The calibration of masks used in x-ray lithography has been successfully accomplished in the scanning electron microscopy (SEM) by utilizing the transmitted scanning electron detection technique. This has been made possible because these masks present a measurement subject different from most (if not all) other objects used in semiconductor processing because the support membrane is, by design, x-ray transparent. This characteristic can be used as an advantage in electron beam-based mask metrology since, depending upon the incident electron beam energies, substrate composition and substrate thickness, the membrane can also be essentially electron transparent.