ENHANCED CRYSTALLIZATION OF AMORPHOUS SI CONTAINING HYDROGEN WITHOUT OXYGEN DURING ION-BEAM IRRADIATION AT 310-DEGREES-C AND DURING FURNACEANNEALING BELOW 450-DEGREES-C

The epitaxial crystallization rates of amorphous Si layers on crystall ine Si substrates containing a considerable number of hydrogen atoms a re markedly increased in the absence of oxygen atoms. This enhanced cr ystallization occurs both during 1-MeV Xe-ion-beam irradiation at 310 degrees C and during furnace annealing in vacuum at temperatures below 450 degrees C. Implantation-amorphized crystal Si layers epitaxially grown on the (100)-crystalline Si substrates by ultrahigh vacuum chemi cal vapor deposition (UHV-CVD) are epitaxially crystallized by furnace annealing in vacuum at temperatures below 450 degrees C. Implantation -amorphized bulk-crystal Si substrates, however, are not entirely crys tallized by the same low-temperature annealing. Nanometer-scale microc rystallites, remaining at the near-surface region in the amorphous Si layer after 80-keV phosphorus implantation into the UHV-CVD epitaxial Si layer, grow three-dimensional during 1-MeV Xe-ion-beam irradiation at 310 degrees C, but not during furnace annealing at 600 degrees C in dry Ar ambient. This three-dimensional crystal growth does not occur in implantation-amorphized bulk-crystal Si substrates, even during 1-M eV Xe-ion-beam irradiation. Amorphous Si layers directly deposited by low-pressure CVD (LP-CVD) are crystallized epitaxially by 1-MeV Xe-ion -beam irradiation at 310 degrees C. The crystallization rate of the LP -CVD sample heated in the deposition furnace after evacuation is twice as high as that of the sample heated before evacuation. All these res ults are explained consistently by the presence of a considerable amou nt of hydrogen in polyhydride states in the amorphous Si layers in the absence of oxygen. It is suggested that the mechanism of low-temperat ure crystalline of amorphous Si containing hydrogen in polyhydride sta tes closely related, in terms of vacant spaces and dangling-bonds, to the mechanism of ion-beam-induced epitaxial crystallization. (C) 1997 American Institute of Physics.