Study of Charging Induced Attraction Phenomenon in Cobalt Silicide Defects

This paper investigates the detrimental effects of surface charging induced by Cobalt silicide (CoSi2) processes that involve spin processing, such as the Deionized Water (DIW) Scrubber rinse process. Due to high-speed rotation involved in the spin-cleaning process, high surface charge is accumulated on the wafer. This poses adverse effects on the wafer, such as charge-induced defectivity which is further studied in this paper. A technique used to prevent charge build-up is through the injection of Carbon Dioxide (CO2) into the Ultra-pure water (UPW), which reduces its resistivity and enables the static charges to be safely dissipated. An experiment was conducted to understand the effects of surface charging on the wafer at different CO2injection levels. It was found that below a certain threshold level of CO2injection, an undesirable phenomenon was observed with the formation of a unique wafer defect, characterized by localized Cobalt (Co) defect on Cobalt Silicide (CoSi2) regions. The failure mechanism is unraveled in this paper as a charge-induced particle attraction phenomenon. This emphasizes the critical role of surface potential control in eliminating charge-induced defects in advanced silicide processes.