WO2005047974A2 - Mesure et compensation d'erreurs dans des interferometres - Google Patents

Mesure et compensation d'erreurs dans des interferometres Download PDF

Info

Publication number
WO2005047974A2
WO2005047974A2 PCT/US2004/037553 US2004037553W WO2005047974A2 WO 2005047974 A2 WO2005047974 A2 WO 2005047974A2 US 2004037553 W US2004037553 W US 2004037553W WO 2005047974 A2 WO2005047974 A2 WO 2005047974A2
Authority
WO
WIPO (PCT)
Prior art keywords
stage
measurement
location
measurement axis
along
Prior art date
Application number
PCT/US2004/037553
Other languages
English (en)
Other versions
WO2005047974A3 (fr
Inventor
Henry A. Hill
Original Assignee
Zygo Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zygo Corporation filed Critical Zygo Corporation
Publication of WO2005047974A2 publication Critical patent/WO2005047974A2/fr
Publication of WO2005047974A3 publication Critical patent/WO2005047974A3/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02015—Interferometers characterised by the beam path configuration
    • G01B9/02027—Two or more interferometric channels or interferometers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
    • G01B11/306—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces for measuring evenness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/02056—Passive reduction of errors
    • G01B9/02059—Reducing effect of parasitic reflections, e.g. cyclic errors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/0207—Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/0207—Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer
    • G01B9/02072—Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer by calibration or testing of interferometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02083—Interferometers characterised by particular signal processing and presentation
    • G01B9/02084—Processing in the Fourier or frequency domain when not imaged in the frequency domain
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70691—Handling of masks or workpieces
    • G03F7/70775—Position control, e.g. interferometers or encoders for determining the stage position
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
    • G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
    • G03F9/7049—Technique, e.g. interferometric
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
    • G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
    • G03F9/7088—Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
    • G01B2290/60—Reference interferometer, i.e. additional interferometer not interacting with object
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
    • G01B2290/70—Using polarization in the interferometer

Definitions

  • This invention relates to interferometry and to compensating for errors in interferometric measurements.
  • Distance measuring interferometers monitor changes in the position of a measurement object relative to a reference object based on an optical interference signal.
  • the interferometer generates the optical interference signal by overlapping and interfering a measurement beam reflected from the measurement object with a reference beam reflected from a reference object.
  • the measurement and reference beams have orthogonal polarizations and different frequencies. The different frequencies can be produced, for example, by laser Zeeman splitting, by acousto-optical modulation, or internal to the laser using birefringent elements or the like.
  • the orthogonal polarizations allow a polarizing beam-splitter to direct the measurement and reference beams to the measurement and reference objects, respectively, and combine the reflected measurement and reference beams to form overlapping exit measurement and reference beams.
  • the overlapping exit beams form an output beam that subsequently passes through a polarizer.
  • the polarizer mixes polarizations of the exit measurement and reference beams to form a mixed beam. Components of the exit measurement and reference beams in the mixed beam interfere with one another so that the intensity of the mixed beam varies with the relative phase of the exit measurement and reference beams.
  • a detector measures the time-dependent intensity of the mixed beam and generates an electrical interference signal proportional to that intensity.
  • the electrical interference signal includes a "heterodyne" signal having a beat frequency equal to the difference between the frequencies of the exit measurement and reference beams. If the lengths of the measurement and reference paths are changing relative to one another, e.g., by translating a stage that includes the measurement object, the measured beat frequency includes a Doppler shift equal to 2vnpl ⁇ ,
  • v is the relative speed of the measurement and reference objects
  • ⁇ is the wavelength of the measurement and reference beams
  • n is the refractive index of the medium through which the light beams travel, e.g., air or vacuum
  • p is the number of passes to the reference and measurement objects.
  • Changes in the phase of the measured interference signal correspond to changes in the relative position of the measurement object, e.g., a change in phase of 2 ⁇ corresponds substantially to a distance change L of ⁇ f(2np) .
  • Distance 2L is a round-trip distance change or the change in distance to and from a stage that includes the measurement object.
  • the observable interference phase. ⁇ is not always identically equal to phase ⁇ .
  • Many interferometers include, for example, non-linearities such as those known as "cyclic errors.”
  • the cyclic errors can be expressed as contributions to the observable phase and/or the intensity of the measured interference signal and have a sinusoidal dependence on the5 change in for example optical path length 2pnL .
  • a first order cyclic error in phase has for the example a sinusoidal dependence on (A ⁇ pnL) I ⁇ and a second order cyclic error in phase has for the example a sinusoidal dependence on 2 (A ⁇ pnL)! ' ⁇ .
  • Higher order cyclic errors can also be present as well as sub-harmonic cyclic errors and cyclic errors that have a sinusoidal dependence of other phase parameters of an interferometer system comprising detectors and signal processing electronics. Different techniques for quantifying such cyclic errors are described in commonly owned U.S. Patent Nos. 6,137,574, 6,252,688, and 6,246,481 by Henry A. Hill.
  • Non-cyclic non-linearities or non-cyclic errors there are in addition to the cyclic errors, non-cyclic non-linearities or non-cyclic errors, so named because they tend to vary in a non-sinusoidal, non-linear way with respect to the optical path length.
  • One example of a source of a non-cyclic error is the diffraction of optical beams in the measurement paths of an interferometer.
  • Non-cyclic error due to diffraction has been determined for example by analysis of the behavior of a system such as found in the work of J.-P. Monchalin, M. J. Kelly, J. E. Thomas, N. A. Kurnit, A. Szoke, F. Zernike, P. H. Lee, and ) A.
  • Beam shears can be caused for example by a change in direction of 5 propagation of the input beam to an interferometer or a change in orientation of the object mirror in a double pass plane mirror interferometer such as a differential plane mirror interferometer (DPMI) or a high stability plane mirror interferometer (HSPMI).
  • DPMI differential plane mirror interferometer
  • HSPMI high stability plane mirror interferometer
  • multiple distance measuring interferometers can be used to monitor multiple degrees of freedom of a measurement object.
  • interferometry o systems that include multiple displacement interferometers are used to monitor the location of a plane mirror measurement object in lithography tools. Monitoring the location of a stage mirror relative to two parallel measurement axes provides information about the angular orientation of the stage mirror relative to an axis normal to the plane in which the two measurement axes lie. Such measurements allow a user to monitor the location and orientation of the stage relative to !5 other components of the lithography tool to relatively high accuracy.
  • SUMMARY Imperfections in an interferometer such as surface and bulk imperfections, and surface variations due to imperfections in a plane mirror measurement object of an interferometry system introduce errors in displacement and angle measurements made using the interferometry system.0
  • the effect of these errors may be amplified when determining the location of a mark located away from the interferometer's measurement axis.
  • the effect of these errors on off- axis measurements can be reduced or eliminated if the contribution to the measurements by the imperfections is known.
  • Interferometry systems that utilize two interferometers to monitor a plane mirror > measurement object along two parallel measurement axes can be used to map the mirror surface profile along a scan line and to characterize errors due to interferometer imperfections.
  • the mirror surface can be mapped by monitoring the displacement of the mirror surface relative to a reference point on each of the two measurement axes while scanning the mirror in a direction orthogonal to the measurement axes where the mirror is sufficiently close to the interferometers o so that effects of imperfections in the interferometer is negligible.
  • the difference between the displacement measurements provides a measure of the average slope of the mirror surface between the two measurement axes.
  • integrating the slope over the scan line provides a measure of 5 the departure of the mirror surface from a perfectly planar surface (also referred to as mirror "unevenness").
  • the invention features a method for determining the location of an alignment mark on a stage using an interferometry system, including measuring a location, of a stage along a first measurement axis using the interferometry system, measuring a location, x 2 , of the stage along a second measurement axis, and determining a location of the alignment mark along a third axis based on x ⁇ , xi, and a correction tenn, ⁇ , calculated from predetermined o information comprising information characterizing imperfections in the interferometry system determined using the interferometry system and the stage.
  • Embodiments of the method can include one or more of the following features and/or features of other aspects.
  • x ⁇ and x can correspond to the location of a mirror at the first and second measurement
  • the first measurement axis can be parallel to the second measurement axis.
  • the first measurement axis can be parallel to the third measurement axis.
  • Information characterizing imperfections in the interferometry system can be determined by monitoring the location of the stage using the interferometry system during a calibration procedure.
  • the calibration procedure can include monitoring x ⁇ and x 2 while scanning the stage along a patho non-parallel (e.g., orthogonal) to the first measurement axis.
  • the calibration procedure can further include characterizing surface variations of the mirror based on J I and x 2 monitored while scanning the stage along the path non-parallel (e.g., orthogonal) to the first measurement axis.
  • the calibration procedure can further include monitoring x ⁇ and x 2 while scanning the stage along a path (e.g., a path parallel to the first measurement axis).
  • the calibration procedure can5 also include determining an error term associated with the interferometer based on x ⁇ and x 2 monitored while scanning the stage along the path (e.g., the path parallel to the first measurement axis).
  • the calibration procedure can include monitoring the location of the stage along a third measurement axis and a fourth measurement axis using the interferometry system.
  • the third and fourth measurement axes can be non-parallel (e.g., orthogonal) to the first measurement axis.0
  • the location of the stage along the third and fourth measurement axes can correspond to the location of a second mirror along the third and fourth measurement axes.
  • the calibration procedure can further mclude characterizing surface variations of the second mirror based on the locations of the mirror along the third and fourth measurement axes monitored while scanning the stage along the path (e.g., the path parallel to the first measurement axis).
  • the calibration procedure can also include determining an error term associated with the interferometer based on x ⁇ and X 2 monitored while scanning the stage along the path (e.g., the path parallel to the first measurement axis) and the characterized surface variations of the second mirror.
  • the information characterizing imperfections in the interferometry system can include a differential mode error term associated with the interferometer and or a differential mode error term associated with the mirror.
  • the invention features a method, including monitoring the location of a stage along a first measurement axis using an interferometry system while scanning the stage along one or more paths, monitoring the location of the state along a second measurement axis non-parallel (e.g., orthogonal) to the first measurement axis using the interferometry system while scanning the stage along the one or more paths, and determining information related to imperfections in the interferometry system based on t ie monitored locations.
  • Embodiments of the method can include one or more of the following features and or features of other aspects.
  • the location of the stage along the first measurement axis can correspond to the location of a first mirror along the first measurement object.
  • One of the scanned paths can be non-parallel (e.g., orthogonal) to the first measurement axis. Determining information can include characterizing errors due surface variations of the first mirror based on the monitored locations of the stage while scanning the stage along the non-parallel path to the first measurement axis.
  • the location of the stage along the second measurement axis can correspond to the location of a second mirror along the second measurement object.
  • One of the paths can be no-parallel the second measurement axis.
  • One of the paths can be parallel to the first measurement axis.
  • Determining information can include characterizing errors due to surface variations of the second mirror based on the monitored locations of the stage while scanning the stage along a path (e.g., a path parallel to the first measurement axis). In some embodiments, determining information includes characterizing errors due to imperfections in an interferometer of the interferometry system based on the monitored locations of the stage while scanning the stage along a path (e.g., a path parallel to the first measurement axis). The interferometer can be used to monitor the location of the stage along the first measurement axis. Imperfections in the interferometry system can include variations in the surface of a mirror used in the interferometry system.
  • the information related to imperfections in the interferometry system can include a differential mode error term and/or a common mode error term associated with the mirror.
  • imperfections in the interferometry system can include imperfections in an interferometer used in the interferometry system.
  • the information related to imperfections in the interferometry system can include a differential mode error term associated with the interferometer.
  • the invention features an interferometry system, including an interferometer configured to monitor a location, x ⁇ , of a stage along a first axis, and an electronic controller coupled to the interferometer, wherein during operation the electronic controller determines a location of the stage along a third axis based onxi, a location, x , of the stage along a second axis and a correction term, ⁇ , calculated from predetermined information 5 comprising information characterizing imperfections in the interferometry system determined using the interferometry system and the stage.
  • Embodiments of the interferometry system can include one or more of the features of other aspects.
  • the electronic controller can be configured to acquire the information characterizing o imperfections in the interferometry system during a calibration procedure.
  • the invention features an interferometry system, including a first interferometer configured to monitor the location of a stage along a first measurement axis, a second interferometer configured to monitor the location of the stage along a second measurement axis non-parallel to the first measurement axis, and an electronic controller coupled5 to the first and second interferometers and configured to monitor the location of the stage along the first and second measurement axes while the stage is scanned along one or more paths, and to determine infonnation related to imperfections in the interferometry system based on the monitored locations.
  • Embodiments of the interferometry system can include one or more features of other0 aspects.
  • the invention features a lithography system for use in fabricating integrated circuits on a wafer, including a stage for supporting the wafer, an illumination system for imaging spatially patterned radiation onto the wafer, a positioning system for adjusting the position of the stage relative to the imaged radiation, and foregoing interferometry system for monitoring the position of the wafer relative to the imaged radiation.
  • the invention features a lithography system for use in fabricating integrated circuits on a wafer including a stage for supporting the wafer, and an illumination system including a radiation source, a mask, a positioning system, a lens assembly, and the foregoing interferometry system, wherein during operation the source directs radiation through the mask to produce spatially patterned radiation, the positioning system adjusts the position of the mask relative to the wafer, the lens assembly images the spatially patterned radiation onto the wafer, and the interferometry system monitors the position of the mask relative to the wafer.
  • an illumination system including a radiation source, a mask, a positioning system, a lens assembly, and the foregoing interferometry system, wherein during operation the source directs radiation through the mask to produce spatially patterned radiation, the positioning system adjusts the position of the mask relative to the wafer, the lens assembly images the spatially patterned radiation onto the wafer, and the interferometry system monitors the position of the mask relative to the wafer.
  • the invention features a beam writing system for use in fabricating a lithography mask including a source providing a write beam to pattern a substrate, a stage supporting the substrate, a beam directing assembly for delivering the write beam to the substrate, a positioning system for positioning the stage and beam directing assembly relative one another, and the foregoing interferometry for monitoring the position of the stage relative to the beam directing assembly.
  • the invention features a lithography method for use in fabricating integrated circuits on a wafer including supporting the wafer on a moveable stage, imaging spatially patterned radiation onto the wafer, adjusting the position of the stage, and monitoring the position of the stage using one the foregoing the methods.
  • the invention features a lithography method for use in the fabrication of integrated circuits including directing input radiation through a mask to produce spatially patterned radiation, positioning the mask relative to the wafer, monitoring the position of the mask relative to the wafer using one of the foregoing methods, and imaging the spatially patterned radiation onto a wafer.
  • the invention features a lithography method for fabricating integrated circuits on a wafer including positioning a first component of a lithography system relative to a second component of a lithography system to expose the wafer to spatially patterned radiation and monitoring the position of the first component relative to the second component using one of the foregoing methods.
  • the invention features a method for fabricating integrated circuits, the method including one of the foregoing lithography methods or one of the foregoing lithography 5 systems.
  • the invention features a method for fabricating a lithography mask including directing a write beam to a substrate to pattern the substrate, positioning the substrate relative to the write beam, and monitoring the position of the substrate relative to the write beam using one of the foregoing methods.
  • Embodiments of the invention may include one or more of the following advantages. Errors in determining the location of off-axis markers due to imperfections in interferometers and/or a plane mirror measurement object can be reduced, particularly those errors that occur with spatial frequencies ⁇ 2 ⁇ I d , and harmonics thereof.
  • the disclosed methods can also be used to reduce errors in on-axis measurements. ⁇ 5
  • the contribution of interferometer and mirror imperfections to phase measurements can be characterized using an interferometry system used in the application in which the interferometry system is ultimately used. This error characterization can be performed in situ. Mapping can be repeated to account for changes that may occur over the lifetime of the system. Due to the disclosed error correction methods, the error tolerances of an interferometer 20 and/or other components can be relaxed without compromising measurement accuracy. Accordingly, in some embodiments, the system can use less expensive components (e.g., mirrors) without compromising measurement accuracy.
  • FIG. 1 is a perspective view of an embodiment of a lithography tool.
  • FIG. 2 is a plan view of the stage and interferometry system of the lithography tool shown in FIG 1.
  • FIG. 3 is a schematic of a high stability plane mirror interferometer.
  • FIG. 4 is a schematic showing an Abbe offset error.
  • FIG. 5 is a schematic diagram of an embodiment of a lithography tool that includes an interferometer.
  • FIG. 6(a) and FIG. 6(b) are flow charts that describe steps for making integrated circuits.
  • FIG. 7 is a schematic of a beam writing system that includes an interferometry system.
  • Like reference symbols in the various drawings indicate like elements.
  • an exemplary lithography tool 100 includes an exposure system 110 positioned to image a reticle 120 onto an exposure region of a wafer 130.
  • Wafer 130 is supported by a stage 140, which scans wafer 130 in a plane orthogonal to an axis 112 of exposure system 110.
  • a stage mirror 180 is mounted on stage 140.
  • Stage mirror 180 includes two nominally orthogonal reflecting surfaces 182 and 184.
  • An interferometry system monitors the position of stage 140 along orthogonal x- and y- measurement axes. Thez- andj ⁇ -axes intersect with axis 112 of exposure system 110.
  • interferometry system includes four interferometers 210, 220, 230, and 240.
  • Interferometers 210 and 220 respectively direct measurement beams 215 and 225 parallel to the.y-axis to reflect from mirror surface 182.
  • interferometers 230 and 240 respectively direct measurement beams 235 and 245 parallel to the x-axis to reflect twice from mirror surface 184.
  • each measurement beam is combined with a reference beam 5 to form an output beam.
  • a phase of each output beam is related to the optical path length difference between the measurement and reference beam paths.
  • Detectors 212, 222, 232, and 242 detect the output beams from interferometers 210, 220, 230, and 240, respectively, and communicate optical path length difference information to an electronic controller 170, which determines the stage position from the information and adjusts the position of stage 140 relative 0 to exposure system 110 and reticle 120 accordingly.
  • the input beam for each interferometer is derived from a common source, laser light source 152.
  • Beam splitters 211, 221, 231, and mirrors 241 and 251 direct light from light source 152 to the interferometers.
  • Each interferometer splits its input beam into a measurement beam and a reference beam. In the present embodiment, each interferometer directs its respective measurement beam along a path that contacts a surface of mirror 180 twice.
  • Interferometers 230 and 210 monitor co-ordinates x l and y of the location of mirror surfaces 184 and 182. along the x- and y-axes, respectively. Additionally, interferometers 240 and 220 monitor the location of stage 140 along a second set of axes, offset from but parallel to the brand y-axes, respectively. The secondary measurements provide co-ordinates x 2 and y 2 of mirror surfaces 184 and 182, respectively. The separations of these secondary measurement axes from the x- and _y-axes are known, and are indicated as d ⁇ and d ⁇ in FIG. 2. In some embodiments, interferometers 210, 220, 230, and 240 are high stability plane mirror interferometers (HSPMIs).
  • HSPMIs high stability plane mirror interferometers
  • an HSMPI 300 includes a polarizing beam splitter (PBS) 310, a retroreflector 320, and a reference mirror 330.
  • HSPMI 300 also includes quarter wave plates 340 and 350, positioned between PBS 310 and minor surface 184 or reference mirror 330, respectively.
  • PBS 310 splits the input beam, indicated as beam 360 in FIG. 3, into orthogonally polarized components.
  • One component, measurement beam 335A is transmitted by PBS 310 and reflects from mirror surface 184 back towards PBS 310.
  • the polarization state of the measurement beam is now orthogonal to its original polarization state due to the passing through quarter wave plate 340 twice, and the measurement beam is reflected by PBS 310 towards retroreflector 320.
  • Retroreflector 320 directs the measurement beam back towards PBS 310, which reflects the measurement beam towards minor surface 184.
  • the measurement beam is indicated as beam 335B.
  • mirror surface 184 reflects beam 335B towards PBS 310.
  • the double pass through quarter wave plate 340 transforms the polarization state of the measurement beam back to its original state, and it is transmitted by PBS 310 and exits HSPMI 300 as a component of an output beam 370.
  • the reference beam is the component of input beam 360 initially reflected by PBS 310.
  • the reference beam passes between PBS 310 and reference mirror 330 twice. On each pass, quarter wave plate 350 transforms the polarization state of the reference beam by 90°.
  • PBS 310 transmits the reference beam.
  • PBS 310 reflects the reference beam, which exits the interferometer 300 as a component of output beam 370.
  • Displacement measuring interferometers other than HSPMFs can also be used in lithography tool 100.
  • interferometers 210 and 220 can be replaced by a multi-axis interferometer.
  • Examples of other displacement measuring interferometers include single beam interferometers and/or high accuracy plane mirror interferometers (in which the measurement beam can pass to the measurement object more than twice, e.g., four times). Additional examples of interferometer configurations are described in U.S. Patent Application Serial No. 10/364,300 entitled “SEPARATED BEAM MULTIPLE DEGREE OF FREEDOM INTERFEROMETER,” which claims priority to U.S. Provisional Patent Applications No. 60/356,394 entitled “SEPARATED BEAM MULTIPLE DEGREE OF FREEDOM INTERFEROMETERS" and U.S. Patent Application Serial No. 10/351,707 entitled “MULTIPLE DEGREE OF FREEDOM INTERFEROMETER,” which claims priority to U.S.
  • interferometers 230 and 240 respectively monitor x ⁇ and x 2 along interferometer axes 280 and 282, which are separated by a distance d ⁇ .
  • exposure system 110 is positioned with axis 112 coincident with axis 280, which conesponds to the -axis.
  • x corresponds to the stage's position along the x- axis.
  • measurements of x l and x 2 can be used to determine the position stage 140 along a user defined axis between axis 280 and axis 282.
  • the stage position can be determined along a measurement axis midway between interferometer axes 280 and 282 as x' ⁇ ⁇ ( ] + x 2 ) . More generally, the stage position can be determined on a measurement axis 284 separated from axis 280 by ⁇ d ⁇ according to the formula
  • Lithography tool 100 also includes an alignment scope 160, positioned off-axis from axis 112.
  • Alignment scope 160 is positioned to locate objects at a position on the ⁇ -axis, offset from the x-axis (corresponding to axis 280) by an amount d 2 + ⁇ d x , where d 2 is the separation o between axis 284 and another axis 286, parallel to the x-axis, on which the alignment scope is located.
  • a user locates an alignment mark 165 with alignment scope 160. Because the position of alignment scope 160 with respect to exposure system 110 and the x- and j -axes is known, locating the alignment mark 165 with the scope registers the alignment mark with respect to the exposure system.
  • alignment mark 165 provides a set of reference co-ordinates indicative of the alignment mark's location on the stage. Based on these reference co-ordinates, the user can accurately translate the wafer on the stage with respect to the exposure system to locate target regions of the wafer on axis 112. Any repositioning of the stage based on the reference co-ordinates should account for theo angular orientation of the stage when alignment mark 165 is located by alignment scope 160.
  • stage orientation is illustrated in FIG. 4, which shows axes 280 and 282, measurement axis 284, and axis 286. The location of a position along axis 286 is denoted as _x 3 .
  • Interferometer errors also referred to as non-cyclic non-linear errors, can arise due to wavefront distortions in the measurement and/or reference beams and due to beam shear between the components of the output beam at the detector.
  • Wavefront distortions arise, for example, from imperfections in components of the interferometer, including surface imperfections (e.g., ) scratches, dust or other foreign particles on a surface, or departures of a surface from a flat surface) and bulk imperfections (e.g., bulk inhomogeneities or birefringence). Scattering from such imperfections can distort a beam's wavefront profile from a nominal form (e.g., from a plane wave) and can affect a measured phase when interfered with another beam. Where the distortion of one wavefront of a beam of the interferometer varies as a function of mirror 5 displacement, the distortion can result in errors in a monitored interference phase.
  • surface imperfections e.g., ) scratches, dust or other foreign particles on a surface, or departures of a surface from a flat surface
  • bulk imperfections e.g., bulk inhomogeneities or birefringence
  • Beam shearing refers to a displacement of the component beams in the output beam relative to each other (i.e., differential mode beam shear) or a displacement of the output beam relative to a nominal output beam path (i.e., common mode beam shear).
  • Beam shears can be caused for example by a change in direction of propagation of the input beam to an ,0 interferometer or a change in orientation of the object mirror in a double pass plane mirror interferometer such as a high stability plane mirror interferometer (HSPMI).
  • HSPMI high stability plane mirror interferometer
  • a wavefront distortion in the measurement beam will vary relative to the reference beam resulting in a varying contribution to the detected phase, in turn5 resulting in errors in the measured interference phase.
  • wavefront distortions in combination with beam shear can cause phase errors and reduce the accuracy of interferometric measurements.
  • the linear displacement x 3 can be determined from
  • ⁇ is an error correction term accounting for imperfections in the surface of the mirror and in the interferometers.
  • the linear displacement x 3 and error correction term ⁇ given by Eqs. (6) and (7), respectively, may be written in terms of differential mode components of linear displacement and of error correction terms, i.e., (x 2 - j ) and (y/ 2 ⁇ ⁇ ⁇ ) , respectively, and common mode components of linear displacement and of error correction terms, i.e., (x 2 + x ) and (x ⁇ 2 + ⁇ ⁇ ) : respectively, in order to more easily establish correspondence with available measured quantities.
  • the corresponding equations are
  • the differential mode components ⁇ i ⁇ ⁇ ⁇ ) an( l ⁇ i ⁇ ⁇ ⁇ )M ' res P ec tively, are each amplified by the factor (T/J + ⁇ -1/2) and that the common mode components enter only as an average value with no amplification. Accordingly, in some embodiments, the common mode components can be negligible and this error term need not be determined when calculating ⁇ j.
  • ⁇ 3 can be determined by characterizing components of the interferometers and the mirror prior to their installation in lithography tool 100. Alternatively, certain contributions to ⁇ can be determined in situ (i.e., once installed within lithography tool 100). Methods for characterizing interferometer errors and interferometer component errors prior to installation (or once installed, but using a separate characterization apparatus) are described, for example, in U.S. Patent Application Serial No. 10/366,587 and entitled "CHARACTERIZATION AND COMPENSATION OF NON-CYCLIC ERRORS TN INTERFEROMETRY SYSTEMS,” by Henry A.
  • ⁇ 3 can be determined in situ by running an error characterization procedure, also referred to as the error characterization mode.
  • a first section, Section 1, of the ereor characterization mode addresses the effect of errors in the surface of mirror 184 and a second section, Section 2, of the error characterization mode addresses certain effects of errors introduced by the interferometers.
  • stage 140 is translated in the y -direction while keeping the x-position of the stage substantially constant and while monitoring x x and x 2 .
  • stage 140 is translated in the x -direction while keeping the y -position of the stage substantially constant and while monitoring x x and x 2 .
  • Scans are repeated in Section 2 for a number of nominal stage orientation angles.
  • the stage is scanned for the x-position closest to interferometers 230 and 240, x min , and for 3(x,y) nominally equal to zero (hereinafter 3 ).
  • Measurement beams 235 and 245 of interferometers 230 and 240 scan mirror surface 184 along a datum line and generate signals containing 5 information indicative of the mirror surface angular orientation and apparent surface departure (i.e., surface unevenness) in the x - y plane from a nominal plane, along with any contributions due to variations in the translation mechanism for moving stage 140 and other sources of error (e.g., cyclic non-linearities, and stationary and non-stationary effects of a gas in measurement paths of beams of interferometers 230 and 240).
  • the scan produces X (x, y,3 0 ) i o and X 2 (x, y, Q ) , corresponding to displacement measurements from interferometers 230 and 240 respectively.
  • interferometers 210 and 220 monitor the orientation of mirror surface 182 for fixed intercept points of measurement beams 215 and 225 with surface 182. This step permits monitoring changes in 3 , due to, for example, the rotation of stage 140 due to mechanical contributions of its translation
  • Measurement of the angular orientation of mirror surface 182 provides a redundant measure of the angular orientation, 3(x,y) , of stage 140 during the scan, which can be used to remove the contribution of angular rotations of stage 140 from the X x (x,y,3) and X 2 (x,y,3) data.
  • the stage is scanned in Section 1 of the error characterization mode for the x-
  • Deviations of the measured position of the mirror surface from the nominal reference surface calculated from slope (dxl y) f and intercept X (0, 0, 3) - X (0, 0, 3) ⁇ are
  • Section 2 determines the differential mode component ( ⁇ 20 " ⁇ io) / ⁇ f° r mirror surface 182.
  • the second step of Section 2 determines the sum of the differential mode components
  • the results of the first step of Section 2 is then subtracted from the results of the second step of Section 2 to obtain the differential mode component ( ⁇ 2 - ⁇ i ) 7 for interferometers 230 and 240.
  • the stage is scanned for the y -position closest to interferometers 210 and 220, min, and for 3(x,y) nominally equal to zero.
  • Measurement beams 215 and 225 of interferometers 210 and 220 scan mirror surface 182 along a datum line and generate signals containing information indicative of the mirror surface angular orientation and apparent surface departure (i.e., surface unevenness) in the x- y plane from a nominal plane, along with any contributions due to variations in the translation mechanism for moving stage 140 and other sources of ereor (e.g., cyclic non-linearities, and stationary and non-stationary effects of a gas in measurement paths of beams of interferometers 210 and 220).
  • the scan produces 7 10 (x, y, 3) and Y 20 (x, y, 3) , corcesponding to displacement measurements from interferometers
  • interferometers 230 and 230 Simultaneous with translation of stage 140 in the x -direction, interferometers 230 and
  • 3(x, y) of stage 140 during the scan, which can be used to remove the contribution of angular rotations of stage 140 from the Y lQ (x,y,3) andY 2Q (x,y,3) data.
  • the stage is scanned in the first step of Section 2 for the y -position closest to interferometers 210 and 220 and for 3(x,y) nominally equal to zero. Beam shears are typically reduced when 3(x, y) nominally equal to zero and the displacement of the mirror from the interferometers is smallest so that the contribution of errors due to beam shear to Y ] 0 (x, y, 3) and ⁇ 20 (x, y, 3) for this scan can be ignored.
  • Deviations of the measured position of the mirror surface 182 from a nominal position of the mirror surface calculated from slope (dyldx) f ⁇ t and intercept ⁇ 2Q (0,0,3)- ⁇ 1Q (0,0,3) ⁇
  • the step one of Section 2 is repeated except for . (x, y) having nominal non-zero values determined by an end use application.
  • the corresponding deviations of the measured average slope of the mirror surface 182 obtained in the step 2 of Section 2 from the corresponding average slope of the mirror surface 182 obtained from the first step of Section 2 are attributed to interferometer imperfections ( ⁇ 2 - ⁇ - ⁇ ) j . Contributions to ⁇ and ⁇ 2 from imperfections in the interferometers are expected to be dependent on nominal x values and nominal 3 values. In the absence of mirror and interferometer imperfections, and stage rotations, X 2 - X should remain constant for each scan in x .
  • Sections 1 and 2 of the error characterization mode are used to correct for the differential mode components ( ⁇ 2 - ⁇ ) and (y 2 — ⁇ ) . in Equations (10) and (11).
  • the results of Sections land 2 of the enor characterization mode can be used to correct for the common mode component ( ⁇ 2 + ⁇ ) M & Equations (10) and (11), as discussed below.
  • Variations between the minor profiles are parameterized as functions of x, y, and 3.
  • the variations may be stored in a lookup table in controller 170 and used to compensate measurements during operation of lithography tool 100.
  • the enor terms may be represented functionally.
  • the enor terms may be represented by a multidimensional power series in x, y, and 3 , or in a series of orthogonal functions and coefficients of the representations stored in the lookup tables.
  • information obtained during the enor characterization mode may be "spatially filtered" to obtain the requisite information from differential mode components about certain of the common mode components of ⁇ 3 .
  • Spatial filtering involves transforming scan data using an integral transform (e.g., a Fourier transform) to devolve the scan information into different spatial frequency components.
  • the enor conection term is obtained by integrating, or summing, the contribution from different spatial frequency components. Different spatial frequency components can be weighted differently to reduce the contribution (i.e., remove the contribution) from those components that reduce the accuracy of the enor conection term and/or to increase the sensitivity of the conection term to certain spatial frequency components.
  • ⁇ 2 ⁇ ⁇ > y> °) ⁇ ( » y + d >°) M (17) and is a consequence of the fact that the second measurement axis is simply displaced from the I o first measurement axis with respect to minor 184.
  • ⁇ ⁇ is first derived from ( ⁇ 2 - ⁇ ⁇ ) M such as given in the following series of equations. Using Equation (13), the Fourier transform of ( ⁇ // 2 ⁇ ⁇ ⁇ ) M is written as
  • Equation (21) the Fourier transform of ⁇ M is expressed in terms of the Fourier transform of ( 2 - ⁇ x ) M as The Fourier transform of the common mode component, ( ⁇ 2 + ⁇ ⁇ ) M can be obtained in terms of the Fourier transform of ⁇ ⁇ ⁇ from a similar set of spatial filtering algorithms such as derived in the following series of equations.
  • Equations (21) and (26) are combined to obtain F with the result
  • Equation (22) of (27), respectively, a multiplicative weighting function should be introduced when integrating the contribution of different frequency components to the enor terms given by Equations (22)or (27), respectively, to limit the effect of the singularities.
  • the design of the multiplicative weighting function can be based on considerations of the signal-to-noise ratios as a function of spatial frequency.
  • One example of a multiplicative weighting function is
  • Equations (22) and (27) include a weighing function sin -1 (Kd 12) , in other embodiments other weighting functions may be used.
  • the weighting function should increase sensitivity to those components of the minor surface profile to which the minor characterization method is least sensitive. Examples of weighting functions include linear, geometric, and exponential functions o ⁇ K.
  • information about the minor and/or the interferometers obtained during the enor characterization mode can be used to conect for on-axis measurements as well.
  • minor surface 182 and/or interferometers 210 and 220 can also be characterized using a similar enor characterization mode and this information can be used to reduce enors in both on and/or off-axis measurements along the ⁇ -axis.
  • the off-axis measurement is conected for enors prior to the off- axis position information being sent to a control system that controls the orientation of stage 140, thereby preventing transferal of these enors to the position of the stage.
  • additional enors introduced by various components in the interferometry system can be reduced using other methods. For example, the effect of cyclic non-linear enors can be reduced by techniques such as described in commonly owned U.S.
  • Patent Application Serial No. 10/097,365 entitled “CYCLIC ERROR REDUCTION IN AVERAGE INTERFEROMETRIC MEASUREMENTS”
  • U.S. Patent Application Serial No. 10/616,504 entitled “CYCLIC ERROR COMPENSATION IN INTERFEROMETRY SYSTEMS”
  • U.S. Provisional Application No. 60/394,418 entitled “ELECTRONIC CYCLIC ERROR COMPENSATION FOR LOW SLEW RATES,” all of which are by Henry A. Hill, the contents of which are incorporated herein in their entirety by reference.
  • An example of another cyclic enor compensation technique is described in U.S. Patent Application Serial No.
  • a further example of a cyclic enor compensation technique is described in U.S. Patent Application Serial No. 60/314,490 filed entitled “TILTED INTERFEROMETER,” by Hemy A. Hill, the contents of which is herein incorporated in their entirety by reference.
  • Other techniques for cyclic enor compensation include those described in U.S. Patent Application Serial No.
  • Lithography tools such as tool 100, are especially useful in lithography applications used in fabricating large scale integrated circuits such as computer chips and the like. Lithography is the key technology driver for the semiconductor manufacturing industry. Overlay improvement is one of the five most difficult challenges down to and below 100 nm line widths (design rules), see, for example, the Semiconductor Industry Roadmap, p.82 (1997).
  • Overlay depends directly on the performance, i.e., accuracy and precision, of the distance measuring interferometers used to position the wafer and reticle (or mask) stages. Since a lithography tool may produce $50-100M/year of product, the economic value from improved performance distance measuring interferometers is substantial. Each 1% increase in yield of the lithography tool results in approximately $lM/year economic benefit to the integrated circuit so manufacturer and substantial competitive advantage to the lithography tool vendor.
  • the function of a lithography tool is to direct spatially patterned radiation onto a photoresist-coated wafer. The process involves determining which location of the wafer is to receive the radiation (alignment) and applying the radiation to the photoresist at that location (exposure).
  • the wafer includes alignment marks on the wafer that can be measured by dedicated sensors.
  • the measured positions of the alignment marks define the location of the wafer within the tool.
  • This information along with a specification of the desired patterning of the wafer surface, guides the alignment of the wafer relative to the spatially patterned radiation.
  • a translatable stage supporting the photoresist-coated wafer moves the wafer such that the radiation will expose the conect location of the wafer.
  • a radiation source illuminates a patterned reticle, which scatters the radiation to produce the spatially patterned radiation.
  • the reticle is also refened to as a mask, and these terms are used interchangeably below.
  • a reduction lens collects the scattered radiation and forms a reduced image of the reticle pattern.
  • the scattered radiation propagates a small distance (typically on the order of microns) before contacting the wafer to produce a 1 :1 image of the reticle pattern.
  • the radiation initiates photo-chemical processes in the resist that convert the radiation pattern into a latent image within the resist.
  • Interferometry systems are important components of the positioning mechanisms that control the position of the wafer and reticle, and register the reticle image on the wafer. If such interferometry systems include the features described above, the accuracy of distances measured by the systems increases as cyclic enor contributions to the distance measurement are minimized.
  • the lithography system typically includes an illumination system and a wafer positioning system.
  • the illumination system includes a radiation source for providing radiation such as ultraviolet, visible, x-ray, electron, or ion radiation, and a reticle or mask for imparting the pattern to the radiation, thereby generating the spatially patterned radiation.
  • the illumination system can include a lens assembly for imaging the spatially patterned radiation onto the wafer. The imaged radiation exposes resist coated onto the wafer.
  • the illumination system also includes a mask stage for supporting the mask and a positioning system for adjusting the position of the mask stage relative to the radiation directed through the mask.
  • the wafer positioning system includes a wafer stage for supporting the wafer and a positioning system for adjusting the position of the wafer stage relative to the imaged radiation.
  • Fabrication of integrated circuits can include multiple exposing steps.
  • Interferometry systems described above can be used to precisely measure the positions of each of the wafer stage and mask stage relative to other components of the exposure system, such as the lens assembly, radiation source, or support structure.
  • the interferometry system can be attached to a stationary structure and the measurement object attached to a movable element such as one of the mask and wafer stages.
  • the situation can be reversed, with the interferometry system attached to a movable object and the measurement object attached to a stationary object.
  • such interferometry systems can be used to measure the position of any one component of the exposure system relative to any other component of the exposure system, in which the interferometry system is attached to, or supported by, one of the components and the measurement object is attached, or is supported by the other of the components.
  • FIG. 5 Another example of a lithography tool 1100 using an interferometry system 1126 is shown in Fig. 5.
  • the interferometry system is used to precisely measure the position of a wafer (not shown) within an exposure system.
  • stage 1122 is used to position and support the wafer relative to an exposure station.
  • Scanner 1100 includes a frame 1102, which carries other support structures and various components carried on those structures.
  • An exposure base 1104 has mounted on top of it a lens housing 1106 atop of which is mounted a reticle or mask stage 1116, which is used to support a reticle or mask.
  • a positioning system for positioning the mask relative to the exposure station is indicated schematically by element 1117.
  • Positioning system 1117 can include, e.g., piezoelectric transducer elements and conesponding control electronics.
  • one or more of the interferometry systems described above can also be used to precisely measure the position of the mask stage as well as other moveable elements whose position must be accurately monitored in processes for fabricating lithographic structures (see supra Sheats and Smith Microlithography: Science and Technolos ).
  • Suspended below exposure base 1104 is a support base 1113 that carries wafer stage 1122.
  • Stage 1122 includes a plane minor 1128 for reflecting a measurement beam 1134 directed to the stage by interferometry system 1126.
  • a positioning system for positioning stage 1122 relative to interferometry system 1126 is indicated schematically by element 1119.
  • Positioning system 1119 can include, e.g., piezoelectric transducer elements and conesponding control electronics.
  • the measurement beam reflects back to the interferometry system, which is mounted on exposure base 1104.
  • the interferometry system can be any of the embodiments described previously.
  • a radiation beam 1110 e.g., an ultraviolet (UV) beam from a UV laser (not shown)
  • UV ultraviolet
  • a mask carried by mask stage 1116.
  • the mask (not shown) is imaged onto a wafer (not shown) on wafer stage 1122 via a lens assembly 1108 carried in a lens housing 1106.
  • Base 1104 and the various components supported by it are isolated from environmental vibrations by a damping system depicted by spring 1120.
  • one or more of the interferometry systems described previously can be used to measure distance along multiple axes and angles associated for example with, but not limited to, the wafer and reticle (or mask) stages.
  • other beams can be used to expose the wafer including, e.g., x-ray beams, electron beams, ion beams, and visible optical beams.
  • the lithographic scanner can include what is known in the art as a column reference.
  • the interferometry system 1126 directs the reference beam (not shown) along an external reference path that contacts a reference minor (not shown) mounted on some structure that directs the radiation beam, e.g., lens housing 1106.
  • the reference minor reflects the reference beam back to the interferometry system.
  • the interference signal produce by interferometry system 1126 when combining measurement beam 1134 reflected from stage 1122 and the reference beam reflected from a reference minor mounted on the lens housing 1106 indicates changes in the position of the stage relative to the radiation beam.
  • the interferometry system 1126 can be positioned to measure changes in the position of reticle (or mask) stage 1116 or other movable components of the scanner system.
  • FIG. 6(a) is a flow chart of the sequence of manufacturing a semiconductor device such as a semiconductor chip (e.g., IC or LSI), a liquid crystal panel or a CCD.
  • Step 1151 is a design process for designing the circuit of a semiconductor device.
  • Step 1152 is a process for manufacturing a mask on the basis of the circuit pattern design.
  • Step 1153 is a process for manufacturing a wafer by using a material such as silicon.
  • Step 1154 is a wafer process which is called a pre-process wherein, by using the so prepared mask and wafer, circuits are formed on the wafer through lithography. To form circuits on the wafer that conespond with sufficient spatial resolution those patterns on the mask, interferometric positioning of the lithography tool relative the wafer is necessary. The interferometry methods and systems described herein can be especially useful to improve the effectiveness of the lithography used in the wafer process.
  • Step 1155 is an assembling step, which is called a post-process wherein the wafer processed by step 1154 is formed into semiconductor chips.
  • Step 1156 is an inspection step wherein operability check, durability check and so on of the semiconductor devices produced by step 1155 are canied out. With these processes, semiconductor devices are finished and they are shipped (step 1157).
  • FIG. 6(b) is a flow chart showing details of the wafer process.
  • Step 1161 is an oxidation process for oxidizing the surface of a wafer.
  • Step 1162 is a CVD process for forming an insulating film on the wafer surface.
  • Step 1163 is an electrode forming process for forming electrodes on the wafer by vapor deposition.
  • Step 1164 is an ion implanting process for implanting ions to the wafer.
  • Step 1165 is a resist process for applying a resist (photosensitive material) to the wafer.
  • Step 1166 is an exposure process for printing, by exposure (i.e., lithography), the circuit pattern of the mask on the wafer through the exposure apparatus described above. Once again, as described above, the use of the interferometry systems and methods described herein improve the accuracy and resolution of such lithography steps.
  • Step 1167 is a developing process for developing the exposed wafer.
  • Step 1168 is an etching process for removing portions other than the developed resist image.
  • Step 1169 is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are formed and superimposed on the wafer.
  • the interferometry systems described above can also be used in other applications in wliich the relative position of an object needs to be measured precisely.
  • a write beam such as a laser, x-ray, ion, or electron beam
  • the interferometry systems can be used to measure the relative movement between the substrate and write beam.
  • a schematic of a beam writing system 1200 is shown in FIG. 7.
  • a source 1210 generates a write beam 1212
  • a beam focusing assembly 1214 directs the radiation beam to a substrate 1216 supported by a movable stage 1218.
  • an interferometry system 1220 directs a reference beam 1222 to a minor 1224 mounted on beam focusing assembly 1214 and a measurement beam 1226 to a minor 1228 mounted on stage 1218. Since the reference beam contacts a minor mounted on the beam focusing assembly, the beam writing system is an example of a system that uses a column reference. Interferometry system 1220 can be any of the interferometry systems described previously. Changes in the position measured by the interferometry system conespond to changes in the relative position of write beam 1212 on substrate 1216. Interferometry system 1220 sends a measurement signal 1232 to controller 1230 that is indicative of the relative position of write beam 1212 on substrate 1216.
  • Controller 1230 sends an output signal 1234 to a base 1236 that supports and positions stage 1218.
  • controller 1230 sends a signal 1238 to source 1210 to vary the intensity of, or block, write beam 1212 so that the write beam contacts the substrate with an intensity sufficient to cause photophysical or photochemical change only at selected positions of the substrate.
  • controller 1230 can cause beam focusing assembly 1214 to scan the write beam over a region of the substrate, e.g., using signal 1244.
  • controller 1230 directs the other components of the system to pattern the substrate. The patterning is typically based on an electronic design pattern stored in the controller.
  • the write beam patterns a resist coated on the substrate and in other applications the write beam directly patterns, e.g., etches, the substrate.
  • An important application of such a system is the fabrication of masks and reticles used in the lithography methods described previously.
  • the beam writing system encloses the electron beam path in a vacuum.
  • the beam focusing assembly includes electric field generators such as quadrapole lenses for focusing and directing the charged particles onto the substrate under vacuum.
  • the beam focusing assembly includes conesponding optics and for focusing and directing the radiation to the substrate.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Mathematical Physics (AREA)
  • Multimedia (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Instruments For Measurement Of Length By Optical Means (AREA)

Abstract

De manière générale, cette invention concerne dans un de ses aspects un procédé destiné à déterminer l'emplacement d'un repère d'alignement sur une platine consistant à mesurer un emplacement, x1, d'une platine le long d'un premier axe de mesure au moyen d'un système d'interférométrie, à mesurer un emplacement, x2, de la platine le long d'un second axe de mesure parallèle au premier, et à déterminer un emplacement du repère d'alignement le long d'un troisième axe parallèle au premier basé sur, x1, x2, et un terme correctif, γ3, calculé à partir d'informations prédéfinies notamment des informations caractérisant les imperfections dans le système d'interférométrie déterminées au moyen du système d'interférométrie et de l'élément.
PCT/US2004/037553 2003-11-10 2004-11-10 Mesure et compensation d'erreurs dans des interferometres WO2005047974A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US51888903P 2003-11-10 2003-11-10
US60/518,889 2003-11-10

Publications (2)

Publication Number Publication Date
WO2005047974A2 true WO2005047974A2 (fr) 2005-05-26
WO2005047974A3 WO2005047974A3 (fr) 2007-04-19

Family

ID=34590315

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2004/037553 WO2005047974A2 (fr) 2003-11-10 2004-11-10 Mesure et compensation d'erreurs dans des interferometres

Country Status (1)

Country Link
WO (1) WO2005047974A2 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107036528A (zh) * 2011-03-30 2017-08-11 迈普尔平版印刷Ip有限公司 干涉仪模块
WO2022111940A1 (fr) * 2020-11-26 2022-06-02 Asml Netherlands B.V. Procédé d'étalonnage de positions de points de miroir, appareil lithographique et procédé de fabrication de dispositif

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5790253A (en) * 1996-04-05 1998-08-04 Nikon Corporation Method and apparatus for correcting linearity errors of a moving mirror and stage

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5790253A (en) * 1996-04-05 1998-08-04 Nikon Corporation Method and apparatus for correcting linearity errors of a moving mirror and stage

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107036528A (zh) * 2011-03-30 2017-08-11 迈普尔平版印刷Ip有限公司 干涉仪模块
WO2022111940A1 (fr) * 2020-11-26 2022-06-02 Asml Netherlands B.V. Procédé d'étalonnage de positions de points de miroir, appareil lithographique et procédé de fabrication de dispositif

Also Published As

Publication number Publication date
WO2005047974A3 (fr) 2007-04-19

Similar Documents

Publication Publication Date Title
US7812964B2 (en) Distance measuring interferometer and encoder metrology systems for use in lithography tools
US7283248B2 (en) Multi-axis interferometers and methods and systems using multi-axis interferometers
US7289226B2 (en) Characterization and compensation of errors in multi-axis interferometry systems
US20020171844A1 (en) Cyclic error reduction in average interferometric position measurements
US7075619B2 (en) In-process correction of stage mirror deformations during a photolithography exposure cycle
US7528961B2 (en) Compensation of turbulent effects of gas in measurement paths of multi-axis interferometers
WO2005106383A2 (fr) Systemes d'interferometrie et procedes d'utilisation de systemes d'interferometrie
US7030994B2 (en) Method and apparatus to measure fiber optic pickup errors in interferometry systems
US7330274B2 (en) Compensation for geometric effects of beam misalignments in plane mirror interferometers
US6924896B2 (en) Interferometry system error compensation in twin stage lithography tools
US7321432B2 (en) Measurement and compensation of errors in interferometers
US7262860B2 (en) Compensation for errors in off-axis interferometric measurements
US7286240B2 (en) Compensation for geometric effects of beam misalignments in plane mirror interferometer metrology systems
US20040061869A1 (en) Compensation for errors in off-axis interferometric measurements
US7433049B2 (en) Multi-axis interferometer with procedure and data processing for mirror mapping
US7274462B2 (en) In SITU measurement and compensation of errors due to imperfections in interferometer optics in displacement measuring interferometry systems
JP4633624B2 (ja) 軸外干渉計測における誤差に対する補償
WO2005047974A2 (fr) Mesure et compensation d'erreurs dans des interferometres

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A2

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BW BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE EG ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NA NI NO NZ OM PG PH PL PT RO RU SC SD SE SG SK SL SY TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW

AL Designated countries for regional patents

Kind code of ref document: A2

Designated state(s): BW GH GM KE LS MW MZ NA SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LU MC NL PL PT RO SE SI SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase