Solid-state imaging device, method for producing same, and camera
A solid-state imaging device includes a substrate having a first surface and a second surface, light being incident on the second surface side; a wiring layer disposed on the first surface side; a photodetector formed in the substrate and including a first region of a first conductivity type; a transfer gate disposed on the first surface of the substrate and adjacent to the photodetector, the transfer gate transferring a signal charge accumulated in the photodetector; and at least one control gate disposed on the first surface of the substrate and superposed on the photodetector, the control gate controlling the potential of the photodetector in the vicinity of the first surface.
1. A solid-state imaging device comprising:
a substrate having a first surface and a second surface, light being incident on the second surface side;
a wiring layer disposed on the first surface side;
a photodetector formed in the substrate, the photodector including an n-type charge-accumulation region and a p-type hole-accumulation region that is disposed on the first surface side;
a transfer gate of a transfer transistor disposed on the first surface of the substrate and adjacent to the photodetector, the transfer gate transferring a signal charge accumulated in the photodetector; and
a control gate disposed on the first surface of the substrate and provided separately from the transfer gate of the transfer transistor to control a potential of the photodetector in a vicinity of the first surface of the substrate, the control gate being disposed such that the control gate only partially overlaps the photodetector along a direction parallel to the first surface of the substrate, and the p-type hole-accumulation region being disposed at least in a part of the photodector that is not overlapped by the control gate.
2. The solid-state imaging device according to claim 1 , wherein the photodetector further includes another p-type hole-accumulation region that is disposed on the second surface side.
3. A camera comprising:
a solid-state imaging device that includes a substrate having a first surface and a second surface, light being incident on the second surface side;
an optical system that guides incident light to the second surface side; and
a signal-processing circuit that processes an output signal of the solid-state imaging device,
wherein,
the solid-state imaging device further includes
(a) a wiring layer disposed on the first surface side,
(b) a photodetector disposed in the substrate, the photodector including an n-type charge-accumulation region and a p-type hole-accumulation region that is disposed on the first surface side,
(c) a transfer gate of a transfer transistor disposed on the first surface of the substrate and adjacent to the photodetector, the transfer gate transferring a signal charge accumulated in the photodetector; and
(d) a control gate disposed on the first surface of the substrate and provided separately from the transfer gate of the transfer transistor to control a potential of the photodetector in a vicinity of the first surface of the substrate, the control gate being disposed such that the control gate only partially overlaps the photodetector along a direction parallel to the first surface of the substrate, and the p-type hole-accumulation region being disposed at least in a part of the photodector that is not overlapped by the control gate.
4. The solid-state imaging device according to claim 1 , further comprising:
an insulating film disposed on the second surface of the substrate with a light-shading film disposed on the insulating film and a protective film disposed on the light-shading film;
a color filter overlaid over the protective film that transmits light with a predetermined wavelength; and
a microlens that allows incident light to converge on the photodetector, the microlens being disposed on the color filter.
5. The solid-state imaging device according to claim 1 , wherein a concentration of impurities within the n-type charge-accumulation region of the photodector increases towards the first surface of the substrate.
6. The solid-state imaging device according to claim 1 , wherein the p-type hole-accumulation region is a shallow p-type hole-accumulation region.
7. The solid-state imaging device according to claim 1 , wherein the transfer gate and the control gate are separated from the first surface of the substrate by a gate-insulating film.
8. The solid-state imaging device according to claim 1 , wherein the solid-state imaging device is configured such that a negative voltage is applied to the control gate during a period of charge accumulation in the photodector so that holes are accumulated in the vicinity of the first surface of the substrate to reduce a dark current.
9. The solid-state imaging device according to claim 1 , wherein the control gate is disposed next to the transfer gate of the transfer transistor along the direction parallel to the first surface of the substrate, and the transfer gate and the control gate are separated from each other by an insulating film.
10. The solid-state imaging device according to claim 1 , wherein the control gate and the p-type hole-accumulation region do not overlap.