Positron characterization of defects formed during solid phase epitaxy of cobalt silicide

Cobalt films of thickness nm have been deposited on Si(100) substrates and subsequently annealed to temperatures of 400, 500, 600 and for 2 h. These anneals resulted in the formation of overlayers consisting of Co , CoSi and (600 and ). The various phases are easily distinguishable using both Rutherford backscattering (RBS) and positron annihilation spectroscopy (PAS). The values of the Doppler broadening S parameter for CoSi and (formed at ) are equal to the stoichiometrically weighted averages of the S parameters of the constituents. Consequently, it is proposed that positron trapping sites previously detected in using re-emitted positron spectroscopy are most likely grain boundaries and dislocations. Open volume defects (possibly voids) were detected by PAS in the sample formed at . Using in situ PAS measurements during annealing of an initially unreacted 60 nm Co film, transitions between the various phases were observed.