Role of hydrogen addition to SiF4-H2-He plasma to control the amorphous/microcrystalline phase in Si:H films

The effects of H2 addition to SiF4-H2-He mixture are investigated on the net deposition rate and the structure of hydrogenated silicon films obtained by means of plasma enhanced chemical vapor deposition. The decrease of net deposition rate with increasing the hydrogen dilution is discussed in terms of gamma ratio that is proportional to etching/growth rates ratio. The gamma ratio determination by optical emission spectroscopy is effective in controlling and identifying the amorphous/crystalline transition phase of silicon. The increase of H2 flow rate from 5 to 30 sccm at a fixed SiF4-He mixture gives an increase in the crystalline volume fraction from 0 to 100%.