Transition from thermally grown gate dielectrics to deposited gate dielectrics for advanced silicon devices: A classification scheme based on bond ionicity

Abstract

This article discusses the bonding chemistry of alternative high-k gate dielectrics that have been considered for advanced complementary metal–oxide–semiconductor devices. The replacement of SiO 2 by alternative gate dielectrics requires a transition from a thermally deposited native oxide to a deposited gate dielectric. A classification scheme based on bond ionicity separates alternative gate dielectric materials into three groups that are differentiated by their amorphous morphology and electronic structure and properties. This scheme establishes trends between bond ionicity and (i) the average bonding coordination of the constituent atoms, (ii) the thermal stability against chemical phase separation and/or crystallization, and (iii) the dielectric constant. It also provides a framework for the evaluation of different criteria that have been proposed for optimization of alternative high-kmetal and transition metal oxides, and their alloys with SiO 2 and Al 2 O 3 . Based on technology targets for device and wafer performance and reliability, there is as yet no ideal replacement for SiO 2 that increases capacitance while at the same time maintaining low levels of interfacial defects.