The interface of fluorinated amorphous carbon with copper metallization

We have studied fluorinated amorphous carbon (a-F:C) films, prepared by High Density Plasma Chemical Vapor Deposition (HDP-CVD) methods from CH4 and C4F8, as candidates for low-k inter metal dielectric (IMD) applications. In order to enhance the film's adhesion to the adjacent layers, an adhesion promoter layer was introduced. The samples used for the current research consist of a metal layer (Cu or its diffusion barriers Ta or TaN) and the a-F:C film, with the adhesion promoter sandwiched in between. In order to learn about the film and interfaces stability the samples were annealed at 400 and 500 degreesC for 30 min. Up to 400 degreesC, no metal diffusion into the adhesion promoter was observed. After 30 min of 500 degreesC annealing, no Cu outdiffusion was observed by XPS nor was a change in the Cu2p transition peak's form suggesting that no serious chemical reaction has occurred at the interface. No major Cu diffusion was detected by RBS but SIMS measurements have showed Cu diffusion into the adhesion promoter after 500 degreesC annealing, 30 min. The dielectric constant of the film is similar to 2.7 (measured by C-V at 1 MHz) after 400 degreesC annealing and much higher after 500 degreesC annealing. The results obtained so far show that the integration of a-F:C as IMD is possible but there are some problems to be solved. (C) 2001 Elsevier Science B.V. All rights reserved.