Color image sensor with embedded microlens array

• US 20010010952A1
• Filed: 03/09/2001
• Published: 08/02/2001
• Est. Priority Date: 12/23/1999
• Status: Active Grant

• Current Assignee: Intellectuals High-Tech KFT
• Original Assignee: Tower Semiconductor Limited
• Inventors: Abramovich, Irit
• Granted Patent: US 6,362,498 B2
• Time in Patent Office: Days
• US Class Current: 438/151
• CPC Class Codes: H01L 27/14601 Structural or functional details thereof
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements

Abstract

A method for producing a color CMOS image sensor including a matrix of pixels (e.g., CMOS APS cells) that are fabricated on a semiconductor substrate. A silicon-nitride layer is deposited on the upper surface of the pixels, and is etched using a reactive ion etching (RIE) process to form microlenses. A protective layer including a lower color transparent layer formed from a polymeric material, a color filter layer and an upper color transparent layer are then formed over the microlenses. Standard packaging techniques are then used to secure the upper color transparent layer to a glass substrate.

Claims

1. A method for forming a microlens over an image sensing element in an image sensor, the method comprising:

depositing a dielectric layer over the image sensing element, the dielectric layer having a first index of refraction;

reactive ion etching the dielectric layer to form a microlens; and

forming a protective layer on the microlens, the protective layer having a second index of refraction;

wherein the first index of refraction of the dielectric layer is different from the second index of refraction of the protective layer.

2. The method according to

claim 1

, wherein depositing the dielectric layer comprises depositing silicon nitride.

3. The method according to

claim 1

, wherein reactive ion etching comprises:

depositing photoresist layer on the dielectric layer;

forming the photoresist layer into a lens-shaped photoresist portion; and

performing an anisotropic reactive ion etching process such that the lens-shaped photoresist portion is copied into the dielectric layer, thereby forming the microlens.

4. The method according to

claim 1

, wherein forming the protective layer comprises depositing packaging adhesive directly onto the microlens.

5. The method according to

claim 1

, wherein forming the protective layer comprises:

depositing a lower color transparent layer over the microlens;

planarizing the lower color transparent layer;

forming a color filter layer on the lower color transparent layer; and

depositing an upper color transparent layer on the color filter layer.

6. The method according to

claim 5

, further comprising:

applying a cement layer to the upper color transparent layer; and

attaching a packaging substrate to the cement layer.

7. The method according to

claim 1

, further comprising attaching a packaging substrate to the protective layer.

8. The method according to

claim 1

, further comprising:

depositing a passivation layer over the image sensing element;

planarizing the passivation layer; and

depositing an oxi-nitride layer on an upper surface of the passivation layer,

wherein depositing the dielectric layer over the image sensing element comprises depositing a silicon-nitride layer on an upper surface of the oxi-nitride layer.

9. A method for forming a microlens over an image sensing element in a color image sensor, the method comprising:

depositing a silicon-nitride layer over the image sensing element;

etching the silicon-nitride layer to form a microlens;

forming a first color transparent layer on the microlens; and

forming a color filter on the first color transparent layer.

10. The method according to

claim 9

, further comprising forming a second color transparent layer on the color filter.

11. The method according to

claim 9

, wherein etching comprises:

depositing photoresist layer on the silicon-nitride layer;

forming the photoresist layer into a lens-shaped photoresist portion; and

performing an anisotropic reactive ion etching process such that the lens-shaped photoresist portion is copied into the silicon-nitride layer, thereby forming the microlens.

12. The method according to

claim 9

, further comprising:

applying a cement layer to the upper color transparent layer; and

attaching a packaging substrate to the cement layer.

13. The method according to

claim 9

, further comprising:

depositing a passivation layer over the image sensing element;

planarizing the passivation layer; and

depositing an oxi-nitride layer on an upper surface of the passivation layer,

wherein the silicon-nitride layer is deposited on an upper surface of the oxi-nitride layer.

14. An image sensor comprising:

an image sensing element formed in a semiconductor substrate;

a microlens located over the image sensing element, the microlens being formed from a dielectric material having a first index of refraction; and

a protective layer formed on the microlens, the protective layer having a second index of refraction,

wherein a first index of refraction of the dielectric material is different from the second index of refraction of the protective layer.

15. The image sensor according to

claim 14

, wherein the dielectric material is silicon-nitride.

16. The image sensor according to

claim 14

, wherein the protective layer comprises packaging cement.

17. The image sensor according to

claim 14

, wherein the protective layer comprises:

a lower color transparent layer formed on the microlens;

a color filter layer formed on the lower color transparent layer; and

an upper color transparent layer formed on the color filter layer.

18. The image sensor according to

claim 17

, wherein the lower color transparent layer comprises an acrylic polymer.

19. The image sensor according to

claim 17

, further comprising a packaging substrate attached to an upper surface of the upper color transparent layer.

20. The image sensor according to

claim 14

, further comprising:

a passivation layer formed over the image sensing element; and

an oxi-nitride layer formed on an upper surface of the passivation layer,

wherein the silicon-nitride layer Is deposited on an upper surface of the oxi-nitride layer.