Investigation of waveguide modes in EUV mask absorbers

Self Cite

Background: The increasing demands on computational lithography and computational imaging in the design and optimization of lithography processes necessitate rigorous modeling of EUV light diffracted from the mask. Traditional electromagnetic field (EMF) solvers are inefficient for large-scale technology problems, while deep neural networks rely on a huge amount of expensive rigorously simulated or measured data [1].Aim: In order to overcome these constraints, we explore the potential of physics-informed neural networks (PINN)[2] as a promising solution for addressing complex optical problems in the field of EUV lithography.Approach: We extend the existing MaxwellNet[3] to simulate the light diffraction from typical reflective EUV masks. The coupling of the predicted diffraction spectrum with image simulations enables the evaluation of PINN performance in predicting relevant lithographic metrics and typical mask 3D effects. Results:The results of modeling near-and far-field diffraction using PINN showcase a good performance in terms of convergence behavior, stability, accuracy, and a significant speed-up (up to ×10000) compared to the rigorous 3D mask simulation using an established numerical EMF solver. In contrast to other machine learning approaches, PINN is able to accurately simulate the near field, learns the involved physics, and captures the optical and mask-induced 3D effects. PINNs can predict lithographic process windows with sufficient accuracy. Conclusions: Differently from numerical solvers, once trained, generalized PINN can simulate light scattering in several milliseconds without re-training and independently of problem complexity. This opens up the capabilities for partially coherent imaging simulations without the Hopkins approach, source optimization, and fast investigation of mask 3D effects.

Section: Contrast Fadingmentioning

confidence: 99%

3d mask simulation and lithographic imaging using physics-informed neural networks

Medvedev,

Erdmann,

Rosskopf

2024

Self Cite

“…The impact of the EUV mask on image formation and lithometrics such as contrast, best focus shifts, CD variations, pattern placement errors and non-telecentricity has been studied extensively for many years 5,6,7,8,9 . It is well-known that Ta-based binary masks, being the leading mask type for EUV HVM in the industry, suffer from image fading, often referred to as M3D fading.…”

Section: Mask3d Fadingmentioning

confidence: 99%

Improving EUV sub-40nm via single patterning using wavefront and pupil co-optimization

Kim,

Chung,

Maeng

et al. 2024

The stochastic effect in contact single patterning is one of the primary challenges in extending into sub-40nm pitch with 0.33NA EUV. EUV stochastic defects induced by EUV photon shot noise are known to strongly correlate to image contrast. Mitigation of Mask3D induced contrast fading is one of the key solutions to enable further shrink, while maintaining sufficient defect-free process latitude. Wavefront and pupil co-optimization is designed to compensate the Mask 3D phase error that leads to contrast fading. For application in HVM, the newly developed Pupil/Mask/Wavefront co-optimization gives the best imaging performance while maintaining the illumination efficiency and decreasing the rms wavefront for the final optimal wavefront to ensure there is no negative impact on the rest of the patterns that are not included in the optimization.In this paper, we investigate how to apply Pupil/Mask/Wavefront co-optimization to improve the image contrast of a sub-40nm pitch contact hole array, including in-resist verification. We will first explain the fundamentals of Mask 3D fading mitigation via phase injection for a 1D feature and how to extend this concept to 2D features. We will compare the effectiveness of new Pupil/Mask/Wavefront co-optimization versus Zernike Z5 or Z6 only phase injection method. Finally, we will show the potential benefit in combination with using a low-n phase shifting mask for which the optimum image contrast is achieved with the co-optimized wavefront, pupil and mask.

“…For example, a thick absorber can improve the contrast, but reduces the THRS. The guiding of light through the openings of low-n absorbers 17 helps improve NILS and THRS, but the increased sensitivity of best focus shifts can reduce the DoF of overlapping process windows. Therefore, it is essential to find imaging solutions that provide a high resolution with the best tradeoff between achievable NILS, THRS, and DoF.…”

Section: Introductionmentioning

confidence: 99%

Exploring the limits of high contrast contact imaging using split pupil exposures in high-NA EUV lithography

Erdmann,

Mesilhy,

Evanschitzky

et al. 2024

The lithographic imaging performance of contact holes is limited by the efficient use of light and contrast fading caused by 3D mask effects. "Split pupil" exposures have been proposed to mitigate contrast fading for linespace-patterns. 1 We present a simulation study investigating the extendibility of split pupil exposures to dense arrays of contacts on dark field and light field masks using different mask absorber options. Our simulations indicate that the combination of split pupil exposures and low-n/low-k absorbers can offer comfortable imaging performance for arrays of 10 nm square contacts with a pitch of 20 nm on a dark field mask. These results indicate the potential of combining low-n absorbers and split pupil exposure strategies to enable high-NA EUV lithography to reach its ultimate optical resolution limits.