Improved high-field reliability for a SiC metal–oxide–semiconductor device by the incorporation of nitrogen into its HfTiO gate dielectric

Abstract

Materials with high dielectric constant (k) have been used in SiC-based metal–oxide–semiconductor (MOS) devices to reduce the electric field in the gate dielectric and thus suppress a high-field reliability problem. In this work, high-k gate dielectrics HfxTi1−xO2 and HfxTi1−xON are applied in SiC MOS devices and an ultrathin thermally grown SiO2 is used as an interlayer between SiC and the high-k materials to block electron injection from SiC into the low-barrier high-k materials. Incorporating nitrogen into the Hf-Ti oxide (by adding nitrogen gas during its sputtering) stacked with a SiO2 interlayer (HfxTi1−xO∕SiO2) results in a better gate dielectric for the MOS capacitor, such as smaller frequency dispersion in the capacitance-voltage curve, less oxide charges, and better interface quality. Moreover, the nitrogen incorporation increases the dielectric constant of the oxide, but causes higher dielectric leakage, which can be suppressed by the SiO2 interlayer. High-field stress under constant electric field is performed on the stacked/nonstacked Hf-Ti oxides and oxynitrides, and it turns out that the two oxynitrides show a much smaller flatband shift and a less stress-induced leakage current compared with the two oxides. Based on these results, the HfxTi1−xON∕SiO2 stack could be a promising high-k gate dielectric for SiC MOS devices with enhanced reliability.