Investigating the edge effects of Cu electroplating on the SAMs-coated Si substrate

Self-assembled monolayers (SAMs) are used to pattern the surface for metal deposition to study its effect on Cu deposition. Here, Cu electrodeposition was studied under diffusion and kinetic control regimes on an octadecyltrichlorosilane SAMs-coated (OTS SAMs) patterned Si/Cu substrate. First, the SAM-modified surfaces of the Si substrates were confirmed by contact angle and infrared spectroscopy. Cyclic voltammetry and electrochemical impedance spectroscopy show that the OTS SAMs hindered ion migration to the Cu and Si substrates and charge transfer on the Si surface. Constant voltage electrodeposition of Cu was performed on the patterned Si/Cu substrate. Under kinetic control conditions, the edge effect was reflected in the edge lump Cu growth with higher current density, and the edge Cu growth could be suppressed by OTS SAMs. Under diffusion control conditions, due to the defects and desorption of SAMs, the growth of Cu at the edge is rough with large dendrites formed. The formation of Cu dendrites may be resulted by a nonuniform high-impedance suppression layer. The edge effects can be optimized by the overpotential condition and the Cu concentration which could further improve the aspect ratio of Cu metallization for Si solar cell.