Threshold voltage uniformity improvement by introducing charge injection tuning for low-temperature poly-Si thin film transistors with metal/oxide/nitride/oxide/silicon structure

Abstract

Low-temperature poly-Si thin film transistors (TFTs) with a metal/oxide/nitride/oxide/silicon structure were fabricated to investigate the feasibility of suppressing threshold voltage variations between TFTs. By applying relatively high positive and negative gate bias voltages, threshold voltage could be tuned positively and negatively, respectively, by injecting charges into the charge trap layer. Stability of threshold voltage against positive gate bias at a level close to the actual circuit operation was not degraded compared with the case of an as-fabricated TFT. A uniform threshold voltage distribution could be achieved in a preliminary test using 16 TFTs by converging threshold voltages with a target value by tuning the threshold voltage for each TFT.