Solid-state image sensor

• US 20010000623A1
• Filed: 12/04/2000
• Published: 05/03/2001
• Est. Priority Date: 07/04/1997
• Status: Active Grant

• Current Assignee: Kabushiki Toshiba
• Original Assignee: Kabushiki Toshiba
• Inventors: Yamashita, Hirofumi, Inoue, Ikuko, Ihara, Hisanori, Yamaguchi, Tetsuya, Nozaki, Hidetoshi
• Granted Patent: US 6,441,411 B2
• Time in Patent Office: Days
• US Class Current: 257/292
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells

Abstract

A solid-state image sensor comprises a semiconductor substrate, a photoelectric conversion portion formed above the semiconductor substrate, and noise cancelers each formed, adjacent to the photoelectric conversion portion, on the semiconductor substrate through an insulating film, for removing noise of a signal read from the photoelectric conversion portion, wherein the semiconductor substrate has a conductive type opposite to a conductive type of a charge of the signal, and has a first region where concentration of impurities for determining the conductive type is high and a second region where concentration of the impurities on the first region is low.

Claims

1. A solid-state image sensor comprising:

a semiconductor substrate;

a photoelectric conversion portion formed above said semiconductor substrate; and

noise cancelers each formed, adjacent to said photoelectric conversion portion, on said semiconductor substrate through an insulating film, for removing noise of a signal read from said photoelectric conversion portion, wherein

said semiconductor substrate has a conductive type opposite to a conductive type of a charge of said signal, and has a first region where concentration of impurities for determining said conductive type is high and a second region where concentration of said impurities on said first region is low.

2. A solid-state image sensor according to

claim 1

, wherein said impurity concentration in said first region is 1×

10¹⁸ cm<sup>−

3</sup> or higher.

3. A solid-state image sensor according to

claim 1

, wherein said impurity concentration in said second region is gradually lower toward a surface of said semiconductor substrate.

4. A solid-state image sensor according to

claim 3

, wherein said second region is formed by epitaxial growth.

5. A solid-state image sensor according to

claim 1

, wherein

said second region is formed by thermal solid-phase diffusion;

and

said impurities are diffused from said first region toward said second region to thereby provide said impurity concentration in said second region with a desired concentration gradient.

6. A solid-state image sensor according to

claim 5

, wherein temperature for use in said solid-phase diffusion is between 1000°

and 1300°

C. and diffusion time is between 10 and 480 minutes.

7. A solid-state image sensor comprising:

a semiconductor substrate;

a photoelectric conversion portion formed above said semiconductor substrate;

a third region formed above said photoelectric conversion portion, having a same conductive type as that of a first region and having almost a same impurity concentration as that of said first region; and

noise cancelers each formed, adjacent to said photoelectric conversion portion, on said semiconductor substrate through an insulating film, for removing noise of a signal read from said photoelectric conversion portion, wherein

said semiconductor substrate has a conductive type opposite to a conductive type of an electric charge of said signal, and has said first region where concentration of impurities for determining said conductive type is high and a second region where concentration of said impurities on said first region is low.

8. A solid-state image sensor according to

claim 7

, wherein said impurity concentration in said first region is 1×

10¹⁸ cm<sup>−

3</sup> or higher.

9. A solid-state image sensor according to

claim 7

, wherein said impurity concentration in said second region is gradually lower toward a surface of said semiconductor substrate.

10. A solid-state image sensor according to

claim 8

, wherein said second region is formed by epitaxial growth.

11. A solid-state image sensor according to

claim 7

, wherein

said second region is formed by thermal solid-phase diffusion;

and

said impurities are diffused from said first region toward said second region to thereby provide said impurity concentration in said second region with a desired concentration gradient.

12. A solid-state image sensor according to

claim 11

, wherein temperature for use in said solid-phase diffusion is between 1000°

and 1300°

C. and diffusion time is between 10 and 480 minutes.