Solid-state imaging device, manufacturing method of the same, and electronic apparatus
View Patent ↗A solid-state imaging device includes plural photodiodes which are formed in a photodiode area of a unit pixel with no element separating area interposed therebetween and in which impurity concentrations of pn junction areas are different from each other.
1. A solid-state imaging device comprising:
a pixel having a photodiode area;
a buried-type first photodiode formed by ion-implanting impurities using a first side wall of a transmission gate electrode as a mask, the first photodiode including a first area and a second area;
a buried-type second photodiode formed in the photodiode area by ion-implanting impurities using the transmission gate electrode as a mask;
a floating diffusion area formed by ion-implanting impurities using another side of the transmission gate electrode as a mask; and
a second side wall formed on the another side of the transmission gate electrode,
wherein,
a low impurity concentration of the second photodiode is closer to the transmission gate than that of a high impurity concentration of the first photodiode, the low impurity concentration being less than that of the high impurity concentration, and
a charge storage area is positioned below the first area and the second area of the first photodiode, the charge storage area having an end that is aligned with an end of the first sidewall.
2. The solid-state imaging device according to claim 1 , wherein:
the second photodiode includes a first area and a second area,
the second area of the first photodiode is a first conductive type semiconductor area serving as a main charge storage area,
the first area of the first photodiode is a second conductive type semiconductor area that is closer to a semiconductor surface than that of the first conductive type semiconductor area of the first photodiode,
the second area of the second photodiode is a first conductive type semiconductor area, and
the first area of the second photodiode is a second conductive type semiconductor area that is closer to the semiconductor surface than that of the first conductive semiconductor area of the second photodiode.
3. The solid-state imaging device according to claim 2 , wherein:
the second conductive type semiconductor area of the second photodiode comprises a boron-implanted area, and
the second conductive type semiconductor area of the first photodiode comprises in an indium-implanted area.
4. The solid-state imaging device according to claim 2 , wherein the first conductive type semiconductor areas include a plurality of high impurity concentration charge storage areas having different impurity concentrations that decrease in an increasing depth direction.
5. The solid-state imaging device according to claim 2 , wherein at least portions of the first and second conductive type semiconductor areas of the first and second photodiodes are continuously formed.
6. The solid-state imaging device according to claim 1 , wherein:
the second photodiode includes a first area and a second area,
each of the first areas has impurity concentrations different from each other,
each of the second areas has impurity concentrations different from each other,
each of the first areas is layered on a corresponding one of the second areas, and
the impurity concentrations of the second areas respectively decrease in a depth direction and another direction perpendicular to the depth direction.
7. A solid-state imaging device comprising:
a pixel having a photodiode area;
a first photodiode comprising a first conductivity type area and a second conductivity type area, the first photodiode being in the photodiode area; and
a second photodiode comprising a first conductivity type area and a second conductivity type area, the second photodiode being adjacent to the first photodiode in the photodiode area,
wherein,
the second photodiode is closer to a transmission gate electrode than the first photodiode,
the first conductivity type area of the second photodiode has an impurity concentration that is less than that of the first conductivity type area of the first photodiode,
the transmission gate electrode is between first sidewalls, and
a charge storage area is positioned below the first conductivity type area and the second conductivity type area of the first photodiode, the charge storage area having an end that is aligned with an end of one of the first sidewalls.
8. The solid-state imaging device of claim 7 , further comprising:
a floating diffusion area on a side of the transmission gate electrode that is opposite to that of the first photodiode and the second photodiode.
9. The solid-state imaging device of claim 7 , wherein:
the first conductivity type is p-type,
the second conductivity type is n-type, and
the charge storage area is n-type.
10. The solid-state imaging device of claim 7 , wherein:
the charge storage area has an impurity concentration that is less than that of the second conductivity type area of the first photodiode.