Poly-Si TFTs with bottom-gate structure using excimer laser crystallisation for AMOLED displays

An n-type polycrystalline silicon thin-film transistor (poly-Si TFT) with a bottom-gate structure using excimer laser annealing (ELA) for active matrix organic light-emitting diode displays is proposed. A problem with bottom-gate poly-Si TFTs (BGPs) using ELA, namely, the disconnection of poly-Si at the boundary of the gate metal during the ELA crystallisation, was solved by developing a novel process to control the slope of the gate metal. We realised ELA BGPs with pure-Mo gate having a thickness of more than 150 nm. The BGPs have better breakdown voltage characteristics compared with the conventional top-gate poly-Si TFTs because of its flat channel region and homogeneous electric field distribution in the gate insulator.