Reduction of activation temperature at 150°C for IGZO films with improved electrical performance via UV-thermal treatment

Abstract

Activation using the simultaneous UV-thermal (U-T) treatment of sputter-processed InGaZnO (IGZO) thin-film transistors (TFTs) is suggested. This treatment was performed to lower the activation temperature from 300°C (thermal activation alone) to 150°C as well as to improve the electrical characteristics and stability. Despite the low temperature, the U-T-treated devices showed superior electrical characteristics and stability compared to the devices that were only thermally activated (300°C): the mobility improved from 5.19 ± 1.8 to 16.20 ± 1.5 cm2/Vs, the on-off ratio increased from (5.58 ± 3.21) × 108 to (2.50 ± 2.23) × 109, and the threshold voltage shift (under positive bias stress for 1000 s) decreased from 7.1 to 2.2 V. These improvements are attributed to the following two contributions: (1) generation of reactive oxygen radical at a low temperature and (2) decomposition-rearrangement of the metal oxide (MO) bonds in the IGZO active layer. Contributions (1) and (2) effectively increased the MO bonds and decreased the defect-site-related oxygen vacancies.