Addition of SiF4 to standard SiH4+H2 plasma: an effective way to reduce oxygen contamination in μc-Si:H films

The effect of adding of silicon tetrafluoride (SiF4) to silane (SiH4) hydrogen gas mixture on the properties of highly crystallized microcrystalline silicon (μc-Si:H) films was studied. We found that the addition of a small amount of SiF4, with a ratio to SiH4 not exceeding 1/10, has almost no effect on deposition rate and does not affect the structure of the μc-Si:H films, but strongly reduces oxygen incorporation into the films. Reduction of oxygen content to values below 1019 cm-3 results in intrinsic character of the films with ratio of photo to dark conductivity about 103 in whole studied range of deposition temperatures from 175 to 250 °C in contrast to films, deposited without SiF4 addition, which show strong decrease of photosensitivity with increase of deposition temperature above 200 °C (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)