Experimental evidence is presented which suggests ion-bombardment-induced formation of titanium silicide(s) at the interface of ion implanted Ti/Si structures. Titanium films of 1000 to 2000°A were evaporated onto silicon substrates. The structures were implanted with 1×1015 to 2×101714N+ or 11B+ ions/cm2 at beam energies 50–190 keV and at fixed temperatures ranging from −195° to about 25°C. Using Auger electron spectroscopy combined with active ion sputtering, the thickness of the silicide layers was found to vary with implantation temperature, energy, and fluence. Since relatively high temperatures are required for the formation of titanium silicides (∠650°C), it is unlikely that the formation is due to sample heating upon implantation. This was comfirmed by implanting at different beam fluxes and temperatures. The formation mechanism is most likely one of enhanced diffusion and chemical reaction processes during ionic impact, which competes with the recombination of vacancies and self-interstitials, and other capture processes. This mechanism is supported by data from structures implanted at −195°C which showed silicide layers being thicker than those observed for room temperature implants under otherwise identical implant conditions.
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Wang et al. (1979) studied this question.