US 6402923 B1 An electrochemical reactor is used to electrofill
damascene architecture for integrated circuits. A shield is used
to screen the applied field during electroplating operations to
compensate for potential drop along the radius of a wafer. The
shield establishes an inverse potential drop in the electrolytic
fluid to overcome the resistance of a thin film seed layer of
copper on the wafer. 1. An electrochemical reactor having a
variable field-shaping capability for use in electroplating thin
films, comprising: a reservoir operably configured to retain an
electrolytic fluid; a cathode and an anode disposed in said
reservoir to provide an electrical pathway through electrolytic
fluid when said electrolytic fluid is present in said reservoir;
at least one of said cathode and said anode including a wafer-
holder; a shield positioned in said electrical pathway between
said cathode and said anode and operably configured for
shielding a surface area on a wafer in said wafer-holder when
said wafer is held i