Thiourea- and cyanide-free bath and process for electrolytic etching of gold

• US 7,150,820 B2
• Filed: 09/22/2003
• Issued: 12/19/2006
• Est. Priority Date: 09/22/2003
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Semitool Incorporated (Applied Materials Incorporated)
• Inventors: Hu, Zhongmin, Young, Eric J.
• Primary Examiner(s): King, Roy
• Assistant Examiner(s): Alexander, Michael P.
• Application Number:
  US10/667,795
• Publication Number:
  US 20050061683A1
• Time in Patent Office: 1,184 Days
• Field of Search: 205/674, 205/667, 205/684
• US Class Current: 205/684
• CPC Class Codes: C25F 3/02 Etching

Abstract

An aqueous thiourea-free gold etching bath for electrolytically etching gold from a microelectronic workpiece. One embodiment of the aqueous thiourea-free bath contains: (a) about 0.5–1.5 M iodide; (b) about 0.1–0.3 M sulfite; and (c) about 1.0–3.0 g/L wetting agent. The bath is useful in a process for electrolytically etching gold from a microelectronic workpiece. A tool system in which the baths and processes of the present invention may be used is also described.

Claims

1. A process for electrolytically etching gold from a microelectronic workpiece, said process comprising steps of:

(a) providing an aqueous thiourea-free etching bath comprising;

(1) about 0.5–

1.5 M of iodide;

(2) about 0.1–

0.3 M of sulfite; and

(3) about 1.0–

3.0 g/L of wetting agent;

(b) providing a microelectronic workpiece having at least some amount of gold thereon;

(c) contacting the gold with the etching bath; and

(d) providing an electric current flow between the gold and a cathode disposed in electrical contact with the bath, whereby at least a portion of the gold is removed from the microelectronic workpiece.

2. The process of claim 1, wherein a source of said iodide in said bath is selected from the group consisting of LiI, LiI.3H₂O, NaI, NaI.2H₂O, and KI.

3. The process of claim 1, wherein a source of said iodide in said bath is KI.

4. The process of claim 1, wherein the concentration of said iodide in said bath is about 0.9–

1.1 M.

5. The process of claim 1,wherein a source of said sulfite in said bath is selected from the group consisting of Li₂SO₃.H₂O, Na₂SO₃, Na₂SO₃.7H₂O, and K₂SO₃.2H₂O.

6. The process of claim 1, wherein a source of said sulfite in said bath is Na₂SO₃.

7. The process of claim 1, wherein the concentration of said sulfite in said bath is about 0.18–

0.22 M.

8. The process of claim 1, wherein the wetting agent in said bath is a polyethylene glycol.

9. The process of claim 1, wherein the wetting agent in said bath is a polyethylene glycol having an average molecular weight ranging from about 2,000 to about 35,000.

10. The process of claim 8, wherein the concentration of the wetting agent in said bath is about 2.7–

3.3 g/L.

11. The process of claim 1, wherein the pH of said bath is about 6.4–

8.0.

12. A process for electrolytically etching gold from a microelectronic workpiece, said process comprising steps of:

(a) providing an thiourea-free etching bath having a temperature of about 20–

30°

C., said bath comprising;

(1) about 0.9–

1.1 M of iodide, wherein the source of iodide is selected from the group consisting of LiI, LiI.3H₂O, NaI, NaI.2H₂O, and KI;

(2) about 0.18–

0.22 M of sulfite, wherein the source of sulfite is selected from the group consisting of Li₂SO₃.H₂O, Na₂SO₃, Na₂SO₃.7H₂O, and K₂3.2H₂O;

(3) about 2.7–

3.3 g/L of a polyethylene glycol; and

(4) the balance is water;

(b) providing a microelectronic workpiece having at least some amount of gold thereon;

(c) contacting the gold with the etching bath;

(d) providing electric current flow between the gold and a cathode disposed in electrical contact with the bath; and

(e) removing at least a portion of the gold from said microelectronic workpiece.

13. The process of claim 12, wherein the pH of said bath is about 6.4–

8.0.