Young's modulus, Poisson's ratio, and residual stress and strain in (111)-oriented scandium nitride thin films on silicon

M. A. Moram, Z. H. Barber, C. J. Humphreys, T. B. Joyce, P. R. Chalker
2006 Journal of Applied Physics  
Epitaxial scandium nitride films ͑225 nm thick͒ were grown on silicon by molecular beam epitaxy, using ammonia as a reactive nitrogen source. The main crystallographic orientation of ScN with respect to Si is ͑111͒ ScN ʈ ͑111͒ Si and ͓1-10͔ ScN ʈ ͓0-11͔ Si ; however, some twinning is also present in the films. The films displayed a columnar morphology with rough surfaces, due to low adatom mobility during growth. The strain-free lattice parameter of ScN films grown under optimized conditions
more » ... found to be 4.5047± 0.0005 Å, as determined using high-resolution x-ray diffraction ͑HRXRD͒. In-plane and out-of-plane strains were subsequently evaluated using HRXRD and were used to determine the Poisson ratio of ScN along the ͗111͘ direction, which is found to be 0.188± 0.005. Wafer curvature measurements were made and combined with the strain information to determine the average Young's modulus of the films, which is found to be 270± 25 GPa. Residual film stresses ranged from −1 to 1 GPa ͑depending on film growth temperature and film thickness͒ due to competition between the tensile stress ͑induced by the differential thermal contraction between the ScN film and the Si substrate͒ and intrinsic compressive stresses generated during growth.
doi:10.1063/1.2217106 fatcat:xo6n5zabmrey3otslice3tjzxi