Enhanced electrical performance and reliability of Ti-IGZO thin-film transistors with Hf _1-x Al _x O gate dielectrics

Abstract

Abstract A thin-film transistor (TFT) with a Ti-IGZO channel layer and Hf 1-x Al x O gate dielectric is proposed to improve the performance and reliability of the device. The experimental results show that in three types of TFTs based on HfO 2 /IGZO, Hf 1-x Al x O/IGZO and Hf 1-x Al x O/Ti-IGZO gate dielectric/channel structures, the Hf 0.88 Al 0.12 O/Ti (2.0%)-IGZO TFT exhibits the best device performance with the subthreshold swing of 86 mV dec −1 , field-effect mobility of 28.63 cm 2 ∙V −1 ∙s −1 and on/off current ratio of 3.26 × 10 8 . In particular, it shows a hysteresis voltage as low as 0.02 V and a threshold voltage shift after 1000 s positive/negative gate bias stress/white light illumination of 0.134 V/−0.089 V/−0.195 V, compared with 0.45 V and 0.612 V/−0.507 V/−0.657 V of the HfO 2 /IGZO TFT. These improvements are due to the incorporation of Ti into the IGZO channel, which reduces defect density, while adding Al to HfO 2 improves surface roughness to inhibit surface scattering and charge capture during stress testing.