Ion-Assisted Sputter Deposition of Mo-Si Multilayers

Abstract

Mo-Si multilayer (ML) structures fabricated using DC magnetron sputtering in an Ar plasma show a transition from layer to columnar growth as the deposition pressure is increased above ~1 mTorr. The dominant effect of the increased deposition pressure is the increased thermalization of Ar neutrals, reflected in charge exhange collisions with the sputtering target, striking the substrate surface. At high deposition pressure there is less energy deposited at the substrate surface which, in turn, modifies the adatom mobility. These effects markedly impact the layer morphology. The layers are observed to have significantly increased roughness at higher deposition pressures. Consequently, the x-ray optical properties of the ML coatings are strongly effected. The measured normal incidence reflectivity at 130 Å decreases from ~60% to 14% as the deposition pressure is raised from 2.5 to 10 mTorr [1].