Solid-state imaging device and imaging system
A solid-state imaging device including a plurality of pixels including a photoelectric conversion portion, a charge holding portion accumulating a signal charge transferred from the photoelectric conversion portion, and a floating diffusion region to which the signal charge of the charge holding portion is transferred, wherein the photoelectric conversion portion includes a first semiconductor region of a first conductivity type, and a second semiconductor region of a second conductivity type formed under the first semiconductor region, the charge holding portion includes a third semiconductor region of the first conductivity type, and a fourth semiconductor region of the second conductivity type formed under the third semiconductor region, and a p-n junction between the third semiconductor region and the fourth semiconductor region is positioned deeper than a p-n junction between the first semiconductor region and the second semiconductor region.
1. A solid-state imaging device comprising:
a plurality of pixels each of which includes:
a photoelectric conversion portion which photoelectrically converts incident light to generate a signal charge;
a charge holding portion that accumulates the signal charge transferred from the photoelectric conversion portion;
a floating diffusion region to which the signal charge of the charge holding portion is transferred;
a first transfer gate configured to transfer the signal charge from the photoelectric conversion portion to the charge holding portion; and
a second transfer gate configured to transfer the signal charge from the charge holding portion to the floating diffusion region,
wherein:
the photoelectric conversion portion includes a first semiconductor region of a first conductivity type, and a second semiconductor region of a second conductivity type including a majority carrier of a polarity of the signal charge formed under the first semiconductor region,
the charge holding portion includes a third semiconductor region of the first conductivity type, and a fourth semiconductor region of the second conductivity type formed under the third semiconductor region,
in a cross section including the charge holding portion, the floating diffusion region and the second transfer gate, a first side edge of the fourth semiconductor region on the floating diffusion region side is provided between the floating diffusion region and a first side edge of the third semiconductor region on the floating diffusion region side, and
in the cross section, the floating diffusion region and the fourth semiconductor region are isolated by a semiconductor region of the first conductivity type, the semiconductor region being in contact with a surface of a semiconductor substrate.
2. The solid-state imaging device according to claim 1 , wherein the fourth semiconductor region has a higher impurity concentration than the second semiconductor region.
3. The solid-state imaging device according to claim 1 , wherein an area of the charge holding portion is larger than an area of the photoelectric conversion portion.
4. The solid-state imaging device according to claim 1 , wherein the charge holding portion further has a fifth semiconductor region of the first conductivity type, which is formed in contact with a bottom of the fourth semiconductor region.
5. The solid-state imaging device according to claim 1 , wherein the photoelectric conversion portion further has a sixth semiconductor region which is formed in contact with an end of the first semiconductor region at a side of the charge holding portion, and has a lower impurity concentration than the first semiconductor region.
6. The solid-state imaging device according to claim 1 , wherein the charge holding portion further has a seventh semiconductor region of the first conductivity type, which is formed in contact with an end of the third semiconductor region at a side of the floating diffusion region, and has a lower impurity concentration than the third semiconductor region.
7. The solid-state imaging device according to claim 1 , wherein the charge holding portion further has an eighth semiconductor region of the first conductivity type, which is formed in contact with an end of the third semiconductor region at a side of the photoelectric conversion portion, and has a lower impurity concentration than the third semiconductor region.
8. The solid-state imaging device according to claim 1 , wherein the charge holding portion further has a ninth semiconductor region of the second conductivity type, which is arranged in a vicinity of an end of the third semiconductor region at a side of the floating diffusion region.
9. The solid-state imaging device according to claim 1 , wherein the charge holding portion further has a tenth semiconductor region of the second conductivity type, which is arranged in a vicinity of an end of the third semiconductor region at a side of the photoelectric conversion portion.
10. The solid-state imaging device according to claim 5 , wherein the sixth semiconductor region extends to a region below the first transfer gate.
11. The solid-state imaging device according to claim 8 , wherein the ninth semiconductor region extends to a region below the second transfer gate.
12. The solid-state imaging device according to claim 9 , wherein the tenth semiconductor region extends to a region below the first transfer gate.
13. The solid-state imaging device according to claim 1 , wherein the first transfer gate extends to an upper part of the charge holding portion.
14. The solid-state imaging device according to claim 1 , wherein in the cross section, a part of the fourth semiconductor region is provided under the second transfer gate.
15. The solid-state imaging device according to claim 14 , wherein a p-n junction between the third semiconductor region and the fourth semiconductor region is positioned at a different depth from a p-n junction between the first semiconductor region and the second semiconductor region.
16. The solid-state imaging device according to claim 1 , wherein the fourth semiconductor region and the floating diffusion region are isolated by a semiconductor region of the first conductivity type.
17. The solid-state imaging device according to claim 1 , wherein in a second cross section including the photoelectric conversion portion, the charge holding portion and the first transfer gate, a second side edge of the fourth semiconductor region on the photoelectric conversion portion side is provided between the second semiconductor region and a second side edge of the third semiconductor region on the photoelectric conversion portion side.
18. The solid-state imaging device according to claim 17 , wherein in the second cross section, a part of the fourth semiconductor region is provided under the first transfer gate.
19. The solid-state imaging device according to claim 17 , wherein a plane including the first cross section is different and distant from a plane including the second section.
20. An imaging system comprising:
the solid-state imaging device according to claim 1 ; and
an optical system which forms an object image on the solid-state imaging device.