Density functional theory study on reaction mechanisms of Co(tbu2DAD)2 for area selective-atomic layer deposition of Co films on metal surfaces

Abstract

As electronic devices scale in size approaching nm scales, the smaller feature sizes become more difficult and expensive to pattern. The most common patterning technique currently used in microelectronics industry, ArF laser immersion lithography, requires more and more steps to pattern one layer, the smaller the pitch becomes. Area selective-atomic layer deposition (AS-ALD) is one possible solution that allows for both fewer patterning steps and smaller feature sizes. However, the fundamental mechanisms of surface selectivity and the role of reducers in ALD growth are not fully understood. This modeling work focuses on the detailed atomic scale processes of AS-ALD deposition of Co metal on various substrate surfaces. Co is of particular interest for its capability in reducing resistance of metal interconnects in back end of lines when replacing Cu lines below 16 nm in critical dimension, and such a small linewidth can be achieved by the AS-ALD growth of Co films. This work shows the mechanisms and properties associated with the growth of Co on various surfaces (Cu, Pt, Co, and SiO2) as well as the role of a reducing agent in facilitating surface reactions during ALD processes. Density functional theory was used to describe the reaction mechanisms and accurately describe the system’s energetic and electronic characteristics during the deposition process. These findings provide insight into the fundamental mechanisms of selective ALD growth on metal surfaces against oxide surfaces and the catalytic role of reducers in facilitating the kinetics of ALD precursor reactions on metal surfaces.