To reduce the stochastic defect caused by insufficient photon numbers of extreme ultraviolet lithography, a simple additional process has been designed and experimented. The additional process consists of one coating and washing process after pattern formation by lithography. The coating material was named stochastic defect removal coating and was carefully designed to reduce the stochastic defects without harming the lithographic margin. The defect reduction up to 48% was accomplished by failure-free latitude measurement and defect inspection.

Strong challenge on EUV photoresist includes overcoming the stochastic effect caused by the lack of photons. At the different dose range, the relationship of LCDU and dose moves differently. This ‘breaking point’ in the relationship of LCDU and dose is measured at different pitches with photoresists and masks with different uniformity. Smaller pitch patterning requires more dose, whereas photoresist and mask does not affect the ‘breaking point.’ Combining these speculations show the limitation of the EUV at the low dose process, which is critical for high volume manufacturing.