Towards Aluminum Oxide/Aluminum Nitride Insulating Stacks on 4H-SiC by Atomic Layer Deposition

Galizia, Bruno and Fiorenza, Patrick and Schilirò, Emanuela and Pécz, Béla and Fogarassy, Zsolt and Greco, Giuseppe and Saggio, Mario and Cascino, Salvatore and Lo Nigro, Raffaella and Roccaforte, Fabrizio (2024) Towards Aluminum Oxide/Aluminum Nitride Insulating Stacks on 4H-SiC by Atomic Layer Deposition. MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING : FUNCTIONAL MATERIALS FOR (OPTO)ELECTRONICS, SENSORS, DETECTORS, AND GREEN ENERGY, 174. No.-108244. ISSN 1369-8001 (print); 1873-4081 (online)

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Abstract

Stacked aluminum oxide/aluminum nitride (Al2O3/AlN) layers were deposited on n-type (0001) 4H–SiC by atomic layer deposition (ALD) processes. The structural and chemical properties have been investigated and are consistent with the growth of ∼9 nm oriented (0001) AlN layer, and an upper 20 nm amorphous Al2O3 layer. The entire Al2O3/AlN stack was electrically characterized and compared with respect to a single Al2O3 layer having the same total thickness. The Al2O3/AlN bilayer exhibited a higher dielectric constant (κ = 8.7), a significant reduction of the oxide trapped charges (NOT) from 7.8 × 1012 to 1.8 × 1012 cm−2, as well as a decrease of a factor 2 of the interface traps density (Dit) compared with the Al2O3 single layer values. A large positive flat band voltage shift was observed in the C–V curves acquired on MIS capacitors. The comparison of the behaviour of MIS capacitors fabricated on both n-type and p-type 4H–SiC demonstrated that deep interface states (near the 4H–SiC mid gap) acting as acceptors or donors for the n-type and p-type MIS contribute to the observed behavior. This hypothesis has been also corroborated by TCAD simulations.

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