Analytical Electron Microscopy of Antimony Doped 4H-SiC/SiO₂ and 4H-SiC/Boron and Phosphorus Doped SiO₂ Interface Structures in MOS Devices

A high density of electronic defects at the SiC/SiO₂ interface adversely affects SiC-based MOS devices. Various treatments are known to improve device performance. Annealing in nitric oxide (NO) passivates electronic defects at the interface and raises the carrier mobility in the active region by an order of magnitude, to 35-40 cm²/Vs, but passivation with phosphorus¹ or boron² improves upon NO by a factor of 3, increasing the mobility to over 120 cm²/Vs.¹ Antimony doping of the SiC in conjunction with NO annealing also increases the mobility over 100 cm²/Vs.³ We investigate the chemical and structural effects of these treatments on the SiC/SiO₂ interface using high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy Spectrum Imaging (EELS SI). The latter allows identification of the composition and types of bonding at the interface. Machine learning techniques applied to the EELS data reveal intermediate bonding states within this region as well as inhomogeneous distribution of the P and B dopants. ¹G. Liu et al., Appl Phys Rev. 2, 021307 (2015). ²D. Okamoto et al., IEEE Electron Device Lett. 35, 1176 (2014). ³A. Modic et al., IEEE Electron Device Lett. 35, 894 (2014).