Thermal conductivity measurement at the micrometer scales

To measure the thermal conductivity of microscale specimens, the methodology and capability of a novel thermal conductivity measurement technique, applicable to micro- and nanoscale scale measurement, is discussed. The methodology integrates a device consisting of two identical microheaters with thin-filmed platinum heating elements and integrated resistance temperature devices (RTDs) on trenched, thermally isolated silicon substrates. The platinum RTDs used for temperature measurement were calibrated by monitoring the melting points of three metallic microspheres placed on the device as its power was increased. We validated our measurement technique by measuring thermal conductivities of several micrometer-sized metallic wire standards with known values. A multiphysical analysis based on a 3D finite element method (FEM) has been conducted to simulate both the electric and thermal behaviors of the microheaters. These FEM simulations describing the heating and heat flow in the device facilitated optimizing the device geometrical configuration to minimize heat loss and thus to realize high measurement fidelity. The temperature profiles near the microheaters obtained during measurement confirmed the device design objective of localizing heat only to microheaters to achieve the desired high measurement fidelity.