Method for manufacturing image sensor

1. A method for manufacturing an image sensor structure, comprising:

forming a light-sensing region in a substrate;

forming a storage node adjacent to light-sensing region in the substrate; forming a front side isolation structure partially surrounding an upper portion of the light-sensing region;

forming a trench fully surrounding a bottom portion of the light-sensing region to expose a bottom surface of the front side isolation structure; forming a backside isolation structure in the trench: and wherein the front side isolation has an opening such that a portion of the light sensing region and the storage node are not separated by the front side isolation structure.

2. The method for manufacturing an image sensor structure as claimed in claim 1 , wherein the front side isolation structure is made of a first material and the backside isolation structure is made of a second material different from the first material.

3. The method for manufacturing an image sensor structure as claimed in claim 2 , wherein the first material is a dielectric material and the second material is metal.

4. The method for manufacturing an image sensor structure as claimed in claim 1 , further comprising:

forming a gate structure over a front side of the substrate, wherein the gate structure partially overlaps with the light sensing region and the front side isolation structure.

5. The method for manufacturing an image sensor structure as claimed in claim 1 , wherein the storage node partially overlaps with the backside isolation structure.

6. The method for manufacturing an image sensor structure as claimed in claim 1 , further comprising:

forming an interconnect structure layer over a frond side of the substrate; and

forming a light shielding layer over a backside of the substrate, wherein the light shielding layer overlaps with the front side isolation structure and the backside isolation structure.

7. The method for manufacturing an image sensor structure as claimed in claim 1 , wherein the bottom surface of the front side isolation structure is in direct contact with a top surface of the backside isolation structure.

8. A method for manufacturing an image sensor structure, comprising:

forming a light-sensing region in a substrate;

forming a storage node adjacent to the light-sensing region;

forming a first trench partially surrounding an upper portion of the light-sensing region in the substrate;

forming a front side isolation structure in the first trench;

forming a second trench surrounding a bottom portion of the light-sensing region and partially vertically overlaps with the storage node in the substrate; and

forming a backside isolation in the second trench.

9. The method for manufacturing an image sensor structure as claimed in claim 8 , wherein the front side isolation structure is formed before the second trench is formed.

10. The method for manufacturing an image sensor structure as claimed in claim 8 , wherein the front side isolation structure and the backside isolation structure are made of different materials.

11. The method for manufacturing an image sensor structure as claimed in claim 10 , wherein the front side isolation structure is in direct contact with the backside isolation structure.

12. The method for manufacturing an image sensor structure as claimed in claim 8 , wherein the substrate comprises a first wafer and a second wafer bonded to the first wafer, and the front side isolation structure is formed in the first wafer and the backside isolation structure is formed in the second wafer.

13. The method for manufacturing an image sensor structure as claimed in claim 8 , wherein a portion of the light sensing region and the storage node are not separated by the first isolation structure.

14. The method for manufacturing an image sensor structure as claimed in claim 8 , wherein the first isolation structure is separated from the second isolation structure by a portion of the substrate.

15. A method for manufacturing an image sensor structure, comprising:

forming a light-sensing region in a substrate;

forming a first trench from a front side of the substrate, wherein the first trench partially surrounds the light-sensing region;

filling a first material in the first trench to form a front side isolation structure;

forming a second trench from a backside of the substrate, wherein the second trench fully surrounds the light-sensing region; and

filling a second material in the second trench to form a backside isolation structure,

wherein the first material is different from the second material and is in direct contact with the second material, and the first material is a dielectric material and the second material is metal.

16. The method for manufacturing an image sensor structure as claimed in claim 15 , wherein a bottom surface of the front side isolation structure is exposed by the second trench.

17. The method for manufacturing an image sensor structure as claimed in claim 15 , further comprising:

forming a gate structure over the front side of the substrate,

wherein the gate structure overlaps with the backside isolation structure.

18. The method for manufacturing an image sensor structure as claimed in claim 17 , further comprising:

forming an interconnect structure layer over the frond side of the substrate; and

forming a light shielding layer over the backside of the substrate.

19. The method for manufacturing an image sensor structure as claimed in claim 18 , wherein the light shielding layer overlaps with the front side isolation structure and the backside isolation structure.

20. The method for manufacturing an image sensor structure as claimed in claim 19 , wherein a portion of the light sensing region and the storage node are not separated by the first isolation structure.