Apparatuses and methods for maintaining pH in nickel electroplating baths

Patent metadata

Field	Value
Publication number	US-10190232-B2
Application number	US-201313960624-A
Country	US
Kind code	B2
Filing date	Aug 6, 2013
Priority date	Aug 6, 2013
Publication date	Jan 29, 2019
Grant date	Jan 29, 2019

Abstract

Disclosed herein are electroplating systems for electroplating nickel onto a semiconductor substrate having an electroplating cell for holding an electrolyte solution during electroplating which includes a cathode chamber and an anode chamber configured to hold a nickel anode, and having an oxygen removal device arranged to reduce oxygen concentration in the electrolyte solution as it is flowed to the anode chamber during electroplating and during idle times when the system is not electroplating. Also disclosed herein are methods of electroplating nickel onto a substrate in an electroplating cell having anode and cathode chambers, which include reducing the oxygen concentration in an electrolyte solution, flowing the electrolyte solution into the anode chamber and contacting a nickel anode therein, and electroplating nickel from the electrolyte solution onto a substrate in the cathode chamber, wherein the electrolyte solution in the cathode chamber is maintained at a pH of between about 3.5 and 4.5.

First claim

We claim:

1. An electroplating system for electroplating nickel onto a semiconductor substrate comprising:
an electroplating cell configured to hold an electrolyte solution during electroplating, the electroplating cell comprising:
(a) a cathode chamber;
(b) an anode chamber configured to hold a soluble nickel anode during electroplating;
(c) the soluble nickel anode positioned in the anode chamber, wherein the soluble nickel anode is configured to generate nickel ions during electroplating;
(d) a porous separator between the anode chamber and the cathode chamber permitting passage of ionic current during electroplating, but inhibiting the passage of electrolyte solution; and
(e) a semiconductor substrate holder for holding the semiconductor substrate during electroplating; and

an oxygen removal device arranged to reduce oxygen concentration in the electrolyte solution as it is flowed to the anode chamber during electroplating and during idle times when the system is not electroplating; and
a pH meter configured to measure the pH of the electrolyte solution and logic for operating the oxygen removal device in response to values output by the pH meter.

2. The electroplating system of claim 1 , wherein the porous separator is capable of maintaining a difference in oxygen concentration between the anode and cathode chambers.

3. The electroplating system of claim 1 , further comprising an oxygen sensor configured to measure the concentration of oxygen in the electrolyte solution.

4. The electroplating system of claim 1 , wherein the oxygen removal device comprises a degasser located in an anode chamber recirculation loop upstream from the anode chamber.

5. The electroplating system of claim 1 , wherein the oxygen removal device is configured to reduce the oxygen concentration in the electrolyte solution flowing to the anode chamber during some or all idle times to a level such that the pH of the electrolyte solution does not appreciably increase when the electrolyte solution contacts the nickel anode during idle time.

6. An electroplating system for electroplating nickel onto a semiconductor substrate comprising:
an electroplating cell configured to hold an electrolyte solution during electroplating, the electroplating cell comprising:
(a) a cathode chamber;
(b) an anode chamber configured to hold a soluble nickel anode during electroplating;
(c) the soluble nickel anode positioned in the anode chamber, wherein the soluble nickel anode is configured to generate nickel ions during electroplating;
(d) a porous separator between the anode chamber and the cathode chamber permitting passage of ionic current during electroplating, but inhibiting the passage of electrolyte solution; and
(e) a semiconductor substrate holder for holding the semiconductor substrate during electroplating;

an oxygen removal device arranged to reduce oxygen concentration in the electrolyte solution as it is flowed to the anode chamber during electroplating and during idle times when the system is not electroplating;
a semiconductor substrate electrical contact configured to supply a voltage bias to the semiconductor substrate while it is held in the semiconductor substrate holder;
a counterelectrode electrical contact configured to supply a voltage bias to a counterelectrode while contacting the counterelectrode;
an acid generating surface configured to generate free hydrogen ions in the electrolyte solution upon supply of sufficient positive voltage bias relative to the counterelectrode electrical contact; and
one or more electrical power units configured to supply a negative voltage bias to the semiconductor substrate electrical contact relative to the counterelectrode electrical contact sufficient to reduce and plate nickel ions from the electrolyte solution onto the semiconductor substrate surface, and to supply a positive voltage bias to the acid generating surface relative to the counterelectrode electrical contact sufficient to generate free hydrogen ions at the acid generating surface thereby decreasing the pH of the electrolyte solution.

7. The electroplating system of claim 6 , wherein the free hydrogen ions are generated at the acid generating surface by electrolysis of water molecules in the electrolyte solution.

8. The electroplating system of claim 6 , wherein the acid generating surface comprises:
a body comprising an electrically conductive, corrosion-resistant material which does not substantially corrode in the electrolyte solution; and
a coating on the body, the coating comprising either platinum or one or more metal oxides selected from the oxides of platinum, niobium, ruthenium, iridium, and tantalum.

9. The electroplating system of claim 8 , wherein the electrically conductive, corrosion-resistant material is selected from the group consisting of titanium, tantalum, niobium, and zirconium.

10. The electroplating system of claim 6 , further comprising:
an acid generating bath reservoir having a fluidic inlet and a fluidic outlet, the reservoir configured to hold a volume of the electrolyte solution, and within which the acid generating surface is located; and
an acid generating bath reservoir recirculation loop fluidically coupling the acid generating bath reservoir's fluidic outlet with the anode chamber's fluidic inlet and/or cathode chamber's fluid inlet, and fluidically coupling the acid generating bath reservoir's fluidic inlet with the anode chamber's fluidic outlet and/or cathode chamber's fluidic outlet;

wherein the counterelectrode electrical contact is further configured to supply a voltage bias to a counterelectrode located within the acid generating bath reservoir; and
wherein, during circulation of the electrolyte solution through the acid generating bath reservoir recirculation loop, the electrolyte solution flowing through the acid generating bath reservoir's fluidic outlet has a lower pH than the electrolyte solution flowing through the reservoir's fluidic inlet.

11. An electroplating system for electroplating nickel onto a semiconductor substrate comprising:
an electroplating cell configured to hold an electrolyte solution during electroplating, the electroplating cell comprising:
(a) a cathode chamber;
(b) an anode chamber configured to hold a nickel anode during electroplating;
(c) a porous separator between the anode chamber and the cathode chamber permitting passage of ionic current during electroplating, but inhibiting the passage of electrolyte solution; and
(d) a semiconductor substrate holder for holding the semiconductor substrate during electroplating;

an oxygen removal device arranged to reduce oxygen concentration in the electrolyte solution as it is flowed to the anode chamber during electroplating and during idle times when the system is not electroplating;
an electrolyte recirculation system, wherein the electrolyte recirculation system is configured for mixing an electrolyte removed from the cathode chamber and an electrolyte removed from the anode chamber, and re-introducing the electrolyte after mixing to the electroplating cell, wherein the electrolyte recirculation system comprises an anode chamber recirculation loop and a cathode chamber recirculation loop, the loops having one or more shared fluid delivery lines, wherein the oxygen removal device comprises a degasser located in the anode chamber recirculation loop upstream from the anode chamber and downstream from a bath reservoir, and wherein the degasser is not located in the cathode chamber recirculation loop;
a semiconductor substrate electrical contact configured to supply a voltage bias to the semiconductor substrate while it is held in the semiconductor substrate h

Assignees

• Lam Res Corp

Inventors

• Buckalew Bryan L
• Ponnuswamy Thomas A
• Foley Ben
• Mayer Steven T

Classifications

• C25D21/12

  Process control or regulation (controlling or regulating in general G05) · CPC title

• C25D21/14

  Controlled addition of electrolyte components · CPC title

• C25D17/001

  Apparatus specially adapted for electrolytic coating of wafers, e.g. semiconductors or solar cells · CPC title

• C25D17/002

  Cell separation, e.g. membranes, diaphragms · CPC title

• C25D3/12 Primary

  of nickel or cobalt · CPC title