JPS60168104A - Electron beam exposing method - Google Patents

Abstract

PURPOSE:To draw a pattern in a remarkably short time, and to raise remarkably a throughput by controlling an intensity distribution, a shape, etc. of a beam, and exposing one pitch of a diffraction grating, a Fresnel lens, etc. by a scan of once. CONSTITUTION:A shape of a forming beam is made a right-angled triangle which is long in the X direction. Subsequently, an area to be exposed of a sample 17 is divided into (n) pieces as frames 1, 2-(n) whose X direction is prescribed by a length in the long side direction of a beam 22. In this state, the frame 1 is exposed by a beam scan of once, the frame 2 is exposed by the next beam scan, and also the frames 3-(n) are exposed successively. In this way, by making a beam shape a triangle, one pitch of a diffraction grating can be brought to picture-drawing by a beam scan of once, an exposure time can be shortened, and a throughput is raised remarkably. The shape of the forming beam is not limited to a right-angled triangle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electron beam exposure method for efficiently drawing diffraction gratings, Fresnel lenses, etc.

[Technical background of the invention and its problems]

Conventionally, when producing an echelette diffraction grating or a Fresnel lens, the process is as shown in FIG. It is necessary to pattern the resist 2 on the workpiece 1 so that its cross section has a sawtooth wave shape.

For this reason, when exposing a resist with an electron beam, it is necessary to change the dose applied to the resist in a sawtooth waveform, and to achieve this, multiple exposures are performed multiple times in the areas where a high dose is applied. Ta.

However, since this type of method requires multiple exposures, it takes several tens of hours to expose one diffraction grating or one Fresnel lens, and the throughput is extremely low. Furthermore, there is a problem in that the long-term stability of the system immediately affects manufacturing accuracy.

[Purpose of the invention]

An object of the present invention is to provide an electron beam exposure method that can expose one pitch of a diffraction grating, Fresnel lens, etc. with one beam scan, and can improve the manufacturing accuracy and throughput of these. be.

[Summary of the invention]

The gist of the present invention is to control the beam intensity distribution, beam shape, etc. so that one pitch of a diffraction grating, Fresnel lens, etc.
The purpose is to perform exposure using multiple beam scans.

That is, the present invention provides an electron beam exposure method in which a resist on a workpiece is irradiated with an electron beam to expose the resist. An electron beam is formed in which the beam width in a second direction perpendicular to the direction ' changes linearly with respect to the first direction, and the beam is spread at a pitch equal to the beam length in the first direction. In this method, the workpiece is sequentially scanned relative to the workpiece on a straight line or a curved line intersecting the first direction.

〔Effect of the invention〕

According to the present invention, compared to the conventional method of performing multiple exposure,
Diffraction gratings and 7-renel lenses can be drawn in 1/0 of the time, and throughput can be significantly improved.

Moreover, since the exposure time is short, highly accurate exposure can be performed even if the long-term stability of the system is somewhat poor. Also,
It is possible to obtain an accurate sawtooth wave dosing profile rather than a staircase approximation, which is extremely effective in the production of diffraction gratings and Fresnel lenses.

[Embodiments of the invention]

FIG. 2 is a schematic configuration diagram showing an electron beam exposure apparatus used in a method according to an embodiment of the present invention. 11 in the figure is an electron gun,
The electron beam emitted from this electron gun 11 is passed through a condenser lens 12 to an aperture mask 13 for beam shaping.
．． 14 is irradiated. The masks 13 and 14 have a structure that allows them to be minutely rotated around the optical axis 9 by a mechanical drive mechanism, for example, so that the apex angle θ and XY of the shaped beam, which will be described later, can be adjusted.
The relative angle to the coordinate system is variable. The beams formed after passing through the apertures 13a and 14a of the masks 13 and 14 are reduced by a reduction lens 15 and then directed to a sample (workpiece) 17 by an objective lens 16.
imaged on top. Here, the sample 17 serves as a base for making, for example, a rainbow lentic diffraction grating, and a positive resist is coated thereon.

On the other hand, alignment coils 18 and 19 for deflecting the beam are arranged above the mask 13, and the mask 14
Below the axial alignment coil 20°-se゛' coil
1, the optical shaping state of each of the apertures 13a+14h is controlled as shown in FIG. 3, for example, so that a triangular shaped beam can be obtained. Although not shown in FIG. 2, a beam deflection system for scanning the shaped beam on the sample 17 and a blanking system for controlling ON/OFF of the beam are also provided.

Next, a method for producing a rainbow lentic diffraction grating using the electron beam exposure apparatus having the above configuration will be described.

First, the shape of the shaped beam is shown in FIG.
J a + 14 A is a right triangle that is long in the X direction (first direction), as shown by the overlapping squares (shaded areas). Next, as shown in FIG. 4, the triangular beam 22 is directed onto the sample 17.
L1i 14th scanning is performed in the Y direction (second direction) with a pitch equal to the beam length in the X direction.

In other words, the area to be exposed of the sample 17 is divided into frames ■■ to ■J- whose width in the X direction is defined by the length in the long side direction of the beam 22.
h117Al/rAGILll+2. J-1-rIIr
Frame (2) is exposed with i1M ray/, kihon, frame (2) is exposed in the next beam scan, and frames (2) to (2) are further exposed sequentially. At this time, the dose amount is small in the portion where the vicinity of the top of the beam 22 passes, and the dose amount is large in the portion where the vicinity of the bottom of the beam 22 passes. Therefore, the dose amount (resist dose amount) on the sample 17 in the X direction is:
As shown in FIG. 4(a), it has a sawtooth wave shape. Also, Y
The dose amount with respect to the direction is constant.

When the resist exposed as described above is developed with a prescribed developer, the thickness of the resist in the X direction is as shown in Figure 5(b).
As shown in the figure, a sawtooth wave shape is formed depending on the dose amount.

In other words, one pitch of the diffraction grating can be drawn with one beam scan. From this point on, the entire surface is etched using a dry etching method or the like to reflect the cross-sectional shape of the resist on the sample 17, thereby obtaining a desired diffraction grating.

As described above, according to the method of this embodiment, by making the beam shape triangular, one pitch of the diffraction grating can be drawn by one beam scan. Therefore, the exposure time can be reduced to several tenths of that of the conventional method that required multiple exposures, and the throughput can be greatly improved. Moreover, since the overall exposure time required to draw one diffraction grating is short, the diffraction grating pattern can be exposed with high precision without requiring long-term stability in the electron beam exposure apparatus. Furthermore, as can be seen from FIG. 5(b), the cross-sectional shape of the resist can be accurately made into a sawtooth wave shape rather than a staircase approximation, which is extremely effective for drawing a diffraction grating. Further, by varying the apex angle θ of the triangular beam depending on the overlapping state of the i+ -chas 13a+14a, there is an advantage that the change in the plugist thickness (the inclination angle α shown in FIG. 5) can be easily changed. .

Note that the present invention is not limited to the embodiments described above. For example, the shape of the shaped beam is not limited to a right triangle, but may be an isosceles triangle or any other shape in which the beam width in the second direction changes linearly with respect to the direction of Ml. Furthermore, in order to control the shape of the beam,
The intensity distribution of the beam may also be controlled.

Alternatively, if the beam shape is a normal rectangle and the beam intensity varies linearly in the first direction, a dose distribution similar to that of the triangular beam described above can be achieved. This is possible. Furthermore, as a means for scanning the beam relative to the workpiece, it goes without saying that a table or the like on which the workpiece is placed may be moved. Furthermore, the beam shape and beam intensity distribution may be determined as appropriate depending on the desired resist pattern.

Further, the present invention can also be applied to drawing a Fresnel lens in addition to a diffraction grating. In this case, the beam may be scanned on the circumference by rotating the table on which the workpiece is placed, and one pitch of the Fresnel lens may be exposed with one beam scan. Furthermore, in the case of a Fresnel lens, it is necessary to change the pitch or depth of the sawtooth wave near the center and at the periphery. In that case, if you make the current flowing through the deflection coils 18, 19, 20, and 21 in Figure 2 variable, change the overlap of the antennas 13a and 14a in Figure 3, and change the beam length, good. Furthermore, the electron beam exposure apparatus is not limited to the structure shown in FIG. 2, but may be of any type as long as it can control the beam shape or beam intensity distribution as described above. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a resist pattern for producing an echelette-type diffraction grating, and FIG. 2 is a schematic configuration diagram showing an electron beam exposure apparatus used in an embodiment of the method of the present invention.
FIG. 3 is a schematic diagram for explaining the beam shaping method using the above device, FIG. 4 is a schematic diagram for explaining the exposure method using the above device, and FIGS. FIG. 3 is a characteristic diagram showing the dose amount of the resist and the thickness change after development with respect to the direction. 1.17... Sample (workpiece), 2... Resist,
11...electron gun, 12.15.16...lens, 1
3゜14...beam forming i! -Chamask, 13
a. 14a...Aperture, 18. ~, 2... Coil for axis alignment, 22... Forming beam. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 5

Claims (3)

[Claims] (1) In an electron beam exposure method in which a resist on a workpiece is irradiated with an electron beam to expose the resist, the beam intensity changes linearly with respect to a first direction or with respect to the first direction. An electron beam is formed in which the beam width in a second orthogonal direction changes linearly with respect to the first direction, and this beam is placed at a precise pitch with respect to the beam length in that direction with respect to the first direction. , an electron beam exposure method characterized in that the workpiece is sequentially scanned relative to the workpiece on a straight line or a curved line intersecting the first direction. (2) The electron beam exposure method according to claim 1, wherein a beam having substantially uniform beam intensity and a triangular beam shape is used as the electron beam. (3) The electron beam is a rectangular beam whose long side is in the first direction and whose beam intensity changes linearly with respect to the first direction. electron beam exposure method.