Lithographic apparatus, device manufacturing method, and angular encoder
AssigneeASML Netherlands B.V.
InventorsMartinus Hendrikus Antonius Leenders, Hendricus Johannes Maria Meijer, Engelbertus Antonius Fransiscus Van Der Pasch, Michael Jozef Mathijs Renkens, Theo Anjes Maria Ruijl
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Abstract
In a lithographic projection apparatus, a measuring system configured to measure the position of the projection system relative to a reference frame includes sensors rigidly mounted in relation to counterpart sensors of a measuring system measuring the substrate table position. An angular encoder which sends light from a target down two optical paths having opposite sensitivities to tilt is used to measure rotation of the projection system about its optical axis.
Claims21
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 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;
- a reference frame;
- a first measuring system configured to measure at least one of positions and displacements of the substrate table relative to the reference frame, the measuring system including a plurality of first sensors mounted on the reference frame and having respective measurement axes;
- and
- a second measuring system configured to measure at least one of positions and displacements of the projection system relative to the reference frame, the measuring system including a plurality of second sensors mounted on the reference frame and having respective measurement axes, wherein at least one sensor of the second measuring system has a measurement axis passing through an invariant point of the projection system and the second measuring system comprises three linear sensors configured to measure along measurement axes passing through the invariant point.
A device manufacturing method, comprising:
- projecting a patterned beam of radiation onto a target portion of a layer of radiation-sensitive material at least partially covering a substrate using a projection system;
- measuring at least one of positions and displacements of the substrate table relative to a reference frame using a first measuring system including a plurality of first sensors mounted on the reference frame and having respective measurement axes;
- measuring at least one of positions and displacements of the projection system relative to the reference frame using a second measuring system including a plurality of second sensors mounted on the reference frame and having respective measurement axes, wherein at least one sensor of the second measuring system has a measurement axis passing through an invariant point of the projection system and is mounted rigidly in relation to the corresponding sensor of the first measuring system, wherein the second measuring system comprises three linear sensors configured to measure along measurement axes passing through the invariant point.
An angular encoder comprising:
- a target;
- an optical module comprising a first beam splitter configured to direct light from the target into first and second optical paths;
- a first optical element in at least one of the optical paths, wherein one of the paths has an opposite sensitivity to tilt than the other of the optical paths;
- and
- a second optical element configured to recombine light from the first and second optical paths and to project two overlapping images of the target, wherein relative rotation of the target and the optical module causes relative movement of the two overlapping images, wherein the target comprises a grating.
Dependencies are inferred from the claim text.