Use of Nanocrystalline Ceria in EUV Lithography Optics Polishing
P.G. Murray, T. Böhm and H. Maltor
Nanophase Technologies Corporation, US
nanoparticle, ceria, polishing
EUV lithography promises a huge gain in resolution due to the extremely short wavelength. The necessity of aspherical off-axis mirrors dramatically increased the challenge of manufacture compared to refractive designs. Due to the short wavelength of only 13.5-nm, microroughness is one of the driving forces to push fabrication technology toward new areas. A homogeneous roughness and RMS values of 2-angstroms and below are necessary for sufficient throughput and high uniformity. The required microroughness values are obtained by complex polishing processes. In these processes a stable slurry with very well defined properties is crucial.
Carl Zeiss SMT evaluated a number of cerium oxide slurries manufactured by Nanophase Technologies Corporation. The cerium oxide was manufactured using a patented plasma arc process that produces particles with very well defined physical properties. Because of the unique manufacturing process, these particles have highly controlled surface chemistry which results in the ability to prepare extremely stable dispersions in water. These dispersions are useful in polishing processes where a small particle and a tightly controlled particle size distribution are required to access increasingly stringent surface roughness requirements.
The new slurry products will be described and the polishing results of Zeiss presented.
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Nanotech 2006 Conference Program Abstract