A Novel Alignment System for Imprint Lithography

A novel alignment system for imprint lithography in the deep sub-100-nm realm is proposed. The new system is inherently more precise than the alignment systems used in conventional projection lithography because alignment marks on an imprint mold (the functional equivalent of a photomask in projection lithography) are directly compared to alignment marks on a wafer with no intermediate optics or reference points. If the measured misalignment is so severe that all marks cannot be brought into registration simultaneously by the usual s-y translations and rotations, the mold is deliberately deformed with a system of piezoelectric actuators in such a way that its induced distortions precisely match those on the wafer and all of the alignment marks at each chip site can be pulled into registration simultaneously. Finite-element analysis indicates that using actuators to distort the mold is superior to distorting the wafer. The cost of such a system is not expected to be much more than the cost of an alignment system for a typical deep-ultraviolet stepper.