Effects of implanted oxygen on the crystallization of silicon films and polysilicon TFT characteristics have been investigated. Oxygen ions were implanted with various doses into silicon films deposited by LPCVD at $540\,^\circ\!C$ from $SiH_4$. The implantion energy was 50 KeV and doses were $5\times10^{14}$, $1\times10^{15}$, $3\times10^{15}$ and $5\times10^{15}[cm^{-2}]$. Then these silicon films were crystallized at $600\,^\circ\!C$ in $N_2$ ambient and the oxygen effects on the crystallization of silicon films were investigated by XRD (X-Ray Diffraction) and TEM (Transmission Electron Microscopy). As a whole, incubation times were increased and crystallization rates were reduced due to the implanted oxygen. But the intensities of final XRD peaks showed a little different feature. In the cases of two high doses ($3\times10^{15}$, $5\times10^{15}[cm^{-2}]$), the final XRD peaks were higher than those of the cases of unimplanted and two low doses. No large differences were found on the final grain sizes of each film. Polysilicon TFT's were fabricated using these oxygen ion implanted and unimplanted silicon films after 96 hours' crystallization, and the device characteristics were measured. The unimplanted case showed the best device characteristics of all. In the cases of two low doses, ON currents and mobilities were about 30\% lower and subthreshold slopes, trap densities and leakage currents were higher than the unimplanted case. Especially, in the case the lowest dose, the device characteristics were than any other. On the contrary, in the case of dose of $3\times10^{15}[cm^{-2}]$, the device characteristics were nearly no worse than the unimplanted case. This is thought to be realated to the fact that in the cases of two high doses, the final XRD peaks were higher than those of the other cases, and can be explained as follows. Since implantations, with high doses over a value which forms the concentrations of about $10^{20}$[cm$^{-3}$] of implanted ions in the target film, can lower the activation energy for neucleation of the target film, in the cases of two high cases, as the result, the crystallinity of the film after crystallization process and the device characteristics might be a little more improved against the effects of implanted oxygen.
