High dynamic range, backside-illuminated, low crosstalk image sensor with walls on backside surface to isolate photodiodes

Abstract

A backside-illuminated image sensor includes photodiodes in photodiode regions electrically isolated by filled trenches with openings in a dielectric layer over the photodiodes. The image sensor has a metal grid aligned over the trenches, the metal grid within 80 nanometers of the trenches. The image sensor is formed by: fabricating photodiodes in photodiode regions of a frontside of a silicon substrate with source-drain regions of transistors, the photodiodes electrically isolated by deep trenches, each photodiode within a photodiode region of the substrate; forming the filled trenches in a backside of the semiconductor substrate; forming protective oxide and process stop layers over the backside of the semiconductor substrate; depositing a metal grid over the deep trenches, removing the process stop layer from over photodiode regions; and depositing color filters over the photodiode regions.