Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
1998-07-20
2001-02-20
Smith, Matthew (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C700S120000, C700S121000, C378S035000
Reexamination Certificate
active
06192510
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of preparing a partial one-shot electron beam exposure mask, and a method of direct-writing patterns by use of a partial one-shot electron beam exposure.
In recent years, a design rule requires a scaling down or downsizing of mask patterns to be used for a lithography. The lithography is classified into a photo-lithography, an X-ray lithography and an electron beam lithography. The X-ray lithography and the electron beam lithography are more attractive as the next generation lithography as being responsible for the scaling down or the downsizing in accordance with the requirement of the design rule. Further, a high throughput is required for manufacturing semiconductor devices. The high throughput is also required for the lithography for writing fine patterns on a resist over a wafer. A projection mode electron beam exposure has been proposed which uses an electron beam mask with fine patterns which are to be projected onto the resist over the wafer. This electron beam mask with some predetermined fine patterns is used for a partial one-shot of the electron beam. The partial one-shot electron beam mask has an aperture for a variable shaped electron beam exposure and some predetermined aperture patterns which, for example, correspond to contact hole patterns and line&space patterns. Such predetermined aperture patterns are extracted from device design data or computer aided design data. The predetermined aperture patterns of the mask constitute unit cells or structures which repeat a large number of times. This is disclosed in, for example, the Japanese laid-open patent publication No. 5-13313.
The mask for the partial one-shot direct-writing is prepared by use of CAD-data which have been prepared in a conventional method of preparation of the partial one-shot direct-writing mask data. The fine patterns are written by use of the mask prepared. If, however, the fine patterns are divided on the CAD-data, then the repeating unit cell or structure including the divided patterns is extracted for couductios a partial one-shot. This may cause a displacement between the partial one-shots or a deformation such as disconnection of the pattern. For example, as illustrated in
FIG. 1
, contact hole patterns are divided into repeating unit cells
1
, each of which has a plurality of rectangles half-divided from the square-shaped control hole pattern for preparation of CAD-data
3
. The repeating unit cell
1
is extracted from the CAD-data for forming an aperture pattern on a partial one-shot mask
2
. For this reason, as illustrated in
FIG. 2
, there might be caused a disconnection “C” of the contact hole pattern or a displacement “D” between divided rectangular-shaped parts of the contact hole patter.
In the above circumstances, it had been required for conducting the electron beam partial one-shot direct-writing to optimize an extraction of partial one-shot mask data independently from the repeating unit cells on the CAD-data for preparing a mask in accordance with the extracted partial one-shot mask data so as to improve an accuracy of writing the pattern on the resist.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a novel method of preparing a partial one-shot electron beam exposure mask free from the above problems.
It is a further object of the present invention to provide a novel method of direct-writing patterns by use of a partial one-shot electron beam exposure.
One aspect of the present invention provides a method of extracting data of at least one aperture mask pattern from design data which include write-required patterns and repeating units, so that boundary lines of the at least one aperture mask pattern are different from boundary lines of the repeating unit on the design data and so that the at least one aperture mask pattern completely includes at least one of the write-required patterns without partially or incompletely including the write-required pattern,
In the above aspect of the present invention, the data for forming the aperture mask pattern on the partial one-shot electron beam exposure mask are extracted from the design-data so that the aperture mask pattern is different from the repeating unit pattern on the design-data so that the aperture mask pattern includes complete write-required patterns only with no part of individual write-required patterns nor incomplete write-required patterns, thereby optimizing the extraction of the partial one-shot mask data independently from the repeating unit cells on the design-data for preparing a mask in accordance with the extracted partial one-shot mask data so as to improve an accuracy of writing the pattern on the resist.
The above and other objects, features and advantages of the present invention will be apparent from the following descriptions.
REFERENCES:
patent: 4744047 (1988-05-01), Okamoto et al.
patent: 5489509 (1996-02-01), Kawabata et al.
patent: 5546225 (1996-08-01), Shiraishi
patent: 5655110 (1997-08-01), Krivokapic et al.
patent: 5895925 (1999-04-01), Nakasuji
patent: 6004701 (1999-12-01), Uno et al.
patent: 9-97759 (1997-04-01), None
Ito (“An automated system for LSI fine pattern inspection based on comparison of SEM images and CAD data”, Proceedings of 1999 International Conference on Robotics and Automation, 1995, vol. 1, May 21 1995, pp. 544-549).
Wani et al. (“Edge-region-based segmentation of range images”, IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 16, No. 3, Mar. 1994, pp. 314-319).
Mandlick et al. (“PC based image analyser for mask inspection”, IEEE/CHMT International Electronic Manufacturing Technology Symposium, pp. 327-329A, Sep. 25, 1989).
Kik Phallaka
NEC Corporation
Smith Matthew
Young & Thompson
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