Retargeting of forbidden-dense-alternate structures for lithography capability improvement in advanced nodes

He, Jianfang; Dong, Lisong; Zhao, Lei; Wei, Yayi; Ye, Tianchun

doi:10.1364/ao.57.007811

Cited by 1 publication

(2 citation statements)

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“…In deep ultraviolet (DUV) lithography, many articles have reported the FPs behaviors, 4 – 6 and various solutions have been proposed to solve the FPs phenomenon. For example, assist features (AFs) 7 – 9 can be inserted to improve the image contrast and overlapped process window, and biasing of the FP structure can allow for more tolerance to the mask optimization (MO) 10 and design rules 11 …”

Section: Introductionmentioning

confidence: 99%

“…For example, assist features (AFs) [7][8][9] can be inserted to improve the image contrast and overlapped process window, and biasing of the FP structure can allow for more tolerance to the mask optimization (MO) 10 and design rules. 11 Unlike DUV lithography, EUV lithography has a series of unique effects to be accounted for, such as the shadowing effect. 12,13 The shadowing effect in EUV lithography is caused by the oblique illumination coupled with the thick mask absorber, [14][15][16] which leads to the phenomenon of FPs becoming more sensitive in EUV lithography.…”

Section: Introductionmentioning

confidence: 99%

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

Dong

Fan

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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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.

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