A novel four terminal poly-Si TFT suppressing kink and improving reliability

摘要

We fabricated a new device, which employs counter-doped lateral body terminal (CLBT) in order to suppress kink effects and improve the device stability. Proposed device also employs a buried channel (BC), which increases ON-current and operatingfrequency. Although LDD structure is not employed in the proposed device, low OFF-current is successfully obtained due to elimination of minority carrier through CLBT. We have measured the dynamic properties of poly-Si TFT device and circuit. Thereliability of TFT and circuits after AC stress is also discussed in our paper.The proposed poly-Si TFT has high ON-current and low OFF-current compared with conventional 3-terminal poly-Si TFT. The 4-terminal device characteristics were measured with source and CLBT shorted. The proposed device exhibits superior performance toconventional device in ON-current because BC prevents carrier scattering to gate oxide. We have performed bias and high temperature stress test of ring oscillator in order to investigate dynamic reliability between conventional poly-Si TFT and proposed4-terminal poly-Si TFT. Our experimental results show that BC enables the device to have high mobility and switching frequency (33MHz at V{sub}(DD)=15V). The minority carrier elimination of CLBT suppresses kink effects and makes superb dynamic reliability of CMOS circuit.