Lithographic apparatus, level sensor, method of inspection, device manufacturing method, and device manufactured thereby
AssigneeASML Netherlands B.V.
InventorsPaulus Antonius Andreas Teunissen, Petrus Johannes Maria Broodbakker, Rene Marinus Gerardus Johan Queens
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Abstract
A level sensor for a lithographic projection apparatus according to one embodiment of the invention includes a light source, a first reflector, a second reflector and a detector. The first reflector is positioned to direct light from the light source towards a wafer surface, and the second reflector is positioned to direct light reflected from the wafer surface to the detector. The first and second reflectors are selected to incur a minimal process dependent apparent surface depression.
Claims52
A lithographic apparatus comprising a level sensor configured to measure a height of a wafer surface, said level sensor comprising:
- a first reflector configured to direct a beam from a light source toward the wafer surface;
- and
- a second reflector configured to direct the beam from the wafer surface to a detector,
- wherein a magnitude of an apparent depression of the wafer surface due to translation of the beam at reflective surfaces of the first and second reflectors is less than thirty-five nanometers.
A plurality of lithographic projection apparatus comprising:
- a radiation system configured to provide a projection beam of radiation;
- a support structure configured to support a patterning structure, the patterning structure serving to pattern the projection beam according to a desired pattern;
- a substrate table configured to hold a substrate;
- and
- a projection system configured to project the patterned beam onto a target portion of the substrate,
- wherein each lithographic apparatus includes a level sensor comprising:
- a first reflector positioned to direct light from a light source towards a wafer surface;
- and
- a second reflector positioned to direct light reflected from the wafer surface to a detector,
- wherein the first reflectors of the level sensors of the plurality of lithographic apparatus are substantially identical to one another, and
- wherein the second reflectors of the level sensors of the plurality of lithographic apparatus are substantially identical to one another.
A lithographic apparatus comprising a level sensor, said level sensor comprising:
- a first reflector configured to direct a beam from a light source toward a wafer surface;
- and
- a second reflector configured to direct the beam from the wafer surface to a detector,
- wherein a reflective surface of the first reflector has a coating, said coating having an optical thickness of 430 nanometers ±60 nanometers at a central wavelength of the beam, and
- wherein a reflective surface of the second reflector has a coating, said coating having an optical thickness of 430 nanometers ±60 nanometers at a central wavelength of the beam.
A lithographic apparatus comprising a level sensor, said level sensor comprising:
- a first reflector configured to direct a beam from a light source toward a wafer surface;
- and
- a second reflector configured to direct the beam from the wafer surface to a detector,
- wherein a reflective surface of the first reflector has a coating, and
- wherein a reflective surface of the second reflector has a coating, and
- wherein the optical thickness of the coating of the reflective surface of the first reflector at a central wavelength of the beam differs from the optical thickness of the coating of the reflective surface of the second reflector at a central wavelength of the beam by 205 nanometers ±60 nanometers.
A lithographic apparatus comprising a level sensor configured to measure a height of a wafer surface, said level sensor comprising:
- a first reflector configured to direct a beam from a light source toward the wafer surface;
- and
- a second reflector configured to direct the beam from the wafer surface to a detector,
- wherein a reflective surface of at least one of the first and second reflectors comprises aluminum having a coating of native oxide.
A lithographic apparatus comprising a level sensor, said level sensor comprising:
- a first reflector configured to direct a beam from a light source toward a wafer surface;
- and
- a second reflector configured to direct the beam from the wafer surface to a detector,
- wherein the first reflector includes a first surface configured to direct the beam toward the wafer surface and a second surface configured to direct the beam toward the first surface, and
- wherein the second reflector includes a first surface configured to direct the beam to the detector and a second surface configured to direct the beam toward the first surface.
A method comprising:
- positioning a first reflector of a level sensor of a lithographic apparatus to direct a light beam from a light source toward a surface of a wafer;
- positioning a second reflector of a level sensor of a lithographic apparatus to direct the beam from the surface of the wafer to a detector;
- and
- selecting the first and second reflectors to obtain a minimum total effective translation of the beam at the surfaces of the first and second reflectors.
A lithographic method comprising:
- using a first reflector of a level sensor of a lithographic apparatus to direct a light beam from a light source toward a wafer surface;
- using a second reflector of a level sensor of a lithographic apparatus to direct the beam from the wafer surface to a detector;
- and
- determining a height of the surface of the wafer based on the beam incident on the detector,
- wherein a magnitude of an apparent depression of the surface of the wafer due to translation of the beam at reflective surfaces of the first and second reflectors is less than thirty-five nanometers.
Dependencies are inferred from the claim text.