KEYWORDS: Lamps, Signal to noise ratio, Sensors, Interference (communication), Signal detection, Ellipsometry, Error analysis, Modulation, Data processing, Polarization
The influence of statistical noise such as lamp instability, photon shot noise, and detection noise on the signal quality in
rotating compensator based ellipsometry (RCE) is investigated by means of mathematical modeling and simulations. The
results uncover the transfer route from noise to measurement error under different experimental conditions, and thus
provide a basis for noise diagnosis and control in RCE systems.
Scanning white-light interferometry (SWLI) surface profiling for geometrical characterization and device inspection is described in this paper, which is quick, non-destructive, non-contact, and easy to carry out at the wafer scale with sub-micrometer lateral resolution and nanoscale vertical resolution. The measurement system is based on a Mirau microscopic interferometer, using a piezo objective nano-positioner to realize accurate scanning in vertical direction in the range of one hundred micrometers. It employs the method called centroid algorithm to extract the envelope peak position. Comparing with phase shifting interferometry, it has a large measurement range. The measurement accuracy of the system is calibrated by a step height standard which is certificated by NIST. A micro resonator is employed to illustrate the capabilities of SWLI as a measurement and process characterization tool.
Microscopic interferometry is up to now the most widely used technique for microstructure surface profiling, and is also capable of measuring out-of-plane motion and deflection of microstructures with stroboscopic illumination. In this paper we put forward a stroboscopic Mirau microscopic interferometer system, which is built of commercially available components and instruments based on virtual instrument technology. An improved Fourier transform method (FTM) is described, and two interferograms with different phase shifting are processed for achieving reliable phase demodulation. The system is applied to the measurement of microcantilever surface profile and out-of-plane deflection and motion. Finally, experiment results are compared with that of temporal phase-shifting method for validating the process method.
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