Mechanistic Study Of Plasma Damage Of Low k Dielectric Surfaces

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Date

2007-10

Authors

Bao, J. J.
Shi, H. L.
Liu, J. J.
Huang, H.
Ho, P. S.
Goodner, M. D.
Moinpour, M.
Kloster, G. M.

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Abstract

Plasma damage to low k dielectric materials was investigated from a mechanistic point of view. Low k dielectric films were treated by plasma Ar, O-2, N-2/H-2, N-2 and H-2 in a standard RIE chamber and the damage was characterized by Angle Resolved X-ray Photoelectron Spectroscopy (ARXPS), X-Ray Reflectivity (XRR), Fourier Transform Infrared Spectroscopy (FTIR) and Contact Angle measurements. Both carbon depletion and surface densification were observed on the top surface of damaged low k materials while the bulk remained largely unaffected. Plasma damage was found to be a complicated phenomenon involving both chemical and physical effects, depending on chemical reactivity and the energy and mass of the plasma species. A downstream hybrid plasma source with separate ions and atomic radicals was employed to study their respective roles in the plasma damage process. Ions were found to play a more important role in the plasma damage process. The dielectric constant of low k materials can increase up to 20% due to plasma damage and we attributed this to the removal of the methyl group making the low k surface hydrophilic. Annealing was generally effective in mitigating moisture uptake to restore the k value but the recovery was less complete for higher energy plasmas. Quantum chemistry calculation confirmed that physisorbed water in low k materials induces the largest increase of dipole moments in comparison with changes of surface bonding configurations, and is primarily responsible for the dielectric constant increase.

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Junjing Bao, Hualiang Shi, Junjun Liu, Huai Huang, P. S. Ho, M. D. Goodner, M. Moinpour, and G. M. Kloster. AIP Conference Proceedings 945, 125 (Oct., 2007); doi: 10.1063/1.2815773