Control of Nucleation and Solidification Direction of Polycrystalline Silicon by Excimer Laser Irradiation

The nucleation site and solidification direction of polycrystalline silicon were controlled by excimer laser crystallization. The sidewall and the top of the amorphous silicon island, which includes a gradually narrowing region, were covered with a thick layer of polycrystalline silicon, and single-shot irradiation was performed from the back surface. The formation of only one nucleus was observed in a gradually narrowing region of width two times that of the lateral growth distance. Solidification from the nucleus toward a narrower width region was then effected in a region 2 µm in width and 3 µm in length. The growth mechanism is explained on the basis of the temperature gradient formed by the covering of the polycrystalline silicon and the gradually narrowing structure.