Lithographic apparatus and semiconductor device manufacturing method

摘要

In a lithographic apparatus, a feedforward transfer function of a control system, is determined by : a) iteratively learning a feedforward output signal of the control system by iterative learning control for a given setpoint signal; b) determining a relation between the learned feedforward output signal and the setpoint signal; and c) applying the relation as the feedforward transfer function of the control system. A learned feedforward, which has been learned for one or more specific setpoint signals only, can be adapted to provide a setpoint signal dependent feedforward output signal. The learned feedforward can be made more robust against setpoint variations.