Effects of electrical bias stress on the performance of ZnO-based TFTs fabricated by RF magnetron sputtering

ZnO-based thin film transistors (TFTs) were fabricated on a SiNx/ indium tin oxide (ITO)/glass substrate by radio frequency (rf) magnetron sputtering at 350 degrees C. The transfer characteristics of the fabricated TFT showed a drain current on/off ratio of 10(5), a field effect mobility of 1.698 cm(2)/Vs, an off current lower than 8 nA, and a threshold voltage of 2.5 V. The stability of the ZnO TFTs was examined under various electrical bias stress conditions. The operation of ZnO TFT was stable at the electrical bias stress (-10 <= V-GS <= 10 at V-DS = 5, 10 V ) for stress time of 200 s. However, with increasing bias stress and the duration of the stress, the transfer characteristics of ZnO TFT were degraded, and the devices were physically damaged due to heavy charge accumulation in the ZnO channel layer. In addition, trapping of tunneling electrons in the SiNx caused threshold voltage shift. (c) 2006 The Electrochemical Society.