Front-to-back bonding with through-substrate via (TSV)

1. A method for forming a semiconductor device structure, comprising:

forming a conductive feature in a first wafer, wherein the conductive feature is formed in an insulating layer and above a first transistor;

forming a first bonding layer over the conductive feature;

forming a second bonding layer over a second wafer;

bonding the first wafer and the second wafer by bonding the first bonding layer and the second bonding layer;

thinning a front-side of the second wafer;

forming a second transistor in the front-side of the second wafer;

after forming the second transistor in the front-side of the second wafer, forming at least one first TSV in the second wafer, wherein a bottom surface of the first TSV is level with a bottom surface of the first bonding layer; and

forming a second TSV through the first wafer and the second wafer, wherein the second TSV is through the insulating layer.

2. The method as claimed in claim 1 , wherein the second TSV directly contact a redistribution (RDL) structure formed over a backside of the first wafer.

3. The method as claimed in claim 2 , further comprising:

thinning a backside of the first wafer to expose the second TSV.

4. The method as claimed in claim 1 , wherein the second TSV has a second height greater than a first height of the first TSV.

5. The method as claimed in claim 1 , further comprising:

forming an interconnect structure over the front-side of the second wafer, wherein the interconnect structure is electrically connected to the conductive feature of the first wafer.

6. The method as claimed in claim 1 , wherein the first bonding layer and the second bonding layer are made of silicon oxide, silicon oxynitride or silane oxide.

7. The method as claimed in claim 1 , wherein no devices are formed in the second wafer before the step of thinning the front-side of the second wafer.

8. A method for forming a semiconductor device structure, comprising:

bonding a first semiconductor wafer to a second semiconductor wafer by a bonding layer, wherein the bonding layer is formed between the first semiconductor wafer and the second semiconductor wafer, wherein a first transistor is formed over a front-side of the first semiconductor wafer;

forming a conductive feature in an insulating layer in the first semiconductor wafer, wherein the conductive feature is above the first transistor;

thinning a portion of the second semiconductor wafer to form an exposed surface;

forming a second transistor in the exposed surface of the second semiconductor wafer;

after forming the second transistor in the exposed surface of the second semiconductor wafer, forming a first TSV in the second semiconductor wafer, wherein the first TSV passes through the bonding layer, wherein the step of forming the conductive feature comprises forming a first surface of the conductive feature having a first portion in direct contact with the bonding layer and a second portion in direct contact with the first TSV; and

forming a second TSV through a portion of the first wafer and the second wafer, wherein the second TSV is in direct contact with the insulating layer.

9. The method as claimed in claim 8 , further comprising:

forming an interconnect structure over the second semiconductor wafer, wherein the interconnect structure is electrically connected to a conductive feature of the first semiconductor wafer through the first TSV.

10. The method as claimed in claim 9 , wherein the interconnect structure comprises a first conductive line and a second conductive line, the first conductive line has a first surface facing a top surface of the first TSV.

11. The method as claimed in claim 8 , further comprising:

forming a first redistribution (RDL) structure on a backside of the first semiconductor wafer, wherein the second TSV contacts with the first RDL structure.

12. The method as claimed in claim 11 , wherein forming the first RDL structure comprises:

forming a metal pad on a bottom surface of the second TSV;

forming an under bump metallization (UBM) layer on the metal pad; and

forming a conductive element on the UBM layer.

13. A method for forming a semiconductor device structure, comprising:

forming a first transistor in a first wafer;

forming a conductive feature in an insulating layer and above the first transistor;

forming a first bonding layer over the conductive feature;

forming a second bonding layer over a second wafer;

bonding the first bonding layer and the second bonding layer;

thinning a portion of the second wafer;

forming a second transistor in a front-side of the second wafer;

after forming the second transistor in the front-side of the second wafer, forming a first TSV through the second wafer, such that the first TSV stops at the first bonding layer;

forming a second TSV through the second wafer and a portion of the first wafer, wherein the second TSV is in direct contact with the insulating layer; and

after forming the second TSV, thinning the first wafer to expose a bottom surface of the second TSV.

14. The method as claimed in claim 13 , further comprising:

forming a first redistribution (RDL) structure on a backside of the first wafer, wherein the second TSV directly contacts with the first RDL structure.

15. The method as claimed in claim 13 , wherein the first bonding layer and the second bonding layer made of silicon oxide, silicon oxynitride or silane oxide.

16. The method as claimed in claim 13 , wherein the first TSV as a first depth, the second TSV has a second depth greater than the first depth.

17. The method as claimed in claim 13 , wherein the first TSV contacts with the conductive feature.

18. The method as claimed in claim 13 , further comprising:

forming an interconnect structure over the front-side of the second wafer, wherein the interconnect structure comprises a first conductive line and a second conductive line, the first conductive line has a first surface facing a top surface of the first TSV.

19. The method as claimed in claim 1 , further comprising:

forming a first transistor in the first wafer;

forming a conductive feature over the first transistor, such that the conductive feature has a first surface which is in direct contact with the first bonding layer and the first TSV.

20. The method as claimed in claim 8 , further comprising:

after forming the second TSV, thinning the first semiconductor wafer to expose a bottom surface of the second TSV.