Beam position measurement method and charged particle beam drawing method

Abstract

The invention provides a beam position measurement method and a charged particle beam drawing method, and provides a beam position measurement method capable of accurately measuring the beam position and suppressing a reduction in the processing amount, and a charged particle beam drawing method for drawing with high precision using a beam corrected based on the accurate beam position measurement result. A beam position measurement method according to an embodiment of the present invention scans a mark provided on a stage on which a substrate is placed with a charged particle beam, measures a beam irradiation position under each condition, scans the mark under a reference condition, calculates a drift amount on the basis of an obtained measurement result of the beam irradiation position under the reference condition, and measures the beam irradiation position under the reference condition. And correcting the beam irradiation position under each of the measured conditions using the drift amount.

Description

[0001] This application is based on Japanese Patent Application No. 2023-129380 (filing date: August 8, 2023) and claims the priority of the basic application. The present application incorporates the entire contents of the basic application by reference. Technical Field

[0002] The present invention relates to a beam position measuring method and a charged particle beam mapping method. Background Art

[0003] As LSI becomes more highly integrated, the circuit line width of semiconductor devices becomes increasingly finer. As a method for forming an exposure mask (a mask used in a stepper or scanner is also called an intermediate mask) for forming circuit patterns on these semiconductor devices, an electron beam drawing technique with excellent resolution is used.

[0004] The electron beam imaging device controls the voltage applied to the deflector to adjust the deflection amount of the electron beam and irradiates the electron beam to the desired position on the substrate. In order to ensure the irradiation position of the electron beam on the substrate with high precision, it is important to accurately grasp the deflection sensitivity. Therefore, while changing the deflection voltage, the beam irradiation position under multiple different deflection voltages is measured and the deflection sensitivity is calculated. The beam position can be measured by scanning the mark arranged on the workbench with the beam and detecting the reflected electrons.

[0005] As an electron beam drawing device, a drawing device using multiple beams is being developed. By using multiple beams, more beams can be irradiated compared to the case of drawing with a single electron beam, so the processing volume can be greatly improved. In a multi-beam drawing device, for example, an electron beam emitted from an electron source is passed through a shaped aperture array substrate provided with a plurality of openings to form multiple beams, and blanking control of each beam is performed, and each beam that is not blocked by the limiting aperture component is irradiated onto the substrate.

[0006] In a multi-beam drawing device, multiple beams are irradiated at one time, and beams formed by the same opening or different openings of the aperture array substrate are connected to each other to draw a pattern of a desired graphic shape. Therefore, the shape of the overall image of the multi-beams irradiated on the substrate (beam array shape) is expressed as the connection accuracy of the drawn pattern.

[0007] In order to ensure high multi-beam drawing accuracy, it is important to accurately grasp the beam array shape. Therefore, the beam array shape is measured by switching the beam-on area while turning on only a part of the area and measuring the beam position by using the beam-on scanning mark.

[0008] In electron beam drawing devices, organic matter or the like is attached to aperture components such as limiting aperture components that cut off the beam, and charges are accumulated due to the beam cut off by them, which may cause beam position fluctuation (drift). If such beam position fluctuation occurs, it is impossible to accurately measure the deflection sensitivity and beam array shape, which may deteriorate the drawing accuracy. Summary of the invention

[0009] The present invention provides a beam position measuring method capable of accurately measuring a beam position and suppressing a reduction in throughput, and a charged particle beam drawing method for accurately drawing using a beam corrected based on an accurate beam position measurement result.

[0010] A beam position measurement method according to one embodiment of the present invention is to use a charged particle beam to scan a mark set on a workbench on which a substrate is mounted, measure the beam irradiation position under each condition, scan the mark under a reference condition, calculate a drift amount based on the measurement result of the beam irradiation position under the reference condition, and use the drift amount to correct the beam irradiation position under each condition measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of a multi-charged particle beam imaging device according to an embodiment of the present invention.

[0012] Figure 2 is a schematic diagram of a shaped aperture array substrate.

[0013] Figure 3 is a top view of the reflective marker.

[0014] Figure 4 is a flow chart illustrating a method for measuring a beam array shape.

[0015] Figure 5 It is a diagram for explaining a method of measuring a beam array shape.

[0016] Figure 6 It is a diagram showing an example of a calculated beam array shape.

[0017] Figure 7 It is a diagram showing an example of the timing of beam position measurement under the reference condition.

[0018] Figure 8 is a flowchart illustrating a method for calculating a beam array shape.

[0019] Explanation of symbols:

[0020] 1: drawing unit; 2: lens barrel; 4: electron source; 6: illumination lens; 8: forming aperture array substrate; 10: blanking aperture array substrate; 12: reduction lens; 14: aperture limiting component; 15: objective lens; 16: coil; 17: main deflector; 20: drawing chamber; 22: XY worktable; 100: control unit; 110: control computer. DETAILED DESCRIPTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiment, a configuration using an electron beam is described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam, and may be an ion beam or the like.

[0022] Figure 1 2 is a conceptual diagram showing the structure of the drawing device of this embodiment. Figure 1 In the drawing device, there is a drawing unit 1 and a control unit 100. The drawing device is an example of a multi-charged particle beam drawing device. The drawing unit 1 is provided with a lens barrel 2 and a drawing chamber 20. An electron source 4, an illumination lens 6, a forming aperture array substrate 8, a blanking aperture array substrate 10, a reduction lens 12, an aperture limiting component 14, an objective lens 15, a coil 16, a main deflector 17 (deflector) and an auxiliary deflector (not shown) are arranged in the lens barrel 2.

[0023] An XY stage 22 and a detector 26 are arranged in the drawing chamber 20. A substrate 70 to be drawn is arranged on the XY stage 22. The substrate 70 includes an exposure mask for manufacturing a semiconductor device or a semiconductor substrate (silicon wafer) for manufacturing a semiconductor device. In addition, the substrate 70 includes a mask blank coated with a resist and not subjected to any drawing.

[0024] A reflective mirror 24 for measuring the position of the XY stage 22 is disposed on the XY stage 22. In addition, a metal reflective mark M for beam calibration is provided on the XY stage 22. The reflective mark M is formed in a cross shape, for example, so that the position can be easily detected by scanning with an electron beam (see Figure 3 ) The detector 26 detects the reflected electrons from the reflective mark M when scanning the cross of the reflective mark M with the electron beam.

[0025] The control unit 100 includes a control computer 110, a deflection control circuit 130, a digital-to-analog converter (DAC) amplifier 131, a coil control circuit 132, a lens control circuit 133, a detection amplifier 134, a table position detector 135, and a storage device 140 such as a magnetic disk device.

[0026] The deflection control circuit 130, the coil control circuit 132, the lens control circuit 133, the detection amplifier 134, the stage position detector 135, and the storage device 140 are connected to the control computer 110 via a bus. The storage device 140 stores drawing data input from the outside.

[0027] The deflection control circuit 130 is connected to a DAC amplifier 131. The DAC amplifier 131 is connected to the main deflector 17. The coil 16 is connected to the coil control circuit 132. The objective lens 15 is connected to the lens control circuit 133.

[0028] The control computer 110 has the functions of a drawing data processing unit 111, a drawing control unit 112, and a beam array shape measuring unit 113. The functions of each unit of the control computer 110 may be realized by hardware or by software. In the case of being constituted by software, a program that realizes at least a part of the functions of the control computer 110 may be stored in a recording medium, read into a computer including a circuit, and executed. The recording medium is not limited to a removable medium such as a magnetic disk or an optical disk, but may also be a fixed recording medium such as a hard disk device or a memory.

[0029] Figure 2 8 is a conceptual diagram showing the structure of the formed aperture array substrate 8. Figure 2 As shown, a plurality of openings 80 are formed in a matrix at a predetermined arrangement pitch in the longitudinal (y direction) and transverse (x direction) directions on the aperture array substrate 8. Each opening 80 is formed in a rectangular shape of the same size. Alternatively, it can also be a circle of the same diameter.

[0030] The electron beam 30 emitted from the electron source 4 illuminates the entire aperture array substrate 8 substantially vertically through the illumination lens 6. The electron beam 30 illuminates the region including the plurality of openings 80 of the aperture array substrate 8. By passing a portion of the electron beam 30 through the plurality of openings 80, the aperture array substrate 8 is formed. Figure 1 Multiple beams 30a-30e as shown.

[0031] In the blanking aperture array substrate 10, Figure 2 Passage holes (openings) for passing each beam of the multi-beam are formed at positions corresponding to each opening 80 of the shaped aperture array substrate 8. Electrodes (blankers: blanking deflectors) for blanking deflection of the deflected beams are arranged near each passage hole.

[0032] The electron beams 30a to 30e passing through each aperture are deflected independently by the voltage applied from the blanker. Blanking control is performed by this deflection. In this way, the plurality of blankers perform blanking deflection of the corresponding beams among the multiple beams passing through the plurality of openings 80 of the aperture array substrate 8.

[0033] After passing through the blanking aperture array substrate 10, the multiple beams 30a to 30e are reduced in beam size and arrangement pitch by the reduction lens 12, and move toward the opening formed in the center of the limiting aperture component 14. The orbital displacement of the electron beam deflected by the blanker of the blanking aperture array substrate 10 is offset from the opening in the center of the limiting aperture component 14, and is blocked by the limiting aperture component 14. On the other hand, the electron beam not deflected by the blanker of the blanking aperture array substrate 10 passes through the opening in the center of the limiting aperture component 14.

[0034] The limiting aperture member 14 blocks each electron beam deflected to a beam-off state by the blanker of the blanking aperture array substrate 10 .

[0035] The multiple beams 30a to 30e passing through the limiting aperture member 14 are aligned and adjusted by the coil 16 and focused by the objective lens 15 to form a pattern image of a desired reduction ratio on the substrate 70. The main deflector 17 deflects the electron beams (the entire multiple beams) passing through the limiting aperture member 14 in the same direction and irradiates the drawing position (irradiation position) on the substrate 70.

[0036] When the XY stage 22 moves continuously, tracking control is performed by the main deflector 17 so that the beam drawing position (irradiation position) follows the movement of the XY stage 22. The position of the XY stage 22 is measured by irradiating a laser from the stage position detector 135 toward the reflective mirror 2 on the XY stage 22 and using the reflected light.

[0037] The multiple beams irradiated at one time are ideally arranged at a pitch obtained by multiplying the arrangement pitch of the multiple openings 80 of the aperture array substrate 8 by the desired reduction ratio. When the drawing device draws a desired pattern by raster scanning by continuously and sequentially irradiating the emission beams, the necessary beams are controlled to be beam-on by blanking control according to the pattern.

[0038] The drawing data processing unit 111 of the control computer 110 reads the drawing data from the storage device 140, performs multi-stage data conversion, and generates emission data. The emission data defines whether or not to irradiate each of the plurality of irradiation areas divided into a grid-like shape of the drawing surface of the substrate 70 by the beam size, and the irradiation time.

[0039] The drawing control unit 112 outputs a control signal to the deflection control circuit 130 based on the transmission data and the stage position information. The deflection control circuit 130 controls the applied voltage of each blanker of the blanking aperture array substrate 10 based on the control signal. In addition, the deflection control circuit 130 calculates the deflection amount data (tracking deflection data) for beam deflection to follow the movement of the XY stage 22. The tracking deflection data as a digital signal is output to the DAC amplifier 131, and the DAC amplifier 131 converts the digital signal into an analog signal and then amplifies it, and applies it to the main deflector 17 as a tracking deflection voltage.

[0040] In a multi-beam type drawing device, a plurality of beams arranged at a pitch obtained by multiplying the arrangement pitch of a plurality of openings 80 of a forming aperture array substrate 8 by a predetermined reduction ratio are irradiated at once to a substrate 70 to be drawn, and a pattern of a desired graphic shape is drawn by connecting the beams to each other to fill the beam pitch. Therefore, before and during the drawing process, it is necessary to detect the beam position, measure the beam array shape and adjust the size, or modulate the irradiation amount of each beam.

[0041] The drawing device of this embodiment uses a position measurement mark to measure the beam array shape. As the position measurement mark, a transmission mark set on the workbench to transmit multiple beams one by one for measurement, or a reflection mark set on the workbench or on the mask substrate to measure reflected electrons can be used. In this embodiment, as the position measurement mark, a configuration using a reflection mark M set on the XY workbench 22 is described. The reflection mark M is, for example, Figure 3 The beam of only a part of the area is turned on, and the main deflector 17 deflects the turned-on beam forward, backward, left, and right (x direction and y direction) to scan the cross of the reflection mark M. The reflected electrons are detected by the detector 26, and after being amplified and converted into digital data by the detection amplifier 134, the measurement data is output to the control computer 110.

[0042] The beam array shape measuring unit 113 calculates the position of the beam (the center of the beam-on region) based on the distribution diagram of the reflected electrons measured in time series (the change in the intensity of the reflected electrons) and the position of the worktable at that time. The beam array shape measuring unit 113 measures the beam array shape based on the beam position of each beam-on region. Figure 4 The flowchart shown explains the method of measuring the beam array shape.

[0043] The blanking aperture array substrate 10 is divided into a plurality of measurement areas, and the beam corresponding to each measurement area is used to scan the reflective mark M. In other words, the shaped aperture array substrate 8 is divided into a plurality of measurement areas, and the beam passing through the opening 80 of each measurement area is turned on to scan the reflective mark M.

[0044] First, the number of region divisions n (n is an integer greater than or equal to 2) of the blanking aperture array substrate 10 is determined (step S21). The blanking aperture array substrate 10 (shaped aperture array substrate 8) is divided into a plurality of measurement regions in order to measure strain for each region of the shaped aperture array substrate 8. In addition, the maximum deflection amount of the main deflector 17 used in beam scanning is not large enough to cover the entire region of the blanking aperture array substrate 10, and therefore, the deflection amount used in the measurement is preferably small enough not to generate strain on the beam array shape.

[0045] An area that has not been measured is selected to determine the measurement area (step S22). The XY stage 22 is moved to arrange the reflective mark M at a position directly below the beam in the measurement area (step S23).

[0046] For example, the applied voltage of the blanker in the measurement area is set to 0V, and the applied voltage of the blanker in other areas (non-measurement areas) is set to 5V. The multiple beams opened by the blanker beam in the measurement area are deflected in the XY direction by the main deflector 17, and the reflection mark M is scanned. The detector 26 detects the reflected electrons (step S24).

[0047] The control computer 110 generates a distribution diagram (changes in the intensity of reflected electrons) in which the reflected electrons detected by the detector 26 are arranged in time series (step S25 ).

[0048] The beam array shape measuring unit 113 calculates the beam position (center coordinates of the beam-on region) corresponding to the measurement region using the stage position detected by the stage position detector 135 (step S26).

[0049] Such stage movement, scanning of the reflective mark M, and calculation of the open beam position are performed on all the n measurement areas of the blanking aperture array substrate 10 (steps S22 to S27). Figure 5 The example shown is that the XY stage 22 is moved along with the switching of the measurement area, and the reflective mark M is arranged at a position directly below the beam of the measurement area.

[0050] After the measurement of all measurement areas is completed (step S27_Yes), the beam array shape measuring unit 113 calculates the beam array shape based on the beam position of each measurement area (step S28). For example, the beam array shape measuring unit 113 fits the center coordinates of the open beam area corresponding to the n measurement areas by a cubic polynomial to obtain a polynomial representing the beam array shape. If the polynomial is plotted on a graph, for example, Figure 6 Beam array shape as shown. Figure 6This is a diagram showing the beam array shape in a visually easy-to-understand manner by setting an ideal grid and plotting the deviation from the ideal grid.

[0051] In the drawing device, organic matter or the like is attached to the aperture member such as the limiting aperture member 14 that cuts off the beam, and charges are accumulated due to the beam cut off by them, causing beam position variation (drift). Therefore, it is preferable to measure the beam position variation, correct the beam position measurement result, and calculate the beam array shape.

[0052] For example, the beam position is measured regularly under reference conditions to obtain the position change (drift). The beam position used for beam array shape calculation is corrected based on the obtained position change. The beam position measurement under reference conditions is, for example, the position measurement of the central beam. Only one or more beams located in the center of the blanking aperture array substrate 10 (forming aperture array substrate 8) are turned on, and the reflection mark M is scanned by the turned-on beam, and the beam position is measured based on the detection result of the reflected electrons. Then, the difference between the measurement result and the design value (ideal value) is obtained as the drift.

[0053] Since the drift changes greatly immediately after the measurement (drawing) starts, the interval of beam position measurement (drift measurement) under the reference condition is shortened. After the drift converges over time, the interval of drift measurement is lengthened. This can suppress the reduction of the processing amount.

[0054] exist Figure 7 2 shows an example of the timing of beam position measurement (drift measurement) under the reference condition and beam position measurement under conditions 1 to n. Conditions 1 to n have different open beam regions.

[0055] After the measurement (drawing) is started, the drift measurement is performed at the first drift measurement interval t1. That is, the beam position is measured under the reference condition every time the time t1 elapses, and the drift amount is obtained.

[0056] The beam position measurement results under conditions 1 to n are corrected based on the drift amount obtained immediately before. For example, Figure 7 The beam position measurement result under condition 3 is corrected using the drift amount measured at time t1. Similarly, the beam position measurement result under condition 5 is corrected using the drift amount measured at time 2×t1.

[0057] The drift amount used in the correction of the beam position measurement results under conditions 1 to n may be calculated by interpolating the drift amounts obtained from the previous and next drift measurements. For example, the drift amount in the beam position measurement under condition 2 may be estimated by interpolating the drift amount measured at time t0 and the drift amount measured at time t1, and the beam position measurement result under condition 2 may be corrected using the estimated drift amount.

[0058] The drift amount during the beam position measurement under conditions 1 to n may be estimated by extrapolation instead of interpolation.

[0059] After the measurement interval change time T0 (T0>t1) has passed, the measurement interval of the drift measurement is increased, and the drift measurement is performed at the second drift measurement interval t2 (t2>t1). After a further period of time has passed, the drift measurement interval may be changed from t2 to t3 (t3>t2). Furthermore, the measurement interval change time may be gradually changed (updated) from T0 to T1, T2, ... (T0>t1). <T1<T2<……)。

[0060] The beam array shape can be obtained by correcting the beam position measurement results under conditions 1 to n by the amount of drift and performing polynomial fitting. Instead of correcting the beam position measurement results by the amount of drift, when performing beam position measurement under conditions 1 to n, the deflection position may be corrected by the amount of drift to scan the reflective mark M.

[0061] Figure 8 This is a flowchart for explaining a method of calculating a beam array shape while updating the settings of a drift measurement interval and a measurement interval change time.

[0062] The beam position is measured under the reference condition, and the drift amount is calculated (steps S101 and S102).

[0063] When the timing of updating the setting of the measurement interval change time is updated (step S103_Yes), the measurement interval change time is updated (step S104). For example, the measurement interval change time is updated from T0 to T1. The timing of updating the setting of the measurement interval change time is arbitrary, and may be after a specified time or after a specified number of drift measurements.

[0064] When the measurement interval change time has elapsed (step S105_Yes), the drift measurement interval is changed (step S106). For example, the drift measurement interval is changed from t1 to t2.

[0065] When the drift measurement interval has elapsed since the last drift measurement and the drift measurement timing is reached (step S107_Yes), the drift measurement is performed (steps S101 and S102). Figure 7 When time t1 has elapsed from the first drift measurement (beam position measurement under the reference condition) shown, the second drift measurement is performed.

[0066] The conditions are switched (the beam-on region is changed), and the beam position measurement is performed (step S108). The beam position measurement result is corrected using the drift amount obtained by the previous drift measurement or the like.

[0067] Steps S101 to S108 are repeated until the beam position measurement is performed under all conditions (conditions 1 to n).

[0068] When the beam position measurement under all conditions is completed (step S109_Yes), the beam array shape is calculated based on the beam position measurement result corrected using the drift amount (step S110).

[0069] Thus, according to the present embodiment, it is possible to suppress the reduction in processing volume, accurately measure the beam position, and obtain the beam array shape with high precision. Based on the obtained beam array shape, the beam irradiation conditions such as the irradiation amount of each beam, the position and size of the pattern to be drawn, and the electron optical conditions of the beam are corrected to avoid the influence of the strain of the beam array shape, thereby making it possible to draw the desired pattern with high precision.

[0070] In the above embodiment, an example is described in which the measurement interval of the drift measurement is changed when the measurement interval change time elapses. However, the measurement interval may be changed when the drift measurement is performed a predetermined number of times.

[0071] Alternatively, a table in which measurement intervals and measurement frequencies are preset may be created, and measurement may be performed based on the table.

[0072] In the above-mentioned embodiment, the measured drift amount is used for beam position correction when measuring the beam array shape, but it can also be used for beam position correction when measuring the deflection sensitivity of the main deflector 17 and the auxiliary deflector. While changing the deflection voltage, the beam position under a plurality of deflection voltages is measured, and the beam position measurement result is corrected by the amount of drift amount to obtain the deflection sensitivity (the rate of change of the deflection distance with respect to the deflection voltage). In the beam position measurement (drift measurement) under the reference condition, for example, the deflection amount (deflection voltage) is set to zero. Then, the deflection range is confirmed based on the obtained deflection sensitivity.

[0073] In the above-mentioned embodiment, an example in which a multi-beam drawing device is used as the electron beam drawing device is described, but it can also be applied to deflection sensitivity correction of a single-beam drawing device.

[0074] In addition, the present invention is not limited to the above-mentioned embodiments themselves, and the constituent elements may be deformed and concretized in the implementation stage without departing from the scope of the main purpose. In addition, various inventions can be formed by appropriate combinations of multiple constituent elements disclosed in the above-mentioned embodiments. For example, several constituent elements may be deleted from all constituent elements shown in the embodiments. Furthermore, constituent elements across different embodiments may also be appropriately combined.

Claims

1. A method for determining a beam position, wherein: The charged particle beam is used to scan the mark set on the worktable on which the substrate is placed, and the beam irradiation position is measured under each condition. Scanning the mark under the reference condition, calculating the drift amount based on the measurement result of the beam irradiation position under the reference condition, The beam irradiation position under each of the measured conditions is corrected using the drift amount.

2. The beam position measuring method according to claim 1, wherein: The above-mentioned condition is the beam position or the deflection voltage of the above-mentioned charged particle beam.

3. The beam position measuring method according to claim 1, wherein: The drift amount is measured at a preset measurement interval or a preset measurement frequency, or after a predetermined measurement time or a predetermined number of measurements have elapsed, the drift amount is measured by changing the measurement interval or the measurement frequency.

4. The beam position measuring method according to claim 2, wherein: The condition is the beam position, the multi-charged particle beam is divided into a plurality of regions, the mark is scanned for each region, and the beam array shape of the multi-charged particle beam is calculated based on the corrected beam irradiation position.

5. The beam position measuring method according to claim 4, wherein: The reference condition is one or more open beams located in the center of the multi-charged particle beam.

6. The beam position measuring method according to claim 2, wherein: The condition is a deflection voltage applied to the deflector, and the deflection sensitivity of the charged particle beam is calculated using the corrected beam irradiation positions under a plurality of different deflection voltages.

7. The beam position measuring method according to claim 6, wherein: Under the above-mentioned reference conditions, the deflection voltage applied to the above-mentioned deflector is set to zero.

8. A charged particle beam characterization method, wherein: Based on the beam array shape calculated by the beam position measuring method according to claim 4, the irradiation conditions of the multi-charged particle beam are corrected to draw a pattern on the substrate.

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