Ultra clean process gas recycling system for plasma process using krypton and xenon

Introduction of rare Kr(Xe) gases into ULSI mass production requires the recycling of exhaust gases. We describe a gas pumping system that enables efficient recycling of Kr and Xe gases. A newly developed screw pump is able to exhaust without involving the atmosphere in its exhaust gases. Moreover, this screw pump needs a smaller volume of purge gases to realize clean pumping than conventional dry pumps. A novel bellows pump can compress recycle gases without involving the atmosphere. These pumping systems enable ultra clean process gas recycling system for the plasma process using krypton and xenon.