Impact of mask errors on imaging quality in surface plasmon lithography

Plasmon lithography leverages the involvement of evanescent waves generated at metal surfaces to overcome the classical diffraction limit. In this work, we investigate a surface plasmon resonant cavity lithography (SPRCL) system and compare its imaging performance and process robustness with traditional surface plasmon lithography (SPL) systems under various mask fabrication deviations. By constructing a lithographic structural model and integrating optical transfer function (OTF) theory with rigorous coupled-wave analysis (RCWA), we show that the SPRCL system facilitates super-resolution imaging by efficiently transmitting higher-order evanescent components. Simulations conducted using COMSOL validate the superior performance of the SPRCL structure in the presence of global and local feature size variations, isolated defects, positional deviations, and finite-period patterning. Results indicate that under global mask critical dimension (CD) variation, the mask error enhancement factor (MEEF) of SPRCL ranges from 0.67 to 3.10, with improved imaging contrast and more stable normalized image log-slope (NILS). For local CD perturbations, the average MEEF of SPRCL is 1.11, significantly lower than that of SPL, and can be optimized to as low as 0.33 under appropriate exposure thresholds. Overlay analysis shows that SPRCL achieves an R_ovl of 46.6%, substantially lower than 93.4% in SPL systems. In limited-period patterning, SPRCL enables high-fidelity imaging with contrast exceeding 0.8 and NILS above 1.5 in mode with a total stretch of 2.4 µm. In summary, the SPRCL architecture demonstrates enhanced process tolerance and imaging fidelity, offering a promising pathway for advancing super-resolution lithography.