Imaging device and method of manufacturing imaging device
An imaging device includes a plurality of pixels. Each of the pixels includes a photoelectric conversion unit provided in a first semiconductor region of a first conductivity type, a transfer transistor including a second semiconductor region of a second conductivity type to which charge generated in the photoelectric conversion unit is transferred, a third semiconductor region of the first conductivity type provided in a portion deeper than the second semiconductor region and having a higher impurity concentration than the first semiconductor region, and a counter doped region provided around the second semiconductor region. A part of the third semiconductor region and a part the counter doped region are overlapped with a gate electrode of the transfer transistor in a plan view. An overlap of the counter doped region with respect to the gate electrode is larger than an overlap of the third semiconductor region with respect to the gate electrode.
1. An imaging device comprising:
a plurality of pixels disposed two-dimensionally, each of the plural pixels including:
a photoelectric conversion unit provided in a first semiconductor region of a first conductivity type;
a transfer transistor including a second semiconductor region of a second conductivity type which is provided in the first semiconductor region and to which charge generated in the photoelectric conversion unit is transferred;
a third semiconductor region of the first conductivity type provided in a portion deeper than the second semiconductor region and having an impurity concentration higher than an impurity concentration of the first semiconductor region; and
a counter doped region provided around the second semiconductor region,
wherein at least a part of the third semiconductor region and at least a part of the counter doped region are overlapped with a gate electrode of the transfer transistor in a plan view, and
a first overlap of the counter doped region with respect to the gate electrode is larger than a second overlap of the third semiconductor region with respect to the gate electrode.
2. The imaging device according to claim 1 , further comprising a fourth semiconductor region of the second conductivity type provided at the same depth as a depth at which the counter doped region is provided and overlapping the third semiconductor region and the gate electrode in a plan view.
3. The imaging device according to claim 1 , further comprising a fourth semiconductor region of the first conductivity type provided at the same depth as a depth at which the counter doped region is provided and overlapping the third semiconductor region and the gate electrode in a plan view,
wherein a carrier concentration of the fourth semiconductor region of the first conductivity type is not more than a carrier concentration of the first conductivity type of a portion of the first semiconductor region, the portion being provided at the same depth as the depth at which the counter doped region is provided, and the portion overlapping with neither the third semiconductor region nor the counter doped region.
4. The imaging device according to claim 1 , wherein the photoelectric conversion unit and the second semiconductor region of the transfer transistor are provided in an active region, and
the counter doped region is provided in an overall area of the active region in a plan view.
5. The imaging device according to claim 1 , wherein the second semiconductor region is adjacent to the photoelectric conversion unit of another pixel with a device isolation region interposed therebetween, and
the third semiconductor region forms a potential barrier against the charge generated in the photoelectric conversion unit of the other pixel between the second semiconductor region and the photoelectric conversion unit of the other pixel.
6. The imaging device according to claim 1 , wherein the transfer transistor further includes a fourth semiconductor region of the second conductivity type, and transfers the charge generated in the photoelectric conversion unit to the second semiconductor region from the fourth semiconductor region, and
the counter doped region is disposed in a region shallower than the fourth semiconductor region.
7. The imaging device according to claim 6 , wherein the photoelectric conversion unit is configured by a p-n junction between the first semiconductor region and the fourth semiconductor region.
8. The imaging device according to claim 1 , wherein the first conductivity type is a p-type, and the second conductivity type is an n-type.
9. An imaging system comprising:
an imaging device according to claim 1 ; and
a signal processing unit processing a signal given from the imaging device.
10. The imaging device according to claim 1 , wherein the third semiconductor region forms a potential barrier against the charge generated in the photoelectric conversion unit.
11. The imaging device according to claim 1 , wherein the third semiconductor region is provided to surround the photoelectric conversion unit in a planar view.
12. The imaging device according to claim 1 , wherein the counter doped region is provided over a region deeper than the second semiconductor region from a surface of a semiconductor substrate.
13. The imaging device according to claim 1 , wherein the counter doped region serves to compensate carriers based on an impurity of the first conductivity type implanted in a vicinity of a surface of a semiconductor substrate when forming the third semiconductor region.
14. The imaging device according to claim 1 , wherein the third semiconductor region is configured by a plurality of semiconductor regions disposed at different depths, and has an impurity concentration of at least 1×10 17 cm −3 .