A method for forming a semiconductor structure. A semiconductor substrate including a plurality of dies mounted thereon is provided. The substrate includes a first portion proximate to the dies and a second portion distal to the dies. In some embodiments, the first portion may include front side metallization. The second portion of the substrate is thinned and a plurality of conductive through substrate vias (TSVs) is formed in the second portion of the substrate after the thinning operation. Prior to thinning, the second portion may not contain metallization. In one embodiment, the substrate may be a silicon interposer. Further back side metallization may be formed to electrically connect the TSVs to other packaging substrates or printed circuit boards.