Effects of Target Quality on Electrical Performance and Stability of In-Sn-Zn-O Thin-Film Transistors

Abstract

In this work, we study the intrinsic connection between target quality and performance of sputtered In-Sn-Zn-O (ITZO) thin-film transistors. Using a dense target, the ITZO device overall performance can be improved synergistically. The optimized device exhibits a steep subthreshold swing of 0.13 V/decade, a high on/off current ratio of 2.47×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> , a threshold voltage of -0.03 V, a saturation field-effect mobility ( μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FE</sub> ) of 36.1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs, and a small threshold voltage shift (ΔV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) of -0.55 V under negative bias stress (-20 V, 3600 s). In contrast, the μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FE</sub> shows a reverse trend to ΔV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> when using a target with a relatively small density and poor crystallinity. In this case, although the amount of oxygen vacancy in the films can be reduced for better stability via increasing the sputtering power, the film density observably drops due to serious preferential sputtering, leading to smaller μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FE</sub> .