Defect detection system
US6538730B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 6, 2001 |
| Grant date | Mar 25, 2003 |
| Priority date | — |
| Expiry date | Apr 6, 2021 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/21
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Scattered radiation from a sample surface is collected by means of a collector that collects radiation substantially symmetrically about a line normal to the surface. The collected radiation is directed to channels at different azimuthal angles so that information related to relative azimuthal positions of the collected scattered radiation about the line is preserved. The collected radiation is converted into respective signals representative of radiation scattered at different azimuthal angles about the line. The presence and/or characteristics of anomalies are determined from the signals. Alternatively, the radiation collected by the collector may be filtered by means of a spatial filter having an annular gap of an angle related to the angular separation of expected pattern scattering. Signals obtained from the narrow and wide collection channels may be compared to distinguish between micro-scratches and particles. Forward scattered radiation may be collected from other radiation and compared to distinguish between micro-scratches and particles. Intensity of scattering is measured when the surface is illuminated sequentially by S- and P-polarized radiation and compared to disting…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.