An aberration control of projection optics for multi-patterning lithography

Ohmura, Yasuhiro; Ogata, Taro; Hirayama, Toru; Nishinaga, Hisashi; Shiota, Takeshi; Ishiyama, Satoshi; Isago, Susumu; Kawahara, Hidetaka; Matsuyama, Tomoyuki

doi:10.1117/12.879616

Cited by 13 publications

(5 citation statements)

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“…The sensitivity of CD to all single Zernike terms and their second-order effects can be determined by Eqs. ( 7)- (8).…”

Section: The Identification Of Key Aberrations By the Dsd Methodsmentioning

confidence: 99%

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Identification of key aberrations that affect pattern imaging in EUVL

Wang,

Su,

Wei

2024

DTCO and Computational Patterning III

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In EUVL, aberrations play a crucial role in critical dimension (CD) and pattern shift (PS) errors. It is significant to decide aberration compensation and optimization strategies for compensating exposure errors. The modeling process of aberration is time-consuming, mainly because of the need to consider numerous aberrations. In order to save the runtime for aberration modeling, this paper proposes a methodology for identifying the key aberrations that have significant impacts on imaging results. Three different techniques are employed and compared, including single parameter sensitivity analysis, definitive screening design (DSD) method, and SOBOL method that consider the coupling effects of different orders. By comparing the deviations between the imaging results considering only key aberrations and all aberrations, it is found that the identified aberrations achieve extremely high accuracy for various patterns and illumination conditions. Even though the proportion of key aberrations among all aberrations is only a small fraction. All the three methods can achieve that the average CD and PS deviations do not surpass 1%, using 40% of the total 37 aberration items. Thereby, the feasibility of using identified key aberrations for aberration modeling is validated. In addition, we also compare the accuracies of three techniques under the same conditions and found that the SOBOL method is the most suitable technique for identifying key aberrations. Consequently, for specific illumination conditions and corresponding layout patterns, the use of key aberrations is an effective way to characterize the impacts of all 37 aberrations, accelerating the aberration compensation and optimization without sacrificing accuracy.

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“…The sensitivity of CD to all single Zernike terms and their second-order effects can be determined by Eqs. ( 7)- (8).…”

Section: The Identification Of Key Aberrations By the Dsd Methodsmentioning

confidence: 99%

“…At present, aberration compensation and optimization are also important approaches for aberration control 3,[6][7][8][9][10] . For optical systems with circular pupil, orthogonal Zernike polynomials are commonly used to represent the influence of aberration on wavefront 11 , as shown in equation (1): 1 ( , ) ( , ),…”

Section: Introductionmentioning

confidence: 99%

Identification of key aberrations that affect pattern imaging in EUVL

Wang,

Su,

Wei

2024

DTCO and Computational Patterning III

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“…A scheme was shown in Fig. 6 where the DM was assembled at the pupil, as mentioned in [1,3]. Due to no vignetting in lithography systems, a DM at the pupil would have the same compensation for all fields.…”

Section: B Dm In Lithography Lensmentioning

confidence: 99%

“…A basic requirement for DMs in lithography systems that perfect the generation of the desired deformation is hard to satisfy. The DM in a Nikon S620D objective taking a tradeoff between deformation modes and accuracy could generate only the astigmatism mode with an error less than 0.02 nm [3]. Currently, DMs in lithography systems are required to be generating multimode deformation at a range of −10-10 nm, with a residual less than 0.1 nm [4].…”

Section: Introductionmentioning

confidence: 99%

Concept and modeling analysis of a high fidelity multimode deformable mirror

Zhou

Wang

et al. 2015

Appl. Opt.

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Conventional deformable mirrors (DM) cannot meet the requirement of aberration controlling for advanced lithography tools. This paper illustrates an approach using the property that deformation of a thin plate is similar to optical modes to realize a high fidelity multimode deformable mirror whose deformation has characteristics of optical aberration modes. The way to arrange actuators is also examined. In this paper, a 36-actuator deformable mirror is taken as an example to generate low-order Zernike modes. The result shows that this DM generates the fourth fringe Zernike mode (Z4) defocus, and primary aberration Z5-Z8 with an error less than 0.5%, generates the fifth-order aberration Z10-Z14, and generates the seventh-order aberration Z17-Z20 with an error less than 1.1%. The high fidelity replication of the Zernike mode indicates that the DM satisfies the demand of controlling aberrations corresponding to the first 20 Zernike modes in an advanced lithography tool.

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“…Thus, thermal aberration induced by lens heating becomes more and more important. As a result of laser absorption, lens heating, which leads to temperature rise and inhomogeneous thermal distribution, results in thermal elastic deformation, refractive index change, and thermal stress [2][3][4]. Among these three main reasons, refractive index change caused by inhomogeneous thermal distribution is a dominating factor for projection lens performance degeneration [4,5].…”

Section: Introductionmentioning

confidence: 99%

Analysis and experiments of the thermal–optical performance for a kinematically mounted lens element

Zhang

et al. 2014

Appl. Opt.

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In order to evaluate the thermal-optical performance of a kinematic mounting applied in lithographic projection lens, the optical surface figure and wavefront changes of the lens element under a certain thermal load are investigated with both experimental and numerical simulation methods. From the experimental and numerical results, the temperature on the edge of the lens element rises up to 22.51°C, and the center of lens is 5.3°C higher. As a result, this thermal nonuniformity leads to a 9.622 nm RMS change of the optical surface figure and 71.905 nm RMS change of the index inhomogeneity, consisting mainly of Z4, Z9, and Z16. Because of the radial flexibility of the supporting legs of the kinematic mounting, aberrations such as pri trefoil and sec trefoil are less than 2% of the total wavefront changes, and other nonaxisymmetric aberrations are negligible. The Zernike coefficient differences between experiments and simulation are less than 2 nm, which supports the correctness of our method. The kinematic mounting shows good thermal adaptability, and the method for evaluation of the thermal-optical characteristics is proved effective.

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An aberration control of projection optics for multi-patterning lithography

Cited by 13 publications

References 0 publications

Identification of key aberrations that affect pattern imaging in EUVL

Identification of key aberrations that affect pattern imaging in EUVL

Concept and modeling analysis of a high fidelity multimode deformable mirror

Analysis and experiments of the thermal–optical performance for a kinematically mounted lens element

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