Method and apparatus for inspecting substrates
US6566674B1 · kind B1 · utility
77Cited by
32References
30Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Jun 21, 1999 |
| Grant date | May 20, 2003 |
| Priority date | — |
| Expiry date | Jun 21, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/88
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Apparatus for detecting defects in a substrate comprises a laser for providing a laser beam, and a bi-cell photodiode comprising two cells. Circuitry coupled to the bi-cell photodiode provides a signal equal to (L−R)/(L+R), where L and R equal the signal strengths of the signals provided by the left and right photodiode cells, respectively. The photodiode is biased so that it exhibits reduced capacitance, and can provide increased output signal bandwidth.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.