Single crystalline In-Ga-Zn oxide films grown from c-axis aligned crystalline materials and their transistor characteristics

Abstract

In this study, we analyzed the crystallinity of c-axis aligned crystalline In-Ga-Zn oxide (CAAC-IGZO) and single crystalline (sc) IGZO films. CAACIGZO films were formed on (111)-oriented yttria-stabilized-zirconia substrates by magnetron sputtering using a In : Ga : Zn = 1 : 1 : 5 target. Sc- IGZO films were obtained by annealing CAAC-IGZO films at 1200 °C. The proportion of Zn in the composition changed during growth of the films, and as a result, sc-InGaO3(ZnO)3 films were obtained. By using CAAC-IGZO films as the starting material, sc-IGZO films were formed even without a ZnO layer. This is presumably because the CAAC-IGZO film originally exhibits c-axis orientation. In addition, the characteristics of transistors fabricated using sc-IGZO and CAAC-IGZO films were compared, and no significant difference in current drivability, i.e., field-effect mobility, was observed between the different transistors. In this sense, CAAC-IGZO films that require no high temperature annealing are favorable for industrialization. © 2014 The Japan Society of Applied Physics.