Residual gas analysis (RGA) was used for troubleshooting tetra (ethoxyorthosilicate) (TEOS) and tungsten silicide chemical vapor deposition processes. In each process, RGA identified reactor impurity sources later proven to be the root cause of film defects and foreign material deposition. RGA verified the effectiveness of modified reactor hardware and operating procedures. This paper describes two case studies that represent RGA contributions to the 0.5-μ process development at the IBM semiconductor manufacturing facility in Essex Junction, Vermont.