ZrO₂ Based Multilayered Stacks with Al₂O₃, Y₂O₃ or La₂O₃ Interlayers for SiC Power Devices

ZrO₂ is a promising high-k dielectric for SiC power devices due to its favorable bandgap alignment with SiC. However, it exhibits low breakdown fields and excessively high leakage currents for thicker layers. This paper presents an approach to suppress this leakage current by integrating thin interlayers of Al₂O₃, Y₂O₃, or La₂O₃ into the ZrO₂ film. These interlayers significantly reduce the charge carrier transport through ZrO₂ films and, thereby, the leakage current of the stack. Among the investigated interlayers, Al₂O₃ shows the most pronounced effect, reducing the leakage of ZrO₂-based thick films by 2 orders of magnitude and achieving a breakdown field of 7.4 MV/cm. This is comparable to the value measured for pure Al₂O₃ (7.7 MV/cm). These improvements can be attributed to the amorphous nature of the laminated oxide as the crystallization temperature could be increased from 350 °C for pure ZrO₂ up to 750 °C for the nanolaminate. Notably, the dielectric constant of this optimized stack is 13, which is twice as high as that of pure Al₂O₃. No additional charge trapping due to the interlayers was detected by Capacitance-Voltage hysteresis measurements. Furthermore, by additional optimization of the stack's deposition conditions, the charge trapping was reduced by 50% compared to pure ZrO₂ films.