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

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 degrees C (thermal activation alone) to 150 degrees 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 degrees C): the mobility improved from 5.19+/-1.8 to 16.20+/-1.5 cm(2)/Vs, the on-off ratio increased from (5.58+/-3.21) x 10(8) to (2.50+/-2.23) x 10(9), 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.