Apparatus for processing an object with high position accurancy

摘要

A apparatus processes an object ( 19 ), such as a semi-conductor wafer at accurately controlled positions. The object ( 19 ) is supported by a working platform ( 12 ) that is moveable along a path. A suspension actuator part ( 14 ) attached to the working platform ( 12 ), contains a soft magnetic core ( 24 ) with poles facing the surface of a soft magnetic element ( 34 ) on the support structure along the path and a winding ( 20 ) for application of a current to generate a magnetic field that runs through the core ( 24 ) v the poles and returns via the soft magnetic element ( 34 ). A sensor ( 17 ) senses a measured position of the suspension actuator part ( 14 ) relative to the position reference element ( 16 ). A control circuit comprises an outer control circuit ( 40 ) and an inner control circuit ( 42 ). The outer control circuit ( 40 ) receives a sensing result and determines force set point information to regulate the measured position of the actuator part ( 14 ) to a required value. The inner control circuit ( 42 ) receives the force set point information and controls the current to realize a force between the actuator part ( 14 ) and the support structure ( 10 ) according to the force set point information.