Position measurement unit, measurement system and lithographic apparatus comprising such position measurement unit
US7362446B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 15, 2005 |
| Grant date | Apr 22, 2008 |
| Priority date | — |
| Expiry date | May 15, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B2290/70
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A measurement unit to determine a position in a first and second dimension includes a diffraction type encoder and an interferometer. The diffraction type encoder determines by means of a diffraction on a first and a second diffraction grating the position in the first dimension of the second grating with respect to the first grating, The interferometer determines the position in the second dimension of a mirror. The measurement unit includes a combined optical unit to transfer an encoder measurement beam as well as an interferometer measurement beam. Further, the measurement unit may include a combined light source for the encoder as well as the interferometer. One of the first and second diffraction gratings may further show some degree of zero order reflection to provide the mirror of the interferometer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.