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US 7,791,724 B2Granted
Characterization of transmission losses in an optical system
AssigneeASML Netherlands B.V.
InventorsArie Jeffrey Den Boef, Wilhelmus Maria Corbeij, Mircea Dusa, Markus Gerardus Martinus Van Kraaij
Life of this patent
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Abstract
The illumination profile of a radiation beam is initially measured using a CCD detector. A reference mirror is then placed in the focal plane of the high aperture lens and the reflected radiation measured. By comparing the illumination profile and the detected radiation it is possible to determine the transmission losses for S and P polarisation which can then be used in scatterometry modeling.
Claims21
A method for characterizing transmission losses in an optical system, comprising:
- splitting a radiation beam into a reference portion and a measurement portion;
- during a measurement of the reference portion, detecting an illumination profile of the reference portion reflected from a moveable reference mirror in a first position;
- during a measurement of the measurement portion, detecting an illumination profile of the measurement portion after the radiation beam has traveled through the optical system and detecting the illumination profile of the reference portion reflecting from the reference mirror in a second position, the second position being different than the first position;
- and
- comparing the illumination profile of the reference portion to the illumination profile of the measurement portion to characterize the transmission losses in the optical system.
2 more elements
A method for measuring properties of a substrate, comprising:
- projecting a radiation beam onto the substrate, wherein the radiation beam is directed through an optical system;
- detecting an intensity distribution of a reflected radiation beam that is indicative of the properties of the substrate;
- characterizing transmission losses of the optical system by
- splitting the radiation beam into a reference portion and a measurement portion;
- during a measurement of the reference portion, detecting an illumination profile of the reference portion reflected from a moveable reference mirror in a first position,
- during a measurement of the measurement portion, detecting an illumination profile of the measurement portion after the radiation beam has traveled through the optical system and detecting the illumination profile of the reference portion reflecting from the reference mirror in a second position, the second position being different than the first position, and
- comparing the illumination profile of the reference portion to the illumination to the illumination profile of the measurement portion to characterize transmission losses in the optical system;
- and
- subtracting the transmission losses from the reflected radiation beam.
6 more elements
An inspection apparatus configured to measure a property of a substrate, comprising:
- a radiation projector configured to project a radiation beam through an optical system onto the substrate;
- a detector configured to detect radiation reflected from the substrate;
- a moveable reference mirror;
- a data handling unit configured to normalize the detected radiation beam by taking into account the transmission losses from P and S polarized light, wherein the data handling unit characterizes the transmission losses by,
- splitting the radiation beam into a reference portion and a measurement portion;
- during a measurement of the reference portion, detecting an illumination profile of the reference portion reflected from a reference mirror in a first position;
- during a measurement of the measurement portion, detecting an illumination profile of the measurement portion after the radiation beam has traveled through the optical system and detecting the illumination profile of the reference portion reflecting from the reference mirror in a second position, the second position being different than the first position;
- and
- comparing the illumination profile of the reference portion to the illumination profile of the measurement portion to characterize the transmission losses in the optical system.
6 more elements
Dependencies are inferred from the claim text.