US Patent 10535631 3D Chip-on-wager-on-substrate structure with via last process

Disclosed herein is a package comprising a first redistribution layer (RDL) disposed on a first side of a first semiconductor substrate and a second RDL disposed on a second semiconductor substrate, wherein the first RDL is bonded to the second RDL. First conductive elements are disposed in the first RDL and the second RDL. First vias extend from one or more of the first conductive elements through the first semiconductor substrate to a second side of the first semiconductor substrate opposite the first side. First spacers are interposed between the first semiconductor substrate and the first vias and each extend from a respective one of the first conductive elements through the first semiconductor substrate.