Patent ID: 6878214
Filing Date: 2005-04-12
Classification: H01J,H01L,Y10S

Abstract:
1. A method for determining an endpoint of a cleaning process running in a chamber that comprises steps of: directing radiation having wavelengths overlapping an absorption band of a byproduct of the cleaning process into an exhaust line of the chamber; receiving radiation from the exhaust line; filtering the radiation received from the exhaust line through a first filter that transmits radiation at said absorption band of said byproduct; filtering the radiation received from the exhaust line through a second filter that transmits radiation in a band of wavelengths different from said absorption band of said byproduct; determining a measure of absorbance of the radiation by the byproduct by subtracting the radiation filtered through the second filter from the radiation filtered through the first filter; amplifying said measure of absorbance to provide a voltage signal; and determining the endpoint when the voltage signal reaches a predetermined voltage level.