On-product overlay improvement with an enhanced alignment system

Dosho, Tomonori; Shiba, Yuji; Okamoto, Takanobu; Yamamoto, Hajime; Hikida, Yujiro; Brown, J.; Ichinose, Go; Morita, Masahiro; Shibazaki, Yuichi

doi:10.1117/12.2257659

Cited by 2 publications

(2 citation statements)

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“…Overall, the total overlay on the wafer can be described as the on-product overlay which reflects the final overlay performance of the lithography with customer structures and process effects 23 . Total OPO consists of single machine overlay (SMO), mixed machine overlay (MMO), litho OPO, long term stability OPO, and process OPO 24 . For different research needs, various classification methods for overlay have emerged from its sources, quality control, correcting models, etc.…”

Section: Overlay Classificationsmentioning

confidence: 99%

Review of overlay error and controlling methods in alignment system for advanced lithography

Hao¹,

Qi²

2022

Thirteenth International Conference on Information Optics and Photonics (CIOP 2022)

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Acting as one of the three critical indicators to evaluate the performance of lithography scanners, overlay has been a vital factor which seriously affects the electric property, life span and reliability of integrated circuits (IC). With continuous developments of technology nodes and applications of resolution enhancement technologies (RET), current resolution of the scanners has shrunk to 7 nm and beyond, proposing more stringent requirements for measuring, monitoring and correcting the overlay error. To ensure that the overlay budget fully met by the scanner, advanced optical technologies and holistic alignment approaches have been gradually applied to the alignment system of the scanner, revealing that an integrated methodology in which multiple technologies are adopted proved to be valid and effective in reducing the overlay error in present technology nodes.In this article, the exact concept of overlay error is provided, and on this basis different methods to describe the overlay error are comprehensively analyzed from the perspectives of classifications, sources, quality control and correcting models. Then the systematic relationship between alignment and overlay is illustrated. Recent improvements in the alignment system are also the key points here to systematically reduce the overlay error, including the optimization of the alignment optical path, mark types and design procedures, as well as the application of optimal color weighting (OCW), wafer alignment model mapping (WAMM) and sampling scheme optimization (SSO) algorithms. Based on the combined application and iteration of these technologies, it is believed that the on-product overlay (OPO) can be further compressed to support the continuous tightening of the overlay budget in the industry of IC.

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Section: Overlay Classificationsmentioning

confidence: 99%

Review of overlay error and controlling methods in alignment system for advanced lithography

Hao¹,

Qi²

2022

Thirteenth International Conference on Information Optics and Photonics (CIOP 2022)

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“…Overlay accuracy is one of the key factors that impacts the performance of the lithography machine. Together with the feature size and productivity, these three factors are referred to as core technical indicators of the lithography machine [2]. The alignment system is responsible for measuring the relative position of the lithography mask and wafer.…”

Section: Introductionmentioning

confidence: 99%

Depth–Depth of Focus Moiré Fringe Alignment via Broad-Spectrum Modulation

Yu,

Liu,

Zhou

et al. 2024

Photonics

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Alignment precision is a crucial factor that directly impacts overlay accuracy, which is one of three fundamental indicators of lithography. The alignment method based on the Moiré fringe has the advantages of a simple measurement optical path and high measurement accuracy. However, it requires strict control of the distance between the mask and wafer to ensure imaging quality. This limitation restricts its application scenarios. A depth–DOF (depth of focus) Moiré fringe alignment by broad–spectrum modulation is presented to enhance the range of the alignment signals. This method establishes a broad–spectrum Moiré fringe model based on the Talbot effect principle, and it effectively covers the width of dark field (WDF) between different wavelength imaging ranges, thereby extending the DOF range of the alignment process, and employs a hybrid of genetic algorithms and the particle-swarm optimization (GA–PSO) algorithm to combine various spectral components in a white spectrum. By calculating the optimal ratio of each wavelength and using white light incoherent illumination in combination with this ratio, it achieves the optimal DOF range of a broad–spectrum Moiré fringe imaging model. The simulation results demonstrate that the available DOF range of the alignment system has been expanded from 400 μm to 800 μm. Additionally, the alignment precision of the system was analyzed, under the same conditions, and the accuracy analysis of the noise resistance, translation amount, and tilt amount was conducted for the Moiré fringe and broad–spectrum Moiré fringe. Compared to a single wavelength, the alignment precision of the broad–spectrum Moiré fringe decreased by an average of 0.0495 nm, equivalent to a 1.5% reduction in the original alignment precision, when using a 4 μm mask and a 4.4 μm wafer. However, the alignment precision can still reach 3.795 nm, effectively enhancing the available depth of focus range and reducing the loss of alignment precision.

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On-product overlay improvement with an enhanced alignment system

Cited by 2 publications

References 0 publications

Review of overlay error and controlling methods in alignment system for advanced lithography

Review of overlay error and controlling methods in alignment system for advanced lithography

Depth–Depth of Focus Moiré Fringe Alignment via Broad-Spectrum Modulation

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