Plasma sealing of a low-k dielectric polymer

The promising low-k property of polymers is offset by the ease of penetration of their inherently porous internal matrix during processing. In this study, plasma chemistry is applied to seal a low-k polymer against penetration of adventitious species. Spectroscopic ellipsometry, water contact angle measurements, and X-ray photoelectron spectroscopy are used to monitor the refractive index, thickness, and chemical composition change of a polymer exposed to plasmas containing oxygen and nitrogen. Depending on the densification versus etching rates, the plasmas seal, partially seal, or destroy the polymer. After annealing the samples to 350 °C, ellipsometric porosimetry has been used to examine the integrity of the sealing property. When an etching reaction occurs during the sealing process, the annealing destroys the sealing. In contrast, samples treated under non-etching conditions remain sealed. This result is confirmed by analyzing the penetration of tungsten precursors into the polymer during atomic layer deposition (ALD) of WCₓNy barriers.status: publishe