Methods and Apparatus for Via Last Through-Vias

Methods for forming via last through-vias. A method includes providing an active device wafer having a front side including conductive interconnect material disposed in dielectric layers and having an opposing back side; providing a carrier wafer having through vias filled with an oxide extending from a first surface of the carrier wafer to a second surface of the carrier wafer; bonding the front side of the active device wafer to the second surface of the carrier wafer; etching the oxide in the through vias in the carrier wafer to form through oxide vias; and depositing conductor material into the through oxide vias to form conductors that extend to the active carrier wafer and make electrical contact to the conductive interconnect material. An apparatus includes a carrier wafer with through oxide vias extending through the carrier wafer to an active device wafer bonded to the carrier wafer.