Method for endpointing CVD chamber cleans following ultra low-k film treatments

A method of determining the endpoint for cleaning a CVD chamber, the method comprising:

• providing a CVD chamber with a device configured to monitor optical emission intensities from within the CVD chamber, the chamber having silicon-based and organic-based ULK precursor film residues on its internal surfaces;
• exposing the residues on the interior surfaces of the CVD chamber to an oxidizing plasma treatment employing oxygen-containing and fluorine-containing source gases and an inert background gas;
• monitoring the intensity of one or more optical emission lines of one or more atomic and/or molecular species that are products of the oxidation of the organic-based residues and of one or more emission lines of a species originating from the inert background gas during the plasma exposure;
• and
• determining the substantially complete removal of the residues when the ratio of the optical emission intensity of the one or more species that are products of the oxidation of the organic-based residues to the one or more emission lines of a species originating from the inert background gas reaches a low steady state level.