Mitigating the forbidden pitch of extreme ultraviolet lithography using mask optimization based on genetic algorithm

Ling Ma; Lisong Dong; Taian Fan; Xu Ma; Yayi Wei

doi:10.1117/1.JMM.21.4.043204

20 December 2022 Mitigating the forbidden pitch of extreme ultraviolet lithography using mask optimization based on genetic algorithm

Ling Ma, Lisong Dong, Taian Fan, Xu Ma, Yayi Wei

Author Affiliations +

Journal of Micro/Nanopatterning, Materials, and Metrology, Vol. 21, Issue 4, 043204 (December 2022). https://doi.org/10.1117/1.JMM.21.4.043204

Abstract

Background

In advanced technology nodes, forbidden pitches (FPs) can reduce the depth of focus and limit the overlapped process window of lithography. In extreme ultraviolet (EUV) lithography, one pattern in a different orientation or different position of arc slit field will have a different shadowing effect, due to the chief ray angle and azimuthal angle of the incident light. Therefore, it is necessary to mitigate the FP effect of EUV lithography.

Aim

With the purpose of mitigating the phenomenon of FPs in the arc slit exposure field, we propose an optimization method based on a genetic algorithm (GA).

Approach

The optimization method is derived from the basic flow of the GA. Three mask parameters are selected as the variables, including the mask bias and the width and position of the assist feature. The cost function is designed to evaluate the process window, normalized image log slope, and contrast of different fields in the arc slit. After multiple iterations, an optimal combination of three variables is obtained.

Results

The simulation results show that the optimized mask structure given by the proposed method in the arc slit exposure field can improve the process window in the horizontal and vertical orientations, respectively.

Conclusions

The limitation of FPs to the process window is removed using mask optimization based on the GA. The proposed optimization method has the potential to be an effect candidate for FPs mitigation.

Citation Download Citation

Ling Ma, Lisong Dong, Taian Fan, Xu Ma, and Yayi Wei "Mitigating the forbidden pitch of extreme ultraviolet lithography using mask optimization based on genetic algorithm," Journal of Micro/Nanopatterning, Materials, and Metrology 21(4), 043204 (20 December 2022). https://doi.org/10.1117/1.JMM.21.4.043204

Received: 16 May 2022; Accepted: 1 December 2022; Published: 20 December 2022

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KEYWORDS

Source mask optimization

Extreme ultraviolet lithography

Diffraction

Nanoimprint lithography

Lithography

Genetic algorithms

Mathematical optimization

Background

Aim

Approach

Results

Conclusions

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