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-κ) 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-κ Tm₂O₃ a-IGZO TFT annealed at 400°C exhibited a lower threshold voltage of 1.68 V, a higher field effect mobility of 11.8 cm²/V-s, a larger I_on/I_off ratio of 3.9×107, 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-κ Tm₂O₃ IGZO TFTs was also explored under positive bias stress.