Protective nanometer films for reliable Cu-Cu connections

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.