Patent ID: 8869076

Claim:
A method for processing data associated with a substrate, comprising: performing measurements on a plurality of groups of targets on a substrate, the plurality of groups of targets comprising a first type of targets and a second type of targets, the first type of targets being measured at a first group of locations on the substrate to generate a first group of measurement values, the second type of targets being measured at a second group of locations on the substrate to generate a second group of measurement values, the plurality of groups of measurement values being influenced by variations in a global parameter that is a function of location on the substrate; defining a combined measurement function representing a combination of the plurality of groups of measurement values taking into account of the locations of the measurements, at least one group of measurement values being transformed prior to combining with another group or other groups of measurement values, the transformations being defined by a set of coefficients; determining, using a computer, values for the coefficients of the transformation; and determining, using the computer, variations in the global parameter based on the combined measurement function and a predetermined relationship between the measurement values and the global parameter.