Liquid silicide formation on the Si wafer free surface during Ni diffusion at 1200°C
An investigation of nickel diffusion in silicon wafers at 1200°C, which is above a few Ni-Si eutectic and peritectic temperatures, has been performed. Czochralski Si wafers with nickel film on the back surfaces and mechanical damages on the front surfaces were annealed in different ambients for various periods of time. The wafers annealed in vacuum showed that a liquid phase rich in nickel has been formed at their front (initially free) surfaces at the annealing temperature. The amount of the liquid-phase material increases with an increase of the annealing time. After cooling down, the solidified materials showed various morphologies: spheres, polygons, dendrites, and terraces. The thermodynamic driving force leading to this phenomenon is attributed to the Si (free) surface energy.
Li, J; Yang, WS; Tan, TY; Chevacharoenkul, S; Chapman, R
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