Patent ID: 6542221
Filing Date: 2003-04-01
Classification: G03F

Abstract:
A method of determining a best focus for an integrated circuit stepper, comprising the steps of:for a plurality of different focus levels, the steps of: forming a first element group on a wafer, wherein 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; defining a first reference point for the first element group at a position relative to the shape of the one or more elements in the first element group; forming a second element group on the wafer, wherein the second group comprises one or more elements and each of the one or more elements in the second element group has a shape; defining a second reference point for the second element group at a position relative to the shape of the one or more elements in the second element group; 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; and selecting as the best focus a focus level from the plurality of different focus levels and corresponding to a selected one of the distance measurements.