The Role of High-kappa TiHfO Gate Dielectric in Sputtered ZnO Thin-Film Transistors

Abstract

In this study, we demonstrate the role of a titanium hafnium oxide (TiHfO) gate dielectric in improving the overall electronic performance of a ZnO thin-film transistor (TFT). Ti(x)Hf(1-x)O (x = 0.63) was fabricated by the rf co-sputtering technique. Using TiHfO as the gate dielectric, the device fabricated in this study exhibits a threshold voltage of 0.34 V, a subthreshold swing of 0.23 V/dec, a field-effect mobility of 2.1 cm(2) V(-1) s(-1), and an ON/OFF current ratio of 10(5). The small subthreshold swing and low positive threshold voltage are attributed to the higher value of kappa of 40 for the dielectric. This result enables device operation below 2 V, allowing its use in low-power driving circuits in display applications. (C) 2010 The Japan Society of Applied Physics