JP4048573B2 - Deflection data and correction data acquisition method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is necessary in the case of performing exposure using a so-called block mask, which is a transmission mask plate formed by forming a plurality of so-called block patterns, or a so-called block mask, for shaping a cross-sectional shape of a charged particle beam. The present invention relates to a deflection data and correction data acquisition method for acquiring deflection data and correction data.
[0002]
[Prior art]
FIG. 6 is a conceptual diagram showing a main part of an example of an electron beam exposure apparatus configured to be able to perform block exposure. In FIG. 6, 1 is a column unit, and 2 is a control unit for controlling the column unit 1. It is.
[0003]
In the column section 1, 3 is an electron gun for emitting an electron beam, 4 is an electron beam emitted from the electron gun 3, 5 is an optical axis, 6 and 7 are irradiation lenses, 8 and 9 are shaping lenses, and 10 is a shaping lens. The reduction lenses 11 and 12 are projection lenses.
[0004]
Further, 13 is a rectangular shaped aperture plate for shaping the electron beam 4 into a rectangle, 14 is a shaping deflector used when the electron beam 4 is shaped into a variable rectangle, 15 is a block mask formed with a plurality of block patterns, Reference numeral 16 denotes a mask stage for holding the block mask 15.
[0005]
FIG. 7 is a schematic plan view showing the block mask 15. FIG. 7A is a schematic plan view showing the entire block mask 15, and reference numerals 19 to 30 denote deflection regions where the electron beam can be deflected. The deflection regions 19 to 30 are selected by moving the block mask 15 by the mask stage 16.
[0006]
FIG. 7B is a schematic plan view showing the deflection area 26 of the block mask 15 in an enlarged manner. Reference numerals 31 to 34 denote rectangular transmission patterns 35-1 and 35 used for calibration and variable rectangular shaping. −2 to 35-40 are block pattern portions on which block patterns are formed.
[0007]
FIG. 7C is a schematic plan view showing the block pattern portion 35-23 in an enlarged manner, and 36-1, 36-2,... 36-16 are for exposing a contact hole pattern. This is a rectangular opening.
[0008]
In FIG. 6, reference numerals 38-1 and 38-2 indicate that the electron beam 4 is selected from among the block pattern portions 35-1 to 35-40 provided in the block mask 15. Mask deflectors 38-3 and 38-4 for deflecting to the block pattern are mask deflectors for returning the electron beam 4 that has passed through the selected block pattern back to the optical axis 5.
[0009]
Reference numeral 39 denotes an astigmatism correction coil for correcting astigmatism generated in the electron beam 4 by the deflection by the mask deflectors 38-1 and 38-2, and reference numeral 40 denotes an electron by the deflection by the mask deflectors 38-1 and 38-2. It is a focus correction coil that corrects the defocus generated in the beam 4.
[0010]
Further, 41 is a blanking deflector for controlling the passage of the electron beam 4, 42 is a round aperture plate formed with a round aperture 42A for determining the opening angle of the electron beam with respect to the projection lens 11, and 43 is a main composed of an electromagnetic deflector. A deflector 44 is a sub-deflector made of an electrostatic deflector, 45 is a wafer to be exposed, and 46 is a wafer stage for holding the wafer 45.
[0011]
In the control unit 2, 47 is a central CPU of the control unit 2, 48 is a clock unit that generates a clock for controlling the operation timing of each unit in the control unit 2, and 49 is necessary for variable rectangular exposure. The buffer memory stores pattern data, block data necessary for performing block exposure, deflection data for the main deflector 43, and the like.
[0012]
Reference numeral 50 denotes a division of pattern data required for variable rectangular exposure stored in the buffer memory 49 into beam size data and beam position data, and individual block data required for block exposure. It is a pattern generator (PG) unit that performs pattern data code (PDC) conversion indicating a block pattern.
[0013]
Reference numeral 51 denotes, for each pattern data code, deflection data BSX1 and BSY1 for the mask deflector 38-1, deflection data BSX2 and BSY2 for the mask deflector 38-2, and deflection data BSX3 for the mask deflector 38-3. , BSY3, mask data for storing deflection data BSX4, BSY4 for the mask deflector 38-4, correction data DSX, DSY for the astigmatism correction coil 39, and correction data DF for the focus correction coil 40. is there.
[0014]
Reference numeral 52 denotes a pattern correction unit that corrects pattern data (beam size data and beam position data) for the shaping deflector 14 and the sub deflector 44, and 53 denotes a main deflector 43 stored in the buffer memory 49. This is a main deflector control unit that controls the main deflector 43 based on the deflection data.
[0015]
In the electron beam exposure apparatus configured as described above, when block exposure is performed, the electron beam 4 emitted from the electron gun 3 is shaped into a rectangle by the rectangular shaping aperture 13 and then mask deflector 38-1. 38-2, the block pattern formed on the block mask 15 is deflected to the selected block pattern, and the cross-sectional shape is shaped into the same pattern as the selected block pattern.
[0016]
In this way, the electron beam 4 whose cross-sectional shape is shaped by the block pattern is converged by the electron lens 9 and returned to the optical axis 5 by the mask deflectors 38-3 and 38-4, and at the same time, the mask deflector 38. -1 and 38-2 are corrected by astigmatism correction coil 39 and focus correction coil 40, respectively.
[0017]
Then, the electron beam 4 turned back to the optical axis 5 is reduced by the reduction lens 10, passes through the round aperture 42 </ b> A, and is exposed on the wafer 45 by the projection lenses 11 and 12.
[0018]
In this way, in order to perform block exposure, deflection data BSX1, BSY1 to BSX4, BSY4 and correction data DSX, DSY, DF for each block pattern stored in the mask memory 51 are measured in advance before exposure. Must be the optimal one.
[0019]
Conventionally, the optimum values of the deflection data BSX1, BSY1 to BSX4, BSY4 and the correction data DSX, DSY, DF are changed by changing the deflection data BSX1, BSY1 to BSX4, BSY4 every time the correction data DSX, DSY, DF are changed. The axis of the electron beam 4 was aligned with respect to the round aperture 42A, and the current was obtained by measuring the round aperture passing current value via the Faraday cup 55 as shown in FIG.
[0020]
The reason why the deflection data BSX1, BSY1 to BSX4, and BSY4 are changed every time the correction data DSX, DSY, and DF are changed to adjust the axis of the electron beam 4 with respect to the round aperture 42A is astigmatism correction coil 39 and focus correction. The coil 40 changes the cross-sectional shape of the electron beam 4 on the round aperture 42A. However, when the correction data DSX, DSY, and DF are changed, the position of the electron beam 4 on the round aperture 42A also changes. It is because it ends up.
[0021]
Incidentally, FIGS. 9A and 9B are schematic diagrams showing the relationship between the change in the cross-sectional shape of the electron beam 4 on the round aperture plate 42 and the positional deviation when the correction data DSX and DSY are changed. FIG. 9C is a schematic plan view showing the relationship between the change in the sectional shape of the electron beam 4 on the round aperture plate 42 and the positional deviation when the correction data DF is changed.
[0022]
[Problems to be solved by the invention]
Here, in the conventional method for obtaining the optimum values of the deflection data BSX1, BSY1 to BSX4, BSY4 and the correction data DSX, DSY, DF, the correction data DSX, DSY, DF are changed in n ways, and the correction data DSX, DSY, When it is necessary to change the deflection data BSX1, BSY1 to BSX4, and BSY4 for axis alignment for each way of the DF m times, in order to obtain the optimum value (target value) Q, as shown in FIG. In addition, the measurement point P becomes n × m, and there is a problem that a great deal of time is required.
[0023]
In view of this point, the present invention reduces the time required to obtain the optimum values of deflection data and correction data necessary for performing block exposure, and is an efficient charged particle beam exposure apparatus capable of performing block exposure. It is an object of the present invention to provide a method for acquiring deflection data and correction data that enables easy operation.
[0024]
[Means for Solving the Problems]
In the present invention, the first invention (deflection data and correction data acquisition method according to claim 1) is a method in which a charged particle beam on an optical axis is formed on a block mask by first and second mask deflectors. After the plurality of block patterns are deflected to a selected block pattern and the cross-sectional shape is shaped, they are returned to the optical axis by the third and fourth mask deflectors, and the first and second Necessary when performing block exposure in which astigmatism and defocus caused by deflection of the mask deflector are corrected by the astigmatism correction coil and focus correction coil, respectively, and exposure is performed on the exposure target through the reduction lens, round aperture, and projection lens. Optimal deflection data for driving the first, second, third, and fourth mask deflectors and optimum correction data for driving the astigmatism correction coil and the focus correction coil. In the deflection data and correction data acquisition method, the charged particle beam output from the reduction lens is scanned two-dimensionally on the round aperture plate including the round aperture each time the correction data is changed. After measuring the intensity of the charged particle beam passing through the aperture and obtaining the maximum value as the intensity of the charged particle beam passing through the round aperture, the optimum correction data is obtained. Deflection data when the deflection data is changed and the axis of the charged particle beam output from the reduction lens is aligned with the round aperture to obtain the maximum value as the intensity of the charged particle beam that has passed through the round aperture Is obtained as the optimum deflection data
[0025]
According to the first aspect of the present invention, after the correction data is changed to obtain the optimum value of the correction data, the optimum correction data is used and the deflection data is changed to obtain the optimum value of the deflection data. Therefore, the number of combinations of correction data values and deflection data values when measuring the intensity of the charged particle beam can be reduced, and the time required to obtain the optimum values of deflection data and correction data can be shortened. .
[0026]
In the present invention, the second invention (deflection data and correction data acquisition method according to claim 2) is the first invention, wherein the measurement of the intensity of the charged particle beam every time the correction data is changed is two-dimensional. The scanning is performed a plurality of times, and the measurement time of the intensity of the charged particle beam is set to be shorter than the time required to perform the two-dimensional scanning once, and the intensity of the charged particle beam is measured at each two-dimensional scanning. The start time is determined while being shifted by a predetermined time relative to the scan start time for each two-dimensional scan.
[0027]
In the present invention, according to the second invention, the same action as that of the first invention can be obtained, and the measurement data of the intensity of the charged particle beam acquired when the two-dimensional scanning is performed once is 2 Compared to the case where the intensity of the charged particle beam is measured over the entire time during which the dimensional scanning is performed, the number can be reduced.
[0028]
In the present invention, the third invention (deflection data and correction data acquisition method described in claim 3) is the time required for performing two-dimensional scanning of TA once in the second invention, and TB1 is two-dimensionally. When the charged particle beam intensity measurement start time and TC in the first scan of a simple scan are the charged particle beam intensity measurement time in one two-dimensional scan, the kth (where k is an integer of 2 or more). The charged particle beam intensity measurement start time TBk at the time of two-dimensional scanning is TB1 + (TA + TC) × (k−1).
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described by taking as an example the case of acquiring deflection data BSX1, BSY1 to BSX4, BSY4 and correction data DSX, DSY, DF necessary for the electron beam exposure apparatus shown in FIG.
[0030]
1 to 5 are diagrams for explaining one embodiment of the present invention. In one embodiment of the present invention, first, correction is performed on the assumption that the correction data DSX, DSY, and DF are changed in n ways. As shown in FIG. 1, the electron beam 4 is scanned in the X-axis direction while moving the electron beam 4 on the round aperture plate 42 including the round aperture 42A from the start point 60 in the Y-axis direction as shown in FIG. 1 for each of the data DSX, DSY, and DF. The intensity of the electron beam that has passed through the round aperture 42A is measured as, for example, reflected electron intensity.
[0031]
Here, the scanning range of the electron beam 4 is such that the electron beam 4 is round as indicated by a two-dot chain line 62 in FIG. 2 even when an axis deviation due to the astigmatism correction coil 39 or the focus correction coil 40 occurs. The aperture 42 </ b> A and its peripheral part are set in a range that can be scanned.
[0032]
Such scanning of the electron beam 4 is, for example, a saw having a period of several tens to several hundreds of μs as a drive signal for scanning in the X-axis direction with respect to the shaping deflector 14 as shown in FIG. In addition to supplying the wave signal S15X, a sawtooth wave signal S15Y having a period of several to several hundred ms as shown in FIG. 3B can be supplied as a drive signal for Y-axis direction scanning.
[0033]
When such scanning is performed, when the electron beam 4 converges on the round aperture plate 42 as the intensity waveform of the electron beam that has passed through the round aperture 42A, a waveform as shown in FIG. When the electron beam 4 is not converged on the round aperture plate 42, a waveform as shown in FIG. 4B can be obtained.
[0034]
The measurement of the intensity of the electron beam that has passed through the round aperture 42A is performed for each of the correction data DSX, DSY, and DF in n ways, and the maximum value can be obtained as the intensity of the electron beam that has passed through the round aperture 42A. In this case, the correction data DSX, DSY, and DF are set as optimum correction data.
[0035]
Thereafter, the optimum correction data DSX, DSY, and DF are used, and the deflection data BSX1, BSY1 to BSX4, and BSY4 are changed to align the axis of the electron beam 4 with respect to the round aperture 42A, and the electron beam passing through the round aperture 42A is adjusted. The intensity is measured, and the deflection data BSX1, BSY1 to BSX4, BSY4 when the maximum value can be obtained as the intensity of the electron beam that has passed through the round aperture 42A is set as the optimum deflection data.
[0036]
In this case, the correction data DSX, DSY, and DF need to be changed in n ways, and even when the deflection data BSX1, BSY1 to BSX4, and BSY4 need to be changed in m ways, the deflection data BSX1, BSY1 In order to obtain the optimum values of ˜BSX4, BSY4 and correction data DSX, DSY, DF, it is sufficient to perform n + m searches.
[0037]
Here, for example, if the scanning time for one scanning plane is 40 ms and the sampling interval of the electron beam intensity passing through the round aperture is 1.24 μs, the time during which the electron beam 4 passes the round aperture 42A is the entire scanning plane. Since the time of one round scan is smaller than the time of scanning once and the width of one round aperture passing electron beam intensity waveform is 10 μs, if the round aperture passing electron beam intensity is sampled over the entire period of scanning the scanning plane, all measurements are performed. A time width in which a necessary signal is measured with respect to time is very small, that is, an electron beam intensity waveform passing through a round aperture having an extremely small duty ratio is acquired, and a storage device having an extremely large storage capacity is required. Therefore, in one embodiment of the present invention, the electron beam intensity passing through the round aperture is Measurements are performed as shown in FIG.
[0038]
In FIG. 5, TA is the time required to scan the scanning surface once, TB1 is the round aperture passing electron beam intensity measurement start time when performing the first scanning of the scanning surface, and TC is the round aperture passing electron beam intensity measurement time. TD is the time required to analyze the peak value, TB2 is the round aperture passing electron beam intensity measurement start time when the second scan of the scanning plane is performed, and TB3 is the round aperture when the third scanning of the scanning plane is performed. The passing electron beam intensity measurement start time is shown.
[0039]
That is, in one embodiment of the present invention, the measurement of the intensity of the electron beam passing through the round aperture every time the correction data DSX, DSY, and DF are changed is k times on the scanning plane (where k is an integer of 2 or more. ) Is measured so that the measurement start time TBk at the time of scanning becomes TB1 + (TA + TC) × (k−1), and the correction data when the peak value of the round aperture passing electron beam intensity becomes maximum is determined as the optimum correction data. Is done.
[0040]
The round aperture aperture electron beam intensity is measured a plurality of times, and the correction data DSX, DSY, and DF when the maximum value is obtained as the round aperture aperture electron beam intensity are set as the optimum correction data. In this case, more optimal correction data can be obtained.
[0041]
Thus, according to an embodiment of the present invention, after obtaining the optimum correction data by changing the correction data DSX, DSY, DF, the deflection data BSX1, BSY1-BSX4, BSY4 is changed to obtain the optimum deflection data. Since the number of combinations of correction data DSX, DSY, DF and deflection data BSX1, BSY1 to BSX4, BSY4 when measuring the electron beam intensity passing through the round aperture is reduced, the optimum deflection data and the optimum The time required for acquiring the correction data can be shortened, and an efficient operation of the electron beam exposure apparatus as shown in FIG. 6 can be achieved.
[0042]
According to one embodiment of the present invention, the round aperture passing electron beam intensity is measured every time the correction data DSX, DSY, and DF are changed, and the scanning surface is scanned a plurality of times. The intensity measurement time is shorter than the time required for one scan of the scan plane, and each time scanning of the scan plane is repeated, the round aperture passing electron beam intensity measurement start time is set as the scan start time for each scan plane scan. As a reference, the measurement data of the round aperture passing electron beam intensity obtained when the scanning surface is scanned once is rounded over the entire time of scanning the scanning surface. The round aperture can be reduced compared to the case of measuring the electron beam intensity passing through the aperture. As a storage device for storing the measurement data of the passing electron beam intensity, as compared to the case of measuring the round aperture passing electron beam intensity over the entire period of scanning the scanning surface is sufficient to provide a small memory storage capacity.
[0043]
【The invention's effect】
In the present invention, according to the first invention (deflection data and correction data acquisition method according to claim 1), after obtaining the optimum value of the correction data by changing the correction data, the optimum correction data is used, Since the optimum value of the deflection data is obtained by changing the deflection data, the number of combinations of the correction data value and the deflection data value when measuring the intensity of the charged particle beam is reduced, and the deflection data and the correction data Since the time required to obtain the optimum value can be shortened, the charged particle beam exposure apparatus capable of performing block exposure can be efficiently operated.
[0044]
In the present invention, according to the second or third invention (the deflection data and correction data acquisition method according to claim 2 or 3), the same effect as that of the first invention can be obtained and two-dimensional. Since the charged particle beam intensity measurement data acquired in the case of performing a single scan can be reduced as compared with the case where the charged particle beam intensity is measured over the entire time for two-dimensional scanning. As a storage device for storing the measurement data of the particle beam intensity, prepare a storage device with a smaller storage capacity compared to the case where the intensity measurement of the charged particle beam is performed for the entire time when two-dimensional scanning of the charged particle beam is performed. It's enough.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an embodiment of the present invention.
FIG. 2 is a diagram for explaining an embodiment of the present invention.
3 is a waveform diagram showing drive signals supplied to a shaping deflector included in the electron beam exposure apparatus shown in FIG.
FIG. 4 is a diagram showing a round aperture passing electron beam intensity waveform obtained by executing one embodiment of the present invention.
FIG. 5 is a diagram for explaining a method of measuring intensity of electron beam passing through a round aperture performed in an embodiment of the present invention.
FIG. 6 is a conceptual diagram showing a main part of an example of an electron beam exposure apparatus.
7 is a schematic plan view showing a block mask provided in the electron beam exposure apparatus shown in FIG. 6;
FIG. 8 is a diagram for explaining a conventional method for obtaining optimum values of deflection data and correction data required when performing block exposure in the electron beam exposure apparatus shown in FIG. 6;
FIG. 9 is a schematic plan view showing a relationship between a change in cross-sectional shape of an electron beam on a round aperture plate and a positional deviation when correction data is changed.
10 is a diagram for explaining a problem of a conventional method for obtaining optimum values of deflection data and correction data necessary for performing block exposure in the electron beam exposure apparatus shown in FIG. 6; FIG.
[Explanation of symbols]
(Figure 1)
4 Electron beam 42 Round aperture plate 42A Round aperture 60 Start point of scanning (FIG. 6)
38-1 Mask deflector 38-2 Mask deflector 38-3 Mask deflector 38-4 Mask deflector 39 Astigmatism correction coil 40 Focus correction coil

Claims (3)

The charged particle beam on the optical axis is deflected to a selected block pattern out of a plurality of block patterns formed on the block mask by the first and second mask deflectors, and the cross-sectional shape is shaped. Thereafter, the astigmatism and the defocus caused by the deflection of the first and second mask deflectors are returned to the optical axis by the third and fourth mask deflectors, respectively, and the astigmatism correction coil and the focus. For driving the first, second, third, and fourth mask deflectors necessary for performing block exposure in which exposure is performed on an object to be exposed through a reduction lens, a round aperture, and a projection lens. In a deflection data and correction data acquisition method for acquiring optimal deflection data and optimal correction data for driving the astigmatism correction coil and the focus correction coil. ,
Each time the correction data is changed, the charged particle beam output from the reduction lens is scanned two-dimensionally on the round aperture plate including the round aperture, and the intensity of the charged particle beam passing through the round aperture Is measured and the correction data when the maximum value can be obtained as the intensity of the charged particle beam that has passed through the round aperture is obtained as the optimum correction data, and then the optimum correction data is used and the deflection data is changed. Then, alignment of the charged particle beam output from the reduction lens with respect to the round aperture is performed, and the deflection data when the maximum value can be obtained as the intensity of the charged particle beam that has passed through the round aperture is used as the optimum deflection data. Deflection data and correction data characterized by How to get. The intensity of the charged particle beam is measured every time the correction data is changed, and the two-dimensional scan is performed a plurality of times, and the measurement time of the intensity of the charged particle beam is set once for the two-dimensional scan. The measurement start time of the charged particle beam intensity during each two-dimensional scan is set at a relatively constant time with reference to the scan start time for each two-dimensional scan. 2. The deflection data and correction data acquisition method according to claim 1, wherein the deflection data and the correction data are acquired while being shifted. TA is a time required to perform the two-dimensional scan once, TB1 is a charged particle beam intensity measurement start time in the first two-dimensional scan, and TC is a charged particle in the two-dimensional scan. In the case of the beam intensity measurement time, the charged particle beam intensity measurement start time TBk at the k-th (where k is an integer of 2 or more) two-dimensional scanning is TB1 + (TA + TC) × (k−1). The deflection data and correction data acquisition method according to claim 2, wherein:

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