WO2021228723A1 - Procédé de mesure par interférométrie d'une forme d'une surface - Google Patents

Procédé de mesure par interférométrie d'une forme d'une surface Download PDF

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Publication number
WO2021228723A1
WO2021228723A1 PCT/EP2021/062216 EP2021062216W WO2021228723A1 WO 2021228723 A1 WO2021228723 A1 WO 2021228723A1 EP 2021062216 W EP2021062216 W EP 2021062216W WO 2021228723 A1 WO2021228723 A1 WO 2021228723A1
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WO
WIPO (PCT)
Prior art keywords
calibration
wave
sphere
waves
test
Prior art date
Application number
PCT/EP2021/062216
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German (de)
English (en)
Inventor
Sebastian Fuchs
Jochen Hetzler
Hans Michael STIEPAN
Original Assignee
Carl Zeiss Smt Gmbh
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Publication of WO2021228723A1 publication Critical patent/WO2021228723A1/fr

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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
    • G01B9/02034—Interferometers characterised by particularly shaped beams or wavefronts
    • G01B9/02038—Shaping the wavefront, e.g. generating a spherical wavefront
    • G01B9/02039—Shaping the wavefront, e.g. generating a spherical wavefront by matching the wavefront with a particular object surface shape
    • 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
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
    • 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
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/005—Testing of reflective surfaces, e.g. mirrors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
    • G01M11/0271—Testing optical properties by measuring geometrical properties or aberrations by using interferometric methods
    • 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
    • G01B2290/30—Grating as beam-splitter
    • 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
    • G01B9/02057—Passive reduction of errors by using common path configuration, i.e. reference and object path almost entirely overlapping

Definitions

  • the invention relates to a method and a measuring device for interferometric measurement of a shape of a surface of a test object.
  • the diffractive optical element is designed, for example, as a computer-generated hologram (CGH) and configured in such a way that it generates a test wave with a wave front that is adapted to the desired shape of the surface.
  • CGH computer-generated hologram
  • Diffractive structures required for this can be determined by a computer-aided simulation of the measuring device together with the target surface and then produced on a substrate as CGH. By superimposing a reference wave on the test wave reflected from the surface, deviations from the target shape can be determined very precisely.
  • Such a measuring arrangement is conventionally configured as a Fizeau interferometer with a Fizeau element for splitting a light wave into a test wave and a reference wave.
  • the test wave is then transformed by the CGH into a test wave with a wave front adapted to the target shape of the surface to be measured.
  • the test wave reflected from the surface is transformed back by the CGH and, after passing through the Fizeau element again, is superimposed with the reference wave.
  • DE 102018203795 A1 describes a calibration method in which two spherical calibration shafts and calibration mirrors adapted to them are used.
  • the measuring device is very complex, however, since several calibration spheres have to be produced for each test object and integrated in the measurement setup.
  • the aforementioned object can be achieved according to the invention, for example, with a method for interferometric measurement of a shape of an upper surface of a test object with the steps: generating a test wave and at least two calibration waves by means of a diffractive optical element from an input wave, the test wave having a wavefront that is at least partially adapted to a desired shape of the surface of the test object and the calibration waves each have a spherical wavefront, Providing a calibration sphere, sequentially arranging the calibration sphere in a respective beam path of each of the at least two calibration waves and each determination of calibration deviations of the diffractive optical element from the calibration waves after each reflection on the calibration sphere. Furthermore, the method includes an interferometric measurement of the shape of the surface of the test object by means of the test wave, taking into account the determined calibration deviations.
  • a calibration sphere is understood to mean a calibration object with a spherical surface whose radius of curvature is less than 1 km, in particular less than 100 m or less than 10 m.
  • a calibration wave with a spherical wavefront in the sense of this text is understood to mean a wave whose imaginary source point is at most 1 km, in particular at most 100 m or at most 10 m from the diffractive optical element. The imaginary source point corresponds to the center point of a sphere assigned to the spherical wave front.
  • a calibration wave with a spherical wave front is understood to mean a wave which, in the surface area provided for interaction with the calibration sphere, has a maximum deviation from a best-matched sphere of at most 100 nm, in particular of at most 20 nm or at most 5 nm.
  • the calibration waves differ from one another in particular in their direction of propagation.
  • the calibration deviations are determined in particular by interferometric superimposition of the respective reflected calibration wave with a reference wave.
  • the consideration of the determined calibration deviation The interferometric measurement of the surface shape of the test object takes place in particular by correcting the interferometric measurement result on the basis of the calibration deviations.
  • the calibration deviations are determined in particular by superimposing a reference wave with the corresponding calibration wave after reflection on the relevant calibration sphere.
  • the interferometric measurement continues in particular by superimposing the test wave with the reference wave.
  • the calibration sphere is displaced when arranging the same in succession in the respective beam path between different calibration positions.
  • the calibration sphere is initially arranged at a first calibration position in a beam path of the first calibration shaft and then by corresponding displacement at a further calibration position in a beam path of the second calibration shaft.
  • the calibration sphere is moved between different tilt positions when it is arranged one after the other in the respective beam path.
  • a source section is defined for each individual beam of the calibration waves, which extends from the respective center point of a sphere assigned to the wave front of the respective calibration wave to the point of intersection of the individual beam with the diffractive optical element, and the distance between the centers of the spheres of the two Calibration waves have a value which is between 0.1% and 50% of the length of the longest source section of all individual beams of the two calibration waves.
  • the distance between the centers of the spheres of the two calibration waves is between 0.1% and 30%, in particular between 0.1% and 20% of the length of the longest source section of all individual beams of the two calibration waves. This simplifies the calibration using just a single calibration sphere, since the spatial Verschiebebe required for calibration is richly reduced.
  • the term “single beam” refers to the choice of terms used in geometrical optics.
  • the diffractive optical element is configured to generate at least three calibration waves, each with a spherical wave front, and the respective distance between the centers of the spheres of two of the calibration waves has a value which is between 0.1% and 50% of the length of the longest source section of all individual rays of the at least three calibration waves.
  • At least one of the calibration waves is configured as an expanding wave.
  • the center of one of the waves is thus located in front of the sphere assigned to this calibration wave on the input wave side with regard to the diffractive optical element. This means that the diffractive optical element lies between the center point and the calibration sphere.
  • all calibration waves are configured as expanding waves.
  • At least one of the calibration shafts is configured as a converging shaft.
  • the center of one of the wave fronts of the sphere assigned to this calibration wave is on the output shaft side visibly towards the diffractive optical element, i.e. the center is either between the diffractive optical element and the calibration sphere or further away from the diffractive optical element than the calibration sphere arranged in the corresponding calibration position .
  • all calibration waves are configured as converging waves.
  • at least three calibration waves, each with a spherical wave front, are generated by diffraction from the input wave.
  • a calibration wave with a plane wave front is also generated.
  • the test wave is superimposed with a reference wave after interaction with the surface of the test object, the reference wave being split off from the input wave by means of a fish element.
  • the test wave is superimposed with a reference wave after interaction with the surface of the test object, the reference wave being generated from the input wave by means of the diffractive optical element.
  • the reference wave has a planar wavefront and is reflected on a planar reference mirror.
  • the aforementioned object can also be achieved, for example, with a measuring device for interferometric shape measurement of a surface of a test object with a diffractive optical element which is configured to produce a test wave with a wave front that is at least partially adapted to a nominal shape of the surface of the test object by diffraction from an input wave to generate a first calibration wave and at least one second calibration wave.
  • the measuring device comprises a positioning device which is configured to move a calibration sphere between different calibration positions in such a way that the calibration sphere at a first of the calibration positions in a beam path of the first calibration shaft and at another of the calibration positions in a beam path of the second calibration shaft is arranged.
  • the calibration sphere can be displaced in all three spatial directions by means of the positioning device.
  • the positioning device is also configured to tilt the calibration sphere.
  • the positioning device is configured to tilt the calibration sphere in such a way that different tilt positions can be set for the calibration sphere in the various calibration positions. In this way, the size of the calibration sphere required to carry out the calibration in the various calibration positions can be kept small.
  • the measuring device further comprises the calibration sphere.
  • at least one of the calibration waves is configured as a converging wave and a center point of a sphere which is assigned to the wavefront of the calibration wave lies between the diffractive optical element and the calibration sphere arranged at the assigned calibration position.
  • At least one of the calibration waves is configured as a converging wave and the calibration sphere arranged at the assigned calibration position is arranged between the diffractive optical element and a center of a sphere which is assigned to the wavefront of the calibration wave.
  • FIG. 1 shows an embodiment of a measuring device according to the invention for interferometric shape measurement of an optical surface of a test object with a calibration sphere arranged in two different calibration positions
  • FIG. 2 shows a further embodiment of a measuring device according to the invention for interferometric shape measurement of an optical surface of a test object with a calibration sphere arranged in two different calibration positions
  • FIG. 3 areas of the calibration sphere illuminated in the various calibration positions with the measuring device according to FIG. 1,
  • FIG. 4 areas of the calibration sphere illuminated in the various calibration positions with the measuring device according to FIG. 2,
  • 5 shows a further embodiment of a measuring device according to the invention for interferometric shape measurement of an optical surface of a test object
  • 6 shows a further embodiment of a measuring device according to the invention for interferometric shape measurement of an optical surface of a test object with a calibration sphere arranged in two different calibration positions
  • FIG. 7 shows a further embodiment of a measuring device according to the invention for interferometric shape measurement of an optical surface of a test object with a calibration sphere arranged in two different calibration positions
  • FIG. 8 areas of the calibration sphere illuminated in the various calibration positions with the measuring device according to FIG. 6,
  • FIG. 9 areas of the calibration sphere illuminated in the various calibration positions with the measuring device according to FIG. 7,
  • FIG. 10 shows a further embodiment of a measuring device according to the invention for interferometric shape measurement of an optical surface of a test object with a calibration sphere arranged in three different calibration positions, as well as
  • FIG. 11 shows areas of the calibration sphere illuminated in the various calibration positions with the measuring device according to FIG. 10,
  • a Cartesian xyz coordinate system is indicated in the drawing, from which the respective positional relationship of the components shown in the figures results.
  • the x-direction runs perpendicular to the plane of the drawing into this, the z-direction to the right and the y-direction upwards.
  • FIG. 1 illustrates an exemplary embodiment of a measuring device 10 for interferometric shape measurement of an optical surface 12 of a test object 14.
  • a deviation of the actual shape of the surface 12 from a nominal shape can be determined.
  • a mirror of a projection objective for EUV microlithography with a non-spherical surface for reflecting EUV radiation with a wavelength of less than 100 nm, in particular a wavelength of approximately 13.5 nm or approximately 6.8 nm, can be used as the test object 14 , be provided.
  • the non-spherical surface of the mirror can, for example, have a free-form surface with a deviation from each rotationally symmetrical asphere of more than 5 ⁇ m and a deviation from each sphere of at least 1 mm.
  • the measuring device 10 comprises an interferometry module 15, a diffractive optical element 32 and a positioning device 50 for positioning a calibration sphere 52.
  • the interferometry module 15 contains a radiation source 16 for providing a sufficiently coherent measuring radiation 18 in the form of an expanding wave.
  • the radiation source 16 comprises a waveguide 20 with an exit surface at which the expanding wave originates.
  • the waveguide 20 is connected to a Strahlungserzeu generation module 22, for example in the form of a laser.
  • a helium-neon laser with a wavelength of approximately 633 nm can be provided, for example.
  • the measuring radiation 18 can, however, also have a different wavelength have electromagnetic radiation in the visible or invisible wavelength range.
  • the radiation source 16 with the waveguide 20 is just one example of a radiation source 16 that can be used for the measuring device 10.
  • an optical arrangement with lens elements, mirror elements or the like to provide a suitable wave from the measuring radiation 18 can be provided be.
  • the measuring radiation 18 first passes through a beam splitter 24, a collimator 26 and a Fizeau element 28.
  • the collimator 26 converts the expanding wave of the measuring radiation 18 into a plane wave.
  • the Fizeau element 28 has a Fizeau surface 29 on which part of the incoming measurement radiation 18 is reflected as a returning reference wave 30r.
  • the measuring device 10 according to FIG. 1 is thus configured as a Fizeau interferometer.
  • the part of the measuring radiation 18 which has passed through the Fizeau element 28 then hits the diffractive optical element 32 as an input wave 19 Test object 14 to generate.
  • the diffractive optical element 32 of the test optics generates several calibration waves 36, in the present embodiment two calibration waves 36-1 and 36-2 from the incident measurement radiation 18.
  • the calibration waves 36 each have a spherical wave front and different directions of propagation. In the projection onto the plane of the drawing in FIG. 1 (x-z plane), the direction of propagation of the calibration wave 36-1 points slightly to the bottom right and the direction of propagation of the calibration wave 36-2 points slightly to the top right.
  • the calibration shafts 36-1 and 36-2 are assigned virtual original points 38-1 and 38-2, respectively, which each correspond to the center point of a sphere assigned to the wavefront of the respective calibration shaft 36-1 or 36-2.
  • the calibration waves are configured as expanding waves, so that the diffractive optical element 32 is arranged between the virtual origination points 38-1 or 38-2 and the calibration sphere 52.
  • the virtual point of origin 38-1 is arranged in the projection onto the plane of the drawing of FIG. 1 to the right above the point of origin 38-2.
  • the distance d, denoted by reference numeral 37, between the points of origin 38-1 and 38-2 is illustrated in FIG. 1 by means of a double arrow, with the distance between the points of origin 38-1 and 38-2 in three-dimensional space and not in Projection onto the xz plane according to FIG. 1 is to be understood.
  • the diffractive optical element 32 is designed as a complex coded CGFI and comprises a substrate 35 and diffraction structures which are arranged on the diffractive surface 33 of the substrate 35 facing the test object 14. According to the embodiment shown in FIG. 1, the diffraction structures form three diffractive structure patterns superimposed in a plane, specifically one diffractive structure pattern for the test shaft 34 and the two calibration shafts 36-1 and 36-2.
  • the diffractive optical element 32 is therefore also referred to as a triple complex coded computer-generated flologram (CGFI).
  • one of the diffractive structure patterns is configured to generate the test wave 34, which is directed onto the test object 14 and has a wavefront that is at least partially adapted to a desired shape of the optical surface 12.
  • the test wave 34 is reflected on the optical surface 12 of the test object 14 and runs back as a returning test wave 34r to the diffractive optical element 32. Due to the wavefront matched to the nominal shape of the optical surface 12, the test wave 34 strikes the optical surface 12 essentially perpendicularly at every location on the optical surface 12 and is reflected back into itself.
  • the other diffractive structure patterns generate the reference waves 36-1 and 36-2 with the respective spherical wave front.
  • a simply coded CGFI with a diffractive structure or another optical grating can be used instead of the complex coded CGFI.
  • the test wave 34 can be generated for example in a first diffraction order and the calibration waves 36-1 and 36-2 in any other diffraction order on the diffractive structure.
  • test wave 34r returning from the surface 12 passes through the diffractive optical element 32 again and is again deflected in the process.
  • the returning test wave 34r is transformed back into an approximately flat wave, its wavefront exhibiting corresponding deviations from a flat wavefront due to deviations of the surface 12 of the test object from its nominal shape.
  • the measuring device 10 contains a detection device 41 with the aforementioned beam splitter 24 for guiding the combination of the returning test wave 34r and the returning reference wave 30r out of the beam path of the irradiated measurement radiation 18 and an observation unit 47 for detecting an overlay of the test wave 34r with of the reference wave 30r generated interferogram.
  • the returning test wave 34r and the returning reference wave 30r strike the beam splitter 24 as convergent rays and are reflected by the latter in the direction of the observation unit 47. Both convergent beams pass through a diaphragm 42 and an eyepiece 44 of the observation unit 47 and finally hit a two-dimensionally resolving detector 46 of the observation unit 47 Reference wave 30r generated test interferogram.
  • the measuring device 10 comprises an evaluation device 48 for determining the actual shape of the optical surface 12 of the test object 14 from the recorded test interferogram or several recorded test interferograms, taking into account the calibration deviations described in more detail below.
  • the evaluation device has a suitable data ten processing unit and uses corresponding calculation methods known to those skilled in the art.
  • the measuring device 10 can contain a data memory or an interface to a network in order to enable an external evaluation unit to determine the surface shape by means of the interferogram stored or transmitted via the network.
  • the measuring device 10 is operated in a calibration mode. This can take place before or after the above-described interferometric measurement of the optical upper surface 12 of the test object 14.
  • the determination of the calibration deviations enables substrate errors of the substrate 35 and errors resulting from distortion of the diffractive structure patterns arranged on the diffractive surface 33 to be calculated from the surface measurement result.
  • the determination of the calibration deviations enables the measurement errors that occur due to form or profile deviations in the diffractive structure pattern to be reduced.
  • the configuration of the diffractive optical element 32 and the provision of the positioning device 50 for moving the calibration sphere 52 between different calibration positions enables the calibration deviations to be determined using only a single calibration sphere.
  • the calibration sphere 52 used for this purpose can be part of the measuring device 10 and fixedly mounted on the positioning device 50. Alternatively, the calibration sphere 52 can also be removably attached to the positioning device 50, so that a suitable embodiment of the calibration sphere can be used as required.
  • the diffraction structures of the diffractive optical element 32 are configured to generate the calibration waves 36-1 and 36-2 with the properties described in more detail below.
  • the calibration shafts 36-1 and 36-2 are assigned virtual origin points 38-1 and 38-2, respectively.
  • a respective source section 40 is defined for individual rays 39-1 and 39-2. Since the respective source section 40 extends from the corresponding point of origin 38-1 or 38-2 to the respective point of intersection of the respective individual beam 39-1 or 39-2 with the diffractive optical element 32, in particular with the diffractive surface 33 of the diffractive optical element 32.
  • the longest of these source sections is denoted by the reference symbol 40I in FIG. 1 and has the length I which is also denoted by the reference symbol 51.
  • the quotient d / l has a value of about 40%, i.e. the distance d between the virtual points of origin 38-1 and 38-2 is about 40% of the length of the longest source section 40I.
  • the positioning device 50 is configured to move the calibration sphere 52 between different calibration positions in three-dimensional space.
  • the positioning device 50 is set up to move the calibration sphere 52 in three mutually orthogonal degrees of translational freedom 54x (in the x direction), 54y (in the y direction) and 54z (in the z direction).
  • the calibration sphere 52 can be moved from a first calibration position in the beam path of the first calibration shaft 36-1, shown with solid lines, into a second calibration position in the beam path of the second calibration shaft 36-2, shown with broken lines.
  • the calibration sphere 52 is initially arranged in the beam path of the first calibration shaft 36-1.
  • the calibration shaft 36-1 passes through the diffractive optical element 32 after reflection on the calibration sphere 52 and, after reflection on the beam splitter 24, generates a calibration interferogram on the detector 46 by superimposing the reference wave 30r.
  • the evaluation device 48 determines the deviation of the spherical calibration wave 36-1 from its nominal wavefront in the form of an ideal spherical wave.
  • the actual wavefront of the calibration wave 36-1 is thus determined absolutely by means of the calibration sphere 52 in the first calibration position.
  • the deviations of the calibration wave 36-1 from its nominal wavefront are stored as calibration deviations K1.
  • the calibration sphere 52 is then shifted by means of the positioning device 50 into the second calibration position in which the calibration sphere is arranged in the beam path of the second calibration shaft 36-2.
  • a calibration interferogram is recorded, which is generated by superimposing the calibration wave 36-2 after reflection on the calibration sphere 52 with the reference wave 30r.
  • calibration deviations K2 of the calibration shaft 36-2 from its nominal wavefront are determined.
  • the calibration deviations K1 and K2 are taken into account when determining the shape of the optical surface 12 of the test object 14 from the test interferogram (s) recorded.
  • the calibration sphere 52 By arranging the calibration sphere 52 as described above initially in the beam path of the first calibration shaft 36-1 and then pushing the calibration sphere 52 by means of the positioning device 50 into the second calibration position, in which the calibration sphere is arranged in the beam path of the second calibration shaft 36-2 , the calibration sphere is arranged one after the other in a respective beam path of each of the two calibration waves.
  • arranging the calibration sphere one after the other in the respective beam path means arranging the calibration sphere at a first calibration position in a beam path of the first calibration shaft and at a further calibration position in a beam path of the second calibration shaft.
  • FIG. 2 a further exemplary embodiment of a measuring device 10 for interferometric shape measurement of an optical surface 12 of a test object 14 is illustrated.
  • This measuring device differs from the measuring device 1 only in the functioning of the Positioniereinrich device 50 and the size of the calibration sphere 52.
  • Fig. 2 to simplify the drawing, the representation of the test shaft 34 and the test object 14 was omitted ver.
  • the positioning device 50 according to FIG. 2 has, in addition to the degrees of freedom of translation 54x, 54y and 54z, at least one degree of freedom from tilting.
  • this is the degree of freedom of tilt 56x, which defines a tilting movement of the calibration sphere 52 about the tilt axis 58 oriented in the x direction.
  • tilts in the y-direction and / or z-direction can also be provided.
  • the calibration sphere 52 arranged in a first calibration position is shown in solid lines in the beam path of the first calibration shaft 36-1 and the calibration sphere 52 arranged in a second calibration position in the beam path of the second calibration shaft 36-2 in broken lines represents.
  • the calibration sphere 52 is moved from a first tilt position to a second tilt position by tilting relative to the tilt axis 58 by tilting angle a (see FIG. 4) in addition to a corresponding translation movement.
  • the tiltability of the calibration sphere 52 enables the calibration sphere to be designed in a reduced size, as illustrated in FIGS. 3 and 4.
  • 3 shows the illuminated area 60-1 of the calibration sphere 52 in the first calibration position according to FIG. 1 and the area 60-2 of the calibration sphere 52 illuminated in the second calibration position according to FIG Calibration position according to FIG. 2 illuminated area 60-1 of the calibration sphere 52 and the area 60-2 of the calibration sphere illuminated in the second calibration position according to FIG.
  • the calibration sphere 52 according to FIG. 2 or FIG. 4 has a smaller size than the calibration sphere 52 according to FIG. 1 or FIG. 3.
  • the measuring device 10 in the embodiment according to FIG. 2 or FIG. 4 can be made more compact than in the embodiment according to FIG. 1 or FIG. 3.
  • the configuration of the measuring device 10 illustrated in FIG Positioning device 50 with a degree of tilting freedom of 56x can also be used in the embodiments described below with reference to FIGS. 5, 6, 7 and 10.
  • FIG. 6 illustrates a further exemplary embodiment of a measuring device 10 for interferometric shape measurement of an optical surface 12 of a test object 14.
  • This measuring device differs from the measuring device 10 according to FIG. 1 only in the configuration of the diffractive optical element 32 and the size and the radius of curvature of the calibration sphere 52 Test object 14 omitted.
  • the diffractive optical element 32 according to FIG. 6 is configured to generate converging calibration waves 36-1 and 36-2 instead of diverging calibration waves 36-1 and 36-2 as in the embodiment according to FIG Shape of the virtual points of origin 38-1 and 38-2 are arranged between the diffractive optical element 32 and the calibration sphere 52 arranged in one of the calibration positions.
  • the virtual points of origin 38-1 and 38-2 each correspond to the center point of a sphere assigned to the wave front of the respective calibration wave 36-1 or 36-2 after passing through the relevant convergence point.
  • the quotient d / l in the illustrated embodiment has a value of approximately 25%, i.e. the distance d between the virtual points of origin 38-1 and 38-2 is approximately 25% of the length of the longest source section 40I.
  • FIG. 7 a further exemplary embodiment of a measuring device 10 for interferometric shape measurement of an optical surface 12 of a test object 14 is illustrated.
  • This measuring device differs from the measuring device 10 according to FIG. 6 only in the configuration of the diffractive optical element 32 and the size and curvature of the calibration sphere 52.
  • the diffractive optical element 32 according to FIG. 7 is configured to generate the converging calibration waves 36-1 and 36-2 in such a way that the relevant convergence points in the form of the virtual points of origin 38-1 and 38-2 on that side of FIG one of the calibration positions arranged calibrating sphere 52, which is opposite to the diffractive optical element 32, are arranged.
  • the virtual points of origin 38-1 and 38-2 are each further away from the diffractive optical element 32 than the calibration sphere 52 arranged in the corresponding calibration position -1 or 38-2 up to the point of intersection of the respective individual beam 39-1 or 39-2 with the diffractive optical element 32.
  • the individual beams 39-1 and 39-2 are each by means of illustration broken lines 66-1 and 66-2 extended to the corre sponding virtual point of origin 38-1 or 38-2.
  • the quotient d / l has a value of approximately 34%, ie the distance d between the virtual points of origin 38-1 and 38-2 is approximately 34% of the length of the longest of the source sections 40I, denoted by the reference symbol 40I.
  • the respectively illuminated area 60-1 and 60-2 of the calibration sphere 52 of the embodiment according to FIG. 6 is illustrated in the first and second calibration positions.
  • the respectively illuminated area 60-1 and 60-2 of the calibration sphere 52 of the embodiment according to FIG. 7 is illustrated in an analogous manner in the first and second calibration positions.
  • the illuminated areas 60-1 and 60-2 overlap more strongly in the embodiment according to FIG. 6 than in the embodiment according to FIG. 7.
  • the measuring device according to FIG. 7 due to the closer arrangement of the calibration sphere 52 on the diffractive optical element 32 may be made more compact.
  • FIG. 10 A further exemplary embodiment of a measuring device 10 for interferometric shape measurement of an optical surface 12 of a test object 14 is illustrated in FIG. 10.
  • This measuring device differs from the measuring device direction 10 according to FIG. 1 only in the configuration of the diffractive optical element 32 and the size and the radius of curvature of the calibration sphere 52.
  • the test shaft 34 and the test object 14 are not shown to simplify the drawing.
  • the diffractive optical element 32 shown in FIG. 10 is configured to generate three calibration waves 36-1, 36-2 and 36-3.
  • the virtual points of origin 38-1, 38-2 and 38-3 are arranged between the interfe rometriemodul 15 and the diffractive optical element 32 in the embodiment shown.
  • the virtual points of origin 38-1, 38-2 and 38-3 can also be arranged analogously to the embodiments according to FIGS. 6 and 7 on the side opposite the interferometry module 15 with respect to the diffractive optical element 32.
  • the virtual points of origin 38-1 and 38-2 have a distance di2 also denoted by the reference symbol 37-1
  • the virtual points of origin 38-2 and 38-3 also have a distance di2 denoted by the reference symbol 37- 2 and the virtual points of origin 38-1 and 38-3 at a distance di3 from one another, also denoted by the reference symbol 37-3.
  • the longest source section of the calibration shafts 36-1 and 36-2 and of the calibration shafts 36-2 and 36-3 with the length h also identified by the reference number 51-1 is identical and is designated by the reference number 40h.
  • the longest source section 40 of the calibration shafts 36-1 and 36-3 is denoted by the reference symbol 4012 and has the length I2 which is also denoted by the reference symbol 51-2.
  • the quotient d-12 / l ⁇ for the calibration waves 36-1 and 36-2 is about 40%, the quotient d-13/12 for the calibration waves 36-1 and 36-3 is about 49% and the quotient d23 / h for the calibration waves 36-2 and 36-3 about 34%.
  • FIG. 11 the respective areas 60-1, 60-2 and 60-3 illuminated by the calibration shafts 36-1, 36-2 and 36-3 in the different calibration positions on the calibration sphere 52 are illustrated. As can be seen from the figure, they overlap each other adjacent areas 60-1 and 60-2 or 60-2 and 60-3 and areas 60-1 and 60-3.
  • FIG. 5 a further exemplary embodiment of a measuring device 10 for interferometric shape measurement of an optical surface 12 of a test object 14 is illustrated.
  • This measuring device differs from the measuring device 10 according to FIG. 1 only in the configuration for generating the reference wave 30r, which in the embodiment according to FIG. In FIG. 5, in order to simplify the drawing, the test shaft 34 and test object 14 are not shown.
  • the interferometry module 15 in the measuring device 10 according to FIG. 5 does not include a Fizeau element 28. Instead, a reference element 62 designed as a reflective optical element for generating the reference wave 30r is on that side of the diffractive optical Element 32, which is opposite to the interferometer module 15, is provided.
  • the complex coding of the diffractive optical element 32 is provided with a further diffractive structure pattern. This further diffractive structure pattern is used to generate a reference wave 30 from the input wave 19.
  • the reflective optical element 62 is provided with an optically effective surface in the form of a reflection surface 64 for reflecting the reference wave 30 into the returning reference wave 30r.
  • the reference element 62 can also be configured as a lens which, in cooperation with a mirror, generates the returning reference wave 30r.
  • the optically effective surface is understood to mean a lens surface that interacts with the reference shaft 30.
  • the reference element 62 is designed as a flat mirror for back reflection of the reference wave 30 with a flat wavefront.
  • the reference shaft 30 can be a spherical see wave front and the reference element 62 be designed as a spherical mirror.
  • the returning reference wave 30r reflected from the reflection surface of the reflective optical element 32 passes through the diffractive optical element 32 again and is again diffracted in the process.
  • the returning reference wave 30r is transformed back into an approximately flat wave, which corresponds to the wave generated in reflection on the Fizeau element 28 according to FIG. 1.
  • the diffractive optical element 32 thus also serves to superimpose the test wave 34r to be returned or the return reference waves 36-1 and 36-2 with the return reference wave 30r.
  • the configuration of the measuring device 10 illustrated in FIG. 5 with a reflective optical element arranged outside the interferometry module 15 as reference element 62 can also be used in the embodiments described above with reference to FIGS. 6, 7 and 10.
  • one or more further calibration shafts can be provided, of which at least one is configured as plane shafts.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Geometry (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Instruments For Measurement Of Length By Optical Means (AREA)

Abstract

Procédé de mesure par interférométrie d'une forme d'une surface (12) d'un objet à tester (14) consistant : à générer une onde de test (34) et au moins deux ondes d'étalonnage (36-1, 36-2) à partir d'une onde d'entrée (18) au moyen d'un élément optique diffringent (32), l'onde de test présentant un front d'onde au moins en partie adapté à une forme cible de la surface de l'objet à tester et les ondes d'étalonnage présentant chacune un front d'onde sphérique, à fournir une sphère d'étalonnage (52), à agencer successivement la sphère d'étalonnage dans un trajet de faisceau respectif de chacune des au moins deux ondes d'étalonnage (36-1, 36-2), et à déterminer respectivement des écarts d'étalonnage de l'élément optique diffringent à partir des ondes d'étalonnage après une réflexion respective au niveau de la sphère d'étalonnage, et à mesurer par interférométrie la forme de la surface de l'objet à tester au moyen de l'onde de test en tenant compte des écarts d'étalonnage déterminés.
PCT/EP2021/062216 2020-05-11 2021-05-07 Procédé de mesure par interférométrie d'une forme d'une surface WO2021228723A1 (fr)

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DE102022209513A1 (de) 2022-09-12 2023-10-19 Carl Zeiss Smt Gmbh Verfahren zum Kalibrieren einer sphärischen Welle, sowie Prüfsystem zur interferometrischen Bestimmung der Oberflächenform eines Prüflings

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Publication number Priority date Publication date Assignee Title
DE102012217800A1 (de) * 2012-09-28 2014-04-03 Carl Zeiss Smt Gmbh Diffraktives optisches Element sowie Messverfahren
DE102015209489A1 (de) * 2015-05-22 2016-06-02 Carl Zeiss Smt Gmbh Interferometrische Messvorrichtung
DE102018203795A1 (de) 2018-03-13 2018-05-03 Carl Zeiss Smt Gmbh Interferometrische Messanordnung zur Bestimmung einer Oberflächenform
DE102017217369A1 (de) * 2017-09-29 2019-04-04 Carl Zeiss Smt Gmbh Kompensationsoptik für ein interferometrisches Messsystem

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DE102015202695A1 (de) 2015-02-13 2016-08-18 Carl Zeiss Smt Gmbh Prüfvorrichtung sowie Verfahren zum Prüfen eines Spiegels
DE102015209490A1 (de) 2015-05-22 2016-11-24 Carl Zeiss Smt Gmbh Interferometrische Messanordnung
DE102019204096A1 (de) 2019-03-26 2020-10-01 Carl Zeiss Smt Gmbh Messverfahren zur interferometrischen Bestimmung einer Oberflächenform
DE102019210910A1 (de) 2019-07-23 2019-10-31 Carl Zeiss Smt Gmbh Messvorrichtung zur interferometrischen Bestimmung einer Oberflächenform

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102012217800A1 (de) * 2012-09-28 2014-04-03 Carl Zeiss Smt Gmbh Diffraktives optisches Element sowie Messverfahren
DE102015209489A1 (de) * 2015-05-22 2016-06-02 Carl Zeiss Smt Gmbh Interferometrische Messvorrichtung
DE102017217369A1 (de) * 2017-09-29 2019-04-04 Carl Zeiss Smt Gmbh Kompensationsoptik für ein interferometrisches Messsystem
DE102018203795A1 (de) 2018-03-13 2018-05-03 Carl Zeiss Smt Gmbh Interferometrische Messanordnung zur Bestimmung einer Oberflächenform

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