Analysis of 3-Dimensional 4H-SiC MOS Capacitors Grown by Atomic Layer Deposition of Al<sub>2</sub>O<sub>3</sub>

Abstract

3-Dimensional 4H-SiC metal-oxide-semiconductor capacitors have been fabricated to determine the effect of the sidewall on the characteristics of 3-Dimentional gate structures. Al2O3 deposited by Atomic Layer Deposition (ALD) was used as the gate dielectric layer on the trench structure. The 3-D MOS capacitors exhibit increasing accumulation capacitance with excellent linearity as the sidewall area increases, indicating that ALD results in a highly conformal dielectric film. The capacitance – voltage characteristics also show evidence of a second flatband voltage, located at a higher bias than that seen for purely planar devices on the same sample. We also observe that the oxide capacitance of planar and 3-D MOS capacitors increases with temperature. Finally, we have found that the 3-D MOS capacitor has a weaker temperature dependence of flatband voltage in comparison to the conventional planar MOS capacitor due to the incorporation of the (1120) plane in the sidewall.