Systems and Methods for Lithographic Illuminator Beam Deviation Measurement and Calibration Using Grating Sensors
First Claim
1. A system for measuring angular deviations of a beam of radiation with respect to a nominal position, comprising:
- an illumination system configured to produce the beam of radiation;
an optical system including an aperture through which at least a portion of the beam of radiation passes to produce an incident beam directed towards a grating sensor, wherein the grating sensor is configured to produce surface plasmon resonance (SPR) effects at a suitable wavelength range of the beam of radiation;
a set of detection elements, each detection element receiving a portion of a respective beam diffracted from the grating sensor, each diffracted beam corresponding to a diffractive order;
a transducer coupled to the set of detection elements that normalizes a measured intensity data for each diffractive order with respect to a reference beam intensity measured by a reference energy sensor;
a processor coupled to the transducer that determines if a characteristic loss of intensity caused by SPR is detected and adopts an appropriate calibration algorithm to quantify angular deviations of the beam of radiation by analyzing normalized intensity data for each diffractive order; and
an output indicator coupled to the processor that communicates an output to facilitate monitoring and calibration of a lithography tool, wherein the output is generated based on calculated angular deviation data yielded by the calibration algorithm.
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Abstract
Angular deviation of illumination beam is measured with high accuracy for an expanded continuous range of angles using grating sensors that are configured to exhibit Surface Plasmon Resonance effects at actinic wavelengths. The beam deviation measurement systems and procedures are applicable to both mask-based and maskless lithography tools. A control system adopts an appropriate calibration algorithm based on whether the SPR effect is detected or not. Relative intensity shift in an SPR-affected diffractive order, and/or relative position and slope change in non-SPR-affected diffractive orders are used as a basis of the adopted calibration algorithm.
9 Citations
21 Claims
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1. A system for measuring angular deviations of a beam of radiation with respect to a nominal position, comprising:
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an illumination system configured to produce the beam of radiation; an optical system including an aperture through which at least a portion of the beam of radiation passes to produce an incident beam directed towards a grating sensor, wherein the grating sensor is configured to produce surface plasmon resonance (SPR) effects at a suitable wavelength range of the beam of radiation; a set of detection elements, each detection element receiving a portion of a respective beam diffracted from the grating sensor, each diffracted beam corresponding to a diffractive order; a transducer coupled to the set of detection elements that normalizes a measured intensity data for each diffractive order with respect to a reference beam intensity measured by a reference energy sensor; a processor coupled to the transducer that determines if a characteristic loss of intensity caused by SPR is detected and adopts an appropriate calibration algorithm to quantify angular deviations of the beam of radiation by analyzing normalized intensity data for each diffractive order; and an output indicator coupled to the processor that communicates an output to facilitate monitoring and calibration of a lithography tool, wherein the output is generated based on calculated angular deviation data yielded by the calibration algorithm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for measuring angular deviations of a beam of radiation with respect to a nominal position, comprising:
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producing the beam of radiation; positioning an aperture and a grating sensor in an optical path of the beam, such that at least a portion of the beam of radiation, when passed through the aperture, is directed towards the grating sensor, wherein the grating sensor is configured to produce surface plasmon resonance (SPR) effects at a suitable wavelength range of the beam of radiation; positioning a set of detection elements such that each detection element receives a portion of a respective beam diffracted from the grating sensor, each diffracted beam corresponding to a diffractive order; normalizing a measured intensity data for each diffractive order with respect to a measured reference beam intensity; comparing normalized intensity data for each diffractive order with expected SPR response to determine if a characteristic loss of intensity caused by SPR is detected; adopting an appropriate calibration algorithm to yield data quantifying angular deviations of the beam of radiation; and communicating an output to facilitate monitoring and calibration of a lithography tool, wherein the output is generated based on calculated angular deviation data. - View Dependent Claims (20, 21)
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Specification