Thin film thermoelectric energy harvesters for MEMS micropower generation

In this study, we propose a novel thin film thermoelectric energy harvester design based on Cr-Ni thermocouples overlayed on top of a suspended parylene diaphragm. The TE energy harvester can be used to harvest excess heat energy generated at the hot spots in a computer platform. The design can be merged with the previously reported EM energy harvester within a MEMS device to scavenge energy from both vibrations and thermals in a hybrid mode of operation. The performance evaluation of the MEMS integrated thin film thermoelectric energy harvester was done through extensive modeling and optimization accomplished by finite element analysis, and an optimization algorithm implemented in MATLAB. Cr-Ni based thermoelectric generator was then compared to the lateral and vertical thermoelectric designs reported in literature. A power density of 12 μW/cm² can be obtained using Cr and Nickel as thermopile material when the supplied temperature difference is 50 K. Power levels as high as 140 μW/cm² can be reached using n- and p-doped silicon. Thus, this novel topology promises to be an efficient TE harvester with integration of materials with higher Seebeck coefficient like silicon, polysilicon, bismuth to enable hybrid mode operation for specific applications.