Wavelength-dependent effect of ultraviolet irradiation on dielectric constant of boron carbon nitride films

Boron carbon nitride (BCN) films with a low dielectric constant are synthesized by plasma-assisted chemical-vapor deposition. The dielectric constant is measured for the BCN films irradiated with monochromatic ultraviolet lights of 300 and 365 nm in wavelength. It is found that the dielectric constant is decreased due to a 300-nm irradiation while the dielectric constant is enhanced due to a 365-nm irradiation. A reduction in the B–C bond and an increase in the C–N bond occur in the BCN film after the 300-nm irradiation. On the other hand, the 365-nm irradiation leads to an increase in the B–C bond and a reduction in the C–N bond in the film. The 300-nm irradiation is effective in reducing the dielectric constant, suggesting the removal of the molecules with a large polarization.