Roles of copper mechanical characteristics in electropolishing

Abstract

We investigated the effect of film stress, hardness, and grain size of copper films on copper electropolishing, which was considered as a next-generation technique in copper multilevel interconnects. The copper electropolishing rate was found to increase with an increase in the tensile stress of copper films. It was suggested that the tensile stress weakened metallic bonds between copper atoms and assisted the copper electropolishing rate, whereas the hardness and grain size of polished copper films did not relate directly to the copper electropolishing rate due to a negligible etching effect and no mechanical stress applied during copper electropolishing in a concentrated phosphoric acid electrolyte.