Long-range gap detection with interferometric sensitivity using spatial phase of interference patterns
US7247843B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | May 11, 2006 |
| Grant date | Jul 24, 2007 |
| Priority date | — |
| Expiry date | May 11, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7038
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An apparatus and method measures the gap between one substantially planar object, such as a mask, and a second planar object, such as a substrate. A gapping mark is used for measuring a gap between the first and second plates. The gapping mark includes a first grating on a first surface of a first plate, the first grating having a first uniform period in a first direction. A second grating is located on the first surface of the first plate, the second grating being adjacent to the first grating in the first direction, the second grating having a second uniform period in the first direction. The gapping mark also includes a third grating on the first surface of the first plate, the third grating being adjacent to the first grating in a second direction, the second direction being substantially orthogonal to the first direction, the third grating having the second uniform period in the first direction. A fourth grating is located on the first surface of the first plate, the fourth grating being adjacent to the third grating in the first direction.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.