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US 6,388,243 B1Granted
Active pixel sensor with fully-depleted buried photoreceptor
AssigneePhotobit Corporation
InventorsVladimir Berezin, Eric R. Fossum
Life of this patent
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Abstract
A fully depleted photodiode accumulates charge into both the diode and a separate floating diffusion. The floating diffusion has less capacitance that the overall diode, thereby resulting in a knee-shaped transfer characteristic for charge accumulation. The fully depleted photodiode also include two PN junctions, one near the surface and the other buried below the surface.
Claims20
A photosensor comprising:
- a semiconductor substrate;
- a buried photodiode in said semiconductor substrate, having a top surface which is separated from a surface of the substrate by a first area of the substrate, and a bottom surface which contacts said substrate;
- and
- a photocarrier reading element which has a transfer curve with a first portion for a first part of incoming light, that has a first slope, and a second portion for a second part of the light that has a second slope, where said second slope is more gradual than said first slope.
1 more element
A photosensor comprising:
- a semiconductor substrate having an upper surface;
- a photodiode, which is fully depleted, is formed of a first conductivity type material, and is buried below said upper surface to leave a portion of the substrate over the photodiode and a portion of the substrate below the photodiode;
- a floating diffusion region, formed of the same conductivity type of material as the photodiode, and coupled to the photodiode;
- and
- a reset element, selectively erecting a vertical diffusion bridge, which when lowered, allows charge in the photodiode and floating diffusion to spill to and which when raised maintains charge in said floating diffusion and photodiode.
2 more elements
A method comprising:
- using a buried photodiode to accumulate charge in a way that produces a transfer characteristic having a first steeper slope for lower light levels and a second more gradual slope for higher light levels.
A photo sensor, comprising:
- a semiconductor substrate;
- a buried photo diode in said semiconductor substrate, defining a first PN junction, and a second PN junction, wherein said first and second PN junctions have different characteristics, and where said first PN junction is optimized for receiving incoming radiation having different characteristics then said second PN junction.
Dependencies are inferred from the claim text.