Patent ID: 8900910

Claim:
A method of forming a microelectronic unit comprising: forming a recessed portion extending through a packaging layer attached to a front surface of a semiconductor element and terminating at a thin region of a conductive contact, the conductive contact being disposed at the front surface of the semiconductor element, the semiconductor element having a rear surface remote from the front surface and including a light detector disposed adjacent to the front surface, connected to the conductive contact and aligned with a portion of the rear surface to receive light through the rear surface portion, wherein the light detector includes a plurality of light detector elements arranged in an array, wherein the conductive contact has a first thickness at the thin region and includes a thicker region having a second thickness that is thicker than the first thickness; and forming a conductive interconnect extending through the recessed portion to connect to the conductive contact at the thin region, at least a portion of the conductive interconnect being exposed at a surface of the microelectronic unit.