Plasma damage mechanisms in low k organosilicate glass and their inhibition by Ar ion bombardment

Abstract

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.

The efficacy of post porosity plasma protection against vacuum-ultraviolet damage in porous low-k materials

“…From the XRR data, 94% of the film has kept the same density as the pristine material indicating that it was not damaged by the v-UV photons. While v-UV damage from O 2 plasma has been previously reported, [24][25][26] it is difficult to quantitatively compare these literature results with ours since there are major differences in material composition, dielectric constant, and plasma conditions. In our case, only 6.5% of the total film thickness was damaged with a slight but significant increase in density.…”

Organosilicate glass dielectric films with backbone carbon: Enhanced resistance to carbon loss in plasma environments

“…Effects of VUV+O 2 : XPS core level spectra (not shown) exhibited no significant changes before /after exposure of an ebeam cross-linked BTESE film to 10.2 eV photons at 10 -4 Torr O 2 for 4.5 hours. The negligible carbon loss is in sharp contrast to the almost complete loss of carbon from the surface region for OSG films with terminal methyl groups [3], as shown in Fig. 3.…”

“…Principal damage agents include both atomic oxygen [1] and-especially in highly porous films, the interaction of O 2 with radical sites created by VUV induced Si-C bond scission in Si-CH 3 groups [2,3].…”

Atomic layer deposition HfO2 capping layer effect on porous low dielectric constant materials

“…The exposure of low-k dielectric films to oxygen plasma reportedly causes chemical alternation by the abstraction of methyl groups, causing densification and hydroxylation, which increases the dielectric constant [19]. Porous low-k dielectric films are susceptible to damage by oxygen plasma due to the existence of pores [20].…”