High rate sapphire etching using BCl₃-based inductively coupled plasma

Sapphire was etched in an inductively coupled plasma equipment using BCl₃-based gas combination. The etch characteristics of sapphire were investigated as functions of additive gas, inductive power, and dc bias voltage. In the case of additive gas effects, 380 nm/min of etch rate could be obtained in BCl₃/Cl₂ and the anisotropic etch profile could be observed in BCl₃/HBr. From the ion saturation currents measured by Langmuir probe and optical emission intensities by OES, sapphire etch characteristics appeared to be controlled by the BCl radicals in the plasma. The effects of inductive power and dc bias voltage on the sapphire etch rate were studied in BCl₃/HBr/Ar plasmas. The results showed that the increase of inductive power and dc bias voltage increased the sapphire and photoresist etch rates almost linearly. The obtained highest sapphire etch rate in the BCl₃/HBr/Ar plasma was 550 nm/min with about 0.87 of the etch selectivity over photoresist and 75 degree of etch profile angle at 1400 Watts of inductive power and -800 Volts of dc bias voltage.