Hafnium titanate as a high permittivity gate insulator: Electrical and physical characteristics and thermodynamic stability

High permittivity hafnium titanate thin films deposited by chemical vapor deposition have been studied systematically as gate insulators. The electrical and physical characteristics of the films were analyzed using a variety of techniques. It was observed that the films with higher Ti content are more resistant to crystallization when subjected to high temperature annealing. The capacitance-voltage curves for devices with hafnium titanate displayed relatively low (∼50 mV) hysteresis. When the concentration of Hf is comparable to the concentration of Ti, both the interfacial layer equivalent oxide thickness and permittivity of Hfx Ti1-x O2 increase linearly with increasing Ti content. The sample with higher Hf content showed weaker temperature dependence of the current. In metal-oxide-semiconductor field-effect transistor devices with hafnium titanate films, normal transistor characteristics were observed. The devices exhibited electron mobility degradation. The thermodynamic stability of stoichiometric films in contact with Si was also studied.