Method and apparatus for optically detecting surface states in materials
US4750822A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 28, 1986 |
| Grant date | Jun 14, 1988 |
| Priority date | — |
| Expiry date | Mar 28, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/1789
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus is disclosed for detecting defect surface states in any material and in particular semiconductors. In the subject device, a periodic localized excitation is generated at the surface of the sample with an intensity modulated pump laser beam. A probe laser beam is directed to the surface of the sample and changes in the probe beam which are in phase with the modulated pump frequency are detected. In the preferred embodiment, periodic changes in the optical reflectivity of the surface of the sample induced by an intensity modulated excitation beam are detected by measuring the corresponding modulations in the reflected power of the probe beam. Any time dependence of the probe beam modulated reflectance signal is monitored. An evaluation of defect surface states is then made by investigating the time dependence of the magnitude and/or phase of this probe beam modulated reflectance signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.