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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Threshold Ion Energies and Cleaning of Etch Residues During Inductively Coupled Etching of NiO/Ga 2 O 3 in BCl 3
BCl 3 is an attractive plasma etchant for oxides because it is a Lewis acid used to scavenge native oxides on many semiconductors due to the strong B–O bonding. We investigated BCl 3 -based dry etching of the NiO/Ga 2 O 3 heterojunction system. BCl 3 /Ar Inductively Coupled Plasmas produced maximum etch rates for NiO up to 300 Å.min −1 and 800 Å.min −1 for β -Ga 2 O 3 under moderate plasma power conditions suitable for low damage pattern transfer. The selectivity for NiO: Ga 2 O 3 was <1 under all conditions. The ion energy threshold for initiation of etching of NiO was between 35–60 eV, depending on the condition and the etch mechanism was ion-driven, as determined by the linear dependence of etch rate on the square root of ion energy incident on the surface. By sharp contrast, the etching of Ga 2 O 3 had a stronger chemical component, without a well-defined ion energy threshold. The as-etched NiO and Ga 2 O 3 surfaces show chlorine residues, which can be removed on both materials by the standard 1NH 4 OH: 10H 2 O or 1HCl: 10H 2 O rinses used for native oxide removal. According to the location of the Cl 2p 3/2 peak, the Cl is ionically bonded.
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- Award ID(s):
- 1856662
- NSF-PAR ID:
- 10380043
- Date Published:
- Journal Name:
- ECS Journal of Solid State Science and Technology
- Volume:
- 11
- Issue:
- 11
- ISSN:
- 2162-8769
- Page Range / eLocation ID:
- 115005
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1149/2162-8777/ac9ff3
