Split substrate interposer with integrated passive device

A method of forming an interposer, the method comprising:

• forming a first redistribution layer on a front side surface of a first interposer substrate, the first interposer substrate having a backside surface opposite the front side surface;
• forming through-substrate vias in the first interposer substrate that extend from the first redistribution layer to the backside surface of the first interposer substrate;
• forming multiple recesses in the backside surface of the first interposer substrate, each recess being sized to receive a corresponding passive electrical device;
• forming a second redistribution layer on a front side surface of a second interposer substrate, the second interposer substrate having a backside surface opposite the front side surface;
• and
• joining the second interposer substrate to the first interposer substrate such that each of a plurality of electrical contacts on a top surface of the second redistribution layer contact either one of the first through-substrate vias or one of the passive electrical devices.

An interposer comprising:

• a first substrate comprising first bulk material having a first TSV extending through the first bulk material;
• a second substrate comprising second bulk material having a second TSV extending through the second bulk material and a wiring plane formed on the second bulk material in electrical contact with the first TSV;
• a join interface connecting the first and second substrates such that the first wiring plane of the first substrate physically contacts the second substrate and the first TSVs are electrically connected to the second TSVs through the wiring plane;
• and
• a passive electrical device integrated within the interposer at the join interface, wherein the passive electrical device is electrically connected to the wiring plane.