Extreme ultraviolet (EUV) lithography is one of the essential technologies for the 5nm and below technology nodes. However, the presence of aberrations in the system severely affects the exposure results, which can lead to wafer rework and increase costs. In order to investigate the impact of aberrations in EUV lithography systems on exposure results, this paper conducts research on the impact of aberrations on exposure results of patterns that commonly used in EUV single-exposure for the 5nm technology node. A large number of aberration experiments are performed, and the distribution of critical dimension (CD), normalized image log-slope (NILS), Pattern Shift (PS), and process variation band (PVB) of exposure results in relation to all Zernike terms variation within ±50mλ is statistically analyzed. We find that aberrations lead to worse exposure results generally, and the distribution of results does not strictly follow a Gaussian distribution but exhibits significant "tail" phenomena. And the impact of aberrations varies for different patterns. Furthermore, the relationship between the distribution of exposure results and the magnitude of aberrations are investigated. It is observed that as the aberration RMS increases, the probability of deteriorated exposure results also increases. Spherical aberration has a significant impact on CD and PVB, while x-direction coma has a significant impact on the PS of vertical line-space patterns, and y-direction coma has a significant impact on the PS of vertical tip to tip patterns. X-direction astigmatism has a higher probability of causing positive PS, while y-direction astigmatism has a higher probability of causing negative PS. Relatively speaking, the effects of 3-foil, 4-foil, and 5-foil aberrations are smaller. This paper provides a clear reference for the influence of various aberrations on exposure results and can contribute to the future development and aberration control of lithography systems.
Plasmonic lithography can amplify the evanescent wave resonance at the mask and participate in imaging by exciting surface plasmon polaritons (SPPs), breaking the diffraction limit in traditional lithography. Source Optimization (SO) technology is widely used to compensate for imaging distortion in traditional lithography. This paper proposes an effective SO model for plasmonic lithography under the compressed sensing (CS) framework. To accelerate the algorithm, the SO is formulated as an underdetermined linear problem, where the number of equations is much smaller than the source variables. We selected lines, contacts, and complex test patterns to verify the imaging improvements and superiority of the model. The results indicate that compared to the annular sources, optimized sources can achieve better imaging results and higher imaging contrast. This provides favorable conditions for the large-scale application of plasmonic lithography.
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