Metrology method and apparatus, lithographic apparatus, and device manufacturing method
First Claim
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1. A metrology apparatus configured to measure a property of a target on a substrate, the apparatus comprising:
- a first source configured to emit a first illumination beam of radiation;
a second source configured to emit a second illumination beam of radiation wherein the first illumination beam of radiation differs from the second illumination beam of radiation in at least one of spot size and angular distribution;
an aperture plate having first and second openings configured to pass the first and second illumination beams, respectively;
a beam selection device comprising a tiltable mirror tiltable about two axes, wherein the tiltable minor is positioned such that the first illumination beam of radiation is incident on the tiltable mirror at a first angle of incidence and the second illumination beam is incident on the tiltable mirror at a second angle of incidence and wherein the beam selection device is configured to select one of the first and second illumination beams of radiation as a measurement beam of radiation by tilting the tiltable mirror, wherein the tiltable mirror is positioned in a conjugate plane of the substrate and the aperture plate is positioned in a plane that is a Fourier transform of the conjugate plane of the substrate;
an objective lens configured to direct the measurement beam of radiation onto the target on the substrate and to collect radiation diffracted by the target; and
a sensor configured to detect an angle resolved spectrum in a pupil plane of the objective lens.
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Abstract
A metrology apparatus includes first (21) and second (22) radiation sources which generate first (iB1) and second (iB2) illumination beams of different spatial extent and/or angular range. One of the illumination beams is selected, e.g. according to the size of target to be measured. The beam selection can be made by a tillable mirror (254) at a back-projected substrate plane in a Kohler illumination setup.
48 Citations
18 Claims
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1. A metrology apparatus configured to measure a property of a target on a substrate, the apparatus comprising:
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a first source configured to emit a first illumination beam of radiation; a second source configured to emit a second illumination beam of radiation wherein the first illumination beam of radiation differs from the second illumination beam of radiation in at least one of spot size and angular distribution; an aperture plate having first and second openings configured to pass the first and second illumination beams, respectively; a beam selection device comprising a tiltable mirror tiltable about two axes, wherein the tiltable minor is positioned such that the first illumination beam of radiation is incident on the tiltable mirror at a first angle of incidence and the second illumination beam is incident on the tiltable mirror at a second angle of incidence and wherein the beam selection device is configured to select one of the first and second illumination beams of radiation as a measurement beam of radiation by tilting the tiltable mirror, wherein the tiltable mirror is positioned in a conjugate plane of the substrate and the aperture plate is positioned in a plane that is a Fourier transform of the conjugate plane of the substrate; an objective lens configured to direct the measurement beam of radiation onto the target on the substrate and to collect radiation diffracted by the target; and a sensor configured to detect an angle resolved spectrum in a pupil plane of the objective lens. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A lithographic apparatus comprising:
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an illumination optical system arranged to illuminate a pattern; a projection optical system arranged to project an image of the pattern onto a substrate; and a metrology device configured to measure a property of a target on the substrate, the metrology device comprising; a first source configured to emit a first illumination beam of radiation; a second source configured to emit a second illumination beam of radiation, wherein the first illumination beam of radiation differs from the second illumination beam of radiation in at least one of spot size and angular distribution; an aperture plate having first and second openings configured to pass the first and second illumination beams, respectively; a beam selection device comprising a tiltable mirror tiltable about two axes, wherein the tiltable mirror is positioned such that the first illumination beam of radiation is incident on the tiltable mirror at a first angle of incidence and the second illumination beam is incident on the tiltable mirror at a second angle of incidence and wherein the beam selection device is configured to select one of the first and second illumination beams of radiation as a measurement beam of radiation by tilting the tiltable mirror, wherein the tiltable mirror is positioned in a conjugate plane of the substrate and the aperture plate is positioned in a plane that is a Fourier transform of the conjugate plane of the substrate; an objective lens configured to direct the measurement beam of radiation onto the target on the substrate and to collect radiation diffracted by the target; and a sensor configured to detect an angle resolved spectrum in a pupil plane of the objective lens. - View Dependent Claims (16)
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17. A method of measuring a property of a target on a substrate, the method comprising:
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generating first and second illumination beams, the first and second illumination beams differing in at least one of spatial extent and range of angles, the first and second beams being incident on a mirror tiltable about two axes, wherein the first illumination beam of radiation is incident on the mirror at a first angle of incidence and the second illumination beam is incident on the mirror at a second angle of incidence, wherein the first illumination beam of radiation differs from the second illumination beam of radiation in at least one of spot size and angular distribution; passing the first and second illumination beams through first and second apertures of an aperture plate; tilting the mirror such that one of the first and second illumination beams is directed onto the target, wherein the mirror is positioned in a conjugate plane of the substrate and wherein the aperture plate is positioned in a plane that is a Fourier transform of the conjugate plane of the substrate; collecting radiation diffracted from the target using an objective lens; and detecting an angle-resolved spectrum in a pupil plane of the objective lens. - View Dependent Claims (18)
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Specification