Abstract: A radiation filter for reducing transmission of an unwanted wavelength of radiation. The radiation filter includes zirconium and SiN3. The radiation filter may form part of a radiation sensor including a passivation layer arranged to receive radiation transmitted by the radiation filter, a photodiode arranged to receive radiation transmitted by the passivation layer, and circuit elements connected to the photodiode. The radiation sensor may perform optical measurements as part of an extreme ultraviolet lithographic apparatus or a lithographic tool.

Abstract: A lithographic apparatus including a projection system having an optical axis and configured to project a radiation beam. The apparatus includes a measurement unit arranged to measure the radiation beam projected by the projection system, the measurement unit having an opening through which the radiation beam passes in use, and a sensing surface extending transverse to the optical axis and arranged to measure the radiation beam passing through the opening. The apparatus is configured to move the sensing surface in a plane transverse to the optical axis between a plurality of measurement positions. The radiation beam defines a view in the plane, and the measurement unit is configured such that the sensing surface captures, in each measurement position, a portion of the view smaller than 100% of the view.

Abstract: A lithographic apparatus including a projection system having an optical axis and configured to project a radiation beam. The apparatus includes a measurement unit arranged to measure the radiation beam projected by the projection system, the measurement unit having an opening through which the radiation beam passes in use, and a sensing surface extending transverse to the optical axis and arranged to measure the radiation beam passing through the opening. The apparatus is configured to move the sensing surface in a plane transverse to the optical axis between a plurality of measurement positions. The radiation beam defines a view in the plane, and the measurement unit is configured such that the sensing surface captures, in each measurement position, a portion of the view smaller than 100% of the view.

Abstract: A radiation filter for reducing transmission of an unwanted wavelength of radiation. The radiation filter includes zirconium and SiN3. The radiation filter may form part of a radiation sensor including a passivation layer arranged to receive radiation transmitted by the radiation filter, a photodiode arranged to receive radiation transmitted by the passivation layer, and circuit elements connected to the photodiode. The radiation sensor may perform optical measurements as part of an extreme ultraviolet lithographic apparatus or a lithographic tool.

Abstract: A two-dimensional diffraction grating for a phase-stepping measurement system for determining an aberration map for a projection system comprises a substrate provided with a square array of through-apertures, wherein the diffraction grating is self-supporting. It will be appreciated that for a substrate provided with a square array of through-apertures to be self-supporting at least some substrate material is provided between each through-aperture and the adjacent through apertures. A method of designing a two-dimensional diffraction grating for a phase-stepping measurement system for determining an aberration map for a projection system comprises: selecting a general geometry for the two-dimensional diffraction grating, the general geometry having at least one parameter; and selecting values for the least one parameter that result in a grating efficiency map for the two-dimensional diffraction grating so as to control the contributions to a first harmonic of a phase stepping signal.