Plasma deposition chemistry of amorphous silicon–carbon alloys from fluorinated gas

Abstract

Hydrofluorinated amorphous silicon–carbon alloys (a-Si1−xCx:H,F) are obtained by plasma decomposition of SiF4–CH4–H2 mixtures. The analysis of the plasma phase, by mass spectrometry and optical emission spectroscopy, and of the resultant material, by Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy, allows us to gain information about the film growth chemistry. The growth kinetics and the material composition of the a-Si1−xCx:H,F films are studied as a function of the added CH4 amount to the SiF4. The peculiarity of SiF4–CH4 system is that small CH4 addition (10%) to SiF4 produces silicon carbon alloys with high C incorporation (60 at. %). This has been explained on the basis of a growth model in which the chemisorption of CHn on the surface prevails on that of SiFn.