JP2005189248A - Projection optical system and exposure device provided with the projection optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type projection optical system having excellent reflection property even to an X-ray and capable of excellently correcting aberration while restraining the upsizing of a reflection mirror. <P>SOLUTION: The projection optical system is provided with eight reflection mirrors and forms a reduced image on a 1st surface (4) on a 2nd surface (7). It is provided with a 1st reflection image forming optical system (G1) for forming an intermediate image on the 1st surface and a 2nd reflection image forming optical system (G2) for forming the image of the intermediate image on the 2nd surface. The 1st reflection image forming optical system has the 1st reflection mirror (M1), an aperture diaphragm (AS), the 2nd reflection mirror (M2), the 3rd reflection mirror (M3) and the 4th reflection mirror (M4) in the incident order of light from the 1st surface side. The 2nd reflection image forming optical system has the 5th reflection mirror (M5), the 6th reflection mirror (M6), the 7th reflection mirror (M7) and the 8th reflection mirror (M8) in the incident order of the light from the 1st surface side. <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, 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.
In the future, it will be necessary to shorten the wavelength of exposure light. For example, when a KrF excimer laser having a wavelength of 248 nm is used as exposure light, a resolution of 0.25 μm is obtained, and when an ArF excimer laser having a wavelength of 193 nm is used, a resolution of 0.18 μm is 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 using X-rays as exposure light, for example, US Pat. No. 5,815,310, Japanese Patent Application Laid-Open No. 9-212322, US Pat. No. 6, Various reflective optical systems have been proposed, such as the specification of 183,095B1.

In summary,
US Pat. No. 5,815,310 JP-A-9-212322 U.S. Pat. No. 6,183,095B1 and the like.

However, in the conventional reflective optical system disclosed in JP-A-9-212322,
Although it has a configuration of six reflecting mirrors and achieves a relatively bright optical system with NA = 0.25, it is not possible to achieve a brighter NA.

  Further, in the first embodiment shown in US Pat. No. 6,183,095B1, a relatively bright optical system with NA = 0.25 is achieved with six reflecting mirrors. Has also failed to achieve a brighter NA.

The present invention has been made in view of the above-described problems, and an object thereof is to ensure a numerical aperture (NA) of at least 0.26 or more. It is another object of the present invention to provide an exposure apparatus that can secure a large resolving power using, for example, X-rays as exposure light by applying the projection exposure optical system of the present invention to the exposure apparatus.

  In order to solve the above problems, in the first invention of the present invention, in the projection optical system for forming the reduced image of the first surface on the second surface, the first reflection for forming the intermediate image of the first surface. An imaging optical system; and a second reflective imaging optical system for forming an image of the intermediate image on the second surface, wherein the first reflective imaging optical system transmits light from the first surface side. The second reflective imaging optical system includes a concave first reflecting mirror M1, an aperture stop, a concave second reflecting mirror M2, a convex third reflecting mirror M3, and a concave fourth reflecting mirror M4 in the order of incidence. Has a fifth reflecting mirror M5, a concave sixth reflecting mirror M6, a convex seventh reflecting mirror M7, and a concave eighth reflecting mirror M8 in the order of incidence of light from the first surface side. A projection optical system is provided.

In the first embodiment of the present invention, the fifth reflecting mirror M5 has a concave surface.
In another embodiment of the present invention, the fifth reflecting mirror M5 is a flat surface.
In addition to this, the fifth reflecting mirror M5 may be formed of a convex surface.

  According to a preferred aspect of the first invention, it is preferable that the aperture stop is disposed in a space between the first reflecting mirror M1 and the second reflecting mirror M2. Furthermore, when the distance between the first reflecting mirror M1 and the aperture stop is d1, and the surface distance between the first reflecting mirror M1 and the second reflecting mirror M2 is d2, the position of the aperture stop is 0.5 < It is preferable that the condition | d1 | / | d2 | <2.5 is satisfied.

  Further, according to a preferred aspect of the first invention, when the effective diameter of the reflecting mirror is φ and the center radius of curvature of the reflecting mirror is R, the condition of φ / | R | <1 is satisfied for each of the reflecting mirrors M1 to M8. It is preferred that all be satisfied. The image-side numerical aperture NA is preferably at least 0.26 in order to improve the resolution as much as possible. Furthermore, it is preferable to be 0.30.

  In the second invention 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 one aspect of the invention is provided.

  According to a preferred aspect of the second invention, 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, the aperture stop AS is disposed in the space between the first reflecting mirror and the second reflecting mirror, so that the incident angle of the light beam tends to increase and the light beam to the third reflecting mirror tends to be large. The incident angle can be kept small. As a result, in the reflective multilayer film, reflection unevenness hardly occurs and a sufficiently high reflectance can be obtained, so that good reflection characteristics can be secured even for X-rays. Further, by suppressing the incident angle of the light beam to the third reflecting mirror, it is possible to reduce the effective diameter of the fourth reflecting mirror, which tends to increase the effective diameter. That is, 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 that can satisfactorily correct aberrations while suppressing an increase in size of the reflector.

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. The seventh reflecting mirror M7 for reflecting the light reflected by the sixth reflecting mirror M6 and the eighth reflecting mirror M8 for reflecting the light reflected by the seventh reflecting mirror M7.

In the present invention, by adopting a configuration in which a reduced image of the first surface is formed twice on the second surface, distortion (distortion) can be corrected satisfactorily.
In addition, since the aperture stop AS is arranged in the space between the first reflecting mirror M1 and the second reflecting mirror M2, the incident angle of the light beam to the third reflecting mirror M3 where the incident angle of the light beam tends to be large is set. It can be kept small.

  Normally, in an eight-mirror reflective optical system, the aperture stop is generally arranged immediately before the reflecting mirror in order to avoid interference of light beams. In that case, since the position where the aperture stop is arranged is limited to the position immediately before the reflecting mirror, it is 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 in the space between the first reflecting mirror M1 and the second reflecting mirror M2, the position of the aperture stop can be freely set at any position between the two. By setting the aperture stop at a convenient place, it is possible to easily balance the aberrations of the upper and lower frames. In the present invention, it is desirable that the position of the aperture stop satisfies the following conditional expression (1). Here, d1 is a distance between the first reflecting mirror M1 and the aperture stop, and d2 is a surface distance between the first reflecting mirror M1 and the second reflecting mirror M2.

0.5 <| d1 | / | d2 | <2.5 (1)
Since the first reflecting mirror M1 and the second reflecting mirror M2 are disposed so as to be substantially symmetrical with respect to the aperture stop, it is possible to easily balance the aberrations of the upper and lower frames.

  Further, by making the reflecting mirrors on both sides of the aperture stop concave instead of convex, the light beam reflection angle on both the reflecting mirrors of the first reflecting mirror and the second reflecting mirror, and the reflecting mirrors on the outer side thereof, for example, The light beam reflection angle on the third reflecting mirror can be kept small.

Contrary to the above arrangement, the aperture stop AS is disposed between the second reflecting mirror M2 and the third reflecting mirror M3.
Or if it arrange | positions between the 3rd reflective mirror M3 and the 4th reflective mirror M4, since the position of the light beam on the 1st reflective mirror M1 leaves | separates from an optical axis, the effective diameter of the 1st reflective mirror M1 will become large too much. Become.

  In this case, the angle of incidence on the reticle and the angle of reflection from the reticle are determined to be substantially constant because the illumination system mirror must be saved and the imaging performance must be maintained. The optical path length to the (aperture stop) becomes long and the object height of the reticle becomes high. As a result, the imaging magnification must be reduced to 1/5 to 1/6.

  On the other hand, in the present invention, since the aperture stop AS is disposed in the space between the first reflecting mirror M1 and the second reflecting mirror M2, it is small and good optical performance can be maintained while maintaining the imaging magnification at 1/4. Performance can be realized.

By adopting the above arrangement, the maximum diameter of the reflecting mirror can be suppressed, and the arrangement of each reflecting mirror and aperture stop can be appropriately arranged without vignetting.
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.

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 M8 satisfies the following conditional expression (2) in each of the reflecting mirrors M1 to M8.
A <25 ° (2)
Exceeding the upper limit value of conditional expression (2) 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 (3) is satisfied in each of the reflecting mirrors M1 to M8. In conditional expression (3), 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 M8.

φM / | R | <1.0 (3)
If the upper limit value of conditional expression (3) 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 M8 (particularly the fourth reflecting mirror M4) becomes too large. Since accurate shape measurement becomes difficult, it is not preferable.

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 (4).
5 ° <| α | <10 ° (4)
Exceeding the upper limit value of conditional expression (4) is not preferable because a reflection mask is easily affected by reflection when a reflection mask is provided on the first surface. On the other hand, if the lower limit of conditional expression (4) is not reached, it is not preferable because incident light and reflected light interfere with each other when a reflective mask is installed on the first surface.

In the present invention, it is desirable that the effective diameter φM of each of the reflecting mirrors M1 to M8 satisfies the following conditional expression (5) in each of the reflecting mirrors M1 to M8.
φM ≦ 700mm (5)
Exceeding the upper limit of conditional expression (5) 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. Also, with this configuration, when applied to, for example, an exposure apparatus, good imaging is possible even if the wafer has irregularities 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 four reflecting mirrors M5 to M8.

  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 (sag amount) along the optical axis from the tangential plane at the apex of the aspheric surface to the position on the aspheric surface at height y. ) Is z, the apex radius of curvature is r, the conic coefficient is κ, and the nth-order aspherical coefficient is Cn, it is expressed by the following formula (b).

(Equation 1)
z = (y ² / r) / {1+ {1- (1 + κ) · y ² / r ² } ^1/2 }
+ C4 · y ⁴ + C6 · y ⁶ + C8 · y ⁸ + C10 · y ¹⁰ + ... (b)

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, light from the mask 4 (not shown in FIG. 3) is reflected from the reflecting surface of the first concave reflecting mirror M1, 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, the light from the intermediate image of the mask pattern formed through the first reflective imaging optical system G1 is reflected on the reflecting surface of the fifth concave reflecting mirror M5, the reflecting surface of the sixth concave reflecting mirror M6, and the seventh convex reflecting surface. After being sequentially reflected by the reflecting surface of the mirror M 7 and the reflecting surface of the eighth concave reflecting mirror M 8, a reduced image (secondary image) of the mask pattern is formed on the wafer 7.

  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 image side (wafer side) numerical aperture, H0 is the maximum object height on the mask 4, and φ is on the wafer 7. The radius (maximum image height) of the image circle IF, 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 = 0.3
H0 = 152mm
φ = 38mm
LX = 26mm
LY = 2mm

(Optical member specifications)
Surface number rd
(Mask surface) 729.59
1-1224.25-326.96 (first reflecting mirror M1)
2 ∞ -282.62 (Aperture stop AS)
3 1654.39 545.02 (second reflecting mirror M2)
4 451.03-152.90 (Third reflector M3)
5 554.007 588.60 (fourth reflecting mirror M4)
6-8116.54-156.35 (5th reflecting mirror M5)
7 1942.10 287.24 (6th reflector M6)
8 262.50 -382.02 (seventh reflector M7)
9 461.49 422.016 (8th reflector M8)
(Wafer surface)

(Aspheric data)
1 surface κ = 0.000000
C4 = 0.236104 × 10 ⁻⁸ C6 = −0.275756 × 10 ⁻¹³
C8 = 0.35665639 × 10 ⁻¹⁸ C10 = −0.454425 × 10 ⁻²³
C12 = 0.267145 × 10 ⁻²⁸ C14 = 0.8101082 × 10 ⁻³³
C16 = −0.173621 × 10 ⁻³⁷

2 sides κ = 0.000000
C4 = −0.187134 × 10 ⁻⁹ C6 = 0.392812 × 10 ⁻¹⁵
C8 = −0.945690 × 10 ⁻²⁰ C10 = 0.722354 × 10 ⁻²³
C12 = −0.240987 × 10 ⁻²⁷ C14 = 0.118382 × 10 ⁻³¹
C16 = −0.240509 × 10 ⁻³⁶

3 sides κ = 0.000000
C4 = 0.822766 × 10 ⁻⁹ C6 = −0.317441 × 10 ⁻¹²
C8 = 0.221262 × 10 ⁻¹⁶ C10 = −0.994391 × 10 ⁻²¹
C12 = 0.276031 × 10 ⁻²⁵ C14 = −0.433102 × 10 ⁻³⁰
C16 = 0.294394 × 10 ⁻³⁵

4 sides κ = 0.000000
C4 = 0.521104 × 10 ⁻⁹ C6 = −0.196824 × 10 ⁻¹³
C8 = 0.299585 × 10 ⁻¹⁸ C10 = −0.239888 × 10 ⁻²³
C12 = 0.376818 x 10 ^-29 C14 = 0.712863 x 10 ^-34
C16 = −0.358580 × 10 ⁻³⁹

5 sides κ = 0.000000
C4 = 0.959292 × 10 ⁻⁰⁹ C6 = 0.127892 × 10 ⁻¹³
C8 = −0.640113 × 10 ⁻¹⁸ C10 = 0.23914 × 10 ⁻²²
C12 = −0.472773 × 10 ⁻²⁷ C14 = 0.561143 × 10 ⁻³²
C16 = −0.293894 × 10 ⁻³⁷

6 faces κ = 0.000000
C4 = 0.248598 × 10 ⁻⁸ C6 = −0.185306 × 10 ⁻¹³
C8 = 0.008375 × 10 ⁻¹⁸ C10 = −0.3799796 × 10 ⁻²²
C12 = 0.121143 × 10 ⁻²⁶ C14 = −0.224691 × 10 ⁻³¹
C16 = 0.182426 × 10 ⁻³⁶

7 sides κ = 0.000000
C4 = −0.433169 × 10 ⁻⁰⁸ C6 = 0.102954 × 10 ⁻¹¹
C8 = 0.186820 × 10 ⁻¹⁷ C10 = −0.379111 × 10 ⁻²¹
C12 = 0.5888752 × 10 ⁻²⁴ C14 = −0.114627 × 10 ⁻²⁷
C16 = 0.895077 × 10 ⁻³²

8 sides κ = 0.000000
C4 = 0.805181 × 10 ⁻¹⁰ C6 = 0.4050028 × 10 ⁻¹⁵
C8 = 0.216486 × 10 ⁻²⁰ C10 = 0.117978 × 10 ⁻²⁵
C12 = 0.633385 × 10 ⁻³¹ C14 = −0.183719 × 10 ⁻³⁵
C16 = 0.395361 × 10 ^-40

(Values for conditional expressions)
φM4 = 520.11 mm
R4 = 554.07mm
(1) A = 23.18 °
(2) φM / | R | = 0.938 (maximum in the fourth reflecting mirror M4)
(3) | α | = 6.02 ° (105.07 mrad)
(4) φM = 520.11 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. In FIG.
The meridional coma aberration and sagittal coma aberration are shown at an image height of 100%, an image height of 97%, and an image height of 95%. 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.

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 (not shown in FIG. 5) is reflected on the reflecting surface of the first concave reflecting mirror M1, the second After being sequentially reflected by the reflecting surface of the concave reflecting 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. The light from the mask pattern intermediate image formed via the first reflective imaging optical system G1 is reflected on the reflecting surface of the fifth planar reflecting mirror M5, the reflecting surface of the sixth concave reflecting mirror M6, and the seventh convex reflecting mirror. After being sequentially reflected by the reflecting surface of M7 and the reflecting surface of the eighth concave reflecting mirror M8, a reduced image (secondary image) of the mask pattern is formed on the wafer 7.

  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 = 0.3
H0 = 152mm
φ = 38mm
LX = 26mm
LY = 2mm

(Optical member specifications)
Surface number rd
(Mask surface) 730.68
1 -1224.31 -326.69 (first reflecting mirror M1)
2 ∞ -283.99 (Aperture stop AS)
3 1729.86 558.832 (second reflecting mirror M2)
4 471.84 -149.65 (Third reflecting mirror M3)
5 553.40 573.268 (fourth reflector M4)
6 ∞ 158.93 (5th reflector M5)
7 1586.79 289.31 (6th reflector M6)
8 258.12 -382.15 (seventh reflector M7)
9 462.68 425.20 (8th reflector M8)
(Wafer surface)

(Aspheric data)
1 surface κ = 0.000000
C4 = 0.241128 × 10 ⁻⁸ C6 = −0.285619 × 10 ⁻¹³
C8 = 0.386059 × 10 ⁻¹⁸ C10 = −0.524192 × 10 ⁻²³
C12 = 0.410302 × 10 ⁻²⁸ C14 = 0.599534 × 10 ⁻³³
C16 = −0.143417 × 10 ⁻³⁷

2 sides κ = 0.000000
C4 = −0.167087 × 10 ⁻⁹ C6 = 0.722672 × 10 ⁻¹⁵
C8 = −0.1011365 × 10 ⁻¹⁹ C10 = 0.82458 × 10 ⁻²³
C12 = −0.247059 × 10 ⁻²⁷ C14 = 0.120302 × 10 ⁻³¹
C16 = −0.242136 × 10 ⁻³⁶

3 sides κ = 0.000000
C4 = 0.139942 × 10 ⁻⁸ C6 = −0.351424 × 10 ⁻¹²
C8 = 0.321933 × 10 ⁻¹⁶ C10 = −0.981509 × 10 ⁻²¹
C12 = 0.257015 × 10 ⁻²⁵ C14 = −0.380923 × 10 ⁻³⁰
C16 = 0.244864 × 10 ⁻³⁵

4 sides κ = 0.000000
C4 = 0.587117 × 10 ⁻⁹ C6 = −0.211493 × 10 ⁻¹³
C8 = 0.314338 × 10 ⁻¹⁸ C10 = −0.235062 × 10 ⁻²³
C12 = 0.102287 × 10 ⁻²⁹ C14 = 0.973030 × 10 ⁻³⁴
C16 = −0.443593 × 10 ⁻³⁹

5 sides κ = 0.000000
C4 = 0.849183 × 10 ⁻⁰⁹ C6 = 0.162294 × 10 ⁻¹³
C8 = −0.694072 × 10 ⁻¹⁸ C10 = 0.201793 × 10 ⁻²²
C12 = −0.318768 × 10 ⁻²⁷ C14 = 0.224088 × 10 ⁻³²
C16 = −0.280392 × 10 ⁻³⁸

6 faces κ = 0.000000
C4 = 0.222608 × 10 ⁻⁸ C6 = −0.138168 × 10 ⁻¹³
C8 = 0.630566 × 10 ⁻¹⁸ C10 = −0.294160 × 10 ⁻²²
C12 = 0.935911 × 10 ⁻²⁷ C14 = −0.173856 × 10 ⁻³¹
C16 = 0.141471 × 10 ⁻³⁶

7 sides κ = 0.000000
C4 = −0.584322 × 10 ⁻⁰⁸ C6 = 0.107106 × 10 ⁻¹¹
C8 = −0.194686 × 10 ⁻¹⁷ C10 = −0.427719 × 10 ⁻²¹
C12 = 0.627701 × 10 ⁻²⁴ C14 = −0.120060 × 10 ⁻²⁷
C16 = 0.911840 × 10 ⁻³²

8 sides κ = 0.000000
C4 = 0.768996 × 10 ⁻¹⁰ C6 = 0.425944 × 10 ⁻¹⁵
C8 = 0.206837 × 10 ⁻²⁰ C10 = 0.928370 × 10 ⁻²⁶
C12 = 0.134773 × 10 ⁻³⁰ C14 = −0.343953 × 10 ⁻³⁵
C16 = 0.525049 × 10 ^-40
(Values for conditional expressions)
φM4 = 520.09 mm
R4 = 553.40mm
(1) A = 23.11 °
(2) φM / | R | = 0.940 (maximum in the fourth reflecting mirror M4)
(3) | α | = 6.03 ° (105.24 mrad)
(4) φM = 520.09 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. In FIG.
The meridional coma aberration and sagittal coma aberration are shown at an image height of 100%, an image height of 97%, and an image height of 95%. 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.

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, in the projection optical system of the third example as well, the light from the mask 4 (not shown in FIG. 7) is transmitted from the first concave reflecting mirror M1 as in the first and second examples. After being sequentially reflected by the reflecting surface, the reflecting surface of the second concave reflecting 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. The light from the mask pattern intermediate image formed via the first reflective imaging optical system G1 is reflected on the reflecting surface of the fifth convex reflecting mirror M5, the reflecting surface of the sixth concave reflecting mirror M6, and the seventh convex reflecting mirror. After being sequentially reflected by the reflecting surface of M7 and the reflecting surface of the eighth concave reflecting mirror M8, a reduced image (secondary image) of the mask pattern is formed on the wafer 7.

  The following table (3) lists the values of the specifications of the projection optical system according to the third example.

(Table 3)
λ = 13.5nm
β = 1/4
NA = 0.26
H0 = 140mm
φ = 35mm
LX = 26mm
LY = 2mm
(Optical member specifications)
Surface number rd
(Mask surface) 662.34
1-1158.35 -274.88 (first reflecting mirror M1)
2 ∞ -227.11 (Aperture stop AS)
3 1425.98 445.49 (second reflecting mirror M2)
4 402.89-183.04 (Third reflector M3)
5 552.95 610.95 (4th reflector M4)
6 5702.90 -151.72 (5th reflector M5)
7 1376.84 282.26 (6th reflector M6)
8 276.63 -381.95 (seventh reflecting mirror M7)
9 463.67 423.31 (8th reflector M8)
(Wafer surface)

(Aspheric data)
1 surface κ = 0.000000
C4 = 0.247729 × 10 ⁻⁸ C6 = −0.209702 × 10 ⁻¹³
C8 = 0.135890 × 10 ⁻¹⁸ C10 = −0.163445 × 10 ⁻²²
C12 = 0.177588 × 10 ⁻²⁶ C14 = −0.919105 × 10 ⁻³¹
C16 = 0.1877697 × 10 ⁻³⁵

2 sides κ = 0.000000
C4 = −0.537125 × 10 ⁻⁹ C6 = 0.947337 × 10 ⁻¹⁵
C8 = 0.672134 × 10 ⁻¹⁹ C10 = −0.575990 × 10 ⁻²³
C12 = 0.824956 × 10 ⁻²⁷ C14 = −0.518711 × 10 ⁻³¹
C16 = 0.117808 × 10 ⁻³⁵

3 sides κ = 0.000000
C4 = −0.860260 × 10 ⁻⁹ C6 = −0.263124 × 10 ⁻¹²
C8 = 0.2909043 × 10 ⁻¹⁶ C10 = −0.107454 × 10 ⁻²⁰
C12 = 0.335525 × 10 ⁻²⁵ C14 = −0.573368 × 10 ⁻³⁰
C16 = 0.4066573 × 10 ⁻³⁵

4 sides κ = 0.000000
C4 = 0.726843 × 10 ⁻⁹ C6 = −0.214264 × 10 ⁻¹³
C8 = 0.289827 × 10 ⁻¹⁸ C10 = −0.209809 × 10 ⁻²³
C12 = 0.524417 × 10 ⁻²⁹ C14 = 0.125948 × 10 ⁻³⁴
C16 = −0.374855 × 10 ⁻⁴⁰

5 sides κ = 0.000000
C4 = 0.963283 × 10 ⁻⁰⁹ C6 = −0.805355 × 10 ⁻¹⁴
C8 = 0.497479 × 10 ⁻¹⁸ C10 = 0.163821 × 10 ⁻²²
C12 = −0.185908 × 10 ⁻²⁶ C14 = 0.567580 × 10 ⁻³¹
C16 = −0.640937 × 10 ⁻³⁶

6 faces κ = 0.000000
C4 = 0.154038 × 10 ⁻⁸ C6 = 0.100906 × 10 ⁻¹³
C8 = −0.419886 × 10 ⁻¹⁸ C10 = 0.360204 × 10 ⁻²²
C12 = −0.220328 × 10 ⁻²⁶ C14 = 0.671290 × 10 ⁻³¹
C16 = −0.828213 × 10 ⁻³⁶

7 sides κ = 0.000000
C4 = 0.278386 × 10 ⁻⁰⁸ C6 = 0.614923 × 10 ⁻¹²
C8 = 0.882486 × 10 ⁻¹⁷ C10 = 0.79005 × 10 ⁻²⁰
C12 = −0.460292 × 10 ⁻²³ C14 = 0.116209 × 10 ⁻²⁶
C16 = −0.115218 × 10 ⁻³⁰

8 sides κ = 0.000000
C4 = 0.918140 × 10 ⁻¹⁰ C6 = 0.490491 × 10 ⁻¹⁵
C8 = 0.3216222 × 10 ⁻²⁰ C10 = 0.136602 × 10 ⁻²⁵
C12 = −0.208825 × 10 ⁻³⁰ C14 = 0.919116 × 10 ⁻³⁵
C16 = −0.100863 × 10 ⁻³⁹

(Values for conditional expressions)
φM4 = 508.76 mm
R4 = 552.95mm
(1) A = 22.83 °
(2) φM / | R | = 0.920 (maximum in the fourth reflecting mirror M4)
(3) | α | = 6.59 ° (115.02 mrad)
(4) φM = 508.76 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 95%. 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 or 0.3 is secured for the laser plasma X-ray having a wavelength of 13.5 nm, and various aberrations are caused on the wafer 7. A well-corrected 26 mm × 2 mm arc effective exposure area can be secured. Therefore, the pattern of the mask 4 can be transferred to each exposure region having a size of 26 mm × 34, 37 mm on the wafer 7 with a high resolution of 0.1 μm or less by scanning exposure.

  In each of the above-described embodiments, the largest effective diameter of the fourth concave reflecting mirror M4 is about 509 to about 520 mm, which is sufficiently small. Thus, in each Example, the enlargement of a reflecting mirror is suppressed and size reduction of an optical system is achieved.

The maximum φ / R value is also suppressed to 0.920 to 0.940 and 1 or less, and the maximum value A of the light incident angle on each surface is also 22.83 ° to 23.18 ° and 25 °. It is suppressed to the following.
Further, the aspherical order is used up to the 16th order of each surface, satisfies the 10th order or more of the conditions, and the inclination of the image side principal ray is almost 0, which is a telecentric optical system.

  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.

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.

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-M8 Reflector AS Aperture stop IMI Intermediate image

Claims (9)

In a projection optical system for 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 concave first reflecting mirror M1, an aperture stop, a concave second reflecting mirror M2, a convex third reflecting mirror M3, and a concave surface in the order of incidence of light from the first surface side. A fourth reflecting mirror M4,
The second reflective imaging optical system includes a fifth reflecting mirror M5, a concave sixth reflecting mirror M6, a convex seventh reflecting mirror M7, and a concave eighth reflecting mirror in the order of incidence of light from the first surface side. A projection optical system comprising: M8. The projection optical system according to claim 1,
The fifth reflecting mirror M5 has a concave surface, and is a projection optical system. The projection optical system according to claim 1,
The fifth reflecting mirror M5 is a projection optical system comprising a plane. The projection optical system according to claim 1,
The fifth reflecting mirror M5 is a projection optical system having a convex surface. 5. The projection optical system according to claim 1, wherein the aperture stop is disposed in a space between the first reflecting mirror M <b> 1 and the second reflecting mirror M <b> 2. The projection optical system according to claim 5,
d1: Distance between the first reflecting mirror M1 and the aperture stop d2: The position of the aperture stop satisfies the following condition from the surface distance between the first reflecting mirror M1 and the second reflecting mirror M2. Projection optics.
0.5 <| d1 | / | d2 | <2.5 When the effective diameter of the reflector is φ and the center radius of curvature of the reflector is R,
φ / | R | <1
The projection optical system according to any one of claims 1 to 6, wherein all of the reflecting mirrors M1 to M8 satisfy the above condition. 8. 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 includes a light source for supplying X-rays as exposure light, and moves the mask and the photosensitive substrate relative to the projection optical system so that the pattern of the mask is placed on the photosensitive substrate. The exposure apparatus according to claim 8, wherein the projection exposure is performed.