Patent ID: 6837250

Claim:
A method of using PFCs recovered from the effluent of a CVD chamber cleaning process as an influent for the CVD chamber cleaning process, comprising the steps of: (a) selecting a first PFC gas mixture having a first ratio of C 2 F 6 to CF 4 wherein the first ratio of C 2 F 6 to CF 4 is less than or equal to the following equation: ( 1 - C + ( C · U ) ) G · C where U=Utilization of CF 4 in the plasma; G=Generation frequency of CF 4 from C 2 F 6 ; and C=Capture efficiency of CF 4 , (b) providing the first PFC gas mixture as the influent gas to the CVD chamber, wherein the influent gas reacts during the cleaning process to create a CVD chamber effluent gas comprising a second PFC gas mixture having a second ratio of C 2 F 6 to CF 4 ; (c) adding virgin C 2 F 6 or CF 4 to the CVD chamber effluent gas in sufficient quantity to create a third PFC gas mixture having the first ratio of C 2 F 6 to CF 4 ; (d) using the third PFC gas mixture as the influent gas to the CVD chamber; and (e) continuing to add virgin C 2 F 6 or CF 4 to the CVD chamber effluent gas to create the third PFC mixture and continuing to use the third PFC gas mixture as the influent gas to the CVD chamber.