Method and apparatus for angular-resolved spectroscopic lithography characterization

An inspection method, comprising:

• measuring, in a pupil plane of a high numerical aperture lens, a property of a spectrum of a radiation beam reflected from a surface of a substrate;
• normalizing the radiation beam by reflecting it off one or more mirrors;
• measuring and combining at least two images created from different reflection angles of the radiation beam off the one or more mirrors;
• and
• creating a differential equation to reconstruct the illumination profile of the radiation beam.

A scatterometer configured to measure a property of a substrate, comprising:

• a high numerical aperture lens;
• and
• a detector configured to detect an angle-resolved spectrum of a radiation beam reflected from a surface of the substrate,
• wherein the property of the substrate can be measured by measuring, in a pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of angles simultaneously, the scatterometer further comprising:
• a first polarizer configured to linearly polarize the radiation beam;
• a beam splitter configured to split the radiation beam into two orthogonal beam components;
• a second polarizer configured to polarize the reflected beam;
• a variable compensator positioned between the first and second polarizers configured to vary the optical path difference between the orthogonal beam components;
• and
• a 2-dimensional detector configured to detect sinusoidal intensity variation of the beam components.

A scatterometer configured to measure a property of a substrate, comprising:

• a high numerical aperture lens;
• and
• a detector configured to detect an angle-resolved spectrum of a radiation beam reflected from a surface of the substrate,
• wherein the property of the substrate can be measured by measuring, in a pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of angles simultaneously, the scatterometer further comprising
• a second detector branch configured to carry out coarse overlay measurements.

An inspection method, comprising:

• providing two gratings layered in parallel but misaligned, thereby creating an overlay of one grating with respect to the other;
• measuring a reflected spectrum of the gratings using a scatterometer;
• deriving an extent of the overlay from the asymmetry in the reflected spectrum;
• and
• carrying out a coarse overlay measurement of the gratings, comprising determining whether the overlay is greater than a grating pitch.

A scatterometer configured to detect local distortions in a grating, comprising:

• a high numerical aperture lens;
• a grating configured to scatter a radiation beam in a specular direction;
• and
• a detector configured to detect an angle-resolved spectrum of the scattered beam at various angles outside the specular direction,
• wherein a distortion of the grating can be measured by measuring, in a pupil plane of the high numerical aperture lens, a property of the reflected spectrum outside the specular direction at a plurality of angles simultaneously.

A scatterometer configured to simultaneously measure a property of multiple targets on a substrate, comprising:

• a high numerical aperture lens;
• a projector configured to project a plurality of illumination spots onto a substrate;
• and
• a detector configured to detect simultaneously an angle-resolved spectrum of a plurality of radiation spots reflected from a surface of the substrate,
• wherein the property can be measured by measuring, in a pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of angles simultaneously.

A device manufacturing method, comprising:

• projecting a beam of radiation onto a target portion of a substrate;
• dividing the beam into a plurality of beams before the beam reaches the substrate;
• and
• using a scatterometer to measure, in a pupil plane of a high numerical aperture lens, a reflected spectrum of the plurality of beams through a range of angles and wavelengths simultaneously in order to simultaneously measure multiple targets on the substrate.

A scatterometer configured to measure a property of a substrate, comprising:

• a high numerical aperture lens;
• an illuminator configured to produce a radiation beam having an annular intensity distribution in a conjugate plane to the substrate;
• and
• a detector configured to detect an angle-resolved spectrum of the radiation beam reflected from a surface of the substrate,
• wherein the property of the substrate can be measured by measuring, in a pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of angles.

An apparatus to calculate variations in tilt of a substrate, comprising:

• an illuminator configured to create a radiation beam with an annular distribution in a conjugate plane to the substrate;
• a shaped obscuration configured to be in the radiation beam;
• a detector configured to detect a change in a width, shape, or both of an image of the shaped obscuration on the substrate caused by a variation in the substrate tilt;
• and
• a processor configured to calculate the variation in the substrate tilt based on the change detected by the detector.