Investigation On Low-κ SiCOH Films Prepared By ECR-CVD And The Influence Of Fluorine Incorporation

Using decamethylcyclopentasioxane ([Si(CH₃))₂O]₅ as source gas, SiCOH films, which have low dielectric constant (low k) and good insulating ability and thermal stability, were prepared by electron cyclotron resonance chemical vapor deposition (ECR-CVD). The FTIR spectra of the films were measured to know the difference of bond structure between SiCOH films and D5 source. It was verified that the Si-O-Si cage structure was formed in SiCOH films, while -CH₃ spices were lost during the deposition. The dielectric constant decreased from 3.85 to 2.85 after being annealed in 400℃. With the analysis of the bond structure of the film as deposited and annealed, we can infer that the increased content of cage structure comprised of Si-O-Si bond with bigger bond angle may be the reason of decreased dielectric constant.Using CHF3 as fluorine source, we investigated the influence of fluorine incorporation on film structure and deposition rate. It was found that the deposition rate changed as an "N" shape with the increase of CHF₃/D5 flow rate ratio. According to the FTIR and XPS analysis to the film structure and composition, and OES analysis to the radical distribution in the plasma, we inferred this change indicated the transition from F-SiCOH film deposition to a-C: F: H film growth.