Dynamic three-dimensional mask-wafer positioning with nanometer exposure overlay

We describe a means of dynamically controlling the relative mask-wafer posi tion in X, Y, and Z during proximity X-ray exposures. The axis of a point X -ray source is detected by a direct X-ray obscuration scheme. Point-source- induced exposure runout is controlled to <1 nm along the source axis. Nanom eter exposure over-lay is measured by the spatial phase of fringes in resis t, observed with a separate, normal-incidence microscope. These aligning an d gapping techniques, in combination with the method of aligning the axis o f a point X-ray source to a fiducial point on the mask, result in a minimum controlled exposure overlay of 2.5 nm.