JPS6145375B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam exposure method, and more particularly to an improvement in a variable shape electron beam exposure method.

Conventional variable-shape electron beam exposure in which the projected image of the electron beam on the sample surface is shaped into a desired shape, and the shaped beam is moved at a pitch equal to the length of the shaped beam for each shot to draw a desired pattern. This method has the disadvantage that the drawn pattern does not have smooth joints between the patterns of each shot.

In other words, as shown in FIG. 1a, the beam intensity of the rectangular shaped beam 1 is not uniform; for example, B-B
As for the beam intensity 2 in the direction of the arrow, the peripheral part 3 is slightly sagging as shown in FIG. Therefore, the beam shape becomes blurred at the periphery.

If the end portions of such shaped beams are made to overlap for each shot, the connecting portions 4 of the pattern will be overexposed and bulged, as shown in figure c, and conversely, if there is no overlap, the pattern will become bulged, as shown in figure d. As shown in FIG. 2, the connecting portion 4' is underexposed and dented.

In the conventional variable shape electron beam exposure method, it is difficult to control the resulting pattern so that it is smooth without the above-mentioned bulges and depressions.

SUMMARY OF THE INVENTION An object of the present invention is to provide a variable shape electron beam exposure method that can solve the above problems and draw smooth patterns.

A feature of the present invention is that when starting writing, the end of the shaped beam on the writing start point side is aligned with the end of the pattern to be written on the writing start point side, and while this is fixed, the length of the shaped beam is adjusted for each shot. The length of the shaped beam increases in the direction of beam movement, and after the length of the shaped beam reaches the maximum length of the shaped beam used in the exposure process, the shaped beam of the maximum length is used for each shot. After the shaping beam is moved at a pitch smaller than the maximum length and the end of the shaping beam reaches the end of the pattern to be drawn, the end of the shaping beam is fixed and the shaping beam is moved for each shot. The purpose is to provide a substantially uniform exposure amount over the entire area of the pattern to be drawn by reducing the length stepwise and exposing all parts of the pattern to be drawn with multiple shots.

The present invention will be explained below with reference to Examples.

FIG. 2 is a diagram showing the procedure of an embodiment of the present invention.
An example will be described in which a long pattern 11 with a small width is drawn by sequentially moving a rectangular beam in the direction of an arrow 12. Note that 13 and 14 indicate the ends of the pattern 11 on the drawing start point side and the end point side.

In this embodiment, to draw the pattern 11, first exposure is performed with a small rectangular beam 15 as shown in the figure, the next shot is a rectangular beam 16, the next is a rectangular beam 17, and the size of the rectangular beam is determined for each shot. I'll make it bigger. This results in a rectangular beam 18 having a maximum length l used in the exposure process. During this time, the starting point side ends 15' of the rectangular beams 15 to 18
18' is fixed while being aligned with the position of the starting point side end 13 of the pattern 11, and the beam is moved in the direction of movement (arrow 1).
2) increases the length of the rectangular beam. The length of the rectangular beam was determined as follows. That is, the length of the beam 15 used for the first shot is the maximum length l.
Let it be 1/n of In this embodiment, since n=4, the length of the beam 15 is 1/4. Then, the length of the beam 16 is increased by 2 l/4, the length of the beam 17 is increased by 3 l/4, and the length of the beam 18 is increased at a constant rate of l.

After the length of the rectangular beam reaches the maximum length l as described above, the beam length is fixed at l and the position of the beam is changed to the rectangular beams 19, 20, 21, 22 in the direction of arrow 12 for each shot. ,...... and move it at a pitch of l/4.

Thereafter, exposure is carried out by sequentially moving the position of the beam, until the rectangular beam 29 is reached, and the terminal end 23' coincides with the terminal end 14 of the pattern 11. Thereafter, the beam length is reduced by 1/4 for each shot of the rectangular beams 24, 25, and 26, and the entire exposure process of the pattern 11 is completed with the rectangular beam 26 having a length of 1/4 as the final shot. Between the beams 23 to 26, the ends 23' to 26'' of the beams 23' to 26'' are fixed so as to match the ends 14 of the pattern 11.

In the pattern 11 obtained as described above, an exposure amount of 4 bits is given to all the remaining parts except for the joints between each shot. In addition, the exposure amount at the joint between each shot, for example, the connection between beams 17 and 21, is for three shots of beams 18, 19, and 20 and 3 for each peripheral portion of beams 17 and 21 when beams 17 and 21 overlap. [1st
If there is no overlap, the amount is the sum of the three shots of the beams 18, 19, and 20 and the bottom portions of the peripheral portions 3 of the beams 17 and 21. Therefore, the exposure amount at the joint between each shot is less than 5 shots in the maximum case, and more than 3 shots in the minimum case.
The exposure amount is within 4 shots ± 1 shot over the entire pattern 11. In other words, in this example, the variation in exposure amount is ±25 [%] or less,
This was a significant improvement compared to the conventional method, which had fluctuations of up to ±100%. The pattern 11 obtained as a result had no bulges or dents occurring at the joints between the shots, or even if there were bulges or dents, they were very small, resulting in an extremely smooth pattern.

As is already clear from the above explanation, the variation in exposure amount within the drawn pattern is ±100/n.
[%] or less. In this embodiment, n=4, but the value of n may be arbitrarily selected, and by increasing n, the fluctuation in exposure amount can be made smaller.

The above n does not necessarily have to be an integer, and the rate at which the beam length is increased or decreased does not necessarily have to be constant, but in that case, controlling the size and position of the beam becomes very complicated. Therefore, in practice, n is chosen as an integer, and the amount of increase and decrease in beam length and amount of position movement for each shot are all l/n.
It is better to

In the above-mentioned embodiment, an example of drawing a long pattern horizontally (in the X-axis direction) has been described, but the present invention can be applied even if the pattern to be drawn is long in the vertical direction (in the Y-axis direction) or is a diagonal pattern. However, the pattern shape is not limited to a rectangle, but even other shapes such as a parallelogram can be drawn using the present invention.

Although not particularly shown in the drawings, the length of the rectangular beam can be increased or decreased by controlling the deflector for beam shaping and the deflector for beam positioning, which are arranged between a plurality of apertures for beam shaping. It goes without saying that the beam can be moved by controlling the positioning deflector.

As explained above, the present invention provides a variable shape electron beam exposure method that can draw a pattern without unevenness even at the joints between shots.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a conventional variable shape electron beam exposure method, and FIG. 2 is a diagram for explaining a drawing procedure according to an embodiment of the present invention. In the figure, 1 is a rectangular beam, 11 is an elongated pattern to be drawn, 12 is an arrow indicating the moving direction of the beam, 13 and 14 are ends on the drawing start point side and the end point side, 15 to 26 are rectangular beams, and 15' to 18 ' is the end on the drawing start point side, 23'' to 26'' is the end on the drawing end point side,
l indicates the maximum length of the rectangular beam used in the drawing process.

Claims (1)

[Claims] 1 In a variable-shape electron beam exposure method in which a projected image of an electron beam on a sample surface is shaped into a desired shape and the shaped beam is moved at a predetermined pitch to draw a desired pattern, at the start of drawing, The end of the shaped beam on the drawing start point side is made to coincide with the end on the drawing start point side of the pattern to be drawn, and the length of the shaped beam is increased stepwise for each shot while the end of the shaped beam on the drawing start point side is fixed; After the length of the shaped beam reaches the maximum length of the shaped beam used in the exposure process, the maximum length of the shaped beam is moved at a pitch smaller than the maximum length of the shaped beam for each shot, After the end point side end of the shaped beam reaches the end point side end of the pattern to be drawn, the length of the shaped beam is reduced step by step for each shot while keeping the end point side end of the shaped beam fixed. , an electron beam exposure method characterized in that multiple shots are exposed substantially uniformly to all parts of a pattern to be drawn.