Complementary metal oxide semiconductor image sensor and fabrication method thereof

• US 20050087783A1
• Filed: 10/22/2004
• Published: 04/28/2005
• Est. Priority Date: 10/23/2003
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: DONGBU ELECTRONICS CO., LTD. (DB HiTek Co., Ltd.)
• Inventors: Jang, Hoon
• Granted Patent: US 7,397,076 B2
• Time in Patent Office: Days
• US Class Current: 257/292
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/1463 Pixel isolation structures
• CPC Class Codes: H01L 27/14656 Overflow drain structures
• CPC Class Codes: H01L 27/14689 MOS based technologies

Abstract

Disclosed are a CMOS image sensor and a fabrication method thereof, which is adequate to reduce dark current. The CMOS image sensor comprises a device isolation region and an active region, which are formed on a semiconductor substrate; a photocharge generating portion formed on the active region for absorbing light externally and generating and accumulating charges; a transistor portion including at least one transistor for processing the charges accumulated in the photocharge generating portion; and a control terminal for preventing dark current from being introduced into the photocharge generating portion, and ejecting the dark current after temporally storing the dark current. The control terminal is operated to store the dark current for an integration time when a photodiode as the photocharge generating portion receives light, and eject the stored dark current by being grounded when the reset transistor is turned on.

Claims

1. A CMOS image sensor comprising:

a device isolation region and an active region which are formed on a semiconductor substrate;

a photocharge generating portion formed on the active region for absorbing external light and generating and accumulating charges;

a transistor portion including at least one transistor for processing the charges accumulated in the photocharge generating portion; and

a control terminal for preventing dark current from being introduced into the photocharge generating portion, and ejecting the dark current after temporally storing the dark current.

2. The CMOS image sensor of claim 1, wherein the transistor portion includes a reset transistor, a select transistor and an access transistor.

3. The CMOS image sensor of claim 2, wherein the control terminal stores the dark current for an integration time when light is received, and ejects the stored dark current by being grounded when the reset transistor is turned on.

4. The CMOS image sensor of claim 1, further comprising a separating portion for separating the photocharge generating portion from the control terminal.

5. The CMOS image sensor of claim 1, wherein the photocharge generating portion is formed by a photodiode.

6. A method of fabricating a CMOS image sensor, comprising:

forming a device isolation region by etching a semiconductor substrate of a first conductivity type;

forming a transistor portion including at least one transistor on the semiconductor substrate on which the device isolation region is formed;

forming a photocharge generating portion by injecting impurities of a second conductivity type opposite to the first conductivity type into an active region between the device isolation region and the transistor portion on the semiconductor substrate; and

forming a control terminal by injecting impurities of the second conductivity type into a boundary between the photocharge generating portion and the device isolation region in a halo junction form.

7. The method of claim 6, further comprising:

forming a separating portion by injecting impurities of the first conductivity type between the photocharge generating portion and the control terminal.