2015 Volume 28 Issue 5 Pages 653-658
Reduction of impurities such as gels and metals is one of the critical requirements in chemistries used in directed self assembly lithography (DSAL). In this study, we focused on elucidating the forms of the gels and metals in block copolymer (BCP) solution to effectively reduce these impurities. As a result, particles or gels, and ions are suggested as forms of metals. To reduce these multiple forms of metals, multistep filtrations such as repetitive filtration of single filter material and combination of different type of filters are conducted. As a result, more than 99.99% of Li and more than 99.9% of Al are reduced with a combination of Nylon 6,6 10 nm filtration and ion exchange filtration. The order of the filtration steps does not impact the removal efficiency. The results should contribute realizing DSAL in semiconductor device fabrication.