High-Speed
Coherent fourier scatterometry
S. Soman (TU Delft - Applied Sciences)
S.F. Pereira – Promotor (TU Delft - Applied Sciences)
O. El Gawhary – Copromotor (TU Delft - Applied Sciences)
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Abstract
In a wide range of manufacturing industries, including semiconductors, photonics, transportation, healthcare and energy storage, there is a need for increasingly smaller structures with strict tolerances. To continue this trend, fast, non-destructive, and traceable metrology that can keep pace with these developments is essential. Although electron and scanning probe microscopies have excellent spatial resolution, they suffer from low throughput, stringent measurement conditions, and can be destructive to the sample. On the other hand, optics-based techniques are attractive for fast, non-contact metrology in manufacturing environments. Coherent Fourier scatterometry (CFS) meets this need by providing an optical measurement solution that uses low light power, is nondestructive, and has a simple optical design. The technique involves focusing a coherent beam onto a diffraction-limited spot, collecting the field scattered in the Fourier plane after interaction with the sample. By scanning the spot across the surface, a scattering map is constructed from which parameters of the structures can be derived using a forward simulation model. Since scanning time accounts for most of the total measurement time, this thesis focuses on accelerating CFS by investigating different approaches, such as probe multiplexing and non-raster scanning, to increase the scanning speed. The central research question is how each of these options balances speed, optical complexity, alignment effort, and the overall noise floor of the system…