Surface Evolution during the Chemical Mechanical Planarization of Copper

Stressed surfaces are configurationally unstable under chemical etching wherein they may evolve to reduce their total energy. This paper investigates how such an effect may influence the planarization rate in a Chemical Mechanical Planarization (CMP) process. Nano-wear experiments on electro-plated copper surfaces have been conducted with systematic exposures to chemically active slurry. The nano-wear experiments have been first performed to generate local variation of the residual stress levels, followed by chemical etching to investigate the variation of the wear depth and the evolution of surface topography. It is found that the residual stress caused by the mechanical wear enhances the chemical etching rate.