Retardation of nucleation rate for grain size enhancement by deep silicon ion implantation of low-pressure chemical vapor deposited amorphous silicon films

The effects of silicon ion implantation on the crystallization kinetics and grain size of low-pressure chemical vapor deposited amorphous silicon on oxidized silicon substrate have been studied by x-ray diffraction and transmission electron microscopy. The most effective grain size enhancement was achieved by deep silicon ion implantation with the projected range located beyond the bottom interface to allow the maximum kinetic energy transfer at or near that interface. The grain size enhancement was due to a decrease of nucleation rate and an increase of the nucleation activation barrier from 3.9 to 4.9 eV for the Si⁺-implanted sample. The amorphous-to-crystalline grain growth activation barrier of 3.2 eV was not altered by Si⁺ implantation, but the growth rate was decreased. Retardation of nucleation and enhancement of grain size are attributable to the implant-recoiled oxygen. The average grain size increases from ∼0.2 to ∼2.0 μm by using 2×10¹⁵ cm^-2 of Si⁺ implantation at 92 keV for 82-nm-thick films.