|In plasma processing, the process conditions can generally not be completely defined because of the ageing of the process chamber and tool and even more so because of the influence of deposited layers, e.g. polymers, on the chamber walls. Therefore efficient and stable processing in the semiconductor industry requires a robust and reliable monitoring of the "internal state" of the plasma process chamber. In this proposal, critical plasma processes used in high volume IC production are in-situ monitored by means of a novel technique - Self Excited Electron Resonance Spectroscopy (SEERS). Furthermore, the data flow generated is integrated with Advanced Process Control (APC) concepts using SECS/GEM so enabling the control of process values such as etch rates and etch uniformity. This will lead to a general improvement in the overall plasma process stability. The final goal is to show an increase of manufacturing parameters such as Overall Equipment Effectiveness.