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), Rutherford backscattering spectrometry (RBS), positron annihilation and resistivity measurements. In the temperature range 500-600¬?C, Co diffuses out of the amorphous alloy into the substrate to form a CoSi2 layer. After the anneal the remaining amorphous alloy on top of the silicide has been removed by a selective wet etch. It has been found that the greater part (about 68%) of the so-formed CoSi2 film is epitaxial and that a high density of vacancy-type defects (2.6 ?ó 1019/cm3) is present in the material. A second anneal at a higher temperature has been performed to improve the quality of the silicide. This results in a decrease of the RBS minimum yield and of the residual resistivity to values of about 25% and 2.6 OEºOE©¬?cm, respectively. Only few grains of twinned CoSi2 could be detected after the second anneal. By positron annihilation a density of 1.1 ?ó 1018 vacancies/cm3 has been measured. The Schottky barrier height shows a clear dependence on the CoSi2 film properties. ¬© 1993.