Gas-phase silicon etching with bromine trifluoride

We report the first study of gas phase silicon micromachining using pure bromine trifluoride (BrF₃) gas at room temperature. This work includes both the design of a new apparatus and etching characterization. Consistent etching results and high molecular etching efficiency (80%) have been achieved by performing the etching in a controlled pulse mode. This pure gaseous BrF₃ etching process is isotropic and has a high etch rate with superb selectivity over silicon dioxide (3000:1), silicon nitride (400-800:1) and photoresist (1000:1). Moreover, gaseous BrF₃ etching has also been demonstrated in surface micromachining process, where silicon nitride channels and membranes using polysilicon as the sacrificial layer have been successfully fabricated