STRUCTURE AND DEFECT CHARACTERIZATION OF EPITAXIAL COSI2 ON SI(001) FORMED USING AN AMORPHOUS CO75W25 SPUTTERED LAYER

The structure evolution and the defects present in epitaxial CoSi2 for med using the solid-state reaction between an amorphous Co75W25 sputte red layer and Si(001) have been studied by transmission electron micro scopy (TEM), Rutherford backscattering spectrometry (RBS), positron an nihilation and resistivity measurements. By employing anneals between 500 and 600-degrees-C, Co diffuses out of the amorphous alloy into the substrate to form a CoSi2 layer. After the anneal, the remaining amor phous alloy on top of the silicide has been removed by a selective wet etch. It has been found that the greater part (approximately 68%) of the so-formed CoSi2 film is epitaxial and that a high density of vacan cy-type defects (2.6 X 10(19)/cm3) is present in the material. A secon d anneal at a higher temperature has been performed to improve the qua lity of the silicide. This results in a decrease of the RBS minimum yi eld and the residual resistivity to values of approximately 25% and 2. 6 muOMEGa cm, respectively. Only a few grains of twinned CoSi2 could b e detected after the second anneal. By plan-view TEM and RBS dechannel ing energy dependence measurements, a total projected length of disloc ation lines of approximately 1.7 X 10(6) cm/cm2 has been estimated. By positron annihilation a density of 1.1 X 10(18) vacancies/cm3 has bee n measured.