Excimer-laser-induced in-situ fluorine passivation effects on polycrystalline silicon thin film transistors

We report a new fluorine passivation method without ion implantation and additional annealing step by low-temperature process and its effects on p-channel polycrystalline silicon (poly-Si) thin film transistors (TFTs). The proposed method is not post-passivation, but in-situ passivation because fluorine passivation is simultaneous with excimer-laser-induced crystallization by employing excimer laser annealing of fluorine-doped silicon oxide (SiOxFy) on amorphous silicon (a-Si) structure. From experimental results, it has been shown that in-situ fluorine passivation is effective to improve the electrical characteristics, specially held-effect mobility, and the stability of p-channel poly-Si TFTs. The improvement is due to fluorine passivation, which reduces the trap state density and forms the strong Si-F bonds in place of the weak Si-H bonds in poly-Si channel and SiO2/poly-Si interface.