Chemical Vapor Deposition Carbon Film as a Capping Layer in 4H-SiC Based MOSFETs

Radio-frequency plasma enhanced CVD (RF-PECVD) carbon films were grown directly on 4-inch 4H-SiC substrates as a capping layer for MOSFET device applications. An approximately 50-nm-thick CVD carbon capping layer was found to reduce the surface roughness, as determined by atomic force microscopy (AFM). The secondary ion mass spectroscopy (SIMS) depth profile results revealed that carbon capping layer can suppress the dopant out-diffusion on the implanted surface after annealing even at high temperature (1700 °C) for 30 min. The calculated subthreshold swing (S) values of devices with CVD carbon capping layer and photo-resist process (base) measured at room temperature were 460 ± 50 (mV/dec) and 770 ± 70 (mV/dec), respectively. The lower value of 'S' for the device with carbon capping layer was related to the very low density of interface traps at the SiC-SiO2 interface. These results show the potential of CVD carbon as a capping layer for SiC MOSFET device applications.