Spectroscopic Polarized Scatterometry applied to single line profiling

摘要

We have shown through 3 different examples that scatterometry measurement is a very powerful technique to characterize sub wavelengths structures. Using a simple model based on the scalar diffraction theory, it is possible to characterize with high accuracy the structure of Al lines on glass substrate in term of line width and distance between two adjacent lines. It is also possible to estimate a very reasonable value for the grain size at the surface of a polysilicon layer obtained by the annealing of amorphous silicon layer deposited on glass. Finally, we have measured with high accuracy the line width of different isolated lines and etched lines. Using the spectroscopic ellipsometer option of the system, it was possible to characterize in term of thickness and refractive index, the different material of this structure, then a significant contrast between TE and TM diffracted polarizations was obtained by selecting the optimal parameters in term of wavelength and angle of incidence for the source arm. Results show that scalar approach of diffraction is still significant when line width is only 2 times the wavelength of measurement. More rigorous methods, exist to characterize completely these kinds of structures and in particularly the high of the diffractive structures, for which we cannot give any information at this level of our simple analysis. Further developments of this work will be considered in a next future and in particularly the amplitude of the diffraction curves will be used to complete the model we propose. Finally, the combination of a scatterometric and ellipsometric measurements on the same tool appear through these examples very powerful to characterize such structured samples.