Off Axis Illumination Planar Hyperlens for Non-contacted Deep Subwavelength Demagnifying Lithography

Off axis illumination (OAI) technique combined with planar hyperlens is applied to achieve the non-contacted deep subwavelength demagnifying lithography. The designed OAI is confirmed to shift the spatial spectra of mask, leading to enhancement of the featured wavevectors components. On the other hand, the reflection effect of Ag cladding is necessary to obtain high contrast and high fidelity of nanopattern lithography. It is numerically demonstrated that the half-pitch resolution 32 nm with OAI (NA = 1.37) is obtained under 80 nm air working distance, which is about six times than the case of the conventional configuration under normal illumination (NA = 0). Further simulations show that the minimum half-pitch resolution of the planar hyperlens with OAI could reach 18 nm (similar to lambda/20).