Method of direct plating of copper on a ruthenium alloy

• US 20060283716A1
• Filed: 03/09/2006
• Published: 12/21/2006
• Est. Priority Date: 07/08/2003
• Status: Abandoned Application

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Zhu, Lei, Rosenfeld, Aron, Hafezi, Hooman, Sun, Zhi-Wen, Chung, Hua
• Application Number:
  US11/373,635
• Publication Number:
  US 20060283716A1
• Time in Patent Office: Days
• US Class Current: 205/291
• CPC Class Codes: C25D 3/38 of copper
• CPC Class Codes: C25D 5/10 Electroplating with more than one layer of the same or of different metals for bearings C25D7/10
• CPC Class Codes: C25D 5/18 Electroplating using modulated, pulsed or reversing current
• CPC Class Codes: C25D 5/34 Pretreatment of metallic surfaces to be electroplated
• CPC Class Codes: C25D 5/617 Crystalline layers
• CPC Class Codes: H01L 21/2885 using an external electrical current, i.e. electro-deposition
• CPC Class Codes: H01L 21/76843 formed in openings in a dielectric
• CPC Class Codes: H01L 21/76846 Layer combinations
• CPC Class Codes: H01L 21/76861 Post-treatment or after-treatment not introducing additional chemical elements into the layer
• CPC Class Codes: H01L 21/76862 Bombardment with particles, e.g. treatment in noble gas plasmas; UV irradiation
• CPC Class Codes: H01L 21/76868 Forming or treating discontinuous thin films, e.g. repair, enhancement or reinforcement of discontinuous thin films
• CPC Class Codes: H01L 21/76873 for electroplating
• CPC Class Codes: H01L 21/76877 Filling of holes, grooves or trenches, e.g. vias, with conductive material
• CPC Class Codes: H01L 23/53238 Additional layers associated with copper layers, e.g. adhesion, barrier, cladding layers
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A method is disclosed for depositing a copper seed layer onto a substrate surface, generally onto a barrier layer that is an alloy of a group VIII metal and a refractory metal. In one aspect, the alloy consists of at least 50% ruthenium and the balance a copper diffusion barrier material. A copper layer is electroplated on the alloy directly. In one aspect, the surface of the barrier layer is conditioned prior to plating to improve adhesion and reduce the critical current density for plating on the barrier layer. The conditioning may include cathodic pre-treatment or a plasma pre-treatment in a hydrogen or hydrogen/helium mixture. In one aspect, the substrate surface is immersed in an acidic plating bath and a nucleation waveform is applied to form a seed layer. In another aspect, the substrate is immersed in a neutral or alkaline copper solution that includes complexed copper ions.

Claims

1. A method of processing a substrate, comprising:

providing a dielecric layer on a substrate;

forming features into the surface of the dielectric layer;

depositing an electrically continuous barrier/adhesion layer onto the surface of the dielectric layer, wherein the barrier/adhesion layer comprises an alloy, wherein at least 50 atomic % of the alloy comprises a metal from the group consisting of ruthenium, rhodium, palladium, cobalt, nickel, osmium, iridium, platinum and combinations thereof and wherein the balance of the alloy is selected from the group consisting of tantalum, titanium, zirconium, hafnium, niobium, molybdenum, tungsten and combinations thereof; and

directly plating a first copper layer onto the barrier/adhesion layer, the first copper layer being an electrically continuous layer, wherein the process of directly plating a first copper layer comprises;

placing the barrier/adhesion layer into contact with a copper solution, wherein the copper solution comprises copper ions; and

applying a first plating waveform to the barrier/adhesion layer.

2. The method of claim 1, further comprising conditioning the surface of the electrically continuous barrier/adhesion layer prior to plating the first copper layer.

3. The method of claim 2, wherein the process of conditioning the surface of the barrier/adhesion layer comprises:

placing the substrate in a plasma-etch chamber;

flowing a process gas into the chamber, wherein the process gas comprises at least one of the group consisting of hydrogen, a helium-hydrogen mixture and combinations thereof; and

generating a plasma in the chamber.

4. The method of claim 2, wherein the process of conditioning the surface of the barrier/adhesion layer comprises cathodically pre-treating the barrier/adhesion layer in an acid-containing bath.

5. The method of claim 4, wherein the acid-containing bath contains sulfuric acid, wherein the concentration of the sulfuric acid is in the range between about 10 g/l and about 50 g/l.

6. The method of claim 4, wherein cathodically pre-treating the barrier/adhesion layer further comprises performing the cathodic pre-treatment at a current density in the range of about 1 mA/cm² to about 5 mA/cm².

7. The method of claim 4, wherein the cathodic pre-treatment is performed at a potential in the range of about 0 volt to about −

1.0 volt vs. AgCl.

8. The method of claim 2, wherein the process of conditioning the surface of the barrier/adhesion layer comprises cathodically pre-treating the barrier/adhesion layer in an alkaline or neutral bath.

9. The method of claim 2, wherein the process of directly plating a first copper layer onto the barrier/adhesion layer occurs less than about 150 minutes after the process of conditioning the surface of the barrier/adhesion layer.

10. The method of claim 1, wherein the process of applying a first plating waveform to the barrier/adhesion layer further comprises:

applying a nucleation waveform to the barrier/adhesion layer, the nucleation waveform being configured to generate a first current density across the barrier/adhesion layer greater than a critical current density.

11. The method of claim 1, further comprising applying a second plating waveform to the first copper layer while in contact with the copper solution to deposit a second copper layer onto the first copper layer.

12. The method of claim 1, wherein the copper solution further comprises a complexing agent and a pH equal to or greater than 7.0.

13. The method of claim 12, further comprising depositing a second copper layer onto the first copper layer, wherein the process of depositing the second copper layer comprises:

placing the first copper layer into a second copper solution, wherein the second copper solution is acidic and includes free-copper ions; and

applying a second plating waveform to the first copper layer.

14. The method of claim 1, wherein the barrier/adhesion layer comprises a Ru—

Ta alloy of at least about 50 atomic % ruthenium and wherein the balance of the alloy is tantalum.

15. The method of claim 14, wherein the features have sidewalls and the thickness of the barrier/adhesion layer is between about 10 Å

and about 50 Å

on the sidewalls.

16. The method of claim 2 wherein the process of conditioning the surface of the barrier/adhesion layer and the process of plating the first copper layer take place on the same copper plating system.

17. A method of processing a substrate, comprising:

providing a dielecric layer on a substrate;

forming features into the surface of the dielectric layer;

depositing an electrically continuous barrier/adhesion layer onto the surface of the dielectric layer, wherein the barrier/adhesion layer comprises a Ru—

Ta alloy of between about 70 atomic % and 95 atomic % ruthenium and wherein the balance of the alloy is tantalum;

conditioning the surface of the electrically continuous barrier/adhesion layer prior to plating the first copper layer; and

directly plating a first copper layer onto the barrier/adhesion layer, the first copper layer being an electrically continuous layer wherein the process of directly plating a first copper layer comprises;

placing the barrier/adhesion layer into contact with a copper solution, wherein the copper solution comprises copper ions; and

applying a first plating waveform to the barrier/adhesion layer.

18. The method of claim 17, wherein the process of conditioning the surface of the barrier/adhesion layer comprises:

placing the substrate in a plasma-etch chamber;

flowing a process gas into the chamber, wherein the process gas comprises at least one of the group consisting of hydrogen, a helium-hydrogen mixture and combinations thereof; and

generating a plasma in the chamber.

19. The method of claim 17, wherein the process of conditioning the surface of the barrier/adhesion layer comprises cathodically pre-treating the barrier/adhesion layer in an acid-containing bath.

20. The method of claim 19, wherein cathodically pre-treating the barrier/adhesion layer further comprises performing the cathodic pre-treatment at a current density in the range of about 1 mA/cm² to about 5 mA/cm².

21. The method of claim 19, wherein the cathodic pre-treatment is performed at a potential in the range of about 0 volt to about −

1.0 volt vs. AgCl.

22. The method of claim 17, wherein the process of conditioning the surface of the barrier/adhesion layer comprises cathodically pre-treating the barrier/adhesion layer in an alkaline or neutral bath.

23. The method of claim 17, wherein the process of directly plating a first copper layer onto the barrier/adhesion layer occurs less than about 150 minutes after the process of conditioning the surface of the barrier/adhesion layer.

24. The method of claim 17, wherein the process of applying a first plating waveform to the substrate surface further comprises:

applying a nucleation waveform to the substrate surface, the nucleation waveform being configured to generate a first current density across the substrate surface greater than a critical current density.

25. The method of claim 17, further comprising applying a second plating waveform to the substrate surface while in contact with the copper solution to deposit a second copper layer onto the first copper layer.

26. The method of claim 17, wherein the copper solution further comprises a complexing agent and a pH equal to or greater than 7.0.

27. The method of claim 26, further comprising depositing a second copper layer onto the first copper layer, wherein the process of depositing the second copper layer comprises:

placing the first copper layer into a second copper solution, wherein the second copper solution is acidic and includes free-copper ions; and

applying a second plating waveform to the first copper layer.

28. The method of claim 17, wherein the composition of the Ru—

Ta alloy is not homogeneous through the thickness of the alloy.

29. The method of claim 28, wherein the Ru—

Ta alloy is ruthenium-rich adjacent the interface between the barrier/adhesion layer and the first copper layer and is tantalum-rich adjacent the interface between the barrier/adhesion layer and the dielectric layer.

30. The method of claim 17 wherein the features have sidewalls and the thickness of the barrier/adhesion layer is between about 10 Å

and about 50 Å

on the sidewalls.

31. A method of plating an adherent copper layer onto a barrier layer, comprising:

depositing an electrically continuous barrier/adhesion layer onto a substrate surface, wherein the barrier/adhesion layer comprises a Ru—

Ta alloy of between about 70 atomic % and 95 atomic % ruthenium and wherein the balance of the alloy is tantalum;

conditioning the surface of the electrically continuous barrier/adhesion layer prior to plating the first copper layer; and

directly plating a first copper layer onto the barrier/adhesion layer, the first copper layer being an electrically continuous layer wherein the process of directly plating a first copper layer comprises;

placing the substrate surface into contact with a copper solution, wherein the copper solution comprises copper ions; and

applying a first plating waveform to the substrate surface.

32. The method of claim 31, wherein the process of conditioning the surface of the barrier/adhesion layer comprises:

placing the substrate in a plasma-etch chamber;

flowing a process gas into the chamber, wherein the process gas comprises at least one of the group consisting of hydrogen, a helium-hydrogen mixture and combinations thereof; and

generating a plasma in the chamber.

33. The method of claim 31, wherein the process of conditioning the surface of the barrier/adhesion layer comprises cathodically pre-treating the barrier/adhesion layer.

34. The method of claim 31, wherein the process of conditioning the surface of the barrier/adhesion layer comprises cathodically pre-treating the barrier/adhesion layer in an acid-containing bath at a current density in the range of about 1 mA/cm² to about 5 mA/cm².

35. The method of claim 31, wherein the cathodic pre-treatment is performed at a potential in the range of about 0 volt to about −

1.0 volt vs. AgCl.

36. The method of claim 31, wherein the process of directly plating a first copper layer onto the barrier/adhesion layer occurs less than about 150 minutes after the process of conditioning the surface of the barrier/adhesion layer.

37. The method of claim 31, wherein the process of applying a first plating waveform to the substrate surface further comprises:

applying a nucleation waveform to the substrate surface, the nucleation waveform being configured to generate a first current density across the substrate surface greater than a critical current density.

38. The method of claim 31, wherein the copper solution further comprises a complexing agent and a pH equal to or greater than 7.0.

39. The method of claim 31, wherein the Ru—

Ta alloy is ruthenium-rich adjacent the interface between the barrier/adhesion layer and the first copper layer and is tantalum-rich adjacent the interface between the barrier/adhesion layer and the dielectric layer.