Long-Term Lifetime Evolution Mechanism of 4H-SiC MOSFETs Under Nitric Oxide Annealing

Reliability challenges persist with silicon carbide metal-oxide–semiconductor field-effect transistors (SiC MOSFETs) in power electronic applications due to low oxide quality. There are still some issues, such as low mobility, bias temperature instability (BTI), and low lifetime in it. Nitric-oxide (NO) postoxidation annealing is a key technology to achieve high mobility. In this study, we investigate how different annealing processes impact the time-dependent dielectric breakdown (TDDB) reliability of SiC MOSFET devices and explore the reasons for changes in device lifetime under NO passivation. Through X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) profile analysis, the element distribution and chemical bonds under various annealing conditions were tested. A clear conclusion shows that the trap density and distribution are main reason affecting the device long-term reliability. The study reveals that different defect distributions lead to differing degrees of impact ionization and electron tunneling in the TDDB. Notably, high temperature with short-time NO annealing under the same oxidation significantly increases the long-term reliability of SiC MOSFET devices without reducing the device mobility or deteriorating the BTI effects.