Patent ID: 7605907

Claim:
A method of forming a substrate suitable for use in calibrating a metrology tool, comprising: providing a layer of radiation-sensitive material to a surface of a substrate; patterning a first beam of radiation using a patterning device that provides a calibration pattern including a first set of pattern features and a second set of pattern features; projecting the patterned first beam of radiation onto the radiation-sensitive material such that radiation patterned by the first set of pattern features of the calibration pattern forms a first calibration mark having a set of elongate pattern features and radiation patterned by the second set of pattern features of the calibration pattern forms a second calibration mark having a set of elongate pattern features; rotating the substrate by a predetermined angle relative to the projection system about an axis substantially perpendicular to the surface of the substrate; patterning a second beam of radiation using the patterning device and projecting it onto the radiation-sensitive material such that radiation patterned by the first set of pattern features of the calibration pattern forms a third calibration mark having a set of elongate pattern features and radiation patterned by the second set of pattern features of the calibration pattern forms a fourth calibration mark having a set of elongate pattern features; wherein the predetermined angle is such that the orientation of the elongate pattern features of the second calibration mark is substantially parallel to the orientation of the elongate pattern features of the third calibration mark.