The role of oxygen in the intrinsic tensile residual stress evolution in sputter-deposited thin metal films

Abstract

The intrinsic tensile stress and oxygen content in thin Cr films sputter deposited at high argon pressure are investigated as a function of negative substrate bias. With increasing bias from 0 to −100 V, the tensile stress increases to a maximum while the oxygen content decreases. At bias higher than −100 V, the tensile stress decreases but no significant change is observed in the oxygen content. A similar trend in stress evolution with bias is also observed in Cr films capped with Al to protect from postdeposition oxidation. It is concluded that, for a given deposition condition, the incorporation of oxygen may lower the magnitude of tensile stress without affecting the trends in stress evolution with increasing substrate bias. These effects are discussed using a model that correlates the film microstructure with long range attractive forces predicted from interatomic potentials.