Kinetics and morphology of erbium silicide formation

Abstract

The growth kinetics and surface morphology of erbium silicide formation from Er layers on Si(100) substrates are examined using both fast e-beam annealing and furnace annealing. Very smooth erbium silicide layers have been grown using a line-source e beam to heat and react the Er overlayers with the substrate. This contrasts to the severe pitting observed when Er layers are reacted with Si in conventional furnace annealing. The pitting phenomenon can be explained by a thin contaminant layer at the interface between Er and Si. Our results suggest the contamination barrier is not due to oxygen, as usually assumed, but may be related to the presence of carbon. Rapid e-beam heating to reaction temperatures of ∼1200 K permits dispersion of the barrier layer before substantial silicide growth can occur, allowing smooth silicide growth. Heating to shorter times to just disperse the interface barrier allows uniform layer growth by subsequent furnace annealing and has permitted measurement of the kinetics of erbium silicide formation on crystalline Si. The reaction obeys (time)1/2 kinetics but is shown to be not totally diffusion limited by the ability to sustain multiple interface growth from a single Si source. The growth rates are nearly an order of magnitude slower for the Er/Si(100) interface than for the Er/amorphous-Si, but with a similar activation energy near 1.75 eV in both cases.