Stacked-die image sensors with shielding

• US 10,566,375 B2
• Filed: 05/16/2016
• Issued: 02/18/2020
• Est. Priority Date: 01/29/2016
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Madurawe, Raminda, Mauritzson, Richard
• Primary Examiner(s): Nguyen, Cuong B
• Assistant Examiner(s): Park, Samuel
• Application Number:
  US15/155,245
• Publication Number:
  US 20170221954A1
• Time in Patent Office: 1,373 Days
• CPC Class Codes: H01L 25/043 Stacked arrangements of devices
• 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 27/14636 Interconnect structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers

Abstract

A stacked-die image sensor may be provided with an array of image pixels. The stacked-die image sensor may include at least first and second integrated circuit dies stacked on top of one another. Some of the pixel circuitry in each pixel may be formed in the first integrated circuit die and some of the pixel circuitry in each pixel may be formed in the second integrated circuit die. Coupling structures such as conductive pads may electrically couple the pixel circuitry in the first integrated circuit die to the pixel circuitry in the second integrated circuit die. A shielding structure may partially or completely surround each conductive pad to reduce parasitic capacitive coupling between adjacent conductive pads. The shielding structure may be a metal wire coupled to a ground voltage. The shielding structure may extend between columns of image pixels and/or between rows of image pixels.

Claims

1. An image sensor having an image pixel array, comprising:

a first integrated circuit die;

a second integrated circuit die stacked with the first integrated circuit die;

an image sensor pixel having a first floating diffusion region in the first integrated circuit die and a second floating diffusion region in the second integrated circuit die;

a coupling structure that electrically couples the first floating diffusion region in the first integrated circuit die to the second floating diffusion region in the second integrated circuit die; and

a shielding structure having a first portion formed in the first integrated circuit die and a second portion formed in the second integrated circuit die, wherein the shielding structure electrically shields the coupling structure.

2. The image sensor defined in claim 1 wherein the coupling structure comprises a first conductive pad in the first integrated circuit die and a second conductive pad in the second integrated circuit die.

3. The image sensor defined in claim 1 wherein the shielding structure comprises metal.

4. The image sensor defined in claim 3 wherein the shielding structure completely surrounds the coupling structure.

5. The image sensor defined in claim 1 further comprising an additional image sensor pixel having a third floating diffusion region in the first integrated circuit die and a fourth floating diffusion region in the second integrated circuit die.

6. The image sensor defined in claim 5 further comprising an additional coupling structure that electrically couples the third floating diffusion region in the first integrated circuit die to the fourth floating diffusion region in the second integrated circuit die.

7. The image sensor defined in claim 6 wherein the shielding structure is interposed between the coupling structure and the additional coupling structure to reduce parasitic capacitive coupling between the coupling structure and the additional coupling structure.

8. The image sensor defined in claim 1 wherein the image sensor pixel comprises a photodiode in the first integrated circuit die and a source follower transistor in the second integrated circuit die.

19. The image sensor defined in claim 1 wherein the coupling structure comprises a conductive pad, wherein the first portion of the shielding structure extends from a surface of the first integrated circuit die to a first depth in the first integrated circuit die, and wherein the conductive pad extends from the surface of the first integrated circuit die to a second depth in the first integrated circuit die that is substantially similar to the first depth.

9. An image sensor, comprising:

a first integrated circuit die;

a second integrated circuit die that is stacked with the first integrated circuit die;

a first image pixel comprising a first photodiode in the first integrated circuit die and a first row select transistor in the second integrated circuit die;

a second image pixel comprising a second photodiode in the first integrated circuit die and a second row select transistor in the second integrated circuit die;

a first conductive pad that electrically couples the first photodiode in the first integrated circuit die to the first row select transistor in the second integrated circuit die;

a second conductive pad that electrically couples the second photodiode in the first integrated circuit die to the second row select transistor in the second integrated circuit die;

a shielding structure interposed between the first conductive pad and the second conductive pad; and

a grounding structure coupled to the shielding structure and configured to electrically ground the shielding structure.

10. The image sensor defined in claim 9 wherein the shielding structure comprises a metal structure that at least partially surrounds the first conductive pad and the second conductive pad.

11. The image sensor defined in claim 9 wherein the first image pixel comprises a first floating diffusion node in the first integrated circuit die and a second floating diffusion node in the second integrated circuit die, and wherein the first conductive pad is electrically coupled between the first and second floating diffusion nodes.

12. The image sensor defined in claim 9 wherein the first image pixel comprises a floating diffusion node in the first integrated circuit die and a source follower transistor in the second integrated circuit die, and wherein the first conductive pad is electrically coupled between the floating diffusion node and the source follower transistor.

13. The image sensor defined in claim 9 further comprising:

three additional photodiodes in the first integrated circuit die, wherein the first conductive pad electrically couples the three additional photodiodes to the first row select transistor.

14. The image sensor defined in claim 9 wherein the first image pixel comprises a reset transistor in the second integrated circuit die.

15. The image sensor defined in claim 9 wherein the first image pixel comprises a reset transistor in the first integrated circuit die.

16. An image sensor, comprising:

a first integrated circuit die;

a second integrated circuit die that is stacked with the first integrated circuit die;

an image pixel array comprising rows and columns of image pixels, wherein a plurality of image pixels in the rows and columns of image pixels each include circuitry formed in the first integrated circuit die and circuitry formed in the second integrated circuit die;

a conductive pad coupled between the circuitry in the first integrated circuit die and the circuitry in the second integrated circuit die, wherein the conductive pad is shared by the plurality of image pixels; and

metal shielding that is electrically grounded to a ground voltage and configured to reduce parasitic capacitive coupling for the conductive pad, wherein the metal shielding surrounds the conductive pad shared by the plurality of image pixels and wherein the metal shielding has a first portion formed in the first integrated circuit die and a second portion formed in the second integrated circuit die.

17. The image sensor defined in claim 16 wherein the metal shielding extends between the rows of image pixels.

18. The image sensor defined in claim 16 wherein the metal shielding extends between the columns of image pixels.

20. The image sensor defined in claim 16 wherein the plurality of image pixels form a pixel cluster, wherein the conductive pad is formed at a center of the pixel cluster, wherein the circuitry in the first integrated circuit die for each image pixel in the plurality of image pixels is coupled to the circuitry in the second integrated circuit die for each image pixel in the plurality of image pixels via the conductive pad, and wherein the metal shielding is formed at edges of the pixel cluster.