Fabrication of MOS Capacitors by Wet Oxidation of p-type 4H-SiC Preamorphized by Nitrogen Ion Implantation

摘要

4H-SiC p-type MOS capacitors fabricated by wet oxidation of SiC preamorphized by nitrogen ion (N~+) implantation have been investigated. The oxidation rate of the SiC layer preamorphized by high-dose N~+ was much larger than that of crystalline SiC, allowing us to reduce the fabrication time of SiC MOS devices. We found that the presence of the surface amorphous SiC layer before the oxidation process did not influence the interface state density in MOS capacitors. Moreover, the shift of the flat-band voltage is not correlated to the amount of nitrogen in the oxide. On the contrary the density of interface states near the valence band edge increased according with the high concentration of the implanted N at the oxide-SiC interface, as in the case of dry oxidation reported by Ciobanu et al. The generation of positive charges due to the nitrogen embedded inside the oxide layer was smaller compared with dry oxidation. We discuss the difference between wet and dry oxidation for MOS capacitors fabricated with N~+ implantation.