Organosilicon polymeric thin films (SiCxHyOz) have attracted considerable interest due to their wide range of applications such as interlayers in gas/moisture diffusion multi-layer systems, low dielectric constant interconnect materials in microelectronic circuits and biocompatible coatings for medical implants, to name a few. An accurate control of the microstructure and composition of the films is generally required to meet specific requirements in the above-mentioned applications.

 

In this contribution, we report on the control of the composition and structure of films deposited in Ar/organosilicon precursor mixtures by using a remote plasma, i.e. the expanding thermal plasma, CVD process. The characterization of the deposited layers has been carried out by means of Fourier-transform infrared spectroscopy (FTIR), spectroscopic ellipsometry and X-ray photoelectron spectroscopy (XPS). The characterization of thin films showing a tunable chemical composition and optical properties has allowed identifying the main dissociation paths of the deposition precursor as controlled by the argon ions and electrons emanating from the plasma source, i.e. a cascaded arc, in the downstream region, where the monomer is injected. In particular, Ar ions are responsible for the charge exchange reaction with the monomer and electrons participate to the dissociative recombination with the molecular ions generated in the first reaction, as already proven in the case of other molecular gases [1]. An optimum in the monomer structure retention of 35 % has been observed under conditions of low plasma reactivity, i.e. high monomer flow-to-(Ar+,e-) flow rate ratio.

 

[1] M. Creatore, Y. Barrell, J. Benedikt, M.C.M. van de Sanden, Plasma Sources Science & Technology 15 (2006) 421-431.