End point detection in etching wafers and the like
US4317698A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 13, 1980 |
| Grant date | Mar 2, 1982 |
| Priority date | — |
| Expiry date | Nov 13, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/272
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method for detecting the end point of etching wafers and the like by reflective means. Typically, a detected reflectance signal will have a threshold level representing a lack of substantial etching, a dip in the threshold level representing the commencement of etching and an inflection level representing a maximum rate of light amplitude change. The present method involves subtracting the inflection level from the threshold level and taking a predetermined fraction of the resultant level to define a second threshold level further in the etch cycle which anticipates the end of the cycle. By observational experience, the predetermined fraction can be determined. As soon as the second threshold level is reached, brakes are applied to the etching process so that etching will cease shortly after the predetermined level has been identified. In this manner, the actual end of etching will coincide with the attainment of a desired etching condition, such as removal of a layer of undesired metalization, without significant overshoot.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.