SILICIDE FORMATION AND SILICIDE-MEDIATED CRYSTALLIZATION OF NICKEL-IMPLANTED AMORPHOUS-SILICON THIN-FILMS

The nucleation and growth of isolated nickel disilicide precipitates i n Ni-implanted amorphous Si thin films and the subsequent low-temperat ure silicide-mediated crystallization of Si was studied using in situ transmission electron microscopy. Analysis of the spatial distribution of the NiSi2 Precipitates strongly suggested the occurrence of site s aturation during nucleation. NiSi2 precipitates were observed in situ to migrate through the amorphous Si thin films leaving a trail of crys talline Si at temperatures as low as approximately 484-degrees-C. Init ially, a thin region of epitaxial Si formed on {111} faces of the octa hedral NiSi2 precipitates with a coherent interface which was shown by high-resolution electron microscopy to be Type A. Migration of the Ni Si2 precipitates led to the growth of needles of Si which were paralle l to [111] directions. The growth rate of the crystalline Si was limit ed by diffusion through the NiSi2 precipitates, and an effective diffu sivity was determined at 507 and 660-degrees-C. A mechanism for the en hanced growth rate of crystalline Si is proposed.