Role of the Oxidation State in Cobalt Chemical Mechanical Planarization

ABSTRACT Cobalt (Co) is a promising next‐generation contact metal to replace tungsten for the system‐large‐scale integration devices beyond the 5 nm technology node due to its low resistivity and high gap‐filling capability at high aspect ratios. To complete Co metallization, surface roughness control after chemical mechanical planarization (CMP) is critical because it directly influences contact resistance. However, a low removal rate during CMP hinders achieving low surface roughness. Here, we have designed the Co oxide layer with a unique oxidation state, crystallinity, and thickness to enhance the removal rate with low roughness. The physicochemical properties of a Co oxidant are controlled by the reduction potential and diffusion coefficient of the oxidant associated with the thermodynamics and kinetics, respectively. Co oxide layer with a dominant oxidation state of Co (II), an amorphous phase, and a thin thickness improves CMP performance. As a result, compared to the conventional metal CMP slurry with H 2 O 2 , the designed oxide layer increases the removal rate by 254% and reduces the surface roughness by 41%.