Structural Properties and Electrical Characteristics of High-κ Tm2O3 Gate Dielectrics for InGaZnO Thin Film Transistors

In this paper, we studied the structural properties and electrical characteristics of high-dielectric constant (high-kappa) Tm2O3 gate dielectrics for amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) applications. We used X-ray diffraction to determine the growth directions and crystallinity of the Tm2O3 films, X-ray photoelectron spectroscopy to analyze the chemical structure of the films, and to monitor the morphological feature of the Tm2O3 films after annealing at various temperatures. The high-kappa Tm2O3 a-IGZO TFT annealed at 400 degrees C exhibited a lower threshold voltage of 1.68 V, a higher field effect mobility of 11.8 cm(2)/V-s, a larger I-on/I-off ratio of 3.9x10(7), and a smaller SS of 420 mV/dec., relative to those of the systems that had been subjected to other annealing conditions. This result suggests the Tm2O3 film featuring a higher dielectric constant as well as a smoother surface. The V-TH stability on high-kappa Tm2O3 IGZO TFTs was also explored under positive bias stress.