Overlay metrology tool calibration

Binns, Lewis A.; Dasari, Prasad; Smith, Nigel; Ananew, G.; Fink, Hans‐Werner; Ausschnitt, Christopher P.; Morningstar, Jennifer; Thomison, C.; Yerdon, R. J.

doi:10.1117/12.712769

Cited by 3 publications

(3 citation statements)

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“…The blossom key in Fig. 3 has the feature [5][6][7] of being able to measure the overlay of multiple layers simultaneously with a single target, and the Auros key has the feature of being able to minimize the aberration error.…”

Section: Conventional Overlay Target Designmentioning

confidence: 99%

“…For this reason, a modified form is used instead of using the grid pattern as it is. [5][6][7] Figure 9 is an overlay target designed to suppress cross-interference, and it is designed by filling in the intersecting points with blanks to eliminate cross-interference. The design of inserting an intersection pattern on another floor like the GI key is an improvement that puts an intersection pattern on the same floor as the blossom key.…”

Section: Grating Intersection (Gi) Keymentioning

confidence: 99%

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Image-based overlay target design using a grating intersection

Lee¹,

Chang²,

Shin³

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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Background: An overlay target design is essential before performing overlay metrology and has a great impact on overlay performance. In addition, accurate overlay metrology is required to achieve high product yields in semiconductor manufacturing. When asymmetry of the overlay target occurs, it is necessary to increase the area of the pattern existing in the target and stabilize the optical aberration for stable measurement. For this reason, we propose an image-based overlay target design that can secure a larger area compared with the existing overlay target and stabilize the optical aberration by overlapping and exposing the upper and lower patterns of the overlay target.Aim: The effective area of the existing mark design is improved by proposing an overlay target and a measurement method used in image-based overlay measurement.Approach: The proposed overlay target design is configured by arranging different marks orthogonally to the upper and lower layers, and different two-dimensional information can be inserted in the same area. When necessary, single-dimensional information desired by the user can be obtained through a technique called projection, and it has the advantage of using a larger effective area than the existing overlay target.Results: Overlay can be measured using projected signal components, and the possibility and performance of the proposed target can be confirmed through simulation and test wafer. In addition, it was possible to bring about a 15% improvement in total measurement uncertainty performance compared with the existing advanced imaging metrology (AIM) target by taking a wider effective area.Conclusions: An overlay target design is proposed to solve the technical problems of the existing overlay target design. The proposed overlay target has a method that is capable of minimizing the size of the overlay target while maximally maintaining the signal density, a way of reducing the influence of aberration, and various other advantages.In addition, the proposed method provides a design rule that breaks the "lower pattern and upper pattern must not overlap" framework.

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Section: Conventional Overlay Target Designmentioning

confidence: 99%

Section: Grating Intersection (Gi) Keymentioning

confidence: 99%

Image-based overlay target design using a grating intersection

Lee¹,

Chang²,

Shin³

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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“…1 Meeting the requirements for overlay error is critical for semiconductor yield 2,3,4 , and overlay measurement equipment serves as a valuable tool for assessing photolithography process quality and yield monitoring 5,6,7 . Calibration 8,9 using double-layer gratings with specific offsets ensures accurate measurement capabilities of the overlay measurement machine 10 based on DBO overlay metrology 11,12 . Fabrication of such a double-layer gratings involves two key aspects: high-quality fabrication of gratings and alignment between different layers of gratings.…”

Section: Introductionmentioning

confidence: 99%

Analysis and simulation of spatial phase alignment for fabrication of double-layer grating

Shan,

Lu,

Deng

et al. 2023

Optical Design and Testing XIII

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During the chip manufacturing process, meeting overlay error requirements is essential to semiconductor yield. Measuring equipment of overlay error requires standard samples, which the double-layer grating with precise horizontal alignment can be used as, to verify its capability. Thus, we propose a novel alignment and processing method for layer separated processed double-layer gratings. Firstly, the bottom grating is obtained by holographic lithography . The upper and lower layers are aligned based on the homogeneous period of processing diffraction patten and the bottom grating, and manufactured simultaneously. We conducted an optical simulation of the alignment based on FDTD, setting the bottom grating as Ag material, 50 nm depth, 1μm period, and 50% duty cycle. Principally, the alignment accuracy is comparable with the linear encoder.

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