Electrochemical Grafting of an Aminated Poly(methyl methacrylate) (PMMA)-like Liner onto a Silicon Surface for the Metallization of Microfeatures

Abstract

The micro/nanofabrication industry’s transition from physically deposited dielectric films toward relatively inexpensive insulating polymeric materials faces a challenging metallization step in progression. In this work, we demonstrate a metallization scheme constituting simple and completely aqueous chemical steps─from Si passivation to metallization. We first propose a versatile diazonium-based electrochemical process to graft an in situ aminated poly(methyl methacrylate) (PMMA) liner onto Si microfeatures with high step-coverage. These amine-terminated groups functionalize the grafted PMMA-like liner with palladium chloride complex activators and allow direct autocatalytic deposition of Ni–B film while avoiding any further amination step as conventionally required for polymeric surfaces. The obtained Ni–B film exhibiting high uniformity, strong adhesion to the polymer film, and excellent step-coverage from the top, sidewall, and bottom of the microstructures fulfills all requirements of a conducting seed layer for the subsequent electrolytic deposition of copper.