Small angle X-ray scattering (SAXS) was used to characterize the cross section of nanoline gratings fabricated with electron beam lithography (EBL) patterning followed by anisotropic wet etching into a single crystal silicon substrate. SAXS results at normal incidence clearly bear the signature of positional dependent linewidth within the gratings; such non-uniformity is subsequently confirmed with scanning electron microscopy. The proximity effect of EBL is believed to be the cause of the spatial variations of linewidth. To quantitatively fit the SAXS results the linewidth near the periphery of the patterned field needs to be 80% greater than that in the central region, whereas the cross section of nanolines can be modeled as a simple rectangular shape, as expected from the anisotropic wet etching process. Published by Elsevier B.V.