Two approaches for realizing traceability in nanoscale dimensional metrology

Gaoliang Dai; Ludger Koenders; Jens Flügge; Harald Bosse

doi:10.1117/1.OE.55.9.091407

30 March 2016 Two approaches for realizing traceability in nanoscale dimensional metrology

Gaoliang Dai, Ludger Koenders, Jens Flügge, Harald Bosse

Author Affiliations +

Optical Engineering, Vol. 55, Issue 9, 091407 (March 2016). https://doi.org/10.1117/1.OE.55.9.091407

Abstract

Traceability is a fundamental issue for nanoscale dimensional metrology. The lack of traceability in measurements inhibits the comparison of tools from different manufacturers and limits knowledge about the real size of fabricated features. Two approaches for realizing traceability in nanometrology, referred to as a top-down approach and a bottom-up approach, are presented. Following the top-down approach, for instance, realized using metrological atomic force microscopes, the dimension of nanostructures is derived from the displacement of the scanner, which is directly measured by laser interferometers whose optical frequency is calibrated to an iodine frequency-stabilized laser. Thus, the measurement result is directly traceable with an unbroken chain to the International System of Units—the meter. However, to achieve subnanometer measurement accuracy, which is far smaller than the optical wavelength (632.8 nm in this study), the subdivision of the interference fringe is essential for obtaining desired measurement resolution and accuracy. On the contrary, with the bottom-up approach, the dimension of nanostructures is determined using the silicon crystal lattice as an internal ruler. Due to the small dimension of the crystal lattice constant (e.g., d₁₁₁=0.313 nm), the bottom-up approach offers measurements with potential highest accuracy. The crystal lattice constant can be traceably calibrated to the meter by, e.g., a combined optical and x-ray interferometer; thus, the traceability of the bottom-up approach is also ensured. The consistency of the two approaches is experimentally confirmed in this paper.

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Gaoliang Dai, Ludger Koenders, Jens Flügge, and Harald Bosse "Two approaches for realizing traceability in nanoscale dimensional metrology," Optical Engineering 55(9), 091407 (30 March 2016). https://doi.org/10.1117/1.OE.55.9.091407

Published: 30 March 2016

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