Comparative Study of Active-Over-Metal and Metal-Over-Active Amorphous IGZO Thin-Film Transistors With Low-Frequency Noise Measurements

Abstract

Bottom-gate metal-over-active (MOA) and active-over-metal (AOM) amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs), with channel lengths varying from 1 to 16 μm, are investigated with low-frequency noise (LFN) measurements in the linear region of operation. In the low drain-current range, LFN originates from carrier number fluctuations, whereas in the high drain-current range, the noise is affected by the series resistance. The extracted gate-insulator trap densities near the interface lead to the conclusion that the AOM a-IGZO TFTs are superior compared to the MOA devices.