Metal capping of MCM thin film features using a laser

Abstract

A laser process to provide a thin barrier or capping metal, over the copper features of a multichip module thin film (MCM-D) structure is described. Capping of copper features is required to avoid copper corrosion and diffusion into overlaying dielectric layers of thin film structure. Furthermore, in a multilevel thin film structure, certain barrier metals provide improved adhesion for the subsequent dielectric layer. Experiments with XeCl and Nd:YAG lasers were performed to determine the best laser source for a copper/polymer/ceramic material set. The laser capping process is more robust and quicker than conventional photolithography or electroless plating capping processes, while eliminating the wet chemical operations. Also, the laser capping process eliminates the undercapping and variable capping metal thickness problems associated with photolithography and/or electroless plating techniques. The results of capping metal features on bare glass ceramic and polymer surfaces are described.<>