Fabrication and measured performance of a first-generation microthermoelectric cooler

The measured performance of a column-type microthermoelectric cooler, fabricated using vapor-deposited thermoelectric films and patterned using photolithography processes, is reported. The columns, made of p-type Sb₂Te₃ and n-type Bi₂Te₃ with an average thickness of 4.5 μm, are connected using Cr/Au/Ti/Pt layers at the hot junctions, and Cr/Au layers at the cold junctions. The measured Seebeck coefficient and electrical resistivity of the thermoelectric films, which were deposited with a substrate temperature of 130°C, are -74 μV/K and 3.6×10^-5 Ω-m (n-type, power factor of 0.15 mW/K²-m), and 97 μV/K and 3.1×10^-5 Ω-m (p-type, power factor of 0.30 mW/K²-m). The cooling performance of devices with 60 thermoelectric pairs and a column width of 40 μm is evaluated under a minimal cooling load (thermobuoyant surface convection and surface radiation). The average cooling achieved is about 1 K. Fabrication challenges include the reduction of the column width, implementation of higher substrate temperatures for optimum thermoelectric properties, and improvements of the top connector patterning and deposition.