Patent ID: 6534007
Filing Date: 2003-03-18
Classification: C23C,H01J,Y10S

Abstract:
Apparatus for detecting the endpoint of a plasma cleaning process for removing a residue deposited on an interior surface of a chemical vapor deposition chamber, wherein said residue is deposited on said surface by a chemical vapor deposition process performed in the deposition chamber before the cleaning process is performed, comprising:a chemical vapor deposition vacuum chamber having a chamber wall enclosing an interior of the chamber, wherein the chamber wall includes a surface exposed to said interior on which said residue deposits during said chemical vapor deposition process; a plasma source connected to the chamber so as to maintain a plasma in the interior of the vacuum chamber, wherein the plasma includes one or more reactive species that react with said residue on the chamber wall; a first photodetector that produces a first electrical signal responsive to light emissions only at a wavelength substantially equal to a characteristic emission wavelength of one of said reactive species, the first photodetector being optically coupled to receive light from the interior of the vacuum chamber; a second photodetector that produces a second electrical signal responsive to light emissions over a wider range of wavelengths than the first photodetector, wherein the second photodetector is optically coupled to receive light from the interior of the vacuum chamber, and wherein said wider range of wavelengths includes light emissions of at least one background gas in the vacuum chamber; and a circuit, connected to receive the first and second electrical signals, for signalling the occurrence of an endpoint only after the ratio of the first electrical signal to the second electrical signal exceeds a threshold.