ION-IMPLANTATION EFFECTS IN SILICON-CARBIDE

Results from a program, which has existed for some years, on ion implantation effects in alpha and beta silicon carbide will be summarized. Silicon carbide is easily amorphized by ion implantation at room temperature. Amorphization as determined by Rutherford backscattering spectrometry (RBS) occurs for damage energies of about 20 eV/atom, corresponding to 0.2 to 0.3 displacements per atom (dpa), at room temperature. Implantation at higher temperatures ( almost-equal-to 500-degrees-C or above) does not produce an amorphous region for damage levels as high as 17 dpa. Recovery of damage at the subamorphous damage level is fairly complete by 1000-degrees-C. Epitaxial regrowth after amorphization occurs over a very narrow temperature range at almost-equal-to 1500-degrees-C in an almost ''explosive fashion. Damage and amorphization are accompanied by swelling of up to 15%. The hardness and elastic modulus values of amorphous SiC are 40 and 70%, respectively, of the unimplanted single crystalline values, but before amorphization, the hardness first increases during the early damage phase and then decreases upon amorphization. The oxidation and chemical etching rates of the amorphous state are higher than for crystalline material. Amorphization kinetics, annealing kinetics and property changes are broadly compatible with the idea of a critical accumulation model for amorphization.