Synchrotron X-ray scattering and reflectivity studies of the structure of low dielectric constant SiOCH thin films prepared from bistrimethylsilylmethane by chemical vapor deposition

Quantitative, non-destructive grazing-incidence X-ray scattering and specular X-ray reflectivity analysis with synchrotron radiation sources, along with spectroscopic ellipsometry analysis, were successfully used to characterize a series of low dielectric constant, nanoporous SiOCH dielectric thin films with nanometre-scale thicknesses prepared by radio-frequency inductively coupled plasma chemical vapor deposition of bistrimethylsilylmethane precursor and oxygen gas at various flow rate ratios followed by annealing at 298, 473, 573 or 673 K. These analyses provided important information on the structures and properties of the nanoporous films. The average size of the nanopores generated in each film was 3.07 nm in radius or less, depending on the process conditions. The film electron densities ranged from 414 to 569 nm^-3, the refractive indices ranged from 1.434 to 1.512 at 633 nm wavelength, and the porosities ranged from 16.1 to 38.9%. Collectively, the present findings show that SiOCH thin films of the type reported here are suitable for use as low dielectric constant interdielectric layer materials in the fabrication of advanced integrated circuits.