Accurate and fast kernel-based proximity effect correction (PEC) models are indispensable to full-chip proximity effect simulation and correction. The attempt to utilize optical scatterometers for PEC model calibration instead of scanning electron microscopes is primarily motivated by the fact that scatterometry can be faster, more stable, and more informative if carefully implemented. Conventional scatterometry measures periodic patterns and retrieves their dimensional parameters by solving inverse problems of optical scattering with predefined libraries of the periodic patterns. PEC model parameters can be subsequently calibrated with the retrieved dimensional parameters. However, measuring only periodic patterns limits the usage of scatterometry, and the dimensional reconstruction is prone to generate estimation errors for patterns with complex three-dimensional geometry. Previously, we have proposed directly utilizing scattering light for PEC model calibration without the need for the intermediate step of retrieving the dimensional parameters. By iteratively comparing scattered light from predefined calibration patterns measured by a scatterometer to that predicted by the corresponding scattering and lithography models, PEC model parameters can be effectively calibrated with standard numerical optimization algorithms and one-dimensional periodic patterns. In this work, two-dimensional periodic circuit layouts are designed and utilized to study the applicability and potential limitations of the proposed method on the lithography of practical circuit designs.
Line edge roughness (LER) influencing the electrical performance of circuit components is a key challenge for electronbeam
lithography (EBL) due to the continuous scaling of technology feature sizes. Controlling LER within an acceptable
tolerance that satisfies International Technology Roadmap for Semiconductors requirements while achieving high
throughput become a challenging issue. Although lower dosage and more-sensitive resist can be used to improve
throughput, they would result in serious LER-related problems because of increasing relative fluctuation in the incident
positions of electrons. Directed self-assembly (DSA) is a promising technique to relax LER-related pattern fidelity (PF)
requirements because of its self-healing ability, which may benefit throughput. To quantify the potential of throughput
improvement in EBL by introducing DSA for post healing, rigorous numerical methods are proposed to simultaneously
maximize throughput by adjusting writing parameters of EBL systems subject to relaxed LER-related PF requirements.
A fast, continuous model for parameter sweeping and a hybrid model for more accurate patterning prediction are
employed for the patterning simulation. The tradeoff between throughput and DSA self-healing ability is investigated.
Preliminary results indicate that significant throughput improvements are achievable at certain process conditions.