Formation mechanism of concave by dielectric breakdown on silicon carbide metal-oxide-semiconductor capacitor

Adjacent concaves are formed commonly on silicon carbide (SiC) MOS capacitor after time-dependent dielectric breakdown (TDDB). This paper describes the formation mechanism of the concave on the SiC MOS capacitor with aluminum gate electrode on thermally grown silicon dioxide gate dielectric by the dielectric breakdown. At the bottom of an approximately 450 nm-deep concave, a stack structure of the concave surface was found to be surface oxide/C-rich layer/Si-rich layer/SiC substrate. Some C-rich debris adhered on the surface of the concave. The concave surface was speculated to be formed by a sequence of the C-rich surface on the Si-rich surface, the debris adhered on the surface, and the oxide layer containing nitrogen and aluminum. Formation of the concave and its surface is explained based on the physical properties of SiC; (i) a peritectic decomposition of SiC to the solid phase carbon and the liquid phase solution containing silicon and carbon, (ii) a normal freezing process of the liquid phase solution, and (iii) a thermal decomposition on the concave surface to form a graphite layer.