Abstract: A method of processing a wafer is provided. The method includes providing a reference pattern for patterning a wafer. The reference pattern is independent of a working surface of the wafer. A placement of a first pattern on the working surface of the wafer is determined by identifying the reference pattern to align the first pattern. The first pattern is formed on the working surface of the wafer based on the placement.

Abstract: An alignment method includes directing an illumination beam with a varying wavelength or frequency towards an alignment target, collecting diffraction beams from the alignment target and directing towards an interferometer. The alignment method also includes producing, by the interferometer, two diffraction sub-beams from the diffraction beams, wherein the diffraction sub-beams are orthogonally polarized, rotated 180 degrees with respect to each other around an alignment axis, and spatially overlapped. The alignment method further includes measuring interference intensity of the diffraction beams based on a temporal phase shift, wherein the temporal phase shift is a function of the varying wavelength or frequency of the illumination beam and a fixed optical path difference between the diffraction beams. The alignment method also includes determining a position of the alignment target from the measured interference intensity.

Abstract: Message faults are an increasing problem for 5G and expected 6G networks, due to growth, crowding, and signal fading problems. Disclosed are procedures for determining which particular message element of a corrupted message is faulted, and optionally the most likely correction. A receiver can identify the faulted message element by measuring the fluctuations, in phase and amplitude, of the waveform of each message element, as well as the modulation quality, frequency offset, and other signal measurements. Faulted message elements are likely to have higher fluctuations, higher modulation deviations, and higher signal irregularities, than the unfaulted ones. Mitigation can then be applied to the faulted message elements, thereby recovering the correct message and avoiding a costly retransmission delay. AI models may enhance the fault detection sensitivity by exploiting correlations between the various waveform measurement parameters, and then may predict the corrected value of the faulted message elements.

Abstract: An alignment apparatus includes an illumination system configured to direct one or more illumination beams towards an alignment target and receive the diffracted beams from the alignment target. The alignment apparatus also includes a self-referencing Interferometer configured to generate two diffraction sub-beams, wherein the two diffraction sub-beams are orthogonally polarized, rotated 180 degrees with respect to each other around an alignment axis, and spatially overlapped. The alignment apparatus further includes a beam analyzer configured to generate interference between the overlapped components of the diffraction sub-beams and produce two orthogonally polarized optical branches, and a detection system configured to determine a position of the alignment target based on light intensity measurement of the optical branches, wherein the measured light intensity is temporally modulated by a phase modulator.

Abstract: A liquid crystal exposure apparatus has a measurement system having scales arranged apart from each other in the X-axis direction provided at a substrate stage holding a substrate and heads each irradiating the scales with a measurement beam; and a measurement device that measures positions of head units in the Y-axis direction. The measurement system measures a position of the substrate holder in directions of three degrees of freedom within a plane, based on measurement information of at least three heads. Each of the heads move off of one scale while the substrate holder is moved in the X-axis direction and moves to irradiate another scale adjacent to the one scale, and correction information to control movement of the substrate holder using the head moving to irradiate another scale is acquired, based on measurements of at least three heads.

Abstract: An overlay metrology target (T) is formed by a lithographic process. A first image (740(0)) of the target structure is obtained using with illuminating radiation having a first angular distribution, the first image being formed using radiation diffracted in a first direction (X) and radiation diffracted in a second direction (Y). A second image (740(R)) of the target structure using illuminating radiation having a second angular illumination distribution which the same as the first angular distribution, but rotated 90 degrees. The first image and the second image can be used together so as to discriminate between radiation diffracted in the first direction and radiation diffracted in the second direction by the same part of the target structure. This discrimination allows overlay and other asymmetry-related properties to be measured independently in X and Y, even in the presence of two-dimensional structures within the same part of the target structure.

Abstract: A liquid crystal exposure apparatus is equipped with: a substrate holder that is disposed below a projection optical system and holds a substrate; a first drive section that moves the substrate holder along an XY plane; heads that measures the position information of the substrate holder; head stages that support the heads and are movable within the XY plane; and a second drive section that moves the head stages in the X-axis direction and the Y-axis direction, and the second drive section moves the head stages in the X-axis direction or the Y-axis direction when the substrate holder is moved in the X-axis direction or the Y-axis direction by the first drive section.

Abstract: A method for performing optical wavefront sensing includes providing an amplitude transmission mask having a light input side, a light output side, and an optical transmission axis passing from the light input side to the light output side. The amplitude transmission mask is characterized by a checkerboard pattern having a square unit cell of size ?. The method also includes directing an incident light field having a wavelength ? to be incident on the light input side and propagating the incident light field through the amplitude transmission mask. The method further includes producing a plurality of diffracted light fields on the light output side and detecting, at a detector disposed a distance L from the amplitude transmission mask, an interferogram associated with the plurality of diffracted light fields.

Abstract: A method of determining a position of an imprint template in an imprint lithography apparatus. In an embodiment, the method includes illuminating an area of the imprint template in which an alignment mark is expected to be found by scanning an alignment radiation beam over that area, detecting an intensity of radiation reflected or transmitted from the area, and identifying the alignment mark via analysis of the detected intensity.

Abstract: A direction sensor (200) includes sensor cells (215) that respectively correspond to different directions. Each of the sensor cells (215) includes a light sensor (130, 140) and a grating (120) that couples incident light into the light sensor (130, 140) when the incident light has a specific wavelength and is incident on the grating (120) along the direction corresponding to the sensor cell (215).

Abstract: In a system having a substrate holding means for holding a substrate, wherein the substrate holding means is rotatable about an axis of rotation that is perpendicular to an X-Y coordinate system, a method for determining position of the axis of rotation in the X-Y coordinate system, comprising the steps of: providing a reference labeling on the substrate holding means or on the substrate; determining a first X-Y reference position RP of a reference labeling on the substrate holding means or on the substrate by means of optical positional detecting means that is fixed relative to the X-Y coordinate system, rotating the substrate holding means by a defined angle of rotation R around the axis of rotation, determining by means of said fixed optical positional detecting means a second X-Y reference position RP? of the reference labeling that is changed by the rotation, and calculating the X-Y position of the axis of rotation in the substrate.

Abstract: An overlay misalignment amount of patterns on different layers can be accurately measured. To achieve this, a charged particle beam device includes: a charged particle beam source irradiating a sample with a charged particle beam under one irradiation condition; a first detector that detects a signal generated front a first pattern formed on a first layer in an irradiation region; a second detector that detects a signal generated from a second pattern formed on a second layer in the irradiation region at a same time as the first detector; and an image processing unit that calculates an overlay misalignment amount between the first pattern and the second pattern based on a first detection signal and a second detection signal output by the first detector and the second detector, respectively.

Abstract: In a photo alignment method, a substrate and a mask are aligned so that the substrate is spaced apart from the mask by a predetermined gap. An organic layer is formed on the substrate. The mask has a transmission portion and a light blocking portion. Light is irradiated through the mask in a direction substantially parallel with an interface between the transmission portion and the light blocking portion of the mask. Polymer chains are formed on an upper portion of the organic layer. The polymer chains are aligned in an alignment direction toward an incident direction of the light. Locations of the substrate and the mask are sensed in real time. The mask is transported to a predetermined location with respect to the substrate based on the sensed locations of the substrate and the mask.

Abstract: A position measurement system includes a first part and a second part for determining a position of a first member relative to a second member by providing a position signal representing a position of the first part relative to the second part, and a computational unit comprising an input terminal for receiving the position signal. The computational unit is configured to, in use, apply a conversion to the position signal to obtain a signal representing a position of the first member relative to the second member; and apply an adjustment to the conversion to at least partly compensate for a drift of the first part or the second part or both. The adjustment is based on a predetermined drift characteristic of the first part or the second part or both respectively. The predetermined drift characteristic includes one or more base shapes of the first part and/or the second part.

Abstract: A position detector (16), configured to detect a position of a mark on an object to be detected, comprises an image pickup unit (34), an optical system, a noise obtaining unit (36) and a correction unit (38). The image pickup unit picks up an image of the object to be detected. The optical system forms an image of the object to be detected on an image pickup surface of the image pickup unit. The noise obtaining unit obtains noise information by picking up an image of a region other than the mark using the optical system and the image pickup unit in accordance with the result of adjustment of an optical member included in the optical system. The correction unit corrects, using the noise information obtained by the noise obtaining unit, the image of the mark obtained using the optical system and the image pickup unit.

Abstract: An imprint apparatus for imprinting a mold pattern onto a substrate or a member on the substrate includes a light source for irradiating a surface of the mold disposed opposite to the substrate and a surface of the substrate with light; an optical system for guiding the light from the light source to the surface of the mold and the surface of the substrate and guiding reflected lights from these surfaces to a spectroscope; a spectroscope for dispersing the reflected lights guided by the optical system into a spectrum; and an analyzer for analyzing a distance between the surface of the mold and the surface of the substrate. The analyzer calculates the distance between the surface of the mold and the surface of the substrate by measuring a distance between the surface of the mold and a surface formed at a position away from the surface of the mold.

Abstract: According to one embodiment of a method for measuring a stacking overlay error, the method may use a differential interference contrast microscope system to measure a stacking overlay mark and focus on one overlay mark of a lower layer overlay mark and an upper layer overlay mark when measuring the stacking overlay mark. Then, the method uses an image analysis scheme to obtain an image of the stacking overlay mark from a photo-detector and obtains a first reference position of the lower layer overlay mark in a direction and a second reference position of the upper layer overlay mark in the direction from the image; and computes the stacking overlay error in the direction according to the first and the second reference positions.

Abstract: A self-referencing interferometer includes an optical system to split an alignment beam to create a reference beam and a transformed beam. The optical system includes a beam splitter to combine the reference beam and the transformed beam so that the diffraction orders in the reference beam spatially overlap with their respective opposite orders in the transformed beam. A detector system receives the spatially overlapping reference beam and transformed beam from the optical system and determines a position signal. The detector system includes a polarizing system for manipulating the polarization of the beams so that they interfere, and for directing the interfering reference beam and transformed beam to a detector for determining a position signal from the variation of intensity of the interfering beams.

Abstract: A drive system drives a movable body, based on measurement results of a first measurement system which measures the position of the movable body in an XY plane by irradiating a measurement beam from an arm member on a grating placed on a surface parallel to the XY plane of the movable body and measurement results of a second measurement system which measures a variance of the arm member using a laser interferometer. In this case, the drive system corrects measurement errors caused due to a variance of the arm member included in the measurement results of the first measurement system, using the measurement results of the second measurement system.

Abstract: The present invention may include measuring a first phase distribution across a pupil plane of a portion of illumination reflected from a first overlay target of a semiconductor wafer, wherein the first overlay target is fabricated to have a first intentional overlay, measuring a second phase distribution across the pupil plane of a portion of illumination reflected from a second overlay target, wherein the second overlay target is fabricated to have a second intentional overlay in a direction opposite to and having the same magnitude as the first intentional overlay, determining a first phase tilt associated with a sum of the first and second phase distributions, determining a second phase tilt associated with a difference between the first and second phase distributions, calibrating a set of phase tilt data, and determining a test overlay value associated with the first and second overlay target.

Abstract: A drive system drives a movable body, based on measurement results of a first measurement system which measures the position of the movable body in an XY plane by irradiating a measurement beam from an arm member on a grating placed on a surface parallel to the XY plane of the movable body and measurement results of a second measurement system which measures a variance of the arm member using a laser interferometer. In this case, the drive system corrects measurement errors caused due to a variance of the arm member included in the measurement results of the first measurement system, using the measurement results of the second measurement system.

Abstract: A system for performing alignment of two wafers is disclosed. The system comprises an optical coherence tomography system and a wafer alignment system. The wafer alignment system is configured and disposed to control the relative position of a first wafer and a second wafer. The optical coherence tomography system is configured and disposed to compute coordinate data for a plurality of alignment marks on the first wafer and second wafer, and send that coordinate data to the wafer alignment system.

Abstract: The present invention may include measuring a first phase distribution across a pupil plane of a portion of illumination reflected from a first overlay target of a semiconductor wafer, wherein the first overlay target is fabricated to have a first intentional overlay, measuring a second phase distribution across the pupil plane of a portion of illumination reflected from a second overlay target, wherein the second overlay target is fabricated to have a second intentional overlay in a direction opposite to and having the same magnitude as the first intentional overlay, determining a first phase tilt associated with a sum of the first and second phase distributions, determining a second phase tilt associated with a difference between the first and second phase distributions, calibrating a set of phase tilt data, and determining a test overlay value associated with the first and second overlay target.

Abstract: A device for measuring lithography masks is provided, comprising a reticle carrier for the lithography mask to be measured, a measurement objective for reproducing on a detector a section of said lithography mask held by said reticle carrier, a measurement module for measuring the position of said reticle carrier relative to said measurement objective, and a correction module by means of which said reticle carrier can be moved in order to bring it into a predetermined position relative to said measurement objective, wherein said measurement objective and said measurement module are fastened directly to an instrument carrier in a locally fixed manner.

Abstract: The present invention provides a stage apparatus including a first Y-axis interferometer which is supported by a base portion, and configured to detect a position of a first end surface of a table in a Y-axis direction, a second Y-axis interferometer which is supported by the base portion, and configured to detect a position of a second end surface of the table in the Y-axis direction, and a third Y-axis interferometer which is supported by the base portion so as to be spaced apart from the first Y-axis interferometer and the second Y-axis interferometer in an X-axis direction, and configured to detect a distance according to which a distance between the first Y-axis interferometer and the second Y-axis interferometer in the Y-axis direction can be obtained.

Abstract: An alignment measurement system measures an alignment target on an object. A measurement illuminates the target and is reflected. The reflected measurement beam is split and its parts are differently polarized. A detector receives the reflected measurement beam. A processing unit determines alignment on the basis of the measurement beam received by the detector. An alternative arrangement utilizes an optical dispersive fiber to guide a multi-wavelength measurement beam reflected from the object to a detector.

Abstract: An etching amount calculating method that can stably and accurately calculate the amount of etching even if a disturbance is added. Superposed interference light resulting from superposition of interference light of reflected light from a mask film and reflected light from the bottom of a concave portion on other interference light is received. A waveform in a predetermined time period is extracted from a superposed interference wave calculated from the superposed interference light. The period of an interference wave of the reflected light from the mask film and the reflected light from the bottom is detected from the distribution of frequencies of the extracted waveform. The steps described above are repeated while shifting the predetermined time period by a predetermined time, and the detected periods are integrated and averaged at each repetition. The etching amount of the concave portion is calculated based on the integrated and averaged periods.

Abstract: A device for measuring lithography masks is provided, comprising a reticle carrier for the lithography mask to be measured, a measurement objective for reproducing on a detector a section of said lithography mask held by said reticle carrier, a measurement module for measuring the position of said reticle carrier relative to said measurement objective, and a correction module by means of which said reticle carrier can be moved in order to bring it into a predetermined position relative to said measurement objective, wherein said measurement objective and said measurement module are fastened directly to an instrument carrier in a locally fixed manner.

Abstract: A method, structure, system of aligning a substrate to a photomask. The method comprising: directing light through a clear region of the photomask in a photolithography tool, through a lens of the tool and onto a set of at least three diffraction mirror arrays on the substrate, each diffraction mirror array of the set of at least three diffraction mirror arrays comprising a single row of mirrors, all mirrors in any particular diffraction mirror array spaced apart a same distance, mirrors in different diffraction mirror arrays spaced apart different distances; measuring an intensity of light diffracted from the set of at least three diffraction mirror arrays onto an array of photo detectors; and adjusting a temperature of the photomask or photomask and lens based on the measured intensity of light.

Abstract: An apparatus and method for exposing an edge of a substrate are disclosed, in which an exposure time period for exposing the edge of the substrate is reduced. The apparatus for exposing an edge of a substrate includes a loading unit loading the substrate, and an edge exposure unit exposing the edge of the substrate loaded by the loading unit using each of a long side exposure unit and a short side exposure unit. Therefore, since the edge of the substrate is exposed using each of the long side exposure unit and the short side exposure unit, it is possible to reduce the edge exposure time period, thereby improving productivity. In addition, since no rotation of the substrate is required, it is possible to reduce the size of the apparatus. Moreover, since the apparatus is provided in an in-line type, it is possible to easily draw the substrate using a conveyer.

Abstract: Methods and apparatus for compensating for air or gas temperature fluctuations associated with an interferometer beam path are disclosed. According to one aspect of the present invention, a resistance thermometer assembly includes an insulating tube arrangement, a support arrangement, and a resistance arrangement. The insulating tube arrangement includes a first end and a second end, as well as an insulating tube and a metal film layer that coats the insulating tube. The support arrangement is configured to support the first end and the second end of the insulating tube arrangement. The resistance arrangement is configured to measure a resistance associated with the insulating tube arrangement.

Abstract: A lithographic apparatus has a plurality of different alignment arrangements that are used to perform an alignment measurement on the same mark(s) by: detecting a first alignment mark located on an object and producing a first alignment signal by a first detector; detecting the first mark and producing a second alignment signal by a second detector using a different alignment measurement than the first detector; receiving the first alignment signal from the first detector; calculating a first position of the at least first mark based on the first alignment signal; receiving the second alignment signal from the second detector; calculating a further first position of the at least first mark based on the second alignment signal.

Abstract: A method for alignment of a substrate, in which the substrate includes a mark in a scribe lane, and the scribe lane extends along a longitudinal direction as a first direction. The mark has a periodic structure in the first direction. The method includes providing an illumination beam for scanning the mark in a direction perpendicular to a direction of the mark's periodic structure along a first scan path across the mark, scanning the spot of the illumination beam along a second scan path across the mark, the second scan path being parallel to the first scan path, wherein the second scan path is shifted relative to the first scan path over a first shift that corresponds to a fraction of the repeating distance of the periodic structure.

Abstract: A mark structure includes on a substrate, at least four lines. The lines extend parallel to each other in a first direction and are arranged with a pitch between each pair of lines that is directed in a second direction perpendicular to the first direction. The pitch between each pair of selected lines differs from the pitch between each other pair of selected lines.

Abstract: An exposure apparatus includes a plurality modules and a controller, each module exposes a pattern of an original onto a substrate by using light from a light source, wherein each module includes a position detector configured to detect a position of the original or the substrate that has an alignment mark used for an alignment between the original and each shot on the substrate, wherein the controller has information relating to an alignment error of a detection result by the position detector which is set to each module, and wherein the exposure apparatus further includes a reducing unit configured to reduce a difference of the alignment error among modules.

Abstract: A method, structure, system of aligning a substrate to a photomask. The method includes: directing incident light through a pattern of clear regions transparent to the incident light in an opaque-to-the-incident-light region of a photomask, through a lens and onto a photodiode formed in a substrate, the photodiodes electrically connected to a light emitting diode formed in the substrate, the light emitting diode emitting light of different wavelength than a wavelength of the incident lights; measuring an intensity of emitted light from light emitting diode; and adjusting alignment of the photomask to the substrate based on the measured intensity of emitted light.

Abstract: The invention provides a method for determining the center of a rotationally symmetrical alignment mark thereby using an image recognition software. The alignment mark is recognized by the image recognition software in different orientations by rotating the alignment mark around a symmetry angle with respect to which the alignment mark is rotationally symmetrical, and respective reference points are determined. The center of rotation of the determined reference points corresponds to the center of the alignment mark. Moreover, the invention provides a method for aligning two flat substrates each having a rotationally symmetrical alignment mark and being arranged substantially parallel with respect to each other.

Abstract: In general, in a first aspect, the invention features a method that includes using an interferometry assembly to provide three different output beams, each output beam including an interferometric phase related to an optical path difference between a corresponding first beam and a corresponding second beam, each first beam contacting a measurement object at least once, monitoring the interferometric phases for each of the three different output beams, and deriving information about variations in the optical properties of a gas in the first beam paths from the three monitored phases.

Abstract: In general, in one aspect, the invention features interferometry systems that include an interferometer configured to direct a first beam and a second beam derived from common light source along different paths and to combine the two beams to form an output beam including information related to an optical path difference between the different paths, wherein the path of the first beam contacts a measurement object. The interferometry systems also include an afocal system positioned in the path of the first beam and configured to increase a dimension of the first beam as it propagates from the interferometer towards the measurement object and reduces the dimension of the first beam as it returns from the measurement object propagating towards the interferometer.

Abstract: An embodiment of a symmetry forming device for an alignment system can include an interferometer, a compensator, and an analyzer. The interferometer can be configured to receive a light beam, where the light beam can be produced from a light source or from combining beams from a plurality of light sources. Further, the interferometer can be configured to split the light beam into two beams, rotate one beam 180 degrees with respect to the other beam about an axis of rotation, and recombine the two beams to form a recombined beam. The compensator can be configured to adjust a path length of either the combined or the recombined beam in first and second polarization directions to form an adjusted light beam. The analyzer can be configured to pass a polarization direction or an amplitude and phase profile of either the recombined or adjusted light beam, where the recombined or adjusted light beam is directed onto a substrate.

Abstract: An exposure apparatus comprises an optical system support supporting a projection optical system, a stage surface plate, first stage and second stages, a first interferometer configured to measure stage position in a first area, a second interferometer configured to measure stage position in a second area, a third interferometer which is interposed between the first interferometer and the second interferometer, a gap sensor configured to measure a gap between the optical system support and the stage surface plate, and a control unit configured to pass, in the swapping, the measurement result obtained by one of the first interferometer and the second interferometer to the other one of the first interferometer and the second interferometer using the measurement result obtained by the third interferometer, and to correct the passed measurement result based on the measurement result obtained by the gap sensor.

Abstract: Provided are methods to be carried out prior to, while, and/or after performing a photolithographic process to a wafer that involve wafer misalignment assessment. The method involves obtaining curvature and/or deformation information of a surface of the wafer over a plurality of locations so as to obtain a curvature map of the wafer. The curvature map is processed to obtain a stress map of the wafer. The stress map is used to determine displacement of a layer of the wafer. The displacement information is used to determine a degree of misalignment in the photolithographic process.

Abstract: A drive unit drives a wafer stage in a Y-axis direction based on a measurement value of an encoder that measures position information of the wafer stage in the Y-axis direction and based on information on the flatness of a scale that is measured by the encoder. In this case, the drive unit can drive the wafer stage in a predetermined direction based on a measurement value after correction in which a measurement error caused by the flatness of the scale included in the measurement value of the encoder is corrected based on the information on the flatness of the scale. Accordingly, the wafer stage can be driven with high accuracy in a predetermined direction using the encoder, without being affected by the unevenness of the scale.

Abstract: In calibration of overlay performance of an immersion lithographic apparatus, two sets of overlay data are obtained from exposures carried out using, for example, normal and reversed meanders. The two data sets can then be used to eliminate effects due to substrate cooling.

Abstract: This invention aims at preventing a space including the guide surface of a reticle stage from interfering with an exposure light beam. In order to achieve this object, in a movable stage apparatus having a reticle stage on which a reflecting reticle is to be mounted, when the space is divided by a plane including the reflection surface of the reticle, the guide surface for moving the reticle is arranged in a space opposite to a space where an exposure light beam reflected by the reticle passes.

Abstract: A position measuring system includes a laser interferometer, and a wavelength detection unit detecting the wavelength change of a laser beam. A phase compensation unit compensates for the wavelength change detected by the wavelength detection unit based on the phase difference of aerial vibration between the wavelength detection unit and the optical path of the laser interferometer, which is determined based on the difference in length between a first path of the aerial vibration from the aerial vibration source of an air conditioner to the wavelength detection unit and a second path of the aerial vibration from the aerial vibration source to the optical path of the laser interferometer. A position measuring unit compensates for a measurement value obtained by the laser interferometer on the basis of the compensated wavelength change. In the position measuring system, the first path is designed to be shorter than the second path.

Abstract: An exposure apparatus includes a stage configured to hold an original thereon and to move in a horizontal direction, a first interferometer configured to emit first measurement light used for measuring a position of the stage in a vertical direction thereof, a first mirror provided on a bottom surface of the stage, and a second mirror provided directly below the first mirror. The second mirror is disposed so as to guide the first measurement light emitted from the first interferometer to the first mirror.

Abstract: A projection optical system is a system with good imaging performance based on well-balanced compensation for aberration associated with image height and aberration associated with numerical aperture, while ensuring a large effective image-side numerical aperture in the presence of a liquid in the optical path between the projection optical system and an image plane. The projection optical system forms an image of a first plane on a second plane. An optical path between an optical member located nearest to the second plane out of optical members with a refractive power in the projection optical system, and the second plane is fillable with a predetermined liquid. The projection optical system satisfies the condition of 0.02<NA×WD/FA<0.

Abstract: In general, in a first aspect, the invention features a lithography system that includes a stage for supporting a wafer, an illumination system including a radiation source and a lens assembly, wherein the illumination system is configured to direct radiation through a mask to produce spatially patterned radiation, and the lens assembly is configured to image the spatially patterned radiation onto the wafer, a first interferometry system configured to monitor a location of the stage within the lithography system as the stage moves relative to the illumination system, a second interferometry system configured to identify an alignment feature on a surface associated with the stage, and an electronic controller coupled to the interferometry systems, wherein the electronic controller is configured to determine information about a location of the stage when the alignment feature is identified.

Abstract: A device according to one embodiment of the invention may be applied to measure the overlay (e.g. as a machine performance number) quickly and over an expanded range of locations (possibly everywhere) on a wafer. One method using such a device includes measuring the amplitude of a diffraction order of a diffraction pattern that results from interference between a pattern on wafer level and a pattern that is projected on the pattern on wafer level. The pattern that is projected may be present, for example, at reticle level.