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`EP 1 336 887 A1
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`EUROPEfiW PATENT APPLICAHON
`pumished En accordance wi’th Ari“. 488(3) E'F’C
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`<43} Datecfwbficationr
`28.88.2803; Eufietin 2603134
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`('21) Appizcatzan number: 01‘3758673
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`(88) lmemazionefi appfiaafica number:
`pcfggpgfiggggg
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`{22) 03W 01513179? 23410-3091
`
`{8?} Internaiionai pubéicati‘sn number;
`WC} 82/035273 (02.35.2002 Gazette 2502318}
`
`
`{84} Besignated Contracting Siates:
`$35? BE CH CY GE DK ES {3! FF? GS GR IE 51‘ LI LU
`MC NE. 9T SE TR
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`{71) Appiicani: Nikon Corporation
`Takyn 100-8331 (JP;
`
`Des‘égneied Extension Stakes:
`AL E? Di MK 89 SE
`
`{39) Primgiy: 23.30.2030 JP 2000322068
`113312001 3? 2061320006
`354110.200? J? 2001309515
`
`{72) invenmr; TAKAHASM, Tomewaki.
`Nikcm Sorparatian
`Tokya 300v8331 {1?}
`
`{74} Regresentaflve; Waiaski, Jan Fiiip et a?
`Venner, shipiey 3: Cc:x
`28 Lime Britain
`
`Landau ESTA I’m-i {GB}
`
`
`{54)
`
`CATABIOPTMQ SYSTEM ARI?) EX?OS¥JRE SEWCE HAVIM‘G 13128 SYSTEM ‘
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`Description
`
`EP 1 336 887 A1
`
`[0001] The disclosures of the following priority applications are herein incorporated by reference: Japanese Patent
`Application No. 2000—5122068 filed October 23, 2000; Japanese Patent Application No. 2001—003200 filed January 11,
`2001; and Japanese Patent Application No. 2001-3095163 filed October 5, 2001.
`
`TECHNICAL FlELD
`
`[0002] The present invention relates to a catadioptric system and an exposure apparatus having this catadioptric
`system and, more specifically,
`it relates to a high resolution catadioptric type projection optical system ideal in an
`application in an exposure apparatus which is employed when manufacturing semiconductor elements or the like
`through a photoiithography process.
`
`BACKGROUND ART
`
`[0003] As further miniaturization is pursued with increasing vigor in the field of semiconductor production and sem-
`iconductorchip substrate production today, the projection optical system in an exposure apparatus that prints patterns
`needs to achieve higher resolution. The wavelength of the exposure light must be reduced and the NA (numerical
`aperture at the projection optical system) must be increased to raise the resolution However, since light absorption
`becomes a factorthat needs to be taken into consideration, only limited types of optical glass can be utilized in practical
`application in conjunction with exposure light with small wavelengths. For instance, ifthe wavelength is 180nm or less,
`only fluor can be utilized as glass material in practical application.
`‘
`[0004]
`in such a situation, ifthe projection optical system is constituted by using refractive optical members (lenses,
`plane parallel plates, etc.) alone, it is impossibleto correct any chromatic aberration with the refractive projection optical
`system. In other words, it is extremely difficultto constitute a projection optical system achieving the required resolution
`with refractive optical members alone. in response, attempts have been made to constitute a projection optical system
`with reflective optical members, i.e., reflecting mirrors, alone.
`[0005] However, the reflective projection optical system achieved by using reflective optical members alone is bound
`to become large. in addition, aspherical reflecting surfaces must be formed. it is to be noted that it is extremely difficult
`to form a high precision aspherical reflecting surface in the actual manufacturing process. Accordingly, various so-
`called catadioptric reducing optical systems achieved by using refractive optical members constituted of both optical
`glass that can be used in conjunction with exposure light with small wavelengths and reflecting mirrors, have been
`proposed.
`[0006] Among these catadioptric systems, there is a type of catadioptric system that forms an intermediate image
`only once by using a single concave reflecting mirror. In such a catadioptric system, the optical system portion for
`reciprocal paths, of which the concave reflecting mirror is a component, only includes negative lenses and does not
`have any refractive optical member with positive power. As a result, light enters the concave reflecting mirror as a wide
`light flux, which requires that the concave reflecting mirror have a large diameter.
`[0007]
`in particular, when the optical system portion for reciprocal paths having the concave reflecting mirror adopts
`a completely symmetrical configuration, the onus of the aberration correction imposed on the refractive optical system
`portion at the succeeding stage is reduced by minimizing the occurrence of aberration at the optical system portion for
`reciprocal paths. However, a sufficient working distance cannot be readily assured in the vicinity of the first plane in
`the symmetrical optical system for reciprocal paths. In addition, a half prism must be used to branch the optical path.
`[0008]
`Furthermore, if a concave reflecting mirror is used at a secondary image forming optical system provided to
`the rear ofthe position at which the intermediate image is formed, the light needs to enterthe concave reflecting mirror
`as a wide light flux in order to assure the degree of brightness required by the optical system. As a result, it is difficult
`to miniaturize the concave reflecting mirror whose diameter tends to be necessarily large.
`[0009] There is also a type of catadioptric system that forms an intermediate image only once by using a plurality of
`reflecting mirrors. In this type of catadioptric optical system, the number of lenses required to constitute the refractive
`optical system portion can be reduced. However, the following problems must be addressed with regard to such cat—
`adioptric systems.
`[0010]
`In the catadioptric system having the optical system portion for reciprocal paths adopting the structure de—
`scribed above provided toward the second piane on the reduction side, other restrictions imposed with regard to the
`reduction factor make it impossible to assure a sufficiently long distance to the second plane (the wafer surface) over
`which the light travels after it is reflected at the reflecting mirror. For this reason, a large number of lenses cannot be
`inserted in this optical path and the level of brightness achieved at the optical system is bound to be limited. In addition,
`even if an optical system with a large numerical aperture is achieved, numerous refractive optical members must be
`provided in the optical path with a limited length, and thus,
`it is not possible to assure a sufficiently long distance
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`between the wafersuriace at the second plane and the surface of the lens toward the second plane, i.e., the so-called
`working distance WD cannot be set to a sufficiently long value.
`,
`[0011] Since the optical path has to be bent, the catadioptric system in the related art is bound to have a plurality of
`optical axes (an optical axis is a line extending through the center of the curvature of a refractive curved surface or a
`reflective curved surface constituting an optical system). As a result, a plurality of lens barrels must be included in the
`optical system configuration, which makes it extremely difficult to adjust the individual optical axes relative to one
`another and, ultimately, to achieve a high precision optical system. it is to be noted that a catadioptric system having
`all the optical members provided along a single linear optical axis may be achieved by using a pair of reflecting mirrors
`each having an opening (a light transmission portion) at the center. However, in this type of catadioptric system, the
`central light flux must be blocked, i.e., central shielding must be achieved, in order to block off unnecessary light which
`advances along the optical axis without being reflected at the reflecting mirrors. As a result, a problem arises in that
`the contrast becomes lowered in a specific frequency pattern due to the central shielding.
`[0012]
`in addition, positions at which an effective field stop and an effective aperture stop should be installed can
`not be assured in the catadioptric systems in the related art. Also, as explained above, a sufficient working distance
`cannot be assured in the catadioptric systems in the related art. Furthermore concave reflecting mirrors tend to become
`large in the catadioptric systems in the related art, as described above, making it impossible to miniaturize the optical
`systems.
`[0013] While the catadioptric system disclosed in EP1069448A1 achieves advantages in that a sufficient working
`distance is assured toward the second plane (on the wafer—side) and in that the system is configured along a single
`optical axis, it still has a problem in that a sufficiently long working distance cannot be assured toward the first plane
`(on the mask side) (the distance between the mask surface at the first plane and the surface of the lens closest to the
`first plane) . In addition, the catadioptric system disclosed in WO 01/51979A2 poses a problem in that the diameter of
`the reflecting mirror is too large and thus, a sufficiently large numerical aperture cannot be achieved, Likewise, the
`diameter of the reflecting mirror is too large and, as a result, a sufficiently large numerical aperture cannot be achieved
`in the catadioptric system disclosed in Japanese Laid—open Patent Publication No. 2001228401.
`
`DISCLOSURE OF THE INVENTION
`
`[0014] An object of the present invention, which has been achieved by addressing the problems discussed above,
`is to provide a catadioptric system that facilitates adjustment and high precision production of the optical system and
`is capable of achieving a high resolution of 0.1pm or less by using light in a vacuum ultraviolet wavelength range of,
`for instance, 180nm or smaller,
`[0015] Another object of the present invention is to provide a catadioptric system that assures positions at which an
`effective field stop and an effective aperture step should be installed and is capable of achieving a high resolution of
`0.1um or less by using light in a vacuum ultraviolet wavelength range of, for instance, 180nm or smaller.
`[0016] Yet another object of the present invention is to provide a catadioptric system that assures a sufficiently long
`working distance and is capable of achieving a high resolution of 0.1um or less by using light in a vacuum ultraviolet
`wavelength range of, for instance, 180nm or smaller.
`[0017] A further object of the present invention is to provide a catadioptric system that achieves miniaturization of
`the optical system by keeping down the size of concave reflecting mirrors and is also capable of achieving a high
`resolution of 0.1pm or less by using light in a vacuum ultraviolet wavelength range of, for instance, 180nm or smaller.
`[0018] A still further object of the present invention is to provide a catadioptric system that assures asufficiently long
`working distance on the first plane side, achieves a satisfactorily large numerical aperture by keeping down the diameter
`of reflecting mirrors and is capable of achieving a high resolution of 0.1um or less by using light in a vacuum ultraviolet
`wavelength range of, for instance, 180nm or smaller.
`[0019] A still further object of the present invention is to provide an exposure apparatus that utilizes the catadioptric
`system according to the present invention as a projection optical system and is capable of achieving good projection
`exposure with a high resolution of 0.1um or less by using exposure light with a wavelength of, for instance, 180nm or
`smaller.
`
`[0020] A still further project of the present invention is to provide a micro device manufacturing method through which
`a high precision micro device can be manufactured by executing good projection exposure with a high resolution of,
`for instance, 0,1um or less with the exposure apparatus according to the present invention,
`[0021]
`in order to attain the above objects, a catadioptric system according to the present invention comprises: a
`first image forming optical system that includes at least two reflecting mirrors and forms a first intermediate image of
`a first plane with light originating from the first plane; a second image forming optical system that includes at least two
`reflecting mirrors and forms a second intermediate image of the first plane with light having traveled via the first image
`forming optical system; and a refractive type of third image forming optical system that forms a final image of the first
`plane onto a second plane with light having traveled via the second imageforming optical system, and optical members
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`EP 1 336 887 A1
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`constituting the first image forming optical system, the second image forming optical system and the third image forming
`optical system are all disposed along a single linear optical axis.
`[0022]
`In this catadioptric system, it is preferred that a field lens is provided in an optical path between thefirst image
`forming optical system and the second image forming optical system.
`[0023] Also, it is preferred that the first image forming optical system includes the two reflecting mirrors and at least
`one lens element.
`,
`[0024]
`In these cases, it is preferred that a combined optical system comprising the first image forming optical system
`and the field lens achieves telecentrlcity toward the first plane and toward the second plane.
`[0025]
`In each of the above catadioptric systems, it is preferred that the first image forming optical system includes
`at least one negative lens element provided In an optical path between the two reflecting mirrors.
`[0026] Also, it is preferred that the second image forming optical system includes at least one negative lens element
`provided in an optical path between the two reflecting mirrors.
`[0027] Another catadioptric system according to the present invention comprises a plurality of optical members that
`form two intermediate images of a first plane in an optical path between the first plane and a second plane and form
`a third intermediate image of the first plane onto the second plane as afinal image, and the plurality of optical members
`are disposed along a single linear optical axis.
`[0028]
`In this catadioptric system, it is preferred that the intermediate images are formed at positions off the optical
`axis.
`
`[0029] Another catadioptric system according to the present invention comprises a plurality of reflecting mirrors dis-
`posed along a single linear optical axis, and an image over a rectangular area away from the optical axis on a first
`plane is formed onto a second plane.
`[0030]
`In this catadioptric system, it is preferred that a field stop that defines an image area formed atthe catadioptric
`system and an aperture stop that defines a numerical aperture of the catadioptric system, are further provided.
`[0031] Another catadioptric system according to the present invention comprises: a first imagefonning optical system
`that includes at least a first reflecting mirror and a second reflecting mirror and forms a first intermediate image of a
`first plane with light originating from the first plane; a second image forming optical system that includes at least a third
`reflecting mirror and a fourth reflecting mirror and forms a second intermediate image of the first plane with light having
`traveled via the first image forming optical system; and a refractive type of third image forming optical system that
`forms a final image of the first plane onto a second plane with light having traveled via the second image forming optical
`system, and: optical members constituting the first image forming optical system, the second image forming optical
`system and the third image forming optical system are all disposed along a single linear optical axis; and at least one
`negative lens is provided immediately before each of two reflecting mirrors among the first reflecting mirror, the second
`reflecting mirror, the third reflecting mirror and the foutth reflecting mirrors on a reflecting surface side.
`[0032]
`In this catadioptric system, it is preferred that: a magnification factor chromatic aberration is corrected by
`providing at least one negative lens immediately before each of the two reflecting mirrors on the reflecting su rface side;
`and a magnification factor chromatic aberration coefficient LAT satisfies a condition expressed as lLATl < 5 x 10'5. In
`this case or in the above catadioptric system,
`It is preferred that: an on-axis chromatic aberration is corrected by
`providing at least one negative lens immediately before each of the two reflecting mirrors on the reflecting surface side;
`and an on-axis chromatic aberration coefficient AX satisfies a condition expressed as lAXl < 2 x 104.
`[0033] An exposure apparatus according to the present invention comprises: an illumination system that illuminates
`a mask; and a projection optical system that forms an image of a pattern formed at the mask onto a photosensitive
`substrate, and: the projection optical systems comprises a catadioptric system according to any one of claims 1 through
`13; and the mask corresponds to thefirst plane in the catadioptric system and the photosensitive substrate corresponds
`to the second plane in the catadioptric system.
`[0034]
`In this exposure apparatus, it is preferred that a drive system that causes the mask and the photosensitive
`substrate to move relative to the catadioptric system in order to scan the pattern of the mask to expose onto the
`photosensitive substrate, is further provided.
`[0035] A micro device manufacturing method according to the present invention comprises: an exposure step in
`which the pattern of the mask is exposed onto the photosensitive substrate with the above exposure apparatus; and
`a development step in which the photosensitive substrate having undergone the exposure step is developed.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0036]
`
`FIG. ‘I illustrates the basic structure of a catadioptric system according to the present invention;
`FIG. 2 schematically illustrates the overall structure of an exposure apparatus having the catadioptric system
`achieved in any of the embodiments of the present invention provided as a projection optical system;
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`FIG. 3 shows positional relationship between the rectangular exposure area (i.e., the effective exposure area)
`formed on the wafer and the reference optical axis;
`FIG. 4 shows the lens configuration of the catadioptric system achieved in a first embodiment;
`FIG. 5 shows the lateral aberration manifesting at the catadioptric system in the first embodiment;
`FIG. 6 shows the lens configuration of the catadioptric system achieved in a second embodiment;
`FIG. 7 shows the lateral aberration manifesting at the catadioptric system In the second embodiment;
`FIG, 8 shows the lens configuration of the catadioptric system achieved in a third embodiment;
`FIG. 9 shows the lateral aberration manifesting at the catadioptric system in the third embodiment;
`FIG. 10 shows the lens configuration of the catadioptric system achieved in a fourth embodiment;
`FIG. 11 shows the lateral aberration manifesting at the catadioptric system in the fourth embodiment;
`FIG. 12 shows the lens configuration of the catadioptric system achieved in a fifth embodiment;
`FIG. 13 shows the lateral aberration manifesting at the catadioptric system in the fifth embodiment;
`FIG. 14 shows the lens configuration of the catadioptric system achieved in a sixth embodiment;
`FIG. 15 shows that positional relationship between the arch—shaped effective exposure area formed on the wafer
`and the reference optical axis in the sixth embodiment;
`FIG. 16 shows the lateral aberration manifesting at the catadioptric system in the sixth embodiment;
`FlG, 17 shows the lens configuration of the catadioptric system achieved in a seventh embodiment;
`FIG. 18 shows the lateral aberration manifesting at the catadioptric system in the seventh embodiment;
`FIG. 19 shows the lateral aberration manifesting at the catadioptric system in the seventh embodiment;
`FIG, 20 shows the lens configuration of the catadioptric system achieved in an eighth embodiment;
`FIG. 21 shows the lateral aberration manifesting at the catadioptric system in the eighth embodiment;
`FIG. 22 shows the lateral aberration manifesting at the catadioptric system in the eighth embodiment;
`FIG. 23 shows the iens configuration of the catadioptric system achieved in a ninth embodiment;
`FIG. 24 shows the lateral aberration manifesting at the catadioptric system in the ninth embodiment;
`FIG. 25 shows the lateral aberration manifesting at the catadioptric system in the ninth embodiment;
`FIG. 26 presents a flowchart of a method adopted to obtain a micro device constituted of a semiconductor device;
`and
`
`FIG. 27 presents a flowchart of a method adopted to obtain a micro device constituted of a liquid crystal display
`element.
`
`BEST MODE FOR CARRYING OUT THE INVENTION
`
`FIG. 1 illustrates the basic structure adopted in a catadioptric system according to the present invention. it is
`[0037]
`to be noted that in FIG. 1, the catadioptric system according to the present invention is utilized as a projection optical
`system in an exposure apparatus that performs scanning exposure. As shown in FIG. 1, the catadioptric system ac—
`cording to the present invention includes a first image forming optical system G1 forforming a first intermediate image
`of the pattern at a reticle R constituting a projection original which is set at a first plane. It is to be noted that the first
`image forming optical system G1 includes at least two reflecting mirrors i.e., a first reflecting mirror and a second
`reflecting mirror.
`[0038]
`Light having traveled through the first image forming optical system G1 then forms a second intermediate
`image of the pattern at the reticle R via a second image forming optical system G2 having at least two reflecting mirrors;
`i,e., a third reflecting mirror and a fourth reflecting mirror. The light having traveled through the second image forming
`optical system G2 forms a final image of the pattern at the reticle R onto a wafer W constituting a photosensitive
`substrate which is set at a second plane via a refractive third image forming optical system G3 having refractive optical
`members alone with no reflecting mirror. All the optical members constituting the first image forming optical system
`G1, the second image forming optical system G2 and the third image forming optical system G3 are disposed along
`a single linear optical axis AX.
`[0039]
`In a more specific mode of the embodiment, a field lens FL is provided in the optical path between the first
`image forming optical system G1 and the second image forming optical system G2. The field lens FL has a function
`of matching and connecting the first image forming optical system G1 and the second image forming optical system
`G2 without actively contributing to the formation of the first intermediate image.
`In addition, the first image forming
`optical system G1 includes at least one lens element as well as the two reflecting mirrors. Thus, the combined optical
`system constituted of the first image forming optical system G1 and the field lens FL achieves telecentricity toward the
`reticle (toward the first plane) and toward the wafer (toward the second plane). It is to be noted that a field lens may
`also be provided as necessary in the optical path between the second image forming optical system G2 and the third
`image forming optical system GS.
`[0040]
`In the specific mode of the embodiment, it is desirable to provide at least one negative lens element (L13 or
`L21) in the optical path between the two reflecting mirrors at, at least either the first image forming optical system G1
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`or the second image forming optical system G2. This structure makes it possible to correct any chromatic aberration
`in a desirable manner even if the refractive optical members (lens elements) are formed with a single type of optical
`material.
`
`[0041] A field stop FS that defines an area overwhich the image is formed atthe catadioptric system may be provided
`near the field lens FL between the first image forming optical system G1 and the second image forming optical system
`(52 or near a field lens set between the second image forming optical system 62 and the third image forming optical
`system GS. In this case, the need to provide afield stop in the illumination optical system is eliminated. In addition, an
`aperture stop AS may be provided in the optical path at the third image forming optical system GB.
`[0042] As described above, all the optical members are disposed along the single optical axis AX in the catadioptric
`system according to the present invention, unlike in catadioptric systems in the related art having a plurality of optical
`axes. Since this allows the optical system to be achieved without a plurality of lens barrels, the adjustment of the optical
`axes relative to one another becomes unnecessary and any tilting or misalignment of the individual optical members
`set along the single optical axis AX can be optically detected with ease, which, ultimately makes it possible to manu-
`facture a high precision optical system. In addition, by aligning the single optical axis AX along the direction in which
`the gravitational force works (along the vertical direction) in this structure, the flexure of any lens caused by gravity
`can be made to achieve rotational symmetry and, as a result, the deterioration in the image forming performance can
`be minimized through an optical adjustment.
`[0043]
`In particular, by utilizing the catadioptric system adopted in the projection optical system of the exposure
`apparatus in an upright attitude along the single optical axis AX, the reticle R and the wafer W can be set parallel to
`each other along a plane perpendicularto the direction of the gravitational force (i.e., along a horizontal plane) and all.
`the lenses constituting the projection optical system can be set horizontally along the single optical axis AX extending
`along the direction of the gravitational force. As a result, the reticle R, the wafer W and all the lenses constituting the
`projection optical system are held level without becoming asymmetrically deformed due to their own weight, which is
`extremely advantageous in facilitating optical adjustment and mechanical design and in assuring high resolution.
`[0044]
`In addition, the Petzval‘s sum, which tends to be a positive value due to the positive refracting power of the
`refractive optical system portion of the third image forming optical system GS, can be canceled out with the negative
`Petzval's sum at the concave reflecting mirror portion of the first image forming optical system G1 and the second
`image forming optical system G2 and, as a result, the overall Petzval's sum can be kept at exactly 0.
`[0045]
`It is to be noted that the specific setting of the optical path of the reflecting mirrors is a crucial issue in a
`structure achieved by providing all the optical members including the reflecting mirrors along a single optical axis. As
`a solution, an opening (light transmission portion) may be formed at the center of each reflecting mirror as described
`earlier, to set the optical path via the central opening. However, this prior art solution necessitates the formation of
`central shielding over the entrance pupil area and such central shielding may lead to poorer optical image forming
`performance.
`[0046]
`In contrast, the light flux from the reticle pattern travels around the outside of the first reflecting mirror and
`then enters the second reflecting mirror at the first image forming optical system G1. After the light flux having been
`reflected at the second reflecting mirror is reflected at the first reflecting mirror, the light flux travels around the outside
`of the second reflecting mirror and forms thefirst intermediate image. In addition, the light flux from the first intermediate
`image travels around the outside of the third reflecting mirror and enters the fourth reflecting mirror at the second image
`forming optical system G2. After the light flux having been reflected at the fourth reflecting mirror is reflected at the
`third reflecting mirror, the light flux travels around the outside of the fourth reflecting mirror and forms the second
`intermediate image. According to the present invention, the first image forming optical system G1 and the second
`image forming optical system G2 are set substantially symmetrical with respect to each other relative to the position
`at which the first intermediate image is formed. As a result, a large working distance (the distance between the optical
`surface closest to the reticle and the reticle along the optical axis) can be assured on the reticle side. In other words,
`by setting the position of the second intermediate image formed via the second image forming optical system 62 further
`away from the third reflecting mirror, a larger working distance is assured on the reticle side. According to Schupmann‘s
`principal of achromatism, "An achromat of the Schupmann (refer to R. Kingstake, "Lens Design Fundamentals“, Aca-
`demic Press, 1978, page 89)", it is difficult to achieve color correction if the difference between the distances from the
`negative lens to conjugate images (the reticle R and the intermediate image) (= a + b — c, with c representing the
`distance from the reticle R to the second reflecting mirror, b representing the distancefrom the second reflecting mirror
`to the first reflecting mirror and a representing the distance from the first reflecting mirror to the intermediate image in
`FIG. 1) is large. The present invention, in which thefirst imageforming optical system (31 and the second image forming
`optical system G2 are set substantially symmetrical to each other relative to the position at which the first intermediate
`image is formed, allows the difference between the distances from the negative lens at the Image forming optical
`system G1 to the conjugate images manifesting to be canceled out at the second the image forming optical system
`G2, providing an advantage in the chromatic aberration correction as well.
`[0047]
`By adopting the structure described above, central shielding at the entrance pupil can be eliminated and,
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`10
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`15
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`20
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`25
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`30
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`35
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`40
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`45
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`50
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`55
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`EP 1 336 887 A1
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`ultimately, the optical image forming characteristics are not lowered because of central shielding. It is to be noted that
`the optical path can be set so as to run around the outside of the individual reflecting mirrors by selecting an appropriate
`image forming magnification factorfor the entire catadioptn'c system. As a result, the final image of the reticle pattern
`formed over a relatively large rectangular illumination area IR, which is decentered from the optical axis AX in the
`reticle field, can be formed onto a relatively large rectangular effective exposure area ER, which is decentered from
`the optical axis AX at the wafer field, as shown in FIG 1.
`In correspondence, the first intermediate image and the
`second intermediate image of the reticle pattern are formed at positions away from the optical axis AX.
`[0048] The exposure apparatus having the catadioptric system according to the present invention mounted as its
`projection optical system as described above is capable of performing scanning exposure based upon the re