A chemical study of plasma-deposited organosilicon thin films as low-k dielectrics

Thin films with low dielectric constant were deposited by PECVD from different organosilicon precursors. Film structure and properties were strongly affected by the precursor choice. Silane-based precursors resulted in films with permittivities as low as 2.3 with a limited -thickness loss of 6% upon thermal annealing at 400 °C. Films deposited from siloxane monomers were characterized by increased thickness shrinkage of 11%. Thermal stability was correlated not only to the cross-linking degree but also to the presence of methylene bridges in the polymer backbone, which accounts for the better thermal stability of silane-based films. Substrate heating (15O0C) during deposition ensured the best balance between very low permittivities and good thermal stability.