Abstract

This paper presents a phase sensitive measurement technique for determining two independent thermal properties of a thin dielectric film. The technique involves measuring a specimen’s front surface temperature response to a periodic heating signal produced by passing current through a 50 nm thick layer of nichrome deposited on the specimen’s surface. The temperature response is measured with a HgCdTe infrared detector operating at 77 K. The phase shift of the temperature response with respect to the heating signal is fit to an analytical model using thermal diffusivity and effusivity as fitting parameters. From these two parameters, the thermal conductivity and specific heat can be calculated. The method has been applied to 1.72 μm-thick films of SiO2 that were thermally grown on a silicon substrate. One interesting outcome stemming from analysis of the experimental data is the ability to extract both thermal conductivity and specific heat of a thin film from phase information alone. All film thermal conductivities determined so far by this method show a slight decrease with respect to the bulk values. Specific heats were found to be similar to bulk values. Both of these results are consistent with past work on thermally grown films of SiO2.

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