Formation mechanisms of low-density C-related defects in homoepitaxy 3C-SiC MOS capacitors compared with 4H-SiC

Gate oxide quality is a critical factor affecting the reliability of SiC MOSFETs. In this work, we elucidate the effect of differences in the formation mechanisms of low-density C-related defects between 3C-SiC and 4H-SiC on gate oxide quality and report that homoepitaxy 3C-SiC MOS capacitors exhibit extremely superior gate oxide quality compared to 4H-SiC counterparts. This study concluded that the long diffusion channels and low chemical bonding energy of 3C-SiC enable higher oxygen diffusion coefficient and lower diffusion activation energy, forming fewer residual carbon and a dense SiO2 layer, leading to superior gate oxide quality. This result is confirmed by electrical characterization, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy tests. Experimental results demonstrate that homoepitaxy 3C-SiC MOS capacitors achieve low interface trap density (on the order of 1011 cm−2 eV−1), low near-interface trap density (two orders of magnitude lower), high gate oxide breakdown field strength, and more stable threshold voltage and also show that 3C-SiC/SiO2 has a low content of carbon-related defects such as oxidized by-products SiOxCy and carbon clusters, which further verifies that low-density C-related defects are a key factor in achieving high gate oxide quality. The findings in this work allow homoepitaxy 3C SiC to effectively solve the problem of poor gate oxide quality in 4H-SiC MOSFETs.