An apparatus for electrochemically processing a semiconductor substrate includes a processing chamber of the type that is sealable to a peripheral portion of a semiconductor substrate so as to define a covered processing volume. The semiconductor substrate is supported by a substrate support. A magnetic arrangement is disposed outside of the processing chamber and produces a magnetic field. The magnetic field is changed using a controller for controlling the magnetic arrangement. An agitator is disposed within the processing chamber. The agitator comprises a magnetically responsive element which is responsive to changes in the magnetic field of the magnetic arrangement so as to provide a reciprocating motion to the agitator.