Height measurement error determination
AssigneeASML Netherlands B.V.
InventorAttaallah ALMASI
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Abstract
A method of determining a substrate height measurement error, the method including providing a laser beam that is modulated at a given frequency, the laser beam having a wavelength and a polarization, directing the modulated laser beam onto the substrate at an acute angle relative to a normal extending from the substrate, detecting a position of the modulated laser beam after it has been reflected from the substrate, using detection based upon the frequency of the modulation applied to the laser beam to measure a modulation of the detected position of the modulated laser beam, and determining the height measurement error based upon the measured modulation of the detected position of the modulated laser beam, wherein the wavelength or the polarization is modulated.
Claims20
A method of determining a substrate height measurement error, the method comprising:
- directing a laser beam modulated at a given frequency onto the substrate at an acute angle relative to a normal extending from the substrate, the laser beam having a wavelength and a polarization;
- detecting a position of the modulated laser beam after it has been redirected from the substrate;
- using detection based upon the frequency of the modulation applied to the laser beam to measure a modulation of the detected position of the modulated laser beam;
- and
- determining the height measurement error based upon the measured modulation of the detected position of the modulated laser beam, wherein the wavelength or the polarization is modulated.
A substrate height measurement error determination system comprising:
- a modulator configured to apply a modulation at a given frequency to the wavelength or to the polarization of a laser beam emitted by a laser, to obtain a modulated laser beam;
- a detection system comprising a detector configured to detect a position of the modulated laser beam after incidence on and redirection from the substrate;
- a lock-in amplifier configured to receive an output from the detection system and, based upon the frequency of the modulation applied to the wavelength or the polarization of the laser beam, to measure a modulation of the detected position of the modulated laser beam;
- and
- a processor configured to use the measured modulation of the detected position to determine a substrate height measurement error.
Dependencies are inferred from the claim text.