Effect of annealing temperature on structural and electrical properties of high-κYbTi_xO_ygate dielectrics for InGaZnO thin film transistors

This paper describes the effect of annealing temperature on the structural properties and electrical characteristics of high–κ YbTixOy gate dielectrics for indium–gallium–zinc–oxide (IGZO) thin-film transistors (TFTs). X-ray diffraction, x-ray photoelectron spectroscopy and atomic force microscopy were used to study the structural, chemical and morphological features, respectively, of these dielectric films annealed at 200, 300 and 400 °C. The YbTixOy IGZO TFT that had been annealed at 400 °C exhibited better electrical characteristics, such as a small threshold voltage of 0.53 V, a large field-effect mobility of 19.1 cm2 V−1 s−1, a high Ion/Ioff ratio of 2.8 × 107, and a low subthreshold swing of 176 mV dec.−1, relative to those of the systems that had been subjected to other annealing conditions. This result suggests that YbTixOy dielectric possesses a higher dielectric constant as well as lower oxygen vacancies (or defects) in the film. In addition, the instability of YbTixOy IGZO TFT was studied under positive gate-bias stress and negative gate-bias stress conditions.