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A: Yes. Although Epi-Si is opaque in the UV-Vis-NIR wavelength range, Epi-Si is trans-
parent in the infra-red wavelength regime. In fact, the n&k Olympian, with its wavelength
range covering UV-Vis-IR wavelengths, is successfully used for measuring thickness and
n and k spectra of Epi-Si.
A: Yes. The n&k 450-M, a manual load UV-Vis-NIR Scatterometer/Thin Film metrology
tool, is available today for the larger 450mm wafers. The 450-M will provide the necessary
OCD and Thin Film metrology for development of new technology for the 450mm
transition in the most cost effective way.
A: Yes. n&k’s scatterometer, the n&k OptiPrime, is able to decouple FinFET parameters
due to its innovative optics that produces the optimized signal-to-noise ratio of order 2%-
5% per 2nm change in the parameters. The OptiPrime’s wide spectral range helps, be-
cause, in general, if there are changes in the measured raw data at all wavelengths, then
the effect of coupling is not too significant.
A: As can be demonstrated when using the n&k Olympian, a UV-Vis-IR scatterometer, it is necessary to extend the measurements to the infra-red wavelength range when initial measurements using DUV-Vis-NIR wavelengths does not reveal sufficient information to
determine depths, CDs and profiles of 2D and 3D structures. The extension to the infra-red
spectral range is necessary in order to measure complex ultra-deep structures, or struc-
tures with high aspect ratios.
A: Yes, if accuracy and repeatability are important for such measurements. As can be
demonstrated by the Scatterometer/ Thin Film metrology tool, the n&k Gemini, very little
reflected light reaches the detector for cases where the substrate is transparent – most
of it is transmitted. Thus, by including measured transmittance, a better Signal-to-Noise
(S/N), compared to reflectance, is obtained, since more transmitted photons reach the
detector than reflected photons, and the (S/N) ratio is proportional to # of detected pho-
tons. Furthermore, the noise in the reflectance spectrum can overshadow variations in
reflectance due to CD variations, whereas the high (S/N) of transmittance measurements
means CD variations can be better resolved. Same arguments apply to variations in side
A: Scatterometry depends on Rigorous Coupled Wave Analysis (RCWA) of the measured
raw data to determine depths, CDs and Profiles of 2D (trenches) and 2D (contact holes)
structures. In turn, RCWA depends on the n and k spectra of the films comprising structure
that is being measured. Thus, if the n and k values are incorrect, then the RCWA will yield
incorrect results for Depths, CDs and Profiles. Scatterometers that combine physically val-
id dispersion equations for n and k with RCWA, e.g., the n&k Olympian or n&k OptiPrime
will provide the most accurate measurement results.
A: The importance of “All-Reflective Optics” is that there are no beam-splitters, refractive
lenses, or other light absorbing components contained within the optics. Such light absorb-
ing components reduce the amount of light that is sensed by the detector, thus reducing
the signal-to-noise, which in turn affects the accuracy and repeatability of the measure-
ment. Basically, with an “All-Reflective” optical design, the signal-to-noise ratio is opti-
mized, which in turn produces accurate results and excellent repeatability.