Overlay similarity: a new overlay index for metrology tool and scanner overlay fingerprint methodology

Ke, Chih-Ming; Kao, Chiang; Wang, Yu-Hsi; Hu, Jimmy; Chang, Chi Cheng; Tsai, Ya-Jung; Yen, Anthony; Lin, Burn J.

doi:10.1117/12.814852

Cited by 11 publications

(2 citation statements)

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“…Figure 2 shows the overlay maps measured by IBO tool on ADI and AEI stages, and their difference (AEI-ADI). Their point-to-point similarity [4,5] is 95.78 % for the cosine term and 1.00 nm for the vector difference. From model analysis, the expansion terms of AEI-ADI map are 0.0096 ppm (Mx) and 0.0091 ppm (My).…”

Section: Methodsmentioning

confidence: 99%

Reduction of image-based ADI-to-AEI overlay inconsistency with improved algorithm

et al. 2013

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In image-based overlay (IBO) measurement, the measurement quality of various measurement spectra can be judged by quality indicators and also the ADI-to-AEI similarity to determine the optimum light spectrum. However we found some IBO measured results showing erroneous indication of wafer expansion from the difference between the ADI and the AEI maps, even after their measurement spectra were optimized. To reduce this inconsistency, an improved image calculation algorithm is proposed in this paper. Different gray levels composed of inner-and outer-box contours are extracted to calculate their ADI overlay errors. The symmetry of intensity distribution at the thresholds dictated by a range of gray levels is used to determine the particular gray level that can minimize the ADI-to-AEI overlay inconsistency. After this improvement, the ADI is more similar to AEI with less expansion difference. The same wafer was also checked by the diffraction-based overlay (DBO) tool to verify that there is no physical wafer expansion. When there is actual wafer expansion induced by large internal stress, both the IBO and the DBO measurements indicate similar expansion results. The scanning white-light interference microscope was used to check the variation of wafer warpage during the ADI and AEI stages. It predicts a similar trend with the overlay difference map, confirming the internal stress.

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Section: Methodsmentioning

confidence: 99%

Reduction of image-based ADI-to-AEI overlay inconsistency with improved algorithm

et al. 2013

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“…Unfortunately this assumption is unrealistic and leads to inaccuracy [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. There are different types of metrology target asymmetries that contaminate the signal and mix with the overlay-induced asymmetry.…”

Section: Overlay Metrology In the Accuracy Agementioning

confidence: 99%

Accuracy in optical overlay metrology

et al. 2016

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In this paper we discuss the mechanism by which process variations determine the overlay accuracy of optical metrology. We start by focusing on scatterometry, and showing that the underlying physics of this mechanism involves interference effects between cavity modes that travel between the upper and lower gratings in the scatterometry target. A direct result is the behavior of accuracy as a function of wavelength, and the existence of relatively well defined spectral regimes in which the overlay accuracy and process robustness degrades (`resonant regimes'). These resonances are separated by wavelength regions in which the overlay accuracy is better and independent of wavelength (we term these `flat regions'). The combination of flat and resonant regions forms a spectral signature which is unique to each overlay alignment and carries certain universal features with respect to different types of process variations. We term this signature the `landscape', and discuss its universality. Next, we show how to characterize overlay performance with a finite set of metrics that are available on the fly, and that are derived from the angular behavior of the signal and the way it flags resonances. These metrics are used to guarantee the selection of accurate recipes and targets for the metrology tool, and for process control with the overlay tool. We end with comments on the similarity of imaging overlay to scatterometry overlay, and on the way that pupil overlay scatterometry and field overlay scatterometry differ from an accuracy perspective.

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Advanced litho-cluster control via integrated in-chip metrology

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et al. 2013

ASMC 2013 SEMI Advanced Semiconductor Manufacturing Conference

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The high-end semiconductor lithography requirements for overlay and focus control in near-future ITRS nodes are at subnanometer level. This development is extremely challenging for the metrology precision and accuracy, as scaling down to the subangstrom level is required for this. On top of the extreme metrology requirements, direct feed-back control of the lithographic steps is needed to meet the future node requirements. Integrated metrology with in-chip measurements, advanced sampling and control-mechanism (using the highest order of correction possible with scanner interface today), are a few of such technologies considered in this publication.

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Overlay similarity: a new overlay index for metrology tool and scanner overlay fingerprint methodology

Cited by 11 publications

References 0 publications

Reduction of image-based ADI-to-AEI overlay inconsistency with improved algorithm

Reduction of image-based ADI-to-AEI overlay inconsistency with improved algorithm

Accuracy in optical overlay metrology

Advanced litho-cluster control via integrated in-chip metrology

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