Structural characterizaton of deep-submicron lithographic structures using small-angle neutron scattering

As critical dimensions continue to decrease with each technology node, the precise characterization of line width and profile becomes an increasingly challenging task. Small angle neutron scattering (SANS) offers several advantages for the characterization of sub-100 nm structures, particularly as a calibrating measurement method. In this work, SANS is used to characterize three samples prepared with the same mask and focus conditions, but different photoresist formulations. The mask pattern consists of parallel lines with a nominal line width of 180 nm and a 1:2 line to space ratio. Scattering data are taken using both a focused neutron beam instrument (two-dimensional data) and a perfect crystal diffraction ultra-high resolution small angle neutron scattering (USANS) instrument. From the location and intensity of observed diffraction peaks, both the periodicity of each grating pattern and the average line widths are determined from simple analytic expressions with nanometer resolution.