Evaluation of the diffusion barrier continuity on porous low-kfilms using positronium time of flight spectroscopy

Abstract

A depth-profiled positronium time of flight experiment was performed to investigate a diffusion barrier on a spin-on low dielectric constant (low-$k$) porous silica film. We studied a capping layer of 50 nm ${\mathrm{SiO}}_{2}$, which was optimized for 3-keV positron $({e}^{+})$ penetration through the capping and stopping in the porous layer. Maximum positronium intensity was found with a positron implantation energy of 3 keV that reflects the sample structure and is consistent with an open pore fraction $\ensuremath{\eta}<2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ of the capping layer.