Cryogenic versus turbomolecular pumping in a sputtering application

Abstract

Performance comparisons were made using a quadrupole mass spectrometer between nominal 1000 l/s turbomolecular and cryogenic high vacuum pumps on a commercially available sputter deposition system. The quadrupole analyzer was mounted in a differentially ion-getter-pumped sampling chamber to allow gas analysis at sputtering pressures. The cryogenic pump without liquid nitrogen trapping showed pumpdown performance comparable to the turbomolecular pump with liquid nitrogen trapping. We were unable to get repeatable meaningful results of residual gas behavior during sputtering operations when argon was let into the ion-getter-pumped sampling chamber. We have concluded that the 20 l/s ion-getter pump should be replaced with a pump capable of stably handling argon gas loads during sputtering.