Method and apparatus for determining a material's characteristics by photoreflectance using improved computer control
US5270797A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 13, 1989 |
| Grant date | Dec 14, 1993 |
| Priority date | — |
| Expiry date | Sep 13, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2201/0695
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for determining the characteristics of materials, particularly of semiconductors, semiconductor heterostructures and semiconductor interfaces by the use of photoreflectance, in which monochromatic light and modulated light beam reflected from the sample is detected to produce a d.c. signal and an a.c. signal, whereby the d.c. signal is applied to one input of a computer and the a.c. signal is used with another input of the computer which controls the light intensity of the monochromatic light impinging on the sample to maintain the d.c. signal substantially constant. A stepping motor is preferably utilized for varying the light intensity of the monochromatic light which is controlled by a computer to re-establish rapidly a predetermined d.c. signal established during normalization procedures when the light intensity of the monochromatic light changes, especially during change of its wavelength. Additionally, the modulation frequency of the modulated beam and/or the wavelength of the monochromatic light can also be varied by the computer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.