Process control methodology for PSG and PETEOS films in a highly interactive multiprocess CVD system

Abstract

A step-by-step control methodology for targeting and controlling plasma enhanced tetraethylorthosilicate (PETEOS) and phosphosilicate glass (PSG) deposition processes in a single wafer PECVD chamber has been developed. Initially, PSG and PETEOS processes were characterized using two full factorial design of experiments processed through a single CVD reaction chamber utilizing RF power, TEOS ampule temperature, electrode spacing and TMP flow as the control factors, and deprate, film uniformity, film stress, and wt%phos content of the PSG film as responses. Based upon results obtained from the RS/1 analysis of both DOEs, additional experiments were processed to investigate the interactions of significant effects for both films. Using this information, a process control hierarchy was developed for the PETEOS process in the order of adjustment electrode spacing, TEOS ampule temperature and RF power to center PETEOS uniformity, deprate and stress. A similar hierarchy was developed for PSG. Generous limits were established to control the PSG process until long-term interactions between the two processes could be defined. Once these effects were characterized, a combined process methodology for both processes was developed, and PSG control limits for deprate were reduced by +/-50%. The final step was the organization of the combined methodology into a step-by-step procedure for targeting both PETEOS and PSG processes simultaneously. Benefits of this method of process control include increased compliance to SPC limits for both processes and a reduction in the amount of time required for problem troubleshooting.