Abstract:
PROBLEM TO BE SOLVED: To provide a method for modeling a spectrum by an improved free parameter selection method. SOLUTION: A set of parameters used in a model of a spectrometer includes free parameters and fixed parameters. A first set of values for the parameters is set and the model is used to generate a first spectrum. A value of one of the fixed parameters is changed to generate a second spectrum. An inverse of the model of the spectrometer is then applied to the second spectrum to generate a set of values for the parameters, the values being the same as the first set of values except for one or more free parameters. If the free parameter has significantly changed, the fixed parameter is designated as a free parameter. COPYRIGHT: (C)2009,JPO&INPIT
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 the 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.