Stable Interconnect System for Horizontal Thermoelectric Coolers by Thermodynamic-Based Prediction

We studied the improvement of interfacial stability and contact resistance by applying Cu with high electrical conductivity but high diffusivity to thin film type thermoelectric devices. Since the thin film device has a large surface to volume ratio, it is necessary to minimize the contact resistance occurring at the interface in order to minimize heat generation due to resistance. For the reliability of such a device, long duration phase stability is required, especially when using Cu electrodes with high diffusivity. The interconnect system, including Cu and the barrier materials, was selected based on a phase diagram with a thermodynamic-based calculation. The interlayer was required to improve the unstable interface to prevent the reaction of Cu and Bi 2 Te 3 . Ta and Mo, which are low diffusivity materials, were selected as candidates. Thermodynamic calculation results showed that Ta has a stable interface with Bi 2 Te 3 , while Mo reacts with Te. The calculation was confirmed by experiments, and it was determined that the longer the annealing process, the higher the contact resistance is when the Mo interlayer is applied, which is in accordance with the thermodynamic calculation. The thermodynamic calculations are a useful methodology when selecting materials with a stable interface with highly reactive chalcogenide materials. Graphical Abstract