20-KELVIN CRYOPUMPING IN MAGNETRON SPUTTERING SYSTEMS

There is a tendency to employ cryopumps based on closed-cycle cryogenerators in sputtering applications requiring hydrocarbon-free vacuum conditions. It has also been recognized that the residual gas contamination level can be lowered by using high inert gas throughputs. It will be shown that a cryopump of the K-20 type, providing similar 12 W at 20 K plus similar 50 W at 80 K, meets both of the above-mentioned specifications by offering a good (unthrottled) pumping performance at inert gas pressures up to 4 multiplied by 10** minus **1 Pa with throughputs up to 3. 3 multiplied by 10**3 Pa1s** minus **1, without using LN//2. The results, obtained with a standard available AlSi magnetron sputtering system, include pumping speed measurements for several gases and the effect of high gas loads on the pumping performance.