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Moisture Induced Degradation of Porous Low-k Materials
Published online by Cambridge University Press: 01 February 2011
Abstract
Interaction of moisture with porous low-k films is evaluated by using in situ ellipsometry setup. The adsorbed water amount is calculated from change of refractive index measured during the adsorption. Pristine low-k films reversibly adsorb 2 - 5% of water that reflects presence of constitutive hydrophilic centrums. Plasma and thermal treatments increase the number of hydrophilic centrums. Once the amount of these centrums has reached a certain critical value sufficient to form a continuous water film, bulk water condensation is observed. Change of properties during the water adsorption in the damaged films is not fully reversible. Each additional adsorption cycle increases the dielectric function of the film because of decreasing porosity, increasing skeleton density and shrinkage. The pressure corresponding to the bulk condensation allows us to calculate internal contact angle (internal surface energy) of low-k materials. The water molecules adsorbed on separate OH groups play the role of a catalyst that hydrolyses the siloxane bridges initially present on hydrophobic surface.
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- Copyright © Materials Research Society 2006
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