ABSTRACT
Abstract-We have studied the stress evolution in thin metal films on Si substrates as a function of Ar pressure during sputtering, substrate bias and post-deposition ion irradiation. With increasing bombardment, the tensile stress is observed to increase to a maximum, and then transitions to compressive stress that also reaches a maximum. We show that the maximum tensile strain may be estimated from the grain size and the interatomic potential. We further show that the compressive stress maximum is related to the saturation in point defect concentration, with smaller contribution from entrapped Ar. We use dislocation-based models to estimate the film yield strength and show that the maxima in both tensile and compressive residual stresses are set by the film yield strength. Compressive yield strength is higher as compared to tensile strength due to hardening from point defects.
