Electrochemical investigations of p-n junction and copper deposition on semiconductor silicon wafers

Semiconductor silicon plays a significant role in microelectronic industries. This investigation is conducted to study the electrochemical behavior of p-n junction and copper deposition on p(100) and n(100) silicon wafers in dilute hydrofluoric acids. The silicon/solution interface is characterized by use of electrochemical DC polarization and AC impedance techniques under both illuminated and dark conditions. The results reveal that the electrochemical reactions take place favorably and become predominated at the Si/solution interface under illuminated conditions, while silicon is in the depletion region under dark conditions, accordingly, its semiconductor properties play an important role. It can be predicted from the electrochemical studies of p-type and n-type silicon that p-type silicon will behave as a cathode and n-type silicon will act as an anode in p-n junction under the illumination. The reaction rate at the interface of p-n junction is significantly accelerated in the copper contaminated solutions. However, under the dark condition p-type silicon will be an anode and n-type silicon will be a cathode. The nature of copper deposition onto silicon wafer surfaces is investigated by ac impedance spectroscopy, and the effects of illumination and depositing time have been also examined. It has been demonstrated that ac impedance spectroscopy is effective to study the ppb level of copper contamination from dilute HF solutions onto silicon wafer surfaces.