Image sensor with buried light shield and vertical gate

• US 9,842,875 B2
• Filed: 05/20/2016
• Issued: 12/12/2017
• Est. Priority Date: 08/05/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Fan, Xiaofeng, Li, Philip H., Wan, Chung Chun, Sharma, Anup K., Li, Xiangli
• Primary Examiner(s): Mandala, Michelle
• Application Number:
  US15/161,179
• Publication Number:
  US 20160343756A1
• Time in Patent Office: 571 Days
• Field of Search: None
• CPC Class Codes: H01L 27/1462 Coatings
• CPC Class Codes: H01L 27/14623 Optical shielding
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14638 Structures specially adapted for transferring the charges across the imager perpendicular to the imaging plane
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H04N 25/616 involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
• CPC Class Codes: H04N 25/771 comprising storage means other than floating diffusion

Abstract

A pixel in an image sensor can include a photodetector and a storage region disposed in one substrate, or a photodetector disposed in one substrate and a storage region in another substrate. A buried light shield is disposed between the photodetector and the storage region. A sense region, such as a floating diffusion, can be adjacent to the storage region, with the buried light shield disposed between the photodetector and the storage and sense regions. When the photodetector and the storage region are disposed in separate substrates, a vertical gate can be formed through the buried light shield and used to initiate the transfer of charge from the photodetector and the storage region. A transfer channel formed adjacent to, or around the vertical gate provides a channel for the charge to transfer from the photodetector to the storage region.

Claims

1. An image sensor comprising:

a first substrate layer comprising;

a photodetector disposed on a first surface of the first substrate layer;

a second substrate layer comprising;

a first storage region disposed adjacent to a second surface of the second substrate, the second surface opposite the first surface;

a second storage region disposed in the second substrate layer; and

a buried light shield disposed between the first and second substrate layers, wherein the buried light shield is over the first and second storage regions.

2. The image sensor as in claim 1, further comprising:

a vertical gate extending from the first substrate layer through the buried light shield to the second substrate layer;

a transfer channel disposed adjacent to the vertical gate, the transfer channel being operable to provide a channel for charge to transfer from the photodetector to first storage region; and

a dielectric material formed over the transfer channel.

3. The image sensor as in claim 2, wherein the transfer channel comprises a silicon transfer channel.

4. The image sensor as in claim 1, wherein the buried light shield comprises an opaque shield layer disposed between a first dielectric layer and a second dielectric layer.

5. The image sensor as in claim 1, wherein the buried light shield comprises one of a light-blocking material or a light-absorbing material.

6. The image sensor as in claim 1, wherein the buried light shield comprises a material having an index of refraction that is different from a material in the first substrate layer.

7. The image sensor as in claim 1, wherein the buried light shield comprises a silicon-on-insulator layer.

8. The image sensor as in claim 1, wherein the image sensor is a backside illuminated image sensor and the photodetector is adjacent a backside surface of the first substrate layer and the first and second storage regions are adjacent a frontside surface of the second substrate layer.

9. The image sensor as in claim 8, further comprising:

an anti-reflective coating formed over the backside surface of the first substrate layer; and

at least one light shield formed over the anti-reflective coating.

10. An image sensor comprising:

a sensing layer formed in a first substrate, the sensing layer comprising;

a photodetector;

a storage region; and

a buried light shield disposed below the photodetector and over storage region;

a second substrate attached to the first substrate, the second substrate comprising a contact pad;

a vertical gate extending between the first substrate through the buried light shield to the contact pad; and

a transfer channel disposed adjacent to the vertical gate operatively connecting the photodetector to the storage region and providing a charge transfer path between the photodetector and the storage region.

11. The image sensor as in claim 10, further comprising a dielectric material formed over the transfer channel.

12. The image sensor as in claim 10, wherein the buried light shield divides the first substrate into a first substrate layer and a second substrate layer, and wherein the photodetector is disposed in the first substrate layer and the storage region is disposed in the second substrate layer.

13. The image sensor as in claim 12, wherein the storage region comprises a first storage region and the image sensor further comprises a second storage region disposed in the second substrate layer adjacent the first storage region and below the buried light shield.

14. The image sensor as in claim 10, wherein the image sensor comprises a backside illuminated image sensor and the photodetector is adjacent a backside surface of the first substrate and the first and second storage regions are adjacent a frontside surface of the first substrate.

15. The image sensor as in claim 14, further comprising:

an antireflective coating layer disposed over the backside surface of the first substrate; and

at least one light shield formed over the anti-reflective coating.

16. The image sensor as in claim 10, wherein the buried light shield comprises an opaque shield layer disposed between a first dielectric layer and a second dielectric layer.

17. The image sensor as in claim 10, wherein the buried light shield comprises only one of a light-blocking material or a light-absorbing material.

18. The image sensor as in claim 10, wherein the buried light shield comprises a material having an index of refraction that is different from a material in the first substrate.

19. The image sensor as in claim 10, wherein the buried light shield comprises a silicon-on-insulator layer.

20. The image sensor as in claim 10, further comprising a carrier wafer attached to the second substrate.