Method for forming CoWRe alloys by electroless deposition

• US 7,205,233 B2
• Filed: 11/07/2003
• Issued: 04/17/2007
• Est. Priority Date: 11/07/2003
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Lopatin, Sergey, Lubomirsky, Dmitry, Shanmugasundram, Arulkumar, Pancham, Ian A.
• Primary Examiner(s): Le; Thao P.
• Application Number:
  US10/703,769
• Publication Number:
  US 20050101130A1
• Time in Patent Office: 1,257 Days
• Field of Search: 438/678, 438/618, 438/686, 438/679
• US Class Current: 438/678
• CPC Class Codes: C23C 18/1651 Two or more layers only obtained by electroless plating
• CPC Class Codes: C23C 18/1692 Heat-treatment
• CPC Class Codes: C23C 18/1844 with use of organic or inorganic compounds other than metals, first
• CPC Class Codes: C23C 18/50 with alloys based on iron, cobalt or nickel
• CPC Class Codes: H01L 21/288 from a liquid, e.g. electrolytic deposition
• 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 21/76858 by diffusing alloying elements
• CPC Class Codes: H01L 21/76874 for electroless plating

Abstract

A method for fabricating a capping layer with enhanced barrier resistance to both copper and oxygen diffusion, comprises forming a capping layer on a conductive surface of an interconnect, wherein the capping layer comprises cobalt (Co), tungsten (W), rhenium (Re), and at least one of phosphorus (P) and boron (B). In an embodiment of the invention, forming the capping layer comprises exposing the conductive surface to an electroless capping solution comprising a cobalt source, a tungsten source, a rhenium source, and at least one of a phosphorus source and a boron source, and annealing the capping layer.

Claims

1. A method for fabricating a capping layer with enhanced barrier properties, comprising:

forming a capping layer on a conductive surface of an interconnect, wherein the capping layer comprises cobalt, tungsten, rhenium, calcium, and at least one element selected from the group consisting of phosphorus and boron, and annealing the capping layer.

2. The method of claim 1, wherein the capping layer comprises a rhenium concentration of within a range from about 0.1 atomic % to about 10 atomic %.

3. The method of claim 2, wherein the rhenium concentration is within a range of from about 0.5 atomic % to about 4 atomic %.

4. The method of claim 1, wherein the capping layer comprises a phosphorus concentration of less than about 20 atomic %.

5. The method of claim 4, wherein the phosphorus concentration is within a range from about 8 atomic % to about 15 atomic %.

6. The method of claim 1, wherein the capping layer further comprises at least one element selected from the group consisting of aluminum, nickel, and molybdenum.

7. The method of claim 1, wherein the capping layer comprises crystalline grains and grain boundaries, wherein the grain boundaries comprise rhenium.

8. The method of claim 1, wherein the conductive surface comprises at least one element selected from the group consisting of copper, palladium, silver, cobalt, gold, nickel, zinc, platinum, and tin.

9. The method of claim 1, wherein the forming a capping layer comprises depositing the capping layer by exposing the conductive surface to an electroless capping solution comprising a cobalt source, a tungsten source, a rhenium source, a calcium source, and at least one elemental source selected from the group consisting of a phosphorus source and a boron source.

10. The method of claim 9, wherein the electroless capping solution further comprises a complexing agent, a phosphorus-containing or boron-containing reducing agent, and at least one additive selected from the group consisting of a pH adjuster, a buffering agent, a base, a surfactant, and an antifungal compound.

11. The method of claim 9, wherein the electroless capping solution comprises from about 0.01 g/L to about 50 g/L of the rhenium source and from about 5 g/L to about 80 g/L of the phosphorus source to form a capping layer comprising CoWReP wherein the capping layer comprises a rhenium concentration within a range from about 0.1 atomic % to about 10 atomic % and a phosphorus concentration within a range from about 8 atomic % to about 20 atomic %.

12. The method of claim 9, wherein the electroless capping solution comprises:

from about 1 g/L to about 100 g/L of the cobalt source, wherein the cobalt source comprises CoCl₂, CoSO₄, or combinations thereof;

from about 0.01 g/L to about 50 g/L of the tungsten source, wherein the tungsten source comprises CaWO₄, (NH₄)₂WO₄, H₂WO₄, or combinations thereof;

from about 0.01 g/L to about 50 g/L of the rhenium source, wherein the rhenium source comprises Re, ReCl₃, ReCl₅, Re(CO)₅Br, Re(CO)₅Cl, Re₂O₇, [NH₄][ReO₄], [(CH₃)₄N][ReO₄], or combinations thereof;

from about 5 g/L to about 80 g/L of the phosphorus source, wherein the phosphorus source comprises H₃PO₂, Ca(H₂PO₄)₂, CaHPO₄, Ca₁₀(OH)₂(PO₄)₆, (NH₄)₃PO₂, or combinations thereof, and/or from about 1 g/L to about 50 g/L of the boron source, wherein the boron source comprises (CH₃)₂NH.BH₃;

from about 60 g/L to about 90 g/L of ammonium citrate and/or tetramethyl ammonium citrate, or from about 10 g/L to about 20 g/L of ethylene diamine tetra acetic acid as a complexing agent;

from about 0.5 g/L to about 10 g/L of H₃BO₃, and/or a pH adjuster selected from the group consisting of (CH₃)₄NOH, NH₄OH, (CH₃)₂NH, and combinations thereof;

water; and

from about 0.005 g/L to about 1 g/L of a surfactant, a stabilizer, or combinations thereof.

13. The method of claim 9, wherein the electroless capping solution further comprises at least one elemental source selected from the group consisting of an aluminum source, a nickel source, and a molybdenum source.

14. The method of claim 13, wherein the calcium source comprises CaSO₄, CaWO₄, Ca(H₂PO₄)₂, CaHPO₄, Ca₁₀(OH)₂(PO₄)₆, or combinations thereof, the aluminum source comprises Al₂(SO₄)₃, and the molybdenum source comprises Mo(SO₄)₂.

15. The method of claim 9, wherein the forming a capping layer further comprises depositing an activation layer on the conductive surface prior to depositing the capping layer, wherein the activation layer comprises at least one element selected from the group consisting of palladium, silver, cobalt, gold, nickel, zinc, platinum, and tin.

16. The method of claim 1, wherein the forming a capping layer comprises:

electrolessly depositing a multilayer capping layer; and

annealing the multilayer capping layer thereby forming an interface layer therein, wherein the interface layer comprises cobalt, tungsten, rhenium, and at least one element selected from the group consisting of phosphorus and boron.

17. The method of claim 16, wherein the interface layer comprises a rhenium concentration within a range from about 0.1 atomic % to about 10 atomic %.

18. The method of claim 16, wherein the electrolessly depositing a multilayer capping layer comprises sequentially exposing the conductive surface to a first electroless capping solution and a second electroless capping solution.

21. The method of claim 16, wherein the conductive surface comprises at least one element selected from the group consisting of copper, palladium, silver, cobalt, gold, nickel, zinc, platinum, and tin.

22. The method of claim 16, wherein the forming a capping layer further comprises depositing an activation layer on the conductive surface prior to electrolessly depositing the multilayer capping layer, wherein the activation layer comprises at least one element selected from the group consisting of palladium, silver, cobalt, gold, nickel, zinc, platinum, and tin.

19. A method for fabricating a capping layer with enhanced barrier properties, comprising:

forming a capping layer on a conductive surface of an interconnect, wherein the capping layer comprises cobalt, tungsten, rhenium, and at least one element selected from the group consisting of phosphorus and boron;

depositing a multilayer capping layer by sequentially exposing the conductive surface to a first electroless capping solution and a second electroless capping solution, wherein the first electroless capping solution comprises cobalt, rhenium, and at least one element selected from the group consisting of phosphorus and boron, for forming a first layer comprising CoReP, CoReB, or CoRePB, and wherein the second electroless capping solution comprises cobalt, tungsten, and at least one element selected from the group consisting of phosphorus and boron, for forming a second layer comprising CoWP, CoWB, or CoWPB.

20. A method for fabricating a capping layer with enhanced barrier properties, comprising:

forming a capping layer on a conductive surface of an interconnect, wherein the capping layer comprises cobalt, tungsten, rhenium, and at least one element selected from the group consisting of phosphorus and boron;

depositing a multilayer capping layer by sequentially exposing the conductive surface to a first electroless capping solution and a second electroless capping solution, wherein the first electroless capping solution comprises cobalt, tungsten, and at least one element selected from the group consisting of phosphorus and tungsten, for forming a first layer comprising CoWP, CoWB, or CoWPB, and wherein the second electroless capping solution comprises cobalt, rhenium, and at least one element selected from the group consisting of phosphorus and boron, for forming a second layer comprising CoReP, CoReB, or CoRePB.

23. A process for fabricating a capping layer with enhanced barrier properties on a conductive surface, comprising:

pre-cleaning the conductive surface;

depositing an activation layer on the conductive surface;

electrolessly depositing a capping layer on the activation layer, wherein the capping layer comprises cobalt, tungsten, rhenium calcium, and phosphorus; and

annealing the capping layer.

24. The process of claim 23, wherein the pre-cleaning the conductive surface comprises exposing the conductive surface to a pre-cleaning solution, wherein the pre-cleaning solution comprises water, a surfactant, and at least one acid selected from the group consisting of sulfuric acid and hydrochloric acid.

25. The process of claim 23, wherein the depositing an activation layer comprises exposing the conductive surface to an activation solution comprising at least one elemental source selected from the group consisting of a palladium source, a silver source, a cobalt source, a gold source, a nickel source, a zinc source, a platinum source, and a tin source.

26. The process of claim 25, wherein the activation solution comprises water, at least one palladium source selected from the group consisting of PdCl₂, PdSO₄, and Pd acetate, and at least one acid selected from the group consisting of hydrochloric acid, sulfuric acid and hydrofluoric acid.

27. The process of claim 23, wherein the electrolessly depositing a capping layer on the activation layer comprises exposing the activation layer to an electroless capping solution comprising a cobalt source, a tungsten source, a rhenium source, a calcium source, and a phosphorus source, and wherein the annealing the capping layer comprises heating the capping layer to a temperature within a range of about 100°

C. to about 300°

C.

28. A process for fabricating a capping layer with enhanced barrier properties on a conductive surface, comprising:

pre-cleaning the conductive surface;

depositing an activation layer on the conductive surface;

electrolessly depositing a capping layer on the activation layer, wherein the capping layer comprises cobalt, tungsten, rhenium, and at least one element selected from the group consisting of phosphorus and boron; and

annealing the capping layer, wherein the electrolessly depositing the capping layer on the activation layer comprises sequentially exposing the activation layer to a first electroless capping solution for forming a first layer and a second electroless capping solution for forming a second layer, the first electroless capping solution comprising a cobalt source, a rhenium source, and at least one elemental source selected from the group consisting of a phosphorus source and a boron source, the second electroless capping solution comprising a cobalt source, a tungsten source, and at least one elemental source selected from the group consisting of a phosphorus source and a boron source, and wherein the annealing the capping layer comprises heating the first layer and the second layer to a temperature within a range of about 100°

C. to about 300°

C. thereby forming an interface layer comprising cobalt, tungsten, rhenium, and at least one element selected from the group consisting of phosphorus and boron.

29. A process for fabricating a capping layer with enhanced barrier properties on a conductive surface, comprising:

pre-cleaning the conductive surface;

depositing an activation layer on the conductive surface;

electrolessly depositing a capping layer on the activation layer, wherein the capping layer comprises cobalt, tungsten, rhenium, and at least one element selected from the group consisting of phosphorus and boron; and

annealing the capping layer, wherein the electrolessly depositing the capping layer on the activation layer comprises sequentially exposing the activation layer to a first electroless capping solution for forming a first layer and a second electroless capping solution for forming a second layer, the first electroless capping solution comprising a cobalt source, a tungsten source, and at least one elemental source selected from the group consisting of a phosphorus source and a boron source, the second electroless capping solution comprising a cobalt source, a rhenium source, and at least one elemental source selected from the group consisting of a phosphorus source and a boron source, and wherein the annealing the capping layer comprises heating the first layer and the second layer to a temperature within a range of about 100°

C. to about 300°

C. thereby forming an interface layer comprising cobalt, tungsten, rhenium, and at least one element selected from the group consisting of phosphorus and boron.