Optics: measuring and testing – Angle measuring or angular axial alignment – Photodetection of inclination from level or vertical
Reexamination Certificate
2005-10-18
2008-08-12
Connolly, Patrick (Department: 2877)
Optics: measuring and testing
Angle measuring or angular axial alignment
Photodetection of inclination from level or vertical
C356S516000
Reexamination Certificate
active
07411667
ABSTRACT:
The invention relates to a level sensor for determining a height of a substrate. The level sensor generates one or more measurement beam and directs the measurement beam to a measurement spot on the substrate and produces a reflected measurement beam. The level sensor also generates one or more reference beams. A detector detects both the reflected measurement beam and the reference beam, respectively, and produces a measurement signal and a reference signal, respectively, the measurement signal being indicative for the height at the measurement spot. A processor that receives these signals and corrects the measurement signal based on the reference signal. The level sensor has an optical arrangement in a predetermined area close to where the substrate is to be located. The measurement beam and the reference beam propagate along substantially equal optical paths of propagation in the predetermined area. The optical arrangement deviates the reference beam from the substantially equal optical paths of propagation in the predetermined area such that the at least one reference beam does not hit the substrate.
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Bakker Hans Baltus
Balan Oana Cristina
Blokland Huibert
Cheng Lun Kai
Ouwehand Luberthus
ASML Netherlands B.V.
Connolly Patrick
Pillsbury Winthrop Shaw & Pittman LLP
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