Thermal activation effects on the stoichiometry of indium zinc oxide thin-film transistors

Abstract

The thermal activation effects on the stoichiometry of indium zinc oxide (IZO) thin-film transistors (TFTs) deposited by radio frequency magnetron sputtering process under different oxygen pressure, were investigated as a function of annealing temperature and environment conditions. The IZO TFTs, with channel layers deposited at pure Ar, were annealed at different temperature in oxygen ambient. Otherwise, in case of IZO TFTs deposited at Ar/O 2 flow ratio of 40/2, were annealed in different ambient at 300 °C. With IZO layers deposited at pure Ar, deposited at pure Ar, the IZO TFT has Ohmic properties initially. Although, the IZO TFT showed the transfer characteristic after annealed at 300 °C, it was degraded at 500 °C. In case of IZO TFT deposited at Ar/O 2 flow ratio of 40/2, the characteristics were changed from insulating to transfer (in air) or an Ohmic properties (in vacuum) after annealing at 300 °C. X-ray photoelectron spectroscopy (XPS) measurements showed that these thermal activation effects were caused by the stoichiometry changing correlated to the atomic arrangements such as oxygen absorption, the connections of In, Zn, and O clusters, and the deoxidation at In-O bonding.