ElsonYee-hsinLiu

Scatterometry

I am currently working under the supervision of Prof. Fred Terry on scatterometry, which is a optical technique for making high-resolution measurements of the topography of periodic micro- or nanostructures. The procedure for topography extraction by scatterometry consists of two basic steps:

1. Collect experimental optical scattering data. This data may be ellipsometric or reflectometric and it may be spectroscopic or angle-resolved. We use spectroscopic ellipsometry in the specular reflection mode to collect our experimental data.
2. Determine the geometry of grating that produces the scattering response that best fits the experimental data. This generally involves constructing a parametrized model of the grating topography to be utilized in forward-scattering simulations. The forward-scattering simulation may be used to pre-compute a library of scattering responses, or the forward-scattering simulation may be driven by a data-fitting algorithm to search for the parameters that best match the experimental data. We use Levenberg-Marquardt regression to drive a rigorous coupled-wave analysis (RCWA) grating diffraction simulation.

Journal publications

1. Elson Liu and Fred L. Terry, Jr., "Immersion scatterometry for improved nano-scale topography measurements", phys. stat. sol. (a), vol. 205, no. 4, pp. 784–788, 2008 (in press)

Conference abstracts

1. Elson Liu and Fred L. Terry, Jr., "Immersion scatterometry for improved nano-scale topography measurements," Fourth International Conference on Spectroscopic Ellipsometry, 11-15 Jun 2007, Stockholm, Sweden.

References

1. X. Niu, N. Jakatdar, J. Bao, and C. Spanos, “Specular spectroscopic scatterometry,” IEEE Trans. Semiconduct. Manufact., vol. 14, no. 2, pp. 97–111, May 2001.