Anisotropic etching of β-Ga2O3 using hot phosphoric acid

We report a systematic investigation on the anisotropic etching behavior of β-Ga2O3. A wagon wheel pattern was designed and fabricated on (010)-oriented β-Ga2O3 substrates. The wet etching in hot phosphoric acid was found to be effective in reducing the sidewall roughness caused by plasma dry etching. The angular dependence of the sidewall etch rate and inclination angles after wet etching was evaluated. The fins aligned along the [001] direction showed nearly vertical sidewalls after wet etching and a fast sidewall etch rate, making it feasible for the fabrication of ultrascaled vertical channel devices. The fins aligned in the angular range between the [203] and [201] directions showed slanted sidewalls with high tilt angles, which could be useful in reducing the peak electric field near the corners of high power devices. The observed anisotropic etching in this work offers a low-cost, low damage, and controllable fabrication method for ultrascaled and advanced device structures.