Structural Design for Dimensional Stability of Thermocouples in Thermoelectric Energy Harvester

The design of thermoelectric energy harvester in hybrid configuration by CMOS process has been known desirable. Thermal isolation cavity on the top and/or bottom of a thermocouple to increase its thermal resistance is necessary to achieve better harvester performance. However, the thermocouple becomes suspended and may suffer from poor dimension stability on wearable device applications. This paper aims at improving the dimension stability of thermoelectric energy harvester by a structural support design. A harvester with a thermal isolation cavity of 10 $\mu \text{m}$ in depth and a structural support of 4 $\mu \text{m}$ in length is developed to minimize heat leakage and to provide the dimension stability of thermocouples. Compared with many previous works, the harvester design implemented by BiCMOS standard process (TSMC 0.18- $\mu \text{m}$ SiGe 3P6M) is shown to achieve a superior power factor of 0.125 $\mu \text{W}$ /cm 2 K 2 and a voltage factor of 23.53 V/cm 2 K.