JP3316076B2 - Charged particle beam exposure method and exposure apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of semiconductor devices, and more particularly, to speeding up the beam deflection of a sub-deflector when drawing a semiconductor pattern on a sample such as a semiconductor substrate using a charged particle beam such as an electron beam. The present invention relates to a charged particle beam exposure method and an exposure apparatus capable of achieving high accuracy.

In recent years, integrated circuits (ICs) have been widely used in a wide range of industries, such as computers, communications, and machine controls, as their integration degree and functions have been improved. 2. Description of the Related Art High integration of ICs has progressed, and DRAMs having a large storage capacity exceeding, for example, 256 Mbits or 1 Gbits have been manufactured. Such high integration of ICs is caused by the progress of fine processing technology.

In electron beam exposure, fine processing of 0.05 μm or less can be realized with an alignment error of 0.02 μm or less. However, the throughput of such electron beam exposure is generally low in currently marketed apparatuses for performing processing of all patterns by one-time exposure (one-stroke type beam exposure) and in current productivity.
Has not been considered for mass production.

On the other hand, in recent years, the present applicants have proposed a block exposure method and a multi-beam type blanking aperture array (BAA) exposure method. In these methods, 1 cm ^2/1 sec approximately throughput can be expected, and further, superior to their processed fineness, alignment accuracy, quick turn-around, and any reliability very, other methods . In such a blanking aperture array exposure method, it is required to achieve both high-speed and high-accuracy sub-deflector deflection and to use an electron beam advantageously for fine processing.

[0005]

2. Description of the Related Art In a charged particle exposure apparatus used in a conventional multi-beam type charged particle beam exposure system,
The stage 114 on which the sample to be exposed is placed is shown in FIG.
As shown in FIG. 4A, the stage 114 is moved in one direction (hereinafter, the moving direction of the stage 114 is called a Y direction, and the vertical direction of the Y direction is called an X direction), and the charged particle beam is moved by an electromagnetic deflector. (Hereinafter referred to as the main deflector),
In the X direction, for example, as shown in FIG. 14B, the charged particle beam
It is deflected by about 2 mm in width every 0 μm. At one deflection position deflected in this way, an electrostatic deflector (hereinafter, referred to as a sub deflector) further performs one or more substantially straight lines in a region smaller than the deflection region of the main deflector. Deflection on,
That is, scanning (scanning) is performed. For example, scanning in one direction of about 10 lines having a width of 10 μm is performed in a rectangular area having a side length of about 100 μm. Further, the beam is turned on / off in synchronization with this scan, thereby performing exposure.

For example, as shown in FIG. 4, a BAA in which a total of (the number of columns in the X direction) × (the number of rows in the Y direction) openings are arranged in a zigzag pattern in the X direction and the Y direction. , (The number of columns in the X direction) × (the number of groups in the Y direction) independent on / off control circuits (hereinafter, referred to as a data emitting unit) perform on / off control of the beam. In each group of apertures, the beam exiting from the rear row aperture is controlled on / off using data obtained by delaying the on / off data of the front row aperture. For example, the data given to A01 in the figure is delayed, and the same data is shot when the beam exiting from A02 reaches the position of A01. Further, each data output unit outputs data so that shots of openings of different opening groups are shot at predetermined positions. By this method, the minimum unit that can be set with respect to the pattern size and pattern position when designating the pattern to be exposed is reduced, and furthermore, the number of beams turned on in the pattern to perform dose correction and the like is reduced. The pattern unevenness that occurs when reduced is reduced.

As described above, in the conventional exposure system, when the BAA pixels are arranged in a zigzag pattern, the apertures arranged in the scanning direction are obtained by using data shot by the apertures in the previous row. The same position is shot multiple times with some delay.

In the conventional method, a constant sawtooth waveform generated by a circuit such as a television beam scanning circuit is
The beam turned on / off as described above is applied to the sub deflector to scan at a desired position on the sample. This conventional method has advantages of faster scanning and easier circuit design.

Further, in the conventional vector scan type exposure apparatus, correction calculation of deflection distortion is performed for each exposure of one shot. In the case of the vector scan method, a shot is performed after the deflector has settled at a designated position, and therefore, high speed is not required for the deflection correction calculation. Therefore, the correction operation of the deflector is performed based on the digital value, and the corrected digital value is supplied to the input of the DAC.

[0010]

However, according to the conventional multi-beam type charged particle exposure method,
(1) It is difficult to increase the positioning accuracy. (2) It is not easy to correct the deflection of the sub deflector such as gain, rotation, offset, and trapezoidal component. (3) Arbitrarily determine the scan start point. (4) The number of scans cannot be determined arbitrarily, (5) The scan distance cannot be determined arbitrarily, (6) The timing of scanning and exposure cannot be determined arbitrarily,
(7) One-way and two-way scanning cannot be performed arbitrarily, and (8) In order to change the deflection speed, it is necessary to change the elements of the circuit.

As a solution to the above problem, it is conceivable to give a digital value at the same speed as the exposure data rate, convert the digital value into an analog value, and perform deflection. However, a digital / digital converter that converts a digital value having sufficient accuracy into an analog value at the same rate as a desired high-speed exposure data rate.
Analog converters (hereinafter referred to as DACs) are not currently available, and it is difficult to implement analog circuits that can settle at this speed.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a charged particle beam exposure method and apparatus capable of giving a digital value at a speed lower than the exposure data rate and obtaining sufficient positional accuracy. With the goal.

[0013]

According to the charged particle beam exposure method and the exposure apparatus of the present invention, a stage 209 on which a sample to be exposed to a charged particle beam is continuously moved, and the beam is irradiated by a main deflector. Is further deflected by the sub deflector 112 substantially linearly at least once in an area smaller than the deflection area of the main deflector, and the beam is scanned substantially linearly on the sample, and each of the beams is scanned. A charged particle beam exposure method for exposing an IC pattern by controlling a change in exposure data whether the data reaches or does not reach the sample, wherein a digital value changing stepwise is converted into a digital / analog value for the sub deflector. And a digital / analog converter 10 for converting the digital value to an analog value and smoothing the analog value so as to change in a substantially linear manner. A conversion step, characterized by comprising more voltage applying step of applying the converted analog value as a voltage input sub deflector 112.

Further, in the method and the apparatus according to the present invention, the digital value is supplied by generating a clock for changing the digital value by dividing a clock for changing the exposure data. .

Further, the charged particle beam exposure method and the exposure apparatus of the present invention are arranged in a scanning direction of the charged particle beam and in a direction perpendicular to the scanning direction, and the beam is passed through a plurality of apertures for controlling the trajectory of the beam. Irradiating and changing the digital value in synchronization with a delay time until the beam output from the aperture irradiates an irradiated portion of the beam output from the aperture one row before in the scanning direction. It is characterized by.

Further, in the method and the apparatus according to the present invention, the supply of the digital value sets the value of the starting point of the scan in the digital / analog converter 10 for each scan, and changes during the scan. The digital value changed stepwise by adding a value to the value of the starting point is supplied to the digital / analog converter 10.

Further, according to the method and apparatus of the present invention, the analog waveform smoothed by the conversion step is corrected so as to compensate for the characteristics of the sub-deflector 112 so that a voltage is applied to the sub-deflector 112. It is characterized by being applied.

[0018]

According to the method and apparatus of the present invention, by sequentially providing deflection positions using digital values, positional accuracy in a scan is improved as compared with the case where a sawtooth waveform is provided using an analog circuit. , The position of the start point of the scan, the number of times, the distance, the timing of scanning and exposure, the selection of one-way and two-way scanning, etc. can be easily performed.

That is, according to the method and apparatus of the present invention, by using the waveform by filtering and dulling the waveform, the deflection and the correction operation in the subsequent correction can be operated at a speed lower than the exposure data rate. Become. Accordingly, digital values such as the starting point of the start of scanning and the subsequent deflection position are given at a speed lower than the exposure data rate, and the position accuracy is sufficiently compensated. By synchronizing the timing at which the exposure data changes on / off with the digital value for the deflector,
It is possible to speed up the positioning and arbitrarily determine the timing of scanning and exposure. Further, even when the correction value changes by applying the above correction after converting the digital value into the analog value, it becomes possible to expose a pattern that changes very smoothly.

[0020]

Next, a first embodiment of the present invention will be described with reference to FIG. The same reference numerals in the accompanying drawings referred to in the following description denote the same components.

FIG. 1 shows an exposure beam scanning circuit for converting an input digital value into an analog value and filtering and dulling the analog value according to an embodiment of the present invention. A voltage output DAC 10 which receives a digital value and outputs an analog value, an operational amplifier 14 connected in series to the voltage output DAC 10, a resistor Rs12 connected in series between the operational amplifier 14 and the voltage output DAC 10, ,
The filter is composed of a capacitor C16 and a resistor Rf18 connected in parallel to the operational amplifier 14.
By adjusting the value of the capacitor C16 of such a scan circuit, the output signal from the voltage output DAC 10 can be filtered and dulled.

In the circuit shown in FIG. 1, a voltage output DAC1 for the sub-deflector to which a digital value which changes stepwise is supplied.
The digital value is converted into an analog value by 0, and the converted analog value is changed to be substantially linear, and the analog value is smoothed.
The smoothed analog value is applied as a voltage input to the sub deflector.

FIG. 2 is a diagram showing an input waveform A and an output waveform B of the scan circuit shown in FIG. A sawtooth digital value is input to the voltage output DAC 10 as shown by a waveform A in FIG. 9 and the input waveform A changes to a substantially blunted substantially linear shape by adjusting the value of the capacitor C16 of the scan circuit. Thus, a waveform B is obtained. By changing the resistance Rs12 and the resistance Rf18 of the scan circuit shown in FIG. 2, the scan distance of the exposure beam can be adjusted. According to this method (for example, the accuracy is deteriorated compared to a method of setting using a digital value for each position), the error of the beam scanning position when using a nearly linear waveform is maximum. This corresponds to the size of one beam. Further, since the beam scanning position is guaranteed to coincide at least with the data rate of the digital value input to the voltage output DAC 10, the accuracy of this position is determined by generating a sawtooth wave using an analog circuit. It is much better than if you do.

The scan waveform B obtained by the scan circuit shown in FIG. 2 is substantially linear, but has a slightly convex bulge in detail. It is desirable to synchronize Further, by synchronizing the rate of change of the digital value with the delay time before irradiating the irradiated part of the beam emitted from the aperture one step before in the scanning direction shown in FIG. The accuracy of the relationship can be further improved.

As described above, in the first embodiment of the present invention, a digital / analog converter is used, and the output of the digital / analog converter is smoothed so as to make the output dull, thereby improving the positional accuracy of exposure. It becomes possible to do. Further, since the information on the scanning position, for example, the value of the position of the starting point can be supplied as a digital value, there is obtained an advantage that correction which cannot be easily realized by the conventional analog method can be performed.

FIG. 3 is a view for explaining an embodiment of the charged particle beam exposure apparatus of the present invention using a blanking aperture array. Referring to FIG. 3, the charged particle beam exposure apparatus generally includes an electron optical system 100 that forms and focuses a charged particle beam, and a control system 200 that controls the electron optical system 100. The electron optical system 100 includes an electron beam source 101 as a charged particle beam source, and the electron beam source 101 emits a charged particle beam, for example, an electron beam as a divergent charged particle beam along a predetermined optical axis O.

The electron beam formed by the electron beam source 101 passes through a beam shaping aperture 102a formed on an aperture plate 102 and is deformed. Aperture 10
2a is formed in alignment with the optical axis O, and shapes the incident electron beam into a rectangular cross-sectional shape.

The shaped electron beam is applied to an electron lens 103.
Is focused on the BAA mask 110 on which the blanking aperture array (BAA) is formed. that time,
The lens 103 projects the image of the rectangular aperture on the BAA mask 110. A number of fine apertures are formed on the BAA mask 110 corresponding to a number of exposure dots drawn on the semiconductor substrate, and each aperture is formed with an electrostatic deflector. The electrostatic deflector is controlled by a drive signal E and allows the electron beam to pass as it is in a non-excitation state, but deflects the passing electron beam in an excitation state, and as a result, the direction of the passing electron beam deviates from the optical axis O. as a result,
As described below, an exposure dot pattern corresponding to an aperture in a non-excited state is formed on a semiconductor substrate.

The electron beam passing through the BAA mask 110 is converted into electron lenses 104 and 105 forming a reduction optical system.
After passing through, the on / off of each minute beam is determined depending on whether or not it passes through the round aperture 113a formed on the round aperture plate 113. Then, the electron beam is focused on a semiconductor substrate 115 held on a movable stage 114 by electron lenses 106 and 107 forming another reduction optical system, and the BA
An image of the A mask 110 is formed on the substrate 115. Here, the electron lens 107 functions as an objective lens and includes correction coils 108 and 109 for focus correction and aberration correction, deflectors 111 and 112 for moving the focused electron beam on the substrate surface, and the like.

An electrostatic deflector 116 is formed between the lens 104 and the lens 105. By driving the deflector 116, the path of the electron beam is deviated from the optical axis O passing through the round aperture 113 a of the plate 114. You. As a result, the electron beam can be turned on / off at high speed on the semiconductor substrate. Further, the electron beam deflected by the excitation of the electrostatic deflector in the aperture on the BAA mask 110 described above also causes the round aperture 1
13a, it does not reach the semiconductor substrate. As a result, the exposure dot pattern can be controlled on the substrate 115.

The electron beam exposure apparatus shown in FIG. 3 uses a control system 200 for controlling the exposure operation. Control system 2
00 includes an external storage device 201 such as a magnetic disk device or a magnetic tape device that stores data relating to an element pattern of a semiconductor device to be drawn.

The data stored in the storage device 201 is a CP
The data is read out by the U 202 and decompressed by the data expanding circuit 203, whereby the data is converted into exposure dot data for turning on and off individual openings on the BAA mask 110 according to a desired exposure pattern. This electron beam exposure apparatus sets each exposure point on the substrate 115 N times (for example, N times) in order to enable fine correction of the exposure pattern.
= 8), and configured to perform overlapping exposure with independent exposure patterns. For this reason, the data development circuit 203 is composed of N circuits 203 _{1 to} 203 _{N.
1 to} 203 _N generate independent exposure dot patterns used in the N-times overlapping exposure based on the exposure data supplied from the CPU 202.

Individual circuits 203₁~ 203_NIs the C
Buffer holding exposure data supplied from PU 202
Stored in the buffer memory 203a and the previous buffer memory 203a.
Based on the exposure data obtained.
Data developing section 203b for generating cut pattern data
And the dot pattern developed by the data developing unit 203b.
And the canvas memory 203c for storing
The data expansion circuit 204 is a canvas memory
Corresponds to dot pattern data held in 203c
The output buffer circuit 204 supplies the output data. That is, the output
The buffer circuit 204 includes N data expansion circuits 203.₁~
203_NN holding circuits 204 corresponding to¹~ 204^N
And each holding circuit, eg, circuit 204¹Is
A total of 1 aligned in the X direction on the BAA mask 110
128 circuits 204 corresponding to the 28 openings₁~ 2
04₁₂₈Contains. At this time, the 128 circuits 2
04₁~ 204₁₂₈Each turn the opening on and off
1-bit data stored in the canvas memory 203c.
And keep it. Further, the circuit 204
¹~ 204^NCorresponds to the held 1-bit data
D / A converter 205 ₁~ 205_NConvert to analog signal with
After that, it is supplied to the BAA mask 110. As a result, B
Cooperates with openings aligned in the Y direction on AA mask 110
The electrostatic deflectors are sequentially driven.

The charged particle beam exposure apparatus of FIG.
A control signal is supplied from the CPU 202 based on a control program stored in the external storage device 201, the operation of the data expansion circuit 203 and the output buffer circuit 204, the transfer of data from the data expansion circuit 203 to the buffer circuit 204, and the D / BAA mask 11 by A converter 205
An exposure control device 206 for controlling the driving of the zero is provided. The exposure controller 206 further includes a main deflector control circuit 207 and a correction circuit 207a, and a sub deflector control circuit 2
The main deflector 111 and the sub-deflector 112 are controlled via the correction circuit 08 and the correction circuit 208 a to scan the substrate 115 with the electron beam.

The memory 211, which uses the main deflection amount from the main deflector control circuit 207 as an address, stores the corresponding correction operation coefficients GX, GY (gain), RX, RY (rotation), OX, OY (offset), HX, HY (trapezoid)
Is output to the correction circuit 208a. The correction circuit 208a corrects the sub-deflection amount using these correction operation coefficients, and
12 is output. The memory 211 outputs the corresponding correction operation coefficients DX and DY (distortion) to the correction circuit 207a using the main deflection amount as an address. The correction circuit 207 a corrects the main deflection amount with a correction operation coefficient and outputs the result to the main deflector 111. Further, the memory 211 stores the dynamic stigs SX and SY and the dynamic focus F corresponding to the main deflection amount, and the correction circuit 207a reads out the SX, SY and F corresponding to the main deflection amount and reads the correction coil 109 and the focus. The correction coil 108 is driven.

Further, the apparatus shown in FIG. 3 is provided with a refocus control circuit 203e for correcting the spread of the beam due to the Coulomb repulsion generated when the electron beam is focused, and the refocus control circuit 203e performs refocus. At the same time, the refocusing data is stored in the refocus data storage unit 215 and the refocus coil of the electronic lens 106 is driven according to the data stored in the refocus data storage unit 215 at the time of exposure. And adjust the strength appropriately.

Next, the configuration of the BAA mask 110 will be briefly described with reference to FIG.

Referring to FIG. 4, in a typical example, BA
On the A mask 110, 128 openings in the X direction and 8 openings in the Y direction are provided in a staggered pattern. A01 and A02, B01 and B02, C01 and C02, D01 and D02 in the Y direction form a pair, respectively. Note that, in the drawing, the even-numbered rows in the X direction of the houndstooth check cannot be formed at the same locations as the odd-numbered rows, and are provided at shifted locations. Here, the openings in which the electrodes are provided on the opposite sides on both sides form pixels. One electrode of the pixel of this aperture is kept at a constant potential, and the other electrode is externally controlled to be in a state of a certain potential and the above-mentioned constant potential, so that the aperture is irradiated and passes through the opening. The trajectory of the moving electron beam is controlled. Depending on whether the electron beam passing through the opening passes through the opening of the round aperture located further inside the optical column, each minute beam reaches the sample (the beam is turned on) or does not reach (the beam is turned on). Is off). Further, by controlling the voltage applied to each electrode of the BAA in synchronization with the deflection, the microbeams that have reached the sample are collected and the pattern is exposed on the sample (hereinafter, such an exposure method is referred to as a multi-beam method). (Called charged particle beam exposure).

In FIG. 4, a group of openings (indicated by dotted lines in FIG. 4) which are shifted by a half pitch in the X or Y direction, for example, openings A01 and A02, B01 and B02, C01 and C
02, D01 and D02 form opening groups A, B, C and D, respectively. Further, in each of the opening groups, data delayed by a predetermined time of data given to the preceding opening is given to the following opening. That is, for example, the delayed data of the data given to the opening A01 is given to the opening A02. As a result, the BAA mask 110 forms an electron beam group including a plurality of electron beam elements arranged in a matrix corresponding to each opening group, and each electron beam element is typically formed on a substrate 115 by a cell. Exposure dots having a size of 0.08 μm × 0.08 μm, which is the maximum size of the stripe, are exposed. At this time, a maximum of 8 × 128 exposure dots are simultaneously exposed on the substrate 115.

The electron beam elements constituting the electron beam group are scanned in the Y direction in the figure by the deflector 112, and each point on the substrate has a maximum of 8 exposure dots corresponding to each of the opening groups A to D. Exposure is repeated twice. More specifically, on the substrate 115, A02, B01, B02, C01, and C02 overlap with the exposure dot row exposed corresponding to the opening row A01.
Exposure is performed at positions shifted by 1/2 pitch from 02, D01, and D02. However, the exposure dot rows shifted by one pitch in the X direction and three pitches in the Y direction interpolate with each other to form a single exposure dot row aligned in the X direction. Thus, by forming the opening rows in each opening group so as to be shifted from each other by one pitch, the Coulomb interaction generated when the electron beam elements shaped by the BAA mask 110 are too close to each other is minimized. This has the advantage that the data at the close position is output with a shift. When such Coulomb interaction occurs,
As described above, the electron beam elements repel each other, and the effective focal length of the electron lens becomes longer.

In the BAA mask 110 shown in FIG. 4, for example, the opening forming the opening group A and the opening forming the adjacent opening group B are shifted by ピ ッ チ pitch in the X direction. A similar relationship holds for the opening groups A, B, C, and D. That is, generally, in an exposure mask having an opening group of N columns, an opening in one opening group and a corresponding opening in an opening group adjacent to the opening group are arranged such that M is N It is shifted by M / N pitch (M <N) as an arbitrary smaller integer. When the group of apertures is divided into four groups, A, B, C and D, the arrangement where the beam is exposed is:---------------------- -----------------------------------------------------

BAA having such M / N pitch shift
In the case of performing exposure using a mask, the same exposure data is most simply stored in the opening rows A01, A02, B01, B02, C01, and C.
02, D01, and D02, exposure dots are repeatedly exposed at a desired exposure amount, and a desired exposure pattern is exposed. On the other hand, in the BAA mask 110, it is possible to very finely correct the exposure pattern by changing the exposure data in each opening group. For this reason, the BAA mask 110 shown in FIG. 4 is extremely useful for correcting a so-called proximity effect in which an electron beam is reflected or scattered by a substrate to cause extra exposure. FIG.
By using the BAA mask 110, the electron beam scanning in the Y direction can be simultaneously performed at different positions in the Y direction on the substrate 115 corresponding to the respective opening rows A _{1 to} D ₂ , Proximity effects can be efficiently corrected.

FIG. 5 is composed of an exposure control section 206, a sub-differential scanning section 208, and a sub-differential correction section 208a.
FIG. 3 is a schematic diagram of a circuit that supplies an exposure signal for performing drive control of an AA mask. The first is supplied with an exposure data clock control signal for validating the reference clock and the exposure data clock.
ON / OFF gate 20 outputs an exposure data clock. The second on / off gate to which the reference clock divided by the frequency divider 22 and the scan clock control signal indicating the scan interval are supplied outputs a scan clock. The exposure data clock is supplied to the BAA data output unit, and the scan clock is input to the load counter 26 supplied with the initial value of the scan control data from the scan initial value register 28, and the initial value is supplied from the load counter 26. Are output in accordance with the scan clock. Here, by setting the scan clock to be slower than the exposure data clock, for example, by setting the exposure data clock to 400 MHz and the scan clock to 100 MHz, the digital value can be changed later than the change in the exposure data. The value increased or decreased by the load counter 26 is input to a digital-to-analog converter (DAC) 10 and converted into an analog value. This analog data is shown in FIG.
Are filtered by the smoothing and amplifying filter 32 as shown in (1), corrected by the correction unit 34 based on the analog value, and input to the sub deflector.

In this circuit, a scan initial value is set in the scan initial value register 28 and a clock is supplied to obtain a scan control signal for the sub deflector. Here, the scan clock input to the load-capable counter 26 capable of loading data uses the same frequency as the exposure data clock or a frequency lower than the frequency of the exposure data clock.
Furthermore, the timing of the start and end of the scan clock,
The start and end timings of the exposure data clock are separately controlled.

FIG. 6 is a timing chart of signals in the circuit shown in FIG. 5 described above. The scan clock control signal supplied to the exposure control unit 206 and the exposure control unit 20
6 and the scan clock output from the exposure control unit 20
6 shows an exposure data clock control signal supplied to an exposure control unit 6 and an exposure data clock output from the exposure control unit 206.

FIG. 7 is a time chart showing the time relationship between exposure and scanning. According to the method of the present invention for performing scan positioning using the DAC 10 and generating a scan waveform between two positioned adjacent points by dulling (smoothing) the waveform between the two points, an output waveform is obtained. Has a delay with respect to the value of the input data as shown in FIG.
That is, a certain period of time is required from the start of scanning until the linearity of the scan waveform is improved. Therefore, immediately after setting the value of the starting point in the voltage output DAC and starting the scan, and after setting the next starting point, the output waveform slightly deviates from the linear waveform. Here, by the circuit shown in FIG. 5, the time at which scanning is performed and the time at which exposure is performed can be controlled separately, so that exposure is performed only at a portion where the waveform of the deflector is stable. For example, the position accuracy of the exposure can be improved by starting the scan before the exposure, starting the exposure after the scan waveform is stabilized, and terminating the exposure before the end of the scan.

FIG. 8 is a diagram showing a beam arrangement on a sample obtained by exposure using the BAA arrangement shown in FIG. In FIG. 2, beam 2 and beam 2 are on the same column, so that the same position as the position irradiated by beam 1 is repeatedly exposed after a lapse of a certain time from the irradiation of beam 1. The time interval from the irradiation of the beam 1 to the irradiation of the beam 2, that is, the delay time is represented by t _d . As shown in FIG. 2, the digital input waveform A is dulled by the DAC 10 and the smoothing / amplifying unit 32, and a waveform B that is linear but may slightly draw a curve is obtained. It is guaranteed that the deviation of the waveform B from the straight line disappears when a new digital value is given to the DAC 10 and the digital-to-analog conversion is performed. On the other hand, between the time when the digital-to-analog conversion is performed and the time when the next digital-to-analog conversion is performed, the waveform that has been blunted by the smoothing and amplifying unit 32 is the time from the digital-to-analog conversion (hereinafter, phase ). That is, the deviation from the straight line changes according to the conversion cycle of the digital-to-analog conversion.

[0048] Figure 9 is a diagram showing two kinds of digital input waveform, varying the period of the digital values, a waveform 1 that matches the delay time t _d of the two beams, and two other waveform Is shown. As the waveform 1, if the period of the change in the digital value matches the delay time t _d, since a plurality of beams the phase of the superposed exposure coincides misalignment error of the beam is reduced. If the input waveform is an integral submultiple of the delay time t _d is similarly positional displacement error is reduced.
Furthermore, there is an advantage that also suppressed positional deviation error when the input waveform is an integer multiple of the delay time t _d. As described above, by synchronizing the change in the digital value with the delay time, it becomes possible to improve the positioning accuracy of exposure.

In the exposure method according to one embodiment of the present invention using the circuit shown in FIG. 5, the step of setting the value of the starting point in the scan initial value register 28 and the step of setting the value in the scan initial value register 28 at the start of scanning are performed. The value of the starting point is loaded into the loaded counter 26, and this is set as the starting point of the scan,
Adding a predetermined value to the value of the starting point, counting up the value, and inputting this value to the DAC 10;
The steps include a step of inputting a waveform of an analog value output by 10 to a smoothing circuit for dulling the waveform and dulling the waveform, and a step of correcting the dulled output signal and applying the corrected output signal to a sub deflector.

According to one embodiment of the present invention, the step of setting the value of the starting point further includes the step of fixing the value to be counted up in one positive or negative direction, or the step of setting the value to be counted up to positive or negative. It consists of alternating steps.

FIG. 10 is a diagram showing the scanning direction of the actual exposure of the sub deflector. As shown in (a) of the figure, the value of the starting point is set to a value on one side of the sub-deflector deflection area, and one of the positive and negative values is added to this value, so that scanning in one direction can be performed. Done. On the other hand, FIG.
As shown in, by setting the value of the starting point alternately to the value on both sides of the sub-deflector deflection area, and adding a positive or negative value to this,
A bidirectional scan is performed.

Therefore, according to the apparatus using the digital / analog converter according to the embodiment of the present invention, generally, the scanning having the characteristic that the one-way scanning is superior in accuracy and the bidirectional scanning is faster in processing speed. , It is possible to switch between one-way scanning and two-way scanning.

FIG. 11 is a diagram for explaining a scanning method adapted to a predetermined pattern. When the value of the starting point is set to a predetermined value and the number of steps of the digital value input to the DAC is increased or decreased, a predetermined value is obtained. Only the part corresponding to the pattern part is scanned. This eliminates the need to scan a portion having no pattern, thereby reducing the time required for scanning and shortening the exposure time.

The region exposed by scanning has a delay between the timing of inputting a digital value and the timing of beam deflection according to the digital value. It may deviate with a deviation, ie, an offset. In contrast, FIG.
As shown in FIG. 2, offset adjustment of the exposure area can be performed by adjusting the starting point. In the figure,
The value of the starting point is adjusted by a certain amount corresponding to the offset of the exposure area.

In a variable rectangular exposure apparatus that can move the position of a conventional rectangular exposure area that handles digital values, the deflection distortion of the sub deflector is calculated before converting the digital values into analog values. According to the present invention, however, according to the present invention, by performing a correction operation using an analog value, correction can be performed with a relatively simple circuit, and furthermore, a rounding error due to digitization that occurs when the correction result changes is reduced. An exposure pattern that does not occur and changes smoothly can be obtained.

In the exposure method and apparatus of the present invention, since the raster scan method is employed, the exposure is performed without setting the deflector. Therefore, extremely high speed is required for the correction calculation for each shot.
The value output from 10 is calculated in an analog manner. FIG.
FIG. 9 is a block diagram of an embodiment of a correction circuit 208 that performs correction calculation of a sub deflector. The correction circuit 208 includes a correction circuit pre-stage 64 that is supplied with a scan signal from the scan control circuit smoothing and amplification circuit 32 and changes according to the type of a wafer to be exposed, and a deflector paired with a stage of the exposure apparatus. The stage includes a stage for performing correction and a deflector correction unit 68. In this way, by adopting the separated configuration, it is only necessary to change the value of the preceding stage of the correction circuit when replacing the wafer. The correction circuit pre-stage unit 64 further includes a stage feedback unit 54 for correcting a stage shift from when the value of the main deflector is set, an eddy current correction unit (ECC) 56 for correcting eddy currents, and speed fluctuation. A speed correction unit 58 for correcting the position deviation, a refocus feedback correction unit 60 for correcting a positional deviation due to refocus, a main deflector settling feedback unit 62 for correcting the delay of settling of the main deflector, and the correction unit And an adder 66 for adding the correction amount from the adder and supplying it to the subsequent stage. By using the correction circuit 208, the correction operation can be performed, for example, by, for example,
This is performed by designating the amplification factor of the operational amplifier. This amplification factor can be changed by changing the magnitude of the resistance of the operational amplifier feedback unit, for example, by changing a value that can be digitally changed, changing the value of this amplification factor, and correcting Operations can be controlled.

[0057]

As described above, according to the present invention, a digital value is converted from digital to analog, and the converted value is filtered and dulled to perform a linear scan.
High-speed exposure can be performed using currently available DACs. Further, by giving an exposure position using a digital value, the degree of freedom of scanning, that is, the number of parameters that can be adjusted for scanning increases, so that the range of available scanning methods increases, and a high speed applied to conditions such as an exposure pattern. Exposure becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a scan control unit of a charged particle beam exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing input / output waveforms of a scan control unit of the charged particle beam exposure apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an overall configuration of a configuration example of a charged particle beam exposure apparatus according to the present invention.

FIG. 4 is a diagram showing a configuration of a BAA mask used in the exposure apparatus of FIG.

FIG. 5 is a diagram showing a configuration of an exposure control device and a sub differential scanning device of the exposure device of FIG.

FIG. 6 is a timing chart illustrating the operation of the exposure control device of FIG. 5;

FIG. 7 is a diagram illustrating timings of a scan time and an exposure time of a sub deflector of the exposure apparatus of FIG.

8 is a diagram showing an arrangement of beams to be exposed on a sample placed in the exposure apparatus of FIG.

9 is a diagram illustrating a relationship between a digital waveform input to a scan control unit of the exposure apparatus of FIG. 3 and a delay time between beams.

FIG. 10 is a diagram illustrating a scanning method in a sub deflector of the exposure apparatus of FIG.

FIG. 11 is a view for explaining a pattern-type scanning method in the sub deflector of the exposure apparatus of FIG. 3;

12 is a diagram illustrating offset correction of an exposure area by adjusting a starting point in a sub deflector of the exposure apparatus of FIG. 3;

13 is a diagram showing a configuration of a sub-deflector correction circuit of the exposure apparatus of FIG.

FIG. 14 is a diagram illustrating an exposure method using a blanking aperture array method.

[Explanation of symbols]

Reference Signs List 10 voltage output digital / analog converter 12, 18 resistor 14 amplifier 16 capacitor 20, 24 on / off gate 22 frequency divider 26 load counter 28 scan initial value register 32 smoothing and amplification filter 34 sub deflector correction circuit 54 stage feedback Unit 56 eddy current correction unit 58 speed correction unit 60 refocus feedback correction unit 62 main deflector settling feedback unit 64 correction circuit pre-stage 66 correction circuit addition unit 68 stage-to-deflector correction unit 100 charged particle beam exposure apparatus electron optical system 101 Electron beam source 102, 102a Beam shaping aperture 103, 104, 105, 106, 107 Electron lens 108 Focus correction coil 109 Sting correction coil 110 BAA mask 112 Sub-deflector 113 Wound aperture plate 113a round aperture 115 substrate 200 a charged particle beam exposure apparatus control system 201 external storage device 202 CPU 203,203 ₁ ~203 _N data expansion circuit 203a buffer memory 203b data developing unit 203c canvas memory 203e refocus circuit 204, 204 ¹ ２０４204 ^N , 204 ₁ ２０４204 ₁₂₈
BAA data storage and output circuit 205, 205 _{1 to} 205 _N BAA drive circuit 206 Exposure control circuit 207 Main deflection scan control circuit 207a Main deflection correction circuit 208 Sub deflection scan control circuit 208a Sub deflection correction circuit 209 Stage 210 Autoloader 211 Memory

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Junichi Kai 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Hiroshi Yasuda 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited ( 56) References JP-A-6-53129 (JP, A) JP-A-5-206016 (JP, A) JP-A-5-175108 (JP, A) JP-A-5-166707 (JP, A) JP-A-5-267135 (JP, A) JP-A-7-201701 (JP, A) JP-A-7-220993 (JP, A) JP-A-60-1828 (JP, A) JP-A-57-90858 (JP , A) JP-A-1-183819 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20

Claims (16)

(57) [Claims] 1. A stage (209) on which a sample to be exposed to a charged particle beam is mounted is continuously moved, the beam is deflected by a main deflector, and the main deflection is performed by a sub deflector (112). Scanning the beam substantially linearly at least once in a region smaller than the deflection region of the detector to scan the beam in a substantially linear manner on the sample, and exposing whether each of the beams reaches or does not reach the sample. A charged particle beam exposure method for controlling a change in data and exposing an IC pattern, comprising:
A supply step of supplying the analog value to the analog converter (10); a conversion step of converting the digital value into an analog value by the digital / analog converter (10) and smoothing the analog value so as to change substantially linearly. Applying a voltage to the sub-deflector (112) as a voltage input to the sub-deflector (112). 2. The method according to claim 1, further comprising: changing the digital value input to the digital / analog converter in synchronization with the control of the change of the exposure data. Item 7. A charged particle beam exposure method according to Item 1. 3. The charged particle beam exposure method according to claim 1, wherein said supplying step further comprises the step of: changing the digital value at a lower speed than the speed at which the exposure data changes. 4. The charged particle beam according to claim 3, wherein said supplying step further comprises: using one of frequency divisions of a clock for changing the exposure data as a clock for changing the digital value. Exposure method. 5. The charged particle beam exposure method according to claim 1, wherein the exposure is performed in a time shorter than a time required for scanning the beam on the sample in a substantially linear manner. 6. A method of irradiating a plurality of openings arranged in a scanning direction of the charged particle beam and a direction perpendicular to the scanning direction and controlling a trajectory of the beam with the beam; Changing the digital value in synchronization with a delay time until the beam irradiates an irradiated portion of the beam output from the aperture one line before in the scanning direction. The charged particle beam exposure method according to claim 1. 7. A step of setting a value of a starting point of a scan in the digital / analog converter (10) for each scan; and a positive or negative direction during the scan. And supplying the digital value changed stepwise to the digital / analog converter (10) by adding a value that changes to the starting point value to the digital / analog converter (10). 2. The charged particle beam exposure method according to claim 1, wherein scanning is performed in one direction. 8. The method of claim 1, further comprising: setting a value of a starting point of the scan in the digital / analog converter (10) for each scan; and alternately in the positive and negative directions during the scan. Adding a changing value to the value of the starting point and supplying the digital value changed bidirectionally to the digital / analog converter (10). 2. The charged particle beam exposure method according to claim 1, wherein the scanning is performed in a scanning direction. 9. The digital / analog converter (10)
9. The charged particle beam according to claim 7, wherein the number of times that a digital value given to the scan changes during one scan is controlled for each scan, and the moving distance of the beam during the scan is adjusted. Exposure method. 10. The charging method according to claim 7, wherein the supplying step further comprises the step of: setting a value of the starting point so as to correct a positional deviation of an area to be exposed on the sample. Particle beam exposure method. 11. The voltage applying step corrects the analog waveform smoothed by the conversion step so as to compensate for characteristics of the sub deflector (112), and applies a voltage to the sub deflector (112). The charged particle beam exposure method according to claim 1, further comprising a step of applying. 12. A stage (209) on which a sample to be exposed to a charged particle beam is to be continuously moved, the beam is deflected by a main deflector, and the main deflection is performed by a sub deflector (112). Scanning the beam substantially linearly at least once in a region smaller than the deflection region of the detector to scan the beam in a substantially linear manner on the sample, and exposing whether each of the beams reaches or does not reach the sample. What is claimed is: 1. A charged particle beam exposure apparatus for controlling a change in data and exposing an IC pattern, comprising the steps of:
Supply means (26, 2) for supplying the analog converter (10)
8) converting means (32) for converting the digital value into an analog value by the digital / analog converter (10) and smoothing the analog value so as to change in a substantially linear manner; And a voltage applying means for applying a value as a voltage input to the sub deflector (112). 13. The supply means (26, 28) divides a clock for changing the exposure data and generates a clock for changing the digital value.
13. The charged particle beam exposure apparatus according to claim 12, comprising: 14. The charged particle beam is irradiated in a scanning direction of the charged particle beam and a plurality of openings arranged in a direction perpendicular to the scanning direction and controlling a trajectory of the beam, and the supply means (26, 28) includes: Means for changing the digital value in synchronization with a delay time until the beam output from the aperture irradiates an irradiated portion of the beam output from the aperture one row before in the scanning direction. 13. The charged particle beam exposure apparatus according to claim 12, wherein: 15. A supply means (26, 28) for setting a value of a starting point of scanning in the digital / analog converter (10) for each scanning, and a value changing during the scanning. 13. A charged particle beam exposure apparatus according to claim 12, further comprising means for adding the digital value changed stepwise by adding to the value of the starting point to the digital / analog converter (10). . 16. The sub-deflector (112) corrects the analog waveform smoothed by the conversion means so as to compensate for the characteristics of the sub-deflector (112) and applies a voltage to the sub-deflector (112). 13. The charged particle beam exposure apparatus according to claim 12, further comprising means for applying.