JP2008021830A - Measuring method and apparatus, and exposure method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure by using a slit with a high contrast the optical intensity distributions of the spatial images of a plurality of periodic patterns having different periodic directions. <P>SOLUTION: The measuring method is the one wherein the optical intensity distributions of the images 63P, 65P of two L&S patterns arranged in different directions are measured. A slit 61C has as its longitudinal direction the direction orthogonal to the periodic direction of the image 63P of the first L&S pattern to form its light shade 61Cb, in a portion present in its longitudinal direction. The measuring method has a process for subjecting the slit 61C and the image 63P to a relative scanning to receive the light passed through the slit 61C, and has a process for subjecting the slit 61C, and the image 65P of the second L&S pattern to a relative scanning to receive the light passed through the slit 61C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a measurement technique for measuring a light intensity distribution of an image of a periodic pattern, and an exposure technique using this measurement technique.

  A semiconductor device, a liquid crystal display device, and the like are manufactured through a so-called photolithography process in which a pattern formed on a mask such as a reticle is transferred onto a substrate such as a wafer coated with a resist (photosensitive material). In this photolithography process, in order to transfer the pattern on the mask onto the substrate via the projection optical system, a step-and-repeat type projection exposure apparatus (stepper, etc.) and a step-and-scan type projection exposure An exposure apparatus such as an apparatus (scanning stepper, etc.) is used.

  In this type of exposure apparatus, it is required to further improve imaging characteristics such as wavefront aberration of the projection optical system as the pattern becomes finer due to higher integration of semiconductor devices and the like. For this purpose, for example, it is desirable to periodically actually project an image of the evaluation pattern via the projection optical system and measure the imaging characteristics of the projection optical system based on the position of the image. An aerial image that measures the light intensity distribution of the image by scanning the image (spatial image) with a slit previously incorporated in the stage to efficiently measure the position of the image of the evaluation pattern. A measurement system is used (see, for example, Patent Document 1).

Further, when obtaining wavefront aberrations, particularly when obtaining wavefront aberrations in the form of coefficients of Zernike polynomials, measurement points on a plurality of straight lines passing through the optical axis on the pupil plane of the projection optical system, that is, different angular directions are used. It is desirable to obtain phase information of the imaged light flux at a plurality of measurement points. For this reason, conventionally, as the evaluation pattern, a plurality of line and space patterns (hereinafter referred to as L & S patterns) having different periodic directions and a plurality of slits whose longitudinal direction is a direction orthogonal to the periodic directions. The light intensity distribution was obtained by scanning each L & S pattern image in the periodic direction with the corresponding slit.
JP 2002-14005 A

  In a conventional aerial image measurement system, when the number of slits in different directions that can be arranged is limited due to the space that can be secured on the stage, etc., the L & S with the direction orthogonal to the longitudinal direction of each slit as the periodic direction Since the light intensity distribution of the pattern image can be measured, the angle direction of the phase information measurement point on the pupil plane of the projection optical system is limited. As a result, there is a possibility that the accuracy when the wavefront aberration is obtained by the coefficient of the Zernike polynomial is lowered.

In addition, in order to increase the number of phase information measurement points in the angular direction, when a single slit is used to scan a plurality of L & S pattern images having different periodic directions, the direction orthogonal to the longitudinal direction of the slit And the periodic direction of the L & S pattern to be measured are deviated, the contrast of the measured light intensity distribution is lowered, and the measurement accuracy of the wavefront aberration is lowered.
In view of such circumstances, the present invention provides a measurement technique capable of measuring a light intensity distribution of a spatial image of a plurality of periodic patterns having different periodic directions using a single slit with high contrast, and an exposure technique using the measurement technique. The purpose is to provide.

  The measuring method according to the present invention is a measuring method for measuring the light intensity distribution of the images (63P, 64P) of the first and second periodic patterns arranged in different directions, wherein the first periodic pattern The longitudinal direction is a direction orthogonal to the periodic direction of the image, and the slit (61) having the light shielding portion (61b) formed in a part of the longitudinal direction and the image of the first periodic pattern are relatively scanned. A first step of receiving light passing through the slit, and a second step of receiving light passing through the slit by relatively scanning the slit and the image of the second periodic pattern It is.

  The measuring device according to the present invention is a measuring device for measuring the light intensity distribution of the images (63P, 64P) of the first and second periodic patterns arranged in different directions, the first periodic A direction perpendicular to the periodic direction of the pattern image is defined as a longitudinal direction, and a slit (61) having a light shielding portion (61b) formed in a part of the longitudinal direction, and a photoelectric detector that receives light passing through the slit (61). 89) and a relative scanning mechanism (WST) that relatively scans the images of the first and second periodic patterns and the slits thereof.

  According to the present invention, the first and second periodic pattern images and the slits are sequentially sequentially scanned to increase the light intensity distribution of the first and second periodic pattern images. It can be detected by contrast. At this time, the periodic direction of the second periodic pattern and the direction orthogonal to the longitudinal direction of the slit are not parallel (shifted), but since the light shielding portion is provided in the slit, the contrast is increased. Is improved.

  The exposure method according to the present invention is an exposure method in which a pattern is illuminated with an exposure beam, and the object (W) is exposed with the exposure beam through the pattern and the projection optical system (PL). And a measurement process for measuring the light intensity distribution of the images (63P, 64P) of the first and second periodic patterns arranged on the object plane of the projection optical system, and a measurement result of the measurement process. And a calculation step for obtaining the imaging characteristics of the projection optical system, and a correction step for correcting the imaging characteristics of the projection optical system based on the calculation result of the calculation step.

  An exposure apparatus according to the present invention is an exposure apparatus that illuminates a pattern with an exposure beam and exposes an object (W) with the exposure beam via the pattern and the projection optical system (PL). A stage (WST) that holds and moves the object, an arithmetic unit (50) that obtains imaging characteristics of the projection optical system using detection information of the photoelectric detector (89) of the measuring device, And a correction mechanism (73, 74) for correcting the imaging characteristics of the projection optical system based on the calculation result of the calculation device.

  In addition, although the reference numerals in parentheses attached to the predetermined elements of the present invention correspond to members in the drawings showing an embodiment of the present invention, each reference numeral of the present invention is provided for easy understanding of the present invention. The elements are merely illustrative, and the present invention is not limited to the configuration of the embodiment.

Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a schematic configuration of a scanning stepper type projection exposure apparatus 10 (exposure apparatus) of this example. In FIG. 1, the projection exposure apparatus 10 includes an exposure light source 14 for generating a laser beam LB, illumination. Optical system 12, reticle stage RST that holds and moves reticle R (mask), projection optical system PL, wafer stage WST that holds and moves wafer W coated with a resist as a substrate (object), and these A main controller 50 including a computer that performs overall control is provided.

In this example, an ArF excimer laser light source (oscillation wavelength of 193 nm) whose on / off of light emission is controlled by the main controller 50 is used as the light source 14. As the light source 14, a KrF excimer laser (wavelength 248 nm), an F ₂ laser (wavelength 157 nm), a harmonic generator of a solid-state laser (YAG laser, semiconductor laser, etc.), a mercury lamp (i-line etc.), or the like can be used. .

  The illumination optical system 12 includes a beam shaping optical system 18 that shapes the cross-sectional shape of the laser beam LB from the light source 14, a fly-eye lens 22 (optical integrator) that forms a large number of light source images from the laser beam LB, and a fly-eye lens. 22 includes an illumination system aperture stop plate 24 disposed in the vicinity of the exit surface 22 (pupil surface of the illumination optical system 12), a beam splitter 26 having a small reflectance and a large transmittance, a first relay lens 28A, and a second relay lens 28B. A relay optical system, a fixed blind 30A, a movable blind 30B, a mirror M, a condenser lens 32, and the like are provided. Hereinafter, the laser beam LB emitted from the light source image formed by the fly-eye lens 22 is referred to as illumination light IL as an exposure beam (exposure light).

  The light source 14 and the illumination optical system 12 are also used as an illumination system for a later-described aerial image measurement. In the illumination optical system 12, the illumination system aperture stop plate 24 is provided with an aperture stop (normal stop) made of, for example, a normal circular aperture, and an aperture for reducing the coherence factor (σ value) made of a small circular aperture at substantially equal angular intervals. Aperture (small σ stop), an aperture stop for annular illumination (annular stop), an aperture stop for deformed illumination (bipolar illumination, quadrupole illumination, etc.) formed by decentering a plurality of apertures, etc. Is arranged. The illumination system aperture stop plate 24 selectively sets one of the aperture stops on the optical path of the illumination light IL by the rotation operation of the driving device 40 controlled by the main controller 50.

  The fixed blind 30A is disposed on a surface slightly defocused from the conjugate plane with respect to the pattern surface of the reticle R (hereinafter referred to as the reticle surface), and defines a rectangular illumination area IAR on the reticle R. The movable blind 30B arranged in the vicinity of the fixed blind 30A further restricts the illumination area IAR in accordance with an instruction from the main controller 50 in order to prevent unnecessary exposure at the start and end of scanning exposure. The movable blind 30B is also used to control the width of the illumination area IAR in the non-scanning direction.

The laser beam LB emitted from the light source 14 at the time of exposure becomes illumination light IL in the illumination optical system 12, and the illumination light IL is bent vertically downward by the mirror M and then passes through the condenser lens 32. A slit-like illumination area IAR elongated in the non-scanning direction of the reticle surface is illuminated with a uniform illuminance distribution.
On the other hand, a part of the illumination light IL reflected by the beam splitter 26 in the illumination optical system 12 is received by an integrator sensor 46 including a photoelectric detector via a condenser lens 44, and a photoelectric conversion signal of the integrator sensor 46 is received. The signal is supplied to the main controller 50 via a signal processing device 48 having a peak hold circuit and an A / D converter. The measurement value of the integrator sensor 46 is used not only for exposure amount control on the wafer W but also for calculating the irradiation amount for the projection optical system PL. That is, in main controller 50, the irradiation amount of illumination light IL is integrated based on the output of integrator sensor 46. The imaging characteristic fluctuation prediction unit (here, a function on the software) in the main controller 50 irradiates the irradiation from the accumulated value (irradiation history) and the coefficient previously obtained and stored in the memory 51. A fluctuation amount of a predetermined imaging characteristic of the projection optical system PL corresponding to the history is predicted. Note that the fluctuation amount of the predetermined imaging characteristic may be predicted in consideration of fluctuations in the environmental conditions such as atmospheric pressure along with the irradiation history.

  Under the illumination light IL, the pattern in the illumination area IAR of the reticle R is resist (photosensitive) at a predetermined projection magnification (for example, a reduction magnification of 1/4, 1/5, etc.) via the projection optical system PL. Is projected onto an exposure area IA on one shot area of the wafer W coated with the material. The projection optical system PL of this example is a refractive system, but a catadioptric system or the like can also be used. Hereinafter, the Z-axis is taken in a direction parallel to the optical axis AX of the projection optical system PL, the X-axis is taken in a direction perpendicular to the paper surface of FIG. 1 within a plane perpendicular to the Z-axis, and the direction parallel to the paper surface of FIG. A description will be given taking the Y axis. In this example, the scanning direction of reticle R and wafer W during scanning exposure is a direction parallel to the Y axis (Y direction), and illumination area IAR on reticle R and exposure area IA on wafer W are in the scanning direction, respectively. This is an elongated region in the non-scanning direction (X direction) orthogonal to.

Further, the projection optical system PL of the present example is provided with an imaging characteristic correction device for correcting (controlling) the predetermined imaging characteristics.
FIG. 2 is a cross-sectional view showing a part of the imaging characteristic correction apparatus for the projection optical system PL shown in FIG. 1. In FIG. 2, a predetermined one of a plurality of optical members constituting the projection optical system PL is shown. The lens element 71 is rotated around an axis parallel to the Z direction (optical axis direction), the X axis, and the Y axis by a lens holder 72 and driving elements (for example, piezo elements) 73 disposed at three positions around the optical axis. It is supported so that it can be driven minutely in the rotation direction. Actually, other lens elements (not shown) of the lens element 71 are also supported by the drive element so as to be driven.

  In this example, the drive voltage (drive amount of the drive element) applied to each drive element 73 is controlled by the imaging characteristic correction controller 74 in accordance with a command from the main controller 50. An imaging characteristic correction apparatus is configured including the drive element 73 and the imaging characteristic correction controller 74. With this correction device, for example, as disclosed in Japanese Patent Laid-Open No. 4-134913, the variation amount of the predetermined imaging characteristic predicted by the imaging characteristic variation prediction unit in the main controller 50 is canceled. As described above, the predetermined imaging characteristics of the projection optical system PL are corrected. The number of movable lens elements may be arbitrary.

  Returning to FIG. 1, the reticle R is held on the reticle stage RST by vacuum suction or the like. The reticle stage RST is moved in the X direction and Y direction within the XY plane on the reticle base RBS by a reticle stage drive system 56R including a linear motor or the like. In the direction of rotation and the rotation direction around the Z axis, and can be moved on the reticle base RBS at a scanning speed designated in the Y direction.

  On reticle stage RST, movable mirror 52R (including two corner reflectors for Y axis and a movable mirror for X axis) that reflects a laser beam from laser interferometer 54R having three axes or more is included. The position of the reticle stage RST in the XY plane is always detected by the reticle interferometer 54R with a resolution of about 0.1 nm, for example. Position information of reticle stage RST from laser interferometer 54R is sent to stage controller 49 and to main controller 50 via this. The stage control device 49 controls the movement of the reticle stage RST via the reticle stage drive system 56R according to an instruction from the main control device 50.

  In addition, a reticle mark plate RFM as a reference member on which an aerial image measurement pattern is formed is fixed so as to be aligned with reticle R in the vicinity of the end in the −Y direction of reticle stage RST. Reticle stage RST has a movement stroke in the Y direction such that the entire surface of reticle R and the entire surface of reticle mark plate RFM can cross at least optical axis AX of projection optical system PL. Reticle stage RST and reticle base RBS each have an opening through which illumination light IL passes.

  In FIG. 1, a wafer stage WST is mounted on an XY stage 42, which is mounted on a wafer base 16 so that it can be driven two-dimensionally in the X and Y directions by a wafer stage drive system 56W including a linear motor. And a Z tilt stage 38 mounted thereon. A wafer W is held on the Z tilt stage 38 via a wafer holder 25 by vacuum suction or the like. The Z tilt stage 38 independently drives the three internal Z position driving units to adjust the position of the wafer W in the optical axis AX direction (focus position) and the rotation angle around the X axis and Y axis. Control.

  In addition, the projection optical system PL includes an irradiation system 60a and a light receiving system 60b on the side surface, and is an oblique detector that detects the focus positions of a plurality of measurement points on the test surface (such as the surface of the wafer W) on the image plane side of the projection optical system PL. An incident type multipoint focal position detection system (60a, 60b) is provided. A detailed configuration of the same focal position detection system is disclosed in, for example, Japanese Patent Laid-Open No. Hei 6-283403. Information on the focus position thus detected is supplied to the stage controller 49, and the stage controller 49 aligns the surface of the wafer W with the image plane of the projection optical system PL based on the information during exposure. The Z tilt stage 38 is driven so as to be focused.

  In FIG. 1, a movable mirror 52 </ b> W (including X-axis and Y-axis movable mirrors) that reflects a laser beam from two or more axes of laser interferometer 54 </ b> W is fixed on the Z tilt stage 38. Wafer interferometer 54W always detects the position of wafer stage WST (Z tilt stage 38) in the XY plane with a resolution of, for example, about 0.1 nm. Position information (or speed information) of wafer stage WST is supplied to stage controller 49 and main controller 50 via this. The stage controller 49 controls the position of the wafer stage WST in the XY plane via the wafer stage drive system 56W in accordance with an instruction from the main controller 50.

  Above the reticle R, a pair of reticles for simultaneously observing a mark on the reticle R or reticle mark plate RFM and a reference mark (not shown) on the wafer stage WST via the projection optical system PL. An alignment microscope (not shown) is provided. Further, an FIA (Field Image Alignment) type (image processing type) alignment sensor ALG is provided on the side surface of the projection optical system PL to detect an alignment mark on the wafer W or a predetermined reference mark. Yes. Based on the detection results of these reticle alignment microscope and alignment sensor ALG, alignment of reticle R and wafer W is performed.

  Next, the scanning exposure operation in the projection exposure apparatus 10 of this example will be briefly described. First, main controller 50 sets an illumination condition optimal for exposure using reticle R for actual exposure. Then, after the above alignment is performed, the shot area to be next exposed on the wafer W is positioned on the front side of the optical axis AX by the stepping of the wafer stage WST. Next, irradiation with the illumination light IL is started, and exposure is performed through the wafer stage WST in synchronization with the movement of the reticle R in the Y direction at a predetermined speed Vr with respect to the illumination area IAR through the reticle stage RST. An operation of moving one shot area on the wafer W with respect to the area IA in the Y direction at a speed β · Vr (β is a projection magnification of the projection optical system PL) and a stepping operation between shots are repeated. The pattern image of the reticle R is transferred to all shot areas on the wafer W by the AND scan method.

  By the way, in the above-described scanning exposure operation, in order to transfer the pattern of the reticle R onto the wafer W with high resolution and high accuracy via the projection optical system PL, the imaging characteristics of the projection optical system PL are in a predetermined state. It needs to be adjusted. Therefore, in this example, as described above, the fluctuation amount of the predetermined imaging characteristic is predicted by the imaging characteristic fluctuation prediction unit in the main controller 50 using the measurement value of the integrator sensor 46 of FIG. The image formation characteristic is corrected by an image formation characteristic correction apparatus including the image formation characteristic correction controller 74 of FIG. 2 so as to cancel the amount. However, since the predicted value of the fluctuation amount of the imaging characteristics may gradually deviate from the actual fluctuation amount, in this example, the predetermined value of the projection optical system PL is periodically used, for example, using the aerial image measurement system as follows. The imaging characteristic is measured (measurement process), the predicted value of the fluctuation amount of the imaging characteristic is corrected based on the measurement result (calculation process), and the imaging characteristic correction device is operated based on the corrected predicted value. The imaging characteristics are corrected by using (correction step).

In the following, it is assumed that a predetermined imaging characteristic of the projection optical system PL to be measured and corrected is a predetermined aberration. Further, assuming that wavefront aberration is used to classify the aberration, and that the aberration function indicating the wavefront aberration on the pupil plane PP (exit pupil) of the projection optical system PL in FIG. 2 is W (ρ, θ), ρ is a normalized position (radial radius) of the pupil plane PP in the radial direction, and θ is an angle. The aberration function W (ρ, θ) can be expanded in series using a Zernike's Polynomial, which is a complete orthogonal system polynomial in which the radial ρ and angle θ are separated. is there. The coefficient Z _i of the i-th order (i is an integer of 1 or more) Zernike polynomial fi (ρ, θ) at the time of series expansion may be regarded as an aberration (or aberration amount) represented by the i-th order Zernike polynomial. it can.

The aberration of the projection optical system PL can be classified into a lateral aberration that is a lateral shift of the image and a longitudinal aberration that is a change in the contrast of the image. When an aberration Z _i represented by a coefficient of an i-th order Zernike polynomial is used, The aberrations are aberrations Z ₉ and Z ₁₆ , the coma aberration is aberrations Z ₇ , Z ₈ , Z ₁₄ , and Z ₁₅ , and the distortion is aberrations Z ₂ and Z ₃ . In this example, the wavefront aberration represented by the Zernike polynomial up to a predetermined order (for example, the 16th order) can be individually corrected by the imaging characteristic correction apparatus including the imaging characteristic correction controller 74 of FIG.

  Further, in order to measure the wavefront aberration expressed by the coefficient of the higher-order Zernike polynomial of the projection optical system PL, a plurality of straight lines intersecting with each other through the optical axis in the pupil plane PP of the projection optical system PL of FIG. It is necessary to obtain phase information at the upper measurement point. Therefore, in FIG. 2, a first L & S pattern (line and space pattern) 63 whose periodic direction is in the Y direction and a periodic direction as the plurality of periodic patterns having different periodic directions on the pattern surface of the reticle mark plate RFM. A second L & S pattern 64 shifted from the Y direction by an angle larger than 0 ° and smaller than 90 ° is formed. The ratio (duty ratio) between the width of the light transmitting portion and the width of the light shielding portion of these L & S patterns 63 and 64 is 1: 1, and the positions of the images (aerial images) of these patterns by the projection optical system PL and By measuring the contrast, it is possible to obtain phase information at a plurality of measurement points on two straight lines passing through the optical axis in the pupil plane PP. Actually, the positions and contrasts of the images of the other L & S patterns having the same periodic direction as that of the first L & S pattern 63 but having different pitches are also measured.

  With reference to FIG. 2, the configuration of the aerial image measurement system 59 provided in the wafer stage WST of this example used for this purpose will be described. In FIG. 2, a slit plate 90 is fitted from above to a protruding portion 58 provided on the upper surface of the end portion of the Z tilt stage 38 of the wafer stage WST and having an opening formed in the upper portion so as to cover the opening. . The slit plate 90 is configured by forming a reflective film 83 that also serves as a light-shielding film on the upper surface of a rectangular flat glass substrate 82 parallel to the XY plane, and a direction parallel to the X axis in a part of the reflective film 83. A slit 61 is formed in the longitudinal direction. As the material of the glass substrate 82, here, synthetic quartz or fluorite having good transparency with respect to the ArF excimer laser light that is the illumination light IL is used.

  3A shows a plan view of the slit plate 90. In FIG. 3A, the slit 61 is formed with light transmitting portions 61a and light shielding portions 61b alternately along the longitudinal direction (X direction). Has been. In other words, the light shielding portions 61b are formed in the slit 61 at a predetermined pitch along the longitudinal direction. The length and pitch of the light shielding part 61b will be described later. As shown in a later modification, the slit 61 may be provided with only one light shielding portion 61b.

  In this example, the L & S pattern image is measured with the slit 61 and the light intensity of the illumination light transmitted through the slit 61 is relatively scanned in the scanning direction (here, the Y direction) indicated by the arrow F perpendicular to the longitudinal direction of the slit 61. To do. In this example, the slit 61 is moved in the Y direction by the wafer stage WST (relative scanning mechanism) for the relative scanning. However, the L & S pattern image may be slightly moved in the Y direction by the reticle stage RST. By storing the measured value of the light intensity with respect to the Y coordinate of the slit 61, the light intensity distribution in the Y direction of the image of the L & S pattern can be obtained. Therefore, from the aspect of measurement accuracy, the slit width 2D, which is the width of the slit 61 in the scanning direction (Y direction), is preferably as small as possible. However, in reality, since there is a certain restriction on the scanning speed at the time of aerial image measurement in terms of throughput, if the slit width 2D is too small, the amount of light transmitted through the slit 61 becomes too small and measurement is difficult. turn into. In this example, the slit width 2D is set to be smaller than the width of the bright part (or dark part) of the image of the L & S pattern having the smallest pitch to be measured. As an example, the slit width 2D is set to about 200 nm or less, for example, about 100 to 150 nm.

  FIG. 2 shows a state in which the L & S pattern 63 of the reticle mark plate RFM is illuminated with the illumination light IL, and the slit 61 is located at a position substantially conjugate with the L & S pattern 63 with respect to the projection optical system PL. In this case, the aerial image measurement system 59 provided on the Z tilt stage 38 of the wafer stage WST converts the slit plate 90 on which the slit 61 is formed and the light (illumination light IL) that has passed through the slit 61 into a substantially parallel light beam. A lens 84, a mirror 88 that reflects light emitted from the lens 84 substantially in the Y direction, a lens 86 that collects the light reflected by the mirror 88, and a photoelectric sensor 89 that photoelectrically converts the collected light. It is comprised including. The lens 84 and 86 constitute a relay lens system.

  As the photoelectric sensor 89, a photodiode or the like can be used. In order to detect weak light, a photomultiplier tube (photomultiplier tube) may be used as the photoelectric sensor 89. As described above, when a photomultiplier tube is used as the photoelectric sensor 89 and a sufficient space cannot be secured in the Z tilt stage 38, the photoelectric sensor 89 is disposed outside the Z tilt stage 38. A light transmission optical system (or a flexible optical fiber cable or the like) that passes through the slit 61 may be disposed between the Z tilt stage 38 and the photoelectric sensor 89. The detection signal PS, which is a photoelectric conversion signal from the photoelectric sensor 89, is converted into digital data through, for example, an amplifier, a sample hold circuit, an A / D converter, etc. in the signal processing device 48 of FIG. Is supplied to the operation unit (for example, one function on software).

  When performing aerial image measurement using the aerial image measurement system 59 of FIG. 2, the main controller 50 of FIG. 1 drives the wafer stage WST in the + Y direction (or -Y direction) via the wafer stage drive system 56W. To do. Accordingly, in FIG. 3A, the slit 61 is in the + Y direction (or -Y direction) with respect to the image 63P of the L & S pattern 63 in FIG. 2 (the bright and dark pattern having a periodic direction in the Y direction and a pitch). Scanned. During this scanning, light (illumination light IL) passing through the slit 61 is received by the photoelectric sensor 89 of FIG. 2, and the detection signal PS is supplied to the arithmetic unit in the main controller 50 via the signal processing device 80. The Information on the X and Y coordinates of the slit 61 (Z tilt stage 38) at that time is also supplied to the calculation unit, and the X and Y coordinates of the slit 61 (Z tilt stage 38) are supplied to the calculation unit. By storing the detection signal PS of the photoelectric sensor 89 in the memory 51 in correspondence with the above, information on the light intensity distribution of the image of the L & S pattern to be measured can be obtained.

  FIG. 3B shows an example of a detection signal (light intensity signal) PS obtained at the time of the aerial image measurement. In this case, the detection signal PS is represented as a function of the Y coordinate of the slit 61 because the periodic direction corresponds to an image of the L & S pattern 63 whose Y direction is the Y direction. In this case, as shown in FIG. 3A, the L & S pattern image 63P having the Y direction as the periodic direction is scanned with the slit 61 having the X direction as the longitudinal direction in the Y direction. The contrast of the detection signal PS is extremely high, and the light intensity distribution of the image 63P can be measured with high accuracy even using the slit 61 in which the light shielding portions 61b are periodically formed. Since the light intensity distribution includes information on the image formation position (lateral shift) and amplitude (contrast) in the horizontal direction of the image 63P, the calculation unit in the main controller 50 uses the information to calculate the wavefront. Aberration can be obtained.

Next, a case where the light intensity distribution of the image of the L & S pattern 64 in FIG. 2 whose period direction is inclined from the Y direction is measured will be described.
4A shows a state when the image 64P of the second L & S pattern 64 of FIG. 2 is scanned by the slit 61. In FIG. 4A, the periodic direction of the image 64P indicated by the arrow 67 is indicated by an arrow. 3 is inclined clockwise by an angle θ (deg) (0 <θ <90 °) from the periodic direction (Y direction) of the image 63P of the first L & S pattern shown in FIG. Further, the image 64P is obtained by arranging a bright part 64Pa and a dark part 64Pb with a duty ratio of 1: 1 and a pitch p1 in the periodic direction, and the length d of the dark part 64Pb in the periodic direction is as follows.

d = p1 / 2 (1)
Further, the pitch p2 of the arrangement with respect to the longitudinal direction (X direction) of the light shielding portion 61b of the slit 61 is set as follows.
p2 = p1 / sinθ (2)
This is because the pitch p2 of the light shielding portion 61b of the slit 61 is set equal to the pitch p3, where p3 is the pitch of the bright and dark portions of the image 64P in the X direction parallel to the longitudinal direction of the slit 61 indicated by the dotted line 68. It means to do. In FIG. 4A, the pitches p2 and p3 are represented by different lengths for convenience of explanation.

Further, when the duty ratio of the L & S pattern 64 (and thus the image 64P) is 1: 1 as in this example, the lengths of the light transmitting portion 61a and the light shielding portion 61b in the slit 61 in the longitudinal direction are the pitch p2 respectively. And the following relationship is established from the equations (1) and (2).
Length of light shielding part 61b = length of light transmitting part 61a = p2 / 2 = d / sin θ (3)
When the duty ratio of the L & S pattern 64 is out of 1: 1, the value of the ratio of the light transmitting part 61a and the light shielding part 61b of the slit 61 is the ratio of the light transmitting part and the light shielding part of the L & S pattern 64. It may be set equal to the value.

In FIG. 4A, the natural number n is used, and the total number of the light transmitting portions 61a and the light shielding portions 61b constituting the slit 61 is (2n + 1). Therefore, in the longitudinal direction (X direction) of the slit 61, The slit length L, which is the length, is as follows.
L = (2n + 1) d / sin θ (4)
In Expression (4), when n = 1, the slit 61 extends over 1.5 periods in the X direction of the L & S pattern image 64P, and when n = 2, the slit 61 is 2.5 of the L & S pattern image 64P. This is a case that spans a cycle. Note that the slit 61 can be regarded as having a light-shielding portion having a length of d / sin θ outside one end portion in the X direction. In this case, when n = 1, the slit 61 is 2 of the image 64P. It will span the cycle.

  For example, when n is 3 or more, in FIG. 4A, the slit 61 is scanned with respect to the image 64P in the Y direction indicated by the arrow 66 (the same direction as the periodic direction of the image 63P in FIG. 3A). Then, the detection signal PS detected through the aerial image measurement system 59 of FIG. 2 is as shown in FIG. In FIG. 4B, the horizontal axis is the Y coordinate of the slit 61, and the contrast (= AC1 / DC1≈2) when the average value of the detection signal PS at the center in the Y direction is DC1 and the amplitude is AC1. Alternatively, the S / N ratio has a theoretical maximum value of about 2, and the light intensity distribution of the image 64P can be detected with high accuracy. Therefore, the position (lateral shift) and contrast of the image 64P can be obtained with high accuracy from the light intensity distribution.

In FIG. 4B, if the pitch in the Y direction of the detection signal PS is p4, the following relationship exists between the pitch p1 in the periodic direction of the L & S pattern image 64P and the pitch p4 of the detection signal PS. is there.
p1 = p4 · cos θ (5)
Therefore, the arithmetic unit in the main controller 50 in FIG. 2 multiplies the Y coordinate of the detection signal PS obtained as shown in FIG. A detection signal corresponding to the light intensity distribution in the periodic direction may be obtained.

  Further, since the periodic direction of the image 64P is inclined by the angle θ with respect to the Y direction, in order to accurately obtain the position of the image 64P in the periodic direction, the Y direction of the image 64P obtained from FIG. Using the position (lateral shift) Ya and the X coordinate Xa of the slit 61 (Z tilt stage 38) at that time, the calculation unit in the main controller 50 in FIG. The direction position (lateral shift) Ra may be calculated.

Ra = (Xa ² + Ya ² ) ^1/2 (6)
In order to compare with the case of using the slit 61 of this example, as shown in FIG. 5A, consider a case where an image 64P of an L & S pattern is scanned in the Y direction by a conventional slit 62 consisting of only a light transmitting portion. The light quantity (maximum value) when the slit 62 is at the position A is 1, and the light quantity (minimum value) when the slit 62 is at the position B (or C) is about ½. Therefore, the detection signal PS obtained by photoelectrically converting the amount of light that has passed through the slit 62 has an average value DC2 of about 3/4 and an amplitude AC2 of about 1 with respect to the Y coordinate of the slit 62 as shown in FIG. Therefore, the contrast (= AC2 / DC2≈2 / 3) is approximately 2/3, which is approximately 1/3 of the contrast in FIG. 4B when the slit 61 of this example is used. Therefore, by using the slit 61 of this example, the light intensity distribution of the image 64P of the L & S pattern can be measured with high accuracy with a contrast approximately three times that in the case of using the conventional slit.

  Next, since the relationship of the formula (2) is sufficient between the shape of the slit of the aerial image measurement system of this example and the image of the L & S pattern to be measured, the period direction is different using one slit. The light intensity distribution of three or more periodic patterns, for example, three L & S pattern images 63P, 64P, and 65P having different periodic directions shown in FIGS. 6A, 6B, and 6C can be measured. In this case, the periodic direction of the image 63P is the Y direction, and the periodic directions of the images 64P and 65P are inclined clockwise by angles θB and θC (> θB), respectively, with respect to the Y direction. The pitch of the image 63P is arbitrary, the pitch of the image 64P is pB, the width of the dark part is dB (= pB / 2), the pitch of the image 65P is pC (> pB), and the width of the dark part is dC (= pC / 2).

  The slit 61A in FIG. 7A is used in place of the slit 61 of the aerial image measurement system 59 in FIG. 2 when measuring the light intensity distribution of the images 63P, 64P, 65P in FIGS. 6A to 6C. The slit 61A is configured by alternately arranging two light transmitting portions 61Aa and one light shielding portion 61Ab in the X direction, and the pitch p2 of the arrangement in the longitudinal direction (X direction) of the light shielding portion 61Ab is: Corresponding to equation (2),

p2 = pB / sin θB = pC / sin θC (7)
In other words, the light intensity distributions of the images 64P and 65P of two L & S patterns having different periodic directions are relatively scanned by the slit 61A whose longitudinal direction is different from the longitudinal direction of the bright part (or dark part) of these images. In order to measure, the relationship of pB / sin θB = pC / sin θC on the right side in equation (7) is necessary. The lengths of the light transmitting portion 61Aa and the light shielding portion 61Ab of the slit 61A in the X direction are p2 / 2, and the slit length of the slit 61A in the X direction is 3 · p2 / 2.

  Considering the case where the L & S pattern image 64P of FIG. 7A (same as the image 64P of FIG. 6B) is scanned in the Y direction indicated by the arrow 66 by the slit 61A, the slit 61A is at the position A. The light amount (minimum value) when the slit 61A is at the position B (or C) is almost zero. Therefore, the detection signal PS obtained through the slit 61A has an average value DC3 of approximately 1/2 and an amplitude AC3 of approximately 1 with respect to the Y coordinate, as shown in FIG. AC3 / DC3≈2) is a theoretical maximum value of about 2.

  Similarly, considering the case where the L & S pattern image 65P of FIG. 8 (same as the image 65P of FIG. 6C) is scanned in the Y direction by the slit 61A, since the equation (7) is established, the slit 61A The light amount (maximum value) when is at position A is 1, and the light amount (minimum value) when slit 61A is at position B is almost zero. Accordingly, the contrast with respect to the Y coordinate of the detection signal PS obtained through the slit 61A has a maximum value of about 2.

In FIG. 7A, when the length of the image 64P in the X direction is long, instead of the slit 61A, as shown in FIG. 9, three light transmitting portions are arranged in the longitudinal direction (X direction). A slit 61B configured by alternately arranging 61Aa and two light shielding portions 61Ab may be used. Also in the case of FIG. 9, Expression (7) is established regarding the pitch p2 in the X direction of the light shielding portion 61Ab, the inclination angle θB in the periodic direction of the image 64P of the L & S pattern, and the pitch pB in the periodic direction of the image 64P. The width dB (equal to the width of the bright part 64 Pa) is pB / 2. Further, the slit length L1 in the X direction of the slit 61B is as follows using the equation (7). This corresponds to the case of n = 2 in FIG.
L1 = 5 · p2 / 2 = (5/2) pB / sin θB (8)
Even when the image 64P is scanned in the Y direction by the slit 61B in FIG. 9, the detection signal becomes the maximum value when the slit 61B is at the position A, and the detection signal becomes almost 0 when the slit 61B is at the position B. The contrast is a maximum value of about 2.

  Next, another example of the embodiment of the present invention will be described with reference to FIGS. The configurations of the projection exposure apparatus and the aerial image measurement system of this example are the same as those of the projection exposure apparatus 10 of FIG. 1 and the aerial image measurement system 59 of FIG. As shown in FIG. 10A, the difference is that a slit 61C in which the boundary lines 61Cc and 61Cd in the longitudinal direction (X direction) of the light shielding part 61Cb are parallel and inclined with respect to the Y direction is used. The measurement target of this example is the image 63P of the L & S pattern in FIG. 10A and the image 65P of the L & S pattern in FIG. 10B (the same as the image 63P in FIG. 6A and the image 65P in FIG. 6C, respectively). .)

  Formula (7) is satisfied for the pitch p2 of the arrangement in the X direction of the light shielding part 61Cb of the slit 61C, and the length of the light shielding part 61Cb in the X direction is p2 / 2. Further, the boundary lines 61Cc and 61Cd of the light shielding portion 61Cb are as shown in the longitudinal direction (FIG. 6C) of the bright portion 65Pa (or the dark portion 65Pb) of the image 65P of the measurement target L & S pattern in FIG. (A direction inclined by an angle θC clockwise with respect to the X axis).

  In this case, as shown in FIG. 10A, when the slit 61C is scanned in the Y direction indicated by the arrow 66 with respect to the image 63P whose periodic direction is the Y direction, the detection signal becomes the maximum value at the position A1, and the position B1 Then, since the detection signal is almost 0, the contrast of the detection signal becomes a maximum value of about 2. As shown in FIG. 10B, when the slit 61C is scanned in the Y direction indicated by the arrow 66 with respect to the image 65P whose periodic direction is inclined from the Y direction, the detection signal is maximum at the position B2. Since the detection signal is substantially 0 at the position A2, the contrast of the detection signal is approximately the maximum value of 2.

  Further, when the image 65P is scanned by the slit 61C of this example as shown in FIG. 11A, the longitudinal boundary line of the light shielding portion 61Ab of FIG. 7A is formed by the slit 61A parallel to the Y direction. When the detection signal PS is compared with the case of scanning, when the scanning is performed by the slit 61A, for example, in the triangular portions 61e and 61f, the light amount is decreased or increased. Therefore, as shown in FIG. 11B, the detection signal PSC when scanning with the slit 61C is increased with respect to the detection signal PSA when scanning with the slit 61A, and the minimum value is decreased. Is improved. Therefore, by using the slit 61C of this example, the light intensity distribution of the image 65C of the L & S pattern can be measured with higher contrast.

  In the above embodiment, for example, in FIG. 4, the L & S pattern image 64 </ b> P is scanned by the slit 61 in the Y direction different from the periodic direction, and the light intensity distribution is measured. When the light intensity distribution of the image 63P is measured, the relative scanning direction of the slit 61 can be made common, and the measurement process can be simplified. However, in FIG. 4, in order to measure the light intensity distribution of the image 64P, the slit 61 may be scanned with respect to the image 64P in the periodic direction indicated by the arrow 67 of the image 64P. Thus, the light intensity distribution in the periodic direction of the image 64P can be directly measured without performing coordinate conversion.

  In each of the above embodiments, the case where the present invention is applied to a scanning exposure type projection exposure apparatus has been described. However, the present invention is not limited thereto, and the reticle pattern is transferred onto the wafer while the reticle and the wafer are stationary. The present invention can also be applied to the case where exposure is performed with a static exposure type (collective exposure type) projection exposure apparatus such as a stepper. The present invention can also be applied to exposure using an immersion type exposure apparatus disclosed in, for example, International Publication No. 99/49504, International Publication No. 2004/019128.

Further, the present invention is not limited to an exposure apparatus for manufacturing a semiconductor device, but is used for manufacturing a display including a liquid crystal display element, a plasma display, and the like. An exposure apparatus for transferring a device pattern onto a glass plate and a thin film magnetic head. Applicable to exposure equipment that transfers device patterns used in ceramics onto ceramic wafers, as well as exposure equipment used to manufacture imaging devices (CCD, etc.), organic EL, micromachines, MEMS (Microelectromechanical Systems), and DNA chips. can do.
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.

  According to the present invention, by using a slit shape that takes into account the pitch and period direction of the aerial image of the pattern to be measured, a single slit can accurately measure the light intensity distribution of a plurality of aerial images in different periodic directions. It becomes possible. Therefore, when the present invention is applied to the measurement of the imaging characteristics of the projection optical system, it is possible to obtain wavefront aberrations at aberration measurement points in an angular direction larger than the number of slits, and to accurately evaluate the imaging characteristics.

It is the figure which notched the part which shows the structure of the projection exposure apparatus of an example of embodiment of this invention. FIG. 2 is a partially cutaway view illustrating an imaging characteristic correction mechanism and an aerial image measurement system in FIG. 1. FIG. 3A is an enlarged view showing a slit 61 in FIG. 2, and FIG. 3B is a diagram showing an example of a detection signal detected using the slit 61. (A) is an enlarged view showing the relationship between the image 64P of the L & S pattern and the slit 61, and (B) is a diagram showing an example of a detection signal obtained by scanning the image 64P with the slit 61. FIG. (A) is an enlarged plan view showing the relationship between the image 64P and the slit 62, and (B) is a diagram showing an example of a detection signal obtained by scanning the image 64P with the slit 62. FIG. (A) is an enlarged view showing an L & S pattern image 63P, (B) is an enlarged view showing an L & S pattern image 64P, and (C) is an enlarged view showing an L & S pattern image 65P. (A) is an enlarged view showing the relationship between the image 64P and the slit 61A, and (B) is a diagram showing an example of a detection signal obtained by scanning the image 64P with the slit 61A. It is an enlarged view which shows the relationship between the image 65P and the slit 61A. It is an enlarged view which shows the relationship between the image 64P and the slit 61B. (A) is an enlarged view showing the relationship between the image 63P and the slit 61C in another example of the embodiment of the present invention, and (B) is an enlarged view showing the image 65P. (A) is an enlarged view showing a relationship between an image 65P and slits 61A and 61C in another example of the embodiment, and (B) shows an example of a detection signal obtained by scanning the image 65P with the slits 61A and 61C. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Projection exposure apparatus, 12 ... Illumination optical system, 14 ... Light source, IL ... Illumination light, R ... Reticle, RFM ... Reticle mark board, PL ... Projection optical system, W ... Wafer, 50 ... Main controller, 59 ... Space Image measurement system, 61, 61A, 61B, 61C ... slit, 61Ab, 61Cb ... light shielding part, 61Cc, 61Cd ... boundary line, 63, 64 ... L & S pattern, 63P, 64P, 65P ... L & S pattern image, 74 ... image formation Characteristic correction controller 89 ... Photoelectric sensor 90 ... Slit plate

Claims (10)

A measurement method for measuring light intensity distributions of images of first and second periodic patterns arranged in different directions,
A direction perpendicular to the periodic direction of the image of the first periodic pattern is a longitudinal direction, and a slit having a light shielding portion formed in a part of the longitudinal direction and the image of the first periodic pattern are relatively scanned. A first step of receiving light passing through the slit;
And a second step of receiving light passing through the slit by relatively scanning the slit and the image of the second periodic pattern. The light shield is periodically formed along the longitudinal direction,
The angle formed by the periodic direction of the image of the second periodic pattern with respect to the periodic direction of the image of the first periodic pattern is θ, and the pitch in the periodic direction of the image of the second periodic pattern is p1. P2 = p1 / sin θ per pitch p2 of the light-shielding portion in the longitudinal direction of the slit
The measurement method according to claim 1, wherein the relationship is established.   The relative scanning direction of the first and second periodic pattern images and the slit in the first step and the second step is parallel to the periodic direction of the first periodic pattern image. The measurement method according to claim 1, wherein the measurement method is characterized.   The second step includes a step of converting a light amount distribution detected by relative scanning between the image of the second periodic pattern and the slit into a distribution in a periodic direction of the image of the second periodic pattern. The measuring method according to claim 3.   5. The boundary of the light shielding portion of the slit is substantially parallel to a longitudinal direction of a bright portion or a dark portion of the image of the second periodic pattern. The measurement method described. A measuring device that measures light intensity distributions of images of first and second periodic patterns arranged in different directions,
A slit in which a light shielding portion is formed in a part of the longitudinal direction, with a direction perpendicular to the periodic direction of the image of the first periodic pattern as a longitudinal direction;
A photoelectric detector that receives light that has passed through the slit;
A measuring apparatus comprising: a relative scanning mechanism that relatively scans the images of the first and second periodic patterns and the slit. The light shield is periodically formed along the longitudinal direction,
The angle formed by the periodic direction of the image of the second periodic pattern with respect to the periodic direction of the image of the first periodic pattern is θ, and the pitch in the periodic direction of the image of the second periodic pattern is p1. P2 = p1 / sin θ per pitch p2 of the light-shielding portion in the longitudinal direction of the slit
The measurement apparatus according to claim 6, wherein the relationship is established. In an exposure method of illuminating a pattern with an exposure beam and exposing an object with the exposure beam through the pattern and a projection optical system,
The measurement which measures the light intensity distribution of the image of the said 1st and 2nd periodic pattern arrange | positioned on the object surface of the said projection optical system using the measuring method as described in any one of Claim 1 to 5. Process,
A calculation step of obtaining an imaging characteristic of the projection optical system based on a measurement result of the measurement step;
An exposure method comprising: a correction step of correcting an imaging characteristic of the projection optical system based on a calculation result of the calculation step. In an exposure apparatus that illuminates a pattern with an exposure beam and exposes an object with the exposure beam via the pattern and a projection optical system,
A measuring device according to claim 6 or 7,
A stage that holds and moves the object;
An arithmetic unit for obtaining imaging characteristics of the projection optical system using detection information of the photoelectric detector of the measuring device;
An exposure apparatus comprising: a correction mechanism that corrects an imaging characteristic of the projection optical system based on a calculation result of the calculation apparatus. The slit of the measuring device is provided on the stage,
The exposure apparatus according to claim 9, wherein the relative scanning mechanism of the measuring apparatus is the stage.

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