Dimensional Control of Line Gratings by Small Angle X-Ray Scattering: Shape and Roughness Extraction

The capabilities of Small Angle X-ray Scattering (SAXS) for dimensional control of line gratings are reviewed. We first introduce different experimental methodologies used to extract the pitch, the critical dimension (CD) and the side-wall angle (SWA) of line gratings. A special focus is done on line roughness extraction. We already demonstrated that the SAXS technique has the sensitivity to measure line roughness amplitude below 1 nm on a set of line gratings designed with a controlled line roughness [1]. Fast Fourier Transforms (FFT) simulations revealed that the Line Width Roughness (LWR) defined as a Power Spectral Density (PSD) can be measured in a SAXS pattern at some specific positions in the reciprocal space [2]. In the present study, a comparison of the LWR PSD extracted by SAXS and by Scanning Electron Microscope (SEM) on one set of samples was done.