Nickel-disilicide-assisted excimer laser crystallization of amorphous silicon

Polycrystalline silicon (poly-Si) thin film has been prepared by means ofnickel-disilicide (NiSi$_{2})$ assisted excimer laser crystallization (ELC).The process to prepare a sample includes two steps. One step consists of theformation of NiSi$_{2}$ precipitates by heat-treating the dehydrogenatedamorphous silicon (a-Si) coated with a thin layer of Ni. And the other stepconsists of the formation of poly-Si grains by means of ELC. According tothe test results of scanning electron microscopy (SEM), another grain growthmodel named two-interface grain growth has been proposed to contrast withthe conventional Ni-metal-induced lateral crystallization (Ni-MILC) model and the ELC model. That is, an additional grain growth interface other than that inconventional ELC is formed, which consists of NiSi$_{2}$ precipitates anda-Si. The processes for grain growth according to various excimer laserenergy densities delivered to the a-Si film have been discussed. It isdiscovered that grains with needle shape and most of a uniform orientationare formed which grow up with NiSi$_{2}$ precipitates as seeds. The reasonfor the formation of such grains which are different from that of Ni-MILC withoutmigration of Ni atoms is not clear. Our model and analysis point out amethod to prepare grains with needle shape and mostly of a uniformorientation. If such grains are utilized to make thin-film transistor,its characteristics may be improved.