The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 10, 1999
Filed:
Feb. 18, 1998
Tadao Yasuzato, Tokyo, JP;
Shinji Ishida, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
To a projection lens system is added spherical aberration of 0.1.lambda., and the exposure is performed by using a phase-shifting mask having a phase difference of 200 degrees which is provided with a phase error of 20 degrees corresponding to the spherical aberration amount. Therefore, the focus characteristic can be more remarkably flattened as compared with the prior art in which the phase difference of the mask is set to 180 degrees and the spherical aberration of the projection lens system is set to zero, so that the depth of focus can be enlarged by about 0.2 micron and the precision of the pattern dimension of semiconductor devices manufactured by using the exposure method can be enhanced.