Serrated Fourier filters and inspection systems
US7397557B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 6, 2005 |
| Grant date | Jul 8, 2008 |
| Priority date | — |
| Expiry date | Jun 27, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/95623
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Serrated Fourier filters and inspection systems are provided. One Fourier filter includes one or more blocking elements configured to block a portion of light from a wafer. The Fourier filter also includes periodic serrations formed on edges of the one or more blocking elements. The periodic serrations define a transition region of the one or more blocking elements. The periodic serrations are configured to vary transmission across the transition region such that variations in the transmission across the transition region are substantially smooth. One inspection system includes a Fourier filter configured as described above and a detector that is configured to detect light transmitted by the Fourier filter. Signals generated by the detector can be used to detect the defects on the wafer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.