Room-Temperature Recrystallization in Thick Bias-Sputtered Copper Deposits

Deposits of copper up to 1 mm thick were formed at room temperature in a triode sputtering apparatus using a krypton discharge under various conditions of sputtering rate, gas purity, and substrate bias. Room-temperature recrystallization and grain growth displaying no twins were observed within 9 h after removal from the sputtering apparatus. This resulted in a dominant orientation of {100} planes parallel to the substrate-deposit interface. Recrystallization rate increased as a function of increasing deposition rate, gas purity, and substrate bias. It was hypothesized that high intrinsic stress levels in the deposit provided both vacancies and the driving force for their diffusion to grain boundaries. Grain boundaries composed of {100} planes then adsorbed vacancies and moved by a combination of climb and glide. This movement was made possible by the elimination of barrier impurities, primarily oxygen, with the negative bias applied to the substrate during sputtering.