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

Abstract

To correct a beam drift during drawing processing in real time.SOLUTION: A charged particle beam lithography apparatus comprises: a charged particle beam source that discharges a charged particle beam to be applied to a substrate subjected to drawing; a deflector that deflects the charged particle beam to a desired irradiation position on the substrate; a detector that detects electrons reflected or discharged toward the deflector from the substrate; a correction amount generation unit that calculates a drift amount of the charged particle beam applied to the substrate from a current amount obtained from the detected electrons and a time from the detection of the current to correction of them; and a control unit that corrects the irradiation position on the basis of shot data for the charged particle beam generated from drawing data and the correction amount.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a charged particle beam drawing apparatus, a drift amount calculation 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 year by year. To form the desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision original pattern (mask, or particularly one used in steppers and scanners, called a reticle) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure apparatus. The high-precision original pattern is drawn by 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 of the lithography system, such as the deflection electrodes, and the contamination becomes charged by scattered electrons from the substrate to be 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 the correction error becomes large when the drift tendency changes significantly, and the writing accuracy deteriorates. If the measurement interval of the beam irradiation position is shortened to suppress the correction error, the throughput decreases. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-256112 [Patent Document 2] Japanese Patent Application Publication No. 8-274002 [Patent Document 3] JP 2007-019246 A Summary of the Invention [Problem to be solved by the invention]

[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 are capable of correcting beam drift during drawing processing in real time. [Means for solving the problem]

[0007] A charged particle beam drawing apparatus according to one embodiment of the present invention includes a deflector that adjusts an irradiation position of a charged particle beam irradiated onto a substrate to be drawn, a shot data generation unit that generates shot data including a shot position and a beam on / off time for each shot from drawing 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 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 an amount of deflection by the deflector based on the shot data and the correction information.

[0008] A drift amount calculation method according to one embodiment 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 an amount of current obtained by the electrons detected by the detector and a time from detection of the current to correction.

[0009] A charged particle beam writing method according to one embodiment of the present invention includes a step of calculating a correction amount for an 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. Effect of the Invention

[0010] According to the present invention, beam drift during drawing processing can be corrected in real time. [Brief description 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. [Diagram 2] FIG. 2 is a perspective view of a first shaping aperture and a second shaping aperture. [Diagram 3] FIG. 4 is a conceptual diagram illustrating a deflection region. [Figure 4] 4A and 4B are diagrams showing examples of the arrangement of electrodes of a detector. [Diagram 5] FIG. 2 is a diagram illustrating an example of the configuration of a voltage measuring device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 may be an ion beam or the like.

[0013] Fig. 1 is a conceptual diagram showing a configuration of a drawing apparatus according to an embodiment. In Fig. 1, drawing apparatus 100 includes drawing unit 150 and control unit 160. Drawing unit 150 includes electron optical column 102 and drawing chamber 103. In electron optical column 102, 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 are arranged.

[0014] An XY stage 105 that is movable in the XY directions is placed in the pattern writing chamber 103. A substrate 101 that is coated with resist and 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 an electron beam. The reflected 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 emitted from an electron gun 201 (emitting portion) provided in an electron optical lens barrel 102 passes through a blanking deflector 212, the blanking deflector 212 switches whether or not the electron beam is irradiated onto the substrate 101.

[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 having 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 that time, the deflection of the first aperture image projected onto the second shaping aperture 206 is controlled by a shaping deflector 205, and it is possible to change the shape and dimensions of the electron beam passing 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 generating unit 50, a drift correcting unit 52 (correction amount generating unit), a parameter calculating unit 53, and a writing control unit 54. Each function of the shot data generating unit 50, the drift correcting unit 52, the parameter calculating unit 53, and the writing control unit 54 may be configured by software or hardware.

[0023] Fig. 3 is a conceptual diagram for explaining a deflection region. As shown in Fig. 3, the drawing region 10 of the substrate 101 is virtually divided into a plurality of stripe regions 20 in a rectangular shape, for example, 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 become the deflection regions of the main deflector 208 (main deflection regions).

[0024] This main deflection region is virtually divided into a plurality of sub-fields (SF) 30 in a mesh shape with a deflection possible size of the sub-deflector 209. Then, each SF 30 is virtually divided into a plurality of under sub-fields (here, abbreviated as "TF" for Tertiary Deflection Field, meaning the third deflection, the same applies below) 40 in a mesh shape with a deflection possible size of the sub-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 of each shot is performed.

[0026] The control circuit 120 applies a deflection voltage for shaping deflection to the shaping deflector 205. The deflection voltage deflects the electron beam 200 to a specific position of the second shaping aperture 206 to form 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. The electron beam 200 is deflected by this deflection voltage, 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) virtually divided into a mesh shape. In addition, when drawing is performed while the XY stage 105 is moving continuously, the deflection voltage also includes a deflection voltage for tracking that follows 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 each shot of the beam is deflected to each shot position 42 within the TF 40.

[0030] In the drawing apparatus 100, a multiple-stage deflector is used to perform drawing processing for each stripe region 20. 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 addition, 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-stage deflectors is not limited to this.

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

[0032] The main deflector 208 deflects the electron beam 200 sequentially to the reference position A of the SF 30 so as to follow the movement of the XY stage 105. The sub-deflector 209 deflects the electron beam 200 sequentially 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 manner, the main deflector 208, the sub deflector 209, and the sub-sub deflector 210 have deflection regions of different sizes. The TF 40 is the smallest deflection region among the deflection regions 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 of 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 traveling direction 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 to the electrode side, making it possible to prevent the resist on the surface of the substrate 101 from becoming charged.

[0036] In electron beam lithography devices, 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 attached to the electrodes of the deflector becomes charged by reflected electrons and secondary electrons that are emitted from the substrate surface and move upward inside the electron optical column 102, causing a change in the trajectory of the electron beam.

[0037] Therefore, in this embodiment, the amount of reflected electrons and secondary electrons from the substrate 101 is detected using the detector 230, 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 the 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 contamination on the electrode surface of the main deflector 208. Therefore, in order to calculate the amount of charge accumulation on the surface of the main deflector 208, it is preferable to install the detector 230 in the vicinity of the main deflector 208. For example, the detector 230 is disposed 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 arrangement of the electrodes when the detector 230 has eight electrodes, and Fig. 4B shows an example of the arrangement of the electrodes when the detector 230 has four electrodes.

[0040] The detector 230 is connected to a 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 applied to 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 obtained 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 charge accumulation at the start of the i-th measurement is Q i Then, the amount of charge stored at the end of the i-th measurement (the start of the i+1-th measurement) is Q i+1 can be expressed by the following formula. In the following formula, Q max is the saturation electron amount, t int is the measurement time (the specified time above), t shot is the total beam-on time during the measurement, 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, and q stl is the current when the beam is off, q i is the i-th current measurement result (average current).

[0043]

number

[0044] Current amount q when beam is on (shot on) shot and the current at beam off (shot off) q 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 when the beam is off vary depending on the pattern density of the pattern to be drawn on the substrate 101. For this reason, while performing a pattern drawing operation at a specific pattern density in advance, the reflective mark 107 is scanned with an 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 number of different pattern densities. The parameter calculation unit 53 calculates, from the acquired data, the saturated electron amount Q that reproduces all beam drift trends. max and time constant τ c , τ d Calculate the parameter values.

[0046] In this way, the previously obtained 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 drift amount Dx in the x direction and the drift amount Dy in the y direction can be calculated using the following formula: i,n is the amount of charge stored in electrode n at the start of the i-th current measurement.

[0048] Dx=-(Qi,1 *cos(θ 1 )+Q i,2 *cos(θ 2 )+Q i,3 *cos(θ 3 )+Q i,4 *cos(θ 4 )+Q i,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] Drift correction unit 52 retrieves the calculation formula data from storage device 140. Drift correction unit 52 monitors the measurement value of 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 obtains a drift correction amount 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 provides the correction amount of the beam position and beam shape to the control circuit 120 using the correction information.

[0053] The shot data generating unit 50 performs multiple stages of data conversion processing on the drawing data stored in the storage device 140, divides each figure pattern to be drawn into shot figures of a size that can be irradiated in one shot, and generates shot data in a format specific to the drawing device. For each shot, the shot data defines, 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 drawing 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 the beam shape. As a result, the beam irradiation position and the beam shape are corrected in the drawing unit 150.

[0055] In this manner, 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 with respect to the surface of the substrate 101 to suppress 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 are used in the detector is given, but a single electrode may be used. For example, when 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 be performed together with the drift correction by the 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 result of the mark measurement. Furthermore, if the drift amount is different from the result of the mark measurement by a predetermined threshold or more, the real-time drift correction of this embodiment may be stopped.

[0061] Also, after detecting the amount of current and calculating the amount of drift, 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 suppressed 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] In the above embodiment, a drawing device using a single beam has been described, but a multi-beam drawing device may 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 position deviations and beam array shape deviations due to drift.

[0064] The present invention is not limited to the above-described embodiment, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

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

Claims

1. a charged particle beam source that emits a charged particle beam that is irradiated onto a substrate to be written; a deflector that deflects the charged particle beam to a desired irradiation position on the substrate; a detector for detecting electrons reflected or emitted from the substrate toward the deflector; a correction amount generating unit that calculates a drift amount of the charged particle beam irradiated to the substrate from an amount of current obtained from the detected electrons and a time from detection of the current to correction, and generates a correction amount for irradiation position deviation based on the drift amount; 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; A charged particle beam writing apparatus comprising:

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

3. 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 deflector includes: a first deflector that deflects the charged particle beam to reference positions of a plurality of first small regions obtained by virtually dividing a drawing region 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 a reference position of each first small area to reference positions of a plurality of second small areas obtained by virtually dividing each first small area into a mesh shape; a third deflector that deflects the charged particle beam from a reference position of each second small area to a shot position of the beam that is irradiated into the second small area; having 2. The charged particle beam drawing apparatus according to claim 1, wherein the detector is disposed immediately below the first deflector.

5. a focus correction lens for correcting the focus of the charged particle beam in accordance with the surface height of the substrate; 2. The charged particle beam writing apparatus of claim 1, wherein the focus correction lens is an electrostatic lens and operates in a positive voltage range with respect to the surface of the substrate.

6. emitting a charged particle beam which is incident on a substrate to be written; deflecting the charged particle beam to a desired irradiation position on the substrate; generating shot data including a shot position and a beam on / off time for each shot from the drawing data; detecting electrons reflected or emitted from the substrate toward the deflector; calculating a first drift amount of an irradiation position of the charged particle beam irradiated onto the substrate from an amount of current obtained by the electrons detected by the detector and a time from detection of the current to correction; The drift amount calculation method includes the steps of:

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

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

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