Co-MOCVD processed seed layer for through silicon via copper metallization

Abstract

A novel metallization for vertical integration in microsystems technology using through-silicon-via (TSV) was investigated. Cobalt metal-organic chemical vapor deposition (Co-MOCVD) process is capable of forming an excellent conformal ultra-thin film with good adhesion to the copper conductive and diffusion barrier layers. Co layer as a seed layer provides a direct copper electrochemical deposition (Cu-ECD). The main challenge of this metallization module is to reduce Co corrosion under the influence of Cu electrolyte. Based on the experimental results, the optimized deposition recipes have been obtained and discussed by varying the ECD parameters, and characterizing the deposited films. Thereby, the Co corrosion was minimized even for the ultra-thin film of 5 nm.Metallization processes were performed on blank and structured samples (on both coupons and 300 mm wafers). Barrier films stack deposition and in-vacuo annealing were carried out without breaking the vacuum in the 300 mm cluster tool. Afterwards, ECD processes were accomplished on coupon level in a lab-scale plating cell. Moreover, different metrology, ex-situ characterizations and measurements were performed by time-of-flight secondary ion mass spectroscopy (ToF-SIMS), transmission electron microscopy (TEM), cross sectional scanning electron microscopy (XSEM) and x-ray reflectometry (XRR), for revealing thickness loss, corrosion percentage and elemental depth profile.