Numerics for Control & Identification (N4CI)

Without doubt, Extreme UV Lithography represents today's most advanced optical imaging method, operating at the shortest wavelength ever employed for high-resolution and wide field imaging. The technique, being considered indispensible for the fabrication of the next generation of semiconductor circuits, represents a major challenge for optics development in general. Typically, sub-tenth nanometer precision is required for the optics' accuracy and positioning, while, simultaneously, kilowatt-power level EUV light sources cause tremendous thermal loads on the optics, leading to distortions of the fine imaging process.

The obvious, though so far unexplored, solution to this challenge is to add adaptive functionality where it is most effective, namely in the EUV-reflective multilayer coatings. These Bragg-reflecting layers, for which the team holds a world reflectivity record, have enabled the success of early EUV wafer scanners. Yet, they must now be modified to include adaptive figure and spectral functionality to reach the required accuracy and stability.

We propose a rigorous new multilayer composition, including piezo- and pyro-electrical materials so that the periodic Bragg structure can be interactively manipulated. Steering such control layers by external electrical or thermal signals will then allow wavefront corrections and localized reflectivity changes.

The aim of this project is to achieve an integrated system, where adaptive optics specifically suitable to the EUV are individually manipulated to obtain optimized EUVL system performance. These 'interactive-EUV' multilayer optics will need to be grown with layer-thicknesses that have a precision well into the sub-nanometer range, while at the same time having chemical and thermal stability, and atomically sharp optical index profiles.

To meet these requirements, fundamental challenges in optics, materials science, and thin-film physics must be resolved. In the SMILE project, the essential elements are uniquely combined to achieve these goals:

• a unique thin film deposition and analysis instrumentation, as well as a proven deposition technology, ideally suited to produce the ultrathin layers from the complex piezo materials while preserving their adaptive properties,
• a positive assessment of critical adaptive and multilayer control concepts, showing more than adequate dimensional change effects for the proposed adaptive multilayer coatings, including a patent on this adaptive EUV optics,
• a new analysis technique in the form of state-of-the-art EUV interferometry with picometer resolution,
• substantial support from our industrial partner on design, analysis, and system engineering,
• a proven track record of the team in transfer of know-how to industry.