Abstract: An apparatus to measure the position of a mark, the apparatus including an objective lens to direct radiation on a mark using radiation supplied by an illumination arrangement; an optical arrangement to receive radiation diffracted and specularly reflected by the mark, wherein the optical arrangement is configured to provide a first image and a second image, the first image being formed by coherently adding specularly reflected radiation and positive diffraction order radiation and the second image being formed by coherently adding specularly reflected radiation and negative diffraction order radiation; and a detection arrangement to detect variation in an intensity of radiation of the first and second images and to calculate a position of the mark in a direction of measurement therefrom.

Abstract: Apparatus, systems, and methods are used for detecting the alignment of a feature on a substrate using a polarization independent interferometer. The apparatus, system, and methods include optical elements that receive light that has diffracted or scattered from a mark on a substrate. The optical elements may split the diffracted light into multiple subbeams of light which are detected by one or more detectors. The diffracted light may be combined optically or during processing after detection. The system may determine alignment and/or overlay based on the received diffracted light having any polarization angle or state.

Abstract: An apparatus to measure the position of a mark, the apparatus including an illumination arrangement to direct radiation across a pupil of the apparatus, the illumination arrangement including an illumination source to provide multiple-wavelength radiation of substantially equal polarization and a wave plate to alter the polarization of the radiation in dependency of the wavelength, such that radiation of different polarization is supplied; an objective to direct radiation on the mark using the radiation supplied by the illumination arrangement while scanning the radiation across the mark in a scanning direction; a radiation processing element to process radiation that is diffracted by the mark and received by the objective; and a detection arrangement to detect variation in an intensity of radiation output by the radiation processing element during the scanning and to calculate from the detected variation a position of the mark in at least a first direction of measurement.

Abstract: An apparatus to measure the position of a mark, the apparatus including an objective lens to direct radiation on a mark using radiation supplied by an illumination arrangement; an optical arrangement to receive radiation diffracted and specularly reflected by the mark, wherein the optical arrangement is configured to provide a first image and a second image, the first image being formed by coherently adding specularly reflected radiation and positive diffraction order radiation and the second image being formed by coherently adding specularly reflected radiation and negative diffraction order radiation; and a detection arrangement to detect variation in an intensity of radiation of the first and second images and to calculate a position of the mark in a direction of measurement therefrom.

Abstract: An apparatus (AS) measures positions of marks (202) on a lithographic substrate (W). An illumination arrangement (940, 962, 964) provides off-axis radiation from at least first and second regions. The first and second source regions are diametrically opposite one another with respect to an optical axis (O) and are limited in angular extent. The regions may be small spots selected according to a direction of periodicity of a mark being measured, or larger segments. Radiation at a selected pair of source regions can be generated by supplying radiation at a single source feed position to a self-referencing interferometer. A modified half wave plate is positioned downstream of the interferometer, which can be used in the position measuring apparatus. The modified half wave plate has its fast axis in one part arranged at 45° to the fast axis in another part diametrically opposite.

Abstract: A method of device inspection, the method comprising providing an asymmetric marker on a device to be inspected, the form of asymmetry of the marker being dependent upon the parameter to be inspected, directing light at the marker, obtaining a first measurement of the position of the marker via detection of diffracted light of a particular wavelength or diffraction angle, obtaining a second measurement of the position of the marker via detection of diffracted light of a different wavelength or diffraction angle, and comparing the first and second measured positions to determine a shift indicative of the degree of asymmetry of the marker.

Abstract: A method of device inspection, the method comprising providing an asymmetric marker on a device to be inspected, the form of asymmetry of the marker being dependent upon the parameter to be inspected, directing light at the marker, obtaining a first measurement of the position of the marker via detection of diffracted light of a particular wavelength or diffraction angle, obtaining a second measurement of the position of the marker via detection of diffracted light of a different wavelength or diffraction angle, and comparing the first and second measured positions to determine a shift indicative of the degree of asymmetry of the marker.