Cregeen, Joseph (2018) Low temperature thermal oxidation of epitaxial 3C-SiC. MA thesis, University of Warwick.

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Abstract

Silicon Carbide (SiC) is a wide-bandgap semiconductor which has promising potential as a future material for power electronics devices such as metal-oxide-semiconductor field effect transistors (MOSFETs). The aim of this project was to take cubic SiC (3C-SiC) grown on silicon (Si) substrates by reduced-pressure chemical vapour deposition (RPCVD) and investigate whether low-temperature (< 1000 ⁰C) dry oxidation is a suitable method for growing the dielectric oxide layers vital for device fabrication. To this end, heteroepitaxially grown 3C-SiC was oxidised at 985 ⁰C and a range of physical and electrical characterisation techniques were employed to assess the grown oxide.

X-ray reflectance (XRR) and cross-sectional transmission electron microscopy (X-TEM) analysis suggested a growth rate of around 4.08 × 10-2 nm/min, comparable to that achieved on 4H-SiC. Qualitative analysis showed that this oxide closely followed the surface morphology of the 3C-SiC, and atomic force microscopy (AFM) proved that the oxide did not significantly alter the surface roughness of the as-grown 3C-SiC epilayers. X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) showed that the oxide had carbon (C) distributed inhomogeneously throughout the oxide, which may have served as charge traps at the oxide/3C-SiC interface and contributed to leakage through the oxide by trap-assisted tunnelling (TAT). The highest concentration of C was at the interface, totalling 25% of the material present.

Capacitance-voltage (CV), conductance-voltage (GV), and current-voltage (IV) analysis provided information about the electrical properties of the grown oxide. While a small inversion population was observed in the CV data, this quickly collapsed under negative bias. Relatively high leakage current through the oxide is the suspected cause of this. While leakage was high, the oxide/3C-SiC interface showed a relatively small interface state density (Dit) of 1 × 1010 cm-2eV-1, which is comparable to that seen on similar material after post-oxidation annealing (POA), despite the fact that none was performed on this material. POA may further improve this Ditfigure by up to an order of magnitude. In summary, this work provides some evidence that heteroepitaxially grown 3C-SiC is a viable material for power device applications, but optimisation of the oxidation method and post-oxidation treatment is required to make this material realise its full potential.

Item Type:	Thesis (MA)
Subjects:	Q Science > QC Physics
Library of Congress Subject Headings (LCSH):	Silicon carbide -- Oxidation, Silicon carbide -- Thermal properties
Official Date:	November 2018
Dates:	Date Event November 2018 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	MA
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Myronov, Makysm
Format of File:	pdf
Extent:	xiii, 105 leaves : illustrations (chiefly color)
Language:	eng

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