UV-nanoimprint lithography

Jeong J, Sim Y, Sohn H, Lee E. UV-nanoimprint lithography using an elementwise patterned stamp. Microelectronic Engineering 2004, 75, 165-171. 

Liquid photo-curable resin is used in UV nanoimprint lithography (UV-NIL).i Basic ideas of photopolymerization are shown in Chapter 1. Liquid photo-curable resins change from liquid to solid by UV irradiation. The change is produced by polymerization of a monomer or oligomer constituted in the resin. Initiators induce polymerization by UV irradiation. Resins of UV-NIL are classified into several types by polymerization systems radical polymerization, ion polymerization, and ene-thiol polymerization. Details of those systems are described in below. 

Nanoimprinting A master stamp is used directly for hot embossing of a substrate, usually made of a polymer. This allows the stamp to produce many patterned substrates. Although there is no diffraction hmit here, hot embossing has been applied mainly for low-resolution applications, in various fields such as miniaturized total-analysis Systems (p.TAS), microfluidics, and microoptics. UV-nanoimprint lithography corresponds to contact printing with UV exposure. 

Kubenz, M., Reuther, F., Gruetzner, G., and Torres, C.M.S. (2007) Reverse-contact UV nanoimprint lithography for multilayered structure fabrication. 

Many UV-assisted nanoimprint lithography (UV-NIL) processes, described in the next section, rely on capillary forces to fill the mold, so the distinction of CFL as a separate lithography technique is blurred. 

The thiol-ene imprint resists find use in a form of UV-NIL called nanocontact molding (NCM) imprint lithography, soft step and flash imprint lithography (SSFIL), and soft nanoimprint lithography (SNIL) where sub-100 nm features have been successfully replicated.The mechanical properties and surface chemistries of thiol-ene photopolymers have also been thoroughly investigated. 

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