The degradation induced by oxygen (O-2) plasma irradiation to the various low dielectric constant materials (low-k; k = 3.0-2.5) has been investigated in this study. The dielectric constant was observed to increase upon O2 plasma treatment due to carbon atom depletion and Si-OH bond formation, which is strongly influenced by the bonding structure or strength of the low-k materials, and less related to the porosity. Moreover, the O2 damage can be suppressed by densifying the low-k film's surface induced by He/H-2 remote plasma treatment. Additionally, the role of ions, photons, and radicals in the plasma in inducing the low-k material degradation was clarified by using a special designed structure. The experimental results showed that all components in the plasma have contributions in degrading the electrical and reliability performance of low-k film. Moreover, the synergy between the radicals, the photons, and the ions enhanced the damage. (C) 2014 Elsevier B.V. All rights reserved.