As optical lithography advances toward the 10 nm mark, much effort is being expended to push electron beam lithography into the deep sub-10-nm regime. A significant issue at this length scale is the ability to accurately measure and compare linewidths. Measurements using secondary electron micrographs have a bias of a few nanometers and are therefore difficult to interpret in the sub-10-nm regime. Transmission electron microscopy can give greater accuracy but requires significant effort. This article shows that the use of a backscattered electron image together with a metal coating where appropriate can yield better measurement results than by using secondary electrons. With the use of a suitable model, linewidths for sub-10-nm hydrogen silsesquioxane lines were extracted with an estimated error of 1 nm. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3505129]