Dual-Stage Annealing for Enhanced Thulium Oxynitride Passivation on a 4H-SiC MOS Capacitor

Enhancement of the metal-oxide-semiconductor (MOS) characteristics for a thulium oxynitride (Tm _x O _y N _z ) passivation layer (PL) on 4H-silicon carbide (SiC) was achieved through the development of a dual-stage process. This methodology comprised rapid thermal annealing in a nitrogen (N₂) ambient, followed by normal annealing (NA) in a forming gas-oxygen-forming gas (FOF) mixture. Analysis by grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS) confirmed the successful formation of the Tm _x O _y N _z PL. The additional RTA step enhanced nitrogen incorporation at the Tm _x O _y N _z /4H-SiC interface, effectively reducing oxygen vacancies (V _o). Data from X-ray reflectivity (XRR) and cross-sectional FESEM corroborated these findings, indicating that the accumulation of nitrogen ions facilitated the development of a thinner interfacial SiO₂ layer with a thickness of 2.422 nm. Consequently, the electrical properties of the dual-stage annealed Tm _x O _y N _z PL were enhanced with a higher dielectric constant (k = 13.1), lower slow trap density (STD = 4.24 × 10¹¹ cm^-2), lower interface trap density (D _it), and lower leakage current density (J).