Method of measuring focus of a lithographic projection apparatus
US8289516B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 19, 2008 |
| Grant date | Oct 16, 2012 |
| Priority date | — |
| Expiry date | Apr 3, 2030 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70683
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method of measuring focus of a lithographic projection apparatus includes exposure of a photoresist covered test substrate with a plurality of verification fields. Each of the verification fields includes a plurality of verification markers, and the verification fields are exposed using a predetermined focus offset FO. After developing, an alignment offset for each of the verification markers is measured and translated into defocus data using a transposed focal curve. The method according to an embodiment of the invention may result in a focus-versus alignment shift sensitivity up to 50 times higher (typically dX,Y/dZ=20) than conventional approaches.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.