Selective Wet and Dry Etching of NiO over β-Ga2O3

Patterning of NiO/Ga2O3 heterojunctions requires development of selective wet and dry etch processes. Solutions of 1:4 HNO3:H2O exhibited measurable etch rates for NiO above 40 degrees C and activation energy for wet etching of 172.9 kJ.mol(-1) (41.3 kCal.mol(-1), 1.8 eV atom(-1)), which is firmly in the reaction-limited regime. The selectivity over beta-Ga2O3 was infinite for temperatures up to 55 degrees C. The strong negative enthalpy for producing the etch product Ga(OH)(4) suggests HNO3-based wet etching of NiO occurs via formation and dissolution of hydroxides. For dry etching, Cl-2/Ar Inductively Coupled Plasmas produced etch rates for NiO up to 800 angstrom.min(-1), with maximum selectivities of beta-Ga2O3. The ion energy threshold for initiation of etching of NiO was similar to 55 eV and the etch mechanism was ion-driven, as determined the linear dependence of etch rate on the square root of ion energy incident on the surface.

Automated summary

Patterning of NiO/Ga2O3 heterojunctions requires development of selective wet and dry etch processes. Wet etching of NiO using 1:4 HNO3:H2O solution showed measurable etch rates above 40 degrees C, with infinite selectivity over β-Ga2O3 below 55 degrees C. Dry etching using Cl-2/Ar plasma achieved etch rates up to 800 angstrom.min(-1), with maximum selectivities for β-Ga2O3.