PHOTOGATE CMOS PIXEL FOR 3D CAMERAS HAVING REDUCED INTRA-PIXEL CROSS TALK
First Claim
1. A CMOS photodetector pixel comprising:
- a substrate having first polarity and impurity concentration;
an epitaxial layer formed above the substrate including a first region having the same polarity but a lower impurity concentration from that of the substrate;
an oxide layer formed above the epitaxial layer; and
a gate arrangement formed on the oxide layer including a first gate,wherein the epitaxial layer includes a shielding structure having a polarity, impurity concentration and geometry such that it functions to substantially absorb electrons generated in the epitaxial layer by photons impinging on the pixel, except for electrons generated in close enough proximity to the first gate as to be attracted by an electric field generated when the first gate is electrically energized.
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Abstract
A CMOS photodetector pixel formed of a substrate, an epitaxial layer above the substrate including a first region having the same polarity but a lower impurity concentration as that of the substrate, and a gate arrangement including a first gate that forms a charge accumulation region in the epitaxial layer when the gate is energized, wherein the charge accumulation region extends deeper toward the substrate than in conventional constructions. The epitaxial layer includes a shielding structure for absorbing electrons generated therein by photons impinging on the pixel, except electrons generated close to the charge accumulation region. The shielding structure may have opposite polarity from that of the substrate, including a first portion under the first gate, and a second portion extending upward from the first portion at the margin of the pixel. Alternatively, the shielding structure may have the same polarity as the substrate, but a lower impurity concentration.
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Citations
20 Claims
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1. A CMOS photodetector pixel comprising:
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a substrate having first polarity and impurity concentration; an epitaxial layer formed above the substrate including a first region having the same polarity but a lower impurity concentration from that of the substrate; an oxide layer formed above the epitaxial layer; and a gate arrangement formed on the oxide layer including a first gate, wherein the epitaxial layer includes a shielding structure having a polarity, impurity concentration and geometry such that it functions to substantially absorb electrons generated in the epitaxial layer by photons impinging on the pixel, except for electrons generated in close enough proximity to the first gate as to be attracted by an electric field generated when the first gate is electrically energized. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A photodetector comprising pixels formed in a semiconductor substrate, each pixel comprising:
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a photogate for controlling a depletion region in the substrate under the photogate; diffusion regions on either side of the depletion region; gates on either side of the photogate for controlling electric fields between the depletion region and the diffusion regions; and a substantially electrically conductive boundary region in the substrate that contains the depletion and diffusion regions.
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Specification