Implant and impurity redistribution during ion induced TaSi2 formation

Abstract

The formation of TaSi2 by 121Sb+ bombardment of Ta films on 〈100〉 Si was examined as a function of ion dose, temperature during implantation, and postimplantation rapid thermal annealing. The redistribution of Sb, C, and O was determined during the various treatments. In addition, the influence of this redistribution on silicide formation was evaluated. Ion induced TaSi2 growth exhibited a linear dose dependence that was weakly influenced by substrate temperature (200–400 °C) during ion bombardment. Under these conditions, TaSi2 growth was dominated by atomic mixing rather than radiation enhanced diffusion. Interfacial carbon layers were readily dispersed by ion bombardment, and did not greatly influence TaSi2 growth. In contrast, O and Sb segregated to the surface and the TaSi2/Si interface during ion bombardment. These O- and Sb-rich layers inhibited both Si diffusion and subsequent TaSi2 growth. Postimplant annealing resulted in the buildup of both interfacial C and O. Complete silicide formation was only accomplished at temperatures (1000 °C) sufficient for Si diffusion through the interfacial barriers and Sb surface depletion. Film characterization was performed using Rutherford backscattering spectrometry, secondary ion mass spectrometry, scanning electron microscopy, and x-ray diffraction.