Hafnium oxide/germanium oxynitride gate stacks on germanium: Capacitance scaling and interface state density

The chemical state of Ge in HfO(2)/GeO(x)N(y)/Ge gate stacks and electrical property correlations are investigated to understand their capacitance scaling potential. We obtained gate stacks with low interface state density (D(it)similar to 3x10(11) cm(-2) eV(-1)) and a small capacitance equivalent oxide thickness (CET) of similar to 1.35 nm by nitridation of Ge (100) and atomic layer deposition of HfO(2). The nitrogen content of the GeO(x)N(y) affects both the crystalline structure of the overlying HfO(2) and Ge diffusion into the HfO(2). Introduction of Ge impurity by forming gas anneal coincided with the formation of a higher-k HfO(2) phase, consistent with CET reduction.