Patent ID: 8867041

Claim:
An apparatus for measuring characteristics of a sample, the apparatus comprising: an optical metrology instrument comprising focusing optics for focusing light onto the sample and collecting the light reflected from the sample so as to record an optical response from nanoimprint structures on the sample, wherein the nanoimprint structures have an orientation that varies over a surface of the sample; a sample stage configured to support the sample; and at least one computer, which is connected to the metrology instrument and the sample stage and is configured to run a computer program which causes the sample stage to rotate the sample so as to present multiple different locations on the sample to the optical metrology instrument such that the orientation of the nanoimprint structures at the multiple different locations remains fixed with respect to a plane of the focusing optics of the metrology instrument in order to eliminate polarization effects, wherein the computer program causes the at least one computer to extract measured characteristics of the nanoimprint structures from a theoretical model of the sample while making use of the fixed orientation of the nanoimprint structures in extraction of the measured characteristics.