JP2005172988A - Projection optical system and exposure device equipped with the projection optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection-type projection optical system which is equipped with a reflector having an aspherical reflecting surface, capable of employing a spherical surface correction processing method and can conduct aberration correction, while suppressing increase in the size of the reflector. <P>SOLUTION: This system is equipped with a 1st reflective imaging optical system (G1) for forming an intermediate image of a 1st surface (4) and a 2nd reflective imaging optical system (G2) for forming an image of the intermediate image on a 2nd surface (7). The 1st reflective imaging optical system has a 1st reflector M1, an aperture stop, a 2nd reflector M2, a 3rd reflector M3, and a 4th reflector M4, in the order of the incidence of light from the 1st surface side. The 2nd reflective imaging optical system has a 5th reflector M5 and a 6th reflector M6, in the order of the incidence of light from the 1st surface side. The reflecting surface of the 2nd reflector M2 and the reflecting surface of the 4th reflector M4 are formed aspherical to be 0.6 μm or lower in sagging quantity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a projection optical system and an exposure apparatus provided with the projection optical system, and is suitable for an X-ray projection exposure apparatus that transfers a circuit pattern on a mask onto a photosensitive substrate by a mirror projection method using X-rays, for example. The present invention relates to a reflection type projection optical system.

  2. Description of the Related Art Conventionally, in an exposure apparatus used for manufacturing a semiconductor element or the like, a circuit pattern formed on a mask (reticle) is projected and transferred onto a photosensitive substrate such as a wafer via a projection optical system. A resist is coated on the photosensitive substrate, and the resist is exposed by projection exposure through the projection optical system, and a resist pattern corresponding to the mask pattern is obtained.

Here, the resolving power W of the exposure apparatus depends on the wavelength λ of the exposure light and the numerical aperture NA of the projection optical system, and is expressed by the following equation (a).
W = k · λ / NA (k: constant) (a)

  Therefore, in order to improve the resolving power of the exposure apparatus, it is necessary to shorten the wavelength λ of the exposure light or increase the numerical aperture NA of the projection optical system. In general, since it is difficult to increase the numerical aperture NA of the projection optical system to a predetermined value or more from the viewpoint of optical design, it is necessary to shorten the wavelength of exposure light in the future. For example, when a KrF excimer laser having a wavelength of 248 nm is used as exposure light, a resolution of 0.25 μm can be obtained, and when an ArF excimer laser having a wavelength of 193 nm is used, a resolution of 0.18 μm can be obtained. When X-rays having a shorter wavelength are used as exposure light, for example, a resolution of 0.1 μm or less at a wavelength of 13 nm can be obtained.

  By the way, when X-rays are used as the exposure light, there are no transmissive optical materials and refractive optical materials that can be used. Therefore, a reflective mask is used and a reflective projection optical system is used. Conventionally, as a projection optical system applicable to an exposure apparatus that uses X-rays as exposure light, for example, Japanese Patent Application Laid-Open No. 9-212322 (application corresponding to US Pat. No. 5,815,310), US Pat. No. 6,183. , 095B1 specification, etc., various reflection optical systems have been proposed.

JP-A-9-212322 US Pat. No. 6,183,095B1

  In the conventional reflecting optical system disclosed in Japanese Patent Laid-Open No. 9-212322, a bright optical system with NA = 0.25 is achieved with a configuration including six reflecting mirrors having aspherical reflecting surfaces. Yes. The sag amount of the reflecting surface of each reflecting mirror (the definition thereof will be described later) is 31.4 μm, 0.8 μm, 2.4 μm, 1.2 μm from the first reflecting mirror M 1 to the sixth reflecting mirror M 6 in order. 22.0 μm and 7.6 μm.

  The sag amount of the second reflecting mirror M2 is 0.8 μm and 1 μm or less, and is relatively small. In the case of an aspherical surface with such a relatively small sag amount, it is expected that processing (grinding, polishing) and measurement will be relatively easy if normal aspherical processing and inspection are performed. However, after processing and measuring the aspherical surface as a spherical surface, a correction method corresponding to the sag amount, which is the difference between the best-fit spherical surface and the aspherical surface, that is, a sag of 0.8 μm is required to incorporate the spherical surface correction processing method. The amount is too big. Therefore, an aspherical surface with a sag amount of about 0.8 μm is usually treated as an aspherical surface from the beginning. The method of processing and measuring as an aspherical surface from the beginning requires preparations such as the design and manufacture of a null lens as compared with the spherical surface correction processing method, which requires much labor, time and cost, and the difference is very large. For this reason, although the amount of sag is relatively small, the same amount of work as a normal aspherical surface is required.

  Also, in the first embodiment described in US Pat. No. 6,183,095B1, a brighter NA = 0.25 is obtained with a configuration including six reflecting mirrors having aspherical reflecting surfaces. The optical system has been achieved. In the embodiment, Maximum aspheric departure across Instantaneous clear aperture of the first reflecting mirror M1 to the sixth reflecting mirror M6 is displayed, and their amounts are 15.0 μm, 0.5 μm, 13.0 μm, 2 .6 μm, 5.0 μm, and 6.3 μm. When these amounts are recalculated with the sag amount defined in the present invention, the sag amounts of the reflecting surfaces of the first reflecting mirror M1 to the sixth reflecting mirror M6 are 6.8 μm, 4.5 μm, 1 It was found to be 0.5 μm, 3.7 μm, 10.0 μm, and 17.1 μm.

  The minimum value of the sag amount of the aspherical reflecting surface in the first embodiment described in US Pat. No. 6,183,095B1 is 1.5 μm, which is disclosed in JP-A-9-212322. It is larger than 0.8 μm which is the minimum value of the sag amount of the aspherical reflecting surface in the reflecting optical system. Accordingly, the first embodiment described in US Pat. No. 6,183,095B1 is more aspheric than the reflective optical system disclosed in the first embodiment of Japanese Patent Laid-Open No. 9-212322. It is assumed that processing and measurement will be more difficult. However, if the minimum sag amount of the first embodiment described in US Pat. No. 6,183,095B1 and the first embodiment of Japanese Patent Laid-Open No. 9-212322 is seen, the spherical surface correction processing method is adopted. Shows that the amount of sag is too large.

  The present invention has been made in view of the above-described problems, and includes a reflecting mirror having an aspherical reflecting surface capable of adopting a spherical correction processing method, and has excellent aberration correction while suppressing an increase in size of the reflecting mirror. It is an object of the present invention to provide a reflection type projection optical system that can be performed in a simple manner. It is another object of the present invention to provide an exposure apparatus that can secure a large resolving power by using, for example, X-rays as exposure light by applying the projection optical system of the present invention to the exposure apparatus.

In order to solve the above problems, in the first embodiment of the present invention, in the projection optical system that includes six reflecting mirrors and forms a reduced image of the first surface on the second surface,
A first reflective imaging optical system for forming an intermediate image of the first surface; and a second reflective imaging optical system for forming an image of the intermediate image on the second surface;
The first reflective imaging optical system includes a first reflecting mirror M1, an aperture stop, a second reflecting mirror M2, a third reflecting mirror M3, and a fourth reflecting mirror M4 in the order of incidence of light from the first surface side. And
The second reflective imaging optical system includes a fifth reflecting mirror M5 and a sixth reflecting mirror M6 in the order of incidence of light from the first surface side,
The reflecting surface of the fourth reflecting mirror M4 is formed in an aspherical shape with a sag amount of 0.6 μm or less.

  According to a preferred aspect of the first form, the reflecting surface of the fourth reflecting mirror M4 is formed in an aspherical shape with a sag amount of 0.4 μm or less. More preferably, the reflecting surface of the fourth reflecting mirror M4 is formed in an aspherical shape with a sag amount of 0.1 μm or less.

In the second embodiment of the present invention, in the projection optical system that includes six reflecting mirrors and forms a reduced image of the first surface on the second surface,
A first reflective imaging optical system for forming an intermediate image of the first surface; and a second reflective imaging optical system for forming an image of the intermediate image on the second surface;
The first reflective imaging optical system includes a first reflecting mirror M1, an aperture stop, a second reflecting mirror M2, a third reflecting mirror M3, and a fourth reflecting mirror M4 in the order of incidence of light from the first surface side. And
The second reflective imaging optical system includes a fifth reflecting mirror M5 and a sixth reflecting mirror M6 in the order of incidence of light from the first surface side,
The reflecting surface of the second reflecting mirror M2 is formed in an aspherical shape with a sag amount of 0.6 μm or less.

  According to a preferred aspect of the second embodiment, the reflecting surface of the second reflecting mirror M2 is formed in an aspherical shape with a sag amount of 0.4 μm or less. The reflecting surface of the second reflecting mirror M2 is further preferably formed in an aspherical shape with a sag amount of 0.1 μm or less.

According to a third aspect of the present invention, in a projection optical system that includes six reflecting mirrors and forms a reduced image of the first surface on the second surface, the first reflecting connection for forming the intermediate image of the first surface. An image optical system and a second reflective imaging optical system for forming an image of the intermediate image on the second surface;
The first reflective imaging optical system includes a first reflecting mirror M1, an aperture stop, a second reflecting mirror M2, a third reflecting mirror M3, and a fourth reflecting mirror M4 in the order of incidence of light from the first surface side. And
The second reflective imaging optical system includes a fifth reflecting mirror M5 and a sixth reflecting mirror M6 in the order of incidence of light from the first surface side,
The projection optical system is characterized in that the reflection surface of the second reflection mirror M2 and the reflection surface of the fourth reflection mirror M4 are each formed in an aspherical shape with a sag amount of 0.6 μm or less.

  According to a preferred aspect of the third mode, the reflecting surface of the second reflecting mirror M2 and the reflecting surface of the fourth reflecting mirror M4 are each formed in an aspherical shape with a sag amount of 0.4 μm or less. More preferably, the reflecting surface of the second reflecting mirror M2 and the reflecting surface of the fourth reflecting mirror M4 are each formed in an aspherical shape with a sag amount of 0.1 μm or less.

  According to the preferable aspect of the first to third embodiments, the maximum incident angle A of the light beam to each of the reflecting mirrors M1 to M6 satisfies the condition of A <25 ° in each of the reflecting mirrors M1 to M6. In addition, it is preferable that the inclination α of the light beam from the first surface to the first reflecting mirror M1 with respect to the optical axis of the principal ray satisfies a condition of 5 ° <| α | <10 °.

  According to the preferred embodiment of the first to third embodiments, the effective diameter φM of each of the reflecting mirrors M1 to M6 satisfies the condition of φM ≦ 700 mm in each of the reflecting mirrors M1 to M6. The reflecting surfaces of the reflecting mirrors M1 to M6 are preferably formed in an aspherical shape that is rotationally symmetric with respect to the optical axis, and the maximum order of the aspherical surface that defines each reflecting surface is preferably 10th or higher. Moreover, it is preferable that the optical system is substantially telecentric on the second surface side.

  In a fourth embodiment of the present invention, an illumination system for illuminating the mask set on the first surface, and a first for exposing the mask pattern onto the photosensitive substrate set on the second surface. An exposure apparatus comprising the projection optical system according to the first to third embodiments is provided.

  According to a preferred aspect of the fourth aspect, the illumination system has a light source for supplying X-rays as exposure light, and moves the mask and the photosensitive substrate relative to the projection optical system, The mask pattern is projected and exposed on the photosensitive substrate.

  In the projection optical system of the present invention, since the optical performance is afforded by appropriately arranging each reflecting mirror and the aperture stop, the sag of the aspheric reflecting surfaces of the second reflecting mirror M2 and the fourth reflecting mirror M4 is generated. The amount can be kept sufficiently small, and a spherical correction processing method can be employed in processing and measuring these aspherical reflecting surfaces. As a result, the production of the aspherical surface is greatly simplified, and the aspherical surface can be produced very advantageously in terms of time, cost and accuracy. That is, in the present invention, a reflective projection optical system that includes a reflecting mirror having an aspherical reflecting surface that can adopt a spherical correction processing method, and that can satisfactorily correct aberrations while suppressing an increase in size of the reflecting mirror. A system can be realized.

  Further, by applying the projection optical system of the present invention to an exposure apparatus, X-rays can be used as exposure light. In this case, the mask and the photosensitive substrate are moved relative to the projection optical system, and the mask pattern is projected and exposed onto the photosensitive substrate. As a result, a highly accurate microdevice can be manufactured under good exposure conditions using a scanning exposure apparatus having a large resolving power.

  In the projection optical system of the present invention, light from the first surface (object surface) forms an intermediate image of the first surface via the first reflective imaging optical system G1. Then, the light from the intermediate image of the first surface formed via the first reflective imaging optical system G1 passes through the second reflective imaging optical system G2 to generate an intermediate image (a reduced image of the first surface). ) On the second surface (image surface).

  Here, the first reflective imaging optical system G1 reflects the light reflected by the first reflecting mirror M1, the aperture stop AS, and the first reflecting mirror M1 for reflecting the light from the first surface. The second reflecting mirror M2, the third reflecting mirror M3 for reflecting the light reflected by the second reflecting mirror M2, and the fourth reflecting mirror M4 for reflecting the light reflected by the third reflecting mirror M3. It is comprised by. The second reflective imaging optical system G2 includes a fifth reflecting mirror M5 for reflecting light from the intermediate image, and a sixth reflecting mirror M6 for reflecting light reflected by the fifth reflecting mirror M5. It is comprised by.

  In the present invention, by adopting a configuration in which the reduced image of the first surface is formed twice on the second surface, it is possible to satisfactorily correct distortion. In addition, since the aperture stop AS is disposed in the optical path between the first reflecting mirror M1 and the second reflecting mirror M2, the incident angle of the light beam on the third reflecting mirror M3 where the incident angle of the light beam tends to be large. Can be kept small. In general, in such a six-mirror optical system, the aperture stop is generally disposed immediately before the reflecting mirror in order to avoid interference of light beams. In that case, the aperture position is limited, and it becomes difficult to balance the aberrations of the upper and lower frames. On the other hand, in the present invention, since the aperture stop AS is disposed between the first reflecting mirror M1 and the second reflecting mirror M2, the degree of freedom of the stop position is ensured and the upper and lower frames are secured. It is possible to easily balance the aberration.

  If the aperture stop AS is disposed between the second reflecting mirror M2 and the third reflecting mirror M3, or between the third reflecting mirror M3 and the fourth reflecting mirror M4, the effective diameter of the first reflecting mirror M1 is increased. In addition, since the angle of incidence on the reticle and the angle of reflection from the reticle are determined, the optical path length from the reticle to the exit pupil (aperture stop) increases, and the object height of the reticle increases, resulting in image formation. The magnification must be reduced to 1/5 to 1/6. On the other hand, in the present invention, since the aperture stop AS is arranged between the first reflecting mirror M1 and the second reflecting mirror M2 (intermediate), the image forming magnification is kept small at 1/4, Good optical performance can be realized.

  Further, by suppressing the incident angle of the light beam to the third reflecting mirror M3, the effective diameter of the fourth reflecting mirror M4, whose effective diameter tends to be large, can be suppressed small. As described above, according to the present invention, it is possible to realize a reflection type projection optical system that has good reflection characteristics with respect to X-rays and can perform aberration correction satisfactorily while suppressing an increase in the size of the reflecting mirror. Can do.

  Furthermore, in the present invention, by adopting the above arrangement, the maximum diameter of the reflecting mirror can be kept relatively small, and each reflecting mirror and aperture stop are appropriately arranged without causing vignetting of the light beam. be able to. As a result of such an appropriate arrangement, there is a margin in optical performance, so that the amount of sag on the reflecting surfaces of some reflecting mirrors, particularly the second reflecting mirror M2 and the fourth reflecting mirror M4, is kept sufficiently small. Can do.

  By the way, although the effective diameter of the fourth reflecting mirror M4 is suppressed as small as possible, it must be increased to some extent due to the configuration of the optical system, and there are many in processing and measuring the aspherical reflecting surface. Usually comes with difficulties. In particular, in the fourth reflecting mirror M4, the portion where the light beam is actually incident is small in area in spite of the large effective diameter, and the shape is a broad bean shape. Therefore, the part of the reflector other than the part where the light beam actually enters is removed in order to avoid interference with other light beams, and the entire shape of the reflector must be rotationally asymmetric with respect to the optical axis. I don't get it.

  As described above, it is usually more difficult to process and measure the aspherical surface of the fourth reflecting mirror M4 having a broad bean shape whose overall shape is rotationally asymmetric. However, in the present invention, since the sag amount of the reflecting surface of the fourth reflecting mirror M4 is suppressed to about 0.4 μm to 0.1 μm or less, the sag is processed after processing and measuring the aspherical reflecting surface as a spherical surface. By adopting a spherical surface correction method that performs minute correction processing by the amount, it becomes possible to dramatically simplify and execute aspherical surface processing and measurement. In addition, by suppressing the sag amount of the reflecting surface of the fourth reflecting mirror M4 to 0.05 μm or less, the processing and measurement of the aspheric surface can be further simplified and executed.

  On the other hand, the effective diameter of the second reflecting mirror M2 is not so large compared to the fourth reflecting mirror M4. However, in the second reflecting mirror M2, similarly to the fourth reflecting mirror M4, the aspherical reflecting surface is regarded as a spherical surface by suppressing the sag amount of the reflecting surface to about 0.4 μm to 0.1 μm or less. By adopting a spherical surface modification method in which a minute amount of sag is corrected after processing and measurement, it becomes possible to dramatically simplify and execute aspherical surface processing and measurement. Further, by limiting the sag amount of the reflecting surface of the second reflecting mirror M2 to 0.05 μm or less, it becomes possible to dramatically simplify and execute the processing and measurement of the aspheric surface.

  As described above, according to the present invention, since the optical performance can be afforded by appropriately arranging the reflecting mirrors and the aperture stop, the aspherical reflecting surfaces of the second reflecting mirror M2 and the fourth reflecting mirror M4 can be used. The amount of sag can be suppressed sufficiently small, and the spherical surface correction processing method can be adopted when processing and measuring these aspherical reflecting surfaces. As a result, the production of the aspherical surface is greatly simplified, and the aspherical surface can be produced very advantageously in terms of time, cost and accuracy.

In the present invention, it is desirable that the maximum incident angle A of the light beam to each of the reflecting mirrors M1 to M6 satisfies the following conditional expression (1) in each of the reflecting mirrors M1 to M6.
A <25 ° (1)
Exceeding the upper limit value of conditional expression (1) is preferable because the maximum incident angle A of the light beam to the reflective multilayer film becomes too large, and uneven reflection tends to occur and a sufficiently high reflectance cannot be obtained. Absent.

In the present invention, it is preferable that the following conditional expression (2) is satisfied in each of the reflecting mirrors M1 to M6. In conditional expression (2), φM is the effective diameter (diameter) of each of the reflecting mirrors M1 to M6, and R is the radius of curvature of the reflecting surface of each of the reflecting mirrors M1 to M6.
φM / | R | <1.0 (2)

  If the upper limit value of conditional expression (2) is exceeded, the opening angle (NA at the time of reflecting mirror measurement) when measuring the shape of each of the reflecting mirrors M1 to M6 (particularly the fourth reflecting mirror M4) becomes too high. Since accurate shape measurement becomes difficult, it is not preferable. In order to enable more accurate shape measurement, it is more preferable to set the upper limit value of conditional expression (2) to 0.9.

In the present invention, it is desirable that the inclination α of the principal ray of the light beam from the first surface to the first reflecting mirror M1 with respect to the optical axis satisfies the following conditional expression (3).
5 ° <| α | <10 ° (3)

  Exceeding the upper limit value of conditional expression (3) is not preferable because when the reflective mask is provided on the first surface, it is easily affected by shadows due to reflection. On the other hand, if the lower limit value of conditional expression (3) is not reached, it is not preferable because incident light and reflected light interfere with each other when a reflective mask is provided on the first surface.

In the present invention, it is desirable that the effective diameter φM of each of the reflecting mirrors M1 to M6 satisfies the following conditional expression (4) in each of the reflecting mirrors M1 to M6.
φM ≦ 700mm (4)
Exceeding the upper limit of conditional expression (4) is not preferable because the effective diameter of the reflecting mirror becomes too large and the optical system becomes large.

  Further, in the present invention, in order to improve the optical performance by satisfactorily correcting the aberration, the reflecting surface of each reflecting mirror is formed in an aspherical shape that is rotationally symmetric with respect to the optical axis, and an aspherical surface that defines each reflecting surface is formed. The maximum order is desirably 10th order or more. In the present invention, it is desirable that the optical system be almost telecentric on the second surface side. With this configuration, for example, when applied to an exposure apparatus, it is possible to form a good image even if the wafer is uneven within the depth of focus of the projection optical system.

  Further, by applying the projection optical system of the present invention to an exposure apparatus, X-rays can be used as exposure light. In this case, the mask and the photosensitive substrate are moved relative to the projection optical system, and the mask pattern is projected and exposed onto the photosensitive substrate. As a result, a highly accurate microdevice can be manufactured under good exposure conditions using a scanning exposure apparatus having a large resolving power.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the positional relationship between the arc-shaped exposure area (that is, the effective exposure area) formed on the wafer and the optical axis. In FIG. 1, the Z axis along the optical axis direction of the projection optical system, that is, the normal direction of the wafer as the photosensitive substrate, the Y axis in the direction parallel to the paper surface of FIG. The X axis is set in the direction perpendicular to the paper surface of FIG.

  The exposure apparatus shown in FIG. 1 includes, for example, a laser plasma X-ray source 1 as a light source for supplying exposure light. The light emitted from the X-ray source 1 enters the illumination optical system 3 via the wavelength selection filter 2. Here, the wavelength selection filter 2 has a characteristic of selectively transmitting only X-rays having a predetermined wavelength (13.5 nm) from light supplied from the X-ray source 1 and blocking transmission of other wavelength light.

  The X-rays transmitted through the wavelength selection filter 2 illuminate the reflective mask 4 on which the pattern to be transferred is formed via the illumination optical system 3 composed of a plurality of reflecting mirrors. The mask 4 is held by a mask stage 5 that can move along the Y direction so that its pattern surface extends along the XY plane. The movement of the mask stage 5 is configured to be measured by a laser interferometer (not shown). In this way, an arcuate illumination area symmetric with respect to the Y axis is formed on the mask 4.

  The light from the illuminated pattern of the mask 4 forms an image of the mask pattern on the wafer 7 that is a photosensitive substrate via the reflective projection optical system 6. That is, on the wafer 7, as shown in FIG. 2, an arcuate exposure region symmetric with respect to the Y axis is formed. Referring to FIG. 2, in a circular area (image circle) IF having a radius φ centered on the optical axis AX, the length in the X direction is LX and the length in the Y direction so as to contact the image circle IF. An arc-shaped effective exposure region ER with LY is set.

  The wafer 7 is held by a wafer stage 8 that can move two-dimensionally along the X and Y directions such that the exposure surface extends along the XY plane. The movement of the wafer stage 8 is configured to be measured by a laser interferometer (not shown) as in the mask stage 5. Thus, scanning exposure (scanning exposure) is performed while the mask stage 5 and the wafer stage 8 are moved along the Y direction, that is, while the mask 4 and the wafer 7 are moved relative to the projection optical system 6 along the Y direction. As a result, the pattern of the mask 4 is transferred to one exposure area of the wafer 7.

  At this time, when the projection magnification (transfer magnification) of the projection optical system 6 is 1/4, the scanning speed is set by setting the moving speed of the wafer stage 8 to 1/4 of the moving speed of the mask stage 5. Further, by repeating the scanning exposure while moving the wafer stage 8 two-dimensionally along the X direction and the Y direction, the pattern of the mask 4 is sequentially transferred to each exposure region of the wafer 7. Hereinafter, a specific configuration of the projection optical system 6 will be described with reference to the first to third examples.

  In each embodiment, the projection optical system 6 includes a first reflective imaging optical system G1 for forming an intermediate image of the mask 4 pattern, and an intermediate image of the mask pattern (secondary image of the mask 4 pattern). Are formed on the wafer 7 and a second reflective imaging optical system G2. Here, the first reflective imaging optical system G1 includes four reflecting mirrors M1 to M4, and the second reflective imaging optical system G2 includes two reflecting mirrors M5 and M6.

  In each embodiment, the reflecting surfaces of all the reflecting mirrors are formed in an aspherical shape that is rotationally symmetric with respect to the optical axis. In each embodiment, an aperture stop AS is disposed in the optical path from the first reflecting mirror M1 to the second reflecting mirror M2. Further, in each embodiment, the projection optical system 6 is an optical system telecentric on the wafer side (image image).

In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is y, and the distance along the optical axis from the tangent plane at the apex of the aspheric surface to the position on the aspheric surface at height y is z. When the apex radius of curvature is r, the cone coefficient is κ, and the n-th aspherical coefficient is C _n , it is expressed by the following mathematical formula (b).
z = (y ² / r) / {1+ {1- (1 + κ) · y ² / r ² } ^1/2 }
+ C ₄ · y ⁴ + C ₆ · y ⁶ + C ₈ · y ⁸ + C ₁₀ · y ¹⁰ + (b)

  In the present invention, the sag amount of the reflecting surface of each reflecting mirror is the maximum value of the distance along the optical axis between the best-fit spherical surface of each reflecting mirror and the aspherical surface (reflecting surface) of each reflecting mirror. Here, the best-fit spherical surface of each reflecting mirror is the original spherical surface having a radius of curvature that best fits when the spherical inspection original is pressed against the aspherical surface.

[First embodiment]
FIG. 3 is a diagram showing the configuration of the projection optical system according to the first example of the present embodiment. Referring to FIG. 3, in the projection optical system of the first embodiment, the light from the mask 4 is reflected from the reflecting surface of the first concave reflecting mirror M1, the reflecting surface of the second concave reflecting mirror M2, and the third convex reflecting mirror M3. After being sequentially reflected by the reflecting surface and the reflecting surface of the fourth concave reflecting mirror M4, an intermediate image of the mask pattern is formed. Then, after the light from the mask pattern intermediate image formed via the first reflective imaging optical system G1 is sequentially reflected by the reflecting surface of the fifth convex reflecting mirror M5 and the reflecting surface of the sixth concave reflecting mirror M6. Then, a reduced image (secondary image) of the mask pattern is formed on the wafer 7. An aperture stop AS is disposed in the optical path between the first concave reflecting mirror M1 and the second concave reflecting mirror M2.

  The following table (1) lists the values of the specifications of the projection optical system according to the first example. In Table (1), λ is the wavelength of the exposure light, β is the projection magnification, NA is the numerical aperture on the image side (wafer side), and φ is the radius (maximum image height) of the image circle IF on the wafer 7. , LX represents the dimension along the X direction of the effective exposure area ER, and LY represents the dimension along the Y direction of the effective exposure area ER.

  Further, the surface number is the order of the reflective surfaces from the mask side along the direction in which the light beam travels from the mask surface that is the object surface to the wafer surface that is the image surface, and r is the apex radius of curvature (mm) of each reflective surface. , D indicates the on-axis interval of each reflecting surface, that is, the surface interval (mm). Note that the surface distance d changes its sign each time it is reflected. The curvature radius of the convex surface toward the mask side is positive and the curvature radius of the concave surface is negative regardless of the incident direction of the light beam. The above notation is the same in the following Tables (2) and (3).

(Table 1)
(Main specifications)
λ = 13.5nm
β = 1/4
NA = 0.26
φ = 35mm
LX = 26mm
LY = 2mm

(Optical member specifications)
Surface number rd
(Mask surface) 747.172113
1 -1130.06947 -277.863560 (First reflector M1)
2 ∞ -245.618417 (Aperture stop AS)
3 1381.65795 423.481977 (Second reflector M2)
4 429.46798 -239.140458 (Third reflector M3)
5 576.67239 828.915838 (4th reflector M4)
6 313.63229 -369.775380 (5th reflector M5)
7 452.38730 408.975380 (6th reflector M6)
(Wafer surface)

(Aspheric data)
1 surface κ = 0.000000
C ₄ = 0.164022 × 10 ⁻⁸ C ₆ = −0.202149 × 10 ⁻¹³
C ₈ = 0.389997 × 10 ⁻¹⁸ C ₁₀ = −0.246457 × 10 ⁻²²
C ₁₂ = 0.261787 × 10 ⁻²⁶ C ₁₄ = −0.184279 × 10 ⁻³⁰
C ₁₆ = 0.695303 × 10 ⁻³⁵ C ₁₈ = −0.105077 × 10 ⁻³⁹

3 sides κ = 0.000000
C ₄ = −0.621915 × 10 ⁻¹¹ C ₆ = −0.698272 × 10 ⁻¹⁵
C ₈ = 0.442169 × 10 ⁻¹⁸ C ₁₀ = −0.131552 × 10 ⁻²¹
C ₁₂ = 0.241039 × 10 ⁻²⁵ C ₁₄ = −0.263140 × 10 ⁻²⁹
C ₁₆ = 0.157654 × 10 ⁻³³ C ₁₈ = −0.398665 × 10 ⁻³⁸

4 sides κ = 0.000000
C ₄ = 0.283050 × 10 ⁻⁸ C ₆ = −0.226889 × 10 ⁻¹²
C ₈ = −0.117586 × 10 ⁻¹⁶ C ₁₀ = 0.2444230 × 10 ⁻²⁰
C ₁₂ = −0.771026 × 10 ⁻²⁵ C ₁₄ = −0.582558 × 10 ⁻²⁹
C ₁₆ = 0.469919 × 10 ⁻³³ C ₁₈ = −0.9514449 × 10 ⁻³⁸

5 sides κ = 0.000000
C ₄ = 0.672896 × 10 ⁻⁹ C ₆ = −0.835163 × 10 ⁻¹⁴
C ₈ = 0.108601 × 10 ⁻¹⁸ C ₁₀ = −0.194685 × 10 ⁻²³
C ₁₂ = 0.152287 × 10 ⁻²⁸ C ₁₄ = 0.173711 × 10 ⁻³³
C ₁₆ = −0.351863 × 10 ⁻³⁸ C ₁₈ = 0.156643 × 10 ⁻⁴³

6 faces κ = 0.000000
C ₄ = 0.240291 × 10 ⁻⁹ C ₆ = 0.909294 × 10 ⁻¹²
C ₈ = −0.324458 × 10 ⁻¹⁶ C ₁₀ = 0.255764 × 10 ⁻¹⁹
C ₁₂ = −0.155502 × 10 ⁻²² C ₁₄ = 0.5550420 × 10 ⁻²⁶
C ₁₆ = −0.102831 × 10 ⁻²⁹ C ₁₈ = 0.774385 × 10 ⁻³⁴

7 sides κ = 0.000000
C ₄ = 0.907459 × 10 ⁻¹⁰ C ₆ = 0.545634 × 10 ⁻¹⁵
C ₈ = 0.398678 × 10 ⁻²⁰ C ₁₀ = −0.109280 × 10 ⁻²⁴
C ₁₂ = 0.801967 × 10 ⁻²⁹ C ₁₄ = −0.293363 × 10 ⁻³³
C ₁₆ = 0.558925 × 10 ⁻³⁸ C ₁₈ = −0.404473 × 10 ⁻⁴³

(Values for conditional expressions)
Sag amount of the first reflecting mirror M1 = 50.4 μm
Sag amount of the second reflecting mirror M2 = 0.084 μm
Sag amount of the third reflecting mirror M3 = 9.758 μm
Sag amount of the fourth reflecting mirror M4 = 0.013 μm
Sag amount of the fifth reflecting mirror M5 = 5.125 μm
Sag amount of the sixth reflecting mirror M6 = 10.197 μm
(1) A = 19.1 °
(2) φM / | R | = 0.899
(3) | α | = 6.016 °
(4) φM = 513.2 mm (maximum in the fourth reflecting mirror M4)

  FIG. 4 is a diagram showing coma aberration in the projection optical system of the first example. FIG. 4 shows meridional coma aberration and sagittal coma aberration at an image height of 100%, an image height of 97%, and an image height of 94%. As is apparent from the aberration diagrams, in the first example, it can be seen that the coma is corrected well in the region corresponding to the effective exposure region ER. Although not shown, it has been confirmed that in the region corresponding to the effective exposure region ER, other aberrations other than coma, such as spherical aberration and distortion, are also corrected well.

[Second Embodiment]
FIG. 5 is a diagram showing the configuration of the projection optical system according to the second example of the present embodiment. Referring to FIG. 5, in the projection optical system of the second embodiment, as in the first embodiment, the light from the mask 4 is reflected on the reflecting surface of the first concave reflecting mirror M1 and on the reflecting surface of the second concave reflecting mirror M2. After being sequentially reflected by the reflecting surface of the third convex reflecting mirror M3 and the reflecting surface of the fourth concave reflecting mirror M4, an intermediate image of the mask pattern is formed. Then, after the light from the mask pattern intermediate image formed via the first reflective imaging optical system G1 is sequentially reflected by the reflecting surface of the fifth convex reflecting mirror M5 and the reflecting surface of the sixth concave reflecting mirror M6. Then, a reduced image (secondary image) of the mask pattern is formed on the wafer 7. An aperture stop AS is disposed in the optical path between the first concave reflecting mirror M1 and the second concave reflecting mirror M2. The following table (2) lists the values of the specifications of the projection optical system according to the second example.

(Table 2)
(Main specifications)
λ = 13.5nm
β = 1/4
NA = 0.26
φ = 35mm
LX = 26mm
LY = 2mm

(Optical member specifications)
Surface number rd
(Mask surface) 748.032536
1 -1144.10442 -279.552281 (First reflector M1)
2 ∞ -238.143932 (Aperture stop AS)
3 1405.04077 417.696213 (Second reflector M2)
4 422.05291 -244.264964 (3rd reflector M3)
5 577.77778 831.654517 (4th reflector M4)
6 315.84099 -367.389553 (5th reflector M5)
7 449.84061 407.389553 (6th reflector M6)
(Wafer surface)

(Aspheric data)
1 surface κ = 0.000000
C ₄ = 0.157492 × 10 ⁻⁸ C ₆ = −0.1988813 × 10 ⁻¹³
C ₈ = 0.348925 × 10 ⁻¹⁸ C ₁₀ = −0.137352 × 10 ⁻²²
C ₁₂ = 0.103379 × 10 ⁻²⁶ C ₁₄ = −0.521461 × 10 ⁻³¹
C ₁₆ = 0.110142 × 10 ⁻³⁵

3 sides κ = 0.000000
C ₄ = −0.209458 × 10 ⁻¹¹ C ₆ = 0.138806 × 10 ⁻¹⁵
C ₈ = −0.410443 × 10 ⁻²⁰ C ₁₀ = −0.740955 × 10 ⁻²⁴
C ₁₂ = 0.468624 × 10 ⁻²⁷ C ₁₄ = −0.524929 × 10 ⁻³¹
C ₁₆ = 0.201006 × 10 ⁻³⁵

4 sides κ = 0.000000
C ₄ = −0.136727 × 10 ⁻⁸ C ₆ = 0.565133 × 10 ⁻¹³
C ₈ = −0.144746 × 10 ⁻¹⁷ C ₁₀ = −0.156641 × 10 ⁻²¹
C ₁₂ = 0.133854 × 10 ⁻²⁵ C ₁₄ = −0.371446 × 10 ⁻³⁰
C ₁₆ = 0.287638 × 10 ⁻³⁵

5 sides κ = 0.000000
C ₄ = 0.927857 × 10 ⁻⁹ C ₆ = −0.229305 × 10 ⁻¹³
C ₈ = 0.321823 × 10 ⁻¹⁸ C ₁₀ = −0.200475 × 10 ⁻²³
C ₁₂ = −0.309384 × 10 ⁻²⁹ C ₁₄ = 0.110873 × 10 ⁻³³
C ₁₆ = −0.431614 × 10 ⁻³⁹

6 faces κ = 0.000000
C ₄ = 0.450011 × 10 ⁻⁹ C ₆ = 0.947412 × 10 ⁻¹²
C ₈ = −0.277769 × 10 ⁻¹⁶ C ₁₀ = 0.161884 × 10 ⁻¹⁹
C ₁₂ = −0.783883 × 10 ⁻²³ C ₁₄ = 0.202419 × 10 ⁻²⁶
C ₁₆ = −0.208865 × 10 ⁻³⁰

7 sides κ = 0.000000
C ₄ = 0.917979 × 10 ⁻¹⁰ C ₆ = 0.560554 × 10 ⁻¹⁵
C ₈ = 0.395047 × 10 ⁻²⁰ C ₁₀ = −0.815108 × 10 ⁻²⁵
C ₁₂ = 0.534141 × 10 ⁻²⁹ C ₁₄ = −0.152140 × 10 ⁻³³
C ₁₆ = 0.181435 × 10 ⁻³⁸

(Values for conditional expressions)
Sag amount of the first reflecting mirror M1 = 48.303 μm
Sag amount of the second reflecting mirror M2 = 0.011 μm
Sag amount of the third reflecting mirror M3 = 7.003 μm
Sag amount of the fourth reflecting mirror M4 = 0.022 μm
Sag amount of the fifth reflecting mirror M5 = 6.826 μm
Sag amount of the sixth reflecting mirror M6 = 11.988 μm
(1) A = 19.7 °
(2) φM / | R | = 0.90
(3) | α | = 6.01 °
(4) φM = 520 mm (maximum in the fourth reflecting mirror M4)

  FIG. 6 is a diagram showing coma aberration in the projection optical system of the second example. FIG. 6 shows meridional coma aberration and sagittal coma aberration at an image height of 100%, an image height of 97%, and an image height of 94%. As is apparent from the aberration diagrams, in the second example as well, as in the first example, it can be seen that coma is corrected well in the region corresponding to the effective exposure region ER. Although not shown, it has been confirmed that in the region corresponding to the effective exposure region ER, other aberrations other than coma, such as spherical aberration and distortion, are also corrected well.

[Third embodiment]
FIG. 7 is a diagram showing the configuration of the projection optical system according to the third example of the present embodiment. Referring to FIG. 7, also in the projection optical system of the third embodiment, the light from the mask 4 is reflected by the reflecting surface of the first concave reflecting mirror M1 and the second concave reflecting surface, as in the first and second embodiments. After being sequentially reflected by the reflecting surface of the mirror M2, the reflecting surface of the third convex reflecting mirror M3, and the reflecting surface of the fourth concave reflecting mirror M4, an intermediate image of the mask pattern is formed. Then, after the light from the mask pattern intermediate image formed via the first reflective imaging optical system G1 is sequentially reflected by the reflecting surface of the fifth convex reflecting mirror M5 and the reflecting surface of the sixth concave reflecting mirror M6. Then, a reduced image (secondary image) of the mask pattern is formed on the wafer 7. An aperture stop AS is disposed in the optical path between the first concave reflecting mirror M1 and the second concave reflecting mirror M2. The following table (3) lists the values of the specifications of the projection optical system according to the third example.

(Table 3)
(Main specifications)
λ = 13.5nm
β = 1/4
NA = 0.26
φ = 35mm
LX = 26mm
LY = 2mm

(Optical member specifications)
Surface number rd
(Mask surface) 754.134388
1 -1241.91280 -288.420750 (First reflector M1)
2 ∞ -256.557828 (Aperture stop AS)
3 1458.23138 444.271770 (Second reflector M2)
4 418.34456 -231.573840 (Third reflector M3)
5 571.08746 822.452156 (4th reflector M4)
6 324.28920 -366.528326 (5th reflector M5)
7 448.79526 408.227826 (6th reflector M6)
(Wafer surface)

(Aspheric data)
1 surface κ = 0.000000
C ₄ = 0.141922 × 10 ⁻⁸ C ₆ = −0.201230 × 10 ⁻¹³
C ₈ = 0.381402 × 10 ⁻¹⁸ C ₁₀ = −0.140144 × 10 ⁻²²
C ₁₂ = 0.103941 × 10 ⁻²⁶ C ₁₄ = −0.557410 × 10 ⁻³¹
C ₁₆ = 0.127309 × 10 ⁻³⁵

3 sides κ = 0.000000
C ₄ = 0.180612 × 10 ⁻¹⁰ C ₆ = −0.134431 × 10 ⁻¹⁵
C ₈ = −0.630161 × 10 ⁻²⁰ C ₁₀ = 0.265754 × 10 ⁻²³
C ₁₂ = −0.331934 × 10 ⁻²⁷ C ₁₄ = 0.245646 × 10 ⁻³¹
C ₁₆ = −0.808630 × 10 ⁻³⁶

4 sides κ = 0.000000
C ₄ = 0.334541 × 10 ⁻⁹ C ₆ = −0.162674 × 10 ⁻¹²
C ₈ = 0.149034 × 10 ⁻¹⁶ C ₁₀ = −0.795711 × 10 ⁻²¹
C ₁₂ = 0.211464 × 10 ⁻²⁵ C ₁₄ = −0.122423 × 10 ⁻³⁰
C ₁₆ = −0.375443 × 10 ⁻³⁵

5 sides κ = 0.000000
C ₄ = 0.124195 × 10 ⁻⁸ C ₆ = −0.255373 × 10 ⁻¹³
C ₈ = 0.300852 × 10 ⁻¹⁸ C ₁₀ = −0.174282 × 10 ⁻²³
C ₁₂ = 0.348777 × 10 ⁻²⁹ C ₁₄ = −0.480864 × 10 ⁻³⁵
C ₁₆ = 0.792537 × 10 ^-40

6 faces κ = 0.000000
C ₄ = 0.948100 × 10 ⁻⁹ C ₆ = 0.05586 × 10 ⁻¹¹
C ₈ = −0.298187 × 10 ⁻¹⁶ C ₁₀ = 0.112104 × 10 ⁻¹⁹
C ₁₂ = −0.589152 × 10 ⁻²³ C ₁₄ = 0.170383 × 10 ⁻²⁶
C ₁₆ = −0.194798 × 10 ⁻³⁰

7 sides κ = 0.000000
C ₄ = 0.906968 × 10 ⁻¹⁰ C ₆ = 0.563149 × 10 ⁻¹⁵
C ₈ = 0.364739 × 10 ⁻²⁰ C ₁₀ = −0.450302 × 10 ⁻²⁵
C ₁₂ = 0.306648 × 10 ⁻²⁹ C ₁₄ = −0.806143 × 10 ⁻³⁴
C ₁₆ = 0.954520 × 10 ⁻³⁹

(Values for conditional expressions)
Sag amount of the first reflecting mirror M1 = 42.318 μm
Sag amount of the second reflecting mirror M2 = 0.399 μm
Sag amount of the third reflecting mirror M3 = 9.635 μm
Sag amount of the fourth reflecting mirror M4 = 0.109 μm
Sag amount of the fifth reflecting mirror M5 = 6.467 μm
Sag amount of the sixth reflecting mirror M6 = 10.006 μm
(1) A = 18.9 °
(2) φM / | R | = 0.90
(3) | α | = 6.016 °
(4) φM = 519 mm (maximum in the fourth reflecting mirror M4)

  FIG. 8 is a diagram showing coma aberration in the projection optical system of the third example. FIG. 8 shows meridional coma aberration and sagittal coma aberration at an image height of 100%, an image height of 97%, and an image height of 94%. As is apparent from the aberration diagrams, in the third example as well, as in the first and second examples, it can be seen that the coma aberration is well corrected in the region corresponding to the effective exposure region ER. Although not shown, it has been confirmed that in the region corresponding to the effective exposure region ER, other aberrations other than coma, such as spherical aberration and distortion, are also corrected well.

  As described above, in each of the above-described embodiments, an image-side numerical aperture of 0.26 is secured for the laser plasma X-ray having a wavelength of 13.5 nm, and various aberrations are favorably corrected on the wafer 7. In addition, an effective exposure area having a circular arc shape of 26 mm × 2 mm can be secured. Therefore, the pattern of the mask 4 can be transferred to each exposure region having a size of, for example, 26 mm × 33 mm on the wafer 7 with a high resolution of 0.1 μm or less by scanning exposure.

  In the first and second embodiments described above, the sag amount of the reflecting surface of the second reflecting mirror M2 and the sag amount of the reflecting surface of the fourth reflecting mirror M4 are both suppressed to 0.1 μm or less. In the example, since the sag amount of the reflecting surface of the fourth reflecting mirror M4 is suppressed to approximately 0.1 μm and the sag amount of the reflecting surface of the second reflecting mirror M2 is suppressed to 0.4 μm or less, the aspherical reflection By adopting a spherical surface correction processing method in which a surface is processed as a spherical surface and processed and measured, and a minute correction processing is performed by the amount of sag, aspherical surface processing and measurement can be greatly simplified and executed. As a result, the fabrication of the aspheric surfaces in the second reflecting mirror M2 and the fourth reflecting mirror M4 is dramatically simplified, and the fabrication of the aspheric surfaces is very advantageous in terms of time, cost, and accuracy. Can do.

  Further, in each of the above-described embodiments, the angle α formed between the light axis incident on the mask 4 and the optical axis AX of the light beam group reflected by the mask 4 is suppressed to about 6 °, so that the reflective mask 4 Even if is used, interference between incident light and reflected light can be avoided, and it is difficult to be affected by shadows due to reflection, and therefore performance is not easily deteriorated. Further, there is an advantage that even if a slight error occurs in the setting position of the mask 4, it is difficult to cause a large change in magnification.

  In the exposure apparatus according to the above-described embodiment, the illumination system illuminates the mask (illumination process), and exposes the transfer pattern formed on the mask using the projection optical system onto the photosensitive substrate (exposure process). Microdevices (semiconductor elements, imaging elements, liquid crystal display elements, thin film magnetic heads, etc.) can be manufactured. Hereinafter, referring to the flowchart of FIG. 9 for an example of a method for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of this embodiment. I will explain.

  First, in step 301 of FIG. 9, a metal film is deposited on one lot of wafers. In the next step 302, a photoresist is applied on the metal film on the lot of wafers. Thereafter, in step 303, using the exposure apparatus of the present embodiment, the pattern image on the mask (reticle) is sequentially exposed and transferred to each shot area on the wafer of one lot via the projection optical system. .

  Thereafter, in step 304, the photoresist on the one lot of wafers is developed, and in step 305, the resist pattern is etched on the one lot of wafers to form a pattern on the mask. Corresponding circuit patterns are formed in each shot area on each wafer. Thereafter, a device pattern such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer. According to the semiconductor device manufacturing method described above, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput.

  In the above-described embodiment, a laser plasma X-ray source is used as a light source for supplying X-rays. However, the present invention is not limited to this. For example, synchrotron radiation (SOR) light is used as the X-rays. You can also

  In the above-described embodiment, the present invention is applied to an exposure apparatus having a light source for supplying X-rays. However, the present invention is not limited to this, and light having a wavelength other than X-rays is supplied. The present invention can also be applied to an exposure apparatus having a light source.

  Further, in the above-described embodiment, the present invention is applied to the projection optical system of the exposure apparatus. However, the present invention is not limited to this, and the present invention is also applied to other general projection optical systems. be able to.

It is a figure which shows schematically the structure of the exposure apparatus concerning embodiment of this invention. It is a figure which shows the positional relationship of the arc-shaped exposure area | region (namely, effective exposure area | region) formed on a wafer, and an optical axis. It is a figure which shows the structure of the projection optical system concerning the 1st Example of this embodiment. It is a figure which shows the coma aberration in the projection optical system of 1st Example. It is a figure which shows the structure of the projection optical system concerning the 2nd Example of this embodiment. It is a figure which shows the coma aberration in the projection optical system of 2nd Example. It is a figure which shows the structure of the projection optical system concerning 3rd Example of this embodiment. It is a figure which shows the coma aberration in the projection optical system of 3rd Example. It is a figure which shows the flowchart about an example of the method at the time of obtaining the semiconductor device as a microdevice.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser plasma X-ray source 2 Wavelength selection filter 3 Illumination optical system 4 Mask 5 Mask stage 6 Projection optical system 7 Wafer 8 Wafer stages M1-M6 Reflector AS Aperture stop

Claims (16)

In a projection optical system comprising six reflecting mirrors and forming a reduced image of the first surface on the second surface,
A first reflective imaging optical system for forming an intermediate image of the first surface; and a second reflective imaging optical system for forming an image of the intermediate image on the second surface;
The first reflective imaging optical system includes a first reflecting mirror M1, an aperture stop, a second reflecting mirror M2, a third reflecting mirror M3, and a fourth reflecting mirror M4 in the order of incidence of light from the first surface side. And
The second reflective imaging optical system includes a fifth reflecting mirror M5 and a sixth reflecting mirror M6 in the order of incidence of light from the first surface side,
The projection optical system according to claim 4, wherein the reflecting surface of the fourth reflecting mirror M4 is formed in an aspherical shape with a sag amount of 0.6 μm or less. 2. The projection optical system according to claim 1, wherein the reflecting surface of the fourth reflecting mirror M <b> 4 is formed in an aspherical shape with a sag amount of 0.4 μm or less. 2. The projection optical system according to claim 1, wherein the reflecting surface of the fourth reflecting mirror M <b> 4 is formed in an aspherical shape with a sag amount of 0.1 μm or less. In a projection optical system comprising six reflecting mirrors and forming a reduced image of the first surface on the second surface,
A first reflective imaging optical system for forming an intermediate image of the first surface; and a second reflective imaging optical system for forming an image of the intermediate image on the second surface;
The first reflective imaging optical system includes a first reflecting mirror M1, an aperture stop, a second reflecting mirror M2, a third reflecting mirror M3, and a fourth reflecting mirror M4 in the order of incidence of light from the first surface side. And
The second reflective imaging optical system includes a fifth reflecting mirror M5 and a sixth reflecting mirror M6 in the order of incidence of light from the first surface side,
The projection optical system according to claim 1, wherein the reflecting surface of the second reflecting mirror M2 is formed in an aspherical shape with a sag amount of 0.6 μm or less. 5. The projection optical system according to claim 4, wherein the reflecting surface of the second reflecting mirror M2 is formed in an aspherical shape with a sag amount of 0.4 [mu] m or less. 5. The projection optical system according to claim 4, wherein the reflecting surface of the second reflecting mirror M2 is formed in an aspherical shape with a sag amount of 0.1 [mu] m or less. A projection optical system comprising six reflecting mirrors and forming a reduced image of the first surface on the second surface, a first reflective imaging optical system for forming an intermediate image of the first surface, and the intermediate image A second reflective imaging optical system for forming the image on the second surface,
The first reflective imaging optical system includes a first reflecting mirror M1, an aperture stop, a second reflecting mirror M2, a third reflecting mirror M3, and a fourth reflecting mirror M4 in the order of incidence of light from the first surface side. And
The second reflective imaging optical system includes a fifth reflecting mirror M5 and a sixth reflecting mirror M6 in the order of incidence of light from the first surface side,
The projection optical system, wherein the reflecting surface of the second reflecting mirror M2 and the reflecting surface of the fourth reflecting mirror M4 are each formed in an aspherical shape with a sag amount of 0.6 μm or less. 8. The projection according to claim 7, wherein the reflecting surface of the second reflecting mirror M <b> 2 and the reflecting surface of the fourth reflecting mirror M <b> 4 are each formed in an aspherical shape with a sag amount of 0.4 μm or less. Optical system. 8. The projection according to claim 7, wherein the reflecting surface of the second reflecting mirror M2 and the reflecting surface of the fourth reflecting mirror M4 are each formed in an aspherical shape with a sag amount of 0.1 [mu] m or less. Optical system. The maximum incident angle A of the light beam to each of the reflecting mirrors M1 to M6 is the respective reflecting mirrors M1 to M6.
A <25 °
The projection optical system according to claim 1, wherein the following condition is satisfied. The inclination α of the light beam from the first surface to the first reflecting mirror M1 with respect to the optical axis of the principal ray is:
5 ° <| α | <10 °
The projection optical system according to claim 1, wherein the following condition is satisfied. The effective diameter φM of each of the reflecting mirrors M1 to M6 is as follows.
φM ≦ 700mm
The projection optical system according to claim 1, wherein the following condition is satisfied. The reflecting surfaces of the reflecting mirrors M1 to M6 are formed in an aspherical shape that is rotationally symmetric with respect to the optical axis,
The projection optical system according to any one of claims 1 to 12, wherein the maximum order of the aspheric surface defining each reflecting surface is 10th or higher. The projection optical system according to claim 1, wherein the projection optical system is a substantially telecentric optical system on the second surface side. 15. An illumination system for illuminating a mask set on the first surface, and a projection exposure of a pattern of the mask onto a photosensitive substrate set on the second surface. An exposure apparatus comprising the projection optical system according to the item. The illumination system has a light source for supplying X-rays as exposure light,
16. The exposure apparatus according to claim 15, wherein the mask and the photosensitive substrate are moved relative to the projection optical system to project and expose the mask pattern onto the photosensitive substrate.

Images