Elastic and thermal properties of mesotaxial CoSi2 layers on Si

Abstract

Single crystalline 110 nm thick CoSi2 layers formed on both (100)- and (111)-oriented Si wafers by high dose 59Co implantation and thermal annealing were analyzed by x-ray double crystal diffractometry. The lateral mismatch of both (100)- and (111)-oriented samples are similar (~–0.7%) at room temperature, meaning that the average spacing between misfit dislocations is roughly the same (~30 nm). But the perpendicular mismatch differs for the two substrate orientations, reflecting the elastic anisotropy of the single-crystalline CoSi2 layers. The three elastic constants of cubic CoSi2 (C11 = 277, C12C12= 222, C44 = 100 GPa) were extracted from these lattice mismatches and the sample curvature measurements. X-ray rocking curves were also recorded up to ~500 °C. The average spacing between the misfit dislocations remains unchanged, meaning that the misfit dislocations do not shear up to 500 °C. The linear thermal expansion coefficient of CoSi2 (9.5 × 10^–6/°C) was obtained under the assumption that the elastic constants do not change with temperature.