Patent ID: 7966142

Claim:
A method for assessing a metrology tool under test (MTUT) comprising: measuring a target parameter from a plurality of test structures using the MTUT to generate a test data set, the test data set corresponds to a test variable; measuring a first reference parameter from the plurality of test structures using a reference metrology tool (RMT) to generate a first reference data set, the first reference data set corresponds to a first reference variable; measuring a second reference parameter, which is different from the first reference parameter, from the plurality of test structures using the RMT to generate a second reference data set, the second reference data set corresponds to a second reference variable, wherein the first and second reference parameters measured by the RMT are compared with the target parameter measured by the MTUT, and wherein the first reference parameter is the same as the target parameter and the second reference parameter influences the target parameter; and performing a multi-variable regression analysis, wherein a multi-variable model of the multi-variable regression analysis is based on the test variable of the test data set from the MTUT and first and second reference variables of the first and second reference data sets from the RMT.