Identification and Control of Surface Charge Defect Induced by Wafer Spin-Cleaning Process

An arcing-like phenomenon taking place around the wafer center area during the wafer spin-cleaning process was investigated. Due to the high-speed rotating operation, friction between materials with very high resistivity such as DI(Deionized) water, dielectric films and non-conductive clean tool hardware builds up surface charge on the wafer. Then it causes arcing or local Si damage by an instantaneous discharge when conductive chemical mixture contact with the surface. In this study, a detailed evolution of the accumulated wafer surface charge was monitored by the real-time electro-static meter, and the disruptive discharging phenomenon was successfully revealed. In order to control the surface charge defects in spin-cleaning process, it was found to be effective to implement an improved cleaning sub-process adding a wafer backside pre-injection step, which safely releases the accumulated surface charge, as well as to adopt a conductive tool chuck and CO2 dissolved water. In addition, it was found through CFD(Computational fluid dynamics) analysis that the charge distribution of the wafer surface is greatly affected by flow characteristics such as the wall shear stress in the DI water rinse process.