Charged particle beam drawing device, shot data correction method, and charged particle beam drawing method

Abstract

To reduce the impact on drawing accuracy caused by vibrations generated by stage movement.SOLUTION: A charged particle beam drawing device includes an emission unit that emits a charged particle beam, a movable stage on which a substrate to be drawn is placed, a shot data correction unit that corrects shot data generated from drawing data using a relationship between a predetermined stage speed and a positional deviation amount caused by a change in the stage speed, and a drawing unit that irradiates the charged particle beam onto the substrate using the corrected shot data and sequentially draws patterns for each of a plurality of stripe regions obtained by dividing a drawing region of the substrate by a predetermined width.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a charged particle beam drawing apparatus, a shot data correction method, and a charged particle beam drawing method. [Background technology]

[0002] As LSIs become more highly integrated, the circuit line width required for semiconductor devices is becoming finer every year. To form the desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision original pattern (called a mask, or a reticle, especially when used in steppers and scanners) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure system. The high-precision original pattern is drawn using an electron beam drawing system, using so-called electron beam lithography technology.

[0003] In electron beam lithography systems, patterns are written onto a substrate on a moving stage while measuring the stage position. Because vibrations generated by stage movement degrade writing accuracy, vibration control has traditionally been performed using a vibration isolation table. However, there are limitations to mechanical vibration characteristics, and effective vibration control is sometimes not possible. For example, in a long, slender structure such as a microscope tube, if vibrations in a mode that bends the structure are excited, the vibration isolation table is barely able to detect them.

[0004] Cited Document 1 describes a method of attaching a sensor to the telescope tube, analyzing the sensor signal, calculating the amount of beam deviation, and then performing correction. However, this method is constantly affected by noise from the sensor, and the amount of beam deviation could not be sufficiently corrected. In addition, it is necessary to install a system for processing sensor signals and noise according to the type and number of sensors, which is costly. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-246134 [Patent Document 2] Japanese Patent Application Publication No. 11-16815 [Patent Document 3] Japanese Patent Application Publication No. 6-163374 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-191087 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 apparatus, a shot data correction method, and a charged particle beam drawing method that can reduce the influence of vibrations generated by stage movement on drawing accuracy. [Means for solving the problem]

[0007] According to one aspect of the present invention, a charged particle beam lithography apparatus includes: an emitter that emits a charged particle beam; a shot data generator that generates shot data from lithography data; a movable stage that supports a substrate to be lithographed; a storage device that stores positional deviation data indicating a positional deviation of a beam irradiation position on the substrate due to mechanical vibrations generated by movement of the stage; a shot data corrector that corrects the shot data so that the positional deviation based on the positional deviation data is corrected; and a lithography unit that irradiates the beam onto the substrate mounted on the stage moving in a predetermined direction using the corrected shot data to lithograph a pattern. The lithography unit sequentially lithographs patterns for each of a plurality of stripe regions obtained by dividing a lithography region on the substrate by a predetermined width. The shot data corrector corrects the shot data corresponding to the beam irradiated onto at least the leading portion of each stripe region.

[0008] A shot data correction method according to one aspect of the present invention is a method for correcting shot data for drawing a pattern by irradiating a charged particle beam onto a substrate placed on a moving stage, and includes the steps of: generating the shot data from drawing data; and correcting the shot data corresponding to the beam irradiated when the stage velocity changes, using a relationship between the stage velocity that has been determined in advance and a positional deviation amount that occurs due to a change in the stage velocity.

[0009] A charged particle beam writing method according to one aspect of the present invention uses the shot data corrected by the above-mentioned shot data correction method to irradiate the charged particle beam onto the substrate placed on the stage moving in a predetermined direction, thereby sequentially writing patterns. [Effects of the Invention]

[0010] According to the present invention, it is possible to reduce the influence of vibrations caused by stage movement on the drawing accuracy. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of an electron beam writing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram illustrating an example of a drawing operation. [Figure 3] FIG. 3A is a graph showing an example of a change in stage speed, and FIG. 3B is a graph showing an example of a change in beam irradiation position deviation amount. [Figure 4] 10 is a flowchart illustrating a method for drawing an evaluation pattern. [Figure 5] 10 is a flowchart illustrating a method for writing a reference pattern. [Figure 6] 10 is a flowchart illustrating an electron beam writing method according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[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 as an example of a charged particle beam will be described. However, the charged particle beam is not limited to an electron beam, and a beam using other charged particles, such as an ion beam, may also be used.

[0013] FIG. 1 is a schematic diagram of a drawing apparatus according to this embodiment. The drawing apparatus includes a control unit 1 and a drawing unit 2. The drawing apparatus is an example of a multi-charged particle beam drawing apparatus. The drawing unit 2 includes an electron optical column 20 and a drawing chamber 30. Arranged within the electron optical column 20 are an electron source 21, an illumination lens 22, a shaping aperture array substrate 23, a blanking aperture array substrate 24, a reduction lens 25, a limiting aperture member 26, an objective lens 27, and a deflector 28. Both the reduction lens 25 and the objective lens 27 are electromagnetic lenses, and the reduction lens 25 and the objective lens 27 form a reduction optical system.

[0014] An XY stage 32 is arranged in the patterning chamber 30. A substrate 40 to be patterned is placed on the XY stage 32. The substrate 40 is an exposure mask used when manufacturing a semiconductor device, a semiconductor substrate (silicon wafer) on which a semiconductor device is manufactured, a mask blank coated with resist and on which nothing is yet to be patterned, or the like.

[0015] A mirror 34 is placed on the XY stage 32 for measuring the position using a laser.

[0016] The control unit 1 includes storage devices 17 and 18 such as magnetic disk devices, a control computer 10, a drawing control circuit 14, a laser length measurement device 15, a stage control unit 16, and the like.

[0017] The control computer 10 has a shot data generation unit 11, a positional deviation amount calculation unit 12, and a shot data correction unit 13. The shot data generation unit 11, the positional deviation amount calculation unit 12, and the shot data correction unit 13 may be configured as software such as a program executed by a computer, or may be configured as hardware such as an electric device or an electronic device, or may be configured as a combination of software and hardware, or may be configured as a combination of firmware and hardware.

[0018] The laser length measuring device 15 irradiates the mirror with a laser, receives the reflected light, measures the position of the XY stage 32, and outputs the stage position to the control computer 10.

[0019] The stage control unit 16 outputs a stage control signal to control the speed and acceleration of the XY stage 32 .

[0020] The drawing control circuit 14 controls and drives each device of the drawing unit 2 .

[0021] 1 shows only the components necessary for explaining the embodiment, but other components normally required for a drawing device may also be included.

[0022] A shaping aperture array substrate 23 installed in the electron optical column 20 has m rows and n columns (m, n≧2) of apertures formed in a matrix at a predetermined arrangement pitch. Each aperture is formed in the same rectangular or circular shape with the same dimensions.

[0023] Electron beam B emitted from electron source 21 illuminates the entire shaping aperture array substrate 23 almost perpendicularly via illumination lens 22. Electron beam B passes through multiple openings in shaping aperture array substrate 23, forming a multi-beam MB consisting of individual beams arranged in m rows and n columns.

[0024] The blanking aperture array substrate 24 has through holes formed in alignment with the positions of the openings of the shaping aperture array substrate 23. A pair of two electrodes (blankers: blanking deflectors) is disposed in each through hole. An amplifier that applies a voltage is disposed on one of the two electrodes for each beam, and the other is grounded. The individual beams that pass through each through hole are deflected independently by the voltages applied to the pair of electrodes. Blanking of each beam is controlled by this deflection of the individual beams.

[0025] The multi-beams MB that have passed through the blanking aperture array substrate 24 are reduced in size by the reduction lens 25 and proceed toward the central opening formed in the limiting aperture member 26. The individual beams deflected by the blanker of the blanking aperture array substrate 24 are shifted away from the central opening of the limiting aperture member 26 and are blocked by the limiting aperture member 26. On the other hand, the individual beams that have not been deflected by the blanker pass through the central opening of the limiting aperture member 26.

[0026] In this way, the limiting aperture member 26 blocks each beam deflected by the blanker to be in the beam-off state. Then, the beam for one shot is formed by the beams that pass through the limiting aperture member 26 from when the beams are turned on until when they are turned off.

[0027] The multi-beams MB that have passed through the limiting aperture member 26 are focused by the objective lens 27 to form a pattern image with the desired reduction ratio, and are then deflected collectively by the deflector 28 to be irradiated onto the substrate 40. For example, when the XY stage 32 is moving continuously, the deflector 28 controls the irradiation position of the beam so as to follow the movement of the XY stage 32.

[0028] The multiple beams MB irradiated at one time are ideally arranged at a pitch obtained by multiplying the above-mentioned desired reduction ratio by the arrangement pitch of the multiple apertures in the shaping aperture array substrate 23. The drawing device performs drawing operations using a raster scan method in which shot beams are continuously irradiated in order, and when drawing a desired pattern, the beams required for the pattern are turned on by blanking control.

[0029] 2, the writing region 50 on the substrate 40 is virtually divided into a plurality of stripe regions 52 each having a predetermined width in the y direction. Each stripe region 52 is a unit writing region. For example, the XY stage 32 is moved and adjusted so that the irradiation region that can be irradiated with one multi-beam MB irradiation is positioned at the left end of the first stripe region 52, and writing begins. By moving the XY stage 32 in the -x direction, writing can proceed relatively in the x direction (FWD writing).

[0030] After writing the first stripe region 52 is completed, the stage position is moved in the -y direction, and writing is started so that the irradiation region is positioned at the right end of the second stripe region 52. Then, by moving the XY stage 32, for example, in the x direction, writing is performed in the -x direction (BWD writing).

[0031] The writing time can be reduced by alternately changing the direction of writing, such as writing in the x direction in the third stripe region 52 and writing in the -x direction in the fourth stripe region 52. However, writing is not limited to alternately changing the direction of writing, and writing in each stripe region 52 may proceed in the same direction.

[0032] This drawing apparatus accelerates the XY stage 32 to a predetermined speed, and then starts drawing a pattern while maintaining the stage speed constant. For example, as shown in Figure 3A, acceleration of the XY stage 32 begins at time t0, and when the predetermined speed V is reached at time t1, the acceleration is stopped, and a pattern is drawn in the stripe region 52 while maintaining the stage speed constant.

[0033] It is known that in a writing apparatus, mechanical vibrations caused by movement of the XY stage 32 deteriorate writing accuracy, and the present inventors have conducted extensive research to solve this problem and have found that, as shown in Fig. 3B, the deviation of the beam irradiation position is large immediately after starting writing of the stripe region 52 (at the beginning of the stripe region 52) and the deviation gradually decreases. The present inventors have found that the above problem can be solved by measuring in advance the amount of deviation of the beam irradiation position caused by stage movement, for example, the amount of deviation caused by mechanical vibration, and correcting the beam irradiation position based on the deviation measured in advance during pattern writing.

[0034] The amount of deviation of the beam irradiation position caused by the movement of the stage can be found by drawing an evaluation pattern and a reference pattern and deriving the difference between the drawing position of the evaluation pattern and the drawing position of the reference pattern.

[0035] 4 is a flowchart illustrating a method for drawing an evaluation pattern. Acceleration of the XY stage 32 begins (step S11), and is stopped when the stage speed reaches a target speed. The stage speed is kept constant, and an evaluation pattern is drawn on an evaluation substrate coated with resist (steps S12 and S13). The shape of the evaluation pattern is not particularly limited, and may be a line-and-space pattern or a dot pattern. After the evaluation pattern is drawn, the XY stage 32 is decelerated and stopped (step S14).

[0036] 5 is a flowchart illustrating a method for drawing a reference pattern. Acceleration of the XY stage 32 begins (step S21), and when the stage speed reaches a target speed, the stage speed is maintained for a certain period of time (step S22). After the certain period of time has elapsed, a reference pattern is drawn on the evaluation substrate while maintaining the stage speed (step S23). The shape of the reference pattern is identical to the evaluation pattern. After the reference pattern has been drawn, the XY stage 32 is decelerated and stopped (step S24).

[0037] The reference pattern is preferably written near the evaluation pattern. Therefore, when writing the reference pattern, the acceleration of the XY stage 32 starts from a position where the evaluation substrate is farther from the multi-beam irradiable area than when writing the evaluation pattern, and the multi-beams begin to irradiate the evaluation substrate when a certain time has elapsed since the stage speed reached the target speed.

[0038] The evaluation pattern starts to be written when the stage speed reaches the target speed, and therefore includes the amount of deviation in the beam irradiation position caused by mechanical vibrations generated by stage movement. On the other hand, the reference pattern starts to be written a certain time after the stage speed reaches the target speed, and therefore the amount of deviation in the beam irradiation position caused by mechanical vibrations generated by stage movement is extremely small.

[0039] After the evaluation pattern and reference pattern are written, processing such as development is performed, and the positions of the formed resist patterns (evaluation pattern and reference pattern) are measured using a position measurement device. By subtracting the difference between the writing position of the reference pattern and the design position from the difference between the writing position of the evaluation pattern and the design position, position error components due to factors other than vibration can be removed, and positional deviation amount data of the irradiation position of each beam caused by vibration can be obtained. This positional deviation amount data is map data that defines the positional deviation amount in a map format.

[0040] The misalignment amount is large immediately after the start of writing the stripe region 52 (at the beginning of the stripe region 52) and gradually decreases (see FIG. 3B). Therefore, the misalignment amount data may be map data of a size from the beginning of the stripe region, for example, about 1 / 4 of the length of the stripe region. The misalignment amount data may be map data for one stripe region.

[0041] The target speed is changed, and the evaluation pattern and the reference pattern are written for a plurality of target speeds to obtain positional deviation data. Positional deviation data for each stage travel direction (FWD writing / BWD writing) is also obtained. The positional deviation data is obtained in advance and stored in the storage device 18 (see FIG. 1).

[0042] Next, the pattern writing method according to this embodiment will be described with reference to the flowchart shown in FIG.

[0043] The control computer 10 reads out the positional deviation amount data from the storage device 18 (step S31). Since the stage speed during pattern writing is determined in advance, the control computer 10 reads out the positional deviation amount data corresponding to the stage speed.

[0044] The shot data generating unit 11 reads out the drawing data from the storage device 17 (step S32). The drawing data defines, for example, the arrangement coordinates of the figure pattern, the figure type, the figure size, and the like.

[0045] The shot data generator 11 performs multiple stages of data conversion on the drawing data to generate shot data (step S33). The shot data defines whether or not to irradiate each irradiation area, which is obtained by dividing the drawing area 50 on the substrate 40 into a plurality of irradiation areas (pixels) in a grid pattern, for example, by the beam size, and the amount of irradiation (irradiation time) for each irradiation area.

[0046] The misalignment amount calculation unit 12 refers to the misalignment amount data read out in step S31 and calculates the misalignment amount of each beam in the stripe region (step S34). The misalignment amount data to be referred to is switched depending on the drawing progress direction of the stripe region.

[0047] The shot data corrector 13 corrects the shot data so that the beam misalignment amount calculated in step S34 is corrected (step S35). For example, the misalignment can be corrected by allocating the irradiation amount to adjacent pixels on the opposite side of the misalignment direction in accordance with the area ratio of the misalignment.

[0048] Using the corrected shot data, the substrate 40 is irradiated with the multi-beam MB to write a pattern (step S36). Using the shot data, the writing control circuit 14 outputs a blanking control signal to a control circuit for individual blanking formed on the blanking aperture array substrate 24. The signal is converted into an analog signal in the control circuit, and deflection voltages are applied to corresponding electrodes of the multiple blankers. In this way, the writing control circuit 14 controls the multiple blankers using the shot data.

[0049] When the stage speed reaches the target speed, acceleration is stopped, the XY stage 32 is kept constant, and pattern writing begins from the beginning of the stripe region 52. In this embodiment, the amount of positional deviation of the beam irradiation position caused by mechanical vibrations generated by stage movement is corrected, so the impact of vibrations generated by stage movement on writing accuracy can be effectively reduced.

[0050] In the above embodiment, a drawing apparatus using multiple beams has been described, but the present invention can also be applied to a single-beam drawing apparatus. In the case of a single beam, the shot position defined in the shot data is corrected based on the beam position deviation amount.

[0051] In the above embodiment, an example was described in which the writing process within the stripe region was carried out while the stage speed was kept constant, but the stage speed may be changed midway through the stripe region. In this case, positional deviation amount data corresponding to the changed stage speed is read from the storage device 18, and the shot data after the stage speed change is corrected.

[0052] If there are many different stage velocities and it is difficult to store positional deviation data for all stage velocities in storage device 18, the positional deviation may be stored as a function of time and converted into a function of position according to the stage velocity for calculation. For example, the positional deviation may be decomposed into multiple frequency components, and the parameters of each frequency component may be made dependent on the stage velocity.

[0053] In the above embodiment, an example has been described in which the amount of positional deviation is corrected by correcting the shot position in the shot data. However, it is also possible to calculate the average value of the amount of positional deviation of each beam of multiple beams and correct the amount of deflection of the deflector 28 based on the average value.

[0054] 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]

[0055] 1. Control section 2. Drawing section 10 Control computer 11 Shot data generation unit 12 Position deviation calculation unit 13 Shot data correction section 32 XY stage 40 boards 50 drawing area 52 Stripe Area

Claims

1. an emission section that emits a charged particle beam; a movable stage on which a substrate to be drawn is placed; a shot data correction unit that corrects shot data generated from drawing data using a relationship between the stage velocity and a positional deviation amount caused by a change in the stage velocity, the relationship being determined in advance; a drawing unit that irradiates the substrate with the charged particle beam using the corrected shot data, and sequentially draws patterns in each of a plurality of stripe regions obtained by dividing a drawing region of the substrate by a predetermined width; A charged particle beam writing apparatus comprising:

2. a storage device for storing a plurality of positional deviation amount data corresponding to a plurality of stage speeds; 2. The charged particle beam drawing apparatus according to claim 1, wherein the shot data correction unit reads out, from the storage device, positional deviation data corresponding to a stage speed when the beam is irradiated onto the substrate, and corrects the shot data.

3. further comprising a storage device for storing a function with a plurality of stage velocities as variables; 2. The charged particle beam drawing apparatus according to claim 1, wherein the shot data correction unit uses the function read from the storage device to obtain positional deviation data corresponding to a stage speed when irradiating the substrate with the beam, and corrects the shot data.

4. 1. A method for correcting shot data for drawing a pattern by irradiating a substrate placed on a moving stage with a charged particle beam, comprising: generating the shot data from drawing data; correcting the shot data corresponding to the beam irradiated when the stage velocity is changed, using a relationship between the stage velocity and a positional deviation amount caused by a change in the stage velocity that has been obtained in advance; A shot data correction method comprising:

5. 5. A charged particle beam lithography method, comprising: irradiating the substrate placed on the stage moving in a predetermined direction with the charged particle beam, using the shot data corrected by the shot data correction method according to claim 4, thereby sequentially drawing patterns.

6. 6. The charged particle beam writing method according to claim 5, wherein the charged particle beam is a multi-beam including a plurality of individual beams.

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