Optical gain approach for enhancement of overlay and alignment systems performance
US7602491B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 23, 2008 |
| Grant date | Oct 13, 2009 |
| Priority date | — |
| Expiry date | Apr 23, 2028 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70633
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A resultant image of a grating target may be obtained by dividing an image of the target into first and second portions and optically modifying the first and/or second portion such that a final image formed from their combination is characterized by a Moiré pattern. The resultant image may be analyzed to determine a shift in the grating target from a shift in the Moiré pattern. Optical alignment apparatus may include a first beam splitter, an image transformation element optically coupled to the first beam splitter, and a second beam splitter. The first beam splitter divides an image of a grating target into first and second portions. The second beam splitter combines the first portion and the second portion. The image transformation element optically modifies the first and/or second portion such that a final image formed from their combination is characterized by a Moiré pattern.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.