Effect of Ti Content on the Structural and Electrical Characteristics of ErTi_xO_y Charge Storage Layer in InGaZnO Thin-Film Transistor Nonvolatile Memories

This paper describes the effect of titanium content on the structural and electrical properties of ErTi_xO_y charge storage layers in amorphous indium-gallium-zinc oxide (α-IGZO) thin-film transistor (TFT) nonvolatile memory (NVM) devices. X-ray diffraction, Auger electron spectroscopy, and X-ray photoelectron spectroscopy were used to study the film structural, depth profiling, and chemical features, respectively, of these films as the functions of the growth conditions (Ti plasma powers of 60, 100, and 140 W). The ErTi_xO_y IGZO TFT NVM devices fabricated at the 100-W condition exhibited a larger memory window of 4.1 V, a smaller charge loss of 13% (after ten years), and a better endurance characteristic (up to 10⁵ program/erase cycles), as compared with other conditions. This result suggests that the Er₂TiO₅ film featuring a high dielectric constant and reducing an Er(OH)_x layer can provide the higher charge-trapping efficiency and deeper electron trapping levels.