Nitridation of electrolessly deposited cobalt

• US 6,962,873 B1
• Filed: 12/10/2002
• Issued: 11/08/2005
• Est. Priority Date: 12/10/2002
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Park, Heung L.
• Primary Examiner(s): Fourson, George
• Assistant Examiner(s): Pham, Thanh V.
• Application Number:
  US10/317,373
• Time in Patent Office: 1,064 Days
• Field of Search: 438/678, 438/687, 438/618, 438/628, 438/641, 438/643, 438/653, 438/468, 438/627
• US Class Current: 438/627
• CPC Class Codes: C23C 18/161 from plating step, e.g. inkjet
• CPC Class Codes: C23C 18/1689 After-treatment
• 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 21/76856 by treatment in plasmas or gaseous environments, e.g. nitriding a refractory metal liner

Abstract

A method describing a low temperature process of forming a cobalt nitride layer using electroless deposition, followed by a nitridation step, is disclosed. The process described is useful in integrated circuit device fabrication applications, especially those involving the use of copper. The invention can be used to create a highly effective capping layer in high interconnect copper devices.

Claims

1. A method of forming a capping layer on copper lines of a semiconductor device, the method comprising:

(a) electrolessly depositing a cobalt layer on an exposed surface of the semiconductor device such that the cobalt layer deposits on at least the copper lines of the exposed surface; and

(b) exposing the cobalt layer deposited in (a) to a nitrogen containing plasma using temperatures no greater than about 500 degrees Celsius, thereby nitriding at least an upper portion of the cobalt layer deposited in (a) to form a cobalt nitride capping layer effective for reducing at least one of diffusion of copper and electromigration of copper from the copper line.

3. The method in claim 1, wherein the cobalt layer comprises at least one of boron and phosphorus and tungsten.

4. The method in claim 1, wherein the cobalt nitride capping layer ranges between about 20 and 400 angstroms in thickness.

5. The method in claim 1, wherein the nitriding converts the entire cobalt layer to the cobalt nitride capping layer.

6. The method of claim 1, wherein electrolessly depositing a cobalt layer comprises contacting the exposed surface with a plating bath comprising a reducing agent selected from the group consisting of dimethylamine borane (DMAB), hydrazine, and ammonium hypophosphite.

7. The method of claim 6, wherein the plating bath contains boron and cobalt in a molar ratio of between about 0.005:

1 to 0.06;

1.

8. The method of claim 6, wherein the plating bath comprises ammonium hypophosphite.

9. The method of claim 6, wherein the plating bath comprises DMAB.

10. The method of claim 1, wherein electrolessly depositing a cobalt layer comprises contacting the exposed surface with a plating bath comprising at least one compound including at least one of boron, phosphorus, and tungsten, wherein the cobalt layer comprises at least one of boron, phosphorus, and tungsten.

2. The method in clam 1, wherein the capping layer is selectively deposited on the surfaces of copper lines, without depositing significantly on surrounding dielectric surfaces.