Electrical, structural, and chemical analysis of silicon carbide-based metal-oxide-semiconductor field-effect-transistors

In this study we investigated the morphology and interfacial chemistry of (0001) 4H-SiC-based metal-oxide-semiconductor field-effect transistors (MOSFETs) as a function of post-oxidation annealing in nitric oxide (NO) following wet oxidation. Energy-filtered transmission electron microscopy analyses showed enhanced C/Si concentrations (up to 13%) at distinct locations along the SiO₂/SiC interface in the MOSFETs that were not annealed in NO. In contrast, regions of enhanced C/Si concentration were not detected in the MOSFETs that were annealed in NO; instead, these samples showed a trace amount of interfacial N. The introduction of N may therefore be associated with a reduction of C in these samples and may contribute to the higher channel mobility (∼38 cm²/V s) in the samples annealed in NO relative to the samples that were not annealed in NO (∼9 cm²/V s). Rough SiO₂/4H-SiC interfaces and nonuniform oxide thickness were observed on both the NO- and the non-NO-annealed samples. The rough interfaces shown in the transmission electron microscopy bright field images may also be an important factor limiting the channel mobility in SiC-based MOSFETs. © 2004 American Institute of Physics.