Patent ID: 7990546
Filing Date: 2011-08-02
Classification: G01N,G03F

Abstract:
1. A method comprising: with a first measurement system having a first resolution, generating a reference calibration table of parameter variation that occurs on a surface of a sample object; dividing the surface of the sample object into pixels which are characterized by the parameter variation; defining blocks of the surface as respective groups of the pixels; with a second measurement system having a second resolution less than the first resolution (i) irradiating the pixels in multiple scans over the surface with radiation having different, respective types of polarization, and (ii) detecting returning radiation from the pixels in response to each of the scans; for each of the scans, (i) constructing respective block signatures of the blocks in response to the returning radiation from the group of pixels in each block, and (ii) determining a block signature variation using the respective block signatures of the blocks; and in response to a correlation between the block signature variation and the reference calibration table of parameter variation, the reference calibration table of parameter variation based on measurements at the first resolution and the block signature variation based on measurements at the second resolution less than the first resolution, selecting one of the types of polarization for use in subsequent examination of a test object.