Mask Cleaning in EUV and Nano-Imprint Lithography

Extreme Ultra-Violet Lithography (EUVL) and Nano-Imprint Lithography (NIL) are the two leading candidates for next generation lithography (NGL). New image projection methods and materials have led to inherent changes in the way EUVL masks and NIL templates are manufactured, handled, stored and processed. Where a pellicle is used to protect the patterned area of a conventional optical mask, both EUV masks and NIL templates are without surface protection and thus more susceptible to contamination during transportation, storage and the photolithography process. Zero tolerance levels for impurities, particles, pattern defects and/or surface layer damage is driving the development of new cleaning technology that can eliminate contamination and preserve the integrity of the mask/ template. In this paper, key cleaning challenges for EUV masks and NIL templates are addressed and novel cleaning techniques are demonstrated that remove contamination without pattern damage or surface properties changes.