Hybrid approach for the design of mirror array to produce freeform illumination sources in immersion lithography

Wei, Lidong; Li, Yanqiu

doi:10.1016/j.ijleo.2014.06.116

Optik

2014

DOI: 10.1016/j.ijleo.2014.06.116

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Hybrid approach for the design of mirror array to produce freeform illumination sources in immersion lithography

Lidong Wei

Yanqiu Li

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Cited by 7 publications

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“…1 In recent years, the diffractive optical element and mirror array have been used to realize the freeform pixelated pupil in deep ultraviolet lithography. 8,9 For EUV lithography, however, adding additional elements to the illumination system is not advisable since it would greatly reduce the light energy efficiency of the system. Until now, there has been no illumination system for EUV lithography capable of generating the freeform pixelated pupil with different intensities per pixels.…”

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Illumination system with freeform fly’s eye to generate pixelated pupil prescribed by source-mask optimization in extreme ultraviolet lithography

Jiang

Mei

et al. 2017

Opt. Eng

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Abstract. Source-mask optimization (SMO) has emerged as a key technique for 7-nm node and beyond in extreme ultraviolet (EUV) lithography. The pupil required by SMO is usually pixelated, with a free choice of intensity per pixel. However, due to the discrete nature of the EUV illumination system, pupil intensity in current EUV SMO must also be discretized. An illumination system with a freeform fly's eye that is able to generate the pixelated pupil is proposed. Clear apertures of the field facets in the fly's eye are different from each other so that the intensity of each pixel on the pupil can meet the requirements of SMO. Each of the field facets is constructed with a freeform surface to get the required arc-shaped illuminated area on the reticle. A method integrated with a numerical method and an optimization process is used to design the freeform surface of the field facets. The simulation result of the design for a prescribed freeform pixelated pupil shows that the uniformity on the reticle is 96.4%, and the pupil intensity error is approximated to be 0.035. The results indicate that the system is effective in generating the required freeform pixelated pupil and reducing the restrictions imposed on the SMO process in EUV lithography.

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Illumination system with freeform fly’s eye to generate pixelated pupil prescribed by source-mask optimization in extreme ultraviolet lithography

Jiang

Mei

et al. 2017

Opt. Eng

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Angle monitor of micromirror array for freeform illumination in lithography systems

Zhang,

Hu,

Yang

et al. 2024

AIP Advances

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Source and mask optimization is a critical technique for further resolution enhancement in immersion lithography systems, wherein the optimal illumination source shape is widely generated by the micromirror array. Accordingly, the accurate achievement of the allocated angles of micromirrors is a key prerequisite for the implementation of arbitrary illumination patterns. In this paper, we propose an angle monitor to ensure the high-precision tilting of thousands of biaxial micromirrors. As one of the critical modules for closed-loop control of the two-dimensional micromirror array, the online monitor feeds the monitored high-precision tilt angle back to the processing system. The angle monitor mainly consists of the spot scanning module and the angle detection module. Among them, an f-θ lens and a Fourier transform lens with satisfied performances are designed and evaluated by CODE V. Furthermore, a galvanometer and the designed f-θ lens are adopted for the generation of the spot array irradiated on the electrostatic actuated mirrors. Meanwhile, the designed Fourier transform lenses are employed to detect the corresponding tilt angles. In addition, the performance of the proposed system is identified by simulations and experiments individually. It is demonstrated that the monitorable biaxial tilt range of the system is (−2.5°, +2.5°) with a repeatability of better than 0.005°. The large-format micromirror array can be monitored completely without optical cross-talk. Through the device, a 16 × 16 micromirror array is monitored, where the initial angle with no bias voltage applied is captured and the voltage–angle relation for individual micromirrors is obtained. In general, the proposed system can be utilized in the illumination system, providing an efficient and reliable method for complex source shape generation.

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Gradient-Based Source Mask Optimization for Extreme Ultraviolet Lithography

Wang

Chen

et al. 2019

IEEE Trans. Comput. Imaging

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Hybrid approach for the design of mirror array to produce freeform illumination sources in immersion lithography

Cited by 7 publications

References 12 publications

Illumination system with freeform fly’s eye to generate pixelated pupil prescribed by source-mask optimization in extreme ultraviolet lithography

Illumination system with freeform fly’s eye to generate pixelated pupil prescribed by source-mask optimization in extreme ultraviolet lithography

Angle monitor of micromirror array for freeform illumination in lithography systems

Gradient-Based Source Mask Optimization for Extreme Ultraviolet Lithography

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