Endpoint detection system and method for plasma etching
US4954212A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 26, 1989 |
| Grant date | Sep 4, 1990 |
| Priority date | — |
| Expiry date | Sep 26, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J37/32935
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A plasma etching endpoint detection system and method for plasma etching systems generates an endpoint signal when the etching system completes the etching of a designated layer on a semiconductor wafer and begins etching the layer below the designated layer. An impedance transformation circuit is tuned so that the selected tuning point has a predefined relationship to the point at which minimum power reflection occurs. As a result, when the etching system completes the etching of a designated layer, the amount of power reflected by the plasma etcher will change in a predefined fashion so as to facilitate the generation of an endpoint signal. In one embodiment, a tuning capacitor in the etcher's impedance transformation circuit is set at a level at which it is known that the amount of reflected power will increase when the designated layer has been completely etched. As a result, the intensity of light generated in the plasma will decrease at the endpoint of etching the designated layer. An optical sensor, which is tuned to a frequency at which light is generated while the designated layer is being etched, generates an endpoint signal when the emission intensity decreases below a s…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.