Highly Uniform Plasmonic Interference Lithography Assisted by Hyperbolic Multilayer Graphene

Plasmonic interference lithography (PIL) is able to break the diffraction limit, realizing deep-subwavelength resolution in a large area. However, because the energy of surface plasmon polariton (SPP) wave is mainly confined on the surface of the metallic layer, the interference patterns in the photoresist layer often suffer from shallowness and nonuniformity. In this work, a PIL structure with highly uniform patterns is proposed, working in the wavelength of 193 nm. The structure consists of a silicon substrate and a photoresist sandwiched by two multilayer graphene films. Due to the hyperbolic property of the multilayer graphene, a slot SPP mode which is weakly dependent on the photoresist thickness is stimulated through volume plasmon polaritons in the hyperbolic multilayer graphene. A uniform periodic pattern with a half-pitch resolution of 29 nm (λ/6.7) maintains even the photoresist thickness that is larger than 80 nm. Our findings may provide a new method to realize robust PIL patterns.