Stacked semiconductor structure and method

1. A method comprising:

depositing a first dielectric layer over a first chip comprising a plurality of first active circuits and a first connection pad;

patterning the first dielectric layer to form a first opening over the first connection pad;

filling the first opening with a first conductive material to form a connector in contact with the first connection pad;

depositing a second dielectric layer over the first dielectric layer;

patterning the second dielectric layer to form a second opening over the connector;

filling the second opening with a second conductive material to form a first bonding pad in contact with the connector, wherein a width of the first bonding pad is different from a width of the connector;

stacking a second chip on the first chip, wherein the second chip comprises a plurality of second active circuits and a second bonding pad; and

bonding the first chip and the second chip together to form a stacked semiconductor device through applying a hybrid bonding process to the first bonding pad and the second bonding pad.

2. The method of claim 1 , further comprising:

depositing a third dielectric layer over the second chip;

patterning the third dielectric layer to form a third opening; and

filling the third opening with a third conductive material to form the second bonding pad.

3. The method of claim 2 , wherein:

a width of the second bonding pad is greater than the width of the first bonding pad; and

the width of the first bonding pad is greater than the width of the connector.

4. The method of claim 2 , further comprising:

the first conductive material is tungsten;

the second conductive material is copper; and

the third conductive material is copper.

5. The method of claim 1 , further comprising:

after the step of applying the hybrid bonding process to the first bonding pad and the second bonding pad, placing the stacked semiconductor device into a chamber with inert gases, and

applying an annealing process to the stacked semiconductor device.

6. The method of claim 1 , wherein:

after the step of applying the hybrid bonding process to the first bonding pad and the second bonding pad, a homogeneous layer is formed between the first bonding pad and the second bonding pad.

7. The method of claim 1 , further comprising:

thinning a non-bonding side of the second chip;

removing portions of a substrate of the second chip to expose an interconnect structure of the second chip; and

forming a second connection pad on the interconnect structure of the second chip.

8. A method comprising:

depositing a first dielectric layer over a first chip comprising a plurality of first connection pads;

patterning the first dielectric layer to form a plurality of first openings over the respective first connection pads;

filling the plurality of first openings with a first conductive material to form a plurality of connectors over the respective first connection pads;

forming a plurality of first bonding pads over the respective connectors, wherein a width of a first bonding pad is greater than a width of a corresponding connector;

depositing a second dielectric layer over a second chip;

patterning the second dielectric layer to form a plurality of second openings;

filling the plurality of second openings with a second conductive material to form a plurality of second bonding pads in the second dielectric layer; and

bonding the first chip and the second chip together to form a stacked chip structure through applying a thermal process to the first chip and the second chip and forming a homogenous layer between two adjacent bonding pads.

9. The method of claim 8 , further comprising:

stacking the second chip on the first chip, wherein a second bonding pad of the second chip is aligned with a corresponding first bonding pad of the first chip.

10. The method of claim 8 , wherein:

the first chip comprises a first substrate and a first interconnect structure over the first substrate; and

the second chip comprises a second substrate and a second interconnect structure over the second substrate, and wherein a non-substrate side of the second chip is face-to-face bonded on a non-substrate side of the first chip.

11. The method of claim 10 , further comprising:

thinning a substrate side of the second chip;

removing portions of the second substrate of the second chip to expose the second interconnect structure; and

forming a plurality of connection pads on the second interconnect structure.

12. The method of claim 10 , wherein:

the plurality of first bonding pads and the plurality of second bonding pads are formed of copper; and

the homogenous layer is formed as a result of copper inter-diffusion between the two adjacent bonding pads.

13. The method of claim 10 , wherein:

the two adjacent bonding pads and the homogenous layer between the two adjacent bonding pads form a uniform bonded feature.

14. A method comprising:

depositing a first dielectric layer over a first chip comprising a first substrate, a first interconnect structure over the first substrate, and a first connection pad over the first interconnect structure, wherein a top surface of the first connection pad is lower than a top surface of the first dielectric layer;

patterning the first dielectric layer to form a first opening over the first connection pad;

filling the first opening with a first conductive material to form a first bonding pad over the first connection pad, wherein a width of the first connection pad is greater than a width of the first bonding pad;

depositing a second dielectric layer over a second chip comprising a second substrate and a second interconnect structure over the second substrate;

patterning the second dielectric layer to form a second opening;

filling the second opening with a second conductive material to form a second bonding pad, wherein a width of the second bonding pad is greater than the width of the first bonding pad;

stacking the second chip on the first chip; and

applying a hybrid bonding process to the first chip and the second chip to form a stacked chip device.

15. The method of claim 14 , further comprising:

during the hybrid bonding process, forming a homogenous layer between the first bonding pad and the second bonding pad.

16. The method of claim 14 , further comprising:

forming a connector between the first connection pad and the first bonding pad, wherein the width of the first bonding pad is greater than a width of the connector.

17. The method of claim 16 , wherein:

the first connection pad is formed of aluminum;

the connector is formed of tungsten;

the first bonding pad is formed of copper; and

the second bonding pad is formed of copper.

18. The method of claim 14 , further comprising:

after filling the first opening with the first conductive material, performing a first planarization process on the first conductive material until a top surface of the first dielectric layer is exposed.

19. The method of claim 14 , further comprising:

after filling the second opening with the second conductive material, performing a second planarization process on the second conductive material until a top surface of the second dielectric layer is exposed.

20. The method of claim 14 , further comprising:

thinning the second substrate of the second chip;

removing a portion of the second substrate of the second chip to expose the second interconnect structure; and

forming a connection pad on the second interconnect structure.