Method of detecting aberrations of an optical imaging system
US6248486A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 29, 1999 |
| Grant date | Jun 19, 2001 |
| Priority date | — |
| Expiry date | Sep 29, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70358
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Aberrations of an imaging system can be detected in an accurate and reliable way by imaging, by means of the imaging system, a circular phase structure on a photoresist, developing the resist and scanning it with a scanning detection device which is coupled to an image processor. The circular phase structure is imaged in a ring structure and each of several possible aberrations, like coma, astigmatism, three-point aberration, etc. causes a specific change in the shape of the inner contour and the outer contour of the ring and/or a change in the distance between these contours, so that the aberrations can be detected independently of each other. The new method may be used for measuring a projection system for a lithographic projection apparatus.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.