In-situ x-ray photoelectron spectroscopy and ex-situ Fourier transform infrared spectroscopy studies of vacuum ultraviolet (VUV) photons with or without O2, and O radicals point to distinct mechanisms of carbon abstraction in nanoporous organosilicate glass (OSG) films. VUV alone in the absence of O2 results in Si-CH3 bond scission and recombination preferentially at silicon monomethyl sites, obeying diffusion kinetics. In contrast, the presence of O2 interferes with recombination, resulting in diffusion-dominated carbon loss kinetics, enhanced Si oxidation, and greatly accelerating the rate of carbon loss in both the near surface and bulk regions of the OSG, at both monomethyl and dimethyl sites. Carbon abstraction due to exposure to (O(3P)) does not follow diffusion kinetics, and such interactions yield a SiO2-like surface layer inhibiting further O diffusion. Results indicate that diffusion-dominated carbon abstraction kinetics previously observed for OSG exposure to O2 plasma damage is primarily attributable to the diffusion of O2 down OSG nanopores, reacting at photoactivated sites, rather than the diffusion of O radicals. OSG pretreatment by 900 eV Ar+ bombardment effectively inhibits both VUV + O2 and O damage mechanisms by formation of ∼1 nm thick SiO2-like surface region that inhibits both O and O2 diffusion.
In-situ x-ray photoelectron spectroscopy (XPS) and ex-situ Fourier transform infrared studies of He plasma and Ar+ ion bombardment pretreatments of organosilicate glass demonstrate that such pretreatments inhibit subsequent O2 plasma-induced carbon loss by forming a SiO2-like damaged overlayer, and that the degree of protection correlates directly with increased ion kinetic energies, but not with the thickness of the SiO2 overlayer. This thickness is observed by XPS to be roughly constant and <1 nm regardless of ion energies involved. The data indicate that ion kinetic energies are an important parameter in protective noble gas plasma pretreatments to inhibit O2 plasma-induced carbon loss.
Articles you may be interested inEffects of plasma and vacuum-ultraviolet exposure on the mechanical properties of low-k porous organosilicate glass J. Appl. Phys. 116, 044103 (2014); 10.1063/1.4891501 Reaction mechanisms of oxygen plasma interaction with organosilicate low-k materials containing organic crosslinking groups J. Vac. Sci. Technol. A 30, 061302 (2012); 10.1116/1.4755898 Time-dependent dielectric breakdown of plasma-exposed porous organosilicate glass Appl. Phys. Lett. 100, 112905 (2012); 10.1063/1.3693526Fundamental mechanisms of oxygen plasma-induced damage of ultralow-k organosilicate materials: The role of thermal P 3 atomic oxygen Ar þ ion bombardment (900 eV) of organosilicate glass (OSG) in the presence of NH 3 (1 Â 10 À6 Torr) yields an overlayer containing Si-NH x bonds. The NH x layer decreases the rate of carbon loss from the remaining film upon subsequent oxygen plasma exposure, due to preferential removal of N from the surface region. Ab initio density functional theory calculations have been performed to investigate the stability of the bonds present in low-k dielectrics utilizing a trimethyltrisiloxane model system. Calculated bond energies are 6.30 eV (Si-NH 2 ), 6.27 eV (Si-OH), 5.69 eV (Si-CH 3 ), and 5.54 eV (Si-H). The slightly higher calculated Si-NH 2 bond energy is consistent with experiment and indicates that the nitrided OSG surface layer inhibits carbon loss in part by inhibition of O 2 diffusion into the bulk.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.