Method of producing adhesion-barrier layer for integrated circuits

• US 20040192021A1
• Filed: 03/27/2003
• Published: 09/30/2004
• Est. Priority Date: 03/27/2003
• Status: Active Grant

• Current Assignee: ASM International NV
• Original Assignee: ASM International NV
• Inventors: Li, Wei-Min
• Granted Patent: US 6,955,986 B2
• Time in Patent Office: Days
• US Class Current: 438/622
• CPC Class Codes: H01L 21/28562 Selective deposition
• CPC Class Codes: H01L 21/76846 Layer combinations
• CPC Class Codes: H01L 21/76871 Layers specifically deposited to enhance or enable the nucleation of further layers, i.e. seed layers

Abstract

A process produces a layer of material which functions as a copper barrier layer, adhesion layer and a copper seed layer in a device of an integrated circuit, particularly in damascene or dual damascene structures. The method includes a step of depositing a diffusion barrier layer over a dielectric, a step of depositing a layer of graded metal alloy of two or more metals, and a step of depositing a copper seed layer, which step is essentially a part of the step of depositing the alloy layer.

Claims

1. A method of forming a multilayer structure comprising a barrier layer, an adhesion layer and a copper seed layer for an integrated circuit comprising:

depositing a diffusion barrier layer comprising at least one refractory metal over a dielectric layer of the integrated circuit by an atomic layer deposition type process; and

depositing over the diffusion barrier layer a graded metal alloy layer comprising copper and the refractory metal of the diffusion barrier layer by plasma enhanced atomic layer deposition, wherein the deposition of the graded metal alloy layer begins with deposition of the metal of the diffusion barrier layer and is finished with deposition of metallic copper.

2. The method of claim 1, wherein the diffusion barrier layer comprises the refractory metal and its nitride.

3. The method of claim 2, wherein the diffusion barrier layer further comprises a carbide of the refractory metal.

4. The method of claim 1, wherein the diffusion barrier layer is a nanolaminate of the refractory metal and its nitride.

5. The method of claim 1, wherein the diffusion barrier layer is a sandwich structure of the refractory metal and its nitride.

6. The method of claim 1, wherein the refractory metal of the diffusion barrier layer is tantalum.

7. The method of claim 1, wherein the refractory metal of the diffusion barrier layer is tungsten.

8. The method of claim 1, wherein the diffusion barrier layer comprises tungsten, tungsten nitride and tungsten carbide.

9. The method of claim 1, wherein the graded alloy layer is deposited by repeating and alternating depositing cycles of copper and depositing cycles of one or more metals and no more than one atomic layer of one metal is deposited during each depositing cycle.

10. The method of claim 9, wherein one depositing cycle of a metal comprises:

introducing a pulse of vapor phase metal precursor into a reaction chamber of an atomic layer deposition type reactor provided with a substrate;

introducing a purging pulse, introducing hydrogen plasma over the substrate; and

introducing a purging pulse.

11. The method of claim 1, wherein the process for producing the graded alloy layer comprises steps wherein a fluoride of the refractory metal is pulsed over a substrate and thereafter a copper precursor is pulsed over the substrate to form a layer that contains the refractory metal and copper fluoride, and the fluoride ligand and any other ligands attached to the metal atoms on the substrate are stripped away with hydrogen plasma to provide a metal alloy layer of the refractory metal and copper.

12. The method of claim 11, wherein the fluoride precursor of the refractory metal is tungsten hexafluoride (WF₆) and the precursor of copper is copper chloride (CuCl).

13. The method of claim 1, wherein the process for producing the graded alloy layer comprises copper deposition cycles wherein a stable solid phase of copper fluoride (CuF₂) is formed over the substrate and the fluoride ligand is stripped away with hydrogen plasma to provide no more than one atomic layer of copper metal over the substrate.

14. The method of claim 13, wherein the copper fluoride layer is formed in an exchange reaction between a copper precursor that is attached to the substrate and a compound vapor phase fluoride precursor.

15. The method of claim 14, wherein the vapor phase fluoride precursor is tungsten hexa-fluoride (WF₆), tantalum pentafluoride (TaF₅), niobium pentafluoride (NbF5), carbon tetrafluoride (CF₄) or nitrogen trifluoride (NF₃).

16. A multilayer structure forming a diffusion barrier for copper and an adhesion layer and a seed layer for a metallization layer of an integrated circuit comprising:

a diffusion barrier layer comprising a refractory metal deposited over a dielectric layer of the integrated circuit; and

a graded alloy layer of copper and said refractory metal over the diffusion barrier layer wherein a copper concentration is zero close to a bottom of the graded alloy layer and the graded alloy layer is covered with a layer of metallic copper.

17. The multi layer structure of claim 16, wherein the copper concentration of the graded metal alloy layer at the bottom of the layer is zero within a distance of 3 Å

from the bottom.

18. A method of forming a forming a graded metal alloy layer over a diffusion barrier in an integrated circuit comprising:

depositing a graded metal alloy layer consisting essentially of metals by atomic layer deposition (ALD).

19. The method of claim 18, wherein the deposition of the graded metal alloy layer begins with deposition of a first metal and is finished with deposition of a second metal.

20. The method of claim 19, wherein the first metal is a metal present in the diffusion barrier.

21. The method of claim 19, wherein the second metal is copper.

22. The method of claim 18, wherein the graded metal alloy layer is deposited by plasma enhanced ALD.

23. The method of claim 19, wherein depositing the graded alloy layer comprises contacting the substrate with a metal halide precursor.

24. The method of claim 23, wherein the metal halide is a metal fluoride.

25. The method of claim 23, wherein depositing the graded alloy layer additionally comprises contacting the substrate with a copper precursor.