The interior of a vacuum chamber is maintained at a specified pressure by introducing a specified gas into the vacuum chamber having a plasma trap provided therein. Simultaneously, therewith, evacuation of the chamber is performed by a pump as an evacuating device, and a high-frequency power of 100 MHz...http://www.google.de/patents/US20050011453?utm_source=gb-gplus-sharePatent US20050011453 - Plasma processing method and apparatus
