From Event: SPIE Optical Engineering + Applications, 2016
We have analyzed the mechanisms of leakage current conduction in passivating silicon dioxide (SiO2) films grown on (0
0 0 1) silicon (Si) face of n-type 4H-SiC (silicon carbide). It was observed that the experimentally measured gate current
density in metal-oxide-silicon carbide (MOSiC) structures under positive gate bias at an oxide field Eox above 5 MV/cm
is comprised of Fowler-Nordheim (FN) tunneling of electrons from the accumulated n-4H-SiC and Poole-Frenkel (PF)
emission of trapped electrons from the localized neutral traps in the SiO2 gap, IFN and IPF, respectively at temperatures
between 27 and 200 °C. In MOSiC structures, PF mechanism dominates FN tunneling of electrons from the accumulation
layer of n-4H-SiC due to high density (up to 1013 cm-2) of carbon-related acceptor-like traps located at about 2.5 eV
below the SiO2 conduction band (CB). These current conduction mechanisms were taken into account in studying hole
injection/trapping into 10 nm-thick tunnel oxide on the Si face of 4H-SiC during electron injection from n-4H-SiC under
high-field electrical stress with positive bias on the heavily doped n-type polysilicon (n+-polySi) gate at a wide range
of temperatures between 27 and 200 °C. Holes were generated in the n+-polySi anode material by the hot-electrons
during their transport through thin oxide films at oxide electric fields Eox from 5.6 to 8.0 MV/cm (prior to the intrinsic
oxide breakdown field). Time-to-breakdown tBD of the gate dielectric was found to follow reciprocal field (1/E) model
irrespective of stress temperatures. Despite the significant amount of process-induced interfacial electron traps contributing
to a large amount of leakage current via PF emission in thermally grown SiO2 on the Si-face of n-4H-SiC, MOSiC devices
having a 10 nm-thick SiO2 film can be safely used in 5 V TTL logic circuits over a period of 10 years.
Piyas Samanta and Krishna C. Mandal, "Leakage current conduction and reliability assessment of passivating thin silicon dioxide films on n-4H-SiC," Proc. SPIE 9968, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVIII, 99680E (Presented at SPIE Optical Engineering + Applications: August 29, 2016; Published: 9 September 2016); https://doi.org/10.1117/12.2238875.
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