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:
Jun. 21, 1994
Filed:
Mar. 08, 1993
Hitachi, Ltd., Tokyo, JP;
Abstract
In a reduction-type projection exposure apparatus provided by the present invention, a spatial filter having a predetermined complex amplitude-transmission distribution is fixed approximately at the pupil position of a projection lens thereof or at such a position that the spatial filter conjugates with the pupil. The complex amplitude transmittance of the spatial filter is controlled by a multiple-interference effect of the multi-layer coating forming the spatial filter or by the surface reflection occurring on the surface of the film which constitutes the spatial filter and has an index of refraction different from the air. The filter can thus be prevented from absorbing light, incurring neither thermal damage nor damage due to dissipated heat. As a result, the reduction-type projection exposure apparatus offers excellent resolution and an outstanding depth of focus.