Abstract: Measurement marks are applied throughout the area of an e-beam projection mask on a grillage of struts extending between sub-field membrane mask areas concurrently with patterning the sub-field membrane mask areas. The thickness of the struts prevents printing of the measurement marks on the resist at the target plane even if inadvertently illuminated by the e-beam system. Measurement of the relative locations of the measurement marks after fabrication and incremental periods of use supports the development of compensation or correction in the electron-optical system for distortions of the mask which may be detected from the measurement marks by adjustment of operating parameters thereof.