The effects of ICP dry etching and HF wet etching on the morphology of SiO 2 surface

Shariar, Kazy F; Zhang, Jie; Coasey, Keith; Sufian, Md Abu; Remy, Roddell; Qu, Jing; Mackay, Michael; Zeng, Yuping

doi:10.1088/2053-1591/aad591

Patterning of NiO/Ga 2 O 3 heterojunctions requires development of selective wet and dry etch processes. Solutions of 1:4 HNO 3 :H 2 O exhibited measurable etch rates for NiO above 40 °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 β -Ga 2 O 3 was infinite for temperatures up to 55 °C. The strong negative enthalpy for producing the etch product Ga(OH) 4 suggests HNO 3 -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 Å.min −1 , with maximum selectivities of <1 over β -Ga 2 O 3 . The ion energy threshold for initiation of etching of NiO was ∼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.

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