Rf glow discharge of SiF4-H2 mixtures: Diagnostics and modeling of the a-Si plasma deposition process

Hydrogenated and fluorinated amorphous silicon films (a-Si:H,F) have been deposited in a
parallel-plate rf plasma reactor fed with SiF4-H2 mixtures. The plasma phase
characterization has been performed by optical emission spectroscopy for the analysis of the
emitting species (SiF3*,SiF2*,SiF*,H*, and H2*), mass spectrometry for the analysis of
stable species, and Langmuir electrical probes for the evaluation of electron density (ne) and
temperature (kTe). The deposition rate (rD) has been monitored by laser interferometer.
The effect of the rf power, gas composition, total pressure, and dopant ( B2H6, PH3) addition
on the plasma phase composition and on the film growth rate has been studied. The
data have been discussed on the basis of a chemical model where the chemisorption of SiF4
and SiF2 and the subsequent interaction with H atoms are the determinant steps also
from the kinetic point of view. It has been found that the rate equation rD proportional [H][SiF2] is able to fit the experimental results.