We describe here a means of improving pattern placement accuracy in the ele
ctron-beam lithographic manufacture of membrane masks. Our method is based
on collection of the beam transmitted through the membrane with a detector
fixed to the mask assembly. A fiducial grid overlaid onto the detector is u
sed to provide a global reference for measurement of the beam position duri
ng lithographic patterning. We give results from-recent experiments with co
mponents of such a system, and estimate I sigma accuracy in our method to b
e on the order of 1.5 nm. We discuss the effect of beam scattering on our t
echnique, and possible improvements in our implementation. [S0734-211X(98)0
3606-3].