System and method for focus control in extreme ultraviolet lithography systems using a focus-sensitive metrology target

Abstract

A focus-sensitive metrology target may be formed and read-out by a fabrication tool. A resulting overlay signal may be translated into a focus offset by comparison to a previously-determined calibration curve. One or more translated signals may be fed back to the fabrication tool for focus correction or used for prediction of on-device overlay (correction of overlay metrology results). In one embodiment, focus and overlay may be measured using a single target, where one portion of the target is formed on a first layer and includes a focus-sensitive design, and where another portion of the target is formed on a second layer and includes a relatively less focus-sensitive design. In some embodiments, a relative difference in focus response may be used to estimate an impact of focus error on device overlay and calculate non-zero offset contributions.