Improving pattern placement using through-the-membrane signal monitoring

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].