Irradiation-induced damage in porous low-k materials during low-energy heavy-ion elastic recoil detection analysis

With the implementation of time-of-flight elastic recoil detection (ToF-ERD) for the analysis of thin films with high depth resolution using a standard ‘low-energy’ accelerator, routine application of ERD in semiconductor technology becomes possible. In case of irradiation-sensitive materials, like organosilicate low-k films, the energetic incident beam damages the sample during the measurement, resulting in loss of the lighter elements and, as a consequence, altering the sample composition.The ion beam induced damage is investigated for 19F, 35Cl, 63Cu, 79Br and 127I beams at energies of 6–16 MeV and typical fluences for ERD analysis. By means of Fourier transform infrared (FTIR) spectroscopy a direct correlation between elemental losses and molecular broken bonds is obtained. The H losses can be described by the bulk molecular release model, with the associated release cross section for H linearly dependent on the energy deposited by the primary beam in the film.