Evidence of noble metal diffusion in polymers at room temperature and its retardation by a chromium barrier

Recent applications of organic low-k dielectrics in microelectronics have stimulated many investigations of metal diffusion in polymers. Here we report results from radiotracer measurements of110mAg diffusion in trimethylcyclohexane polycarbonate. Serial sectioning was carried out with 190 eV krypton ions in and opposite to the diffusion direction to rule out sputtering artifacts. Ag was found to be strongly immobilized by self aggregation. In contrast to earlier reports, however, trace amounts of Ag were clearly seen to diffuse into the polymer even at room temperature. A chromium film of only one tenth of a monolayer turned out to be an effective diffusion barrier.