Coherent Fourier scatterometry using rotational scanning
Sarika Soman (TU Delft - Applied Sciences)
Bastiaan In 't Velt (Student TU Delft)
Roland Horsten (TU Delft - Applied Sciences)
Silvania Pereira (TU Delft - Applied Sciences)
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Abstract
We present a rotation-based coherent Fourier scatterometry (CFS) system for high-speed, high-resolution surface metrology. Traditional CFS systems rely on piezoelectric stages for point-by-point raster scanning, which limits scan speed due to constant accelerations and decelerations. In our approach, the fast-axis piezo stage is replaced by a rotation stage moving at constant angular velocity, whereas the slow-axis piezo is used to step radially outward to generate concentric scan paths. We introduce a frequency spread–based technique to compensate for probe centering deviation and demonstrate the capability of measuring axial wobble using depth-sensitive CFS signals. Application of the system is shown through the detection of 0.4μm polystyrene latex particles and the calibration of etched pits with diameters ranging from 225 to 1125 nm at the wavelength of 633 nm. The proposed system offers a scalable and low-complexity solution for fast, noncontact nanometrology.
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