EFFECTS OF CHLORIDE ION ON COPPER DEPOSITION INTO POROUS SILICON

摘要

To understand the inhibition effect of chloride ions on the immersion plating of copper into porous silicon, some electrochemical experiments were carried out in CuSO_4 solutions containing NaCl and CuCl. Current-potential measurements show that the reduction of copper ions occurs in two steps which shift in opposite directions as the concentration of NaCl increases. They are attributed to the reduction of Cu(Ⅱ) to Cu(Ⅰ) and Cu(Ⅰ) to Cu(0). This suggests that cuprous species can be stable over a certain potential range if there is an excess amount of chloride ions in the CuSO_4 solution. Consequently, whether copper is deposited or not on porous silicon is determined by the rest potential established when porous silicon is immersed in the solution. The inhibition effect associated with the existence of cuprous species is discussed by considering the rest potential of porous silicon in various copper ionic solutions.