Charged particle beam drawing device, drift amount calculation method, and charged particle beam drawing method

Abstract

The present invention corrects beam drift during drawing processing in real time. A charged particle beam drawing device according to the present invention comprises: a charged particle beam source that emits a charged particle beam to be irradiated on a substrate on which drawing is performed; a deflector that deflects the charged particle beam to a desired irradiation position on the substrate; a detector that detects electrons reflected or emitted from the substrate toward the deflector; a correction amount generation unit that calculates a drift amount of the charged particle beam irradiated on the substrate from a current amount obtained from the detected electrons and a time from the detection of the current to correction, and generates a correction amount for an irradiation position deviation on the basis of the drift amount; and a control unit that corrects the irradiation position on the basis of shot data of the charged particle beam, generated from drawing data, and the correction amount.

Description

Charged particle beam lithography device, drift amount calculation method, and charged particle beam lithography method

[0001] The present invention relates to a charged particle beam drawing apparatus, a drift amount calculation method, and a charged particle beam drawing method.

[0002] With the increasing integration density of LSIs, the circuit line width required for semiconductor devices has been getting finer year by 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 a stepper or scanner) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure apparatus. The high-precision original pattern is drawn using an electron beam drawing apparatus, and so-called electron beam lithography technology is used.

[0003] In electron beam lithography systems, a phenomenon called beam drift can occur, in which the irradiation position of the electron beam shifts over time during lithography due to various factors. For example, beam drift occurs when contamination adheres to the irradiation system, such as the deflection electrodes of the lithography system, and the contamination becomes charged by scattered electrons from the substrate being lithographed. Drift correction is performed to cancel this beam drift.

[0004] In conventional drift correction, the measurement mark is scanned with an electron beam at a predetermined timing during the writing process to measure the beam irradiation position, and the difference from the previous measurement is used as the drift correction amount. However, with this method, there is a problem that correction errors become large when the drift tendency changes significantly, resulting in a deterioration of writing accuracy. If the measurement interval of the beam irradiation position is shortened to suppress the correction error, throughput will decrease.

[0005] JP 10-256112, JP 8-274002, JP 2007-019246

[0006] An object of the present invention is to provide a charged particle beam drawing apparatus, a drift amount calculation method, and a charged particle beam drawing method that can correct beam drift during drawing processing in real time.

[0007] A charged particle beam lithography apparatus according to one aspect of the present invention includes: a deflector that adjusts the irradiation position of a charged particle beam that is irradiated onto a substrate to be irradiated with writing; a shot data generation unit that generates shot data including a shot position and beam on / off times for each shot from writing data; a detector that detects secondary electrons from the substrate; a drift correction unit that calculates an amount of drift of the irradiation position of the charged particle beam that is irradiated onto the substrate from an amount of current corresponding to the secondary electrons detected by the detector and generates correction information for correcting a deviation in the irradiation position based on the drift amount; and a control unit that controls the amount of deflection by the deflector based on the shot data and the correction information.

[0008] A drift amount calculation method according to one aspect of the present invention includes the steps of: emitting a charged particle beam to be irradiated onto a substrate to be written; deflecting the charged particle beam to a desired irradiation position on the substrate; generating shot data from writing data, the shot data including a shot position and a beam on / off time for each shot; detecting electrons reflected or emitted from the substrate toward the deflector; and calculating a first drift amount of the irradiation position of the charged particle beam irradiated onto the substrate from the amount of current obtained by the electrons detected by the detector and the time from detection of the current to correction.

[0009] A charged particle beam writing method according to one aspect of the present invention includes a step of calculating a correction amount for irradiation position deviation based on the first drift amount calculated by the drift amount calculation method, and a step of correcting the irradiation position based on the shot data and the correction amount.

[0010] According to the present invention, beam drift during writing processing can be corrected in real time.

[0011] 4A and 4B are diagrams showing an example of the arrangement of electrodes of a detector; and FIG. 4B is a diagram showing an example of the configuration of a voltage measuring device.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this 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 an ion beam or the like may also be used.

[0013] Fig. 1 is a conceptual diagram showing the configuration of a drawing apparatus according to an embodiment. In Fig. 1, the drawing apparatus 100 includes a drawing unit 150 and a control unit 160. The drawing unit 150 includes an electron optical column 102 and a drawing chamber 103. The electron optical column 102 contains an electron gun 201, an illumination lens 202, a blanking deflector 212, a blanking aperture 214, a first shaping aperture 203, a projection lens 204, a shaping deflector 205, a second shaping aperture 206, an objective lens 207, a main deflector 208, a sub-deflector 209, a sub-sub-deflector 210, a detector 230, and an electrostatic correction lens 240.

[0014] An XY stage 105 that is movable in the X and Y directions is placed in the patterning chamber 103. A substrate 101 that is coated with resist and that is to be patterned is placed on the XY stage 105. The substrate 101 includes an exposure mask, a silicon wafer, a mask blank, etc. for manufacturing a semiconductor device.

[0015] A reflective mark 107 for measuring the drift amount of the electron beam is provided on the XY stage 105 at a position separate from the area where the substrate 101 is placed. The reflective mark 107 has, for example, a cross or dot shape, and is formed on the silicon substrate from a heavy metal such as tantalum or tungsten.

[0016] A detector 220 is provided above the XY stage 105 to detect electrons reflected by the reflective mark 107 when the reflective mark 107 is scanned with the electron beam. The electrons detected by the detector 220 are converted into a current value and notified to the control computer 110. The control computer 110 can calculate the irradiation position of the electron beam (beam position) from the change in the current value.

[0017] When an electron beam 200 is emitted from an electron gun 201 (emission section) provided in the electron optical lens barrel 102, the blanking deflector 212 switches whether or not the electron beam is irradiated onto the substrate 101 as it passes through the blanking deflector 212.

[0018] The electron beam 200 is irradiated onto a first shaping aperture 203 having a rectangular opening A1 (see FIG. 2) by an illumination lens 202. By passing through the opening A1 of the first shaping aperture 203, the electron beam 200 is shaped into a rectangle.

[0019] The electron beam 200 of the first aperture image that has passed through the first shaping aperture 203 is projected onto a second shaping aperture 206 having a variable shaping aperture A2 (see FIG. 2) by a projection lens 204. At this time, the deflection of the first aperture image projected onto the second shaping aperture 206 is controlled by a shaping deflector 205, making it possible to change the shape and dimensions of the electron beam that passes through the variable shaping aperture A2 (perform variable shaping).

[0020] The electron beam 200 of the second aperture image that passes through the variable shaping opening A2 of the second shaping aperture 206 is focused by the objective lens 207, deflected by the main deflector 208, the sub-deflector 209, and the sub-sub-deflector 210, and irradiated onto the substrate 101 placed on the continuously moving XY stage 105.

[0021] The control unit 160 includes a control computer 110 , a memory 112 , a control circuit 120 , a voltage measuring device 130 , and a storage device 140 .

[0022] The control computer 110 includes a shot data generation unit 50, a drift correction unit 52 (correction amount generation unit), a parameter calculation unit 53, and a writing control unit 54. Each function of the shot data generation unit 50, the drift correction unit 52, the parameter calculation unit 53, and the writing control unit 54 may be configured by software or hardware.

[0023] 3 is a conceptual diagram for explaining a deflection region. As shown in Fig. 3, the writing region 10 on the substrate 101 is virtually divided into a plurality of stripe regions 20, each of which is shaped like a rectangle, in the y direction, by the deflection width of the main deflector 208. The regions obtained by dividing the stripe region 20 in the x direction by the deflection width of the main deflector 208 are the deflection regions (main deflection regions) of the main deflector 208.

[0024] This main deflection area is virtually divided into a plurality of sub-fields (SF) 30 in a mesh shape, at a size that can be deflected by the sub-deflector 209. Each SF 30 is then virtually divided into a plurality of under-sub-fields (here, abbreviated as "TF" for Tertiary Deflection Field, meaning the third deflection; the same applies hereinafter) 40 in a mesh shape, at a size that can be deflected by the sub-deflector 210. A shot figure is written at each shot position 42 of each TF 40.

[0025] The control circuit 120 applies a deflection voltage for blanking control to the blanking deflector 212. The electron beam 200 is deflected by this deflection voltage, and blanking control for each shot is performed.

[0026] The control circuit 120 applies a deflection voltage for shaping deflection to the shaping deflector 205. This deflection voltage deflects the electron beam 200 to a specific position of the second shaping aperture 206, thereby forming an electron beam of a desired size and shape.

[0027] The control circuit 120 applies a deflection voltage for main deflection control to the main deflector 208. This deflection voltage deflects the electron beam 200, and the beam of each shot is deflected to a reference position A (for example, the center position or the lower left corner position of the corresponding SF) of a predetermined subfield (SF) that is virtually divided into a mesh shape. Furthermore, when drawing is performed while the XY stage 105 is continuously moving, the deflection voltage also includes a deflection voltage for tracking the stage movement.

[0028] The control circuit 120 applies a deflection voltage for sub-deflection control to the sub-deflector 209. The electron beam 200 is deflected by this deflection voltage, and the beam of each shot is deflected to the reference position B of the TF 40 (for example, the center position or the lower left corner position of the corresponding TF) which is the minimum deflection area.

[0029] The control circuit 120 applies a deflection voltage for sub-deflection control to the sub-deflector 210. The electron beam 200 is deflected by this deflection voltage, and the beam of each shot is deflected to each shot position 42 in the TF 40.

[0030] In the writing apparatus 100, a writing process is performed for each stripe region 20 using multiple stages of deflectors. Here, as an example, a three-stage deflector including a main deflector 208, a sub-deflector 209, and a sub-sub-deflector 210 is used. In the configuration shown in Fig. 1, the main deflector 208, the sub-deflector 209, and the sub-sub-deflector 210 are arranged in this order from the upstream side in the traveling direction of the electron beam, but the arrangement order of the three stages of deflectors is not limited to this.

[0031] While the XY stage 105 is continuously moved, for example, in the -x direction, writing proceeds in the x direction for the first stripe region 20. Then, after writing of the first stripe region 20 is completed, writing of the second stripe region 20 proceeds in the same manner or in the opposite direction. Thereafter, writing of the third and subsequent stripe regions 20 proceeds in the same manner.

[0032] The main deflector 208 sequentially deflects the electron beam 200 to the reference position A of the SF 30 so as to follow the movement of the XY stage 105. The sub-deflector 209 sequentially deflects the electron beam 200 from the reference position A of each SF 30 to the reference position B of the TF 40. The sub-sub-deflector 210 then deflects the electron beam 200 from the reference position B of each TF 40 to the shot position 42 of the beam to be irradiated within that TF 40.

[0033] In this way, the main deflector 208, the sub-deflector 209, and the sub-sub-deflector 210 have deflection areas of different sizes. TF40 is the smallest deflection area among the deflection areas of the multiple stages of deflectors.

[0034] The focus correction lens 240, which is an electrostatic lens, performs dynamic focus adjustment in response to height variations on the surface of the substrate 101. The focus correction lens 240 is disposed downstream of the deflectors (main deflector 208, sub-deflector 209, or sub-sub-deflector 210) in the direction of travel of the electron beam. The focus correction lens 240 is also disposed within the magnetic field of the objective lens 207.

[0035] The focus correction lens 240 has a ring-shaped electrode to which a positive voltage is applied, and the focus correction lens 240 is operated in a positive voltage range with respect to the surface of the substrate 101. As a result, reflected electrons and secondary electrons from the substrate 101 irradiated with the electron beam (primary beam) are attracted toward the electrode, preventing the resist on the surface of the substrate 101 from becoming charged.

[0036] In electron beam lithography systems, a phenomenon called beam drift occurs, in which the irradiation position and beam shape of the electron beam shift over time during lithography. This phenomenon occurs when contamination adhering to the deflector electrodes becomes charged by reflected electrons and secondary electrons that are emitted from the substrate surface and travel upward inside the electron optical column 102, causing a change in the trajectory of the electron beam.

[0037] Therefore, in this embodiment, the detector 230 is used to detect the amount of reflected electrons and secondary electrons from the substrate 101, and the amount of charge accumulation on the surface of the deflector (main deflector 208, sub-deflector 209, or sub-sub-deflector 210) is calculated from the detection result. Then, the amount of drift is calculated based on the amount of charge accumulation, and charge drift due to the charge-up phenomenon of the deflector is corrected in real time.

[0038] The reflected electrons and secondary electrons are deflected by the electric field of the main deflector 208 and tend to charge contaminants on the electrode surface of the main deflector 208. Therefore, in order to calculate the amount of charge accumulated on the surface of the main deflector 208, it is preferable to install the detector 230 near the main deflector 208. For example, the detector 230 is placed directly below the main deflector 208.

[0039] The detector 230 has a plurality of electrodes corresponding to the plurality of electrodes of the main deflector 208, etc., and the plurality of electrodes are arranged at equal intervals so as to surround the beam passing region. Fig. 4A shows an example of the electrode arrangement when the detector 230 has eight electrodes, and Fig. 4B shows an example of the electrode arrangement when the detector 230 has four electrodes.

[0040] The detector 230 is connected to the voltage measuring device 130. For example, as shown in FIG. 5 , the voltage measuring device 130 has a resistor 131 and a digital multimeter 132 that measures the voltage across the resistor 131. When electrons flow into the resistor 131 via the electrodes of the detector 230, a voltage drop occurs. By measuring the change in voltage with the digital multimeter 132, the amount of current can be calculated from the reflected electrons and secondary electrons detected for each electrode of the detector 230. The amount of current is transmitted to and input into the control computer 110.

[0041] The voltage measuring device 130 continuously measures the current amount, and the drift correction unit 52 calculates the average current amount within a predetermined time. That is, the drift correction unit 52 calculates the average current amount every predetermined time. The predetermined time is not particularly limited as long as it is sufficiently longer than one shot of the drawing process, and is, for example, about 200 ms.

[0042] The amount of charge stored at the start of the i-th measurement is Q ｉ Then, the charge accumulation amount Q at the end of the i-th measurement (at the start of the i+1-th measurement) is ｉ＋１ can be expressed by the following formula: In the following formula, Q ｍａｘ is the saturated electron amount, t ｉｎｔ is the measurement time (the above-mentioned predetermined time), t ｓｈｏｔ is the total beam-on time within the measurement time, t ｓｔｌ is the total time the beam is off during the measurement, τ ｃ is the charging time constant, τ ｄ is the discharge time constant, q ｓｈｏｔ is the current when the beam is on, q ｓｔｌ is the current when the beam is off, q ｉ is the i-th current measurement result (average current amount).

[0043]

[0044] Current amount q when beam is on (shot on) ｓｈｏｔ and the current amount q at the time of beam off (shot off) ｓｔｌ is measured and obtained in advance by the voltage measuring device 130.

[0045] The state of charging due to reflected electrons and secondary electrons during beam irradiation (beam on) and the state of discharge during beam off vary depending on the pattern density of the pattern to be drawn on the substrate 101. Therefore, while performing a pattern drawing operation at a specific pattern density in advance, the reflective mark 107 is scanned with the electron beam at regular time intervals, the beam position is measured, and beam drift data is acquired. Such beam drift data acquisition is performed at a plurality of different pattern densities. The parameter calculation unit 53 calculates the saturated electron amount Q that reproduces all the beam drift trends from the acquired data. ｍａｘ and time constant τ ｃ , τ ｄ Calculate the parameter values.

[0046] In this way, the previously calculated q ｓｈｏｔ , q ｓｔｌ , Q ｍａｘ , τ ｃ , τ ｄ The calculation formula data for calculating the amount of accumulated charge, including various parameters such as the above, is stored in the storage device 140.

[0047] The drift correction unit 52 calculates the amount of drift using the amount of accumulated charge calculated from the amount of current corresponding to each electrode of the detector 230. For example, as shown in FIG. 4A, the detector 230 has eight electrodes, and the angles of the electrodes 1 to 8 with respect to the x-axis are defined as θ １ ~θ ８ In this case, the amount of drift Dx in the x direction and the amount of drift Dy in the y direction can be calculated using the following equations: ｉ，ｎ is the amount of charge stored in electrode n at the start of the i-th current measurement.

[0048] Dx = -(Q ｉ，１ *cos(θ １ ) + Q ｉ，２ *cos(θ ２ ) + Q ｉ，３ *cos(θ ３ ) + Q ｉ，４ *cos(θ ４ ) + Qｉ，５ *cos(θ ５ ) + Q ｉ，６ *cos(θ ６ ) + Q ｉ，７ *cos(θ ７ ) + Q ｉ，８ *cos(θ ８ )) Dy = -(Q ｉ，１ *sin(θ １ ) + Q ｉ，２ *sin(θ ２ ) + Q ｉ，３ *sin(θ ３ ) + Q ｉ，４ *sin(θ ４ ) + Q ｉ，５ *sin(θ ５ ) + Q ｉ，６ *sin(θ ６ ) + Q ｉ，７ *sin(θ ７ ) + Q ｉ，８ *sin(θ ８ ))

[0049] Such calculation formula data for calculating the amount of drift is stored in the storage device 140.

[0050] The drift correction unit 52 retrieves the calculation formula data from the storage device 140. The drift correction unit 52 monitors the measurement value of the voltage measuring device 130, calculates the average current amount at predetermined time intervals, and substitutes the calculated value into the calculation formula to calculate the amount of charge accumulation corresponding to each electrode.

[0051] The drift correction unit 52 calculates the amount of drift from the amount of charge stored in each electrode, and determines the amount of drift correction that cancels the amount of drift.

[0052] The drift correction unit 52 generates correction information for the deflection amount of the electron beam (beam irradiation position and beam shape) based on the drift correction amount, and provides it to the writing control unit 54. The writing control unit 54 uses this correction information to provide the correction amount for the beam position and beam shape to the control circuit 120.

[0053] The shot data generation unit 50 performs multiple stages of data conversion processing on the writing data stored in the storage device 140, divides each figure pattern to be written into shot figures of a size that can be irradiated in one shot, and generates shot data in a format specific to the writing device. The shot data defines, for each shot, for example, a figure code indicating the figure type of each shot figure, figure size (shot size), shot position, beam on / off time, etc. The generated shot data is temporarily stored in the memory 112. The writing control unit 54 transfers the shot data to the control circuit 120.

[0054] The control circuit 120 applies a deflection voltage for deflection control to the deflector based on the shot data and the correction amount of the beam position and beam shape, thereby correcting the beam irradiation position and beam shape in the drawing unit 150.

[0055] In this way, according to this embodiment, the amount of reflected electrons and secondary electrons during writing can be detected and the amount of drift can be calculated.

[0056] The drift correction unit 52 may correct the shot position and beam shape in the shot data by the irradiation amount based on the correction amount.

[0057] A constant positive voltage may be applied to the electrode of the detector 230 relative to the surface of the substrate 101 to suppress the retention of secondary electrons.

[0058] The deflector itself may be used as a detector for reflected electrons and secondary electrons.

[0059] In this embodiment, an example in which a plurality of electrodes is used in the detector has been given, but a single electrode may also be used. For example, if the charging location is a specific location (electrode), the correction amount can be calculated by detecting the amount of electrons with a single electrode of the detector corresponding to that location (electrode).

[0060] The drift correction of this embodiment may also be performed together with drift correction based on conventional mark measurement, to complement the measurements. In this case, the parameters, algorithms, etc. of this embodiment may be changed based on the difference in the amount of drift obtained by comparing with the mark measurement results. Furthermore, if a deviation in the amount of drift from the mark measurement results exceeds a predetermined threshold, the real-time drift correction of this embodiment may be stopped.

[0061] Furthermore, after detecting the current amount and calculating the drift amount, drift correction may be performed immediately (in real time), or drift correction may be performed after a delay such as performing an error check, etc. In this case, the delay for the error check can be reduced compared to the delay due to drift correction based on mark measurement.

[0062] In the above embodiment, a configuration using an electron beam has been described as an example of a charged particle beam, but the charged particle beam is not limited to an electron beam, and may be a beam using charged particles such as an ion beam.

[0063] Although the above embodiment has been described as a lithography system using a single beam, a multi-beam lithography system may also be used. In this case, the shot data defines the shot position, the on / off time for each individual beam, etc., and a detector detects positional deviations and beam array shape deviations due to drift.

[0064] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the present invention. This application is based on Japanese Patent Application No. 2023-193098, filed on November 13, 2023, and is incorporated by reference in its entirety.

[0065] 50 Shot data generation unit 52 Drift correction unit 53 Parameter calculation unit 54 Drawing control unit 100 Drawing device 110 Control computer 150 Drawing unit 160 Control unit 230 Detector

Claims

1. A charged particle beam drawing device comprising: a charged particle beam source that emits a charged particle beam to be irradiated onto a substrate to be drawn; a deflector that deflects the charged particle beam to a desired irradiation position on the substrate; a detector that detects electrons reflected or emitted from the substrate towards the deflector; a correction amount generating unit that calculates an amount of drift of the charged particle beam to be irradiated onto the substrate from an amount of current obtained from the detected electrons and a time period from detection of the current to correction, and generates a correction amount for irradiation position deviation based on the drift amount; and a control unit that corrects the irradiation position based on shot data of the charged particle beam generated from drawing data and the correction amount.

2. The charged particle beam drawing device according to claim 1, wherein the detector is provided with a plurality of electrodes corresponding to a plurality of the deflectors, and the correction amount generating unit further calculates the drift direction using the respective amounts of current obtained from the plurality of the electrodes of the detector.

3. The charged particle beam drawing apparatus according to claim 1, wherein the deflection amount of the deflector or the shot data is corrected based on the correction amount.

4. The charged particle beam drawing apparatus of claim 1, wherein the deflector comprises: a first deflector that deflects the charged particle beam to a reference position of a plurality of first small regions obtained by virtually dividing a drawing area of ​​the substrate into a mesh shape so as to follow the movement of a stage on which the substrate is placed; a second deflector that deflects the charged particle beam from the reference position of each first small region to a reference position of a plurality of second small regions obtained by virtually dividing each first small region into a mesh shape; and a third deflector that deflects the charged particle beam from the reference position of each second small region to a shot position of the beam to be irradiated into the second small region, and the detector is disposed directly below the first deflector.

5. The charged particle beam drawing apparatus according to claim 1, further comprising a focus correction lens that corrects the focus of the charged particle beam in accordance with the surface height of the substrate, the focus correction lens being an electrostatic lens that operates in a positive voltage range with respect to the surface of the substrate.

6. A drift amount calculation method comprising: a step of emitting a charged particle beam to be irradiated onto a substrate to be written; a step of deflecting the charged particle beam to a desired irradiation position on the substrate; a step of generating shot data including a shot position and a beam on / off time for each shot from writing data; a step of detecting electrons reflected or emitted from the substrate towards the deflector; and a step of calculating a first drift amount of the irradiation position of the charged particle beam irradiated onto the substrate from the amount of current obtained by the electrons detected by the detector and the time from detection of the current to correction.

7. A drift amount calculation method according to claim 6, comprising: a step of calculating a second drift amount by scanning a measurement mark provided on a stage on which the substrate is placed; and a step of comparing the first drift amount with the second drift amount.

8. A charged particle beam drawing method comprising: a step of calculating a correction amount for irradiation position deviation based on the first drift amount calculated by the drift amount calculation method according to claim 6; and a step of correcting the irradiation position based on the shot data and the correction amount.

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