Image sensor and method for fabricating the same

1. An image sensor, comprising:

a second semiconductor substrate including a second metal interconnection and a second interlayer dielectric;

a second via penetrating the second interlayer dielectric so that the second via is connected to the second metal interconnection;

a first semiconductor substrate on the second interlayer dielectric, the first semiconductor substrate having a unit pixel;

a pre-metal dielectric on the first semiconductor substrate;

a first via penetrating the pre-metal dielectric and the first semiconductor substrate, the first via being connected to the second via;

a first interlayer dielectric on the pre-metal dielectric including the first via;

a first metal interconnection on the first interlayer dielectric and connected to the first via and the unit pixel;

a conductive barrier layer on the first metal interconnection; and

a color filter and a microlens on the first interlayer dielectric on the unit pixel.

2. The image sensor according to claim 1 , wherein the first metal interconnection comprises copper (Cu).

3. The image sensor according to claim 1 , wherein the conductive barrier layer comprises cobalt (Co) or nickel (Ni) alloy.

4. The image sensor according to claim 1 , wherein the first metal interconnection has a top surface lower than that of the first interlayer dielectric, such that the first metal interconnection and the first interlayer dielectric have a height difference.

5. The image sensor according to claim 1 , wherein the second metal interconnection comprises copper (Cu) or aluminum (Al).

6. The image sensor according to claim 1 , wherein the conductive barrier layer has at top surface substantially even with the top surface of the first interlayer dielectric.

7. The image sensor according to claim 1 , wherein the first via and the second via comprise the same material.

8. The image sensor according to claim 1 , wherein the second semiconductor substrate provides metal interconnections for connection to a power line and an external signal line.

9. A method for fabricating an image sensor, the method comprising:

forming a pre-metal dielectric on a first semiconductor substrate including a unit pixel;

forming a first via penetrating the pre-metal dielectric and at least a portion of the first semiconductor substrate corresponding to a non unit-pixel region;

forming a first interlayer dielectric on the first semiconductor substrate including the first via;

forming a first metal interconnection on the first interlayer dielectric such that the first metal interconnection is connected to the unit pixel and the first via;

forming a conductive barrier layer on the first metal interconnection;

forming a color filter and a microlens on the first interlayer dielectric for the unit pixel;

preparing a second semiconductor substrate including a second metal interconnection and a second interlayer dielectric;

forming a second via penetrating the second interlayer dielectric, such that the second via is connected to the second metal interconnection; and

bonding the first via of the first semiconductor substrate with the second via of the second semiconductor substrate.

10. The method according to claim 9 , wherein the forming of the first metal interconnection comprises:

forming a trench in the first interlayer dielectric;

forming a copper plating layer in the trench; and

planarizing the copper plating layer.

11. The method according to claim 10 , wherein the planarizing of the copper plating layer comprises performing a chemical mechanical polishing process until a height difference between the top surface of the first metal interconnection and the top surface of the first interlayer dielectric is established.

12. The method according to claim 9 , wherein the first metal interconnection is formed such that the first metal interconnection and the interlayer dielectric have a height difference.

13. The method according to claim 12 , wherein the forming of the conductive barrier layer comprises forming the conductive barrier layer on only the first metal interconnection and removing the height difference.

14. The method according to claim 9 , wherein the forming of the conductive barrier layer comprises performing an electroless plating process.

15. The method according to claim 14 , wherein the etching of the backside of the first semiconductor substrate comprises performing a back grinding process to remove a thickness of about 10-50 μm from the backside of the first semiconductor substrate.

16. The method according to claim 9 , wherein the conductive barrier layer comprises cobalt (Co) or nickel (Ni) alloy.

17. The method according to claim 9 , wherein the second metal interconnection comprises copper (Cu) or aluminum (Al).

18. The method according to claim 9 , wherein the bonding of the first via of the first semiconductor substrate with the second via of the second semiconductor substrate comprises:

etching a backside of the first semiconductor substrate to expose the first via;

forming a via hole exposing the metal interconnection of the second semiconductor substrate, and depositing a metal layer in the via hole to form a second via; and

aligning the first via and the second via, and performing a process of bonding the first semiconductor substrate with the second semiconductor substrate.

19. The method according to claim 9 , wherein the bonding of the first via of the first semiconductor substrate with the second via of the second semiconductor substrate comprises bonding the first semiconductor substrate and the second semiconductor substrate together by performing a polymer bonding, a silicon fusion bonding, a copper-to-copper bonding, or an eutectic bonding.

20. The method according to claim 9 , wherein the first via and the second via are formed of the same material.