Thermal conductivity determination of micromachined membranes

In this work we present a novel approach for the thermal conductivity determination in micromachined membrane-based devices. Due to their low thermal and electrical conductivity and its availability in the standard microelectronic fabrication technologies, Si₃N₄ and SiO₂ have been widely used in micromachined structures [1-5]. Nevertheless, the variety of reported values of thermal conductivity of these materials when deposited as thin-film layers provides evidence of their dependence both on the type of deposition process (LPCVD, PECVD, etc..) and on their processing parameters (temperature, gas concentration, pressure...)- The proposed methodology is based on the fitting of experimental and simulated thermal dissipation of two resistive elements. This allows to determine the thermal conductivity of both the materials composing the membrane and the material used in the heating element patterning of a flow sensor structure.