Wet etching of Bi2Te3 thin films compatible with microelectronic fabrication processes

A major limitation in fabricating a monolithic Bi₂Te₃-based thermoelectric thin film device is patterning poorly adhesive Bi₂Te₃ and Bi_0.5Sb_1.5Te₃ thin films. In this paper, we present a simple wet etching process that can prevent the delamination of thermoelectric thin films. This process is compatible with standard IC fabrication technology and can pattern Bi₂Te₃ thin films down to micrometer scale dimensions. We use an etching solution of HNO₃:CH₃COOH:H₂O₂:H₂O, and a single-layer photoresist etch mask. Etch rate of ~100 nm/min has been measured. Inclusion of H₂O₂ changes the etching mechanism, where H₂O₂ replaces HNO₃ as the oxidizer. Etching uniformity and controllability can be achieved by incorporating H₂O₂. With this etching process, the fabrication of a monolithic thin film thermoelectric cooling device using wet chemistry becomes feasible.