Development of the Photolithography Process for the Fabrication of a Flexible Thin Film Thermoelectric Generator

— Thermoelectric generators (TEGs) are reliable, have a long service life, and do not require maintenance. Flexible TEGs can become an alternative to chemical current sources. The development of the technology of a computer-tunable photomask (electronic photomask) for the fabrication of flexible thin-film TEGs is an urgent task. In this paper a setup for exposing the pattern on a photoresist without preparing a photomask is presented. It is shown that the developed setup allows forming elements with the minimum size of 50 × 50 µm 2 . Ge 2 Sb 2 Te 5 and Bi 2 Te 3 thermoelectric materials (TEMs) are used for the formation of p - and n -type legs, respectively, in a flexible thin-film TEG. The results of studying the temperature dependences of the electrical conductivity and Seebeck coefficient for the Ge 2 Sb 2 Te 5 and Bi 2 Te 3 thin films are used to calculate the power factor. It is found that the power factors of these films are weakly dependent on the temperature in the studied temperature ranges and at room temperature are 2.9 and 3.0 mW/m K –2 for Bi 2 Te 3 and Ge 2 Sb 2 Te 5 , respectively. Based on the results of the study of adhesion, a polyimide substrate and a contact system based on a conductive Cu layer and an Ni barrier sublayer are chosen for the fabrication of a flexible thin-film TEG. The technological process is developed and a flexible thin-film TEG with a vertical arrangement of the thermoelement legs is fabricated. For the formation of the topological patterns for all the layers, explosive photolithography (five photolithography processes) is carried out using the developed setup for exposing the pattern on the photoresist.