Improving the Dynamical Behaviour of a High Mass, High Accuracy Mechanical System

A new extreme ultra violet light source is designed for ASML for the next generation of their machines. The company Settels Savenije van Amelsvoort has been asked to design the mechanical part of this mechatronic system. The challenge with this mechanical design, is that the components in this design are very heavy and have relatively high position stability requirements. In the current design is everything mounted with high stiffness relative to each other. However, due to the large masses of the subsystems, it is a challenge to achieve the desired high eigenfrequencies. The objective of this research is to develop methods to design heavy systems with high performance requirements. In this specific case, the heavy subsystems require impossible high stiffnesses to reach the needed natural frequencies (100-200Hz). One of the two main methods discussed in this report is a method to reduce the mass which must be dynamically stable. A possible solution is to make the sensors less sensitive for positioning errors by adding reference points. The best solution is to make an optical reference point which is much lighter than a camera and its housing. The reference is now responsible for the accuracy of the measurement. The vibrations of the camera have almost no influence on the measurement any more. The other method is to rearrange the stiffnesses between the masses. By cleverly choosing and rearranging the stiffnesses between the masses, the performance is also optimized. With this method, lower stiffnesses are needed to achieve the same dynamical positioning stability. Or when comparable stiffnesses are used, at least a factor two improvement of the dynamical error-reduction can be made. It can be concluded that the overall performance can be increased relative to the current design. The research is done for a general case where the EUV-light source is used as a guideline. Because these methods are analyzed for any type of system, it can also be used for another high precision system with comparable performance challenges.Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin