SOLID-STATE IMAGING DEVICE

• US 20120037960A1
• Filed: 09/21/2011
• Published: 02/16/2012
• Est. Priority Date: 03/26/2009
• Status: Active Grant

• Current Assignee: Panasonic Semiconductor Solutions Co., Ltd. (Winbond Electronics Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: HIROFUJI, Yuichi, YOKOYAMA, Haruhisa, SAKOH, Hiroshi, YAMASHITA, Kazuhiro, YASUHIRA, Mitsuo
• Granted Patent: US 8,395,194 B2
• Time in Patent Office: Days
• US Class Current: 257/230
• CPC Class Codes: H01L 27/14623 Optical shielding
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14656 Overflow drain structures

Abstract

A solid-state imaging device according to the present invention is of a MOS type and includes a plurality of pixels arranged in rows and columns, and includes: a semiconductor substrate; a photodiode which is formed in the semiconductor substrate and converts, into a signal charge, light that is incident from a first main surface of the semiconductor substrate; a transfer transistor which is formed in a second main surface of the semiconductor substrate and transfers the signal charge converted by the photodiode; a light shielding film which is conductive and formed on a boundary between the pixels, above the first main surface of the semiconductor substrate; an overflow drain region electrically connected to the light shielding film and formed in the first main surface of the semiconductor substrate; and an overflow barrier region formed between the overflow drain region and the photodiode.

Claims

1. A solid-state imaging device which is of a MOS type and includes a plurality of pixels arranged in rows and columns, said solid-state imaging device comprising:

a semiconductor substrate;

a photoelectric conversion unit included in each of the pixels, formed in said semiconductor substrate, and configured to convert, into a signal charge, light that is incident from a first main surface of said semiconductor substrate;

a transfer transistor which is included in each of the pixels and formed in a second main surface of said semiconductor substrate, and transfers the signal charge converted by said photoelectric conversion unit, the second main surface being located opposite to the first main surface;

a first light shielding film which is conductive and formed on at least part of a boundary between the pixels, above the first main surface of said semiconductor substrate;

an overflow drain region formed in the first main surface of said semiconductor substrate and electrically connected to said first light shielding film; and

an overflow barrier region formed between said overflow drain region and said photoelectric conversion unit.

2. The solid-state imaging device according to claim 1,

wherein said overflow drain region is formed on the at least part of the boundary between the pixels, and

said first light shielding film covers said overflow drain region.

3. The solid-state imaging device according to claim 1,

wherein a plurality of first light shielding films each being said first light shielding film are formed, and

each of said first light shielding films is linearly formed along the boundary between the pixels, for each boundary in a row direction or in a column direction of the pixels.

4. The solid-state imaging device according to claim 1,

wherein said first light shielding films are formed in a grid pattern on boundaries between the pixels.

5. The solid-state imaging device according to claim 1,

wherein a plurality of overflow drain regions each being said overflow drain region are formed, and

each of said overflow drain regions is formed on a grid point at which a boundary line between two pixels adjacent in the row direction intersects with a boundary line between two pixels adjacent in the column direction.

6. The solid-state imaging device according to claim 1,

wherein a plurality of overflow drain regions each being said overflow drain region are formed, and

each of said overflow drain regions is formed on the boundary between the pixels in the column direction or in the row direction.

7. The solid-state imaging device according to claim 1,

wherein a plurality of overflow drain regions each being said overflow drain region are formed, and

each of said overflow drain regions is linearly formed to cover the boundary between the pixels in the column direction or in the row direction.

8. The solid-state imaging device according to claim 1,

wherein said overflow drain region is formed in a grid pattern to cover the boundary between the pixels in the column direction and the row direction.

9. The solid-state imaging device according to claim 1,

wherein a potential barrier of said overflow barrier region is lower than a potential barrier under a gate electrode of said transfer transistor when said transfer transistor is shut off.

10. The solid-state imaging device according to claim 1, further comprising:

a second light shielding film which is conductive and formed on at least part of the boundary between the pixels, above the first main surface of said semiconductor substrate; and

a substrate contact region formed in the first main surface of said semiconductor substrate and electrically connected to said second light shielding film.

11. The solid-state imaging device according to claim 10,

wherein said substrate contact region is formed on the boundary between the pixels, and

said second light shielding film covers said substrate contact region.

12. The solid-state imaging device according to claim 10,

wherein a plurality of first light shielding films each being said first light shielding film and a plurality of second light shielding films each being said second light shielding film are formed,

each of said first light shielding films and each of said second light shielding films are linearly formed for each row or column of the pixels, and

said first light shielding films and said second light shielding films are alternately arranged in the row or column direction of the pixels.

13. The solid-state imaging device according to claim 10, further comprising

a first drive unit configured to supply, to said second light shielding film, a voltage that achieves a potential lower than a potential of said semiconductor substrate when reading, via said transfer transistor, the signal charge accumulated in said photoelectric conversion unit.

14. The solid-state imaging device according to claim 1, further comprising

a second drive unit configured to discharge, prior to an exposure period, the charge accumulated in said photoelectric conversion unit, by applying a first voltage to said first light shielding film, and to cause said photoelectric conversion unit to accumulate the charge during the exposure period by applying, to said first light shielding film, a second voltage that is lower than the first voltage.