Interferometer for measuring perpendicular translations

An interferometer, a technology for measuring light beams, applied in the field of interferometers, can solve problems such as dynamic range limitations

Inactive Publication Date: 2007-02-21
AGILENT TECH INC
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Problems solved by technology

These elevation measurements are generally limited by the dynamic range mentioned

Method used

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  • Interferometer for measuring perpendicular translations
  • Interferometer for measuring perpendicular translations
  • Interferometer for measuring perpendicular translations

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Embodiment Construction

[0017] According to one aspect of the present invention, an interferometer capable of measuring the vertical displacement of an object horizontally spaced from the interferometer may employ a measurement reflector and a reference reflector on the measured object, a first wave above the measured object Porro prism and a second Porro prism in the interferometer optics. A polarizing beam splitter in the interferometer splits the input beam into a measurement beam and a reference beam, which are both directed towards the object.

[0018] The measurement beam travels horizontally to the measurement reflector, travels vertically to the first Porro prism, returns vertically to the measurement reflector, and returns horizontally to the interferometer optics where it can be recombined with the reference beam and measured. Thus, during one pass from the interferometer optics to returning to it, the measuring beam is reflected twice from the measuring reflector.

[0019] During the firs...

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Abstract

An interferometer provides a large dynamic range for perpendicular displacement measurements. In operation, a measurement reflector on an object reflects a measurement beam to an overlying Porro prism, and a reference reflector on the object returns a reference beam to the interferometer. A second Porro prism in the interferometer can return the reference beam for a second pass to the reference reflector, while the measurement beam complete only one pass. Reductions in beam walk-off result from retroreflections in the Porro prisms and the matching effects that some object rotations have on measurement and reference beams. Perpendicular motion of the object relative to the first Porro prism causes a Doppler shift only in the measurement beam. Accordingly, a beat frequency found when combining the measurement and reference beams can indicate a residual Doppler shift associated with the motion in the perpendicular direction.

Description

technical field [0001] The invention relates to interferometers for measuring vertical movement. Background technique [0002] Plane mirror interferometers can be used to measure the position, orientation or motion of precision stages in wafer processing systems. For this purpose, a flat mirror is usually mounted on the stage being measured and an interferometer collimates one or more measurement beams for reflection from the flat mirror. Each measurement beam generally corresponds to a separate interferometer channel, but some interferometers, often called two-pass interferometers, make each The measuring beam is aimed for two reflections from the flat mirror. [0003] Multiple interferometer channels can use the same flat mirror to measure distances to different points on the plane, allowing measurements of multiple degrees of freedom of the stage. Specifically, three interferometer channels measuring the movement of three different points on the same planar mirror can ...

Claims

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Application Information

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IPC IPC(8): G01B9/02H01L21/66G03F7/20G03F9/00
CPCG01B9/02003G01B9/02016G01B2290/70G03F7/70775
Inventor 威廉·克莱·施卢赫特尔
Owner AGILENT TECH INC
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