Method and apparatus for article inspection including speckle reduction
US6798505B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 12, 2003 |
| Grant date | Sep 28, 2004 |
| Priority date | — |
| Expiry date | May 12, 2023 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/479
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for reducing speckle during inspection of articles used in the manufacture of semiconductor devices, including wafers, masks, photomasks, and reticles. The coherence of a light beam output by a coherent light source, such as a pulsed laser, is reduced by disposing elements in a light path. Examples of such elements include optical fiber bundles; optical light guides; optical gratings; an integrating sphere; and an acousto-optic modulator. These various elements may be combined as desired, such that light beams output by the element combinations have optical path length differences that are greater than a coherence length of the light beam output by the coherent light source.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.