Resumen de Protective nanometer films for reliable Cu-Cu connections
Tobias Berthold, Guenther Benstetter, Werner Frammelsberger, Manuel Bogner, Rosana Rodríguez, Montserrat Nafria i Maqueda
Abstract In this work, we report on the protective effect of platinum and carbon based films deposited onto Cu surfaces subject to pre-bonding temperature stress. The protection of Cu surfaces is an important and advantageous procedure to improve the reliability of Cu-Cu connections. The results were obtained from combined non-destructive Scanning Electron Microscopy (SEM) techniques and PeakForce Kelvin Probe Force Microscopy (PF-KPFM). As an indicator of degradation, the oxidation of the Cu surface was used. It could be shown that a C layer provides a much better protective effect than a Pt layer. Besides very local sporadically distributed Cu oxide grains, a gradual degradation of the protective carbon film was not even observable at the nanoscale for a stress temperature of 200 °C and layer thicknesses down to 3 nm. In contrast, with a 10 nm thick Pt film the Cu surface exhibits already at a stress temperature of 150 °C locally grown Cu oxide grains. The introduced carbon coating passivation of Cu surfaces has the potential of being a key technique for a reliable Cu-Cu wire bonding.
