Integrated circuit system with automated best focus determination based on change in alignment due to predictable pattern degradation

Abstract

A method ( ) of determining a best focus for an integrated circuit stepper ( ). The method repeats various steps for a plurality of different focus levels. The repeated steps include forming a first element group (C ) on a wafer ( ), where the first element group comprises one or more elements and each of the one or more elements in the first element group has a shape. The repeated steps further include defining a first reference point (C ) for the first element group at a position relative to the shape of the one or more elements in the first element group. Similarly, the repeated steps include forming a second element group (C ) on the wafer, where the second group comprises one or more elements and each of the one or more elements in the second element group has a shape, and defining a second reference point (C ) for the second element group at a position relative to the shape of the one or more elements in the second element group. Still another repeated step is measuring a distance between the first reference point and the second reference point such that a distance measurement is identified for each of the plurality of different focus levels. Finally, the method selects as the best focus a focus level from the plurality of different focus levels and corresponding to a selected one of the distance measurements.