Selective electrochemical release etching of eutectically bonded microstructures

This paper reports on the successful demonstration of a novel microfabrication method in which eutectic gold bonded microstructures are selectively electrochemically release etched. This method offers several advantages: both a strong permanent bond and a temporary bond is achieved on the same die, the footprint of the temporary bonded structures is allowed to be larger than the footprint of the permanently bonded structures and the used etchants provide a larger process compatibility than the etchants of other release etch methods. Eutectically bonded 350 µm wide silicon structures were fully released after 1 hour of electrochemical etching followed by 1.5 hours wet etching of the TiW adhesion layer.