Anti-reflection structures for CMOS image sensors

• US 8,716,771 B2
• Filed: 03/13/2012
• Issued: 05/06/2014
• Est. Priority Date: 05/14/2008
• Status: Active Grant

• Current Assignee: Smartsens Technology (Cayman) Co., Ltd.
• Original Assignee: International Business Machines Corporation
• Inventors: Adkisson, James W., Ellis-Monaghan, John J., Gambino, Jeffrey P., Musante, Charles F.
• Primary Examiner(s): Mandala, Victor A
• Application Number:
  US13/418,706
• Publication Number:
  US 20120168835A1
• Time in Patent Office: 784 Days
• Field of Search: 257/258, 257/291, 257/293, 257/432, 257/436, 257/462, 257/E31.053, 257/E31.079, 257/E31.082
• US Class Current: 257/292
• CPC Class Codes: H01L 2224/04042 Bonding areas specifically adapted for wire connectors, e.g. wirebond pads
• CPC Class Codes: H01L 2224/05 of an individual bonding area
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48464 the other connecting portion not on the bonding area also being a ball bond, i.e. ball-to-ball
• CPC Class Codes: H01L 2224/4847 the connecting portion on the bonding area of the semiconductor or solid-state body being a wedge bond
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/73 Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/1462 Coatings
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14629 Reflectors
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01019 : Potassium [K]
• CPC Class Codes: H01L 2924/0102 : Calcium [Ca]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01032 : Germanium [Ge]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/12043 : Photo diode
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15311 : being a ball array, e.g. BGA
• CPC Class Codes: H01L 2924/15312 : being a pin array, e.g. PGA
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding
• CPC Class Codes: H01L 31/02165 : using interference filters, e.g. multilayer dielectric filters interference filters G02B5/28
• CPC Class Codes: H01L 31/0236 : Special surface textures
• CPC Class Codes: H01L 31/103 : the potential barrier being of the PN homojunction type
• CPC Class Codes: Y02E 10/50 : Photovoltaic [PV] energy

Abstract

Optical structures having an array of protuberances between two layers having different refractive indices are provided. The array of protuberances has vertical and lateral dimensions less than the wavelength range of lights detectable by a photodiode of a CMOS image sensor. The array of protuberances provides high transmission of light with little reflection. The array of protuberances may be provided over a photodiode, in a back-end-of-line interconnect structure, over a lens for a photodiode, on a backside of a photodiode, or on a window of a chip package.

Claims

1. A semiconductor structure comprising:

a photodiode located in a semiconductor layer;

a transistor located on said semiconductor layer, wherein a source of said transistor is of integral construction with said photodiode; and

a dielectric layer located overlying said photodiode, laterally surrounding and overlying a gate electrode of said transistor, and comprising a protuberance-containing dielectric portion which overlies said photodiode and includes an array of protuberances, wherein a pitch of said array of protuberances is less than 270 nm.

2. The semiconductor structure of claim 1, further comprising an intermediate dielectric layer vertically abutting said photodiode, said gate electrode, and said dielectric layer.

3. The semiconductor structure of claim 1, wherein said dielectric layer vertically abuts said photodiode and said gate electrode.

4. The semiconductor structure of claim 1, wherein said pitch is a sub-lithographic dimension.

5. The semiconductor structure of claim 1, wherein said dielectric layer further comprises a flat dielectric portion located over said gate electrode and a drain region of said transistor and having a same composition as said protuberance-containing dielectric portion.

6. A semiconductor structure comprising:

a photodiode located in a semiconductor layer;

a transistor located on said semiconductor layer, wherein a source of said transistor is of integral construction with said photodiode; and

a dielectric layer located overlaying said photodiode, laterally surrounding and overlying a gate electrode of said transistor, and comprising a protuberance-containing dielectric portion which overlies said photodiode and includes an array of protuberances, wherein said dielectric layer further comprises a flat dielectric portion located over said gate electrode and a drain region of said transistor and having a same composition as said protuberance-containing dielectric portion, and wherein said flat dielectric portion has a first thickness, and wherein each of said protuberances has a height from a base to an apex, and wherein said protuberance-containing dielectric portion comprises a constant thickness portion abutting each base of said protuberances and having a second thickness, wherein said first thickness is substantially equal to a sum of said second thickness and said height.

7. The semiconductor structure of claim 6, further comprising an intermediate dielectric layer vertically abutting said photodiode, said gate electrode, and said dielectric layer.

8. The semiconductor structure of claim 6, wherein said dielectric layer vertically abuts said photodiode and said gate electrode.

9. The semiconductor structure of claim 6, wherein a pitch of said array of protuberances is less than 270 nm.

10. The semiconductor structure of claim 9, wherein said pitch is a sub-lithographic dimension.

11. A semiconductor structure comprising:

a photodiode located in a semiconductor layer;

a dielectric material layer containing a lens and located over said photodiode, wherein said lens is located in an optical path of said photodiode; and

a protuberance-containing dielectric portion located directly on said dielectric material layer, wherein said protuberance-containing dielectric portion comprises an array of protuberances.

12. The semiconductor structure of claim 11, wherein said lens is a flat-top convex-bottom lens vertically abutting a bottom surface of said protuberance-containing dielectric portion.

13. The semiconductor structure of claim 11, wherein said lens is a convex-top flat-bottom lens embedded in said dielectric material layer and separated from and located underneath said protuberance-containing dielectric portion.

14. The semiconductor structure of claim 11, wherein said protuberance-containing dielectric portion has an interface with an ambient gas or vacuum.

15. The semiconductor structure of claim 11, further comprising a bond pad located in a metal pad area and having an exposed bond pad top surface, wherein dielectric material layer is located above said bond pad outside said metal pad area.

16. The semiconductor structure of claim 11, further comprising a flat dielectric portion having a same composition as, and being of integral construction as, said protuberance-containing dielectric portion, and vertically abutting said dielectric material layer.

17. The semiconductor structure of claim 16, wherein said flat dielectric portion has a first thickness, and wherein each of said protuberances has a height from a base to an apex, and wherein said protuberance-containing dielectric portion comprises a constant thickness portion abutting each base of said protuberances and having a second thickness, wherein said first thickness is substantially equal to a sum of said second thickness and said height.