Effect of reverse flow by differential pressure on the protection of critical surfaces against particle contamination

TLDR: In this paper, a reverse flow concept by introducing differential pressure between different operating zones (mask zone with higher pressure and optics zone with lower pressure) is introduced for protection of critical surfaces against particulate contamination.

Abstract: Mask protection from particulate contaminants is one of the most serious concerns for the success of deploying extreme ultraviolet lithography (EUVL) technology for future semiconductor manufacturing. Standard pellicles are not applicable for an EUVL mask surface because of the high absorption of the EUV beam by any material. Therefore, methods such as thermophoresis and electrophoresis are desirable for protection, instead of using organic membrane pellicles. A reverse flow concept by introducing differential pressure between different operating zones (mask zone with higher pressure and optics zone with lower pressure) is introduced for protection of critical surfaces against particulate contamination. In this study, we show systematic investigations of the differential pressure effect on the protection of critical surfaces using 125nm polystyrene latex spheres at a chamber pressure of 50mTorr, whereas the critical surface zone pressure was varied up to 550mTorr. We found that a higher particle speed nee...