Effect of bridging groups of precursors on modulus improvement in plasma co-polymerized low-k films

We have demonstrated that the mechanical strength of organic silica low-k films can be enhanced by introducing a reinforcement monomer in a matrix monomer under plasma excitation. The modulus improvement mechanism was investigated by analyzing the film structure. Pyrolysis gas chromatography / mass spectrometry (Py-GC/MS) revealed incorporation of a reinforcement monomer in the matrix through co-polymerization reactions. Compositional analysis of the films showed that the extent of reinforcement is associated with co-polymerization ratio or the monomer content in the film. It is also indicated that the modulus enhancement depends on the content of 3D aromatic bridge structure, which is affected by the chemical structure of the reinforcement monomers.