Photodetector for imaging system

A substrate comprising:

• a plurality of photodetectors;
• a first active area on a first surface of the substrate;
• and
• a second active area on a second surface of the substrate,
• wherein the plurality of photodetectors are each provided with a conductive via electrically isolated from the substrate, each conductive via extending through its corresponding photodetector from the first surface of the substrate to the second surface of the substrate for connecting the first active area to the second surface of the substrate, and each conductive via being fully and continuously filled with a conductive material, and having no joints;
• each conductive via having:
• a first portion entirely of a first width extending from the first surface into the substrate by a first depth, the first portion not extending perpendicularly from the first surface such that an extrapolation of the first portion to the second surface does provide an opening of the first width at the second surface which does not align with an opening of the first portion of the first width at the first surface;
• and a second portion entirely of a second width extending from the second surface into the substrate by a second depth to abut the first portion, wherein the first width is smaller than the second width and the first depth is larger than the second depth;
• an oxide layer formed over the second surface and having openings aligned with the openings of the first portion of the plurality of conductive vias at the first surface, the openings in the oxide layer exposing only the conductive material filling of the second portion at the second surface;
• and
• the second surface comprising electrical connections for the first and second active areas.