Wet etching of Bi2Te3 thin films compatible with microelectronic fabrication processes

A major limitation in fabricating a monolithic Bi
₂
Te
₃
-based thermoelectric thin film device is patterning poorly adhesive Bi
₂
Te
₃
and Bi
_0.5
Sb
_1.5
Te
₃
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 Bi
₂
Te
₃
thin films down to micrometer scale dimensions. We use an etching solution of HNO
₃
:CH
₃
COOH:H
₂
O
₂
:H
₂
O, and a single-layer photoresist etch mask. Etch rate of ~100 nm/min has been measured. Inclusion of H
₂
O
₂
changes the etching mechanism, where H
₂
O
₂
replaces HNO
₃
as the oxidizer. Etching uniformity and controllability can be achieved by incorporating H
₂
O
₂
. With this etching process, the fabrication of a monolithic thin film thermoelectric cooling device using wet chemistry becomes feasible.