ION-IMPLANTATION EFFECTS IN SILICON-CARBIDE

Results from a program, which has existed for some years, on ion impla ntation effects in alpha and beta silicon carbide will be summarized. Silicon carbide is easily amorphized by ion implantation at room tempe rature. Amorphization as determined by Rutherford backscattering spect rometry (RBS) occurs for damage energies of about 20 eV/atom, correspo nding to 0.2 to 0.3 displacements per atom (dpa), at room temperature. Implantation at higher temperatures ( almost-equal-to 500-degrees-C o r above) does not produce an amorphous region for damage levels as hig h as 17 dpa. Recovery of damage at the subamorphous damage level is fa irly complete by 1000-degrees-C. Epitaxial regrowth after amorphizatio n occurs over a very narrow temperature range at almost-equal-to 1500- degrees-C in an almost ''explosive fashion. Damage and amorphization a re accompanied by swelling of up to 15%. The hardness and elastic modu lus values of amorphous SiC are 40 and 70%, respectively, of the unimp lanted single crystalline values, but before amorphization, the hardne ss first increases during the early damage phase and then decreases up on amorphization. The oxidation and chemical etching rates of the amor phous state are higher than for crystalline material. Amorphization ki netics, annealing kinetics and property changes are broadly compatible with the idea of a critical accumulation model for amorphization.