Microstructure evolution of electroplated Cu during room temperature transient

Abstract

Previously the Cu resistance transient time was found to be dependent on the electroplating current. It was shown that longer transient times were correlated with a greater incorporation of plating impurities for the bath chemistry used in this study. The present work shows that the grain growth that occurs during the resistance transient is initiated by the formation of abnormally large grains, where the transformed structure reveals strong /spl Sigma/3 type twinning. The increase in the fraction of twin grain boundaries with transient time is quantified, and a comparison of the time dependencies of resistivity and the grain size shows that the Mayadas-Shatzkes model can qualitatively describe grain boundary resistivity. X-ray analysis revealed that the structure is strongly {111} textured and the contribution of {200} texture increases during transformation. Atomic Force Microscopy (AFM) and imaging with the secondary electron in-lens detector showed that surface morphology of Cu structures varies across the film and is dependent on the plating current.