System identification of anti-vibration units in semiconductor exposure apparatus

System identification of semiconductor exposure apparatus is discussed. It has a multi-degrees-of-freedom mechanism which includes anti-vibration units for microvibration control. A dynamical model of the mechanism is necessary in order to design the microvibration controller. The model is practically constructed in a short time using a subspace method. Identification results are evaluated through experimental data in comparison with a conventional frequency response method.