Ultra Shallow Junction Formation Using Diffusion from Silicides: II . Diffusion in Silicides and Evaporation

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Abstract
The phenomena associated with dopant redistribution in , , , , and , as would be used in a silicide‐As‐diffusion‐source process, were examined. Segregation of dopant (B) into a surface layer, evaporation of dopant, and slow, grain‐boundary diffusion, were found to occur in annealed, implanted silicides. For , were found to segregate to the silicide surface, independent of the initial implant dose, possibly as . The evaporation coefficient was found to have an activation energy of 4.4 eV for B in , 2.0 eV for As in , and 2.3 eV for As in . Implanted boron was found to otherwise homogeneously diffuse throughout , and As moved readily in and . Other dopants diffused predominately via grain boundaries and had very low bulk diffusivity in the silicides. Because of these three phenomena, it was necessary to use very high ion implantation doses to achieve high (≈1020 cm−2) dopant concentrations at the silicon‐silicide interface.

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