CMOS image sensor having enhanced near infrared quantum efficiency

Patent metadata

Field	Value
Publication number	US-9991309-B1
Application number	US-201715642177-A
Country	US
Kind code	B1
Filing date	Jul 5, 2017
Priority date	Jul 5, 2017
Publication date	Jun 5, 2018
Grant date	Jun 5, 2018

Abstract

An image sensor comprises a semiconductor material having an illuminated surface and a non-illuminated surface; a photodiode formed in the semiconductor material extending from the illuminated surface to receive an incident light through the illuminated surface, wherein the received incident light generates charges in the photodiode; a transfer gate electrically coupled to the photodiode to transfer the generated charges from the photodiode in response to a transfer signal; a floating diffusion electrically coupled to the transfer gate to receive the transferred charges from the photodiode; a near infrared (NIR) quantum efficiency (QE) enhancement structure comprising at least two NIR QE enhancement elements within a region of the photodiode, wherein the NIR QE enhancement structure is configured to modify the incident light at the illuminated surface of the semiconductor material by at least one of diffraction, deflection and reflection, to redistribute the incident light within the photodiode to improve an optical sensitivity, including near-infrared light sensitivity, of the image sensor.

First claim

What is claimed is:

1. An image sensor, comprising:
a semiconductor material having an illuminated surface and a non-illuminated surface;
a photodiode formed in the semiconductor material extending from the illuminated surface to receive an incident light through the illuminated surface, wherein the received incident light generates charges in the photodiode;
a transfer gate electrically coupled to the photodiode to transfer the generated charges from the photodiode in response to a transfer signal;
a floating diffusion electrically coupled to the transfer gate to receive the transferred charges from the photodiode;
a near infrared (NIR) quantum efficiency (QE) enhancement structure comprising at least two NIR QE enhancement elements within a photosensitive region of the photodiode, wherein the NIR QE enhancement structure is configured to modify the incident light at the illuminated surface of the semiconductor material by at least one of diffraction, deflection and reflection, to redistribute the incident light within the photodiode to improve an optical sensitivity, including near-infrared light sensitivity, of the image sensor.

2. The image sensor of claim 1 , wherein each NIR QE enhancement element of the NIR QE enhancement structure comprises a dielectric material having a refractive index smaller than a refractive index of the semiconductor material.

3. The image sensor of claim 1 , wherein the at least two NIR QE enhancement elements have a uniform size and shape, and are disposed in a periodic pattern.

4. The image sensor of claim 1 , wherein each NIR QE enhancement element of the NIR QE enhancement structure comprises a shape of one of a parallelepiped, a polygon, a cylinder, an ellipsoids, a hemispheroid, and a hemisphere.

5. The image sensor of claim 1 , wherein the illuminated surface of the semiconductor material is one of a front side surface and a back side surface of the semiconductor material.

6. The image sensor of claim 1 , wherein each NIR QE enhancement element of the NIR QE enhancement structure extends from the illuminated surface of the semiconductor material in the photodiode.

7. The image sensor of claim 1 , wherein each NIR QE enhancement element of the NIR QE enhancement structure is disposed at least partially on the illuminated surface of the semiconductor material.

8. The image sensor of claim 1 , wherein an isolation region surrounds, at least partially, the photodiode, and isolates the photodiode electrically and optically.

9. The image sensor of claim 1 , further comprising a reset transistor electrically coupled to the floating diffusion to reset the charges received in the floating diffusion.

10. The image sensor of claim 1 , further comprising an amplifier transistor electrically coupled to the floating diffusion to amplify the charges received in the floating diffusion.

11. An imaging system, comprising:
a semiconductor material having an illuminated surface and a non-illuminated surface;
a plurality of photodiodes formed in the semiconductor material extending from the illuminated surface to receive an incident light through the illuminated surface, wherein the received incident light generates charges in the photodiodes;
a plurality of isolation structures, wherein each of the plurality of isolation structures is disposed between two adjacent photodiodes of the plurality of photodiodes;
a plurality of transfer gates electrically coupled to the plurality of photodiodes to transfer the generated charges from the plurality of photodiodes to one or more floating diffusions;
A plurality of near infrared (NIR) quantum efficiency (QE) enhancement structures, wherein each of NIR QE enhancement structures comprises at least two NIR QE enhancement elements within the a photosensitive region of individual photodiode of the plurality of photodiodes, wherein the NIR QE enhancement structures are configured to modify incident light at the illuminated surface of the semiconductor material by at least one of diffraction, deflection and reflection, to redistribute the incident light within the photodiode to improve an optical sensitivity, including near infrared light sensitivity, of the image system.

12. The imaging system of claim 11 , further comprising a plurality of reset transistors, wherein each of the plurality of reset transistors electrically coupled to the one or more floating diffusions to reset the charges received in the one or more floating diffusions.

13. The imaging system of claim 11 , further comprising a plurality of amplifier transistors, wherein each of the plurality of amplifier transistors electrically coupled to the one or more floating diffusions to amplify the charges received in the one or more floating diffusions.

14. The imaging system of claim 11 , further comprising a control circuitry and a readout circuitry, wherein the control circuitry controls operation of the plurality of photodiodes, and the readout circuitry reads out image data from the plurality of photodiodes.

15. The imaging system of claim 11 , wherein each NIR QE enhancement element of the NIR QE enhancement structures comprises a dielectric material having a refractive index smaller than a refractive index of the semiconductor material.

16. The imaging system of claim 11 , wherein at least two NIR QE enhancement elements of the NIR QE enhancement structures have a uniform size and shape, and are disposed in a periodic pattern.

17. The imaging system of claim 11 , wherein each NIR QE enhancement element of the NIR QE enhancement structures comprises a shape of one of a parallelepiped, a polygon, a cylinder, an ellipsoids, a hemispheroid, and a hemisphere.

18. The imaging system of claim 11 , wherein each NIR QE enhancement element of the NIR QE enhancement structures extends from the illuminated surface of the semiconductor material in the photodiode.

19. The imaging system of claim 11 , wherein each NIR QE enhancement element of the NIR QE enhancement structures is disposed at least partially on the illuminated surface of the semiconductor material.

20. The imaging system of claim 11 , wherein the illuminated surface of the semiconductor material is one of a front side surface and a back side surface of the semiconductor material.

Assignees

• Omnivision Tech Inc

Inventors

• Yang Cunyu
• Zhao Cheng
• Chen Gang
• Tai Dyson
• Lu Chen-Wei

Classifications

• H04N25/77

  Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components · CPC title

• H04N25/00

  Circuitry of solid-state image sensors [SSIS]; Control thereof · CPC title

• H01L27/1464

  Electricity · mapped topic

• H01L27/1463

  Electricity · mapped topic

• H04N5/3745

  Electricity · mapped topic