Use of necked-down areas to control nucleation site and direction of solidification of polycrystalline silicon using excimer laser crystallization

We successfully controlled the nucleation site and direction of solidification of polycrystalline silicon films by irradiation with an excimer laser. An amorphous silicon island, including a gradually narrowing region, was formed on a quartz glass substrate. The gradually narrowing region intentionally included a necked-down area. The sidewall and top of the amorphous silicon island were covered by a thick polycrystalline silicon film. A single pulse of excimer laser irradiation from the back through the quartz glass substrate was used to melt the island. This method resulted in lateral growth from the inner region of the island toward the outer region, at the edges of the island. When the width of the necked-down area was twice the distance of the lateral growth, only one nucleus was formed in the necked-down region. Solidification from the nucleus toward the region with the narrower width then occurred in an area 2 μm wide and 3 μm long. This method enabled position-controlled formation of large grains.