Photosensitive imager contact pad structure

Abstract

A method of forming a contact for a photosensitive element of a photosensitive imager including a common electrode separated from a bottom contact by intervening layers of an SiOx transistor passivation layer over the bottom contact and an SiNx diode passivation layer over the transistor passivation layer. Controlled etching through the passivation layers exposes but does not damage the thin film transistor passivation layer extending in regions beyond the common electrode, and also improves adherence of a protective gasket in such regions. The contact pad formed in this process has a layer of diode passivation material and a layer of transistor passivation material disposed between the upper common electrode material layer and the underlying source and drain electrode material layer, with a via provided having smooth and sloped sidewalls over which the common electrode material extends to provide electrical contact between the common electrode material layer and the source and drain electrode material layer.