Fabrication of sub-100nm Patterns using Near-field Mask Lithography with Ultra-thin Resist Process

Super-resolution near-field lithography using planar silver lenses: A review of recent developments

“…There are no insurmountable barriers, and the most important issues to be addressed are: planarisation of the spacer layers; elimination of surface roughness on silver and dielectric films; and development of ultra-high-resolution i-line photoresists (noting that some good work has begun in this area already [14]). …”

“…Factors to be addressed include minimizing interface roughness and maintaining intimate contact during the long exposures that are required; the latter effect has been quantified for near-field contact lithography [23], with the conclusion that a sub-20 nm gap is required to maintain sub-50 nm half pitch resolution. Reducing the line edge roughness of the resists is also important, and encouraging results have recently been reported in a contact lithography experiment [14].…”

“…The finished masks are then brought into vacuum contact with resist-coated samples for lithographic processing, and after development the resultant resist patterns are imaged using an atomic force microscope (AFM). Pattern transfer has not been attempted at this stage, but other work on near-field exposure into thin resist layers has shown that this is possible [14].…”

“…The seminal work for super-resolved near-field imaging was that of Betzig et al [9], but the history for photolithography somewhat older; in 1981 Fischer and Zingsheim [10] showed that intimate-contact photolithography has a resolution limit beyond that of projection photolithography, provided that the imaging occurs in the near field (mask-substrate separations much less that the wavelength, including the thickness of the phtotoresist). Extensive studies of a number of more sophisticated near-field photolithography techniques were carried out over a decade later [11][12][13], and recent work has shown that resolution down to 20 nm can be achieved for 365 nm exposures, with high aspect ratio resist features that should be amenable to subsequent pattern transfer [14].…”

Plasmonic Nanolithography: A Review

“…Recently, many sorts of near-field lithography systems have been reported [18][19][20][21][22]. Conventional near-field lithography has achieved sub-50 nm resolution using special masks such as lightcoupling mask or phase-shift mask [23].…”