The impact of SiN_x gate insulators on amorphous indium-gallium-zinc oxide thin film transistors under bias-temperature- illumination stress

The threshold voltage instability (V_th) in indium-gallium-zinc oxide thin film transistor was investigated with disparate SiN_x gate insulators under bias-temperature-illumination stress. As SiN_x film stress became more tensile, the negative shift in V_th decreased significantly from -14.34 to -6.37 V. The compressive films exhibit a nitrogen-rich phase, higher hydrogen contents, and higher N-H bonds than tensile films. This suggests that the higher N-H related traps may play a dominant role in the degradation of the devices, which may provide and/or generate charge trapping sites in interfaces and/or SiN_x insulators. It is anticipated that the appropriate optimization of gate insulator properties will help to improve device reliability.