Photodetector for backside-illuminated sensor

• US 7,656,000 B2
• Filed: 05/24/2007
• Issued: 02/02/2010
• Est. Priority Date: 05/24/2007
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Hsu, Tzu-Hsuan, Wang, Ching-Chun, Yaung, Dun-Nian
• Primary Examiner(s): Nguyen; Dao H
• Assistant Examiner(s): NGUYEN, TRAM HOANG
• Application Number:
  US11/753,480
• Publication Number:
  US 20080290441A1
• Time in Patent Office: 985 Days
• Field of Search: 257/98, 257/E33.61, 257/E31.129, 257/E31.001, 257/E27.133, 257/219, 257/225, 257/79, 257291-294, 257E27082-E27083, 257460-462, 257/732, 257/432, 257/228, 257/21, 257/53, 257/80, 257/81, 257/83, 257/88, 257/184, 257232-233, 438/60, 438/75, 438/144
• US Class Current: 257/460
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers

Abstract

A backside-illuminated sensor including a semiconductor substrate. The semiconductor substrate has a front surface and a back surface. A plurality of pixels are formed on the front surface of the semiconductor substrate. At least one pixel includes a photogate structure. The photogate structure has a gate that includes a reflective layer.

Claims

1. A backside-illuminated sensor comprising:

a semiconductor substrate having a front surface and a back surface, wherein the semiconductor substrate is configured such that radiation incident the back surface is sensed by a plurality of pixels formed on the front surface; and

the plurality of pixels formed on the front surface of the semiconductor substrate, wherein at least one pixel comprises a photogate structure, the photogate structure having a gate including a reflective layer.

2. The sensor of claim 1, wherein the reflective layer is positioned on a side of the gate opposite to the semiconductor substrate.

3. The sensor of claim 1, wherein the at least one pixel includes an n-type photosensor.

4. The sensor of claim 1, wherein the reflective layer includes silicide.

5. The sensor of claim 1, wherein the reflective layer includes a silicide selected from the group consisting of nickel silicide, cobalt silicide, tungsten silicide, tantalum silicide, titanium silicide, platinum silicide, erbium silicide, and palladium silicide.

6. The sensor of claim 1, wherein the gate is a poly-silicide gate.

7. The sensor of claim 1, further comprising:

a transfer transistor, a reset transistor, a source follower transistor, and a selector transistor.

8. The sensor of claim 1, wherein the semiconductor substrate is between approximately 2 μ

m and 4 μ

m thick.

17. The sensor of claim 1, wherein the gate further includes a gate dielectric layer underlying the reflective layer.

18. The sensor of claim 1, wherein the gate further includes a gate electrode layer underlying the reflective layer.

9. A back-side illuminated sensor, comprising:

a substrate having a front surface and a back surface;

means for sensing radiation incident on the back surface of the substrate; and

means for reflecting radiation, the means for reflecting the radiation including a reflective layer formed on the front surface of the substrate, wherein the reflective layer is included in a gate structure formed on the front surface of the substrate.

10. The back-side illuminated sensor of claim 9, further comprising:

means for transferring a charge corresponding to the sensed radiation.

11. The sensor of claim 9, wherein the means for sensing radiation includes a gate structure, the reflective layer being formed on the gate structure.

12. The sensor of claim 9, wherein the reflective layer includes a silicide.

19. The sensor of claim 9, wherein the gate structure further includes a gate dielectric layer.

13. An image sensor comprising:

a semiconductor substrate comprising a photodetector including a gate having gate dielectric layer and a reflective layer formed on the gate dielectric layer, wherein the reflective layer is formed on the semiconductor substrate on a side of the semiconductor substrate opposite an incident radiation beam, wherein the incident radiation beam is to be detected by the photodetector.

14. The image sensor of claim 13, wherein the photodetector comprises a photogeneration region coupled to a gate.

15. The image sensor of claim 14, wherein the reflective layer is positioned over the photogeneration region.

16. The image sensor of claim 13, wherein the reflective layer comprises at least one of a silicide and a metal.