Vacancy-induced plastic deformation in electrodeposited copper films

A tensile stress developed in polycrystalline copper films during room-temperature aging was computed using a diffusion equation for excess vacancies migrating to the grain boundaries. This theory is based on an assumption that a free volume created by the arrival of excess vacancies at the grain boundaries of thin copper films is instantly eliminated and this action introduces a biaxial tensile stress over the film plane. The tensile stress was calculated as a function of aging time, grain size, and excess vacancy concentration. It was found that the tensile stress could exceed the yield stress of copper. This result suggests that a plastic deformation could occur in electrodeposited copper films during room-temperature aging, consistent with experimental observations. copyright The Electrochemical Society.