Charge transfer circuit with storage nodes in image sensors
First Claim
Patent Images
1. An image sensor pixel, comprising:
- a photodiode;
a first charge storage node;
a first transfer gate between the photodiode and the first charge storage node and configured to transfer charge from the photodiode to the first charge storage node;
a second charge storage node;
a second transfer gate between the first charge storage node and the second charge storage node and configured to transfer charge from the first charge storage node to the second charge storage node;
a third charge storage node; and
a third transfer gate between the second charge storage node and the third charge storage node and configured to transfer charge from the second charge storage node to the third charge storage node;
wherein the second transfer gate comprises a transfer circuit gate that is included in a transfer circuit, the transfer circuit comprising;
a first region under a portion of the transfer circuit gate proximate the first charge storage node and configured to have a first variable potential;
a second region laterally offset from the first region under a remaining portion of the transfer circuit gate and configured to have a second variable potential, the second region extending away from the first region and beyond the transfer circuit gate to the second charge storage node; and
a pinning layer over the second charge storage node and over a portion of the second region not under the transfer circuit gate, the pinning layer and the portion of the second region not under the transfer circuit gate forming a barrier between the second region under the transfer circuit gate and the second charge storage node, whereinthe transfer circuit gate is configured to control the first and the second variable potentials based on a transfer signal provided to the transfer gate.
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Abstract
Apparatuses and methods for charge transfer in image sensors are disclosed. One example of an image sensor pixel may include a first charge storage node and a second charge storage node. A transfer circuit may be coupled between the first and second charge storage nodes, and the transfer circuit may have a first region proximate the first charge storage node and configured to have a first potential. The transfer circuit may also have a second region proximate the second charge storage node configured to have a second, higher potential. An input node may be configured to control the first and second potentials based on a transfer signal provided to the input node.
196 Citations
19 Claims
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1. An image sensor pixel, comprising:
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a photodiode; a first charge storage node; a first transfer gate between the photodiode and the first charge storage node and configured to transfer charge from the photodiode to the first charge storage node; a second charge storage node; a second transfer gate between the first charge storage node and the second charge storage node and configured to transfer charge from the first charge storage node to the second charge storage node; a third charge storage node; and a third transfer gate between the second charge storage node and the third charge storage node and configured to transfer charge from the second charge storage node to the third charge storage node; wherein the second transfer gate comprises a transfer circuit gate that is included in a transfer circuit, the transfer circuit comprising; a first region under a portion of the transfer circuit gate proximate the first charge storage node and configured to have a first variable potential; a second region laterally offset from the first region under a remaining portion of the transfer circuit gate and configured to have a second variable potential, the second region extending away from the first region and beyond the transfer circuit gate to the second charge storage node; and a pinning layer over the second charge storage node and over a portion of the second region not under the transfer circuit gate, the pinning layer and the portion of the second region not under the transfer circuit gate forming a barrier between the second region under the transfer circuit gate and the second charge storage node, wherein the transfer circuit gate is configured to control the first and the second variable potentials based on a transfer signal provided to the transfer gate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An integrated circuit, comprising:
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a photodiode; a first node comprising a first dopant type operatively coupled to the photodiode and configured to store charge; a second node comprising the first dopant type operatively coupled to the first node and configured to receive charge from the first node; and a transfer circuit coupling the first node to the second node, the transfer circuit comprising; a transfer gate positioned between the first and the second nodes; a barrier region comprising a second dopant type under a portion of the transfer gate proximate the first node, the barrier region having a first variable potential configured to be controlled by a transfer signal applied to the transfer gate; a storage region comprising the first dopant type laterally offset from the barrier region under a remaining portion of the transfer gate and having a second variable potential configured to be controlled by the transfer signal applied to the transfer gate, the storage region extending away from the barrier region beyond the transfer gate to the second node; and a pinning layer formed over the second node and a portion of the storage region not under the transfer gate, the pinning layer and the portion of the storage region not under the transfer gate forming a barrier between the portion of the storage region under the transfer gate and the second node, wherein the second variable potential is higher than the first variable potential. - View Dependent Claims (11, 12, 13)
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14. An image sensor pixel, comprising:
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a photodiode; a first charge storage node comprising a first dopant type and operatively connected to the photodiode; a second charge storage node comprising the first dopant type operatively connected to the first charge storage node through a transfer circuit positioned between the first and the second charge storage nodes, the transfer circuit comprising; a transfer gate; a first region comprising a second dopant type positioned below a portion of the transfer gate proximate the first charge storage node; and a second region comprising the first dopant type between the first region and the second charge storage node, wherein a first portion of the second region is positioned below a remaining portion of the transfer gate and a second portion of the second region extends beyond the transfer gate to the second charge storage node; and a pinning layer comprising the second dopant type positioned over the second charge storage node and the second portion of the second region, wherein a dopant concentration of the second region is less than a dopant concentration of the second charge storage node. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification