A new polycrystalline silicon TFT with a single grain boundary in the channel

A new excimer laser annealing method, which results in large lateral polysilicon grains exceeding 1.5 μm, has been proposed and polycrystalline silicon thin film transistors (poly-Si TFTs) with a single grain boundary in the channel have been successfully fabricated. The proposed method employs a lateral grain growth phenomenon obtained by excimer laser irradiation on an amorphous silicon layer with pre-patterned aluminum film. The aluminum patterns act as a masking layer of the incident laser beam for the selective melting of the amorphous silicon layer. Uniform and large grains are obtained near the edge of the aluminum patterns. When two aluminum patterns are separated by a 2 μm space, the solidified region (i.e., poly-Si channel) exhibits a single grain boundary. The n-channel poly-Si TPT fabricated by the proposed method shows considerably improved I-V characteristics, such as high field effect mobility exceeding 240 cm²/Vs.