KR20230000964A - Projecting optical system, exposure apparatus, and article manufacturing method - Google Patents

Abstract

An advantageous technique is provided for reducing aberrations in a projecting optical system including a correction optical system which corrects magnification. A projecting optical system which projects the pattern of the object surface onto the image surface comprises: an imaging optical system which forms an image of a pattern on the object surface on the image surface at an inhomogeneous magnification; a first correction optical system including a first pair of curved surfaces with different signs of power, and configured to correct a magnification of the imaging optical system in a first direction parallel to the image surface; a second correction optical system including a second pair of curved surfaces with different signs of power, for correcting magnification of the imaging optical system in a second direction parallel to the image surface and intersecting the first direction; and a third correction optical system including a third pair of curved surfaces with different signs of power, and configured to correct the magnification of the imaging optical system in the first direction and the second direction.

Description

Projection optical system, exposure apparatus, and article manufacturing method

The present invention relates to a projection optical system, an exposure apparatus, and a method for manufacturing an article.

Devices such as semiconductor elements and image display devices are manufactured through a photolithography process. In the photolithography process, an exposure apparatus including, for example, a projection optical system is used, and a pattern of an original plate is projected onto a substrate coated with a photosensitive material (resist) through the projection optical system to transfer the pattern of the original plate to the photosensitive material on the substrate. can [0003] In recent years, since the degree of integration of circuits has improved along with higher performance of devices, high resolution is required of exposure apparatuses.

In an exposure apparatus, a change in magnification may occur in a projection optical system due to, for example, thermal expansion and contraction of the original plate and/or the substrate during exposure. Therefore, it is required to correct the change in magnification in order to obtain high resolving power. In Patent Document 1, a first optical system for correcting magnification in the X direction, a second optical system for correcting magnification in the Y direction, and a third optical system for isotropically correcting magnification in the X direction and Y direction are provided. A projection optical system has been proposed. In the projection optical system described in Patent Literature 1, magnification and astigmatism can be corrected independently by setting the magnification correction amount by these optical systems to a predetermined relationship. Further, Patent Literature 2 proposes a projection optical system including a plurality of optical elements each having a cylindrical surface and/or an inclined plane. In the projection optical system described in Patent Literature 2, magnification and focus can be adjusted by changing intervals between a plurality of optical elements.

Japanese Patent No. 5595001 Japanese Unexamined Patent Publication No. 2013-219089

When the correction optical system described in Patent Document 1 or Patent Document 2 is provided in the projection optical system, the image forming performance of the projection optical system may be degraded due to the influence of aberrations generated in the correction optical system. In particular, when the projection optical system is a non-magnification system (magnification system or reduction system), the degree of difficulty in aberration correction increases, and the effect can become significant. For example, as one method of improving the imaging performance of the projection optical system, there is a method of introducing an aspherical surface into the projection optical system. However, when the projection optical system is an unequal magnification system, only introducing an aspherical surface is insufficient to reduce the effect.

Accordingly, an object of the present invention is to provide an advantageous technique for reducing aberration in a projection optical system including a correction optical system for correcting magnification.

In order to achieve the above object, a projection optical system as one aspect of the present invention is a projection optical system for projecting a pattern on an object surface onto an image plane, and an imaging optical system for forming an image on the image plane at a non-equivalent magnification; , a first pair of curved surfaces disposed on an optical path between the object surface and the pupil surface of the imaging optical system and having different power signs, and the imaging optical system in a first direction parallel to the image plane. A first correction optical system for correcting the magnification of , and a second pair of curved surfaces disposed on an optical path between the image surface and the pupil surface and having different signs of power, parallel to the image surface and A second correction optical system for correcting the magnification of the imaging optical system in a second direction intersecting the first direction, disposed on an optical path between one of the image plane and the object plane and the pupil plane, and a power sign includes a third pair of curved surfaces different from each other, and a third correction optical system for correcting the magnification of the imaging optical system in the first direction and the second direction; Among the curved surfaces, the power of the curved surface close to the object surface is φ ₁ , the power of the curved surface close to the upper surface among the second pair of curved surfaces is φ ₂ , and the power of the curved surface close to the one of the third pair of curved surfaces When is φ ₃ , φ ₁ and φ ₂ have the same sign of power, φ ₃ has a different power sign for φ ₁ and φ ₂ , and the distance between the first pair of curved surfaces is d ₁ , The distance between the second pair of curved surfaces is d ₂ , the magnification of the imaging optical system is β (|β|≠1), the smaller one of d ₁ and (d ₁ ×|β|) is d _min , and the larger one is d min . It is characterized in that d _min × (1-k) ≤ d ₂ ≤ d _max × (1+k) is satisfied when the side is set to d _max and the constant k is 0 ≤ k ≤ 1.

Additional objects or other aspects of the present invention will be clarified by preferred embodiments described below with reference to the accompanying drawings.

According to the present invention, it is possible to provide an advantageous technique for reducing aberration in a projection optical system including, for example, a correction optical system for correcting magnification.

1 is a schematic diagram showing a configuration example of a projection optical system according to the present invention;
2 is a schematic diagram showing a configuration example of a Y correction optical system, an X correction optical system, and an I correction optical system;
3 is a diagram showing a thin-walled model of a correction optical system;
4 is a diagram showing a change in focus position and a change in magnification occurring in a correction optical system for each type of correction optical system.
Fig. 5 is a diagram schematically showing the refraction of a light ray generated on a refracting surface;
6 is a diagram showing a configuration that a correction optical system can take
Fig. 7 is a diagram showing calculation results regarding the lens interval d _i in the correction optical system on the image plane side;
Fig. 8 is a diagram showing the effect on the _wavefront aberration of the ratio of the lens distance d 0 in the correction optical system on the object plane side to the lens distance d _i in the correction optical system on the image plane side.
Fig. 9 is a diagram showing an example of an object region and an image region in a projection optical system;
10 is an optical diagram of Examples of the present invention, Comparative Examples 1 and 2
11A is a diagram showing RDNs for each surface of Example, Comparative Example 1 and Comparative Example 2 according to the present invention;
11B is a diagram showing aspherical surface coefficients of Example, Comparative Example 1 and Comparative Example 2 according to the present invention;
12 is a diagram showing evaluation values of optical performance in Example, Comparative Example 1 and Comparative Example 2 according to the present invention.
Fig. 13 is a diagram showing a configuration example of an exposure apparatus provided with a projection optical system according to the present invention;

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In addition, the following embodiment does not limit the invention concerning the claim. Although a plurality of features are described in the embodiment, not all of these plurality of features are essential to the invention, and a plurality of features may be combined arbitrarily. In addition, in the accompanying drawings, the same reference numerals are attached to the same or similar structures, and overlapping descriptions are omitted.

<First Embodiment>

A first embodiment of the present invention will be described. 1 is a schematic diagram showing a configuration example of a projection optical system PO of the first embodiment. The projection optical system PO includes an imaging optical system IO that forms an image of the pattern of the object plane 1 on the image plane 7 at a magnification of β, and the pattern of the object plane 1 is formed by the imaging optical system IO. Projected onto the upper surface (7). In the case of the present embodiment, the imaging optical system IO is configured to form an image of the pattern of the object surface 1 on the image surface 7 at an unequal magnification (|β|≠1). That is, the projection optical system PO is configured to project the pattern of the object surface 1 onto the image surface 7 at an unequal magnification (|β|≠1). Further, when the projection optical system PO of the present embodiment is used in an exposure apparatus, the object surface 1 corresponds to a pattern surface of an original plate (mask, reticle) on which an arbitrary pattern is formed, and the upper surface 7 is formed of a photosensitive material. It may correspond to the side of the applied substrate (wafer, glass plate).

As a projection optical system used in an exposure apparatus, a reduction system of β = -0.2 is generally used for a stepper for semiconductor manufacturing, and an equal magnification system for β = -1 for a scanner for display manufacturing. On the other hand, in recent years, especially in exposure apparatus for display manufacturing, examination of a projection optical system (magnification system) having a magnification of β < -1 has been desired for the purpose of reducing the size of the original plate. Opener optical systems and Dyson optical systems employed as projection optical systems of exposure apparatuses for display manufacturing are characterized by symmetric power arrangement with respect to the pupil of the optical system, and this symmetry is important from the viewpoint of aberration correction. When these optical systems are unequal magnification, it becomes difficult to suppress aberrations that have been suppressed due to the fact that they are symmetrical optical systems, and the difficulty of optical design increases as |β| is increased.

When the projection optical system PO (imaging optical system IO) of the present embodiment is a magnifying system, the magnification β satisfies 1.005≤|β|. However, since it is known that in an opener optical system having a magnification magnification, an imaging magnification β of up to 2.0 is preferable from the viewpoint of aberration suppression, more preferably 1.05≤|β|≤2.0 is satisfied. On the other hand, when the projection optical system PO (imaging optical system IO) of the present embodiment is a reduction system, the magnification β satisfies 0<|β|≤0.995, but more preferably satisfies 0.1≤|β|≤0.95. You can do it.

Here, the imaging optical system IO of the present embodiment exemplifies an opener optical system mainly composed of a reflective optical member. It is the first concave mirror 3, the convex mirror 4 and the second concave mirror 5 that provide the main optical power of the opener optical system. In addition, the plane mirrors 2 and 6 are designed to prevent interference between the original plate stage, which is movable by holding the original plate placed on the object surface 1, and the substrate stage, which is movable by holding the substrate, placed on the upper surface 7. It is arranged to deflect the light path to . In addition, projection optical system PO of this embodiment is not limited to the structure shown in FIG. 1, For example, the structure which does not contain the flat mirrors 2 and 6 may be sufficient. Further, the imaging optical system IO may not be an opener optical system, but may be an optical system composed of a plurality of refractive optical element groups.

In the exposure apparatus in which the projection optical system PO is used, since the substrate or the original plate may expand and contract anisotropically during operation (for example, during exposure), a correction optical system for correcting this anisotropic magnification component is provided in the projection optical system ( PO) can be provided. As the correction optical system, the first correction optical system disposed on the optical path between the object plane 1 and the pupil surface of the imaging optical system IO, and the optical path between the image surface 7 and the pupil surface of the imaging optical system IO. The disposed second correction optical system and third correction optical system may be used. In this embodiment, the Y correction optical system 10 is applied as the first correction optical system, the X correction optical system 20 is applied as the second correction optical system, and the I correction optical system 30 is applied as the third correction optical system. . 1, the pupil surface of the imaging optical system IO is the reflection surface of the convex mirror 4.

The Y correction optical system 10 includes a first pair of curved surfaces disposed on an optical path between the object surface 1 and the pupil surface of the imaging optical system IO and having different signs of power, and an upper surface 7 ), the magnification of the imaging optical system IO in the first direction (Y direction in this embodiment) parallel to ) is corrected. In the configuration example of Fig. 1, the Y correction optical system 10 (first pair of curved surfaces) is disposed on the optical path between the object surface 1 and the flat mirror 2. In the Y correction optical system 10, the magnification of the imaging optical system IO in the first direction (Y direction) can be changed by relatively moving the first pair of curved surfaces.

The X correction optical system 20 is disposed on the optical path between the image plane 7 and the pupil plane of the imaging optical system IO and includes a second pair of curved surfaces having different signs of power, and the image plane 7 The magnification of the imaging optical system IO in the second direction (X direction in this embodiment) parallel to and intersecting the first direction is corrected. In the configuration example of FIG. 1 , the X correction optical system 20 (the second pair of curved surfaces) is disposed on the optical path between the image surface 7 and the flat mirror 6 . In the X correction optical system 20, the magnification of the imaging optical system IO in the second direction (X direction) can be changed by relatively moving the second pair of curved surfaces.

The I correction optical system 30 is disposed on the optical path between one of the object plane 1 and the image plane 7 and the pupil plane of the imaging optical system IO, and a third pair of curved surfaces having different power signs. Including, the magnification of the imaging optical system IO in the first direction (Y direction) and the second direction (X direction) is isotropically corrected. In this embodiment, the I correction optical system 30 (third pair of curved surfaces) is disposed on the optical path between the image plane 7 and the pupil plane of the imaging optical system IO, and in the case of the configuration example of FIG. 1, the image plane It is arranged on the optical path between (7) and the plane mirror (6). In the I correction optical system 30, the magnification of the imaging optical system IO in the first direction (Y direction) and the second direction (X direction) is isotropically moved by relatively moving the third pair of curved surfaces. can be changed

Next, detailed configurations of the Y correction optical system 10, the X correction optical system 20, and the I correction optical system 30 will be described with reference to FIG. Fig. 2 is a schematic diagram showing a configuration example of the Y correction optical system 10, the X correction optical system 20, and the I correction optical system 30, and a ZY cross section and a ZX cross section are shown. In the following description, the terms "upper surface" and "lower surface" are used for each of the optical elements 11 to 15, but "upper surface" refers to the object surface 1 side (+Z direction side). , that is, the light incident surface, and the “lower surface” is the surface on the upper surface 7 side (-Z direction side), that is, the light exit surface.

The Y correction optical system 10 may be composed of two optical elements 11 and 12 . The optical element 11 is a plano-concave cylindrical lens whose upper surface is flat and whose lower surface is a Y cylindrical surface 10a having negative optical power in the Y direction. The optical element 12 is a Y cylindrical surface 10b having a positive optical power in the Y direction, and a flat convex cylindrical lens with a flat bottom surface. The first pair of curved surfaces in the Y correction optical system 10 may be composed of the Y cylindrical surface 10a of the optical element 11 and the Y cylindrical surface 10b of the optical element 12. . In addition, since the Y cylindrical surface 10 of the optical element 11 and the Y cylindrical surface 10b of the optical element 12 do not have optical power in the X direction, they are shown as planes in the ZX cross section. there is.

The X correction optical system 20 and the I correction optical system 30 may be composed of three optical elements 13 to 15. The optical element 13 is a plano-concave lens whose upper surface is a flat surface and whose lower surface is a spherical surface 30a having negative optical power. The optical element 14 is a lens whose upper surface is a spherical surface 30b having positive optical power and whose lower surface is an X cylindrical surface 20a having positive optical power in the X direction. The optical element 15 is a concave flat cylindrical lens whose upper surface is an X cylindrical surface 20b having negative optical power in the X direction and whose lower surface is a plane. The second pair of curved surfaces in the X correction optical system 20 may be composed of the X cylindrical surface 20a of the optical element 14 and the X cylindrical surface 20b of the optical element 15. . Also, the third pair of curved surfaces in the I-correction optical system 30 may be composed of the spherical surface 30a of the optical element 13 and the spherical surface 30b of the optical element 14. In addition, since both the X cylindrical plane 20a of the optical element 14 and the X cylindrical plane 20b of the optical element 15 do not have optical power in the Y direction, they are shown as planes in the ZY cross section. there is.

Here, in this embodiment, one curved surface of the X correction optical system 20 and one curved surface of the I correction optical system 30 are formed on the same optical element 14, but it is not limited thereto. For example, instead of the optical element 14, a flat convex lens whose upper surface is composed of a curved surface and a flat surface having positive optical power, and a plano-convex cylinder having a flat upper surface and a positive optical power in the X direction on the lower surface. You may provide two optical elements of a curl lens. In addition, the I-correction optical system 30 is an optical surface having anisotropic power in the XY direction, and a cylindrical surface having no curvature is exemplified in a cross section orthogonal to the cross section having curvature, but is not limited thereto. For example, it may be a toric surface having different curvatures in orthogonal cross sections.

Next, a paraxial focal position change and a magnification change caused by a pair of curved surfaces included in each of the correction optical systems 10 to 30 of the present embodiment will be explained using equations. As described above, the correction optical systems 10 to 30 of the present embodiment have a pair of opposing curved surfaces, and their optical powers have opposite signs. In the following, the object plane 1 and the image plane 7 are referred to as optical conjugate planes of the projection optical system PO. Among the pair of curved surfaces in each of the correction optical systems 10 to 30, the curved surface on the side close to the optical conjugate surface is referred to as a "curved surface on the conjugate surface side", and the curved surface opposite to the curved surface on the conjugate surface side, that is, imaging optics The curved surface on the side located in the measurement is referred to as "the curved surface of imaging optical measurement".

In the case of this embodiment, the Y correction optical system 10 disposed between the object plane 1 and the pupil plane of the imaging optical system IO (in the pair of curved surfaces 10a and 10b, the curved surface close to the object plane 1) (10a) corresponds to the "curved surface on the conjugate surface side", and the curved surface 10b far from the object surface 1 corresponds to the "curved surface of the imaging optical system". In the X correction optical system 20 (a pair of curved surfaces 20a and 20b) disposed between the writing surfaces, the curved surface 20b close to the upper surface 7 corresponds to the "curved surface on the conjugate surface side", and the upper surface 7 The curved surface 20a far from 20a corresponds to the "curved surface of the imaging optical system."In addition, one of the object surface 1 and the image surface 7 (image surface 7 in the configuration example of Fig. 2) is connected to the optical system IO. In the I-correction optical system 30 (a pair of curved surfaces 30a and 30b) disposed between the writing surfaces, the curved surface 30b closer to the one side corresponds to the "curved surface on the conjugate surface side." The curved surface 30a corresponds to the &quot;curved surface of imaging optical measurement&quot;.

Fig. 3(a) shows two thin-walled lenses _Loa and _Lob having powers _φoa and _φob with different signs from each other disposed near the object surface 1. The object viewed from the thin-thick lens _Lob with the thin-thin lens L _oa as a reference, the position of the object plane and the image plane _viewed from the thin-thick lens L _oa as s _oa and s _oa ', respectively. The position of the surface and the position of the upper surface are respectively s _ob and s _ob '. At this time, the relationship of the following formulas (1) to (2) is established from the formula for formation.

_{If do is the position of the thin-thick lens Lob with respect to the thin-thick lens L oa and s o is the amount} of position movement of the object surface by the thin-thick lenses L _oa and _Lob , the following equation (3) is obtained from the geometric relationship The relationship of (4) to is established.

Further, when equations (1) to (3) are substituted into equation (4), equation (5) is obtained. Here, as an example of the design, both φ _oa and φ _ob are about 10 ^-5 mm ^-1 , s _a is about _-300 mm, and do is about 30 mm. Taking these into account and ignoring terms with small contributions, equation (5) is approximated as equation (6).

Next, the magnification β _o generated by the correction optical system is expressed by Expression (7) in that it is a product of the respective magnifications of the thin-walled lenses L _oa and _Lob . And, by applying an approximation to a minute amount, the magnification β _o is expressed by equation (8).

Here, when φ _oa =φ _o +φ _o and φ _ob =-φ _o are substituted, Equations (6) and Equations (8) are represented by the following Equations (9) and Equations (10), respectively.

As can be seen from equation (10), the change in magnification during actual operation can be dynamically corrected by configuring the correction optical system so that the distance d _o between the pair of curved surfaces is variable. If the amount of change in magnification when the distance d _o is changed in a small amount is referred to as the magnification sensitivity, the magnification sensitivity is expressed as -φ _o from equation (10). For example, when the amount of change in magnification when the interval d _o is changed by +1 mm is 10 ppm, φ _o may be -10 ^-5 mm ^-1 . In actual design, φ _o can be determined to make this magnification sensitivity a predetermined value. The value of the magnification sensitivity can be determined in consideration of the driving accuracy or driving resolution of a driving mechanism for driving the optical element, the range of magnification to be corrected, the distance between the optical elements, and the like.

FIG. 3(b) shows two thin-walled lenses Li _ia , Li _ib having powers φ _ia , φ _ib having different signs from each other, disposed near the image surface 7 . The object viewed from the thin-thick lens _{Li ib} with the thin-thin lens _{Li ia} as a reference, the position of the object plane and the image plane viewed from the thin-thin lens _{Li ia} as s _ia and s _ia ', respectively, The position of the face and the position of the top face are s _ib and s _ib '. In addition, the position of the thin lens _{Li ib} when the thin lens Li _ia is taken as a reference is denoted by d _i . At this time, if the same discussion as for the thin lenses L _oa and _Lob described above is made, the change in focus position Δs _i and the change in magnification β _i are derived according to the following equations (11) to (12). However, φ _ia = -φ _i , φ _ib = φ _i +Δφ _i , and s _k '= s _ia -d _i .

The X correction optical system 20 generates a change in focus position and a change in magnification expressed by equations (9) to (12) in a cross section including the X axis. Similarly, the Y correction optical system 10 generates a change in focus position and a change in magnification expressed by equations (9) to (12) in the cross section including the Y axis. Accordingly, astigmatism occurs when the difference between the focal position change generated by the X correction optical system 20 and the focal position change generated by the Y correction optical system 10 is not zero. In addition, when the difference between the magnification change generated by the X correction optical system 20 and the magnification change generated by the Y correction optical system 10 is not zero, a magnification difference in the XY direction (hereinafter, XY magnification difference) occurs will do Each correction optical system of the present embodiment intentionally generates astigmatism and XY magnification difference by changing the distance between a pair of curved surfaces, and corrects the effect of performance change of the imaging optical system IO and expansion and contraction of the original plate and substrate. can be introduced. However, the astigmatism and XY magnification difference may be designed to be zero when the distance between the pair of curved surfaces is not changed (that is, the design value).

Below, the requirements (configuration requirements, configuration conditions) of the correction optical systems 10 to 30 in the projection optical system PO of the present embodiment are described.

(Requirement 1)

In the projection optical system PO of this embodiment, the Y correction optical system 10 for correcting the magnification in the Y direction and the X correction optical system 20 for correcting the magnification in the X direction are mutually interposed with the imaging optical system IO therebetween. It is required to be placed on the opposite side. This corresponds to a necessary condition for independently performing the correction of the anisotropic magnification component and the correction of the astigmatism. In order to generate the XY magnification difference while setting the astigmatism change to zero, or to generate the astigmatism while keeping the XY magnification difference to zero, it is necessary to satisfy this requirement.

(Requirement 2)

Further, in the projection optical system PO of the present embodiment, the sign of the optical power φ ₁ of the curved surface 10a on the side of the conjugate surface in the Y correction optical system 10 and the conjugate surface in the X correction optical system 20 It is required that the sign of the optical power φ ₂ of the curved surface 20b on the side is the same. The reason for this is explained below.

Regarding a single correction optical system, the configuration in which positive optical power and negative optical power are arranged in order from the object plane side is classified as PN type, and conversely, the configuration in which negative optical power and positive optical power are arranged in order is classified as NP type. . And, for example, when the Y correction optical system 10 disposed on the object surface 1 side is a PN type and the X correction optical system 20 disposed on the image surface 7 side is an NP type, the I correction optical system 30 ) is expressed as Y(PN)/X(NP). However, in this embodiment, it is not limited to the configuration in which the Y correction optical system 10 is disposed on the object plane 1 side and the X correction optical system 20 is disposed on the image plane 7 side, and the configuration may be reversed. . That is, a configuration may be employed in which the Y correction optical system 10 is disposed on the image plane 7 side and the X correction optical system 20 is disposed on the object plane 1 side. Therefore, below, the symbols of Y and X in the above Y(PN)/X(NP) are omitted and expressed as PN/NP. In this case, since there are two configurations on the object surface 1 side and two configurations on the upper surface 7 side, as a whole, a total of four types of PN/PN, PN/NP, NP/PN, and NP/NP configuration can be taken.

4(a) shows the sign of the change in focus position and the sign of the change in magnification occurring in a single correction optical system when Δφ _o =0 or Δφ _i =0 in the above equations (9) to (12). indicates In Fig. 4(a), the subscript "c" is a symbol representing "o" or "i" (that is, "o" or "i" is input). For example, φ _c indicates φ _o (quantity on the object surface 1 side) or φ _i (quantity on the upper surface 7 side).

In the case where the object surface 1 side is a PN type, since the curved surface on the conjugate surface side has positive (P) power and the imaging optical measurement curved surface has negative (N) power, φ _o > 0. In addition, since s _oa <0 and d _o > 0, the sign of Δs _o is always positive from the above expression (9). And, if the change in magnification by the correction optical system on the object surface 1 side is defined as Δβ _o = β _o -1, from the above equation (10), when Δφ _o = 0, Δβ _o = -d _o φ _o , when the object surface 1 side is a PN type, the sign of Δβ _o is always negative.

On the other hand, in the case where the image surface 7 side is a PN type, since the curved surface on the conjugate surface side has negative (N) power and the imaging optical system side has positive (P) power, φ _i <0. In addition, since s _k '>0 and d _i >0, the sign of Δs _i is always negative from the above equation (11). Then, if the change in magnification by the correction optical system on the image plane side is defined as Δβ _i = β _i -1, from the above equation (12), Δβ _i = d _i φ _i when Δφ _i = 0, and the image plane (7) When the side is a PN type, the sign of Δβ _i is always negative.

It is also understood from Fig. 4(a) that in the case of Δφ _o =0 or Δφ _i =0, the astigmatism and the XY magnification difference cannot become zero at the same time. For example, in the case of the PN/PN type, in the PN type correction optical system on the object surface 1 side and the PN type correction optical system on the image surface 7 side, since the sign of the change in magnification is the same, the XY magnification difference can be corrected. However, the astigmatism cannot be corrected because the signs of the change in focus position are opposite to each other. This tendency is also true for the other three configurations. Regarding the performance of the side that cannot be corrected when Δφ _o = 0 or Δφ _i = 0, by setting Δφ _o or Δφ _i to an appropriate value, the generation amount within a single correction optical system is approached to zero. it becomes necessary

Next, the behavior of the change in focus position and change in magnification when Δφ _o and Δφ _i are not zero will be described. 4(b) shows the sign of the change in focus position and the sign of the change in magnification for Δφ _o and Δφ _i , which increase the absolute value of the power of the curved surface on the conjugate plane side in each correction optical system. In the case where the object surface 1 side is a PN type, the point where φ _o > 0 among the powers φ o = φ _o + _{Δφ o} of interest indicates a power change such that Δφ _o > 0. Similarly, in the case of the PN type on the top surface side, it refers to a power change at which Δφ _i < 0 at the point where φ _i < 0 among the powers φ _ib = φ _i + Δφ _i of interest. In comparison with (a) of FIG. 4, it is understood that these power changes change in the direction of reducing the focal position change and magnification change that always occur at Δφ _o =0 or Δφ _i =0. For example, when the object surface 1 side is a PN type, when Δφ _o = 0, Δs _o > 0 and Δβ _o < 0, but by setting Δφ _o > 0, Δs _o is negative and Δβ _o is positive It becomes possible to change From the above, in any configuration, by increasing the absolute value of the power of the curved surface on the conjugated surface 1 side, it is possible to reduce the focal position change and magnification change occurring in a single correction optical system, and as a result, astigmatism and XY It becomes possible to reduce the magnification difference. Expressing this using φ _oa , φ _ob , φ _ia , φ _ib , |φ _oa |>|φ _ob | It can be said that setting |φ _ia |<|φ _ib | is a necessary condition for suppressing astigmatism and XY magnification difference.

Specifically, in the Y correction optical system 10 in the configuration example of FIG. 2 , the power of the Y cylindrical surface 10a, which is a curved surface on the conjugate surface side, is φ ₁ , and the Y cylindrical surface 10b, which is a curved surface for imaging optical measurement. ) can be a requirement of |φ ₁ |>|φ ₁ '| when the power of φ ₁ '| In the X correction optical system 20, when the power of the X cylindrical surface 20b, which is the curved surface on the conjugate surface side, is φ ₂ , and the power of the X cylindrical surface 20a, which is the curved surface of the imaging optical system, is φ ₂ ', |φ ₂ |>|φ ₂ '| Further, in the I correction optical system 30, when the power of the spherical surface 30b, which is a curved surface on the conjugate surface side, is φ ₃ , and the power of the spherical surface 30a, which is a curved surface in the imaging optical system, is φ ₃ ′, |φ ₃ | >|φ ₃ '| can be a requirement.

Next, field curvature generated in the correction optical system will be described. The Petzval coefficient P representing the magnitude of field curvature is expressed as P = -φ/N when a thin lens having a power φ and a refractive index N is placed in air. The Petzval coefficient in a single correction optical system is the sum of the Petzval coefficients in two thin-walled lenses. If the power of the correction optical system on the object plane (1) side is φ _oa =φ _o +Δφ _o , φ _ob = -φ _o and the refractive index N is assumed to be common, the Petzval of the correction optical system on the object plane (1) side The coefficient P _o is represented by P _o = -Δφ _o /N. Similarly, if the power of the correction optical system on the image plane 7 side is φ _ia =-φ _i , φ _ib = φ _i +Δφ _i , and the refractive index N is the same, the Petzval of the correction optical system on the image plane 7 side The coefficient P _i is represented by P _i = -Δφ _i /N.

The X correction optical system 20 generates a quadratic field curvature with respect to the X coordinate in the cross section including the X axis. Similarly, the Y correction optical system 10 generates a quadratic field curvature with respect to the Y coordinate in the cross section including the Y axis. From the viewpoint of correcting the astigmatism and the XY magnification difference, Δφ _o and Δφ _i do not become zero, and thus the field curvature also does not become zero. In order to properly correct the field curvature, the direction of the field curvature generated by the X correction optical system 20 and the field curvature generated by the Y correction optical system 10 are set in the same direction, and their sum is calculated by the I correction optical system 30. It is preferable to correct in the reverse direction. In order for the field curvature generated in the X correction optical system 20 and the field curvature generated in the Y correction optical system 10 to be in the same direction, the signs of both Petzval coefficients need only be the same. That is, when the Petzval coefficient of the Y correction optical system 10 is P1 and the Petzval coefficient of the X correction optical system 20 is P2, P1 and P2 need only have the same sign. Therefore, Δφ _o and Δφ _i may have the same sign.

A configuration that satisfies both the requirements for correcting the above-mentioned astigmatism and XY magnification difference and the requirements for correcting the field curvature is preferable. That is, Δφ _o and Δφ _i must be set so as to increase the absolute value of the power of the curved surface on the conjugate surface side, and Δφ _o and Δφ _i must have the same sign. As a configuration in which these are compatible, the types of the Y correction optical system 10 and the X correction optical system 20 may be employed so that Δφ _o /Δφ _i in FIG. 4 (b) have the same sign, PN/NP or NP/PN this is suitable In other words, by the configuration in which the sign of the power of the curved surface on the conjugate plane side is the same in the Y correction optical system 10 and the X correction optical system 20, astigmatism and XY magnification difference correction and field curvature correction are compatible.

(Requirement 3)

In the projection optical system PO of the present embodiment, the sign of the optical power φ ₃ of the curved surface 30b on the conjugate surface side in the I correction optical system 30 is the sign of the optical power φ ₁ and the optical power φ ₂ It is a requirement that it is different (opposite) from the sign of As described above, the optical power φ ₁ is the optical power of the curved surface 10a on the conjugate surface side in the Y correction optical system 10, and the optical power φ ₂ is the optical power of the conjugate surface in the X correction optical system 20. is the optical power of the side curved surface 20b. The reason for this is explained below.

As shown in (a) of FIG. 5, it is assumed that light flux converging on the imaging plane is refracted on a refracting surface having a radius of curvature of R _k . With respect to the refracting surface, the refractive index of the medium on the image plane side is N', and the refractive index of the medium on the opposite side is N. Also, the position of the imaging plane viewed from the apex of the plane of the refracting plane is s _k '. In the case where there is no refracting surface, for an off-axis peripheral ray imaged at a height h ₀ and an angle α on the imaging surface, if the change in the height of the ray due to refraction at the apex of the surface is formulated, it is related to coma of the third order As a term, the term represented by the following formula (13) is included.

Based on this, the coma aberration occurring in a single corrective optical system is formulated. As shown in (b) of FIG. 5, consider two refracting surfaces having radii of curvature R _ka and R _kb . The refractive index of the region between the two refracting surfaces is 1 (air), and the refractive index of the other regions is N. Further, the position of the upper surface viewed from the refracting surface of curvature R _ka is s _k '+d, and the position of the upper surface viewed from the refracting surface of curvature R _kb is s _k '. The coma aberration generated in a single correction optical system is a term that is the sum of the above equation (13) and is proportional to a term expressed by the following equation (14). Further, when equation (14) = 0 is transformed, the following conditional expression (15) relating to coma aberration correction is derived.

Since both s _k ' and d in Expression (15) are positive, a necessary condition for reducing coma aberration generated in a single correction optical system is |R _ka |>|R _kb |. The above discussion was discussed on the image plane side, but the same conclusion is derived even when examined from the object plane side. More generally, it is necessary to suppress coma aberration in a single correction optical system to make the absolute value of the radius of curvature of the curved surface on the side of the conjugate surface smaller than the absolute value of the radius of curvature of the opposing curved surface (curved surface in imaging optical measurement). It is a condition. In other words, from the viewpoint of optical power, the absolute value of the optical power of the curved surface on the side of the conjugated surface should be greater than the absolute value of the power of the opposite surface (curved surface for imaging optical measurement). This coincides with the above-mentioned requirements for astigmatism and XY magnification difference correction.

An example of a configuration of a possible correction optical system including the I correction optical system 30 will be described with reference to FIG. 6 . The configuration of the Y correction optical system 10 and the X correction optical system 20 is limited to either PN/NP or NP/PN so as to satisfy the above requirements. And, for each of PN/NP and NP/PN, since the I-correction optical system 30 can take either a PN type or a NP type, there are a total of four. 6, the Y correction optical system 10, the imaging optical system IO, the I correction optical system 30, and the X correction optical system 20 are arranged in this order from the object surface 1 side. , only four are listed, but are not necessarily limited to this order. For example, the X correction optical system 20 and the I correction optical system 30 may be reversed, and the I correction optical system 30 may be on the same side as the Y correction optical system 10 with respect to the imaging optical system IO. That is, although there may be arrangements other than those shown in Fig. 6, four candidates similar to those shown in Fig. 6 can be cited for arrangements of other correction optical systems, so this configuration is exemplified here as a representative. In Fig. 6, symbols corresponding to curved surfaces on the conjugate surface side are indicated in bold letters.

In order to suppress coma aberration occurring in a single correction optical system, the absolute value of the power of the curved surface on the conjugate surface side in each correction optical system must be greater than the absolute value of the power of the opposing surface (curved surface in imaging optical measurement). Therefore, in configuration 2 of FIG. 6 , the absolute value of the positive power P among the NPs of the I correction optical system 30 must be greater than the absolute value of the negative power N.

On the other hand, from the point of view of correcting the field curvature, as described above, the direction of the field curvature generated by the X correction optical system 20 and the direction of the field curvature generated by the Y correction optical system 10 are set in the same direction, and the sum of them is It is preferable to correct in the reverse direction in the I correction optical system 30 . In configuration 2 of FIG. 6 , in both the Y correction optical system 10 and the X correction optical system 20, the absolute value of the positive power P is greater than the absolute value of the negative power N. In this case, a negative value is taken as the Petzval coefficient. On the other hand, from the point of view of correcting the coma aberration, the absolute value of the positive power (P) is larger than the absolute value of the negative power (N) in the I correction optical system 30, but at this time, the Petzval coefficient takes a negative value as well. Therefore, in configuration 2 of FIG. 6 , on the premise that the coma aberration is corrected, the Petzval coefficients of the Y correction optical system 10 and the X correction optical system 20 and the I correction optical system 30 have the same sign. becomes At this time, the field curvature directions of the Y correction optical system 10 and the X correction optical system 20 coincide with the field curvature directions of the I correction optical system, and the field curvature is not corrected satisfactorily.

Next, configuration 1 in FIG. 6, in which the type of the I-correction optical system 30 is different from configuration 2 in FIG. 6, will be considered. In Configuration 1, from the viewpoint of correcting the coma aberration, the absolute value of the negative power N in the I correction optical system 30 is greater than the absolute value of the positive power P, and a positive value is taken as the Petzval coefficient at this time. do. Therefore, in Configuration 1, the signs of the Petzval coefficients of the Y correction optical system 10 and the X correction optical system 20 and the Petzval coefficients of the I correction optical system 30 are different. That is, when the Petzval coefficients of the Y correction optical system 10, the X correction optical system 20, and the I correction optical system 30 are P1, P2, and P3, respectively, P3 has a different sign from those of P1 and P2. That is, it is possible to achieve both correction of coma aberration in a single correction optical system and correction of field curvature in the entire correction optical system. In Fig. 6, in addition to configuration 1, configuration 4 also corresponds to this condition. Such a configuration is the sign of the power of the curved surface on the conjugate surface side in the Y correction optical system 10 and the X correction optical system 20, and the code of the power of the curved surface on the conjugate surface side in the I correction optical system 30. are different configurations, which can be generalized and expressed.

In the configuration example shown in Fig. 2, with respect to the imaging optical system IO, the Y correction optical system 10 arranged on the object plane 1 side is of NP type, and the I correction optical system 30 arranged on the image plane 7 side is NP type. Type, the X correction optical system 20 disposed on the upper surface 7 side is of the PN type, and corresponds to configuration 4 in FIG. 6 . Therefore, it is a configuration based on requirements suitable for suppressing aberrations occurring in the correction optical system.

(Requirement 4)

In addition, in the projection optical system PO of this embodiment, it is required to satisfy d _min x (1-k) ≤ d ₂ ≤ d _max x (1+k). In this expression, the distance between the pair of curved surfaces in the Y correction optical system 10 is d ₁ , the distance between the pair of curved surfaces in the X correction optical system 20 is d ₂ , and the projection optical system PO (imaging optical system (IO)) is set to β(|β|≠1). Then, the smaller one of d ₁ and (d ₁ ×|β|) is set to d _min , the larger one to d _max , and the constant k is set to 0≤k≤1. In other words, using the variables shown in FIG. 3 , the projection optical system PO of the present embodiment requires that d _min × (1-k) ≤ d _{i ≤} d _max × (1+k) be satisfied. do. In this expression, d _o is the distance between the lenses in the correction optical system disposed near the object surface 1, and d _i is the distance between the lenses in the correction optical system disposed near the image surface 7. The smaller one of _o and (d _o ×|β|) is set to d _min , and the larger one is set to d _max . The reason for this is explained below.

In order to suppress the above-mentioned astigmatism, the value obtained by multiplying the focus position change Δs _o on the object surface 1 side by the square of the magnification of the imaging optical system IO β ² and the focus position change Δs _i on the image plane 7 side The values need to be equal. That is, the following equation (16) needs to be satisfied. In addition, in order to correct the XY magnification described above, the value of the magnification β _o generated by the correction optical system on the object surface 1 side and the value of the magnification β _i generated by the correction optical system on the image surface 7 side are equal Needs to be. That is, the following formula (17) needs to be satisfied.

In order to satisfactorily correct the field curvature, it is preferable that the correction optical system arranged on the object plane 1 side and the correction optical system arranged on the image plane 7 side have the same value (absolute value) of the Petzval coefficient. For example, when the Petzval coefficients of the Y correction optical system 10, the X correction optical system 20, and the I correction optical system 30 are P1, P2, and P3, respectively, |P1|, |P2|, and |P3| It is desirable that these match. Assuming that the glass materials used in all correction optical systems are equal, this condition is expressed as the following equation (18).

Here, it is assumed that φ _o = φ _i . As described above, φ _o and φ _i correspond to magnification sensitivities to changes in the spacing of a pair of curved surfaces, and may be set to equal values unless there is a particular reason. Based on the above equations (9) to (12), equations (16) to (18) and the above assumptions, if the equations are arranged for d _i , the quadratic equation represented by the following equation (19) is is obtained

As a solution of equation (19), d _i for suppressing the aberration satisfactorily is derived for given β, s _o , s _k ', and d _o . Here, the case of β<-1 is considered. This corresponds to the case where the imaging optical system IO is a magnifying system. According to the inventors' examination, when d _i is calculated based on equation (19) for any s _o , s _k ', and d _o , d _o is the lower limit of d _i , and (d _o ×|β| ) was found to be obtained. That is, when the imaging optical system IO is a magnifying system, for any s _o , s _k ', and d _o , d _i for suppressing aberration satisfactorily during the condition of d _o ≤ d _{i ≤} d _o × |β| exists. In the upper part of Fig. 7, at β = -1.5, d _o = 10, and 30 mm, the result of calculating d _i based on equation (19) for any s _o , s _k ' of 1000 mm or less is shown as a histogram. . From the histogram shown at the top of FIG. 7 , it can be confirmed that d _i is distributed in the range of d _o ≤ d _{i ≤} d _o × |β|. Next, consider the case of -1<β<0. This corresponds to the case where the imaging optical system IO is a reduction system. From the same examination, when d _i is calculated based on equation (19) for any s _o , s _k ', and d _o , the lower limit of d _i is (d _o ×|β|) and the upper limit of d _o is It turned out to be obtained. That is, when the imaging optical system IO is a reduction system, d _i for suppressing aberration satisfactorily during the condition d _o ×|β|≤d _i ≤d _o for any s _o , s _k ', and d _o exists. In the lower part of Fig. 7, at β = -0.5, d _o = 10, 30 mm, the result of calculating d _i based on equation (19) for any s _o , s _k ' of 1000 mm or less is shown as a histogram. . From the histogram shown in the lower part of FIG. 7 , it can be confirmed that d _i is distributed in the range of d _o ×|β|≤d _{i≤d o} .

Putting these together, the requirements for good correction (suppression) of astigmatism, XY magnification difference, and field curvature are d _o and (d _o ×|β|), where d _min is the smaller one and d _max is the larger one. , it can be expressed as satisfying d _{min ≤} d _{i ≤} d _max .

However, it cannot be said that the aberration greatly increases immediately when d _i is omitted from the above conditions. Fig. 8 is a diagram showing the result of configuring a correction optical system satisfying the requirements of the present embodiment in the projection optical system PO of β ₌ -1.25 and designing it by changing di. The abscissa is the ratio of d _i and d _o , and the ordinate axis evaluates the maximum-minimum within the angle of view for the Z4 term fitting the wavefront aberration to the Zernike polynomial, and qualitatively represents the degree of field curvature. Since it is assumed that an ideal lens that does not generate aberration is used as the imaging optical system IO, FIG. 8 shows aberrations generated only in the correction optical system. As expected from the results of the considerations so far, aberrations are most suppressed in the vicinity of d _i /d _o =1.2 and in the relationship close to |β|. However, for example, when d _i /d _o = 1.6, there is a possibility that it can withstand practical use. Therefore, the above conditions may be relaxed, and for this reason, a relaxation coefficient k is introduced, and the condition related to d _i is set to d _min × (1-k) ≤ d _{i ≤} d _max × (1 + k). The relaxation coefficient k may vary depending on the application of the projection optical system PO of the present embodiment. For example, when the projection optical system PO of the present embodiment is applied to an exposure apparatus, the depth of focus is small in an exposure process including a thin line width near the limit resolution, and the term Z4 is used to secure exposure margin. For example, it needs to be suppressed to 25 mλ or less. However, in an exposure process including thick line widths spaced from the limiting resolution, the depth of focus is large, so there is room for exposure latitude, and the Z4 term may be, for example, 40 mλ or less. Based on the design result of Fig. 8, the relaxation coefficient k can be a value within the range of 0.3 to 0.5, and 0.4 is an example. At this time, d _i can take d _min x 0.6 ? d _i ? d _max x 1.4, but even in this range, aberration suppression at a level that does not cause a problem in practical use can be achieved.

(Requirement 5)

Further, in the projection optical system PO of the present embodiment, the coordinates of the center of curvature of the spherical surface or the generatrix of the cylindrical plane included in each correction optical system and the coordinates of the center of gravity (center) of the rectangle circumscribed to the object domain or image domain. It is good also as a requirement that it is comprised so that the difference of may be small. This requirement may be provided in order to reduce aberrations such as curvature of field that increase in proportion to the power of the distance from the generatrix or the center of curvature. In order to suppress the amount of aberration generated in a single correction optical system, it is preferable to align the optical center of gravity (centre) near the center of gravity (near the center) of the object area or image area to be used. Here, this requirement is such that the difference between the coordinates of the center of curvature of the generatrix or curved surface and the coordinates of the center of gravity of a rectangle circumscribing the object domain or image domain (hereinafter sometimes referred to as a circumscribed rectangle) is projected so that it falls within the allowable range. It may be understood as what constitutes the optical system PO. Ideally, the coordinates of the center of curvature of the generatrix or curved surface coincide with the coordinates of the center of gravity of the circumscribed rectangle. In addition, the object area is an optical path area (which may be understood as a light irradiation area) on the object surface 1, and the image area is an optical path area (which may be understood as a light irradiation area) on the upper surface 7. . In addition, the allowable range may be a range of the difference set so that each aberration and magnification difference generated in each correction optical system converges within a predetermined range.

If this requirement is specifically explained, with respect to the Y correction optical system 10, the Y coordinate (first direction) of the generatrix of the Y cylindrical surfaces 10a and 10b constituting the pair of curved surfaces in the Y correction optical system 10 coordinate of) and the Y coordinate of the center of gravity of the circumscribed rectangle of the object area. In addition, with respect to the X correction optical system 20, the X coordinates of the generatrix lines of the X cylindrical surfaces 20a and 20b constituting the pair of curved surfaces in the X correction optical system 20 (coordinates in the second direction); The difference between the X coordinates of the centers of gravity of the circumscribed rectangles of the image area is small. Regarding the I-correction optical system 30, the XY coordinates of the centers of gravity of the spheres 30a and 30b constituting the pair of surfaces in the I-correction optical system 30 and the circumscribed rectangle of the image domain (or object domain) It is configured so that the difference of XY coordinates of the center of gravity becomes small.

Here, in an example in which the projection optical system PO is an opener optical system, the object region 50 and the image region 54 of an arc shape other than the Y axis indicated by the lattice-shaped portion in FIG. 9 are used. In addition, here, the imaging optical system IO has an enlargement magnification (β<-1), and the image region 54 is drawn larger than the object region 50, but the reduction system (-1<β<0) In the case of , the image area 54 becomes smaller with respect to the object area 50 . In the case of this example, the correction optical system arranged on the object plane 1 side, as shown in FIG. It can be configured so that the difference between the coordinates of the optical center of each curved surface of is small (preferably, the coordinates coincide). Similarly, the correction optical system arranged on the image surface 7 side, as shown in FIG. It can be configured so that the difference of the coordinates of (center of gravity) becomes small (preferably, the coordinates match).

For example, when the Y correction optical system 10 is disposed on the object plane 1 side, the Y coordinate of the generatrix of the Y cylindrical plane and the center of gravity 52 of the circumscribed rectangle 51 of the object domain 50 The position of the Y correction optical system 10 may be adjusted so that the difference in Y coordinates becomes small. That is, the Y correction optical system 10 may be eccentric in the Y direction with respect to the optical axis 53 of the imaging optical system IO. Further, when the I-correction optical system 30 is disposed on the image plane 7 side, the difference between the YX coordinates of the center of curvature of the spherical surface and the image region 54 and the XY coordinates of the center of gravity 56 of the circumscribed rectangle 55 is small. The position of the I correction optical system 30 may be adjusted so as to be correct. That is, the I correction optical system 30 may be eccentric in the XY direction with respect to the optical axis 57 of the imaging optical system IO. Further, when the X correction optical system 20 is arranged on the image plane 7 side, the X coordinate of the generatrix of the X cylindrical plane and the X coordinate of the center of gravity 56 of the circumscribed rectangle 55 of the image region 54 are The position of the X correction optical system 20 can be adjusted so that the difference becomes small.

Here, in the projection optical system PO of this embodiment, the object domain 50 and the image domain 54 are symmetrical with respect to the Y-axis, and the center of gravity 52 of the circumscribed rectangle 51 on the object plane 1 side and the center of gravity 56 of the circumscribed rectangle 55 on the upper surface 7 side are all on the Y-axis. In this case, the X correction optical system 20 is not eccentric with respect to the optical axis of the imaging optical system IO, but the coordinates of the generatrix of the X cylindrical plane and the optical axis 57 (or optical axis ( 53)) may be configured so that the difference in coordinates becomes small (preferably coincident). On the other hand, when the object area 50 and the image area 54 are asymmetrical with respect to the Y axis, that is, the center of gravity 52 of the circumscribed rectangle 51 and the center of gravity 56 of the circumscribed rectangle 55 are on the Y axis. There are cases where it is not in In this case, the X correction optical system 20 with respect to the optical axis 57 of the imaging optical system IO so that the difference between the X coordinate of the center of gravity 52 or the center of gravity 56 and the X coordinate of the generatrix of the X cylindrical plane becomes small. ) may be eccentric in the X direction. Ideally, the optical center of each curved surface and the center of gravity of the circumscribed rectangle of the object area 50 or the image area 54 are perfectly matched. do.

[Example]

Next, examples of the first embodiment will be described. Here, Comparative Example 1 and Comparative Example 2 are used as comparative examples for comparison with Examples. In Example, Comparative Example 1, and Comparative Example 2, the X correction optical system, Y correction optical system, and I correction optical system were provided in the opener optical system with magnification (β = -1.25), and the result of optimization design is shown. Fig. 10 shows optical intensities of Example, Comparative Example 1 and Comparative Example 2, and "X", "Y" and "I" in the figure indicate an X correction optical system, a Y correction optical system, and an I correction optical system. . 11A to 11B show each surface RDN and aspherical surface coefficient as detailed design values, respectively, and FIG. 12 shows evaluation values of optical performance. In all examples, an X correction optical system and an I correction optical system are provided on the object plane side, and a Y correction optical system is provided on the image plane side.

In the embodiment, the X correction optical system is NP type, the I correction optical system is PN type, and the Y correction optical system is PN type, so as to satisfy the above requirements. On the other hand, Comparative Example 1 differs from the Example in that the Y correction optical system is of the NP type. Further, Comparative Example 2 differs from the Example in that the I correction optical system is of the NP type. The spacing of a pair of curved surfaces included in each correction optical system is common in all examples, and is 25 mm in the X correction optical system, 30 mm in the I correction optical system, and 31.3 mm in the Y correction optical system. In addition, the absolute values of the curvature radii of a pair of curved surfaces included in each correction optical system are all 23700 mm. For each column of each surface RDN in FIG. 11A, "No." is the surface number, "Type" is the type of surface, "RY" is the radius of curvature of the Y cross section, "RX" is the radius of curvature of the X cross section, and "D" denotes the face spacing, respectively. In the third column of FIG. 11A, when the curved surface is a transmissive surface, the type of glass material is described, and when the curved surface is a reflective surface, "refl" is described. In "Type", "r" represents a spherical surface, "asp" represents an aspheric surface, and "cyl" represents a cylindrical surface. In Example, Comparative Example 1, and Comparative Example 2, S3, S4, S12, S13, S14, S15, S16, S17, S18, S24, S25, and S26 are quadratic surfaces defined by the following formula (20) It is the aspherical surface of the base.

Here, “R” is the radius of curvature, “k” is the conic constant, “h” is the distance from the center of the optical axis, and “C _i ” is the i-order aspherical surface coefficient. However, S13 and S17, and S14 and S16 are the same planes through which light rays pass twice. The image side numerical aperture (NA) of the optical system is 0.1, and the design wavelength is 365 to 435 nm. In addition, the object area|region and the image area|region are circular arc shape, the radius of curvature of the circular arc on the object surface side is 550 mm, the X-direction width is ±400 mm, and the Y-direction width is 70 mm.

The wavefront aberration shown in (a) of FIG. 12 is a value obtained by averaging the wavefront aberration in the Y direction in the image region for each term obtained by fitting the wavefront aberration for a wavelength of 405 nm to the Zernike polynomial, as the range from the maximum to the minimum in the X direction. it was evaluated Aberrations generated in the correction optical system are basically low-order aberrations, and evaluation values of terms corresponding to Z4 terms to Z8 terms of the Zernike coefficient are shown here. Z4 is a term corresponding to focus, Z5 and Z6 to astigmatism, and Z7 and Z8 to coma aberration. In addition, the wavefront aberration shown in (b) of FIG. 12 is the root mean square of the terms Z4 to Z36 by averaging in the Y direction within the image region for each term obtained by fitting the wavefront aberration for a wavelength of 405 nm to the Zernike polynomial. After calculating (RMS), the maximum value in the X direction was evaluated. The wavefront aberration RMS is an index representing the overall imaging performance of the projection optical system. Regarding Examples In Comparative Example 1, the wavefront aberration is large in all terms shown. Further, in Comparative Example 2, the Z5 term and Z6 term corresponding to astigmatism are better than those of the Examples, but Z7 corresponding to coma aberration is very large at 400 mλ. Looking at the wavefront aberration RMS, compared to 50 mλ in Comparative Example 1 and 84 mλ in Comparative Example 2, it is as small as 19 mλ in Example. From the above, the aberration suppression effect of the configuration of the embodiment satisfying the above requirements is understood.

<Second Embodiment>

A second embodiment of the present invention will be described. In this embodiment, the exposure apparatus 100 provided with the projection optical system PO of 1st Embodiment is demonstrated, referring FIG. The exposure apparatus 100 may include an illumination optical system IL, a projection optical system PO, and a control unit CNT. The control unit CNT is constituted by, for example, a computer having a CPU or a memory, and controls each unit of the exposure apparatus 100 to control exposure of the substrate. In addition, in the exposure apparatus 100 shown in FIG. 13, the light source 80 is provided as a component of the illumination optical system IL, but is not limited thereto, and the light source 80 is a component of the illumination optical system IL. It may not be.

Illumination light emitted from the light source 80 included in the illumination optical system IL is irradiated to the original plate 90 disposed on the object plane of the projection optical system PO through various optical elements 81 to 85 . As the light source 80, a mercury lamp, excimer laser, LED or the like is generally used. An optical integrator 82 may be configured in the illumination optical system IL in order to increase the uniformity of the illuminance distribution or angle distribution of the surface to be irradiated. As an example of the optical integrator 82, although a fly-eye lens is used in FIG. 13, it is not limited thereto, and an optical rod or the like may be used, for example. In addition, an optical diaphragm 83 may be provided to control the angular distribution of the surface to be irradiated.

The projection optical system PO projects the pattern of the original plate 90 onto the substrate 92 arranged on the image surface of the projection optical system PO. In this way, the pattern of the original plate 90 can be transferred onto the substrate through the projection optical system PO. As described above, the projection optical system PO has an imaging optical system IO, a Y correction optical system 10, an X correction optical system 20, and an I correction optical system 30, and has both an object plane and an image plane. It can be configured to have telecentricity in . The original plate 90 and the substrate 92 are respectively held and driven by the original plate driving mechanism 91 (original plate stage) and the substrate driving mechanism 93 (substrate stage). In addition, the controller CNT controls the timing of exposure of the substrate 92 and driving of the original plate and the substrate, so that the pattern of the original plate 90 is transferred onto the substrate 92 (that is, the processing of the substrate 92). exposure treatment). According to the exposure apparatus 100 of the present embodiment, since the imaging performance of the projection optical system PO can be improved with a relatively simple configuration, more precise patterning is possible.

<Embodiment of the manufacturing method of an article>

The method for manufacturing an article according to an embodiment of the present invention is suitable for manufacturing an article such as a micro device such as a semiconductor device or an element having a microstructure, for example. The article manufacturing method of the present embodiment includes a step of forming a latent image pattern on a photosensitive agent applied to a substrate using the exposure apparatus (step of exposing the substrate), and developing (processing) the substrate on which the latent image pattern is formed in this step. include the process In addition, this manufacturing method includes other well-known processes (oxidation, film formation, vapor deposition, doping, planarization, etching, resist removal, dicing, bonding, packaging, etc.). Compared with conventional methods, the article manufacturing method of the present embodiment is advantageous in at least one of product performance, quality, productivity, and production cost.

The present invention is not limited to the above embodiments, and various changes and modifications are possible without departing from the spirit and scope of the present invention. Accordingly, the claims are appended to clarify the scope of the present invention.

1: Object plane
2: plane mirror
3: first concave mirror
4: convex mirror
5: second concave mirror
6: plane mirror
10: Y correction optical system
20: X correction optical system
30: I correction optical system
PO: projection optics
IO: imaging optics

Claims (16)

It is a projection optical system that projects the pattern of the object surface onto the image surface,
an imaging optical system for forming an image on the image surface at a non-magnification of the pattern of the object surface;
A first pair of curved surfaces arranged on an optical path between the object surface and the pupil surface of the imaging optical system and having different power signs, and the imaging optical system in a first direction parallel to the image plane. A first correction optical system for correcting magnification;
In a second direction including a second pair of curved surfaces disposed on an optical path between the upper surface and the pupil surface and having different power signs, parallel to the upper surface and intersecting the first direction a second correction optical system for correcting the magnification of the imaging optical system;
a third pair of curved surfaces disposed on an optical path between one of the upper surface and the object surface and the pupil surface and having different power signs; Third correction optical system for correcting the magnification of the imaging optical system
to provide,
Among the first pair of curved surfaces, the power of the curved surface close to the object surface is φ ₁ , the power of the curved surface of the second pair of curved surfaces close to the upper surface is φ ₂ , and the power of the curved surface of the third pair of curved surfaces is φ 2 . When the power of the curved surface closer to one side is φ ₃ , φ ₁ and φ ₂ have the same power sign, and φ ₃ has a different power sign for φ ₁ and φ ₂ ,
The distance between the first pair of curved surfaces is d ₁ , the distance between the second pair of curved surfaces is d ₂ , the magnification of the imaging optical system is β (|β| ≠ 1), and d ₁ and (d When the smaller one of ₁ ×|β|) is d _min , the larger one is d _max , and the constant k is 0 ≤ k ≤ 1,
d _min ×(1-k)≤d ₂ ≤d _max ×(1+k)
A projection optical system characterized in that it satisfies. The method of claim 1, wherein the power of a curved surface far from the object surface among the first pair of curved surfaces is φ ₁ ', and the power of a curved surface far from the upper surface among the second pair of curved surfaces is φ ₂ ', wherein When the power of the curved surface farther from one of the third pair of surfaces is φ ₃ ', |φ ₁ |>|φ ₁ '|, |φ ₂ |>|φ ₂ '| and |φ ₃ |>|φ ₃ '|. The method of claim 1 or 2, wherein the magnification β of the imaging optical system is 0 <|β|≤0.995 and 1.005≤|β| A projection optical system that satisfies any of the above. The projection optical system according to claim 1 or 2, wherein the magnification β of the imaging optical system satisfies one of 0.1≤|β|≤0.95 and 1.05≤|β|≤2.0. The method of claim 1 or 2, wherein when the Petzval coefficients of the first correction optical system, the second correction optical system, and the third correction optical system are P1, P2, and P3, respectively, P1 and P2 have the same sign, , P3 has a different sign from those of P1 and P2. The projection optical system according to claim 5, wherein |P1| coincides with |P2| and |P3|. The projection optical system according to claim 1 or 2, wherein the constant k is within a range of 0.3 to 0.5. The method according to claim 1 or 2, wherein the pair of surfaces of the first correction optical system are cylindrical planes, and the pair of planes of the second correction optical system are cylindrical planes, respectively. A projection optical system characterized in that each of the pair of surfaces in the three-correction optical system is a spherical surface. The method according to claim 1, wherein the first correcting optical system comprises a coordinate in the first direction of a generatrix of a cylindrical surface constituting the first pair of curved surfaces in the first correcting optical system, and A projection optical system characterized in that a difference in coordinates in the first direction of a center of gravity of a rectangle circumscribed in an optical path region of the projection optical system is configured to be small. The method according to claim 1, wherein the second correcting optical system comprises: coordinates in the second direction of generatrix of cylindrical surfaces constituting the second pair of curved surfaces in the second correcting optical system; A projection optical system characterized in that a difference in coordinates in the second direction of a center of mass of a rectangle circumscribed in an optical path area of ? is small. The method of claim 1, wherein the third correction optical system comprises coordinates in the first direction and the second direction of a center of gravity of a sphere constituting the third pair of curved surfaces in the third correction optical system; A projection optical system characterized in that a difference in coordinates of a center of mass of a rectangle circumscribed in an optical path region on one side is small in the first direction and in the second direction. 12. The projection optical system according to any one of claims 9 to 11, wherein the object plane and an optical path region on the object plane have an arc shape. The method according to claim 1 or 2, wherein in the first correction optical system, the magnification of the imaging optical system in the first direction is changed by relatively moving the first pair of curved surfaces,
In the second correction optical system, the magnification of the imaging optical system in the second direction is changed by relatively moving the second pair of curved surfaces;
In the third correction optical system, the magnification of the imaging optical system in the first direction and the second direction is changed by relatively moving the third pair of curved surfaces.
A projection optical system characterized in that. The projection optical system according to claim 1 or 2, wherein telecentricity is provided on both the object plane and the image plane. An exposure device for exposing a substrate,
An illumination optical system for illuminating the original plate;
The projection optical system according to claim 1 or 2
to provide,
The exposure apparatus according to claim 1, wherein the projection optical system projects the pattern of the original plate disposed on the object surface onto the substrate disposed on the image surface. An exposure step of exposing a substrate using the exposure apparatus according to claim 15;
A processing step of processing the substrate exposed in the exposure step;
An article manufacturing method characterized in that an article is manufactured from the substrate processed in the processing step.

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