Fabrication of High Quality Silicide Layers by Ion Implantation

Abstract

Buried layers of CoSi₂ have been successfully fabricated in (100) single crystal silicon by implanting 350 keV Co⁺ to doses in the range 2 - 7 × 10¹⁷ cm⁻² at a temperature of ∼550°C. For doses ≥ 4 × 10^{17 59}Co⁺ cm⁻², a continuous buried layer of CoSi₂ grows epitaxially, during implantation. After annealing (1000°C 30 minutes) continuous layers of stoichiometric CoSi₂ which are coherent with the matrix are produced for doses ≥ 4 × 10^{17 59}Co⁺ cm⁻². For doses of ≤ 2 × 10^{17 59}Co⁺, cm⁻², discrete octahedral precipitates of monocrystalline CoSi₂ are observed. Isochronal annealing (for 5s) at temperatures in the range 800–1200°C, shows that at temperatures ≥ 900°C there is significant redistribution of the Co from B-type or interstitial sites → substitutional A-type lattice sites. As the anneal temperature is increased there is a corresponding improvement in the crystallinity and coherency of the Si and CoSi₂ lattices. This shows that at a given temperature much of the Co redistribution takes place within the first 5s of the anneal.