In Situ Stress Measurements During Copper Deposition

Abstract

In situ stress measurements were made during copper electrodeposition onto (111)-textured Au from acidic sulfate electrolyte using the wafer curvature method. During the bulk deposition of Cu, there is a rapid increase in tensile stress during the first 20 nm of growth that we attribute to nuclei coalescence and grain boundary formation. The magnitude of the tensile stress as well as the film thickness at which the maximum stress occurs are both dependent upon the electrode potential due to its influence on the nucleation density. As the deposit thickens, the average film stress decreases rather quickly and can become compressive in deposits formed at small deposition overpotentials. Both of these observations are consistent with stress-generation models proposed in the literature. When deposition is interrupted, both tensile and compressive components of the stress relax but are quickly re-established when deposition is resumed, suggesting that the relaxation is reversible and not due to irreversible microstructural changes.