ION-BEAM MIXED ULTRA-THIN COBALT SILICIDE (COSI2) FILMS BY COBALT SPUTTERING AND RAPID THERMAL ANNEALING

The influence of ion-beam mixing on ultra-thin cobalt silicide (CoSi2) formation was investigated by characterizing the ion-beam mixed and u nmixed CoSi2 films. A Ge+ ion-implantation through the Co film prior t o silicidation causes an interface mixing of the cobalt film with the silicon substrate and results in improved silicide-to-silicon interfac e roughness. Rapid thermal annealing was used to form Ge+ ion mixed an d unmixed thin CoSi2 layer from 10 nm sputter deposited Co film. The s ilicide films were characterized by secondary neutral mass spectroscop y, x-ray diffraction, tunneling electron microscopy (TEM), Rutherford backscattering, and sheet resistance measurements. The experimental re sults indicate that the final rapid thermal annealing temperature shou ld not exceed 800 degrees C for thin (<50 nm) CoSi2 preparation. A com parison of the plan-view and cross-section TEM micrographs of the ion- beam mixed and unmixed CoSi2 films reveals that Ge+ ion mixing (45 keV , 1 x 10(15) cm(-2)) produces homogeneous silicide with smooth silicid e-to-silicon interface.