High energy ion implantation at BNL

Silicon carbide (SiC) has several properties such as wide band gap and high voltage breakdown, that give it a significant advantage over silicon for the next generation of medium and high frequency applications. To fully realize these advantages, requires deep ion implantation (~> 6μm). Unfortunately, the energy of conventional ion implanters limits the implantation depth in SiC to approximately 1µm. Brookhaven National Laboratory (BNL) has developed a system that uses the 15 MV MP-class Tandem Van de Graaffs to implant ions in SiC to a depth >15 µm. By changing the ion beam energy in discrete steps, the overlapping implantations can build a uniform implantation profile from the maximum implantation depth to the surface. To implant ions near the surface of the SiC wafer requires the use of an energy absorber to degrade the ion energy from 10’s of MeV to a few keV. BNL has built a system to demonstrate the feasibility of this approach. The BNL system is described, and the results of high energy implantation for high voltage SiC devices are presented. Future improvements to the system are also discussed.