Image Sensor Element For Backside-Illuminated Sensor

• US 20090078973A1
• Filed: 09/24/2007
• Published: 03/26/2009
• Est. Priority Date: 09/24/2007
• 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
• Granted Patent: US 7,999,342 B2
• Time in Patent Office: Days
• US Class Current: 257/292
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures

Abstract

Provides is a backside-illuminated sensor including a semiconductor substrate having a front surface and a back surface. A plurality of image sensor elements are formed on the front surface of the semiconductor substrate. At least one of the image sensor elements includes a transfer transistor and a photodetector. The gate of the transfer transistor includes an optically reflective layer. The gate of the transfer transistor, including the optically reflective layer, overlies the photodetector. In one embodiment, the gate overlies the photodetector by at least 5%.

Claims

1. A backside-illuminated sensor comprising:

a semiconductor substrate having a front surface and a back surface; and

a plurality of image sensor elements formed on the front surface of the semiconductor substrate, wherein at least one image sensor element comprises a transfer transistor and a photodetector, and wherein a gate of the transfer transistor comprises a reflective layer and overlies the photodetector.

2. The sensor of claim 1, wherein the reflective layer overlies at least 5% of the photodetector.

3. The sensor of claim 1, further comprising

at least one well formed on the semiconductor substrate between the plurality of image sensor elements;

and

an isolation structure formed in the at least one well.

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

5. The sensor of claim 1, wherein the reflective layer includes a material selected from the group consisting of nickel silicide, cobalt silicide, tungsten silicide, tantalum silicide, titanium silicide, platinum silicide, erbium silicide, palladium silicide, Cu, W, Ti, Ta, TiN, TaN, and combinations thereof.

6. The sensor of claim 1, wherein the photodetector includes a photodiode.

7. The sensor of claim 1, wherein the photodetector includes a pinned-photodiode.

8. The sensor of claim 1, wherein the photodetector is operable to detect radiation incident on the back surface of the substrate, and wherein the photodetector is further operable to detect radiation reflected from the reflective layer.

9. The sensor of claim 1, wherein the at least one image sensor element further comprises a reset transistor, a source follower transistor, and a selector transistor.

10. The sensor of claim 1, wherein the semiconductor substrate includes a thickness between approximately 1 μ

m and 5 μ

m.

11. A back-side illuminated sensor, comprising:

a substrate;

a transfer gate formed on the substrate and including an optically reflective material;

a photogeneration region formed on the substrate underlying the transfer gate, whereby the transfer gate overlies at least a portion of the photogeneration region.

12. The sensor of claim 11, the transfer gate overlies at least approximately 25% of the photogeneration region.

13. The sensor of claim 11, the transfer gate overlies at least approximately 50% of the photogeneration region.

14. The sensor of claim 11, further comprising:

a floating diffusion region formed on the substrate adjacent to and at one side of the transfer gate, the one side being away from and opposite the photogeneration region.

15. The sensor of claim 11, further comprising:

an implanted region formed on the photogeneration region, wherein the implanted region has a first type of conductivity and the photogeneration region has a second type of conductivity, and wherein the substrate has the first type of conductivity.

16. The sensor of claim 11, further comprising

a pinned photodiode including the photogeneration region.

17. An apparatus comprising:

a substrate including a first surface and a second surface;

a photodetector formed adjacent the second surface of the substrate;

a transistor including an optically reflective layer formed on the second surface of substrate and disposed over the photodetector, wherein the optically reflective layer is configured to reflect a radiation beam incident on the first surface of the substrate towards the photodetector.

18. The apparatus of claim 17, wherein the transistor is a transfer transistor and a gate electrode of the transfer transistor includes the optically reflective layer.

19. The apparatus of claim 17, wherein the radiation beam incident the first surface passes through the photodetector before being reflected by the optically reflective layer.