Influence of Deposition Conditions of a-Si1-xCx on Film Composition Before and After Excimer Laser Annealing

Recently we reported an ELA process for the fabrication of polycrystalline TFTs from silicon reach a-Si_1-xC_x:H films, with x=0.23 and x=0.17, deposited at 1 torr and 63 mW/cm². In this work we discuss the effect of increasing C content (x), as well as depositing at lower pressure and higher power density in the C composition of the a-Si_1-xC_x:H, looking for stoichiometric films to use in TFTs. Amorphous films were afterwards poly-crystallized by excimer laser annealing (ELA) using a KrF excimer laser with wavelength of 248 nm and 20 ns pulse duration. Samples were studied by FTIR and Raman spectra to determine and compare the presence and relative amount of the different chemical bonds expected to appear, as well as structural and predominant bonds changes after ELA. It was determined that all deposited films presented the Si-C bond characteristic peak in the FTIR spectra before and after ELA. At the same time, as C content in the film increased, intense C-C bond peaks appeared in the Raman spectra, suggesting carbon segregation, which is an undesirable effect in layers to be used for TFTs fabrication