Characterization and real time fault detection of vacuum leaks in plasma nitridation tools

Plasma nitridation processes for the nitridation of thin gate insulators has been common practice throughout the industry since the late 1990´s. Although considerably robust there have been a number of events in the recent past where the vacuum integrity was compromised as a result of mechanical fatigue of chamber components. The work described here was intended to investigate the effects of vacuum leaks on the resultant film composition via the introduction of both artificial leaks and those observed as a result of true field failure. Silicon oxynitride films were synthesized for a number of different leak rates and under a number of different conditions. X-ray photoelectron spectroscopy (XPS) was used to characterize the films in terms of their nitrogen/oxygen content and thickness. A residual gas analyzer (RGA) was configured to analyze the composition of the process gasses in a compromised chamber and indicates the introduction of oxygen. In-situ real time leak detection was an additional objective of the investigation and control methodologies were constructed around optical emission spectroscopy (OES) and univariate numerical models. Results indicate that the broadband emission spectra are sensitive to contaminate gasses however, the location of chamber leak was found to be a important factor in the successful employment of an OES based detection strategy.