Effects of plasma-pretreatment on substrates before deposition of polycrystalline silicon films

Polycrystalline silicon (poly-Si) films were simultaneously deposited on glass and single-crystal Si substrates that were exposed to either N-2 or CF4 plasma excited using different RF power values (0-80W) prior to the film deposition, under 300degreesC by plasma enhanced chemical vapor deposition using a SiH4/SiF4 mixture. Structural changes of the poly-Si films were investigated by X-ray diffraction, Raman spectroscopy, electron spin resonance, infrared absorption and atomic force microscope measurements. All poly-Si films were deposited under fixed conditions. Without pretreatment, the resultant Si film was amorphous. However, (110) preferentially oriented poly-Si films were observed to grow suddenly when substrates were exposed to the plasma, and increased RF power resulted in improved crystalline qualities. These results were examined on the basis of the effect of various mechanisms on the crystalline properties, although these mechanisms may jointly determine the properties.