JPH08327318A - Position detector - Google Patents

Abstract

PURPOSE: To detect the position of a position detection mark accurately and surely even if the mark has a considerably small change in height. CONSTITUTION: The illumination light at the pupil face of an illumination optical system illuminating a position detection mark 11 on a substrate 10 is limited to a zonal area having an optical axis AX as the center. At the same time, phases of image luminous fluxes distributed in an area to be in the image formation relation with the zonal area on the pupil face of the illumination optical system and the other area on a pupil face of an image formation optical system receiving the light from the position detection mark 11 and forming an image of the light on an image pick-up element 28 are made different approximately by π/2 [rad]. Moreover, supposing that the shortest wavelength and the longest wavelength of a wavelength band of the illumination light contributing to the formation of an image signal are λ1, λ2, and the cycle of the position detection mark 11 is P, an outer radius ro and the inner radius ri of the zonal area on the pupil face of the illumination optical system are set to satisfy ri>=λ2/(2×P) and (ro-ri)<=λ1/P.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask pattern and a photosensitive substrate applied to an exposure apparatus used in a photolithography process in which a mask pattern is exposed on a photosensitive substrate when manufacturing a semiconductor device or the like. And a technique for detecting a mark pattern on a photosensitive substrate.

[0002]

2. Description of the Related Art In a photolithography process for manufacturing, for example, a semiconductor device, a liquid crystal display device, a thin film magnetic head, an image pickup device (CCD), a magneto-optical disk, etc., a photomask or reticle on which a transfer pattern is formed. An image of (hereinafter collectively referred to as "reticle") is transferred onto a photoresist-coated wafer or a photosensitive substrate such as a glass plate by a projection exposure method via a projection optical system or a proximity exposure method. An exposure device is used.

In such an exposure apparatus, it is necessary to perform alignment of the reticle and the wafer with high accuracy prior to exposure. In order to perform this alignment, it was formed on the wafer in the previous process (exposure transfer)
The formed position detection mark (alignment mark) is formed. By detecting the position of this alignment mark, the accurate position of the wafer (circuit pattern on the wafer) can be detected.

As a method of detecting the alignment mark,
For example, there is a laser beam scanning method, a laser interference method, or the like that detects scattered laser light and diffracted light. However, the laser light has a strong monochromaticity, and the position detection accuracy may be deteriorated due to adverse effects such as multiple interference between the photoresist surface and the mark surface. On the other hand, a method of illuminating an alignment mark with a broadband light flux using a lamp as a light source, capturing an image of the alignment mark through an imaging optical system, and performing position detection based on the image signal (hereinafter referred to as "imaging method"). This is referred to as "position detection") and has the advantage that it is unlikely to be adversely affected by the photoresist or the like.

[0005]

In recent years, with the miniaturization of semiconductor integrated circuits and the like, a process of flattening the wafer surface has been introduced after the film forming process and before the photolithography process. To this end, the effect of improving the device characteristics by making the thickness of the generated film on which the circuit pattern is formed uniform,
In the photolithography process, there is an effect of improving the adverse effect of the unevenness of the wafer surface on the line width error of the transfer pattern.

However, in the method of detecting the position based on the unevenness change and the reflectance change in the alignment mark portion on the wafer surface, the unevenness change in the alignment mark portion is significantly reduced by the flattening process, and thus the alignment mark is removed. It may not be detected. Particularly in a process for an opaque generation film (metal or semiconductor film), the alignment mark is covered with an opaque film having a uniform reflectance. Therefore, the position detection depends only on the change in the unevenness of the mark, and the flattening is the most important step for the opaque generated film.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a position detecting device capable of accurately and reliably detecting the position of a position detection mark having an extremely small variation (step). To aim.

[0008]

The present invention provides an illumination optical system for irradiating a position detection mark on a substrate with illumination light in a predetermined wavelength range (for example, broadband light or multi-wavelength light), and the position detection mark. A device for detecting the position of the position detection mark based on an image signal output from the image pickup device, which comprises an imaging optical system that forms an image of the position detection mark on the image pickup device by entering the generated light. It is applied.

In the present invention, the illumination light on the first surface (pupil surface) in the illumination optical system, which has a substantially optical Fourier transform relationship with the position detection mark, is converted into the optical axis of the illumination optical system. And a second surface (pupil surface) in the image forming optical system having a substantially optical Fourier transform relationship with respect to the position detection mark. A phase difference member that makes the phases of the image-forming light fluxes distributed respectively in the second region, which is in a substantially annular shape and has an image-forming relationship with the first region, and the other regions is provided.

Alternatively, a light flux limiting member for limiting the illumination light on the first surface in the illumination optical system to a substantially annular first region centered on the optical axis thereof and a first light flux limiting member in the imaging optical system. You may make it provide the phase-difference member which distributes | distributes on two surfaces and which makes the phase of 0th-order light from a position detection mark and the other light differ. Alternatively, an optical member that enhances the intensity distribution of the illumination light on the first surface in the illumination optical system or the intensity of the secondary light source (surface light source) in the ring-shaped first region compared to other regions, and an imaging optical system. A second zone having a substantially annular shape in an image forming relationship with the first area on the second surface inside
You may make it provide the phase difference member which makes the phase of the image-forming light beam respectively distributed in an area | region and the area other than that differ.

Alternatively, a diaphragm member for transmitting the illumination light flux distributed in the first zone-shaped area on the substantial pupil plane of the illumination optical system and the first surface on the second surface in the imaging optical system. A phase difference member for changing the phases of the image-forming light fluxes distributed in the substantially annular second region having an image formation relationship with the region and the other region may be provided. Alternatively, on the substantial pupil plane of the illumination optical system, a plurality of secondary light sources having a substantially annular shape centered on the optical axis (or a plurality of secondary light sources in an approximately annular zone centered on the optical axis on the pupil surface). Image forming member, which forms a light source image of the image forming optical system, and an image which is distributed in a substantially ring-shaped region having an image forming relationship with the secondary light source on the substantial pupil plane of the image forming optical system and the other region. You may make it provide the phase difference member which makes the phase of a light beam differ.

Alternatively, an optical member that enhances the light intensity distribution on the substantial pupil plane of the illumination optical system in a substantially annular zone centered on the optical axis of the illumination optical system as compared with an inner region thereof.
Provided is a phase difference member for varying the phases of the image-forming light fluxes distributed in a substantially circular region having an image-forming relationship with the inner region and the other region on the substantial pupil plane of the image-forming optical system. You may do it.

Further, it is desirable to have a member for dimming the image forming light flux distributed in the annular zone on the second surface in the image forming optical system, that is, the 0th order light distributed on the second surface. . The dimming member may be formed integrally with the phase difference member, may be arranged in the vicinity of the phase difference member, or may be arranged in a plane (pupil conjugate plane) substantially conjugate with the phase difference member. Good. Further, the phase difference member is disposed between the image-forming light beam distributed in the second region and the image-forming light beam distributed in the other region to be approximately (2 m +
1) It is desirable to give a phase difference of π / 2 ± π / 4 [rad] (m is an integer). At this time, either the phase of the image forming light beam distributed in the second region or the phase of the image forming light beam distributed in the other region may be shifted. Further, the phase shift amounts of the two light beams may be different from each other to give the above-mentioned phase difference.

Further, the shortest wavelength in the wavelength range of the luminous flux that contributes to the formation of the image signal in the illumination light is λ1, and the longest wavelength is λ.
2. If the period of the position detection mark is P,
It is desirable that the outer radius ro and the inner radius r i of the region satisfy the relationship of ri ≧ λ2 / (2 × P) ro-ri ≦ λ1 / P. Further, it is desirable that the numerical aperture NAo of the imaging optical system satisfies the relationship of NAo ≧ ro + λ2 / P.

Further, it is preferable to provide a member for holding the phase difference member in the optical path of the imaging optical system so that the phase difference member can be inserted and removed. Further, at this time, a light flux limiting member (or an optical member, a diaphragm member, a secondary light source (light source image) forming member) with respect to the optical path of the illumination optical system.
It is advisable to also provide a member for holding the insertable and detachable. Further, an image forming means for forming an image of the index mark is provided on the image sensor,
The positional deviation between the image of the position detection mark and the image of the index mark may be detected based on the image signal output from the image sensor. This image forming means includes an index plate having an index mark, an illumination system that illuminates the index plate with a light beam different from the illumination light that illuminates the substrate, and the image generated by entering the light generated from the index mark. It is desirable to have an imaging system formed on the image sensor. In particular, the index plate is arranged on a surface substantially conjugate with the substrate in the imaging optical system, and the image of the position detection mark is formed on the index plate by the imaging optical system. The image of the index mark may be formed on the image sensor.

Further, for example, in accordance with the change in the light amount of the image-forming light beam from the position detection mark incident on the image pickup element due to the insertion / removal or replacement of the light beam restriction member (or the optical member etc.) with respect to the optical path of the illumination optical system. It is desirable to provide a member for adjusting the intensity of the light beam that illuminates the index mark. As an example, in conjunction with the exit of the light flux limiting member from the illumination optical path,
Increase the intensity of the light beam. This adjusting member may be one that changes the power (current, voltage) supplied to the light source that emits the light beam, or one that replaces a plurality of neutral density filters with different transmittances and arranges them in the beam optical path.

Further, an optical member which enhances the intensity distribution of the illumination light (or the secondary light source) on the first surface in the illumination optical system in the first zone-shaped region compared to the other regions is the other region. A diaphragm member having a light-shielding portion that substantially covers other areas may be used so that the light intensity of the above is almost zero. Further, it is desirable that the optical member has a strength distribution changing member that changes at least one of the outer radius and the inner radius of the first zone-shaped region. The intensity distribution changing member includes a plurality of diaphragm members in which at least one of the outer radius and the inner radius of the ring-shaped aperture is different, and a plurality of diaphragm members in which one of the plurality of diaphragm members is arranged in the optical path of the illumination optical system. It may have a member for holding the diaphragm member. Further, it is desirable that the retardation member changes at least one of the radial width and the position of the ring-shaped second region in accordance with the change of at least one of the outer radius and the inner radius of the first region.

Further, the outer radius and inner radius (that is, the width and position in the radial direction) of the first zone-shaped region (secondary light source) and the intensity distribution of the illumination light are changed by, for example, a liquid crystal element or an electrochromic device. This can be realized by arranging an aperture stop made of elements on the pupil plane, or by exchanging a plurality of stop members having different outer and / or inner radii of the apertures and arranging them in the optical path. Alternatively, it is possible to arrange the variable aperture stop on the pupil plane and arbitrarily change its aperture diameter (or to replace a plurality of aperture stops having different aperture diameters and arrange them in the optical path) to change the outer radius, In addition, a plurality of circular light shielding plates having different diameters may be replaced with each other so that they can be arranged in the optical path to change the inner radius.

Furthermore, the outer radius and inner radius (that is, the position and width in the radial direction) of the second zone-shaped region can be changed by, for example, a zone-shaped phase shifter (dielectric film or the like) or a zone-shaped recess. This can be realized by replacing a plurality of transparent substrates having different radial positions and / or widths (or convex portions) so that they can be arranged in the optical path. Instead of providing the ring-shaped phase shifter, the phase shifter may be provided in a region other than the ring-shaped second region. Or
A plurality of circular transparent plates having substantially the same optical thickness but different diameters may be replaced with each other so that they can be arranged in the optical path. However, when the outer radius of the first area is changed, the phase difference between the image forming light flux in the second area and the image forming light flux outside the second area, which has an image forming relationship with the changed first area, is changed. However, there is no problem if the image contrast and fidelity are not deteriorated to the extent that desired position detection accuracy cannot be obtained by the change. When deterioration of image contrast or fidelity becomes a problem, for example, a variable aperture stop may be used to block the image forming light flux distributed outside the second region.

[0020]

The "dark field microscope" and the "phase contrast microscope" are known as optical systems for detecting only the "step" portion on a substantially flat object. A dark-field microscope is provided with a light-shielding area on the pupil plane (Fourier transform surface for a test object) of an imaging optical system, and the test object (for example, a position detection mark on a wafer) is irradiated with illumination light to that test object. Of the reflected diffracted light generated from, the 0th-order diffracted light (regularly reflected light) is blocked and an image is formed only by the higher-order diffracted light (and scattered light). Of these, the 0th-order diffracted light contains almost no information about the unevenness of the test object and the reflectance change, but the higher-order (1st-order or higher) diffracted light contains such information. Therefore, in the dark field microscope, the 0th-order diffracted light is blocked and an image is formed only by the high-order diffracted light, so that it is possible to visualize the step difference (clearly with high contrast) more clearly than an ordinary (brightfield) microscope. Become.

On the other hand, the phase contrast microscope gives a phase difference between the 0th-order diffracted light and the diffracted light (and scattered light) of other orders on the pupil plane of the imaging optical system, and transmits the phase difference filter. Is provided. Although the amount of high-order (1st or more) diffracted light generated from a mark pattern with a low step is extremely small, the 0th-order diffracted light with a large amount of light can also contribute to image formation in a phase-contrast microscope. A brighter (higher intensity) image can be obtained. In addition, 0
If the intensity ratio between the diffracted light of the second order and the diffracted lights of other orders is extremely large, the image contrast is lowered, so that the 0th order diffracted light may be dimmed.

However, when the conventional phase difference microscope is used to detect the position detection mark on the wafer, not only the 0th-order diffracted light unnecessary for image formation but also diffracted light of other orders (useful diffraction that contributes to image formation) There is a problem that the contrast and fidelity of the image are deteriorated because the phase difference is added and the effect of dimming is exerted on (light). Therefore, in the present invention, attention is paid to the fact that a position detection mark on a substrate such as a wafer usually has a certain periodicity (period P) in the position detection direction, and diffracted light other than the 0th order caused by the periodicity is noted. So as not to be affected by the phase difference member as much as possible, the shape of the phase difference member and the secondary light source of the illumination optical system (illumination luminous flux distribution on the pupil plane of the illumination optical system or intensity distribution of the illumination light) Since it was set, 0
It is possible to add a phase difference to only the second-order diffracted light, and further reduce the light.

That is, according to the present invention, the illumination light flux on the first surface (pupil surface) in the illumination optical system, which has a substantially optical Fourier transform relationship with the position detection mark, is substantially centered on the optical axis. It is limited to the first zone-shaped area and is connected to the first area on the second surface (pupil surface) in the imaging optical system that has a substantially optical Fourier transform relationship with the position detection mark. The phases of the image-forming light fluxes distributed respectively in the substantially annular second region and the other regions having an image relationship are made different from each other, in other words, the zero-order light from the position detection marks distributed on the second surface thereof. I tried to make the phase different from other light.

Alternatively, the intensity distribution of the illumination light (or the secondary light source or the surface light source) on the first surface in the illumination optical system is increased in the annular zone first area as compared with other areas, or the illumination optical system On the substantial pupil plane of the illumination optical system, which transmits the illumination luminous flux distributed in the first zone-shaped zone, or on the substantial pupil plane of the illumination optical system, which has a substantially annular zone centered on the optical axis thereof. A plurality of light source images may be formed in a substantially annular zone centered on the optical axis of the secondary light source (surface light source) or substantially on the pupil plane of the illumination optical system. In addition, the substantial light intensity distribution on the pupil plane of the illumination optical system is made higher in a substantially annular zone centered on the optical axis of the illumination optical system than in the area inside thereof, and The phases of the image-forming light fluxes distributed in the substantially circular area and the other area, which have an image-forming relationship with the inner area of the pupil plane, may be different.

Therefore, it is possible to reliably perform position detection (with a high-contrast image) even with respect to a position detection mark having an extremely small unevenness change (step). The shapes of the first and second regions and the secondary light source (surface light source) described above are annular (circular) shapes, but may be rectangular, square, or polygonal (particularly regular polygonal). good. Further, the first area on the first surface (pupil surface) in the illumination optical system is partially shielded (or dimmed), that is, the first area is divided into a plurality of partial areas (the shape may be arbitrary, for example, an arc shape). It may be circular, linear, or the like). Correspondingly, the second area on the second surface (pupil surface) in the imaging optical system may have the same shape as the first area, or the first area thereof.
An annular zone that substantially includes a plurality of partial areas that have an imaging relationship with the area,
It may be rectangular or polygonal.

Further, a member for reducing the image-forming light beam distributed in the annular zone on the second surface in the image-forming optical system, that is, the 0th-order diffracted light distributed on the second surface is provided. As a result, the intensity ratio between the 0th-order diffracted light from the position detection mark and the diffracted light of other orders can be reduced, and the image of the position detection mark can be detected with higher contrast. Further, if the shortest wavelength in the wavelength range of the light flux that contributes to the formation of the image signal in the illumination light is λ1, the longest wavelength is λ2, and the period of the position detection mark is P, the outer radius ro of the first zone-shaped region is ro.
, And the inner radius ri are set so as to satisfy the relationship of ri ≧ λ2 / (2 × P) ro-ri ≦ λ1 / P. Further, the numerical aperture NAo of the imaging optical system is set so as to satisfy the relationship of NAo ≧ ro + λ2 / P. Therefore, it is possible to detect an image of a position detection mark having a low step with higher contrast.

Further, the second surface (pupil surface) in the imaging optical system,
Alternatively, a variable aperture stop (NA stop) for changing the numerical aperture NAo of the imaging optical system may be provided on the conjugate surface so as not to mechanically interfere with the phase difference member. This allows
Even if the cycle of the position detection mark changes, the numerical aperture of the imaging optical system can be set to a value corresponding to that cycle so that the above conditions are satisfied, and the mark image is always detected with high contrast. it can. The variable aperture stop may be arranged so as to be displaced in the optical axis direction from the pupil plane of the imaging optical system or its conjugate plane.

Further, a member for holding the phase difference member detachably with respect to the optical path of the imaging optical system is provided. Therefore, it is possible to switch to the bright field detection, and it is possible to detect the mark image by selecting the presence or absence of the phase difference member according to the step amount of the position detection mark. Therefore, it is possible to always obtain a mark image having a high contrast regardless of the step amount of the position detection mark, and it is possible to improve the position detection accuracy.

Further, with respect to the optical path of the illumination optical system, a light flux limiting member (or optical member, diaphragm member, secondary light source forming member).
Also provided is a member that holds the plug in a removable manner. Therefore, the annular illumination and the normal illumination can be switched, and when the position detection mark does not have a low step, even if the reflectance thereof is low, the mark image can be reliably detected by the normal illumination.

Further, the optical member for increasing the intensity distribution of the illumination light (secondary light source, surface light source) on the first surface in the illumination optical system in the first zone-shaped region compared to the other regions is a zone-shaped region. Has a strength distribution changing member for changing at least one of the outer radius and the inner radius of the first region. Therefore, even if the cycle of the position detection mark changes, at least one of the outer radius and the inner radius of the first zone-shaped region should be set to a value corresponding to the cycle so that the above conditional expression is satisfied. You can Therefore, it is possible to always obtain a mark image having a high contrast regardless of the cycle of the position detection mark. The outer radius and inner radius of the ring-shaped first region do not need to be changed in conjunction with the change in the period of the position detection mark, and the change causes the image contrast and fidelity to obtain a desired position detection accuracy. The outer radius and the inner radius may be changed only when the deterioration has occurred to the extent that the deterioration cannot be achieved.

Further, the retardation member has a ring-shaped second portion according to a change in at least one of the outer radius and the inner radius of the first region.
At least one of the radial width and the position of the area is changed. Therefore, even if at least one of the outer radius and the inner radius of the ring-shaped first region changes in accordance with the cycle of the position detection mark, a phase difference is always imparted to only the 0th-order diffracted light and is incident on the image sensor. Can be made. It is not necessary to change the width and position of the ring-shaped second region of the imaging optical system in conjunction with the change of the outer radius and inner radius (cycle of the position detection mark) of the ring-shaped first region. Only when the image contrast and fidelity deteriorate due to the change to the extent that desired position detection accuracy cannot be obtained, the width and position of the phase shift portion may be changed. Further, it is not necessary to change both the outer radius and the inner radius of the second region in association with the change of the outer radius and the inner radius of the first region, and for example, only the inner radius of the second region may be changed.

[0032]

Embodiments of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic overall configuration of the position detecting device of this embodiment. In FIG. 1, a broadband illumination luminous flux (broadband light) emitted from a light source 1 such as a halogen lamp.
Enters the illumination field stop 4 through the condenser lens 2 and the wavelength selection element (sharp cut filter, interference filter, or the like) 3.

The wavelength selection element 3 is a photoresist (exposure wavelength is, for example, 365) applied on the wafer 10 described later.
nm or 248 nm), only a light beam in a non-photosensitive wavelength range (for example, a wavelength of 550 nm to 750 nm) is transmitted. However, if the present invention is applied to a position detection device for a substrate not covered with photoresist, for example, an overlay position detection device for a circuit pattern and a transferred resist pattern on a wafer after exposure and development processing, Light fluxes of shorter wavelengths (closer to the exposure wavelength) can also be used, since it is not necessary to prevent the photoresist from being exposed.

The light flux transmitted through the illumination field stop 4 passes through the relay lens 5 and the illumination light flux limiting member (aperture stop) of the present invention.
It is incident on 6. Further, the illumination light is transmitted through the beam splitter 8 and the objective lens group 9 to the position detection mark 11
It is incident on the wafer 10 on which is formed. The illumination light flux limiting member 6 is attached to the surface (position detection mark 11) of the wafer 10 via the objective lens group 9 and the beam splitter 8.
It is arranged on a plane (hereinafter abbreviated as “illumination system pupil plane”) optically related to Fourier transform. That is, the illumination optical system (1 to 5,
The amount of positional deviation of the optical axes 8 and 9) from the optical axis AXI is proportional to the sine of the incident angle of the illumination light flux passing through the predetermined point with respect to the surface of the wafer 10.

Here, the illumination light flux limiting member 6 has an annular opening and is held by the movable member 7 so that the center of the annular opening coincides with the optical axis AXI of the illumination optical system. The movable member 7 is, for example, a turret plate or a slider, and allows the illumination light flux limiting member 6 to be inserted into and removed from the optical path of the illumination optical system. Therefore, in this embodiment, the movable member 7 can switch between the annular illumination and the normal illumination,
Either one can be selected according to the step amount (and / or the fineness (period, line width, etc.)) of the position detection mark 11. For example, for the low step position detection mark and the high step fine position detection mark, the annular illumination is selected and the illumination light flux limiting member 6 is inserted in the optical path, and for the high step rough position detection mark, the normal illumination is selected. As a result, the illumination light flux limiting member 6 is retracted outside the optical path.

The illumination field stop 4 includes a series of optical systems 5-5.
Surface of wafer 10 (position detection mark 11)
Is substantially conjugate with (imaging relationship), and the illumination range on the wafer 10 can be limited according to the shape and size of the transmission part of the illumination field stop 4. Illumination field diaphragm 4
Is composed of, for example, a plurality of movable blades, and the size and shape of the opening defined by the plurality of movable blades are changed according to the size and shape of the position detection mark 11 to change the illumination range on the wafer 10. Can be changed.

The wafer 10 is mounted on a wafer stage 12 which is two-dimensionally movable, and a mirror 14 for reflecting the laser beam from the laser interferometer 15 is fixed to the end of the wafer stage 12. The position of the wafer stage 12 (wafer 10) in the X and Y directions is constantly detected by the laser interferometer 15 with a resolution of, for example, about 0.01 μm. Further, the wafer stage 12 is provided with a reference plate 13 on which reference marks used for baseline measurement and the like are formed.

Now, the wafer 10 (position detection mark 11)
The light flux reflected by (1) reaches the phase difference member (phase difference filter) 16 of the present invention through the objective lens group 9 and the beam splitter 8. The phase difference filter 16 is used for the wafer 1
With respect to the surface of 0 (position detection mark 11), through the objective lens group 9 and the beam splitter 8, a surface (hereinafter abbreviated as "imaging system pupil plane") that is optically in a Fourier transform relationship is formed. It is arranged. That is, the amount of positional deviation of the predetermined point in the phase difference filter 16 from the optical axis AX of the imaging optical system is the sine of the exit angle of the light beam (image forming light beam) passing through the predetermined point with respect to the surface of the wafer 10. Proportional to.

The specific structure of the phase difference filter 16 will be described in detail later, but the phase difference filter 16 is held by the movable member 17 so that the center thereof coincides with the optical axis AX of the image forming optical system. . The movable member 17 is, for example, a turret plate or a slider, and allows the phase difference filter 16 to be inserted into and removed from the optical path of the imaging optical system. Therefore, in the present embodiment, it is possible to switch to bright field detection by the movable member 17, and the position detection mark 1
Either one can be selected according to the step amount of 1. For example, the phase difference filter 16 is inserted in the optical path for a position detection mark with a low step, and the bright field detection is selected for a position detection mark with a high step, and the phase difference filter 1 is selected.
6 is saved outside the optical path.

The relationship of the optical Fourier transform will be described with reference to FIG. 2. In FIG. 2, one of the objective lens groups 9 (the focal length is f) represented by one lens 9 '. If the wafer 10 is placed on the focal plane of, the other focal plane becomes the "optical Fourier transform plane (pupil plane)" FP. Then, the light fluxes whose incidence and exit angles are θ on the wafer 10 are respectively on the optical axis A on the Fourier transform plane (pupil plane) FP.
It will pass a position away from X by f · sin θ.

In FIG. 2, the objective lens group 9 is represented by a single lens 9 ', but there is essentially no difference even if this is a lens system composed of a plurality of lenses, and a composite of a plurality of lenses is used. When the wafer 10 is placed on the focal plane, the other focal plane becomes the Fourier transform plane (pupil plane). By arranging the beam splitter 8 between the objective lens group 9 and the pupil plane, it becomes possible to separate the light-transmitting side (illumination system) pupil plane and the light-receiving side (imaging system) pupil plane. . Further, the two separated pupil planes are both Fourier transform planes for the wafer 10, that is, the illumination system pupil plane and the imaging system pupil plane are substantially through the wafer 10, the objective lens group 9, and the beam splitter 8. Are conjugated (image formation relationship).

The image-forming light flux that has passed through the phase difference filter 16 forms an image of the position detection mark 11 on the index plate 24 through the lens system 18 and the beam splitter 19. On the other hand, the index plate 24 is an optical system for illuminating the index plate 20-2.
It is also illuminated by 3. The optical system for illuminating the index plate is
Light source 20 such as light emitting diode, condenser lens 2
1, an index plate illumination field stop 22, and a relay lens 23. The index plate illumination field diaphragm 22 is a relay lens 2
3 and the beam splitter 19 and the index plate 24, and thus the surface of the wafer 10.
Further, the index plate 24 has a reference index (index mark) used for detecting the position detection mark 11 as described later.
Are formed. The index plate illumination field stop 22 has an opening in a region having an image forming relationship with the reference index so that only the reference index on the index plate 24 is irradiated with the illumination light from the light source 20.

Since the index plate illuminating optical systems 20 to 23 are for illuminating the reference index, the illumination light from the light source 20 is different from the illumination light from the light source 1 for irradiating the position detection mark 11. Monochromatic light may be used. Further, since the illumination light from the light source 20 is not irradiated on the wafer 10, the wavelength may be the photosensitive wavelength of the photoresist. Therefore, in this embodiment, the wavelength of the light source 20, which is a light emitting diode, is set to about 500 nm, and the reflecting surface of the beam splitter 19 is a dichroic mirror, so that the utilization efficiency of the imaging light flux from the wafer 10 and the index illumination light is increased. (That is, the loss of light quantity can be suppressed). In this embodiment, since the illumination field stop 4 limits the illumination range on the wafer 10, the image of the position detection mark 11 is not formed on the reference index.

The image of the position detection mark 11 and the image of the reference index formed on the index plate 24 are respectively relay lens 25,
An image is formed on an image pickup device 28 such as a CCD by 27.
The image processing system 29 calculates the positional relationship (positional shift amount) between the reference index image and the image of the position detection mark 11 based on the output signal from the image sensor 28. Position detection mark 11
Since the image position of (1) naturally reflects the position of the position detection mark 11 on the orthogonal coordinate system XY defined by the laser interferometer 15, the position of the position detection mark 11 can be detected. That is, the position of the position detection mark 11 is obtained from the position shift amount calculated by the image processing system 29 and the coordinate position output from the interferometer 15.

Here, for example, when the illumination light flux limiting member 6 is inserted or removed by the movable member 7 or is replaced, the light amount of the imaging light flux incident on the image pickup element 28 from the position detection mark 11 changes. Therefore, the mark image and the reference index image have different intensities (brightness) on the image sensor 28, and if the intensity difference becomes large, the positional deviation detection accuracy in the image processing system 29 may deteriorate. is there. Therefore, in this embodiment, the reference index is changed in accordance with the change in the light amount of the image-forming light flux so that the intensities of the image of the position detection mark 11 and the image of the reference index formed on the image sensor 28 are always substantially equal. The intensity of the illumination light from the light source 20 that illuminates In this embodiment, the light emission intensity is adjusted by adjusting the injection current to the light source (light emitting diode) 20, and for example, when the illumination light flux limiting member 6 is withdrawn from the optical path of the illumination optical system, Increase the emission intensity. In addition, between the light source 20 and the index plate 24, a member (turret plate, slider, etc.) for holding a plurality of neutral density filters having different transmittances is provided, and the holding member is driven to drive the plurality of neutral density filters. They may be replaced with each other and arranged in the optical path. Although not shown, the insertion / removal or replacement of the illumination light flux limiting member 6 and the phase difference filter 16 is performed based on information (such as the period of the position detection mark 11 and the amount of step difference) from the input device (keyboard, etc.). The controller that integrally controls the entire device of No. 1 automatically performs this. Further, the controller adjusts the emission intensity of the light source 20 according to the type and presence of the illumination light flux limiting member 6 and the phase difference filter 16.

By the way, the aperture stop 26 is a plane (conjugate (image-forming relationship) with the phase difference filter 16) in the image-forming optical system (9 to 27) having a substantially optical Fourier transform relationship with the wafer 10. Of the image forming optical system and limits the numerical aperture of the image forming optical system. In this embodiment, the numerical aperture of the imaging optical system can be arbitrarily changed by the aperture stop 26. Further, although the index plate 24 is arranged in the optical path of the imaging optical system in FIG. 1, the index plate 24 is arranged outside the optical path, and an image of the reference index is formed on the image sensor 28 via the imaging system. It may be configured as follows. For example, if the image pickup device 28 is arranged in place of the index plate 24 and the index plate 24 is arranged in place of the index plate illumination field stop 22, the relay lenses 25, 27.
Is unnecessary and the entire apparatus can be downsized. At this time, it is advisable to shield the area other than the reference index on the index plate 24 so that light from other than the reference index does not enter the image sensor 28. Further, the aperture stop 26 is the phase difference filter 16
It should be placed close to it so as not to mechanically interfere with it.

Here, the shape of the position detection mark 11, the index plate 24, the index plate illumination field stop 22, and the illumination field stop 4 are shown.
An example of the shape of each transmission part and the intensity distribution of the image formed on the image sensor 28 will be described with reference to FIGS. 3 and 4. FIG. 4A shows a top view of the position detection mark 11, and FIG.
FIG. 4B shows a sectional view in the position measuring direction (X direction in FIG. 4A). That is, in this embodiment, the position detection marks 11 composed of three band-shaped concave portions arranged in the X direction at the period P are formed on the surface of the wafer 10. Also, the wafer 1
As shown in FIG.
0'is applied.

As shown in FIG. 3 (A), the illumination field stop 4 is a light-shielding portion (hatched portion) except for the rectangular transmission portion 4M that limits the illumination area on the wafer 10. Then, the transmissive portion 4M is projected onto the wafer 10 to illuminate only the partial region including the position detection mark 11. This illumination area corresponds to the mark area M (width W in the X direction) in FIG. 4B, and also corresponds to the mark image area MI on the index plate 24 shown in FIG. 3C. That is, the image of the position detection mark 11 is formed in the mark image area MI on the index plate 24.

On the other hand, the index plate illumination field stop 22 is also shown in FIG.
As shown in (B), two quadrangular transparent portions 4L, 4R
Except for the above, all are light-shielding portions (hatched portions). The transmitted light from the transmissive portions 4L and 4R illuminates rectangular regions (transmissive portions) LI and RI on the index plate 24 shown in FIG. In the rectangular areas LI and RI, the above-mentioned reference indexes (bar marks) 24L and 24R, which are light shielding portions, are formed.

From the above, the image intensity distribution formed on the image pickup device 28 is as shown in FIG. That is, with the image IM of the position detection mark 11 illuminated by the illumination light from the light source (halogen lamp) 1 as the center, the reference indices 24L, 24R illuminated by the illumination light from the light source (light emitting diode) 20 on the left and right sides of the image IM. Images (dark images) IL and IR are formed. As described above, when the brightness of the image IM of the position detection mark 11 and the brightness of the reference indices 24L and 24R on the images IL and IR are too different, the detection accuracy of the positional deviation between the two images may be deteriorated. A mechanism (not shown) is provided to adjust the current injected into the (light emitting diode) 20 so that the two images have substantially equal intensities.

Further, in the sectional view of FIG. 4B, the left and right regions L and R of the position detection mark 11 are flat regions, but the states of these regions L and R are used for the position detection of the position detection mark 11. Has no influence (is not illuminated by illumination light), so there is no problem even if a circuit pattern or the like exists here. The image processing system 29, based on the light amount signal as shown in FIG. 4C output from the image pickup device 28, the image IM of the position detection mark 11 and the images IL and IR of the reference indices 24L and 24R.
Calculate the positional relationship with. This calculation process is exactly the same as the process generally performed in the conventional imaging position detection. For example, slice positions (Lo, Li, M _{1 to} Mn, Ri, Ro) of the light amount signal at a predetermined slice level SL.
The position may be detected on the basis of, or the position may be detected on the basis of the correlation between a certain template signal and the light amount signal of the mark portion.

Prior to the detection of these positions, the wafer 10 having the reference indexes 24L and 24R, which serve as the reference of the detection positions, is detected.
It is necessary to measure the positional relationship with respect to (wafer stage 12). This is also a conventionally known process called baseline check, and this embodiment is basically the same as the conventional process. That is, the position detection mark 11 is formed on the surface of the reference plate 13 fixed on the wafer stage 12.
A reference mark having the same shape as the reference mark is formed. Prior to detecting the position detection mark 11, the wafer stage 12 is driven to move the reference mark below the objective lens group 9, and the reference mark and the reference index 24L, The positional relationship with 24R is detected. At the same time, the position of the wafer stage 12 (the position of the mirror 14 on the wafer stage 12) at this time is measured by the laser interferometer 15. The sum of the output value of the interferometer 15 and the detected value (the positional relationship detected by the image processing system 29) is stored as the "baseline amount". Then, the position detection mark 11 and the reference index 24 obtained from the output value of the interferometer 15 at the time of measuring the position detection mark 11 and the light amount signal described above.
"Baseline amount" from the sum of the positional relationship with L and 24R
The value obtained by subtracting is the position of the position detection mark 11 with respect to the reference mark.

When the present invention is applied to the position detection system (alignment system) of the projection exposure apparatus, based on the above position detection values and the exposure shot array data stored in the projection exposure apparatus. , Each shot area on the wafer is moved under a projection optical system (not shown), and overlay exposure is performed.
Next, regarding the illumination light flux limiting member 6 and the phase difference filter 16 of the present embodiment, the position detection mark 11 with a cycle of 8 μm
Will be irradiated with an illumination light beam having a wavelength range of 550 to 750 nm to detect its position.

FIGS. 5A and 5B show examples of the structures of the illumination light flux limiting member 6 and the phase difference filter 16 which are suitable for this condition. The U-axis and V-axis directions in each figure are equal to the X-axis and Y-axis directions of the position detection mark 11 shown in FIG. 4A, but the illumination light flux limiting member 6 and the phase difference filter 16 are respectively located. Since it is arranged on the optical Fourier transform plane (pupil plane) with respect to the detection mark 11, it is represented by U-axis and V-axis according to the convention.

As shown in FIG. 5A, the illumination light flux limiting member 6 has an inner radius centered on the optical axis (intersection point of the U axis and V axis) of the illumination optical system (1 to 9) on the light shielding substrate. ri is 0.1
6 (the unit is the numerical aperture, that is, the sine of the incident angle of the light flux that has passed through a predetermined point on a circle of radius ri to the position detection mark 11; the same applies below), and the outer radius ro is 0.20. The band-shaped transparent portion I is formed. The illumination light flux limiting member 6 has a ring-shaped aperture formed in a specific portion on a metal light-shielding plate, or has a light-shielding film formed of metal or the like on a transparent substrate such as glass, and the light-shielding film at the specific portion is removed. To use.

On the other hand, the phase difference filter 16 adds a phase difference in the shape of an annular zone having an image-forming relationship with the annular zone transparent section I at a position conjugate with the annular zone transparent section I on the illumination light flux limiting member 6. Department S
(Hatched portion in the figure) is formed. Figure 6
FIG. 6 is a sectional view taken along the U axis in FIG. As shown in FIG. 6, the phase difference filter 16 is a transparent substrate 16 such as glass.
A thin metal film So and a dielectric film S1 are laminated on the surface of A. The thin metal film So attenuates the transmitted light and the dielectric film S1 shifts the phase of the transmitted light. Therefore, the phases of the image forming light beams from the position detection marks 11 distributed in the phase difference adding portion S and the other regions are different from each other, that is, a predetermined phase difference is given between the two light beams. Such a structure is similar to a phase difference filter in a conventional phase difference microscope or a “halftone phase shift reticle” which has recently begun to be used in a photolithography process, and can be manufactured by using various manufacturing methods thereof. it can.

Further, the phase difference given to the transmitted light by the metal thin film So and the dielectric film S1 (the phase difference from the transmitted light of other parts) is optimally π / 2 [rad] (that is, 1/4 wavelength). Therefore, the thickness of the dielectric film S1 is λ where n is its refractive index.
/ (4 (n-1)). At this time, λ is the central wavelength of the light flux of the illumination light that contributes to image formation (65 in the example of FIG. 6).
0 nm). However, even if there is some error in the phase difference amount (phase shift amount) of the phase difference adding portion S, the position detection mark 1
Since the image contrast of 1 does not decrease sharply, the phase difference to be given to the transmitted light of the phase difference adding section S is π / 2 ± π / 4.
Within the range of [rad], it is possible to obtain an image with relatively good contrast, which enables accurate position detection. Also,
In particular, if this phase difference is suppressed to about π / 2 ± π / 6 [rad], an image with better contrast can be obtained.

Here, when the wavelength range of the light flux contributing to image formation is narrow (that is, the illumination light is substantially monochromatic), the thickness of the dielectric film S1 is (2k + 1) λ / (4 (n −1)) (the phase difference is (2k + 1) π / 4 [rad]) (where k is a natural number). On the other hand, when the wavelength range of the light flux that contributes to image formation is wide, the phase difference becomes (2k + 1) π / 4 [rad] (optimum condition) as the value of k increases with respect to wavelengths other than the central wavelength.
The thickness of the dielectric film S1 is λ / (4 (n−
1)) is good. When the phase difference filter 16 under such conditions is used, it is possible to obtain a mark image having a clear contrast in which the concave portion of the position detection mark 11 is bright and the convex portion is dark.

Further, as the phase difference filter, only the metal thin film So may be formed in the phase difference adding portion S and the dielectric film S1 may be formed in the other portion. in this case,
The phase of the 0th order light is π / 2 [rad] with respect to the diffracted lights of other orders.
Since it has advanced, the image of the position detection mark 11 is shown in FIG.
Unlike the case where the phase difference filter 16 is used, the concave portion of the position detection mark 11 becomes dark and the convex portion becomes a bright image. However,
It goes without saying that the image contrast is equal and high in all cases.

Further, the phase difference adding portion S does not necessarily have to have a light-reducing effect, and in this case, the metal thin film So
Need not be added. Further, instead of forming the dielectric film S1 to add a phase difference, the transparent substrate 16A may be dug by etching. Further, the size of the phase difference adding portion S is set to 0.15 for the inner radius ri 'and 0.21 for the outer radius ro' so that the size of the phase difference adding portion S is slightly larger than that of the annular zone transmitting portion I on the illumination light flux limiting member 6. did. This is the position detection mark 1
This is because the above-mentioned phase difference is more reliably added to the 0th-order diffracted light in consideration of the fact that the 0th-order diffracted light from 1 spreads slightly on the phase difference filter 16. In addition, the numerical aperture NAo (radius of the pupil plane of the image forming system) of the image forming optical system is set to 0.30. In FIG. 1, the aperture stop 26 that defines the actual numerical aperture is
However, the numerical aperture NAo here is not the same position as the phase difference filter 16 but its conjugate position.
When the numerical aperture of the aperture diaphragm 26 is smaller than that of the objective lens group 9, it represents the numerical aperture (effective numerical aperture) of the aperture diaphragm 26. Further, the outer radius of the illumination light flux limiting member 6 is sufficiently larger than the numerical aperture (radius of the illumination system pupil plane) of the illumination optical system, and the transmitted light distributed outside the annular light transmitting portion I is naturally located at the position. It does not reach the detection mark 11.

FIG. 5B shows one first-order diffracted light generated from the position detection mark 11 by irradiation of the illumination light transmitted through the annular light-transmitting portion I on the illumination light flux limiting member 6 of FIG. 5A. The distribution on the phase difference filter 16 (area D surrounded by two dashed circles in the figure) is shown. The position detection mark 1
Of the diffracted light from 1, the 0th-order diffracted light is distributed on the phase difference adding portion S that is conjugate (and one size larger than it) with the annular light transmitting portion I, is attenuated by the metal thin film So, and is A phase difference is added by the body film S1. Of course, actually, diffracted lights of orders other than this are also distributed, but here, the 0th order and the 1st order, which are dominant in the formation of the image of the position detection mark 11, are distributed.
Consider only the following diffracted light.

By the way, as shown in FIG. 5B, a part of the first-order diffracted light is attenuated by the phase difference adding portion S, but in the present embodiment, as shown in FIG. 5A. Since the inner radius ri and the outer radius ro of the ring zone transmission portion I are appropriately determined, the attenuation of the first-order diffracted light and the addition of the phase difference by the phase difference addition portion S are suppressed to the minimum. Hereinafter, the reason will be described.

First, the inner and outer circumferences of the phase difference adding section S and U
The U coordinates of the intersection with the axis are ri ', ro' (and -r, respectively)
i ', -ro'). On the other hand, the U coordinate of the intersection of the boundary of the area D where the first-order diffracted light is distributed (two dashed circles) and the U axis is D
When pi, Dpo, Dmi, and Dmo are defined, these values are Dpi = λ / P + ri, Dpo = λ / P + ro Dmi = λ / P-ri, and Dmo = λ / P-ro.

At this time, in particular, if the value of Dpi is smaller than ro 'or the value of Dmo is smaller than -ri', the degree of extinction of the first-order diffracted light by the phase difference adding section S becomes large. It is clear from 5 (B). Further, even if the value of Dmi is larger than ri ', the degree of dimming also increases. In the example of FIG. 5A, the period P of the position detection mark 11 is 8 μm, and the inner radius ri of the ring zone transmission portion I is 0.1.
6, the outer radius ro is 0.20, and the range of the wavelength λ of the illumination light is 550 nm for the shortest wavelength λ1 and 750 for the longest wavelength λ2.
Therefore, when λ = λ1, the minimum value of Dpi is Dpi = λ1 / P + ri = 0.23 (1), which is larger than ro ′ (= 0.21), and the minimum value of Dmo is λ = When λ1, Dmo = λ1 / P−ro = −0.13 (2), which is larger than −ri ′ (= −0.15).

Further, the maximum value of Dmi is Dmi = λ2 / P-ri = -0.07 (3) when λ = λ2, which is smaller than ri '(= 0.15). Therefore, the degree of dimming of the 1st-order diffracted light by the phase difference adding unit S becomes small, but generalizing the condition for this, Dpi = λ1 / P + ri ≧ ro ′ (4) Dmo = λ1 / P−ro ≧ − ri ′ (5) Dmi = λ2 / P−ri ≦ ri ′ (6)

The outer radius ro 'of the phase difference adding portion S is larger than the outer radius ro of the ring zone transmitting portion I, and the inner radius ri' of the phase difference adding portion S is larger than the inner radius ri of the ring zone transmitting portion I. Therefore, the above inequalities (4) to (6) are expressed as follows: Dpi = λ1 / P + ri ≧ ro (7) Dmo = λ1 / P-ro ≧ -ri (8) Dmi = λ2 / P-ri ≦ ri (9) Also good. In particular, the inequalities (7) and (8) are both equivalent to ro-ri ≦ λ1 / P (10), and the inequality (9) is equivalent to ri ≧ λ2 / (2 × P) (11).

Therefore, in general, the inner radius ri of the annular transmission portion I is
And the outer radius ro satisfies the inequalities (10) and (11), the degree of dimming of the first-order diffracted light by the phase difference adding section S can be made extremely small. By the way, depending on the value of the numerical aperture NAo of the imaging optical system, the first-order diffracted light may be blocked by not only the light reduction by the phase difference adding section S but also the limitation by the numerical aperture NAo. In order to avoid this, the value of Dpo = λ / P + ro is the numerical aperture NA mentioned above.
It is desirable that it is not more than o. The maximum value of Dpo is λ = λ
Since it becomes λ2 / P + ro when 2, the numerical aperture NAo
Preferably satisfies the following relationship: NAo ≧ λ2 / P + ro (12)

In the above description, only the 1st-order diffracted light generated on one side (+ U direction) with respect to the 0th-order diffracted light has been described, but the 1st-order diffracted light generated in the opposite direction (-U direction) is also completely absent. The same is true, and the above condition (inequality) remains unchanged. Further, the period P of the position detection mark 11 and the wavelength range (λ1, λ2) of the illumination light flux are not limited to the above values, and these conditions (inequality) are satisfied even under other conditions.

Next, the effect of the position detecting device of the present embodiment will be described based on the simulation result of the image of the position detecting mark having a very small change in unevenness (step). FIG.
The simulation result of the position detection mark image having a step of 5 nm obtained by the position detection device of the present embodiment is shown. The mark formation condition is that the period is 12 μm, the width of the concave portion is equal to the width of the convex portion, and the material of the mark surface is uniform (refractive index is 3.5.
5), and a photoresist having a refractive index of 1.68 was applied thereon in a thickness of 1 μm. The wavelength range of the illumination light is 550 nm (= λ1) to 750 nm (= λ).
2), and the inner radius and the outer radius of the ring zone transmission portion I on the illumination light flux limiting member 6 are respectively ri = 0.10 ≧ λ2 / (2 × P) = 0.750 according to the above-mentioned condition (inequality). /24=0.031 ro = 0.14 (ro-ri = 0.04 ≦ λ1 / P = 0.550 / 12 = 0.046).

The structure of the phase difference filter 16 is shown in FIG.
The inner radius and the outer radius of the phase difference adding portion S are equal to the inner radius ri and the outer radius ro of the annular transmission portion I, respectively, and the numerical aperture NAo of the imaging optical system is equal to the above condition (inequality). ), NAo = 0.22 ≧ λ2 / P + ro = 0.750 / 12 + 0.14 = 0.23.

Further, the transmittance of the phase difference adding portion S is set to 1%, and the dielectric film S1 has a refractive index so as to add a phase difference of π / 2 [rad] to the central wavelength of 650 nm of the illumination light. Was 1.5 and the thickness was 325 nm. The image intensity distribution shown in FIG. 7 is for one cycle of the position detection mark 11, the position 0 on the horizontal axis indicates the center of the mark (recess), and the broken line of ± P / 4 is the edge of the mark (recess and protrusion). Boundary). Also,
The intensity distribution on the vertical axis is standardized so that the maximum value of the image intensity for one cycle is 1.

Further, FIG. 8 shows a simulation result in the case where only the numerical aperture NAo is set to 0.18 and the above-described conditional expression (12) of the numerical aperture NAo is not satisfied under substantially the same conditions as in FIG. Although the mark image of FIG. 8 is slightly inferior in sharpness of the dark portion (edge portion of the mark) to the image shown in FIG. 7, it has sufficient contrast to detect the edge position, that is, the mark position. There is. Therefore, among the above conditional expressions (10) to (12) according to the present embodiment,
It is understood that the conditional expression (12) of the numerical aperture NAo does not necessarily have to be strictly satisfied.

Similarly, in FIG. 9, only the outer radius ro of the ring zone transmission portion I is set to 0.18 under substantially the same conditions as in FIG. 7, and the above-mentioned conditional expression (10) of the outer radius ro is satisfied. The simulation result when there is not is shown. In this case, FIG.
It can be seen that the deterioration of the image contrast is more remarkable than that of the image shown in FIG. 8, and therefore good detection accuracy cannot be obtained by position detection based on such an image.

Further, in FIG. 10, the conditions of the outer radius ro described above are set to be substantially the same as the conditions of FIG. 7 with the inner radius ri of the annular zone I being 0.02 and the outer radius ro being 0.06. Although the expression (10) is satisfied, the conditional expression (11) of the inner radius ri
Shows the simulation result when not satisfied. In this case, although the image has a high contrast, a slight dark part is generated not only in the mark edge but also in the center of the concave part, and the image fidelity is reduced, which may adversely affect the position detection. Difficult to do.

Unlike FIG. 7 to FIG. 10, in FIG. 11, the annular transmission portion I on the illumination light flux limiting member 6 is a circle (normal σ stop) centered on the optical axis, and on the phase difference filter 16. The simulation result when the phase difference adding part S of is also a circle centering on the optical axis is shown. In this case, the transparent portion I at this time,
The radii of the phase difference adding portions S were both set to 0.66 (0.3 as the σ value). The wavelength range, numerical aperture, and other conditions are the same as the conditions in FIG. 7. The image in this case also has reduced image fidelity as in FIG. 10, and is difficult to use for position detection.

In FIG. 12, for comparison, the shapes of the annular zone transmission portion I of the illumination light flux limiting member 6 and the phase difference adding portion S on the phase difference filter 16 satisfy the conditions of the present invention shown in FIG. Although the same as the example, the transmittance of the phase difference adding part S is 0% (the phase difference adding part S is a light shielding part), that is, a mark image by a dark field microscope is shown. It should be noted that only in FIG. 12, the scale of the vertical axis is set to be the same as that in FIG. 7 for easy comparison. Even with such a dark-field microscope, a light-dark change (contrast) occurs in the image of the position detection mark having a low step, but the intensity thereof is equal to the image intensity (FIG. 7) of the position detection device of the present invention.
Since the mark image is about / 5 and the mark image is dark, the image signal output from the image sensor 28 also has a poor S / N ratio.

Further, FIG. 13 shows an image obtained by a normal (bright field) microscope. The radius of the σ diaphragm is 0.176 (0.8 as the σ value), and of course, the phase difference adding section S is not provided. Other conditions are the same as the conditions of FIG. FIG.
As is clear from FIG. 3, when a bright field microscope is used for a position detection mark with a low step (5 nm), there is almost no change in contrast (contrast) in the image, and position detection is impossible.

As described above, the images obtained by the position detecting device of the present invention shown in FIGS. 7 and 8 are not only sufficient in contrast as compared with the images shown in FIGS. Since the portions respectively correspond to the concave portions and the convex portions of the mark, reliable position detection can be performed using such a mark image. As described above, the illumination light flux limiting member 6 and the phase difference filter 16 in the above-described embodiment are extremely effective for detecting the position detection mark having a small step, but the step having a large step (for example, 100 nm or more). Sufficient detection accuracy can be obtained with respect to the position detection mark even with the conventional position detection device. Therefore, when detecting a mark with a large step, the illumination light flux limiting member 6 and the phase difference filter 16 are replaced by a replacement mechanism (movable). Alternatively, the members 7 and 17 may be used to evacuate the optical path. In addition, when there is a risk that the aberration state of the optical system changes due to the retracting of the phase difference filter 16 (or the illumination light flux limiting member 6) made of a glass substrate, the phase difference filter 16 (or the illumination light flux limiting member 6) may be saved during the retracting. Instead of 6), it is necessary to insert a transparent member having an optical thickness equivalent to that. this is,
If the exchange mechanisms 7 and 17 hold the transparent members respectively, the exchange can be easily performed.

In the above simulation, the step 5
Although the position detection mark of nm is assumed, for a mark having such a low level difference, for example, a mark having a level difference of several tens nm, the phase difference for performing the light reduction and the phase difference shown in FIG. In addition to the filter, a phase difference filter that adds only the phase difference and does not reduce light can be used.
FIG. 14 shows a simulation result when such a phase difference filter is used for a position detection mark having a step difference of 40 nm. At this time, the shapes of the annular transmission portion I on the illumination light flux limiting member 6 and the phase difference adding portion S on the phase difference filter 16 are the same as those in the example of FIG. 7. As is clear from FIG. 14, for a position detection mark having a large level difference, an image with sufficiently high contrast can be obtained even if the transmittance of the phase difference adding portion S is high (even if the light is not dimmed so much).

Therefore, the exchange mechanism 17 holds the phase difference filter 16 shown in FIG. 6 and the phase difference filter (or the phase difference filter having a relatively high transmittance) for only adding the phase difference, and the position detection mark is held. The two phase difference filters may be exchanged and arranged in the image forming optical path according to the amount of the step difference. For a mark having a lower step, a phase difference filter having a low transmittance is selected and loaded.

For comparison, FIG. 15 shows a simulation result when a position detection mark with a step difference of 40 nm is detected using a bright field microscope under the same conditions as in FIG. As is clear from FIG. 15, even if the step is 40 nm, sufficient contrast cannot be obtained with a bright field microscope, and the difference in contrast with the image according to the present invention shown in FIG. 14 is clear.

By the way, in the above-mentioned embodiment, the inner and outer radii of the ring-shaped secondary light source formed by the illumination light flux limiting member 6, that is, the ring-shaped transparent portion I, and the phase difference conjugate with the ring-shaped transparent portion I. The inner radius and outer radius of the phase difference adding portion S on the filter 16,
And the numerical aperture of the imaging optical system is the wavelength range of the illumination light flux (λ1 to λ1
λ2), but when a wavelength selection element such as a sharp cut filter is inserted between the position detection mark 11 and the image sensor 28, or the image sensor 2
When the spectral sensitivity of 8 is narrower than the wavelength range of the illumination light flux, etc., these values are taken into consideration, that is, each value is determined based on the wavelength range that actually contributes to the formation of the image signal of the position detection mark 11. become.

Further, the illumination light flux limiting member 6 used in the above-mentioned embodiment transmits only the light flux in the annular zone I of the light flux distributed on the pupil plane of the illumination system, and shields the other light fluxes. Although a band-shaped secondary light source is formed, the illumination light flux is collected in the annular zone on the pupil plane of the illumination system by using, for example, an optical fiber or a combination of a concave conical prism and a convex conical prism. You may make it light-emit and form a secondary light source. In this case, there is an advantage that the light quantity loss is significantly reduced.

Further, an optical integrator (for example, a fly's eye lens) that receives light from the light source 1 and forms a plurality of light source images on the pupil plane of the illumination system may be provided. In this case, there is an advantage that the illuminance uniformity of the illumination light on the position detection mark 11 is significantly improved. However, in order to form a ring-shaped secondary light source on the pupil plane of the illumination system, for example, an aperture stop (FIG. 5 (A)) having a ring-shaped aperture is arranged near the exit side or the entrance side of the fly-eye lens. Will be done. In addition, in order to minimize the light amount loss, the above-mentioned concave and convex conical prisms or an optical fiber having a ring-shaped exit end is arranged between the light source 1 and the fly-eye lens, or the light source 1 and the fly eye lens are arranged. By utilizing the aberration of the input lens arranged between the eye lens and the eye lens, the intensity distribution of the illumination light on the entrance surface of the fly's eye lens can be adjusted in the annular zone around the optical axis more than in other areas. It is preferable to raise it.

Further, a plurality of apertures having at least one of the outer radius and the inner radius of the annular zone transparent portion I different, in other words, having at least one of the radial width (annular zone ratio) and position of the annular zone transparent portion I different. A diaphragm may be provided in the exchange mechanism 7, and the plurality of aperture diaphragms may be respectively replaced and arranged in the illumination optical path. In this case, according to the change of the fineness (cycle P) of the position detection mark 11, the conditional expression (10),
It is possible to select the aperture stop that satisfies the condition (11) and is optimum for the period and arrange it in the illumination optical path. Therefore, it is possible to always obtain a high-contrast mark image regardless of the cycle of the position detection mark 11. In addition, a plurality of circular light-shielding plates having different diameters and a plurality of diaphragm members (σ diaphragms) having different diameters of circular openings are provided in the exchange mechanism 7, and the circular light-shielding plate is used to adjust the inner radius of the annular zone transmission portion I by the σ diaphragm. The outer radius is defined, and the width in the radial direction of the ring-shaped secondary light source (illumination luminous flux distribution or light intensity distribution) on the pupil plane of the illumination system is determined by combining the circular light shield and the σ diaphragm. The position may be changed. Here, instead of providing a plurality of σ diaphragms in the exchanging mechanism 7, a zoom lens system is arranged between the light source 1 and the exchanging mechanism 7, or a variable aperture diaphragm (iris diaphragm) is arranged close to the circular light shielding plate. However, the luminous flux diameter (size) of the illumination light, that is, the outer radius of the ring zone transmission portion I may be arbitrarily changed by this zoom lens system or the iris diaphragm.

Also, the exchange mechanism 7 having a plurality of aperture stops
Instead of, the aperture stop made of, for example, a liquid crystal element or an electrochromic element may be arranged on the pupil plane of the illumination system. In this case, the shape, size, and position of the transmission part I on the pupil plane of the illumination system can be arbitrarily changed. Furthermore, by combining the concave conical prism and the convex conical prism, the conditional expression (10) above on the pupil plane of the illumination system,
An annular luminous flux distribution (or light intensity distribution) satisfying (11) may be formed. At this time, this 2
The two prisms may be configured to be relatively movable in the optical axis direction, and the radial position of the annular luminous flux distribution (light intensity distribution) may be changed. Also, the light source 1 and this 2
A zoom lens system is placed between the two prisms to change the diameter (size) of the illumination luminous flux incident on the conical prism on the light source side, and the radius of the annular luminous flux distribution (light intensity distribution). The width in the direction may be changed.

The outer and inner radii of the ring-shaped transmission portion I (secondary light source) do not need to be changed in conjunction with the change in the cycle of the position detection mark 11, and the change can improve the image contrast and fidelity. The outer radius and the inner radius may be changed only when the desired position detection accuracy is deteriorated. Further, if the desired position detection accuracy can be obtained even if the image contrast and the fidelity are slightly deteriorated, the illumination light flux distributed in the area other than the ring zone transmission portion I on the illumination system pupil plane is not completely blocked. May be. That is, a region other than the ring-shaped region on the illumination system pupil plane may be used as the dimming unit, and the point is that the intensity distribution of the illumination light (secondary light source) on the illumination system pupil plane is centered around the optical axis. The band area may be higher than the other areas. As an example, at least one lens system arranged between the light source 1 and the illumination system pupil plane such that the light intensity distribution on the illumination system pupil plane is higher in the annular zone than in other areas, for example, Figure 1
The aberration of the relay lens 5 may be adjusted. At this time,
A plurality of relay lenses having different amounts of aberration correction may be exchanged and arranged in the illumination optical path to change the light intensity distribution on the pupil plane of the illumination system.

Further, a laser such as a semiconductor laser may be used as the illumination light source 1. Also in this case, since it is desirable that the illumination light flux has a certain wavelength range, it is preferable to use a laser that oscillates at multiple wavelengths, for example, a dye laser or a plurality of lasers that oscillate at different wavelengths.
Further, the phase difference filter 16 has a phase difference adding section S
Although the member (metal thin film So) for dimming the image forming light flux (0th order light) is integrally formed, for example, a transparent substrate having a ring-shaped metal thin film (darkening portion) is used as the phase difference filter 16
May be arranged in close proximity to, or may be arranged on a plane (pupil conjugate plane) substantially conjugate with the phase difference filter 16.

Further, the outer radius and the inner radius of the phase difference adding portion S on the imaging system pupil plane are linked with the change of at least one of the outer radius and the inner radius of the ring zone transmission portion I on the pupil plane of the illumination system. At least one of the above may be changed. For example, a plurality of phase difference filters in which at least one of the outer radius and the inner radius of the phase difference adding part S is different, in other words, at least one of the radial width (ring ratio) and the position of the phase difference adding part S is different, It suffices to provide the exchanging mechanism 17 so that the plurality of phase difference filters are exchanged and arranged in the imaging optical path. In this case, as described above, the position detection mark 1
Even if at least one of the outer radius and the inner radius of the annular zone transmissive portion I changes according to the cycle of 1, the optimum phase difference filter for the changed annular zone transmissive portion I is selected and placed in the imaging optical path. can do. Therefore, it is possible to always add a phase difference only to the 0th-order diffracted light and make it enter the image pickup device 28. still,
It is not necessary to change the width and the position of the phase difference adding portion S on the pupil plane of the imaging system in conjunction with the change of the outer radius and the inner radius of the annular transmission portion I on the pupil plane of the illumination system. Only when the image contrast or the fidelity deteriorates to the extent that desired position detection accuracy cannot be obtained, the light shielding width or position may be changed.

Further, instead of a plurality of phase difference filters having phase difference adding portions having different outer and / or inner radii as described above, for example, a plurality of circular shapes having substantially the same optical thickness but different diameters. It is also possible to provide a transparent plate in the exchange mechanism 17 and replace the plurality of circular transparent plates with each other so that they can be arranged in the imaging optical path. However, when changing the outer radius of the ring-shaped transmission part I on the pupil plane of the illumination system, the image-forming light flux in the ring-shaped region which is in an image-forming relationship with the changed ring-shaped transmission part and the image forming outside thereof are formed. A phase difference cannot be added to the light flux, but there is no problem if the change does not degrade the image contrast and fidelity to the extent that desired position detection accuracy cannot be obtained.
When deterioration of image contrast or fidelity becomes a problem, for example, the aperture stop 26 may block at least a part of the image-forming light flux distributed outside the annular region. At this time, the aperture diameter of the aperture stop 26 is set within a range that substantially satisfies the above inequality (12) (the deterioration of image contrast and fidelity due to the change of the numerical aperture NAo of the imaging optical system does not pose a practical problem). It is desirable to change.

Further, both the annular zone transmitting portion I and the phase difference applying portion S described above are assumed to have an annular (annular) shape.
For example, it may be a rectangle, a square, or a polygon (particularly a regular polygon). Further, the annular zone transmissive portion S on the pupil plane of the illumination system is partially shielded (or dimmed), that is, the annular zone transmissive portion I is divided into a plurality of partial translucent portions (the shape may be arbitrary, for example, an arc or a circle). , Or may be linear or the like). Corresponding to this, the phase difference addition unit S on the pupil plane of the imaging system is
The shape may be the same as that of the annular zone transmissive portion I, or may be an annular zone, a rectangle, or a polygonal shape that substantially includes a plurality of partial regions that form an image-forming relationship with the partial translucent portion. still,
When the annular transmissive part I on the pupil plane of the illumination system is square, the distance between the inner edge of the square transmissive part and the optical axis is the above-mentioned inner radius ri, and the distance between the outer edge and the optical axis is the above-mentioned. Considering the outer radius ro, each value may be determined so as to satisfy the above conditional expressions (10) and (11). However, it is desirable that the numerical aperture NAo of the imaging optical system is set to be larger than the numerical aperture determined from the conditional expression (12).

Although the above embodiments have been described on the premise of an apparatus for detecting the position of a mark on a semiconductor substrate, the present invention is not limited to various apparatuses used in a photolithography process (exposure apparatus, etc.) It can be applied to optical devices for other purposes. For example, if the present invention is applied to a general optical microscope used for visual inspection and observation,
Similar to the above, a high-contrast image can be obtained with respect to a low step pattern. Furthermore, the same effect can be obtained by applying the present invention to a microscope using transmitted illumination such as a biological microscope.

[0093]

As described above, according to the present invention, it is possible to obtain a mark image having a sufficiently high contrast even with the position detection mark in which the unevenness change (step) is extremely reduced by the flattening process or the like. Therefore, the mark position can be detected with high accuracy by using the image intensity distribution with high contrast.

Further, it is possible to realize an optical device (optical microscope or the like) capable of detecting images of various patterns with a small surface level difference or a small phase change of the light flux with a higher contrast than before.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic overall configuration of a position detection device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a relationship of optical Fourier transform in the present invention.

FIG. 3A is a diagram showing a configuration of an illumination field diaphragm, and FIG.
FIG. 4 is a diagram showing a configuration of an illumination field diaphragm for an index plate, and (C) is a diagram showing a configuration of an index plate.

4A and 4B are diagrams showing a specific configuration of a position detection mark, and FIG. 4C is a diagram showing an image intensity distribution formed on an image sensor.

5A is a diagram showing a specific configuration of an illumination light flux limiting member, and FIG. 5B is a diagram showing a specific configuration of a phase difference filter.

FIG. 6 is a sectional view of a phase difference filter according to an embodiment of the present invention.

FIG. 7 is a diagram showing a simulation result of an image of a position detection mark having a low step obtained by the position detection device according to the embodiment of the present invention.

8 is a diagram showing a simulation result of an image of a position detection mark having a low step obtained by changing only the numerical aperture of the imaging optical system in the simulation conditions of FIG.

9 is a diagram showing a simulation result of an image of a position detection mark having a low step obtained by changing only the outer radius of the ring zone transmission portion on the pupil plane of the illumination system among the simulation conditions of FIG. 7.

FIG. 10 is a diagram showing a simulation result of an image of a position detection mark having a low step obtained by changing only the inner radius of the ring zone transmission portion on the pupil plane of the illumination system among the simulation conditions of FIG. 7.

FIG. 11 is a diagram showing a simulation result of an image of a position detection mark having a low step obtained when each of the transmission part on the pupil plane of the illumination system and the phase difference adding part on the pupil plane of the imaging system is circular.

FIG. 12 is an image of a low step position detection mark obtained by a so-called dark-field microscope in which only the transmittance of the phase difference adding portion on the pupil plane of the imaging system is changed to 0% among the simulation conditions of FIG. 7. The figure which shows the simulation result of.

FIG. 13 is a diagram showing a simulation result of an image of a position detection mark having a low step obtained by a bright field microscope.

FIG. 14 shows that the transmittance of the phase difference adding portion on the pupil plane of the imaging system is 10
The figure which shows the simulation result of the image of the position detection mark of a low level difference obtained when it is 0%.

FIG. 15 is a diagram showing a simulation result of an image of a position detection mark having a relatively high step obtained by a bright field microscope.

[Explanation of symbols]

 4 Illumination field stop 6 Illumination light flux limiting member 16 Phase difference filter 22 Index plate Illumination field stop 24 Index plate 28 Image sensor 29 Image processing system

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/30 525P 525B

Claims (29)

[Claims] 1. An illumination optical system for irradiating a position detection mark on a substrate with illumination light in a predetermined wavelength range, and light generated from the position detection mark is incident to form an image of the position detection mark on an image sensor. A device for detecting the position of the position detection mark based on an image signal output from the image pickup element, the device including an imaging optical system for forming, and a relationship of substantially optical Fourier transform with respect to the position detection mark. And a light flux limiting member for limiting the illumination light flux on the first surface in the illumination optical system to a substantially annular first region centered on the optical axis of the illumination optical system; On the second surface in the image forming optical system having substantially the relationship of optical Fourier transform, respectively, into a substantially annular zone second region having an image forming relationship with the first region and the other region. The degree to which the phase of the distributed image-forming light flux is changed Position detecting device characterized by comprising a differential member. 2. The apparatus according to claim 1, further comprising a member for dimming an imaging light beam distributed in the second region. 3. The phase difference member is disposed on the second surface in the image forming optical system, and is approximately (2m + 1) π / between the image forming light fluxes distributed in the second region and the other regions.
The device according to claim 1, wherein the device is an optical filter that gives a phase difference of 2 ± π / 4 [rad] (m is an integer). 4. When the shortest wavelength in the wavelength range of the light flux of the illumination light that contributes to the formation of the image signal is λ1, the longest wavelength is λ2, and the period of the position detection mark is P, the ring-shaped first 4. The device according to claim 1, wherein the outer radius ro and the inner radius r i of one region satisfy the relationship of ri ≧ λ2 / (2 × P) ro-ri ≦ λ1 / P. . 5. The outer radius of the ring-shaped first region is ro,
Assuming that the period of the position detection mark is P and the longest wavelength in the wavelength range of the light flux of the illumination light that contributes to the formation of the image signal is λ2, the numerical aperture NAo of the imaging optical system is NAo ≧ ro + λ2 / The device according to claim 1, wherein the relationship P 1 is satisfied. 6. The apparatus according to claim 1, further comprising a member that holds the phase difference member so that it can be inserted into and removed from the optical path of the imaging optical system. 7. The apparatus according to claim 6, further comprising a member that holds the light flux limiting member in a removable manner with respect to an optical path of the illumination optical system. 8. An image forming means for forming an image of the index mark on the image pickup device, wherein the image of the position detection mark and the image of the index mark are formed based on an image signal output from the image pickup device. The device according to any one of claims 1 to 7, which detects a positional deviation. 9. The image forming means includes an index plate having the index mark, an illumination system for irradiating the index plate with a light beam different from the illumination light, and the light generated from the index mark to enter the index plate. 9. An apparatus according to claim 8, including an imaging system for forming an image on the image sensor. 10. The index plate is disposed on a surface substantially conjugate with the substrate in the image forming optical system, and the image forming optical system forms an image of the position detection mark on the index plate. 10. The apparatus according to claim 9, further comprising forming an image of the position detection mark and an image of the index mark on the image sensor. 11. The illumination system includes a member that adjusts the intensity of a light beam that illuminates the index mark in accordance with a change in the amount of an image forming light beam from the position detection mark that is incident on the image pickup element. 11. The method according to claim 9 or 10, wherein
An apparatus according to claim 1. 12. An illumination optical system for irradiating a position detection mark having a periodicity on a substrate with an illumination light of a predetermined wavelength range, and light generated from the position detection mark is incident to detect the position on an image sensor. A device for detecting the position of the position detection mark based on an image signal output from the image pickup device, the device including an imaging optical system that forms an image of the mark, wherein the position detection mark is substantially optically A light flux limiting member for limiting the illumination light flux on the first surface in the illumination optical system, which has a Fourier transform relationship, within a substantially annular zone centered on the optical axis of the illumination optical system; and the position detection mark. A phase difference member that makes the phases of the 0th-order light and the other light from the position detection mark distributed on the second surface in the imaging optical system that have a substantially optical Fourier transform relationship with respect to And is equipped with Position detector. 13. The apparatus according to claim 12, further comprising a member that attenuates 0th order light from the position detection mark. 14. The phase difference member is disposed on the second surface in the image forming optical system, and is approximately (2m + 1) π / 2 between the 0th-order light from the position detection mark and other light. ± π /
14. The device according to claim 12, which is an optical filter that gives a phase difference of 4 [rad] (m is an integer). 15. The ring-shaped area, where λ1 is the shortest wavelength, λ2 is the longest wavelength in the wavelength range of the light flux of the illumination light that contributes to the formation of the image signal, and P is the period of the position detection mark. 15. The apparatus according to claim 12, wherein the outer radius ro and the inner radius ri of the above satisfy the relationship of ri ≧ λ2 / (2 × P) ro-ri ≦ λ1 / P. 16. The outer radius of the ring-shaped region is ro, the period of the position detection mark is P, and the longest wavelength in the wavelength region of the illumination light that contributes to the formation of the image signal is λ.
The numerical aperture NAo of the imaging optical system satisfies the following formula: NAo ≧ ro + λ2 / P. 17. An illumination optical system for irradiating a position detection mark on a substrate with illumination light in a predetermined wavelength range, and light generated from the position detection mark is incident to form an image of the position detection mark on an image sensor. A device for detecting the position of the position detection mark based on an image signal output from the image pickup element, the device including an imaging optical system for forming, and a relationship of substantially optical Fourier transform with respect to the position detection mark. And an optical member that enhances the intensity distribution of the illumination light on the first surface in the illumination optical system in a substantially annular first region around the optical axis of the illumination optical system as compared to other regions. A substantially annular second region having an image-forming relationship with the first region on the second surface of the image-forming optical system having a substantially optical Fourier transform relationship with the position detection mark; Imaging light distributed in other areas Position detecting device characterized by comprising a phase difference members to vary the phase of the. 18. The apparatus according to claim 17, further comprising a member for dimming an image forming light beam distributed in the second region. 19. The phase difference member is arranged on a second surface in the image forming optical system, and is approximately (2m + 1) π between image forming light fluxes distributed in the second region and the other regions.
18. An optical filter which gives a phase difference of / 2 ± π / 4 [rad] (m is an integer), 18.
8. The device according to item 8. 20. When the shortest wavelength in the wavelength range of the light flux of the illumination light that contributes to the formation of the image signal is λ1, the longest wavelength is λ2, and the period of the position detection mark is P, the ring-shaped first 20. The apparatus according to claim 17, wherein an outer radius ro and an inner radius r i of one region satisfy a relationship of ri ≧ λ2 / (2 × P) ro-ri ≦ λ1 / P. . 21. The outer radius of the ring-shaped first region is ro
, P is the period of the position detection mark, and λ2 is the longest wavelength in the wavelength range of the light flux that contributes to the formation of the image signal in the illumination light, the numerical aperture NAo of the imaging optical system is NAo ≧ ro + λ2 The apparatus according to any one of claims 17 to 20, wherein the relationship of / P is satisfied. 22. The optical member includes a diaphragm member having a light-shielding portion that substantially covers the other area so that the light intensity in the other area on the first surface is substantially zero. The device according to any one of claims 17 to 21. 23. The optical member includes a strength distribution changing member that changes at least one of an outer radius and an inner radius of the ring-shaped first region.
2. The device according to any one of 2. 24. The intensity distribution changing member includes a plurality of diaphragm members having at least one of an outer radius and an inner radius of a ring-shaped opening, and one of the plurality of diaphragm members disposed in an optical path of the illumination optical system. 24. A device according to claim 23, comprising a member for holding the plurality of diaphragm members for placement. 25. The retardation member sets at least one of a radial width and a position of the ring-shaped second region in accordance with a change in at least one of an outer radius and an inner radius of the first region. 25. The device according to any of claims 17-24, characterized in that it is varied. 26. An illumination optical system for irradiating a position detection mark on a substrate with illumination light in a predetermined wavelength range, and light generated from the position detection mark is incident to form an image of the position detection mark on an image sensor. An image forming optical system for forming the image, and an apparatus for detecting the position of the position detection mark based on an image signal output from the image pickup element, wherein the illumination optical system is substantially on a pupil plane of the illumination optical system. A diaphragm member for transmitting an illumination light flux distributed in a first zone-shaped region centered on the optical axis of the system; and an image formation relationship with the first region on a substantial pupil plane of the image forming optical system. And a phase difference member that makes the phases of the image-forming light fluxes distributed respectively in the second region having a substantially annular shape and the other region that are different from each other. 27. An illumination optical system for irradiating a position detection mark on a substrate with illumination light in a predetermined wavelength range, and light generated from the position detection mark is incident to form an image of the position detection mark on an image sensor. An image forming optical system for forming the image forming device, which detects the position of the position detection mark based on an image signal output from the image pickup device, wherein the illumination optical system is provided on a substantial pupil plane of the illumination optical system. A secondary light source forming member that forms a secondary light source in a substantially annular shape centered on the optical axis of the system; and on a substantial pupil plane of the imaging optical system,
A position detecting device comprising: a phase difference member that makes the phases of image-forming light fluxes distributed respectively in a substantially annular region having an image-forming relationship with the secondary light source and a region other than the region. 28. An illumination optical system for irradiating a position detection mark on a substrate with illumination light in a predetermined wavelength range, and light generated from the position detection mark is incident to form an image of the position detection mark on an image sensor. An image forming optical system for forming, which detects a position of the position detection mark based on an image signal output from the image pickup element, wherein a light intensity distribution substantially on a pupil plane of the illumination optical system. With an optical member for enhancing the optical axis of the illumination optical system in a substantially ring-shaped region as compared with an inner region thereof; forming an image with the inner region on a substantial pupil plane of the imaging optical system. 1. A position detecting device, comprising: a phase difference member that makes the phases of image-forming light fluxes distributed in a substantially circular region and a region other than the related region different from each other. 29. The apparatus according to claim 1, wherein the illumination optical system includes a light source that emits broadband light or multi-wavelength light as the illumination light.