Supreme performance of zinc oxynitride thin film transistors via systematic control of the photo-thermal activation process

Abstract

Zinc oxynitride (ZnON) is a relatively novel class of material, often regarded as a promising alternative to oxide semiconductors, owing to its relatively high electron mobility and low concentration of oxygen-related defects that affect the device reliability. In the present study, thermal annealing of ZnON for thin film transistor (TFT) applications is performed in conjunction with a source of ultraviolet (UV) radiation, as an attempt to lower the heat treatment temperature. The oxygen radicals and ozone produced in this process appear to oxidize the ZnON surface. As the annealing temperature increases in the presence of UV light, chemically stable ZnO and non-stoichiometric Zn_xN_y bonds are formed without significant change in the oxygen/nitrogen ratio within the film. Such a phenomenon is accompanied by a slight reduction in the field effect mobility and device stability under positive bias stress, however under optimized photo-thermal annealing conditions, ZnON TFTs fabricated at a relatively low annealing temperature (150 °C) exhibit high field effect mobility values exceeding 50 cm² V⁻¹ s⁻¹ and reasonable reliability, as examined under positive bias stress conditions.