EUV APSM mask prospects and challenges

Lin, Shy-Jay; Lee, Chien-Min; Chen, Yen-Liang; Tai, Kuo-Lun; Chen, Lee-Feng; Huang, Chien-Chao; Tsai, Frankie F. G.

doi:10.1117/12.2688111

Cited by 3 publications

(3 citation statements)

References 24 publications

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“…Note that low-n absorbers are still under development and the mask process has not yet been established as discussed in Ref. 27.…”

Section: Weakly Guiding Approximationmentioning

confidence: 99%

Accelerating extreme ultraviolet lithography simulation with weakly guiding approximation and source position dependent transmission cross coefficient formula

Tanabe,

Jinguji,

Takahashi

2024

J. Micro/Nanopattern. Mats. Metro.

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Background: Mask three-dimensional (3D) effects distort diffraction amplitudes from extreme ultraviolet masks. In a previous work, we developed a convolutional neural network (CNN) that predicted distorted diffraction amplitudes very fast from input mask patterns.Aim: In this work, we reduce both the time for preparing the training data and the time for image intensity integration. Approach: We reduce the time for preparing the training data by applying weakly guiding approximation to 3D waveguide model. The model solves Helmholtz type coupled vector wave equations of two polarizations. The approximation decomposes the coupled vector wave equations into two scalar wave equations, reducing the computation time to solve the equations. Regarding the image intensity integration, Abbe's theory has been used in electromagnetic (EM) simulations. The transmission cross coefficient (TCC) formula is known to be faster than Abbe's theory, but the TCC formula cannot be applied to source position dependent diffraction amplitudes in EM simulations. We derive source position dependent TCC (STCC) formula starting from Abbe's theory to reduce the image intensity integration time.Results: Weakly guiding approximation reduces the time of EM simulation by a factor of 5, from 50 to 10 min. STCC formula reduces the time of the image intensity integration by a factor of 140, from 10 to 0.07 s. Conclusions:The total time of the image intensity prediction for 512 nm × 512 nm area on a wafer is ∼0.1 s. A remaining issue is the accuracy of the CNN.

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“…Note that low-n absorbers are still under development and the mask process has not yet been established as discussed in Ref. 27.…”

Section: Weakly Guiding Approximationmentioning

confidence: 99%

Accelerating extreme ultraviolet lithography simulation with weakly guiding approximation and source position dependent transmission cross coefficient formula

Tanabe,

Jinguji,

Takahashi

2024

J. Micro/Nanopattern. Mats. Metro.

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“…However, recent TSMC results from Lin et al indicate good progress in engineering absorbers having desired ðn; κÞ pairs. 8 While the best way to maximize the image contrast is by engineering new absorber materials, for the tantalum boron nitride (TaBN) absorber currently in use, with a non-vanishing φ AB , can we improve the image contrast further? We may notice that in Eq.…”

mentioning

confidence: 99%

“…However, recent TSMC results from Lin et al. indicate good progress in engineering absorbers having desired (n,κ) pairs 8 …”

mentioning

confidence: 99%

Maximizing image contrast in printing dense lines-and-spaces patterns

Yen,

Gao

2024

J. Micro/Nanopattern. Mats. Metro.

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Elementary analysis shows that maximizing the aerial-image contrast in printing dense lines and spaces leads to a monotonically increasing relationship between ð1 − nÞ and κ, where n and κ are real and imaginary parts of the refractive index of the absorber material of the photomask, respectively, and this relationship is affected by the space-to-pitch ratio in the mask absorber. For the tantalum boron nitride mask absorber presently in use, improvement in image contrast can be made by displacing the illuminating dipoles away from their nominal positions in conjunction with a focus offset.

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Weakly guiding approximation of a three-dimensional waveguide model for extreme ultraviolet lithography simulation

Tanabe,

Jinguji,

Takahashi

2024

J. Opt. Soc. Am. A

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A three-dimensional (3D) waveguide model is applied in extreme ultraviolet (EUV) lithography simulations. The 3D waveguide model is equivalent to rigorous coupled-wave analysis, but fewer field components are used to solve Maxwell’s equations. The 3D waveguide model uses two components of vector potential, A x and A y , corresponding to the two polarizations. The electric field of the A x polarization is approximately parallel to the x axis, and the electric field of the A y polarization is approximately parallel to the y axis. The 3D waveguide model solves a coupled vector wave equation for two polarizations. The refractive index of conventional EUV absorbers is close to that of vacuum. The weakly guiding approximation in optical fiber theory is applied to the 3D waveguide model. The coupled vector wave equations for the two polarizations are decoupled into two independent scalar wave equations. Maxwell’s equations are simplified to a set of scalar wave equations. The weakly guiding approximation reduces the computation time to solve the equations. The computation time required to solve the weakly guiding approximation is about 1/5 of the time to solve the original 3D waveguide model.

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EUV APSM mask prospects and challenges

Cited by 3 publications

References 24 publications

Accelerating extreme ultraviolet lithography simulation with weakly guiding approximation and source position dependent transmission cross coefficient formula

Accelerating extreme ultraviolet lithography simulation with weakly guiding approximation and source position dependent transmission cross coefficient formula

Maximizing image contrast in printing dense lines-and-spaces patterns

Weakly guiding approximation of a three-dimensional waveguide model for extreme ultraviolet lithography simulation

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