A New Approach for Form Polycrystalline Silicon by Excimer Laser Irradiation with a Wide Range of Energies

We develop a new crystallization method, the "double layer method". This method has two steps involving the preparation of polycrystalline silicon film, each of which consists of a deposition of amorphous silicon followed by exciter laser irradiation while the substrate is heated. The mechanism for the formation of polycrystalline silicon by the double layer method is based on the concept that the remaining crystalline silicon formed by the incomplete melting of the first polycrystalline silicon layer during the second laser irradiation step acts as a seed for the growth of polycrystalline silicon. This mechanism provides stable crystal growth and makes it possible to form high quality polycrystalline silicon over a wide range of laser energies. Using this new crystal growth method, a field-effect mobility of 300 cm2/Vs was achieved for n-channel thin-film transistors.