System and method for plasma etching endpoint detection
US5405488A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 13, 1993 |
| Grant date | Apr 11, 1995 |
| Priority date | — |
| Expiry date | Sep 13, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J37/32963
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A plasma etching endpoint detection system monitors two optical wavelengths during etching of a non-opaque dielectric film. A controller coupled to the optical monitoring equipment generates an endpoint detection signal corresponding to a predefined mathematical combination of the monitored intensity of light at the first wavelength and the monitored intensity of light at the second wavelength. When the endpoint detection signal crosses a threshold level, the etching of the dielectric layer is stopped. In a preferred embodiment the two monitored wavelengths differ by approximately a factor of two. More generally, the two monitored wavelengths are selected such that the combined intensity signal has a proportionally smaller false endpoint peak than either of the individual monitored intensity signals. The present invention is beneficial primarily for plasma etching systems in which the optical path of the optical monitoring equipment is not parallel to the surface of wafer being etched, which results in a premature or false endpoint signal produced by alternating constructive and destructive interference between reflected and refracted light.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.