JP3065472B2 - Adjustment method of rectangular beam size and positioning in charged particle beam writing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam drawing apparatus in which an electron beam or an ion beam is shaped into a rectangular section and the beam having the rectangular section is projected onto a material to be drawn. Also, the present invention relates to a method for adjusting the positioning of a rectangular beam.

[0002]

2. Description of the Related Art As an electron beam lithography apparatus, an apparatus of a type in which a cross section of an electron beam is variably drawn is widely used. In this apparatus, an electron beam is irradiated on a first aperture, and an aperture image of the first aperture is formed on a second aperture. Then, the projection position of the aperture image of the first aperture on the second aperture is changed by a deflector arranged between the first and second apertures, so that an electron having a rectangular cross section of an arbitrary area is obtained. The beam is shaped.

In such an electron beam writing system,
Measuring the size of a beam having a rectangular cross section and adjusting the size as specified is important for writing accuracy. The measurement of the beam size will be described with reference to FIGS. In FIG. 1, reference numeral 1 denotes a knife edge, and the knife edge 1 has a rectangular opening 2. The knife edge 1 is placed at a position where a material to be drawn is arranged, and a Faraday cup 3 for detecting an electron beam passing through the opening 1 is provided below the knife edge 1. The signal detected by the Faraday cup 3 is supplied to a step counter 7 via a first differentiating circuit 4, a second differentiating circuit 5, and a third differentiating circuit 6.

With such a configuration, a rectangular shaped electron beam is applied to the opening 2 of the knife edge 1. Thereafter, when the electron beam is scanned in the direction of arrow X in the figure, the signal shown in FIG. That is, at first, all of the electron beam passes through the aperture 2, and
Full beam current is detected. Thereafter, by scanning the beam, the beam is gradually cut by the knife edge 1 and the detected beam current is reduced accordingly, and finally all of the beam is cut by the knife edge 1 and The signal goes to zero.

[0005] The detection signal of the Faraday cup 3 is differentiated by a first differentiating circuit 4 to obtain a signal shown in FIG. The signal shown in FIG. 2B is differentiated by the differentiating circuit 5 to become the signal shown in FIG. 2C, and further differentiated by the differentiating circuit 6 to obtain the signal shown in FIG. 2D. This figure 2
Based on the signal (d), the trigger signal (low level) shown in FIG. 2E is obtained. During this trigger signal, the step counter 7 counts clock pulses to obtain a signal corresponding to the beam size. ing. That is, the scanning of the electron beam is performed digitally one step at a time by a clock pulse, and the scanning width of one step of the scanning is predetermined. Therefore, the beam size can be measured by counting the clock pulses included between the trigger signals. (2
Beam scanning is performed on a member (for example, a mark) having a linear end formed of a material having a different generation rate of secondary electrons and reflected electrons, and a signal detected by the scanning has a waveform similar to the one-time differential signal. Therefore, in this case, it is only necessary to differentiate the detection signal twice.

An error between the prescribed beam size and the actual size is obtained based on the measured value of the beam size, and the size of the rectangular beam is adjusted based on the error. The beam size adjustment in the X direction can be performed by the above steps. For the beam size in the Y direction, the beam is scanned in the direction of arrow Y in FIG. 1 and the beam size is adjusted in the same steps as described above. Is performed.

[0007]

The beam size measuring method described above has the following problems. When a signal delay is caused by each differentiating circuit, the trigger signal is delayed by an amount corresponding to the delay.
At this time, the delay on the positive side and the delay on the negative side are slightly different. Therefore, the width of the trigger signal is different from the case where there is no delay due to the differentiating circuit.

When a change in the magnitude of a signal occurs due to each differentiating circuit, for example, when the level becomes higher, each differentiating signal is delayed, causing such a problem as follows. When the trigger level at the time of generating the trigger signal changes, the width of the trigger signal differs from that when the trigger level does not change.

[0009] Since there are the above-mentioned things,
Even if the actual beam size is different from the measured beam size and the measured beam size becomes a predetermined value, for example, the pattern is drawn after adjusting the beam size with a shaping deflector, Accuracy decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the size and the size of a rectangular beam which can accurately and simply adjust the size of a rectangular beam and a deflector for positioning a rectangular beam. The purpose is to realize a positioning adjustment method.

[0011]

According to a first aspect of the present invention, there is provided a charged particle beam writing apparatus for adjusting the size of a rectangular beam, comprising: forming an aperture image of a first aperture on a second aperture; In a charged particle beam drawing apparatus configured to project a charged particle beam having a rectangular cross section transmitted through an opening of an aperture 2 onto a material to be drawn, a unit rectangular beam formed into a unit size is substantially cut across a linear boundary portion. The scanning is performed twice, the beam affected by the boundary portion is detected, and two types of signals obtained by differentiating the detection signal are stored in a memory. The beam is shifted and stored by the unit size of the beam, and the size of the shaped rectangular beam is adjusted based on the superimposed signal of the two signals stored in the memory. It is characterized by a door.

In the charged particle beam drawing apparatus according to the second aspect of the present invention, a method for adjusting the positioning of a rectangular beam is described in the first aspect.
Forming an aperture image of the aperture on the second aperture,
In a charged particle beam drawing apparatus configured to project a charged particle beam having a rectangular cross section transmitted through an opening of a second aperture onto a material to be drawn, a linear boundary portion is arranged at one end of a drawing field, The first scan is performed on the unit rectangular beam shaped to the unit size across the linear boundary, the beam affected by the boundary is detected, and the detected signal is differentiated. The boundary is then mechanically moved by the drawing field, and after the movement, a second scan is performed at the boundary to detect a beam affected by the boundary, After differentiating the detection signal, the signal is stored in the memory in accordance with the second scan, and when the differential signal based on the first and second scans is stored in the memory, each signal is stored in a unit rectangle. Is stored by shifting the unit size of the over-time, based on the superimposition signal of the two signals stored in memory, it is characterized in that to perform the adjustment of the positioning deflector.

[0013]

According to the present invention, a rectangular beam is scanned substantially twice across a linear boundary such as a knife edge, and a signal obtained based on each scan is differentiated once to obtain a differentiated signal. The size of the rectangular beam is adjusted and the positioning deflector for the rectangular beam is adjusted based on a signal obtained by superimposing the two types of differential signals stored in the same memory.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 3 shows an example of a variable area type electron beam writing apparatus for carrying out the present invention. An electron gun 11 generates an electron beam EB. The electron beam EB generated from the electron gun 11 is
The light is irradiated onto the forming aperture 13. The aperture image of the first shaping aperture is formed on the second shaping aperture 16 by the shaping lens 14, and the position of the image can be changed by the shaping deflector 15. The image formed by the second forming aperture 16 is irradiated onto the drawing material 20 via the reduction lens 17 and the objective lens 18. The irradiation position on the drawing material 20 can be changed by the positioning deflector 19.

A computer 21 transfers the pattern data from a pattern data memory 22 to a data transfer circuit 23. Data transfer circuit 2
3 is supplied to the shot divider 24 to be divided into shots. A signal corresponding to the drawing data from the shot divider 24 performs a deflection control circuit 25 for controlling the shaping deflector 15, a control circuit 26 for controlling the positioning deflector 19, and blanking of an electron beam generated from the electron gun 11. It is supplied to a blanking control circuit 28 for controlling the blanking electrode 27.

Further, the computer 21 controls a drive mechanism 30 of a stage 29 on which the material 20 is placed for moving the material in each field. Note that a beam detection structure 31 composed of a combination of a knife edge and a Faraday cup is provided on a portion of the stage 29 where the material 20 is not placed. FIG. 4 shows a more specific configuration of the beam detection structure 31 and an example of a detection signal processing circuit of the beam detection structure 31.

In FIG. 4, the beam detecting structure 31 includes a knife edge 32 and a Faraday cup 33. The detection signal of the Faraday cup 33 is supplied to a differentiating circuit 34 to be differentiated, and then supplied to the computer 21 via an AD converter 35. Computer 21
Writes the supplied signal into the waveform memory 36. The operation of such a configuration will now be described.

First, a normal drawing operation will be described.
The pattern data stored in the pattern data memory 22 is sequentially read out and supplied to the shot divider 24 via the data transfer circuit 23. Based on the data divided by the shot divider 24, the deflection control circuit 25 controls the shaping deflector 15, and the control circuit 26 controls the positioning deflector 1
9 is controlled.

As a result, the cross section of the electron beam is formed into a unit pattern shape by the shaping deflector 15 based on each divided pattern data, and the unit patterns are sequentially shot on a material to form a desired shape pattern. Drawing is performed. At this time, the blanking control circuit 2
In response to a blanking signal from 8 to the blanking electrode 27, blanking of the electron beam is executed in synchronization with the shot of the electron beam on the material 20.

Next, a method for adjusting the size of the rectangular beam irradiated on the material 20 will be described. When adjusting the rectangular beam size, first, the drive mechanism 30 is driven by an instruction from the computer 21 to move the stage 29. Then, the beam detection structure 31 combining the knife edge and the Faraday cup on the stage 29 is positioned directly below the optical axis of the electron beam.

Thereafter, similarly to the conventional method, a rectangular shaped electron beam is applied to the opening 37 of the knife edge 32. Thereafter, the first scanning of the electron beam is performed in the direction of arrow X in the figure. The signal shown in FIG. 5A is obtained from the Faraday cup 33 by this scanning. That is, first, all of the electron beams pass through the opening 37, and the entire beam current is detected. Thereafter, by scanning the beam, the beam will be gradually cut by the knife edge 32, and the detected beam current will be reduced accordingly, and finally all of the beam will be cut by the knife edge 32 and the detection The signal goes to zero.

The signal detected by the Faraday cup 33 is differentiated by a differentiating circuit 34 to obtain a signal shown in FIG. This differential signal is converted into a digital signal by the AD converter 35,
1 is supplied. The computer 21 stores the supplied signal in the memory 36. Next, the second scanning of the electron beam is performed in the direction of arrow X in the figure. In the second scanning, the starting point of the scanning is shifted from the time of the first scanning by the size of the unit rectangular beam in the X direction. Do it. By this scanning, the Faraday cup 33 is used as in FIG.
The signal of (a) is obtained.

The detection signal of the Faraday cup based on the second scanning is also differentiated by the differentiating circuit 34.
A signal similar to the signal (b) is obtained. This differential signal is supplied to the computer 21 after being converted into a digital signal by the AD converter 35. The computer 21 stores the supplied signal in the memory 36. The memory 36 stores signals based on the first electron beam scanning and the second electron beam scanning.
FIG. 5 (c) shows the two signals stored in the memory 36, S ₁ is the signal based on a scan of the first round, S ₂
Is a signal based on the second scan.

As described above, in the first and second electron beam scans, since the starting point of the scan is shifted by the size of the rectangular beam, it is assumed that the actual rectangular beam size is as specified. The joint between the signals obtained by superimposing the two signals is flat. However, if the size of the rectangular beam deviates from the prescribed length, the joint of the signal may be concave or protrude. The signal in FIG. 5D is a superimposed signal of two signals, and in this case, the joint of the signals (the portion surrounded by a circle) is concave.

The case of the depression is a case where the size of the unit rectangular beam is shorter than the specified length. FIG. 3 shows that the concave portion is flattened by the computer 21.
And the signal supplied to the shaping deflector 15 is adjusted so that the rectangular electron beam formed by the first shaping aperture and the second shaping aperture has a prescribed size. In the case of FIG. 5D, the adjustment is performed so that the size of the unit rectangular beam is increased.

In the case of FIG. 5D, the seam of the superimposed signal is concave, but when the seam protrudes, the size of the unit rectangular beam is longer than the specified length. The size of the beam is adjusted to be small. The adjustment of the actual size of the unit rectangular beam may be performed, for example, while an operator looks at the superposition signal shown in FIG. 5D displayed on a cathode ray tube or the like. May be automatically determined based on the size, and the size may be automatically adjusted.

The above-described adjustment of the size of the rectangular beam is performed in order to perform the adjustment from the shape of the irradiation amount of the beam equivalent to that in the case of actually performing the drawing operation, as compared with the conventional method in which the beam size is actually measured. Thus, a result that is in good agreement with the drawing result can be obtained. Therefore, it is not necessary to measure the beam size and adjust the beam size as in the related art, and then perform drawing, and then perform fine adjustment of the beam size again based on the result. .

In the above embodiment, two electron beam scans are performed, and the starting point for each scan is shifted by the size of the unit rectangular beam. Other than this method, 2
Scans are performed from the same starting point, and two kinds of signals are stored in the memory 3.
6, the two signals may be stored at different positions on the memory 36 by the size of the unit rectangular beam. The electron beam may be scanned once, and a single signal may be stored on the memory 36 while being shifted by the size of the unit rectangular beam. Further, in order to improve the signal-to-noise ratio of the signal, it is effective to perform each scan a plurality of times and integrate the detection signals.

FIG. 6 is a diagram for explaining an embodiment in which the present invention is used for adjusting the positioning of a rectangular beam. An area F indicated by a square in the drawing indicates a drawing field. This field does not depend on the mechanical movement of the material to be drawn,
This is an area where writing is performed only by deflection of the electron beam.
In a normal drawing operation, a desired drawing is performed by deflecting an electron beam in a unit of a field, and when drawing of the field is completed, the material to be drawn is mechanically moved by the length of the field, and then drawing of an adjacent field is performed. Do.

Such a drawing method is called a step-and-repeat method. In this method, however, the accuracy of connection of drawing patterns between adjacent fields is very important. Factors that degrade the accuracy of this connection are that the beam size of the rectangular beam is not as specified and that the positioning accuracy of the rectangular beam by the positioning deflector 19 (the accuracy of the amplitude of the deflector).

In order to improve the positioning accuracy, according to the present invention, after the beam size is adjusted, first, one end position P of the drawing field F shown in FIG.
Place a knife edge on ₁ . In this state, the rectangular electron beam is deflected and scanned linearly across the knife edge. According to this scanning, a signal similar to that shown in FIG. 5A is obtained, and the signal is differentiated to obtain the signal shown in FIG.
The signal of (b) is obtained. This differentiated signal is stored in the waveform memory 36. The signal stored in the waveform memory 37 has a waveform W ₁ of FIG. 7 (a).

Next, the knife edge portion is mechanically moved in the X direction by the length of one side of the drawing field. In this embodiment, the drive circuit 30 is controlled by the computer 21 to move the stage 29 in the embodiment shown in FIG. Stage 2
The movement of 9 is monitored by a laser interferometer, not shown, and the movement distance is accurately controlled. As a result, the other knife edge to the end position P ₂ of the drawing fields F of Figure 6 is placed. In this state, the rectangular electron beam is deflected and scanned linearly across the knife edge. A signal similar to that shown in FIG. 5A is obtained according to this scanning, and a signal shown in FIG. 5B is obtained by differentiating the signal. In this scanning, the starting point of the scanning with respect to the edge of the knife edge is shifted by the size of the unit rectangular beam. The differentiated signal obtained as a result is stored in the waveform memory 36, and this signal is represented by the waveform W _{2 in} FIG.
Becomes

As described above, the stage 29 is moved by the drawing field F, the rectangular beam is scanned across the knife edge before and after the stage 29, the detection signal based on each scan is differentiated once, and the differentiated signal is superimposed on the memory. When the stored signal is read out and displayed in FIG.
The signal of (b) is obtained. The control circuit 26 is controlled from the computer 21 so that the dent or protrusion at the center of the signal shown in FIG.
If the amplitude of the deflection signal supplied to the positioning deflector 19 is adjusted, it is possible to connect adjacent fields with high accuracy. The end P of the field F shown in FIG.
By performing the above operation also in ₃ and P ₄ Prefecture, it is possible to perform the amplitude adjustment of the Y-direction deflection signal.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, although a variable area type electron beam writing apparatus has been described as an example, the present invention can be applied to an ion beam writing apparatus. In addition, a knife edge was provided, and a beam passing through the opening of the knife edge was detected by a Faraday cup, but a member having a linear end formed of a material having a different generation rate of secondary electrons and reflected electrons was arranged. Alternatively, the beam may be scanned across the linear end to detect secondary electrons and reflected electrons generated by the scanning.

[0035]

As described above, according to the present invention, a rectangular beam is scanned substantially twice across a linear boundary such as a knife edge, and a signal obtained based on each scan is obtained. Differentiation is performed once, the differentiated signal is stored in the same memory, and the size of the rectangular beam is adjusted and the positioning deflector for the rectangular beam is adjusted based on the superimposed signal of the two stored differential signals. Therefore, the adjustment can be performed while measuring the signal in the same state as the irradiation dose distribution of the beam when the image is actually drawn, and the beam size and the positioning deflector can be adjusted with high accuracy. In the present invention, fine adjustment after viewing the drawing result becomes unnecessary.

Further, since the beam can be adjusted by performing only one differentiation of the signal detected in accordance with the scanning of the beam, the signal is delayed or dull due to the signal processing as compared with the related art in which the differentiation is performed a plurality of times. , The adjustment can be performed with a signal closer to the actual one. Further, even if the level of the detection signal changes, the beam size is adjusted using the distribution waveform of the beam, so that the influence of the change in the signal level is small.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional configuration for measuring the size of a rectangular beam.

FIG. 2 is a diagram showing a signal waveform according to the configuration of FIG. 1;

FIG. 3 shows an example of an electron beam writing system for implementing the method according to the invention.

FIG. 4 is a diagram showing an example of a processing path of a detection signal for performing the method of the present invention.

FIG. 5 is a diagram showing signal waveforms for explaining the operation of the embodiment of the present invention.

FIG. 6 is a diagram showing a drawing field and a scanning position of a rectangular beam in one embodiment of the present invention.

FIG. 7 is a diagram showing signal waveforms for explaining the operation of the embodiment in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Electron gun 12 Illumination lens 13, 16 Molding aperture 14 Molding lens 15, 19 Deflector 17 Reduction lens 18 Objective lens 20 Material 21 Computer 22 Memory 23 Data transfer circuit 24 Shot splitter 25 Molding deflector control circuit 26 Positioning deflector control Circuit 27 Blanking electrode 28 Blanking control circuit 29 Stage 30 Drive mechanism 31 Beam detection structure 32 Knife edge 33 Faraday cup 34 Differentiator 35 A / D converter 36 Waveform memory

Claims (5)

(57) [Claims] An image of an aperture of a first aperture is formed on a second aperture, and a charged particle beam having a rectangular cross section transmitted through the aperture of the second aperture is projected on a material to be drawn. In a particle beam writing apparatus, a unit rectangular beam shaped into a unit size is scanned twice substantially across a linear boundary, a beam affected by the boundary is detected, and the detection signal is differentiated. The two kinds of signals are stored in a memory, and at the time of this storage, the signals are mutually shifted by a unit size of a unit rectangular beam and stored, and based on a superimposed signal of the two kinds of signals stored in the memory. And adjusting the size of the shaped rectangular beam in the charged particle beam drawing apparatus. 2. An image forming apparatus, wherein an aperture image of a first aperture is formed on a second aperture, and a charged particle beam having a rectangular cross section transmitted through the aperture of the second aperture is projected on a material to be drawn. In the particle beam writing apparatus, a linear boundary is disposed at one end of the writing field, and a first scan is performed with a unit rectangular beam formed into a unit size across the linear boundary. After detecting the beam affected by the section and differentiating the detection signal, the signal is stored in a memory according to the scanning position, and then the boundary is mechanically moved by the drawing field, and after the movement, A second scan is performed at the boundary, a beam affected by the boundary is detected, the detection signal is differentiated, and then stored in a memory according to the second scan, and the first and second scans are performed. The first run When storing the differentiated signal in the memory based on the inspection, the signals are shifted and stored by the unit size of the unit rectangular beam, and based on the superimposed signal of the two signals stored in the memory, the positioning deflector is used. A method for adjusting the positioning of a rectangular beam in a charged particle beam drawing apparatus for adjusting the position of a beam. 3. The adjustment method according to claim 1, wherein the first and second scans of the rectangular beam are performed, and the starting point of each scan is shifted by a unit size of the unit rectangular beam. 4. The first and second rectangular beam scans are performed, the second rectangular beam scan is started from the same starting point as the first rectangular beam scan, and the second rectangular beam scan is performed. 3. The adjustment method according to claim 1, wherein, when the differential signal based on the scanning is stored in the memory, the differential signal is shifted by the size of the unit rectangular beam and stored. 5. A method for writing a differential signal based on substantially one rectangular beam scan of a rectangular beam into a memory,
2. The adjustment method according to claim 1, wherein the differentiated signal based on the first scan is shifted by a unit size and written in the memory redundantly so that the second scan with the rectangular beam is not performed.