spectroscopic scatterometry

Spectroscopic scatterometry measures critical dimensions and profile shapes by analyzing wavelength-dependent light scattering from periodic structures, providing non-destructive, rapid metrology for patterned wafers. The technique illuminates gratings with broadband light, measures reflected spectra, and uses rigorous coupled-wave analysis (RCWA) to solve Maxwell's equations, comparing measured spectra to simulated spectra from candidate profiles. By fitting measured data to physical models, scatterometry extracts CD, sidewall angle, height, and profile shape. Benefits include speed (seconds per site), non-destructive measurement, and sensitivity to profile details invisible to CD-SEM. Challenges include model complexity, correlation between parameters, and requirement for periodic structures. Spectroscopic scatterometry is essential for advanced process control, providing rapid, accurate CD measurements for lithography and etch monitoring. It represents optical metrology's evolution toward model-based, information-rich measurements.