JPH0620931A - Method for electron beam exposure - Google Patents

Abstract

PURPOSE:To reduce the number of shots required for lithography and to prevent a.decrease in a throughput by multiple exposing rectangles having different aspect ratios to be inscribed with an oblique part of an oblique figure, and resolving the oblique part by utilizing bulges of a pattern generated by a proximity effect. CONSTITUTION:When wide figures 2-7 are formed in order to reduce the number of shots while suppressing deterioration of resolution of an oblique part of an oblique figure, exposure amounts are always increased as compared with stepwise parts on superposed parts of the two figures on shaded parts. Then, bulges are generated in the stepwise figures by an influence from the part. This is caused by a proximity effect of an electron beam. If a generally oblique figure is resolved by utilizing a deformation by the proximity effect, the number of shots is decreased. Thus, even when the oblique figure is formed, the number of the shots can be reduced, and a decrease in a throughput can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method capable of reducing the number of shots and preventing a decrease in throughput even when an oblique figure is drawn by an electron beam drawing apparatus.

[0002]

2. Description of the Related Art Conventionally, when an oblique figure is drawn by using a variable shaping type electron beam drawing apparatus, the oblique part is divided into thin strip-shaped rectangles and drawn. This utilizes the fact that if the step-like step formed as a result of the rectangular decomposition is smaller than the resolution of the resist, it becomes smooth and is not reflected in the drawing result. However, since a large number of thin rectangular beams are required for drawing an oblique figure, the number of shots increases, which causes a decrease in throughput.

[0003]

The present invention is based on FIG. 1 (a).
As shown in FIG. 3, there is a need to provide an electron beam exposure method that does not require a large number of strip-shaped beams even when drawing an oblique figure, prevents an increase in the number of shots, and prevents a decrease in throughput. .

[0004]

[Means for Solving the Problems] Instead of dividing an oblique figure into strips, multiple exposure is performed using rectangles with different aspect ratios that are inscribed in the oblique portions, and the swelling of the pattern generated by the proximity effect is used to remove the oblique portions. The resolution is reduced, the number of shots required for writing is reduced, and the decrease in throughput is prevented.

[0005]

In the electron beam writing apparatus, it is known that the electron beam irradiated on the sample is scattered in the resist and the substrate, so that a drawing effect changes from a desired shape to the proximity effect. This is because the electron beam is scattered inside the substrate and the resist, so that the energy of the electron beam is accumulated outside the desired drawing figure. Especially when drawing a figure with the same exposure amount in this area. Excessive exposure causes bulging of the figure. For example, when drawing the staircase-shaped figure shown in FIG. 1B, if the exposure amount of the shaded portion in the drawing is intentionally increased, it is possible to cause the step portion to be rounded due to the proximity effect. By controlling this exposure amount, the degree of rounding can be controlled. For this reason,
It is possible to substitute the drawing with the strip beam shown in (a).

[0006]

FIG. 2 is an exposure pattern showing an embodiment of the present invention. The oblique pattern is divided into a basic rectangular portion (not shown) and the remaining triangular portion 1 by the electron beam exposure apparatus. At this time, in order to reduce the number of shots while suppressing the deterioration of the resolution of the oblique portion to the minimum, the figures 2 to 7 having a width larger than the strip beams 2'to 12 'used in the conventional method are drawn. In the shaded area of FIG. 2 (b), the exposure amount is always larger than that of the stepped portion in the overlapping portion of the two figures, so the stepwise figure is changed due to the influence of the electron beam scattering from this portion. The bulge as shown in FIG. 1B is generated. This is due to the proximity effect of the electron beam,
By utilizing the deformation of the figure due to the proximity effect to resolve the roughly oblique figure portion, the number of shots can be reduced, and the decrease in throughput can be prevented.

Here, in the method of dividing a rectangle, the figure 2 which is maximum in the horizontal direction and is equivalent to the strip 12 'is obtained, and then the rectangle having the maximum horizontal width inscribed in the remaining triangles with the predetermined stair width. Decide on 3. Further, the rectangle 4 is determined by the same procedure.

Next, if rectangles 5, 6 and 7 are defined in the vertical direction according to the above procedure, the horizontally and vertically elongated rectangular groups 2 to 7 as shown in FIG. 2B are allowed. can get. Here, when these are exposed, the exposure amount of the shaded portion in the figure where they are overlapped is twice as large as that of the other portion, so that the step-like figure can be brought closer to the desired diagonal figure by the proximity effect. Further, the finished shape can be controlled by changing the exposure amount of each rectangle with respect to the reference value.

In the embodiment shown in FIG. 2, the effect of reducing the number of shots is estimated. In this embodiment, rectangular beams having different lengths in the horizontal direction and the vertical direction so as to have a level difference twice that of the strip-shaped beam are disassembled and allowed to overlap. In the example, it is understood that the number of shots can be reduced to about 6/11, which is about half that of the case where the conventional strip-shaped beam is used for decomposition. This reduction rate is determined by the step width of the stepped figure with respect to the width of the strip. The larger the step width is, the greater the reduction effect is, but the resolution is degraded in the oblique portion, and therefore the optimum reduction rate is determined by the allowable dimensional accuracy. FIG. 2C shows an example in which the rectangles are divided so that the overlapping of the rectangles does not become three or more.

FIG. 3 is an exposure figure showing another embodiment of the present invention, and in particular, the case of drawing an isolated polygon 31 such as a through hole. FIG. 3A shows an example in which five shots of rectangles 32 'to 36' are required in the conventional method. As shown in FIG. 3B, the maximum rectangles 32 and 33 inscribed in the polygon are obtained, and the rectangle groups 32 and 33 are obtained.
Is generated as drawing data, and drawing is performed with mutual duplication allowed. The exposure amounts of the overlapping rectangles 32 and 33 are determined in advance according to the shape accuracy of the diagonal portion. The reduction rate of the number of shots at this time is 2/5, and it is possible to prevent a decrease in throughput. Similar to FIG. 3B, FIG. 3C shows a case where the rectangles 34 and 35 are obtained and then the rectangular beam 36 is supplementarily drawn to improve the shape accuracy. The shot number reduction rate in this case is 3/5.

FIG. 4 shows still another embodiment of the present invention. In order to improve the shape accuracy of the diagonal part, the rectangular beam 4
The maximum inscribed rectangular beams 47 and 48 are obtained in the unexposed portion of the figure 31 to be drawn, which is generated by drawing 2, 43, and auxiliary drawing is performed. The reduction rate of the number of shots is 4/5. In this embodiment, the reduction rate of the number of shots is inferior to that in the embodiment, but it has an advantage that shape accuracy can be secured.

[0012]

According to the present invention, even when an oblique figure is drawn,
Since it is possible to reduce the number of shots as compared with the conventional technique, it is possible to prevent a decrease in throughput.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle of the present invention.

FIG. 2 is an explanatory diagram of an exposure pattern according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of an exposure pattern according to the second embodiment of the present invention.

FIG. 4 is an explanatory diagram of an exposure pattern according to the third embodiment of the present invention.

[Explanation of symbols]

1 ... Oblique figure to be drawn, 2 ... Strip beam, 2-7,
33 ... A group of rectangles generated by allowing duplication.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Kono 5-20-1 Kamimizuhoncho, Kodaira-shi, Tokyo Hitachi, Ltd. Musashi factory

Claims (3)

[Claims] 1. A so-called variable shaping type electron beam drawing apparatus comprising means for dividing a drawn figure into rectangular units and means for generating an electron beam having a sectional shape corresponding to the divided rectangles. In (3), drawing data is generated as a plurality of rectangles inscribed in a triangle resulting from dividing an oblique figure into rectangles with different aspect ratios, and these are drawn while allowing a part of them to be duplicated. Electron beam exposure method. 2. A group of one or more horizontally long rectangles inscribed in the polygon when drawing an isolated polygon other than the rectangle,
Similarly, an electron beam exposure method characterized in that one or more vertically elongated rectangular groups inscribed in the polygon are generated as drawing data, and a part of them is allowed to be reproduced. 3. The rectangle having the maximum area that can be inscribed in each of the non-overlapping portions of the polygon formed by the group of rectangles that are allowed to overlap and the drawing figure to be originally drawn, according to claim 1 or 2. An electron beam exposure method that generates and draws with a separately determined exposure amount.