Nitrogen implantation in (100)-β-SiC layers grown on Si substrate

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Abstract
Molecular N ions (N+2) have been implanted at an incident energy of 30 keV in a heteroepitaxial β-SiC layer grown on a (100)-Si substrate to form an n+ layer in the substrate. Furnace and rapid-thermal annealing are carried out on N-implanted substrates. Crystalline properties of the implanted layers have been characterized by Rutherford backscattering measurements and transmission electron microscope observations. An anodic oxide growth and removal technique has been developed, by which a very thin SiC layer can be reproducibly stripped from the substrate. Carrier-concentration and mobility profiles for n-type layers formed under various implant and annealing conditions have been investigated by differential Hall measurements combined with the layer stripping process. Rutherford backscattering data indicate that heating of substrate during implantation is important to reduce the amount of defects existing in the substrate after annealing. It has been revealed that rapid thermal annealing is useful for achieving high electrical activation of implanted N atoms. A very shallow (<100 nm) n+ layer with a maximum carrier concentration of around 1×1020/cm3 can be formed in the SiC layer by N implantation at 400 °C and by subsequent rapid thermal annealing at 1100 °C for 10 s. This highly doped layer is applicable to an emitter in a SiC/Si heterobipolar transistor. It has been also shown that implantation with a very high dose, e.g., 1.2×1016/cm2, gives rise to the formation of Si3N4 in the substrate after annealing, suppressing electrical activation of implanted atoms.