Methods and apparatus for increased dynamic range of an image sensor
Various embodiments of the present technology may comprise methods and apparatus for increasing dynamic range of an image sensor. According to an exemplary embodiment, the image sensor comprises a backside-illuminated hybrid bonded stacked chip image senor having a pixel circuit array. A capacitor is formed on each pixel circuit along two adjacent sidewalls of an epitaxial substrate layer facing a deep trench isolation region. The capacitor may also extend along an upper surface of the epitaxial substrate layer.
1. A pixel circuit for a solid-state high dynamic range image sensor, comprising:
a micro lens;
a color filter disposed immediately adjacent the micro lens;
an epitaxial substrate layer disposed adjacent the color filter opposite the micro lens;
a first oxide layer disposed along a first sidewall of the epitaxial substrate layer facing a deep trench isolation region;
a second oxide layer disposed along an upper surface of the epitaxial substrate layer;
a silicon layer disposed between the second oxide layer and the color filter; and
a capacitor, comprising:
a first capacitor surface extending along the first oxide layer of the epitaxial substrate layer facing the deep trench isolation region; and
a second capacitor surface extending along at least one of:
the first oxide layer disposed along a second sidewall of the epitaxial substrate layer facing the deep trench isolation region; and
an upper surface of the second oxide layer below the silicon layer.
2. A pixel circuit according to claim 1 , wherein the second capacitor surface extends along both of the second sidewall of the epitaxial substrate layer and the upper surface of the second oxide layer.
3. A pixel circuit according to claim 1 , further comprising:
a frontside oxide layer disposed along a lower portion of the first sidewall below the first oxide layer; and
a third capacitor surface disposed along the frontside oxide layer.
4. A pixel circuit according to claim 1 , wherein:
the first and second oxide layers each comprise a high k material; and
the capacitor comprises a transparent electrode.
5. A pixel circuit according to claim 4 , wherein the high k material comprises hafnium oxide.
6. A pixel circuit according to claim 4 , wherein the transparent electrode comprises indium tin oxide.
7. A pixel circuit according to claim 1 , wherein the second capacitor surface extending along the second oxide layer comprises a transparent electrode.
8. A pixel circuit according to claim 7 , wherein the transparent electrode comprises indium tin oxide.
9. A solid-state high dynamic range image sensor, comprising:
an array of pixel circuits isolated from each other by a deep trench isolation region,
wherein each pixel circuit in the array comprises:
a micro lens;
a color filter disposed immediately adjacent the micro lens;
an epitaxial substrate layer disposed adjacent the color filter opposite the micro lens;
a first oxide layer disposed along a first sidewall and a second sidewall of the epitaxial substrate layer facing a deep trench isolation region;
a high k dielectric layer disposed along the upper surface of the epitaxial substrate layer;
a silicon layer disposed between the high k dielectric layer and the color filter; and
a capacitor, comprising:
a first capacitor surface extending along the first oxide layer on the first sidewall; and
a second capacitor surface extending along the first oxide layer on the second sidewall.
10. A solid-state high dynamic range image sensor according to claim 9 , wherein the capacitor further comprises a third capacitor surface extending along the upper surface of the epitaxial substrate layer between the high k dielectric layer and the silicon layer.
11. A solid-state high dynamic range image sensor according to claim 10 , wherein the third capacitor surface comprises a transparent electrode.
12. A solid-state high dynamic range image sensor according to claim 11 , wherein the transparent electrode comprises indium tin oxide.
13. A solid-state high dynamic range image sensor according to claim 9 , wherein:
the first oxide layer comprises a high k material; and
the capacitor comprises a transparent electrode.
14. A solid-state high dynamic range image sensor according to claim 13 , wherein the high k material and the high k dielectric layer each comprise hafnium oxide.
15. A solid-state high dynamic range image sensor according to claim 13 , wherein the transparent electrode comprises indium tin oxide.
16. A method of forming a capacitor for a solid-state high dynamic range image sensor, comprising:
forming a first capacitor surface extending along a first oxide layer disposed along a first sidewall of an epitaxial substrate layer facing a deep trench isolation region separating a first pixel circuit from a second pixel circuit; and
forming second capacitor surface extending along at least one of:
the first oxide layer disposed along a second sidewall of the epitaxial substrate layer facing the deep trench isolation region separating the first pixel circuit from a third pixel circuit; and
an upper surface of a high k dielectric layer disposed along an upper surface of the epitaxial substrate layer.
17. A method of forming a capacitor according to claim 16 , wherein the second capacitor surface extends along both of the second sidewall of the epitaxial substrate layer and the upper surface of the high k dielectric layer.
18. A method of forming a capacitor according to claim 16 ,
the first and second oxide layers each comprise a high k material; and
the capacitor comprises a transparent electrode.
19. A method of forming a capacitor according to claim 18 , wherein the transparent electrode comprises indium tin oxide.
20. A method of forming a capacitor according to claim 16 , further comprising:
forming a silicon layer disposed between the high k dielectric layer and a color filter; and
forming a micro lens along an upper surface of the color filter.