Cu-Cu hybrid bonding as option for 3D IC stacking

Cu-Cu bonding is seen as possible option to enable 3D-IC integration within a reasonable cost. In case of 3D stacking, the TSVs can be revealed (nails) at wafer back side and bonded directly on a Cu landing pad. This can offer small pitch IOs and save the cost of extra processing like RDL (Re-Distribution Layer) and bumping.