With lithographic patterning dimensions decreasing well below 50 nm, it is of high importance to understand metrology at such small scales. This paper presents results obtained from dense arrays of contact holes (CHs) with various Critical Dimension (CD) between 15 and 50 nm, as patterned in a chemically amplified resist using an ASML EUV scanner and measured at ASML and TNO. To determine the differences between various (local) CD metrology techniques, we conducted an experiment using optical scatterometry, CD-Scanning Electron Microscopy (CD-SEM), Helium ion Microscopy (HIM), and Atomic Force Microscopy (AFM). CD-SEM requires advanced beam scan strategies to mitigate sample charging; the other tools did not need that. We discuss the observed main similarities and differences between the various techniques. To this end, we assessed the spatial frequency content in the raw images for SEM, HIM, and AFM. HIM and AFM resolve the highest spatial frequencies, which are attributed to the more localized probe-sample interaction for these techniques. Furthermore, the SEM, HIM, and AFM waveforms are analyzed in detail. All techniques show good mutual correlation, albeit the reported CD values systematically differ significantly. HIM systematically reports a 25% higher CD uniformity number than CD-SEM for the same arrays of CHs, probably because HIM has a higher resolution than the CD-SEM used in this assessment. A significant speed boost for HIM and AFM is required before these techniques are to serve the demanding industrial metrology applications like optical critical dimension and CD-SEM do nowadays.
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October 2015
Research Article|
October 07 2015
Sub-50 nm metrology on extreme ultra violet chemically amplified resist—A systematic assessment
D. J. Maas
;
D. J. Maas
a)
1
Netherlands Organization for Applied Scientific Research
, TNO, Stieltjesweg 1, 2628CK Delft, The Netherlands
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T. Fliervoet;
T. Fliervoet
2
ASML
, de Run 6665, 5504DR Veldhoven, The Netherlands
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R. Herfst;
R. Herfst
1
Netherlands Organization for Applied Scientific Research
, TNO, Stieltjesweg 1, 2628CK Delft, The Netherlands
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E. van Veldhoven;
E. van Veldhoven
1
Netherlands Organization for Applied Scientific Research
, TNO, Stieltjesweg 1, 2628CK Delft, The Netherlands
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J. Meessen;
J. Meessen
2
ASML
, de Run 6665, 5504DR Veldhoven, The Netherlands
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V. Vaenkatesan;
V. Vaenkatesan
2
ASML
, de Run 6665, 5504DR Veldhoven, The Netherlands
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H. Sadeghian
H. Sadeghian
1
Netherlands Organization for Applied Scientific Research
, TNO, Stieltjesweg 1, 2628CK Delft, The Netherlands
3Department of Precision and Microsystems Engineering,
Delft University of Technology
, Delft, The Netherlands
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a)
Author to whom correspondence should be addressed. Electronic mail: diederik.maas@tno.nl
Rev Sci Instrum 86, 103702 (2015)
Article history
Received:
June 13 2015
Accepted:
September 17 2015
Citation
D. J. Maas, T. Fliervoet, R. Herfst, E. van Veldhoven, J. Meessen, V. Vaenkatesan, H. Sadeghian; Sub-50 nm metrology on extreme ultra violet chemically amplified resist—A systematic assessment. Rev Sci Instrum 1 October 2015; 86 (10): 103702. https://doi.org/10.1063/1.4932038
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