Influence of interface and Al structure on layer exchange during aluminum-induced crystallization of amorphous silicon

Aluminum-induced crystallization of amorphous silicon (a-Si) is studied using various microscopy techniques and x-ray photoelectron spectroscopy. During the isothermal annealing of subsequently deposited aluminum and a-Si films on glass, a layer exchange process is induced, while a continuous polycrystalline silicon film (poly-Si) on glass is formed within the initial metal layer and therefore displaces it. This crystallization process is conducted at temperatures ranging from 350 degrees C to 500 degrees C, significantly below the eutectic temperature of the Si-Al binary system of 577 degrees C. The results presented focus on the influences of the polycrystalline structure of the evaporated Al, the Si-Al layer sequence, and the interface layer between the Al and Si films on the overall crystallization process. They reveal that the larger the Al grain size of the initial polycrystalline Al layer, the larger the grain size of the final poly-Si film and the slower the entire layer exchange process. It is further shown that the layer sequence, although influencing the speed of the poly-Si formation, has little impact on the overall layer exchange process. Additionally, evidence is given that an Al oxide interface layer separates the continuous poly-Si layer from the Al, independent of the original layer sequence. The analyzed oxide interface layer remains at its position throughout the entire Al and Si layer exchange process. An existing phenomenological model of the diffusion-controlled crystallization during the layer exchange is extended to embrace the role of the parameters discussed in this paper. (C) 2000 American Institute of Physics. [S0021-8979(00)00514-4].