Two‐stage degradation in n‐channel LTPS‐TFTs under negative and positive bias stresses

Abstract

Device degradation behaviors of n‐channel low‐temperature polycrystalline silicon thin film transistors under negative bias stress and positive bias stress were investigated. It was found that the threshold‐voltage has a two‐stage degradation, shifting to different direction with time. The mobility and the subthreshold swing SS both show a dependence on the stress time. It was determined that the interface trap states, the grain boundary trap states, and electron trapping together dominate the time‐dependent degradation behaviors. The trap is caused by the rupture of Si─H and Si─O bonds. A comprehensive model is proposed to explain the time‐dependent degradation behaviors clearly. In addition, after removing the stress, the recovery behaviors of threshold voltage Vth can be observed, which provide the evidence supporting the degradation model proposed.

The Investigation of Indium-Free Amorphous Zn-Al-Sn-O Thin Film Transistor Prepared by Magnetron Sputtering

“…The current TFTs mainly include amorphous silicon (a-Si) TFTs, low temperature polycrystalline silicon (LTPS) TFTs, amorphous oxide semiconductor (AOS) TFTs, organic semiconductor TFTs (OTFTs), etc. However, a-Si TFTs [2] have low open current and cost a lot, the uniformity of LTPS TFTs [3,4] is poor and the OTFTs [5] have poor stability. AOS TFTs possess a broad development prospect in this field due to their excellent stability [6], good uniformity, high mobility [7] and low-cost, which has attracted the attention of scholars worldwide.…”

Analysis of self-heating-related instability in n-channel low-temperature polysilicon TFTs with different S/D contact hole densities

“…[8][9] Therefore, there is a need to develop n-channel LTPS TFTs with high electron mobility. [10][11][12] However, their fabrication process is more difficult due to hard dopant thermal activation limiting its process temperature. 13,14) In addition, owing to the poor thermal conductivity of LTPS TFTs, self-heating and Joule-heating usually occur under high current operation.…”