JP2008304711A - Projection optical system, exposure device, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection optical system of six-mirror reflection type, which is capable of obtaining the image-side numerical aperture greater than, for example, 0.26 while securing imaging performance more satisfactory than a conventional one and restraining an increase in size of a reflecting mirror. <P>SOLUTION: The projection optical system that forms a reduced image on a first face (4) onto a second face (7) includes a first reflective imaging optical system G1 that forms an intermediate image on the first face, and a second reflective imaging optical system G2 that forms the final reduced image onto the second face. The first reflective imaging optical system G1 has a first concave reflecting mirror M1, a second convex reflecting mirror M2, a third convex reflecting mirror M3, and a fourth concave reflecting mirror M4. The second reflective imaging optical system G2 has a fifth convex reflecting mirror M5 and a sixth concave reflecting mirror M6. An aperture diaphragm AS is disposed in an optical path extending from the second reflecting mirror M2 to the third reflecting mirror M3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a projection optical system, an exposure apparatus, and a device manufacturing method. For example, the reflection type 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. This relates to a projection optical system.

  Conventionally, an exposure apparatus using X-rays has attracted attention as an exposure apparatus used for manufacturing semiconductor elements and the like. When X-rays are used as the exposure light, there are no transmissive optical materials and refractive optical materials that can be used, so that a reflective mask and a reflective projection optical system are 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 (corresponding to JP-A-9-212322) and US Pat. No. 183,095B1 proposes a six-mirror reflective optical system composed of six reflecting mirrors.

US Pat. No. 5,815,310 US Pat. No. 6,183,095B1

  In the conventional six-mirror reflection type projection optical system disclosed in the first embodiment of Patent Document 1 and Patent Document 2, the image-side numerical aperture NA is 0.25, but in order to achieve high resolution, There is a demand for further increasing the image-side numerical aperture NA while ensuring good imaging performance.

  The present invention has been made in view of the above-described problems, and ensures an image-side numerical aperture larger than 0.26, for example, while ensuring better imaging performance than before and suppressing an increase in the size of the reflecting mirror. An object of the present invention is to provide a six-mirror reflection type projection optical system capable of performing the above. 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 and perform projection exposure with high resolution by applying the projection optical system of the present invention to the exposure apparatus. And

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 G1 for forming an intermediate image of the first surface based on light from the first surface; and a reduced image on the second surface based on light from the intermediate image. A second reflective imaging optical system G2 for forming
The first reflective imaging optical system G1 includes a first reflecting mirror M1 having a concave reflecting surface and a second reflecting mirror M2 having a convex reflecting surface in the order of incidence of light from the first surface. A third reflecting mirror M3 having a convex reflecting surface and a fourth reflecting mirror M4 having a concave reflecting surface;
The second reflective imaging optical system G2 includes a fifth reflecting mirror M5 having a convex reflecting surface and a sixth reflecting mirror M6 having a concave reflecting surface in the order of incidence of light from the intermediate image. And
An aperture stop is provided in the optical path from the second reflecting mirror M2 to the third reflecting mirror M3;
The distance along the optical axis from the reflecting surface of the fifth reflecting mirror M5 to the reflecting surface of the sixth reflecting mirror M6 is D56, and the on-axis distance between the first surface and the second surface is TT. and when,
0.33 <D56 / TT <0.52
A projection optical system that satisfies the above conditions is provided.

  In the second aspect of the present invention, an illumination system for illuminating the mask set on the first surface, and a first for projecting the mask pattern onto the photosensitive substrate set on the second surface. There is provided an exposure apparatus comprising a projection optical system of the form.

  The third aspect of the present invention includes an exposure step of exposing the photosensitive substrate with the pattern of the mask using the exposure apparatus of the second aspect, and a development step of developing the photosensitive substrate that has undergone the exposure step. A device manufacturing method is provided.

  In the embodiment of the present invention, an aperture stop is provided in the optical path from the second reflecting mirror M2 to the third reflecting mirror M3 in the six-mirror reflecting and twice-imaging type projection optical system, and the fifth reflecting mirror is provided. The distance along the optical axis from the reflecting surface of M5 to the reflecting surface of the sixth reflecting mirror M6 is set so as to satisfy a required conditional expression. As a result, in the projection optical system according to the embodiment of the present invention, an image-side numerical aperture greater than, for example, 0.26 is secured while ensuring better imaging performance than before and suppressing an increase in the size of the reflecting mirror. 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 on the photosensitive substrate with high resolution. As a result, a highly accurate device can be manufactured under good exposure conditions using a scanning exposure apparatus having a large resolving power.

  The projection optical system according to the embodiment of the present invention includes six reflecting mirrors M1 to M6, and light from the first surface (object surface) is reflected on the first surface via the first reflective imaging optical system G1. An intermediate image is formed. The light from the intermediate image formed via the first reflective imaging optical system G1 passes through the second reflective imaging optical system G2 to convert the final reduced image (intermediate image) of the first surface to the second surface. Formed on (image plane). That is, an intermediate image of the first surface is formed in the optical path between the first reflective imaging optical system G1 and the second reflective imaging optical system G2.

  The first reflective imaging optical system G1 includes a first concave reflecting mirror M1, a second convex reflecting mirror M2, a third convex reflecting mirror M3, and a fourth concave reflecting mirror M4 in the order of incidence of light from the first surface. And have. The second reflective imaging optical system G2 includes a fifth convex reflecting mirror M5 and a sixth concave reflecting mirror M6 in the order of incidence of light from the intermediate image. An aperture stop AS is provided in the optical path from the second reflecting mirror M2 to the third reflecting mirror M3.

In the projection optical system of the present invention, the following conditional expression (1) is satisfied in the basic configuration of the six-mirror reflection type and double-imaging type as described above. In conditional expression (1), D56 is the distance along the optical axis from the reflecting surface of the fifth reflecting mirror M5 to the reflecting surface of the sixth reflecting mirror M6, and TT is between the first surface and the second surface. This is the on-axis interval (ie, the distance between object images).
0.33 <D56 / TT <0.52 (1)

  If the upper limit value of conditional expression (1) is exceeded, the distance D56 becomes too large, and the optical system becomes large in the optical axis direction (direction along the optical axis). If the lower limit of conditional expression (1) is not reached, the distance D56 becomes too small, and in particular, the maximum incident angle of light rays on the reflecting surface of the fifth reflecting mirror M5 and the reflecting surface of the sixth reflecting mirror M6 can be kept small. Since it becomes difficult and it becomes difficult to suppress the aberration which generate | occur | produces in these reflective surfaces, imaging performance tends to fall.

  In other words, by satisfying the conditional expression (1) in the basic structure of the six-mirror reflection type and the double-imaging type as described above, in particular, the reflecting surface of the fifth reflecting mirror M5 and the sixth reflecting mirror M6 For example, an image-side numerical aperture larger than 0.26 can be ensured while suppressing the aberration generated on the reflecting surface to ensure better imaging performance than before and suppressing the enlargement of the reflecting mirror. In addition, in order to exhibit the effect of this invention still more favorably, it is preferable to set the upper limit of conditional expression (1) to 0.45. Moreover, it is preferable to set the lower limit of conditional expression (1) to 0.36.

  Hereinafter, the characteristic configuration and operation of the present invention will be described in more detail. The projection optical system of the present invention employs a configuration in which the reduced image of the first surface is formed twice on the second surface, so that distortion (distortion) can be corrected satisfactorily. Further, since the aperture stop AS is arranged in the optical path between the second reflecting mirror M2 and the third reflecting mirror M3, for example, compared with a configuration in which the aperture stop AS is arranged on the reflecting surface of the second reflecting mirror M2. Thus, the incident angle of the light beam on the third reflecting mirror M3, which tends to increase the incident angle of the light beam, can be suppressed to be small, which is advantageous for correcting aberrations and forming a reflective film.

  In general, in the six-mirror reflection type projection optical system as described above, in order to avoid interference of light beams, it is common to arrange an aperture stop on or just before the reflection surface of the reflection mirror. In this case, there is no degree of freedom regarding the arrangement of the aperture stop, and the position thereof is limited. Therefore, the upper coma (the right part of the meridional coma aberration in FIGS. 4 and 6) and the lower coma (FIG. 4. It becomes difficult to balance the aberration with the left portion of the meridional coma aberration in FIG.

  On the other hand, in the present invention, in the optical path between the second reflecting mirror M2 and the third reflecting mirror M3, it is at a required position so as not to be too close to the second reflecting mirror M2 and the third reflecting mirror M3. By freely disposing the aperture stop AS, it becomes easy to balance the aberrations of the upper and lower frames, and good image performance can be obtained. In addition, since the pair of reflecting mirrors M2 and M3 sandwiching the aperture stop AS are both convex reflecting mirrors, and the refractive power arrangement in the first reflective imaging optical system G1 is set symmetrically with respect to the aperture stop AS, It is easier to balance the aberration with the coma.

  Generally, when an aperture stop is disposed between the first reflecting mirror M1 and the second reflecting mirror M2 or on the reflecting surface of the second reflecting mirror M2, the reflection of the fourth reflecting mirror M4 disposed after the third reflecting mirror M3. Since the position of the light beam on the surface is away from the optical axis, the effective diameter of the fourth reflecting mirror M4 becomes too large. In the present invention, the aperture stop AS can be freely arranged at a required position between the second reflecting mirror M2 and the third reflecting mirror M3. It is possible to suppress the spread of the light flux of the fourth reflecting mirror M4, and as a result, it is possible to prevent the fourth reflecting mirror M4 from being enlarged in the radial direction. In the present invention, by adopting the above-described configuration, the maximum effective diameter of the reflecting mirror is suppressed as small as possible, and each of the reflecting mirrors M1 to M6 and the aperture stop AS are appropriately arranged without blocking an effective imaging light beam. can do.

  As described above, in the projection optical system of the present invention, the aperture stop AS is disposed in the optical path between the second reflecting mirror M2 and the third reflecting mirror M3, so that the incident angle of the light beam tends to be large. The incident angle of the light beam on the third reflecting mirror M3 can be kept small. As a result, particularly in the reflective multilayer film that forms the reflective surface of the third reflector M3, reflection unevenness is unlikely to occur and a sufficiently high reflectivity can be obtained. Can be secured. 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. That is, in the projection optical system of the present invention, it is possible to satisfactorily correct aberrations while ensuring good reflection characteristics for X-rays and suppressing an increase in the size of the reflecting mirror.

  In the projection optical system of the present invention, when the aperture stop AS is positioned in the optical path from the second reflecting mirror M2 to the third reflecting mirror M3, the diameter of the first reflecting mirror M1 and the fourth reflecting mirror M4 are adjusted. It is preferable to take a ratio of the distance from the second reflecting mirror M2 to the aperture stop and the distance from the aperture stop to the third reflecting mirror M3 so as to be substantially close to the ratio to the diameter. With this configuration, the occurrence of the upper and lower frames can be controlled in a well-balanced manner, and aberrations can be corrected well.

In the projection optical system of the present invention, it is preferable that the absolute value RM6 of the center curvature radius (vertex curvature radius) of the reflecting surface of the sixth reflecting mirror M6 satisfies the following conditional expression (2).
470mm <RM6 (2)

  If the lower limit value of conditional expression (2) is not reached, the central curvature of the reflecting surface of the sixth reflecting mirror M6 becomes too large, and it becomes difficult to suppress the aberration that occurs on the reflecting surface of the sixth reflecting mirror M6. It is not preferable. In other words, it is possible to satisfy the conditional expression (2) by ensuring a large distance D56 between the fifth reflecting mirror M5 and the sixth reflecting mirror M6 to the extent that the conditional expression (1) is satisfied. The aberration generated on the reflecting surface of the six reflecting mirror M6 can be suppressed to be small, and good imaging performance can be ensured. In order to achieve the effect of the present invention more satisfactorily, it is preferable to set the lower limit of conditional expression (2) to 480 mm.

In the projection optical system of the present invention, it is preferable that the following conditional expression (3) is satisfied. In conditional expression (3), φM4 is the effective diameter (diameter) of the fourth reflecting mirror M4, Y0 is the maximum image height on the second surface, and NA is the numerical aperture on the second surface side (image side). . Here, the effective diameter φM4 of the fourth reflecting mirror M4 is the diameter of a circle around the optical axis that circumscribes the reflecting area (use area) of the fourth reflecting mirror M4.
φM4 / (Y0 × NA) <68.0 (3)

  If the upper limit of conditional expression (3) is exceeded, the effective diameter φM4 of the fourth reflecting mirror M4, which is the largest reflecting mirror, becomes too large, and the optical system becomes larger in the radial direction (direction perpendicular to the optical axis). Therefore, it is not preferable. In other words, by satisfying conditional expression (3), the effective diameter φM4 of the fourth reflecting mirror M4 can be kept small, and the optical system can be downsized in the radial direction. In order to achieve the effect of the present invention more satisfactorily, it is preferable to set the upper limit of conditional expression (3) to 66.0.

In the projection optical system of the present invention, it is preferable that the following conditional expression (4) is satisfied. In conditional expression (4), RM4 is the absolute value of the center curvature radius (vertex curvature radius) of the reflecting surface of the fourth reflecting mirror M4. As described above, φM4 is the effective diameter of the fourth reflecting mirror M4, and NA is the image-side numerical aperture.
φM4 / (RM4 × NA) <4.3 (4)

  Exceeding the upper limit value of conditional expression (4) is not preferable because the effective diameter φM4 of the fourth reflecting mirror M4, which is the largest reflecting mirror, becomes too large and the optical system becomes larger in the radial direction. In other words, by satisfying conditional expression (4), the effective diameter φM4 of the fourth reflecting mirror M4 can be kept small, and the optical system can be downsized in the radial direction. In order to achieve the effect of the present invention more satisfactorily, it is preferable to set the upper limit of conditional expression (4) to 4.0.

In the projection optical system of the present invention, it is preferable that the following conditional expression (5) is satisfied. In conditional expression (5), TT is the distance between the object images as described above, and Y0 is the maximum image height as described above.
TT / Y0 <32.0 (5)

  Exceeding the upper limit value of conditional expression (5) is not preferable because the total length of the optical system becomes too large and the optical system becomes larger in the optical axis direction. In other words, by satisfying conditional expression (5), the total length of the optical system can be kept small, and the optical system can be downsized in the optical axis direction. In addition, in order to exhibit the effect of this invention still more favorably, it is preferable to set the upper limit of conditional expression (5) to 3.1.

In the projection optical system of the present invention, it is preferable that the following conditional expression (6) is satisfied. In conditional expression (6), TT is the distance between the object images as described above, and RM4 is the absolute value of the center curvature radius of the reflecting surface of the fourth reflecting mirror M4 as described above.
TT / RM4 <2.1 (6)

  Exceeding the upper limit of conditional expression (6) is not preferable because the total length of the optical system becomes too large and the optical system becomes larger in the optical axis direction. In other words, by satisfying conditional expression (6), the total length of the optical system can be kept small, and the optical system can be downsized in the optical axis direction. In order to achieve the effect of the present invention more satisfactorily, it is preferable to set the upper limit of conditional expression (6) to 1.9.

In the projection optical system of the present invention, the maximum value A of the incident angle of the principal ray incident on the reflecting surface of each of the reflecting mirrors M1 to M6 from the position of the central object height in the projection field on the first surface is the following condition: It is preferable to satisfy Formula (7). Here, the incident angle of the principal ray to the reflecting surface is defined as the absolute value of the angle of the principal ray with respect to the normal of the reflecting surface at the incident position of the principal ray.
A <35 ° (7)

  If the upper limit value of conditional expression (7) is exceeded, the maximum incident angle A of the light beam on the reflective multilayer film that forms the reflective surface of the reflector becomes too large, and uneven reflection tends to occur and a sufficiently high reflectance. Is not preferable because it cannot be obtained.

In the projection optical system of the present invention, the inclination α with respect to the optical axis of the principal ray incident on the reflecting surface of the first reflecting mirror M1 from the position of the central object height in the projection field on the first surface is expressed by the following conditional expression ( It is desirable to satisfy 8).
| Α | <10 ° (8)

  Exceeding the upper limit value of conditional expression (8) is not preferable because when the reflection mask is provided on the first surface, the influence of the reflected light beam being blocked by the absorber pattern becomes too great. However, if the inclination α of the principal ray is made too small, it becomes difficult to separate the incident light and the reflected light from the reflection mask when the reflection mask is installed on the first surface.

In the projection optical system of the present invention, it is preferable that the maximum value φM of the effective diameters (diameters) of the reflecting mirrors M1 to M6 satisfy the following conditional expression (9). Here, the maximum value φM of the effective diameter of each reflecting mirror is a circle circumscribing the reflecting area around the optical axis in the reflecting mirror (the largest reflecting mirror) having the reflecting area (usage area) farthest from the optical axis. Is the diameter.
φM ≦ 700mm (9)

  Exceeding the upper limit value of conditional expression (9) is not preferable because the effective diameter φM of the largest reflecting mirror becomes too large and the optical system becomes larger in the radial direction. In other words, by satisfying conditional expression (9), the effective diameter φM of the largest reflecting mirror can be kept small, and the optical system can be downsized in the radial direction.

  In the projection optical system of the present invention, 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, and the maximum order of the aspherical surface that defines each reflecting surface is 10th or higher. It is preferable. By introducing a higher-order aspherical surface in this way, aberration can be corrected well and optical performance can be improved. By setting the maximum order to 18 or more, a more complicated and fine aspherical shape can be expressed, and sufficient aberration correction can be achieved.

  The projection optical system of the present invention is preferably an optical system that is substantially telecentric on the image side (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.

  By the way, in the projection optical system of the present invention, an intermediate image is formed in the optical path between the fourth reflecting mirror M4 and the fifth reflecting mirror M5, but a clear intermediate image is not formed due to the influence of aberration or the like. Absent. It is not necessary to form a clear intermediate image, and the purpose is to form the final image clearly on the second surface. Even if dust exists near the formation position of the intermediate image, if the intermediate image does not form a clear image, the dust image on the second surface tends to be greatly blurred. It is better not to image. However, when the intermediate image is formed in the very vicinity of the reflecting surface of the reflecting mirror, there is a possibility that an image such as a fine structure or adhering dust on the mirror surface of the reflecting mirror overlaps with the projected image on the second surface, The partial diameter of the reflecting mirror (the effective diameter of the light beam on the reflecting surface of the reflecting mirror) becomes too small, which tends to cause a problem in terms of manufacturing tolerances. Therefore, an intermediate image must be formed at a position somewhat away from the reflecting surface of each reflecting mirror.

  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 effective imaging region 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. As the X-ray source, a discharge plasma light source or other X-ray sources can be used. 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 wavelength selection filter 2 is not essential, and other forms of wavelength selection means such as a wavelength selection film formed on a reflecting mirror may be used. Further, the wavelength selection filter 2 and the wavelength selection unit itself may not be arranged.

  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). On the mask 4, an arcuate illumination region that is symmetrical with respect to the Y axis is formed. The illuminated light from the mask 4 forms an image of a mask pattern on a wafer 7 which is a photosensitive substrate via a reflective projection optical system 6.

  That is, on the wafer 7, as shown in FIG. 2, an arc-shaped effective image formation 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 imaging region ER with LY is set. Thus, the arc-shaped effective imaging region ER is a part of a ring-shaped region centered on the optical axis AX, and the length LY is in a direction connecting the center of the arc-shaped effective imaging region ER and the optical axis. This is the width dimension of the effective imaging region ER along.

  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. The specific configuration of the projection optical system 6 will be described below with reference to the first and second examples.

  In each embodiment, the projection optical system 6 includes a first reflection imaging optical system G1 for forming an intermediate image of the pattern of the mask 4 and a final reduced image (intermediate image) of the pattern of the mask 4 on the wafer 7. The second reflective imaging optical system G2 is formed on the top. That is, the intermediate image of the mask pattern is formed in the optical path between the first reflective imaging optical system G1 and the second reflective imaging optical system G2.

  The first reflective imaging optical system G1 is constituted by four reflecting mirrors M1, M2, M3 and M4, and the second reflective imaging optical system G2 is constituted by two reflecting mirrors M5 and M6. In each embodiment, the reflecting surfaces of all the reflecting mirrors M1 to M6 are formed in an aspherical shape that is rotationally symmetric with respect to the optical axis. In each embodiment, the projection optical system 6 is an optical system that is substantially telecentric on the wafer side (image side).

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 aspheric coefficient is C _n , it is expressed by the following formula (a).

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 + C ₁₂ · y ¹²
+ C ₁₄ · y ¹⁴ + C ₁₆ · y ¹⁶ + C ₁₈ · y ¹⁸ + C ₂₀ · y ²⁰ (a)

[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 a concave reflection surface of the first reflection mirror M1, a convex reflection surface of the second reflection mirror M2, and a third reflection. After being sequentially reflected by the convex reflecting surface of the mirror M3 and the concave reflecting surface of the fourth reflecting mirror M4, an intermediate image I1 of the mask pattern is formed. The light from the intermediate image I1 formed via the first reflective imaging optical system G1 was sequentially reflected by the convex reflecting surface of the fifth reflecting mirror M5 and the concave reflecting surface of the sixth reflecting mirror M6. Thereafter, a reduced image (secondary image) of the mask pattern is formed on the wafer 7. An aperture stop AS is provided at a predetermined position in the optical path from the second reflecting mirror M2 to the third reflecting mirror M3.

  The following table (1) lists the values of the specifications of the projection optical system according to the first example. In the column of main specifications 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), H0 is the maximum object height on the mask 4, φ Is the radius (maximum image height Y0) of the image circle IF on the wafer 7, LX is the dimension along the X direction of the effective imaging region ER, and LY is the dimension along the Y direction of the effective imaging region ER ( The width dimension of the arc-shaped effective imaging region ER) is shown respectively.

  Further, the surface number is the order of the reflecting surfaces from the mask side along the direction in which the light beam travels from the object surface mask surface to the image surface wafer surface, and r is the vertex curvature radius (center curvature) of each reflecting surface. (Radius: mm), and d represents the axial distance between the reflecting surfaces, that is, the surface distance (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 table (2).

Table (1)
(Main specifications)
λ = 13.5nm
β = 1/4
NA = 0.27
H0 = 140mm
φ = Y0 = 35mm
LX = 26mm
LY = 1mm

(Optical member specifications)
Surface number rd Optical member (mask surface) 439.22
1 -456.27 -136.24 (First reflector M1)
2 -597.27 65.11 (Second reflector M2)
138.22 (Aperture stop AS)
3 786.79 -359.75 (Third reflector M3)
4 623.00 873.91 (4th reflector M4)
5 348.57 -424.16 (5th reflector M5)
6 498.81 466.16 (6th reflector M6)
(Wafer surface)

(Aspheric data)
1 surface κ = 0.000000
C ₄ = 0.108628 × 10 ⁻⁸ C ₆ = −0.411393 × 10 ⁻¹⁴
C ₈ = 0.219463 × 10 ⁻¹⁷ C ₁₀ = −0.3066733 × 10 ⁻²¹
C ₁₂ = 0.289446 × 10 ⁻²⁵ C ₁₄ = −0.180592 × 10 ⁻²⁹
C ₁₆ = 0.720358 × 10 ⁻³⁴ C ₁₈ = −0.166663 × 10 ⁻³⁸
C ₂₀ = 0.170047 × 10 ⁻⁴³

2 sides κ = 0.000000
C ₄ = 0.143722 × 10 ⁻⁷ C ₆ = 0.732571 × 10 ⁻¹³
C ₈ = −0.102261 × 10 ⁻¹⁵ C ₁₀ = 0.637864 × 10 ⁻¹⁹
C ₁₂ = −0.358818 × 10 ⁻²² C ₁₄ = 0.1463314 × 10 ⁻²⁵
C ₁₆ = −0.385019 × 10 ⁻²⁹ C ₁₈ = 0.561868 × 10 ⁻³³
C ₂₀ = −0.331446 × 10 ⁻³⁷

3 sides κ = 0.000000
C ₄ = −0.117889 × 10 ⁻⁷ C ₆ = 0.129736 × 10 ⁻¹²
C ₈ = 0.429866 × 10 ⁻¹⁶ C ₁₀ = −0.131918 × 10 ⁻¹⁹
C ₁₂ = 0.245534 × 10 ⁻²³ C ₁₄ = −0.304406 × 10 ⁻²⁷
C ₁₆ = 0.241811 × 10 ⁻³¹ C ₁₈ = −0.111077 × 10 ⁻³⁵
C ₂₀ = 0.224097 × 10 ⁻⁴⁰

4 sides κ = 0.000000
C ₄ = −0.621735 × 10 ⁻¹⁰ C ₆ = −0.462112 × 10 ⁻¹⁵
C ₈ = 0.791118 × 10 ⁻²⁰ C ₁₀ = −0.166220 × 10 ⁻²⁴
C ₁₂ = 0.154370 × 10 ⁻²⁹ C ₁₄ = −0.290153 × 10 ⁻³⁵
C ₁₆ = −0.760500 × 10 ⁻⁴⁰ C ₁₈ = 0.658501 × 10 ⁻⁴⁵
C ₂₀ = −0.171411 × 10 ⁻⁵⁰

5 sides κ = 0.000000
C ₄ = 0.147703 × 10 ⁻⁷ C ₆ = 0.517096 × 10 ⁻¹²
C ₈ = −0.402600 × 10 ⁻¹⁶ C ₁₀ = 0.564671 × 10 ⁻¹⁹
C ₁₂ = −0.483975 × 10 ⁻²² C ₁₄ = 0.271886 × 10 ⁻²⁵
C ₁₆ = −0.929142 × 10 ⁻²⁹ C ₁₈ = 0.172007 × 10 ⁻³²
C ₂₀ = −0.129370 × 10 ⁻³⁶

6 faces κ = 0.000000
C ₄ = 0.291435 × 10 ⁻¹⁰ C ₆ = 0.225336 × 10 ⁻¹⁵
C ₈ = 0.410474 × 10 ⁻²¹ C ₁₀ = 0.617353 × 10 ⁻²⁵
C ₁₂ = −0.498807 × 10 ⁻²⁹ C ₁₄ = 0.311382 × 10 ⁻³³
C ₁₆ = −0.123124 × 10 ⁻³⁷ C ₁₈ = 0.270799 × 10 ⁻⁴²
C ₂₀ = −0.250482 × 10 ⁻⁴⁷

(Values for conditional expressions)
D56 = 424.2mm
TT = 1062.47mm
φM4 = 600.18mm
Y0 = 35.0mm
RM4 = 623.00mm
(1) D56 / TT = 0.40
(2) RM6 = 498.81mm
(3) φM4 / (Y0 × NA) = 63.51
(4) φM4 / (RM4 × NA) = 3.57
(5) TT / Y0 = 30.4
(6) TT / RM4 = 1.71
(7) A = 29.09 ° (maximum in the third reflecting mirror M3)
(8) | α | = 4.64 °
(9) φM = 600.18 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 99%, and an image height of 97%. 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 imaging region ER. Although not shown, it has been confirmed that in the region corresponding to the effective imaging region ER, various aberrations other than the coma aberration, such as spherical aberration and distortion, are well corrected.

[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, also in the projection optical system of the second embodiment, the light from the mask 4 is reflected from the concave reflecting surface of the first reflecting mirror M1 and the convex surface of the second reflecting mirror M2, as in the first embodiment. Are sequentially reflected by the reflecting surface, the convex reflecting surface of the third reflecting mirror M3, and the concave reflecting surface of the fourth reflecting mirror M4, and then an intermediate image I1 of the mask pattern is formed. The light from the intermediate image I1 formed via the first reflective imaging optical system G1 was sequentially reflected by the convex reflecting surface of the fifth reflecting mirror M5 and the concave reflecting surface of the sixth reflecting mirror M6. Thereafter, a reduced image (secondary image) of the mask pattern is formed on the wafer 7. Similarly to the first embodiment, an aperture stop AS is provided at a predetermined position in the optical path from the second reflecting mirror M2 to the third reflecting mirror M3. 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 = 0.27
H0 = 140mm
φ = Y0 = 35mm
LX = 26mm
LY = 1mm

(Optical member specifications)
Surface number rd Optical member (mask surface) 440.35
1 -458.06 -136.44 (First reflector M1)
2 -607.41 65.58 (Second reflector M2)
138.12 (Aperture stop AS)
3 769.48 -358.88 (Third reflector M3)
4 620.55 869.55 (4th reflector M4)
5 347.07 -420.68 (5th reflector M5)
6 495.01 462.68 (6th reflector M6)
(Wafer surface)

(Aspheric data)
1 surface κ = 0.000000
C ₄ = 0.100892 × 10 ⁻⁸ C ₆ = −0.382657 × 10 ⁻¹⁴
C ₈ = 0.214032 × 10 ⁻¹⁷ C ₁₀ = −0.301007 × 10 ⁻²¹
C ₁₂ = 0.286608 × 10 ⁻²⁵ C ₁₄ = −0.180412 × 10 ⁻²⁹
C ₁₆ = 0.725174 × 10 ⁻³⁴ C ₁₈ = −0.168789 × 10 ⁻³⁸
C ₂₀ = 0.172964 × 10 ⁻⁴³

2 sides κ = 0.000000
C ₄ = 0.143463 × 10 ⁻⁷ C ₆ = 0.546222 × 10 ⁻¹³
C ₈ = −0.999571 × 10 ⁻¹⁶ C ₁₀ = 0.677755 × 10 ⁻¹⁹
C ₁₂ = −0.409329 × 10 ⁻²² C ₁₄ = 0.175193 × 10 ⁻²⁵
C ₁₆ = −0.476056 × 10 ⁻²⁹ C ₁₈ = 0.715775 × 10 ⁻³³
C ₂₀ = −0.441798 × 10 ⁻³⁷

3 sides κ = 0.000000
C ₄ = −0.119994 × 10 ⁻⁷ C ₆ = 0.136677 × 10 ⁻¹²
C ₈ = 0.423673 × 10 ⁻¹⁶ C ₁₀ = −0.130399 × 10 ⁻¹⁹
C ₁₂ = 0.242444 × 10 ⁻²³ C ₁₄ = −0.300524 × 10 ⁻²⁷
C ₁₆ = 0.238972 × 10 ⁻³¹ C ₁₈ = −0.109991 × 10 ⁻³⁵
C ₂₀ = 0.2225044 × 10 ^-40

4 sides κ = 0.000000
C ₄ = −0.628027 × 10 ⁻¹⁰ C ₆ = −0.443459 × 10 ⁻¹⁵
C ₈ = 0.7438871 × 10 ⁻²⁰ C ₁₀ = −0.161763 × 10 ⁻²⁴
C ₁₂ = 0.154912 × 10 ⁻²⁹ C ₁₄ = −0.339751 × 10 ⁻³⁵
C ₁₆ = −0.722375 × 10 ⁻⁴⁰ C ₁₈ = 0.650554 × 10 ⁻⁴⁵
C ₂₀ = −0.172553 × 10 ⁻⁵⁰

5 sides κ = 0.000000
C ₄ = 0.150698 × 10 ⁻⁷ C ₆ = 0.525713 × 10 ⁻¹²
C ₈ = −0.408593 × 10 ⁻¹⁶ C ₁₀ = 0.612996 × 10 ⁻¹⁹
C ₁₂ = −0.551870 × 10 ⁻²² C ₁₄ = 0.321817 × 10 ⁻²⁵
C ₁₆ = −0.113362 × 10 ⁻²⁸ C ₁₈ = 0.216053 × 10 ⁻³²
C ₂₀ = −0.168145 × 10 ⁻³⁶

6 faces κ = 0.000000
C ₄ = 0.296525 × 10 ⁻¹⁰ C ₆ = 0.234626 × 10 ⁻¹⁵
C ₈ = 0.376096 × 10 ⁻²¹ C ₁₀ = 0.751955 × 10 ⁻²⁵
C ₁₂ = −0.626690 × 10 ⁻²⁹ C ₁₄ = 0.391550 × 10 ⁻³³
C ₁₆ = −0.154245 × 10 ⁻³⁷ C ₁₈ = 0.338640 × 10 ⁻⁴²
C ₂₀ = −0.313741 × 10 ⁻⁴⁷

(Values for conditional expressions)
D56 = 420.7mm
TT = 1060.28mm
φM4 = 600.12mm
Y0 = 35.0mm
RM4 = 620.55mm
(1) D56 / TT = 0.40
(2) RM6 = 495.01mm
(3) φM4 / (Y0 × NA) = 63.50
(4) φM4 / (RM4 × NA) = 3.58
(5) TT / Y0 = 30.3
(6) TT / RM4 = 1.71
(7) A = 29.12 ° (maximum in the third reflecting mirror M3)
(8) | α | = 4.65 °
(9) φM = 600.12 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 99%, and an image height of 97%. As is apparent from the aberration diagrams, in the second example as well, as in the first example, it can be seen that the coma aberration is corrected well in the region corresponding to the effective imaging region ER. Although not shown, it has been confirmed that in the region corresponding to the effective imaging region ER, various aberrations other than the coma aberration, such as spherical aberration and distortion, are well corrected.

  As described above, in each of the above-described embodiments, good imaging performance and a relatively large image-side numerical aperture of 0.27 are secured for X-rays having a wavelength of 13.5 nm, and on the wafer 7. It is possible to secure a 26 mm × 1 mm arc-shaped effective imaging region in which various aberrations are corrected favorably. Therefore, the pattern of the mask 4 can be transferred to each exposure region having a size of, for example, 26 mm × 34 mm or 26 mm × 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, EUV (Extreme UltraViolet) light having a wavelength of 13.5 nm is used as an example, but EUV light having a wavelength of about 5 to 20 nm can be used, for example. . In each of the above-described embodiments, the largest effective diameter of the fourth concave reflecting mirror M4 is about 600 mm, which is sufficiently small as compared with the prior art. Thus, in each embodiment, the size of the reflecting mirror is suppressed and the size of the optical system is reduced. As a result, measurement and processing at the time of manufacturing each reflecting mirror can be performed with high accuracy. Further, in each of the above-described embodiments, the chief ray has an inclination of almost zero over the entire arc-shaped effective imaging region ER, and a substantially telecentric optical system is achieved on the image side.

  In each of the above-described embodiments, the maximum value A of the incident angle of the principal ray incident on the reflecting surfaces of the reflecting mirrors M1 to M6 from the position of the central object height in the projection field on the mask 4 surface is about 29 ° or less. Is suppressed. As a result, reflection unevenness does not substantially occur in the reflective multilayer film forming the reflective surface of the reflecting mirror, and a sufficiently high reflectance can be obtained.

  In each of the above-described embodiments, the principal ray incident on the reflecting surface of the first reflecting mirror M1 from the position of the central object height in the projection field on the mask 4 surface, ie, the inclination α with respect to the optical axis AX, that is, the mask 4 is incident. The angle α formed between the principal ray and the optical axis AX of the principal ray reflected by the mask 4 is suppressed to about 5 °. As a result, even if the reflective mask 4 is used, incident light and reflected light can be separated, and the influence of the reflected light beam being blocked by the absorber pattern can be reduced, so that the imaging performance is reduced. Hard to get worse. 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. 7 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 the present embodiment. I will explain.

  First, in step 301 of FIG. 7, 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 one 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 the 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. In the above-described embodiment,

  Furthermore, 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 sixth surface is provided with a reduced image of the first surface as the second surface. The present invention can also be applied to other general projection optical systems formed above. In addition, all the constituent elements shown in the above-described embodiment are not essential, and some constituent elements may not be used, and arbitrary constituent elements may be used in appropriate combination.

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 effective imaging 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 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 stage G1, G2 Reflection imaging optical system M1-M6 Reflective mirror AS Aperture stop

Claims (15)

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 G1 for forming an intermediate image of the first surface based on light from the first surface; and a reduced image on the second surface based on light from the intermediate image. A second reflective imaging optical system G2 for forming
The first reflective imaging optical system G1 includes a first reflecting mirror M1 having a concave reflecting surface and a second reflecting mirror M2 having a convex reflecting surface in the order of incidence of light from the first surface. A third reflecting mirror M3 having a convex reflecting surface and a fourth reflecting mirror M4 having a concave reflecting surface;
The second reflective imaging optical system G2 includes a fifth reflecting mirror M5 having a convex reflecting surface and a sixth reflecting mirror M6 having a concave reflecting surface in the order of incidence of light from the intermediate image. And
An aperture stop is provided in the optical path from the second reflecting mirror M2 to the third reflecting mirror M3;
The distance along the optical axis from the reflecting surface of the fifth reflecting mirror M5 to the reflecting surface of the sixth reflecting mirror M6 is D56, and the on-axis distance between the first surface and the second surface is TT. and when,
0.33 <D56 / TT <0.52
Projection optical system that satisfies the above conditions. In the aperture stop, the ratio of the distance from the second aperture mirror M2 to the aperture aperture and the distance from the aperture aperture to the third reflector is equal to the diameter of the first reflector M1 and the fourth reflector. The projection optical system according to claim 1, wherein the projection optical system is positioned so as to be substantially close to a ratio with a diameter of M4. The absolute value RM6 of the center curvature radius of the reflecting surface of the sixth reflecting mirror M6 is:
470mm <RM6
The projection optical system according to claim 1, wherein the following condition is satisfied. When the effective diameter of the fourth reflecting mirror M4 is φM4, the maximum image height on the second surface is Y0, and the numerical aperture on the second surface side is NA,
φM4 / (Y0 × NA) <68.0
The projection optical system according to any one of claims 1 to 3, wherein the following condition is satisfied. When the effective diameter of the fourth reflecting mirror M4 is φM4, the absolute value of the center curvature radius of the reflecting surface of the fourth reflecting mirror M4 is RM4, and the numerical aperture on the second surface side is NA,
φM4 / (RM4 × NA) <4.3
The projection optical system according to any one of claims 1 to 4, wherein the following condition is satisfied. The projection optical system according to claim 1, wherein a numerical aperture NA on the second surface side is larger than 0.26. When the axial distance between the first surface and the second surface is TT, and the maximum image height on the second surface is Y0,
TT / Y0 <32.0
The projection optical system according to claim 1, which satisfies the following condition. When the axial distance between the first surface and the second surface is TT, and the absolute value of the central radius of curvature of the reflecting surface of the fourth reflecting mirror M4 is RM4,
TT / RM4 <1.76
The projection optical system according to claim 1, wherein the following condition is satisfied. The maximum value A of the incident angle of the chief ray incident on the reflecting surface of each of the reflecting mirrors M1 to M6 from the position of the central object height in the projection field on the first surface is
A <35 °
The projection optical system according to any one of claims 1 to 8, wherein the following condition is satisfied. The inclination α of the principal ray incident on the reflecting surface of the first reflecting mirror M1 from the position of the central object height in the projection field on the first surface with respect to the optical axis is
| Α | <10 °
The projection optical system according to any one of claims 1 to 9, wherein the following condition is satisfied. The maximum effective diameter φM of each of the reflecting mirrors M1 to M6 is
φM ≦ 700mm
The projection optical system according to claim 1, which satisfies the following condition. The projection optical system according to claim 1, wherein the projection optical system is an optical system that is substantially telecentric on the second surface side. 13. An illumination system for illuminating a mask set on the first surface, and a pattern of the mask projected onto a photosensitive substrate set on the second surface. An exposure apparatus comprising the projection optical system described in 1. The illumination system has a light source for supplying X-rays as exposure light,
The exposure apparatus according to claim 13, 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. 15. A device manufacturing method comprising an exposure step of exposing the pattern of the mask onto the photosensitive substrate using the exposure apparatus according to claim 13 and a developing step of developing the photosensitive substrate that has undergone the exposure step.

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