Monitoring and control of vacuum processes using a remote plasma emission spectroscopy based sensor

Some form of monitoring of the vacuum is essential for the efficient operation of any vacuum processes. In particular, residual gas analysis (RGA) can be performed with quadrupole mass spectrometers. Residual Gas Analysis allows for detection and identification of individual species within the vacuum. This can result higher process yields through faster troubleshooting, scrappage reduction through contamination detection, or a more controlled vacuum environment. The limiting factor for Quadrupole RGAs is the pressure range over which they can operate. Above 1𝑥10−4 mbar damage will occur to the sensor’s filament. An alternative residual gas monitoring sensor that operates directly at pressures above 1𝑥10−4 has been built around plasma emission monitoring. A small “remote” plasma can be generated inside a vacuum sensor. Consequently, species that are present within the vacuum will become excited in the sensor’s plasma, emitting a spectrum of light, which can then be used to identify and monitor the emitting species, resulting in a robust, lower-cost, multi-purpose vacuum sensor. Presented are examples and findings from using this method for monitoring of plasma treatment and deposition in a roll-to-roll system, leak detection in semi-conductor fabrication, contaminant detection in a tool coating system and comparisons with an equivalent differentially pumped RGA.