Maturing ion-implantation technology and its device applications in SiC

Ion-implantation is an indispensable technique for planar selective area doping of SiC devices, because thermal diffusion of the desired dopants at temperatures where SiC doesn't decompose is not possible. Incongruent evaporation of Si from the SiC wafer during post-implantation annealing limits the maximum annealing temperature that can be used to repair the lattice damage and steer the implant into the substitutional lattice positions. Other problems include the nonstoichiometric disturbances caused by the ion-implantation, which result in non-uniform Si and C atom concentration and vacancy concentration depth distributions in the implanted region; and the difficulty in restoring the lattice quality back to the virgin level if as-implant lattice damage is of amorphous level. Ion-implantation in SiC needs to be performed at an elevated temperature in the range of 500 - 1000 /spl deg/C. An additional problem is the deep ionization energies of the useful donor (/spl sim/ 80 meV) and acceptor (> 240 meV) impurities in SiC, which limit the maximum carrier concentration . Results of donor, acceptor, and compensation species ion-implantations in 6H- and 4H-SiC are presented.