Plasma enhanced ALD of tantalum nitride and bilayer

• US 7,186,446 B2
• Filed: 10/31/2003
• Issued: 03/06/2007
• Est. Priority Date: 10/31/2003
• Status: Expired due to Fees

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Kim, Hyungjun, Rossnagel, Stephen M., Kellock, Andrew J.
• Primary Examiner(s): CHEN, BRET P
• Application Number:
  US10/699,226
• Publication Number:
  US 20050095443A1
• Time in Patent Office: 1,222 Days
• Field of Search: 427/569, 427/576
• US Class Current: 427/569
• CPC Class Codes: C23C 16/34 Nitrides C23C16/303 takes precedence
• CPC Class Codes: C23C 16/45525 Atomic layer deposition [ALD]
• CPC Class Codes: C23C 16/45542 Plasma being used non-continuously during the ALD reactions
• CPC Class Codes: H01L 21/28562 Selective deposition
• CPC Class Codes: H01L 21/76843 formed in openings in a dielectric

Abstract

A method to deposit TaN by plasma enhanced layer with various nitrogen content. Using a mixture of hydrogen and nitrogen plasma, the nitrogen content in the film can be controlled from 0 to N/Ta=1.7. By turning off the nitrogen flow during deposition of TaN, a TaN/Ta bilayer is easily grown, which has copper diffusion barrier properties superior to those of a single Ta layer or a single TaN layer.

Claims

1. A method for forming a bilayer of tantalum nitride and tantalum on a substrate, the method comprising:

depositing a first layer on the substrate by plasma enhanced atomic layer deposition of a tantalum halide precursor in the presence of a plasma containing hydrogen and nitrogen;

wherein the depositing comprises;

a. exposing the substrate to the tantalum halide carried by an inert gas;

b. exposing the substrate to the plasma; and

c. repeating a. and b. approximately 40–

800 times until a desired thickness of the first layer is obtained; and

depositing a second layer by continuing plasma enhanced atomic layer deposition of a tantalum halide precursor in the presence of a plasma by reducing concentration of nitrogen in the plasma to zero so that a substantially nitrogen free second layer of amorphous tantalum is formed.

2. The method as recited in claim 1, further comprising varying concentration of nitrogen in the plasma to thereby vary the amount of nitrogen in the first layer.

3. The method as recited in claim 2, wherein the concentration of nitrogen plasma is varied so that the first layer has a nitrogen to tantalum concentration ratio of between 0 and 1.7.

4. The method as recited in claim 1, wherein the bilayer is used as a diffusion barrier for copper.

5. The method as recited in claim 1, wherein temperature of the substrate is between 100°

C. and 450°

C.

6. The method as recited in claim 1, wherein temperature of the substrate is 300°

C.

7. The method as recited in claim 1, wherein the bilayer is deposited on a substrate selected from the group consisting of silicon, silicon having a layer of silicon dioxide on the silicon, and a porous substrate.

8. A method as recited in claim 7, wherein the substrate is a low dielectric constant substrate and has a dielectric constant in the range of 2.0–

3.0.

9. A method as recited in claim 7, wherein the substrate has copper conductors, and the bilayer serves as a diffusion barrier for said copper.

10. A method as recited in claim 1, wherein the tantalum halide is tantalum pentachloride.

11. A method as recited in claim 1, wherein the exposing of the substrate to the tantalum halide carried by the inert gas is performed at a pressure of 3.0×

10<sup>−

2</sup> Torr.

12. A method as recited in claim 1, wherein during the exposing of the substrate to the hydrogen and nitrogen plasma, partial pressure of hydrogen is 2.5×

10<sup>−

2</sup> Torr.

13. A method as recited in claim 1, wherein the exposing of the substrate to the tantalum halide carried by the inert gas is carried out for approximately 2 seconds;

and the exposing of the substrate to the hydrogen and nitrogen plasmas is carried out for approximately 5 seconds.

14. The method as recited in claim 1, comprising switching off a source of nitrogen to reduce said concentration of nitrogen in the plasma to zero.

15. The method as recited in claim 1, wherein the first layer and the second layer are sequentially deposited while the substrate is in a chamber by switching off a source of nitrogen to thereby reduce said concentration of nitrogen in the plasma to zero.