JP2005516206A - Multipath interferometer - Google Patents

Abstract

The interferometer system includes a multipath interferometer having a plurality of reflectors (12, 26) that reflect at least two beams along a plurality of paths through the interferometer (10). The multiple passages include a first set of passages and a second set of passages. The reflector has a first orientation orthogonal to the direction of the path of the beam reflected by the reflector. The two beams provide information about a first position change ($ g (D1)) on one of the reflectors after the first set of paths, and the second set of paths. Information about the change in the first position and the change in the second position ($ g (D2)) on the subsequent one reflector is supplied. The beam path is deviated between the first set of paths and the second set of paths when at least one of the plurality of reflectors has an orientation other than the first orientation. The interferometer system is arranged after the first set of passages and before the second set of passages so that the deviation occurring between the second set of passages cancels out the deviation occurring between the first set of passages. An optical system (28) for changing the direction of the beam is included.

Description

  The present invention relates to an interferometer, for example a displacement measuring dispersive interferometer that measures the angular and linear displacements of a measurement object such as a mask stage or wafer stage of a lithography scanner or stepper system.

(Quoted by reference)
The following documents are hereby incorporated by reference: Henry A. Hill, US Provisional Patent Application No. 60 / 309,608, filed Aug. 2, 2001 (Z-336), Henry A. Hill, US Provisional Patent Application No. 60 / 314,345, filed Aug. 23, 2001 (Z-343), Henry A. Hill, US Provisional Patent Application No. 60 / 314,568, filed Aug. 23, 2001 (Z-345), Henry A. Hill, US Provisional Patent Application No. 60 / 352,341, filed Jan. 28, 2002 (Z-391), Henry A. Hill, US Provisional Patent Application No. 60 / 352,425, filed Jan. 28, 2002 (Z-396), and Henry A. US patent application Ser. No. 10 / 227,167 filed Aug. 23, 2002 (Z-345) by Hill.

  The displacement measurement interferometer monitors a relative change in the position of the measurement object relative to the reference object based on the optical interference signal. The interferometer generates an optical interference signal by superimposing and interfering with the measurement beam reflected from the measurement object and the reference beam reflected from the reference object.

  In many applications, the measurement and reference beam polarizations are orthogonal and the frequencies are different. Different frequencies may be generated inside the laser, for example, by Zeeman splitting or acousto-optic modulation by the laser, or using a birefringent element or the like. The orthogonal polarization allows the measurement and reference beams to be directed to the measurement and reference objects, respectively, by a polarizing beam splitter and the reflected measurement and reference beams can be combined to form overlapping exit measurement and reference beams. This overlapping exit beam forms the output beam and then passes through the polarizer.

  The polarizer mixes the polarizations of the measurement and reference exit beams to form a mixed beam. The components of the measurement and reference exit beams in the mixed beam interfere with each other, and the intensity of the mix beam changes according to the relative phase of the measurement and reference exit beams. A detector measures the time-dependent intensity of the mixed beam and generates an electrical interference signal proportional to the intensity. Because the frequency of the measurement and reference beams are different, this electrical interference signal includes a “heterodyne” signal having a beat frequency equal to the difference between the frequency of the measurement and reference exit beams. For example, if the measurement and reference path lengths change relative to each other by translating the stage containing the measurement object, the beat frequency measurement includes a Doppler shift equal to 2νnp / λ. Where ν is the relative velocity of the measurement and reference object, λ is the wavelength of the measurement and reference beam, n is the refractive index of the medium, such as air or vacuum, through which the light beam passes, and p is the number of passes to the reference and measurement object. is there. The change in the relative position of the measurement object corresponds to the phase change of the measurement value of the interference signal, and the phase change of 2π is substantially equal to the change in distance L of λ / (np). Here, L is a change in the reciprocating distance, for example, a change in the distance from the stage to the stage including the measurement object to the return.

  Unfortunately, this equation is not always accurate. Further, the amplitude of the interference signal measurement can vary. As the amplitude changes, the accuracy of subsequent phase change measurements can be reduced. Many interferometers include non-linearities, known as “periodic errors”. This periodic error can be expressed as the phase and / or intensity of the interference signal measurement value, and has a sine wave dependency on the change in the optical path length pnL. Specifically, the phase first harmonic period error has a sine wave dependency on (2πpnL) / λ, and the phase second harmonic period error has a sine wave dependency on 2 × (2πpnL) / λ. Have sex. There may also be higher order harmonic period errors.

  If the interferometer reference and measurement beam components contain wavefront errors, the “non-periodic” as caused by the change in lateral displacement (ie, “beam misalignment”) between the reference beam component and the measurement beam component of the output beam Also exists. This phenomenon can be explained as follows.

  Interferometer optics inhomogeneities cause wavefront errors in the reference and measurement beams. If the reference and measurement beams propagate collinearly with each other due to such inhomogeneities, the resulting wavefront errors will be the same and their contributions to the interference signal will cancel each other. More generally, however, the reference beam component and the measurement beam component of the output beam are laterally displaced from one another, i.e., these components have a relative beam offset. Such a beam shift causes a wavefront error, and the error affects an interference signal generated from the output beam.

  Also, in many interferometer systems, beam misalignment changes as the position or angular orientation of the measurement object changes. For example, a change in relative beam shift is caused by a change in the angular orientation of the plane mirror measurement object. Therefore, a corresponding error occurs in the interference signal due to a change in the angular orientation of the measurement object.

  The effects of beam misalignment and wavefront error will depend on the procedure used to mix the components of the output beam associated with the component polarization states, detect the mixed output beam, and generate an electrical interference signal. The mixed output beam can be detected, for example, by a detector without concentrating the mixed beam on the detector, by detecting the mixed output beam as a beam condensing on the detector, or the mixed output beam by a single mode or multimode optical fiber. Can be detected by detecting a portion of the mixed output beam that is emitted into the optical fiber and carried by the optical fiber. The effects of beam misalignment and wavefront error will also depend on the performance of the beam stop if it is used in the procedure for detecting a mixed output beam. In general, multiple errors in the interference signal are mixed when the mixed output beam is transmitted to the detector using an optical fiber.

  The amplitude variation of the measurement interference signal is the net result of a number of mechanisms. One mechanism is a relative beam shift between the reference component and the measurement component of the output beam, and this beam shift is a result of, for example, a change in the posture of the measurement object.

  In dispersion measurement applications, optical path length measurements are made at multiple wavelengths, eg, 532 nm and 1064 nm, and this measurement is used to measure the dispersion of the gas in the measurement path of the distance measurement interferometer. Dispersion measurement can be used when converting an optical path length measured by a distance measurement interferometer into a physical length. Such a conversion is important because even if the physical distance to the measurement object does not change, the change in the measurement optical path length occurs due to gas turbulence and / or due to a change in the average density of the gas in the measurement arm. .

  The interferometers described above are often an integral component of scanner and stepper systems for use in lithography to form integrated circuits on semiconductor wafers. Such lithography systems typically support a movable stage that supports and fixes the wafer, condensing optics used to direct the illumination beam onto the wafer, a scanner or stepper system that moves the stage relative to the exposure beam. , And one or more interferometers. Each interferometer directs the measurement beam to a plane mirror attached to the stage and receives the reflected measurement beam from the plane mirror. Each interferometer causes its reflected measurement beam to interfere with the corresponding reference beam, and as a whole, the interferometer accurately measures changes in the position of the stage relative to the illumination beam. The interferometer allows the lithography system to accurately control which areas of the wafer are exposed to the illumination beam.

  In many lithography systems and other applications, the measurement object includes one or more planar mirrors that reflect the measurement beam from each interferometer. Small changes in the angular orientation of the measurement object, such as pitching and yawing of the stage, can change the direction of each measurement beam reflected by the plane mirror. If left uncompensated, these altered measurement beams reduce the overlap of the exit measurement beam and the exit reference beam in each relevant interferometer. Also, these exit measurement beams and exit reference beams do not propagate parallel to each other or their wave fronts do not coincide when forming a mixed beam. As a result, the interference between the exit measurement beam and the exit reference beam changes in a plane perpendicular to the direction of travel of the mixed beam, so that the interference information encoded in the light intensity measured by the detector is corrupted. .

  In order to address this problem, many conventional interferometers include a retroreflector that redirects the measurement beam back to a plane mirror so that the measurement beam is interferometer and object to be measured. "Pass twice" the path between. Providing a retroreflector ensures that the direction of the exit measurement beam is insensitive to changes in the angular orientation of the measurement object. When implemented in a plane mirror interferometer, this configuration is commonly referred to as a high stability plane mirror interferometer (HSPMI). However, even with the retroreflector, the lateral position of the exit measurement beam remains sensitive to changes in the angular orientation of the measurement object. Also, the path of the measurement beam passing through the optical system in the interferometer remains sensitive to changes in the angular orientation of the measurement object.

  In fact, an interferometer system is used to measure the position of the wafer stage along multiple measurement axes. For example, defining a Cartesian coordinate system in which the wafer stage is located in the xy plane, the measurement is typically performed on the stage relative to the z-axis as well as the x and y position of the stage as the wafer stage moves along the xy plane. This is also performed with respect to the angle orientation. It is also desirable to monitor the tilt of the wafer stage out of the xy plane. For example, such accurate characterization of the slope is required to calculate the Abbe offset error at the x and y positions. Thus, there are up to five degrees of freedom to measure, depending on the desired application. In some applications, it is also desirable to monitor the position of the wafer stage relative to the z-axis to monitor six degrees of freedom.

  To measure each degree of freedom, an interferometer is used to monitor the distance change along the relevant measurement axis. For example, in a system that measures the angular orientation of the stage relative to the x, y, and z axes as well as the x and y position of the stage, at least three spatially separated measurement beams are reflected on one side of the wafer stage, At least two spatially separated measurement beams are reflected on the other side of the wafer stage. See, for example, US Pat. No. 5,801,832 entitled “Method and Apparatus for Repetitively Imaging a Mask Pattern on a Substrate Using Five Measurement Axes”. The contents of this document are hereby incorporated by reference. Each measurement beam is recombined with the reference beam to monitor the change in optical path length along the corresponding measurement axis. Since different measurement beams impinge on the wafer stage at different positions, the angular orientation of the wafer stage can be obtained by an appropriate combination of optical path length measurements. Thus, to monitor each degree of freedom, the system includes at least one measurement beam that impinges on the wafer stage. Further, as described above, since each measurement beam passes through the wafer stage twice, it is possible to prevent degradation of the interference signal due to a change in the angular orientation of the wafer stage. The measurement beam can be generated by a physically independent interferometer or a multi-axis interferometer that generates multiple measurement beams.

  The present invention has no or very small beam misalignment at one or more detectors or fiber optic pickups (FOPs) when measuring a few or more degrees of freedom. And a multi-degree-of-freedom measuring plane mirror interferometer assembly. In certain embodiments of the present invention, the beam misalignment difference between the reference beam and the measurement beam in one or more interferometers of the interferometer assembly is very small. The interferometer assembly can include a single interferometer optical assembly. A two-degree-of-freedom measuring plane mirror interferometer assembly with no or very little beam deviation at one detector or FOP measures two linear displacements at two spaced locations on the plane mirror, or It can be configured to measure both linear and angular displacement of the plane mirror. In one configuration, the difference between the beam deviations of the reference beam and the measurement beam in one of the corresponding interferometers of the configuration is very small.

  Henry A. The technique described herein is further extended using the interferometer configuration disclosed in US patent application 60 / 352,341 filed Jan. 28, 2002 (Z-391) by Hill. Degrees of freedom can be measured and this patent document is incorporated herein by reference. Such an embodiment comprising a three-degree-of-freedom measuring plane mirror interferometer assembly with no or very little beam misalignment at one or more detectors and / or FOPs can be achieved at three spaced locations on the plane mirror. Can be configured to measure one linear displacement and two orthogonal angular displacements of a plane mirror, or to measure two linear displacements and one angular displacement. In some configurations, the difference in beam offset between the reference beam and the measurement beam in one or more of the interferometers in that configuration is very small. Yet another embodiment that includes four or more degrees of freedom measuring plane mirror interferometer assemblies with no or very little beam misalignment at one or more detectors and / or FOPs is another combination of linear displacement and It can be configured to measure angular displacement. In some configurations, the difference in beam offset between the reference beam and the measurement beam in one or more of the interferometers in that configuration is very small.

  A single plane mirror can be used as both a reference object and a measurement object when measuring a change in the posture of the object. The reference beam and measurement beam used for angle measurement form a single path to a single plane mirror. The interferometer optics assembly can include either or both of a linear displacement interferometer and an angular displacement interferometer with a very stable configuration. The interferometer optics assembly can be configured so that there is no or very small beam misalignment between the reference beam component and the measurement beam component at one detector or FOP for the beam used for angle measurement. . The beam deviation of the reference and measurement beams on a single plane mirror is zero for the reference and measurement beams used in the angular displacement interferometer. Two or more linear displacement output beams and angular displacement output beams have a common measurement beam path in the path to a single plane mirror. The interferometer optical assembly is such that the respective reference beam path length and measurement beam path length of the linear displacement interferometer and the angular displacement interferometer are equal in glass and / or equal in gas. Configured.

  In general, in one aspect, the invention features an apparatus that includes a multi-pass interferometer. The multipath interferometer includes a plurality of reflectors that reflect at least two beams along a plurality of paths through the interferometer, the plurality of paths including a first set of paths and a second set of paths. Including passageways. The reflector has a first orientation orthogonal to the direction of the path of the beam reflected by the reflector. The two beams provide information regarding a change in the first position on one of the reflectors after the first set of passages. The two beams provide information regarding the first position change and the second position change on one reflector after the second set of passages. The beam path is deviated between the first set of paths and the second set of paths when at least one of the plurality of reflectors has an orientation other than the first orientation. The interferometer includes a beam after the first set of passages and before the second set of passes so that the shift that occurs between the second set of passes cancels out the shift that occurs between the first set of passes. Including an optical system that changes the orientation of the lens.

Apparatus embodiments can include one or more of the following features.
The optical system is configured to change the direction of the beam while maintaining the magnitude and direction of the deviation between the two beams. The propagation path of one of the two beams after being redirected by the optical system is parallel to the propagation path of the other of the two beams after the first set of paths has ended. . The reflecting plate has a planar reflecting surface. The beam includes a reference beam directed in the direction of one of the plurality of reflectors held in a fixed position relative to the interferometer. The beam includes a measurement beam directed toward one of the plurality of reflectors movable relative to the interferometer. An optical path length difference is defined by the path of the reference beam and the measurement beam, and the change in the optical path length indicates a change in the position of one of the reflectors that can move with respect to the interferometer. The plurality of reflectors include a first reflector and a second reflector, and the beam includes a first beam directed to the first reflector and a second beam directed to the second reflector, Each of the first reflector and the second reflector is movable with respect to the interferometer.

  The optical path length difference is defined by the paths of the first and second beams, and the change in the optical path length difference indicates a change in the relative position of the first and second reflectors. The first set of passages consists of two passages, and between each passage, each of the beams is reflected at least once by one of the reflectors. The second set of passages consists of two passages, and between each passage, each of the beams is reflected at least once by one of the reflectors. The multipath interferometer includes a beam splitter that separates an input beam into beams and directs the beam toward a reflector. The beam splitter includes a polarizing beam splitter. The optical system has an odd number of reflecting surfaces. The normal of the reflecting surface lies in a common plane. The reflective surface includes a planar reflective surface.

  For each beam redirected by the optical system, the beam is reflected by the reflecting surface such that the sum of the angles between the incident beam and the reflected beam on each reflecting surface is zero or an integer multiple of 360 degrees, and the angle Are measured in the direction from the incident beam to the reflected beam, and the angle has a positive value when measured counterclockwise and a negative value when measured clockwise.

  The interferometer combines the beams after the beams have propagated through the first and second sets of paths to form a superimposed beam that exits the interferometer. The optical system is composed of one reflecting surface. The optical system has an even number of reflecting surfaces. The optical system includes a cube corner retroreflector. The interferometer includes a differential plane mirror interferometer. The two beams have different frequencies.

  In general, in another aspect, the invention features a lithography system for use in fabricating an integrated circuit on a wafer. The lithography system includes a detector that is responsive to optical interference between the superimposed beams and generates an interference signal indicative of the optical path length difference between the beam paths. The detector includes a photodetector, an amplifier, and an analog-to-digital converter. The analyzer is connected to the detector and estimates a change in the optical path length difference of the beam based on the interference signal. The irradiation source supplies a beam.

  In general, in another aspect, the invention features a lithography system for use in fabricating an integrated circuit on a wafer. The lithography system includes a stage that supports a wafer, an illumination system that images a spatially patterned irradiation line onto the wafer, a positioning system that adjusts the position of the stage relative to the imaged irradiation line, and One of the interferometer devices. The interferometer apparatus includes an interferometer that measures the position of the stage relative to the patterned radiation.

  In general, in another aspect, the invention features a lithography system for use in fabricating an integrated circuit on a wafer. The lithography system includes a stage that supports a wafer on which an integrated circuit is formed, and an illumination system that includes an illumination source, a mask, a positioning system, a lens assembly, and any of the interferometer devices described above. In the operating state, the irradiation source directs the irradiation beam through the mask to generate a spatially patterned irradiation beam, and the positioning system adjusts the position of the mask relative to the irradiation beam from the irradiation source; The lens assembly images the spatially patterned radiation onto the wafer and monitors the position of the mask relative to the wafer using the interferometer of the interferometer apparatus.

  In general, in another aspect, the invention features a lithography system for use in manufacturing a lithography mask. The lithography system includes an irradiation source that irradiates a writing beam to form a pattern on a lithography mask, a stage that supports the lithography mask, a beam directing assembly that directs the writing beam to the lithography mask, and a stage and beam directing A positioning system for positioning the assemblies relative to each other and any of the interferometer devices described above. The interferometer apparatus includes an interferometer that measures the position of the stage relative to the beam directing assembly.

  The integrated circuit uses any of the lithography systems described above to support the wafer, image a spatially patterned irradiation line on the wafer, and position the stage relative to the imaged irradiation line In this case, an interferometer is used to measure the position of the stage.

  The integrated circuit uses any of the lithographic systems described above to support the wafer and direct the irradiation from the irradiation source through the mask to spatially patterned irradiation onto the wafer. It can be manufactured by generating a line, adjusting the position of the mask relative to the irradiation line from the irradiation source and imaging the spatially patterned irradiation line on the wafer. The position of the mask relative to the wafer is measured using the interferometer of the lithography system.

  The lithographic mask is manufactured by using any of the lithographic systems described above to support the lithographic mask, supply a write beam to the lithographic mask, and position the stage and beam directing assembly relative to each other. Can do. The position of the stage relative to the beam directing assembly is measured using the interferometer of the lithography system.

  In general, in another aspect, the invention features a method that directs a first measurement beam to a first region on a measurement object along a first set of paths through an interferometer. Directing the first reference beam to a reference object along a first set of paths through the interferometer; after the first measurement beam and the first reference beam have finished the first set of paths, the first measurement beam And combining the first reference beam to generate a first output beam, determining a change in position of the first region on the measurement object, and directing a portion of the first measurement beam using an optical system Forming a second measurement beam, directing a portion of the first reference beam using an optical system to form a second reference beam, and passing the second measurement beam through a second set of interferometers. Directing the second area on the object to be measured along the path; Directing the system along the second set of paths through the interferometer to the reference object, after the second measurement beam and the second reference beam have finished the second set of paths, the second measurement beam and the second reference Combining the beams to generate a second output beam, and determining a change in position of the second region on the measurement object. The rotation of the measurement object relative to the direction of the path of the first and second measurement beams incident on the measurement object causes a beam shift in the first measurement beam between the first set of paths, and between the second set of paths. In addition, a beam shift occurs in the second measurement beam. The optical system changes the orientation of a portion of the first measurement output beam and the first reference output beam, so that a shift that occurs in the second measurement beam between the second set of paths is reduced between the first set of paths. It is configured to cancel out the deviation that occurs in one measurement beam.

The method further includes another feature corresponding to any of the features described above in connection with different devices.
In general, in another aspect, the invention features a lithographic method for use in fabricating an integrated circuit on a wafer. This lithographic method supports the wafer on a movable stage, images the spatially patterned radiation on the wafer, and adjusts the position of the stage relative to the imaged radiation. Monitoring the position of the stage relative to the imaged radiation using any of the interferometer operating methods described above.

  In general, in another aspect, the invention features a lithographic method for use in the manufacture of an integrated circuit. The lithography method directs the input radiation through the mask to produce a spatially patterned radiation, positioning the mask with respect to the input radiation, and the position of the mask relative to the input radiation. Monitoring using any of the interferometer operating methods described above, and imaging a spatially patterned illumination line on the wafer.

  In general, in another aspect, the invention features a lithographic method of manufacturing an integrated circuit on a wafer. The lithographic method includes positioning a first component of a lithography system relative to a second component of the lithography system to expose the wafer with spatially patterned irradiation radiation, the first to the second component. Monitoring the position of the component using any of the interferometer operating methods described above.

  In general, in another aspect, the invention features a lithographic method for use in the manufacture of a lithographic mask. This lithographic method involves directing the write beam toward the substrate to form a pattern on the substrate, positioning the substrate relative to the write beam, and positioning the substrate relative to the write beam by any of the interferometer operating methods described above. Including using and monitoring.

  In general, in another aspect, the invention features an apparatus that includes a multi-axis interferometer that measures changes in the position of a measurement object with respect to multiple degrees of freedom. The interferometer receives the input beam and directs the first measurement beam generated from the input beam to form first and second paths to the measurement object in the vicinity of the first point on the measurement object. And then combining the first measurement beam with a first reference beam generated from the input beam to generate a first output beam that includes information regarding the change in distance to the first point on the measurement object. Composed. The interferometer further directs a second measurement beam generated from the input beam to form first and second paths to the measurement object in the vicinity of the second point on the measurement object, and then The second measurement beam is configured to be combined with a second reference beam generated from the input beam to generate a second output beam that includes information regarding a change in distance to a second point on the measurement object. The interferometer comprises a folding optical system arranged to reflect a portion of the first output beam an odd number of times in a plane defined by the incidence of the measurement beam on the measurement object to form a secondary input beam. . The second measurement beam and the second reference beam are generated from the secondary input beam.

Apparatus embodiments can include one or more of the following features.
The interferometer includes a polarizing beam splitter that directs different beams along respective paths of the beam, a first quarter wave plate positioned between the polarizing beam splitter and a reference object, and the polarizing beam splitter and the measurement object. 2nd quarter wave plate located between these. The reference object includes a plane mirror that is oriented substantially perpendicular to the incident beam portion. The folding optical system includes a non-polarizing beam splitter that separates a portion of the first output beam to form a secondary input beam and directs the secondary input beam back to the non-polarizing beam splitter. In addition, it is arranged to generate a second measurement beam and a second reference beam. The folded optical system has a plurality of reflecting surfaces arranged to direct the secondary input beam from the non-polarizing beam splitter to the polarizing beam splitter, and the non-polarizing beam splitter and the plurality of reflecting surfaces have the second input beam The second input beam is reflected an odd number of times before reaching the polarizing beam splitter. The non-polarizing beam splitter reflects the first output beam to generate a secondary input beam, and the plurality of reflecting surfaces reflect the secondary input beam an even number of times. The apparatus includes a first optical fiber pickup that inputs a first output beam to a detector and a second optical fiber pickup that inputs a second output beam to the detector.

  In general, in another aspect, the invention features a lithography system for use in fabricating an integrated circuit on a wafer. The lithography system includes a stage that supports a wafer, an illumination system that images a spatially patterned irradiation line on the wafer, and a positioning system that adjusts the position of the stage relative to the imaged irradiation line. Any of the interferometer devices described above that monitor the position of the wafer relative to the imaged radiation.

  In general, in another aspect, the invention features a lithography system for use in fabricating an integrated circuit on a wafer. The lithography system includes a stage that supports a wafer and an illumination system that includes any of an illumination source, mask, positioning system, lens assembly, and interferometer apparatus described above. In the operating state, the irradiation source directs the irradiation beam through the mask to generate a spatially patterned irradiation beam, and the positioning system adjusts the position of the mask relative to the irradiation beam from the irradiation source; The lens assembly images a spatially patterned illumination line onto the wafer, and the interferometer of the interferometer apparatus monitors the position of the mask relative to the illumination line from the illumination source.

  In general, in another aspect, the invention features a beam writing system for use in fabricating a lithographic mask. The system includes an illumination source that irradiates a writing beam to form a pattern on a substrate, a stage that supports the substrate, a beam directing assembly that supplies the writing beam to the substrate, and the stage and beam directing assembly relative to each other. A positioning system for positioning and any of the interferometer devices described above for monitoring the position of the stage relative to the beam directing assembly.

  Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In the event of a conflict in a published article, patent application, patent and other reference mentioned above that is incorporated into the present disclosure by reference, the present specification, including definitions, will prevail.

  The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

    Like reference symbols in the various drawings indicate like elements.

  Embodiments of the invention comprise an interferometer assembly that includes one or more linear displacement interferometers and one or more angular displacement interferometers. The interferometer assembly can include a single or integrated optical assembly. The linear displacement interferometer includes a double-pass (two-pass) interferometer such as a high stability plane mirror interferometer (HSPMI) or a differential plane mirror interferometer (DPMI). The angular displacement interferometer includes a plane mirror interferometer in which a single plane mirror functions as both the reference beam object and the measurement beam object of the angle measurement interferometer. Embodiments of the interferometer assembly are described in a manner in which the interferometer assembly includes one or more linear displacement interferometers and one or more angular displacement interferometers.

  Referring to FIG. 1, an interferometer assembly 10 includes a high stability plane mirror interferometer (HSPMI) and a four-pass linear displacement interferometer provided in a single assembly. The input beam 14 forms two paths through the first HSPMI to form a pair of overlapping output beams 30. A phase of a part of the output beam 30 is measured to obtain a change in the displacement X1 of the measurement mirror 12 at a certain position. A portion of the output beam 30 is used as an input beam to the second HSPMI to form a 4-pass interferometer. The four-pass interferometer measures the change of the displacement X1 + X2, where X2 is the displacement of the measuring mirror 12 at the second position. The displacements X1 and X2 are used to measure the linear and rotational movement of the mirror 12 relative to the reference point. The reflector assembly 28 (encircled by a broken line) reduces the beam deviation between the measurement beam and the reference beam caused by the tilt of the mirror 12, and thus the change in the displacement X2 can be measured with higher accuracy.

  The input beam 14 is configured to have orthogonal linear polarization components with a frequency difference small enough for heterodyne detection. Polarization beam splitter (PBS) 16 includes a beam separation surface 82 that separates the orthogonal component of input beam 14 into reference beam 20 and measurement beam 18 at point P5. Reference beam 20 and measurement beam 18 form two paths through the interferometer assembly and exit PBS 16 to form exit beam 30.

  The measurement beam 18 (transmitting through the surface 82) is mostly polarized in a direction parallel to the entrance surface. Here, the incident surface is parallel to the paper surface of FIG. The reference beam 20 (reflected by the surface 82) is mostly polarized in a direction perpendicular to the entrance surface.

  The reference beam 20 propagates along a first reference path that collides with the reference mirror 26. The measurement beam 18 propagates along a first measurement path that impacts the measurement mirror 12. Both the reference mirror and the measurement mirror are plane mirrors. In the figure, the beam overlaps the path that the beam propagates, so the beam and path are drawn with the same line. The measurement mirror 12 can be attached to an object (for example, a lithography stage).

  Hereinafter, a path through which these beams propagate after the measurement beam 18 and the reference beam 20 are separated at the point P5 and recombined as the output beam 30 will be described. In the description of FIG. 1, it is assumed that the measurement mirror 12 and the PBS 16 are aligned in the initial state, and the surface of the mirror 12 is arranged to be inclined by 45 degrees with respect to the beam separation surface 82.

  After being reflected by surface 82 at point P5, reference beam 20 forms two paths through interferometer assembly 10 before exiting PBS 16 as a component of output beam 30. During the first path, the reference beam 20 propagates toward the mirror 26, passes through the quarter wave plate 52, and is reflected by the mirror 26 at point P9. The reference beam 26 passes through the quarter-wave plate 52 for the second time, propagates toward the retroreflector 22, and is reflected by the retroreflector 22 at points P13 and P14.

  During the second path, the reference beam 26 propagates toward the mirror 26, passes through the quarter-wave plate 52 for the third time, and is reflected by the mirror 26 at a point P10. The reference beam 26 passes through the quarter-wave plate 52 for the fourth time, propagates toward the surface 82, is reflected by the surface 82 at point P6, and then propagates toward the detector 24 to propagate the output beam 30. Form ingredients.

  After passing through surface 82 at point P5, measurement beam 20 forms two paths through interferometer assembly 10 before exiting PBS 16 as a component of output beam 30. During the first path, the measurement beam 18 propagates towards the mirror 12, passes through the quarter wave plate 54, and is reflected by the mirror 12 at point P1. The measurement beam 18 passes through the quarter-wave plate 54 a second time and is reflected by the surface 82 at point P5. The measurement beam 18 propagates towards the retroreflector 22 and is reflected by the retroreflector 22 at points P13 and P14.

  During the second path, the measurement beam 18 propagates towards the surface 82, is reflected by the surface 82 at point P6, and propagates towards the mirror 12. The measurement beam 18 passes through the quarter-wave plate 54 for the third time and is reflected by the mirror 12 at the point P2. The measurement beam 18 passes through the quarter-wave plate 54 for the fourth time, passes through the surface 82 at point P6, and then propagates toward the detector 24 to become a component of the output beam 30.

The measurement beam 18 and the reference beam 20 form an output beam 30 that overlaps after exiting the PBS 16 and propagates toward the detector 24. The non-polarizing beam splitter 36 splits the beam 30 into a beam 32 and a beam 34. Beam 32 passes through polarizer 62 and is detected by detector 24. When the measurement mirror 12 moves from the position 38 to another position 40, the optical path length difference between the first reference path and the first measurement path changes, and the superimposed exit beam 32 detected by the detector 24 changes. Appears as a change in interference. The analyzer then calculates the physical change at position Δ ₁ based on the change in optical path length difference. Δ ₁ represents the average position change of points P 1 and P 2 on mirror 12 relative to PBS 16.

  Beam splitter 36 is part of reflector assembly 28 that receives beam 30 and redirects a portion of beam 30 to become beam 42. The beam 42 becomes an input beam of the second HSPMI. The beam 42 is separated into a reference beam 44 and a measurement beam 46 by a beam separation surface 82 at a point P7. The reference beam 44 propagates along a second reference path that impacts the reference mirror 26, and the measurement beam 46 propagates along a second measurement path that impacts the measurement mirror 12. Hereinafter, a path through which the measurement beam 46 and the reference beam 44 propagate until the measurement beam 46 and the reference beam 44 are separated at the point P7 and recombined as the output beam 48 will be described.

  After being reflected by surface 82 at point P7, reference beam 44 forms two further paths through interferometer assembly 10 before leaving PBS 16 as a component of output beam 48. During the third path, the reference beam 44 propagates towards the mirror 26, passes through the quarter wave plate 52, and is reflected by the mirror 26 at point P12. The reference beam 44 passes through the quarter-wave plate 52 for the second time, propagates toward the retroreflector 22, and is reflected by the retroreflector 56 at points P16 and P15.

  During the fourth path, the reference beam 44 propagates toward the mirror 26, passes through the quarter-wave plate 52 for the third time, and is reflected by the mirror 26 at point P11. The reference beam 44 passes through the quarter-wave plate 52 for the fourth time, propagates toward the surface 82, is reflected by the surface 82 at point P8, then propagates toward the detector 50, and the output beam 48 Of ingredients.

  After passing through surface 82 at point P7, measurement beam 46 forms two additional paths through interferometer assembly 10 before exiting PBS 16 as a component of output beam 48. During the third path, the measurement beam 46 propagates towards the mirror 12, passes through the quarter wave plate 54, and is reflected by the mirror 12 at point P4. The measurement beam 18 passes through the quarter-wave plate 54 for the second time and is reflected by the surface 82 at point P7. The measurement beam 18 propagates towards the retroreflector 56 and is reflected by the retroreflector 56 at points P16 and P15.

  During the fourth path, the measurement beam 18 propagates towards the surface 82, is reflected by the surface 82 at point P8, and propagates towards the mirror 12. The measurement beam 18 passes through the quarter-wave plate 54 for the third time, and is reflected by the mirror 12 at the point P3. The measurement beam 18 passes through the quarter-wave plate 54 for the fourth time, passes through the surface 82 at point P8, then propagates toward the detector 50, and becomes a component of the output beam 48.

The measurement beam 46 and the reference beam 44 form a second HSPMI superimposed output beam 48 after leaving the PBS 16, which propagates toward the detector 50. Beam 48 passes through polarizer 64 and is detected by detector 50. When the measurement mirror 12 moves from position 38 to position 40 (in addition to the change in optical path length difference between the first reference path and the first measurement path), the optical path between the second reference path and the second measurement path. The length difference changes and appears as a change in interference of the superimposed exit beam 48 detected by the detector 50. Next, the analyzer calculates a physical change of Δ = Δ ₁ + Δ ₂ based on the change in the optical path length difference. The change in position Δ ₂ is obtained by subtracting Δ ₁ from Δ. Δ ₂ represents the average position change of points P3 and P4 on mirror 12 relative to PBS 16.

By measuring Δ ₁ and Δ ₂ and calculating (Δ ₁ + Δ ₂ ) / 2, the average linear movement of the mirror 12 relative to the PBS 16 can be determined. (Δ ₁ -Δ ₂₎ can also be determined rotational movement by computing, the (Δ ₁ -Δ ₂₎ is divided by the distance between the midpoint of the midpoint of the P1 and P2 and P3 and P4 Then, it becomes substantially equal to the rotation angle of the mirror 12 with respect to the PBS 16.

  As shown in FIG. 2, when the mirror 12 rotates from position 58 to another position 60, a relative deviation δ1 occurs between the two components of the output beam 32 (measurement beam 18 and reference beam 20). The reflector assembly 28 changes the direction of the beam 34 to form the beam 42. A relative shift δ2 occurs between the two components of the beam 42 (which later become beams 44 and 46). The reflector assembly 28 is configured such that the relative deviation δ2 is substantially the same as the relative deviation δ1. The direction of deviation between the reference beam of the beam 42 and the measurement beam is also substantially the same as the direction between the reference beam of the beam 42 and the measurement beam.

  After passing through point P7, the measurement beam 46 forms two third and fourth passages through the PBS 16. If the deviation between the measurement beam 46 and the ideal measurement path (the path through which the measurement beam propagates when the mirror 12 is at position 58) is tracked, the deviation produced between the first and second paths is the measurement beam. Is offset in forming the third and fourth passages through the interferometer system 10.

  An advantage of using the interferometer system 10 is that when the mirror 12 is tilted, the relative beam shift (or beam shift difference) of the component of the output beam 48 from the second HSPMI is zero. The overall relative beam shift of the component of the output beam 48 from the second HSPMI (relative to the beam path of interest when the mirror 12 is not tilted) is also zero. The two components constituting the output beam 30 in the first HSPMI are parallel. The two components that make up the output beam 48 in the second HSPMI are also parallel.

  Hereinafter, the configuration of the reflector assembly 28 will be described. In addition to the beam splitter 36, the reflector assembly 28 includes reflectors 66 and 68. The beam splitter 36 and the reflectors 66 and 68 can be arranged in several different configurations. 3 and 4 show examples of configurations suitable for the reflector assembly 28. FIG. The beam splitter 36 and the reflectors 66 and 68 are arranged so that the sum of the angles between the incident beam and the reflected beam is zero or an integral multiple of 360 degrees.

  For example, the beam 30 is reflected by the beam splitter 36 to become the beam 34, the beam 34 is reflected by the reflecting plate 66 to become the beam 70, and the beam 70 is reflected by the reflecting plate 68 to become the beam 42. In FIG. 2, angle α has a negative value (representing a clockwise direction from beam 30 to beam 34), and angle β has a positive value (counterclockwise direction from beam 34 to beam 70). The angle γ has a positive value. The beam splitter 36 and the reflection plates 66 and 68 are arranged so that α + β + γ = 0.

  In FIG. 3, the angles α, β and γ have negative values (representing a clockwise rotation from the incident beam to the reflected beam of the mirror). The beam splitter 36 and the reflection plates 66 and 68 are arranged so that α + β + γ = 360 degrees. The mirrors can be arranged in different configurations as long as the sum of the angles α, β and γ is zero or 360 degrees.

  3 and 4, the beam splitter and the reflector have normals that lie in a common plane (the plane of FIGS. 3 and 4). In general, the normals of the beam splitter and reflector are not in a common plane, but the reflector assembly can be designed to compensate for the deviation caused by the tilt of the measurement mirror. For example, in FIG. 5, reflector assembly 80 includes a mirror beam splitter 36, reflectors 66, 68, and a cube corner retroreflector 72 having a total of six reflective surfaces (the normal of the reflective surface of the retroreflector). Are not in a common plane).

  Beam splitter 36 and reflectors 66, 68 are such that beam 74 (formed after reflection by beam splitter 36 and reflectors 66, 68) is parallel to beam 30 and both beams 30 and 74 are in the same direction. Arranged to propagate. The retroreflector 72 changes the direction of the beam 74 into the beam 42. Beam 42 is parallel to beam 30 but propagates in the opposite direction. Since the reflector assembly 80 has the same conversion characteristics as the reflector assembly 28 of FIG. 3 or 4, the magnitude and direction of the beam deviation of the beam 42 is the same as the magnitude and direction of the beam deviation of the beam 30.

  In the example shown in FIGS. 1-4, the reflector assembly 28 includes three planar reflective surfaces (one in the beam splitter 36 and two in the reflectors 66 and 68). In other examples, another odd number (greater than 3) of planar reflectors can be used. Due to the odd number of reflections by the beam splitter and reflector having a normal in the common plane, the direction and magnitude of the deviation between the incident beams on the reflector assembly caused by the tilt of the measuring mirror is reflected by the reflector assembly. It becomes the same as the direction and size of the deviation between the beams.

  The reflector assembly shown in FIGS. 1-5 compensates for beam misalignment caused by any rotation of the measurement mirror, ie, rotation about one of two axes that are orthogonal to each other and orthogonal to the normal of the measurement mirror. can do. Regardless of the magnitude and direction of the deviation due to the tilt of the measurement mirror, the deviation that occurs in the measurement beam between the first and second paths is offset by the deviation that occurs in the measurement beam between the third and fourth paths. Will be.

  Variations of the interferometer system described above include an interferometer system that measures more than two degrees of freedom by including an additional linear displacement interferometer and an angular displacement interferometer within the interferometer assembly or a single interferometer assembly. In this configuration of the interferometer system, the output beam of the additional interferometer nulls or reduces the beam offset difference at each detector / FOP. Variations of the interferometer system can include one or more dynamic elements to compensate for any tilt at the measurement object. For example, dynamic elements can be employed to input the output beam (s) from the interferometer to the detector. The dynamic element can compensate for any changes in the overall propagation direction of the output beam caused by changes in the angular orientation of the measurement object. Such dynamic elements are disclosed in US Pat. No. 6,271,923 and US Pat. No. 6,313,918 owned by the applicant with the present application, the contents of which are hereby incorporated by reference. Quoted by reference in

  Note that in any of the interferometer systems described above, the planar mirror reference object can be integrated with the interferometer assembly. Alternatively, the plane mirror reference object can be part of the second measurement object, as in a differential plane mirror interferometer. In such an embodiment, the interferometer can include additional optics that couple the beam to a reference mirror on the second measurement object.

  The above-described interferometer system allows very high accuracy measurements. Such a system is particularly useful in lithographic applications for use in large scale integrated circuits such as computer chips. Lithography is a very important technology driver for the semiconductor manufacturing industry. Improvement in superposition is one of the five most difficult challenges to achieve line widths below 100 nm line width (design rules), see, eg, Semiconductor Industry Roadmap, p82 (1997).

  The overlay is directly dependent on the performance, i.e. accuracy and accuracy, of the distance measuring interferometer used to position the wafer stage and reticle (or mask) stage. Since the lithographic tool can produce $ 50-100 million per year, the economic benefits of distance-measuring interferometers with improved performance are enormous. For every 1% increase in lithographic tool yield, there is an economic benefit of approximately $ 1 million per year for integrated circuit manufacturers, with significant benefits comparable to lithographic tool vendors.

  The function of the lithography tool is to direct spatially patterned radiation to a wafer covered with photoresist. In this process, it is determined which position on the wafer receives the irradiation (alignment) and the irradiation is applied to the photoresist at that position (exposure).

  In order to properly position the wafer, the wafer includes alignment marks on the wafer, which are measured by dedicated sensors. The position of the wafer in the tool is determined by the measured position of the alignment mark. This information is used in conjunction with specifications for patterning the wafer surface into the desired shape to align the wafer with the spatially patterned radiation. Based on such information, a movable stage that supports the wafer covered with photoresist moves the wafer so that the correct position of the wafer is exposed by the radiation.

  During exposure, the illumination source illuminates the patterned reticle, which scatters the radiation to produce a spatially patterned radiation. A reticle is also referred to as a mask, and these terms are used interchangeably below. In the case of reduction lithography, a reduction lens collects scattered radiation and forms a reduced image of the reticle pattern. Alternatively, in the case of proximity transfer, the scattered radiation propagates a short distance (typically on the order of micrometers) before reaching the wafer to produce a 1: 1 image of the reticle pattern. Irradiation initiates a photo-chemical process in the resist, which converts the radiation pattern into a latent image in the resist.

  The interferometer system is an important element of a positioning mechanism that controls the position of the wafer and reticle and transfers the reticle image to the wafer. When such an interferometer system includes the above-described features, the accuracy of the distance measured by the system is improved as the influence of the periodic error on the distance measurement is minimized.

  In general, a lithography system, also referred to as an exposure system, typically includes an illumination system and a wafer positioning system. An irradiation system includes an irradiation source that supplies an irradiation line such as ultraviolet light, visible light, x-ray, electron beam, or ion irradiation line, and a reticle that generates a spatially patterned irradiation line by applying a pattern to the irradiation line. Or include a mask. For reduced lithography, the illumination system can also include a lens assembly that images a spatially patterned illumination line onto the wafer. The resist on the wafer is exposed by the imaged irradiation beam. The illumination system also includes a mask stage that supports the mask, and a positioning system that adjusts the position of the mask stage relative to the radiation directed through the mask. The wafer positioning system includes a wafer stage that supports the wafer and a positioning system that adjusts the position of the wafer stage relative to the imaged irradiation line. Integrated circuit manufacturing involves a number of exposure steps. As a general reference for lithography, see, for example, J. Org. R Sheets and B.R. W. See Microlithography by Smith: Science and Technology (Marcel Dekker, Inc., New York, 1998). The contents of this reference are incorporated herein by reference.

  The interferometer system described above can be used to accurately measure the position of the wafer stage and mask stage relative to other elements of the exposure system such as a lens assembly, radiation source or support structure. In such a case, the interferometer system can be attached to a fixed structure and the measurement object can be attached to a movable element such as one of a mask stage and a wafer stage. Alternatively, the arrangement can be reversed and the interferometer system can be attached to a movable object and the measurement object can be attached to a stationary object.

  In general, such an interferometer system can also be used to measure the position of any one element of the exposure system relative to any other element of the exposure system, in which case the interferometer system comprises the elements and It is attached or supported on one of the measurement objects, or is attached or supported on the other of the elements.

  An example of a lithography scanner 1100 that uses an interferometer system 1126 is shown in FIG. An interferometer system is used to accurately measure the position of a wafer (not shown) within the exposure system. Here, the stage 1122 is used to place and support the wafer relative to the exposure station. The scanner 1100 includes a frame 1102, which mounts other support structures and various elements mounted on these structures. The exposure base 1104 has a lens housing 1106 mounted on the top, a reticle or mask stage 1116 mounted on the top of the housing, and this stage is used to support the reticle or mask. A positioning system for positioning the mask relative to the exposure station is shown schematically as element 1117. The positioning system 1117 can include, for example, a piezoelectric transducer and corresponding control electronics. Although not included in the embodiments described herein, it is necessary to use one or more of the interferometer systems described above to monitor the position with high accuracy in the manufacturing process of a lithographic structure, as well as the mask stage. It is also possible to accurately measure the position of certain other movable elements (see Microlithography by Sciences and Science: Science and Technology above).

  Extending below the exposure base 1104 is a support base 1113, on which the wafer stage 1122 is mounted. Stage 1122 includes a plane mirror 1128 that reflects a measurement beam 1154 directed to the stage by an interferometer system 1126. A positioning system that positions stage 1122 relative to interferometer system 1126 is shown schematically as element 1119. The positioning system 1119 can include, for example, a piezoelectric transducer and corresponding control electronics. The measurement beam is reflected back to the interferometer system mounted on the exposure base 1104. The interferometer system can be any of the previously described embodiments.

  In operation, an illumination beam 1110, for example, an ultraviolet (UV) beam from a UV laser (not shown) passes through the beam shaping optical assembly 1112 and propagates downward after being reflected by the mirror 1114. Thereafter, the irradiation beam passes through a mask (not shown) mounted on the mask stage 1116. A mask (not shown) is imaged onto a wafer (not shown) on wafer stage 1122 through lens assembly 1108 housed in lens housing 1106. Base 1104 and the various elements it supports are separated from ambient vibrations by a vibration damping system, shown as spring 1120.

  In other embodiments of a lithographic scanner, one or more of the previously described interferometer systems may be used to limit distances along multiple axes, such as, but not limited to, a wafer stage and a reticle (or mask) stage. The angle with respect to can be measured. In addition, the wafer can be exposed using another beam instead of the UV laser beam. Examples of these beams include an x-ray beam, an electron beam, an ion beam, and a visible light beam.

  In some embodiments, the lithographic scanner can include what is known in the art as a column reference. In such an embodiment, the interferometer system 1126 directs a reference beam (not shown) along an external reference path to impinge on a reference mirror (not shown), which is a structure such as a lens. Attached to housing 1106 directs the illumination beam. The reference mirror reflects the reference beam back to the interferometer system. The interference signal generated by the interferometer system 1126 when combining the measurement beam 1154 reflected by the stage 1122 and the reference beam reflected by the reference mirror mounted on the lens housing 1106 is the position of the stage relative to the irradiation beam. Showing change. In other embodiments, the interferometer system 1126 can also be arranged to measure changes in the position of the reticle (or mask) stage 1116 or other movable element of the scanner system. Finally, the interferometer system can be used in a manner similar to a lithography system that includes a stepper in addition to or instead of a scanner.

  As is well known, lithography is an important part of a manufacturing method for making semiconductor devices. For example, US Pat. No. 5,483,343 outlines the steps of such a manufacturing method. These steps are described below with respect to FIGS. FIG. 7 is a flow chart of an order of manufacturing a semiconductor device such as a semiconductor chip (IC or LSI), a liquid crystal panel, or a CCD. Step 1151 is a design process for designing a circuit of the semiconductor device. Step 1152 is a mask manufacturing process based on 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 called a preliminary process, in which a circuit is formed on the wafer by lithography using the prepared mask and wafer. In order to form on the wafer a circuit corresponding to the circuit pattern on the mask with sufficient spatial resolution, positioning of the lithography tool relative to the wafer by interference spectroscopy is required. The interferometry and systems described herein can be particularly useful to improve the effectiveness of lithography used in wafer processes.

  Step 1155 is an assembly step called a post-process in which the wafer processed in step 1154 is formed on a semiconductor chip. This process includes assembly (square cutting and bonding) and mounting (chip sealing). Step 1156 is an inspection step, in which an inspection of the operability of the semiconductor device created in Step 1155, an inspection of durability, and the like are performed. Through these processes, the semiconductor device is completed and shipped (step 1157).

  FIG. 8 is a flowchart showing details of the wafer process. Step 1161 is an oxidation process for oxidizing the surface of the wafer. Step 1162 is a CVD process for forming an insulating film on the wafer surface. Step 1163 is an electrode formation process for forming electrodes on the wafer by vapor deposition. Step 1164 is an implantation process for implanting ions into the wafer. Step 1165 is a resist process for adding a resist (photosensitive material) to the wafer. Step 1166 is an exposure process in which the circuit pattern of the mask is printed on the wafer by the exposure apparatus described above by exposure (ie, lithography). Again, as described above, the accuracy and resolution of such a lithography process is improved by using the interferometer systems and methods described herein.

  Step 1167 is a growth process for growing the exposed wafer. Step 1168 is an etching process for removing portions other than the grown resist image. Step 1169 is a resist separation process for separating the resist material remaining on the wafer after the etching process. By repeating these processes, a circuit pattern is formed and superimposed on the wafer.

  The interferometer system described above can also be used in other applications where it is necessary to accurately measure the relative position of an object. For example, in applications where a writing beam, such as a laser, x-ray, ion, or electron beam, marks a pattern on a substrate as the substrate or beam moves, an interferometer system is used to write to the substrate. It is possible to measure the relative motion with the beam.

  As an example, a beam writing system 1200 is schematically illustrated in FIG. Source 1210 generates a write beam 1212. Beam focusing component 1214 directs the radiation beam toward substrate 1216 supported by movable stage 1218. To determine the relative position of the stage, interferometer system 1220 directs reference beam 1222 to mirror 1224 mounted on beam focusing component 1214 and measurement beam 1226 to mirror 1228 mounted on stage 1218. Turn. The beam writing system is an example of a system that uses a column reference because the reference beam contacts a mirror mounted on the beam focusing component. Interferometer system 1220 can be any of the previously described interferometer systems. The change in position measured by the interferometer system corresponds to a change in the relative position of the writing beam 1212 on the substrate 1216. Interferometer system 1220 transmits a measurement signal 1232 representing the relative position of write beam 1212 on substrate 1216 to controller 1230. The controller 1230 sends an output signal 1234 to the base 1236 that supports and positions the stage 1218. Further, to change the intensity of the writing beam 1212 such that the writing beam contacts the substrate 1216 with sufficient intensity to cause photophysical or photochemical changes only at selected locations of the substrate, or To block 1212, the controller 1230 sends a signal 1238 to the source 1210.

  Further, in some examples, the controller 1230 can cause the beam focusing component 1214 to scan the writing beam over the area of the substrate using, for example, the signal 1244. As a result, the controller 1230 guides other elements of the system to pattern the substrate. Patterning is usually based on electronic design patterns stored in the controller. In some applications, the write beam patterns the resist coated on the substrate, and in other applications, the write beam patterns directly, such as etching the substrate.

  An important field of application of such systems is the manufacture of masks and reticles used in previously described lithographic methods. For example, a chromium-coated glass substrate can be patterned using an electron beam to produce a lithographic mask. In cases where the writing beam is an electron beam, the beam writing system encapsulates the electron beam path in a vacuum. Also, when the writing beam is an electron beam or ion beam, the beam focusing component includes an electric field generating device such as a quadrupole lens for focusing and directing charged particles onto the substrate under vacuum. In other cases where the writing beam is a radiation beam, such as x-ray, UV, or visible radiation, the beam focusing component includes corresponding optics for focusing and directing the radiation onto the substrate.

  While various embodiments have been described above, various changes may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the claims.

It is a figure which shows an interferometer system. It is a figure which shows an interferometer system. It is a figure which shows a reflecting plate assembly. It is a figure which shows a reflecting plate assembly. It is a figure which shows a reflecting plate assembly. 1 is a schematic diagram of a lithography system used to manufacture an integrated circuit. FIG. It is a flowchart showing the manufacturing process of an integrated circuit. It is a flowchart showing the manufacturing process of an integrated circuit. It is a schematic diagram of a beam writing system.

Claims (52)

A device,
With a multipath interferometer,
The multipath interferometer includes a plurality of reflectors and an optical system,
The plurality of reflectors reflect at least two beams along a plurality of paths through the interferometer, the plurality of paths including a first set of paths and a second set of paths, the reflector being , Having a first orientation orthogonal to the direction of the path of the beam reflected by the reflector;
The two beams provide information regarding a change in a first position on one of the plurality of reflectors after the first set of passages;
The two beams provide information on the change in the first position and the change in the second position on the one reflector after the second set of passages;
The path of the beam is between the first set of paths and between the second set of paths when at least one of the plurality of reflectors has an orientation other than the first orientation. Slipped between,
The optical system is arranged after the first set of passages and the second set of passages such that a deviation occurring between the second set of passages cancels a deviation produced between the first set of passages. A device that changes the direction of the beam in front of. The apparatus of claim 1, wherein the optical system is configured to change the orientation of the beam while maintaining the magnitude and direction of the deviation between the two beams. The propagation path of one of the two beams after being redirected by the optical system is the propagation path of the other of the two beams after the first set of paths is finished. The apparatus of claim 1, wherein the apparatus is parallel to The apparatus according to claim 1, wherein the reflecting plate has a planar reflecting surface. The apparatus of claim 1, wherein the beam comprises a reference beam directed toward one of the plurality of reflectors held in a fixed position relative to the interferometer. The apparatus of claim 5, wherein the beam comprises a measurement beam that is directed toward one of the plurality of reflectors that is movable relative to the interferometer. An optical path length difference is defined by a path of the reference beam and the measurement beam, and a change in the optical path length difference is a position of the one reflector among the plurality of reflectors movable with respect to the interferometer. The apparatus of claim 6, wherein the apparatus exhibits a change in The plurality of reflectors include a first reflector and a second reflector, and the beam is directed to the first reflector and the second beam is directed to the second reflector. The apparatus of claim 1, wherein each of the first reflector and the second reflector is movable relative to the interferometer. The apparatus according to claim 8, wherein an optical path length difference is defined by a path of the first and second beams, and a change in the optical path length difference indicates a change in a relative position of the first and second reflectors. 2. The first set of passages according to claim 1, wherein the first set of passages includes two passages, and each of the beams is reflected at least once by one of the plurality of reflection plates between the passages. apparatus. 11. The apparatus of claim 10, wherein the second set of passages comprises two passages, and each of the beams is reflected at least once by a reflector of the plurality of reflectors between each passage. . The apparatus of claim 1, wherein the multipath interferometer comprises a beam splitter that splits an input beam into the beam and directs the beam toward the reflector. The apparatus of claim 12, wherein the beam splitter comprises a polarizing beam splitter. The apparatus of claim 1, wherein the optical system has an odd number of reflective surfaces. The apparatus of claim 14, wherein the normal of the reflective surface is in a common plane. The apparatus of claim 14, wherein the reflective surface comprises a planar reflective surface. For each beam redirected by the optical system, the beam is reflected by the reflecting surface such that the sum of the angles between the incident and reflected beams on each reflecting surface is zero or an integer multiple of 360 degrees. The angle is measured in a direction from the incident beam to the reflected beam, the angle having a positive value when measured counterclockwise and a negative value when measured clockwise. 15. The apparatus of claim 14, comprising: The apparatus of claim 1, wherein the interferometer combines the beams after the beams propagate through the first and second sets of paths to form a superimposed beam exiting the interferometer. The apparatus of claim 18, further comprising a detector that is responsive to optical interference between the superimposed beams and generates an interference signal indicative of an optical path length difference between the paths of the beams. The apparatus of claim 19, wherein the detector comprises a photodetector, an amplifier, and an analog to digital converter. 21. The apparatus of claim 20, further comprising an analyzer connected to the detector and estimating a change in optical path length difference of the beam based on the interference signal. The apparatus according to claim 1, wherein the optical system includes a single reflecting surface. The apparatus of claim 1, wherein the optical system has an even number of reflective surfaces. 24. The apparatus of claim 23, wherein the optical system comprises a cube corner retroreflector. The apparatus of claim 1, further comprising an illumination source that provides the beam. The apparatus of claim 1, wherein the interferometer comprises a differential plane mirror interferometer. The apparatus of claim 1, wherein the two beams have different frequencies. A lithography system for use in manufacturing an integrated circuit on a wafer comprising:
A stage for supporting the wafer;
An illumination system that images a spatially patterned radiation onto the wafer;
A positioning system for adjusting the position of the stage with respect to the imaged irradiation line;
A lithography system comprising: an apparatus according to claim 1 for monitoring the position of the stage relative to the imaged irradiation line. A lithography system for use in manufacturing an integrated circuit on a wafer comprising:
A stage for supporting the wafer;
An illumination source comprising an illumination source, a mask, a positioning system, a lens assembly, and an apparatus according to claim 1;
In an operating state, the irradiation source directs the irradiation line through the mask to generate a spatially patterned irradiation line, and the positioning system includes the mask for the irradiation line from the irradiation source. A lithographic system, wherein the lens assembly images the spatially patterned radiation on the wafer, and the interferometer measures the position of the mask relative to the wafer. A lithography system for use in manufacturing a lithography mask, comprising:
An irradiation source for irradiating a writing beam to form a pattern on the lithography mask;
A stage for supporting the lithography mask;
A beam directing assembly that directs the writing beam to the lithography mask;
A positioning system for positioning the stage and beam directing assembly relative to each other;
An apparatus according to claim 1, wherein the apparatus monitors the position of the stage relative to the beam directing assembly. A method for manufacturing an integrated circuit, comprising:
29. A lithography system according to claim 28, wherein a wafer is supported, a spatially patterned irradiation line is imaged on the wafer, and the position of the stage relative to the imaged irradiation line is adjusted. Monitoring the position of the stage relative to the radiation imaged using the interferometer. A method for manufacturing an integrated circuit, comprising:
30. A lithographic system according to claim 29, wherein a wafer is supported, and radiation from the radiation source is directed through a mask to produce a spatially patterned radiation on the wafer. Adjusting the position of the mask relative to the radiation from the radiation source, imaging the spatially patterned radiation on the wafer, and using the interferometer, the mask relative to the wafer A method comprising monitoring the position of the. A method for manufacturing a lithography mask, comprising:
A lithographic system according to claim 30, wherein the lithographic mask is supported, a writing beam is supplied to the lithographic mask, the stage and beam directing assembly are positioned relative to each other, and the interferometer is used to Measuring the position of the stage relative to a beam directing assembly. A method,
Directing the first measurement beam to a first region on the measurement object along a first set of paths through the interferometer;
Directing a first reference beam to a reference object along a first set of paths through the interferometer;
Combining the first measurement beam and the first reference beam to generate a first output beam after the first measurement beam and the first reference beam have finished the first set of paths;
Determining a change in the position of the first region on the measurement object;
Directing a portion of the first measurement beam using an optical system to form a second measurement beam;
Directing a portion of the first reference beam using the optical system to form a second reference beam;
Directing the second measurement beam to a second region on the measurement object along a second set of passages through the interferometer;
Directing the second reference beam to the reference object along a second set of paths through the interferometer;
Combining the second measurement beam and the second reference beam to generate a second output beam after the second measurement beam and the second reference beam have finished the second set of paths;
Determining a change in position of the second region on the measurement object;
The rotation of the measurement object relative to the direction of the path of the first and second measurement beams incident on the measurement object causes a beam shift in the first measurement beam between the first set of paths, and A beam shift occurs in the second measurement beam between two sets of passages,
The optical system changes a direction of a part of the first measurement output beam and the first reference output beam, and a deviation generated in the second measurement beam between the second set of passages is changed in the first set. A method configured to offset a deviation caused in the first measurement beam during a passage. A lithographic method used in the manufacture of integrated circuits on a wafer, comprising:
Supporting the wafer on a movable stage;
Imaging a spatially patterned radiation on the wafer;
Adjusting the position of the stage relative to the imaged irradiation line;
35. A lithographic method comprising monitoring the position of the stage relative to the imaged irradiation line using the method of claim 34. A lithography method used in the manufacture of integrated circuits, comprising:
Directing the input radiation through the mask to produce a spatially patterned radiation,
Positioning the mask with respect to the input radiation;
Monitoring the position of the mask relative to the input radiation using the method of claim 34;
Lithographic method comprising imaging the spatially patterned radiation on a wafer. A lithographic method for manufacturing an integrated circuit on a wafer, comprising:
Positioning the first component of the lithography system relative to the second component of the lithography system and exposing the wafer with spatially patterned radiation;
35. A lithographic method comprising monitoring the position of the first component relative to the second component using the method of claim 34. An integrated circuit manufacturing method comprising the lithography method according to claim 34. 36. A method of manufacturing an integrated circuit comprising the lithography method according to claim 35. An integrated circuit manufacturing method comprising the lithography method according to claim 36. 38. A method of manufacturing an integrated circuit comprising the lithography method according to claim 37. A method for manufacturing a lithography mask, comprising:
Directing a writing beam toward the substrate to form a pattern on the substrate;
Positioning the substrate relative to the writing beam;
35. A method comprising monitoring the position of the substrate relative to the writing beam using the method of claim 34. A device,
A multi-axis interferometer that measures changes in the position of the measurement object with respect to multiple degrees of freedom
The interferometer receives an input beam and generates a first measurement beam generated from the input beam so as to form first and second paths to the measurement object with respect to a first point on the measurement object. And then combining the first measurement beam with a first reference beam generated from the input beam to include a first output that includes information regarding a change in distance to the first point on the measurement object. Configured to generate a beam,
The interferometer further directs a second measurement beam generated from the input beam so as to form first and second paths to the measurement object with respect to a second point on the measurement object, and And combining the second measurement beam with a second reference beam generated from the input beam to generate a second output beam including information relating to a change in distance to the second point on the measurement object. Composed of
The interferometer is a folded optical element arranged to reflect a part of the first output beam an odd number of times within a plane defined by the incidence of the measurement beam on the measurement object to form a secondary input beam. Equipped with a system,
The apparatus, wherein the second measurement beam and the second reference beam are generated from the secondary input beam. The interferometer includes a polarizing beam splitter that directs different beams along their respective paths, a first quarter-wave plate positioned between the polarizing beam splitter and a reference object, and the polarizing beam. 44. The apparatus of claim 43, comprising a second quarter wave plate located between a splitter and the measurement object. 45. The apparatus of claim 44, wherein the reference object comprises a plane mirror oriented substantially perpendicular to the incident beam portion. The folding optical system includes a non-polarizing beam splitter, and the non-polarizing beam splitter separates a part of the first output beam to form the auxiliary input beam, and the auxiliary input beam is converted into the non-polarizing beam splitter. 45. The apparatus of claim 44, wherein the apparatus is arranged to direct back to generate the second measurement beam and the second reference beam. The folding optical system has a plurality of reflecting surfaces arranged to direct the secondary input beam from the non-polarizing beam splitter to the polarizing beam splitter, and the non-polarizing beam splitter and the plurality of reflecting surfaces are 47. The apparatus of claim 46, wherein the second input beam reflects the second input beam an odd number of times before reaching the polarizing beam splitter. 48. The apparatus of claim 47, wherein the non-polarizing beam splitter reflects the first output beam to generate the secondary input beam, and the plurality of reflective surfaces reflect the secondary input beam an even number of times. 44. The apparatus of claim 43, further comprising: a first optical fiber pickup that inputs the first output beam to a detector; and a second optical fiber pickup that inputs the second output beam to the detector. A lithography system for use in manufacturing an integrated circuit on a wafer comprising:
A stage for supporting the wafer;
An illumination system that images a spatially patterned radiation onto the wafer;
A positioning system for adjusting the position of the stage with respect to the imaged irradiation line;
44. An apparatus according to claim 43, wherein the apparatus monitors the position of the wafer relative to the imaged radiation. A lithography system for use in manufacturing an integrated circuit on a wafer comprising:
A stage for supporting the wafer;
An illumination source comprising an illumination source, a mask, a positioning system, a lens assembly, and an apparatus according to claim 43;
In an operating state, the irradiation source directs the irradiation line through the mask to generate a spatially patterned irradiation line, and the positioning system includes the mask for the irradiation line from the irradiation source. The lens assembly images the spatially patterned radiation on the wafer, and the interferometer determines the position of the mask relative to the radiation from the illumination source. Lithography system to monitor. A beam writing system for use in manufacturing a lithographic mask, comprising:
An irradiation source for irradiating a writing beam to form a pattern on the substrate;
A stage for supporting the substrate;
A beam directing assembly for supplying the writing beam to the substrate;
A positioning system for positioning the stage and beam directing assembly relative to each other;
45. A beam writing system comprising: an apparatus for monitoring the position of the stage relative to the beam directing assembly.

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