Engineering Interface Fixed Charges in AlON/SiO ₂ via In Situ Nitrogen Doping: Toward Threshold-Voltage Matching for SiC CMOS

Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) with conventional thermal SiO2 gate oxides are plagued by issues such as low channel mobility, threshold voltage instability, and premature oxide breakdown. To address these challenges, high-κ dielectrics, specifically aluminum oxynitride (AlON) with a SiO2 interlayer, have been employed to mitigate electric field effects and improve interface properties. In this work, AlON/SiO2 stacks with tunable nitrogen doping ratios were fabricated via plasma-enhanced atomic layer deposition. An analytical method for extracting the flat-band voltage and quantifying fixed interface charges is presented, which remains unaffected by interface states or oxide traps. Optimized in situ N-doping (10.37%) minimizes the fixed charge density at the AlON/SiO2 interface to −4.16 × 1012 cm–2. Based on calculations from MOSCAPs data, this controlled charge engineering enables precise tuning of the threshold voltage in SiC p-MOSFETs from −3.3 to −5.5 V, independent of process-induced variations. The study elucidates the role of nitrogen bonding configurations in governing interface charges and provides a reproducible strategy for their modulation, offering critical material-level insights for advancing SiC complementary metal-oxide-semiconductor (CMOS) technology.