Surface chemistry of planarized SiLK-films studied by XPS

SiLK** is an isotropic, low dielectric constant polymer specifically designed as new passivation layer within the existing Al/W based metallizations schemes in microelectronic applications. The deposition of the polymer on Al patterned lines causes a topography, which must be afterwards planarized by a chemical-mechanical polishing process (CMP). The changes in the surface chemistry of SiLK** as result of this process using commercially available slurries were investigated by X-ray photoelectron spectroscopy (XPS) taking into account C 1s/O 1s core levels, shake up effects and SiLK valence bands. Oxidized carbon species were found on top of the polymer surface as a residue of the CMP. There concentrations containing at least hydroxyl reactive groups show a dependence on the slurry pH-value. The concentration increases at acid degrees far from the neutral point, the minimum position.