Fabrication of Thermoelectric Devices by Applying Microsystems Technology

Microsystems technologies were applied in the fabrication of thermoelectric (TE) microconverters. Common techniques used in microelectromechanical systems (MEMS) fabrication, namely wet etching, lift-off (with SU-8 photoresist), reactive ion etching (RIE), and lithography-electroplating-molding, were compared in the fabrication process of TE microsystems based on Bi, Sb, and Te thin-film compounds. Thin films of bismuth and antimony tellurides were deposited by co-evaporation, with figures of merit comparable to those of bulk materials. Test structures were fabricated using lithography and wet etching. The etching recipe was optimized by varying the etchant dilution and composition until higher etch rates and desired material selectivity were attained. Since the etching process is applied after deposition, this process allows prior deposition of TE materials by any deposition method; thus, films with high figure of merit can be fabricated. Moreover, wet etching does not require the use of expensive equipment.