Method and apparatus for controlling charge transfer in CMOS sensors with a transfer gate work function

• US 7,800,145 B2
• Filed: 12/30/2004
• Issued: 09/21/2010
• Est. Priority Date: 12/30/2004
• Status: Active Grant

• Current Assignee: RE Secured Networks LLC
• Original Assignee: ESS Technology Incorporated (Semiconductor Holding Corp.)
• Inventors: Toros, Zeynep, Mann, Richard, Bencuya, Selim
• Primary Examiner(s): Pizarro, Marcos D.
• Application Number:
  US11/026,582
• Publication Number:
  US 20060146157A1
• Time in Patent Office: 2,091 Days
• Field of Search: 257/59, 257/233, 257/291, 257/292, 257/E27.133
• US Class Current: 257/292
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14654 Blooming suppression
• CPC Class Codes: H01L 27/14689 MOS based technologies
• CPC Class Codes: H04N 25/616 involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
• CPC Class Codes: H04N 25/623 by evacuation via the output or reset lines
• CPC Class Codes: H04N 25/626 Reduction of noise due to residual charges remaining after image readout, e.g. to remove ghost images or afterimages
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/65 applied to reset noise, e.g. KTC noise related to CMOS structures by techniques other than CDS

Abstract

An improved CMOS sensor integrated circuit is disclosed, along with methods of making the circuit and computer readable descriptions of the circuit.

Claims

1. An image sensor integrated circuit, comprising:

a plurality of photodetectors generating electrons excited by incident photons;

a plurality of nodes, wherein each of the plurality of photo detectors has a corresponding node of the plurality of nodes;

a plurality of transfer devices controlling a transfer of the electrons from said each of the plurality of photodetectors to the corresponding node, each of the plurality of transfer devices including;

a first terminal coupled to one of the plurality of photodetectors;

a second terminal coupled to one of the plurality of nodes; and

a body between the first terminal and the second terminal; and

a control terminal electrically coupled to the body, wherein the transfer of the electrons occurs through the body between the first terminal and the second terminal in response to a control voltage of sufficient value applied to the control terminal, and in an absence of the control voltage the control terminal creates an electric field tending to repel the electrons from a portion of the body by the control terminal;

a plurality of p-type regions having a concentration stronger than a background p-type concentration of the plurality of transfer devices, wherein each of the plurality of p-type regions has a lateral position only partly under the control terminal of a transfer device of the plurality of transfer devices, the plurality of p-type regions controlling the transfer of electrons from a photodetector of the plurality of photodetectors to the corresponding node of the photodetector, and the plurality of p-type regions has the lateral position at least partly under the corresponding node, and the plurality of p-type regions has the lateral position stopping short of the plurality of photodetectors and stopping short of a plurality of reset devices;

the plurality of reset devices, wherein each of the plurality of nodes has a corresponding reset device of the plurality of reset devices, and said each of the plurality of nodes is reset when the corresponding reset device is active;

row and column circuitry; and

a plurality of signal devices coupling the plurality of nodes to the row and column circuitry.

2. The circuit of claim 1, wherein the control terminal is made of p-type polysilicon.

3. The circuit of claim 1, wherein the body has a first Fermi level, the control terminal has a second Fermi level, and a difference between the first Fermi level and the second Fermi level causes the electric field.

4. The circuit of claim 1, wherein the control terminal is made of metal.

5. The circuit of claim 1, wherein a doping of the control terminal is graded in a direction along a channel length in the body.

6. The circuit of claim 1, wherein the electric field reduces dark current in the portion of the body by the control terminal.

7. The circuit of claim 1, further comprising:

a plurality of p-type regions isolating neighboring photodetectors from each other.

8. The circuit of claim 1, wherein each of the plurality of transfer devices includes a dielectric between the control terminal and the body, the dielectric satisfying a lifetime specification of the image sensor integrated circuit when the control signal is applied with the channel formed, the dielectric failing the lifetime specification of the image sensor integrated circuit if the control signal is applied with at least one of the first terminal and the second terminal at a ground voltage of the image sensor integrated circuit.

9. The circuit of claim 1, wherein the plurality of signal devices includes a plurality of row select transistors coupled to the row and column circuitry and a plurality of source follower transistors coupled to the plurality of nodes.

10. The circuit of claim 1, wherein the plurality of photodetectors is a plurality of photodiodes.

11. The circuit of claim 1, wherein each measurement of the total of the photons is corrected by correlated multiple sampling with a prior measurement of the total of the photons.

12. A computer readable description of an image sensor integrated circuit comprising:

a plurality of photo detectors generating electrons excited by incident photons;

a plurality of nodes, wherein each of the plurality of photodetectors has a corresponding node of the plurality of nodes;

a plurality of transfer devices controlling a transfer of the electrons from said each of the plurality of photodetectors to the corresponding node, each of the plurality of transfer devices including;

a first terminal coupled to one of the plurality of photodetectors;

a second terminal coupled to one of the plurality of nodes; and

a body between the first terminal and the second terminal; and

a control terminal electrically coupled to the body, wherein the transfer of the electrons occurs through the body between the first terminal and the second terminal in response to a control voltage of sufficient value applied to the control terminal, and in an absence of the control voltage the control terminal creates an electric field tending to repel the electrons from a portion of the body by the control terminal;

a plurality of p-type regions having a concentration stronger than a background p-type concentration of the plurality of transfer devices, wherein each of the plurality of p-type regions has a lateral position only partly under the control terminal of a transfer device of the plurality of transfer devices, the plurality of p-type regions controlling the transfer of electrons from a photodetector of the plurality of photodetectors to the corresponding node of the photodetector, and the plurality of p-type regions has the lateral position at least partly under the corresponding node, and the plurality of p-type regions has the lateral position stopping short of the plurality of photodetectors and stopping short of a plurality of reset devices;

the plurality of reset devices, wherein each of the plurality of nodes has a corresponding reset device of the plurality of reset devices, and said each of the plurality of nodes is reset when the corresponding reset device is active;

row and column circuitry; and

a plurality of signal devices coupling the plurality of nodes to the row and column circuitry.