JP2010098171A - Optical system and aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical system, arranging pupillary surface near the reflecting surface of reflecting optical element, which is capable of reducing the heterogeneity of numerical aperture. <P>SOLUTION: The projection optical system includes a mirror M2 arranged so that the direction of light of incidence 37I is different from the direction of reflection light 37R. The pupillary surface 35A of the projection optical system in a part 37Ia, which is not superposed with the reflection light 37R among the light of incidence 37I, is formed above the reflection surface of the mirror M2. The pupillary surface 35B in the part 37Ra, which is not superposed with the light of incidence 37I among the reflection light 37R, is formed above the reflection surface thereof. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical system including a reflective optical element, an exposure apparatus including the optical system, and a device manufacturing method using the exposure apparatus.

  A batch exposure type (for example, a stepper) or a scanning exposure type (for example, scanning) used to transfer and expose a pattern such as a reticle onto a photosensitive substrate in a photolithography process for manufacturing a device (electronic device) such as a semiconductor device. In an exposure apparatus such as a stepper), the exposure wavelength has been shortened to increase the resolution, and recently, KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), or the like is used as exposure light. Furthermore, an exposure apparatus (EUV exposure apparatus) that uses extreme ultraviolet light (Extreme Ultraviolet Light: hereinafter referred to as EUV light) having a wavelength of about 100 nm or less as exposure light has been developed.

Since there is no optical material that transmits EUV light at present, the illumination optical system and projection optical system of the EUV exposure apparatus each include a plurality of mirrors whose reflecting surfaces are flat, spherical, or aspherical. It is. In such a reflective optical system, the pupil plane on which the aperture stop is to be placed is substantially superimposed on the reflective surface of a certain mirror (see, for example, Patent Document 1), so that the pupil plane is, for example, between mirrors. Compared with the case where the lens is placed in the middle, it becomes easier to separate incident light and reflected light on the pupil plane, and the degree of freedom in optical design increases.
JP 2007-109958 A

  In a reflection optical system in which a pupil plane is placed almost on a reflection surface of a conventional mirror, it is difficult to dispose a mechanical aperture stop on the reflection surface. Further, a variable aperture stop having a movable part is usually used as the aperture stop, and it is extremely difficult to dispose the variable aperture stop close to the reflecting surface. For this reason, the aperture stop is disposed at a position away from the reflecting surface of the mirror to some extent. Since the aperture stop moves away from the pupil plane (pupil position) in this way, the portion where the light beam cannot be accurately focused (the contour portion of the pupil) increases depending on the image height, so the numerical aperture (NA) between the image points is increased. Non-uniformity occurs and imaging characteristics become non-uniform.

  Also, the incident light to the mirror in the reflective optical system is not perpendicularly incident, and the direction of the incident light and the direction of the reflected light are different, so the aperture stop is placed at a position away from the mirror's reflective surface (pupil surface). In this case, the aperture shape of the aperture stop needs to be a shape that includes both incident light and reflected light. However, since the shape is complicated depending on the shape of the illumination area, the structure of the aperture stop is complicated.

Furthermore, even if the design is made by shifting the position of the pupil surface above the reflection surface of the mirror, the incident light and the reflected light partially overlap in the vicinity of the reflection surface, so the pupil surface is placed on the incident light side. Even if it is arranged on either side of the reflected light, it becomes impossible to accurately squeeze a part of the outline of the pupil to be squeezed by the aperture stop. Therefore, the numerical aperture is non-uniform.
In view of such circumstances, the present invention provides an optical system in which a pupil plane is disposed in the vicinity of the reflective surface of the reflective optical element and can reduce the non-uniformity of the numerical aperture, an exposure apparatus including the optical system, and the exposure An object of the present invention is to provide a device manufacturing method using an apparatus.

  The optical system according to the present invention is an optical system including a reflective optical element arranged so that the direction of incident light and the direction of reflected light are different. In the first optical system of the present invention, the pupil of the optical system in the portion of the incident light that does not overlap with the reflected light is formed above the reflective surface of the reflective optical element, The pupil in a portion not overlapping with the incident light is formed above the reflecting surface.

In the second optical system according to the present invention, the pupil plane of the optical system intersects the reflective surface of the reflective optical element, and the pupil plane at the end of the incident light opposite to the reflected light is It is located above the reflecting surface, and the pupil surface at the end of the reflected light opposite to the incident light is located above the reflecting surface.
In the third optical system according to the present invention, the first portion of the pupil of the optical system is formed on the incident light side, and the second portion of the pupil of the optical system is formed on the reflected light side. is there.

Next, an exposure apparatus according to the present invention illuminates a pattern with exposure light and exposes the substrate with the exposure light through the pattern and the projection optical system. It is to be prepared.
Another exposure apparatus according to the present invention is an exposure apparatus that projects and exposes an image of a first surface onto a second surface, and includes the optical system of the present invention.

  The device manufacturing method according to the present invention includes a step of exposing a substrate using the exposure apparatus of the present invention and a step of processing the exposed substrate.

  According to the optical system of the present invention, when the pupil plane is arranged in the vicinity of the reflective surface of the reflective optical element, the pupil plane in the portion of the incident light that does not overlap with the reflected light (end on the side opposite to the reflected light) Both the (first part of the pupil) and the pupil surface (second part of the pupil) in the part of the reflected light that does not overlap with the incident light (the end opposite to the incident light) can be arranged above the reflective surface. . Accordingly, since the aperture stop can be easily installed on the pupil plane with both incident light and reflected light, the non-uniformity of the numerical aperture can be reduced.

An example of an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view schematically showing the overall configuration of the exposure apparatus 100 of the present embodiment. The exposure apparatus 100 is an EUV exposure apparatus that uses EUV light (Extreme Ultraviolet Light) of, for example, 11 nm or 13 nm within a wavelength range of about 3 nm to about 50 nm as illumination light EL (exposure light) for exposure. . In FIG. 1, an exposure apparatus 100 includes a laser plasma light source 10 that generates a pulse of illumination light EL, and an illumination optical system that illuminates an illumination region 27R on a pattern surface (lower surface in this case) of a reticle R (mask) with the illumination light EL. ILS, reticle stage RST that moves reticle R, and projection optical system PO that projects an image of a pattern in illumination area 27R of reticle R onto wafer W (photosensitive substrate) coated with a resist (photosensitive material). I have. Further, the exposure apparatus 100 includes a wafer stage WST that moves the wafer W, a main control system 31 that includes a computer that controls the overall operation of the apparatus, and the like.

In the present embodiment, since EUV light is used as the illumination light EL, the illumination optical system ILS and the projection optical system PO are configured by reflective optical members such as a plurality of mirrors except for a specific filter or the like (not shown). The reticle R is also a reflection type. For example, the reflective optical member is obtained by processing a surface of a member made of quartz (or a metal having high heat resistance) into a predetermined curved surface or a plane with high accuracy, and then molybdenum (Mo) and silicon (Si) on the surface. A multilayer film (an EUV light reflecting film) is formed as a reflecting surface. The multilayer film may be another multilayer film in which a substance such as ruthenium (Ru) or rhodium (Rh) and a substance such as Si, beryllium (Be), or carbon tetraboride (B ₄ C) are combined. . The reticle R, for example, forms a multilayer film on the surface of a quartz substrate to form a reflective surface, and then absorbs EUV light such as tantalum (Ta), nickel (Ni), or chromium (Cr) on the reflective surface. A transfer pattern is formed by an absorption layer made of a material to be transferred.

Further, in order to prevent the EUV light from being absorbed by the gas, the exposure apparatus 100 is accommodated in the box-like vacuum chamber 1 as a whole, and the space in the vacuum chamber 1 is evacuated through the exhaust pipes 32Aa, 32Ba and the like. Large vacuum pumps 32A, 32B and the like are provided. Further, a plurality of sub-chambers (not shown) are also provided in order to further increase the degree of vacuum on the optical path of the illumination light EL in the vacuum chamber 1. As an example, the pressure in the vacuum chamber 1 is about 10 ⁻⁵ Pa, and the pressure in the subchamber (not shown) that houses the projection optical system PO in the vacuum chamber 1 is about 10 ⁻⁵ to 10 ⁻⁶ Pa.

  Hereinafter, in FIG. 1, the Z axis is taken in the normal direction of the surface (bottom surface of the vacuum chamber 1) on which the wafer stage WST is placed, and a plane perpendicular to the Z axis (in this embodiment, a plane substantially parallel to the horizontal plane). In the following description, the X axis is perpendicular to the paper surface of FIG. 1 and the Y axis is parallel to the paper surface of FIG. In the present embodiment, the illumination area 27R of the illumination light EL on the reticle R has an arc shape elongated in the X direction (non-scanning direction), and the reticle R and the wafer W are in the Y direction with respect to the projection optical system PO during exposure. Scanning is performed in synchronization with (scanning direction).

  First, the laser plasma light source 10 includes a high-power laser light source (not shown), a condensing lens 12 that condenses laser light supplied from the laser light source through the window member 15 of the vacuum chamber 1, xenon, and the like. This is a gas jet cluster type light source including a nozzle 14 for ejecting a target gas and a condensing mirror 13 having a spheroidal reflection surface. For example, the illumination light EL pulse-emitted from the laser plasma light source 10 at a frequency of several kHz is condensed on the second focal point of the condenser mirror 13. The illumination light EL condensed at the second focal point becomes a substantially parallel light beam via the concave mirror (collimator optical system) 21, enters the first fly-eye optical system 22, and is reflected by the first fly-eye optical system 22. The illumination light EL enters the second fly's eye optical system 23. The pair of fly-eye optical systems 22 and 23 constitutes an optical integrator. Further, the illumination light from the laser plasma light source 10 performs Koehler illumination on the first fly's eye optical system 22.

  As an example, as shown in FIG. 2A, the first fly's eye optical system 22 is composed of a large number of mirror elements 22a having an arcuate outer shape similar to two-dimensionally arranged illumination areas. . The second fly's eye optical system 23 corresponds to the many mirror elements 22a of the first fly's eye optical system 22, as shown in FIG. A plurality of mirror elements 23a having an outer shape. The shape and arrangement of each mirror element of the fly-eye optical systems 22 and 23 are also disclosed in, for example, US Pat. No. 6,452,661.

  In FIG. 1, the reflecting surface of each mirror element of the first fly-eye optical system 22 is substantially conjugate with the pattern surface of the reticle R, and is in the vicinity of the reflecting surface of the second fly-eye optical system 23 (near the exit surface of the optical integrator). ), A substantial surface light source (a set of a large number of minute secondary light sources) having a predetermined shape is formed. That is, the surface on which the substantial surface light source is formed is the pupil plane of the illumination optical system ILS, and the aperture stop 28 is disposed at this pupil plane or a position near this pupil plane. The aperture stop 28 representatively represents a plurality of aperture stops having openings of various shapes, and the illumination condition is changed to normal illumination by exchanging the aperture stop 28 under the control of the main control system 31. It can be switched to annular illumination, dipole illumination, quadrupole illumination, or the like.

  The illumination light EL that has passed through the aperture stop 28 enters the curved mirror 24, and the illumination light EL reflected by the curved mirror 24 is reflected by the concave mirror 25, and then is an arcuate illumination area on the pattern surface of the reticle R. 27R is illuminated obliquely from below with a uniform illuminance distribution. The curved mirror 24 and the concave mirror 25 constitute a condenser optical system. By the condenser optical system, the reflected light of the multiple mirror elements of the first fly-eye optical system 22 or the light from the surface light source in the aperture stop 28 illuminates the illumination area 27R in a superimposed manner. The illumination optical system ILS is configured including the concave mirror 21, the fly-eye optical systems 22 and 23, the aperture stop 28, the curved mirror 24, and the concave mirror 25. In this case, the illumination light EL from the laser plasma light source 10 Koehler-illuminates the first fly's eye optical system 22, and consequently the pattern surface of the reticle R. In the example of FIG. 1, the curved mirror 24 is a convex mirror, but the curved mirror 24 may be formed of a concave mirror, and the curvature of the concave mirror 25 may be reduced by that amount.

Further, in order to substantially define the shape of the illumination area 27R, the first blind 26A that shields the outer edge portion (−Y direction) of the illumination light EL incident on the illumination area 27R and the illumination area 27R are reflected. In addition, a reticle blind (variable field stop) including a second blind 26B that shields an outer edge (+ Y direction) of the illumination light EL is provided.
Next, the reticle R is attracted and held on the bottom surface of the reticle stage RST via the electrostatic chuck RH. The reticle stage RST is, for example, a two-dimensional magnetic levitation type along a guide surface parallel to the XY plane of the outer surface of the vacuum chamber 1 based on a measurement value of a laser interferometer (not shown) and control information of the main control system 31. It is driven with a predetermined stroke in the Y direction by a drive system (not shown) composed of a linear actuator, and is also driven in a minute amount in the X direction and the rotation direction around the Z axis (θZ direction). The reticle R is installed in a space surrounded by the vacuum chamber 1 through an opening on the upper surface of the vacuum chamber 1. A partition 8 is provided so as to cover the reticle stage RST on the vacuum chamber 1 side, and the inside of the partition 8 is maintained at an atmospheric pressure between the atmospheric pressure and the atmospheric pressure in the vacuum chamber 1 by a vacuum pump (not shown).

  The illumination light EL reflected by the illumination region 27R of the reticle R travels to the projection optical system PO that forms a reduced image of the pattern on the object plane (first surface) on the image plane (second surface). As an example, the projection optical system PO is configured by holding six mirrors M1 to M6 with a lens barrel (not shown), and is non-telecentric on the object plane (pattern surface of the reticle R) side and has an image plane (wafer W Is a telecentric reflecting optical system on the surface side, and the projection magnification is a reduction magnification such as 1/4. The illumination light EL reflected by the illumination area 27R of the reticle R is reduced in a part of the pattern of the reticle R on the exposure area 27W (area conjugate to the illumination area 27R) on the wafer W via the projection optical system PO. Form.

  In the projection optical system PO, the illumination light EL from the reticle R is reflected upward (+ Z direction) by the first mirror M1, subsequently reflected downward by the second mirror M2, and then the third mirror M3. And reflected downward by the fourth mirror M4. Next, the illumination light EL reflected upward by the fifth mirror M5 is reflected downward by the sixth mirror M6, and forms an image of a part of the pattern of the reticle R on the wafer W. As an example, the mirrors M1, M2, M4, and M6 are concave mirrors having aspherical reflecting surfaces, and the other mirrors M3 and M5 are convex mirrors having aspherical reflecting surfaces. Further, the projection optical system PO of the present embodiment is a coaxial optical system in which the optical axes of the mirrors M1 to M6 are overlapped with the optical axis AX in common. Hereinafter, the optical axis AX is also referred to as the optical axis of the projection optical system PO.

Further, in the present embodiment, pupil surfaces 35A and 35B that can be approximated by two planes intersecting the vicinity of the reflection surface of the second mirror M2 of the projection optical system PO are formed, and along these pupil surfaces 35A and 35B. An aperture stop AS is arranged. The pupil surfaces 35A and 35B and the aperture stop AS will be described later.
Wafer W is attracted and held on wafer stage WST via electrostatic chuck WH. Wafer stage WST is arranged on a guide surface arranged along the XY plane. Wafer stage WST is driven in the X direction and the Y direction by a drive system (not shown) composed of, for example, a magnetic levitation type two-dimensional linear actuator based on the measured value of a laser interferometer (not shown) and the control information of main control system 31. It is driven by a predetermined stroke, and is also driven in the θZ direction or the like as required.

  In the vicinity of the wafer W on the wafer stage WST, for example, an irradiation amount monitor 29 including a plurality of photoelectric sensors arranged in the X direction is installed, and a detection signal of the irradiation monitor 29 is supplied to the main control system 31. As an example, based on the measurement result of the irradiation monitor 29, the main control system 31 causes the oscillation frequency and pulse of the laser plasma light source 10 so that the integrated exposure amount after scanning exposure is within an allowable range at each point on the wafer W. The energy and / or the scanning speed of reticle stage RST (and wafer stage WST) are controlled.

At the time of exposure, the wafer W is disposed inside the partition 7 so that the gas generated from the resist on the wafer W does not adversely affect the mirrors M1 to M6 of the projection optical system PL. The partition 7 is formed with an opening through which the illumination light EL passes, and the space in the partition 7 is evacuated by a vacuum pump (not shown) under the control of the main control system 31.
When one die (shot area) on the wafer W is exposed, the illumination light EL is irradiated onto the illumination area 27R of the reticle R by the illumination optical system ILS, and the reticle R and the wafer W are projected onto the projection optical system PO. It moves synchronously in the Y direction at a predetermined speed ratio according to the reduction magnification of the optical system PO (scanned synchronously). In this way, the reticle pattern is exposed to one die on the wafer W. Thereafter, wafer stage WST is driven to move wafer W stepwise in the X and Y directions, and then the pattern of reticle R is scanned and exposed on the next die on wafer W. Thus, the pattern of the reticle R is sequentially exposed to a plurality of dies on the wafer W by the step-and-scan method.

Next, the pupil plane and aperture stop AS of the projection optical system PO of this embodiment will be described in detail.
FIG. 3 shows a part of the reticle R and the projection optical system PO of FIG. In FIG. 3, the reflecting surface M2a facing the −Z direction (image plane side) of the second mirror M2 of the projection optical system PO is a gentle concave surface having a large curvature radius as an example, and rotates about the center of the reflecting surface M2a. There is an optical axis AX that is an axis of symmetry. The optical axis AX may not be at the center of the reflecting surface M2a, and the optical axis AX may be off the reflecting surface M2a. The illumination light from the illumination region 27R of the reticle R is reflected by the first mirror M1 and incident obliquely as incident light 37I from the −Y direction side on the reflection surface M2a of the mirror M2. The incident light 37I is reflected obliquely to the + Y direction side by the reflecting surface M2a and travels toward the third mirror M3 as reflected light 37R. That is, the incident light 37I is not perpendicularly incident on the reflecting surface M2a, and the direction of the incident light 37I and the direction of the reflected light 37R are different, and the pupil plane of the projection optical system PO is formed in the vicinity of the reflecting surface M2a. The

  Further, in the present embodiment, the pupil plane of the projection optical system PO is the smallest section on which a plurality of parallel light beams incident on the projection optical system PO along various directions from the illumination area 27R (object plane) are condensed. It is defined as a surface that is substantially in contact with the minimum condensing region (minimum circle of confusion) that is the area of the area. In addition, when the plurality of minimum condensing areas where the parallel light beams are collected are discontinuous, for example, one or a plurality of planes connected to the plurality of minimum condensing areas by the least square method, or One or a plurality of curved surfaces (surfaces such as a cylindrical shape, a conical surface, or a spherical shape) may be determined, and one or more planes or curved surfaces thereof may be used as the pupil plane.

Further, the pupil of the projection optical system PO is an outline portion of a minimum condensing region (minimum circle of confusion) of a plurality of parallel light beams incident on the projection optical system PO along various directions from the illumination region 27R (object plane). Alternatively, it is defined as an area surrounded by the contour portion.
Then, when the illumination condition by the illumination optical system ILS in FIG. 1 is normal illumination, the center regular reflection light (0th order) among the plurality of parallel light beams emitted in various directions from the illumination region 27R in FIG. Light beam ELC indicated by a solid line having a predetermined reflection angle counterclockwise around an axis parallel to the X axis corresponding to (light), and a one-dot chain line having a reflection angle smaller than that of light beam ELC (inclined in the −Y direction). Assume a light beam ELA and a light beam ELB indicated by a dotted line having a larger reflection angle than the light beam ELC (tilted in the + Y direction). The luminous fluxes ELA to ELC are parallel luminous fluxes when they are emitted from the illumination area 27R, but are condensed when entering the mirror M2. In this case, the central light beam ELC is reflected by the mirror M1, condensed on the minimum condensing region 36C at the center (here, on the optical axis AX) of the reflecting surface M2a of the mirror M2, and then reflected by the reflecting surface M2a. Head to mirror M3.

  4A is a perspective view showing incident light and reflected light with respect to the mirror M2 in FIG. 3, and FIG. 4B is a plan view showing a reflecting surface of the mirror M2 in FIG. 4A. Other parallel light beams (not shown) inclined in the X direction with respect to the light beam ELC emitted from the illumination region 27R in FIG. 3 are compared with the minimum light collection region 36C on the reflection surface M2a in FIG. The light is condensed in the minimum light condensing region that is shifted in the + X direction or the −X direction. Therefore, from the above definition, on the cross section M2f (see FIG. 3) passing through the optical axis AX and parallel to the XZ plane in the mirror M2, the pupil plane of the projection optical system PO passes through the optical axis AX on the reflective surface M2a and becomes the X axis. Is formed in the surface region 35C along.

  In FIG. 3, the light beam ELA inclined in the −Y direction with respect to the light beam ELC is reflected by the mirror M1, and in the region on the −Y direction side from the center of the reflection surface M2a of the mirror M2 (above the upper surface) In addition, after condensing in the minimum condensing region 36A (in the −Z direction), the light is reflected by the reflecting surface M2a toward the mirror M3. Similarly, other parallel light beams (not shown) that are inclined in the −Y direction with respect to the light beam ELC are also formed on the reflective surface M2a in the region on the −Y direction side from the surface region 35C of the reflective surface M2a in FIG. The light is focused on the front minimum condensing region (not shown), and these minimum condensing regions 36A and the like intersect the reflecting surface M2a at the surface region 35C and gradually reflect from the surface region 35C in the −Y direction. It is substantially in contact with the curved surface moving away from M2a. Accordingly, from the above definition, in the region on the −Y direction side from the surface region 35C of the reflecting surface M2a of the mirror M2, the curved surface gradually moving away from the reflecting surface M2a is the pupil surface 35A of the projection optical system PO. Further, the incident light 37I forms a minimum condensing region on the pupil surface 35A.

  On the other hand, in FIG. 3, the light beam ELB inclined in the + Y direction with respect to the light beam ELC is reflected by the mirror M1, reflected by the reflection surface M2a of the mirror M2, and then in the region on the + Y direction side from the center of the reflection surface M2a. After condensing on the minimum condensing region 36B in front of the reflecting surface M2a (above and in the −Z direction), it is directed to the mirror M3. Similarly, another parallel light beam (not shown) tilted in the + Y direction with respect to the light beam ELC is also reflected by the reflective surface M2a in FIG. 4A, and is then + Y direction side from the surface region 35C of the reflective surface M2a. In the region, the light is condensed on a minimum condensing region (not shown) in front of the reflecting surface M2a, and these minimum condensing regions 36B and the like intersect the reflecting surface M2a at the surface region 35C and from the surface region 35C. It is substantially in contact with the curved surface gradually moving away from the reflecting surface M2a on the + Y direction side. Therefore, from the above definition, in the region on the + Y direction side from the surface region 35C of the reflecting surface M2a of the mirror M2, the curved surface gradually moving away from the reflecting surface M2a is the pupil surface 35B of the projection optical system PO. In addition, the reflected light 37R forms a minimum condensing region on the pupil surface 35B.

Accordingly, as shown in FIG. 4B, a portion 37Ia of the incident light 37I that is shaded and does not overlap with the reflected light 37R passes through the pupil plane 35A in the −Y direction above the reflecting surface M2a of the mirror M2. In the reflected light 37R, a hatched portion 37Ra that does not overlap with the incident light 37I passes through the pupil plane 35B in the + Y direction.
Further, in FIG. 3, the illumination light emitted in the same direction from the + Y direction and −Y direction ends of the illumination region 27R is condensed on the minimum condensing regions 36A and 36B above the reflecting surface M2a, respectively. . Accordingly, two light beams emitted from the different points on the illumination area 27R at the same opening angle pass through the same area on the pupil planes 35A and 35B on the mirror M2. In this case, in FIG. 4A, the incident light 37I includes solid line incident light 37I1 and dotted line incident light 37I2 emitted from different points on the illumination region 27R in FIG. It is assumed that the light is reflected by M2a and becomes reflected light 37R1 and 37R2, respectively. If the opening angles of the incident light 37I1 and 37I2 are the same, the contour portions 35Aa in the −Y direction on the pupil surface 35A of the incident light 37I1 and 37I2 are the same, and the corresponding pupil surfaces 35B of the emitted light 37R1 and 37R2 are the same. The upper + Y-direction contour portion 35Ba is the same.

  Therefore, from the above definition, a half-circumferential contour portion 35Aa, which is the contour of the minimum condensing region in the −Y direction on the pupil surface 35A shown in FIG. 4B, and the + Y direction on the pupil surface 35B. The half-circumferential contour portion 35Ba, which is the contour of the minimum condensing region in the Y direction, becomes the pupil of the projection optical system PO. Note that the region surrounded by the contour portions 35Aa and 35Ba can be regarded as the pupil of the projection optical system PO. In this embodiment, the illumination light emitted from different positions (object points) of the illumination area 27R of the reticle R at the same opening angle is near the reflecting surface M2a of the mirror M2, and the pupil plane 35A of the projection optical system PO. , 35B, that is, the same region within the pupil of the projection optical system PO. Therefore, by arranging the aperture stop AS along the pupil surfaces 35A and 35B as described later and defining the region of the light beam passing through the pupil surfaces 35A and 35B, it corresponds to different object points on the illumination region 27R. The opening angles of the light beams incident on different image points on the exposure area 27W on the wafer W in FIG. 1 and hence the numerical aperture (NA) are equal to each other. Therefore, the numerical aperture of each point on the image plane of the projection optical system PO is uniform.

  FIG. 4C shows a transmission optical system equivalent to the reflection optical system of FIG. 4A of the present embodiment. In FIG. 4C, incident light 47I becomes transmitted light 47T through a refracting surface 44 of a predetermined lens (refractive optical element). The refracting surface 44 can be regarded as a thin lens. In this transmission optical system, the pupil plane corresponding to the pupil planes 35A and 35B in FIG. 4A is a pupil plane 45 indicated by a dotted line that is inclined so as to intersect the refracting plane 44. In this case, a part of the pupil plane 45 is formed in the right half of the incident light 47I, and the remaining portion of the pupil plane 45 is formed in the left half of the transmitted light 47T.

  Next, FIG. 5A is a perspective view showing the aperture stop AS of this embodiment arranged on the reflection surface M2a of the mirror M2 of FIG. 4A, and FIG. 5B is the view of FIG. It is the side view seen from the VB direction. In FIG. 5A, the aperture stop AS is a first light shielding plate 38A disposed substantially along the pupil plane 35A on the −Y direction side, and a second disposed substantially along the pupil plane 35B on the + Y direction side. The light shielding plates 38A and 38B are connected in a V shape at a position close to the surface region 35C passing through the center (optical axis AX) of the reflecting surface M2a, which is the boundary line between the pupil surfaces 35A and 35B. ing. As shown in FIG. 5B, the pupil planes 35A and 35B may not necessarily be flat surfaces but may be curved surfaces. When the pupil planes 35A and 35B are curved surfaces, as an example, the light shielding of the aperture stop AS is performed. The plates 38A and 38B are curved.

  In FIG. 5A, substantially semicircular openings 38Aa and 38Ba are respectively formed in flat light shielding plates 38A and 38B made of a metal having high heat resistance that shields the illumination light EL, and the openings 38Aa, 38A, 38Ba forms a substantially circular or substantially elliptical opening as a whole. The numerical aperture of the projection optical system PO is defined by the size of the openings 38Aa and 38Ba. The shapes of the apertures 38Aa and 38Ba are set so that the light beam condensed at each point on the image plane of the projection optical system PO has a conical shape with a predetermined numerical aperture. When the numerical aperture is switched, the aperture stop AS may be replaced with another aperture stop having a different aperture size by an exchange mechanism (not shown). Even when the numerical aperture of the projection optical system PO is switched in this way, illumination light emitted in the same direction from different points in the illumination area 27R is incident on each point on the pupil planes 35A and 35B. Is incident on the corresponding (conjugate) point of the exposure area 27W, so that the opening angle of the illumination light incident on each point on the image plane, and hence the numerical aperture, is uniform.

Effects and the like of this embodiment are as follows.
(1) The projection optical system PO of the exposure apparatus 100 of the present embodiment is an optical system that includes a mirror M2 (reflection optical element) arranged so that the direction of the incident light 37I and the direction of the reflected light 37R are different. . In the projection optical system PO, the pupil of the projection optical system PO in the portion 37Ia of the incident light 37I in FIG. 4B that does not overlap with the reflected light 37R is formed above the reflection surface M2a of the mirror M2, and the reflected light 37R. The pupil of the portion 37Ra that does not overlap the incident light 37I is formed above the reflecting surface M2a.

  In the projection optical system PO, the pupil surfaces 35A and 35B of the projection optical system PO intersect with the reflection surface M2a of the mirror M2 in FIG. 4A, and the end of the incident light 37I opposite to the reflected light 37R. Is located above the reflecting surface M2a, and the pupil surface 35B at the end opposite to the incident light 37I of the reflected light 37R is located above the reflecting surface M2a. In this case, the pupil plane 35A is formed on the incident light 37I side, and the pupil plane 35B is formed on the reflected light 37R side.

Further, in the projection optical system PO, a contour portion 35Aa (first portion) in the −Y direction (incident light side) of the pupil of the projection optical system PO is formed on the incident light 37I side, and the + Y direction (reflected light) of the pupil is formed. Side) contour portion 35Ba (second portion) is formed on the reflected light 37R side.
According to the projection optical system PO of the present embodiment, the pupil surfaces 35A and 35B are arranged in the vicinity of the reflection surface M2a of the second mirror M2 in the projection optical system PO. Further, the portion of the incident light 37I that does not overlap with the reflected light 37R and the portion of the pupil surface 35A (or contour portion 35Aa) and the reflected light 37R that does not overlap with the reflected light 37R does not overlap with the incident light 37I. Both of the pupil plane 35B (or contour portion 35Ba) at 37Ra (the end opposite to the incident light) can be arranged above the reflecting surface M2a. Accordingly, the aperture stop AS can be easily installed on the pupil planes 35A and 35B (optimal pupil position) for both incident light and reflected light. The numerical aperture of the illumination light EL at a point can be made uniform. In other words, in-pupil nonuniformity does not occur at any image point, and in-pupil nonuniformity does not vary from image point to image point. Therefore, the uniformity of the imaging characteristics is improved, and the pattern image of the reticle R can be transferred onto the wafer W with high accuracy as a whole.

  (2) In this case, the pupil of the projection optical system PO is the minimum condensing area (minimum circle of confusion) 36A to 36C of a plurality of parallel light beams incident on the projection optical system PO in various directions from the illumination area 27R (object plane). The contour portions 35Aa and 35Ba or the inside thereof. Further, the pupil surfaces 35A and 35B of the projection optical system PO are surfaces that substantially contact the minimum condensing region (minimum circle of confusion). Therefore, at the time of optical design of the projection optical system PO, the position of the pupil or the pupil plane can be easily set by, for example, tracing light rays from the object plane to the image plane.

Since the projection optical system PO in FIG. 1 is a type that performs intermediate imaging, the pupil or the pupil plane is formally present in two places in the projection optical system PO, of which the aperture stop AS is installed. The numerical aperture of the projection optical system PO is defined by this part.
Note that the pupil plane of the projection optical system PO may be defined as an optical Fourier transform plane with respect to the object plane. In this case, the pupil of the projection optical system PO is an outline of an area through which an effective imaging light beam passes on the pupil plane or an area surrounded by the outline.

(3) In addition, the pupils corresponding to the contours 35Aa and 35Ba of the minimum condensing region on the pupil planes 35A and 35B in FIG. 4A are bent substantially symmetrically (including an ellipse) as a whole. Shape. Therefore, the aperture stop AS having a V-shaped cross section having an opening along the pupil can be easily installed without mechanically interfering with the reflecting surface M2a of the mirror M2.
(4) The projection optical system PO further includes the aperture stop AS shown in FIG. 5A, and the aperture stop AS is disposed substantially on the pupil planes 35A and 35B, and is, for example, substantially circular or elliptical for limiting the pupil. Shaped openings 38Aa and 38Ba are formed. Therefore, the numerical aperture of the projection optical system PO can be set to a desired value depending on the shape of the aperture of the aperture stop AS.

  The light shielding plates 38A and 38B of the aperture stop AS may be disposed in the vicinity of the pupil planes 35A and 35B. The vicinity of the pupil planes 35A and 35B means that an interval that allows the numerical aperture at each point on the image plane of the projection optical system PO to be considered to be substantially uniform is allowed. Therefore, even if the pupil surfaces 35A and 35B are complicated curved surfaces, the light shielding plates 38A and 38B of the aperture stop AS may be flat surfaces arranged along the average planes of these curved surfaces.

Further, the aperture stop AS is not formed from a single flat plate, but the separated light shielding plates 38A and 38B may be held by a holding member (not shown).
(5) Note that the variable aperture stop shown in FIG. 6 may be used as the aperture stop AS. In FIG. 6, the aperture stop AS includes a first frame 51A and a second frame 51B, a large number of light shielding members 52A that move in parallel independently of each other by, for example, a feed screw method along the first frame 51A, and a second frame 51B. A number of light shielding members 52B that move independently of each other by, for example, a feed screw method. In this case, a large number of light shielding members 52A are arranged along the pupil plane 35A in FIG. 4A, and the light shielding members 52B are arranged along the pupil plane 35B. By using the aperture stop AS having such a configuration, the position of the plurality of light shielding members 52A and 52B is individually controlled by a control system (not shown), so that the aperture shape of the aperture stop AS is substantially arbitrary. As a result, the numerical aperture of the projection optical system PO can be set to an arbitrary value.

  (6) Further, the pupil of the projection optical system PO formed by the contour portions 35Aa and 35Ba in FIG. 4A can be regarded as pupil surfaces 35A and 35B which are two curved surfaces to be connected (approximately respectively planes). Is formed on). However, even if the pupil plane of the projection optical system PO is formed from three planes that can be regarded as connected substantially planes, the pupil of the projection optical system PO is formed on these three planes (for example, substantially planes). Good.

  (7) The projection optical system PO is a reflection system including a plurality of coaxial aspherical mirrors M1 to M6, and is in the vicinity of the reflection surface of one of the mirrors M1 to M6. A pupil plane is formed. In the case of the mirrors M1 to M6, it is difficult to dispose the aperture stop AS close to the reflecting surface, but the reflecting surface intersects with the reflecting surface as in the present embodiment, and at the end in the Y direction. By forming the pupil surfaces 35A and 35B located above the aperture stop AS, the aperture stop AS can be easily arranged.

(8) The projection optical system PO is a projection optical system that forms an image of the pattern surface (first surface) of the reticle R on the surface (second surface) of the wafer W. Therefore, the numerical aperture at each point on the second surface can be made uniform.
The present invention can also be applied to the illumination optical system ILS of the exposure apparatus 100 in FIG. In this case, the pupil plane of the illumination optical system ILS is formed in the vicinity of the reflection surface of the second fly's eye optical system 23 (aggregate of minute reflection optical elements) in the illumination optical system ILS. It may be set above the reflecting surface at both ends in the Y direction (direction in which the direction of incident light and reflected light changes) intersecting the reflecting surface of the two fly's eye optical system 23. Then, by arranging, for example, an aperture stop bent in a V shape along the pupil plane, the opening angle of the illumination light EL at each point on the illumination area 27R (irradiated surface), and hence the numerical aperture, are made uniform. it can.

(9) The exposure apparatus 100 is an exposure apparatus that illuminates the pattern of the reticle R with the illumination light EL, and exposes the wafer W with the illumination light EL via the pattern and the projection optical system PO. The pupil plane (pupil) of the system PO is formed in the vicinity of the mirror M2 as described above. Therefore, the pattern of the reticle R can be exposed on the wafer W with high accuracy.
Further, in the exposure apparatus 100, the pupil plane of the projection optical system PO is disposed in the vicinity of the reflection surface of the mirror M2 and substantially parallel to the reflection surface, or is disposed in the optical path between the mirror M2 and the mirror M3, for example. Thus, in the illumination optical system ILS, the pupil plane may intersect with the reflection surface of the second fly's eye optical system 23 and be set above the reflection surface at both ends in the Y direction. In this case, the illumination condition can be set with higher accuracy.

Next, a comparative example for the above embodiment will be described with reference to FIGS. 8 (A) to (D) and FIGS. 9 (A) to (D). 8 (A), (B), (D) and FIGS. 9 (A), (B), (D), the portions corresponding to FIGS. 4 (A), (B), (C) are the same. Or a similar code | symbol is attached | subjected and the detailed description is abbreviate | omitted.
8A is a perspective view showing the mirror M2 of the projection optical system of the first comparative example, FIG. 8B is a plan view showing the arrangement surface of the aperture stop ASA in FIG. 8A, and FIG. 8C. Is a diagram showing a corresponding illumination region 27R, and FIG. 8D is a diagram showing a transmission optical system equivalent to FIG. 8A. In FIG. 8A, the pupil plane 35D of the projection optical system is disposed on the same plane as the reflection surface of the mirror M2, and the aperture stop ASA in which the aperture 39 for limiting the incident light 37I and the reflected light 37R is formed is the mirror. It arrange | positions in the position of predetermined spacing from the reflective surface of M2. The aperture stop ASA is provided with, for example, an exchange mechanism or a mechanism that makes the aperture variable, and it is difficult to arrange the aperture stop ASA close to the reflection surface of the mirror M2, and thus the aperture stop ASA is arranged away from the reflection surface.

  In this case, incident light 37I emitted from the four corner points a to d of the illumination area 27R in FIG. 8C and incident on the mirror M2 is indicated by a dotted line in FIG. 8B on the arrangement surface of the aperture stop ASA. It passes through circular regions 41a to 41d that are slightly deviated by. Correspondingly, the reflected light 37R passes through the regions 42a to 42d obtained by shifting the regions 41a to 41d in the Y direction. Accordingly, the opening 39 of the aperture stop AS is set wide so as to surround these regions 41a to 41d and 42a to 42d. As a result, the illumination light emitted from the points a and c in the illumination area 27R mainly passes through the projection optical system PO in the portion extending in the −X direction, and the illumination light emitted from the points b and d In addition, since the portion spread in the + X direction passes through the projection optical system PO, the spread angle of the illumination light, and hence the numerical aperture, becomes slightly nonuniform at the corresponding points on the image plane of the projection optical system PO.

In the equivalent transmission optical system of FIG. 8D, the pupil plane 45D is set on the refracting surface 44, and the apertures 49A and 49B of the aperture stop are respectively the half surface side of the incident light 47I and the half surface side of the transmitted light 47T. Placed in. Accordingly, the numerical aperture becomes non-uniform depending on the position on the image plane.
9A is a perspective view showing the mirror M2 of the projection optical system of the second comparative example, FIG. 9B is a plan view showing the arrangement surface of the aperture stop ASB in FIG. 9A, and FIG. FIG. 9C is a diagram showing a corresponding illumination area 27R, and FIG. 9D is a diagram showing a transmission optical system equivalent to FIG. 9A. In FIG. 9A, the pupil plane 35E of the projection optical system is disposed at a predetermined distance from the reflection surface of the mirror M2, and the aperture stop ASB in which the aperture 40 that restricts the incident light 37I and the reflected light 37R is formed. It is arranged on the same plane as the pupil plane 35E. The pupil surface 35E is formed on the incident light 37I side.

  In this case, the incident light 37I emitted from the four corner points a to d of the illumination area 27R in FIG. 9C and entering the mirror M2 is common to the arrangement surface (pupil surface 35E) of the aperture stop ASB. It passes through the circular area 35Ea in FIG. However, the reflected light 37R passes through the regions 42a to 42d corresponding to the positions a to d on the illumination region 27R. Therefore, the aperture 40 of the aperture stop ASB is set wide so as to surround these regions 35Ea and 42a to 42d. As a result, the illumination light emitted from the points a and b of the illumination area 27R mainly passes through the projection optical system PO at a portion that spreads in the + Y direction. Therefore, at the corresponding points on the image plane of the projection optical system PO, The spread angle of the illumination light and thus the numerical aperture becomes slightly non-uniform. Similarly, even if the pupil surface 35E is formed on the reflected light 37R side, the numerical aperture becomes slightly non-uniform.

In the equivalent transmission optical system of FIG. 9D, the pupil plane 45E is set on the optical path of the incident light 47I away from the refractive surface 44, and the apertures 50A and 50B of the aperture stop are respectively the half surface side of the incident light 47I and It arrange | positions at the half surface side of the transmitted light 47T. Accordingly, the numerical aperture becomes non-uniform depending on the position on the image plane.
According to the projection optical system PO of the above embodiment with respect to the first and second comparative examples, the numerical aperture is uniform at each point on the image plane of the projection optical system PO.

  An embodiment of the projection optical system PO in FIG. 1 will be described with reference to FIG. FIG. 7 shows an optical path diagram of the projection optical system PO. In FIG. 7, the pattern surface of the reticle R of FIG. 1 is arranged on the object plane OP, and the surface of the wafer W is arranged on the image plane IP. The projection optical system PO is substantially telecentric on the image plane IP side, and pupil surfaces 35A and 35B of the projection optical system PO are formed so as to intersect with the reflection surface of the mirror M2, and apertures are formed along the pupil surfaces 35A and 35B. An aperture AS is disposed. The optical specifications of the projection optical system PO in FIG. 7 are as follows.

[Table 1] Optical specifications Illumination light (exposure light) wavelength λ: 13.5 nm
Projection magnification β: 1/4
Numerical aperture NA (image side): 0.25
Object height: 134-142mm
Image height: 33.5 to 35.5 mm
Table 2 shows surface data of the reflecting surfaces of the mirrors M1 to M6 of the projection optical system PO. In Table 2, r represents the apex radius of curvature of each reflecting surface, and d represents the axial distance (surface spacing) of each reflecting surface. The unit of r and d is mm. Note that the surface distance d changes its sign each time it is reflected. Regardless of the incident direction of the light beam, the radius of curvature is positive when the center of curvature is on the image plane IP (wafer) side with respect to the reflecting surface, and the center of curvature is on the object plane OP (reticle) side with respect to the reflecting surface. The radius of curvature is negative.

また、図７の投影光学系ＰＯのミラーＭ１〜Ｍ６の反射面は全て表３の非球面データで表される非球面である。表３において、Ｋは円錐係数（コーニック定数）、係数Ａ_ｎ(ｎ＝４，６，８，１０，１２，１４）はｎ次の非球面係数である。また、係数Ａ_ｎ のデータ中でＥ−ｊ（ｊは整数）は、×１０^−ｊを意味する。 [Table 2] Surface data

In addition, the reflecting surfaces of the mirrors M1 to M6 of the projection optical system PO in FIG. In Table 3, K is a conic coefficient (conic constant), and a coefficient _An (n = 4, 6, 8, 10, 12, 14) is an n-order aspheric coefficient. Moreover, (the j integer) E-j in the data of the coefficient _{A n} means × ^{10 -j.}

共軸のミラーＭ１〜Ｍ６の非球面の光軸ＡＸに垂直な方向の高さをｙとし、非球面の頂点における接平面から高さｙの非球面上の位置までの光軸ＡＸに沿った距離をｚ（ｙ）とすると、上記の表２の頂点曲率半径ｒ、表３の円錐係数Ｋ、及び非球面係数Ａ_ｎ を用いて、距離ｚ（ｙ）は以下の式で表される。 [Table 3] Aspheric data

The height of the coaxial mirrors M1 to M6 in the direction perpendicular to the optical surface AX of the aspheric surface is y, and along the optical axis AX from the tangential plane at the apex of the aspheric surface to the position on the aspheric surface of height y. When the distance is referred to as z (y), using the above table 2 the radius of curvature at the top r, a conical coefficient of Table 3 K, and the aspheric coefficients a _n, the distance z (y) is expressed by the following equation.

本実施例の設計を適用した場合、図７の瞳面３５Ａ，３５Ｂは、ミラーＭ２の反射面に対して入射光及び射出光の両端部でそれぞれ約１ｍｍ上方に位置している。また、投影光学系ＰＯの収差は約０．１７λと良好である。

When the design of the present embodiment is applied, the pupil planes 35A and 35B in FIG. 7 are located approximately 1 mm above both reflection light surfaces of the mirror M2 at both ends of the incident light and the emitted light. The aberration of the projection optical system PO is as good as about 0.17λ.

The following modifications can be made to the above-described embodiment.
First, in the above-described embodiment, the gas jet cluster type laser plasma light source is used as the exposure light source in FIG. 1, but the present invention is not limited to this. For example, a droplet type laser plasma light source using tin or the like as a target is also used. Good. In the above-described embodiment, the laser plasma light source is used as the EUV light source. However, the present invention is not limited to this, but a SOR (Synchrotron Orbital Radiation) ring, a betatron light source, a discharged light source (discharge excitation plasma light source, rotary discharge) Any of an excitation plasma light source or the like) or an X-ray laser may be used.

In the embodiment of FIG. 1, the case where the EUV light is used as the exposure beam and the all-reflection projection optical system including only six mirrors is used is described as an example. For example, an exposure apparatus having a projection optical system composed of only four mirrors as disclosed in Japanese Patent Application Laid-Open No. 11-345761, as well as a VUV light source having a wavelength of 100 to 160 nm, such as an Ar ₂ laser (wavelength) 126 nm), the present invention can be applied to an exposure apparatus including a projection optical system having 4 to 8 mirrors.

  Furthermore, the present invention can also be applied to a case where a projection optical system composed of a catadioptric system using ArF excimer laser light (wavelength 193 nm) or the like as exposure light is used. Thus, when the present invention is applied to a catadioptric system in which a lens and a mirror are combined, a pupil plane of the projection optical system is formed in the vicinity of the reflection surface of the mirror, and this pupil plane is, for example, the central portion and the reflection surface. What is necessary is just to make it cross | intersect and to be above the reflective surface in both ends. This reduces the numerical aperture non-uniformity at each point on the image plane.

  Further, when an electronic device (or microdevice) such as a semiconductor device is manufactured using the exposure apparatus of the above embodiment, the electronic device performs function / performance design of the electronic device as shown in FIG. Step 222 for manufacturing a mask (reticle) based on this design step, Step 223 for manufacturing a substrate (wafer) as a base material of the device and applying a resist, Exposure apparatus (EUV exposure apparatus, etc.) of the above-described embodiment ) Exposing the mask pattern to the substrate (sensitive substrate), developing the exposed substrate, heating (curing) the developed substrate, etching step, etc., device assembly step (dicing step, 225), including processing steps such as bonding and packaging It is produced through the 査 step 226 or the like.

In other words, the device manufacturing method includes exposing the substrate (wafer) using the exposure apparatus of the above-described embodiment, and processing the exposed substrate (step 224). At this time, according to the exposure apparatus of the above-described embodiment, since good imaging characteristics can be obtained on the substrate, a highly functional device can be manufactured with high accuracy.
In addition, this invention is not limited to the above-mentioned embodiment, A various structure can be taken in the range which does not deviate from the summary of this invention.

It is sectional drawing which shows schematic structure of the exposure apparatus of an example of embodiment. (A) is a figure which shows the 1st fly eye optical system 22 in FIG. 1, (B) is a figure which shows the 2nd fly eye optical system 23 in FIG. It is a figure which shows a part of reticle R and projection optical system PO in FIG. 3A is a perspective view showing incident light and reflected light with respect to the mirror M2 in FIG. 3, FIG. 4B is a plan view showing a light beam on the reflecting surface in FIG. 4A, and FIG. 4C is FIG. It is a figure which shows the transmission optical system equivalent to. (A) is a perspective view showing a state in which an aperture stop AS is installed on the mirror M2 of FIG. 4 (A), and (B) is a side view seen from the VB direction of FIG. 5 (A). It is a perspective view which shows another structural example of aperture stop AS. It is an optical path diagram which shows the projection optical system PO of an Example. (A) is a perspective view showing the mirror M2 of the first comparative example, (B) is a plan view showing a light beam on the reflecting surface of FIG. 8 (A), (C) is a view showing an illumination area 27R, (D ) Is a diagram showing a transmission optical system equivalent to that shown in FIG. (A) is a perspective view showing a mirror M2 of the second comparative example, (B) is a plan view showing a light beam on the reflecting surface of FIG. 9 (A), (C) is a view showing an illumination region 27R, (D ) Is a diagram showing a transmission optical system equivalent to that shown in FIG. It is a flowchart which shows an example of the manufacturing process of an electronic device.

Explanation of symbols

  ILS ... illumination optical system, R ... reticle, PO ... projection optical system, W ... wafer, M1-M6 ... mirror, AS ... aperture stop, 35A, 35B ... pupil plane, 37I ... incident light, 37R ... reflected light, 38A, 38B ... light shielding plate, 38Aa, 38Ba ... opening

Claims (17)

An optical system comprising a reflective optical element arranged so that the direction of incident light and the direction of reflected light are different,
The pupil of the optical system in a portion of the incident light that does not overlap the reflected light is formed above the reflective surface of the reflective optical element,
The optical system, wherein the pupil in a portion of the reflected light that does not overlap the incident light is formed above the reflective surface.   The optical system according to claim 1, wherein the pupil has a shape obtained by bending the circumference substantially symmetrically.   The optical system according to claim 1, wherein the pupil is a contour portion of a region where a minimum circle of confusion of each light beam passing through the optical system is formed.   4. The apparatus according to claim 1, further comprising an aperture stop disposed on a surface on which the pupil is formed or a surface in the vicinity thereof, and having an aperture for limiting the pupil. 5. Optical system. An optical system comprising a reflective optical element arranged so that the direction of incident light and the direction of reflected light are different,
The pupil plane of the optical system intersects the reflective surface of the reflective optical element;
The pupil plane at the end of the incident light opposite to the reflected light is located above the reflecting surface;
An optical system, wherein the pupil plane at the end of the reflected light opposite to the incident light is positioned above the reflective surface.   The optical system according to claim 5, wherein the pupil plane is a plane in contact with a region where a minimum circle of confusion of each light beam passing through the optical system is formed.   7. The apparatus according to claim 5, further comprising an aperture stop disposed on the pupil plane or a plane in the vicinity thereof, and having an aperture for limiting at least one light beam of the incident light and the reflected light. The optical system described. An optical system comprising a reflective optical element arranged so that the direction of incident light and the direction of reflected light are different,
A first portion of the pupil of the optical system is formed on the incident light side;
An optical system, wherein a second portion of the pupil of the optical system is formed on the reflected light side.   The optical system according to claim 8, wherein the pupil is formed on at least two planes.   The optical system according to claim 8, wherein the pupil is a contour portion of a region where a minimum circle of confusion of each light beam passing through the optical system is formed.   11. The apparatus according to claim 8, further comprising an aperture stop that is disposed on a surface on which the pupil is formed or a surface in the vicinity of the pupil, and in which an aperture for limiting the pupil is formed. Optical system. The optical system is a reflection system including a plurality of coaxial aspherical mirrors,
The optical system according to claim 1, wherein one of the plurality of aspherical mirrors is the reflective optical element.   The optical system according to any one of claims 1 to 11, wherein the optical system is a catadioptric system including the reflective optical element and a refractive optical element.   The optical system according to claim 1, wherein the optical system is a projection optical system that forms an image of a pattern of a first surface on a second surface. In an exposure apparatus that illuminates a pattern with exposure light and exposes the substrate through the pattern and the projection optical system with the exposure light,
An exposure apparatus comprising the optical system according to claim 14 as the projection optical system. An exposure apparatus that projects and exposes an image of a first surface onto a second surface,
An exposure apparatus comprising the optical system according to claim 1. A step of exposing the substrate using the exposure apparatus according to claim 15 or 16,
And a step of processing the exposed substrate.

Images