Lithographic apparatus, device manufacturing method, and computer program
AssigneeASML Netherlands B.V.
InventorsJohannes Mathias Theodorus Antonius Adriaens, Marcel Hendrikus Maria Beems, Engelbertus Antonius Fransiscus Van Der Pasch
Life of this patent
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Abstract
In an interferometric displacement measuring system, a correction for beamshear is made. The correction may be a polynomial of a variable proportional to the length of the optical path traversed by the measurement beam and the angle of the measurement mirror. The correction compensates for errors caused by non-planarity of the wavefront of the measurement beam.
Claims20
A lithographic projection apparatus, comprising:
- a radiation system configured to provide a beam of radiation;
- a support configured to support a patterning device, the patterning device configured to pattern the beam of radiation according to a desired pattern;
- a substrate table configured to hold a substrate;
- a projection system configured to project the patterned beam onto a target portion of the substrate;
- and
- an interferometric displacement measuring system configured to measure displacements of a moveable component of the apparatus and comprising a model, the model relating sensor measurements to displacements of the moveable component, wherein the model incorporates at least one correction term that is a function of a variable representing beamshear of a measurement beam of the interferometric displacement measuring system, and the interferometric displacement measuring system is configured to determine displacements as a function of moveable component rotation and moveable component position, and to determine interferometer model parameters, including coefficients for terms dependent on a variable representing beamshear of a measurement beam, using a least square fit.
A device manufacturing method using a lithographic projection apparatus, the method comprising:
- providing a substrate that is at least partially covered by a layer of radiation-sensitive material;
- providing a beam of radiation using a radiation system;
- using a patterning device to endow the projection beam with a pattern in its cross-section;
- projecting the patterned beam of radiation onto a target portion of the layer of radiation-sensitive material;
- measuring displacements of a moveable component of the lithographic projection apparatus using an interferometric displacement measuring system comprising a model, the model relating sensor measurements to displacements of the moveable component, wherein the model incorporates at least one correction term that is a function of a variable representing beamshear of a measurement beam of the interferometric displacement measuring system;
- determining displacements as a function of moveable component rotation and moveable component position;
- and
- determining interferometer model parameters, including coefficients for terms dependent on a variable representing beamshear of a measurement beam, using a least square fit.
A computer program embodied on a computer readable medium, comprising:
- a program code that, when executed on a computer system, instructs the computer system to calculate displacements of a moveable object in a lithographic projection apparatus from sensor measurements of an interferometric displacement measuring system, calculate at least one correction term that is a function of a variable representing beamshear of a measurement beam of the interferometric displacement measuring system, determine displacements as a function of moveable object rotation and moveable object position, and determine interferometer model parameters, including coefficients for terms dependent on a variable representing beamshear of a measurement beam, using a least square fit.
A method of calibrating an interferometer for measuring displacements of a moveable object in a lithographic projection apparatus, the method comprising:
- determining displacements as a function of moveable object rotation and moveable object position;
- and
- determining interferometer model parameters, including coefficients for terms dependent on a variable representing beamshear of a measurement beam, using a least square fit.
Dependencies are inferred from the claim text.