METHOD AND APPARATUS FOR DERIVING CORRECTIONS, METHOD AND APPARATUS FOR DETERMINING A PROPERTY OF A STRUCTURE, DEVICE MANUFACTURING METHOD

An optical system delivers illuminating radiation and collects radiation after interaction with a target structure on a substrate. A measurement intensity profile is used to calculate a measurement ofthe property of the structure. The optical system may include a solid immersion lens. In a calibration method, the optical system is controlled to obtain a first intensity profile using a first illumination profile and a second intensity profile using a second illumination profile. The profiles are used to derive a correction for mitigating the effect of ghost reflections. Using, e.g., half-moonillumination profiles in different orientations, the method can measure ghost reflections even where a SIL would cause total internal reflection. The optical system may include a contaminant detectionsystem to control a movement based on received scattered detection radiation. The optical system may include an optical component having a dielectric coating to enhance evanescent wave interaction. 光学系统传送照射辐射并收集在与衬底上的目标结构的相互作用