Ion Implanted p+/n 4H-SiC Junctions: effect of the Heating Rate during Post Implantation Annealing

Structural, morphological and electrical characteristics of Al-implanted p+/n 4H-SiC diodes are compared for the same implantation process and post implantation annealing with identical stationary and cooling cycles but different heating rate. Al+ ions were implanted at 400°C, with energies in the range 250-350 keV and 1.2 × 1015 cm-2 fluence. Post implantation annealing processes were done at 1600°C for 30 min with a constant heating rate in the range 7-40°C/s and an abrupt cooling cycle. Gas in the annealing ambient was high purity Ar. The Al depth profile of annealed and as implanted samples were equal except for concentrations below 1017 cm-3 where the former profiles showed a diffusion tail. With the increase of the heating rate of the post implantation annealing process, the sheet resistance of the Al implanted layer and diode leakage current decrease while the surface roughness increases.