Optimal measurement method for scatterometer-based overlay metrology

Ku, Yi-Sha; Hsu, Wei-Feng; Chou, Sen-Yih; Shyu, Deh-Ming

doi:10.1117/1.2969120

Cited by 2 publications

(1 citation statement)

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“…Thus, this technique contributes to the robustness of the electromagnetic modeling approach. Recent paper [9] presented a hybrid method which allows extraction of the overlay from differential signal measurements by using two sets of four grating targets for bi-azimuth measurements, and includes a simple linear response model. It could overcome the measurement uncertainty from process variations, the low sensitivity to overlay compared with other parameters, and the nonlinear relationship between the overlay and the diffraction signals.…”

Section: Introductionmentioning

confidence: 99%

Improved diffraction-based overlay metrology by use of two dimensional array target

Pang

Hsu

et al. 2009

SPIE Proceedings

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We report results of theoretical modeling into a scatterometry-based method relevant to overlay measurement. A set of two array targets were designed with intentional offsets difference, d and d+20 nm, between the top and bottom grid arrays along the X and Y directions. The correlation of bi-azimuth measurements is the first critical issue been taken into account. The method linearizes the differential values of scatterometry signatures at the first diffraction order with respect to designed offsets, and hence permits determination of overlay using a classical linear method. By evaluating the process variations (eg. CD, roundness and thickness) on overlay measurement error, a set of two overlay target design were optimized to minimize the correlation of bi-azimuth measurements and maximize the measurement sensitivity.

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Section: Introductionmentioning

confidence: 99%