Improvement of Physical and Electrical Characteristics in 4H-SiC MOS Capacitors Using AlON Thin Films Fabricated via Plasma-Enhanced Atomic Layer Deposition

In this study, we investigate the improvement of physical and electrical characteristics in 4H-silicon carbide (SiC) MOS capacitors using Aluminum Oxynitride (AlON) thin films fabricated via Plasma-Enhanced Atomic Layer Deposition (PEALD). AlON thin films are grown on SiC substrates using a high ratio of NH₃ and O₂ as nitrogen and oxygen sources through PEALD technology, with improved material properties and electrical performance. The AlON films exhibited excellent thickness uniformity, with a minimal error of only 0.14%, a high refractive index of 1.90, and a low surface roughness of 0.912 nm, demonstrating the precision of the PEALD process. Through XPS depth profiling and electrical characterization, it was found that the AlON/SiC interface showed a smooth transition from Al-N and Al-O at the surface to Al-O-Si at the interface, ensuring robust bonding. Electrical measurements indicated that the SiC/AlON MOS capacitors demonstrated Type I band alignment with a valence band offset of 1.68 eV and a conduction band offset of 1.16 eV. Additionally, the device demonstrated a low interface state density (D_it) of 7.6 × 10¹¹ cm^-2·eV^-1 with a high breakdown field strength of 10.4 MV/cm. The results highlight AlON's potential for enhancing the performance of high-voltage, high-power SiC devices.