Improved near field lithography by surface plasmon resonance in groove-patterned masks

摘要

Near field lithography (NFL) provides an effective way for obtaining lithography features' sizes far beyond the diffraction limit. However, optical transmission through isolated subwavelength apertures is very low in the lithography process. It also makes it difficult to obtain a uniform lithography pattern where isolated and arrayed slit structures coexist because of different optical transmission through these two kinds of structures. It is proposed in this paper that using appropriately designed groove structures around subwavelength metallic slits could solve this problem. Numerical calculations performed by the finite-difference time-domain (FDTD) method demonstrate that about ten times transmission enhancement could be obtained. This occurs as a surface plasmon is resonantly excited and light is concentrated into nanometer scale apertures, resulting in not only greatly enhanced NFL efficiency but also uniform distribution of light intensity for isolated and arrayed slit patterns. Also discussed is the enhancement dependence on the structural parameters of NFL masks.