Charged particle beam drawing method and charged particle beam drawing apparatus

Abstract

To improve drawing accuracy by drift correction while suppressing a decrease in throughput.SOLUTION: In a drawing method according to the present embodiment, patterns are sequentially drawn for a plurality of stripes, and a drift correction amount of an irradiation position of a charged particle beam radiated onto a substrate at a predetermined timing is calculated. In this method, the process of sequentially drawing the plurality of stripes is defined as one stroke, and the drawing process for the stroke is performed multiple times. In the (j-k)-th stroke (j is an integer of 2 or more, and k is an integer from 1 to j-1 inclusive), a drift amount is calculated and stored. In the j-th stroke, a drift correction amount is calculated using the stored drift amount of the (j-k)-th stroke and the drift amount calculated in the j-th stroke, and the pattern drawing position is corrected using the calculated drift correction amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] As LSIs become more highly integrated, the circuit line width of semiconductor devices becomes ever finer. Electron beam lithography, which offers excellent resolution, is used to create exposure masks (also called reticles when used in steppers and scanners) for forming circuit patterns on these semiconductor devices.

[0003] In electron beam lithography systems, a phenomenon called beam drift occurs, in which the electron beam irradiation position shifts during lithography due to various factors. Drift correction is performed to cancel this beam drift. In conventional drift correction, during the lithography process, the electron beam scans a measurement mark formed on a mark substrate on the stage to measure the electron beam irradiation position, and the difference from the previous measurement value is used as the drift correction amount. As a result, the difference between the amount of beam drift in the previous section and the amount of beam drift in the next section becomes a correction residual, which hinders improvement in lithography accuracy.

[0004] Although the correction residual can be reduced by shortening the measurement interval of the beam irradiation position, there is a problem in that the throughput decreases. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-093678 [Patent Document 2] Japanese Patent Publication No. 2020-141022 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-178461 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above-described conventional situation, and an object of the present invention is to provide a charged particle beam drawing method and a charged particle beam drawing apparatus that can improve drawing accuracy by drift correction while suppressing a decrease in throughput. [Means for solving the problem]

[0007] A charged particle beam lithography method according to one aspect of the present invention is a charged particle beam lithography method that irradiates a substrate with a charged particle beam while moving the substrate, sequentially draws a pattern for each of a plurality of stripes obtained by dividing a drawing area of ​​the substrate by a predetermined width, and calculates a drift correction amount of an irradiation position of the charged particle beam irradiated onto the substrate at a predetermined timing, wherein the process of sequentially drawing the plurality of stripes is defined as one stroke, and the drawing process of the stroke is performed a plurality of times; In the jk-th stroke (j is an integer of 2 or more, k is an integer of 1 or more and j-1 or less), the drift amount is calculated and stored, and in the j-th stroke, the drift correction amount is calculated using the stored drift amount of the jk-th stroke and the drift amount calculated in the j-th stroke, and the calculated drift correction amount is used to correct the pattern drawing position.

[0008] A charged particle beam drawing apparatus according to one aspect of the present invention comprises: a drawing unit that, while moving a substrate, sequentially draws a pattern for each of a plurality of stripes obtained by dividing a drawing area of ​​the substrate by a predetermined width; and a control unit that controls the drawing unit to perform drawing processing for one stroke to draw the plurality of stripes a plurality of times, calculates a drift amount of the irradiation position of the charged particle beam irradiated on the substrate for each stroke a plurality of times, calculates the drift amount for the jk-th stroke (j is an integer of 2 or more, k is an integer of 1 to j-1), performs the drift correction based on the calculated drift amount, calculates and stores a drift correction residual, calculates a drift correction amount for the j-th stroke using the stored drift amount for the jk-th stroke and the drift amount calculated for the j-th stroke, and corrects the pattern drawing position using the calculated drift correction amount. [Effects of the Invention]

[0009] According to the present invention, it is possible to improve the drawing accuracy by correcting the drift while suppressing a decrease in throughput. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a drawing device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of a shaped aperture array substrate. [Figure 3] 10(a) and 10(b) are diagrams illustrating an example of a drawing operation. [Figure 4] 10(a) to 10(c) are diagrams illustrating stroke drawing. [Figure 5] 10 is a flowchart illustrating a drawing method according to the embodiment. [Figure 6] FIG. 10 is a diagram showing a residual error correction table. [Figure 7] 10 is a flowchart illustrating a drawing method according to the embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of timing for measuring drift for each stroke. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiment, a configuration using an electron beam will be described as an example of a beam. However, the beam is not limited to an electron beam, and a charged particle beam such as an ion beam or a beam using laser light may also be used.

[0013] Fig. 1 is a schematic diagram of a drawing apparatus according to an embodiment. As shown in Fig. 1, the drawing apparatus 100 includes a drawing unit 150 and a control unit 160. The drawing apparatus 100 is an example of a multi-charged particle beam drawing apparatus. The drawing unit 150 includes an electron optical column 102 and a drawing chamber 103. Inside the electron optical column 102, an electron source 201, an illumination lens 202, a shaping aperture array substrate 203, a blanking aperture array substrate 204, a reduction lens 205, a limiting aperture member 206, an objective lens 207, a deflector 208, and a detector 211 are arranged.

[0014] An XY stage 105 is placed in the writing chamber 103. A substrate 101 to be written is placed on the XY stage 105. A resist to be irradiated with a charged particle beam is applied to the upper surface of the substrate 101, and the substrate 101 is, for example, a substrate to be processed into a mask (mask blank) or a semiconductor substrate (silicon wafer) to be processed into a semiconductor device.

[0015] A mark 106 and a mirror 210 for measuring the position of the stage are arranged on the XY stage 105 .

[0016] The stage position detector 139 emits a laser beam, receives the light reflected from the mirror 210, and detects the position of the XY stage 105 based on the principle of laser interference.

[0017] The control unit 160 has a control computer 110, a deflection control circuit 130, a detection circuit 132, a stage position detector 139, and storage units 140 and 142. Writing data is input from the outside and stored in the storage unit 140.

[0018] The control computer 110 has a beam position measurement unit 111, a position deviation calculation unit 112, a position correction unit 113, a data processing unit 114, and a writing control unit 115. Each unit of the control computer 110 may be configured with hardware such as an electric circuit, or may be configured with software such as a program that executes these functions, or may be configured with a combination of hardware and software.

[0019] Fig. 2 is a conceptual diagram showing the configuration of shaping aperture array substrate 203. As shown in Fig. 2, apertures 22 are formed in m rows (y direction) x n columns (x direction) (m, n ≥ 2) at a predetermined arrangement pitch on shaping aperture array substrate 203. Each aperture 22 is formed, for example, as a rectangle of the same dimensions. Each aperture 22 may also be a circle of approximately the same diameter.

[0020] An electron beam 200 emitted from an electron source 201 is illuminated almost perpendicularly by an illumination lens 202 onto the entire shaping aperture array substrate 203. The electron beam 200 illuminates an area that includes all of the apertures 22. A portion of the electron beam 200 passes through the multiple apertures 22 in the shaping aperture array substrate 203, and the remaining beam is stopped by the shaping aperture member. As the electron beam 200 passes through the multiple apertures 22 in the shaping aperture array substrate 203, a multibeam 20 including multiple individual beams is formed. The overall shape of the beam array of the multibeam 20 is, for example, rectangular.

[0021] The blanking aperture array substrate 204 has beam passage holes formed in alignment with the positions of the apertures 22 on the shaping aperture array substrate 203. A pair of electrodes (blankers) is disposed in each passage hole. The electron beams passing through each passage hole are independently controlled to a beam-on or beam-off state by the voltage applied to the blankers. When the beam is on, the opposing electrodes of the blanker are controlled to the same potential, and the blanker does not deflect the beam. When the beam is off, the opposing electrodes of the blanker are controlled to different potentials, and the blanker deflects the beam.

[0022] The multi-beams 20 that have passed through the blanking aperture array substrate 204 are reduced in size by a reduction lens 205 .

[0023] A beam controlled to be in the beam-off state is deflected by the blanker on the blanking aperture array substrate 204, travels on a trajectory that passes outside the opening of the limiting aperture member 206, and is blocked by the limiting aperture member 206. On the other hand, a beam controlled to be in the beam-on state is not deflected by the blanker, and therefore passes through the opening of the limiting aperture member 206. In this way, the beam is turned on and off by blanking control on the blanking aperture array substrate 204.

[0024] The limiting aperture member 206 blocks each beam deflected by the multiple blankers to be in a beam-off state. Then, multiple beams for one shot are formed by the beams that pass through the limiting aperture member 206 from when the beam is turned on until when the beam is turned off.

[0025] The multi-beams that have passed through the limiting aperture member 206 are focused by the objective lens 207 and projected onto the substrate 101 at a desired reduction ratio. The multi-beams are all deflected in the same direction by the deflector 208, and are irradiated onto the desired position on the substrate 101.

[0026] When the XY stage 105 is moving continuously, the beam trajectory is controlled by the deflector 208 so that the irradiation position of the beam on the substrate 101 follows the movement of the XY stage 105 .

[0027] Fig. 3 is a conceptual diagram for explaining the drawing operation. As shown in Fig. 3, the drawing region 30 on the substrate 101 is divided, for example, into a plurality of rectangular stripe regions 34 with a predetermined width in the y direction (first direction). First, the XY stage 105 is moved and adjusted so that the irradiation region 35 that can be irradiated with one multi-beam irradiation is positioned at the left end of the first stripe region 34, and drawing begins.

[0028] When writing the first stripe region 34, the XY stage 105 is moved in the -x direction, thereby relatively progressing writing in the +x direction. The XY stage 105 is moved continuously at a predetermined speed. After writing the first stripe region 34 is completed, the stage position is moved in the -y direction, and adjusted so that the irradiation region 35 is positioned at the right end of the second stripe region 34. Next, as shown in FIG. 3(b), the XY stage 105 is moved in the +x direction, thereby writing in the -x direction.

[0029] In the third stripe region 34, writing is performed in the +x direction, and in the fourth stripe region 34, writing is performed in the -x direction. Writing time can be reduced by alternately changing the direction of writing. It is also possible to write each stripe region 34 in the same direction.

[0030] The writing device 100 performs multiple writing, in which patterns are repeatedly written on top of each other, in order to improve the positional accuracy of the figure to be written. In this embodiment, writing is performed multiple times, sequentially from the first stripe region 34 to the last stripe region 34, to write (almost) the entire surface of the writing region 30. Hereinafter, writing the entire surface of the writing region 30 once is also referred to as one-stroke writing.

[0031] Furthermore, in this embodiment, the position (drawing start position) of the stripe region 34 is shifted in the y direction for each stroke, and multiple strokes are drawn.

[0032] An example of four-stroke drawing is shown in Figures 4(a) to 4(c). For simplicity, the drawing area is divided into four stripe areas. As shown in Figure 4(a), the four stripe areas (#1 to #4) are drawn in order to draw the first stroke.

[0033] As shown in Figure 4(b), in the second stroke, the position (reference point) of each stripe area is shifted in the y direction from when the first stroke was drawn, and four stripe areas (#5 to #8) are drawn in sequence. The shift amount D of the stripe areas is assumed to be smaller than the width W of the stripe area. Figure 4(c) shows four stripe areas (#9 to #12) drawn in the third stroke and four stripe areas (#13 to #16) drawn in the fourth stroke. Note that in Figures 4(b) and 4(c), the positions of the stripe areas drawn with each stroke are shifted in the x direction as well for illustrative purposes, but they do not need to be shifted in the x direction.

[0034] In the writing apparatus 100, a phenomenon called beam drift occurs, in which the beam irradiation position shifts during writing due to various factors. Drift correction is performed to cancel this beam drift. In drift correction, a mark 106 provided on the XY stage 105 is scanned with a beam during writing processing, and electrons reflected by the mark 106 are detected by a detector 211. A detection circuit 132 transmits the amount of electrons detected by the detector 211 to a control computer 110. A beam position measurement unit 111 obtains a scan waveform from the detected amount of electrons and measures the beam irradiation position based on the position of the XY stage 105. The position of the XY stage 105 is detected by a stage position detector 139. A position deviation calculation unit 112 calculates the amount of position deviation (drift amount) of the measured beam irradiation position from the ideal position.

[0035] For example, among the multiple beams, a plurality of beams located in the center are grouped, and only this group of beams is turned on to scan the mark 106 and calculate the beam position. The amount of misalignment of this beam position can be used as the amount of misalignment of the multiple beams. Alternatively, grouping of some beams of the multiple beams and calculation of their beam positions may be repeated within the beam array to calculate the amount of misalignment of the plurality of beam positions, and the average of the misalignment amounts may be used as the amount of misalignment of the multiple beams.

[0036] The position corrector 113 calculates a correction amount for correcting the amount of drift, and shifts the position of the pattern defined in the drawing data based on the correction amount.

[0037] Beam position measurement (drift measurement) is performed at predetermined time intervals. For example, the correction amount calculated from the difference between the drift amount based on the kth measurement result (k is an integer equal to or greater than 1) and the drift amount based on the k+1th measurement result is used in the drawing process from the k+1th measurement to the k+2th measurement. However, this correction amount does not necessarily match the actual drift amount in the interval from the k+1th measurement to the k+2th measurement, and the difference between the actual drift amount and the correction amount becomes the correction residual.

[0038] The inventors have discovered that when drawing multiple strokes, similar correction residuals occur between the strokes, and therefore the accuracy of pattern drawing position can be improved by adding a correction amount to remove the correction residual generated in drawing the jth stroke when correcting the drift in drawing the j+1th stroke (j is an integer greater than or equal to 1).

[0039] The writing method according to this embodiment will be described with reference to a flowchart. As shown in Fig. 5, the first stroke writing is started, and the stripe region is written in order (step S1). When the timing for a predetermined drift measurement arrives (step S2_Yes), the amount of drift is measured (step S3). As described above, the mark 106 is scanned with a beam, electrons reflected by the mark 106 are detected by the detector 211, the beam irradiation position is measured from the waveform of the detected electron amount, and the amount of drift is calculated.

[0040] The timing of the drift measurement is arbitrary. For example, drift measurement may be performed at regular time intervals, or the drift measurement interval may be gradually increased within one stroke drawing. Furthermore, the drift measurement interval for the j+1th stroke drawing may be longer than that for the jth stroke drawing.

[0041] This drift amount corresponds to the correction residual for the interval between the previous drift measurement and the current drift measurement. The correction residual for that interval of the first stroke drawing is saved in the storage unit 142 (step S4). As a result, a correction residual table is created in the storage unit 142, as shown in FIG. 6, in which the correction residuals in the X and Y directions are associated with the Y coordinate for that interval. At this time, the correction residual may also be associated with time.

[0042] The position corrector 113 calculates the amount of position correction based on the amount of drift calculated in step S3 (step S5).

[0043] Steps S1 to S5 are repeated until writing is completed for all stripe regions in the writing region 30 (step S6). In the writing process for the stripe regions, the position corrector 113 reads writing data from the storage unit 140 and shifts the position of the pattern defined in the writing data based on the position correction amount calculated in step S5.

[0044] When the first stroke drawing is completed, the second stroke drawing is started as shown in Fig. 7, and the stripe region is drawn in order (step S11). When the timing for the predetermined drift measurement arrives (step S12_Yes), the drift amount is measured (step S13).

[0045] This drift amount corresponds to the correction residual in the section from the previous drift measurement to the current drift measurement. The correction residual in the section in question for the second stroke drawing is stored in the storage unit 142 (step S14).

[0046] The position correction unit 113 calculates a position correction amount for removing the drift amount of the previous section and the correction residual error in the previous stroke drawing based on the drift amount calculated in step S13 and the correction residual error table created when the previous (first) stroke was drawn (step S15). In calculating the position correction amount, the position correction unit 113 extracts from the correction residual error table the correction residual error in the previous (first) stroke drawing in the area corresponding to the section between the current drift measurement and the next drift measurement.

[0047] Steps S11 to S15 are repeated until writing is completed for all stripe regions in the writing region 30 (step S16). In the writing process for the stripe regions, the position corrector 113 reads writing data from the storage unit 140, and shifts the position of the pattern defined in the writing data based on the position correction amount calculated in step S15.

[0048] The third and subsequent strokes are drawn in the same manner as the second stroke drawing shown in Fig. 6. However, in the final stroke drawing, the process of recording the correction residual in step S14 can be omitted.

[0049] In the stripe region writing process, the data processing unit 114 divides each stripe region into meshes of a predetermined size. The mesh size is, for example, the size of one beam (individual beam) of the multi-beam. The data processing unit 114 calculates the pattern area density of the pattern overlapping each divided mesh (pixel) and an area density map (area density distribution) that is a map of the pattern area density. The data processing unit 114 calculates the beam irradiation amount for each pixel by multiplying the pattern area density by a reference irradiation amount, and creates an irradiation amount map that defines the irradiation amount for each pixel in stripe units.

[0050] The data processing unit 114 converts the irradiation dose into irradiation time and rearranges it in the shot order along the drawing sequence. The irradiation time is obtained, for example, as a value obtained by dividing the irradiation dose for each mesh by the current density of the beam. Since the irradiation time map in stripe units is obtained by this process, a set of meshes irradiated by one multi-beam shot is selected from the meshes of this map to create the irradiation time array data for one shot. The rearranged irradiation time array data is output to the deflection control circuit 130.

[0051] The deflection control circuit 130 outputs the irradiation time array data to the control circuit of each blanker. Further, the deflection control circuit 130 controls the deflection amount of the deflector 208 and controls the irradiation position of the multi-beam.

[0052] Thus, according to the present embodiment, by creating a correction residual table for each stroke drawing and calculating the drift correction amount for the next section using the drift amount in the previous section and the correction residual in the area corresponding to the next section in the previous stroke drawing, it is possible to improve the drawing accuracy by drawing so as to cancel the correction residual generated in each stroke drawing. In addition, since there is no need to shorten the interval of drift measurement for suppressing the correction residual, it is possible to suppress the decrease in throughput.

[0053] Further, it is only necessary to extract the correction residual at the time of the previous stroke drawing by referring to the correction residual table, and there is no need to match the timing of drift correction between the previous stroke drawing and the current stroke drawing.

[0054] For example, as shown in FIG. 8, consider the case where, in the j-th stroke drawing, four drift measurements are performed every time T1, and in the (j + 1)-th stroke drawing, three drift measurements are performed every time T2 (T1 < T2). The correction amount for the section K22 between the second and third drift measurements in the (j + 1)-th stroke drawing is calculated using the drift amount generated in the previous section K21 and the correction residual in the area corresponding to the section K22 in the j-th stroke drawing.

[0055] The area corresponding to section K22 in the j-th stroke drawing straddles sections K12 and K 13. Therefore, for example, the correction residual for section K12 and the correction residual for section K13 are extracted from the correction residual table, and the average of the two extracted correction residuals is set as the correction residual for the area corresponding to section K22 in the j-th stroke drawing.

[0056] In the final stroke drawing, it is preferable to calculate a correction amount from the reproducible drift results that have occurred in the multiple strokes up to that point, predict the correction residual that will occur in the final stroke drawing, and draw using a correction amount that will cancel out the predicted correction residual.

[0057] In the above embodiment, an example has been described in which the position of the stripe region is shifted in the y direction for each stroke, but it is not necessary to shift it.

[0058] Although the above embodiment has been described as an example of a drawing apparatus using multiple beams, the present invention can also be applied to a drawing apparatus using a single beam.

[0059] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0060] 100 Drawing device 110 Control computer 111 Beam position measurement unit 112 Position deviation calculation unit 113 Position correction section 114 Data Processing Unit 115 Drawing control unit 150 Drawing section 160 control section

Claims

1. 1. A charged particle beam lithography method comprising: irradiating a substrate with a charged particle beam while moving the substrate; sequentially drawing patterns for each of a plurality of stripes obtained by dividing a drawing area of ​​the substrate by a predetermined width; and calculating a drift correction amount of an irradiation position of the charged particle beam irradiated onto the substrate at a predetermined timing, A process of drawing the plurality of stripes in order is regarded as one stroke, and the drawing process of the stroke is performed a plurality of times; Calculate and store the amount of drift in the j-kth stroke (j is an integer of 2 or more, and k is an integer of 1 or more and j-1 or less), In the j-th stroke, a drift correction amount is calculated using the stored drift amount in the j-k-th stroke and the drift amount calculated in the j-th stroke; A charged particle beam writing method, wherein the calculated drift correction amount is used to correct the pattern writing position.

2. 2. The charged particle beam writing method according to claim 1, wherein a correction residual after drift correction based on a drift measurement result is stored as the drift amount within a j-kth stroke (j is an integer of 2 or more, and k is an integer of 1 or more and j-1 or less).

3. 3. The charged particle beam writing method according to claim 1, wherein in an i-th stroke (i is an integer of 2 or more), a drift correction residual occurring in the i-th stroke is predicted using the drift amount calculated in strokes prior to the i-th stroke, and a drift correction amount that cancels out the predicted drift correction residual is calculated.

4. 4. The charged particle beam writing method according to claim 3, wherein the i-th stroke is a final stroke.

5. 2. The charged particle beam writing method according to claim 1, wherein the timing of calculating the drift amount or the reference point of the stripe is different between the jth stroke and the j+1th stroke.

6. 2. The charged particle beam drawing method according to claim 1, wherein in the j-th stroke, a drift correction amount is calculated using the drift amount in the j-k+1-th stroke that is further stored.

7. a drawing unit that draws a pattern sequentially for each of a plurality of stripes obtained by dividing a drawing area of ​​the substrate by a predetermined width while moving the substrate; a control unit that controls the writing unit, performs writing processing of one stroke for writing the plurality of stripes a plurality of times, calculates a drift amount of the irradiation position of the charged particle beam irradiated on the substrate for each stroke a plurality of times, calculates the drift amount in a j-k-th stroke (j is an integer of 2 or more, k is an integer of 1 to j-1), performs the drift correction based on the calculated drift amount, calculates and stores a drift correction residual, calculates a drift correction amount in a j-th stroke using the stored drift amount of the j-k-th stroke and the drift amount calculated in the j-th stroke, and corrects the pattern writing position using the calculated drift correction amount; A charged particle beam writing apparatus comprising:

Images