Image sensor photodiode
An image sensor including a plurality of pixels each including a charge collection region including an N-type region bounded by P-type regions and having an overlying P-type layer; and an insulated gate electrode positioned over the P-type layer and arranged to receive a gate voltage for conveying charges stored in the charge collection region through the P-type layer.
1. An image sensor comprising a plurality of pixels each comprising:
a charge collection region comprising an N-type region bounded by P-type regions and having an overlying P-type layer, wherein the N-type region has a depth that is greater than a width thereof; and
an insulated gate electrode positioned directly over the overlying P-type layer and the N-type region, and arranged to receive a gate voltage, the insulated gate electrode configured to convey charges between the charge collection region and the overlying P-type layer and between the overlying P-type layer and a sensing node, wherein an entirety of the insulated gate electrode is positioned directly over the N-type region.
2. The image sensor of claim 1 , wherein one of said P-type regions is a heavily doped P-type region between said charge collection region and an isolation trench.
3. The image sensor of claim 1 , wherein said charge collection region is formed in a P-type substrate, wherein said charge collection region is bounded on at least one side by a P-type region, and wherein said P-type region has a higher doping concentration than said P-type substrate.
4. The image sensor of claim 1 , wherein the sensing node is positioned adjacent to said insulated gate electrode, and wherein said gate voltage conveys charges through the overlying P-type layer to the sensing node.
5. The image sensor of claim 4 , wherein said sensing node at least partially overhangs said charge collection region.
6. The image sensor of claim 1 , wherein the charge collection region has a depth of between 0.5 μm and 2 μm.
7. The image sensor of claim 1 , wherein the charge collection region has a width of between 0.05 μm and 0.4 μm.
8. The image sensor of claim 7 , wherein said N-type region of the charge collection region has a doping concentration in the range of 10 15 to 5×10 17 at./cm 3 .
9. The image sensor of claim 1 , wherein said P-type layer has a doping concentration of between 10 16 and 10 18 at./cm 3 .
10. The image sensor of claim 1 , wherein said P-type layer has a thickness of between 20 and 150 nm.
11. The image sensor of claim 1 , wherein each pixel further comprises a source follower transistor formed within a pixel region delimited by isolation trenches, said source follower transistor being isolated on at least one side by a shallow trench isolation.
12. An electronic device comprising the image sensor of claim 1 .
13. A mobile telephone comprising the image sensor of claim 1 .
14. A method of manufacturing an image sensor comprising forming each pixel of said image sensor by:
forming in a substrate an N-type region of a charge collection region delimited by P-type regions and an overlying P-type layer, wherein the N-type region is formed to have a depth that is greater than a width thereof; and
forming an insulated gate electrode directly over said overlying P-type layer and said N-type region, the insulated gate electrode arranged to receive a gate voltage for conveying charges between said charge collection region and said overlying P-type layer and between said overlying P-type layer and a sensing node, wherein an entirety of the insulated gate electrode is positioned directly over the N-type region.
15. The method of claim 14 , further comprising forming the sensing node in said P-type substrate adjacent to said insulated gate electrode.
16. An image sensor pixel for an image sensor, comprising:
a charge collection region comprising an N-type region formed in a P-type substrate; wherein the N-type region has a depth that is greater than a width thereof;
an insulated gate positioned in its entirety directly over the N-type region;
a P-type layer between the N-type region and the insulated gate and overlying the N-type region; and
a sensing node, wherein the insulated gate is configured to control flow of charges between the charge collection region and the overlying P-type layer and between the overlying P-type layer and the sensing node in response to a gate voltage.
17. An image sensor pixel as defined in claim 16 , further comprising a heavily-doped P-type barrier and a deep trench isolation, wherein the heavily-doped P-type barrier is located between the charge collection region and the deep trench isolation.
18. An image sensor pixel as defined in claim 16 , wherein the sensing node at least partially overlaps the N-type region.
19. An image sensor pixel as defined in claim 16 , wherein the insulated gate is a gate of a transfer transistor that controls flow of charge between the charge collection region and the sensing node.
20. An image sensor pixel as defined in claim 16 , further comprising a source follower transistor having a gate coupled to the sensing node.
21. An image sensor pixel as defined in claim 20 , wherein the source follower transistor is isolated by a shallow trench isolation.
22. An image sensor pixel as defined in claim 16 , wherein a depth of the N-type region is greater than a width of the N-type region.
23. An image sensor pixel as defined in claim 16 , wherein a width of the N-type region is in a range of 0.05 micrometer to 0.4 micrometer and a depth of the N-type region is in a range of 0.5 micrometer to 2 micrometers.
24. An image sensor pixel as defined in claim 16 , wherein the P-type layer has the same or slightly lower doping concentration than the P-type substrate.
25. An image sensor pixel as defined in claim 16 , wherein the P-type layer has a doping concentration between 10 16 and 10 18 at./cm 3 .
26. An image sensor pixel as defined in claim 16 , wherein the P-type layer has a thickness between 20 and 150 nanometers.
27. An image sensor pixel as defined in claim 16 , wherein the N-type region has a doping concentration in a range of 10 14 to 10 17 at./cm 3 .
28. An image sensor pixel as defined in claim 16 , wherein charge is transferred through a top of the N-type region.
29. A method for making an image sensor pixel of an image sensor, comprising:
forming a charge collection region comprising an N-type region in a P-type substrate,. including forming the N-type region to have a depth that is greater than a width thereof;
forming an insulated gate positioned in its entirety directly over the N-type region;
forming a P-type layer between the N-type region and the insulated gate and overlying the N-type region; and
forming a sensing node, wherein the insulated gate is configured to control flow of charges between the charge collection region and the overlying P-type layer and between the overlying P-type layer and the sensing node in response to a gate voltage.
30. A method as defined in claim 29 , further comprising forming a deep trench isolation in the substrate and forming a heavily-doped P-type barrier between the charge collection region and the deep trench isolation.
31. A method as defined in claim 29 , further comprising forming a source follower transistor in the image sensor pixel.
32. A method as defined in claim 29 , wherein forming the charge collection region comprises forming the N-type region such that a depth of the N-type region is greater than a width of the N-type region.
33. A method as defined in claim 29 , wherein forming a charge collection region comprises forming the N-type region with a width in a range of 0.05 micrometer to 0.4 micrometer and a depth in a range of 0.5 micrometer to 2 micrometers.
34. A method as defined in claim 29 , wherein forming a P-type layer comprises forming the P-type layer with a thickness in a range of 20 to 150 nanometers.
35. A method as defined in claim 29 , wherein the charge collection region is formed such that charge is transferred from the top of the N-type region.