Copper electroplating process for uniform across wafer deposition and void free filling on ruthenium coated wafers

• US 8,703,615 B1
• Filed: 02/07/2012
• Issued: 04/22/2014
• Est. Priority Date: 03/06/2008
• Status: Expired due to Fees

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Ponnuswamy, Thomas A., Sukamto, John H., Reid, Jonathan D., Mayer, Steven T., Zhu, Huanfeng
• Primary Examiner(s): Shepard, Sonya D McCall
• Application Number:
  US13/367,710
• Time in Patent Office: 805 Days
• Field of Search: None
• US Class Current: 438/687
• CPC Class Codes: C25D 3/38 of copper
• CPC Class Codes: C25D 5/18 Electroplating using modulated, pulsed or reversing current
• CPC Class Codes: C25D 5/50 by heat-treatment
• CPC Class Codes: C25D 5/605 Surface topography of the layers, e.g. rough, dendritic or nodular layers
• CPC Class Codes: C25D 5/617 Crystalline layers
• CPC Class Codes: C25D 7/123 Semiconductors first coated with a seed layer or a conductive layer
• CPC Class Codes: H01L 21/2885 using an external electrical current, i.e. electro-deposition
• CPC Class Codes: H01L 21/76843 formed in openings in a dielectric
• CPC Class Codes: H01L 21/76864 Thermal treatment
• CPC Class Codes: H01L 21/76873 for electroplating
• CPC Class Codes: H01L 2221/1089 Stacks of seed layers

Abstract

Disclosed are methods of depositing and annealing a copper seed layer. A copper seed layer may be deposited on a ruthenium layer disposed on a surface of a wafer and on features in the wafer. The thickness of the ruthenium layer may be about 40 Angstroms or less. The copper seed layer may be annealed in a reducing atmosphere having an oxygen concentration of about 2 parts per million or less. Annealing the copper seed layer in a low-oxygen atmosphere may improve the properties of the copper seed layer.

Claims

1. A method comprising:

providing a semiconductor wafer having a ruthenium layer about 40 Angstroms thick or less on a surface of and on features in the semiconductor wafer;

depositing a copper seed layer on the ruthenium layer; and

annealing the copper seed layer in a reducing atmosphere having an oxygen concentration of about 2 parts per million or less.

2. The method of claim 1, further comprising:

electroplating a bulk-layer of copper onto the annealed copper seed layer.

3. The method of claim 1, wherein the reducing atmosphere includes forming gas.

4. The method of claim 1, wherein an annealing temperature is about 100°

C. to 400°

C.

5. The method of claim 1, wherein the semiconductor wafer is annealed for a period of about 10 seconds to 1000 seconds.

6. The method of claim 1, further comprising:

before depositing the copper seed layer, annealing the ruthenium layer.

7. The method of claim 1, wherein the deposited copper seed layer has a thickness of about 15 Angstroms to 60 Angstroms.

8. The method of claim 1, wherein the depositing the copper seed layer on the ruthenium layer is performed using an electroplating process, the electroplating process including forward current operations and reverse current operations.

9. The method of claim 8, wherein the forward current operations include a current of about 0.5 amps to 1.25 amps for a period of about 2 seconds to 5 seconds, wherein the reverse current operations include a current of about 1 amp to 2 amps for a period of about 50 milliseconds to 200 milliseconds, and wherein the forward current operations and the reverse current operations are alternately repeated for a period of about 15 seconds to 60 seconds.

10. The method of claim 1, wherein the ruthenium layer on the surface of the semiconductor wafer is about 30 Angstroms thick or less.

11. The method of claim 1, wherein the reducing atmosphere has an oxygen concentration of about 1 part per million or less.

12. The method of claim 1, wherein a root mean square roughness of the copper seed layer is about 40 Angstroms or less after annealing the copper seed layer.

13. The method of claim 1, further comprising:

applying photoresist to the semiconductor wafer;

exposing the photoresist to light;

patterning the photoresist and transferring the pattern to the semiconductor wafer; and

selectively removing the photoresist from the semiconductor wafer.

14. A method comprising:

providing a semiconductor wafer having a ruthenium layer about 40 Angstroms thick or less on a surface of and on features in the semiconductor wafer;

depositing a copper alloy seed layer on the ruthenium layer; and

annealing the copper alloy seed layer in a reducing atmosphere having an oxygen concentration of about 2 parts per million or less.

15. The method of claim 14, wherein an alloying element of the copper alloy seed layer is selected from the group consisting of chromium, iron, cobalt, nickel, zinc, ruthenium, rhodium, palladium, silver, indium, tin, tellurium, platinum, gold, and lead.

16. The method of claim 14, wherein the deposited copper alloy seed layer includes about 0.1 weight percent to 5 weight percent of an alloying element.

17. The method of claim 14, wherein the depositing the copper alloy seed layer on the ruthenium layer is performed using an electroplating process, the electroplating process including forward current operations and reverse current operations.

18. The method of claim 17, wherein the forward current operations include a current of about 0.5 amps to 1.25 amps for a period of about 2 seconds to 5 seconds, wherein the reverse current operations include a current of about 1 amp to 2 amps for a period of about 50 milliseconds to 200 milliseconds, and wherein the forward current operations and the reverse current operations are alternately repeated for a period of about 15 seconds to 60 seconds.

19. The method of claim 14, wherein the ruthenium layer on the surface of the semiconductor wafer is about 30 Angstroms thick or less.

20. The method of claim 14, wherein the reducing atmosphere has an oxygen concentration of about 1 part per million or less.

21. The method of claim 14, wherein a root mean square roughness of the copper alloy seed layer is about 40 Angstroms or less after annealing the copper alloy seed layer.

22. A non-transitory computer machine-readable medium comprising program instructions for control of an apparatus, the instructions comprising code for:

providing a semiconductor wafer having a ruthenium layer about 40 Angstroms thick or less on a surface of and on features in the semiconductor wafer;

depositing a copper seed layer on the ruthenium layer; and

annealing the copper seed layer in a reducing atmosphere having an oxygen concentration of about 2 parts per million or less.

23. A system comprising:

an electroplating apparatus;

an annealing furnace; and

one or more controllers including program instructions for conducting a process including;

receiving a semiconductor wafer in the electroplating apparatus;

depositing a copper seed layer on the wafer in the electroplating apparatus with an electroplating process, under conditions for depositing the copper seed layer on a ruthenium layer having a thickness of about 40 Angstroms or less on the semiconductor wafer surface and on features in the semiconductor wafer; and

annealing the copper seed layer in a reducing atmosphere having an oxygen concentration of about 2 parts per million or less in the annealing furnace.

24. The system of claim 23, further comprising:

a stepper.