Influence of UV-ozone treatment on the performance of HfO2 films and indium aluminum zinc oxide thin film transistors

The effects of UV-ozone treatment on the performance of HfO 2 dielectric layers and indium aluminum zinc oxide (IAZO) thin film transistors (TFTs) were investigated. After UV-ozone treatment, the HfO 2 film exhibited higher film quality and fewer internal defects, and the root mean square roughness of the HfO 2 film surface was optimized from 0.101 to 0.051 nm. Regardless of whether being treated using UV-ozone or not, the HfO 2 films showed high relative dielectric constants over 15 and breakdown voltages exceeding −10 V. For the devices, the IAZO TFT with UV-ozone treated HfO 2 dielectric layer exhibited more outstanding output and transfer characteristics as well as improved electrical performance when compared with the untreated counterpart, including a higher saturation mobility of 13.64 cm 2 /Vs, a lower threshold voltage of 0.67 V, a smaller subthreshold swing of 0.11 V/dec and a more ideal on-off current ratio of 1.18 × 10 7 .