Thermal conductivity and diffusivity of free-standing silicon nitride thin films

The thermal conductivity and diffusivity of free-standing silicon nitride (Si-N) films of 0.6 and 1.4 μm in thickness are measured. A new experimental technique, the amplitude method, is proposed and applied to measurement of the thin-film thermal diffusivity. The thermal diffusivity is determined by three independent experimental approaches: the phase-shift method, the amplitude method, and the heat-pulse method. Good agreement among the measured thermal diffusivities obtained by the three methods indicates the validity of the amplitude method. High-resolution electron microscopy studies show a large quantity of voids in the 1.4 μm Si-N films. In contrast, very few voids are found in the 0.6 μm films. This difference may be responsible for the measured lower conductivity of the 1.4 μm Si-N films as compared to the 0.6 μm thin films.