Polymerization occurring during fluorocarbon plasma treatment as a potential
method for pore sealing was investigated. CHF3 was used as a
reactant gas to expedite the rate of polymerization due to the presence of
hydrogen and the low C/F ratio. The reactor pressure was varied from 30mTorr
to 90mTorr to change the number of neutrals that act as the polymerizing
species. The films were exposed to the plasma for times of 1min, 3min, and 5
min to observe the penetration depth of neutrals and the thickness of
modified layer as a function of time. Dielectric constants were measured
before and after plasma treatment. The film morphology was investigated by
scanning electron microscopy before and after plasma treatment and a
featureless surface morphology was observed at 90mTorr on a 56% porosity
film. After plasma treatment, the average pore neck size decreases which may
help reduce metal precursor penetration during metallization.