Method and apparatus for optically determining defects in a semiconductor material
US4652757A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 2, 1985 |
| Grant date | Mar 24, 1987 |
| Priority date | — |
| Expiry date | Aug 2, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/1719
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Individual defects in or near the surface of a silicon wafer (16) are detected by directing a time-modulated laser beam (44), having an energy level above the bandgap energy of the silicon material, towards the wafer. The beam (44) is focused to a one to two micron spot (48) on the wafer surface to photoexcite (i.e., pump) a high density of electrons and holes which changes the infrared reflectance in the area of the pumped spot. A probe beam (34) of infrared radiation is directed at the surface (0.126 square mm in area) of the substrate (16) and at a small angle thereto and the reflection thereof monitored by a detector (54). The pumped spot (48) is raster scanned within the area of the probe beam spot (38). The detector (54) detects only that portion of the intensity of reflected probe beam (34) that is modulated by the pump beam frequency to create a video display having a high spatial resolution showing individual defects.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.