Pixel and imager device having high-k dielectrics in isolation structures
AssigneeMicron Technology, Inc.
InventorChandra Mouli
Life of this patent
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Abstract
An imager device that has an isolation structure such that pinned photodiode characteristics are maintained without increasing doping levels. The invention provides an isolation structure to maintain pinned photodiode characteristics without increasing doping levels around the photodiode. By creating a substrate region surrounding the charge-collection region of the photodiode, the photodiode may be electrically isolated from the bulk substrate. This region fixes the depletion region so that it does not migrate toward the surface of the substrate or the STI region. By doing so, the region prevents charge from being depleted from the substrate and the accumulation region, reducing dark current.
Claims18
A pixel cell comprising:
- a photodiode in a substrate, the photodiode comprising a top region, a middle region, and a bottom region connected to the top region through an n-type intermediate region wherein the middle region is a p-type material and the top and bottom are n-type material;
- and
- a first high-k dielectric material having excess positive charge over the top n-type region to provide electron accumulation in the top region and intermediate region.
A pixel cell comprising:
- a photodiode comprising a p-type charge-collection region, top accumulation region, bottom accumulation region and side accumulation region, wherein each of the top accumulation region, bottom accumulation region, and side accumulation region are n-type and adjacent the p-type charge-collection region;
- and
- an isolation structure comprising;
- a trench containing a first high-k dielectric material having excess positive charge, the trench being adjacent the side n-type accumulation region, wherein the excess positive charge of the first high-k dielectric material causes electron accumulation in the side n-type accumulation region;
- and
- a second high-k dielectric material having excess positive charge residing over the trench and the photodiode, wherein the excess positive charge of the second high-k dielectric material causes electron accumulation in the top n-type accumulation region.
Dependencies are inferred from the claim text.