Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
1998-04-27
2001-06-26
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S296000
Reexamination Certificate
active
06251541
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a partial collective mask for charged particle beam exposure implementing the collective transfer of a plurality of desired patterns.
A high throughput is the prerequisite with the production of modern semiconductor devices. This is also true with lithography for forming fine patterns in a semiconductor wafer. To realize a high throughput, there has been proposed a transfer procedure using a charged particle beam mask equivalent to a mask or a reticle formed with a desired pattern beforehand and adapted for light or X rays. A partial collective mask for this kind of transfer procedure and adapted for a charged particle beam is usually formed with openings for variable shaping and openings representative of contact patterns, line-and-space patterns or similar repetitive patterns derived from device design data.
To produce the partial collective mask, a silicon (Si) wafer as thick as 20 &mgr;m has customarily been subjected to trench etching so as to form device patterns or openings. However, the problem is that the patterns to be formed in the mask each need a particular etching time in accordance with the area of its opening. It is a common practice to enhance the shaping accuracy by optimizing the composition and flow rate of a gas, etching time and so forth. The opening areas of device patterns sometimes differ from each other by 70% or more. This, coupled with the fact that differences between etching conditions in the wafer plane are not negligible, brings about a scatter in the size of the pattern or opening. Therefore, when the pattern or opening has a size smaller than a designed size, there occur various faults including the defective draw of contacts and defective partial-collective connection; in the worst case, snapping and other critical faults occur. The mask cannot be corrected in shape even in the event of such a critical fault.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a partial collective mask for charged particle beam exposure and capable of obviating inaccurate writing ascribable to inaccurate openings.
In accordance with the present invention, in a partial collective mask for shaping a charged particle beam implemented as an electron beam output from an electron gun or an ion beam output from an ion source, auxiliary patterns in the form of openings are formed in addition to desired main patterns in the form of openings.
Also, in accordance with the present invention, in an exposing method using a charged particle beam, patterns are written by using a partial collective mask for shaping a charged particle beam implemented as an electron beam output from an electron gun or an ion beam output from an ion source. The partial collective mask includes desired main patterns and auxiliary patterns.
Further, in accordance with the present invention, a partial collective mask for charged particle beam exposure for transferring a plurality of desired patterns collectively includes a desired main pattern in the form of openings, and auxiliary patterns in the form of openings for reshaping. When any one of the main patterns has a size smaller than a designed size, the auxiliary patterns adjoining the main pattern are reshaped and joined with the main pattern. As a result, snapping or similar connection fault ascribable to the size smaller than the designed size is obviated.
Moreover, in accordance with the present invention, a partial collective mask for use in an electron beam writing device for electron beam exposure which transfers a plurality of desired patterns collectively includes desired main patterns in the form of openings, and auxiliary patterns in the form of openings each having a size not resolving when subjected to an electron beam. The auxiliary patterns are positioned such that a portion bridging the end or the corner of any one of the main patterns and one of the auxiliary patterns adjoining it is removable.
REFERENCES:
patent: 5849437 (1998-12-01), Yamazaki et al.
patent: 5885747 (1999-03-01), Yamasaki et al.
patent: 58-200238 (1983-11-01), None
patent: 8-45808 (1996-02-01), None
Foley & Lardner
Huff Mark F.
Mohamedulla Salcha R.
NEC Corporation
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