Electroless CoMn alloy exhibiting excellent diffusion barrier property against Cu diffusion

The demand for a low-cost metal filling technology to TSVs of 3D integration is increasing. In this situation, we studied a new diffusion barrier metal of Co-Mn alloy formed by electroless plating. We used hydrazine-hydrate as a reducing agent to obtain a low electrical resistivity of Co-alloy, compared to other barrier metals such as CoB, and CoWB. CoMn was able to deposit by this method, and an excellent barrier property against Cu diffusion was confirmed after 350 °C annealing. Furthermore, electrical resistivity of the CoMn film was reduced to 25 μΩcm by 400 °C annealing in vacuum (1x10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> Pa). We found a segregation of Mn at the interface between Cu and CoMn after annealing, which brought about formation of the thin CoMnO layer consisting of 2 % Mn. It is suggested that this layer has an important role to prevent Cu from diffusion to Si. This method is very effective to obtain a highly reliable TSV fabrication process with a low cost.