Characterization of polycrystalline Si films produced by ArF excimer laser irradiation

ArF excimer laser irradiation of amorphous silicon (a-Si) films has great potential on the production of poly-crystalline silicon (poly-Si) thin film transistor liquid crystal displays (TFT-LCDs). The main advantage of using poly-Si films instead of a-Si films to fabricate high performance electronic devices is due to its ability to obtain higher field effect mobility. However, the surface morphology, grain size and defect density of the poly-Si film have profound effect on whether this is to be achieved. The specimens used in this study contain a 100 nm-thick a-Si thin film grown on glass substrate by plasma enhanced chemical vapor deposition (PECVD) technique. The influence of processing parameters such as laser fluence, shot number and repetition rate on the surface morphology and recrystallization behaviour of laser annealed a-Si films was investigated in this study. The results showed that the threshold fluence for partially melting a-Si thin films at 1Hz and single shot was around 150 mJ/cm(2). Further increasing laser fluence and shot number resulted in the formation of microvoids trapped inside poly-Si film due to the evolution of hydrogen gas during the laser annealing process. The surface morphology induced by laser annealing of a-Si thin films is found dependent upon the laser fluence and shot number. The super-lateral grown (SLG) poly-Si grains can be obtained at the fluence around 190 mJ/cm(2).