Abstract: Spots of illumination directed at a target are described. Ghost reflections often prevalent in wafer alignment sensors are reduced or eliminated. First, second, and third optical elements are described. The first optical element receives illumination along a first axis, reflects a first portion of the illumination away from the first axis, and transmits a second portion of the illumination along the first axis. The second first optical element receives the first portion of the reflected illumination and at least partially reflects a third portion of the illumination along a second axis. The third first optical element receives and fully reflects a fourth portion of the illumination along a third axis. The second portion, third and fourth portions of the illumination are directed toward the target at different angles relative to each other to create three different spots of illumination.

Abstract: Some embodiments of this disclosure can improve measurement of target mark asymmetry in metrology apparatuses for improving accuracy in measurements performed in conjunction with lithographic processes. For example, a metrology system can include a projection system configured to receive a plurality of diffraction orders diffracted from a target on a substrate. The metrology system can further include a detector array and a waveguide device configured to transmit the plurality of diffraction orders between the projection system and the detector array. The detector array can be configured to detect each of the plurality of diffraction orders spatially separate from other ones of the plurality of diffraction orders.

Abstract: A method includes determining optical aberrations of an optical system, identifying an illumination profile that compensates for the optical aberrations of the optical system, and curing a layer of optical cement of an optical device using a modulated energy beam to achieve the identified illumination profile.

Abstract: An alignment method includes directing an illumination beam with a first polarization state to form a diffracted beam with a second polarization state from an alignment target, and passing the diffracted beam through a polarization analyzer. The alignment method further includes measuring a polarization state of the diffracted beam and determining a location of the alignment target from the measured polarization state relative to its initial polarization state. The alignment target includes a plurality of diffraction gratings with a single pitch and two or more duty cycles, wherein the pitch is smaller than a wavelength of the illumination beam, and the location of the alignment target corresponds to the duty cycle of the diffraction grating.

Abstract: An apparatus for and method of sensing alignment marks in which a self-referencing interferometer based sensor outputs standing images of the alignment marks and camera device is used to capture the images as output by the sensor and a detector is used to obtain phase information about the alignment marks from the images as output by the sensor.

Abstract: An apparatus for and method of sensing multiple alignment marks in which the optical axis of a detector is divided into multiple axes each of which can essentially simultaneously detect a separate alignment mark to generate a signal which can then be multiplexed and presented to a single detector or multiple detectors thus permitting more rapid detection of multiple marks.

Abstract: A system (500) includes an illumination system (502), a lens element (506), and a detector (504). The illumination system generates a beam of radiation (510) having a first spatial intensity distribution (800) at a pupil plane (528) and a second spatial intensity distribution (900) at a plane of a target (514). The first spatial intensity distribution comprises an annular intensity profile (802) or an intensity profile corresponding to three or more beams. The lens element focuses the beam onto the target. The second spatial intensity distribution is a conjugate of the first intensity distribution and has an intensity profile corresponding to a central beam (902) and one or more side lobes (904) that are substantially isolated from the central beam. The central beam has a beam diameter of approximately 20 microns or less at the target. The detector receives radiation scattered by the target and generates a measurement signal based on the received radiation.

Abstract: A calibration system includes a plate, a fixed alignment mark, and a variable diffraction grating. The plate is adjacent to a wafer alignment mark disposed on a wafer. The fixed alignment mark is disposed on the plate and is configured to act as a reference mark for an initial calibration of the calibration system. The variable diffraction grating is disposed on the plate and includes a plurality of unit cells configured to form a plurality of variable alignment marks. The variable diffraction grating is configured to calibrate a shift-between-orders of one of the variable alignment marks and the fixed alignment mark.

Abstract: An apparatus for and method of sensing multiple alignment marks in which the optical axis of a detector is divided into multiple axes each of which can essentially simultaneously detect a separate alignment mark to generate a signal which can then be multiplexed and presented to a single detector or multiple detectors thus permitting more rapid detection of multiple marks.

Abstract: An apparatus and system for determining alignment of a substrate in which a periodic alignment mark is illuminated with spatially coherent radiation which is then provided to a compact integrated optical device to create self images of the alignment mark which may be manipulated (e.g., mirrored, polarized) and combined to obtain information on the position of the mark and distortions within the mark. Also disclosed is a system for determining alignment of a substrate in which a periodic alignment mark is illuminated with spatially coherent radiation which is then provided to an optical fiber arrangement to obtain information such as the position of the mark and distortions within the mark.

Abstract: A calibration system includes a plate, a fixed alignment mark, and a variable diffraction grating. The plate is adjacent to a wafer alignment mark disposed on a wafer. The fixed alignment mark is disposed on the plate and is configured to act as a reference mark for an initial calibration of the calibration system. The variable diffraction grating is disposed on the plate and includes a plurality of unit cells configured to form a plurality of variable alignment marks. The variable diffraction grating is configured to calibrate a shift-between-orders of one of the variable alignment marks and the fixed alignment mark.

Abstract: A method of applying a measurement correction includes determining an orthogonal subspace used to characterize a first principal component of the measurement and a second principal component of the measurement, and rotating the orthogonal subspace by a first angle such that the first principle component rotates to become a first factor vector and the second principle component rotates to become a second factor vector. An asymmetry vector is generated by rotating the second factor vector by a second angle, where the asymmetry vector and the first factor vector define a non-orthogonal subspace. An asymmetry contribution is determined in the measurement based on the projection of the measurement onto the first factor vector in the non-orthogonal subspace. The method also includes subtracting the asymmetry contribution from the measurement.

Abstract: A system (500) includes an illumination system (502), a lens element (506), and a detector (504). The illumination system generates a beam of radiation (510) having a first spatial intensity distribution (800) at a pupil plane (528) and a second spatial intensity distribution (900) at a plane of a target (514). The first spatial intensity distribution comprises an annular intensity profile (802) or an intensity profile corresponding to three or more beams. The lens element focuses the beam onto the target. The second spatial intensity distribution is a conjugate of the first intensity distribution and has an intensity profile corresponding to a central beam (902) and one or more side lobes (904) that are substantially isolated from the central beam. The central beam has a beam diameter of approximately 20 microns or less at the target. The detector receives radiation scattered by the target and generates a measurement signal based on the received radiation.

Abstract: A method of applying a measurement correction includes determining an orthogonal subspace used to characterize the measurement as a plot of data. A first axis of the orthogonal subspace corresponds to constructive interference output from an interferometer of the metrology system plus a first error variable and a second axis of the orthogonal subspace corresponds to destructive interference output from the interferometer of the metrology system plus a second error variable. The method also includes determining a slope of the plot of data and determining a fitted line to the plot of data in the orthogonal subspace based on the slope.

Abstract: An apparatus for and method of sensing alignment marks in which a self-referencing interferometer based sensor outputs standing images of the alignment marks and camera device is used to capture the images as output by the sensor and a detector is used to obtain phase information about the alignment marks from the images as output by the sensor.

Abstract: A system for and method of processing a wafer in which a scan signal is analyzed locally to extract information about alignment, overlay, mark quality, wafer quality, and the like.

Abstract: An alignment method includes directing an illumination beam with a first polarization state to form a diffracted beam with a second polarization state from an alignment target, and passing the diffracted beam through a polarization analyzer. The alignment method further includes measuring a polarization state of the diffracted beam and determining a location of the alignment target from the measured polarization state relative to its initial polarization state. The alignment target includes a plurality of diffraction gratings with a single pitch and two or more duty cycles, wherein the pitch is smaller than a wavelength of the illumination beam, and the location of the alignment target corresponds to the duty cycle of the diffraction grating.

Abstract: A method of applying a measurement correction includes determining an orthogonal subspace used to characterize the measurement as a plot of data. A first axis of the orthogonal subspace corresponds to constructive interference output from an interferometer of the metrology system plus a first error variable and a second axis of the orthogonal subspace corresponds to destructive interference output from the interferometer of the metrology system plus a second error variable. The method also includes determining a slope of the plot of data and determining a fitted line to the plot of data in the orthogonal subspace based on the slope.

Abstract: A method of applying a measurement correction includes determining an orthogonal subspace used to characterize a first principal component of the measurement and a second principal component of the measurement, and rotating the orthogonal subspace by a first angle such that the first principle component rotates to become a first factor vector and the second principle component rotates to become a second factor vector. An asymmetry vector is generated by rotating the second factor vector by a second angle, where the asymmetry vector and the first factor vector define a non-orthogonal subspace. An asymmetry contribution is determined in the measurement based on the projection of the measurement onto the first factor vector in the non-orthogonal subspace. The method also includes subtracting the asymmetry contribution from the measurement.

Abstract: An alignment sensor apparatus includes an illumination system, a first optical system, a second optical system, a detector system, and a processor. The illumination system is configured to transmit an illumination beam along an illumination path. The first optical system is configured to transmit the illumination beam toward a diffraction target on a substrate. The second optical system includes a first polarizing optic configured to separate and transmit an irradiance distribution. The detector system is configured to measure a center of gravity of the diffraction target based on the irradiance distribution outputted from a first polarization branch and a second polarization branch. The processor is configured to measure a shift in the center of gravity of the diffraction target caused by an asymmetry variation in the diffraction target and determine a sensor response function of the alignment sensor apparatus based on the center of gravity shift.