He plasma pretreatment effects on oxygen plasma-induced carbon loss and surface roughening in an ultralow-k organosilicate glass film

Abstract

Ex situ Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) have been used to characterize the effects of He plasma pretreatment on O2 plasma-induced modification of the surface composition and structure of nanoporous ultralow dielectric constant (k) organosilicate glass (OSG) films. Oxygen plasma induces Si–C bond scission and carbon abstraction, and increased k values. Carbon abstraction exhibits diffusion-dominated kinetics. FTIR data, however, indicate that He plasma pretreatment prior to O2 plasma exposure induces pore sealing in the OSG film interior, inhibiting carbon abstraction, but only at longer O2 plasma exposure times (exposure time >5 min). The data are consistent with XPS data showing that OSG exposure to He plasma results in a more SiO2-like surface layer, but that atomic O will diffuse through a continuous SiO2 film. AFM data also indicate that He plasma pretreatment inhibits subsequent OSG surface roughening upon exposure to oxygen plasma.