Effects of Low-temperature NH[sub 3] Treatment on the Characteristics of HfO[sub 2]∕SiO[sub 2] Gate Stack

Abstract

The effects of postdeposition low-temperature (∼400°C) NH3 treatment (LTN treatment) on the characteristics of the HfO2∕SiO2 gate stack with the TiN gate electrode were studied in this work. After the HfO2 films were deposited using an AIXTRON Tricent atomic vapor deposition system, the LTN treatment was performed prior to the postdeposition annealing (PDA) step to prevent the growth of an additional interfacial layer, which is known to accompany the traditional high-temperature nitridation technique. The effective electrical oxide thickness for the devices annealed at 700°C PDA, either with or without LTN treatment, was estimated to be about 2.2 and 2.3 nm, respectively, without considering quantum effects. It was found that the LTN treatment effectively improves the characteristics of the HfO2∕SiO2 stack gates, such as capacitance-voltage (C-V) characteristics, frequency dispersion, trap generation rate, and dielectric breakdown voltage even at the high PDA temperature of 700°C.