Geometric Study of Polymer Embedded Micro Thermoelectric Cooler with Optimized Contact Resistance

Aditya S Dutt^1,2, Kangfa Deng¹, Guodong Li^1,3, Nithin B Pulumati^1,2, David A Lara Ramos^1,2, Vida Barati^1,2, Javier Garcia^1,4, Nicolas Perez¹, Kornelius Nielsch^1,2, Gabi Schierning^1,5, Heiko Reith¹*

¹ Institute for Metallic Materials, Leibniz Institute of Solid State and Materials Research, Dresden, Germany 

²TU Dresden, Faculty of Mechanical Engineering, George-Bahr-Strasse 3c, 01069 Dresden, Germany

³Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China

⁴Department of Physics, University of Oviedo, 33007 Oviedo, Spain

⁵Faculty of Physics, University of Bielefeld, 100131, Bielefeld, Germany

*E-mail of the corresponding author: h.reith@ifw-dresden.de

Summary

Thermoelectric devices can be used for refrigeration, power generation or in sensor applications. Here, we present the fabrication of µTEDs using optimized geometry and contact resistance combined with a novel packaging technique that is fully compatible with on-chip integration.

We developed a process for the fabrication of micro thermoelectric coolers (μTECs) with vertically free-standing leg pairs without top plate. Photoresist is used as filling material because of its low thermal conductivity. The µTECs with and without photoresist were characterized by thermoreflectance thermal imaging technique to study the cooling efficiency of the devices and the influence of the photoresist matrix on the performance.

The fabrication of the µTECs is based on photolithographic patterning process in combination with electrochemical deposition of Bi2(TexSe1-x)3 and Te as n-type and p-type thermoelectric materials, respectively. Using the optimized geometry and contact resistance, the maximum net cooling temperature and the cycling reliability was enhanced. The geometric optimized µTEC showed a maximum cooling of around 10.8K at an applied electrical current of 235mA, a rapid response time of 700µs and survived over 100 million cooling cycles in our reliability studies.

The as-fabricated µTECs were later embedded in photoresist for using the devices in potential applications. The photoresist matrix acts as thermal shortcut introducing additional thermal loss that results in a slight reduction of the maximum cooling from 10.8K to 9.6K. While the thermal response time of the device was not significantly affected, the cycling reliability was a little reduced to 85 million cooling cycles. This simple packaging technique together with the robust device performance is a step toward wide-spread application of µTEDs.