Detection of plasma-induced, nanoscale dielectric constant variations in carbon-doped CVD oxides by electrostatic force microscopy

Electrostatic force microscopy was used to detect nanoscale dielectric constant variations in two different, carbon-doped oxide low-k dielectrics deposited by plasma-enhanced chemical vapour deposition and subjected to oxidizing isotropic plasmas and inert gas isotropic plasmas. Samples were polished at 10 deg. to the sample normal to enhance the through-the-thickness spatial resolution. We observed that the technique was able to detect k∼0.1 variations of dielectric constant with ∼10 nm spatial resolution. We also observed that the oxidizing isotropic plasma caused damage to a depth of approximately 10-50 nm and that one of the carbon-doped oxides was more susceptible to plasma-induced damage. The estimated increase of dielectric constant from the oxidizing plasma was from k∼2.5-3 to k>4-5. The damage from the inert gas plasma was observed to be deeper but less severe. (author)