Thin film thickness monitor
US5241366A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 4, 1992 |
| Grant date | Aug 31, 1993 |
| Priority date | — |
| Expiry date | Mar 4, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/0625
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A thin film thickness monitor using successive reflection of a polychromatic light beam off of reference thin film of variable optical thickness and a sample thin film whose thickness is to be determined, in which a monochromatic light source is used beforehand to first determine the actual optical thickness of the reference thin film at each relative position of the beam and reference thin film. In one embodiment, the ratio S/R of detected light intensity S from the sample thin film and detected light intensity R from the reference thin film is found for each relative position and the position at which the ratio is a maximum is determined. In another embodiment, this ratio is corrected by a corresponding ratio S.sub.1 /R.sub.1 derived from a bare wafer substrate. The sample can then be located behind additional optical surfaces, such as a vacuum port without causing substantial errors. In yet a third embodiment, the detected light intensity R2 from two reflections off of the reference thin film is used in place of intensity R, allowing very thin films to be accurately measured.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.