Process control based on quadrupole mass spectrometry

Real-time feedback control of semiconductor processes based on in situ sensors can complement present statistical process control techniques. In this article, we explore the potential of quadrupole mass spectrometry as an in situ sensing technique. We show that it is possible to sense the fluxes of important species in a plasma process and use these measurements to implement a multivariable control scheme. As an example, the control of hydrogen, unreacted ammonia, and direct current bias in a plasma enhanced chemical vapor deposition silicon nitride process is demonstrated. (C) 1996 American Vacuum Society.