Design of an astigmatically neutral mirror using thermal path optimization

Design of an astigmatically neutral mirror using thermal path optimization

van Mierlo, Martin (TU Delft Mechanical, Maritime and Materials Engineering)

Delft University of Technology

Mechanical Engineering | Optomechatronics

2019-10-31

The production of Extreme UltraViolet (EUV) light requires a high power CO2 laser which fires upon droplets of tin. The focus of this thesis shall lie in two aspects of this process: the heat load resulting from the high power and the contamination resulting from the rapid phase change of the droplets. The wavefront of the laser suffers aberrations from the variations in the surface profiles of the mirrors in the system. The variations are dominated by the thermal load that exists due to the imperfect reflectivity of the mirrors. A new mirror design seeks to limit the negative aberrations due to the high power laser. Additionally, the act of firing on a tin droplet creates contamination on surfaces in proximity of the EUV generation. The contamination results in a reduction in performance of the mirror and an associated swap time for the mirror decreases availability of the machine. The proposed design leverages principles not classically seen in high power mirror design. The design seeks to demonstrate that the shortest thermal path (resulting in the lowest temperature) is not the only avenue to create a high performance, high power mirror; and indeed, there exists opportunity for performance improvement. A design is proposed with 5 to 10X improvement in optical performance and 4X improvement in swap time in comparison with the current design.

EUV
mirror
laser

http://resolver.tudelft.nl/uuid:3c1000eb-2fe9-450a-ad9b-a47b6e8053e9

Student theses

master thesis

© 2019 Martin van Mierlo