Design of Micro-Arrayed Thin Film Thermocouples (TFTC)

We designed the thin film thermocouples (TFTC) made by T-type (Copper-Constantan) thermocouple arrays in order to measure temperature distribution at higher spatial resolutions. This sensor consists of a few different layers; silicon wafer, thin aluminum nitride (AlN) layer, and thin film thermocouple layers. The thickness of the thin aluminum nitride (AlN) layer is 100nm and the layer is located between silicon wafer and thin film thermocouples to construct an electrical insulator and thermal conductor. T-type (Copper-Constantan) thermocouples are deposited on the aluminum nitride (AlN) layer over the silicon wafer and the copper thickness and constantan thickness are 50nm, repectively. The sensor area is 10mm × 10mm, and has 10 × 10 junction arrays, and each junction has 100μm × 100μm surface area. According to the measured data, electrical resistivitives of thin films are almost 5 times greater than those of bulk materials. This is based on the comparison of thermal simulation and measured data of 1-D heat conduction in steady state. Seebeck coefficients between copper bulk material and constantan thin film are calculated and the weight factor is defined due to Seebeck coefficient mismatches of bulk materials and thin films. Thermal simulation of 2-dimensional heat conduction in steady state calculated by finite element analysis and compared with the measured data, resulting in a good agreement between simulations and measured data.