Effect of Oxygen Impurities on Thermal Diffusivity of AlN Thin Films Deposited by Reactive RF Magnetron Sputtering

Abstract

The thermal diffusivities of AlN thin films with a thickness of about 600 nm deposited by reactive rf magnetron sputtering were measured by the pulsed light heating thermoreflectance technique. The AlN films contain oxygen impurities ranging from 1.1 to 13.6 at. % depending on the sputtering conditions. The measured thermal diffusivity increases from 1.5×10-6 to 12×10-6 m2 s-1 with the decrease in oxygen concentration. An X-ray diffraction study shows that the AlN lattice parameter of the c-axis decreases with the increase in oxygen concentration. The average crystal diameter of the AlN films derived from the X-ray diffraction peaks is 41 nm. The dependence of the thermal conductivity of the AlN films on the oxygen concentration was discussed on the basis of the thermal resistance induced by oxygen impurities and phonon scattering by grain boundaries.