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Autori: P.C. Logofatu
Editorial: Applied Optics, 41, p.7187-7192, 2002.
Phase-modulation scatterometry is a metrology technique for determining, by means of a phase modulator
as a key device, the parameters of gratings. The main source of error to be dealt with are the
fluctuations of the phase-modulation amplitude. The grating zeroth-order reflectance modulated by the
phase modulator is converted into a signal by the photodetector. The measurables are the direct term
and the first two harmonics of the signal. For experimental data fitting, we used the ratio of the
harmonics over the direct term because it significantly improves the accuracy. A sensitivity analysis
was performed for two samples, one real and one theoretical, to find the measurement configuration that
insures optimum determination precision for the grating parameters. For the real sample, comparison
of the theoretical predictions for sensitivity with the actual values showed a good agreement. For both
samples the sensitivity analysis indicated subnanometric precision for the critical dimension grating
Cuvinte cheie: scaterometrie, optimizare de sensibilitate, modulare de faza // scatterometry, sensitivity optimization, phase-modulation