Design of micro-temperature sensor array with thin film thermocouples

We are in the process of developing a micro-temperature sensor array with T-type (copper-constantan) thin film thermocouples (TFTCs) to measure the chip temperature distribution of electronic packages. A thin aluminum nitride (AlN) layer of 100 nm thickness was deposited on a silicon substrate. AlN acts not only as an electrical insulator but also as a thermal conductor between the silicon substrate and thin film thermocouples. Copper thin film with a thickness of 50 nm and constantan thin film with the same thickness were deposited on the AlN layer The sensor array has 10 X 10 junctions within a 9 mm X 9 mm area, and each junction covers a 100 mu m X 100 mu m area. Electro-thermal forces measured by TFTCs using one-dimensional steady-state heat conduction were compared with the electro-thermal forces measured by standard thermocouples, and the difference between the Seebeck coefficients of the copper material and the constantan thin film was calculated according to these measurements. In order to verify the sensor array, it was placed under two-dimensional steady-state heat conduction, and electro-thermal forces were measured and converted to temperatures. Finite element analysis simulation results were compared with the temperatures, and with experimental measurements were found to be in agreement with the simulated values.