METHOD FOR DESIGNING AN OVERLAY MARK

摘要

Precision in scatterometry measurements is improved by designing the reticle, or the target grating formed by the reticle, for greater overlay measurement sensitivity. Parameters of the structure and material of the substrate are first determined. These parameters may include the material composition, thickness, and sidewall angles of the sample substrate. The target grating is then designed so that the overlay measurement, on the sample substrate, is made more sensitive. A suitable measurement wavelength is selected, optionally via computer simulation, to further improve the sensitivity. This method increases the change of reflective signatures with overlay offsets, and thus improves the sensitivity of overlay measurement.