Characterization of Nano-Scale Protective Oxide Films: Application on Metal Chemical Mechanical Planarization

This study focuses on the characterization of nano-scale metal oxide films for chemical mechanical planarization (CMP) applications. The protective nature of the self-grown metal oxide layers in the CMP slurry environment enable topographic selectivity required for metallization of interconnects. Tungsten was selected as the model metal film to study the formation and characteristics of the metal oxide nano-layers since tungsten CMP is very well-established in conventional semiconductor manufacturing. The tungsten oxide nano-films were characterized for thickness, density and surface topography in addition to evaluation of their protective nature by calculation of the Pilling-Bedworth (P-B) ratios. It was observed that in addition to controlling the self-protective characteristics, the oxidizer concentration also affects the surface structure of the metal oxide films resulting in significant changes in the CMP process performance in terms of material removal rates and surface finish with a sweet-spot detected at 0.075 M H2O2 concentration.