Interconnect structure formed in porous dielectric material with minimized degradation and electromigration

• US 6,528,409 B1
• Filed: 04/29/2002
• Issued: 03/04/2003
• Est. Priority Date: 04/29/2002
• Status: Active Grant

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Schonauer, Diana, Lopatin, Sergey, Wang, Fei, Avanzino, Steven C.
• Primary Examiner(s): TSAI, H JEY
• Application Number:
  US10/134,883
• Time in Patent Office: 309 Days
• Field of Search: 438/618-620, 438/622-687
• US Class Current: 438/618
• CPC Class Codes: H01L 21/288 from a liquid, e.g. electrolytic deposition
• CPC Class Codes: H01L 21/76805 the opening being a via or contact hole penetrating the underlying conductor
• CPC Class Codes: H01L 21/76814 post-treatment or after-treatment, e.g. cleaning or removal of oxides on underlying conductors
• CPC Class Codes: H01L 21/7682 the dielectric comprising air gaps
• CPC Class Codes: H01L 21/76828 thermal treatment
• CPC Class Codes: H01L 21/76829 characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers
• CPC Class Codes: H01L 21/76843 formed in openings in a dielectric
• CPC Class Codes: H01L 21/76844 Bottomless liners
• CPC Class Codes: H01L 21/76846 Layer combinations
• CPC Class Codes: H01L 21/76849 the layer being positioned on top of the main fill metal
• CPC Class Codes: H01L 21/76862 Bombardment with particles, e.g. treatment in noble gas plasmas; UV irradiation
• CPC Class Codes: H01L 21/76865 Selective removal of parts of the layer H01L21/76844 takes precedence
• CPC Class Codes: H01L 21/76867 characterized by methods of formation other than PVD, CVD or deposition from a liquids PVD H01L21/2855; CVD H01L21/28556; deposition from liquids H01L21/288
• CPC Class Codes: H01L 21/76874 for electroless plating
• CPC Class Codes: H01L 2221/1047 the air gaps being formed by pores in the dielectric
• CPC Class Codes: H01L 2221/1089 Stacks of seed layers

Abstract

For fabricating an interconnect structure within an interconnect opening formed within a porous dielectric material, the interconnect opening is initially formed within a low-K precursor material that is not completely cured. The interconnect opening is then filled with a conductive fill material being contained within the interconnect opening and with a top surface of the conductive fill material within the interconnect opening being exposed. A capping material is formed on the top surface of the conductive fill material, and the capping material is an amorphous alloy or is a microcrystalline alloy having stuffed grain boundaries. A thermal curing process is then performed for curing the low-K precursor material to become a porous low-K dielectric material. The capping material on the top surface of the conductive fill material is impervious to at least one of oxygen, carbon, hydrogen, chlorine, and porogen fragments that are generated as out-gassing volatile by-products from the low-K precursor material during the thermal curing process to preserve the integrity of the interconnect structure. In another aspect for fabricating an interconnect structure, an interconnect opening is formed within a porous dielectric material with opened pores at sidewalls of the interconnect opening. A diffusion barrier material is formed at a bottom wall of the interconnect opening. The diffusion barrier material is then sputtered away from the bottom wall of the interconnect opening and onto the sidewalls of the interconnect opening to substantially fill the opened pores at the sidewalls with the diffusion barrier material. The interconnect opening is then filled with a conductive fill material after the opened pores at the sidewalls of the interconnect opening are filled with the diffusion barrier material.

Claims

1. A method for fabricating an interconnect structure within an interconnect opening formed within a porous dielectric material, the method comprising the steps of:

A. forming said interconnect opening within a low-K precursor material that is not completely cured;

B. filling said interconnect opening with a conductive fill material being contained within said interconnect opening and with a top surface of said conductive fill material within said interconnect opening being exposed;

C. forming a capping material on said top surface of said conductive fill material, wherein said capping material is an amorphous alloy or is a microcrystalline alloy having stuffed grain boundaries; and

D. performing a thermal curing process for curing said low-K precursor material to become a porous low-K dielectric material after said steps B and C;

wherein said capping material on said top surface of said conductive fill material is impervious to at least one of oxygen, carbon, hydrogen, chlorine, and porogen fragments that are generated as out-gassing volatile by-products from said low-K precursor material during said thermal curing process of said step D.

2. The method of claim 1, wherein said step A includes the steps of:

forming a diffusion barrier material at said sidewalls of said interconnect opening formed in said low-K precursor material that is not completely cured;

filling said interconnect opening with said conductive fill material after forming said diffusion barrier material at said sidewalls; and

polishing away any of said conductive fill material and said diffusion barrier material from any dielectric surface surrounding said interconnect opening such that said conductive fill material and said diffusion barrier material are contained within said interconnect opening,

wherein said capping material is selectively formed on any exposed surface of said conductive fill material and said diffusion barrier material after said step of polishing.

3. The method of claim 2, further including the step of:

performing a post polish cleaning process by applying a rotating brush to scrub any dielectric surface surrounding said interconnect opening and then applying a cleaning solution on said dielectric surface surrounding said interconnect opening to clean away copper containing particles from said dielectric surface surrounding said interconnect opening, after said step of polishing.

4. The method of claim 3, wherein said cleaning solution is comprised of citric acid, 5-aminotetrazol, and water (H₂O);

or is comprised of citric acid, benzotriazole (BTA), and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), amidizole, and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), triethanolamine, and water (H₂O).

5. The method of claim 1, further including the step of:

forming a hard-mask material on top of said low-K precursor material before forming said interconnect opening through said hard-mask material and within said low-K precursor material, wherein said hard-mask material on top of said low-K precursor material is transparent to said porogen fragments that are generated as out-gassing volatile by-products during said thermal curing process of said step D.

6. The method of claim 5, wherein said hard-mask material on top of said low-K precursor material is comprised of alkoxysilane.

7. The method of claim 1, wherein said conductive fill material is comprised of copper, and wherein said step C includes the step of:

forming said capping material that is a ternary alloy comprised of cobalt; and

one of W (tungsten), Mo (molybdenum), or Re(rhenium); and

one of P (phosphorous) or B (boron),

wherein said capping material that is said ternary alloy is selectively formed on said conductive fill material during an electroless deposition process.

8. The method of claim 7, further including the step of:

performing a cleaning process by applying a rotating brush to scrub any dielectric surface surrounding said interconnect opening and then applying a cleaning solution on said dielectric surface surrounding said interconnect opening to clean away copper containing particles from said dielectric surface surrounding said interconnect opening, after forming said capping material.

9. The method of claim 8, wherein said cleaning solution is comprised of citric acid, 5-aminotetrazol, and water (H₂O);

or is comprised of citric acid, benzotriazole (BTA), and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), amidizole, and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), triethanolamine, and water (H₂O).

10. The method of claim 7, wherein said capping material is formed in said electroless deposition process with an electrolyte comprised of:

from about 10 grams/liter to about 40 grams/liter of CoSO₄ (cobalt sulfate) as a cobalt source;

from about 0.05 grams/liter to about 30 grams/liter of ammonium tungstate or tetramethyl ammonium tungstate as a tungsten source for forming CoWP or CoWB as said capping material, or from about 0.05 grams/liter to about 30 grams/liter of ammonium molybdenate or tetramethyl ammonium molybdenate as a molybdenum source for forming CoMoP or CoMoB as said capping material, or from about 0.05 grams/liter to about 30 grams/liter of ammonium rhenate or tetramethyl ammonium rhenate as a rhenium source for forming CoReP or CoReB as said capping material;

from about 60 grams/liter to about 90 grams/liter of ammonium citrate or tetramethyl ammonium citrate as a complexing agent;

from about 40 grams/liter to about 80 grams/liter of ammonium hydroxide or tetramethyl ammonium hydroxide as a pH adjuster for adjusting the pH of said electroless deposition electrolyte to be in a range of from about 6.5 to about 14;

from about 10 grams/liter to about 40 grams/liter of ammonium hypophosphite for a phosphorus source as a reducing agent for forming CoWP, CoMoP, or CoReP as said capping material, or from about 10 grams/liter to about 40 grams/liter of borane dimethylamine for a boron source as a reducing agent for forming CoWB, CoMoB, or CoReB as said capping material;

water (H₂O); and

from about 0.01 grams/liter to about 0.02 grams/liter total of at least one of a surfactant and a stabilizer.

11. The method of claim 10, wherein said surfactant is comprised of RE610, and wherein said stabilizer is comprised of 2,2′

-dipyridyl.

12. The method of claim 10, wherein said electrolyte for said electroless deposition process during formation of said capping material is at a temperature of from about 55°

Celsius to about 92°

Celsius.

13. The method of claim 10, wherein said capping material is comprised of CoWP (cobalt tungsten phosphide) with a phosphorous content of about 7-12 atomic percent and with a tungsten content of about 2-4 atomic percent.

14. The method of claim 13, wherein said step C includes the steps of:

wetting said top surface of said conductive fill material in H₂O or H₂O with surfactant;

etching away copper oxides (Cu₂O or CuO) from said top surface of said conductive fill material using one of hydrochloric acid (H₂O with HCl) or sulfuric acid (H₂O with H₂SO₄);

rinsing said top surface of said conductive fill material in H₂O;

forming said capping material that is comprised of CoWP (cobalt tungsten phosphide) with said electrolyte for said electroless deposition process at a temperature of from about 60°

Celsius to about 85°

Celsius for a time period of from about 0.5 minutes to about 2 minutes for forming said capping material having a thickness of from about 100 Å

(angstroms) to about 500 Å

(angstroms);

rinsing said capping material formed on said conductive fill material in H₂O; and

drying said capping material formed on said conductive fill material in a nitrogen gas (N₂) flow.

15. The method of claim 7, further including the step of:

forming an activation layer comprised of one of Pd (palladium), Ag (silver), Co (cobalt), Ni (nickel), Zn (zinc), Pt (platinum), or Sn (tin) on said surface of said conductive fill material before formation of said capping material on said activation layer.

16. The method of claim 15, wherein said activation layer is comprised of Pd (palladium) having a thickness of from about 10 Å

(angstroms) to about 50 Å

(angstroms) formed in an activation solution comprised of 0.1-2 milli-liter/liter of PdCl₂ (palladium chloride), 2-5 milli-liter/liter of HF (hydrofluoric acid), 1-5 milli-liter/liter of HNO₃ (nitric acid), 1-30 milli-liter/liter of HCl (hydrochloric acid), and water (H₂O).

17. The method of claim 15, further including the step of:

performing a thermal anneal process at a temperature in a range of from about 150°

Celsius to about 350°

Celsius such that said activation layer forms an adhesion layer between said conductive fill material and said capping material.

18. The method of claim 15, wherein said capping material is formed in said electroless deposition process with an electrolyte comprised of:

from about 10 grams/liter to about 40 grams/liter of CoSO₄ (cobalt sulfate) as a cobalt source;

from about 0.05 grams/liter to about 30 grams/liter of ammonium tungstate or tetramethyl ammonium tungstate as a tungsten source for forming CoWP or CoWB as said capping material, or from about 0.05 grams/liter to about 30 grams/liter of ammonium molybdenate or tetramethyl ammonium molybdenate as a molybdenum source for forming CoMoP or CoMoB as said capping material, or from about 0.05 grams/liter to about 30 grams/liter of ammonium rhenate or tetramethyl ammonium rhenate as a rhenium source for forming CoReP or CoReB as said capping material;

from about 60 grams/liter to about 90 grams/liter of ammonium citrate or tetramethyl ammonium citrate as a complexing agent;

from about 40 grams/liter to about 80 grams/liter of ammonium hydroxide or tetramethyl ammonium hydroxide as a pH adjuster for adjusting the pH of said electroless deposition electrolyte to be in a range of from about 6.5 to about 14;

from about 10 grams/liter to about 40 grams/liter of ammonium hypophosphite for a phosphorus source as a reducing agent for forming CoWP, CoMoP, or CoReP as said capping material, or from about 10 grams/liter to about 40 grams/liter of borane dimethylamine for a boron source as a reducing agent for forming CoWB, CoMoB, or CoReB as said capping material;

water (H₂O); and

from about 0.01 grams/liter to about 0.02 grams/liter total of at least one of a surfactant and a stabilizer;

wherein said electrolyte for said electroless deposition process during formation of said capping material is at a temperature of from about 55°

Celsius to about 65°

Celsius.

19. The method of claim 15, further including the step of:

performing a cleaning process by applying a rotating brush to scrub any dielectric surface surrounding said interconnect opening and then applying a cleaning solution on said dielectric surface surrounding said interconnect opening to clean away copper containing particles from said dielectric surface surrounding said interconnect opening, after forming said activation layer.

20. The method of claim 19, wherein said cleaning solution is comprised of citric acid, 5-aminotetrazol, and water (H₂O);

or is comprised of citric acid, benzotriazole (BTA), and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), amidizole, and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), triethanolamine, and water (H₂O).

21. The method of claim 1, wherein said interconnect opening is one of a metal line, a via hole, or a dual damascene opening, having a width dimension of hundreds or tens of nanometers.

22. A method for fabricating an interconnect structure within an interconnect opening formed within a dielectric material, the method comprising the steps of:

A. forming said interconnect opening within said dielectric material comprised of silicon dioxide (SiO₂) formed from TEOS (tetraethoxysilane) or from FTEOS (fluorine-doped tetraethoxysilane);

B. filling said interconnect opening with a conductive fill material being contained within said interconnect opening and with a top surface of said conductive fill material within said interconnect opening being exposed; and

C. forming a capping material on said top surface of said conductive fill material, wherein said capping material is an amorphous alloy or is a microcrystalline alloy having stuffed grain boundaries;

wherein said capping material comprised of said amorphous alloy or said microcrystalline alloy having stuffed grain boundaries minimizes electromigration failure of said interconnect structure.

23. The method of claim 22 wherein said step A includes the steps of:

forming a diffusion barrier material at said sidewalls of said interconnect opening before filling said interconnect opening with said conductive fill material; and

polishing away any of said conductive fill material and said diffusion barrier material from any dielectric surface surrounding said interconnect opening such that said conductive fill material and said diffusion barrier material are contained within said interconnect opening,

wherein said capping material is selectively formed on any exposed surface of said conductive fill material and said diffusion barrier material after said step of polishing.

24. The method of claim 23 further including the step of:

performing a post polish cleaning process by applying a rotating brush to scrub any dielectric surface surrounding said interconnect opening and then applying a cleaning solution on said dielectric surface surrounding said interconnect opening to clean away copper containing particles from said dielectric surface surrounding said interconnect opening, after said step of polishing.

25. The method of claim 24, wherein said cleaning solution is comprised of citric acid, 5-aminotetrazol, and water (H₂O);

or is comprised of citric acid, benzotriazole (BTA), and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), amidizole, and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), triethanolamine, and water (H₂O).

26. The method of claim 22, further including the step of:

forming a hard-mask material on top of said dielectric material comprised of silicon dioxide (SiO₂) formed from TEOS (tetraethoxysilane) or from FTEOS (fluorine-doped tetraethoxysilane) before forming said interconnect opening through said hard-mask material and within said dielectric material.

27. The method of claim 22 wherein said conductive fill material is comprised of copper, and wherein said step C includes the step of:

forming said capping material that is a ternary alloy comprised of cobalt; and

one of W (tungsten), Mo (molybdenum), or Re(rhenium); and

one of P (phosphorous) or B (boron),

wherein said capping material that is said ternary alloy is selectively formed on said conductive fill material during an electroless deposition process.

28. The method of claim 27 further including the step of:

performing a cleaning process by applying a rotating brush to scrub any dielectric surface surrounding said interconnect opening and then applying a cleaning solution on said dielectric surface surrounding said interconnect opening to clean away copper containing particles from said dielectric surface surrounding said interconnect opening, after forming said capping material.

29. The method of claim 28 wherein said cleaning solution is comprised of citric acid, 5-aminotetrazol, and water (H₂O);

or is comprised of citric acid, benzotriazole (BTA), and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), amidizole, and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), triethanolamine, and water (H₂O).

30. The method of claim 27, wherein said capping material is formed in said electroless deposition process with an electrolyte comprised of:

from about 10 grams/liter to about 40 grams/liter of CoSO₄ (cobalt sulfate) as a cobalt source;

from about 0.05 grams/liter to about 30 grams/liter of ammonium tungstate or tetramethyl ammonium tungstate as a tungsten source for forming CoWP or COWB as said capping material, or from about 0.05 grams/liter to about 30 grams/liter of ammonium molybdenate or tetramethyl ammonium molybdenate as a molybdenum source for forming CoMoP or CoMoB as said capping material, or from about 0.05 grams/liter to about 30 grams/liter of ammonium rhenate or tetramethyl ammonium rhenate as a rhenium source for forming CoReP or CoReB as said capping material;

from about 60 grams/liter to about 90 grams/liter of ammonium citrate or tetramethyl ammonium citrate as a complexing agent;

from about 40 grams/liter to about 80 grams/liter of ammonium hydroxide or tetramethyl ammonium hydroxide as a pH adjuster for adjusting the pH of said electroless deposition electrolyte to be in a range of from about 6.5 to about 14;

from about 10 grams/liter to about 40 grams/liter of ammonium hypophosphite for a phosphorus source as a reducing agent for forming CoWP, CoMoP, or CoReP as said capping material, or from about 10 grams/liter to about 40 grams/liter of borane dimethylamine for a boron source as a reducing agent for forming CoWB, CoMoB, or CoReB as said capping material;

water (H₂O); and

from about 0.01 grams/liter to about 0.02 grams/liter total of at least one of a surfactant and a stabilizer.

31. The method of claim 30, wherein said surfactant is comprised of RE610, and wherein said stabilizer is comprised of 2,2′

-dipyridyl.

32. The method of claim 30, wherein said electrolyte for said electroless deposition process during formation of said capping material is at a temperature of from about 55°

Celsius to about 92°

Celsius.

33. The method of claim 30, wherein said capping material is comprised of CoWP (cobalt tungsten phosphide) with a phosphorous content of about 7-12 atomic percent and with a tungsten content of about 2-4 atomic percent.

34. The method of claim 33, wherein said step C includes the steps of:

wetting said top surface of said conductive fill material in H₂O or H₂O with surfactant;

etching away copper oxides (Cu₂O or CuO) from said top surface of said conductive fill material using one of hydrochloric acid (H₂O with HCl) or sulfuric acid (H₂O with H₂SO₄);

rinsing said top surface of said conductive fill material in H₂O;

forming said capping material that is comprised of CoWP (cobalt tungsten phosphide) with said electrolyte for said electroless deposition process at a temperature of from about 60°

Celsius to about 85°

Celsius for a time period of from about 0.5 minutes to about 2 minutes for forming said capping material having a thickness of from about 100 Å

(angstroms) to about 500 Å

(angstroms);

rinsing said capping material formed on said conductive fill material in H₂O; and

drying said capping material formed on said conductive fill material in a nitrogen gas (N₂) flow.

35. The method of claim 27, further including the step of:

forming an activation layer comprised of one of Pd (palladium), Ag (silver), Co (cobalt), Ni (nickel), Zn (zinc), Pt (platinum), or Sn (tin) on said surface of said conductive fill material before formation of said capping material on said activation layer.

36. The method of claim 35, wherein said activation layer is comprised of Pd (palladium) having a thickness of from about 10 Å

(angstroms) to about 50 Å

(angstroms) formed in an activation solution comprised of 0.1-2 milli-liter/liter of PdCl₂ (palladium chloride), 2-5 milli-liter/liter of HF (hydrofluoric acid), 1-5 milli-liter/liter of HNO₃ (nitric acid), 1-30 milli-liter/liter of HCl (hydrochloric acid), and water (H₂O).

37. The method of claim 35 further including the step of:

performing a thermal anneal process at a temperature in a range of from about 150°

Celsius to about 350°

Celsius such that said activation layer forms an adhesion layer between said conductive fill material and said capping material.

38. The method of claim 35, wherein said capping material is formed in said electroless deposition process with an electrolyte comprised of:

from about 10 grams/liter to about 40 grams/liter of CoSO₄ (cobalt sulfate) as a cobalt source;

from about 0.05 grams/liter to about 30 grams/liter of ammonium tungstate or tetramethyl ammonium tungstate as a tungsten source for forming CoWP or CoWB as said capping material, or from about 0.05 grams/liter to about 30 grams/liter of ammonium molybdenate or tetramethyl ammonium molybdenate as a molybdenum source for forming CoMoP or CoMoB as said capping material, or from about 0.05 grams/liter to about 30 grams/liter of ammonium rhenate or tetramethyl ammonium rhenate as a rhenium source for forming CoReP or CoReB as said capping material;

from about 60 grams/liter to about 90 grams/liter of ammonium citrate or tetramethyl ammonium citrate as a complexing agent;

from about 40 grams/liter to about 80 grams/liter of ammonium hydroxide or tetramethyl ammonium hydroxide as a pH adjuster for adjusting the pH of said electroless deposition electrolyte to be in a range of from about 6.5 to about 14;

from about 10 grams/liter to about 40 grams/liter of ammonium hypophosphite for a phosphorus source as a reducing agent for forming CoWP, CoMoP, or CoReP as said capping material, or from about 10 grams/liter to about 40 grams/liter of borane dimethylamine for a boron source as a reducing agent for forming CoWB, CoMoB, or CoReB as said capping material;

water (H₂O); and

from about 0.01 grams/liter to about 0.02 grams/liter total of at least one of a surfactant and a stabilizer;

wherein said electrolyte for said electroless deposition process during formation of said capping material is at a temperature of from about 55°

Celsius to about 65°

Celsius.

39. The method of claim 35, further including the step of:

performing a cleaning process by applying a rotating brush to scrub any dielectric surface surrounding said interconnect opening and then applying a cleaning solution on said dielectric surface surrounding said interconnect opening to clean away copper containing particles from said dielectric surface surrounding said interconnect opening, after forming said activation layer.

40. The method of claim 39, wherein said cleaning solution is comprised of citric acid, 5-aminotetrazol, and water (H₂O);

or is comprised of citric acid, benzotriazole (BTA), and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), amidizole, and water (H₂O);

or is comprised of citric acid, polyvinyl alcohol (PVA), triethanolamine, and water (H₂O).

41. The method of claim 22, wherein said interconnect opening is one of a metal line, a via hole, or a dual damascene opening, having a width dimension of hundreds or tens of nanometers.

42. A method for fabricating an interconnect structure, the method comprising the steps of:

A. forming an interconnect opening within a porous dielectric material with opened pores at sidewalls of said interconnect opening;

B. forming a diffusion barrier material at a bottom wall of said interconnect opening; and

C. sputtering said diffusion barrier material away from said bottom wall of said interconnect opening and onto said sidewalls of said interconnect opening to substantially fill said opened pores at said sidewalls with said diffusion barrier material.

43. The method of claim 42 wherein said step B includes the step of depositing said diffusion barrier material onto said bottom wall of said interconnect opening after said interconnect opening is formed in said step A.

44. The method of claim 42 wherein said steps A and B include the steps of depositing said diffusion barrier material onto a conductive material of a bottom interconnect structure and then forming said porous dielectric material and said interconnect opening over said diffusion barrier material such that said diffusion barrier material forms said bottom wall of said interconnect opening.

45. The method of claim 44, wherein said step B further includes the step of:

depositing an additional amount of diffusion barrier material on said bottom wall of said interconnect opening after forming said interconnect opening.

46. The method of claim 42, wherein said diffusion barrier material is comprised of one of CoWP (cobalt tungsten phosphide), CoWB (cobalt tungsten boride), CoMoP (cobalt molybdenum phosphide), CoMoB (cobalt molybdenum boride), CoReP (cobalt rhenium phosphide), or CoReB (cobalt rhenium boride), formed in an electroless deposition process.

47. The method of claim 46, wherein said diffusion barrier material is formed in said electroless deposition process with an electroless deposition electrolyte comprised of:

from about 10 grams/liter to about 40 grams/liter of CoSO₄ (cobalt sulfate) as a cobalt source;

from about 5 grams/liter to about 20 grams/liter of ammonium tungstate or tetramethyl ammonium tungstate as a tungsten source for forming CoWP or CoWB as said diffusion barrier material, or from about 5 grams/liter to about 20 grams/liter of ammonium molybdenate or tetramethyl ammonium molybdenate as a molybdenum source for forming CoMoP or CoMoB as said diffusion barrier material, or from about 5 grams/liter to about 20 grams/liter of ammonium rhenate or tetramethyl ammonium rhenate as a rhenium source for forming CoReP or CoReB as said diffusion barrier material;

from about 70 grams/liter to about 90 grams/liter of ammonium citrate or tetramethyl ammonium citrate as a complexing agent;

from about 5 grams/liter to about 50 grams/liter of ammonium chloride or tetramethyl ammonium chloride;

from about 5 grams/liter to about 15 grams/liter of ammonium hypophosphite for a phosphorus source as a reducing agent for forming CoWP, CoMoP, or CoReP as said diffusion barrier material, or from about 5 grams/liter to about 20 grams/liter of borane dimethylamine for a boron source as a reducing agent for forming CoWB, CoMoB, or CoReB as said diffusion barrier material;

water (H₂O); and

from about 0.01 grams/liter to about 0.1 grams/liter of a surfactant.

48. The method of claim 42, further including the step of:

forming an activation layer on said bottom wall of said interconnect opening before forming said diffusion barrier material on said activation layer.

49. The method of claim 48, wherein said activation layer is comprised of one of Pd (palladium), Ag (silver), Co (cobalt), Ni (nickel), Zn (zinc), Sn (tin), or Au (gold).

50. The method of claim 49, wherein said activation layer is comprised of Pd (palladium) formed in an activation solution comprised of 0.1-2 milli-liter/liter of PdCl₂ (palladium chloride), 2-5 milli-liter/liter of HF (hydrofluoric acid), 1-5 milli-liter/liter of HNO₃ (nitric acid), 1-30 milli-liter/liter of HCl (hydrochloric acid), and water (H₂O), and wherein said step of forming said activation layer includes the step of applying surfactant and water (H₂O) on said bottom wall of said interconnect opening before formation of said activation layer on said bottom wall.

51. The method of claim 48 further including the step of:

cleaning exposed surfaces of any dielectric material and said bottom wall of said interconnect opening with citric acid, sulfuric acid, hydrochloric acid, and water (H₂O) before formation of said activation layer.

52. The method of claim 48, further including the step of:

sputtering further down said activation layer away from said bottom wall of said interconnect opening onto said diffusion barrier material on said sidewalls of said interconnect opening.

53. The method of claim 52, further including the step of:

filling said interconnect opening with a conductive fill material after sputtering said activation layer onto said sidewalls of said interconnect opening.

54. The method of claim 52 wherein said bottom wall of said interconnect opening before deposition of said activation layer is comprised of a conductive material, and wherein the method further includes the step of:

sputtering further down said conductive material away from said bottom wall of said interconnect opening onto said activation layer on said sidewalls of said interconnect opening.

55. The method of claim 54, further including the step of:

filling said interconnect opening with a conductive fill material after sputtering said conductive material onto said sidewalls of said interconnect opening.

56. The method of claim 42, further including the step of:

filling said interconnect opening with a conductive fill material after sputtering said diffusion barrier onto said sidewalls of said interconnect opening.

57. The method of claim 56, further including the steps of:

depositing an additional diffusion barrier material onto said sidewalls of said interconnect opening after said step C and before said step of filling said interconnect opening with said conductive fill material.

58. The method of claim 57, wherein said additional diffusion barrier material is comprised of one of WN (tungsten nitride), TaN (tantalum nitride), or TiSiN (titanium silicon nitride) deposited in one of a CVD (chemical vapor deposition) process or an ALD (atomic layer deposition) process.

59. The method of claim 56, wherein said diffusion barrier material is completely sputtered away from said bottom wall of said interconnect opening such that substantially none of said diffusion barrier material is at said bottom wall of said interconnect opening before said step of filling said interconnect opening with said conductive fill material.

60. The method of claim 56, wherein said conductive fill material is comprised of copper deposited to fill said interconnect opening in an electroless deposition process.

61. The method of claim 60, wherein said copper conductive fill material is deposited in said electroless deposition process with an electroless deposition electrolyte comprised of:

from about 4 grams/liter to about 10 grams/liter of CuSO₄ (copper sulfate) as a copper source;

from about 10 grams/liter to about 20 grams/liter of EDTA (ethylene diamine tetra acetic acid) as a complexing agent;

from about 15 grams/liter to about 30 grams/liter of tetramethyl ammonium hydroxide as a pH adjuster;

from about 1 grams/liter to about 5 grams/liter of glyoxylic acid as a reducing agent;

water (H₂O); and

from about 0.01 grams/liter to about 0.1 grams/liter total of RE610 as a surfactant, 2,2′

-dipyridyl as a stabilizer, and Triton as a wetting agent.

62. The method of claim 42, further including the step of:

depositing a layer of hard-mask dielectric material on said porous dielectric material before forming said interconnect opening through said layer of hard-mask dielectric material and said porous dielectric material.

63. The method of claim 42, further including the step of:

cleaning exposed surfaces of any dielectric material and said bottom wall of said interconnect opening with citric acid, sulfuric acid, hydrochloric acid, and water (H₂O) before formation of said diffusion barrier material at said bottom wall of said interconnect opening.

64. The method of claim 42, wherein said step C is performed in an argon sputtering process with a base pressure of 2-5×

10<sup>−

7</sup> torr, with an argon gas pressure of 5-15×

10<sup>−

3</sup> torr, with an argon gas flow rate of 35-45 sccm (standard cubic centimeters per minute), for a time period of 1-30 seconds for sputtering said diffusion barrier material having a thickness of about 1-30 nanometers at said bottom wall of said interconnect opening.

65. The method of claim 42, wherein said step C is performed in an argon sputtering process with a base pressure of 2-5×

10<sup>−

7</sup> torr, with an argon and nitrogen (Ar and N₂) gas pressure of 1-5×

10<sup>−

3</sup> torr, with an argon gas flow rate of 15-25 sccm (standard cubic centimeters per minute), with a nitrogen (N₂) gas flow rate of 5-15 sccm (standard cubic centimeters per minute), for a time period of 1-60 seconds for sputtering said diffusion barrier material having a thickness of about 1-30 nanometers at said bottom wall of said interconnect opening.

66. The method of claim 42 wherein said interconnect opening is one of a metal line, a via hole, or a dual damascene opening having a width dimension of hundreds or tens of nanometers.

67. A method for fabricating an interconnect structure, the method comprising the steps of:

A. forming a layer of porous dielectric material and a layer of hard-mask dielectric material on said layer of porous dielectric material;

B. forming an interconnect opening through said layer of hard-mask dielectric material and said porous dielectric material with opened pores at sidewalls of said interconnect opening, wherein said interconnect opening is one of a metal line, a via hole, or a dual damascene opening having a width dimension of hundreds or tens of nanometers;

C. cleaning exposed surfaces of any dielectric material and said bottom wall of said interconnect opening with citric acid, sulfuric acid, hydrochloric acid, and water (H₂O);

D. applying surfactant and water (H₂O) on said bottom wall of said interconnect opening and forming an activation layer on said bottom wall of said interconnect opening, wherein said activation layer is comprised of Pd (palladium) formed in an activation solution comprised of 0.1-2 milli-liter/liter of PdCl₂ (palladium chloride), 2-5 milli-liter/liter of HF (hydrofluoric acid), 1-5 milli-liter/liter of HNO₃ (nitric acid), 1-30 milli-liter/liter of HCl (hydrochloric acid), and water (H₂O);

E. forming a diffusion barrier material at a bottom wall of said interconnect opening, wherein said diffusion barrier material is comprised of one of CoWP (cobalt tungsten phosphide), CoWB (cobalt tungsten boride), CoMoP (cobalt molybdenum phosphide), CoMoB (cobalt molybdenum boride), CoReP (cobalt rhenium phosphide), or CoReB (cobalt rhenium boride), formed in an electroless deposition process with an electroless deposition electrolyte comprised of;

from about 10 grams/liter to about 40 grams/liter of CoSO₄ (cobalt sulfate) as a cobalt source;

from about 5 grams/liter to about 20 grams/liter of ammonium tungstate or tetramethyl ammonium tungstate as a tungsten source for forming CoWP or CoWB as said diffusion barrier material, or from about 5 grams/liter to about 20 grams/liter of ammonium molybdenate or tetramethyl ammonium molybdenate as a molybdenum source for forming CoMoP or CoMoB as said diffusion barrier material, or from about 5 grams/liter to about 20 grams/liter of ammonium rhenate or tetramethyl ammonium rhenate as a rhenium source for forming CoReP or CoReB as said diffusion barrier material;

from about 70 grams/liter to about 90 grams/liter of ammonium citrate or tetramethyl ammonium citrate as a complexing agent;

from about 5 grams/liter to about 50 grams/liter of ammonium chloride or tetramethyl ammonium chloride;

from about 5 grams/liter to about 15 grams/liter of ammonium hypophosphite for a phosphorus source as a reducing agent for forming CoWP, CoMoP, or CoReP as said diffusion barrier material, or from about 5 grams/liter to about 20 grams/liter of borane dimethylamine for a boron source as a reducing agent for forming CoWB, CoMoB, or CoReB as said diffusion barrier material;

water (H₂O); and

from about 0.01 grams/liter to about 0.1 grams/liter of a surfactant;

F. sputtering said diffusion barrier material away from said bottom wall of said interconnect opening and onto said sidewalls of said interconnect opening to substantially fill said opened pores at said sidewalls with said diffusion barrier material, wherein the step of sputtering is performed in an argon sputtering process with a base pressure of 2-5×

10<sup>−

7</sup> torr, with an argon gas pressure of 5-15×

10<sup>−

3</sup> torr, with an argon gas flow rate of 35-45 sccm (standard cubic centimeters per minute), for a time period of 1-30 seconds for sputtering said diffusion barrier material having a thickness of about 1-30 nanometers at said bottom wall of said interconnect opening;

G. depositing an additional diffusion barrier material onto said sidewalls of said interconnect opening, wherein said additional diffusion barrier material is comprised of one of WN (tungsten nitride), TaN (tantalum nitride), or TiSiN (titanium silicon nitride) deposited in one of a CVD (chemical vapor deposition) process or an ALD (atomic layer deposition) process; and

H. filling said interconnect opening with a conductive fill material comprised of copper deposited in an electroless deposition process with an electroless deposition electrolyte comprised of;

from about 4 grams/liter to about 10 grams/liter of CuSO₄ (copper sulfate) as a copper source;

from about 10 grams/liter to about 20 grams/liter of EDTA (ethylene diamine tetra acetic acid) as a complexing agent;

from about 15 grams/liter to about 30 grams/liter of tetramethyl ammonium hydroxide as a pH adjuster;

from about 1 grams/liter to about 5 grams/liter of glyoxylic acid as a reducing agent;

water (H₂O); and

from about 0.01 grams/liter to about 0.1 grams/liter total of RE610 as a surfactant, 2,2′

-dipyridyl as a stabilizer, and Triton as a wetting agent.