Method of fabricating a radiation imager with common passivation

Abstract

A solid state radiation imager pixel having a thin film transistor (TFT) coupled to a photodiode in which the photodiode and the TFT each comprise a common dielectric layer, that is, a single dielectric layer that extends across the pixel and that has a gate dielectric layer portion and a photodiode body passivation portion. The common dielectric layer comprises a monolithic dielectric material such as silicon nitride or silicon oxide. Further, the bottom electrode of the photosensor body and the gate electrode are each disposed on a common surface of the substrate and comprise the same conductive material, the conductive material having been deposited on the pixel in the same deposition process. The source and drain electrodes and the common contact electrode for the photodiode each comprises the same source/drain metal conductive material, the conductive material having been deposited on the pixel in the same deposition process. A method of fabricating an imager array includes, for each pixel in the array, the steps of depositing a first conductive layer on a substrate, forming a gate electrode and a photosensor bottom electrode from the first conductive layer, forming a photosensor body disposed on at least a portion of the photosensor bottom electrode, depositing a common dielectric layer over the gate electrode and over the photosensor body and exposed portion of the photosensor bottom electrode, and completing fabrication of the pixel TFT and the photosensor such that the TFT is electrically coupled to the respective photosensor. The portion of the common dielectric layer disposed over the gate electrode comprises the gate dielectric layer and the portion disposed over the photosensor body comprises the photosensor passivation layer.