Abstract
This paper presents the fabrication and characterization of energy harvesting thermoelectric micro generators using the commercial complementary metal oxide semiconductor (CMOS) process. The micro generator consists of 33 thermocouples in series. Thermocouple materials are p-type and n-type polysilicon since they have a large Seebeck coefficient difference. The output power of the micro generator depends on the temperature difference in the hot and cold parts of the thermocouples. In order to increase this temperature difference, the hot part of the thermocouples is suspended to reduce heat-sinking. The micro generator needs a post-CMOS process to release the suspended structures of hot part, which the post-process includes an anisotropic dry etching to etch the sacrificial oxide layer and an isotropic dry etching to remove the silicon substrate. Experiments show that the output power of the micro generator is 9.4 μW at a temperature difference of 15 K.
Highlights
Thermoelectric micro generators can convert waste heat into electrical power to achieve waste energy recycling, and they can be applied in electronic devices providing additional power
Where Vout represents the output voltage of the thermoelectric generator; n is the number of thermocouples in series; α1 is the Seebeck coefficient of p-type polysilicon; α2 is the Seebeck coefficient of n-type polysilicon; Th is the temperature of the hot junctions in thermocouples and Tc is the temperature of the cold junctions in thermocouple
The output power of the generator depended on the temperature difference between the hot and cold parts in the thermocouples
Summary
Thermoelectric micro generators can convert waste heat into electrical power to achieve waste energy recycling, and they can be applied in electronic devices providing additional power. Nishibori et al [7] utilized bulk-Si wet etching to make a micromachined thermoelectric power generator with a ceramic catalyst combustor, and a thermopile of 20 thin-film couples of B-doped. Strasser et al [8] adopted surface micromachining to fabricate a thermoelectric micro generator for converting waste heat into electrical power, and the thermoelectric materials in the generator were poly-Si0.7Ge0.3 and poly-Si. Fabrication of MEMS devices using the commercial CMOS process is called CMOS-MEMS technique [9,10], and microdevices manufactured by this technique usually need a post-process to release the suspended structures [11,12] or to add the functional films [13,14]. The post-process of the generator utilizes an anisotropic dry etching to remove the sacrificial oxide layer and an isotropic dry etching to etch the silicon substrate
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