Interactions of photoresist stripping plasmas with nanoporous organo-silicate ultra low dielectric constant dielectrics

To evaluate potential solutions for reducing the damage to ultra low-k dielectrics during photoresist stripping in advanced interconnect technology, we have investigated the mechanisms of interactions between remote H₂, D₂ and N₂ discharges and porous organo-silicate materials. Extended sub-surface modifications take place in high carbon-content organo-silicates, whereas silica-rich dielectrics show negligible chemical damages during the same treatments. The nature of plasma/dielectric interactions depends primarily on the organic fraction of the ULK material. Methyl groups in silica-rich organo-silicates withstand the interaction with the plasma species. Conversely, large organic compounds in carbon-rich dielectrics experience cleavage reactions leading to volatile hydrocarbon formation and compositional changes. For conditions where stripping-induced damage is introduced, the effects scale with the substrate temperature in the range 200 °C-300 °C. The permeation of the ULK material by remote plasma species depends on its porosity.