Chemical state of phosphorous at the SiC/SiO2 interface

The chemical nature of sub-monolayer phosphorous impurities at the SiC/SiO2 interface is a critical surface science problem related to device performance and other applications. In this study, SiO2 films containing phosphorus were deposited by sputtering on both the Si and C-faces of SiC substrates, and on silicon (Si(100)) substrates. After oxide removal by etching, a significant amount of phosphorus was retained on both SiC surfaces, while no phosphorus was observed on the Si surface. Chemical ambient investigation, quantification by XPS, and water contact angle measurements indicate that the phosphorus on the SiC surface is trivalent bonded, mainly to oxygen. Based on these results, a SiO2/SiC interfacial structure is proposed: Si-C-Si-|-O-P-O2-SiO2. These results provide new insights into the role of phosphorus, its incorporation, and stability, as a passivating agent in the performance of SiC MOS structures.