Enhanced formation and morphological stability of low-resistivity CoSi2 nanodot arrays on epitaxial Si0.7Ge0.3 virtual substrate

We report here the first successful growth of large-area, low-resistivity cobalt disilicide (CoSi2) nanodot arrays on epitaxial (0 0 1)Si0.7Ge0.3 substrates by using the nanosphere lithography (NSL) technique with an interposing amorphous Si (a-Si) thin film serving as the sacrificial layer. For the Co/a-Si bilayer nanodots array on Si0.7Ge0.3 samples after annealing, polycrystalline CoSi2 appears to form as the only silicide phase at an annealing temperature as low as 500 °C The a-Si interlayer with appropriate thickness was found to effectively prevent Ge segregation and maintain the morphological stability in forming CoSi2 nanodots on Si0.7Ge0.3 substrate. The size, interparticle spacing, and triangular shape of the CoSi2 nanodots remain almost unchanged even after annealing at 950 °C. For the Co/a-Si nanodot samples further annealed at 1000 °C, amorphous SiOx nanowires, 15–35 nm in diameter, were observed to grow from CoSi2 nanodot regions. The observed results present the exciting prospect that the NSL technique in conjunction with a sacrificial a-Si interlayer process promises to be applicable in fabricating periodic arrays of other low-resistivity silicide nanocontacts with controlled size, shape, and periodicity on Si1−xGex substrates.