In developing high sensitivity extreme ultraviolet (EUV) resists, we focused on the fact that EUV photon absorption by
chalcogen atoms is larger than that by carbon or hydrogen atoms. We chose this focus because it is considered that in
EUV the absorption of incident radiation by base polymers influences acid generation. To determine the effects of
introducing chalcogen atoms into base polymers under EUV exposure on lithography performance, we synthesized novel
co-polymers of novel methacylate monomers that included oxygen and sulfur atoms in acid-cleavable moiety as well as
polar monomers, and evaluated their sensitivity under EUV and ArF exposure. The sensitivity of polymers that were rich
in chalcogen atom content improved more under EUV exposure than under ArF exposure. We also used a highsensitivity
quadrupole mass spectrometer (QMS) to observe the outgassing species generated from these polymers under
EUV exposure in detail.
In recent years, ArF lithography has required a half-pitch size (DRAM) of 45 nm or less. To achieve the
requirement, line edge roughness (LER) is recognized as one of the most serious problems in lithography today,
because LER directly degrades device characteristics and affects system performances. Although the uniformity of
polymer film is important for reducing LER, little is known about polymer morphology after coating. In this study, we
observed the surface of poly(methacrylate) samples after coating with AFM tapping mode and found specific
morphology in the phase images for the first time (the height image was flat).
We report effects of methacrylates with polar group on resist performance determined by Quartz crystal microbalance (QCM) method. We found that high composition ratio of mevalonic lactone methacrylate accelerates dissolution of the resist film, which is suitable for high resolution resist. In addition, dissolution rate of the resist film depends on the structure of polar monomer. Also, a difference of swelling depending on the structure of polar monomer was observed in a low exposure dose. We think that the polymer polarity and acid dissociation energy of pendant group were influential to these phenomena. This information is also useful to develop new materials for ArF lithography.