rf glow discharge of SiF4-H2 mixtures: Diagnostics and modeling of the <i>a</i>-Si plasma deposition process

Abstract

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 (SiF*3,SiF*2,SiF*,H*, and H*2), 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 ∝ [H][SiF2] is able to fit the experimental results.