CoSi2 heteroepitaxy on patterned Si(100) substrates

Abstract

The influence of starting surface topography on the nucleation and growth of epitaxial silicide layers was investigated. CoSi2 layers were grown via the template technique on one-dimensionally patterned Si(100) substrates. These substrates contained mesa stripes, running parallel to Si[011], and exhibited either a number of Si {hkl} facets, or ‘‘smoothly varying’’ sinusoidal profiles. Conventional plan view and high resolution cross section transmission electron microscopy showed that the orientation and morphology of the CoSi2 grains depend on the angle (θ) between the CoSi2/Si interface normal and Si(100). CoSi2(100) grains nucleated on mesa tops and trench bottoms, where θ<5°, and formed atomically sharp interfaces. CoSi2(110) and CoSi2(221) grains nucleated along sidewalls of the mesa structures, in regions where 5°<θ<11° and θ≳5°, respectively. CoSi2(110) grains formed highly stepped interfaces with the substrate which were punctuated by step bunches at the grain boundary/substrate triple points. CoSi2(221) grains formed rough interfaces with the substrate which were punctuated by facets and B-type silicide/substrate interfaces along Si{111} planes. Analysis of these data suggests that nucleation of CoSi2(110) grains is associated with the presence of double height steps and step bunches with small surface misorientation, and that nucleation of CoSi2(221) grains is associated with Si{111} facets, Si{311} facets, and step bunches with larger surface misorientation.