The Effect of In-Plane Thermocouple Dimension on the Performance of CMOS and BiCMOS Thermoelectric Generators

With the advances of thin-film process technology in foundry services, recent development is to design thermoelectric generator (TEG) with in-plane thermocouple of polysilicon or polycrystalline silicon germanium by CMOS or BiCMOS process. However, the small thermal resistance and adversely large electrical resistance in a thermocouple of micron dimension lead to small temperature gradient and excessive heat loss hence to poor harvester performance. Optimal design of thermocouple dimension is therefore critical to TEG performance. A model of the effect of thermocouple dimension on TEG performance is developed. For TEG design by TSMC CMOS process with P-and N-thermoleg of thickness 0.275 em and 0.180 em, respectively, the model shows that the optimal thermocouple is 60 em × 2 e m (length × width). For design by TSMC BiCMOS process with P-and N-thermoleg of thickness 0.380 em and 0.200 em, respectively, it is 45 em × 2 em. Numerical simulation and experimental verification on the latter show that better TEG performance can be achieved by optimal thermocouple dimension that matching the electrical and thermal resistances.