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