16 nm 패턴 형성을 위한 극자외선 마스크 결함 및 펠리클 영향 연구

Abstract

Extreme ultraviolet lithography (EUVL) is leading lithography technologies for making small patterns with 22 nm half pitch and below. There are a lot of different processes in EUVL compared with present lithography processes. In order to make smaller patterns, we should make sure all of the EUVL processes including the source, mask and exposure tool are controllable. Especially mask defect is one of the biggest problems in EUVL technology. It can change the pattern size on the wafer by 10% or more. Thus, the influence of the mask defect becomes important in EUVL process. And we must investigate the mask defect and try to remove it. We studied the influence of the defects on the mask for 16 nm node line and space pattern. We changed the sizes and positions of the defect on the mask; on the top of the absorber, on the space and on the both sides of the absorber. We also investigated the defect dependency on shadow effect that the horizontal line width is different from the vertical line width. We found that the location of the defect gave different influence to the wafer pattern even though the defect size was the same. Defect weight factor is suggested to show this kind of different influence. Recently, there are many researches on the use of pellicle in EUVL. Pellicle has been used in ArF lithography to protect printability by the contamination on the mask. EUVL process is totally different from ArF lithography and most materials would absorb EUV light unlike ArF pellicle. And we need a EUV pellicle to protect the mask from the defect and contamination in EUVL. In this study, the influences on the EUV pattern due to silicon pellicle were studied. Reflection with and without pellicle and Carbon contamination effect to the pattern are tested for the possible EUV pellicle use.