Abstract: A dark field digital holographic microscope and associated metrology method is disclosed which is configured to determine a characteristic of interest of a structure. The dark field digital holographic microscope includes an illumination branch for providing illumination radiation to illuminate the structure; a detection arrangement for capturing object radiation resulting from diffraction of the illumination radiation by the structure; and a reference branch for providing reference radiation for interfering with the object radiation to obtain an image of an interference pattern formed by the illumination radiation and reference radiation. The reference branch has an optical element operable to vary a characteristic of the reference radiation so as to reduce and/or minimize variation in a contrast metric of the image within a field of view of the dark field digital holographic microscope at a detector plane.

Abstract: Disclosed is a method for obtaining a computationally determined interference electric field describing scattering of radiation by a pair of structures comprising a first structure and a second structure on a substrate. The method comprises determining a first electric field relating to first radiation scattered by the first structure; determining a second electric field relating to second radiation scattered by the second structure; and computationally determining the interference of the first electric field and second electric field, to obtain a computationally determined interference electric field.

Abstract: Disclosed is a method for obtaining a computationally determined interference electric field describing scattering of radiation by a pair of structures comprising a first structure and a second structure on a substrate. The method comprises determining a first electric field relating to first radiation scattered by the first structure; determining a second electric field relating to second radiation scattered by the second structure; and computationally determining the interference of the first electric field and second electric field, to obtain a computationally determined interference electric field.

Abstract: Disclosed is a method and associated apparatus for measuring a characteristic of interest relating to a structure on a substrate. The method comprises calculating a value for the characteristic of interest directly from the effect of the characteristic of interest on at least the phase of illuminating radiation when scattered by the structure, subsequent to illuminating said structure with said illuminating radiation.

Abstract: Described is a metrology system for determining a characteristic of interest relating to at least one structure on a substrate, and associated method. The metrology system comprises a processor being configured to computationally determine phase and amplitude information from a detected characteristic of scattered radiation having been reflected or scattered by the at least one structure as a result of illumination of said at least one structure with illumination radiation in a measurement acquisition, and use the determined phase and amplitude to determine the characteristic of interest.

Abstract: Disclosed is a method of measuring a periodic structure on a substrate with illumination radiation having at least one wavelength, the periodic structure having at least one pitch. The method comprises configuring, based on a ratio of said pitch and said wavelength, one or more of: an illumination aperture profile comprising one or more illumination regions in Fourier space; an orientation of the periodic structure for a measurement; and a detection aperture profile comprising one or more separated detection regions in Fourier space. This configuration is such that: i) diffracted radiation of at least a pair of complementary diffraction orders is captured within the detection aperture profile, and ii) said diffracted radiation fills at least 80% of the one or more separated detection regions. The periodic structure is measured while applying the configured one or more of illumination aperture profile, detection aperture profile and orientation of the periodic structure.

Abstract: A dark field digital holographic microscope is disclosed which is configured to determine a characteristic of interest of a structure. The dark field digital holographic microscope comprises an illumination device configured to provide at least: a first beam pair comprising a first illumination beam of radiation (1010) and a first reference beam of radiation (1030) and a second beam pair comprising a second illumination beam of radiation (1020) and a second reference beam of radiation (1040); and one or more optical elements (1070) operable to capture a first scattered radiation and to capture a second scattered radiation scattered by the structure resultant from the first and second illumination beams respectively. The beams of the first beam pair are mutually coherent and the beams of the second beam pair are mutually coherent. The illumination device is configured to impose incoherence (ADI) between the first beam pair and second beam pair.

Abstract: Disclosed is a method for a metrology measurement on an area of a substrate comprising at least a portion of a target structure. The method comprises receiving a radiation information representing a portion of radiation scattered by the are, and using a filter in a Fourier domain for removing or suppressing at least a portion of the received radiation information that does not relate to radiation that has been scattered by the target structure for obtaining a filtered radiation information for the metrology measurement, wherein characteristics of the filter are based on target information about the target structure.

Abstract: Disclosed is a method of determining a complex-valued field relating to a structure, comprising: obtaining image data relating to a series of images of the structure, for which at least one measurement parameter is varied over the series and obtaining a trained network operable to map a series of images to a corresponding complex-valued field. The method comprises inputting the image data into said trained network and non-iteratively determining the complex-valued field relating to the structure as the output of the trained network. A method of training the trained network is also disclosed.

Abstract: Described is a metrology system for determining a characteristic of interest relating to at least one structure on a substrate, and associated method. The metrology system comprises a processor being configured to computationally determine phase and amplitude information from a detected characteristic of scattered radiation having been reflected or scattered by the at least one structure as a result of illumination of said at least one structure with illumination radiation in a measurement acquisition, and use the determined phase and amplitude to determine the characteristic of interest.

Abstract: Disclosed is a method for obtaining a computationally determined interference electric field describing scattering of radiation by a pair of structures comprising a first structure and a second structure on a substrate. The method comprises determining a first electric field relating to first radiation scattered by the first structure; determining a second electric field relating to second radiation scattered by the second structure; and computationally determining the interference of the first electric field and second electric field, to obtain a computationally determined interference electric field.

Abstract: Methods and apparatus are disclosed for determining a characteristic of a structure. In one arrangement, the structure is illuminated with first illumination radiation to generate first scattered radiation. A first interference pattern is formed by interference between a portion of the first scattered radiation reaching a sensor and first reference radiation. The structure is also illuminated with second illumination radiation from a different direction. A second interference pattern is formed using second reference radiation. The first and second interference patterns are used to determine the characteristic of the structure. Azimuthal angles of the first and second reference radiations onto the sensor are different.

Abstract: Disclosed is a method and associated apparatus for measuring a characteristic of interest relating to a structure on a substrate. The method comprises calculating a value for the characteristic of interest directly from the effect of the characteristic of interest on at least the phase of illuminating radiation when scattered by the structure, subsequent to illuminating said structure with said illuminating radiation.

Abstract: Disclosed is a method for obtaining a computationally determined interference electric field describing scattering of radiation by a pair of structures comprising a first structure and a second structure on a substrate. The method comprises determining a first electric field relating to first radiation scattered by the first structure; determining a second electric field relating to second radiation scattered by the second structure; and computationally determining the interference of the first electric field and second electric field, to obtain a computationally determined interference electric field.

Abstract: Methods and apparatus are disclosed for determining a characteristic of a structure. In one arrangement, the structure is illuminated with first illumination radiation to generate first scattered radiation. A first interference pattern is formed by interference between a portion of the first scattered radiation reaching a sensor and first reference radiation. The structure is also illuminated with second illumination radiation from a different direction. A second interference pattern is formed using second reference radiation. The first and second interference patterns are used to determine the characteristic of the structure. Azimuthal angles of the first and second reference radiations onto the sensor are different.

Abstract: Disclosed is a method and associated apparatus for measuring a characteristic of interest relating to a structure on a substrate. The method comprises calculating a value for the characteristic of interest directly from the effect of the characteristic of interest on at least the phase of illuminating radiation when scattered by the structure, subsequent to illuminating said structure with said illuminating radiation.

Abstract: Described is a metrology system for determining a characteristic of interest relating to at least one structure on a substrate, and associated method. The metrology system comprises a processor being configured to computationally determine phase and amplitude information from a detected characteristic of scattered radiation having been reflected or scattered by the at least one structure as a result of illumination of said at least one structure with illumination radiation in a measurement acquisition, and use the determined phase and amplitude to determine the characteristic of interest.

Abstract: Described is a metrology system for determining a characteristic of interest relating to at least one structure on a substrate, and associated method. The metrology system comprises a processor being configured to computationally determine phase and amplitude information from a detected characteristic of scattered radiation having been reflected or scattered by the at least one structure as a result of illumination of said at least one structure with illumination radiation in a measurement acquisition, and use the determined phase and amplitude to determine the characteristic of interest.

Abstract: Disclosed is a method for obtaining a computationally determined interference electric field describing scattering of radiation by a pair of structures comprising a first structure and a second structure on a substrate. The method comprises determining a first electric field relating to first radiation scattered by the first structure; determining a second electric field relating to second radiation scattered by the second structure; and computationally determining the interference of the first electric field and second electric field, to obtain a computationally determined interference electric field.

Abstract: Methods and apparatus are disclosed for determining a characteristic of a structure. In one arrangement, the structure is illuminated with first illumination radiation to generate first scattered radiation. A first interference pattern is formed by interference between a portion of the first scattered radiation reaching a sensor and first reference radiation. The structure is also illuminated with second illumination radiation from a different direction. A second interference pattern is formed using second reference radiation. The first and second interference patterns are used to determine the characteristic of the structure. Azimuthal angles of the first and second reference radiations onto the sensor are different.