Performance enhancement of Al/La₂O₃/ZrO₂/4H–SiC MOS device with LaON as interfacial passivation layer

The effect of in-situ LaON surface passivation in between La₂O₃/ZrO₂ bilayer high-k and N₂ plasma pre-treated 4H–SiC substrate formed by using plasma enhanced atomic layer deposition has been investigated. The ~40 nm and ~35 nm thicknesses of high-k bilayer stack with and without LaON on SiC substrate respectively were determined by cross sectional FESEM. The FTIR and XRD results reveal that, the deposition of the La₂O₃ and ZrO₂ as well as the formation of silicate at interface was found on both samples. The presence of the LaON passivation layer in MOS device exhibits significantly improved interfacial and electrical properties in terms of lower density of interface traps (D_it), lower number of effective oxide charges per unit area (Q_eff) and low leakage current density (J_V). Furthermore, the high electric field 8.2 MV/cm without breakdown and dielectric constant of 8.03 was found for Al/La₂O₃/ZrO₂/LaON/SiC as compared to that of Al/La₂O₃/ZrO₂/SiC MOS device. The Fowler–Nordheim tunneling in both 4H–SiC MOS devices has been studied. The results reported here suggest that the Al/La₂O₃/ZrO₂/LaON/SiC devices are useful for high power device applications.