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In addition to EUV Mask measurements, the tools belonging to the Gemini Series are
used extensively for measurements of conventional masks. These tools provide simulta-
neous measurements of polarized reflectance (Rs and Rp) and polarized transmittance
(Ts and Tp) from 190nm to 1000nm of phase-shift and double patterning ArF masks. The
spot size for both the reflectance and transmittance is 50μm. The inclusion of transmit-
tance is very important in order to ensure accuracy. This is because Intensity of Ts and
Tp >> Intensity of Rs and Rp → More transmitted photons reach detector than reflected
photons and the signal-to-noise ratio is in proportion to # of detected photons.Also, there is a direct correlation between transmittance and CD, which in turn furnishes
a fast and accurate way of measuring CDs in a production environment.The tools belonging to the Gemini Series accurately and repeatabley measure film thick-
nesses, for example, thicknesses of all films in a typical stack such as Resist/ARC/CrOx/
CR/MoSi/Quartz-Substrate. Furthermore, height, CD and side wall of phase-shift and
double patterning ArF masks, plus the phase-shift of phase-shift masks are also mea-
sured. In addition the tools provide through-pellicle measurements. Excellent correlation
with other metrology techniques has been obtained. An automated flipper for front-side
and back-side measurements is an option with the n&k Gemini.
System Capabilities
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