Analysis of Convective Mass Transfer by Potential Relaxation: III . Active and Passive Copper Dissolution at a Rotating Disk

Abstract

A linear potential relaxation technique was used successfully to determine effective liquid-phase mass transfer boundary-layer thicknesses during active dissolution and cupric sulfate salt film thicknesses during passive etching for a copper rotating disk electrode immersed in a CuSO4-H2SO4 electrolyte. Experimentally measured concentration overpotentials immediately after current interruption were found to decay linearly with the square-root of time. A theoretical model was derived to calculate liquid-phase effective mass transfer boundary-layer thicknesses or salt film thicknesses from the slope and intercept of the linear potential decay regime. For active copper dissolution, effective mass transfer boundary layer thicknesses were =56% smaller than those for cathodic deposition. The following Sherwood-Schmidt-Reynolds number correlation was developed from these relaxation experiments Sh = 1.39 Sc ~ Re ~176

Surface Chemistry Studies of Copper Chemical Mechanical Planarization

“…27 If the concentration of cupric ions exceeds the saturation limit, the cations might react with water molecules or other dissolved species in the slurry to form solid cupric oxide species on the metal surface. 28 The Cu removal behavior of Fig. 11 might be influenced by whether or not a CuO layer is present on the metal surface during polishing.…”