Electronic structure characterization of ultra low-k carbon doped oxide using soft X-ray emission spectroscopy

In this study we report the electronic structure of ultra low-k dielectric constant carbon doped oxide (CDO) films, which have a k value of 2.4, using synchrotron radiation-excited resonant soft X-ray emission (SXE) spectroscopy. Conventional X-ray photoemission spectroscopy was used to determine that the chemical composition of the material was Si-31%, C-15% and O-54%. The C and O partial density of states for the valence bands has been measured by SXE. Radiation induced changes in the chemical bonding in the material have been identified and these can be minimised by continuously translating the sample during measurement. The spectral changes induced by the radiation damage are consistent with the breaking of Si-CH3 bonds in the material and the formation of graphitic C = C double bonds. Investigation of the origin of a low energy subband in the C Kα spectrum reveal that it can be attributed to O Kα emission excited by second order rather than the hybridization of C 2p states in the CDO layer.