Abstract: 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 of the property of the structure. The optical system may include a solid immersion lens. In a 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, e.g., ghost reflections. Using, e.g., half-moon illumination profiles in different orientations, the method can measure ghost reflections even where a solid immersion lens would cause total internal reflection. The optical system may include a contaminant detection system 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.

Abstract: In an alignment sensor of a lithographic apparatus, position sensing radiation is delivered to a target (P1). After reflection or diffraction from the target, position sensing radiation is processed to determine a position of the target. Reference radiation interferes with the position sensing radiation) while a relative phase modulation is applied between the reference radiation and the position sensing radiation. The interfering radiation includes a time-varying component defined by the applied phase modulation. The interfering radiation is delivered to two photodetectors in such a way that each photodetector receives said time-varying component in anti-phase to that received at the other photodetector. A difference signal (i(t)) from said photodetectors contains an amplified, low noise version of said time-varying component. This is used in determining the position of the target. Mode matching enhances interference. Surface scattered radiation is rejected.

Abstract: A metrology apparatus is disclosed that has an optical system to focus radiation onto a structure and directs redirected radiation from the structure to a detection system. The optical system applies a plurality of different offsets of an optical characteristic to radiation before and/or after redirected by the structure, such that a corresponding plurality of different offsets are provided to redirected radiation derived from a first point of a pupil plane field distribution relative to redirected radiation derived from a second point of the pupil plane field distribution. The detection system detects a corresponding plurality of radiation intensities resulting from interference between the redirected radiation derived from the first point of the pupil plane field distribution and the redirected radiation derived from the second point of the pupil plane field distribution. Each radiation intensity corresponds to a different one of the plurality of different offsets.

Abstract: Devices and methods for processing a radiation beam with coherence are disclosed. In one arrangement, an optical system receives a radiation beam with coherence. The radiation beam comprises components distributed over one or more radiation beam spatial modes. A waveguide supports a plurality of waveguide spatial modes. The optical system directs a plurality of the components of the radiation beam belonging to a common radiation beam spatial mode and having different frequencies onto the waveguide in such a way that each of the plurality of components couples to a different set of the waveguide spatial modes, each set comprising one or more of the waveguide spatial modes.

Abstract: In an alignment sensor of a lithographic apparatus, position sensing radiation is delivered to a target (P1). After reflection or diffraction from the target, position sensing radiation is processed to determine a position of the target. Reference radiation interferes with the position sensing radiation) while a relative phase modulation is applied between the reference radiation and the position sensing radiation. The interfering radiation includes a time-varying component defined by the applied phase modulation. The interfering radiation is delivered to two photodetectors in such a way that each photodetector receives said time-varying component in anti-phase to that received at the other photodetector. A difference signal (i(t)) from said photodetectors contains an amplified, low noise version of said time-varying component. This is used in determining the position of the target. Mode matching enhances interference. Surface scattered radiation is rejected.

Abstract: A method involving providing incident radiation of a first polarization state by an optical component into an interface of an object with an external environment, wherein a surface is provided adjacent the interface and separated by a gap from the interface, detecting, from incident radiation reflected from the interface and from the surface, radiation of a second different polarization state arising from the reflection of incident radiation of the first polarization at the interface as distinct from the radiation of the first polarization state in the reflected radiation, and producing a position signal representative of a relative position between the focus of the optical component and the object.

Abstract: A method including obtaining a plurality of radiation distributions of measurement radiation redirected by the target, each of the plurality of radiation distributions obtained at a different gap distance between the target and an optical element of a measurement apparatus, the optical element being the nearest optical element to the target used to provide the measurement radiation to the target, and determining a parameter related to the target using data of the plurality of radiation distributions in conjunction with a mathematical model describing the measurement target.

Abstract: A method involving providing incident radiation of a first polarization state by an optical component into an interface of an object with an external environment, wherein a surface is provided adjacent the interface and separated by a gap from the interface, detecting, from incident radiation reflected from the interface and from the surface, radiation of a second different polarization state arising from the reflection of incident radiation of the first polarization at the interface as distinct from the radiation of the first polarization state in the reflected radiation, and producing a position signal representative of a relative position between the focus of the optical component and the object.

Abstract: A method and apparatus for position control of a component relative to a surface is disclosed. The method may include calculating an estimated effect of, or derived from, Casimir force acting between the component and the surface, and compensating positioning of the component relative to the surface using the estimated effect.

Abstract: Devices and methods for processing a radiation beam with coherence are disclosed. In one arrangement, an optical system receives a radiation beam with coherence. The radiation beam comprises components distributed over one or more radiation beam spatial modes. A waveguide supports a plurality of waveguide spatial modes. The optical system directs a plurality of the components of the radiation beam belonging to a common radiation beam spatial mode and having different frequencies onto the waveguide in such a way that each of the plurality of components couples to a different set of the waveguide spatial modes, each set comprising one or more of the waveguide spatial modes.

Abstract: A method of position control of an optical component relative to a surface is disclosed. The method may include: obtaining a first signal by a first position measurement process; controlling relative movement between the optical component and the surface for a first range of motion using the first signal; obtaining a second signal by a second position measurement process different than the first position measurement process; and controlling relative movement between the optical component and the surface for a second range of motion using the second signal, the second range of motion being nearer the surface than the first range of motion.

Abstract: A method including obtaining a plurality of radiation distributions of measurement radiation redirected by the target, each of the plurality of radiation distributions obtained at a different gap distance between the target and an optical element of a measurement apparatus, the optical element being the nearest optical element to the target used to provide the measurement radiation to the target, and determining a parameter related to the target using data of the plurality of radiation distributions in conjunction with a mathematical model describing the measurement target.

Abstract: A method of position control of an optical component relative to a surface is disclosed. The method may include: obtaining a first signal by a first position measurement process; controlling relative movement between the optical component and the surface for a first range of motion using the first signal; obtaining a second signal by a second position measurement process different than the first position measurement process; and controlling relative movement between the optical component and the surface for a second range of motion using the second signal, the second range of motion being nearer the surface than the first range of motion.

Abstract: A method and apparatus for position control of a component relative to a surface is disclosed. The method may include calculating an estimated effect of, or derived from, Casimir force acting between the component and the surface, and compensating positioning of the component relative to the surface using the estimated effect.