Electrochemical investigation of copper contamination on silicon wafers from HF solutions

Copper contamination of silicon wafers from 50:1 HF solutions containing 0 to 100 ppb Cu was studied using dc electrochemical techniques. As the level of copper concentration in HF solutions increased, the corrosion current density and corrosion potential of silicon as well as the amount of copper deposition were increased. Upon addition of a nonionic surfactant, the corrosion potential, corrosion current density, and the extent of copper deposition were decreased. However, the levels of deposited copper and surface roughness were dependent on sufactant concentration. When H₂O₂ was added to copper-spiked HF solutions, the open-circuit potential of silicon recovered to a value that is characteristic for silicon immersed in a mixture of H₂O₂ and HF indicating the removal of deposited copper on silicon.