Multi-trench region for accumulation of photo-generated charge in a CMOS imager
First Claim
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1. A method of forming a photosensor, comprising the steps of:
- providing a semiconductor substrate having a doped layer of a first conductivity type;
forming a plurality of trenches in said doped layer to define a photosensitive area, each of said plurality of trenches having a plurality of sidewalls and a bottom;
doping the sidewalls and bottom of each of said plurality of trenches to form a doped region of a second conductivity type; and
forming an insulating layer on the sides and bottom of each of said plurality of trenches over said doped region.
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Abstract
A multiple-trench photosensor for use in a CMOS imager having an improved charge capacity. The multi-trench photosensor may be either a photogate or photodiode structure. The multi-trench photosensor provides the photosensitive element With an increased surface area compared to a flat photosensor occupying a comparable area on a substrate. The multi-trench photosensor also exhibits a higher charge capacity, improved dynamic range, and a better signal-to-noise ratio. Also disclosed are processes for forming the multi-trench photosensor.
67 Citations
21 Claims
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1. A method of forming a photosensor, comprising the steps of:
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providing a semiconductor substrate having a doped layer of a first conductivity type;
forming a plurality of trenches in said doped layer to define a photosensitive area, each of said plurality of trenches having a plurality of sidewalls and a bottom;
doping the sidewalls and bottom of each of said plurality of trenches to form a doped region of a second conductivity type; and
forming an insulating layer on the sides and bottom of each of said plurality of trenches over said doped region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of forming a photosensor, comprising the steps of:
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providing a semiconductor substrate having a doped region of a first conductivity type;
forming a plurality of trenches in said doped region to define a photosensitive area, each of said plurality of trenches having a plurality of sidewalls and a bottom doped to a second conductivity type; and
forming an insulating layer on the sides and bottom of each of said plurality of trenches. - View Dependent Claims (18, 19, 20, 21)
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Specification