A simple method for determination of thermal conductivity coefficients of dielectric films

In this paper, we present a simple method to determine thermal conductivity coefficients (TCC) of dielectric thin films with a compact test microstructure and by using common measuring apparatus. The microstructure can be fabricated by a silicon-based micromachining technique, which is compatible with IC processes. The microstructure consists of a pair of adjacent cantilever beams with different lengths connected by a short tip beam. The beams are composed of two layers. The top one is an n-doped polysilicon thin film (a heating layer) and the below one is a dielectric film (a measured layer). By applying current though the heating layer, a temperature rise throughout the microstructure causes the deflection of the beams. Thereby, a lateral displacement measurable under an optical microscope is generated at a free end of the tip beam. Analytical expressions are derived and characterized to relate the measured displacement to TCC of the dielectric film. Experimental results with silicon dioxide thin films are used to demonstrate the effectiveness of the proposed method. The TCC of the thin films is observed to increase with rising temperature and decrease a little with decreasing film thickness. The films exhibit TCC of around 1.1 w/°Cm at temperature from room temperature to 500°C