Self-aligned LOD antiblooming structure for solid-state imagers
AssigneeEastman Kodak Company
InventorEric G. Stevens
Life of this patent
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Abstract
A self aligned, lateral-overflow drain antiblooming structure that is insensitive to drain bias voltages and therefore has improved insensitivity to process variations. The length of the antiblooming barrier regions are easily adjusted and determined by photolithography. The self aligned, lateral-overflow drain (LOD) antiblooming structure results in a design that saves space, and hence, improves overall sensor performance. In this structure, an antiblooming potential barrier is provided that is smaller (in volts) than the barriers that separate the pixels from one another so that excess charge will flow preferentially into the LOD as opposed to the adjacent pixels.
Claims9
A method of manufacturing an antiblooming structure for image sensors comprising the steps of:
- providing a semiconductor substrate of a first conductivity type, having an antiblooming channel implant of a second conductivity type opposite the first conductivity type on a major surface of the substrate in a laterally uniform manner across a pixel area;
- placing a gate oxide upon the surface of the substrate;
- defining a first masking pattern and a second masking pattern, upon the gate oxide of the substrate, the first masking pattern covering an antiblooming barrier region, the antiblooming barrier region having an inner edge and an outer edge, and the second masking pattern covering a drain region, such that the combination of the first masking pattern and second masking pattern leave an exposed area defining a CCD buried channel;
- implanting within the exposed area of the CCD buried channel a material of the second conductivity type that is self aligned to the outer edges of the first masking layer;
- removing the second masking layer that covers the drain region;
- creating, by masking, a third pattern that exposes only the drain region and portions of the first pattern adjacent to the drain region;
- implanting the drain region with the second conductivity type to form a drain that is self aligned with the inner edges the antiblooming barrier region;
- and
- removing remaining portions of the first and the third masking layers;
- and
- creating a gate electrode over the substrate.
A method of manufacturing an antiblooming structure for image sensors comprising the steps of:
- providing a semiconductor substrate of a first conductivity type, having an antiblooming channel implant of a second conductivity type opposite the first conductivity type contained on a major surface of the substrate;
- defining a CCD buried channel implant from the second conductivity type around an antiblooming barrier region such that the buried channel implant has at least one self aligned edge with the antiblooming barrier region;
- creating a drain region adjacent the antiblooming barrier region such that the drain is self aligned with at least one edge of the antiblooming barrier region;
- and
- creating isolation regions defined by the intersection of the antiblooming barrier region with the CCD buried channel along an entire length of the antiblooming barrier region in all but one phase of each cell of the CCD buried channel.
Dependencies are inferred from the claim text.