Sapphire etching with BCl3/HBr/Ar plasma

The etching of (0 0 0 1) sapphire wafer was studied in an inductively coupled plasma etcher using BCl3/HBr/Ar plasmas. The qualitative relationship between etch rate and inductive power and d.c. bias voltage was studied to obtain high sapphire etch rate. The etch rate was increased almost linearly with the increase of inductive power and d.c. bias voltage. The etch selectivity over photoresist was remained similar for the investigated range of inductive power and d.c. bias voltage except for the low d.c. bias voltages. At the low d.c. bias voltages, the increase of d.c. bias voltage increased the etch selectivity. The highest sapphire etch rate obtained in BCl3/HBr/Ar plasma was 550 nm/min with the etch selectivity over photoresist approximately 0.87 at 1400 W of inductive power and −800 V of d.c. bias voltage. In the etch conditions with the d.c. bias voltage over −600 V, the highly anisotropic sapphire etch profile and the sapphire surface composition similar to non-etched sapphire wafer (reference) could be obtained when observed by a scanning electron microscope and X-ray photoelectron spectroscopy, respectively. The surface roughness of the etched sapphire wafer was examined by atomic force microscopy and was remained similar regardless of d.c. bias voltage.