Ring field projection system
US4711535A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 10, 1985 |
| Grant date | Dec 8, 1987 |
| Priority date | — |
| Expiry date | May 10, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70233
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The present invention is directed to Optical Lithographic Systems which are particularly adapted, among many other possible uses, for use in effecting exposure of photoresist-coated semiconductor wafers, having a ring field projection system which includes at least one concave and one convex mirror arranged around an optical axis in face-to-face relationship with their centers of curvature being nearly concentric and falling on the axis, the convex mirror being smaller than and having a smaller radius of curvature than the concave mirror, an object location and a conjugate real image location, said convex mirror being positioned to reflect to the concave mirror light from the object location initially reflected from the concave mirror whereby light from the object location will be reflected at least twice at said concave mirror and at least once at the convex mirror before being focused at the image location, elements for limiting the image field to an annular zone centered about the optical axis, a first thick, flat parallel plate mounted in the light path between the object and image locations adjacent the object location, a second thick, flat parallel plate nearly identical to t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.