High energy implantation of boron in 4H-SiC

The high energy implantation of boron into n-type Silicon Carbide epitaxial layers of the polytype 4H was investigated for various sample temperatures during implantation and different doping concentrations. Depth profiling using secondary ion mass spectrometry was applied to determine the boron distribution in the as-implanted epilayers and the re-distribution of boron atoms during a half hour heat treatment at a temperature of 1700 degrees C. The SIMS boron profiles are compared to numerical Monte Carlo calculations using the program TRIM96 and to electrical profiling by scanning capacitance microscopy. In general we found that boron is moving towards the implantation damage already during the implantation of a profile with four different energies. The defect enhanced diffusion of boron is more pronounced during the high temperature anneal, where a higher concentration of boron diffusing towards the sample surface was observed. Into the bulk of the epilayer the boron diffusion is on a lower level and shows an exponential decay with a length of up to 5 mu m. An out-diffusion of boron during the post implantation anneal was not observed at implantation temperatures up to 500 degrees C. Electrical profiling using scanning capacitance microscopy revealed that complicated layer structures with several pn-junctions can occur due to the re-distribution of boron during post implantation anneal.