Deposit morphology of electroplated copper

• US 8,197,662 B1
• Filed: 12/17/2010
• Issued: 06/12/2012
• Est. Priority Date: 12/18/2003
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Webb, Eric, Reid, Jonathan D., Takada, Yuichi, Archer, Timothy
• Primary Examiner(s): Van, Luan
• Application Number:
  US12/971,367
• Time in Patent Office: 543 Days
• Field of Search: 205/118, 205/205, 205/210
• US Class Current: 205/210
• CPC Class Codes: C25D 5/34 Pretreatment of metallic surfaces to be electroplated
• 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 21/76877 Filling of holes, grooves or trenches, e.g. vias, with conductive material

Abstract

The present invention provides improved methods and devices for electroplating copper on a wafer. Some implementations of the present invention involve the pre-treatment of the wafer with a solution containing accelerator molecules. Preferably, the bath into which the wafer is subsequently placed for electroplating has a reduced concentration of accelerator molecules. The pre-treatment causes a reduction in roughness of the electroplated copper surface, particularly during the initial phases of copper growth.

Claims

1. A method comprising:

providing a substrate having a copper seed layer;

spraying the copper seed layer with a pretreatment solution including an accelerator additive; and

depositing copper on the copper seed layer in a plating solution including substantially no accelerator additive.

2. The method of claim 1, wherein the accelerator additive of the pretreatment solution includes mercaptopropanesulfonic acid.

3. The method of claim 1, wherein the accelerator additive of the pretreatment solution is selected from the group consisting of:

organic sulfur compounds in different thiol forms having the structure of X—

S—

S—

C—

C—

C—

SO3-;

a derivative of mercaptopropanesulfonic acid;

bis(3-sulfopropyl)disulfide;

3-mercapto-propanesulphonic acid;

bis(3-sulfoethyl)disulfide;

3-(benzothiazolyl-2-mercapto)-propyl-sulfonic acid; and

N,N-dimethyl-dithiocarbamylpropyl sulfonic acid.

4. The method of claim 1, wherein a pH of the pretreatment solution is within a range of 4 to 8.

5. The method of claim 1, wherein the substrate includes a via.

6. The method of claim 1, wherein the plating solution includes a leveler additive.

7. The method of claim 1, wherein the leveler additive is selected from the group consisting of:

a cationic compound including protonated nitrogen-based functional groups;

dodecyltrimethylammonium bromide; and

a leveler of the tetraalkylammonium class.

8. A method comprising:

providing a substrate having a surface having a copper seed layer;

spraying the copper seed layer with a pretreatment solution including an accelerator additive;

applying a DC cathodic current density through the surface to cathodically polarize the copper seed layer with respect to an electroplating solution, the electroplating solution including substantially no accelerator additive; and

immersing the surface in the electroplating solution.

9. The method of claim 8, wherein the DC cathodic current density is applied prior to or less than approximately 5 seconds following the immersing the surface in the electroplating solution.

10. The method of claim 8, wherein DC cathodic current density is between about 0.02 and about 10 milliamperes per square centimeter.

11. The method of claim 8, wherein the DC cathodic current density includes cathodic current pulses superimposed on the DC cathodic current density.

12. The method of claim 11, wherein the cathodic current pulses have a current density between about 25 and about 250 milliamperes per square centimeter.

13. The method of claim 11, wherein the cathodic current pulses have a pulse length between about 0.5 and about 10 milliseconds.

14. The method of claim 8, wherein the DC cathodic current density includes alternating cathodic current pulses and anodic current pulses superimposed on the DC cathodic current density.

15. A method comprising:

providing a substrate having a surface including a field region and a plurality of recessed features, the surface having a copper seed layer;

spraying the surface with a pretreatment solution including an accelerator additive;

immersing the surface in an electroplating solution including copper ions, a leveler additive, and substantially no accelerator additive; and

applying a first DC cathodic current density through the surface, the first DC cathodic current density being sufficiently small such that depletion of the copper ions and the leveler additive is absent at the field region and at the plurality of recessed features.

16. The method of claim 15, further comprising

applying a second DC cathodic current density through the surface, the second DC cathodic current density being at a level such that deposition of copper occurs preferentially on bottoms of the recessed features having the largest aspect ratios;

increasing the second DC cathodic current density until the plurality of recessed features have aspect ratios less than about 0.5; and

further increasing the current density to a level of DC cathodic current density that fills the plurality of recessed features with copper and deposits copper onto the field region.

17. The method of claim 15, wherein the accelerator additive of the pretreatment solution includes mercaptopropanesulfonic acid.

18. The method of claim 15, wherein the accelerator additive of the pretreatment solution is selected from the group consisting of:

organic sulfur compounds in different thiol forms having the structure of X—

S—

S—

C—

C—

C—

SO3-;

a derivative of mercaptopropanesulfonic acid;

bis(3-sulfopropyl)disulfide;

3-mercapto-propanesulphonic acid;

bis(3-sulfoethyl)disulfide;

3-(benzothiazolyl-2-mercapto)-propyl-sulfonic acid; and

N,N-dimethyl-dithiocarbamylpropyl sulfonic acid.

19. The method of claim 15, wherein the leveler additive is at a concentration in a range from 1 ppm to 7 ppm.

20. The method of claim 15, wherein the leveler additive is selected from the group consisting of:

a cationic compound including protonated nitrogen-based functional groups;

dodecyltrimethylammonium bromide; and

a leveler of the tetraalkylammonium class.