JP2004119663A - Position detection device, position detection method, aligner and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detection device which effects highly accurate position detection by suppressing the variation of misregistration of a mark image with respect to the defocus of a mark compared with the size of numerical aperture of an imaging optical system. <P>SOLUTION: The position detection device is equipped with a lighting flux shaping member (3) for shaping a lighting flux in the first surface of a lighting optical system, in the relation of Fourier conversion substantially to the mark (watermark) so as to have a predetermined shape; and an imaging flux shaping member (17) arranged in the second surface of the imaging optical system, in the relation of Fourier conversion substantially to the mark and having a predetermined light transmission coefficient distribution which is higher in a circumferential region without comprising an optical axis than a central region comprising the optical axis of the imaging optical system. The imaging flux shaping member passes the imaging flux in at least one part of the second surface optically conjugate with the predetermined shape of lighting flux in the first surface. According to this constitution, the variation of misregistration of the mark image with respect to the defocus of the mark can be suppressed compared with the size of numerical aperture of the imaging optical system whereby the highly accurate position detection is effected. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a position detection device, a position detection method, an exposure device, and an exposure method, and is particularly mounted on an exposure device used in a lithography process for manufacturing a micro device such as a semiconductor device, an imaging device, a liquid crystal display device, and a thin-film magnetic head. The present invention relates to a position detecting device.
[0002]
[Prior art]
Generally, when manufacturing a device such as a semiconductor element, a plurality of circuit patterns are formed on a wafer (or a substrate such as a glass plate) on which a photosensitive material is applied. For this reason, an exposure apparatus for exposing a circuit pattern on a wafer includes an alignment apparatus for performing relative alignment (alignment) between a mask pattern and each exposure area of a wafer on which a circuit pattern has already been formed. Provided. In recent years, with the miniaturization of the line width of a circuit pattern, high-precision alignment has been required.
[0003]
2. Description of the Related Art Conventionally, as this type of alignment apparatus, an alignment apparatus of an off-axis type and an imaging type has been known as disclosed in JP-A-4-65603 and JP-A-4-273246. The detection system of this imaging type alignment apparatus is also called a FIA (Field Image Alignment) system position detection apparatus. In an FIA type position detecting device, an alignment mark (wafer mark) on a wafer is illuminated with light having a wide wavelength bandwidth emitted from a light source such as a halogen lamp. Then, an enlarged image of the wafer mark is formed on the imaging device via the imaging optical system, and the obtained imaging signal is subjected to image processing to detect the position of the wafer mark.
[0004]
[Patent Document 1]
JP-A-4-65603
[Patent Document 2]
JP-A-4-273246
[0005]
[Problems to be solved by the invention]
Generally, when manufacturing a device such as a semiconductor element, a wafer mark is formed on a scribe line around a chip. In this case, in order to obtain as many chips as possible from one wafer, it is important to reduce the scribe line and thus the mark (the pattern pitch). Then, in order to detect a small mark with the same imaging performance as the conventional one, the numerical aperture NA of the imaging optical system must be increased.
[0006]
Further, when the numerical aperture NA of the imaging optical system is increased, the order of the diffracted light that can be detected (capturable) is increased (increased). There is also an advantage that a position detection error caused by asymmetry can be reduced. This is because a mark image formed by higher-order diffracted light has a smaller positional shift amount due to the asymmetry of the pattern than a mark image formed by lower-order diffracted light.
[0007]
However, in the conventional FIA system position detecting device, when the numerical aperture NA of the imaging optical system is increased, the depth of focus (DOF) of the imaging optical system is reduced, and the positional deviation of the mark image with respect to the defocus of the mark is reduced. Changes become sensitive. Specifically, in a position detecting device in which the numerical aperture NA of the imaging optical system is relatively small, the numerical aperture NA of the imaging optical system is smaller than that of defocusing the mark by a predetermined amount with respect to the object plane of the imaging optical system. When the mark is defocused by the same predetermined amount in a position detecting device having a relatively large mark, the change in the waveform of the mark image becomes larger, and a detection error of the mark position is more likely to occur.
[0008]
The present invention has been made in view of the above-described problems, and has a high precision by suppressing a change in a positional shift of a mark image with respect to defocus of a mark as compared with a size of a numerical aperture of an imaging optical system. It is an object of the present invention to provide a position detecting device and a position detecting method capable of performing accurate position detection. Further, using the highly accurate position detecting device and position detecting method of the present invention, for example, an exposure apparatus capable of performing good exposure by aligning a mask and a photosensitive substrate with high accuracy with respect to a projection optical system, for example. And an exposure method.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, according to a first embodiment of the present invention, there is provided an illumination optical system that illuminates a mark on a substrate, and an imaging optical system that collects light from the mark to form an image of the mark. In a position detection device that detects the position of the mark based on the image of the mark,
An illumination light beam shaping member for shaping an illumination light beam on the first surface in the illumination optical system that is substantially in a Fourier transform relationship with the mark into a predetermined shape;
A peripheral portion that is disposed on the second surface in the imaging optical system that is substantially in a Fourier transform relationship with the mark and that does not include the optical axis than a central region that includes the optical axis of the imaging optical system; An imaging light flux shaping member having a predetermined higher light transmittance distribution in the region,
The position wherein the imaging light flux shaping member transmits the imaging light flux in at least a part of an area on the second surface which is optically conjugate with a predetermined shape of the illumination light flux on the first surface. A detection device is provided.
[0010]
According to a preferred mode of the first aspect, the imaging light flux shaping member has a ring-shaped light passing area centered on the optical axis. In this case, λ is the shortest wavelength of the illuminating light for illuminating the mark, P is the period of the pattern forming the mark, and the radius of the light-blocking area around the optical axis of the imaging light beam shaping member is an aperture. When the number is represented by r, it is preferable that the condition of r ≧ λ / P is satisfied. Alternatively, it is preferable that the imaging light flux shaping member has a multipolar light passing area decentered from the optical axis.
[0011]
According to a preferred aspect of the first aspect, the imaging light beam shaping member restricts the imaging light beam to a predetermined shape, and corrects non-uniformity of the luminance distribution of the imaging light beam having the predetermined shape. Correction means. Further, the imaging light beam shaping member has a first member having a first light transmittance distribution and a second member having a second light transmittance distribution, or independently adjusts a deflection direction of an incident light beam. It is preferable to have a plurality of micromirrors that can be changed. Further, the imaging light beam shaping member is configured to be freely inserted into and removed from an optical path of the imaging optical system.
[0012]
In a second embodiment of the present invention, a mark on a substrate is illuminated via an illumination optical system, and light from the mark is condensed via an imaging optical system to form an image of the mark. In a position detection method for detecting the position of the mark based on an image, limiting the illumination light flux to a predetermined shape on a first surface in the illumination optical system that is substantially in a Fourier transform relationship with the mark, The intensity distribution of the imaging light flux on the second surface in the imaging optical system which is substantially in a Fourier transform relationship with respect to the mark is set to be smaller than the central area including the optical axis of the imaging optical system by the optical axis. Is limited to a higher predetermined light intensity distribution in a peripheral region that does not include an image, and an image is formed in at least a part of a region on the second surface that is optically conjugate with a predetermined shape of the illumination light beam on the first surface. A position detection method characterized by transmitting a light beam. Subjected to.
[0013]
According to a preferred aspect of the second aspect, a first step of detecting the position of the mark in a state where the intensity distribution of the imaging light beam is limited to the first light intensity distribution, A second step of detecting the position of the mark in a state limited to the light intensity distribution of No. 2, and the position of the position detection result of the mark based on the detection result in the first step and the detection result in the second step. And a third step of obtaining a shift correction amount.
[0014]
In a third aspect of the present invention, an illumination system for illuminating a mask on which a predetermined pattern is formed, a projection optical system for forming a pattern image of the mask on a photosensitive substrate, An exposure apparatus comprising: a position detecting device according to a first embodiment for detecting a position.
[0015]
According to a fourth aspect of the present invention, there is provided an exposure method for illuminating a mask on which a predetermined pattern is formed and exposing a pattern image of the illuminated mask onto a photosensitive substrate. An exposure method is provided, wherein the position of the photosensitive substrate is detected by using a position detection method of the present invention.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
According to a typical aspect of the present invention, the imaging light flux on the second surface (that is, the imaging pupil surface or a surface near the imaging pupil surface) in the imaging optical system having a substantially Fourier transform relationship with respect to the mark. The intensity distribution is limited to a predetermined light intensity distribution that is higher (larger) in a peripheral region not including the optical axis than in a central region including the optical axis, for example, to an annular light intensity distribution centered on the optical axis. Specifically, the position of the mark is detected in a state where the imaging light flux shaping member having the annular opening is arranged on the imaging pupil plane or a surface in the vicinity thereof.
[0017]
Generally, on the imaging pupil plane, the phase of the imaging light flux due to defocus changes according to the square of the numerical aperture of the imaging light flux. Therefore, in the related art using an image forming light beam having a circular cross section centered on the optical axis on the image forming pupil plane, a mark image is formed based on all image forming light beam components having different phases. The larger the value, the more sensitive the change of the mark image position shift to the mark defocus. Then, the larger the change in the image shape, the larger the change in the position detected using the image. On the other hand, in the present invention, a mark image is formed based on an imaging light flux component having a relatively small phase difference, for example, since an imaging light flux having a ring-shaped cross section centered on the optical axis is used on the imaging pupil plane. Therefore, the change in the mark image shape due to the defocus of the mark can be suppressed to a small value. That is, since the change in the image shape is small, the change in the position due to defocus can be suppressed to a small value.
[0018]
Thus, with the position detecting device and the position detecting method of the present invention, the change in the positional deviation of the mark image with respect to the defocus of the mark can be suppressed small compared to the size of the numerical aperture of the imaging optical system. Position detection can be performed, which is particularly advantageous when the numerical aperture of the imaging optical system is set to be large. Further, in the exposure apparatus equipped with the position detection device of the present invention, and the exposure method using the position detection device or the position detection method of the present invention, the position of the photosensitive substrate is detected with high accuracy using the high-precision position detection device. In addition, by aligning the mask and the photosensitive substrate with high accuracy, it is possible to perform favorable projection exposure.
[0019]
An embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram schematically illustrating a basic configuration of an exposure apparatus including a position detection device according to an embodiment of the present invention. FIG. 2 is a diagram schematically illustrating a configuration of a wafer mark formed of a step pattern formed on a wafer that is an object whose position is to be detected by the position detection device of the present embodiment.
[0020]
In the present embodiment, the present invention is applied to an FIA-based position detecting device for detecting the position of a photosensitive substrate in an exposure device for manufacturing a semiconductor element. In FIG. 1, the Z axis is parallel to the optical axis AX0 of the projection optical system PL of the exposure apparatus, the X axis is a direction parallel to the plane of FIG. 1 in a plane perpendicular to the Z axis, and the Z axis is The Y-axis is set in a direction perpendicular to the plane of FIG. 1 in a vertical plane.
[0021]
Referring to FIG. 1, the exposure apparatus of the present embodiment includes an exposure illumination system IL for illuminating a reticle R as a mask (projection master) with appropriate exposure light. The reticle R is supported substantially parallel to the XY plane on the reticle stage 30, and a circuit pattern to be transferred is formed in the pattern area PA. The light transmitted through the reticle R reaches the wafer W as a photosensitive substrate via the projection optical system PL, and a pattern image of the reticle R is formed on the wafer W.
[0022]
The wafer W is supported on the Z stage 32 via the wafer holder 31 substantially in parallel with the XY plane. The Z stage 32 is configured to be driven by the stage control system 34 in the Z direction along the optical axis AX0 of the projection optical system PL. The Z stage 32 is further supported on an XY stage 33. The XY stage 33 is also configured to be driven two-dimensionally by the stage control system 34 in an XY plane perpendicular to the optical axis AX0 of the projection optical system PL.
[0023]
As described above, in the exposure apparatus, it is necessary to optically align (align) the pattern area PA on the reticle R and each exposure area on the wafer W prior to the projection exposure. Therefore, a wafer mark (wafer alignment mark) WM having a step pattern as schematically shown in FIG. 2 is formed on the wafer W which is an object to be detected. The position detecting device of the present embodiment is used to detect the position of the wafer mark WM, and thus the position of the wafer W.
[0024]
Specifically, as the wafer mark WM, an X-direction wafer mark WMX as a one-dimensional mark having periodicity in the X direction, and a Y-direction wafer mark WMY (not shown) as a one-dimensional mark having periodicity in the Y direction Are formed on the wafer W. In the present embodiment, two independent one-dimensional marks having periodicity in the X direction and the Y direction are adopted as the wafer marks WM, but two-dimensional marks having periodicity in the X direction and the Y direction are used. Marks can also be employed.
[0025]
The position detection device according to the present embodiment includes a light source 1 for supplying illumination light having a wide wavelength bandwidth (for example, 530 nm to 800 nm). As the light source 1, a light source such as a halogen lamp can be used. Illumination light supplied from the light source 1 is incident on an incident end of a light guide 2 such as an optical fiber via a relay optical system (not shown). Illumination light propagating inside the light guide 2 and emitted from the exit end thereof is restricted via the illumination aperture stop 3 having, for example, a circular opening (light transmitting portion), and is then transmitted to the condenser lens 4. Incident.
[0026]
The illumination light via the condenser lens 4 is incident on the illumination relay lens 6 via the illumination field stop 5 which is arranged optically conjugate with the exposure surface of the wafer W which is the object to be illuminated. The illumination light via the illumination relay lens 6 passes through the half prism 7 and then enters the first objective lens 8. The illumination light having passed through the first objective lens 8 is reflected downward (in the −Z direction) in the drawing on the reflection surface of the reflection prism 9 and then illuminates the wafer mark WM formed on the wafer W.
[0027]
Thus, the light source 1, the light guide 2, the illumination aperture stop 3, the condenser lens 4, the illumination field stop 5, the illumination relay lens 6, the half prism 7, the first objective lens 8, and the reflection prism 9 illuminate the wafer mark WM. And an illumination optical system for performing the operation. The illumination aperture stop 3 is a first surface (that is, an illumination pupil surface or a surface near the illumination pupil surface) in the illumination optical system which has a substantially Fourier transform relationship with respect to the wafer mark WM (and thus with respect to the wafer W). Constitutes an illumination light beam shaping member for shaping the illumination light beam into a predetermined shape.
[0028]
The reflected light (including the diffracted light) from the wafer mark WM with respect to the illumination light enters the half prism 7 via the reflecting prism 9 and the first objective lens 8. The light reflected upward (in the + Z direction) in the figure by the half prism 7 forms an image of the wafer mark WM on the index plate 11 via the second objective lens 10. The light passing through the index plate 11 enters the XY branch half prism 14 via the relay lens system (12, 13).
[0029]
The light reflected by the XY branch half prism 14 is incident on the CCD 15 for Y direction, and the light transmitted through the XY branch half prism 14 is incident on the CCD 16 for X direction. Note that an image forming aperture stop 17 is arranged in the parallel optical path of the relay lens system (12, 13). As described above, the reflecting prism 9, the first objective lens 8, the half prism 7, the second objective lens 10, the index plate 11, the relay lens system (12, 13), the image forming aperture stop 17, and the half prism 14 emit illumination light. An image forming optical system for forming a mark image based on reflected light from the wafer mark WM with respect to.
[0030]
Further, the CCD 15 for the Y direction and the CCD 16 for the X direction constitute a photoelectric detector for photoelectrically detecting the mark image formed via the imaging optical system. Further, the image forming aperture stop 17 is provided on the second surface (that is, at or near the image forming pupil surface) in the image forming optical system having a substantially Fourier transform relation with respect to the wafer mark WM (and thus with respect to the wafer W). And a peripheral region that does not include the optical axis AX of the imaging optical system has a higher (larger) predetermined light transmittance distribution than a central region that includes the optical axis AX of the imaging optical system. Is composed. The specific configuration and operation of the imaging aperture stop 17 as the imaging light beam shaping member will be described later.
[0031]
In this way, a mark image is formed on the imaging surface of the Y-direction CCD 15 and the X-direction CCD 16 together with the index pattern image of the index plate 11. Output signals from the Y-direction CCD 15 and the X-direction CCD 16 are supplied to a signal processing system 18. Further, the position information of the wafer mark WM obtained by the signal processing (waveform processing) in the signal processing system 18 is supplied to the main control system 35. The main control system 35 outputs a stage control signal to the stage control system 34 based on the position information of the wafer mark WM from the signal processing system 18.
[0032]
The stage control system 34 appropriately drives the XY stage 33 in accordance with the stage control signal to perform alignment of the wafer W. A command for the illumination aperture stop 3 and a command for the imaging aperture stop 17 are supplied to the main control system 35 via input means 36 such as a keyboard. The main control system 35 drives the illumination aperture stop 3 via the drive system 19 and drives the imaging aperture stop 17 via the drive system 20 based on these commands.
[0033]
Specifically, the imaging aperture stop 17 includes a ring-shaped aperture stop, a two-pole aperture stop, a four-pole aperture stop, and the like as a plurality of exchangeable aperture stops. The drive system 19 positions a required aperture stop at or near the imaging pupil plane based on a command from the main control system 35. The illumination aperture stop 3 includes a plurality of interchangeable circular aperture stops having different aperture sizes. The drive system 20 positions a required circular aperture stop on or near the illumination pupil plane based on a command from the main control system 35.
[0034]
FIG. 3 is a diagram illustrating a state of a light beam on the illumination pupil plane and the image pupil plane in the first embodiment for shaping the imaging light beam into an annular shape. FIG. 4 is a diagram showing a change in the mark image waveform when the wafer mark is defocused in the first embodiment. Further, FIG. 5 is a diagram showing, as a comparative example of the first embodiment, a change in a mark image waveform when a wafer mark is defocused in a conventional technique for shaping an image forming light beam into a circular light beam.
[0035]
Referring to the imaging pupil plane of FIG. 3, in the first embodiment, the imaging light flux is shaped (restricted) into an annular light flux centered on the optical axis AX. Here, for example, a relationship of R2 = R1 × (１ ／) is set between the outer diameter (radius) R1 and the inner diameter (radius) R2 of the annular imaging light beam, and the so-called annular ratio is 1 / 2 is set. On the other hand, referring to the illumination pupil plane of FIG. 3, in the first embodiment, the illumination light flux is shaped into a circular light flux having a radius R3 around the optical axis AX.
[0036]
In the illumination pupil plane, a ring-shaped region optically conjugate with the ring-shaped imaging light flux on the imaging pupil plane is indicated by a broken line. Here, a relationship of R3 = R1 ′ is set between the radius R3 of the circular illumination light beam and the outer diameter R1 ′ of the annular region optically conjugate with the annular imaging light beam. (However, in FIG. 3, the radius R3 is shown smaller than the outer diameter R1 'for clarity of the drawing). In other words, the radius R3 of the circular illumination light flux is set to be larger than the inner diameter R2 'of the annular area optically conjugate to the annular imaging light flux.
[0037]
Therefore, in the first embodiment, the image forming light beam passes through the image forming pupil plane in at least a part of the circular region on the image forming pupil surface that is optically conjugate with the circular illumination light beam. Although not shown, in the comparative example of the first embodiment, both the imaging light beam and the illumination light beam are shaped into a circular shape, and the circular illumination light beam and the circular image forming light beam have the same optical size. Is set to In other words, on the illumination pupil plane, the radius of the circular illumination light beam is set to be equal to the radius of the circular region optically conjugate to the circular imaging light beam.
[0038]
Referring to FIG. 4, in the first embodiment, in a state where the wafer mark WM is made to coincide with the object plane of the imaging optical system, that is, in a focus state where the defocus amount Z of the wafer mark WM is 0, the light passes through the imaging optical system. The waveform obtained with respect to the mark image formed as described above is indicated by a thick line 41. On the other hand, the wafer mark WM is shifted from the object plane of the imaging optical system by a predetermined defocus amount Z = Z ₁ A thin line 42 shows a waveform obtained for a mark image formed via the imaging optical system in the defocused state moved only by.
[0039]
Referring to FIG. 5, a bold line 51 shows a waveform obtained for a mark image formed via the imaging optical system in the focus state of the comparative example of the first embodiment. On the other hand, the defocus amount Z = Z ₁ In the defocused state, a thin line 52 shows a waveform obtained for a mark image formed via the imaging optical system. Referring to FIGS. 4 and 5, the first embodiment according to the present invention has the same defocus amount Z = Z than the comparative example according to the prior art. ₁ It can be seen that the change in the waveform of the mark image when defocusing is only small.
[0040]
FIG. 6 is a diagram showing the state of the light flux on the illumination pupil plane and the image pupil plane in the second embodiment in which the imaging light flux is shaped into a dipole. Referring to the imaging pupil plane of FIG. 6, in the second embodiment, the imaging light beam is shaped into a dipole light beam composed of two circular light beams arranged symmetrically with respect to a straight line passing through the optical axis AX. ing. Here, the two circular light beams have the same radius R4 and are adjacent to each other. On the other hand, referring to the illumination pupil plane of FIG. 6, in the second embodiment, the illumination light beam is shaped into a circular light beam having a radius R5 centered on the optical axis AX.
[0041]
In the illumination pupil plane, a dipole region optically conjugate with two circular imaging light beams on the imaging pupil plane is indicated by broken lines. Here, the radius R5 of the circular illumination light beam is set to be equal to the radius of a circle circumscribing the bipolar region. Therefore, also in the second embodiment, the image-forming light beam passes through the image-forming pupil plane in at least a part of the circular region on the image-forming pupil plane which is optically conjugate with the circular illumination light beam. In the second embodiment, although not shown, the wafer mark WM has the same defocus amount Z = Z ₁ It has been confirmed that the change in the waveform of the mark image when only defocusing is performed is smaller than that in the comparative example according to the related art.
[0042]
FIG. 7 is a diagram showing a state of light beams on the illumination pupil plane and the image pupil plane in the third embodiment for shaping the imaging light beam into quadrupoles. Referring to the imaging pupil plane of FIG. 7, in the third embodiment, the imaging light flux is a quadrupolar light flux composed of four circular light fluxes symmetrically arranged with respect to two orthogonal straight lines passing through the optical axis AX. It is shaped into a luminous flux. Here, the four circular light beams have the same radius R6 and are adjacent to each other. On the other hand, with reference to the illumination pupil plane of FIG. 7, in the third embodiment, the illumination light beam is shaped into a circular light beam having a radius R7 about the optical axis AX.
[0043]
Note that, on the illumination pupil plane, four-pole regions optically conjugate to the four circular imaging light beams on the imaging pupil plane are indicated by broken lines. Here, the radius R7 of the circular illumination light beam is set to be equal to the radius of a circle circumscribing the quadrupolar region. Therefore, also in the third embodiment, the image-forming light beam passes through the image-forming pupil plane in at least a part of the circular area on the image-forming pupil plane optically conjugate with the circular illumination light beam. Also in the third embodiment, although not shown, the wafer mark WM is set to the same defocus amount Z = Z ₁ It has been confirmed that the change in the waveform of the mark image when only defocusing is performed is smaller than that in the comparative example according to the related art.
[0044]
FIG. 8 is a diagram illustrating a change in a positional shift of a mark image with respect to defocus of a wafer mark in each of the examples and the comparative example. As described above, in the first to third embodiments, the wafer mark WM is set to the same defocus amount Z = Z ₁ The change in the waveform of the mark image when defocusing only is suppressed to be smaller than in the comparative example. To address this, referring to FIG. 8A, in the first embodiment and the second embodiment, the change in the displacement of the mark image with respect to the defocus of the wafer mark WM is suppressed to be smaller than in the comparative example. I understand.
[0045]
FIG. 8B additionally shows a simulation result of the modification of the first embodiment. In this modification, the annular shape of the imaged light flux is represented by R2 = R1 × (3/5) And the radius of the illumination light beam is set to R3 = R1 ′ × (4/5). Referring to FIG. 8B, it can be seen that also in the modification of the first embodiment, the change in the displacement of the mark image with respect to the defocus of the wafer mark WM can be suppressed smaller than in the comparative example. Although the simulation result of the third embodiment is not shown in FIG. 8, it should be noted that also in the third embodiment, the change in the displacement of the mark image with respect to the defocus of the wafer mark WM is suppressed to be smaller than in the comparative example. I have confirmed.
[0046]
As described above, in the present embodiment, for example, an annular, dipole, or quadrupole imaging light flux is used on the imaging pupil plane, so that the wafer is formed based on the imaging light flux component having a relatively small phase difference. Since a mark image is formed, it is possible to suppress a change in the positional shift of the mark image with respect to the defocus of the wafer mark WM. As a result, in the position detection device of the present embodiment, even if the numerical aperture of the imaging optical system is set to be large, a change in the positional deviation of the mark image with respect to the defocus of the wafer mark WM is suppressed to achieve high-precision position detection. It can be carried out.
[0047]
In the first embodiment, the relationship of R3 = R1 ′ is defined between the radius R3 of the circular illumination light beam and the outer diameter R1 ′ of the annular region optically conjugate with the annular imaging light beam. You have set. In the modification of the first embodiment, the relationship of R3 = R1 '× (4/5) is set between the radius R3 of the illumination light beam and the outer diameter R1' of the annular zone. However, without being limited to this, as the imaging light beam passes through the imaging pupil plane at least in a part of the circular region on the imaging pupil surface optically conjugate with the circular illumination light beam, It is preferable to set the radius R3 of the illumination light beam to be larger than the inner diameter R2 ′ of the annular zone.
[0048]
Furthermore, in the second embodiment and the third embodiment, two circular light beams and four circular light beams are arranged adjacent to each other. However, the present invention is not limited to this, and the number and shape of the light beams are different. Various modifications are possible for the arrangement, arrangement, and the like. Further, in the second embodiment and the third embodiment, the illumination light beam is shaped in a circular shape. However, the present invention is not limited to this, and as shown in FIG. You can also. In this modified example, the same effects as in the second and third embodiments can be obtained.
[0049]
In the second embodiment, since two circular imaging light beams arranged along one direction are used, it is advantageous for detecting the position of a wafer mark formed of a one-dimensional pattern having periodicity in one direction. is there. On the other hand, in the third embodiment, since four circular imaging light beams arranged along directions orthogonal to each other are used, the position of a wafer mark formed of a two-dimensional pattern having periodicity in the directions orthogonal to each other is used. It is advantageous for detection.
[0050]
In the first embodiment and its modifications, the imaging light beam is shaped into a light beam having a ring-shaped cross section. However, the present invention is not limited to this. It is also possible to use an imaging light flux having a light intensity distribution in which the intensity increases toward the center or a light intensity distribution in which the intensity increases from the optical axis toward the periphery in a central circular region having a radius R2. In any case, in the present embodiment, it is important to use an imaging light flux having a larger light intensity distribution in a peripheral region not including the optical axis than in a central region including the optical axis. Note that the fact that the intensity distribution of the imaging section may be a distribution instead of a section (that is, 1 or 0) is the same in the second embodiment and the third embodiment described later.
[0051]
By the way, in the first embodiment and its modifications, the effect increases as the radius R2 of the circular central light-shielding region increases. Here, as one of the techniques for setting the radius R2 for obtaining the effect, the center of the primary light for forming an image can be used as a guide. Assuming that the shortest wavelength of the illuminating light for illuminating the wafer mark WM is λ and the period of the pattern forming the wafer mark WM is P, the center r of the first-order diffracted light is converted into a numerical aperture,
r ≦ λ / P (1)
Therefore, the radius R2 may be set according to the above equation (1).
[0052]
In the above-described embodiment, the image forming aperture stop 17 is configured to be removably insertable into the optical path of the image forming optical system, and the image forming aperture stop 17 is retracted from the optical path. WM position detection can also be performed. At this time, a circular aperture stop is arranged as necessary on or near the imaging pupil plane. Alternatively, the imaging aperture stop 17 may be provided with a circular aperture stop as a replaceable aperture stop, and the circular aperture stop may be introduced into the imaging optical path to perform position detection according to the related art. The same applies to the illumination aperture stop. In addition to the conventional circular aperture stop, the illumination aperture stop for shaping the illumination light beam into a dipole shape, and the illumination light beam into a quadrupole shape. It is also possible to provide an illumination aperture stop for shaping, and select an optimal illumination aperture according to the type of the imaging aperture stop and the type of the pattern to be measured.
[0053]
Further, in the above-described embodiment, as a correction unit for correcting the non-uniformity of the luminance distribution of the imaging light flux having a predetermined shape, for example, a density having a transmittance distribution having a reverse tendency to the luminance distribution of the imaging light flux is used. The filter is located at an image pupil plane (a position having a Fourier transform relationship with respect to the final image plane of the imaging optical system, in FIG. 1, in the optical path between the first objective lens 8 and the second objective lens 10, and a relay). (A position in the optical path between the lens 12 and the relay lens 13). When creating the density filter, the luminance distribution of the image forming light beam is measured to find a corresponding intensity distribution, a distribution obtained by inverting the intensity distribution is obtained, and a transmittance distribution of the density filter is calculated based on the inverted distribution. .
[0054]
Then, an aggregate of light-shielding or light-transmitting fine dots is formed on a light-transmitting substrate, and a method of expressing the transmittance distribution with the density of the fine dots and the density distribution of the light transmittance are provided. A method using an absorption filter or the like can be used. With this configuration, it is possible to correct the non-uniformity of the luminance distribution of the imaging light flux. It should be noted that a density filter as correction means for correcting non-uniformity of the luminance distribution of the imaged light flux is provided inside the illumination optical system instead of or in addition to the density filter in the image forming optical system. It may be provided. At this time, the density filter is located at a pupil position in the illumination optical system (a position having a Fourier transform relationship with a mark as a surface to be illuminated, the position of the illumination aperture stop 3 in FIG. 1, the illumination relay lens 6 and the first (Position in the optical path between the objective lens 8).
[0055]
Further, in the above-described embodiment, for example, the position of the wafer mark WM is detected in a state where the image-forming light beam is limited to a ring shape according to the first example, and the image-forming light beam is limited to a dipole shape according to the second example. In this state, it is preferable to detect the position of the wafer mark WM, and to determine the amount of misregistration correction of the position detection result of the wafer mark WM based on the detection result of the first embodiment and the detection result of the second embodiment. Here, the displacement correction amount is an offset amount for correcting a detection error generated due to aberration of the optical system or asymmetry of the mark.
[0056]
Further, in the above-described embodiment, the illumination aperture stop 3 and the imaging aperture stop 17 are used as the illumination light beam shaping member and the imaging light beam shaping member, respectively. (Digital Micro-mirror Device or Deformable Micro-mirror Device) having a plurality of micromirrors that can be independently changed. The DMD is a light modulation element including a large number of micromirrors arranged in a grid pattern, and is configured such that the directions of the micromirrors are individually controlled. In the DMD, a desired light intensity distribution can be formed by appropriately driving the directions of the micromirrors.
[0057]
In the above-described embodiment, the wafer mark is illuminated by epi-illumination. However, the present invention is not limited to this, and the present invention can be applied to a position detection device that illuminates the wafer mark by transmission. Further, in the above-described embodiment, different CCDs are used for the X-direction mark detection and the Y-direction mark detection, respectively, but one CCD may perform both the X-direction mark detection and the Y-direction mark detection. .
[0058]
Furthermore, in the above-described embodiment, the position of the photosensitive substrate in the exposure apparatus is detected. However, without being limited to this, the position of an object mark formed on a general object to be detected, for example, Japanese Patent Application Laid-Open Nos. 6-58730, 7-71918, 10-122814, 10-122820, and 2000-258119 disclose an overlay accuracy measuring device. Also, the present invention can be applied to an apparatus for measuring a dimension between patterns.
[0059]
【The invention's effect】
As described above, in the position detecting device and the position detecting method of the present invention, for example, an orbicular or dipole-shaped imaging light flux centered on the optical axis is used on the imaging pupil plane, so that the phase difference is relatively small. Since the mark image is formed based on the image forming light beam component, a change in the displacement of the mark image with respect to the defocus of the mark can be suppressed to a small value. As a result, in the present invention, since the change in the positional deviation of the mark image with respect to the defocus of the mark can be suppressed smaller than the size of the numerical aperture of the imaging optical system, highly accurate position detection can be performed. It is possible. In particular, the present invention is effective when the numerical aperture of the imaging optical system is set large.
[0060]
Further, in the exposure apparatus equipped with the position detection device of the present invention, and the exposure method using the position detection device or the position detection method of the present invention, the position of the photosensitive substrate is detected with high accuracy using the high-precision position detection device. In addition, by aligning the mask and the photosensitive substrate with high accuracy, it is possible to perform favorable projection exposure.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating a basic configuration of an exposure apparatus including a position detection device according to an embodiment of the present invention.
FIG. 2 is a diagram schematically showing a configuration of a wafer mark formed of a step pattern formed on a wafer which is an object to be position-detected by the position detection device of the present embodiment.
FIG. 3 is a diagram showing a state of a light beam on an illumination pupil plane and an image formation pupil plane in a first embodiment for shaping an image forming light beam into an annular shape.
FIG. 4 is a diagram showing a change in a mark image waveform when a wafer mark is defocused in the first embodiment.
FIG. 5 is a diagram illustrating, as a comparative example of the first embodiment, a change in a mark image waveform when a wafer mark is defocused in a conventional technique for shaping an image forming light beam into a circular light beam.
FIG. 6 is a diagram illustrating a state of a light beam on an illumination pupil plane and an image formation pupil plane in a second example in which an image forming light beam is shaped into a dipole.
FIG. 7 is a diagram showing a state of a light beam on an illumination pupil plane and an image pupil plane in a third embodiment in which an image forming light beam is shaped into quadrupoles.
FIG. 8 is a diagram showing a change in a positional shift of a mark image with respect to a defocus of a wafer mark in each of Examples and Comparative Examples.
FIG. 9 is a diagram illustrating a state of a light beam on an illumination pupil plane and an imaging pupil plane in a modification of the second embodiment and the third embodiment.
[Explanation of symbols]
1 Halogen lamp
2 Light guide
3 Illumination aperture stop
5. Illumination field stop
7 Half prism
8 First objective lens
9 Reflective prism
10 Second objective lens
11 Indicator board
14 XY branch half prism
15,16 CCD
17 imaging aperture stop
18 Signal processing system
30 reticle stage
31 Wafer holder
32 Z stage
33 XY stage
34 Stage control system
35 Main control system
36 keyboard
Illumination system for IL exposure
R reticle
PA pattern area
PL projection optical system
W wafer
WM wafer mark

Claims (12)

An illumination optical system for illuminating a mark on the substrate, and an imaging optical system for condensing light from the mark to form an image of the mark, and detecting a position of the mark based on the image of the mark In the position detection device that
An illumination light beam shaping member for shaping an illumination light beam on the first surface in the illumination optical system that is substantially in a Fourier transform relationship with the mark into a predetermined shape;
A peripheral portion that is disposed on the second surface in the imaging optical system that is substantially in a Fourier transform relationship with the mark and that does not include the optical axis than a central region that includes the optical axis of the imaging optical system; An imaging light flux shaping member having a predetermined higher light transmittance distribution in the region,
The position wherein the imaging light flux shaping member transmits the imaging light flux in at least a part of an area on the second surface which is optically conjugate with a predetermined shape of the illumination light flux on the first surface. Detection device. The position detecting device according to claim 1, wherein the imaging light flux shaping member has a ring-shaped light passing area centered on the optical axis. The shortest wavelength of the illuminating light for illuminating the mark is λ, the period of the pattern forming the mark is P, and the radius of the light-blocking region centered on the optical axis of the imaging light flux shaping member is converted to a numerical aperture. Where r is
r ≧ λ / P
The position detecting device according to claim 2, wherein the following condition is satisfied. The position detecting device according to claim 1, wherein the imaging light flux shaping member has a plurality of polar light passing areas decentered from the optical axis. The image forming beam shaping member includes a correction unit configured to limit the image forming beam to a predetermined shape and to correct non-uniformity of the luminance distribution of the image forming beam having the predetermined shape. Item 5. The position detecting device according to any one of Items 1 to 4. The said imaging light flux shaping member has the 1st member which has a 1st light transmittance distribution, and the 2nd member which has a 2nd light transmittance distribution, The Claims 1 to 5 characterized by the above-mentioned. Position detection device. The position detecting device according to any one of claims 1 to 5, wherein the imaging light beam shaping member includes a plurality of micromirrors capable of independently changing a deflection direction of an incident light beam. The position detecting device according to any one of claims 1 to 7, wherein the imaging light beam shaping member is configured to be insertable into and removable from an optical path of the imaging optical system. A mark on the substrate is illuminated through an illumination optical system, light from the mark is condensed through an imaging optical system to form an image of the mark, and the position of the mark is determined based on the image of the mark. In the position detection method for detecting
Limiting the illumination light flux to a predetermined shape on a first surface in the illumination optical system that is substantially in a Fourier transform relationship with the mark;
The intensity distribution of the imaging light flux on the second surface in the imaging optical system which is substantially in a Fourier transform relationship with respect to the mark is set to be smaller than the central area including the optical axis of the imaging optical system by the optical axis. Is limited to a predetermined light intensity distribution that is higher in the peripheral area not including
A position detecting method, wherein an imaging light beam is transmitted through at least a part of a region on the second surface optically conjugate to a predetermined shape of the illumination light beam on the first surface. A first step of detecting the position of the mark in a state where the intensity distribution of the imaging light flux is limited to a first light intensity distribution;
A second step of detecting the position of the mark in a state where the intensity distribution of the imaging light flux is restricted to a second light intensity distribution;
10. The method according to claim 9, further comprising: a third step of obtaining a positional deviation correction amount of the mark position detection result based on the detection result in the first step and the detection result in the second step. Position detection method. An illumination system for illuminating a mask on which a predetermined pattern is formed, a projection optical system for forming a pattern image of the mask on a photosensitive substrate, and a position for detecting the position of the photosensitive substrate. An exposure apparatus comprising: the position detection device according to any one of 1 to 8. An exposure method for illuminating a mask on which a predetermined pattern is formed, and exposing a pattern image of the illuminated mask on a photosensitive substrate,
An exposure method, comprising: detecting a position of the photosensitive substrate using the position detection device or the position detection method according to claim 1.

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