 Light-shielding film 84 Glass substrate 86 Multilayer film 88 Absorber membrane 100 drawing device 101 Sample 102 Electron Telescope 103 Drawing room 105 XY stage 110 Control computer 112 memory 130 Deflection 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 Storage device 150 Drawing mechanism 160 Control Circuits 200 electron beam 201 Electron Gun 202 Lighting lens 203 Shaped Aperture Array Substrate 204 Blanking Aperture Array Mechanism 205 Reduction Lens 206 Limiting Aperture Substrate 207 Objective Lens 208 Main deflector 209 Sub deflector 210 Mirror 212 detector 330 Membrane Region

Claims

1. a step of scanning a sample, on which a mark using a line pattern is formed, with an electron beam in a plurality of areas arranged in a direction not parallel to a direction in which the line pattern extends and in the vicinity of the line pattern; determining and outputting a waveform of a background other than the mark from among a plurality of measurement waveforms measured by scanning the plurality of regions; A method for acquiring a background waveform, comprising:

2. further comprising a step of calculating, for at least one combination of two measurement waveforms from the plurality of measurement waveforms obtained in the plurality of regions, a first difference obtained by subtracting a second measurement waveform from a first measurement waveform constituting the combination, and a second difference obtained by subtracting the first measurement waveform from the second measurement waveform, determining the background waveform based on the first difference waveform and the second difference waveform; 2. The method for acquiring a background waveform according to claim 1, wherein:

3. Further, for at least one combination of two measurement waveforms from the plurality of measurement waveforms obtained in the plurality of regions, a first difference is calculated by subtracting a second measurement waveform from a first measurement waveform constituting the combination, determining the background waveform based on the first difference waveform; 2. The method for acquiring a background waveform according to claim 1, wherein:

4. further comprising a step of calculating, for each of a plurality of measurement waveforms obtained in the plurality of regions, a parameter using a difference between the measurement waveform and a template waveform for determining the background waveform; The measured waveform in which the parameter is smaller is determined as the background waveform.

2. The method for acquiring a background waveform according to claim 1, wherein:

5. a step of scanning a sample, on which a mark using a line pattern is formed, with an electron beam in a plurality of areas arranged in a direction not parallel to a direction in which the line pattern extends and in the vicinity of the line pattern; a step of determining a background waveform other than the mark from among a plurality of measurement waveforms measured by scanning the plurality of regions; scanning the sample with an electron beam in an area including the line pattern; a step of removing the background waveform obtained by judgment from a measured waveform measured by scanning an area including the line pattern; calculating and outputting a mark position from the measured waveform from which the background waveform has been removed; A mark position detection method comprising:

6. a step of scanning the sample with an electron beam in a plurality of areas that are arranged in a direction that is not parallel to a direction in which the line pattern extends and that are near the line pattern for each mark of the sample on which a plurality of marks using a line pattern are formed; a step of determining, for each mark, a background waveform that is not a mark from among a plurality of measurement waveforms measured by scanning the plurality of regions; scanning the sample with an electron beam in an area including the line pattern for each mark; a step of removing the background waveform obtained by judgment from a measurement waveform measured by scanning an area including the line pattern for each mark; calculating, for each mark, a mark position from the measured waveform from which the background waveform has been removed; correcting the position of a pattern to be written using the calculated positions of the marks; writing a position-corrected pattern onto the sample using an electron beam; 1. An electron beam writing method comprising:

7. a stage on which a sample having a plurality of marks formed using a line pattern is placed; a scanning mechanism that scans the sample with an electron beam in a plurality of areas that are near the line pattern and aligned in a direction that is not parallel to the extending direction of the line pattern, for each mark on the sample; a determination unit that determines, for each mark, a background waveform that is not a mark from among a plurality of measurement waveforms measured by scanning the plurality of regions; a background waveform removing unit that removes the background waveform obtained by judgment from a measurement waveform measured by scanning the sample with an electron beam in an area including the line pattern for each mark; a mark position calculation unit that calculates the mark position for each mark from the measured waveform from which the background waveform has been removed; a correction unit that corrects the position of a pattern to be written using the calculated positions of the plurality of marks; a drawing mechanism having the stage and the scanning mechanism, and using an electron beam to draw a position-corrected pattern on the sample; 1. An electron beam lithography apparatus comprising:

Images