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

Abstract

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 complementary metal oxide semiconductor (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 resulting in poor harvester performance. The optimal design of thermocouple dimension is therefore critical to the TEG performance. A model of the effect of thermocouple dimension on the TEG performance is developed. For the TEG design by TSMC CMOS process with P- and N-thermoleg of thickness $0.275~\mu \text{m}$ and $0.180~\mu \text{m}$ , respectively, the model shows that the optimal thermocouple is $60\,\,\mu \text {m} \times 2\,\,\mu \text{m}$ (length $\times $ width). For design by TSMC BiCMOS process with P- and N-thermoleg of thickness $0.380~\mu \text{m}$ and $0.200~\mu \text{m}$ , respectively, it is $45\,\,\mu \text {m} \times 2\,\,\mu \text{m}$ . The numerical simulation and experimental verification on the latter show that better TEG performance can be achieved by optimal thermocouple dimension to match the electrical and thermal resistances.