The National Institute of Standards and Technology (NIST) is developing standards and methods for assessing periodic structures using optical reflectance and transmittance measurements through their Optical Grating Scatterometry Program. Scatterometry is a technique that has gained popularity in the semiconductor industry for performing linewidth and line profile metrology.
The scatterometry method relies on the complex behavior of diffracted light from periodic targets as a function of incident angle and wavelength. By comparing measurements with a library of calculated model results, the profile of the target can be determined with extreme sub-nanometer-level sensitivity.
However, there are still some outstanding issues regarding the absolute accuracy of the scatterometry technique. The NIST program aims to address these issues both theoretically and experimentally using various tools and techniques, including SCATMECH, Modeled Integrated Scatter Tool (MIST), Optical Properties of Materials, Bidirectional Optical Scattering Facility, and Focused Beam Spectroscopic Ellipsometer.
Source: https://www.nist.gov/programs-projects/optical-grating-scatterometry
Keywords: Scatterometry, Metrology, Precision, Grating, Spectroscopic
