ABSTRACT
Plasma reactors intended for surface treatment, etching, thin-film deposition, or other forms of plasma processing use a variety of specialized techniques and devices designed to facilitate processing or to improve the quality and uniformity of the result. When implementing a control strategy for plasma processing, it is necessary to measure and control the flow rate, composition, and total pressure of the working gas. In a characteristic plasma-processing application, the vacuum-related parameters that need to be known include the gas flow rate, the working gas pressure, the vacuum system volume, the neutral gas dwell time, and the vacuum pumpingspeed. The working gas flows into the vacuum system in a way normally intended to promote uniformity of effect over the workpiece surface. During plasma processing, and particularly during its initial and final phases, the evolution of reaction products and the gas load on the pumping system may vary.
