Capping of metal interconnects in integrated circuit electronic devices
View Patent ↗A multilayer metal cap over a metal-filled interconnect feature in a dielectric layer for incorporation into a multilayer integrated circuit device, and a method for forming the cap.
1. A method for forming a multilayer metal cap over a metal-filled interconnect feature in a dielectric layer for incorporation into a multilayer integrated circuit device comprising:
depositing a first metal cap layer having a thickness between about 100 and about 300 angstroms over the metal-filled interconnect feature in a first deposition process which constitutes electroless metal deposition from a first electroless solution comprising a source of Co ions and a reducing agent;
depositing a second metal cap layer over the first metal cap layer in a second deposition process which constitutes electroless metal deposition from a second electroless solution which comprises a source of Ni ions and a reducing agent to thereby form the multilayer metal cap as a permanent component distinct from the metal-filled interconnect feature.
2. The method of claim 1 wherein the first electroless solution comprises the source of Co ions and a borane-based reducing agent.
3. The method of claim 1 wherein the first deposition process is self-aligning in that the first metal cap layer is selectively deposited onto the metal-filled interconnect and the second deposition process is self-aligning in that the second metal cap layer is selectively deposited onto the first metal cap layer.
4. The method of claim 1 wherein the metal-filled interconnect feature is a Cu-filled interconnect feature, and the first metal cap layer comprises a metal or metal alloy which is substantially immiscible with Cu.
5. The method of claim 1 comprising discontinuing deposition between the first deposition process and the second deposition process.
6. The method of claim 1 wherein the first metal cap layer comprises a Co-based alloy and the second metal cap layer comprises a Ni-based alloy.
7. The method of claim 1 wherein:
the metal-filled interconnect feature is a Cu-filled interconnect feature;
the second deposition process is an electroless deposition process which is self-aligning in that the second metal cap layer is selectively deposited on the first metal cap layer;
the first deposition process is self-aligning in that the second metal cap layer is selectively deposited on the first metal cap layer; and
the first deposition process is distinct from the second deposition process in that the first deposition process employs a first electroless solution which has a first solution composition distinct from, and prepared separately from, a second electroless solution having a second solution composition employed in the second deposition process.
8. The method of claim 1 wherein:
the metal-filled interconnect feature is a Cu-filled interconnect feature;
the second deposition process is an electroless deposition process;
the first deposition process is distinct from the second deposition process in that the first deposition process employs a first electroless solution which has a first solution composition distinct from, and prepared separately from, a second electroless solution having a second solution composition employed in the second deposition process;
the second metal cap layer has a thickness greater than about 100 angstroms; and
the first metal cap layer having a thickness between about 100 and about 300 angstroms comprises a Co-based alloy.
9. The method of claim 1 wherein:
the metal-filled interconnect feature is a Cu-filled interconnect feature;
the second deposition process is an electroless deposition process;
the first deposition process is distinct from the second deposition process in that the first deposition process employs a first electroless solution which has a first solution composition distinct from, and prepared separately from, a second electroless solution having a second solution composition employed in the second deposition process;
the second metal cap layer comprises a Ni-based alloy and has a thickness greater than about 100 angstroms; and
the first metal cap layer having a thickness between about 100 and about 300 angstroms comprises a Co-based alloy.
10. The method of claim 8 wherein said Co-based alloy is Co-B.
11. The method of claim 8 wherein said Co-based alloy is Co-B-P.
12. The method of claim 8 wherein said Co-based alloy is Co-W-B-P.
13. The method of claim 8 wherein said Co-based alloy is Co-B-W.
14. The method of claim 9 wherein said Co-based alloy is Co-B.
15. The method of claim 9 wherein said Co-based alloy is Co-B-P.
16. The method of claim 9 wherein said Co-based alloy is Co-W-B-P.
17. The method of claim 9 wherein said Co-based alloy is Co-B-W.