JP2000098228A - Projection exposing device, exposing method and reflection reduction projection optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent optical performance by a reduced reflection surface. SOLUTION: A reflection reduction projection optical system 100 is provided with a first catoptric system 10 forming the image of an object on a first surface 11 on a second surface 12 and a second catoptric system 20 forming the image on the second surface on a third surface 13, and the reduced image of the object on the first surface is formed on the third surface. The first catoptric system consists of a pair of first mirrors M1 and M2 constituted of two mirrors, and the second catoptric system consists of a pair of second mirrors M3 and M4 constituted of a convex mirror and a concave mirror.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an exposure method which are used when a device such as a semiconductor element, a liquid crystal display element, or a thin film magnetic head is manufactured by a lithography process. The present invention relates to a reflection reduction projection optical system.

[0002]

2. Description of the Related Art In recent years, the production of semiconductors and semiconductor chip mounting substrates has become increasingly finer, and an exposure apparatus for printing these patterns has been required to have a higher resolution. In order to satisfy this requirement, the wavelength of the light source must be shortened and the NA (numerical aperture of the optical system) must be increased. However, as the wavelength becomes shorter, optical glass that can withstand practical use is limited due to light absorption. Furthermore, there is no optical glass that can be used for ultraviolet rays or X-rays of short wavelength. In such a case,
It is completely impossible to construct a reduction projection optical system using only a refractive optical system or a catadioptric optical system.

For this reason, a reflection reduction optical system which constitutes a projection optical system only with a reflection system has been proposed in, for example, Japanese Patent Application Laid-Open No. 9-211332.

[0004]

The projection optical system disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 9-211332 is composed of two sets of optical systems composed of concave and convex reflecting mirrors, and two sets of reduced projections. An intermediate image is formed between the systems. JP 9-21
The projection optical system of No. 1332 has six reflective surfaces as a whole, and thus has a high degree of freedom in correcting aberrations, but has a problem in that the number of reflective surfaces is too large and a large amount of light is lost. Furthermore, since the imaging performance of the entire projection optical system is reduced due to aberrations caused by manufacturing errors of each reflecting surface, if the number of reflecting surfaces is too large, the tolerance of each reflecting surface must be extremely strictly controlled.
There is a problem that manufacturing is difficult. Therefore, although the imaging performance in the optical design is high, there is a possibility that the imaging performance is not sufficient even though it is actually manufactured.

Accordingly, an object of the present invention is to achieve extremely excellent imaging performance while keeping the number of reflecting surfaces relatively small, and to improve the imaging performance of an actually manufactured product.

[0006]

According to a first aspect of the present invention, there is provided a reflection-reduction projection optical system for imaging an object on a first surface on a second surface. Reflection reduction projection that includes a reflection optical system and a second reflection optical system that forms an image on the second surface on a third surface, and forms a reduced image of an object on the first surface on the third surface. An optical system, wherein the first reflecting optical system includes a first mirror pair including two mirrors, and the second reflecting optical system includes a second mirror pair including a convex mirror and a concave mirror; The mirror pair is the first
After light from the surface passes through the first mirror pair,
An intermediate image is formed on a surface, and light from the intermediate image is positioned so as to pass through the second mirror pair in the order of the convex mirror and the concave mirror toward the third surface.

According to a second aspect of the present invention, there is provided a reflection reduction projection optical system wherein a field stop is arranged on the second surface. In the reflection reduction projection optical system according to claim 3 of the present invention, the first reflection optical system has a reduction magnification. Also, in the reflection reduction projection optical system according to claim 4 of the present invention, the second reflection optical system has a reduction magnification.

The reflection reduction projection optical system according to claim 5 of the present invention further comprises an aperture stop located between respective vertices of the two mirrors constituting the first mirror pair, wherein the aperture stop is provided. Has a shape surrounding the entire circumference of the light beam incident on the aperture stop. In the reflection reduction optical system according to claim 6 of the present invention, the aperture stop is positioned such that the third surface side is telecentric.

Further, in the reflection reduction optical system according to claim 7 of the present invention, the first mirror pair has a concave mirror whose concave surface faces the intermediate image. Further, in the reflection reduction optical system according to claim 8 of the present invention, the curvatures of two mirrors constituting the first mirror pair are C1 and C2, respectively.
The curvature of the convex mirror in the second mirror pair is C3,
When the curvature of the concave mirror in the mirror pair is C4, (1) -0.005 <(C1-C2) <0.005 (2) -0.005 <(C3-C4) <0.005 (3) -0.005 <(C1-C2) ) + (C3-C4) <0.005.

Further, in the reflection reducing optical system according to claim 9 of the present invention, the first reflecting optical system comprises only two mirrors, and the second reflecting optical system comprises only two mirrors. is there. Further, in the reflection reduction projection optical system according to claim 10 of the present invention, the mirror forming the first mirror pair and the mirror forming the second mirror pair are arranged along a common optical axis. Things.

In the reflection reduction projection optical system according to the eleventh aspect of the present invention, the first reflection optical system and the second reflection optical system are arranged so as to have a predetermined interval along the optical axis direction. Is what is done. In the reflection reduction projection optical system according to the twelfth aspect of the present invention, among the plurality of mirrors constituting the reflection reduction projection optical system, at least two mirrors have outer diameters symmetrical with respect to the reference axis of the mirror. Is what it is.

A projection exposure apparatus according to a thirteenth aspect of the present invention provides an illumination optical system for guiding light of a predetermined wavelength to a projection original, and a reduced image of the projection original based on the light from the illumination optical system. A projection optical system formed on a photosensitive substrate, wherein the projection optical system is the reflection reduction projection optical system according to any one of claims 1 to 12, wherein the reflection reduction projection optical system is On the other hand, the exposure is performed while the projection original and the photosensitive substrate are relatively moved.

An exposure method according to a fourteenth aspect of the present invention is an exposure method for guiding light of a predetermined wavelength to a projection master and forming a reduced image of the projection master on a photosensitive substrate based on the light. The reduced image is formed on the photosensitive substrate using the reflection reduction projection optical system according to any one of claims 1 to 12, and the reduced image is scanned on the photosensitive substrate. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic configuration of the present invention will be described below with reference to FIG. FIG. 1 is an optical path diagram of a cross section of a reflection reduction projection optical system according to a first embodiment described later.
In FIG. 1, the width of the light beam is shown only in the transverse section. As shown in FIG. 1, the reflection reduction projection optical system 100 of the present invention includes a first
A configuration including a first reflection optical system 10 for imaging an object on the surface 11 on the second surface 12 and a second reflection optical system 20 for imaging an image on the second surface 12 on the third surface 13 And a reduced image of the object on the first surface 11 is formed on the third surface 13. The first reflecting optical system 10 includes a first mirror pair M1 and M2 including two mirrors, and the second reflecting optical system 20 includes a second mirror pair including a convex mirror M3 and a concave mirror M4.

Then, the light from the first surface 11 forms an intermediate image on the second surface 12 after passing through the first mirror pair M1 and M2, and the light from this intermediate image is transmitted to the convex mirror M3 and the concave mirror M3.
4 passes through the second mirror pair M3 and M4 in the order of 4, and the third surface 13
Head to. With this configuration, the second surface 12
It becomes possible to arrange the field stop FS on the top,
The aperture stop AS can be arranged between the vertices of the first mirror pair M1 and M2 (points on the reflecting surface that intersect with the reference axis of the reflecting surface).

Here, when the field stop FS is arranged on the first surface 12, there is no need to provide a field stop in an illumination system for illuminating the first surface 11. In the present invention, it is preferable that the aperture stop AS is arranged in the optical path between the first surface 11 and the reflection surface M1 closest to the first surface 11 in the first mirror pair. In this case, since the optical system of the present invention has a reduction magnification as a whole, the width of the light beam is suppressed to be narrow on the first surface side, and if the aperture stop AS can be arranged in this portion, the aperture stop AS It is possible to avoid interference with the projection optical path by the mechanical parts that hold the light. Further, in this case, the aperture shape of the aperture stop AS is changed to the aperture stop A.
A shape surrounding the entire circumference of the light beam passing through S,
A normal aperture stop configuration can be employed. At this time, the position of the aperture stop AS in the optical axis direction is preferably positioned so that the third surface 13 side is telecentric.

In the present invention, it is preferable that the first reflection optical system 10 has a reduction magnification, and that the second reflection optical system 20 has a reduction magnification. With such a configuration, the reduction magnification of the entire reflection reduction optical system can be shared by each reflection optical system, so that the load on each reflection optical system can be reduced. Further, in the present invention, it is preferable that the first mirror pair M1 and M2 have a concave mirror M2 having a concave surface facing the intermediate image side (the second surface 12 side).

In the case of this configuration, the concave mirror M2 and the convex mirror M3
And the concave mirror M4 is apparently close to the Offner optical system. However, in this configuration, since the intermediate image is formed between the concave mirror M2 and the convex mirror M3, the principle of aberration correction is different from that of the Offner optical system. different. That is, an optical system in which the Offner-type optical system is modified so as to be used at a reduced magnification (hereinafter, referred to as a modified Offner-type reduced optical system) is configured so that aberrations generated on each of the concave and convex reflecting surfaces are offset each other. Have been. However, when the present invention has the above configuration, the angle of the light beam incident on the concave mirror M2 on the first surface side is smaller than that of the modified Offner type optical system.
The light is incident at an angle to the optical axis (reference axis) of No. 2. That is, the incident light beam on the concave mirror M2 and the concave mirror M2
The angle formed by the exit light from the lens is completely opposite to that of the modified Offner type optical system.

Therefore, in the case of the above configuration, the first
The behavior of the incident and outgoing rays on the reflecting surface of the concave mirror M2 in the mirror pair is completely opposite to that of the modified Offner type optical system in which the aberration generated by the convex mirror M3 and the concave mirror M4 is corrected by the concave mirror M2. Direction. In this configuration, the concave mirror M2 in the first mirror pair is preferably arranged in the optical path between another mirror M1 in the first mirror pair and the second surface 12. As described above, when a light beam is incident on the concave mirror M2 so as to make an angle with the optical axis, the light beam traveling from the first surface 11 to the mirror M1 and the concave mirror M2 from the mirror M1 are reflected by the mirror M1. It is easy to physically separate the light beam traveling toward the second surface and the light beam traveling from the concave mirror M2 toward the second surface. Thereby, it becomes easy to arrange the aperture stop AS in the optical path from the first surface 11 to the mirror M1.

In the present invention, in order to achieve further optical performance, it is desirable to control the image plane. In order to make the image plane as flat as possible, it is preferable to minimize the Petzval sum of each of the reflection optical systems 10 and 20 as much as possible. Therefore, regarding the first reflecting optical system 10, when the curvatures of the two mirrors M1 and M2 constituting the first mirror pair are C1 and C2, respectively, the following satisfies (1) −0.005 <(C1−C2) <0.005. Is preferred.

If the lower limit of conditional expression (1) is exceeded, the intermediate image surface formed on the second surface 12 is too concavely curved, and can be corrected by the convex mirror M3 in the second reflecting optical system 20. , And the image of the field stop is deteriorated. If the upper limit of conditional expression (1) is exceeded, the second condition
The intermediate image plane on the surface 12 is too convexly curved, and exceeds the range that can be corrected by the concave mirror M4 in the second reflection optical system 20, and the image of the field stop is deteriorated.

For the second reflecting optical system 20, when the curvature of the convex mirror M3 in the second mirror pair is C3 and the curvature of the concave mirror in the second mirror pair is C4, (2) −0.005 <(C3 -C4) <0.005 is preferably satisfied. If the lower limit of conditional expression (2) is exceeded, the image plane on the third surface will be excessively concavely curved, and will exceed the range that can be corrected by the convex mirror M3 in the second mirror pair. On the other hand, if the upper limit of conditional expression (2) is exceeded,
The image plane of the third surface is excessively curved so as to exceed the range that can be corrected by the concave mirror M4 in both mirror pairs.

In the entire reflection reduction projection optical system 100, it is preferable that the Petzval sum generated by the two mirror pairs 10 and 20 be canceled each other. (3) -0.005 <(C1-C2) + (C3-C4) <0.005 is preferably satisfied. If the lower limit of conditional expression (3) is deviated, the image plane will be excessively concavely curved, and will exceed the range that can be corrected by the convex mirror M3. If the upper limit of conditional expression (3) is exceeded, the image plane will be excessively curved to be convex, and will exceed the range that can be corrected by concave mirrors M2 and M4.

Here, when the above-mentioned conditional expressions (1) to (3) are simultaneously satisfied, the curvature of the image plane can be corrected extremely well. In the present invention, the first reflecting optical system 10 includes only two mirrors M1 and M2, and the second reflecting optical system 20 includes two mirrors M3 and M2.
Preferably, it consists of only 4. Thereby, the reflection reduction projection optical system 100 of the present invention is provided with a soft X having a wavelength of 5 to 15 nm.
Line region light (in this specification, this light is referred to as “EUV (Extreme)
Ultra Violet)), or when applied to a projection exposure apparatus that uses light in the hard X-ray region below this wavelength as exposure light, even if the reflectance of the reflective film in that wavelength region is low.
Since the number of reflecting surfaces is only four, a practically sufficient amount of light can be secured. Further, there is an advantage that the possibility that the imaging performance is deteriorated due to a surface shape error of the reflection surface is reduced.

In the present invention, the mirrors M1 and M2 forming the first mirror pair and the mirrors M3 and M4 forming the second mirror pair are arranged along a common optical axis Ax. Is preferred. Thereby, each mirror M1
Mounting and adjustment of the M4 lens barrel becomes easy. In the present invention, the first reflection optical system 10 and the second reflection optical system 20 are used.
Is preferably arranged so as to have a predetermined interval along the optical axis direction. Thereby, each mirror M1 to M4
Therefore, the number of off-axis mirrors (shapes having an asymmetric outer shape with respect to the reference axis) can be reduced.

In the present invention, among the plurality of mirrors M1 to M4 constituting the reflection reduction projection optical system 100,
Preferably, the at least two mirrors M1, M4 have outer diameters that are symmetric with respect to the reference axis of these mirrors.
Thereby, the difficulty of the operation at the time of manufacturing the mirror is reduced, and the assembling / adjusting operation becomes easy. Further, in the present invention, it is preferable that all surface shapes of the plurality of mirrors be rotationally symmetric aspherical shapes.

Next, a projection exposure apparatus incorporating the reflection reduction projection optical system 100 according to the present invention will be described with reference to FIG. FIG. 2 schematically shows the entire configuration of a projection exposure apparatus EX incorporating the reflection reduction optical system 100 according to the present invention. The projection exposure apparatus EX is a projection exposure apparatus that performs an exposure operation by a step-and-scan method using light (EUV light) in a soft X-ray region having a wavelength of about 5 to 15 nm as illumination light for exposure. In FIG. 2, the optical axis direction of the reflection reduction projection optical system that forms a reduced image of the reflection type reticle R as the projection master on the wafer W is defined as the Z direction, and the direction in the paper plane perpendicular to the Z direction is defined as the Z direction. The direction perpendicular to the paper plane perpendicular to the YZ directions is defined as the X direction.

The projection exposure apparatus EX converts an image of a part of a circuit pattern drawn on a reflection type reticle R as a projection original (mask) onto a wafer W as a photosensitive substrate through a reflection reduction projection optical system 100. The relative pattern of the reticle R and the wafer W is scanned relative to the reflection reduction projection optical system 100 in a one-dimensional direction (here, the Y-axis direction) while projecting the entire circuit pattern of the reflective reticle R onto the wafer W.
The image is transferred to each of the plurality of upper shot areas by a step-and-scan method.

Here, the EUV light, which is the illumination light for exposure in the present embodiment, has a low transmittance to the atmosphere.
The optical path through which EUV light passes is covered by a vacuum chamber VC and is shielded from outside air. First, the illumination optical system in FIG. 2 will be described. The laser light source 30 has a function of supplying laser light having a wavelength in an infrared region to a visible region, and for example, a YAG laser or an excimer laser excited by a semiconductor laser can be applied. This laser light is condensed by the focusing optical system 31.
And is condensed at the position 32. The nozzle 33 ejects a gaseous object toward the position 32, and the ejected object receives a laser beam of high illuminance at the position 32.
At this time, the ejected object becomes hot due to the energy of the laser light, is excited into a plasma state, and emits EUV light when transitioning to a low potential state.

An elliptical mirror 34 constituting a condensing optical system is arranged around the position 32.
Are positioned such that their first focal point substantially coincides with position 32. On the inner surface of the elliptical mirror 34, a multilayer film for reflecting EUV light is provided, and the EUV light reflected here is once condensed at the second focal point of the elliptical mirror 34 and then condensed. It goes to the parabolic mirror 35 constituting the system. The parabolic mirror 35 is positioned such that its focal point substantially coincides with the second focal position of the elliptical mirror 34, and has a multilayer film on its inner surface for reflecting EUV light.

The EUV light emitted from the parabolic mirror 35 is
In a substantially collimated state, the light goes to a reflective fly-eye optical system 36 as an optical integrator. The reflection type fly-eye optical system 36 includes a first reflection element group 36a formed by integrating a plurality of reflection surfaces, and a first reflection element group 36a.
And a second reflecting element group 36b having a plurality of reflecting surfaces corresponding to the plurality of reflecting surfaces. A multilayer film for reflecting EUV light is also provided on a plurality of reflection surfaces constituting the first and second reflection element groups 36a and 36b.

The collimated EU from the parabolic mirror 35
The V light is wavefront divided by the first reflecting element group 36a,
EUV light from each reflecting surface is collected to form a plurality of light source images. A plurality of reflection surfaces of the second reflection element group 36b are positioned near each of the positions where the plurality of light source images are formed, and the plurality of reflection surfaces of the second reflection element group 36b are: It functions essentially as a field mirror. Thus, the reflection type fly-eye optical system 3
6 forms a large number of light source images as secondary light sources based on the substantially parallel light flux from the parabolic mirror 35. Such a reflective fly-eye optical system 36 has been proposed in Japanese Patent Application No. 10-47400 by the present applicant.

In this embodiment, in order to control the shape of the secondary light source, the σ stop AS1 is provided near the second reflection element 36b. The σ stop AS1 is formed, for example, by providing a plurality of openings having different shapes on a turret. Then, by the σ stop control unit ASC1,
Control is performed on which aperture is to be placed in the optical path.

The EUV light from the secondary light source formed by the reflection type fly-eye optical system 36 travels to the condenser mirror 37 which is positioned so that the vicinity of the secondary light source position is the focal position. After being reflected and condensed by the mirror 37, the light reaches the reflective reticle R via the optical path bending mirror 38. EU surfaces are provided on the condenser mirror 37 and the optical path bending mirror 38.
A multilayer film for reflecting V light is provided. Then, the condenser mirror 37 collects EUV light emitted from the secondary light source and uniformly illuminates the reflective reticle R in a superimposed manner.

In this embodiment, the reflection type reticle R
The illumination system is a non-telecentric system, and the reflection reduction projection optical system is used in order to spatially separate the optical path between the illumination light traveling toward the projection type 9 and the EUV light reflected by the reflection type reticle R toward the projection system 9. 100 is also a reticle-side non-telecentric optical system. On the reflective reticle R, a reflective film made of a multilayer film that reflects EUV light is provided, and the reflective film is formed on a wafer W as a photosensitive substrate.
The pattern corresponds to the shape of the pattern to be transferred upward. The EUV light reflected by the reflection type reticle R and including the pattern information of the reflection type reticle R enters the reflection reduction projection optical system 100.

As described above, the reflection reduction projection optical system 100 is composed of four mirrors M1 to M4, and is located in the optical path between the mirror M1 and the reflective reticle R (the vertex of the mirror M1 and the mirror M2). Variable aperture stop A
S2 is arranged. The variable aperture stop AS2 is configured such that the aperture of the aperture is variable, and the aperture is controlled by the variable aperture stop control unit ASC2.

A field stop FS is disposed at an intermediate image forming position in the optical path between the mirror M2 and the mirror M3. Note that the mirrors M1 to M4 constituting the reflection reduction projection optical system 100 are formed by providing a multilayer film that reflects EUV light on a base material. E reflected by reflective reticle R
The UV light passes through the reflection reduction projection optical system 100 and enters a predetermined reduction magnification β in an arc-shaped exposure area on the wafer W.
(For example, | β | = 1/4, 1/5, 1/6), a reduced image of the pattern of the reflective reticle R is formed. In addition,
In the present embodiment, the shape of the exposure area is defined by the field stop 100 provided in the reflection reduction projection optical system 100.

The reflection type reticle R is supported by a reticle stage RS movable at least along the Y direction, and the wafer W is supported by a wafer stage WS movable along the XYZ directions. The movement of these reticle stage RS and wafer stage WS
Each is controlled by a reticle stage control unit RSC and a wafer stage control unit WSC. At the time of the exposure operation, the reflective reticle R and the wafer W are radiated to the reflective reticle R by the illumination system while the EUV light is irradiated on the reflective reticle R, and the reflective reticle R and the wafer W are determined by the reduction magnification of the projection system. Move at a speed ratio of. Thus, the pattern of the reflective reticle R is scanned and exposed in a predetermined shot area on the wafer W.

In this embodiment, the σ stop AS
1. The variable aperture stop AS2 and the field stop FS are preferably made of a metal such as Au, Ta, or W in order to sufficiently shield EUV light.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, numerical embodiments of the reflection reduction projection optical system according to the present invention will be described. FIG. 1 is an optical path diagram of a cross section of the reflection reduction projection optical system of the first embodiment, and FIG. 4 is an optical path diagram of a cross section of the reflection reduction projection optical system of the second embodiment. In FIGS. 1 and 4, only the width of the light beam in the cross section is shown.

The reflection reduction projection optical system 100 of the first and second embodiments includes a first reflection optical system 10 for forming a reduced image of an object on a first surface 11 on a second surface 12, and a second surface. And a second reflection optical system 20 for reducing and forming an image on the third surface 13 on the third surface 13. The first reflecting optical system 10 includes two mirrors M1,
The second reflecting optical system 20 has a first mirror pair consisting of a convex mirror M3 and a concave mirror M4 each having a rotationally symmetric aspherical shape. Here, the mirror M1 is a rotationally symmetric aspheric surface having no power on the paraxial axis in the first embodiment of FIG. 1 and a rotationally symmetric aspheric surface having a convex shape in the second embodiment of FIG. The mirror M2 is a rotationally symmetric aspherical surface having a concave shape.

Here, the mirrors M1 to M4 are arranged so as to be coaxial with each other along a common optical axis Ax. An aperture stop AS is arranged in the optical path between the two. And
The light from the first surface 11 sequentially passes through the aperture stop AS, the mirror M1, and the mirror M2 to form a reduced image on the second surface 12, and the light from this reduced image passes through the mirror M3 and the mirror M4 in this order. After passing through the third surface 13, a reduced image is formed on the third surface.

As described above, the mirrors M1 to M4 in the first and second embodiments have an aspherical shape. The aspherical shape is represented by the following equation.

[0044]

(Equation 1)

Here, Y is the distance from the central tangent plane to the aspherical surface, c is the central curvature r is the distance from the optical axis k is the conic constant A is the fourth order aspherical coefficient B is the sixth order aspherical coefficient C Is an eighth-order aspherical coefficient D is a tenth-order aspherical coefficient

In the reflection reduction projection optical system of the first embodiment, the reduction magnification | β | is 1/4, the numerical aperture NA on the image side is 0.1, the maximum object height is 120 mm, and the exposure area is It has an annular shape with a radius of 30 mm and a width of 1 mm. Here, by performing the scanning exposure, a total of 26 × 33
Exposure can be performed on a shot area of mm.
The distance between the first surface as the object surface and the third surface as the final image surface is 1451 mm, and a plurality of mirrors M1
Among the effective diameters of M4 to M4, the maximum effective diameter is 542 mm.

In the reflection reduction projection optical system of the second embodiment, the reduction magnification | β | is 1/4, the numerical aperture NA on the image side is 0.1, the maximum object height is 60 mm, and the exposure area is It has a ring shape with a radius of 15 mm and a width of 1 mm. Here, by performing the scanning exposure, a total of 26 × 33
Exposure can be performed on a shot area of mm.
The distance between the first surface as the object surface and the third surface as the final image surface is 1279 mm, and the plurality of mirrors M1
Among the effective diameters of M4 to M4, the maximum effective diameter is 306 mm.

Tables 1 to 4 below show values of specifications of the reflection reduction projection optical systems of the first and second embodiments. In Tables 1 and 3, the left end shows the surface number of each reflecting surface, and RDY
Denotes a radius of curvature of each optical surface, and THI denotes a surface interval between each reflecting surface. The RDY column indicates the paraxial radius of curvature of each reflecting surface, and the THI column indicates each surface interval. Table 1
And in Table 3, D0 is the first surface 11 (reticle surface).
, The distance from the optical surface closest to the first surface, WD is the third
The distance from the optical surface on the surface side to the third surface (final image surface), β is the lateral magnification of the reflection reduction projection optical system when light is incident on the reflection reduction projection optical system from the first surface side, and NA is the first magnification. The numerical apertures on the three surfaces are respectively shown. In Tables 1 and 2, the sign of the paraxial radius of curvature RDY is positive when it is convex toward the first surface 11, and the sign of the surface spacing THI is reversed before and after the reflection surface.

Tables 2 and 4 show aspherical data of each of the mirrors M1 to M4 of the first and second embodiments.

[0050]

Table 1 [Example 1] D0 = 430.079395 WD = 642.640534 | β | = 0.2498 NA = 0.1 Surface number RDY THI 0 ∞ 430.079395 First surface 11 (object surface) 1 ∞ 328.252083 Aperture stop AS 2 ∞ -567.459189 Mirror M1 3 1042.96191 871.304731 Mirror M2 4 ∞ 293.356081 Second surface 12 (intermediate image surface) 5 409.29671 -547.201623 Mirror M3 6 655.87223 642.640534 Mirror M47 7 ∞ Third surface 13 (final image surface)

[0051]

[Table 2]

[0052]

[Second embodiment] D0 = 421.533199 WD = 626.912313 | β | = 0.2500 NA = 0.1 Surface number RDY THI 0 ∞ 421.533199 First surface 11 (object surface) 1 ∞ 195.113908 Aperture stop AS 2 2430.13474 -533.860357 Mirror M1 3 894.29705 851.779609 Mirror M2 4 ∞ 271.729305 Second surface 12 (intermediate image surface) 5 449.09562 -553.918512 Mirror M3 6 651.05560 626.912313 Mirror M47 7 ３ Third surface 13 (final image surface)

[0053]

[Table 4]

Table 5 below shows numerical values corresponding to the conditions of the reflection reduction projection optical systems of the first and second embodiments.

[0055]

Table 5 Example 1 Example 2 Example C1 0.000000 0.0004115 C2 0.0009588 0.0011182 C3 0.0024432 0.0022267 C4 0.0015246 0.0015359 (1) (C1-C2) -0.000959 -0.000707 (2) (C3-C4) 0.000919 0.000691 (3) ( C1-C2) + (C3-C4) -0.000040 -0.000016 FIGS. 3 and 5 show coma aberration diagrams on the first surface of the reflection reduction projection optical systems of the first and second embodiments. This coma aberration diagram is obtained by tracing light rays from the third surface side using light having a wavelength of 13.4 nm. Here, FIG. 3A is a coma aberration diagram in the meridional direction when the object height Y is 122 mm, FIG. 3B is a coma aberration diagram in the meridional direction when the object height Y is 120 mm, and FIG. =
FIG. 3D is a coma aberration diagram in the sagittal direction when the object height Y is 122 mm, FIG. 3E is a coma aberration diagram in the sagittal direction when the object height Y is 120 mm, and FIG. f) is the object height Y
It is a coma aberration figure in the sagittal direction at = 118 mm. FIG. 5A is a coma aberration diagram in the meridional direction at an object height Y = 62 mm, and FIG.
Coma aberration diagram in the meridional direction at 60 mm, FIG.
(C) is a coma aberration diagram in the meridional direction at an object height Y = 58 mm, FIG. 5 (d) is a coma aberration diagram in a sagittal direction at an object height Y = 62 mm, and FIG. 5 (e) is an object height Y =
Coma aberration diagram in the sagittal direction at 60 mm, FIG.
(F) is a coma diagram in the sagittal direction when the object height Y is 58 mm.

As is clear from FIGS. 3 and 5, the reflection reduction projection optical systems of the first and second embodiments use one of EUV light.
At a single wavelength of 3.4 nm, both the spherical aberration and the coma are corrected satisfactorily to almost no aberration, and the distortion in the exposure area is also corrected satisfactorily. In the first and second embodiments, each mirror M1
To M4 are high-order aspherical shapes that are rotationally symmetric with respect to the optical axis, and high-order aberrations generated in the mirrors M1 to M4 are corrected to achieve good imaging performance. Here, in order to correct rotationally asymmetric aberration components caused by surface shape errors of the reflecting surfaces of the respective mirrors and assembling errors in the production of the reflection reduction projection optical system, the rotationally symmetric aspherical surface is made a rotationally asymmetrical aspherical surface. Is also good.

In the first and second embodiments, 13.4 nm of EUV light is used as the wavelength to be used.
The reflection reduction projection optical system according to the present invention is not limited to use under EUV light. The reflection reduction projection optical system according to the present invention is, for example, a hard X-ray region of 5 nm or less,
It can also be used in the vacuum ultraviolet region of up to 200 nm. Here, as a light source in the hard X-ray region, for example, synchrotron radiation can be used, and as a light source in the vacuum ultraviolet region, an ArF excimer laser (wavelength 193 nm), F
2 excimer laser (wavelength 157 nm) or the like can be used.

In the above-described first and second embodiments, the first reflecting optical system is set to the reduction magnification, and the second reflecting optical system is set to the reduction magnification. The two-reflection optical system may have the same magnification or magnification, or the first reflection optical system may have the same magnification or magnification, and the second reflection optical system may have the reduction magnification. In each of the embodiments described above, the aperture stop is arranged in the optical path between the first surface 11 and the mirror M1.
When the distance between the optical path toward the optical path 1 and the optical path from the mirror M1 to the mirror M2 in the direction orthogonal to the optical axis becomes narrow, an aperture stop having a shape that covers the entire circumference of the light beam (an aperture stop having a circular aperture).
May be difficult to arrange. In this case, for example, as proposed in Japanese Patent Application Laid-Open No. 6-230287, an aperture stop that defines a part of the peripheral edge of the light beam is provided in the first reflection optical system 10 and the second reflection optical system 20 is provided with an aperture stop. It is sufficient to provide an aperture stop for defining the other part of the periphery of the light beam. At this time, as shown in FIG. 6, the aperture stop S1 in the first reflection optical system 10 may be arranged at the aperture stop position of the reflection reduction projection optical system in FIG. May be arranged near the position where the principal ray in the light beam traveling from the mirror M3 to the mirror M4 crosses the optical axis Ax.

As described above, the present invention is not limited to the above-described embodiment, and can have various configurations without departing from the gist of the present invention.

[0060]

As described above, according to the present invention, by using an aberration correction principle different from that of the conventional Offner type or the modified Offner type, the number of reflecting surfaces can be kept relatively small and extremely excellent. The imaging performance can be achieved, and the imaging performance of an actually manufactured product can be improved.

[Brief description of the drawings]

FIG. 1 is an optical path diagram of a cross section of a reflection reduction projection optical system according to a first embodiment.

FIG. 2 is a diagram illustrating a configuration of an exposure apparatus including the reflection reduction projection optical system of the present invention.

FIG. 3 is a coma aberration diagram of the first embodiment.

FIG. 4 is an optical path diagram of a cross section of a reflection reduction projection optical system according to a second embodiment.

FIG. 5 is a coma aberration diagram of the second embodiment.

FIG. 6 is an optical path diagram of a modification of the reflection reduction projection optical system.

[Explanation of symbols]

 10: First reflective optical system 11: First surface 12: Second surface 13: Third surface 20: Second reflective optical system 100: Reflection reduction projection optical system AS: Aperture stop Ax: Optical axis FS: Field stop M1 M4: Mirror

Claims (14)

[Claims] 1. A first method for imaging an object on a first surface on a second surface.
Reflection reduction projection that includes a reflection optical system and a second reflection optical system that forms an image on the second surface on a third surface, and forms a reduced image of an object on the first surface on the third surface. In the optical system, the first reflecting optical system includes a first mirror pair including two mirrors, the second reflecting optical system includes a second mirror pair including a convex mirror and a concave mirror, and the first and second mirror pairs. Forms an intermediate image on the second surface after the light from the first surface passes through the first mirror pair, and the light from the intermediate image is transmitted to the second mirror in the order of the convex mirror and the concave mirror. A reflection reduction projection optical system, characterized in that the reflection reduction projection optical system is positioned so as to pass through the pair toward the third surface. 2. The reflection reduction projection optical system according to claim 1, wherein a field stop is arranged on said second surface. 3. The reflection reduction projection optical system according to claim 1, wherein said first reflection optical system has a reduction magnification. 4. The reflection reduction projection optical system according to claim 1, wherein said second reflection optical system has a reduction magnification. 5. An aperture stop located between respective vertices of two mirrors constituting the first mirror pair, wherein the aperture stop surrounds the entire circumference of a light beam incident on the aperture stop. The reflection reduction projection optical system according to any one of claims 1 to 4, wherein 6. The reflection reduction projection optical system according to claim 5, wherein said aperture stop is positioned such that said third surface side is telecentric. 7. The reflection reduction projection optical system according to claim 1, wherein the first mirror pair has a concave mirror whose concave surface faces the intermediate image. 8. The curvature of the two mirrors constituting the first mirror pair is C1, C2, the curvature of the convex mirror in the second mirror pair is C3, and the curvature of the concave mirror in the second mirror pair is 8. And C4 is satisfied, the following condition is satisfied.
The reflection reduction projection optical system according to any one of the above items. -0.005 <(C1-C2) <0.005-0.005 <(C3-C4) <0.005-0.005 <(C1-C2) + (C3-C4) <0.005 9. The system according to claim 1, wherein said first reflecting optical system comprises only two mirrors, and said second reflecting optical system comprises only two mirrors. Reflection reduction projection optical system. 10. A mirror according to claim 1, wherein the mirrors forming the first mirror pair and the mirrors forming the second mirror pair are arranged along a common optical axis. The reflection reduction projection optical system according to any one of the above items. 11. The optical system according to claim 1, wherein the first reflecting optical system and the second reflecting optical system are arranged so as to have a predetermined interval along an optical axis direction. A reflection reduction projection optical system according to claim 1. 12. The mirror according to claim 1, wherein at least two of the plurality of mirrors constituting the reflection reduction projection optical system have symmetric outer diameters with respect to a reference axis of the mirror. The reflection reduction projection optical system according to any one of the above items. 13. An illumination optical system for guiding light of a predetermined wavelength to a projection original, and a projection optical system for forming a reduced image of the projection original on a photosensitive substrate based on the light from the illumination optical system. The projection optical system is the reflection reduction projection optical system according to any one of claims 1 to 12, wherein the projection original and the photosensitive substrate are relatively moved with respect to the reflection reduction projection optical system. A projection exposure apparatus that performs exposure while performing exposure. 14. An exposure method for guiding light of a predetermined wavelength to a projection master and forming a reduced image of the projection master on a photosensitive substrate based on the light. An exposure method, wherein the reduced image is formed on the photosensitive substrate using a reflection reduction projection optical system, and the reduced image is scanned on the photosensitive substrate.