Novel F-Shaped Triple-Gate Structure for Suppression of Kink Effect and Improvement of Hot Carrier Reliability in Low-Temperature Polycrystalline Silicon Thin-Film Transistor

Abstract

A novel F-shaped triple-gate device structure, which suppresses the kink effect of polycrystalline silicon (poly-Si) thin-film transistors (TFTs), was proposed and fabricated without any additional process. The proposed poly-Si TFT exhibits a lateral grain growth in a channel, as observed in the case of TFTs fabricated by sequential lateral solidification (SLS) or CW laser lateral crystallization (CLC). The entire current flow of the proposed device was strongly affected by grain boundaries of lateral grain growth. The F-shaped triple-gate structure consisted of one channel located parallel to the lateral grain growth direction and another channel located vertically to the lateral grain growth direction. It was verified that the proposed device could effectively reduce the kink current of poly-Si TFTs using the asymmetric mobility of the F-shaped gate structure by experiment and simulation. Our experimental results showed that the proposed F-shaped triple TFT could suppress the kink effect more effectively than conventional gate TFTs and then improve reliability under hot carrier stress condition.