ENHANCEMENT OF SP3/SP2 RATIO IN PLASMA DEPOSITED AMORPHOUS HYDROGENATED CARBON-FILMS BY THE ADDITION OF AMMONIA

Ammonia (NH3) and nitrogen (N2) were added to the hydrocarbon precursor 1,3 butadiene (C4H6) during rf plasma deposition of hydrogenated amorphous carbon (a:C-H) films. The effect of the additives on the film characteristics was determined by IR spectroscopy, solid state C-13 cross polarization magic angle spinning nuclear magnetic resonance, and etching in an oxygen plasma. Nitrogen incorporation in the films was studied by Auger electron spectroscopy. Compared to films deposited in the presence of N2, the films deposited from a C4H6/NH3 plasma had an sp3/sp2 ratio that was 40% higher. IR spectra of the films confirm the higher sp3/sp2 ratio. Also, the films deposited from C4H6/NH3 mixtures exhibited lower etch rates in an oxygen plasma. The larger sp3/sp2 ratio is due to the higher concentration of NHx and H species in a C4H6/NH3 plasma.