Provided is a method of optimizing sensitivity of measurements of an optical metrology tool using two or more illumination beams directed to a structure on a workpiece comprising selecting target structures for measurement, obtaining diffraction signals off the selected structures as a function of angle of incidence for each illumination beam, determining a selected angle of incidence for each of the two or more illumination beams, setting sensitivity objectives for optical metrology measurements, developing a design for the optical metrology tool to achieve the corresponding selected angle of incidence of the two or more illumination beams, obtaining sensitivity data using the optical metrology tool, and if the sensitivity objectives are not met, adjusting the selection of target structures, the selected angle of incidence of the two or more illumination beams, the sensitivity objectives, and/or the design of the optical metrology tool, and iterating the developing of the design, obtaining sensitivity data, and comparing sensitivity data to sensitivity objectives until the sensitivity objectives are met.