Methods and apparatus for detecting impurities in semiconductors
US5007741A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 25, 1989 |
| Grant date | Apr 16, 1991 |
| Priority date | — |
| Expiry date | Sep 25, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/8461
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The purpose of the invention is to detect impurities in a semiconductor wafer (20). A laser (21) forms a light beam having a high proportion of its power at an optical frequency capable of being absorbed by the impurity to be measured. The beam is split into first (25) and second (26) light components, one of which is directed at the surface of the semiconductor wafer (20) to be tested and the other at a reference semiconductor wafer (27) containing a known quantity of the impurity to be measured. The light intensities reflected from the two wafers is detected by photodetectors (29, 30) and their difference is taken as a factor in measuring the impurity density in the wafer under test. A polarizer (33) polarizes the beam such as to maximize p-type component and minimize s-type components. Reflection from each of the two wafers (20, 27) is at the principal angle.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.