Process optimization for high electron mobility in nMOSFETs with aggressively scaled HfO/sub 2//metal stacks

The performance of aggressively scaled (1.4nm<T/sub inv/<2.1nm) self-aligned HfO/sub 2/-based nMOSFETs with various metal gate electrodes (W, TaN, TiN, and TaSiN) is optimized. It is shown that high mobility values, competitive with oxynitride controls (SiON/poly-Si, T/sub inv//spl sim/1.8-2.1nm), can be achieved. Detailed studies of the role of interface states, remote charges in the HfO/sub 2/ layer, interfacial layer regrowth, and nitrogen-induced charge lead to the conclusion that high-temperature-induced structural modifications near the SiO/sub 2//HfO/sub 2/ interface substantially improve the electron mobility.