KR20000077410A - Electron beam exposure method - Google Patents

Abstract

The electron beam exposure method used in the manufacture of a semiconductor device according to the present invention comprises the steps of: (a) extracting a depiction pattern requiring correction, (b) extracting a plurality of exposure shot regions including the extracted depiction pattern, ( c) correcting the center to determine exposure of the electron beam suitable for the center of the depiction pattern, and (d) correcting the end to form an auxiliary exposure pattern for correcting variations in pattern dimensions at the ends of the depiction pattern. Steps.

Description

Electron beam exposure method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam exposure method used for manufacturing semiconductor devices, and more particularly, to an electron beam exposure method suitable for correcting proximity effects such as frequently repeated patterns.

In recent years, pattern formation by electron beam exposure methods has been performed in the manufacturing process of semiconductor devices. However, in pattern formation by these electron beam exposure methods, the pattern dimensions differ between the center and the end of the pattern because the proximity effect is caused by scattering of the electron beam.

Therefore, until now, various proximity effect correction methods have been proposed to obtain predetermined pattern dimensions by suppressing fluctuations in pattern ranges due to this proximity effect. Such proximity effect correction methods include a proximity effect correction method by exposure compensation, a GHOST method or a mask bias method that defocuss an inverse-tone pattern to a range of back-scatter diameter.

Among these proximity effect correction methods, the GHOST method is applicable to a large area transfer exposure system. 8 is a schematic view showing the arrangement of the cell array, Figure 9 is a schematic diagram showing a pattern for correcting the proximity effect by the conventional GHOST method. As shown in FIG. 8, when the proximity effect of the frequently repeated pattern 100 is corrected by the GHOST method, a mask that generates the inverse tone pattern 102 as shown in FIG. 9 is used and defocused to the range of the backscattering diameter. By applying the corrected beam, the proximity effect is corrected. 8 and 9 represent electron beam exposure short boundaries 101, respectively.

However, in the large area transfer exposure method of the conventional frequently repeated pattern 100, if the proximity effect correction using the GHOST method is performed using the entire reverse tone pattern 102, the entire reverse tone pattern 102 is made in the correction mask. . Therefore, the opening area of the correction mask becomes large. In particular, if the stencil mask formed at the positions where the holes are to be transmitted through the electron beam is used, there is a problem that the mast strength decreases as the opening space increases. In addition, since it is impossible to form a hole having a closed pattern in the stencil mask, another problem that it is difficult to faithfully form the auxiliary exposure pattern is because it is impossible to form the unexposed pattern surrounded by the exposure area as the entire donut periphery. have.

Furthermore, when only the close effect correction by exposure is applied to large area transfer, the correction between patterns is because the short size is sufficiently large compared with the backscattering diameter in the case of a pattern having a large pattern area density such as a cell array portion. Since the error is large, there is still another problem that the proximity effect (difference between the pattern dimensions at the center and the end) due to backscattering cannot be corrected.

An object of the present invention is to provide an electron beam exposure method that can accurately correct the proximity effect of a frequently repeated pattern even with a large transfer area.

1 is a schematic view showing a semiconductor circuit pattern formed by the electron beam exposure method according to an embodiment of the present invention;

2 is a schematic diagram showing a cell array pattern extracted by data processing;

Fig. 3A is a graph showing the exposure intensity distribution before correction in a pattern with a small interval between each line and each space, with the exposure intensity as the vertical axis and the position as the horizontal axis, and Fig. 3B is a graph showing the exposure intensity distribution after correction. ,

Fig. 4A is a graph showing the exposure intensity distribution before correction in a pattern in which the distance between each line and each space is large, with the exposure intensity as the vertical axis and the position as the horizontal axis, and Fig. 4B is a graph showing the exposure intensity distribution after correction. ,

5 is a schematic diagram showing a cell array pattern having an auxiliary exposure pattern;

6 is a graph showing the exposure intensity distribution and the auxiliary exposure intensity distribution around the cell array unit with the exposure intensity as the vertical axis and the horizontal axis as the position;

7 is a graph showing the exposure intensity distribution and the auxiliary exposure intensity distribution around the cell array unit with the exposure intensity as the vertical axis and the horizontal axis as the position;

8 is a schematic diagram showing the arrangement of a cell array;

9 is a schematic diagram showing a pattern for correcting a proximity effect using a conventional GHOST method.

※ Explanation of symbols for main parts of drawing

1: Cell array part 2: Lead

3: cell array pattern 4: auxiliary exposure pattern

5: electron beam exposure short boundary

The electron beam exposure method according to the present invention used for manufacturing a semiconductor device,

(a) extracting a depiction pattern requiring correction;

(b) extracting a plurality of exposure shot regions including the extracted description pattern;

(c) correcting the center portion to determine exposure of the electron beam suitable for the center portion of the depiction pattern; And

(d) correcting the end portion to form an auxiliary exposure pattern for correcting the variation of the pattern dimensions at the end of the depiction pattern.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

Hereinafter, an electron beam exposure method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First embodiment

In this embodiment, as shown in Fig. 1, the semiconductor circuit pattern has a cell array portion 1 in which the pattern is frequently repeated, and the leads 2 extend from this cell array portion 1. First, in this cell array unit 1, as shown in Fig. 2, the cell array pattern 3, which requires high dimensional accuracy, is extracted by data processing. In this step, if there are a plurality of cell array patterns, each of the plurality of cell array patterns is extracted separately.

In order to describe this extracted cell array pattern, a plurality of exposure shot regions are required as shown in FIG. Here, the exposure shot area is an area exposed to one shot of exposure. As a next step, the exposure shot areas necessary to describe the extracted cell array pattern are extracted. At this time, there is an electron beam exposure shot boundary 5 between the respective exposure shot regions.

Next, the exposure of the central portion of the cell array pattern 3 in which the proximity effect is saturated is determined as the exposure that exposes a plurality of exposure shot regions necessary to describe the extracted cell array pattern. The pattern description of the extracted plurality of exposure shot regions is performed using the first mask in this determined exposure.

If there are a plurality of cell array patterns, the pattern dimensions of the individual cell array patterns may be different in some cases. In the present invention, since the exposure shot regions are extracted for each cell array pattern, the exposure shot regions for each cell array pattern can be exposed with a suitable exposure. Therefore, as shown in Figs. 3A and 4A, the difference in the exposure intensity (r) due to backscattering differs between the case where the pattern composed of lines and spaces is fine and the pattern is coarse. It is different between cases.

According to the present invention, as shown in FIGS. 3B and 4B, the exposure to the exposure corresponding to the pattern line width at the center of the cell array unit 1 in which the proximity effect is saturated can be controlled according to each cell array pattern. .

However, the overall dimensional variation caused by the proximity effect in the cell array unit 1 cannot be corrected by this method alone.

For this reason, the present invention further includes the step of performing dimensional correction of the ends. Therefore, as shown in Fig. 5, another auxiliary exposure mask is formed at a position where the auxiliary exposure pattern 4 having an opening of a predetermined width is formed around the cell array pattern 3. The secondary exposure is performed by an electron beam defocused to a range of backscattering diameter similarly to the GHOST method by arranging this auxiliary exposure mask on the cell array pattern 3 after the depiction. In this exposure method, as shown in FIG. 6, the proximity effect is corrected to lower the exposure intensity distribution (ie, the energy distribution) caused by the backscattering of the electron beam on which the exposure of the auxiliary exposure pattern 4 is performed. By performing correction using (D), the exposure intensity distribution, which is changed by the proximity effect at the end of the cell array unit 1 and appears as a dotted line, is raised so that the exposure intensity distribution becomes the exposure intensity distribution represented by the solid line. It is possible.

Also, for this dimension correction at the end, if there are a plurality of cell array patterns, the area D can be provided around the respective cell array pattern to correct the dimensions.

In this embodiment, even if the area is large and the pattern is repeated frequently, the variation of the pattern dimensions between the center and the end of the cell array unit 1 can be corrected according to the pattern density. Therefore, it is possible to accurately correct the proximity effect in the cell array portion 1, in which particularly high dimensional accuracy is required.

Also, in this embodiment, since the auxiliary exposure opening used to correct the proximity effect is formed only in the periphery of the cell array unit 1, the patterns surrounded by the unexposed areas around the entire donut shape are inverted in the entire exposure area. There is little compared to the conventional GHOST method for describing patterns. Therefore, the auxiliary exposure mask can be easily generated. Furthermore, since there are almost no patterns surrounded by the unexposed areas all around the donut shape, even if a stencil mask is used, there is no problem of insufficient mask strength.

Furthermore, in this embodiment, the exposure intensity of the auxiliary exposure pattern 4 can be adjusted by determining the width of this opening to a value depending on the pattern density of the cell array unit 1 and changing this value. Further, in a pattern such as a logic pattern in which the proximity effect hardly affects, the proximity effect can be corrected by exposure.

Second embodiment

Another embodiment of the present invention will be described in detail with reference to the accompanying drawings. In Fig. 7, the same reference characters are assigned to the same elements as the reference characters in the embodiment shown in Figs. 1 to 6, and detailed description thereof is omitted.

Compared with the first embodiment, this embodiment arranges the auxiliary exposure patterns 4 indicated by hatching as shown in FIG. 5 around the cell array pattern 3 to form them in the same mask, and also the auxiliary The exposure of the exposure pattern 4 differs in that it is performed simultaneously with the main exposure, with the electron beam similarly unfocused when describing the cell array pattern 3. The rest is the same as in the first embodiment.

In this embodiment, the auxiliary exposure pattern 4 is often depicted as the same exposure shot as the exposure shot of the cell array pattern 3. Therefore, the exposure of the auxiliary exposure pattern 4 is the same as the exposure of the main exposure depicting the cell array pattern 3, and the exposure intensity of backscattering is adjusted by varying the aperture width of the auxiliary exposure pattern 4. Therefore, as shown in Fig. 7, correction is performed by using the lower portion of the exposure intensity distribution (energy distribution), i.e., the area D, caused by the backscattering of the electron beam on which the exposure of the auxiliary exposure pattern 4 is performed. By doing this, it is possible to cause the variation in the exposure intensity distribution caused by the proximity effect indicated by the dotted line at the end of the cell array unit 1 to be the exposure intensity distribution indicated by the solid line.

In addition, in the present embodiment, the auxiliary exposure pattern 4 is formed in the mask on which the cell array pattern 3 is formed, so that the defocusing of the electron beam necessary for the auxiliary exposure is not necessary. Therefore, the main exposure depicting the cell array pattern 3 and the secondary exposure for performing the proximity effect correction can be performed simultaneously, thereby making it possible to perform the proximity effect correction in a short turn-around time (TAT). have.

Although the present invention has been described with reference to specific embodiments, this description is not intended to be interpreted in a limiting sense. Various modifications to the disclosed embodiments will be apparent to those skilled in the art with reference to the description of the invention. Therefore, it is understood that the appended claims may include any modifications or embodiments as they fall within the true spirit of the invention.

As described above, in the present invention, the variation in the pattern dimensions at the pattern center portion caused by the difference between the densities in the depiction pattern is corrected by adjusting the exposure, and at the pattern end caused by the difference between the densities in the depiction pattern. By correcting the variation of the pattern dimensions by the auxiliary exposure pattern, it is possible to correct the variation of the respective pattern dimensions by dividing the central portion and the end portion from each other. Therefore, even if the area is large and the pattern is repeated frequently, the proximity effect can be corrected with high accuracy.

Claims (8)

In the electron beam exposure method used to manufacture semiconductor devices, (a) extracting a depiction pattern requiring correction; (b) extracting a plurality of exposure shot regions including the extracted description pattern; (c) correcting the central portion to determine exposure of the electron beam suitable for the central portion of the depiction pattern; And and (d) correcting the end portion to form an auxiliary exposure pattern for correcting the variation in the pattern dimensions at the end of the depiction pattern. The method of claim 1, further comprising: performing a first exposure with a first mask after correcting the central portion; And And performing a second exposure by aligning a second mask having a pattern corresponding to the step of correcting an end portion. The electron beam exposure method of claim 1, further comprising performing exposure with a single mask having a pattern corresponding to correcting the end portion after correcting the center portion. The electron beam exposure method of claim 3, wherein the single mask has a depiction pattern and the auxiliary exposure pattern formed around the depiction pattern. The electron beam exposure method according to claim 1, comprising the step of performing exposure by focusing to the backscattering diameter of the electron beam used after correcting the end portion. The electron beam exposure method according to claim 1, wherein the auxiliary exposure pattern is a pattern in which openings are provided around the depiction pattern. In the electron beam exposure method used to manufacture semiconductor devices, (a) extracting a depiction pattern requiring correction; (b) extracting a plurality of exposure shot regions including the extracted description pattern; (c) correcting the central portion to determine exposure of the electron beam suitable for the central portion of the depiction pattern; And (d) correcting the ends to form a pattern for providing an opening around the depiction pattern; And (e) performing exposure with the exposure determined in the step of correcting the center portion. 8. The electron beam exposure method of claim 7, further comprising performing a second exposure of defocusing the backscattering diameter of the electron beam using a mask according to the pattern formed in the step of correcting the end after performing the exposure. .