ELASTIC AND THERMAL-PROPERTIES OF MESOTAXIAL COSI2 LAYERS ON SI

Single crystalline 110 nm thick CoSi2 layers formed on both (100)- and (111)-oriented Si wafers by high dose Co-59 implantation and thermal annealing were analyzed by x-ray double crystal diffractometry. The lateral mismatch of both (100)- and (111)-oriented samples are similar (approximately -0.7%) at room temperature, meaning that the average spacing between misfit dislocations is roughly the same (approximately 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, C-12 = 222, C44 = 100 GPa) were extracted from these lattice mismatches and the sample curvature measurements. X-ray rocking curves were also recorded up to approximately 500-degrees-C. The average spacing between the misfit dislocations remains unchanged, meaning that the misfit dislocations do not shear up to 500-degrees-C. The linear thermal expansion coefficient of CoSi2 (9.5 x 10(-6)/degrees-C) was obtained under the assumption that the elastic constants do not change with temperature.