Investigation of phenyl methyl sulfoxide as an additive for cobalt super-filling in 3D interconnect

Electrodeposition is a key technology for 3D interconnect in electronic devices, while additives play an essential role in realizing super-filling in 3D interconnect. In this work, the impact of phenyl methyl sulfoxide (PMSO) on cobalt electrodeposition is studied and the underlying mechanism is explored. It is demonstrated that PMSO exhibits excellent inhibition ability even at relatively low concentrations due to its high chemical reactivity, contributed by the active sulfoxide group. We find that a proper concentration (20 ppm) of PMSO is important to achieve low surface roughness around 3.9 nm and uni-hcp (002) orientation due to the effective surface absorption. The nucleation of cobalt is altered to progressive nucleation under the influence of PMSO from instantaneous nucleation in the absence of PMSO, resulting in an even cobalt deposition behavior. Furthermore, the presence of PMSO enhances the wettability and enables the super-filling of cobalt TSV trenches with high quality, thereby indicating that PMSO is an effective additive for practical applications.