Directional nickel-induced fielded aided lateral crystallization of amorphous silicon

For application to active matrix liquid crystal displays (AMLCDs), a low temperature (<900 K) process for the production of polycrystalline silicon is required to permit the use of inexpensive glass substrates. This would allow the integration of drive electronics onto the display panel. Current low temperature processes include excimer laser annealing and solid phase crystallization, both of which are currently unsuitable for the fabrication of low cost, large area devices. The addition of small amounts of metal (e.g., Ni) to the amorphous silicon has been shown to significantly reduce the solid phase crystallization temperature. The rate of this solid phase metal induced crystallization can also be increased as a result of the presence of an electric field. The work presented here reports directional crystallization of amorphous silicon thin films during heat treatment in the presence of an electric field. Models are proposed for metal induced crystallization with and without an applied electric field in which a reaction between Ni and Si to produce NiSi is the rate-limiting step. The crystallization rate is increased through the application of an electric field that leads to the drift of Ni ions to the growth front. The model and experimental data reveal that the crystallization rate increases exponentially with temperature and linearly with electric field strength.