Patent ID: 9110385
Filing Date: 2015-08-18
Classification: G01J,G03F

Abstract:
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.