Vertical Stacking with Si-Cored Substrates

Organic substrates have traditionally been made with a core of epoxy and fibreglass to provide for the rigidity and planarity. Recently, inorganic core materials have gained interest due to their rigidity and planarity. In this work, Si was used as the core material combined with an organic build-up. The Organic build-up is made with semi-additive double sided processing, but can achieve fine line width on both sides down to 3µm L/S and micro-vias down to 10µm. Furthermore, due to the stiffness of the silicon core, the core made of silicon can be made thin enough to embed dies with through-silicon-vias. This allows true 3D stacking and heterogeneous integration to levels not possible otherwise.