Manufacturing of solder bumps with Cu/Ta/Cu as under bump metallurgy

This study investigated the feasibility of the multilayer Cu/Ta/Cu under bump metallurgy (UBM), deposited on AlN/Si where AlN is a thin film. An interdiffusion study found that Ta is an appropriate diffusion barrier layer for the investigated solder bump structure. The temperature profiles and the flux compositions for solder reflow were also investigated. The flux activators investigated include succinic acid, adipic acid, stearic acid, dimethylamine hydrochloride, and diethylamine hydrochloride. Among these, succinic acid was the most appropriate in terms of wetting and cleaning.