Inspection Apparatus and Method, Lithographic Apparatus, Lithographic Processing Cell and Device Manufacturing Method

摘要

The present invention determines property of a target (30) on a substrate (W), such as a grating on a wafer. An inspection apparatus has an illumination source (702,710) with two or more illumination beams (716, 716′, 716″, 716′″) in the pupil plane of a high numerical aperture objective lens (L3). The substrate and target are illuminated via the objective lens from different angles of incidence with respect to the plane of the substrate. In the case of four illumination beams, a quad wedge optical device (QW) is used to separately redirect diffraction orders of radiation scattered from the substrate and separates diffraction orders from the two or more illumination beams. For example four 0th diffraction orders are separated for four incident directions. After capture in multimode fibers (MF), spectrometers (S1-S4) are used to measure the intensity of the separately redirected 0th diffraction orders as a function of wavelength. This may then be used in determining a property of a target.

主权项

1. An apparatus for determining a property of a target on a substrate, the apparatus comprising:
an illumination system configured to provide radiation; an optical system comprising an objective, and configured to illuminate the target via the objective with two or more illumination beams; an optical device configured to separately redirect diffraction orders resulting from the illumination of the target with the two or more illumination beams; one or more detectors in an image plane, the one or more detectors being configured to measure one or more properties of the separately redirected diffraction orders; and a processor configured to determine the property of the target using the measured one or more properties of the separately redirected diffraction orders.