Preparation of low dielectric constant F-doped SiO2 films by plasma enhanced chemical vapor deposition

Signal delays in interlayer films limit the performance of very large scale integrated (VLSI) circuits. Signal delays can be reduced by using interlayer films with low dielectric constants, such as fluorine-doped (F-doped) SiO2 films. We were able to fabricate F-doped SiO2 films with dielectric constants as low as 2.3 and with good step coverage, by adding CF4 to SiH4/N2O plasma-enhanced chemical vapor deposition (PECVD). The reduction of the dielectric constant apparently results from a decrease of the ionic polarization. The improvement of step coverage is due to a decrease of the sticking probability of the film-forming species.