Implementation of assist features in EUV lithography

Jiang, Fan; Burkhardt, Martin; Raghunathan, Ananthan; Torres, Andres; Gupta, Rachit; Word, James

doi:10.1117/12.2085946

Cited by 5 publications

(5 citation statements)

References 3 publications

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“…The use of EUV based assist features (SRAF's) and the placement of these features requires additional discussion than assist features for industry standard immersion lithography. Burkhardt [2] showed experimental results where the insertion of symmetrically spaced SRAF's can create unwanted Bossung tilt and best focus shifts. Hsu et al [4] demonstrated that this tilt and best focus shift behavior was due to phase errors between the 0th and higher diffraction orders.…”

Section: Designmentioning

confidence: 99%

“…Thus, the image formation in EUV projection systems has specific challenges not found in immersion lithography. A number of authors have investigated EUV specific effects such as pattern placement error [1], assist feature placement and resulting Bossung tilt [2] and the stochastic nature of EUV imaging [3]. The recent publication by Hsu et al [4] demonstrated resolution enhancement techniques (RET) to address these EUV specific issues as part of the ASML Brion Tachyon NXE Source Mask Optimization (SMO) application.…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Application of EUV resolution enhancement techniques (RET) to optimize and extend single exposure bi-directional patterning for 7nm and beyond logic designs

Kim

Wood

Crouse³

et al. 2016

Extreme Ultraviolet (EUV) Lithography VII

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EUV lithography is uniquely positioned to extend single exposure solutions for critical imaging layers at the 7 nm technology node and beyond. In this work, we demonstrate the application of advanced EUV resolution enhancement techniques to enable bidirectional printing of 36 and 32 nm pitch standard logic cell and SRAM designs with 0.33 NA optics using an EUV OPC model. Prior work has highlighted the issues of pattern placement errors and image contrast loss due to the non-telecentricity that is inherent in EUV reflective imaging systems and masks. This work has also demonstrated utilizing asymmetric pupil to reduce the pattern placement error. It has been previously shown that there is a potential reduction in common process window due to through-pitch best focus shifts with non-optimized SRAF placement. In this paper, we demonstrate the use of: pattern placement error aware SMO, asymmetric illumination shape, and SRAF placement optimization to increase the overall common process window by as much as 40% compared to OPC only optimization. Consequently, we demonstrate the improved post-RET single patterning solution for 0.33 NA EUV bi-directional 7 nm node logic designs. We show that these techniques can achieve the required performance for MEEF, best focus shift across features, and ILS, which is known to be important for reducing stochastics and subsequent line-edge-roughness (LER).

show abstract

Section: Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Application of EUV resolution enhancement techniques (RET) to optimize and extend single exposure bi-directional patterning for 7nm and beyond logic designs

Kim

Wood

Crouse³

et al. 2016

Extreme Ultraviolet (EUV) Lithography VII

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show abstract

“…In Eq. (26), ϵ D 19 × pixel M and ϵ seed 27 × pixel M . It is noted that for the practical application, the reflectivities N W M , N W S , ϵ D , and ϵ seed should be adjusted according to the experimental data and manufacturing constraints on the product line.…”

Section: Nomentioning

confidence: 99%

“…Recent research proved that the subresolution assist features (SRAFs) are beneficial to the EUV lithography performance. For example, the SRAFs can help to increase the depth of focus [26,27]. The SRAFs also have the potential to reduce the required dose to print a specific CD, thus increasing the throughput [28].…”

Section: Introductionmentioning

confidence: 98%

Gradient-based inverse extreme ultraviolet lithography

Ma¹,

Wang²,

Chen³

et al. 2015

Appl. Opt.

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Extreme ultraviolet (EUV) lithography is the most promising successor of current deep ultraviolet (DUV) lithography. The very short wavelength, reflective optics, and nontelecentric structure of EUV lithography systems bring in different imaging phenomena into the lithographic image synthesis problem. This paper develops a gradient-based inverse algorithm for EUV lithography systems to effectively improve the image fidelity by comprehensively compensating the optical proximity effect, flare, photoresist, and mask shadowing effects. A block-based method is applied to iteratively optimize the main features and subresolution assist features (SRAFs) of mask patterns, while simultaneously preserving the mask manufacturability. The mask shadowing effect may be compensated by a retargeting method based on a calibrated shadowing model. Illustrative simulations at 22 and 16 nm technology nodes are presented to validate the effectiveness of the proposed methods.

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“…1(b). By the nature of the reflective mask structure, the pattern through the arc slit will have different shadowing effects due to the change of the incident azimuthal angle, 10 , 17 as shown in Fig. 2, which impacts the range of the FP in the horizontal and vertical orientations.…”

Section: Introductionmentioning

confidence: 99%

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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Implementation of assist features in EUV lithography

Cited by 5 publications

References 3 publications

Application of EUV resolution enhancement techniques (RET) to optimize and extend single exposure bi-directional patterning for 7nm and beyond logic designs

Application of EUV resolution enhancement techniques (RET) to optimize and extend single exposure bi-directional patterning for 7nm and beyond logic designs

Gradient-based inverse extreme ultraviolet lithography

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

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