LOW-TEMPERATURE GROWTH OF SILICON-BORON LAYER BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION

A polycrystalline silicon-boron (Si-B) layer with a thickness of 180 nm was grown on recrystallized amorphous silicon in an ultrahigh vacuum chemical vapor deposition (UHV/CVD) system using pure SiH4 and B2H6 (1% in H-2). The growth temperature was as low as 550-degrees-C. Auger electron spectroscopy and secondary ion mass spectroscopy showed that the boron concentration is extraordinarily high (2 x 10(22) cm-3). From the analysis of transmission electron diffraction patterns, the phase of silicon hexaboride (SiB6) was found to be present in the as-deposited Si-B layer. After thermal annealing, most of the boron atoms in the Si-B layer were found to be immobile. The presence of SiB6 in the Si-B layer may lead to the reduction of boron diffusivity in the Si-B layer during thermal annealing.