Effect of impurity and illumination on copper oxidation after chemical mechanical polishing

Copper-oxide defect is initiated at the grain boundary on the interconnect surface, and size increases with time and finally reaches a fixed value over a period of time after chemical mechanical polishing. The growth rate of copper oxide increases with increasing impurity content, resulting in more nucleation sites. Illumination significantly enhances and accelerates the growth rate at the initial nucleation stage by providing more electron carriers and acceptors for copper-oxide generation. Additionally, the nucleated reaction can be enhanced by illumination at the grain boundary with more sulfur content. Optical scan and X-ray photoelectron spectroscopy results prove that the illumination effect has a stronger correlation to sulfur than carbon or oxygen. (C) 2008 The Electrochemical Society.