Molecular Design of o-Nitrobenzyl Phenol Ether for Photo-deprotection Resist; Challenge to half-pitch 22 nm using Near-field Lithography

Polyhydroxystyrenes protected with three kinds of o-nitrobenzyl (NB) group are synthesized: 4,5- dimethoxy NB group (DNB), 4- monomethoxy NB group (MNB) and $alpha;-methyl 4,5- dimethoxy NB group (ADNB). Their solutions are formulated as photo-deprotection resists for the near-field lithography (NFL). These resists are evaluated in terms of the fundamental lithographic performances using the propagation i-line light, followed by the NFL experiments. The ADNB has the highest photosensitivity and the DNB provides the resist patterns of the smallest line edge roughness (LER). Hp 22 nm L/S pattern of 10 nm deep is fabricated on the top portion of a single-layer of DNB. Hp 32 nm L/S pattern of 10 nm thick is transferred to the 100 nm thick bottom-layer resist through the tri-layer resist process.