Method and apparatus for dynamic current distribution control during electroplating

Patent metadata

Field	Value
Publication number	US-9909228-B2
Application number	US-201314067616-A
Country	US
Kind code	B2
Filing date	Oct 30, 2013
Priority date	Nov 27, 2012
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

An apparatus for electroplating a layer of metal onto the surface of a wafer includes an auxiliary electrode that is configured to function both as an auxiliary cathode and an auxiliary anode during the course of electroplating. The apparatus further includes an ionic current collimator (e.g., a focus ring) configured to direct ionic current from the main anode to central portions of the wafer. The provided configuration effectively redistributes ionic current in the plating system allowing plating of uniform metal layers and mitigating the terminal effect. In one example, the auxiliary electrode functions as an auxiliary cathode in the beginning of electroplating when the terminal effect is pronounced, and subsequently is anodically biased.

First claim

The invention claimed is:

1. An electroplating apparatus for depositing metal on a wafer substrate, the apparatus comprising:
(a) a plating vessel configured for holding an electroplating solution therein;
(b) a wafer substrate holder configured for holding the wafer substrate in position during electroplating, the wafer substrate holder having one or more electrical power contacts arranged to contact an edge of the substrate and to provide electrical current to the wafer substrate during electroplating, wherein the apparatus is configured for cathodically biasing the wafer substrate during electroplating;
(c) an anode residing in the plating vessel, wherein the anode is configured to be anodically biased at least during a portion of electroplating;
(d) an ionic current collimator proximate the anode, wherein the ionic current collimator is a non-conductive member configured to direct an ionic current from the anode generally in a direction from a periphery to a center of the plating vessel; and
(e) an auxiliary electrode configured to be both cathodically and anodically biased during electroplating, wherein a footprint of the auxiliary electrode onto the anode is at least about 40% of an anode area, and wherein the auxiliary electrode resides between the ionic current collimator and the wafer substrate holder.

2. The apparatus of claim 1 , wherein the ionic current collimator comprises:
(i) a central portion in the form of an open cylinder extending in a direction that is perpendicular to a plating surface of the wafer substrate, wherein the openings of the cylinder provide a route for the ionic current; and
(ii) a current restricting portion connected to the central portion, the current restricting portion extending in a direction that is parallel to the plating surface of the wafer substrate.

3. The apparatus of claim 2 , wherein the current restricting portion of the ionic current collimator extends to sidewalls of the plating vessel, and is configured to block ionic current at the periphery of the plating vessel.

4. The apparatus of claim 3 , wherein the current restricting portion of the ionic current collimator is attached to the sidewalls of the plating vessel.

5. The apparatus of claim 1 , wherein the ionic current collimator is made of a dielectric material that is not permeable to electrolyte and is selected from the group consisting of polycarbonate, polyethylene, polypropylene, polyvinylidene difluoride (PVDF), polytetrafluoroethylene, and polysulphone.

6. The apparatus of claim 1 , wherein the ionic current collimator does not contact the anode and is spaced from the anode by a distance of at least about 15% of the wafer substrate radius.

7. The apparatus of claim 1 , wherein the ionic current collimator is configured to be moveable in a direction that is perpendicular to a plating surface of the wafer substrate during electroplating.

8. The apparatus of claim 1 , wherein the ionic current collimator is configured to be stationary during electroplating.

9. The apparatus of claim 1 , wherein the ionic current collimator serves as a platform supporting the auxiliary electrode.

10. The apparatus of claim 1 , further comprising one or more power supplies configured to bias the auxiliary electrode both negatively and positively during the course of electroplating.

11. The apparatus of claim 1 , wherein the auxiliary electrode comprises copper at least on the surface of the auxiliary electrode.

12. The apparatus of claim 1 , wherein the apparatus is configured to bias the auxiliary electrode negatively in the beginning of electroplating to divert ionic current, and then positively to donate ionic current.

13. The apparatus of claim 1 , wherein the auxiliary electrode has a generally toroidal shape and a thickness of at least about 20 mm.

14. The apparatus of claim 1 , wherein the auxiliary electrode has a working surface of at least about 600 cm 2 .

15. The apparatus of claim 1 , further comprising a controller comprising program instructions and/or built in logic for:
(i) in a first electroplating stage, electroplating metal onto the wafer substrate while cathodically biasing the auxiliary electrode; and
(ii) in a second electroplating stage, electroplating metal onto the wafer substrate while anodically biasing the auxiliary electrode.

16. The apparatus of claim 1 , included in a system, further comprising a stepper.

Assignees

• Lam Res Corp

Inventors

• He Zhian

Classifications

• C25D5/022

  using masking means · CPC title

• C25D21/12

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

• C25D17/10

  Electrodes {, e.g. composition, counter electrode} · CPC title

• C25D17/007

  Current directing devices · CPC title

• C25D17/001 Primary

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