Chemical Generation Mechanism of Copper Flakes on Copper Wafer Surface from CMP Slurry and Post CMP Cleaning Chemistry

Inhalt:
Recently Cu flakes became major defect after Cu CMP process because it generates ring scratch when they adhere to the Cu wafer surface. This paper reports the mechanism of Cu flake formation based on well-known Cu CMP slurry and cleaning chemistry such as surfactant, pH adjuster and corrosion inhibitor. During the Cu CMP and cleaning process, the Cu surface etching can produce Cu ions. These ions are exposed to complex slurry chemistry during polishing. It was found that the Cu metal particles were generated by a chemical redox reaction with different size and shape in specific slurry chemistry, pH, temperature and their concentrations. A new pathway is proposed for the formation of Cu flakes during CMP process. Keywords: Cu CMP, Metal defects, Cu flakes, Redox reaction, pH