JPS6150374B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam exposure method for drawing a device pattern on a substrate using an electron beam.

In recent years, electron beam exposure apparatuses have played an important role in manufacturing wiring patterns for integrated circuits, manufacturing masks for integrated circuits, and the like. This is a device that draws a desired pattern by scanning a sample surface such as a silicon (Si) substrate coated with resist with an electron beam under the control of an electronic computer and moving the sample. To briefly explain this with reference to FIG. 1, it consists of an electron gun 2, electron lenses 4a to 4b, an aperture plate 6 having a rectangular (usually square) aperture, a blanker 8, a deflector 10, etc., as shown in the figure. Place sample 12 at the bottom of the container. An electron beam is emitted from the electron gun 2, and the aperture plate 6 is uniformly irradiated with the electron beam as shown by the solid line a. Therefore, the electron beam exiting the aperture plate 6 has a rectangular cross section. The opening of the opening plate 6 is 100 to 300 on one side.
Although it is relatively large at μm and is too large for drawing wiring patterns of integrated circuits, it is
d to converge as shown by the solid line b, so that the sample surface has a rectangular cross section with a side of 1 μm to 5 μm. Note that the blanker 8 turns the electron beam on and off,
The deflector 10 changes the irradiation position of the electron beam. The electron beam lasts for a certain period of time (usually 1μsec)
degree) A sample is irradiated while stationary, then moved to an adjacent area and irradiated again in a stationary state for a certain period of time, and then a desired pattern is drawn by exposing adjacent areas one after another in the same manner. An example of pattern drawing is shown in FIG. l ₂ is a vertical line, l ₁ is a horizontal line,
These are drawn by joining the above-mentioned rectangular electron beam exposure areas C. As is clear from the drawings, this method has no problem with drawing vertical lines and horizontal lines, but there is a problem with lines in diagonal directions. That is,
For example, when drawing a line ₃ in 45 directions, the exposure area C is shifted in the 45 direction while gradually overlapping the corner portion d of the exposure area C as shown in the figure. Both edges are not straight but step-like. This is not only unsightly, but also poses a risk of wire breakage. When drawing a diagonal pattern, if the size of the unit exposure area C is made smaller, the step-like shape described above becomes finer and becomes closer to a straight line. However, this increases the time required to draw the pattern, and the advantage of the shaped beam method is will be lost.

The present invention has been made in view of the above, and is characterized by an electron beam exposure apparatus comprising an electron gun, an aperture plate having an octagonal or hexagonal aperture, a plurality of electron lenses, and a deflector. The aperture plate is uniformly irradiated with an electron beam from an electron gun, and the electron beam that passes through the aperture plate and has an octagonal or hexagonal cross section is projected onto the sample surface. The purpose is to perform exposure while sequentially moving in a direction perpendicular to the sides of a square or hexagon. The present invention will be described in detail below based on Examples.

FIG. 3 shows an embodiment of the present invention, which is basically the same as FIG. 1, except that the opening of the aperture plate 6a is shaped as shown in FIG. 4A or B. be. In Figure 4A, the aperture is octagonal.
This makes the beam cross section the same octagon. However, the optical system has aberrations, and the corners of the beam cross section tend to be blurred, and the beam cross section imaged on the sample surface tends to have octagonal corners that are rounded. To prevent this, as shown in FIG. 4B, it is preferable to form the opening in a so-called "fish tail" shape, in which the corners of the octagon are sharpened. In this way, the above-mentioned blurring is canceled out, and the electron beam on the sample surface becomes a precise octagon.

By using such an octagonal aperture, not only vertical and horizontal lines but also diagonal lines can be drawn with good contours. That is, to draw a horizontal line, as shown in FIG. 5, one side e of an octagon and one side f of another adjacent octagon are connected one after another so that they slightly overlap. Specifically, in the same way as explained in Figure 2, the beam is projected to a predetermined position _Q1 , held in that state for about 1 μsec, then stepped to the next position _Q2 , and held at that position for 1 μsec.
Let it stand still for a while, and then proceed in the same manner. Both edges P of the horizontal line drawn in this way have some dents, but as is clear from the comparison with Figure 2, the extent of the dents is quite small, and the exposure of the resist has a tendency to blur due to the electron bleeding phenomenon. Therefore, if there are fewer irregularities, it is possible to form a pattern with a more linear outline.

Drawing a vertical line is exactly the same as drawing a horizontal line, just bring the next position Q above or below _Q1 .

The degree of unevenness on both sides of the vertical line formed at this time is exactly the same as that of the horizontal line. When diagonal lines are drawn in 45 directions, the result is as shown in Fig. 6, and as is clear from the drawing, in this case as well, a pattern is drawn using exactly the same procedure as for vertical and horizontal lines, and with the same quality.

When forming patterns on printed circuit boards, vertical and horizontal lines are almost always drawn, and 45 lines are added in some cases.However, when drawing patterns for integrated circuits, there is a little more freedom, with lines drawn at 30° and 60°. It is expected that diagonal lines will also be included. For drawing diagonal lines in the 30° and 60° directions, it is advantageous to use a hexagonal aperture. FIG. 7A shows an aperture plate having this hexagonal aperture, and FIG. 7B shows a hexagonal aperture plate made into a fish tail shape in consideration of blurring of the periphery. To draw vertical and horizontal lines using such an aperture plate, use the method shown in FIG. 8, and to draw 30° or 60° lines, use the method shown in FIG. 9. Both can draw straight line patterns of the same quality using exactly the same method.

If an aperture plate with circular apertures is used, the edges will form an arc, making it difficult to draw a rectangular pattern well. The octagonal or hexagonal aperture allows diagonal lines to be drawn with the same quality as vertical and horizontal lines while maintaining the sharpness of the corners, and provides a practically optimal aperture shape.

In the present invention, when drawing, octagonal or hexagonal unit exposure areas are partially overlapped, and therefore, the overlapping portion becomes overexposed, but this does not pose a problem. In other words, if the overlap is appropriate, as mentioned above, when exposed to an electron beam, the resist in the exposed areas will disappear and the resist in the unexposed areas will remain, so even if the exposure is a little excessive, the result will be The resist in that area will disappear, so there will be no problem. Overexposure becomes a problem in extreme cases where the exposure is tens or hundreds of times higher than normal.
In this case, it has been reported that, contrary to the above, the resist in exposed areas remains and the resist in unexposed areas disappears.

As explained in detail above, according to the present invention, it is possible to draw high-quality lines not only in vertical lines and horizontal lines but also in diagonal directions, so that line drawings of various patterns can be drawn with high quality when drawing wiring patterns for integrated circuits, for example. It is extremely effective as it can be drawn as follows.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a conventional electron beam exposure apparatus.
Figure 2 is an explanatory diagram showing an example of a drawing pattern;
The figures are explanatory diagrams showing embodiments of the present invention, Figures 4A and B
5 is a plan view showing the aperture shape of the aperture plate used in the present invention, FIG. 5 is an explanatory view showing the horizontal line exposure method in the present invention, FIG. 7A and B are plan views showing other aperture plate opening shapes used in the present invention, FIG. 8 is an explanatory diagram showing the horizontal line exposure procedure in the present invention, and FIG. 9 is an oblique line exposure procedure in the present invention. FIG. In the figure, 2 is an electron gun, 4a to 4d are electron lenses,
6a is an aperture plate, 10 is a deflector, and 12 is a sample.

Claims (1)

[Claims] 1. Using an electron beam exposure device including an electron gun, an aperture plate having an octagonal or hexagonal aperture, a plurality of electron lenses, and a deflector, the aperture plate is exposed to an electron beam from the electron gun. An electron beam that is uniformly irradiated and shaped into an octagonal or hexagonal cross section after passing through the aperture plate is projected onto the sample surface, and the sample is sequentially moved in a direction perpendicular to the sides of the octagon or hexagon. An electron beam exposure method characterized by performing exposure while