Investigation of physical and chemical property changes of ultra low-κ SiOCH in aspect of cleaning and chemical repair processes

Abstract

The physical and chemical property changes of chemical vapor deposited ultra low-κ (ULK) SiOCH dielectric films due to different post ash treatments were studied by Auger electron spectroscopy, ellipsometric porosimetry and surface free energy evaluation. Structural changes in the ULK layer with respect to the carbon content were analyzed. Using a downstream and a reactive ion etch process for photo resist removal a reduction of carbon was observed. For different plasma gas chemistries the pore size reduction depends first on the process condition (downstream or reactive ion etch) and then on the gas. Differences in the pore size then also influence the amount of carbon depletion besides the influence of the gases used for photo resist processes. The damage at the surfaces was characterized by contact angle measurements providing both the polar and dispersive part of the surface free energy. The wettability of different solvents and repair chemicals was classified calculating their surface free energies and comparing those energies with the surface free energies of modified ULK surface. It is shown that especially reducing gases provide a surface free energy with a higher dispersive part compared to oxidative plasma treatments. Furthermore it was found that the wettability of repair chemicals and solvents strongly changes for reductive based strip processes with plasma exposure time, since a high variation of the surface free energy occur.