High performance Zn-Sn-O thin film transistors with Cu source/drain electrode

Zn–Sn–O (ZTO) thin film transistors (TFTs) were fabricated with a Cu source/drain electrode. Although a reasonably high mobility (μFE) of 13.2 cm2/Vs was obtained for the ZTO TFTs, the subthreshold gate swing (SS) and threshold voltage (Vth) of 1.1 V/decade and 9.1 V, respectively, were inferior. However, ZTO TFTs with Ta film inserted as a diffusion barrier, exhibited improved SS and Vth values of 0.48 V/decade and 3.0 V, respectively as well as a high μFE value of 18.7 cm2/Vs. The improvement in the Ta‐inserted device was attributed to the suppression of Cu lateral diffusion into the ZTO channel region. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) In this Letter, the authors describe the fabrication of high performance zinc tin oxide thin film transistors with copper source/drain. Direct contact between channel layer and Cu electrode results in the degradation of transistor properties due to the Cu migration during thermal annealing. The Ta diffusion barrier prevents copper atoms from migrating into the channel layer during thermal annealing, leading to a high mobility of 17.8 cm2/Vs and gate swing of 0.48 V/decade.