Rapid freeze-cleaning method for removing nanoparticles

<!-- START_ABSTRACT --> <p> BackgroundOur previously proposed freeze-cleaning method, which actively utilizes the supercooled state of water, demonstrated effective cleaning of photomasks and nanoimprint lithography templates. However, achieving sufficiently high particle removability required repeated freezing and thawing (15 times or more), which highlights the need to reduce the number of cycles for enhanced efficiency.AimWe aimed to reduce the number of freeze–thaw cycles to minimize the total cleaning time.ApproachFirst, the particle reattachment was suppressed. Second, the relationship between particle removability and the temperature distribution of the water film on the substrate at the onset of freezing was evaluated. Finally, the dependence of particle removability on the number of freeze–thaw cycles under conditions that were improved based on these findings was analyzed.ResultsParticle removability was significantly improved by incorporating low-power megasonics during thawing and minimizing the temperature difference in the water film on the substrate at the onset of freezing. Notably, the required number of freeze–thaw cycles was reduced to five.ConclusionsThe number of freeze–thaw cycles was successfully reduced by minimizing particle reattachment and enhancing particle removability. </p> <!-- END_ABSTRACT --> <!-- START_TEMPLATE --> <ul> <li> Source: </li> <li> Tags: </li> </ul> <!-- END_TEMPLATE -->