Method for fabricating CMOS image sensor

• US 7,435,615 B2
• Filed: 07/18/2005
• Issued: 10/14/2008
• Est. Priority Date: 07/20/2004
• Status: Expired due to Fees

• Current Assignee: Dongbuanam Semiconductor, Inc. (DB HiTek Co., Ltd.)
• Original Assignee: DONGBU ELECTRONICS CO., LTD. (DB HiTek Co., Ltd.)
• Inventors: Kim, Su Kon
• Primary Examiner(s): Lee, Eugene
• Assistant Examiner(s): Gumedzoe, Peniel M
• Application Number:
  US11/184,289
• Publication Number:
  US 20060019425A1
• Time in Patent Office: 1,184 Days
• Field of Search: 257/E31.127, 257/E27.133, 438 69- 72
• US Class Current: 438/70
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements

Abstract

A method for fabricating a CMOS image sensor improves the characteristics of device by preventing a pad from being contaminated without damaging a micro-lens. The method includes steps of forming a device protection layer on a semiconductor substrate including at least one photo-sensing device and at least one metal pad disposed in a logic circuit area corresponding to the at least one photo-sensing device, the device protection layer covering the at least one metal pad; forming each of a first planarization layer, a color filter layer, and a second planarization layer in sequence on the device protection layer in correspondence with the at least one photo-sensing device; forming on the second planarization layer a material layer for micro-lens formation; exposing a predetermined portion of the metal pad by selectively etching the device protection layer; and forming a micro-lens for directing incident light onto the at least one photo-sensing device by reflowing, after the exposing step, the material layer for micro-lens formation.

Claims

1. A method for fabricating CMOS image sensor, comprising:

forming a device protection layer on a semiconductor substrate including at least one photo-sensing device and at least one metal pad disposed in a logic circuit area corresponding to the at least one photo-sensing device, the device protection layer covering the at least one metal pad;

forming each of a first planarization layer, a color filter layer, and a second planarization layer in sequence on the device protection layer in correspondence with the at least one photo-sensing device;

forming on the second planarization layer a material layer for micro-lens formation while the device protection layer covers the at least one metal pad;

exposing a predetermined portion of the metal pad by selectively etching the device protection layer, after forming the material layer; and

forming a micro-lens for directing incident light onto the at least one photo-sensing device by reflowing, after said exposing the material layer for micro-lens formation.

2. The method of claim 1, wherein forming said material layer comprises:

patterning the material layer for micro-lens formation according to a pixel size of the CMOS image sensor.

3. The method of claim 2, wherein said patterning is performed before said exposing.

4. The method of claim 1, wherein reflowing the material layer imparts the micro-lens with a convex upper surface for focusing incident light onto the at least one photo-sensing device.

5. The method of claim 1, wherein the device protection layer comprises an undoped silicate glass layer on the metal pad and a silicon nitride layer on the undoped silicate glass layer.

6. The method of claim 1, further comprising:

forming first and second barrier layers for improving conductivity with respect to lower and upper surfaces of the metal pad, respectively.

7. The method of claim 6, wherein the first and second barrier layers comprise at least one of titanium and titanium nitride.

8. The method of claim 6, wherein forming the first and second barrier layers comprises chemical mechanical polishing.

9. The method of claim 1, wherein the predetermined portion of the metal pad corresponds to a surface of the metal pad for enabling a wire bonding with respect to the metal pad during a packaging process of the CMOS image sensor.

10. The method of claim 1, wherein the at least one photo-sensing device comprises a photodiode.

11. A method for fabricating a CMOS image sensor, comprising:

forming a device protection layer on a semiconductor substrate including at least one photo-sensing device and at least one metal pad in a logic circuit area corresponding to the at least one photo-sensing device, the device protection layer covering the at least one metal pad;

forming a first planarization layer, a color filter layer, and a second planarization layer in sequence on the device protection layer over the at least one photo-sensing device;

forming a material layer on the second planarization layer while the device protection layer continues to cover the metal pad;

after forming the material layer, exposing a predetermined portion of the metal pad by selectively etching the device protection layer; and

reflowing the material layer to form a micro-lens.

12. The method of claim 11, said material layer forming comprising:

patterning the material layer according to a pixel size of the CMOS image sensor.

13. The method of claim 11, further comprising bonding a wire to the metal pad.

14. The method of claim 11, wherein said micro-lens directs incident light onto the at least one photo-sensing device.

15. The method of claim 14, wherein said micro-lens has a convex upper surface.

16. The method of claim 12, wherein said material layer is patterned before said predetermined portion of said metal pad is exposed.

17. The method of claim 11, wherein said device protection layer comprises an undoped silicate glass layer on the metal pad.

18. The method of claim 17, wherein said device protection layer comprises a silicon nitride layer on the undoped silicate glass layer.

19. The method of claim 11, wherein forming the metal pad comprises forming a first barrier layer on an insulating layer, forming an aluminum or copper pad thereon, and forming a second barrier layer on the aluminum or copper pad.

20. The method of claim 19, wherein the first and second barrier layers comprise at least one of titanium and titanium nitride.