JP3336622B2 - Imaging characteristic measuring method and apparatus, and exposure apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is, for example, focus of the projection optical system
The present invention relates to an imaging characteristic measuring method and apparatus suitable for measuring a point position, spherical aberration , astigmatism, and the like.

[0002]

2. Description of the Related Art An aberration measuring instrument is used to evaluate whether a lens has aberration characteristics as designed. FIG. 6 shows a conventional aberration measuring instrument. In FIG. 6, reference numeral 2 denotes a test lens to be subjected to aberration measurement. When the lens 2 is a projection lens of a projection exposure apparatus for manufacturing a semiconductor, an LSI pattern or the like drawn on a reticle is transferred to a photoresist-coated wafer via the projection lens 2. The projection lens 2 is a two-sided telecentric lens, and light vertically emitted from the reticle is vertically incident on the wafer. For example, in order to measure spherical aberration, it is desirable to separately place annular zones having different radii on a so-called pupil plane of the lens. However, since the pupil plane of the projection lens 2 is inside the lens, it is actually The zonal plate cannot be placed on the pupil plane.

Therefore, in FIG. 6, a ring plate is put in an illumination system. That is, in FIG. 6, reference numeral 50 denotes an orbicular plate, and the orbicular plate 50 is illuminated with light from a light source (not shown). Form a point image on the reticle virtual surface 52 on which is to be placed. The illumination light emitted from the point image on the reticle virtual surface 52 passes through the orbicular zone on the pupil plane conjugate with the orbicular zone of the orbicular plate 50 of the projection lens 2 to be measured, and is again outside the projection lens 2. Form a point image. A pinhole 53 is located near this point image.
Are arranged, and the light passing through the pinhole 53 enters the light receiving element 55 via the condenser lens 54. Pinhole 53
Is scanned along the optical axis (Z axis) of the projection lens 2, the amount of light incident on the pinhole 53 becomes maximum when the pinhole 53 matches the position of the point image formed by the projection lens 2.

Accordingly, the position on the Z axis of the pinhole 53 when the output signal of the light receiving element 55 becomes maximum is the focal position of the projection lens 2 corresponding to the orbicular plate 50. By changing the radius of the orbicular zone of the orbicular zone plate 50 variously,
The spherical aberration and the like of the projection lens 2 can be measured.

[0005]

However, it is difficult to form a point image correctly on the reticle virtual surface 52 with the above-mentioned conventional aberration measuring device, and the position of the point image by the projection lens 2 by the pinhole 53 is difficult. There is a disadvantage that the measurement error is large. In other words, in the conventional aberration measuring device,
It is difficult to match the position of the point image for light transmission with the reticle virtual surface 52 of the projection lens 2 and match the light receiving position with the wafer surface of the projection lens 2. Further, in the conventional aberration measuring device, it is difficult to accurately measure only the aberration of the projection lens 2 because the influence of the aberration of the condenser lens 51 in the light transmission system is likely to be mixed. The present invention in view of such a point,
High-precision lenses such as projection lenses for projection exposure equipment
An object of the present invention is to provide an imaging characteristic measuring method capable of accurately measuring a focal position and an aberration. Further, the present invention
Imaging characteristic measurement device that can implement
The purpose is to provide. The present invention also relates to such a conclusion.
Provide an exposure apparatus using an image characteristic measuring method or apparatus.
The purpose is also.

[0006]

An imaging characteristic measuring apparatus according to the present invention is a projection optical system for projecting a reticle pattern onto a wafer. in a plane, and so as to pass through the two first point away from the optical axis of the projection optical system, a first phase grating for guiding the first <br/> illumination light to the projection optical system, The projection optical system is used by being switched from the first phase grating and passing through two second points different from the first point in the pupil plane of the projection optical system . The second that guides the illumination light of the second
Phase grating and its projection light with respect to the first phase grating
The first illuminating light passing through the first point is reflected by a reflecting surface provided across the optical system, thereby projecting the projection light.
The first phase returned to the first phase grating via an optical system
Illumination light and its projection optics for its second phase grating
The second illuminating light passing through the second point is reflected by a reflecting surface provided with the system therebetween, so that the projection light
The second phase grating returned to the second phase grating
Measuring means for measuring the imaging characteristics of the projection optical system based on the illumination light . Next, the imaging characteristic measuring method according to the present invention uses the reticle pattern
In an imaging characteristic measuring method for measuring an imaging characteristic of a projection optical system for projecting thereon, the imaging optical system passes two first points in a pupil plane of the projection optical system and separated from an optical axis of the projection optical system. To the projection optical system via the first phase grating .
A second illumination light guided from the first phase grating and passed through two second points different from the first point in the pupil plane of the projection optical system. The second illumination light is guided to the projection optical system through the phase grating of the first illumination device, and the first illumination light passing through the first point is converted to the first illumination light by the first illumination light.
Reflection on the opposite side of the projection optics to the phase grating.
Through the projection optical system, the first phase shape
The first illuminating light returned to the element and the second illuminating light passing through the second point are coupled to the second phase grating
By reflecting off the other side of the projection optics,
Which is returned to the second phase grating via the projection optics
The imaging characteristic of the projection optical system is measured based on the second illumination light . Further, the exposure apparatus according to the present invention is an exposure apparatus including a projection optical system for transferring an image of a pattern formed on a mask onto a photosensitive substrate, and as an apparatus for measuring the imaging characteristics of the projection optical system, An imaging characteristic measuring device is provided.

[0007]

According to the present invention, the lens to be inspected (2)
Is a projection lens for a projection exposure apparatus, the reflecting mirror (1) is arranged at a position where a reticle is arranged, for example, and the transmission type phase grating (3) is arranged near a position where a wafer is arranged, for example. . When the transmission type phase grating (3) is illuminated in this state, the transmission type phase grating (3) is illuminated from the transmission type phase grating (3).
The side is irradiated with + 1st order diffracted light and −1st order diffracted light. In this case, since the light is split by the principle of the phase grating, the light can be efficiently guided in two directions, and the zero-order light unnecessary for the aberration measurement for the aberration measurement is extremely small.

The + 1st-order and -1st-order diffracted lights are:
The pupil plane of the test lens (2) passes through the orbicular zone having a radius corresponding to the diffraction angle of the diffracted light, and faces the reflecting mirror (1);
The reflected light from the reflecting mirror (1) is returned to the lens to be inspected (2).
And the light enters the light receiving element (10) via the transmission type diffraction grating (3). Then, when the transmission diffraction grating (3) matches the focal position of the lens (2) to be inspected, the output signal of the light receiving element (10) is minimized. When the grating pitch of the transmission type phase grating (3) is changed, the radius of the orbicular zone through which the two diffracted lights pass on the pupil plane of the test lens (2) changes. By measuring the focal position of the test lens (2) instead, the spherical aberration of the test lens (2) can be measured.

The direction of the grating of the transmission type phase grating (3) is changed to a radial direction of the lens (2) to be examined, a direction perpendicular to the radial direction, and a direction intersecting these directions at a predetermined angle. Then, the transmission type phase grating (3) is scanned off-axis of the lens (2) in parallel with the optical axis to determine the focal position, thereby reducing the astigmatism of the lens (2). Can be measured.

In the case where the lens to be inspected (2) is a projection lens for a projection exposure apparatus, the reflecting mirror (1) is arranged in the vicinity of the position where the wafer is arranged. Even if (3) is arranged at a position where a reticle is arranged, for example, and its reflecting mirror (1) is scanned in parallel with the optical axis of the lens to be measured (2), aberration measurement can be performed in the same manner.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an aberration measuring apparatus according to the present invention will be described below with reference to FIGS. In the present embodiment, a projection lens that projects a reticle pattern on a wafer is a target of aberration measurement. FIG. 1 shows an aberration measuring device of the present example,
In FIG. 1, reference numeral 1 denotes a mirror, and 2 denotes a projection lens as a lens to be inspected. The mirror 1 is fixed to an accurate position in design where a reticle is installed with respect to the projection lens 2.
That is, the position of the reflecting surface of the mirror 1 is equal to the position of the pattern forming surface of the reticle. The mirror 1 and the projection lens 2 are fixed by a support mechanism (not shown) so as not to move with respect to a base 20 described later.

Reference numeral 3 denotes a transmission-type phase grating, and the transmission-type phase grating 3 is mounted on a measuring unit 4 serving as a Z stage disposed below the projection lens 2. The transmission type phase grating 3 is
The projection lens 2 is arranged near the position where the wafer is set. Reference numeral 5 denotes an illumination system for generating illumination light having a wavelength used in the design of the projection lens 2. In this illumination system 5,
Illumination light emitted from the light source 5a and collected by the reflecting mirror 5b is converted into a substantially parallel light beam by the condenser lens 5c, and the substantially parallel light beam is passed through the filter 6, so that the design wavelength of the projection lens 2 is used. Is selected. Light transmitted through the filter 6 is made incident on one end of a light guide 7 such as a fiber bundle by a condenser lens 5d, and illumination light emitted from the other end of the light guide 7 is guided to a condenser lens 8 side by a half mirror 9. The transmission type phase grating 3 is vertically illuminated from the bottom surface with parallel illumination light emitted from the condenser lens 8.

As shown in FIG. 2, assuming that the pitch of the transmission type phase grating 3 is P and the wavelength of the parallel illumination light 30 is λ, the −1st-order diffracted light 31 has diffraction angles −θ and + θ determined by the following equations. And the + 1st-order diffracted light 32 are emitted from the phase grating 3 to the projection lens 2 side. sin (± θ) = ± λ / P (double sign same order)

Further, in this embodiment, if the depth of the groove of the phase grating 3 is d and the refractive index of the phase grating 3 is n, the following relationship is established. (N-1) d = λ / 2 + mλ (m is an integer) For example, if the refractive index is n = 1.5, λ = 365 nm, and m = 0, the depth d is 365 nm. Further, the duty ratio between the peak and the valley of the phase grating 3 is set to 1: 1. When light is vertically incident on such a phase grating 3, 0
The secondary light disappears, and the intensity of the ± 1st-order diffracted light increases.

Returning to FIG. 1, of the light traveling from the transmission type phase grating 3 to the projection lens 2, for example, the −1st-order diffracted light 31 having a diffraction angle of −θ is once emitted at a point X 1 on the pupil plane 2 a of the projection lens 2. After being converged, it spreads again and enters the mirror 1. The diffracted light reflected by the mirror 1 is reflected on the pupil plane 2 of the projection lens 2 this time.
The light passes through a point X2 symmetrical to the point X1 with respect to the optical axis on a and enters the phase grating 3 as return light 33 at an incident angle θ. vice versa,
The + 1st-order diffracted light having a diffraction angle of + θ from the phase grating 3 is −1
Incident on the phase grating 3 along the optical path opposite to that of the
Incident at θ.

The diffracted light returned to the phase grating 3 is diffracted again, and travels in the opposite direction parallel to the illumination light 30 toward the condenser lens 8. The return light focused by the condenser lens 8 passes through the half mirror 9. Pinhole plate 40
Incident on. At this time, as described later, when the phase grating 3 matches the focal position of the projection lens 2 with respect to the current diffracted light, the amount of light transmitted through the pinhole of the pinhole plate 40 is minimized. The light transmitted through the pinhole is photoelectrically converted by the light receiving element 10 and amplified by the amplifier 11, and the amplified photoelectric conversion signal is converted into an analog / digital (A / D) signal.
The data is taken into the computer 13 via the converter 12.

The computer 13 generates a signal for driving the Z stage and a signal for driving the XY stage, and supplies the former signal for driving the Z stage to the motor 15 via the amplifier 14. With this motor 15, the wedge mechanism 1 of the Z stage
By moving 6, the measuring unit 4 moves in a direction parallel to the optical axis (Z axis) of the projection lens 2. On the other hand, the latter XY
The signal for driving the stage is supplied to the motor 18 via the amplifier 17.
The XY stage 19 can be translated by the motor 18 in an XY plane perpendicular to the optical axis of the projection lens 2. Reference numeral 20 denotes a base of the entire measuring machine, on which an XY stage 19 and a wedge mechanism 1 are sequentially placed.
6, the measuring unit 4 and the phase grating 3 are mounted.

The operation of this embodiment when measuring aberration will be described.
In this case, first, the transmission-type phase grating 3 having a grating constant (grating pitch) P corresponding to a predetermined radius from the optical axis at a point on the pupil plane 2a of the projection lens 2 through which the light beam to be measured passes is represented by Z
It is placed on the optical axis of the projection lens 2 on the measuring section 4 which also serves as a stage. In FIG. 1, the phase grating 3 is exaggerated and enlarged, but is actually large enough to be regarded as a point in the image field of the projection lens 2. After that, the measuring section 4 is scanned in the Z-axis direction. Then, as shown in FIG. 3A, when the position of the phase grating 3 matches the focal position Z1 of the projection lens 2, the -1st-order diffracted light 3
The return light 33 from the first mirror 1 enters the phase grating 3 in the direction opposite to the + 1st-order diffracted light 32, and the return light 34 of the + 1st-order diffracted light 32 from the mirror 1 returns to the phase grating 3 in the opposite direction to the −1st-order diffracted light 31. Incident on. Then, the -1st-order diffracted light of the return light 33 and the + 1st-order diffracted light of the return light 34 are vertically emitted from the phase grating 3 as return light 35 in the direction opposite to the illumination light 30.

In this case, the phases of the -1st-order diffracted light 31 and the + 1st-order diffracted light 32 are different from the 0th-order light by -45 ° and + 45 °, respectively. Are-with respect to the zero-order light, respectively.
Different by 45 ° and + 45 °. Therefore, -1 of the return light 33
Since the phase of the next-order diffracted light and the phase of the + 1st-order diffracted light of the return light 34 finally differ by 180 °, the intensity I of the return light 35 becomes minimum as shown in FIG. On the contrary,
If the position of the phase grating 3 in the Z-axis direction is displaced from the focal position Z1 of the projection lens 2, the −1st-order diffracted light of the return light 33 and the + 1st-order diffracted light of the return light 34 are displaced. Becomes larger. Therefore, the coordinates of the Z axis of the phase grating 3 when the intensity I of the return light is minimum and the photoelectric conversion signal of the light receiving element 10 in FIG. 1 is minimum are obtained as the focal position of the projection lens 2.

Next, the measuring section 4 is scanned in the Z-axis direction by replacing the phase grating 3 with a phase grating having a different lattice constant P.
In this case, since two diffracted lights from the phase grating pass through points different from points X1 and X2 on the pupil plane 2a of the projection lens 2, if there is a spherical aberration, the photoelectric conversion signal of the light receiving element 10 is changed. The focus position on the Z-axis that becomes the minimum is different from the previous position. A plurality of transmission-type phase gratings having different grating constants are sequentially placed on the measuring unit 4, and the measurement of the focal position is repeated a plurality of times. By plotting the focal position, a so-called spherical aberration curve is drawn. Note that a plurality of phase gratings having different lattice constants are formed in the measuring unit 4 in a predetermined positional relationship, and the measuring unit 4 is moved by a predetermined amount in a plane perpendicular to the optical axis of the projection lens 2 instead of exchanging the phase gratings. You may make it move at a time.

Next, XY in response to a command from the computer 13
By moving the stage 19 in parallel in the XY plane perpendicular to the optical axis of the projection lens 2 and detecting the focal position for each of a plurality of lattice constants with the phase grating 3 disposed outside the optical axis of the projection lens 2 And off-axis spherical aberration can also be measured. Further, by moving the phase grating 3 two-dimensionally in a plane perpendicular to the optical axis of the projection lens 2 and measuring the focal position at each point, the field curvature of the projection lens 2 can also be measured. . Further, a region in the Z-axis direction in which the photoelectric conversion signal of the light receiving element 10 falls within a predetermined range from the minimum value can be considered as an effective focal region of the projection lens 2.
According to this example, the effective focal range of the projection lens 2 can also be measured.

Further, as shown in FIG.
When there is periodicity in the axial direction, the focal position measured by shifting the phase grating 3 in the X direction with respect to the optical axis of the projection lens 2 is the focal position of the projection lens 2 on the meridional plane. On the other hand, when the phase grating 3 has a periodicity in the Y-axis direction, the focal position measured by shifting the phase grating 3 in the X direction with respect to the optical axis of the projection lens 2 is the focus position of the projection lens 2. Can be regarded as the focal position on the sagittal plane. Similarly, when the grating of the phase grating 3 has a periodicity in the T direction at a predetermined angle clockwise with respect to the X axis, and when the grating of the phase grating 3 is at a predetermined angle counterclockwise with respect to the X axis.
Even in the case of having periodicity in the direction, by detecting the focal positions, the astigmatism of the projection lens 2 can be measured due to the difference between the focal positions.

Further, for example, in a projection lens for a projection exposure apparatus for manufacturing a semiconductor, the variation of the wavelength used is within about 1 nm. In this regard, by using an interference filter as the filter 6 in the illumination system 5 in FIG. 1 and inclining the filter 6, the wavelength of light passing through the filter 6 can be changed by about 1 nm to 2 nm. Therefore,
In a state where the wavelength of the illumination light 30 is changed by changing the inclination angle of the filter 6, the phase grating 3 is scanned in the Z-axis direction to measure the focal position of the projection lens 2. Chromatic aberration can also be measured.

Next, an example of a grating pattern of the transmission-type phase grating 3 that can be used for measuring various aberrations will be described. FIG.
(A) shows a concentric pattern for measuring spherical aberration,
In FIG. 4A, a hatched portion 36 is an opaque portion such as a chromium vapor-deposited film, and the phase difference between the white transparent portion and the black transparent portion 37 becomes π with respect to the used wavelength λ. Thus, the thickness of the glass as the substrate is changed. This can be performed by dry etching or the like. FIG.
FIG. 4B shows a phase grating for low frequency in which the grating pitch is larger than that of FIG. 4A. Diffracted light from the phase grating of FIG. , Projection lens 2
Pass on a pupil plane 2a closer to the optical axis. However, the phase grating patterns in FIGS. 4A and 4B do not need to be formed over the entire circumference, but may be formed only in a part of the circumference divided.

FIG. 5 shows four types of phase gratings for the X, Y, T and R directions for astigmatism. The example of FIG. 5 is for the diagonal of a square screen, and of course T
The direction and the R direction are not 45 degrees with respect to the X axis and the Y axis. A plurality of such patterns are provided on the transmission-type phase grating 3, and during aberration measurement, other patterns except one of the patterns are covered with a mask or the like, and only the diffracted light from the one pattern is covered. Must be sent to the test lens. Further, the phase gratings shown in FIGS. 4 and 5 are prepared so that the areas of the transmission part having the phase of 0 and the transmission part having the phase of π are equal. Otherwise, zero-order light is generated, and spherical aberration and the like cannot be measured correctly.

In the above embodiment, the mirror 1 is arranged on the reticle side of the projection lens 2 and the phase grating 3 is arranged on the wafer side. Conversely, the phase grating 3 is arranged on the reticle side, and The mirror 1 may be arranged in the mirror. In this case, for example, by fixing the phase grating on the reticle side and scanning the mirror on the wafer side in the optical axis direction of the projection lens 2, the configuration of the mechanical unit such as the measuring unit 4 also serving as the Z stage is simplified. Can be Further, the aberration measuring device of FIG. 1 may be mounted as a focal position detecting mechanism in, for example, a step-and-repeat type reduction projection exposure apparatus (stepper). Accordingly, it is possible to monitor the fluctuation of the focal position of the projection lens 2 as needed. in this way,
The present invention is not limited to the above-described embodiments, and can take various configurations without departing from the gist of the present invention.

[0027]

According to the present invention, the projection optical system is provided with the first point so as to pass through two first points in the pupil plane of the projection optical system and away from the optical axis of the projection optical system. The first illumination light is guided through a phase grating and its first phase is passed in a pupil plane of the projection optics and through two second points different from the first point. The second illumination light is guided to the projection optical system via the second phase grating switched from the grating, and is directed to the first and second phase gratings, respectively.
Reflected by the reflecting surface provided with the projection optical system
The first and second phase gratings returned to the first and second phase gratings
Since the imaging characteristics of the projection optical system are measured based on the illumination light, there is an advantage that the imaging characteristics such as the focal position and spherical aberration of the projection optical system can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of an aberration measuring instrument according to the present invention.

FIG. 2 is a cross-sectional view illustrating a transmission type phase grating according to an example.

FIG. 3 is a diagram for describing a focus position detection method according to the embodiment;

FIG. 4 is a plan view illustrating an example of a pattern of a transmission phase grating.

FIG. 5 is a plan view showing another example of the pattern of the transmission type phase grating.

FIG. 6 is a configuration diagram showing a conventional aberration measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mirror 2 Projection lens as a test lens 3 Transmission type phase grating 4 Measurement part 5 Illumination system 7 Light guide 8 Condenser lens 9 Half mirror 10 Light receiving element 19 XY stage

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01M 11/00 G01M 11/02 H01L 21/027

Claims (12)

(57) [Claims] 1. A reticle pattern is projected onto a wafer.
That the imaging characteristic measuring device of the projection optical system, in the projection optical system in the pupil plane, and so as to pass through the two first point away from the optical axis of the projection optical system, the projection optical system A first phase grating that guides a first illumination light; and a second phase grating that is used by being switched from the first phase grating and that is different from the first point in a pupil plane of the projection optical system.
A second point through the projection optics so as to pass through two second points .
A second phase grating for guiding the illumination light, and the first phase grating with the projection optical system interposed therebetween.
The reflected first surface having passed through the first point .
By reflecting the illumination light, through the projection optical system
Said first illumination light to be returned to the first phase grating, before
The projection optical system is provided with respect to the second phase grating.
The second light passing through the second point on the reflecting surface
The reflected bright light causes the light to be reflected through the projection optical system.
Measuring means for measuring the imaging characteristics of the projection optical system based on the second illumination light returned to the second phase grating. apparatus. 2. The apparatus according to claim 1, wherein the first phase grating and the second phase grating have different grating pitches. 3. The method according to claim 1, wherein the measuring unit is configured to determine a focal position of the projection optical system by the first illumination light passing through the first point and the projection by the second illumination light passing through the second point. 3. The apparatus according to claim 1, wherein the spherical aberration of the projection optical system is measured based on a focal position of the optical system. 4. The apparatus according to claim 1, wherein the first phase grating and the second phase grating have different grating directions. 5. The projection device according to claim 1, wherein the measuring unit is configured to determine a focal position of the projection optical system by the first illumination light passing through the first point and the projection by the second illumination light passing through the second point. The apparatus according to claim 1, wherein an astigmatism of the projection optical system is measured based on a focal position of the optical system. 6. The projection optical system according to claim 1, wherein the first phase grating and the second phase grating are formed on a same substrate. Imaging characteristic measuring device. 7. The first illumination light passing through the first point is formed by ± 1st-order diffracted light emitted from the first phase grating, and the second illumination light passing through the second point . The illumination light of the second
The imaging characteristic measuring apparatus for a projection optical system according to claim 1, wherein the imaging characteristic is formed by ± first-order diffracted light emitted from the phase grating. 8. A reticle pattern is projected onto a wafer.
In imaging characteristic measuring method for measuring the imaging characteristics of the projection optical system that, to pass the in the pupil plane of the projection optical system, and a point two first separated from the optical axis of the projection optical system Guiding the first illumination light to the projection optical system via a first phase grating, and passing through two second points different from the first point in the pupil plane of the projection optical system As described above, the second illumination light is guided to the projection optical system via the second phase grating switched from the first phase grating, and the first illumination light passing through the first point is The first
Reflected on the opposite side of the projection optical system with respect to the phase grating
The first phase through the projection optics
The first illumination light returned to the grating and the second illumination light passing through the second point are directed to the second phase grating
Reflected by the opposite side of the projection optics
Before being returned to the second phase grating via the projection optical system
A method for measuring the imaging characteristics of the projection optical system, wherein the imaging characteristics of the projection optical system are measured based on the second illumination light . 9. The method according to claim 8, wherein the first phase grating and the second phase grating have different grating pitches or grating directions. . Wherein said the passing through the first point first irradiation <br/> said projection optical according to the second illumination light passing through the point of the focus position and the second of said projection optical system by Meiko 10. The method according to claim 8, wherein spherical aberration or astigmatism of the projection optical system is measured based on a focal position of the system. 11. An exposure apparatus provided with a projection optical system for transferring an image of a pattern formed on a mask onto a photosensitive substrate, wherein an imaging characteristic of the projection optical system is measured. An exposure apparatus comprising the imaging characteristic measuring apparatus according to any one of the preceding claims. 12. The first phase grating and the second phase grating are detachably provided at a position where the mask is arranged, and the measuring means is provided on a stage on which the photosensitive substrate is arranged. The exposure apparatus according to claim 11, wherein: