Suppressing mask 3D effects in plasmonic lithography via a single high-k wavevector interference

Plasmonic lithography (PL), a key branch of optical lithography, which relies on the excitation and manipulation of surface plasmon polaritons (SPPs) to enhance evanescent waves, has the ability to achieve sub-diffraction-limited optical imaging. In PL systems employing multilayer structures, the imaging mode is critically dependent on the properties of the multilayer. However, conventional PL structures resembling Ag superlens utilizing multi-order diffraction imaging exhibit inherent instability when subjected to mask three-dimension (M3D) effects, significantly degrading pattern fidelity at advanced technology nodes. In this work, we demonstrate that an alternative imaging mode that leverages spatial frequency filtering characteristics to select a single high-order interference can substantially enhance the imaging quality against M3D effects. Furthermore, through numerical simulations, we quantitatively compared the critical imaging metrics of both modes, considering the M3D effects, including full width at half maximum (FWHM), imaging contrast, and normalized image log-slope (NILS). The results reveal that multi-spatial frequency collaborative imaging exhibits high sensitivity to M3D effects, whereas single high spatial frequency imaging significantly suppresses M3D effects owing to its intrinsic interference purity. The research content of this work contributes to the achievement of high-fidelity nanoscale patterning and may offer a promising pathway for mitigating M3D effects at advanced nodes.