High numerical aperture ring field projection system for extreme ultraviolet lithography
US6188513A · kind A · utility
Inventors
Key dates
| Filing date | Mar 15, 1999 |
| Grant date | Feb 13, 2001 |
| Priority date | — |
| Expiry date | Mar 15, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B17/0657
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An all-reflective optical system for a projection photolithography camera has a source of EUV radiation, a wafer and a mask to be imaged on the wafer. The optical system includes a first convex mirror, a second mirror, a third convex mirror, a fourth concave mirror, a fifth convex mirror and a sixth concave mirror. The system is configured such that five of the six mirrors receive a chief ray at an incidence angle of less than substantially 9.degree., and each of the six mirrors receives a chief ray at an incidence angle of less than substantially 14.degree.. Four of the six reflecting surfaces have an aspheric departure of less than substantially 12 .mu.m. Five of the six reflecting surfaces have an aspheric departure of less than substantially 12 .mu.m. Each of the six reflecting surfaces has an aspheric departure of less than substantially 16 .mu.m.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.