FORMATION AND CHARACTERIZATION OF EPITAXIAL COSI2, ON SI(001)

The formation and characterization of epitaxial CoSi2 layers using the solid-state reaction between an amorphous Co75W25 sputtered layer and Si(001) has been studied by transmission electron microscopy (TEM), R utherford backscattering spectrometry (RBS), positron annihilation and resistivity measurements. In the temperature range 500-600 degrees C, Co diffuses out of the amorphous alloy into the substrate to form a C oSi2 layer. After the anneal the remaining amorphous alloy on top of t he silicide has been removed by a selective wet etch. It has been foun d that the greater part (about 68%) of the so-formed CoSi2 film is epi taxial and that a high density of vacancy-type defects (2.6 x 10(19)/c m(3)) is present in the material. A second anneal at a higher temperat ure has been performed to improve the quality of the silicide. This re sults in a decrease of the RBS minimum yield and of the residual resis tivity to values of about 25% and 2.6 mu Omega.cm, respectively. Only few grains of twinned CoSi2 could be detected after the second anneal. By positron annihilation a density of 1.1 x 10(18) vacancies/cm(3) ha s been measured. The Schottky barrier height shows a clear dependence on the CoSi2 film properties.