Thermal stability of fluorinated SiO(sub 2) films: Effects of hydration and film-substrate interaction

摘要

Fluorinated SiO(sub 2) (SiOF) films have emerged as a leading candidate to replace SiO(sub 2) as an intermetal dielectric (IMD) for future ultra-large scale integrated microelectronics. It is acknowledged, however, that SiOF films can exhibit instability problems, particularly in their tendency for moisture absorption. The thermal stability of fluorinated SiO(sub 2) films (SiOF) was found to be dependent on F content and the type of substrate upon which the film was deposited. SiOF films with a range of F concentrations were deposited using an electron cyclotron resonance (ECR) plasma upon Si, Al/Si, TiN/Al/Si, and Al/SiO(sub 2)/Si substrates. Following deposition, the films were deliberately hydrated and/or annealed and their stability assessed. Hydration was found to only affect the high F content films. Capacitance changes with annealing in the high F content films were found to occur beginning at 200 C. These changes, which were independent of substrate type, likely occurred due to desorption of H(sub 2)O in the films. After annealing of the high F content films up to 400 C, a reduction in F content was found for SiOF films on some substrates. Significant reductions were found for SiOF films on Al/Si substrates, while little or no change was found for films on TiN/Al/Si, Al/SiO(sub 2)/Si, or Si substrates. Local chemical analysis of those films which showed F reduction indicated that the F profile was approximately uniform throughout the layer and did not pile-up at the interface. The substrate-dependent thermal instability exhibited by these films suggests the chemical nature or qualities of the substrate may play a role in the F reduction reaction.