A Novel Method for the Fabrication of 3D-wiring within a Nanoporous Membrane for High-density Circuit Substrates

The authors have developed a new wiring method to obtain high-density wiring and fine vias for ultra-thin package substrates. Nanoporous substrates and photoinduced selective plating consisting of photo-exposure and metal plating processes were used. However, when miniaturization of wiring pitch and via diameter advanced, deformation of patterns and irregular deposition of metal between wiring became obvious. In order to solve these problems, alkali resistance of the photosensitizers after photoirradiation was increased by crosslinking the photosensitizer molecules. Consequently, in the case of use of diazido chalcone as a crosslinking agent, the crosslinking reaction advanced effectively without changing a process and it was found to be possible to fabricate wiring or via patterns with the designed width or diameter. So far, we have fabricated penetrated copper via patterns with 30 μm diameters and surface copper wiring patterns with 10 μm widths simultaneously within substrates.