Method and apparatus for dynamic current distribution control during electroplating

Abstract

A method of electroplating a metal on a cathodically biased wafer substrate employs an electroplating apparatus having a main anode, an auxiliary electrode and an ionic current collimator, where the ionic current collimator is configured to direct ionic current that is generated by the main anode from a periphery of a plating vessel to its center. During electroplating, in a first electroplating stage (e.g., when terminal effect is pronounced), the metal is plated onto the wafer while the auxiliary electrode is cathodically biased; and in a second electroplating stage (e.g., when terminal effect subsides), the metal is plated onto the wafer while the auxiliary electrode is anodically biased. In some embodiments the auxiliary electrode is located between the ionic current collimator and the wafer, and is configured to redistribute ionic current that has passed through the collimator. The method is useful for improving the uniformity of electroplating.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a division of and claims priority to U.S. application Ser. No. 14 / 067,616 filed on Oct. 30, 2013, titled “Method and Apparatus for Dynamic Current Distribution Control during Electroplating” naming Zhian He as the inventor, which claims benefit of prior U.S. Provisional Application No. 61 / 730,285 filed on Nov. 27, 2012, titled “Method and Apparatus for dynamic Current Distribution Control during Electroplating” naming Zhian He as the inventor, which are herein incorporated by reference in their entirety and for all purposes.FIELD OF THE INVENTION[0002]The present invention pertains to methods and apparatuses for electroplating. Specifically, the invention pertains to electroplating tools used for electrodeposition of metals in semiconductor processing.BACKGROUND OF THE INVENTION[0003]The transition from aluminum to copper in integrated circuit (IC) fabrication required a change in process “architecture” (to damascene a...

AI Technical Summary

Benefits of technology

The patent text describes an apparatus and method for electroplating metal onto a wafer substrate. The apparatus includes a plating vessel with an ionic current collimator and an auxiliary electrode with flexible electrical characteristics. The ionic current collimator helps to control the terminal effect, which is the difficulty in controlling the plating process when the seed layer on the wafer is most resistive. The auxiliary electrode can be adjusted to compensate for the terminal effect and make the plating process more uniform. The method involves performing electroplating in two stages, with the auxiliary electrode being cathodically or anodically biased during each stage. The technical effects of this invention include improved control of the terminal effect and more uniform plating on the wafer substrate.

Problems solved by technology

It becomes a very challenging problem to achieve uniform initial plating across the wafer with such resistive seed layers.

Without appropriate means of resistance and voltage compensation, this large edge-to-center voltage drop could lead to an extremely non-uniform plating thickness distribution, primarily characterized by thicker plating at the wafer edge.

The difficulty in controlling the terminal effect is further exacerbated by the fact that it is very pronounced in the beginning of electroplating when the seed layer on the wafer is most resistive, but is rapidly diminishing during the course of electroplating.

However, the use of ionic current collimator alone would have resulted in unnecessarily center-thick plating.

Images