Modulation of Interface Fixed Charge on AlON/SiO₂/SiC with In-Situ Nitrogen Doping

Traditional thermally grown SiO2 gate oxide layers in SiC power MOSFETs are prone to breakdown, reduced carrier mobility, and threshold voltage instability. Replacing SiO2 with high-k gate dielectrics in SiC power MOSFETs reduces the electric field within the oxide and enhances the carrier channel mobility by incorporating a thin SiO2 layer, with the AlON film's low trap chargedensity further improving threshold voltage stability. The PEALD-grown AlON films, characterized by the presence of negative fixed charges, cause a positive shift in the flatband voltage, complicating the design of threshold voltages. This paper investigates the modulation of fixed charges in PEALD grown AlON films by nitrogen doping, reveal a linear increase in flatband voltage with effective oxide thickness. X-rayphotoelectron spectroscopy (XPS) shows that carbon impurities are concentrated at the SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/AlON interface, where nitrogen incorporation enhances the formation of C-N bonds, effectively suppressing interface charges. Nitrogen doping process adjustment impacts C-N bond formation proportion. Alternately introducing NH3 and O2 (not simultaneously) promotes it, increasing the proportion from 8.99% to 13.17%. This creates a better reaction environment, reducing side reactions and enhancing efficiency and selectivity. With an PEALD Alternating growth process, the negative fixed charge density is suppressed to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-4.16\times 10^{12}\text{cm}^{-2}$</tex>, and the flatband voltage hysteresisremains below 0.1V regardless of post-deposition annealing. The process-grown SiO2/ AlON stack exhibits exceptional passivation properties, with an AlON bandgap of 6.53 eV and an oxide breakdownfield strength of 9.8 MV/cm. Even at an equivalent oxide thickness of merely 15 nm, the leakage current density is reduced to the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{nA}/\text{cm}^{2}$</tex> level.