Improvement in reliability of amorphous indium–gallium–zinc oxide thin-film transistors with Teflon/SiO 2 bilayer passivation under gate bias stress

• Published in: Japanese Journal of Applied Physics Vol. 55; no. 2S; p. 2
• Main Authors: Fan, Ching-Lin, Tseng, Fan-Ping, Li, Bo-Jyun, Lin, Yu-Zuo, Wang, Shea-Jue, Lee, Win-Der, Huang, Bohr-Ran
• Format: Journal Article
• Language: English
• Published: 01.02.2016
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.55.02BC17

Abstract The reliability of amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) with Teflon/SiO 2 bilayer passivation prepared under positive and negative gate bias stresses (PGBS and NGBS, respectively) was investigated. Heavier electrical degradation was observed under PGBS than under NGBS, indicating that the environmental effects under PGBS are more evident than those under NGBS. The device with bilayer passivation under PGBS shows two-step degradation. The positive threshold voltage shifts during the initial stressing period (before 500 s), owing to the charges trapped in the gate insulator or at the gate insulator/a-IGZO active layer interface. The negative threshold voltage shift accompanies the increase in subthreshold swing (SS) for the continuous stressing period (after 500 s) owing to H 2 O molecules from ambience diffused within the a-IGZO TFTs. It is believed that Teflon/SiO 2 bilayer passivation can effectively improve the reliability of the a-IGZO TFTs without passivation even though the devices are stressed under gate bias.