Chemical Bonding in Low-k Dielectric Materials for Interconnect Isolation: Characterization using XAS and EELS

Abstract

In chemical vapor deposited (CVD) organosilicate glasses (OSG), which are used as interlayer dielectric (ILD) materials, the substitution of oxygen in SiO2 by methyl groups (−CH3) reduces the permittivity significantly. However, plasma processing for resist stripping, trench etching and post‐etch cleaning removes C and H containing molecular groups from the near‐surface layer of OSG. Therefore, compositional analysis and chemical bonding characterization of structured ILD films with nanometer resolution is necessary for process optimization. OSG thin films as‐deposited and after plasma treatment are studied using X‐ray absorption spectroscopy (XAS) and electron energy loss spectroscopy (EELS). In both techniques, the fine structure near the C‐K absorption or energy loss edge, respectively, allows to differentiate between C–H, C–C, and C–O bonds, and consequently, between individual low‐k materials and their modifications. Examination of the C‐K near‐edge structures reveal a modified bonding of the remaining C atoms in the plasma‐treated sample regions.