We report a new mode of spatial-phase-locked electron-beam lithography based on alignment of each e-beam deflection field to a fiducial grid on the substrate. Before exposing the pattern in a given field, the fiducial grid is sparsely sampled with the electron beam at a subexposure dose. These samples form a two-dimensional moiré pattern that is analyzed to calculate field shift, scale, rotation, nonorthogonality, and trapezoidal distortion. Experimental verification of the approach was carried out with a scintillating fiducial grid quenched by interference lithography. Despite a poor signal-to-noise ratio, we achieved sub-beamstep field-stitching and pattern-placement accuracy.
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Hastings et al. (2000) studied this question.
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