WO2002042728A1 - Procede et dispositif permettant de mesurer les aberrations d'un systeme optique de projection et procede et dispositif d'exposition - Google Patents

Procede et dispositif permettant de mesurer les aberrations d'un systeme optique de projection et procede et dispositif d'exposition Download PDF

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Publication number
WO2002042728A1
WO2002042728A1 PCT/JP2001/010154 JP0110154W WO0242728A1 WO 2002042728 A1 WO2002042728 A1 WO 2002042728A1 JP 0110154 W JP0110154 W JP 0110154W WO 0242728 A1 WO0242728 A1 WO 0242728A1
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WIPO (PCT)
Prior art keywords
optical system
measurement
projection optical
pattern
aberration
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PCT/JP2001/010154
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English (en)
Japanese (ja)
Inventor
Naomasa Shiraishi
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Nikon Corporation
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Application filed by Nikon Corporation filed Critical Nikon Corporation
Priority to JP2002544620A priority Critical patent/JPWO2002042728A1/ja
Priority to AU2002224059A priority patent/AU2002224059A1/en
Publication of WO2002042728A1 publication Critical patent/WO2002042728A1/fr

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    • 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
    • G01M11/0257—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested
    • G01M11/0264—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested by using targets or reference patterns
    • 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

Definitions

  • the present invention relates to a method and an apparatus for measuring aberration of a projection optical system for forming images of various patterns, and an exposure method and an apparatus, for example, a semiconductor element, an image pickup element (such as a CCD), a liquid crystal display element, or a thin film magnetic head. It is suitable for use when measuring the aberration of the projection optical system of a projection exposure apparatus used to transfer a mask pattern onto a photosensitive substrate during the photolithography process for manufacturing various devices such as Things.
  • a semiconductor element for example, an image pickup element (such as a CCD), a liquid crystal display element, or a thin film magnetic head.
  • a reticle or photomask
  • a projection exposure apparatus such as a batch exposure method.
  • the exposure wavelength has been shifted to a shorter wavelength side in order to cope with miniaturization of a semiconductor integrated circuit.
  • the exposure wavelength is mainly 248 nm of KrF excimer laser, but ArF which can be regarded as a shorter wavelength and substantially a vacuum ultraviolet (VUV) region can be considered.
  • Excimer lasers of 193 nm are also entering the stage of practical use. Then, that it has been further F 2 laser and the wavelength 1 5 7 nm short wavelength, even made proposals for a projection exposure apparatus using exposure light source of vacuum ultraviolet region A r 2 laser having a wavelength of 1 2 6 nm.
  • NA numerical aperture
  • the projection optical system of these projection exposure apparatuses is required to have a very small residual error in order to achieve high resolution. Therefore, in the manufacturing process of the projection optical system, the amount of residual aberration is measured with the accuracy of about 1Z1000 of the exposure wavelength by measuring the wavefront aberration using the interference of light, and based on the measured value, the positional relationship of the optical members etc. Is being adjusted. To measure such a small amount of aberration, how the optical path length from one point on the reticle to each point on the wafer via each optical path in the projection optical system changes depending on each optical path It is common to measure the wavefront aberration expressed by Several methods using the principle of the interferometer have been put into practical use and proposed for measuring the wavefront difference.
  • the Fizeau interferometer using a laser of the same wavelength as the exposure wavelength as a light source has high measurement accuracy and is suitable for measuring the wavefront aberration of the projection optical system.
  • the laser as the light source must have a coherence distance (temporal coherence length) in the traveling direction that is longer than the reciprocating distance (2 m or more) of the optical path of the projection optical system that is longer than lm.
  • the exposure wavelength is 248 nm of a KrF excimer laser
  • a laser that is almost equal to that wavelength and has a long temporal coherence for example, a harmonic of an argon laser or a harmonic of a semiconductor laser
  • the wavefront aberration measurement according to another approach Is required.
  • One corresponding image is transmitted through a large transmission pattern, and the transmitted light is made to interfere with the above-mentioned minute pinhole and the large Fourier pattern on the optical Fourier transform plane (pupil plane) through the detection optical system. And form the fringes, and solve the shape of the interference fringes. Doing, the aberration of the projection projection optical system is measured.
  • a light beam transmitted through a minute pinhole on a reticle spreads to the full numerical aperture of the projection optical system due to the diffraction effect of the minute pinhole, and passes through the projection optical system. It loses the wavefront aberration information provided before, ie, by the illumination optics.
  • the two images formed by splitting by the diffraction grating near the image plane contain almost the same wavefront aberration information of the projection optical system, but one of them is the diffraction effect of the minute pinhole formed on the image plane. As a result, the wavefront aberration information of the projection optical system is not lost again, and a uniform spherical wave is emitted from the minute pinhole.
  • PDI is not only the projection optical system for E UV L, the A r F principle in the projection optical system of an excimer laser or F 2 laser, the exposure apparatus as a light source are applicable.
  • the far ultraviolet region wavelength of about 300 to 200 nm
  • vacuum ultraviolet region VUV: wavelength of about 200 to 100 nm
  • EUV region the aberration of the projection optical system used at a wavelength of about 100 nm or less
  • problems in applying the conventional PDI to the actual measurement of the aberration of the projection optical system That is, in the conventional PDI, it is necessary to accurately align the pinhole on the reticle and the pinhole on the wafer surface (image surface) so as to maintain a strict imaging relationship. The alignment accuracy required at this time is about 10% of the resolution of the projection optical system.
  • the alignment accuracy of 10 nm must be achieved.
  • Accurate aberration measurement is not possible.
  • the above alignment accuracy is achieved due to the distortion of the projection optical system, the position error of the pinhole on the reticle pattern for measurement of the aberration measurement device itself, and the position control error of the detection optical system. It was difficult to achieve.
  • a first object of the present invention to provide an aberration measurement technique for a projection optical system which does not require a laser having a long temporal coherence and has high stability. Further, a second object of the present invention is to provide an aberration measurement technique capable of measuring the aberration of the projection optical system with high accuracy without requiring higher alignment accuracy than the conventional technique. Disclosure of the invention
  • the first method for measuring aberrations of a projection optical system is the method for measuring aberrations of a projection optical system which forms an image of a pattern on a first surface on a second surface, wherein the first measurement is performed on the first surface.
  • the pattern (10a) and the second measurement pattern (10b) larger than the first measurement pattern are arranged, and the second measurement pattern (10b) is placed on the second surface or a surface conjugate to the second surface.
  • the first reference pattern (13a) and the second reference pattern (13b) smaller than the first reference pattern are arranged, and the images of the first and second measurement patterns are respectively displayed.
  • the light quantity distribution of the projection optical system is measured, and the aberration of the projection optical system is measured based on the measurement result.
  • the first and second measurement patterns can also be referred to as a minute measurement pattern and a large measurement pattern, respectively, and the first and second reference patterns are respectively large reference patterns. And a fine reference pattern.
  • the two measurement patterns are illuminated with illumination light having coherence with each other. Then, comparing the luminous flux passing through both measurement patterns on the pupil plane with respect to the arrangement plane of the two reference patterns, the first measurement pattern (small measurement pattern) and the first reference pattern (large reference pattern) The first luminous flux that has passed through the projection optical system has a weak diffraction effect on the first reference pattern after passing through the projection optical system, so that the first reference pattern with the wavefront aberration information of the projection optical system is retained.
  • the second luminous flux that has passed through the second measurement pattern (large measurement pattern) and the second reference pattern (fine reference pattern) is diffracted by the second reference pattern to cause the projection optical system to perform a diffraction operation.
  • the wavefront aberration information is lost, the light is emitted as a spherical wave starting from the second reference pattern, and reaches the pupil plane as a substantially plane wave.
  • both light beams have almost the same interference as the interference fringes formed by the plane waves having different incident angles.
  • a fringe will be formed on the pupil plane. Therefore, by measuring and analyzing the shape of this interference fringe, the wavefront aberration of the light beam that has passed through the first reference pattern (micro-measurement pattern), the first reference pattern (large reference pattern), It is possible to measure the wavefront aberration of the projection optical system.
  • the first reference pattern has a size that is about 10 times or more the resolution limit of the projection optical system
  • the second reference pattern has a size that is about the resolution limit of the projection optical system or less.
  • the resolution limit in this case is the resolution limit on the image plane (second surface) side.
  • the first measurement pattern is smaller than the resolution limit of the projection optical system
  • the second measurement pattern is approximately 10 times the resolution limit of the projection optical system. It is desirable that the size be as described above.
  • the resolution limit in this case is the resolution limit on the object plane (first surface) side.
  • the first and second measurement patterns are illuminated with light beams having coherence with each other, and a plurality of measurements of the light amount distribution are performed while changing the phase relationship between the light beams illuminating the two measurement patterns. It is desirable to perform it twice. As a result, the measurement accuracy can be improved by the averaging effect.
  • the two measurement patterns are arranged at a plurality of positions on the first surface, and the aberration of the projection optical system is measured at the plurality of positions.
  • the third and second measurement patterns having the same or larger size as the second measurement pattern are used.
  • Four measurement patterns (10c, 10d) are arranged, and the first and second reference patterns (13a, 13b) are arranged.
  • Third and fourth reference patterns (31a, 31b) having magnitude relations opposite to those of the first and second reference patterns, respectively, at positions where an image-forming relationship is established with respect to the first reference pattern. It is desirable that the light amount distribution is measured by arranging the projection optical system, and the aberration measurement result of the projection optical system is corrected based on the measurement result.
  • the wavefront aberration information of the optical system before that is almost completely lost by the second reference pattern and the third reference pattern (initial reference pattern).
  • the optical system from the arrangement surface of the reference pattern to the light receiving surface (pupil surface) is a measurement optical system
  • the wavefront aberration of the measurement optical system can be measured by measuring the light amount distribution. Therefore, the measurement method (measurement device) can be calibrated by correcting the measurement value of the wavefront difference of the projection optical system by the measurement result, and as a result, the wavefront aberration of the projection optical system is corrected. Measurement accuracy is improved.
  • the third and fourth measurement patterns may be integrated large transmission patterns. Further, it is desirable that the fourth reference pattern be approximately the same size as the image of the second measurement pattern by the projection optical system.
  • the second method for measuring aberration of a projection optical system is the method for measuring aberration of a projection optical system which forms an image of a pattern on a first surface on a second surface.
  • the illumination light is detected through a measurement optical system (15) to obtain aberration information of the projection optical system, and the projection optical system and the first and second reference patterns (of different sizes) are different from each other.
  • 13a, 13b) is detected through third and fourth reference patterns (31a, 31b) whose magnitudes are opposite to those of the first and second reference patterns.
  • the aberration information of the measurement optical system is obtained, and the aberration measurement of the projection optical system is performed based on the two pieces of aberration information.
  • calibration of the first aberration measurement method can be performed.
  • the aberration measuring device for the first projection optical system of the present invention is the aberration measuring device for a projection optical system (PL) for forming an image of a pattern on the first surface on the second surface.
  • the first measurement pattern (10a) and the second measurement pattern (10b) larger than the first measurement pattern and the two measurement patterns are illuminated on the surface corresponding to An illumination optical system (8), a first reference pattern (13a) arranged on the second surface or a surface corresponding to a surface conjugate to the second surface, and the first reference pattern Measurement optical system that optically Fourier transforms a light beam that passes through the two reference patterns after passing through the second reference pattern (13b) and the two measurement patterns, and the projection optical system.
  • a light amount distribution detecting device (16) for measuring the light amount distribution of the light beam passing through the two reference patterns.
  • the first aberration measurement method of the present invention can be implemented.
  • the two measurement patterns are arranged in a plurality of pairs at different positions on the surface corresponding to the first surface, and the two reference patterns and the light amount distribution detecting device are arranged in the plurality of measurement patterns. It is desirable to provide a driving device (14, 20) that sequentially moves to a position corresponding to the image of (1).
  • aberration measurement can be performed at a plurality of positions within the field of view of the projection optical system.
  • third and fourth measurement patterns (10c, 10d) which are arranged so as to be interchangeable with the two measurement patterns and have a size equal to or greater than the second measurement pattern
  • these two reference patterns 3rd and 4th reference patterns (31a, 31b) which are arranged so as to be freely inserted into and removed from the image forming relationship with respect to the first and second reference patterns, and whose magnitude relation is opposite to that of the first and second reference patterns. It is desirable to provide By using these, calibration of the aberration measuring device of the projection optical system can be performed.
  • the illumination optical system illuminates the first and second measurement patterns with light beams having coherence with each other.
  • the illumination optical system may include a pinhole or a diffraction grating.
  • the illumination optical system has a phase variable device that varies the phase relationship between the illumination light applied to the two measurement patterns.
  • a second projection optical system aberration measuring apparatus is a projection optical system aberration measurement apparatus for forming an image of a pattern on a first surface on a second surface.
  • a detection device (16) that detects the illumination light passing through the projection optical system via the measurement optical system (15), and a device for measuring the aberration information of the measurement optical system.
  • First and second reference patterns (13a, 13b) having different sizes arranged on the optical path of the illumination light passing through the projection optical system, and the first and second reference patterns
  • third and fourth reference patterns (31a, 31b) having magnitude relationships opposite to each other, and measure the aberration of the projection optical system based on the two pieces of aberration information.
  • calibration of the aberration measuring device of the first projection optical system can be performed.
  • the method of manufacturing an exposure apparatus and the exposure method of the present invention respectively illuminate a first object (R) with an exposure beam, and project an image of a pattern of the first object via a projection optical system (PL).
  • a method for manufacturing an exposure apparatus for exposing a second object (W) and an exposure method the aberration of a projection optical system is measured by using any one of the aberration measurement methods of the present invention.
  • the first exposure apparatus of the present invention illuminates a first object with an exposure beam, and exposes an image of a pattern of the first object onto a second object via a projection optical system. It is provided with any one of the aberration measuring devices of the present invention.
  • the second exposure apparatus of the present invention illuminates a first object with an exposure beam, and exposes an image of a pattern of the first object onto a second object via a projection optical system. And a projection optical system in which optical elements are replaced or adjusted based on the aberration measured using any of the aberration measurement methods of the present invention.
  • the device manufacturing method of the present invention includes a step of transferring a mask pattern onto a workpiece using the exposure apparatus of the present invention.
  • an exposure method, an exposure apparatus, and a device manufacturing method for example, by correcting the imaging characteristics of the projection optical system according to the measurement result of the aberration of the projection optical system, High exposure accuracy is always obtained.
  • FIG. 1 is a partially cut-away configuration diagram showing an aberration measuring device according to a first embodiment of the present invention.
  • FIG. 2 is an enlarged view showing the measurement patterns 10a and 1Ob formed on the reticle 9 in FIG.
  • FIG. 3 is an enlarged view showing the reference patterns 13a and 13b formed on the reference pattern plate 12 in FIG.
  • (A) is a diagram showing members from the reticle 9 to the image sensor 16 in FIG. 1
  • (B) is a diagram showing interference fringes formed on the image sensor 16 in FIG. 4 (A).
  • FIG. 5 is a diagram showing an arrangement for carrying out the calibration of the measuring device of FIG.
  • FIG. 6 is a diagram showing various configuration examples of the illumination optical system 8 in FIG. FIG.
  • FIG. 7 is a configuration diagram illustrating a main part of an aberration measurement device according to a second embodiment of the present invention.
  • FIG. 8 is a configuration diagram illustrating an example of a projection exposure apparatus including the aberration measurement device according to the first embodiment or the second embodiment of the present invention.
  • FIG. 9 is a diagram showing an example of the stop ( ⁇ stop) in FIG. BEST MODE FOR CARRYING OUT THE INVENTION
  • the present invention is applied when measuring the aberration of a projection optical system mounted on a projection exposure apparatus.
  • FIG. 1 is a schematic configuration diagram showing an aberration measuring device for a projection optical system according to the present embodiment.
  • an exposure light exposure light
  • a projection optical system PL for aberration measurement is used as a light source 1.
  • F 2 single-tHE (oscillation wavelength 1 5 7 nm in the vacuum ultraviolet region (VUV)) is used.
  • an exposure light source light source 1
  • an Ar 2 laser wavelength 126 nm
  • an ArF excimer laser wavelength 193 nm
  • a harmonic generator of a YAG laser or a harmonic generator of a semiconductor laser, etc.
  • the present invention is also effective when a vacuum ultraviolet light source is used. Further, the present invention can be applied to a case where a light source such as a KrF excimer laser (wavelength: 248 nm) or a mercury lamp (i-line, g-line, etc.) is used as the light source.
  • a light source such as a KrF excimer laser (wavelength: 248 nm) or a mercury lamp (i-line, g-line, etc.) is used as the light source.
  • the illumination light IL emitted from the light source 1 reaches the illumination optical system 8 via the shaping optical system 3, the beam expander 5, the mirror 7 for bending the optical path, and the like. Then, the illumination light IL emitted from the illumination optical system 8 enters the reticle 9 on which a pair of measurement patterns 10 (described in detail later) and the like are drawn.
  • the illumination optical system 8 illuminates the pair of measurement patterns 10 with illumination light that can interfere with each other. Then, the pair of light beams ILa and ILb transmitted through the measurement pattern 10 pass through the projection optical system PL for aberration measurement, and form a projected image of the measurement pattern 10 on the light-transmissive reference pattern plate 12.
  • the reticle 9 is arranged such that its pattern surface substantially coincides with the object surface (first surface) of the projection optical system PL, and the reference pattern plate 12 has its surface (the surface on which the reference pattern 13 is formed). ) Are arranged to substantially coincide with the image plane (second surface) of the projection optical system PL.
  • the projection magnification from the reticle 9 (first surface) of the projection optical system PL of the present example to the reference pattern plate 12 (second surface) is, for example, a reduction magnification such as 1/4 or 1/5.
  • the Z axis is taken parallel to the optical axis AX of the projection optical system PL
  • the X axis is taken parallel to the plane of Fig. 1 in the plane perpendicular to the Z axis
  • the Y axis is taken perpendicular to the plane of Fig. 1. explain.
  • the reticle 9 is suction-held on a reticle stage 21 movably mounted in a X direction and a Y direction on a reticle base (not shown).
  • the light beam forming the projected image of the measurement pattern 10 of the reticle 9 is converted into a two-dimensional light by the above-described reference pattern plate 12, a lens system 15 as a measurement optical system, and a CCD type as a light amount distribution detection device. Detection is performed by an image sensor 16 and a measuring mechanism 14 including a box-shaped frame mechanism that accommodates them.
  • the upper surface of the reference pattern plate 12 is perpendicular to the optical axis AX of the projection optical system PL, and is a conjugate surface (image surface) with respect to the pattern surface (object surface) of the reticle 9, and the measurement pattern A pair of reference patterns 13 (details described later) are formed at positions where ten projected images are formed.
  • the lens system 15 collects the light beam transmitted through the reference pattern plate 12 and An optical Fourier transform image of the light beam transmitted through the reference pattern plate 12 is formed on an optical Fourier transform plane (pupil plane) with respect to the upper surface of 2, and the image sensor 16 forms a two-dimensional image on the pupil plane An image of the light amount distribution is picked up, and the image pickup signal is supplied to an analysis device 19 such as an external image processor.
  • an analysis device 19 such as an external image processor.
  • the measuring mechanism 14 is mounted on the base member 20 via air leveling so as to be movable in the X and Y directions.
  • the measuring mechanism 14 is attached to the end of the measuring mechanism 14 in the X and Y directions.
  • the fixed moving mirror 17 and the correspondingly arranged laser interferometer 18 determine the position of the measuring mechanism 14 in the X and Y directions and the rotation angle around the Z axis at a predetermined sampling rate.
  • And the measured value is supplied to the control device 23.
  • the control device 23 controls the position of the measurement mechanism 14 via a drive system 22 and a drive device such as a linear motor (not shown) based on the measured values.
  • a plurality of pairs of measurement patterns identical to the pair of measurement patterns 10 are provided at a plurality of different positions in the field of view of the projection optical system PL (for example, a plurality of positions at different distances from the optical axis AX).
  • the measurement mechanism 14 is driven so that the reference pattern 13 is sequentially superimposed on the positions of the projected images of the plural pairs of measurement patterns, and the light amount distribution is performed by the image sensor 16 for each measurement pattern pair. Is detected.
  • only one pair of measurement patterns 10 is formed on the reticle 9 and the reticle stage 21 is driven to drive the measurement pattern.
  • the measurement may be performed by moving 10 to a different position in the field of view of the projection optical system PL.
  • the analysis device 19 calculates a predetermined aberration of the projection optical system PL (in this example, based on two-dimensional light quantity distribution information on the pupil plane for a pair of measurement patterns 10 or a plurality of pairs of measurement patterns at different positions). Wavefront aberration), and transmits the obtained aberration to a host computer (not shown) via the control device 23.
  • a host computer not shown
  • the aberration exceeds the allowable range, for example, fine adjustment of the position of a predetermined optical element (lens, concave mirror, aberration correction plate, etc.) in the projection optical system PL so that the aberration falls within the allowable range. Is performed. At this time, reprocessing or replacement of the optical element of the projection optical system PL may be performed.
  • a r F excimer laser or F 2 laser is approximately the wavelength of the light source 1 Illumination light IL of about 200 nm or less is emitted, but illumination light IL in that wavelength range is strongly absorbed by ordinary air (particularly oxygen). Therefore, in order to enable the light amount distribution to be detected by the image pickup device 16, a gas on the entire optical path from the light source 1 to the image pickup device 16 is made of a gas having a low absorbance to the wavelength of the illumination light IL, for example, nitrogen, Or, it is necessary to replace with a rare gas (for example, helium, neon, argon, etc.).
  • a rare gas for example, helium, neon, argon, etc.
  • the optical path may be substantially evacuated.
  • a material which transmits the illumination light IL well. synthetic quartz, synthetic quartz doped with predetermined impurity, or it is necessary to use fluorite a (C aF 2), etc.).
  • FIG. 4A is an enlarged view showing a portion from the reticle 9 to the image sensor 16 in the aberration measuring apparatus shown in FIG. 1.
  • the lower surface of the reticle 9 projection optical system
  • a small measurement pattern 10a consisting of a circular transmission area with a diameter d1 less than or equal to the resolution limit on the reticle 9 side of the projection optical system PL, with the light-shielding film as the background
  • a large measurement pattern 10b composed of a circular transmission area having a diameter d2 (d2> d1) larger than the resolution limit is formed at a predetermined interval P1.
  • FIG. 2 shows an enlarged view of the pair of minute measurement patterns 10a and the large measurement pattern 10b (the pair of measurement patterns 10 in FIG. 1).
  • the resolution limit of a projection optical system is approximately expressed by the following equation, where NA is the numerical aperture of the projection optical system and ⁇ is the exposure wavelength.
  • the ordinary projection optical system including the projection optical system PL of this example reduces and projects the image of the pattern on the reticle as a mask onto a wafer as a substrate.
  • a lateral magnification (imaging magnification M) of about 4 to 5 times is applied.
  • the numerical aperture on the reticle side is 1 / M of the numerical aperture on the wafer side.
  • the projection optical system PL of the present embodiment for example, at an exposure wavelength of 157 nm (F 2 laser), ⁇ Assuming that the numerical aperture on the wafer side is 0.75 and the imaging magnification M (magnification from the reference pattern plate 12 to the reticle 9) is 5 times, the numerical aperture on the reticle 9 side is 0.15.
  • the resolution limit of Eq. (1) is about 0.105 m, and the resolution limit on the reticle side is about 0.523 m. Therefore, the diameter d1 of the minute measurement pattern 10a in this example is preferably set to about 0.4 m or less, which is about the above resolution limit or less.
  • the diameter d2 of the large measurement pattern 10b may be a value larger than the resolution limit of the equation (1), but the diameter d2 is desirably about 10 times or more the resolution limit. I just need. Since the resolution limit is about 0.523 / im on the reticle side, the diameter 012 of the large measurement pattern 10 is preferably set to about 5 or more, which is 10 times that in this example.
  • the measurement patterns 10a and 10b are irradiated with mutually coherent illumination light.
  • the transmitted light from the measurement patterns 10a and 10b is condensed by the projection optical system PL, respectively, and the large reference pattern on the reference pattern plate 12 arranged on the image plane (the side of the plane) of the projection optical system PL. 13a and the fine reference pattern 13b.
  • the large reference pattern 13a is larger than the resolution limit of the projection optical system PL on the wafer side, and is preferably composed of a transmissive portion having a size about 10 times or more the resolution limit. It consists of a transmissive part whose size is about the image limit.
  • the light flux ILa indicated by a solid line and the light flux ILb indicated by a dashed line, which form the projected images of the minute measurement pattern 10a and the large measurement pattern 10b, are the large reference pattern 13a and the minute reference pattern 1, respectively. 3b and penetrate.
  • the light fluxes ILa and ILb are condensed by a lens system 15 as a measurement optical system, and are subjected to an optical Fourier transform plane (the pupil plane of the lens system 15) with respect to the plane on which the reference patterns 13a and 13b are formed.
  • the light is irradiated onto the image sensor 16 arranged above.
  • the two measurement patterns 10a and 10b are The transmitted light fluxes ILa and ILb form interference fringes on the image sensor 16 on the pupil plane.
  • the ratio between the reticle-side resolution limit and the wafer-side resolution limit is equal to the imaging magnification M of the projection optical system PL and equal to the reciprocal of the ratio of the numerical apertures (NA) on both sides of the projection optical system PL.
  • the projection optical system PL of this example is a reduction optical system that reduces the pattern of the reticle and transfers it onto the wafer, and its imaging magnification M (magnification from the wafer to the reticle) is 4 or 5 times.
  • the projection optical system PL is assumed to be the same magnification for simplification, and the numerical aperture NA on both sides is assumed to be equal. In the following description, it is needless to say that the same holds for the reduction optical system by changing the resolution limit and the numerical aperture on both sides according to the imaging magnification.
  • the light travels in the projection optical system PL with a spread corresponding to the diffraction angle. Since the diameter d1 of the micro-measurement pattern 10a in this example is about the resolution limit, the following relationship is approximately established from equation (1).
  • the light flux ILa from the minute measurement pattern 10a passes through the projection optical system PL with a spread of about twice the numerical aperture NA of the projection optical system PL.
  • the light beam that spreads at an angle satisfying sin0 ⁇ NA is blocked by the aperture stop 11 etc. of the projection optical system PL, but the light beam ILa transmitted through the minute measurement pattern 10a is It spreads to the full numerical aperture of the PL and passes through the projection optical system PL. That is, the light flux I La loses the information of the wavefront aberration up to now (wavefront aberration of the optical system from the light source 1 to the illumination optical system 8 in FIG. 1) due to the diffraction effect from the minute measurement pattern 10a, and is substantially lost.
  • the light flux I La includes the wavefront aberration (optical path difference) information over the entire NA of the projection optical system PL.
  • the diameter (size) d2 of the large measurement pattern 10b is larger than the resolution limit, the light flux I Lb transmitted through the large measurement pattern 10b is not diffracted much.
  • the luminous flux transmitted through the two measurement patterns 10a and 1 Ob is condensed by the projection optical system PL on the pattern surface of the reference pattern plate 12 arranged on the image plane. Then, as described above, the projection of the minute measurement pattern 10a and the large measurement pattern 10b The image passes through the large reference pattern 13 a and the fine reference pattern 13 b on the reference pattern plate 12, respectively, and forms an interference fringe on the image sensor 16 arranged on the pupil plane of the lens system 15.
  • the large measurement pattern 10b and the fine reference pattern 13b are compared.
  • the transmitted light flux IL1b is diffracted by the fine reference pattern 13b transmitted after passing through the projection optical system PL. Accordingly, the wavefront aberration information of the projection optical system PL is lost from the light beam ILib, and the light beam IL1b is emitted from the minute reference pattern 13b as a spherical wave starting from the minute reference pattern 13b. Then, it becomes a plane wave by the action of the lens system 15 and reaches the image sensor 16 on the pupil plane.
  • the light flux IL 1a transmitted through the minute measurement pattern 10a and the large reference pattern 13a has a large diameter due to the diffraction effect of the large reference pattern 13a after passing through the projection optical system PL. Because of its weakness, the light passes through the large reference pattern 13a with the wavefront aberration information of the projection optical system PL, and reaches the image sensor 16 on the pupil plane as a substantially plane wave due to the action of the lens system 15 as well. .
  • both light beams IL 1 a and IL 1 b on the pupil plane differ according to the distance between the large reference pattern 13 a and the minute reference pattern 13 b, so both light beams have different angles of incidence.
  • An interference fringe substantially similar to the interference fringe formed by the plane wave is formed on the pupil plane. Therefore, by measuring and analyzing the shape of the interference fringes, the wavefront aberration of the light beam IL1a transmitted through the minute measurement pattern 10a and the large reference pattern 13a, that is, the wavefront aberration of the projection optical system PL is measured. It is possible to
  • the reference patterns 13a and 13b will be specifically described.
  • the large reference pattern 13a and the small reference pattern 13b are separated by a distance (center distance between both patterns) P2 on the surface of the reference pattern plate 12 on the projection optical system PL side with the light-shielding film as a background.
  • An open pattern with a diameter d 3 of permeability and an aperture pattern with a diameter d 4 (d 4 ⁇ d 3) are formed.
  • Figure 3 shows an enlarged view.
  • the reference pattern plate 12 has a large reference pattern 13a and a small reference pattern 13b formed by the projection optical system PL of the minute measurement pattern 10a and the large measurement pattern 10b, respectively. It is positioned to match the image position.
  • a projection image of the minute measurement pattern 10a is formed on the large reference pattern 13a, but as described above, the light flux ILa from the minute measurement pattern 10a Since the wavefront aberration information of the projection optical system PL is included, the diameter d3 of the large reference pattern 13a is set so that the wavefront aberration information is not lost due to the diffraction effect. Set to about 10 times or more the resolution limit on the wafer side of the formula.
  • the diameter d3 of the large reference pattern 13a may be about 10 m or more.
  • the luminous flux ILa from the minute measurement pattern 10a passes through the large reference pattern 13a while maintaining the divergence angle of the (wafer side) numerical aperture of the projection optical system PL, and becomes the luminous flux IL1a. Then, the light is radiated by the lens system 15 onto the image sensor 16 arranged on the optical Fourier transform plane (pupil plane) for the reference patterns 13a and 13b.
  • the fine reference pattern 13b has a size equal to or less than the resolution limit on the wafer side, and its diameter d4 is preferably equal to or less than about 0.07 m, which is equal to or less than the above resolution limit.
  • the light flux IL lb transmitted through such a small aperture is the wavefront aberration (wavefront aberration of the optical system including the light source 1 to the illumination optical system 8 and the projection optical system PL) It loses information and becomes an ideal spherical wave whose curvature is centered on the fine reference pattern 13b, and transmits with a large diffraction angle.
  • this light flux IL ib is also radiated by the lens system 15 onto the image sensor 16 arranged on the optical Fourier transform plane (pupil plane) for the reference patterns 13a and 13b.
  • the center distance P2 between a and 13b is the following, with respect to the imaging magnification M (magnification from the wafer to the reticle) of the projection optical system PL and the distance P1 between the minute measurement pattern 10a and the large measurement pattern 10b. It goes without saying that the relationship is true.
  • the optical Fourier transform plane (pupil plane) is a plane where the intersection with the light beam emitted from the arrangement plane of the reference patterns 13a and 13b is determined only by the exit angle regardless of the exit position. . Therefore, the reference patterns 13 a, 1 Of the light beams emitted from 3b, the light beams emitted at the same exit angle reach the same position on the pupil plane.
  • the minute measurement pattern 10a and the large measurement pattern 10b on the reticle 9 are illuminated with mutually coherent light beams, these measurement patterns 10a, 10b are illuminated.
  • the interference fringes 23 (light intensity distribution) of the two light beams IL1a and IL1b are illuminated on the imaging device 16 as shown in Fig. 4 (B). It will be formed.
  • the period (pitch) F1 of the interference fringes 23 is as follows.
  • one beam IL 1a contains the wavefront aberration information of the projection optical system PL
  • the other beam IL 1b is a beam that has lost ideal aberration information.
  • This reflects the wavefront aberration information of the projection optical system PL.
  • the small deformation amount of the interference fringes 23 reflects the wavefront aberration of the projection optical system PL. Therefore, by measuring this small deformation amount, it is possible to measure the wavefront aberration of the projection optical system PL.
  • the analyzer 19 shown in FIG. 1 measures the above-mentioned minute deformation and calculates the wavefront aberration.
  • this processing method is the same as the processing method using the well-known PDI (Point Difference Interferometer) method, and thus the description is omitted.
  • PDI Point Difference Interferometer
  • the period F1 and the directionality of the interference fringes 23 formed in this example are also generated by an alignment error between the projected image of the minute measurement pattern 10a and the large reference pattern 13a. is there.
  • the period and direction shift are terms that are proportional to the first order numerical aperture as wavefront aberrations, and correspond to image shifts (distortion). Therefore, in order to increase the distortion measurement accuracy of the projection optical system in the aberration measurement apparatus of the present example, it is necessary to increase the alignment accuracy thereof.
  • the diameter d2 of the large measurement pattern 10b and the diameter d3 of the large reference pattern 13a are increased. What is necessary is that the transmitted light ILa of the measurement pattern 10a can transmit the large reference pattern 13a, and the transmitted light ILb of the large measurement pattern 10b can transmit the small reference pattern 13b.
  • the transmitted light ILb of the large measurement pattern 10b in order to prevent the transmitted light ILb of the large measurement pattern 10b from transmitting through the large measurement pattern 10b to generate unnecessary transmitted light, the following conditions must be satisfied.
  • the value of the interval P1 may be increased.
  • the diameter d 2 of the large measurement pattern 10 b 1 5 rn
  • the diameter d3 of the large reference pattern 13a is set to 3 / im
  • the interval P1 between the minute measurement pattern 10a and the large measurement pattern 10b is preferably about 20 m or more.
  • the allowable value of the alignment error is about 1 zm or more on the side of the reference patterns 13a and 13b, and a sufficient margin can be secured compared with the mechanical adjustment accuracy.
  • the allowable value of the positioning error when using the conventional PDI method to measure the aberration of the projection optical system PL is about 10 nm
  • the allowable value of the positioning error in this example is PDI. This is about 100 times larger than the method, and the aberration measurement of this example can be performed extremely easily.
  • the two measurement patterns 10a and 10b having the interval P1 of about 20 m or more may be illuminated with luminous fluxes that interfere with each other. There is no need to use light, and this can be easily implemented.
  • period of interference fringe 23: F 1 is about 392 m. Therefore, a normal image sensor having a side of about 20 mm and a pixel size of about 20 m is used as the image sensor 16. This makes it possible to image the interference fringes 23 with high accuracy.
  • the measurement mechanism 14 is fixed and only one point in the field of view of the projection optical system PL can measure the aberration.
  • the measurement mechanism 14 is mounted on the base member 20 and is movable two-dimensionally in a plane perpendicular to the optical axis AX of the projection optical system PL. Is preferred. This makes it possible to measure the wavefront aberration of the projection optical system PL at a plurality of locations within the field of view of the projection optical system PL. In this case, the position of the measurement mechanism 14 is measured by the laser interferometer 18.
  • the position of the measuring mechanism 14 can be measured also in the optical axis AX direction of the projection optical system PL.
  • an oblique incidence type optical sensor that is generally used as an autofocus sensor of a projection exposure apparatus.
  • a laser interferometer can be arranged between the reference surface of the base member 20 and the measurement mechanism 14 so that the position in the optical axis direction can be measured.
  • the reticle 9 (measurement pattern 10) is moved according to the movement of the measurement mechanism 14. Also need to move. For this reason, it is desirable that the reticle 9 on which the measurement pattern 10 is drawn is held on the reticle stage 21 which is movable two-dimensionally in a plane perpendicular to the optical axis AX of the projection optical system PL. Similarly, it goes without saying that the position of reticle 9 should also be measured by a laser interferometer or the like.
  • the distance P 2 between the large reference pattern 13 a and the small reference pattern 13 b is set larger than the size of the projection optical system PL, etc.
  • the interval P 2 is considerably smaller than the size of the projection optical system PL and the lens system 15. Therefore, the light fluxes IL 1 a and IL 1 b transmitted through the large reference pattern 13 a and the small reference pattern 13 b pass through the almost common optical path (common path) to reach the image sensor 16. . Therefore, the wavefront aberration of the lens system 15 itself as the measurement optical system has almost no influence on the measurement of the wavefront aberration of the projection optical system PL.
  • FIG. 5 is an enlarged view showing a portion from the reticle 9 to the image sensor 16 in the aberration measuring apparatus of the present example, similarly to FIG. However, in FIG. 5, instead of the reticle 9 on which the measurement pattern of FIG. 4 is formed, the large measurement pattern 1 is placed at each position corresponding to the minute measurement pattern 10a and the large measurement pattern 10b.
  • there is no particular optimum value for the diameters of these initial measurement patterns 10c and 10d and any size may be used as long as a sufficient amount of transmitted light can be obtained.
  • the measurement patterns 10c and 10d may be connected to form one large transmission pattern.
  • an initial reference pattern plate 30 is disposed near the reference pattern plate 12 on the side of the projection optical system PL.
  • a fine initial reference pattern 31a and a large initial reference pattern 31b made of a transmission pattern are formed in a background made of a light shielding film.
  • the former fine initial reference pattern 3 1 a is arranged so as to coincide with the position of the large reference pattern 13 a on the adjacent reference pattern plate 12, and the latter large initial reference pattern 3 1 b is set to the fine reference pattern 1 3 It is arranged corresponding to the position of b.
  • the diameter of the small initial reference pattern 31a is set to be equal to or less than the resolution limit of the projection optical system PL, similarly to the fine reference pattern 13b, and the diameter of the large initial reference pattern 31b is set to the large reference pattern 13a.
  • the resolution limit is about 10 times or more of the resolution limit of the projection optical system PL.
  • the luminous flux ILc shown by a solid line and the luminous flux ILd shown by a dashed line transmitted through the initial measurement patterns 10c and 10d are respectively the projection optical system PL and the initial reference patterns 31a and 31b.
  • the light is condensed on the reference patterns 13a and 13b on the reference pattern plate 12 via.
  • both transmission parts (the initial reference pattern 31a and the reference Since the diameter of the pattern 13 b) is substantially smaller than the resolution limit of the projection optical system PL, both the diffracted lights IL 1 c and IL 1 d
  • the wavefront aberration information of the optical system and the projection optical system PL will be lost.
  • these diffracted lights ILc and IL1d enter the image sensor 16 via the same optical path as when measuring the wavefront aberration of the projection optical system PL, and form interference fringes there. Therefore, at the time of this calibration measurement, only the wavefront aberration of the lens system 15 is reflected in the minute deformation amount of the interference fringe, and the minute deformation amount is analyzed by the analyzer 19 in FIG. The wavefront aberration of the lens system 15 itself as a measurement optical system can be calculated.
  • the wavefront aberration of the projection optical system PL is calculated as follows. It is possible to obtain with higher accuracy.
  • Such calibration measurement results are the same regardless of where in the field of view of the projection optical system PL, the same measurement results can be obtained. The same result will be obtained even if it is performed. Therefore, the calibration measurement need only be performed once prior to the measurement of the wavefront aberration of the projection optical system PL, whereby the calibration time can be reduced. Of course, by performing calibration measurement periodically, the reliability of the calibration result can be enhanced, and more accurate measurement of the wavefront aberration of the projection optical system PL can be performed. In addition, this calibration measurement may be performed after measuring the wavefront aberration of the projection optical system PL.
  • FIGS. 6A to 6D show examples of various configurations of the illumination optical system 8 with respect to the reticle 9 having the fine measurement pattern 10a and the large measurement pattern 10b of FIG. 4, respectively.
  • the interval PI between the two measurement patterns 10a and 10b is, for example, about 20 to 50 im.
  • a pinhole plate 32 having a pinhole 33 with a diameter da is arranged at a distance hi from the reticle 9 on the light source side (+ Z direction).
  • the diffracted light IL 2 from the pinhole 33 has a diffraction angle of about ⁇ / da [rad]. Because of the spread, a circular area on the reticle 9 with a radius of about h 1 XAZd a will be illuminated coherently. However, it is only in the range of about 1Z4 that it has reliable coherence, and it is in the range of about ⁇ (2 Xd a) [rad] over its entire width. Then, in order to illuminate the minute measurement pattern 10a and the large measurement pattern 10b separated by a distance P 1 coherently, that is, to illuminate with a mutually coherent light flux, the following conditions should be satisfied. .
  • h / da> 255 may be set. That is, the pinhole 33 may be set apart from the measurement patterns 10a and 10b by a distance h1 that is at least 255 times the diameter da. For example, assuming that the diameter da of the pinhole 33 is 1 mm, the pinhole 33 may be installed at a distance of 255 mm in the + Z direction from the measurement patterns 10a and 10b.
  • the pinholes 33 may be respectively set on positions corresponding to the measurement positions.
  • the coherence in the X direction on the reticle 9 (the direction in which the measurement patterns 10a and 10b are arranged) is determined only by the size of the pinhole 33 in the X direction.
  • the magnitude of the direction (the direction perpendicular to the paper surface in FIG. 6 (A)) may be a value larger than the amount determined by the relationship of equation (7), which is advantageous in terms of the amount of illumination. That is, by using a slit pattern having a width in the X direction da and a wider width in the Y direction instead of the pinhole 33, the amount of illumination light can be increased.
  • a diffraction grating 34 having a pitch pb is arranged on the light source (+ Z direction) side of the reticle 9 at an interval h2.
  • the periodic direction of the slit 34a, which is a transmission part of the diffraction grating 34, and the light-shielding part 34b is made to coincide with the direction in which the minute measurement pattern 10a and the large measurement pattern 10b are arranged.
  • the pitch pb of the diffraction grating 34 is defined by the following equation (9), the illumination light from each slit 34a of the diffraction grating 34 Since illumination is performed in a fixed phase relationship, extremely convenient illumination can be realized.
  • the diffraction grating 34 may be installed directly on the entire surface of the reticle 9 on the light source side.
  • an aperture stop 36 provided with a stop (diaphragm stop) 37 is arranged on an optical Fourier transform plane (pupil plane) for the reticle 9 in the illumination optical system. That is, the illumination light IL passing through the ⁇ stop 37 illuminates the measurement patterns 10 a and 10 b of the reticle 9 via the condenser lens system 35.
  • the ⁇ stop 37 defines the incident angle range (illumination ⁇ ) of the illumination light IL to the reticle 9.
  • the illumination NA may be set to 0.0039 or less according to the expression (10). Also, the size of the ⁇ stop 37 in the Y direction at this time may be larger than the above value, as in the example shown in FIG. 6 (6).
  • a diffraction grating 39 having a pitch pb and a slit width db is arranged on an optical Fourier transform plane (pupil plane) for the reticle 9 in the illumination optical system. Accordingly, the illumination light IL passing through the diffraction grating 39 illuminates the reticle 9 via the condenser lens system 35.
  • Fig. 6 (C) shows the width db of one slit of the diffraction grating 39. If the numerical aperture is equal to or less than 0.0039 as in the case of the above example, both measurement patterns 10a and 10b at the interval P1 can be coherently illuminated.
  • the luminous flux illuminated on the minute measurement pattern 10a and the large measurement pattern 10b is made a mutually coherent luminous flux. It is possible. Further, when these members are finely moved in the direction (X direction) in which the minute measurement pattern 10a and the large measurement pattern 10b are arranged, the minute measurement pattern 10a and the large measurement pattern 10a are moved according to the amount of movement. It is possible to change the phase relationship between the illumination light illuminated with the measurement pattern 10b.
  • a movable stage 38 is arranged as a moving device for this purpose. That is, the movable stage 38 can move the aperture stop 36 and the diffraction grating 39 in the X direction, which is the direction in which the measurement patterns 10a and 10b are arranged.
  • a moving device for the pinhole 33 and the diffraction grating 34 may be provided.
  • the shape of the interference fringe formed on the image sensor 16 in FIG. As described above, when the phase relationship of the illuminating light for illuminating the small measurement pattern 10a and the large measurement pattern 10b is changed, the shape of the interference fringe formed on the image sensor 16 in FIG. . The change is largely a shift of the interference fringes in the periodic direction, but the fine structure of the fringes also changes slightly. Then, while changing the phase relationship between the illuminating lights illuminating the two measurement patterns 10a and 10b, the above-described interference fringe intensity distribution measurement and the analysis by the analyzer 19 are repeated a plurality of times to obtain a projection. Optical system PL wavefront aberration measurement and calibration You can do it every time.
  • the pinholes and diffraction gratings provided in the illumination optical system are made of fluorite (C a F
  • a member obtained by patterning a light-shielding member such as a metal thin film on a substrate made of a fluoride crystal such as 2) or a synthetic quartz or a fluorine-added synthetic quartz can be used.
  • a member formed by cutting holes or a linear pattern from a light-shielding thin plate such as a metal thin plate can be used.
  • the diffraction grating in addition to the above-described light and dark diffraction gratings (amplitude type diffraction gratings), in order to increase the efficiency of use of illumination light, a phase type having irregularities or a periodicity in the refractive index distribution is used. Diffraction gratings can also be used.
  • the wavefront aberration of the projection optical system can be brought within an allowable range.
  • a fine pattern can be transferred onto a substrate such as a wafer with high precision.
  • FIG. 7 is also an enlarged view showing a portion corresponding to the members from the reticle 9 to the imaging element 16 in the aberration measuring apparatus of FIG. 1, similarly to FIG.
  • the configuration from to the image plane 41 of the projection optical system PL is the same as in the above-described first embodiment (FIG. 4).
  • the reference pattern plate 12A is not the image plane 41 of the projection optical system PL but the image plane 41 and a part of the measurement optical system. It is placed on a surface that has an image-forming relationship (joint role).
  • the large reference pattern 13Aa and the minute measurement pattern 10a are located at the positions of the projected images of the minute measurement pattern 10a and the large measurement pattern 10b on the reference pattern plate 12A.
  • Reference pattern 13 Ab is placed.
  • the light enters the reference patterns 13Aa and 13Ab via 15d.
  • Each light beam IL 4 a, IL 4 a transmitted through the reference patterns 13 A a and 13 A b b is on the imaging element 16 arranged on a plane (pupil plane) that is in an optical Fourier transform relationship with the reference patterns 13Aa and 13Ab by a part of the lens system 15b of the measurement optical system. To form an interference fringe.
  • the wavefront aberration of the projection optical system PL can be measured by analyzing the interference fringes as in the first embodiment.
  • the members from the relay optical system 15c to the image sensor 16 and a frame mechanism (not shown) that holds them constitute an aberration measurement mechanism 40 of the projection optical system PL.
  • the measurement optical system including the relay optical systems 15c and 15d and the lens system 15b, the reference pattern plate 12A, It is desirable that the measurement mechanism 40 including the imaging element 16 be integrally held.
  • the measurement mechanism 40 is disposed on the movable base member 20 in a plane perpendicular to the optical axis of the projection optical system PL, as in the first embodiment shown in FIG. And the position measurement in the optical axis direction can be performed.
  • the relay optical system 15c, 15d from the image plane 41 of the projection optical system PL to the reference pattern plate 12A is adopted, so that the magnification from the image plane 41 to the reference pattern plate 12A is increased. It is possible to have a large imaging magnification (magnification magnification). As a result, the diameter of the fine reference pattern 13Ab provided on the reference pattern plate 12A and the diameter of the large reference pattern 13Aa can be increased by the imaging magnification as compared with the case where they are provided on the image plane 41. Therefore, there is an advantage that the manufacture of the reference pattern plate 12A becomes easier.
  • this example is also similar in principle to the above-described first embodiment, and is arranged via the relay optical systems 15c and 15d, and only by the magnification of the relay optical system 15c15d. It goes without saying that the enlarged reference patterns 13Aa and 13Ab operate in the same manner as the reference patterns 13a and 13b of FIG.
  • the two light beams ILa and ILb transmitted through the minute measurement pattern 10a and the large measurement pattern 10b used for wavefront aberration measurement are not common even after passing through the projection optical system PL. It passes through the optical path (IL4a, IL4b) and receives different wavefront aberrations.
  • the luminous flux IL 4 b transmitted through the large measurement pattern 10 b is diffracted when passing through the minute reference pattern 13 Ab, and the relay optical system 15 c, 1
  • the wavefront aberration information of 5 d is lost, the light flux I L4 a transmitted through the minute measurement pattern 10 a enters the image sensor 16 with the wavefront aberration information of the relay optical systems 15 c and 15 d.
  • the measured wavefront aberration of the projection optical system PL is mixed with the wavefront aberration of the relay optical systems 15c and 15d.
  • the wavefront aberration of the projection optical system PL is further increased. It is possible to measure with high accuracy.
  • the image plane 41 of the projection optical system PL and the surface on the measurement mechanism 40 side with a light shielding film as a background What is necessary is just to arrange
  • the small initial reference pattern is arranged at a position where the large reference pattern 13Aa and the relay optical system 15c and 15d form an imaging relationship
  • the large initial reference pattern is the small reference pattern 13 Ab.
  • the diameters of the minute initial reference pattern and the large initial reference pattern are set to be approximately one times the diameter of the minute measurement pattern 10a and the diameter of the large measurement pattern 10b, respectively, which are equal to the imaging magnification of the projection optical system PL.
  • an image is formed on the small initial reference pattern 31a and the large initial reference pattern 31b in FIG. The initial measurement pattern where the relevant position is the transmission part of the large aperture is placed.
  • the transmitted light from the minute initial reference pattern passes through the relay optical system 15 c and 15 d through an optical path having a large spread like the optical path (light flux IL 3 a) at the time of measuring the aberration.
  • the transmitted light from the large initial reference pattern passes through the relay optical systems 15c and 15d through an optical path having a small spread like the optical path (light flux IL3b) at the time of measuring the aberration.
  • the optical paths of both light beams after passing through the reference pattern plate 12A are the same as the optical paths at the time of aberration measurement. Then, both light beams enter the imaging device 16 to form interference fringes.
  • the transmitted light from the micro initial reference pattern loses the aberration information of the projection optical system PL because the micro initial reference pattern is small.
  • the large reference pattern 1 When passing through 3 Aa, the diameter is large and is not affected by diffraction, so that the wavefront aberration information of the relay optical system 15 c 15 d is maintained. Therefore, the transmitted light from the very small initial reference pattern has the wavefront aberration information of the relay optical system 15c, 15d and the lens system 15b (the optical path of the light beam IL4a) as the Fourier transform optical system. It is incident on 16.
  • the transmitted light from the large initial reference pattern retains the aberration information of the projection optical system PL because the large initial reference pattern is large.
  • the difference between the aberration of the relay optical system 15c, 15d and the aberration of the optical path of the light flux IL4a and the light flux IL4b, and The sum of those aberrations can be calculated.
  • the wavefront aberration of the projection optical system PL can be measured with higher accuracy.
  • the optical members such as the reticles 9 and 9b, the reference pattern plates 12 and 12A, and the initial reference pattern plate 30 are optical materials that transmit the illumination light IL having the exposure wavelength. Needless to say, it is formed by.
  • synthetic quartz or fluoride crystal is used as the optical material
  • Fluorine-doped synthetic quartz or fluoride is used as the optical material.
  • a thin film such as chromium (Cr) or molybdenum silicate (MoSi 2) can be used as the light-shielding film on the background of the reference pattern plates 12 and 12A.
  • the calibration measurement described in the first and second embodiments is not limited to the combination with the aberration measurement described in each embodiment (FIGS. 4 and 7). It may be used in combination with the aberration measurement method (for example, PDI method).
  • FIGS. 1-10 An example of a projection exposure apparatus equipped with the aberration measuring apparatus of the above embodiment will be described with reference to FIGS. Its basic configuration is the same as a normal projection exposure system It is.
  • FIG. 8 shows a projection exposure apparatus of this embodiment, in FIG. 8, a mercury lamp, K r F or A r F excimer laser, or F 2 Les exposure light source comprising a single THE etc. 1 0 1 origination an exposure beam Illumination light (exposure light) IL passes through Mira-102, shaping optical system 103, Mira-104, reaches input lens 105, and passes through input lens 105. Enters the fly-eye lens 106 as an optical integret (uniformizer or homogenizer).
  • an exposure beam Illumination light (exposure light) IL passes through Mira-102, shaping optical system 103, Mira-104, reaches input lens 105, and passes through input lens 105.
  • the illumination light IL emitted from the fly eye lens 106 is transferred to the pattern surface (lower surface) of the reticle R as a mask via the condenser lens 113, the mirror 114 for bending the optical path, and the condenser lens 115. Illuminate the pattern.
  • the exit surface of the fly-eye lens 106 is an optical Fourier transform surface for the reticle R, where an aperture stop plate 107 is rotatably arranged by a drive motor 108 as an exchange mechanism. ing.
  • FIG. 9 shows an aperture stop plate 107.
  • the aperture stop plate 107 has a circular stop 1109 for normal illumination and a stop made up of a plurality of apertures for deformed illumination.
  • a pinhole-shaped stop 110 for illuminating two adjacent patterns with mutually coherent illumination light, a stop 111 having a diffraction grating, and the like are arranged.
  • the drive motor 108 in FIG. 8 is configured so that a desired aperture ( ⁇ aperture) among these apertures 109 to 112 can be set on the exit surface of the fly-eye lens 106. .
  • the range of the angle of incidence of the illumination light on the reticle R (the numerical aperture of the illumination system) can be limited by the aperture.
  • a prism movable along the optical axis of the illumination optical system may be arranged between the exposure light source 101 and the optical integrée (106).
  • the optical integrator (106) is a fly-eye lens as in this example, the intensity distribution of the illumination light on the incident surface is determined by the optical and integrator (106).
  • the light beam transmitted through reticle R forms an image of the pattern of reticle R on wafer W as a substrate to be exposed via projection optical system PL.
  • the Z axis is taken parallel to the optical axis AX of the projection optical system PL
  • the X axis is taken parallel to the plane of Figure 8 on a plane perpendicular to the Z axis
  • the Y axis is taken perpendicular to the plane of Figure 8 I do.
  • the reticle R is held on the reticle stage 1 16 mounted on the reticle base 1 17 movably in the X and Y directions, and the two-dimensional position of the reticle stage 1 16 moves.
  • the reticle stage control system 1 19 is measured by the mirror 118 M and the laser interferometer 118 based on the measured values and the control information from the main control system 120 that supervises and controls the operation of the entire device. Controls the position and speed of the reticle stage 116 via a linear motor (not shown).
  • the wafer W is held on a wafer stage (Z-repeller stage) 1 21 via a wafer holder (not shown), and the wafer stage 1 2 1 is movable on the wafer base 122 in the X and Y directions. It is placed on.
  • the two-dimensional position of the wafer stage 121 is measured by the moving mirror 123 M and the laser interferometer 123, and based on the measured values and the control information from the main control system 120.
  • the wafer stage control system 124 controls the position and speed of the wafer stage 122 in the X and Y directions via a linear motor or the like (not shown).
  • the wafer stage 122 is provided with a focus position (position in the optical axis AX direction) at a plurality of measurement points on the surface of the wafer W from an unillustrated auto focus sensor (oblique incidence optical sensor). Based on this information, the focus position of the wafer W and the tilt angles around the X and Y axes are determined by the servo method so that the surface of the wafer W is focused on the image plane of the projection optical system PL during exposure. Control.
  • the operation of transferring the image of the pattern of the reticle R by the projection optical system PL to one shot area on the wafer W and the operation of stepping the wafer W are repeated in a step-and-repeat manner.
  • the projection exposure apparatus of this example is of the batch exposure type (stepper type), but the reticle stage 116 is also provided with a scanning mechanism, so that the reticle R and the wafer W can be exposed and the magnification of the projection optical system PL.
  • the operation of synchronously moving with the speed ratio as the speed ratio and the operation of stepping the wafer W are repeated It goes without saying that the present invention is also effective for a scanning exposure type projection exposure apparatus using a step-and-scan method.
  • an aberration measuring device of the projection optical system PL including the measuring mechanism 14 in FIG. 1 or the measuring mechanism 40 in FIG. 7 is installed.
  • the reticle R on the reticle stage 116 is replaced by a reticle 9 on which the measurement pattern 10 of FIG. 1 is formed by a reticle loader system (not shown).
  • a reticle loader system not shown.
  • the position of the projection optical system PL of the measurement mechanism 14 in the optical axis AX direction can be measured by the above-described autofocus sensor.
  • a turret method was applied via a drive motor 108 to irradiate the illumination light with mutual coherence to the minute measurement pattern and the large measurement pattern in the measurement pattern on the reticle 9.
  • the aperture 110 in the form of a pinhole in the aperture stop plate 107 or the aperture 111 composed of a diffraction grating (see FIG. 9) may be installed on the exit surface of the fly-eye lens 106.
  • the aperture 109 may be an iris aperture, and the aperture may be a small aperture on the order of the above conditions.
  • the position of the stop 110 or 111 can be changed by a minute rotation of the turret type aperture stop plate 107.
  • the phase of the illuminating light may be variable between a large measurement pattern and a minute measurement pattern by, for example, minute rotation of the diffractive optical element.
  • an exposure apparatus having an aberration measurement function in other words, an exposure apparatus in which a measurement mechanism (14 or 40) is permanently provided on the wafer stage 121 has been described.
  • the measurement mechanism (14 or 40) may be simply attached to the wafer stage 121 when measuring the difference, or the measurement mechanism may be attached to a movable body different from the wafer stage 121.
  • the movable body may be permanently installed in the exposure apparatus, or may be detachable integrally with the measurement mechanism.
  • the measurement mechanism is incorporated in a dummy holder having substantially the same shape and the same size as the wafer holder, and the dummy holder is placed on the wafer stage 121 in exchange for the wafer holder, and the aberration is similarly reduced.
  • the measurement may be performed.
  • the entire measurement mechanism (14 or 40) does not have to be arranged on the wafer stage (20 or 121), and only a part of the measurement mechanism (14 or 40), for example, the reference pattern plate 12 and the lens system 15 is mounted on the wafer stage. It may be arranged on a stage, and the light beam from the lens system 15 may be transmitted to the imaging device 16 outside the wafer stage using a relay optical system or the like. At this time, it is preferable to measure the wavefront aberration of the relay optical system in advance similarly to the lens system 15, and to remove the wavefront aberration from the wavefront aberration of the projection optical system PL. This is the same in the first and second embodiments.
  • the projection optical system PL may be any one of a refraction system, a catadioptric system, and a reflection system, and has a projection magnification of 1 or more from the object surface (first surface) to the image surface (second surface), that is, a unity magnification system. , Or an expansion system.
  • all the measurement patterns are formed on the reticle (9 or R).
  • the reference pattern plate on which the above-described measurement patterns are formed is mounted on the reticle stage (2 1 or 1 2 1). ), Or a measurement pattern may be formed directly on the reticle stage.
  • a Zernike polynomial is used to calculate the higher-order components of the surface, curvature of field, and the like. It is preferable to replace or adjust at least a part of the projection optical system PL based on the result. At this time, the replacement may be performed for each optical element of the projection optical system, or for a projection optical system having a plurality of lens barrels, the replacement may be performed for each lens barrel. Also, at least one optical element of the projection optical system may be reworked, and in particular, the surface of the lens element may be machined to an aspherical surface if necessary. This optical element is a refractive optical element such as a lens element.
  • the optical element not only the optical element but also a reflective optical element such as a concave mirror, or an aberration correction plate for correcting aberrations (distortion, spherical aberration, etc.) of the projection optical system, particularly non-rotationally symmetric components thereof, may be used.
  • a reflective optical element such as a concave mirror, or an aberration correction plate for correcting aberrations (distortion, spherical aberration, etc.) of the projection optical system, particularly non-rotationally symmetric components thereof, may be used.
  • the projection optical system PL incorporates a mechanism for adjusting the imaging characteristics by driving at least one optical element with a driving element (such as a piezo element). The imaging characteristics may be kept within a predetermined allowable range by using only the above.
  • the measurement pattern is arranged on the reticle side of the projection optical system PL, and the reference pattern is arranged on the wafer side of the projection optical system PL.
  • the pattern is arranged on the edge side of the projection optical system PL, the reference pattern is arranged on the reticle side of the projection optical system PL, and the luminous flux passes from the wafer side to the reticle side is also possible. It goes without saying that the aberration measurement of the present invention is established.
  • the first and second measurement patterns formed on the first surface, the first and second reference patterns formed on the second surface or its conjugate surface, and the second The shapes of the micro initial reference pattern and the initial measurement pattern formed on the surface are both circular transmission parts, but this shape is not limited to a circle, and is not limited to a circular shape.
  • the shape may be a square, a rectangle, a regular hexagon, an ellipse, or the like.
  • the diameter of the circumscribed circle may be set to a value approximately equal to the diameter when each of the above patterns is circular.
  • the illumination light (exposure beam) for exposure is not limited to the above-described ultraviolet light having a wavelength of about 100 to 400 nm, but may be, for example, a laser plasma light source or S ⁇ R (Synchrotron Orbital Radiation ion).
  • EUV light Extreme Ultraviolet Light
  • the illumination optical system and the projection optical system each include only a plurality of reflective optical elements, and a reflective reticle is used. Therefore, the measurement pattern used for aberration measurement
  • the reticle on which the pattern is formed is also of the reflection type, and the optical system incorporated in the measurement mechanism (14 or 40) is also of the reflection type.
  • the projection exposure apparatus of the above embodiment incorporates an illumination optical system composed of a plurality of lenses, and a projection optical system in which various aberrations including wavefront aberration are satisfactorily corrected into the exposure apparatus itself to perform optical adjustment. Then, a reticle stage consisting of a number of mechanical parts was attached to the exposure apparatus body, wiring and piping were connected, and a wavefront aberration measurement mechanism (14 or 40) was installed. It can be manufactured by making adjustments (electrical adjustment, operation confirmation, etc.). It is desirable that the exposure apparatus be manufactured in a clean room in which the temperature, the degree of cleanliness, and the like are controlled.
  • the semiconductor device includes a step of designing the function and performance of the device, and a step of manufacturing a reticle based on this step.
  • the application of the exposure apparatus of the present invention is not limited to an exposure apparatus for manufacturing a semiconductor device.
  • the present invention can be widely applied to an exposure apparatus and an exposure apparatus for manufacturing various devices such as an imaging device (such as a CCD), a micro machine, a thin film magnetic head, and a DNA chip.
  • an exposure step exposure apparatus
  • a mask photomask, reticle, etc.
  • the aberration of the optical system to be measured can be measured by illuminating two measurement patterns arranged close to each other, and therefore, there is an advantage that a laser having a long time coherence is not required as a light source for illumination. There is.
  • the positioning accuracy between the two measurement patterns and the corresponding two reference patterns can be significantly reduced compared to the conventional PDI (Point Diffraction Interferometer) method, so that aberration measurement can be performed stably. It has the advantage of being able to measure aberrations with high accuracy.
  • PDI Point Diffraction Interferometer
  • the aberration measuring method and apparatus of the projection optical system are calibrated. Measurement accuracy can be improved.

Abstract

L'invention concerne un procédé et un dispositif permettant de mesurer les aberrations dans un système optique de projection haute précision. Ce procédé consiste à éclairer un micro-motif (10a) de mesure et un motif (10b) de mesure de grande dimension formés sur un réticule avec des faisceaux lumineux présentant des incohérences. Le flux lumineux passe à travers les motifs (10a, 10b) de mesure puis à travers les systèmes (PL) optiques de projection respectifs devant être mesurés, afin de projeter une image des motifs de mesure sur un motif (13a) de référence de grande dimension, et un micro-motif (13b) de référence formés sur une plaque (12) de motifs de référence. Le flux lumineux transmis par les motifs (13a, 13b) de référence est envoyé à travers un système (15) de lentilles afin de former une frange d'interférence sur un élément (16) imageur. Les aberrations du front d'onde du système optique de projection sont mesurées à partir de l'état de cette frange d'interférence.
PCT/JP2001/010154 2000-11-27 2001-11-21 Procede et dispositif permettant de mesurer les aberrations d'un systeme optique de projection et procede et dispositif d'exposition WO2002042728A1 (fr)

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JP2002544620A JPWO2002042728A1 (ja) 2000-11-27 2001-11-21 投影光学系の収差計測方法及び装置、並びに露光方法及び装置
AU2002224059A AU2002224059A1 (en) 2000-11-27 2001-11-21 Method and apparatus for measuring aberration of projection optical system, and method and apparatus for exposure

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JP2006108597A (ja) * 2004-10-08 2006-04-20 Canon Inc 干渉計を備えた露光装置及び方法、並びに、デバイス製造方法
US7277182B2 (en) 2003-07-05 2007-10-02 Carl Zeiss Smt Ag Apparatus for polarization-specific examination, optical imaging system, and calibration method
US7286245B2 (en) 2002-07-29 2007-10-23 Carl Zeiss Smt Ag Method and apparatus for determining the influencing of the state of polarization by an optical system; and an analyser
US7289223B2 (en) 2003-01-31 2007-10-30 Carl Zeiss Smt Ag Method and apparatus for spatially resolved polarimetry
US7333216B2 (en) 2000-02-23 2008-02-19 Carl Zeiss Smt Ag Apparatus for wavefront detection
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US7602503B2 (en) 2003-01-15 2009-10-13 Asml Holdings N.V. Methods for measuring a wavefront of an optical system
US7760366B2 (en) 2004-06-04 2010-07-20 Carl Zeiss Smt Ag System for measuring the image quality of an optical imaging system
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Cited By (18)

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Publication number Priority date Publication date Assignee Title
US7333216B2 (en) 2000-02-23 2008-02-19 Carl Zeiss Smt Ag Apparatus for wavefront detection
US7286245B2 (en) 2002-07-29 2007-10-23 Carl Zeiss Smt Ag Method and apparatus for determining the influencing of the state of polarization by an optical system; and an analyser
US7602503B2 (en) 2003-01-15 2009-10-13 Asml Holdings N.V. Methods for measuring a wavefront of an optical system
US7595931B2 (en) 2003-01-15 2009-09-29 Asml Holding N.V. Grating for EUV lithographic system aberration measurement
US7411687B2 (en) 2003-01-15 2008-08-12 Asml Holding N.V. Speckle reduction method and system for EUV interferometry
US7289223B2 (en) 2003-01-31 2007-10-30 Carl Zeiss Smt Ag Method and apparatus for spatially resolved polarimetry
US7277182B2 (en) 2003-07-05 2007-10-02 Carl Zeiss Smt Ag Apparatus for polarization-specific examination, optical imaging system, and calibration method
WO2005031466A1 (fr) * 2003-09-26 2005-04-07 Carl Zeiss Smt Ag Procede de determination des proprietes optiques et systeme d'exposition par projection comprenant un systeme de detection de surface d'onde
US7230220B2 (en) 2003-09-26 2007-06-12 Carl Zeiss Smt Ag Method of determining optical properties and projection exposure system comprising a wavefront detection system
JP2005156511A (ja) * 2003-11-28 2005-06-16 Canon Inc 測定方法及び装置、それを利用した露光方法及び装置、並びに、デバイス製造方法
JP4590181B2 (ja) * 2003-11-28 2010-12-01 キヤノン株式会社 測定方法及び装置、露光装置、並びに、デバイス製造方法
US7760366B2 (en) 2004-06-04 2010-07-20 Carl Zeiss Smt Ag System for measuring the image quality of an optical imaging system
US7796274B2 (en) 2004-06-04 2010-09-14 Carl Zeiss Smt Ag System for measuring the image quality of an optical imaging system
US8488127B2 (en) 2004-06-04 2013-07-16 Carl Zeiss Smt Gmbh System for measuring the image quality of an optical imaging system
US8823948B2 (en) 2004-06-04 2014-09-02 Carl Zeiss Smt Gmbh System for measuring the image quality of an optical imaging system
US9429495B2 (en) 2004-06-04 2016-08-30 Carl Zeiss Smt Gmbh System for measuring the image quality of an optical imaging system
JP2006108597A (ja) * 2004-10-08 2006-04-20 Canon Inc 干渉計を備えた露光装置及び方法、並びに、デバイス製造方法
JP2010283308A (ja) * 2009-06-08 2010-12-16 Canon Inc 波面収差の測定装置、露光装置及びデバイス製造方法

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