Method and apparatus for evaluating the thickness of thin films
US5181080A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 23, 1991 |
| Grant date | Jan 19, 1993 |
| Priority date | — |
| Expiry date | Dec 23, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/065
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus is disclosed for measuring the thickness or other optical constants of a thin film on a sample. The apparatus includes a laser for generating a linearly polarized probe beam. The probe beam is tightly focused on the sample surface to create a spread of angles of incidence. The reflected probe beam is passed through a quarter-wave plate and linear polarizer before impinging on a quad cell photodetector. The output signals from the photodetector represent an integration of the intensity of individual rays having various angles of incidence. By taking the difference between the sums of the output signals of diametrically opposed quadrants, a value can be obtained which varies linearly with film thickness for very thin films. The subject device can be used in conjunction with other prior devices to enhance sensitivity for thicker films.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.