Recombination of O and H Atoms on the Surface of Nanoporous Dielectrics

The interaction of O and H atoms with SiOCH nanoporous low-dielectric-constant (low-k) films is studied in the far plasma afterglow in the absence of ion and photon fluxes on the surface. The loss probabilities of O and H atoms are directly measured by plasma-induced actinometry. Modification of low-k films during the experimental scans was studied by the Fourier transform infrared spectroscopy technique. The model of O- and H-atom recombination in nanoporous materials was developed to analyze the experimental data. It is shown that the main mechanism of the O and H loss is their surface recombination. The consumption of these atoms in the reactions with the carbon-containing hydrophobic groups has a minimal contribution. Thus, the surface recombination defines a damage depth in low-k films. It was shown that the oxygen atoms lead to the noticeable removal of CH₃ groups. On the contrary, hydrogen atoms do not break Si-CH₃ bonds, allowing the avoidance of plasma damage in the case of the hydrogen-plasma-based resist strip in appropriate conditions.