AN APPROACH TO IMPROVE INITIAL PUMP-DOWN SPEED OF TURBOMOLECULAR PUMPS BY WATER-REPELLENT COATING ON THE BLADES

Outgassing from turbomolecular pump (TMP) blades affects not only the ultimate pressure but also the initial rate of decrease of the inlet p ressure. A longer evacuation time to attain a high vacuum is required for TMP than for a cryopump, because TMP's pumping speed for wafer, th e dominant species of desorbed gases, is lower than that of the cryopu mp. The aim of this study is to develop a TMP which enables quick evac uation without the use of a cryotrap. The surface free energy or the w ater-repellent characteristics are considered to be important in the e vacuation of water from surfaces. A special surface coating which has better water repellent characteristics than an uncoated surface of alu minum alloy was developed, and outgassing from this surface was invest igated. Copyright (C) 1996 Published by Elsevier Science Ltd.