Image sensor with reduced blooming

• US 9,041,837 B2
• Filed: 03/05/2013
• Issued: 05/26/2015
• Est. Priority Date: 03/05/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Li, Xiangli
• Primary Examiner(s): HERNANDEZ, NELSON D
• Application Number:
  US13/785,070
• Publication Number:
  US 20140253768A1
• Time in Patent Office: 812 Days
• Field of Search: 348/241, 348/248
• US Class Current: 348/248
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14641 Electronic components shared by two or more pixel-elements, e.g. one amplifier shared by two pixel elements
• CPC Class Codes: H01L 27/14672 Blooming suppression
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• CPC Class Codes: H04N 25/622 by controlling anti-blooming drains

Abstract

An image sensor for an electronic device. The image sensor includes a first light sensitive element for collecting charge and having a first saturation value and a well surrounding at least a portion of the first light sensitive element and having a first doping concentration. The image sensor further includes a bridge region defined in the well and in communication with the first light sensitive element and having a second doping concentration and a blooming node in communication with the bridge region and a voltage source. The second doping concentration is less than the first doping concentration and when light sensitive element collects sufficient charge to reach the first saturation value, additional charge received by the light sensitive element travels to the blooming node via the bridge region.

Claims

1. An image sensor for an electronic device, comprising:

a first light sensitive element for collecting charge and having a first saturation value;

a well surrounding at least a portion of the first light sensitive element and having a first doping concentration;

a bridge region defined in the well and in communication with the first light sensitive element and having a second doping concentration; and

a blooming node in communication with the bridge region and a voltage source;

wherein the second doping concentration is less than the first doping concentration; and

when the first light sensitive element collects sufficient charge to reach the first saturation value, additional charge received by the first light sensitive element travels to the blooming node via the bridge region.

2. The image sensor of claim 1, wherein the well and the bridge region are both doped with the same type of dopant.

3. The image sensor of claim 2, wherein the well and the bridge region are doped with a P-type dopant.

4. The image sensor of claim 3, wherein the blooming node is defined by a N-typed doped region.

5. The image sensor of claim 1, further comprising a highly doped surface extending over the first light sensitive element, the well, and at least a portion of the bridge region.

6. The image sensor of claim 5, wherein the highly doped surface has a third doping concentration, wherein the third doping concentration is greater than both the first doping concentration and the second doping concentration.

7. The image sensor of claim 6, wherein the highly doped surface, the well, and the bridge region are all doped with the same dopant type.

8. The image sensor of claim 1, further comprising a second light sensitive element having a second saturation value, wherein the second light sensitive element is in communication with the bridge region.

9. The image sensor of claim 8, wherein the bridge region extends beneath the blooming node.

10. The image sensor of claim 1, wherein the voltage source is pulsed.

11. A camera, comprising:

a lens; and

an image sensor in optical communication with the lens, comprising;

a first pixel including a first photodiode;

a second pixel including a second photodiode;

a blooming junction in communication with the first pixel and the second pixel through a bridge region extending between the blooming junction and the first and second photodiodes, wherein the bridge region defines a blooming path between the first photodiode and the second photodiode to the blooming junction, and wherein the bridge region is doped with a first dopant type and the blooming junction is doped with a second dopant type; and

a blooming voltage source in communication with the blooming junction,

wherein the blooming voltage source determines a potential of the blooming junction;

wherein the lens transmits light to the image sensor, creating charge within the first photodiode and the second photodiode; and

the blooming junction selectively receives charge from the first photodiode and the second photodiode to substantially prevent the first photodiode and the second photodiode from exceeding a saturation value.

12. The camera of claim 11, wherein the bridge region is lightly doped.

13. The camera of claim 11, wherein the image sensor further comprises:

a third pixel having a third photodiode; and

a fourth pixel having a fourth photodiode;

wherein the blooming junction is in communication with the third photodiode and the fourth photodiode.

14. The camera of claim 11, wherein the first photodiode and the second photodiode are substantially surrounded by a well, wherein the well is doped with the first dopant type.

15. The camera of claim 14, wherein the well is doped with a P-type dopant and the blooming junction is doped with an N-type dopant.

16. The camera of claim 14, wherein the image sensor further comprises a highly doped surface extending over the first photodiode, the second photodiode, the well, and at least a portion of the bridge region.

17. The camera of claim 16, wherein the highly doped surface is doped with the first dopant type.

18. The camera of claim 11, wherein the blooming voltage source is a pulsed source.

19. A computing device comprising:

a processor; and

an image sensor in communication with the processor, the image sensor comprising;

a photodiode having a full well value;

a blooming node in communication with the photodiode;

a lightly doped region positioned between the blooming node and the photodiode; and

a voltage source in communication with the blooming node, wherein the voltage source determines a potential of the blooming node;

wherein when the photodiode collects charge exceeding the full well value, excess charge is transmitted to the blooming node through the lightly doped region.

20. The computing device of claim 19, wherein the image sensor further comprises a pinned transfer gate in communication with the photodiode, wherein the transfer gate selectively enables charge from the photodiode to be transmitted to the processor.

21. The computing device of claim 19, wherein the lightly doped region is doped with a first dopant type and the photodiode and the blooming node are doped with a second dopant type.