Ellipsometric and XPS Studies of 4H-SiC/SiO2 Interfaces, and Sacrificial Oxide Stripped 4H-SiC Surfaces

The investigation of the silicon carbide surface after a sacrificial silicon oxidation technique is reported. Oxidation of SiC is a necessary step in the fabrication of MOS devices and device termination features such as field plates. Device processing requires the etching of windows through the oxide layer to form features such as metal / SiC contacts. However, this work indicates that a thin interfacial Si-O-C layer is still present after etching the oxide with hydrofluric acid (HF). Ellipsometry and X-ray photoelectron spectroscopy (XPS) have been used to evaluate this interfacial layer formed after oxide growth and after subsequent removal of oxide layers. An XPS analysis of the surface after removal of the oxide revealed that silicon, oxygen and carbon were all present in the remaining layer, which could not be removed by annealing at temperatures up to 1000°C. The Si-O-C layer could be eliminated by altering the oxidation conditions or by using a sacrificial silicon layer oxidation process. Ni Schottky barrier diodes fabricated on the 4H-SiC surface after removal of the oxide, displayed slightly higher ideality factors than those of diodes fabricated on untreated 4H-SiC samples.