EUV lithography has been delayed due to well-known issues such as source power, debris, pellicle, etc. for high volume
manufacturing. For this reason, conventional optical lithography has been developed to cover more generations with
various kinds of Resolution Enhancement Techniques (RETs) and new process technology like Multiple Patterning
Technology (MPT). Presently, industry lithographers have been adopting two similar techniques of the computational
OPC scheme such as Inverse Lithography Technology (ILT) and Source Mask Optimization (SMO) . Sub-20 nm node
masks including these technologies are very difficult to fabricate due to many small features which are near the limits of
mask patterning process. Therefore, these masks require the unseen level of difficulty for inspection. In other words,
from the viewpoint of mask inspection, it is very challenging to maintain maximum sensitivities on main features and
minimum detection rates on the Sub-Resolution Assist Features (SRAFs). This paper describes the proper technique as
the alternative solution to overcome these critical issues with Aerial Imaging (AI) inspection and High Resolution (HR)
As the design rule shrinks continuously, a reticle inspection is getting harsh and harsh and is now one of the most
critical issues in the mask fabrication process. The reticle inspection process burdens the entire mask process with the
inspectability and detectability problems. Not only aggressive assist features but also small and dense main features
themselves may cause many false detection alarms or nuisance defects, which makes the inspection TAT (Turn-around
Time) longer. Moreover, small and dense patterns inspections always come with the defect detectability issues.
Detectability of a defect in small and dense patterns is usually inferior to the printability of it because of the high MEEF
(Mask Error Enhancement Factor) resulted by those small and dense patterns.
Double Patterning Technology (DPT) can relief the pattern pitch effectively, therefore, DPT reticle pattern can
have a larger pitch than normal Single Patterning Technology (SPT) reticle. We investigate the effect of this pitch
relaxation of DPT reticle on the inspection process.
In this paper, we compare and analyze the difference of pattern inspectability and defect detectability between DPT
reticles and SPT reticles when they have same size of patterns on them. In addition to these results, we also
investigate the printability of defects in comparison with the detectability and derive the requirement of the inspection
for 4x nodes DPT reticles from the results.