Novel multi-layer wiring build-up using Electrochemical Pattern Replication (ECPR)

This paper discloses a novel, high accuracy and low cost integration method based on an electrochemcial pattern replication (ECPR) technology for multi-level stacking applications such as integrated passives, multi-level redistribution layers and top level IC interconnect structures. It is demonstrated how a first copper layer is coated with BCB (bisbenzocyclobutene), which is planarized with CMP (chemical mechanical polishing) to uncover the first layer, where after a second patterned copper layer is fabricated with ECPR. This approach shows the feasibility of fabricating highly accurate multi-level wiring layers and still avoiding the issues related to increasing topography, which are particularly severe for thick metal layers. In addition, the constraints for the dielectric material is significantly reduced, since it does not have to be photosensitive or planarizing, which in turn opens up for the use of alternative dielectric materials, which may have better electrical and physical properties, that have not been usable with the traditional multi-level fabrication methods.