Near-field double-spot photolithography with subwavelength spacing

We theoretically report a method of the near-field double-spot subwavelength-photolithography by attaching an optical anisotropic metamaterial (OAM) and polymer composite film to a solid immersion lens (SIL). The OAM made up of metallic nanowires embedded in a dielectric matrix can realize all-angle negative refraction for TM waves in the visible regime. When the SIL near-field photolithography system with a nanoscale OAM-polymer composite film is illuminated by a linearly-polarized beam, the longitudinal component of electric field in the focal region of the objective is largely enhanced by surface plasmons and the transverse component is suppressed. Consequently, a spot in the conventional near-field photolithography system with a bare SIL is split into two spots with subwavelength spacing. If the present focusing system with an OAM-polymer film is used to near-field photolithography, a subwavelength-spacing (wavelength/5) and deep photoetching pattern can be achieved and, compared with the conventional single-spot photolithography, the photoetching speed can be doubled.