Optimization of Plasma-Enhanced Atomic Layer Deposition of Cobalt for Interconnects

This work describes the various "knobs" that can be used in order to optimize the deposition of cobalt by Plasma-Enhanced Atomic Layer Deposition for applications in microelectronics, using cobaltocene as precursor and ammonia or mixtures of hydrogen and nitrogen as co-reactant, and their effect on the properties of Cobalt layers. In particular, this study analyzes the effects of plasma pressure, plasma chemistry, and DC bias, on the growth rate per cycle, resistivity and crystallinity of the layers. It was observed that higher Nitrogen incorporation on the layers promotes crystallinity, while it also increases the resistivity. To our knowledge, this is the first study of Co PEALD with substrate bias, and the results show lower resistivity and better crystallinity control of Co films