The multi-metal microcontamination of silicon wafer surface was studied by electrochemical impedance spectroscopy (EIS) under the metallic impurity concentrations close to the practical applications (μg/g level) based on the one-metal microcontamination effect. The characteristic EIS spectra were measured in the HF solutions containing one and three or four different metals simultaneously at the levels of 0.5 and 1 μg/g, respectively. The kinetic parameters of electrochemical reactions at the Si/HF interface were evaluated by the equivalent circuit. The cffects of single or multi-metal types on the electrochemical behaviors of silicon were also investigated in combination with SEM observations. Silicon surface became rougher by copper deposition, which is directly accelerated in the presence of iron and nickel by corroding the Si surface and by increasing the charge density of Si surface, respectively, while reduced by calcium due to the formation of CaF2, which acts as a passivated surface to delay copper deposition.

Key words: silicon, metal impurity, EIS, metal coexistence