| Doping plays a significant role in semiconductor device fabrication. In recent years, with the considerable improvement in the quality of SiC wafers, more and more attention has been paid to device fabrication. Due to the requirement of extreme high temperatures (>1800°C) and the lack of a suitable protective mask for thermal diffusion in SiC, selective doping is historically realized by ion implantation. However, the inherent drawbacks of ion implantation limit the potential features offered by SiC.; In this research work, a well-designed diffusion set-up using a vertical double wall water-cooled quartz chamber with induction heating was developed to meet the critical requirements for implementing diffusion in SiC. An equilibrium condition of sublimation and condensation was achieved in the diffusion chamber, which significantly reduced undesirable deterioration on the surface of SiC.; The diffusion mechanism of boron and aluminum in SiC was thoroughly investigated. An elaborated explanation of two-branch diffusion of boron was established and for the first time, it was observed and analyzed that the diffusion of aluminum has strong impact on the diffusion of boron.; Selective diffusion based on graphite mask was successfully realized in SiC. Various techniques were developed to characterize the selectivity of diffusion in SiC, especially, the successful utilization of Photoluminescence (PL), Cathodoluminescence (CL) and anodic oxidation. Selective diffusion in SiC is one of the significant contributions of this research.; A thin graphite film was used to protect the SiC surface from degradation at high temperatures. Atomic force microscopy (AFM) clearly showed that the surface roughness decreases from l5nm (no mask on sample) to 1.5nm (with mask on sample). Prevention of surface degradation during dopant incorporation is another major contribution of this work.; For the first time, planar p-n diodes based on selective diffusion of boron and aluminum were fabricated. The good performance of p-n diodes confirmed the viability of this process. IN characteristics of the 4H-SiC p-n diodes showed excellent rectification properties with a fairly low forward voltage drop (3.3 V at 100 A/cm2) and high blocking voltage (more than 1100 V). |
