Plasma constituent analysis by interferometric techniques
US5225888A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 26, 1990 |
| Grant date | Jul 6, 1993 |
| Priority date | — |
| Expiry date | Dec 26, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/62
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An interferometer (18 or 40) is used to identify trace constituents in a plasma during processing semiconductor devices such as transistors. Light emissions collected from the processing chamber (10) are collimated by lens (14) and transmitted to the interferometer (18 or 40) which selectively allows therethrough particular wavelengths of light which are characteristic of the excitation emissions of certain atoms such as sodium and copper. The light intensity at the selected wavelengths is sensed by a photomultiplier tube (30). In one embodiment, the interferometer (18) is a Fabry-Perot type interferometer and the separation of the plates (20 and 22) which form the Fabry-Perot etalon is controlled using a piezoelectric driver (26). A signal processor (34) correlates the sensed light emissions from the photomultiplier tube (30) with the selected wavelength that is determined by the piezoelectric driver (26). In another embodiment, the interferometer (40) is a narrow bandpass interferometric filter which is tiltable with respect to the collimated incident light from the processing chamber (10). Tilting a narrow bandpass interferometric filter (42) with respect to incident light chang…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.