Enhancement of the amorphous to microcrystalline phase transition in silicon films deposited by SiF4-H-2-He plasmas

Hydrogenated microcrystalline silicon (mu c-Si:H) thin films have been obtained by plasma decomposition of SiF4-H-2-He mixtures at low temperature (120 degrees C). The size of crystalline grain and their volume fraction with respect to the amorphous phase have been found dependent on the r.f. power as evaluated by grazing incidence X-ray diffraction, microRaman and ellipsometry measurements. Chemical and electrical properties change according to the microcrystallinity. Pure and/or highly microcrystalline silicon has been obtained at temperature and r.f. power as low as 120 degrees C and 15 Watt.