Multi-trench region for accumulation of photo-generated charge in a CMOS imager
First Claim
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1. A pixel sensor cell for use in an imaging device, said pixel sensor cell comprising:
- a doped layer of a first conductivity type formed in a substrate;
a plurality of trenched formed in said doped layer, each of said plurality of trenches having a plurality of sidewalls and a bottom;
a first doped region of a second conductivity type formed at the sidewalls and bottom of each of said plurality of trenches;
an insulating layer formed over said first doped region;
a second doped region of a second conductivity type formed in said doped layer and positioned to receive charged from said first doped region of said plurality of trenches; and
a reset transistor formed at the doped layer for periodically resetting a charge level of said second doped region, said second doped region being the source of said reset transistor.
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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.
54 Citations
22 Claims
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1. A pixel sensor cell for use in an imaging device, said pixel sensor cell comprising:
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a doped layer of a first conductivity type formed in a substrate;
a plurality of trenched formed in said doped layer, each of said plurality of trenches having a plurality of sidewalls and a bottom;
a first doped region of a second conductivity type formed at the sidewalls and bottom of each of said plurality of trenches;
an insulating layer formed over said first doped region;
a second doped region of a second conductivity type formed in said doped layer and positioned to receive charged from said first doped region of said plurality of trenches; and
a reset transistor formed at the doped layer for periodically resetting a charge level of said second doped region, said second doped region being the source of said reset transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A pixel sensor cell for use in an imaging device, said pixel sensor cell comprising:
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a doped layer of a first conductivity type formed in a substrate;
a plurality of trenches formed in said doped layer, each of said plurality of trenches having a plurality of sidewalls and a bottom;
a photodiode formed in each of said plurality of trenches, wherein said photodiode comprises a first doped region of a second conductivity type formed at the sidewalls and bottom of each of said plurality of trenches, and an insulating layer formed on an upper surface of said first doped region;
a second doped region of a second conductivity type formed in said doped layer and positioned to receive charges from said first doped region of each of said plurality of trenches; and
a reset transistor formed at the doped layer for periodically resetting a charges level of said second doped region, said doped region being the source of said reset transistor.
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Specification