Abstract: The invention relates to an apparatus for probing a sample comprising a light source for emitting an illuminating light beam, a birefringent element for splitting the illuminating light beam into two sheared beams, a reflective element for reflecting the two sheared beams, wherein the apparatus is configured such that the reflected beams propagate through the birefringent element for recombining the reflected beams, and a detector for detecting the recombined beam, wherein the sample is arrangeable in the optical path of the sheared beams or at the backside of a reflective surface in the optical path of the sheared beams, the reflective surface exhibiting a surface plasmon resonance or a localized surface plasmon resonance.

Abstract: The invention relates to an apparatus for probing a sample comprising a light source for emitting an illuminating light beam, a birefringent element for splitting the illuminating light beam into two sheared beams, a reflective element for reflecting the two sheared beams, wherein the apparatus is configured such that the reflected beams propagate through the birefringent element for recombining the reflected beams, and a detector for detecting the recombined beam, wherein the sample is arrangeable in the optical path of the sheared beams or at the backside of a reflective surface in the optical path of the sheared beams, the reflective surface exhibiting a surface plasmon resonance or a localized surface plasmon resonance.

Abstract: Disclosed is a method of measuring a parameter of a lithographic process, and associated computer program and apparatuses. The method comprises providing a plurality of target structures on a substrate, each target structure comprising a first structure and a second structure on different layers of the substrate. Each target structure is measured with measurement radiation to obtain a measurement of target asymmetry in the target structure, the target asymmetry comprising an overlay contribution due to misalignment of the first and second structures, and a structural contribution due to structural asymmetry in at least the first structure. A structural asymmetry characteristic relating to the structural asymmetry in at least the first structure of each target structure is obtained, the structural asymmetry characteristic being independent of at least one selected characteristic of the measurement radiation.

Abstract: Disclosed is a method of measuring a parameter of a lithographic process, and associated computer program and apparatuses. The method comprises providing a plurality of target structures on a substrate, each target structure comprising a first structure and a second structure on different layers of the substrate. Each target structure is measured with measurement radiation to obtain a measurement of target asymmetry in the target structure, the target asymmetry comprising an overlay contribution due to misalignment of the first and second structures, and a structural contribution due to structural asymmetry in at least the first structure. A structural asymmetry characteristic relating to the structural asymmetry in at least the first structure of each target structure is obtained, the structural asymmetry characteristic being independent of at least one selected characteristic of the measurement radiation.