JP2003302205A - Shearing interference measuring method and shearing interferometer, method of manufacturing for projection optical system, and projection optical system, and projection exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shearing interference measuring method for measuring without being affected by disturbance or aberration on a light source side. <P>SOLUTION: A measuring light flux (L) emitted from a light source is divided to produce two light fluxes (L1, L2) having their wave fronts deviated from each other, the two light fluxes (L1, L2) are projected with their wave fronts deviated onto an inspection subject (PL), and interference fringes occurring at a position (3) at which the wave fronts of the two light fluxes (L1, L2) passing through the inspection subject (PL) overlap each other, are detected. Noise wave fronts superimposed on the wave fronts of the light flux L1 and the noise wave fronts superimposed on the wave fronts of the light flux L2 overlap exactly each other. However, signal wave fronts superimposed on the light flux L1 and the signal wave fronts superimposed on the light flux L2 deviate from each other. It is, therefore, possible to measure without being affected by the disturbance or the aberration on the light source side. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shearing interferometer measuring method, a shearing interferometer, and a projection optical system manufacturing method.
The present invention relates to a projection optical system and a projection exposure apparatus.

[0002]

2. Description of the Related Art It has been proposed to apply a shearing interferometer to inspection of a highly accurate optical system such as a projection lens. FIG. 14 is a diagram showing a conventional shearing interferometer. Figure 1
4A shows a shearing interferometer for measuring the transmitted wavefront of the test object (here, the projection optical system PL), and FIG.
(B) shows a shearing interferometer that measures the wavefront of the return light from the test object (here, the reflected wavefront of the test surface 4).

The shearing interferometer shown in FIG.
A measurement light beam L (a spherical wave diverging from one point on the reticle surface R which is the object surface) is incident on the optical system PL to be measured, and the measurement light beam L emitted from the optical system PL to be measured is incident.
Is divided by the diffractive optical element 2 into two light beams L1 and L2 whose wavefronts are deviated from each other, and interference fringes due to the light beams L1 and L2 are observed by the CCD camera 3 or the like. From this interference fringe, the shape of the transmitted wavefront of the optical system PL to be measured can be obtained.

On the other hand, in the shearing interferometer shown in FIG. 14B, a measurement light beam L (which is a light beam which is incident substantially perpendicularly to the surface 4 to be inspected) is made incident on the surface 4 to be inspected, and Four
The measurement light flux L reflected by the half mirror HM2 or the like is used to generate two light fluxes L1, whose wavefronts are not shown in the drawing, from each other.
It is divided into L2 and the interference fringes due to these light fluxes L1 and L2 are C
It is observed by the CD camera 3 or the like. From this interference fringe, the shape of the reflected wavefront of the surface to be inspected 4 is obtained.

[0005]

However, compared with other interferometers such as the Fizeau type, these conventional shearing interferometers have their measurement accuracy greatly affected by disturbances and aberrations on the light source side of the interferometer. There is a fundamental problem. This is because, in other interferometric measurements, two light fluxes branched from the same light source interfere without shifting the wavefronts, so that the wavefronts indicating disturbances and aberrations on the light source side superimposed on the wavefronts of the two light fluxes (hereinafter referred to as “noise wavefront”). That is, they just overlap,
The interference fringes generated according to the phase difference distribution of the wavefronts of these two light fluxes are not affected by the noise wavefront. On the other hand, in the shearing interferometer, two light beams branched from the same light source (see FIG.
Then, since the light fluxes L1 and L2) interfere by shifting the wavefronts, the noise wavefronts of the two light fluxes are displaced from each other to generate a phase difference distribution, which affects the interference fringes.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a shearing interferometer and a shearing interferometer which can be measured without being affected by disturbances and aberrations on the light source side. Another object of the present invention is to provide a high-performance projection optical system manufacturing method, a high-performance projection optical system, and a high-performance projection exposure apparatus by applying the shearing interferometry method.

[0007]

A shearing interferometry method according to a first aspect of the present invention divides a measurement light beam emitted from a light source to generate two light beams whose wavefronts are deviated from each other, and these two light beams are separated from each other by It is characterized in that light is projected onto an object to be inspected in a shifted state, and an interference fringe occurring at a position where the wavefronts of the two light fluxes passing through the object to be inspected are detected.

A shearing interferometry method according to a second aspect is the shearing interferometry method according to the first aspect, in which a phase shift interferometry method is used in which the phases of the two light beams are shifted and the interference fringes are detected a plurality of times. It is characterized by doing. The shearing interferometer according to claim 3 is arranged in the optical path of a measurement light beam emitted from a light source, divides the measurement light beam to generate two light beams whose wavefronts are deviated from each other, and the two light beams have their wavefronts. And a detector arranged at a position where the wavefronts of the two light beams that have passed through the test object are overlapped with each other.

A shearing interferometer according to a fourth aspect is the shearing interferometer according to the third aspect, wherein the detector is arranged at a position conjugate with the division plane of the division optical system. To do. The shearing interferometer according to claim 5 is the shearing interferometer according to claim 3, wherein the shearing interferometer is transmitted through the test object and is incident on the detector.
A splitting optical system is arranged in the optical path of the light flux so as to divide the two light fluxes again and superimpose the wavefronts of the two light fluxes on the detector.

A shearing interferometer according to a sixth aspect is the shearing interferometer according to the fifth aspect, wherein the splitting optical system for splitting the measurement light beam and the splitting optical system for splitting the two light beams are conjugated. Characterized by being in a relationship. The shearing interferometer according to claim 7 is any one of claims 3 to 6.
In the shearing interferometer according to any one of the above items, a mask for cutting light other than the two light beams whose wave fronts overlap on the detector is arranged in the optical path of the two light beams.

The shearing interferometer according to claim 8 is the shearing interferometer according to any one of claims 3 to 7, characterized in that the splitting optical system comprises a diffractive optical element. . The shearing interferometer according to claim 9 is arranged in the optical path of a measurement light beam emitted from a light source, divides the measurement light beam to generate two light beams whose wavefronts are deviated from each other, and the two light beams have their wavefronts. And a detector arranged at a position where the wavefronts of the two light beams returned from the test object to the split optical system overlap with each other. And

The shearing interferometer according to claim 10 is
The shearing interferometer according to claim 9, wherein the splitting optical system splits the measurement light flux into two light fluxes, a transmitted light flux and a reflected light flux, and the two light fluxes split by the beam splitter. And a deflecting optical system for projecting light onto an object to be inspected in a state where their wavefronts are deviated from each other.

A shearing interferometer as set forth in claim 11,
The shearing interferometer according to claim 10, wherein a polarizing beam splitter is used as the beam splitter, and a polarizing plate is arranged in the optical path of the two light fluxes between the split optical system and the detector. It is characterized by The shearing interferometer according to claim 12 is the shearing interferometer according to claim 9 or 10, wherein the detector is arranged at a position conjugate with the surface to be inspected of the test object. Characterize.

The shearing interferometer according to claim 13 is
The shearing interferometer according to claim 12, wherein the 2
A mask for cutting light other than the two light beams whose wavefronts overlap on the detector is arranged in the optical path of the light beam. A method of manufacturing a projection optical system according to claim 14,
A method of inspecting a part or all of the projection optical system by the shearing interferometry method according to claim 1 or 2 is included.

The projection optical system according to a fifteenth aspect is manufactured by the method for manufacturing a projection optical system according to the fourteenth aspect. The projection exposure apparatus according to claim 16,
A projection optical system according to claim 15 is included.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] A first embodiment of the present invention will be described with reference to FIG. In this embodiment, a shearing interferometer of the present invention of a type that measures a transmitted wavefront of a test object and a shearing interference method thereof will be described. Figure 1
(A) is a block diagram of the shearing interferometer of this embodiment.

Although it is assumed here that the object to be inspected is the projection optical system PL (for example, EUVL) of the projection exposure apparatus, the present invention can be applied to other objects to be inspected. In the shearing interferometer, a measurement light beam L (hereinafter, a spherical wave diverging from one point of the reticle surface R) is incident on the projection optical system PL from the reticle surface R side. Further, a detector such as the CCD camera 3 is arranged on the wafer surface W side of the projection optical system PL.

The measuring light beam L is generated by condensing the light beam emitted from a light source (not shown) on the reticle surface R. Here, in the shearing interferometer of the present embodiment, a splitting optical element (for example, a diffractive optical element G11. Hereinafter referred to as a diffractive optical element G11) is inserted in the measurement light beam L on the reticle surface R side. .

Here, the insertion position of the diffractive optical element G11 is on the light source side with respect to the focusing position (reticle surface R) of the measurement light beam L. The diffractive optical element G11 divides the measurement light beam L into two light beams L1 and L2 whose wavefronts are deviated from each other. For example, the 0th-order diffracted light and the 1st-order diffracted light generated in the diffractive optical element G11 are respectively the light flux L.
1 and the light flux L2.

In FIG. 1 (a), the wavefront of the light beam L1 and the wavefront of the light beam L2 are laterally displaced (in the object height direction), and the condensing positions of both light beams are displaced from each other on the reticle surface R. The position was shown. Here, the diffractive optical element G1
In No. 1, extra light other than the light fluxes L1 and L2 is also generated. Therefore, in this embodiment, the diffractive optical element G11 is used.
It is preferable that a mask M11 that cuts off the excessive light is arranged on the exit side of the. By the way, the most efficient cut can be made in the case of being arranged in the vicinity of the converging point (here, in the vicinity of the reticle surface R).

As shown in the lower part of FIG. 1 (a), the mask M11 has openings at the focal point of the light beam L1 and the focal point of the light beam L2, and the other portions serve as the light shielding portions. It is a mask. Both the light flux L1 and the light flux L2 that have passed through the mask M11 and then passed through the projection optical system PL are focused on the wafer surface W (at mutually displaced positions). Also,
As shown in FIG. 1A, the CCD camera 3 of this embodiment
Of the diffractive optical element G11 with respect to the projection optical system PL.
It is arranged at a position conjugate with (diffraction surface).

In the shearing interferometry of this embodiment, the output of the CCD camera 3 and the measurement light beam L to the light beam L1,
The transmitted wavefront corresponding to the aberration of the projection optical system PL is calculated based on the shear direction and the shear amount toward L2. The shear amount and the shear direction are the design data of the shearing interferometer,
It can be obtained from the data measured by the shearing interferometer. Even in the shearing interferometer having the above configuration, the noise wavefront due to the disturbance or aberration on the light source side is superimposed on the wavefront of the measurement light beam L. Therefore, the same noise wavefront is also superposed on the wavefront of the light flux L1 and the wavefront of the light flux L2 obtained by dividing the measurement light flux L.

However, in this shearing interferometer,
At a position conjugate with the diffractive optical element G11 with respect to the projection optical system PL (here, the imaging surface of the CCD camera 3), the light flux L1
The noise wavefront superposed on the wavefront of 1 and the noise wavefront superposed on the wavefront of the light flux L2 just overlap, and the phase difference between the noise wavefronts becomes almost zero. On the other hand, the light flux L1 and the light flux L2 are incident on the projection optical system PL in a state where their wavefronts are deviated from each other, and thus are superimposed on the light flux L1.
The transmitted wavefront (signal wavefront) corresponding to the aberration information of the projection optical system PL and the signal wavefront superimposed on the light flux L2 are
At that position, a phase difference distribution is generated with a shift from each other.

As a result, the interference fringes formed by the light beams L1 and L2 on the image pickup surface of the CCD camera 3 arranged at that position are affected by the transmitted wavefront (signal wavefront) corresponding to the aberration of the projection optical system PL. While being affected, it is not affected by the noise wavefront. Therefore, based on the output of the CCD camera 3, it is possible to perform the measurement that is not affected by the disturbance or aberration on the light source side.
Next, in the present embodiment, the diffractive optical element G11 and CC
An alignment method for ensuring a conjugate relationship with the D camera 3 will be described.

FIG. 1B is a diagram for explaining the alignment method of the shearing interferometer of this embodiment. In this alignment, whether or not the conjugate relationship is set is detected by whether or not the light flux L1 and the light flux L2 substantially overlap on the imaging surface of the CCD camera 3.

At the time of alignment, first, in the measurement light beam L incident on the diffractive optical element G11, a target T which partially blocks the measurement light beam L is arranged, and the light beams L1,
One of the openings of the mask M11 is shielded to shield one of the light flux L2. The target T is preferably arranged at a position as close to the diffractive optical element G11 as possible.

Further, in order to shield one of the light flux L1 and the light flux L2, the opening portion of the mask M11 is arranged only at one light focus point of the light flux L1 and the light flux L2, and the mask is provided at the other light focus point. The mask M1 is arranged so that the light shielding part of M11 is arranged.
1 may be shifted within the reticle plane R. In this state, the light flux L1 and the light flux L2 are on the imaging surface of the CCD camera 3.
An image of the target T is formed by only one of them.

From the output of the CCD camera 3 at this time, the formation position of the image of the target T on the image pickup surface is stored.
Further, while the target T is arranged at the same position, the output of the CCD camera 3 is referred to while the other of the light flux L1 and the light flux L2 is shielded, and the formation position of the target T on the imaging surface is the same as the stored formation position. The positions of the diffractive optical element G11 and the CCD camera 3 are adjusted so that

By doing so, alignment can be easily performed. (Modification of First Embodiment) FIG. 2 is a view showing a modification of the shearing interferometer of the first embodiment. In the above description,
At the position where the diffractive optical element G11 is arranged, the reticle surface R
Although it is on the light source side (see FIG. 1), in this modification,
As shown in FIG. 2, the position of the diffractive optical element is changed to the reticle surface R.
It is on the projection optical system PL side. Reference numeral G11 ′ in FIG. 2 denotes the diffractive optical element of this modification.

The mask M11 'for cutting off the extra light generated in the diffractive optical element G11' may be arranged near the wafer surface W as shown in FIG. In this case as well, the CCD camera 3 is arranged at a position conjugate with (the diffraction surface of) the diffractive optical element G11 'with respect to the projection optical system PL. [Second Embodiment] A second embodiment of the present invention will be described with reference to FIG.

Also in this embodiment, as in the first embodiment, a shearing interferometer of the present invention of a type for measuring a transmitted wavefront of a test object and a shearing interference method thereof will be described. It should be noted that here, only the differences from the first embodiment will be described, and description of the other parts will be omitted.
FIG. 3A is a configuration diagram of the shearing interferometer of the present embodiment.

The difference from the shearing interferometer of the first embodiment shown in FIG. 1 is that the diffractive optical element as the splitting optical element is not limited to the reticle surface R side of the projection optical system PL,
It is also arranged on the wafer surface W side. This is shown in FIG.
In the configuration of the conventional shearing interferometer shown in (a), a diffractive optical element as a split optical element is used as a projection optical system P.
It is also a configuration in which it is additionally arranged on the reticle surface R side of L.

That is, in the shearing interferometer of this embodiment, diffractive optical elements G21 and G22 are arranged on the reticle surface R side and the wafer surface W side, respectively. Diffractive optical element G2
Similarly to the diffractive optical element G11 of the first embodiment, 1 produces two light beams L1 and L2 whose wavefronts are deviated from each other.
For example, the 0th-order diffracted light and the 1st-order diffracted light generated in the diffractive optical element G21 are used as the light flux L1 and the light flux L2, respectively.

On the other hand, the diffractive optical element G22 integrates the two light fluxes L1 and L2 emitted from the projection optical system PL with a shift amount equivalent to that of the diffractive optical element G21 to form one light flux (reverse shear). It is a thing. Such a diffractive optical element G22 is designed in advance according to the diffraction pattern of the diffractive optical element G11, the magnification of the projection optical system PL, the wavelength used, and the like.

In this shearing interferometer, the diffractive optical element G21, the projection optical system PL, and the diffractive optical element G2.
Due to the interaction of 2, the noise wavefront superposed on the wavefront of the light flux L1 and the noise wavefront superposed on the wavefront of the light flux L2 just overlap, and the phase difference between the noise wavefronts becomes almost zero. Therefore, the interference fringes formed by the light beams L1 and L2 at that position are affected by the transmitted wavefront (signal wavefront) corresponding to the aberration of the projection optical system PL, but are not affected by the noise wavefront.

Further, in the shearing interferometer of this embodiment, if the diffractive optical element G22 (diffractive surface thereof) is arranged at a position conjugate with the diffractive optical element G21 (diffractive surface) of the projection optical system PL, the luminous flux The converging point of L1 and the converging point of the light beam L2 coincide with each other on the wafer surface W, and the wavefront of the light beam L1 and the wavefront of the light beam L2 can travel in the same direction. Can be Generally, the closer to one color, that is, the larger the fringe spacing of the interference fringes, the higher the fringe detection accuracy of the CCD camera 3, and thus the higher the measurement accuracy.

At this time, since the wavefront of the light beam L1 and the wavefront of the light beam L2 after exiting the diffractive optical element G22 always proceed while overlapping, the degree of freedom is given to the position of the CCD camera 3 in the optical axis direction. Therefore, the image pickup surface of the CCD camera 3 can be arranged, for example, at a position conjugate with the pupil of the projection optical system PL to facilitate the evaluation of the projection optical system PL based on the observed interference fringes.

Also in this embodiment, it is preferable to use a mask in order to cut off excess light.
In this embodiment, since two diffractive optical elements are used,
It is preferable that two masks are also used. That is, as shown in FIG. 3A, regarding the extra light generated by the diffractive optical element G21, the mask M21 arranged on the reticle surface R cuts the extra light generated by the diffractive optical element G22. Is a mask M arranged on the wafer surface W.
22 cuts. The diffractive optical element G22 described above is used.
Since the light flux L1 and the light flux L2 emitted from the light are focused on the same point, only one opening is required for the mask M22.

Next, in the present embodiment, an alignment method for ensuring the above-described conjugate relationship (diffractive optical element G21 and diffractive optical element G22) will be described. Figure 3
(B) is a figure explaining the alignment method of the shearing interferometer of this embodiment. This alignment method also
The position adjustment target is the diffractive optical element G21 or the diffractive optical element G.
Only 22 is the same as the alignment method of the shearing interferometer of the first embodiment.

That is, also in the alignment of this embodiment, first, in the measurement light beam L incident on the diffractive optical element G21, the target T which partially blocks the measurement light beam L is arranged, and one of the light beams L1 and L2 is arranged. To shield the light, one of the openings of the mask M21 is shielded. The target T is preferably arranged at a position as close to the diffractive optical element G21 as possible.

Further, in order to shield one of the light flux L1 and the light flux L2, the opening portion of the mask M21 is arranged only at one focus point of the light flux L1 and the light flux L2, and the mask is provided at the other focus point. The mask M2 is arranged so that the light shielding part of M21 is arranged.
1 may be shifted within the reticle plane R. In this state, the light flux L1 and the light flux L2 are on the imaging surface of the CCD camera 3.
An image of the target T is formed by only one of them.

Therefore, from the output of the CCD camera 3 at this time, the formation position of the image of the target T on the imaging surface is stored. Further, while the target T is arranged at the same position, the other of the light flux L1 and the light flux L2 is shielded,
By referring to the output of the CCD camera 3, the positions of the diffractive optical element G21 and the diffractive optical element G22 are adjusted so that the formation position of the target T on the imaging surface becomes the same as the stored formation position.

FIG. 4 shows a diffractive optical element G21 and a diffractive optical element G2 in the shearing interferometer of this embodiment.
2 is a diagram showing a case where the image pickup surface of the CCD camera 3 and the diffractive optical element G21 (diffraction surface thereof) are set in a conjugate relationship instead of being non-conjugated. Even if the diffractive optical element G21 and the diffractive optical element G22 are not set in a conjugate relationship,
In this way, the imaging surface of the CCD camera 3 and the diffractive optical element G2
1 (diffraction surface) is set in a conjugate relationship with the light flux L1
On the imaging surface of the CCD camera 3 and the noise wavefront superimposed on the wavefront of the light flux L2. Therefore, the same effect as that of the first embodiment can be obtained.

In the alignment at this time, the diffractive optical element G21 or the CCD camera 3 may be the object of position adjustment in the above-mentioned alignment method (see FIG. 3B). (Modification of Second Embodiment) FIG. 5 is a view showing a modification of the shearing interferometer of the second embodiment. It should be noted that here, only differences from the shearing interferometer of the second embodiment will be described, and description of other parts will be omitted. Further, it is possible to modify the shearing interferometer of the first embodiment as in the modification described below.

In the second embodiment described above, the direction of deviation between the wavefront of the light beam L1 and the wavefront of the light beam L2 is the "lateral direction" (object height direction), but in the present modification, the thick arrow in FIG. As shown in, the “wavefront direction” (direction along the wavefront). Therefore, the diffractive optical element G21 ′ and the diffractive optical element G22 ′ are inserted between the diffractive optical element G21 and the reticle surface R, and between the diffractive optical element G22 and the wafer surface W, respectively.

The diffractive optical element G21 'is a diffractive optical element G
It is designed in advance so that the light-converging points of the light flux L1 and the light flux L2 emitted from the light source 21 coincide with each other. Diffractive optical element G22 '
Is designed in advance so that the focal points of the light flux L1 and the light flux L2 emitted from the diffractive optical element G22 coincide with each other. Since the light converging points are the same, the masking 31 in the shearing interferometer according to the present embodiment may have only one opening as shown in FIG.

[Supplement to First and Second Embodiments]
In each of the above embodiments, if the interference fringes are detected while shifting at least one of the diffractive optical elements in the same direction as the wavefront division direction (that is, if the phase shift interference method is applied), The measurement accuracy can be further improved. Further, for example, in the inspection of an object using a special wavelength (short wavelength) such as EUVL, it is difficult to use a refraction member as an optical element of a shearing interferometer (because a refraction member that transmits a special wavelength is used). Is difficult to obtain.), The diffractive optical element is used as the splitting optical element in each of the above-described embodiments, but for an object that can use a refracting member, a lens is used as part or all of the splitting optical element. You may.

In each of the above embodiments, the light fluxes L1 and L
Although the direction of the division of 2 is the “lateral direction” or the “wavefront direction”, it may be the optical axis direction (longitudinal direction). [Third Embodiment] A third embodiment of the present invention will be described with reference to FIGS. 6, 7, and 8. In this embodiment, a shearing interferometer of the present invention of a type that measures a wavefront of reflected light from a test object (a reflected wavefront of the test surface 4) and a shearing interfering method thereof will be described.

FIG. 6A is a block diagram of the shearing interferometer of this embodiment. FIG. 6B is a diagram showing the optical paths R1 and R2 of the light fluxes L1 and L2 of the shearing interferometer. The shearing interferometer includes a light source 5 such as a laser for emitting a measurement light beam L to be incident on the surface 4 to be inspected, and two light beams whose wavefronts are deviated by dividing the measurement light beam L before entering the surface to be inspected 4. A splitting optical system 34 for generating L1 and L2 and projecting them onto the surface 4 to be inspected with their wavefronts displaced, and a light beam L1 returning to the splitting optical system 34 after being reflected by the surface 4 to be inspected.
A CCD camera 3 for detecting an interference fringe due to L2 is provided.

Reference numeral 6 is a beam expander for converting the measurement light beam L emitted from the light source 5 into a parallel light beam, and reference numeral H.
M33 is a half mirror that guides the light beams L1 and L2 that have reciprocated through the splitting optical system 34 toward the CCD camera 3, and reference numeral 7 is
1 shows an image forming optical system for forming an image of a light beam (light beams L1 and L2) incident on a CCD camera 3. Here, the surface to be inspected 4 and the imaging surface of the CCD camera 3 are the split optical system 34 and the half mirror H.
There is a conjugate relationship via the M33 and the imaging optical system 7. In addition,
Also in other embodiments described later, the surface to be inspected 4 and the imaging surface of the CCD camera 3 are in a conjugate relationship with each other via an optical system arranged therebetween.

First, the splitting optical system 34 includes two beam splitters P34-1, P34-2 and a mirror M34-.
It consists of 1, 34-2. The measurement light beam L is split by the beam splitter P34-2 into a transmitted light beam and a reflected light beam (hereinafter, the transmitted light beam is referred to as a light beam L1 and the reflected light beam is referred to as a light beam L2). The light flux L1 is reflected by the mirror M34-1 and is incident on the beam splitter P34-1, and the light flux L2 is reflected by the mirror M34-2 and is beam splitter P34-.
Incident on 1.

The beam splitter P34-1 receives the light beam L1.
And transmits the light beam to the surface 4 to be inspected, and reflects the light beam L2 to project it on the surface 4 to be inspected. Further, the positions of the mirror M34-2 and the beam splitter P34-1 are adjusted so that the light flux L1 and the light flux L2 are incident on the surface 4 to be inspected in a state where their wavefronts are deviated from each other (in a state where the optical axis is shifted). Has been done.

Further, light beams L1 and L2 projected from the splitting optical system 34 to the surface 4 to be inspected and reflected on the surface 4 to be inspected.
Travels in the opposite direction through the splitting optical system 34, and then is deflected in the direction of the CCD camera 3 by the half mirror HM33, and C
Interference fringes are formed on the image pickup surface of the CD camera 3.

In the shearing interferometry of this embodiment, the output of the CCD camera 3 and the measured light beam L to the light beam L1,
The reflected wavefront corresponding to the unevenness of the surface 4 to be inspected is calculated based on the shearing direction to L2 and the shearing amount. The shear amount and the shear direction can be obtained from the design data of the shearing interferometer and the data actually measured by the shearing interferometer. here,
Also in the shearing interferometer having the above configuration, the measurement light flux L
On the wavefront of the light source side (beam expander 6, light source 5)
The noise wavefront due to the disturbance or the aberration is superimposed. Therefore, the same noise wavefront is also superposed on the wavefront of the light flux L1 and the wavefront of the light flux L2 obtained by dividing the measurement light flux L.

However, since the light flux L1 following the optical path R1 and the light flux L2 following the optical path R2 shown in FIG. 6B reciprocate in a specific optical path in the split optical system 34, the deviation of their wavefronts ( (Shift of the optical axis) is absorbed, and the wavefronts overlap after the round trip (the optical path R1 includes the half mirror HM33 → beam splitter P34-2 → mirror M34-1 → beam splitter P34-1 → test surface 4 → beam splitter). P
34-1 → mirror M34-1 → beam splitter P34
-2 → the optical path of the half mirror HM33, and the optical path R2
Is a half mirror HM33 → beam splitter P34-
2 → mirror M34-2 → beam splitter P34-1 →
Surface 4 to be inspected → beam splitter P34-1 → mirror M34
-2-> beam splitter P34-2-> half mirror HM
33 optical paths. ).

Therefore, on the image pickup surface of the CCD camera 3,
A noise wavefront superimposed on the wavefront of the light flux L1 and the light flux L
The noise wavefront superposed on the wavefront of No. 2 overlaps with each other and does not cause interference fringes. On the other hand, the light flux L1 following the optical path R1 and the light flux L2 following the optical path R2 are
Since the wavefronts are shifted from each other at the time of incidence on the surface to be inspected 4, the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface to be inspected 4 and the wavefront of the light beam L2 are superimposed on the wavefront of the light beam L1. The signal wavefront that is generated is the wavefront of the light beam L1 and the light beam L2.
When they overlap with the wave front of, they shift from each other.

Therefore, on the image pickup surface of the CCD camera 3,
The reflected wavefront (signal wavefront), which is superimposed on the wavefront of the light beam L1 and corresponds to the unevenness of the surface to be inspected 4, and the signal wavefront which is superimposed on the wavefront of the light beam L2, do not overlap with each other and cause interference fringes. Let As a result, the interference fringes formed by the light flux L1 and the light flux L2 on the imaging surface of the CCD camera 3 are affected by the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface to be inspected 4, while the noise wavefront is affected. Do not receive Therefore, based on the output of the CCD camera 3, it is possible to perform the measurement without being affected by the disturbance or aberration on the light source side.

In the present embodiment, the beam splitter P34-1 or the beam splitter P34- is used in order to increase the light amount of the light beam L1 passing through the optical path R1 and the light beam L2 passing through the optical path R2 to improve the detection accuracy of the interference fringes. A polarizing beam splitter is used for 2, and a polarizing plate 35 is inserted in front of the CCD camera 3 (for example, between the imaging optical system 7 and the half mirror HM33).

For example, when a polarized beam splitter is used as the beam splitter P34-1, the P-polarized light in the light beam L1 transmitted through the beam splitter P34-2 is
The S-polarized light of the light beam L2 reflected by the beam splitter P34-2 is reliably returned in the direction of the optical path R2 after being reflected by the surface to be inspected 4, and is reliably returned in the direction of the optical path R2 after being reflected by the surface to be inspected 4.

In order to further improve the detection accuracy, the beam splitter P34-1 and the beam splitter P34-
It is preferred that polarization beam splitters are used for both. By doing so, the P-polarized component of the measurement light beam L is surely set as the light beam L1 passing through the optical path R1, and the S-polarized component of the measurement light beam L is surely set as the light beam L2 passing through the optical path R2. Therefore, the loss of light amount can be suppressed. If two polarization beam splitters are used together, the deterioration of the extinction ratio of each polarization beam splitter will be compensated for each other.

Further, by applying a known phase shift interferometry method to the above shearing interference measurement, the measurement accuracy can be further improved. To perform the phase shift in this shearing interferometer shown in FIG. 6A, for example, one or both of the mirror M34-1 and the mirror M34-2 may be slightly moved. The moving direction is a direction in which the difference between the optical path lengths R1 and R2 of the light flux L1 and the light flux L2 changes (for example, FIG.
(A) The direction indicated by the middle arrow). During this phase shift, the output data of the CCD camera 3 (brightness distribution data of interference fringes) is sampled multiple times. The calculation method is, for example, as follows.

Luminance distribution I of interference fringes occurring on the imaging surface
Is I = I ₀ + A cos [T−T (s) + 2δ] + ΣB _i cos (N
_i + δ). However, I ₀ is a DC component of the luminance distribution of the interference fringes, A is the amplitude of the light beams L1 and L2, B _i is the amplitude of various noises, i is the number of each interference fringe due to various noises, and N _i is the interference fringe due to each noise. , Δ is the phase modulation by the phase shift of each interference fringe, T is the shape (unit: phase) of the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface 4 to be measured, and T (s) is from the measurement light beam L. This is a change in the shape of the wavefront (unit: phase) due to shearing by the light flux L1 or the light flux L2. Σf (i)
Is the sum of f for each i.

For example, as the phase shift, the eight brightness distribution data I ₁ , ... While gradually shifting the phase by π / 2.
When I ₈ is sampled, each luminance distribution data I ₁ , ...
..I ₈ is expressed as follows. I ₁ = I ₀ + Acos [T−T (s)] + ΣB _i cos (N _i ) I ₂ = I ₀ + Acos [T−T (s) + π / 2] + ΣB _i cos
(N _i + π / 4) I ₃ = I ₀ + A cos [T−T (s) + π] + ΣB _i cos (N _i
+ Π / 2) I ₄ = I ₀ + Acos [TT (s) + 3π / 2] + ΣB _i co
s (N _i + 3π / 4) I ₅ = I ₀ + A cos [T−T (s) + 2π] + ΣB _i cos
(N _i + π) I ₆ = I ₀ + A cos [TT (s) + π / 2] + ΣB _i cos
(N _i + 5π / 4) I ₇ = I ₀ + A cos [T−T (s) + π] + ΣB _i cos (N _i
+ 3π / 2) I ₈ = I ₀ + Acos [TT (s) + 3π / 2] + ΣB _i co
s (N _i + 7π / 4) Therefore, for example, I ₁ + I ₅ = 2I ₀ + 2Acos [T−T (s)] I ₂ + I ₆ = 2I ₀ + 2Acos [T−T (s) + π / 2] I ₃ + I _{7 = 2I 0 + 2Acos [T-} T (s) + π] I 4 + I 8 = 2I 0 + 2Acos luminance distribution data I ₁ as [T-T (s) + 3π / 2], by subtraction calculation of · · · I ₈ For example, canceling the influence of various noises,
The phase distribution (TT (s)) of the interference fringes due to 1 and L2 can be accurately obtained.

Then, if the value of T (s) is obtained from the shearing interferometer, it is possible to obtain only the shape T of the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface to be inspected 4. (Application Example and Modification Example of Third Embodiment) FIG. 7 is a diagram showing an application example of the shearing interferometer of the present embodiment. In the shearing interferometer shown in FIG. 6, the object to be measured is the flat test surface 4, but as shown by A in FIG.
Can be used to measure the curved test surface 4 ′. Further, by using the folded reflection surface 39 as shown by B in FIG. 7, not only the reflected wavefront of the surface to be inspected 4 but also the transmitted wavefront of the object to be inspected (projection optical system PL or the like) 4 ″ can be measured. .

FIG. 8 is a diagram showing a modification of the shearing interferometer of this embodiment. In the shearing interferometer shown in FIG. 6, when a half mirror is used as the beam splitter P34-2, it can be modified as shown in FIG. In the configuration shown in FIG. 8, the splitting optical system 34 ′ is a half mirror HM instead of the one beam splitter P 34-2.
I am using 33.

In this case, the measurement accuracy is lower than in the case of using the polarization beam splitter, but the half mirror HM
Since 33 can also be used, the number of parts of the shearing interferometer can be suppressed.

[Fourth Embodiment] A fourth embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the wavefront of the return light from the test object (the reflected wavefront of the test surface 4)
The shearing interferometer of the present invention of the type that measures In addition, here, only differences from the shearing interferometer of the third embodiment will be described, and description of other parts will be omitted.

FIG. 9A is a block diagram of the shearing interferometer of this embodiment. FIG. 9B is a diagram showing the optical paths R1 and R2 of the light fluxes L1 and L2 of the shearing interferometer.
The splitting optical system 44 of this shearing interferometer is composed of a single beam splitter P44 and a single mirror M44. The reflecting surface of the mirror M44 is the beam splitter P.
It is arranged parallel to the reflective / transmissive surface of 44.

The measurement light flux L is transmitted through the beam splitter P44 and reflected light flux (hereinafter, the transmitted light flux L1,
The reflected light flux is L2. ) Is divided into. The light flux L2 is
The light is projected onto the surface to be inspected 4 as it is. The light flux L1 is reflected by the mirror M
After being reflected by 44, it again enters the beam splitter P44, passes through the beam splitter P44, and is projected onto the surface 4 to be inspected.

Further, the positions of the mirror M44 and the beam splitter P44 are such that the light beams L1 and L2 have wavefronts displaced from each other (in a state where the optical axis is shifted).
Is adjusted to be incident on. In addition, the splitting optical system 44
The light beams L1 and L2 projected from the test surface 4 to the test surface 4 and reflected on the test surface 4 travel in the opposite direction through the splitting optical system 44, and then are deflected in the direction of the CCD camera 3 by the half mirror HM33, and the CCD Interference fringes are formed on the imaging surface of the camera 3.

Also in this shearing interferometer, FIG.
Since the light flux L1 following the optical path R1 and the light flux L2 following the optical path R2 shown in (b) reciprocate in a specific optical path in the split optical system 34, the mutual wavefront deviation (shift of the optical axis) is absorbed. After the round trip, the wavefronts overlap each other (the optical path R1 has a beam splitter P44 → mirror M44 → beam splitter P44 → inspected surface 4 → beam splitter P4).
4 → mirror M44 → beam splitter P44 → half mirror HM33, and optical path R2 is an optical path of beam splitter P44 → inspected surface 4 → beam splitter P44 → half mirror HM33. ).

As a result, for the same reason as described in the third embodiment, the light flux L is formed on the image pickup surface of the CCD camera 3.
The interference fringes formed by 1 and the light flux L2 are affected by the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface to be inspected 4, while noise caused by disturbance or aberration on the light source side (beam expander 6, light source 5). Not affected by wavefront. Therefore, CC
Based on the output of the D camera 3, it is possible to perform the measurement without being affected by the disturbance or aberration on the light source side.

Also in this embodiment, a polarization beam splitter is used as the beam splitter P44 in order to increase the light amount of the light flux L1 passing through the optical path R1 and the light flux L2 passing through the optical path R2 to improve the detection accuracy of interference fringes. , And C
The polarizing plate 35 is inserted in the front stage of the CD camera 3 (for example, between the imaging optical system 7 and the half mirror HM33). By doing so, the P-polarized component of the measurement light beam L is surely made into the light beam L1 that passes through the optical path R1, and S of the measurement light beam L is S.
Since the polarized light component can be reliably the light flux L2 passing through the optical path R2, the loss of the light amount can be suppressed.

Furthermore, if a known phase shift interferometry method (for example, the method described in the third embodiment) is applied to the shearing interference measurement of this embodiment, the measurement accuracy can be further improved. To perform a phase shift in this shearing interferometer shown in FIG. 9A, for example,
One or both of the mirror M44 and the beam splitter P44 may be slightly moved. The moving directions are the luminous fluxes L1 and L2.
This is the direction in which the difference between the optical path lengths R1 and R2 of is changed.

(Modification and Application of Fourth Embodiment) When the beam splitter P44 is a polarization beam splitter, the shearing interferometer shown in FIG.
Alternatively, the phase shift may be performed by another method after being modified to 0 (the phase shift method described below is the same for the third embodiment, the fifth embodiment, and the sixth embodiment. Applicable.).

In the shearing interferometer shown in FIG. 10, a quarter-wave plate 45 is inserted on the incident side of the polarizing plate 35, and the polarizing plate 35 is rotatable about the optical axis. The principal axis of the quarter-wave plate 45 is set to be 45 ° with respect to the P or S polarization direction of the light fluxes L1 and L2. The light beam L1 (P linearly polarized light) and the light beam L2 (S linearly polarized light) incident on the quarter-wave plate 45 are converted into circularly polarized light whose directions are opposite to each other.

At this time, if the polarizing plate 35 is rotated, the phases of the light flux L1 and the light flux L2 change. Therefore, according to this shearing interferometer, the phase shift is caused by the polarization plate 3
This can be done by turning 5 Further, when this phase shift is applied, it is not necessary to move the mirror M44 and the beam splitter P44 of the split optical system 44 relative to each other, so that the mirror M44 and the beam splitter P44 are fixed as shown by the dotted line in FIG. A single split optical element 44 ′ may be used instead of split optical system 44.

The shearing interferometer shown in FIG. 9 or 10 can also measure the curved surface 4'to be measured by using the wavefront conversion element 38 as shown by A in FIG. Further, if the folded reflection surface 39 is used as shown by B in FIG. 7, not only the reflected wavefront of the surface to be inspected 4 but also the transmitted wavefront of the object to be inspected (projection optical system PL or the like) 4 ″ can be measured. [Fifth Embodiment] A fifth embodiment of the present invention will be described with reference to FIG.

The shearing interferometer of the third embodiment and the shearing interferometer of the fourth embodiment are of a type in which the shear direction is the lateral direction, but in this embodiment, the shear direction is the radial direction will be described. To do. It should be noted that here, only the differences from the shearing interferometer shown in FIG. 8 will be described, and description of the other parts will be omitted.

FIG. 11 is a block diagram of the shearing interferometer of this embodiment. Splitting optical system 5 of this shearing interferometer
Reference numeral 4 denotes a beam splitter P34-1, a beam splitter (half mirror in this case) HM33, and a mirror M34-.
1, a mirror M34-2, and beam expanders R54-1 and R54-2 having different magnifications.

The measurement light beam L is split by the half mirror HM33 into a transmitted light beam and a reflected light beam (hereinafter, the transmitted light beam is referred to as a light beam L1 and the reflected light beam is referred to as a light beam L2). Luminous flux L1
Is reflected by the mirror M34-1 and then, via the beam expander R54-1, a beam splitter P34-1.
And is reflected by the half mirror HM33, then enters the mirror M34-2 via the beam expander R54-2, is reflected by the mirror M34-2, and enters the beam splitter P34-1. To do.

The beam splitter P34-1 receives the light beam L1.
And transmits the light beam to the surface 4 to be inspected, and reflects the light beam L2 to project it on the surface 4 to be inspected. In the split optical system 54, the optical axes of the light beam L1 and the light beam L2 incident on the surface 4 to be inspected coincide with each other, but the beam expander R54-
Since the magnifications of 1 and R54-2 are different, the light flux diameters are deviated.

The light flux L1 that reciprocates through the beam expander R54-1 and the light flux L2 that reciprocates through the beam expander R54-2 absorb the mutual deviation of the wavefronts (deviation of the luminous flux diameter), and the reciprocation thereof is performed. Later. The wavefronts of each overlap. As a result, for the same reason as described in the third embodiment, the light flux L is formed on the image pickup surface of the CCD camera 3.
The interference fringes formed by 1 and the light flux L2 are affected by the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface to be inspected 4, while noise caused by disturbance or aberration on the light source side (beam expander 6, light source 5). Not affected by wavefront. Therefore, CC
Based on the output of the D camera 3, it is possible to perform the measurement without being affected by the disturbance or aberration on the light source side.

[Sixth Embodiment] A sixth embodiment of the present invention will be described with reference to FIG. In the shearing interferometer of the third embodiment and the shearing interferometer of the fourth embodiment, the method of shearing shifts the optical axis, but a shearing interferometer of the type that tilts the optical axis will be described.

Here, only differences from the shearing interferometer shown in FIG. 8 will be described, and description of other parts will be omitted. FIG. 12 is a configuration diagram of the shearing interferometer of the present embodiment. The splitting optical system 64 of this shearing interferometer is similar to the splitting optical system 34 'shown in FIG. 8 in that it is a beam splitter (here, a half mirror) HM.
64, beam splitter (here, half mirror) H
An M33, a mirror M34-1, and a mirror M34-2 are arranged.

However, the mirror M34-2 and the half mirror H
The posture of M64 is adjusted so that the light flux L1 and the light flux L2 are incident on the surface 4 to be inspected with their optical axes inclined by θ. Further, in the present embodiment, it is not necessary to use the polarization beam splitter at the position of the half mirror HM64 (note that in the case of the shearing interferometer of FIG.
A polarization beam splitter was used to separate 1 and the light flux L2. ). Along with this, the polarizing plate 35 shown in FIG.
Is unnecessary.

The light beam L1 and the light beam L2 that have entered the surface 4 to be inspected respectively return through different optical paths in the split optical system 64 while keeping their optical axes inclined, and enter the imaging optical system 7 and the CCD camera 3 in order. To do. In the shearing interferometer of this embodiment,
The inclinations of the optical axes of the light beams L1 and L2 at the time of incidence on the surface to be inspected 4 are not absorbed even if they reciprocate through the split optical system 64, but on the imaging surface, the noise wavefront superimposed on the wavefront of the light beam L1. And the noise wavefront superposed on the wavefront of the light flux L2 just overlap, and the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface to be inspected 4 superposed on the light flux L1 and the superposed on the light flux L2. It deviates from the signal wavefront.

Therefore, these light fluxes L are formed on the image pickup surface.
The interference fringe formed by 1 and the light flux L2 is affected by the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface 4 to be detected, but is not affected by the noise wavefront. Therefore, based on the output of the CCD camera 3, it is possible to perform the measurement that is not affected by the disturbance or aberration on the light source side. Further, in this shearing interferometer, it is desirable that the mask M61 be arranged on the focal plane of the imaging optical system 7.

The mask M61 is provided with two openings, and the distance d between the two openings is set to d = 2fθ (f is the focal length of the imaging optical system 7). Further, the direction in which the two openings are arranged is set so as to correspond to the above-described inclination direction of the optical axis. In this way, the light flux L1 and the light flux L2 described above individually pass through one and the other of the two openings to form interference fringes on the imaging surface of the CCD camera 3. Therefore, the interference fringes formed by the light flux L1 and the light flux L2 are detected with high accuracy without being affected by other light.

[Supplement of Each Embodiment] In each of the above embodiments, in order to accurately evaluate the projection optical system PL or the surface 4 to be inspected, the interference fringes are detected at least after changing the direction of wavefront division. It needs to be done once again. The first
In the embodiment or the second embodiment, in order to change the division direction, the division optical element (diffractive optical element) and the mask (mask having two openings) are arranged around the optical axis, respectively. It only has to be rotated by an angle.

[Seventh Embodiment] A seventh embodiment of the present invention will be described with reference to FIG. In this embodiment, a projection exposure apparatus manufactured using each of the above embodiments will be described. FIG. 13 is a schematic configuration diagram of the projection exposure apparatus of this embodiment.

All or a part of the optical system PL of the projection optical system PL mounted in this projection exposure apparatus is inspected by the interferometric measurement of any of the above-described embodiments at the time of manufacturing. Then, at least one surface of the projection optical system PL, and / or
Alternatively, it is assumed that any part of the projection exposure apparatus is adjusted according to the measurement result. According to each of the above-described embodiments, since the measurement is performed with high accuracy, the projection lens and / or the projection exposure apparatus have high performance even if the adjustment method is the same as the conventional method.

The projection exposure apparatus includes at least the wafer stage 108 and the light source section 101 for supplying light.
And a projection optical system PL. Here, the wafer stage 108 can place the wafer w coated with the photosensitive agent on the surface 108a. In addition, the stage control system 107
The position of the wafer stage 108 is controlled. Further, the reticle r and the wafer w are arranged on the object plane P1 and the image plane P2 of the projection optical system PL, respectively. Furthermore, the projection optical system PL
Has an alignment optical system applied to a scan type projection exposure apparatus. Further, the illumination optical system 102 includes an alignment optical system 103 for adjusting the relative position between the reticle r and the wafer w. The reticle r is for projecting an image of the pattern of the reticle r onto the wafer w, and the surface 108 of the wafer stage 108.
Reticle stage 10 capable of translational movement relative to a
Placed on the 5th. Then, the reticle exchange system 104 exchanges and carries the reticle r set on the reticle stage 105. The reticle exchange system 104 also includes a stage driver (not shown) for moving the reticle stage 105 in parallel with the surface 108a of the wafer stage 108. In addition, the main control unit 109 controls the series of processes from alignment to exposure.

[0095]

As described above, according to the present invention, a shearing interferometer and a shearing interferometer capable of performing measurement without being affected by disturbance or aberration on the light source side are realized. Further, according to the present invention, a high-performance projection optical system manufacturing method, a high-performance projection optical system, and a high-performance projection exposure apparatus are realized by applying the shearing interferometry method.

[Brief description of drawings]

FIG. 1A is a configuration diagram of a shearing interferometer of a first embodiment, and FIG. 1B is a diagram illustrating an alignment method of the shearing interferometer of the first embodiment.

FIG. 2 is a diagram showing a modified example of the shearing interferometer of the first embodiment.

3A is a configuration diagram of a shearing interferometer of the second embodiment, and FIG. 3B is a diagram illustrating an alignment method of the shearing interferometer of the second embodiment.

FIG. 4 shows a CC in the shearing interferometer of the second embodiment.
It is a figure which shows what the imaging surface of D camera 3 and the diffractive optical element G21 have a conjugate relationship.

FIG. 5 is a diagram showing a modified example of the shearing interferometer of the second embodiment.

FIG. 6A is a configuration diagram of a shearing interferometer according to a third embodiment. FIG. 6B is a diagram showing optical paths R1 and R2 of the light fluxes L1 and L2 of the shearing interferometer.

FIG. 7 is a diagram showing an application example of the shearing interferometer of the third embodiment.

FIG. 8 is a diagram showing a modified example of the shearing interferometer of the third embodiment.

FIG. 9A is a configuration diagram of a shearing interferometer according to a fourth embodiment. (B) is the luminous flux L of this shearing interferometer
It is a figure which shows the optical paths R1 and R2 of 1 and L2.

FIG. 10 is a diagram showing a modified example of the shearing interferometer of the fourth embodiment.

FIG. 11 is a configuration diagram of a shearing interferometer of a fifth embodiment.

FIG. 12 is a configuration diagram of a shearing interferometer of a sixth embodiment.

FIG. 13 is a schematic configuration diagram of a projection exposure apparatus according to a seventh embodiment.

FIG. 14 is a diagram showing a conventional shearing interferometer.

[Explanation of symbols]

L measurement luminous flux L1, L2 luminous flux G11, G11 ', G21, G22, G21', G2
2 ′ Diffractive optical element M11, M11 ′, M21, M22, M31 Mask 2 Diffractive optical element 3 CCD camera 4, 4, 4 ′, 4 ″ Test surface 5 Light source 6, R54-1, R54-2 Beam expander 7 connection Image optical system HM33, HM64 Half mirror 34, 34 ', 44, 54, 64 Split optical system P34-1, P34-2, P44 Beam splitter M34-1, M34-2, M44 Mirror M61 Mask 35 Polarizing plate 38 Wavefront conversion Element 39 Folding reflection surface 44 'Dividing optical element 45 Quarter wave plate R Reticle surface W Wafer surface PL Projection optical system 101 Light source section 102 Illumination optical system 103 Alignment optical system 104 Reticle exchange system 105 Reticle stage 107 Stage control system 108 Wafer Stage 109 Main controller w Wafer r Reticle

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F064 AA15 CC01 DD08 EE08 GG21                       GG22 GG33 GG38 GG49 HH03                       HH08 LL13                 2G059 BB08 BB10 BB16 DD13 EE02                       EE09 FF01 JJ05 JJ11 JJ13                       JJ19 JJ20 JJ22 KK04 MM09                       NN06                 2G086 HH06                 5F046 BA04 CB21 DA12

Claims (16)

[Claims] 1. A measurement light beam emitted from a light source is divided to generate two light beams whose wavefronts are deviated from each other, and the two light beams are projected onto an object to be inspected with the wavefronts deviated from each other. A method for measuring shearing interference, which comprises detecting an interference fringe that occurs at a position where the wavefronts of the two light fluxes that have passed through are overlapped. 2. The shearing interferometry method according to claim 1, wherein a phase shift interferometry method for detecting the interference fringes a plurality of times while shifting the phases of the two light fluxes is applied. . 3. A measurement light flux emitted from a light source is disposed in the optical path of the measurement light flux, and the measurement light flux is split to generate two light fluxes whose wavefronts are deviated from each other. A shearing interferometer, comprising: a splitting optical system for projecting light onto an inspection object; and a detector arranged at a position where the wavefronts of the two light beams transmitted through the inspection object overlap each other. 4. The shearing interferometer according to claim 3, wherein the detector is arranged at a position conjugate with the division plane of the division optical system. 5. The shearing interferometry method according to claim 3, wherein in the optical paths of the two light fluxes that pass through the test object and enter the detector, the two light fluxes are re-divided and the two light fluxes are separated. A shearing interferometer characterized in that a splitting optical system for superposing a wave front on the detector is arranged. 6. The shearing interferometer according to claim 5, wherein the splitting optical system that splits the measurement light flux and the splitting optical system that splits the two light fluxes are in a conjugate relationship. Interferometer. 7. The shearing interferometer according to any one of claims 3 to 6, wherein a mask that cuts light other than the two light beams whose wavefronts overlap on the detector in an optical path of the two light beams. A shearing interferometer characterized in that 8. The shearing interferometer according to claim 3, wherein the splitting optical system includes a diffractive optical element. 9. A measurement light flux emitted from a light source is arranged in the optical path of the measurement light flux, and the measurement light flux is split to generate two light fluxes whose wavefronts are deviated from each other. A shearing interferometer, comprising: a splitting optical system for projecting light onto an inspection object; and a detector arranged at a position where the wavefronts of the two light beams returned from the inspection object to the splitting optical system overlap. 10. The shearing interferometer according to claim 9, wherein the splitting optical system splits the measurement light flux into two light fluxes, a transmitted light flux and a reflected light flux, and the beam splitter splits the light flux. A shearing interferometer, comprising: a deflection optical system that projects the two light beams onto a test object in a state where their wavefronts are deviated from each other. 11. The shearing interferometer according to claim 10, wherein a polarization beam splitter is used for the beam splitter, and a polarization beam splitter is used for an optical path of the two light fluxes between the split optical system and the detector. A shearing interferometer characterized in that a plate is arranged. 12. The shearing interferometer according to claim 9 or 10, wherein the detector is arranged at a position conjugate with the surface to be inspected of the object to be inspected. . 13. The shearing interferometer according to claim 12, wherein a mask that cuts light other than the two light beams whose wave fronts overlap on the detector is arranged in the optical path of the two light beams. Shearing interferometer. 14. A method of manufacturing a projection optical system, comprising a step of inspecting a part or the whole of the projection optical system by the shearing interferometry method according to claim 1. 15. A projection optical system manufactured by the method for manufacturing a projection optical system according to claim 14. 16. A projection exposure apparatus comprising the projection optical system according to claim 15. Description: