Apparatus for processing an object with high position accurancy

Abstract

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