Growth of uniform epitaxial CoSi2 films on Si(111)

Abstract

Pinhole-free, pseudomorphic CoSi2 films with thicknesses from 1.3 to 16.4 nm have been grown epitaxially on Si(111) by sequentially depositing thin Co and Si films at room temperature, and subsequently annealing the resulting a-Si:Co2Si:Si(111) structure at 670 K. The film morphology is studied by high-resolution Rutherford backscattering, transmission electron microscopy, and reflection high-energy electron diffraction. The absence of pinholes in the as-grown layers is explained by a lowering of the barrier of CoSi2 nucleation owing to the presence of amorphous Si. Upon further heating the films remain uniform up to a temperature of 1000 K. Above that temperature the layers break up in islands, which corresponds with the thermodynamically most stable morphology. The lattice strain in pseudomorphic layers is found to persist even after islanding.