Abstract:
A metrology method relating to measurement of a structure on a substrate, the structure being subject to one or more asymmetric deviation. The method includes obtaining at least one intensity asymmetry value relating to the one or more asymmetric deviations, wherein the at least one intensity asymmetry value includes a metric related to a difference or imbalance between the respective intensities or amplitudes of at least two diffraction orders of radiation diffracted by the structure; determining at least one phase offset value corresponding to the one or more asymmetric deviations based on the at least one intensity asymmetry value; and determining one or more measurement corrections for the one or more asymmetric deviations from the at least one phase offset value.
Abstract:
Method for determining lithographic quality of a structure produced by a lithographic process using a periodic pattern, such as a grating, detects lithographic process window edges and optimum process conditions. Method steps are: 602: printing a structure using a lithographic process using a grating pattern; 604: selecting a first characteristic, such as a polarization direction, for the illumination; 606: illuminating the structure with incident radiation with first characteristic 608: detecting scattered radiation; 610: selecting a second characteristic, such as a different polarization direction, for the illumination; 612: illuminating the structure with incident radiation with the second characteristic; 614: detecting scattered radiation; 616: rotating one or more angularly resolved spectrum to line up the polarizations, thus correcting for different orientations of the polarizations; 618: determining a difference between the measured angularly resolved spectra; and 620: determining a value of lithographic quality of the structure using the determined difference.