Critical illumination condenser for x-ray lithography
US5737137A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 1, 1996 |
| Grant date | Apr 7, 1998 |
| Priority date | — |
| Expiry date | Apr 1, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/702
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A critical illumination condenser system, particularly adapted for use in extreme ultraviolet (EUV) projection lithography based on a ring field imaging system and a laser produced plasma source. The system uses three spherical mirrors and is capable of illuminating the extent of the mask plane by scanning either the primary mirror or the laser plasma source. The angles of radiation incident upon each mirror of the critical illumination condenser vary by less than eight (8) degrees. For example, the imaging system in which the critical illumination condenser is utilized has a 200 .mu.m source and requires a magnification of 26.times.. The three spherical mirror system constitutes a two mirror inverse Cassegrain, or Schwarzschild configuration, with a 25% area obstruction (50% linear obstruction). The third mirror provides the final pupil and image relay. The mirrors include a multilayer reflective coating which is reflective over a narrow bandwidth.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.