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.
Claims24
A lithographic apparatus comprising a level sensor configured to measure a height of a wafer surface, said level sensor comprising:
- a first reflector having at least two layers and being configured to direct a beam from a light source toward the wafer surface;
- and
- a second reflector having at least two layers and being 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 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, wherein the first reflector includes at least two layers;
- 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, wherein the second reflector includes at least two layers;
- 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, wherein the first reflector includes at least two layers;
- using a second reflector of the level sensor of the lithographic apparatus to direct the beam from the wafer surface to a detector, wherein the second reflector includes at least two layers;
- 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.
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, wherein the first reflector includes at least two layers;
- and
- a second reflector configured to direct the beam from the wafer surface to a detector, wherein the second reflector includes at least two layers, and
- wherein the first reflector and the second reflector are selected to obtain a minimum total effective translation of the beam at the surfaces of the first reflector and the second reflector.
Dependencies are inferred from the claim text.