JP2014165291A - Estimation method and device for mask characteristic, and exposure method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate, according to an illuminating condition, the state of diffraction light emitted at a diffraction angle large enough for it not to pass through the aperture diaphragm of a projection optical system from a mask.SOLUTION: A method for estimating the state of diffraction light generated from the pattern of a reticle comprises: a step 102 of setting the light intensity distribution of an illumination pupil; a step 108 of measuring the diffraction intensity distribution in the projection pupil of a projection optical system that forms the image of the pattern of a reticle; steps 110, 112 of obtaining weight coefficients for a plurality of light intensity distributions when the degree of correlation between a diffraction intensity distribution and each of the plurality of light intensity distributions, which are obtained by shifting a 0-order intensity distribution corresponding to the light intensity distribution of illumination pupil, increases; and a step 116 of estimating the state of opening outer diffraction light that does not enter the projection pupil, on the basis of a light intensity distribution outside the projection pupil among light intensity distributions obtained by the weighted sum of the plurality of light intensity distributions.

Description

  The present invention relates to a mask characteristic estimation technique for estimating the state of diffracted light generated from a mask, an exposure technique using this estimation technique, and a device manufacturing technique using this exposure technique.

  In an exposure apparatus (projection exposure apparatus) such as a stepper or a scanning stepper used in a lithography process for manufacturing an electronic device (microdevice) such as a semiconductor device, a reticle (mask) pattern is formed on a wafer or the like with high accuracy. In order to expose the substrate, it is necessary to maintain the optical characteristics (for example, aberration) of the projection optical system within a target range. Further, when the exposure is continued, the optical characteristics of the projection optical system gradually change depending on the accumulated irradiation energy.

  Therefore, conventionally, an imaging characteristic correction system that predicts the amount of change in the optical characteristics of the projection optical system during exposure, for example, according to the integrated irradiation energy, and corrects the position and angle of a predetermined optical member in the projection optical system, for example. Is used to correct the predicted variation in the optical characteristics (see, for example, Patent Document 1). In this case, of the diffracted light (including zero-order light) emitted from the reticle, the diffracted light that enters the entrance pupil of the projection optical system is provided on the stage on the image plane side of the projection optical system, for example, and projected. The light intensity distribution can be measured by a measuring device that measures the light intensity distribution of the exit pupil of the optical system. Based on the measurement result and the integrated irradiation energy, it is possible to predict the variation amount of the optical characteristics of the projection optical system.

US Patent Application Publication No. 2006/244940

  Actually, in addition to the diffracted light that reaches the image plane from the reticle via the projection optical system, that is, the diffracted light that enters the entrance pupil of the projection optical system, the diffraction has a diffraction angle that is so large that it cannot enter the entrance pupil. Light, that is, diffracted light having a diffraction angle larger than the half angle of the aperture on the incident side of the projection optical system (hereinafter referred to as out-of-aperture diffracted light) is also emitted. Such diffracted light outside the aperture does not enter the substrate, but may enter the lens barrel of the projection optical system and affect the temperature distribution of the lens barrel, and thus the temperature distribution of the optical elements in the lens barrel.

  However, there is a problem that the diffracted light outside the aperture cannot be measured by a measuring apparatus that is provided on the image plane side stage of the projection optical system and measures the light intensity distribution of the exit pupil of the projection optical system. Furthermore, the state of the direction, intensity, or light intensity distribution in a certain region of the diffracted light outside the aperture changes in a complicated manner depending on the illumination conditions of the reticle (light intensity distribution of the exit pupil of the illumination optical system, etc.). In order to estimate the state of diffracted light outside the aperture, it is necessary to consider the illumination conditions.

  In view of such circumstances, the aspect of the present invention illuminates a state such as a light intensity distribution or a direction of diffracted light emitted at an angle (diffraction angle) that is so large that the mask cannot enter the entrance pupil of the projection optical system. The purpose is to estimate accurately according to the conditions.

  According to the first aspect of the present invention, a mask characteristic estimation method for estimating the state of diffracted light generated from a mask pattern is provided. This estimation method sets a first light intensity distribution at an exit pupil of an illumination optical system that illuminates the mask pattern, and a projection optical system that forms an image of the mask pattern illuminated by the illumination optical system A plurality of third light intensities obtained by obtaining a second light intensity distribution at the exit pupil of the first optical power source and shifting corresponding distributions corresponding to the first light intensity distribution within the exit pupil of the projection optical system by different amounts. Obtaining a plurality of third light intensity distributions when the degree of correlation between the distribution and the second light intensity distribution is high, and weighting the plurality of third light intensity distributions within the exit pupil of the projection optical system Obtaining individual coefficients of the plurality of third light intensity distributions so that the degree of correlation between the sum and the second light intensity distribution is high, and a plurality of the third light intensity distributions using the individual coefficients. Obtained by weighted sum Based on the light intensity distribution outside the exit pupil of the projection optical system in the fourth light intensity distribution, estimating the state of diffracted light that is generated from the mask pattern and does not enter the entrance pupil of the projection optical system And.

Further, according to the second aspect, there is provided a mask characteristic estimation method for estimating the state of diffracted light generated from a mask pattern. This estimation method stores the first light intensity distribution of the exit pupil of the illumination optical system that illuminates the pattern of the mask, and from a limited region at a plurality of different positions on the exit pupil of the illumination optical system. Illuminating the mask pattern with light sequentially, and a projection optical system that forms an image of the mask pattern illuminated by the illumination optical system when the restricted area is at a plurality of different positions. Determining the second light intensity distribution by the light from the mask pattern at the exit pupil of the mask and the zero-order light and the first or higher order diffraction from the mask pattern based on the determined second light intensity distribution A third light intensity distribution including light, a corresponding distribution corresponding to the first light intensity distribution in the exit pupil of the projection optical system based on the third light intensity distribution, and the pair The fourth light intensity distribution is obtained by superimposing the light intensity distributions shifted in distribution, and the mask is based on the light intensity distribution outside the exit pupil of the projection optical system of the fourth light intensity distribution. And estimating the state of diffracted light that is generated from the pattern and does not enter the entrance pupil of the projection optical system.
In the first and second aspects, obtaining the second light intensity distribution may be measuring the second light intensity distribution at the exit pupil of the projection optical system.

  According to the third aspect, there is provided an exposure method in which a mask pattern is illuminated with illumination light from an illumination optical system, and the substrate is exposed with the illumination light through the pattern and the projection optical system. This exposure method uses the estimation method according to the aspect of the present invention to estimate the state of diffracted light that is generated from the mask pattern and does not enter the entrance pupil of the projection optical system, and the projection optics to be estimated Based on the state of diffracted light that does not enter the entrance pupil of the system, the temperature fluctuation amount of at least one optical member constituting the projection optical system is obtained, and the projection optical system based on the temperature fluctuation amount of the optical member is determined. And correcting the fluctuation amount of the optical characteristic.

  According to the fourth aspect, there is provided a mask characteristic estimation device for estimating the state of diffracted light generated from a mask pattern. The estimation apparatus forms a storage unit that stores information on the first light intensity distribution at the exit pupil of the illumination optical system that illuminates the mask pattern, and an image of the mask pattern illuminated by the illumination optical system. A light intensity distribution measuring unit that measures the second light intensity distribution at the exit pupil of the projection optical system, the first light intensity distribution stored in the storage unit, and the second measured by the light intensity distribution measuring unit. A calculation unit that estimates a state of diffracted light that is generated from the mask pattern based on the light intensity distribution and does not enter the entrance pupil of the projection optical system, and the calculation unit includes an exit pupil of the projection optical system. A plurality of third light intensity distributions obtained by shifting corresponding distributions corresponding to the first light intensity distributions by different amounts from each other and the degree of correlation between the second light intensity distributions increases. 3rd light A plurality of third light intensity distributions such that the degree of correlation between the weighted sum of the plurality of third light intensity distributions and the second light intensity distribution is high within the exit pupil of the projection optical system. Based on the light intensity distribution outside the exit pupil of the projection optical system among the light intensity distributions obtained by calculating individual coefficients and weighted sum of the plurality of third light intensity distributions using the individual coefficients, The state of the diffracted light generated from the mask pattern and not entering the entrance pupil of the projection optical system is estimated.

  According to the fifth aspect, there is provided a mask characteristic estimating apparatus that estimates the state of diffracted light generated from a mask pattern. The estimation apparatus includes a storage unit that stores information on the first light intensity distribution in the exit pupil of the illumination optical system that illuminates the mask pattern, and a plurality of different positions in the exit pupil of the illumination optical system are limited. An illumination controller that sequentially illuminates the mask pattern with light from the area, and images of the mask pattern illuminated by the illumination optical system when the restricted area is at a plurality of different positions. A light intensity distribution measuring unit that measures a second light intensity distribution by light from the mask pattern at the exit pupil of the projection optical system to be formed, the first light intensity distribution stored in the storage unit, and the light intensity Based on the second light intensity distribution measured by the distribution measuring unit, the state of the diffracted light that is generated from the mask pattern and does not enter the entrance pupil of the projection optical system is estimated. A calculation unit, and the calculation unit obtains a third light intensity distribution including zero-order light and first-order or higher diffracted light from the mask pattern based on the measured second light intensity distribution. The fourth light intensity is obtained by superimposing a corresponding distribution corresponding to the first light intensity distribution and a light intensity distribution shifted from the corresponding distribution in the exit pupil of the projection optical system based on the third light intensity distribution. Distribution of the diffracted light that is generated from the mask pattern and does not enter the entrance pupil of the projection optical system based on the light intensity distribution outside the exit pupil of the projection optical system of the fourth light intensity distribution. The state is estimated.

  According to the sixth aspect, there is provided an exposure apparatus that illuminates a mask pattern with illumination light from the illumination optical system and exposes the substrate with the illumination light through the pattern and the projection optical system. The exposure apparatus includes an estimation apparatus according to an aspect of the present invention for estimating a state of diffracted light generated from the mask pattern and not entering the entrance pupil of the projection optical system, and the estimation apparatus estimated by the estimation apparatus. Based on the state of the diffracted light that does not enter the entrance pupil of the projection optical system, a temperature calculation unit that calculates the temperature fluctuation amount of at least one optical member that constitutes the projection optical system, and the optical member that is calculated by the temperature calculation unit And a correction unit that corrects the fluctuation amount of the optical characteristics of the projection optical system based on the temperature fluctuation amount of the projection optical system.

  According to the seventh aspect, there is provided an exposure apparatus that illuminates a mask pattern with illumination light from the illumination optical system and exposes the substrate with the illumination light through the pattern and the projection optical system. The exposure apparatus estimates the state of diffracted light generated from the mask pattern and does not enter the entrance pupil of the projection optical system, and enters the entrance pupil of the projection optical system estimated by the estimation apparatus. A temperature calculation unit for determining a temperature fluctuation amount of at least one optical member constituting the projection optical system based on a state of the diffracted light, and a temperature calculation unit for determining the temperature fluctuation amount of the optical member obtained by the temperature calculation unit. And a correction unit that corrects the fluctuation amount of the optical characteristics of the projection optical system.

  Further, according to the eighth aspect, forming the pattern of the photosensitive layer on the substrate using the exposure method or exposure apparatus of the aspect of the present invention, processing the substrate on which the pattern is formed, A device manufacturing method is provided.

  According to the aspect of the present invention, the information of the light intensity distribution set in the exit pupil of the illumination optical system and the measurement result of the light intensity distribution in the exit pupil of the projection optical system are used, so that A state such as a light intensity distribution or direction of diffracted light emitted at an angle (diffraction angle) that is so large that it cannot enter the entrance pupil can be accurately estimated according to the illumination conditions.

It is the figure which made the section which shows schematic structure of the exposure apparatus which concerns on 1st Embodiment into the cross section. 2 is a block diagram showing a control system and the like of the exposure apparatus of FIG. (A) is an enlarged plan view showing a part of a reticle pattern, (B) is an enlarged plan view showing a part of another reticle pattern, and (C) is a pupil plane (illumination pupil plane) of the illumination optical system. It is a figure which shows an example of light intensity distribution. It is a flowchart which shows an example of the estimation method of the state of diffracted light outside an aperture, and an exposure method. It is a figure which shows the exposure apparatus which is measuring light intensity distribution in the pupil plane (projection pupil plane) of a projection optical system. (A) is a diagram showing an example of the light intensity distribution of the 0th-order diffracted light on the projection pupil plane, (B) is a diagram showing an example of the light intensity distribution of the 0th-order and 1st-order diffracted light on the projection pupil plane, (C) FIG. 4 is a diagram showing a shift direction and a shift amount of a light intensity distribution of 0th-order diffracted light. It is a figure which shows an example of the light intensity distribution of the diffracted light estimated in the calculation area | region of a projection pupil surface. (A) is a figure which shows an example of the light intensity distribution in the illumination pupil plane of 2nd Embodiment, (B) and (C) are projection pupil planes by the illumination light inject | emitted from a mutually different position on an illumination pupil plane. FIG. 4D is a diagram showing a formed light intensity distribution, and FIG. 4D is a diagram showing a light intensity distribution formed on the projection pupil plane by diffracted light from the reticle when perpendicularly incident. It is a flowchart which shows an example of the estimation method of the state of diffracted light outside an aperture concerning a 2nd embodiment. It is a figure which shows the exposure apparatus which is measuring light intensity distribution of a projection pupil surface in 2nd Embodiment. It is a figure which shows an example of the light intensity distribution of the diffracted light estimated in the calculation area of a projection pupil surface in 2nd Embodiment. It is an enlarged plan view which shows a part of pattern of the reticle of a modification. It is a flowchart which shows an example of the manufacturing process of an electronic device.

An embodiment of the present invention will be described. First, in this specification, an area optically conjugate with an entrance pupil of an optical system is an area on a plane optically conjugate with a surface on which the entrance pupil of the optical system is set or a surface in the vicinity thereof. Including. Further, the region optically conjugate with the exit pupil of an optical system includes a region on a surface optically conjugate with a surface on which the exit pupil of the optical system is set or a surface in the vicinity thereof.
Also, setting or measuring or determining the light intensity distribution in the exit pupil of a certain optical system sets the light intensity distribution in a region optically conjugate with the exit pupil of that optical system, or Includes measuring or seeking. Similarly, storing the light intensity distribution at the exit pupil of an optical system includes storing the light intensity distribution in a region optically conjugate with the exit pupil of the optical system. The state of light that does not enter the entrance pupil of an optical system includes the state of light that does not enter a region optically conjugate with the entrance pupil of the optical system. Similarly, performing a certain process based on the light intensity distribution outside the exit pupil of a certain optical system is based on the light intensity distribution in a region outside the region optically conjugate with the exit pupil of this optical system. Including performing.

  Further, a distribution corresponding to a light intensity distribution in an exit pupil of a certain optical system (including a case including a plurality of optical systems) in a region optically conjugate with the exit pupil (hereinafter referred to as a corresponding distribution). Means a light intensity distribution formed in a region optically conjugate with the exit pupil by the light having the light intensity distribution formed in the exit pupil of the optical system. Furthermore, the degree of correlation between one light intensity distribution in an exit pupil of an optical system and another light intensity distribution corresponds to that one light intensity distribution in a region conjugate to the exit pupil of the optical system and the optical system. And the degree of correlation between the distribution corresponding to other light intensity distributions.

[First Embodiment]
A first embodiment will be described with reference to FIGS. FIG. 1 schematically shows the overall configuration of an exposure apparatus EX according to the present embodiment. The exposure apparatus EX is, for example, a scanning exposure type projection exposure apparatus composed of a scanning stepper (scanner). The exposure apparatus EX includes a projection optical system PL. Hereinafter, a reticle R and a semiconductor wafer (hereinafter referred to as a wafer) W are taken in a plane (a plane parallel to a horizontal plane in this embodiment) orthogonal to the Z axis parallel to the optical axis AX of the projection optical system PL. In the following description, the X axis is taken in the direction of the relative scanning and the Y axis is taken in the direction perpendicular to the Z axis and the X axis. In addition, the rotation directions around the axes parallel to the X axis, the Y axis, and the Z axis are also referred to as θx, θy, and θz directions.

  The exposure apparatus EX includes an exposure light source 30 that generates exposure illumination light (exposure light) IL, an illumination optical system ILS that illuminates a reticle R (mask) using the illumination light IL from the light source 30, and a reticle R. Is provided with a reticle stage RST that moves while holding. Further, the exposure apparatus EX includes a projection optical system PL that exposes the wafer W (substrate) with illumination light IL emitted from the reticle R, a wafer stage WST that holds and moves the wafer W, and characteristics of the reticle R (mask characteristics). And a main control device 14 (see FIG. 2) including a computer that comprehensively controls the operation of the entire device. An exposure main body of exposure apparatus EX (a portion including illumination optical system ILS, reticle stage RST, projection optical system PL, and wafer stage WST) is an environmental chamber (not shown) to which a temperature-controlled clean gas is supplied. It is installed inside.

  As the illumination light IL, for example, ArF excimer laser light (wavelength 193 nm) is used. As illumination light, KrF excimer laser light (wavelength 248 nm), harmonics of a YAG laser or a solid-state laser (semiconductor laser, etc.), or a bright line (i-line etc.) of a mercury lamp can be used. The illumination optical system ILS has a predetermined configuration of linearly polarized light supplied from the light source 30 as indicated by a dotted line and disclosed in, for example, US Patent Application Publication No. 2003/0025890. A mirror MR1 that reflects illumination light IL for exposure such as non-polarized light, a spatial light modulator 32 that reflects the reflected light by an array of many tilt angle variable mirror elements, and collects light from the array of mirror elements And a condensing optical system 33 and a mirror MR2 for reflecting, and a fly-eye lens 34 (optical integrator) for forming a surface light source (secondary light source) on the exit surface from the reflected light. In the present embodiment, the exit surface of the fly-eye lens 34 or a surface in the vicinity thereof is a pupil plane (hereinafter referred to as illumination pupil plane) IPP of the illumination optical system ILS.

  The illumination control unit 46 (see FIG. 2) controls the tilt angle of each mirror element of the spatial light modulator 32 under the control of the main control device 14, and thereby the light intensity distribution (light quantity distribution) of the illumination pupil plane IPP. Can be set to a distribution corresponding to various illumination conditions in which the light intensity (light quantity) increases in a circular region, a multipolar region, or a ring-shaped region. If necessary, a variable aperture stop 35 is installed on the illumination pupil plane IPP or in the vicinity thereof. As an example, when a variable aperture stop 35 having a circular aperture is installed at or near the illumination pupil plane IPP, an area within the circular aperture is referred to as an illumination pupil 37. When the variable aperture stop 35 is not installed in the illumination pupil plane IPP or in the vicinity thereof, the contour portion of the light intensity distribution on the illumination pupil plane IPP (this) is reflected by the reflected light from each mirror element of the spatial light modulator 32. The contour portion of the region where the light intensity distribution becomes a predetermined level or more is defined. In this case, as an example, a circular area circumscribing an area where the light intensity distribution is equal to or higher than a predetermined level is referred to as an illumination pupil 37. The illumination pupil 37 is usually a part of a region surrounded by a circumference 71I (see FIG. 3C) where the coherence factor (so-called σ value) is 1. The illumination pupil 37 is an area optically conjugate with the exit pupil of the illumination optical system ILS.

  The illumination optical system ILS further includes a condenser optical system 36 that illuminates an elongated slit-shaped illumination area IAR in the X direction of the pattern surface (lower surface) Ra of the reticle R with illumination light IL from the secondary light source, and illumination It has a variable field stop (not shown) that defines the shape of the region IAR. In place of the spatial light modulator 32, a plurality of diffractive optical elements arranged in the illumination optical path in an interchangeable manner can also be used.

  Further, the illumination optical system ILS is provided with a photoelectric sensor (integrator sensor) (not shown) that measures the amount of light branched from the illumination light IL, and the measurement value of the integrator sensor is supplied to the main controller 14. Yes. The main controller 14 can monitor the integrated irradiation energy of the projection optical system PL from the measured value. In addition, it is also possible to use the exposure duration as alternative information for the integrated irradiation energy.

  The reticle R is held on the upper surface of the reticle stage RST by vacuum suction or the like, and a device pattern such as a circuit pattern and an alignment mark (not shown) are formed on the pattern surface Ra of the reticle R. The reticle stage RST can be driven minutely in the XY plane by the reticle stage drive system 41 of FIG. 2 including, for example, a linear motor and the like, and can be driven at a scanning speed specified in the scanning direction (X direction).

  Position information within the moving surface of the reticle stage RST (including the position in the X direction, the Y direction, and the rotation angle in the θz direction) is transferred to the moving mirror 22 (or mirror-finished) by the reticle interferometer 24 including a laser interferometer. For example, it is always detected with a resolution of about 0.5 to 0.1 nm via the stage end face. The measurement value of reticle interferometer 24 is sent to main controller 14 in FIG. Main controller 14 controls the position and speed of reticle stage RST by controlling reticle stage drive system 41 based on the measured values.

  The projection optical system PL is, for example, telecentric on both sides and has a predetermined projection magnification β (for example, a reduction magnification of 1/4 times, 1/5 times, etc.). The projection optical system PL is configured by holding a plurality of optical elements (not shown) in a predetermined positional relationship within a cylindrical barrel 17. The lens barrel 17 may be formed by connecting a plurality of annular divided lens barrels. An aperture stop AS is provided on the pupil plane (hereinafter referred to as projection pupil plane) PLP of the projection optical system PL. In the present embodiment, a region surrounded by the aperture Asa of the aperture stop AS is referred to as a projection pupil 71A. The projection pupil 71A is optically conjugate with the entrance pupil and the exit pupil of the projection optical system PL. The circumference on the illumination pupil plane IPP optically conjugate with the contour (circumference) of the projection pupil 71A is the circumference where the σ value is 1.

  Further, the projection pupil plane PLP is optically conjugate with the illumination pupil plane IPP, and the projection pupil plane PLP is also an optical Fourier transform plane with respect to the pattern surface Ra of the reticle R (the object plane of the projection optical system PL). is there. The projection optical system PL may be of a type that forms an intermediate image, and the aperture stop AS is installed at a position near the projection pupil plane PLP, a position optically conjugate with the projection pupil plane PLP, or a position near this position. May be. Further, the projection optical system PL may be a refractive system, but may also be a catadioptric system.

  In FIG. 1, when the illumination area IAR of the pattern surface Ra of the reticle R is illuminated by the illumination light IL from the illumination optical system ILS, the illumination area IAR passes through the reticle R and passes through the projection optical system PL. An image of the device pattern is formed in an exposure area IA (an area optically conjugate with the illumination area IAR) of one shot area of the wafer W. As an example, the wafer W includes a wafer formed by applying a photoresist (photosensitive material) with a thickness of about several tens to 200 nm to a disk-shaped base made of a semiconductor such as silicon and having a diameter of about 200 to 450 mm.

  Further, in the exposure apparatus EX, in order to perform exposure using the liquid immersion method, local liquid immersion is performed so as to surround the lower end portion of the optical element on the most image plane side (wafer W side) constituting the projection optical system PL. A nozzle unit 18 that constitutes a part of the apparatus and supplies and recovers the exposure liquid Lq (for example, pure water) in the liquid immersion area including the exposure area IA is provided. The nozzle unit 18 is connected to a liquid supply device 43 and a liquid recovery device 44 (see FIG. 2) via a pipe (not shown) for supplying the liquid Lq. If the immersion type exposure apparatus is not used, the above-mentioned local immersion apparatus need not be provided.

  In addition, a pipe (not shown) installed so as to be in contact with the holding mechanism of the plurality of optical elements in the projection optical system PL is provided with a liquid Co whose temperature is controlled from the temperature control unit 28 via the supply pipe 29A. (For example, pure water, fluorine-based liquid, refrigerant, or the like) is supplied, and the liquid Co that has flowed through the piping in the projection optical system PL is recovered by the temperature control unit 28 via the recovery piping 29B. By circulating the liquid Co whose temperature is controlled by the temperature controller 28 in the projection optical system PL, the temperature rise of the plurality of optical elements in the projection optical system PL due to the integrated irradiation energy of the illumination light IL is suppressed. .

Further, the projection optical system PL includes an imaging characteristic correction system that corrects imaging characteristics represented by wavefront aberrations such as distortion and spherical aberration by controlling the postures of a plurality of predetermined optical elements (for example, lenses) therein. 16 is provided. Such an imaging characteristic correction system is disclosed in, for example, US Patent Application Publication No. 2006/244940.
Further, the exposure apparatus EX performs an alignment of the wafer W with an aerial image measurement system (not shown) that measures the position of the image of the alignment mark of the reticle R by the projection optical system PL in order to align the reticle R. For example, an image processing type (FIA type) alignment system AL, an irradiation system 45a and a light receiving system 45b, and an oblique incidence type multi-point autofocus sensor for measuring Z positions at a plurality of locations on the surface of the wafer W ( (Hereinafter referred to as a multi-point AF system) 45 (see FIG. 2).

  Wafer stage WST is supported in a non-contact manner on an upper surface parallel to the XY plane of base board WB via a plurality of air pads (not shown). Wafer stage WST can be driven in the X and Y directions by a stage drive system 42 (see FIG. 2) including, for example, a planar motor or two sets of orthogonal linear motors. Wafer stage WST includes a stage main body that is driven in the X direction and the Y direction, a wafer holder WH that is provided on the stage main body and holds wafer W by vacuum suction, the Z position of wafer W, the θx direction, and the θy direction. And a Z stage mechanism (not shown) for controlling the tilt angle.

  In addition, a wafer interferometer 26 composed of a laser interferometer is arranged for measuring position information of wafer stage WST. Instead of the wafer interferometer 26, an encoder type position measurement system combining a diffraction grating and a detector may be used. Position information within the moving surface of wafer stage WST (including the position in the X direction, the Y direction, and the rotation angle in the θz direction) is always detected by the wafer interferometer 26 with a resolution of about 0.5 to 0.1 nm, for example. The measured value is sent to the main controller 14. Main controller 14 controls the position and speed of wafer stage WST by controlling stage drive system 42 based on the measurement value.

  In addition, measurement unit 20 capable of measuring the light intensity distribution (light quantity distribution) in projection pupil 71A is incorporated in wafer stage WST. The measuring unit 20 has a surface having the same height as the surface of the wafer W, a flat glass substrate 21A having a pinhole 21Aa formed on the surface, and light reception for condensing illumination light that has passed through the pinhole 21Aa. It has an optical system 21B, a CCD or CMOS type two-dimensional image sensor 21C that receives illumination light collected by the light receiving optical system 21B, and a housing 21D that holds these members. With the pinhole 21Aa moved into the exposure area IA, the light receiving surface of the image sensor 21C is optically conjugate with respect to the projection pupil plane PLP by the light receiving optical system 21B. However, since the light beam incident on the measurement unit 20 is only the light beam that has passed through the aperture stop AS, the projection pupil on the projection pupil plane PLP is processed by processing the detection signal of the image sensor 21C by an image processing unit (not shown). The light intensity distribution of 71A can be measured. The measured light intensity distribution is supplied to the main controller 14. Note that the measurement unit 20 can also be regarded as measuring the light intensity distribution of the exit pupil of the projection optical system PL.

  The main controller 14 composed of a computer includes a plurality of arithmetic processors, a memory, a storage device, and the like. The main control unit 14 includes an input / output unit 48, a recording / reproducing unit 50 that records and reproduces data on a recording medium 51 such as a DVD (digital versatile disk), a CD-ROM, or a flash memory. Data is exchanged between a storage unit 52 such as a semiconductor non-volatile memory, a calculation unit 54 including a calculation processor and a memory, and a host computer 12 that supplies control information to a plurality of exposure apparatuses and a plurality of lithography apparatuses. An interface unit (not shown) is connected. The estimation apparatus 10 that estimates the characteristics of the reticle R includes the illumination control unit 46, the light intensity distribution measurement unit 20, the storage unit 52, and the calculation unit 54. Note that the arithmetic unit 54 may be one function on software of a computer constituting the main control device 14. The program executed by the main control device 14 and the calculation unit 54 is recorded in, for example, the recording medium 51 and can be read from the recording medium 51 by the recording / reproducing unit 50.

  As a basic operation during exposure of the wafer W, after the alignment of the reticle R and the wafer W is performed, the wafer stage WST is moved in the X direction and the Y direction (step movement), so that the shot of the wafer W to be exposed is shot. The area moves to the front of the exposure area of the projection optical system PL. Then, under the control of the main controller 14, the reticle stage RST and the wafer stage WST are synchronously driven while exposing the shot area of the wafer W with an image of a part of the pattern of the reticle R by the projection optical system PL. Thus, by scanning the reticle R and the wafer W with respect to the projection optical system PL in the X direction, for example, using the projection magnification as the speed ratio, the image of the pattern of the reticle R is scanned and exposed over the entire shot area. By repeating the step movement and the scanning exposure in this way, a pattern image of the reticle R is sequentially exposed to a plurality of shot regions of the wafer W by a step-and-scan method.

  If such exposure is continued, a plurality of illumination light IL made of diffracted light (including zero-order light) generated from the pattern of the reticle R passes through the projection optical system PL. The temperature of the optical element gradually increases, and the imaging characteristics (for example, wavefront aberration) of the projection optical system PL change. In the present embodiment, since the temperature-controlled cooling liquid Co is supplied from the temperature control unit 28 into the projection optical system PL, the temperature distribution of these optical elements gradually saturates from the reticle R. It converges to a certain temperature distribution according to the light intensity distribution of the generated diffracted light. Further, each optical element has a very small coefficient of thermal expansion, so that the amount of deformation is small, but the refractive index distribution slightly changes according to the temperature distribution. Therefore, based on the light intensity distribution of the diffracted light and the integrated irradiation energy of the illumination light IL, the variation amount of the temperature distribution of each optical element (or the optical element of the part that contributes the most to the fluctuation of the optical characteristics) and the convergence time By obtaining the temperature distribution by calculation and obtaining the refractive index distribution of the optical element from the obtained temperature distribution, it is possible to calculate the variation amount of the imaging characteristics of the projection optical system PL at each time point during the exposure.

  In the present embodiment, of the diffracted light generated from the pattern of the reticle R, the fluctuation of the wavefront aberration of the projection optical system PL due to the diffracted light that passes through the projection pupil 71A (aperture stop AS) of the projection optical system PL and reaches the image plane. And a diffracted light having a diffraction angle that is so large that it cannot enter the entrance pupil of the projection optical system PL, that is, a diffraction angle larger than the half angle of the opening on the incident side of the projection optical system PL. It is assumed that a fluctuation amount of the wavefront aberration of the projection optical system PL (hereinafter referred to as a second aberration fluctuation amount) due to out-of-aperture diffracted light that is diffracted light is obtained. In this case, the first aberration fluctuation amount is caused by the fluctuation of the temperature distribution caused by the diffracted light passing through the optical element in the projection optical system PL. On the other hand, the second aberration fluctuation amount is that the diffracted light outside the aperture is incident on the lens barrel 17 holding the optical element of the projection optical system PL, the temperature distribution of the lens barrel 17 is fluctuated, and the temperature distribution fluctuates. This is because the temperature distribution of the optical element varies.

  Note that the light intensity distribution of the diffracted light incident on the entrance pupil of the projection optical system PL, that is, the diffracted light passing through the projection pupil 71A (aperture stop AS) can be measured by the measuring unit 20, but cannot pass through the aperture stop AS. The light intensity distribution of the diffracted light outside the aperture cannot be measured by the measuring unit 20. For this reason, in the present embodiment, it is assumed that the diffracted light outside the aperture is incident on a region outside the projection pupil 71A on the projection pupil plane PLP of the projection optical system PL. Are estimated, the direction in which the diffracted light outside the aperture is incident on the projection optical system PL, and / or the state of the light intensity of the diffracted light outside the aperture. Hereinafter, a method for estimating the state of diffracted light outside the aperture generated from the reticle R using the estimation device 10 and a result obtained by this estimation method are used to correct the imaging characteristics as the optical characteristics of the projection optical system PL. An example of a method for exposing a wafer will be described with reference to the flowchart of FIG. This operation is controlled by the main controller 14.

  In the present embodiment, as an example, as shown in FIG. 3A, the reticle R has a pitch (period) px close to the resolution limit (including the case of tilted illumination) of the projection optical system PL in the X direction. It is assumed that a device pattern including a line and space pattern (hereinafter referred to as an L & S pattern) 60X is formed. The L & S pattern 60X includes a line pattern 60Xa including an opening having a width px / 2 in the X direction and a light shielding portion having a width px / 2 in the X direction in the light shielding film 59 on the pattern surface of the light transmissive glass substrate 56. The space patterns 60Xb are alternately arranged. Furthermore, the illumination conditions when using the reticle R are, for example, quadrupole illumination.

  In this case, the light intensity distribution 70 of the illumination pupil 37 on the illumination pupil plane IPP of the illumination optical system ILS in FIG. 1 sandwiches the optical axis AX of the illumination optical system ILS in the X direction, as shown in FIG. The light intensity increases in the pair of regions 70A and 70B arranged in this manner and the pair of regions 70C and 70D arranged so as to sandwich the optical axis AX in the Y direction. The illumination condition using the light intensity distribution 70 in FIG. 3C is an L & S pattern 60Y (line pattern) having a pitch py close to the resolution limit of the projection optical system PL in the Y direction, as shown in FIG. 3B. It can also be used as illumination conditions for reticle R1 on which a device pattern including 60Ya and space pattern 60Yb) is formed.

  First, in step 102 of FIG. 4, the main controller 14 reads the illumination condition of the reticle R from the exposure data file stored in the storage unit 52, and the light intensity distribution 70 corresponding to this illumination condition is set. In addition, the spatial light modulator 32 of the illumination optical system ILS is driven via the illumination control unit 46. However, at this stage, reticle R is not loaded on reticle stage RST. Then, as shown in FIG. 5, for example, in a state where a transparent glass substrate GP is placed on the reticle stage RST, for example, the wafer stage WST is driven to expose the light receiving unit of the measuring unit 20 to the projection optical system PL. Move to a region, illuminate the glass substrate GP with the illumination light IL from the illumination optical system ILS (or illuminate in a transparent state), and the light intensity distribution (hereinafter, 0) in the projection pupil 71A by the measurement unit 20 The next intensity distribution 72 (see FIG. 6A) is measured (step 104). Note that, during measurement using the measurement unit 20, the liquid Lq for immersion exposure may be supplied between the projection optical system PL and the measurement unit 20, but measurement is performed without the liquid Lq. (The same applies hereinafter).

  The zero-order intensity distribution 72 measured in this way is a distribution obtained by expanding and contracting the light intensity distribution 70 in the illumination pupil 37 at a magnification between the illumination pupil plane IPP and the projection pupil plane PLP (a distribution corresponding to the light intensity distribution 70). ). For this reason, as shown in FIG. 6A, the zero-order intensity distribution 72 has a large light intensity in the regions 70AP to 70DP on the projection pupil plane PLP conjugate with the four regions 70A to 70D in FIG. Become. Further, a square area including the projection pupil 71A on the projection pupil plane PLP is divided into a plurality of pixels with a predetermined width in the X direction and the Y direction, and the i th pixel in the X direction and the j th pixel G (xi, yj) in the Y direction. ) Is the value of the function org [i] [j]. The pixel G (xi, yj) corresponds to each pixel of the image sensor 21D of the measurement unit 20. The pixel G (xi, yj) means that the coordinates in the center X direction and Y direction are (xi, yj). Note that i is an integer from 0 to I (I is an integer from several hundred to several thousand), and j is an integer from 0 to J (J is an integer from several hundred to several thousand, for example). At this time, the measured zero-order intensity distribution 72 is represented by the function org [i] [j], and the value of the function org [i] [j] is 0 in the region outside the projection pupil 71A.

  Next, the glass substrate GP is unloaded from the reticle stage RST, the reticle R is loaded onto the reticle stage RST, and alignment is performed (step 106). Then, the reticle R is illuminated with the illumination light IL from the illumination optical system ILS, and the light intensity distribution (hereinafter referred to as diffraction intensity distribution) 74 in the projection pupil 71A due to the diffracted light from the reticle R (see FIG. 6B). Is measured by the measuring unit 20 (step 108). Information of the measured diffraction intensity distribution 74 is stored in the storage unit 52.

  In FIG. 5, from the L & S pattern 60X of the reticle R, the diffraction angle in the θx direction is large in addition to the diffracted light DL (including the 0th order light) incident on the entrance pupil (and thus the projection pupil 71A) of the projection optical system PL. Therefore, out-of-aperture diffracted lights HDA and HDB that do not enter the entrance pupil are also emitted. The diffraction intensity distribution 74 measured in step 108 is a distribution formed by the diffracted light DL. As shown in FIG. 6B, the diffraction intensity distribution 74 in the projection pupil 71A has light intensity in the regions 70AP to 70DP where the 0th order light is incident and the regions 70BD1 and 70AD2 where the ± first order diffracted light in the X direction is incident. Becomes larger. In this case, when the average light intensity of the i-th pixel G (xi, yj) in the X direction and the j-th pixel in the Y direction is the value of the function dif [i] [j] in FIG. The diffraction intensity distribution 74 is expressed by the function dif [i] [j]. The value of the function dif [i] [j] is 0 in the area outside the projection pupil 71A. Information of the measured intensity distributions 72 and 74 is supplied to the calculation unit 54, and the calculation unit 54 performs the calculation processing of the following steps 110 to 116.

  First, in step 110, the 0th-order intensity distribution 72 is virtually shifted on the projection pupil plane PLP in the X direction and / or the Y direction, and is superimposed on the diffraction intensity distribution 74, and is defined by the following expression. Calculate the correlation function v [p] [q]. In this case, the integer p represents the shift amount in the X direction in pixel units, and the integer q represents the shift amount in the Y direction in pixel units.

そして、相関関数ｖが極値（ピーク値）を取るときの０次強度分布７２のＸ方向、Ｙ方向のシフト量を求める。この結果求められた相関関数ｖが極値を取る回数を（Ｋ＋１）回（Ｋは１以上の整数）とする。このとき、相関関数ｖがｋ番目（ｋは０〜Ｋの整数）の極値を取るときの０次強度分布７２のＸ方向、Ｙ方向のシフト量を表す整数（ｐ，ｑ）の組を（p[k], q[k]）で表す。ただし、ｋ＝０は、Ｘ方向、Ｙ方向のシフト量が０の場合（p[k]=0, q[k]=0）（シフト前の０次光の分布）であるとする。

Then, the shift amount in the X direction and the Y direction of the zero-order intensity distribution 72 when the correlation function v takes an extreme value (peak value) is obtained. The number of times the correlation function v obtained as a result takes an extreme value is (K + 1) times (K is an integer of 1 or more). At this time, a set of integers (p, q) representing the shift amounts in the X direction and Y direction of the zero-order intensity distribution 72 when the correlation function v takes the k-th extreme value (k is an integer of 0 to K). (P [k], q [k]). However, k = 0 is assumed to be when the shift amount in the X direction and the Y direction is 0 (p [k] = 0, q [k] = 0) (distribution of 0th-order light before the shift).

  FIG. 6C conceptually shows an example of the distribution of the value of the correlation function v with respect to the set of shift amounts (p, q) (the higher the value, the higher the density is expressed). The peak 76A at the origin (p, q) is a portion having a high correlation with the zero-order light, and the value gradually decreases with respect to the portion 76Aa around the peak 76A and further to the portion 76Ab around it. Similarly, the peaks 76B and 76C are portions where the correlation with the ± first-order diffracted light in the X direction is high, and in FIG. 6C, there are three extreme values of the correlation function v.

  Next, in step 112, the zero-order intensity distribution 72 (function org [i + p [k]] [j + q] shifted in the X and Y directions when the correlation function v takes the kth extreme value. [k]]) are respectively given weighting factors a [k] (k = 0 to K), and the weighted sum of the zero-order intensity distributions 72 shifted in the X and Y directions when K extreme values are taken. The distribution function res [i] [j] is calculated as follows.

そして、その加重和の分布関数res[i][j]と、回折強度分布７４を表す関数dif[i][j]との差分の二乗和が最小になるように、最小二乗法で係数ａ［ｋ］（ｋ＝０〜Ｋ）の値を決定する。具体的に、最尤関数Ｓを以下のように定義する。

The coefficient a is calculated by the least square method so that the square sum of the difference between the distribution function res [i] [j] of the weighted sum and the function dif [i] [j] representing the diffraction intensity distribution 74 is minimized. The value of [k] (k = 0 to K) is determined. Specifically, the maximum likelihood function S is defined as follows.

そして、この最尤関数Ｓの係数ａ［ｋ］による偏微分が次式のように０になるときの係数ａ［ｋ］を決定する（ｋ＝０〜Ｋ）。
∂Ｓ／∂ａ［ｋ］＝０ …（７）
次に、ステップ１１４において、ステップ１１２で決定された係数ａ［ｋ］（ｋ＝０〜Ｋ）、及びこのときのシフト量の組（p[k], q[k]）を用いて０次強度分布７２の関数org[i][j]をシフトした関数を用いて、上記の式（４）の加重和の分布関数res[i][j]の値を画素単位で計算する。ただし、この場合の計算は、図７に示すように、投影瞳面ＰＬＰにおいて、光軸ＡＸを中心とする円形の投影瞳７１Ａ（この半径をｒとする）を囲むように、光軸ＡＸを中心として設定される半径が３ｒの領域（以下、計算領域という）７１Ｂで行われる。このように計算領域７１Ｂの半径が投影瞳７１Ａの半径の３倍になるのは、ステップ１１０で０次強度分布７２をＸ方向、Ｙ方向にシフトさせるときに、０次強度分布７２と回折強度分布７４とが重なる可能性のあるシフト量の絶対値は、最大で投影瞳７１Ａの直径（２ｒ）であり、式（４）で規定される関数の値は、計算領域７１Ｂの外部では０になるからである。

Then, the coefficient a [k] when the partial differentiation of the maximum likelihood function S by the coefficient a [k] becomes 0 as shown in the following equation is determined (k = 0 to K).
∂S / ∂a [k] = 0 (7)
Next, in step 114, using the coefficient a [k] (k = 0 to K) determined in step 112 and the set of shift amounts (p [k], q [k]) at this time, the 0th order Using the function obtained by shifting the function org [i] [j] of the intensity distribution 72, the value of the distribution function res [i] [j] of the weighted sum in the above equation (4) is calculated in units of pixels. However, in this case, as shown in FIG. 7, in the projection pupil plane PLP, the optical axis AX is set so as to surround a circular projection pupil 71A (this radius is r) centered on the optical axis AX. This is performed in an area 71B having a radius 3r set as the center (hereinafter referred to as a calculation area) 71B. Thus, the radius of the calculation area 71B becomes three times the radius of the projection pupil 71A when the 0th-order intensity distribution 72 is shifted in the X and Y directions in step 110, and the 0th-order intensity distribution 72 and the diffraction intensity. The absolute value of the shift amount that may overlap the distribution 74 is the diameter (2r) of the projection pupil 71A at the maximum, and the value of the function defined by the equation (4) is 0 outside the calculation region 71B. Because it becomes.

  The distribution function res [i] [j] of the weighted sum of Expression (4) calculated using the coefficient a [k] determined in Step 112 represents the light intensity distribution 78 in the calculation region 71B of FIG. . As an example, as shown in FIG. 6C, when the extreme value of the correlation function v [p] [q] in the equation (2) has a positive value with the origin (k = 0) and p (k = 1) and when p takes a certain negative value (assuming k = 2), the coefficients a [0], a [1], and a [2] are determined to be certain values. The light intensity distribution 78 calculated using these coefficients a [0] to a [2] is a light intensity distribution of zero-order light in which the light intensity increases in the regions 70AP to 70DP in the projection pupil 71A, and the region 70AP. Light intensity distribution of + 1st order diffracted light of regions 70AD1 to 70DD1 moved in the + X direction through 70DP, and light intensity distribution of -1st order diffracted light in regions 70AD2 to 70DD2 moved in the -X direction of regions 70AP to 70DP. It is out. As an example, the region 70BD1 in the distribution of the + 1st order diffracted light is in the projection pupil 71A, and the region 70AD2 in the distribution of the −1st order diffracted light is in the projection pupil 71A.

  In this case, diffracted light (including zero-order light) incident on the regions 70AD1 to 70DD1, 70BD1, and 70AD2 in the projection pupil 71A is generated from the L & S pattern 60X of the reticle R in FIG. 5 and is incident on the projection optical system PL. Is incident on the light. On the other hand, ± 1st-order diffracted light that virtually enters the regions 70AD1, 70CD1, 70DD1 and 70BD2, 70CD2, 70DD2 in the annular region outside the projection pupil 71A in the calculation region 71B is from the L & S pattern 60X of the reticle R. Out-aperture diffracted light HDA and HDB that are generated and do not enter the entrance pupil of the projection optical system PL. In other words, the light intensity distribution 78a in the projection pupil 71A is the distribution of diffracted light incident on the entrance pupil of the projection optical system PL, and the light intensity distribution 78b outside the projection pupil 71A in the calculation area 71B is out-of-aperture diffraction. Represents the distribution of light. Therefore, the virtual light intensity distribution 78b of the diffracted light outside the aperture on the projection pupil plane PLP can be estimated (calculated).

  In the next step 116, from the virtual light intensity distribution 78b of the diffracted light HDA and HDB outside the aperture obtained in step 114, the outside of the aperture with respect to the lens barrel 17 of the projection optical system PL of FIG. The incident positions and intensities of the diffracted lights HDA and HDB are estimated. As an example, in FIG. 7, the area outside the projection pupil 71A inside the calculation area 71B is divided into a plurality of unit areas H (xi, yj) having a predetermined width in the X and Y directions, and each unit is determined from the light intensity distribution 78b. The average light intensity in the region (xi, yj) is obtained as the light intensity of the diffracted light outside the aperture that is virtually incident on the unit region H (xi, yj). The unit area H (xi, yj) means that the coordinates in the center X direction and Y direction are (xi, yj). The unit area H (xi, yj) may be an integer multiple of one pixel in the projection pupil 71A.

  Further, in the projection pupil plane PLP of FIG. 7, a distance rh (i, j) from the optical axis AX to the center of the unit area H (xi, yj) and a straight line passing through the optical axis AX and parallel to the X axis. Then, an angle φ (i, j) formed by a straight line connecting the optical axis AX and the center of the unit region H (xi, yj) is obtained. At this time, if the outside-aperture diffracted light that virtually enters the unit region H (xi, yj) is the outside-aperture diffracted light HDA in FIG. 1, the incident direction of the outside-aperture diffracted light HDA in the XY plane with respect to the lens barrel 17 Is the angle φ (i, j). Furthermore, when the diffraction angle of the outside-aperture diffracted light HDA in the incident direction is hφA and the focal length of the front group optical system (an optical system between the aperture stop AS and the object plane) of the projection optical system PL is fa, Using the distance rh (i, j) of 7 unit regions H (xi, yj), the following relationship is obtained.

fa · sin (hφA) = rh (i, j) (8)
Accordingly, the diffraction angle hφA of the outside-aperture diffracted light HDA incident on the unit region H (xi, yj) in the region outside the projection pupil 71A can be obtained from Expression (8). Similarly, regarding the out-of-aperture diffracted light HDB emitted in the −X direction in FIG. 1, the incident direction in the XY plane, the diffraction angle hφB in this direction, and the light intensity can be obtained. In this way, the incidence direction, diffraction angle, and light intensity of all out-of-aperture diffracted light incident on the area outside the projection pupil 71A in the calculation area 71B can be estimated in the unit area H (xi, yj) as a unit ( Can be calculated).

  In the following, for the convenience of explanation, it is assumed that the out-of-aperture diffracted light generated from the reticle R is only out-of-aperture diffracted light HDA and HDB. Further, the positional relationship between the reticle R and the projection optical system PL (for example, an average positional relationship during scanning exposure may be known), the shape of the barrel 17 of the projection optical system PL, and the barrel 17 and the barrel. The positional relationship with a plurality of optical elements in 17 is also known. From the positional relationship and shape information, and the incident direction and diffraction angle of the above-mentioned diffracted light HDA, HDB, the incident position of these diffracted light HDA, HDB with respect to the lens barrel 17 can be calculated. Further, the light intensity of the diffracted light HDA and HDB outside the aperture is also obtained as the light intensity of the unit region H (xi, yj). Information on the incident position and light intensity of the diffracted light outside the aperture with respect to the lens barrel 17 thus obtained is stored in the storage unit 52.

  In the next step 118, alignment is performed by loading an unexposed wafer W coated with a photoresist on wafer stage WST. Then, the first aberration calculation unit in the main controller 14 uses the diffraction intensity distribution 74 in the projection pupil 71A of FIG. 6B measured in step 108 and the integrator sensor (not shown) in the illumination optical system ILS. The first aberration fluctuation amount of the projection optical system PL (the fluctuation amount of the wavefront aberration of the projection optical system PL due to the diffracted light passing through the projection pupil 71A) is calculated from the integrated irradiation energy detected via the projection optical system PL (step 120).

  Further, the temperature calculation unit in the main controller 14 is detected via the incident position and light intensity of the outside-aperture diffracted light HDA and HDB obtained in step 116 with respect to the lens barrel 17 and an integrator sensor (not shown). From the integrated irradiation energy, for example, the amount of variation in the temperature distribution of the lens barrel 17 by the finite element method, and thus the optical elements in the lens barrel 17, for example, optical elements close to the position where the diffracted light HDA, HDB outside the aperture enters the lens barrel 17. A fluctuation amount of the temperature distribution (or a fluctuation amount of the temperature average value of the optical element) is calculated. Further, the second aberration calculator in the main controller 14 determines the second aberration fluctuation amount (out-of-aperture diffracted light HDA, The fluctuation amount of the wavefront aberration of the projection optical system PL by HDB is calculated (step 122). Then, the second aberration calculation unit outputs information on the total aberration variation obtained by adding the calculated first aberration variation and second aberration variation to the control unit of the imaging characteristic correction system 16. To do. In response to this, the imaging characteristic correction system 16 corrects the imaging characteristic of the projection optical system PL so as to cancel out the total aberration fluctuation amount (step 124). Thereby, the imaging characteristics of the projection optical system PL are maintained in a good state. The first aberration calculator, the temperature calculator, and the second aberration calculator in the main controller 14 are functions on the software of the computer, but these functions may be realized by hardware.

  In this state, the wafer W is scanned and exposed with an image of the pattern of the reticle R by the projection optical system PL (step 126). After unloading the exposed wafer W (step 128), when the next wafer is exposed (step 130), the operation returns to step 118, and the next wafer is loaded and the imaging characteristics of the projection optical system PL are changed. The calculation and correction of the variation amount and the exposure of the wafer are repeated.

  As described above, according to the present embodiment, the shift amount and the shift direction when the correlation degree with the diffraction intensity distribution 74 is high by shifting the zero-order intensity distribution 72 are obtained, and the shift amount and shift when the correlation degree is high. The value of the coefficient a [k] of the distribution obtained by shifting the zeroth-order intensity distribution 72 in the direction is determined, and the weighted sum of the distribution obtained by the shift is used to move the region outside the projection pupil 71A within the calculation region 71B. The light intensity distribution of diffracted light outside the aperture that is virtually incident is estimated. Therefore, the light intensity distribution of the diffracted light outside the aperture can be estimated accurately and efficiently only by obtaining the 0th-order intensity distribution 72 and the diffraction intensity distribution 74.

  Further, from the light intensity distribution, the position where the diffracted light outside the aperture is incident on the lens barrel 17 of the projection optical system PL and the light intensity at the time of the incidence are obtained to determine the temperature distribution of the lens barrel 17 and thus the optical in the lens barrel 17. Since the temperature distribution of the element is obtained, it is possible to obtain the variation amount of the imaging characteristics of the projection optical system PL due to the diffracted light outside the aperture. Therefore, by correcting the fluctuation amount of the imaging characteristic by the imaging characteristic correction system 16, the imaging characteristic of the projection optical system PL is maintained in a good state even when diffracted light outside the aperture is incident on the lens barrel 17. Thus, exposure can be performed with high accuracy.

  As described above, the exposure apparatus EX of the present embodiment includes the estimation apparatus 10 that estimates the state (reticle characteristics) of diffracted light generated from a reticle pattern. Then, the estimating apparatus 10 stores information on the light intensity distribution 70 (first light intensity distribution) in the illumination pupil 37 (region optically conjugate with the exit pupil) of the illumination optical system ILS that illuminates the pattern of the reticle R. A diffraction intensity distribution 74 (second light) in the projection pupil 71A (region optically conjugate with the exit pupil) of the storage unit 52 and the projection optical system PL that forms an image of the pattern of the reticle R illuminated by the illumination optical system ILS. The state of the diffracted light HDA and HDB outside the aperture that is generated from the pattern of the reticle R based on the light intensity distribution 70 and the diffraction intensity distribution 74 and does not enter the entrance pupil of the projection optical system PL based on the light intensity distribution 70 and the diffraction intensity distribution 74 And a calculation unit 54 that estimates Then, the calculation unit 54 performs the processing of the above steps 110, 112, 114, and 116 to estimate the state of the light intensity distribution and the like in the region outside the projection pupil 71A of the projection pupil plane PLP of the diffracted light HDA and HDB outside the aperture. doing.

  The reticle characteristic estimation method of the present embodiment is a method of estimating the state of diffracted light generated from the pattern of the reticle R using the estimation device 10. This estimation method includes step 102 for setting a light intensity distribution 70 (first light intensity distribution) in the illumination pupil 37 of the illumination optical system ILS that illuminates the pattern of the reticle R, and the reticle R illuminated by the illumination optical system ILS. Measuring 108 the diffraction intensity distribution 74 (second light intensity distribution) in the projection pupil 71A of the projection optical system PL that forms a pattern image. Further, in this estimation method, a plurality of light intensity distributions (org [i + p] [j + q] obtained by shifting the zero-order intensity distribution 72 (corresponding distribution) in the projection pupil 71A corresponding to the light intensity distribution 70. ]: Step 110 for obtaining a plurality of light intensity distributions (org [i + p] [j + q]) when the degree of correlation between the third light intensity distribution) and the diffraction intensity distribution 74 is high, and the projection pupil 71A The correlation between the weighted sum (res [i] [j]) using the weight coefficient a [k] of a plurality of light intensity distributions (org [i + p] [j + q]) and the diffraction intensity distribution 74 Step 112 for obtaining the individual coefficient a [k] so that the value becomes high, and a weighted sum of a plurality of light intensity distributions (org [i + p] [j + q]) using the coefficient a [k] Of the obtained light intensity distribution 78 (fourth light intensity distribution), based on the light intensity distribution 78b outside the projection pupil 71A, an extrarotation that does not enter the projection pupil 71A, which is generated from the pattern of the reticle R. And steps 114 and 116 for estimating the incident direction and light intensity of the folded light HDA and HDB with respect to the lens barrel 17.

  According to the aspect of the present invention, from the reticle R to the projection optical system using the information on the light intensity distribution 70 set on the illumination pupil 37 and the measurement result of the light intensity distribution (diffraction intensity distribution 74) of the projection pupil 71A. Accurately estimate the light intensity distribution, direction, and intensity state of the diffracted light HDA and HDB outside the aperture emitted at a diffraction angle large enough not to enter the PL entrance pupil (cannot enter the projection pupil 71A) according to the illumination conditions. it can.

  Further, the exposure apparatus EX of the present embodiment illuminates the pattern of the reticle R with the illumination light IL from the illumination optical system ILS, and exposes the wafer W (substrate) through the pattern and the projection optical system PL with the illumination light IL. Exposure apparatus. The exposure apparatus EX includes an estimation apparatus 10 that performs processing (steps 102 to 116) for estimating the states of the diffracted light beams HDA and HDB that are generated from the pattern of the reticle R and do not enter the entrance pupil of the projection optical system PL. Main control for performing a process (step 122) for obtaining a temperature fluctuation amount of at least one optical element (optical member) constituting the projection optical system PL based on the state of the diffracted light HDA and HDB outside the aperture estimated by the apparatus 10 A temperature calculation unit in the apparatus 14 and a process of correcting the fluctuation amount of the imaging characteristic (optical characteristic) of the projection optical system PL based on the temperature fluctuation amount of the optical element obtained by the temperature calculation unit (step 124). And an imaging characteristic correction system 16 for performing the operation.

According to the exposure apparatus EX or the exposure method using the exposure apparatus EX, since the fluctuation amount of the imaging characteristic of the projection optical system PL caused by the out-of-aperture diffracted light HDA and HDB generated from the reticle R can be corrected, The pattern image of the reticle R can be exposed on the wafer with higher accuracy while maintaining the imaging characteristics of the system PL in a target state with higher accuracy.
In this embodiment, in step 104, the glass substrate GP is placed on the reticle stage RST (or in a plain state), and the zero-order intensity distribution 72 of FIG. doing. However, in the present embodiment, the magnification between the illumination pupil 37 and the projection pupil 71A is known, and the light intensity distribution 70 in the illumination pupil 37 can accurately set a target distribution by the spatial light modulator 32. A distribution obtained by expanding / contracting the design distribution of the light intensity distribution 70 set in the illumination pupil 37 by the known magnification may be used as the zero-order intensity distribution 72. In this case, the measurement process of step 104 can be omitted.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIGS. Also in this embodiment, the exposure apparatus EX shown in FIGS. 1 and 2 of the first embodiment is used. The exposure apparatus EX includes an estimation apparatus 10 that estimates the state (reticle characteristics) of diffracted light generated from the reticle R. Hereinafter, in FIGS. 8A to 8D and FIG. 11, the same reference numerals are given to the portions corresponding to FIGS. 3C, 6A, and 7, and the detailed description thereof is omitted. . In FIG. 10, the same reference numerals are given to the portions corresponding to those in FIG. 5, and the detailed description thereof is omitted.

  Hereinafter, in the present embodiment, a method for estimating the state of diffracted light outside the aperture generated from the reticle R using the estimation device 10 and the imaging characteristics of the projection optical system PL (using the result obtained by this estimation method) ( An example of a method of exposing a wafer using the exposure apparatus EX while correcting the optical characteristics) will be described with reference to the flowchart of FIG. This operation is controlled by the main controller 14 shown in FIG.

Also in the present embodiment, as an example, the reticle R has an L & S pattern 60X (see FIG. 3A) having a pitch px close to the resolution limit (including the case of tilted illumination) of the projection optical system PL in the X direction. Assume that a device pattern is formed.
First, in step 132 in FIG. 9, main controller 14 in FIG. 2 inputs illumination conditions for reticle R from host computer 12 as an example, and stores the input illumination condition data in storage unit 52. However, in this embodiment, for convenience of explanation, illumination conditions when using the reticle R are, for example, annular illumination (conditions using a light intensity distribution in which the light intensity increases in an annular area in the illumination pupil 37). To do.

  Next, as shown in FIG. 10, the reticle R is loaded onto the reticle stage RST for alignment (step 134). In step 136, wafer stage WST is driven to move the light receiving unit of measuring unit 20 to the exposure area of projection optical system PL. Further, the reflected light from the many mirror elements of the spatial light modulator 32 is a region along a straight line passing through the optical axis AX and parallel to the periodic direction of the L & S pattern 60X on the illumination pupil plane IPP of the illumination optical system ILS. Thus, the light is focused on the small circular region (hereinafter referred to as the first pupil point) B1 that is close to the circumference of 1 with the σ value (here, referred to as + X direction) via the illumination control unit 46. The tilt angle of the plurality of mirror elements of the spatial light modulator 32 is controlled. The shape of the first pupil point B1 may be a square or a rectangle. Further, the illumination pupil 37 (for example, the opening of the variable aperture stop 35) is set to have the same size as the region surrounded by the circumference having a σ value of 1.

  As will be described later, in order to estimate the light intensity distribution of the out-of-aperture diffracted light in the widest possible range on the projection pupil plane PLP, the size (width) of the first pupil point B1 is made as small as possible and the first pupil is It is preferable to make the center of the point B1 as close to the circumference as possible with a σ value of 1. As an example, the size (width) of the first pupil point B1 is preferably 1/10 or less of the radius of the region where the σ value is 1. However, since the light from the first pupil point B1 is actually detected by the measurement unit 20, the size of the first pupil point B1 is a conjugate region (measurement) on the pixel of the measurement unit 20 and the illumination pupil plane IPP. It is not necessary to make it smaller than (resolution).

When the light intensity at the first pupil point B1 becomes too high, light from some of the mirror elements of the spatial light modulator 32 is transmitted to a region outside the aperture of the variable aperture stop 35 ( Alternatively, it may be thrown away in a portion that does not enter the fly-eye lens 34.
Then, light emission of the light source 30 is started, and the L & S pattern 60X of the reticle R is illuminated with the illumination light IL1 from the first pupil point B1. Since the first pupil point B1 is at a position shifted in the + X direction on the illumination pupil plane IPP, the illumination light IL1 as a whole is a reticle as a substantially parallel light beam tilted clockwise around an axis parallel to the Y axis. Incident to R. From the L & S pattern 60X of the reticle R, 0th-order light DL0, + 1st-order diffracted light DL1A, and -1st-order diffracted light DL1B are generated. Among these diffracted lights, the 0th-order light DL0 and the + 1st-order diffracted light DL1A are incident on the entrance pupil of the projection optical system PL and reach the projection pupil 71A, while the −1st-order diffracted light DL1B is incident on the entrance pupil of the projection optical system PL. Can not.

In the next step 138, the measurement unit 20 measures the light intensity distribution in the projection pupil 71A of the projection pupil plane PLP, and stops the emission of the illumination light IL. At this time, as shown in FIG. 8B, the positions and light intensities of the 0th-order light DL0 and the + 1st-order diffracted light DL1A in the projection pupil 71A are measured. The measurement result is stored in the storage unit 52.
In the next step 140, the reflected light from the spatial light modulator 32 is a region along the straight line passing through the optical axis AX and parallel to the periodic direction of the L & S pattern 60X on the illumination pupil plane IPP, and the σ value is 1. A plurality of spatial light modulators 32 via the illumination control unit 46 so that the light is condensed on the other circular region (hereinafter referred to as the second pupil point) B2 on the other side (here, in the −X direction) close to the circumference. Controls the tilt angle of the mirror element. As an example, the shape of the second pupil point B2 is the same as that of the first pupil point B1.

  Then, light emission of the light source 30 is started, and the L & S pattern 60X of the reticle R is illuminated with illumination light from the second pupil point B2 (substantially parallel light beam tilted counterclockwise around an axis parallel to the Y axis). . At this time, the 0th order light DL0, the + 1st order diffracted light DL1A, and the −1st order diffracted light DL1B are generated from the L & S pattern 60X of the reticle R, but this time, the 0th order light DL0 and the −1st order diffracted light DL1B are projection optics. Although it enters the entrance pupil of the system PL and reaches the projection pupil 71A, the + 1st order diffracted light DL1A cannot enter the entrance pupil of the projection optical system PL. In the next step 142, the light intensity distribution in the projection pupil 71A is measured by the measurement unit 20, and the emission of the illumination light IL is stopped. At this time, as shown in FIG. 8C, the positions and light intensities of the 0th-order light DL0 and the −1st-order diffracted light DL1B in the projection pupil 71A are measured. The measurement result is stored in the storage unit 52.

  Next, the illumination condition of the illumination optical system ILS is set to the annular illumination for the reticle R (step 146). For this reason, the illumination control unit 46 drives the spatial light modulator 32 so that the light intensity is increased in the annular zone in the illumination pupil 37. Next, as an example, the calculation unit 54 calculates a light intensity distribution (hereinafter referred to as a 0th-order intensity distribution) 72A in the projection pupil 71A in FIG. 8A corresponding to the light intensity distribution in the illumination pupil 37 by calculation. (Step 148). In the 0th-order intensity distribution 72A, the light intensity increases in an annular area 73P similar to an annular area (not shown) in the illumination pupil 37.

  In the next step 150, the calculation unit 54 combines the measurement results of steps 138 and 142 to thereby generate a region 71C (FIG. 8 (2)) having a radius (2r) that is twice the radius r of the projection pupil 71A of the projection pupil plane PLP. A virtual Fourier transform pattern 79 of the L & S pattern 60X of the reticle R is calculated in (D). This Fourier transform pattern 79 is obtained when the reticle R is illuminated with a parallel light beam parallel to the Z axis (perpendicular incident light with respect to the pattern surface Ra of the reticle R) and zero-order light and ± 1 generated from the L & S pattern 60X of the reticle R This is a light intensity distribution virtually formed in the region 71C by the next diffracted light. Since it is illumination by perpendicular incident light, the 0th-order light DL0 is on the optical axis AX.

  In this embodiment, as shown in FIGS. 8B and 8C, the distance between the first-order diffracted light DL1A, DL1B and the zero-order light DL0 measured in steps 138, 142 is the diameter (2r) of the projection pupil 71A. It is as follows. Therefore, in FIG. 8D, when the position of the 0th-order light DL0 is placed at the center (optical axis AX) of the projection pupil 71A, the positions of the 1st-order diffracted lights DL1A and DL1B are surely within the region 71C having a radius of 2r. Will fit in.

  As shown in FIG. 8D, the calculated Fourier transform pattern 79 of the reticle R includes the zero-order light DL0 in the projection pupil 71A and the ± first-order diffracted light in the region outside the projection pupil 71A in the region 71C. The light intensity distribution of DL1A and DL1B is included. The relative positions of the 0th-order light DL0 and the ± 1st-order diffracted lights DL1A and DL1B in the Fourier transform pattern 79 are the same as the relative positions in FIGS. 8B and 8C, respectively. In the normal incidence, the ± first-order diffracted lights DL1A and DL1B from the reticle R do not enter the entrance pupil of the projection optical system PL and do not reach the projection pupil plane PLP. However, according to the method of the present embodiment, a virtual light intensity distribution formed on the projection pupil plane PLP by the ± first-order diffracted lights DL1A and DL1B from the reticle R at the time of vertical incidence is obtained.

  If the Fourier transform pattern 79 shown in FIG. 8D is obtained, the light intensity distribution on the projection pupil plane PLP is the 0th-order intensity distribution of the illumination condition regardless of the illumination condition of the reticle R. It can be easily obtained by the convolution calculation of the Fourier transform pattern 79 (the light intensity distribution in the projection pupil 71A corresponding to the light intensity distribution of the illumination pupil 37). Therefore, the calculation unit 54 performs a convolution calculation between the zero-order intensity distribution 72A of the annular illumination for the reticle R in FIG. 8A and the Fourier transform pattern 79 of the reticle R in FIG. A light intensity distribution 78A in the calculation region 71B in which the radius of the projection pupil plane PLP shown in FIG. 11 is 3r is obtained. Since the zeroth-order intensity distribution 72A is set in the projection pupil 71A having the radius r and the Fourier transform pattern 79 is in the area 71C having the radius 2r, the light intensity distribution 78A obtained by the convolution is surely calculated. It falls within the area 71B.

  The calculated light intensity distribution 78A includes a zero-order light distribution in which the light intensity increases in the region 73P in the projection pupil 71A and a + first-order diffracted light distribution in which the light intensity increases in the region 73PD1 that moves the region 73P in the + X direction. And a distribution of −1st order diffracted light in which the light intensity increases in the region 73PD2 moved in the −X direction on the region 73P. As an example, a part of the region on the optical axis AX side in the region 73PD1, 73PD2 that is the distribution of ± first-order diffracted light is in the projection pupil 71A. In this case, the diffracted light (including zero-order light) incident on the region (region 73P and part of the regions 73PD1 and 73PD2) in the projection pupil 71A in FIG. 11 has the illumination condition of the illumination optical system ILS in FIG. This light is generated from the L & S pattern 60X of the reticle R and enters the entrance pupil of the projection optical system PL when the band illumination is set. On the other hand, ± 1st-order diffracted light that is virtually incident on the annular zone outside the projection pupil 71A (the majority of the regions 73PD1 and 73PD2) within the calculation region 71B is used as the illumination condition of the illumination optical system ILS in FIG. Out-of-aperture diffracted light HDC and HDD that are generated from the L & S pattern 60X of the reticle R and do not enter the entrance pupil of the projection optical system PL when the band illumination is set. In other words, the light intensity distribution 78Aa in the projection pupil 71A is a distribution of diffracted light incident on the entrance pupil of the projection optical system PL, and the light intensity distribution 78Ab outside the projection pupil 71A in the calculation area 71B is diffraction outside the aperture. Represents the distribution of light. Therefore, the virtual light intensity distribution 78Ab of the diffracted light outside the aperture on the projection pupil plane PLP can be estimated (obtained by calculation).

  In the next step 152, the unit region H (xi, yj) in FIG. 7 is determined from the virtual light intensity distribution 78Ab of the out-of-aperture diffracted light HDC and HDD obtained in step 150, as in step 116 in FIG. When the exposure is performed while performing annular illumination using the reticle R as a calculation unit, the incident position and intensity of the out-of-aperture diffracted light HDC and HDD with respect to the lens barrel 17 of the projection optical system PL in FIG. 10 are estimated. Information on the incident position and light intensity of the diffracted light outside the aperture with respect to the lens barrel 17 thus obtained is stored in the storage unit 52.

  The subsequent operation is the same as in steps 118 to 130 in FIG. 4, and the temperature calculation unit in the main controller 14 determines the incident position and light intensity of the diffracted light outside the aperture obtained in step 152 and the light intensity. Using the integrated irradiation energy detected via the integrator sensor (not shown), the variation amount of the temperature distribution of the lens barrel 17 and the variation amount of the temperature distribution of the optical element in the lens barrel 17 (or the temperature average value) The amount of change). Further, the second aberration calculator in the main controller 14 determines the second aberration fluctuation amount (out-aperture diffracted light HDC, HDC) of the projection optical system PL from the fluctuation amount of the temperature distribution (or average value of the temperature) of the optical element. The fluctuation amount of the wavefront aberration of the projection optical system PL by the HDD is calculated, and the first aberration fluctuation amount (aberration fluctuation amount due to the light intensity distribution in the projection pupil 71A) and the second aberration fluctuation amount are added. The total aberration fluctuation amount obtained is corrected by the imaging characteristic correction system 16. By performing exposure in this state, even when diffracted light outside the aperture is incident on the lens barrel 17, it is possible to perform exposure with high accuracy while maintaining the imaging characteristics of the projection optical system PL in a good state.

  As described above, the exposure apparatus EX of the present embodiment includes the reticle characteristic estimation apparatus 10 that estimates the state (reticle characteristic) of diffracted light generated from a reticle pattern. Then, the estimation device 10 stores information on the light intensity distribution (first light intensity distribution) in the illumination pupil 37 (region optically conjugate with the exit pupil) of the illumination optical system ILS that illuminates the pattern of the reticle R. And an illumination control unit 46 that sequentially illuminates the pattern of the reticle R with light from the first pupil point B1 and the second pupil point B2 (limited regions) at different positions on the illumination pupil 37. Yes. Further, the estimation apparatus 10 includes a projection optical system PL that forms an image of the pattern of the reticle R illuminated by the illumination optical system ILS when the first pupil point B1 and the second pupil point B2 are at different positions. A measuring unit 20 that measures the light intensity distribution (second light intensity distribution) of FIGS. 8B and 8C by light from the pattern of the reticle R in the projection pupil 71A (an area optically conjugate with the exit pupil); (Steps 138 and 142), which are generated from the pattern of the reticle R based on the light intensity distribution stored in the storage unit 54 and the light intensity distribution measured by the measurement unit 20, and enter the entrance pupil of the projection optical system PL. And a calculation unit 54 that estimates the state (direction and light intensity) of the diffracted light HDC and HDD that does not enter.

  Based on the measured light intensity distribution, the calculation unit 54 performs a Fourier transform pattern 79 (third light intensity distribution) on the projection pupil plane PLP including zeroth-order light and first-order or higher diffracted light from the pattern of the reticle R. ) (Step 144), and based on the Fourier transform pattern 79, the zero-order intensity distribution 72A (corresponding distribution) corresponding to the light intensity distribution in the illumination pupil 37 and the zero-order intensity distribution 72A are shifted in the projection pupil 71A. By superimposing the light intensity distributions, a light intensity distribution 78A (fourth light intensity distribution) is obtained (step 150). Based on the light intensity distribution 78Ab outside the projection pupil 71A in the light intensity distribution 78A, the reticle R is obtained. State of the diffracted light HDC and HDD outside the aperture that does not enter the entrance pupil of the projection optical system PL (light intensity distribution, direction, and / or light intensity) The estimates (step 152).

  According to the estimation apparatus 10 or the estimation method of the present embodiment, the information on the light intensity distribution set on the illumination pupil 37 and the measurement results of the light intensity distributions of the zeroth-order light and the first-order diffracted light from the reticle R at the projection pupil 71A. And the intensity distribution, direction, or light intensity of the out-of-aperture diffracted light HDC and HDD that are emitted at an angle (diffraction angle) that is so large that the reticle R cannot enter the entrance pupil of the projection optical system PL. Can be accurately estimated according to the illumination conditions.

In addition, according to the exposure apparatus EX or the exposure method of the present embodiment, since the fluctuation amount of the imaging characteristics of the projection optical system PL caused by the out-of-aperture diffracted light HDC and HDD generated from the reticle R can be corrected, The pattern image of the reticle R can be exposed on the wafer with higher accuracy while maintaining the imaging characteristics of the system PL in a target state with higher accuracy.
In the present embodiment, the following modifications are possible.

  In this embodiment, the illumination light IL is condensed on the first pupil point B1 and the second pupil point B2 using the spatial light modulator 32 in steps 136 and 140. Separately from this, in step 136, instead of the variable aperture stop 35 of FIG. 10, an aperture stop plate 35A in which a small aperture is formed at the first pupil point B1 is installed. The aperture stop 35A may be illuminated with illumination light IL having a uniform light intensity distribution. In step 140, the position of the small aperture of the aperture stop 35A may be moved to the position of the second pupil point B2.

In the present embodiment, in step 148, the zero-order intensity distribution 72A is obtained by calculation. Instead, with the reticle R removed from the reticle stage RST, the illumination light IL is irradiated onto the projection optical system PL from the illumination optical system ILS, and the light intensity distribution of the projection pupil 71A is directly measured by the measurement unit 20. May be. This measurement result is a zero-order intensity distribution 72A.
Further, when the device pattern of the reticle R includes a pattern having a periodic direction other than the X direction (for example, when including the L & S pattern 60Y of FIG. 3B), the same as the pupil points B1 and B2 on the illumination pupil plane IPP It is necessary to set the pupil point in the region in which the σ value is close to 1 at the end in the period direction and repeat the same steps (illumination and measurement) as in steps 136 and 138. In this case, when obtaining the Fourier transform pattern 79 of the light from the reticle R in step 144, it is also necessary to add the light intensity distribution of the first or higher order diffracted light obtained by the additional measurement.

In this embodiment, the state of out-of-aperture diffracted light out of ± first-order diffracted light from reticle R is estimated, but the state of out-of-aperture diffracted light out of second-order or higher diffracted light from reticle R is estimated. Also good.
In addition, the estimation apparatus 10 and the estimation method for estimating the state of diffracted light from the aperture of the reticle according to each of the embodiments described above include the L & S pattern 62X and the like as shown in the device pattern DP2 of the reticle R2 in FIG. In addition to this, the present invention can also be applied to cases including two-dimensional contact hole patterns 63A, 63B, etc., such as pitches p3, p4.

  When an electronic device (microdevice) such as a semiconductor device is manufactured using the exposure apparatus EX or the exposure method of the above embodiment, the electronic device has a function / performance design of the device as shown in FIG. Step 221 to be performed; Step 222 to manufacture a mask (reticle) based on this design step; Step 223 to manufacture a substrate (wafer) that is a base material of the device; Process of exposing pattern to substrate, process of developing exposed substrate, substrate processing step 224 including heating (curing) and etching process of developed substrate, device assembly step (dicing process, bonding process, packaging process, etc.) (Including the process) 225, the inspection step 226, etc. It is produced.

  In other words, the device manufacturing method includes the steps of exposing the substrate (wafer W) through the mask pattern using the exposure apparatus EX or the exposure method of the above embodiment, and processing the exposed substrate. (I.e., developing the resist on the substrate and forming a mask layer corresponding to the mask pattern on the surface of the substrate; and processing the surface of the substrate through the mask layer (heating, etching, etc.) ) Processing step).

According to this device manufacturing method, the reticle pattern image can be exposed onto the wafer with high accuracy in the exposure apparatus or the exposure method, so that the electronic device can be efficiently manufactured with high accuracy.
Note that the reticle characteristic estimation method and estimation apparatus of the above-described embodiment can also be applied to a stepper type exposure apparatus or the like.

In the device manufacturing method of the present embodiment, the method of manufacturing a semiconductor device has been particularly described. However, the device manufacturing method of the present embodiment can be applied to a semiconductor material such as a liquid crystal panel or a magnetic disk in addition to a device using a semiconductor material. The present invention can also be applied to the manufacture of devices using other materials.
In addition, this invention is not limited to the above-mentioned embodiment, A various structure can be taken in the range which does not deviate from the summary of this invention.

EX ... exposure apparatus, ILS ... illumination optical system, R ... reticle, PL ... projection optical system, W ... wafer, IPP ... illumination pupil plane, PLP ... projection pupil plane, 10 ... reticle characteristic estimation apparatus, 14 ... main control apparatus 20 ... Light intensity distribution measurement unit, 37 ... illumination pupil, 52 ... storage unit, 54 ... calculation unit, 71A ... projection pupil, 71B ... calculation area

Claims (22)

An estimation method of mask characteristics for estimating a state of diffracted light generated from a mask pattern,
Setting a first light intensity distribution at an exit pupil of an illumination optical system that illuminates the mask pattern;
Obtaining a second light intensity distribution at an exit pupil of a projection optical system that forms an image of a pattern of the mask illuminated by the illumination optical system;
Correlation degrees between a plurality of third light intensity distributions obtained by shifting corresponding distributions corresponding to the first light intensity distributions by different amounts in the exit pupil of the projection optical system and the second light intensity distributions, respectively. Obtaining a plurality of the third light intensity distributions when increasing;
Individual coefficients of the plurality of third light intensity distributions are obtained so that the degree of correlation between the weighted sum of the plurality of third light intensity distributions and the second light intensity distribution is high within the exit pupil of the projection optical system. And
Based on the light intensity distribution outside the exit pupil of the projection optical system, among the fourth light intensity distributions obtained by the weighted sum of the plurality of third light intensity distributions using the individual coefficients, Estimating a state of diffracted light that is generated and does not enter the entrance pupil of the projection optical system;
The estimation method characterized by including. Obtaining a plurality of the third light intensity distributions includes:
A plurality of shift amounts of the corresponding distribution when the sum of products of the plurality of third light intensity distributions and the second light intensity distributions obtained by shifting the corresponding distributions by different amounts have extreme values. The estimation method according to claim 1, further comprising: Obtaining individual coefficients of a plurality of the third light intensity distributions,
3. The method according to claim 1, further comprising: determining the individual coefficients so that a sum of squares of errors between the weighted sum of the third light intensity distributions and the second light intensity distribution is minimized. Estimation method. An estimation method of mask characteristics for estimating a state of diffracted light generated from a mask pattern,
Storing a first light intensity distribution of an exit pupil of an illumination optical system that illuminates the mask pattern;
Sequentially illuminating the pattern of the mask with light from restricted regions at a plurality of different positions in the exit pupil of the illumination optical system;
When the restricted region is at a plurality of different positions, the light from the mask pattern at the exit pupil of the projection optical system that forms an image of the mask pattern illuminated by the illumination optical system respectively. Obtaining two light intensity distributions;
Obtaining a third light intensity distribution including zero-order light and first-order or higher diffracted light from the mask pattern based on the obtained second light intensity distribution;
Based on the third light intensity distribution, a fourth light intensity is obtained by superimposing a corresponding distribution corresponding to the first light intensity distribution and a light intensity distribution shifted from the corresponding distribution in the exit pupil of the projection optical system. Finding the distribution;
Based on the light intensity distribution outside the exit pupil of the projection optical system in the fourth light intensity distribution, the state of diffracted light that is generated from the mask pattern and does not enter the entrance pupil of the projection optical system is estimated. And
The estimation method characterized by including.   The estimation method according to claim 4, wherein convolution of the correspondence distribution and the third light intensity distribution is performed to obtain the fourth light intensity distribution. The width of the limited region is 1/10 or less of the radius of the region having a coherence factor of 1,
The second light intensity distribution includes zero-order light from the mask pattern and at least one first-order diffracted light in a direction corresponding to a shift direction of the restricted region from the optical axis of the illumination optical system. The estimation method according to claim 4, wherein the estimation method is characterized.   7. The light intensity distribution outside the exit pupil of the projection optical system includes a light intensity distribution in a circular area that is three times the radius of the exit pupil. 8. Estimation method. Estimating the state of diffracted light generated from the mask pattern and not entering the entrance pupil of the projection optical system is to estimate the direction and light intensity of the diffracted light,
Using the estimated direction and light intensity of the diffracted light to determine an optical path in the projection optical system of the diffracted light that is generated from the mask pattern and does not enter the entrance pupil of the projection optical system. The estimation method according to claim 1, wherein the estimation method is characterized. In an exposure method of illuminating a mask pattern with illumination light from an illumination optical system, and exposing the substrate with the illumination light through the pattern and the projection optical system,
Using the estimation method according to any one of claims 1 to 8, estimating a state of diffracted light that is generated from the mask pattern and does not enter the entrance pupil of the projection optical system;
Obtaining a temperature fluctuation amount of at least one optical member constituting the projection optical system based on the estimated state of diffracted light that does not enter the entrance pupil of the projection optical system;
Correcting the fluctuation amount of the optical characteristics of the projection optical system based on the temperature fluctuation amount of the optical member;
An exposure method comprising: An apparatus for estimating a mask characteristic for estimating a state of diffracted light generated from a mask pattern,
A storage unit for storing information on the first light intensity distribution in the exit pupil of the illumination optical system that illuminates the mask pattern;
A light intensity distribution measuring unit that measures a second light intensity distribution at an exit pupil of a projection optical system that forms an image of the pattern of the mask illuminated by the illumination optical system;
Based on the first light intensity distribution stored in the storage unit and the second light intensity distribution measured by the light intensity distribution measurement unit, the light is generated from the mask pattern and applied to the entrance pupil of the projection optical system. A calculation unit that estimates the state of diffracted light that does not enter,
The computing unit is
Correlation degrees between a plurality of third light intensity distributions obtained by shifting corresponding distributions corresponding to the first light intensity distributions by different amounts in the exit pupil of the projection optical system and the second light intensity distributions, respectively. Obtaining a plurality of the third light intensity distributions when increasing,
Individual coefficients of the plurality of third light intensity distributions are obtained so that the degree of correlation between the weighted sum of the plurality of third light intensity distributions and the second light intensity distribution is high within the exit pupil of the projection optical system. ,
Of the light intensity distribution obtained by weighted sum of the plurality of third light intensity distributions using the individual coefficients, the light intensity distribution generated outside the exit pupil of the projection optical system is generated from the mask pattern. And estimating the state of the diffracted light that does not enter the entrance pupil of the projection optical system.   The computing unit calculates a product sum of a plurality of the third light intensity distributions and the second light intensity distributions obtained by shifting the corresponding distributions by different amounts in order to obtain a plurality of the third light intensity distributions. The estimation device according to claim 10, wherein a plurality of shift amounts of the corresponding distribution when the has an extreme value are obtained.   In order to obtain individual coefficients of a plurality of the third light intensity distributions, the arithmetic unit is configured to minimize a sum of squares of errors between the weighted sum of the third light intensity distributions and the second light intensity distributions. 12. The estimation apparatus according to claim 10, wherein the individual coefficient is obtained. An apparatus for estimating a mask characteristic for estimating a state of diffracted light generated from a mask pattern,
A storage unit for storing information on the first light intensity distribution in the exit pupil of the illumination optical system that illuminates the mask pattern;
An illumination controller for sequentially illuminating the pattern of the mask with light from a limited region at a plurality of different positions in the exit pupil of the illumination optical system;
When the restricted region is at a plurality of different positions, the light from the mask pattern at the exit pupil of the projection optical system that forms an image of the mask pattern illuminated by the illumination optical system respectively. A light intensity distribution measuring unit for measuring two light intensity distributions;
Based on the first light intensity distribution stored in the storage unit and the second light intensity distribution measured by the light intensity distribution measurement unit, the light is generated from the mask pattern and applied to the entrance pupil of the projection optical system. A calculation unit that estimates the state of diffracted light that does not enter,
The computing unit is
Based on the measured second light intensity distribution, a third light intensity distribution including zero-order light and first-order or higher diffracted light from the mask pattern is obtained,
Based on the third light intensity distribution, a fourth light intensity is obtained by superimposing a corresponding distribution corresponding to the first light intensity distribution and a light intensity distribution shifted from the corresponding distribution in the exit pupil of the projection optical system. Find the distribution
Based on the light intensity distribution outside the exit pupil of the projection optical system in the fourth light intensity distribution, the state of diffracted light that is generated from the mask pattern and does not enter the entrance pupil of the projection optical system is estimated. An estimation apparatus characterized by that.   The estimation device according to claim 13, wherein the calculation unit performs convolution of the correspondence distribution and the third light intensity distribution in order to obtain the fourth light intensity distribution. The width of the limited region is 1/10 or less of the radius of the region having a coherence factor of 1,
The second light intensity distribution includes zero-order light from the mask pattern and at least one first-order diffracted light in a direction corresponding to a shift direction of the restricted region from the optical axis of the illumination optical system. The estimation apparatus according to claim 13 or 14, characterized in that   16. The light intensity distribution outside the exit pupil of the projection optical system includes a light intensity distribution in a circular region that is three times the radius of the exit pupil. Estimating device. Estimating the state of diffracted light generated from the mask pattern and not entering the entrance pupil of the projection optical system is to estimate the direction and light intensity of the diffracted light,
The calculation unit obtains an optical path in the projection optical system of the diffracted light that is generated from the mask pattern and does not enter the entrance pupil of the projection optical system, using the estimated direction and light intensity of the diffracted light. The estimation apparatus according to any one of claims 10 to 16, wherein the estimation apparatus is characterized in that In an exposure apparatus that illuminates a pattern of a mask with illumination light from an illumination optical system and exposes the substrate with the illumination light through the pattern and the projection optical system,
An estimation apparatus according to any one of claims 10 to 17, for estimating a state of diffracted light generated from the mask pattern and not entering the entrance pupil of the projection optical system;
A temperature calculation unit for obtaining a temperature fluctuation amount of at least one optical member constituting the projection optical system based on a state of diffracted light that does not enter the entrance pupil of the projection optical system estimated by the estimation device;
A correction unit that corrects the fluctuation amount of the optical characteristics of the projection optical system based on the temperature fluctuation amount of the optical member obtained by the temperature calculation unit;
An exposure apparatus comprising: In an exposure apparatus that illuminates a pattern of a mask with illumination light from an illumination optical system and exposes the substrate with the illumination light through the pattern and the projection optical system,
An estimation device for estimating a state of diffracted light generated from the pattern of the mask and not entering the entrance pupil of the projection optical system;
A temperature calculation unit for obtaining a temperature fluctuation amount of at least one optical member constituting the projection optical system based on a state of diffracted light that does not enter the entrance pupil of the projection optical system estimated by the estimation device;
A correction unit that corrects the fluctuation amount of the optical characteristics of the projection optical system based on the temperature fluctuation amount of the optical member obtained by the temperature calculation unit;
An exposure apparatus comprising: A light intensity distribution measuring unit that measures a light intensity distribution in an exit pupil of a projection optical system that forms an image of the pattern of the mask illuminated by the illumination optical system;
The said estimation apparatus estimates the state of the said diffracted light which does not enter into the entrance pupil of the said projection optical system using the light intensity distribution measured by the said light intensity distribution measurement part. Exposure equipment. Forming a pattern of a photosensitive layer on a substrate using the exposure method according to claim 9;
Processing the substrate on which the pattern is formed;
A device manufacturing method including: Forming a pattern of a photosensitive layer on a substrate using the exposure apparatus according to any one of claims 18 to 20,
Processing the substrate on which the pattern is formed;
A device manufacturing method including:

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