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.