Simulation-free determination of structural grating parameters with GISAXS

New technologies such as next-generation semiconductor and lithography techniques rely on complex surface structures with characteristic dimensions in the nanometre range. The functionality of such structures depends greatly on their feature size, thus, dimensional nanometrology is essential for precise control of nanostructured devices. Grazing Incidence Small Angle X-ray Scattering (GISAXS) is a tool for non-destructive length measurement in the nanometre range. Structure parameter retrieval from GISAXS scattering data generally requires simulation of the morphology due to the loss of phase information during image acquisition. Here we present an approach to obtain dimensional parameters of highly ordered surface structures directly from the scattering data without the need of simulation. Line gratings have been investigated with GISAXS and important parameters such as line and groove width, etching depth and period length can be obtained from scattering images by Fourier transformation. The analysis method was applied to different test grating structures as well as to simulated scattering patterns for validation. The experiments were performed at the Four-Crystal Monochromator (FCM) beamline in the PTB laboratory at the electron storage ring BESSY II using the SAXS setup of the Helmholtz-Zentrum Berlin (HZB).