JP2000284178A - Projection optical system and projection exposure device equipped with the projection optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection optical system, etc., which uses a small number of lenses and by which a desired image-side NA(numerical aperture) and a desired image circle are obtained without making a reflector large-sized. SOLUTION: The projection optical system includes 1st and 2nd optical systems G1 and G2 in order from a 1st surface and the 2nd optical system has a partial reflecting surface M1 which transmits and reflects light, a 1st meniscus optical element L21 which is concave to the 1st surface side, a 2nd meniscus optical element L22 which is concave to the 1st surface side, and a reflecting surface M4 which has a specific aperture part AP; and the light passed through the 1st optical system is passed through the partial reflecting surface and the 1st and 2nd optical elements and reflected by the reflecting surface, the light reflected by the reflecting surface is passed through the 2nd and 1st optical elements and reflected by the partial reflecting surface, and the light reflected by the partial reflecting surface is passed through the 1st and 2nd optical elements and aperture part and imaged on a 2nd surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection optical system suitable for a projection exposure apparatus used for manufacturing, for example, a semiconductor device or a liquid crystal display device in a photolithography process, and a projection exposure system having the projection optical system. More particularly, the present invention relates to a projection optical system having a high resolution in an ultraviolet wavelength region by using a reflection system as one element of an imaging optical system in the projection optical system.

[0002]

2. Description of the Related Art In a photolithography process for manufacturing a semiconductor device or the like, a pattern image formed on a photomask or a reticle (hereinafter, collectively referred to as a "mask") is exposed to a photoresist through a projection optical system. There is used a projection exposure apparatus that performs projection exposure on a wafer or a glass plate coated with a film or the like. As the degree of integration of semiconductor elements and the like increases, the resolution required for a projection optical system used in a projection exposure apparatus has been increasing. In order to satisfy this requirement, illumination light (exposure light)
Must be shortened and the numerical aperture (hereinafter referred to as “NA”) of the projection optical system needs to be increased. For example, if the wavelength of the illumination light is 170 nm or less, 0.1
High resolution of μm or less can be achieved.

However, as the wavelength of the illumination light becomes shorter, the light absorption increases, and the types of glass materials that can be used practically are limited. For example, when the wavelength is 300 nm or less, usable glass materials are limited to synthetic quartz or fluorite. When the wavelength is further reduced, and when the wavelength is 170 nm or less, practically usable glass materials are limited to only fluorite. For this reason, it is impossible to correct chromatic aberration in a projection optical system composed only of a refractive lens system, that is, only a lens component that does not include a reflecting mirror having a refractive power (a concave reflecting mirror or a convex reflecting mirror). Further, since the optical performance required of the projection optical system is extremely high, it is necessary to correct various aberrations to almost no aberration. In order to achieve desired optical performance in a refraction type projection optical system, a large number of lens components are required, and it is inevitable to reduce the transmittance and increase the manufacturing cost.

On the other hand, a reflection type optical system using power (refractive power) of a concave reflecting mirror or the like does not cause chromatic aberration, and the sign of the Petzval sum is opposite to that of the lens component. For this reason, an optical system combining a reflective optical system and a refractive optical system, a so-called catadioptric optical system (hereinafter, referred to as a “catadioptric optical system”) does not cause an increase in the number of lenses, and causes chromatic aberration and other factors. Various aberrations can be satisfactorily corrected to almost no aberration. Therefore, a catadioptric optical system is an optical system that includes at least one lens component and at least one reflecting mirror having a refractive power. In the refractive optical system and the reflective optical system,
It goes without saying that a parallel plane plate and a plane reflecting mirror for deflecting the optical path are provided as necessary.

However, if a concave reflecting mirror is used in the optical path of the projection optical system of the projection exposure apparatus, light incident on the concave reflecting mirror from the mask side is reflected and travels back to the original mask side. For this reason, a technique for separating the optical path of the light incident on the concave mirror and the optical path of the light reflected by the concave reflector and guiding the reflected light from the concave mirror toward the wafer,
That is, various techniques for configuring a projection optical system using a catadioptric optical system have been proposed in many cases.

As a typical optical path separation method, US Pat. No. 5,717,518 uses two reflecting mirrors having an opening at the center, and has a large light beam cross section near the pupil of the optical system. 2 so that the light beam is reflected and the light beam passes through the central opening when the light beam cross section is small near the image plane.
There has been proposed a method of performing optical path separation by arranging two reflecting mirrors. When this optical path separation method is used, all the optical elements constituting the optical system can be arranged along a single optical axis. As a result, it is possible to manufacture the optical system with high precision in accordance with the conventional method of adjusting optical components in the projection optical system. An optical system using this optical path separation method is disclosed in US Pat. No. 5,717,518.
JP-A-63-14112 and the like in addition to the above-mentioned publication.

[0007]

However, in the optical system disclosed in U.S. Pat. No. 5,717,518, since an intermediate image is formed, the entire length of the optical system is considerably long. . In addition, since the reflected light passes through the air over a long distance, the effective diameter of the optical system increases, so that the optical components become large, making not only difficult to manufacture, but also
There is a problem that the manufacturing cost increases dramatically.

Further, in this optical system, in order to avoid generation of stray light which reaches the image plane through the central opening without being reflected at all by the two reflecting mirrors, the optical axis of the image forming light beam is changed. It is necessary to block a part of the luminous flux at the center. As a result, the imaging characteristics of the optical system are degraded due to the central shielding of the imaging light beam. Accordingly, US Pat. No. 5,717,51
In order to apply the optical path separation method disclosed in Japanese Patent Publication No. 8 to a projection optical system, in order to obtain sufficient optical performance, the central shielding ratio (hereinafter simply referred to as “central shielding ratio”) of an imaged light beam is reduced. It is important to control. Here, the central shielding factor is
As shown in FIG. 10, of the luminous flux whose one-side opening angle is θ1,
When the portion (hatched portion) of the one-sided opening angle θ2 is shaded, the value is defined by the following equation.

Center shielding ratio = tan θ2 / tan θ1 = r / t In an optical system that performs center shielding, the center shielding ratio is not constant. For example, in the optical system disclosed in Japanese Patent Application Laid-Open No. 63-14112, Since 30% or more of the light beam is blocked, there is a problem that the imaging performance of the optical system is reduced.

The present invention has been made in view of the above problems. For example, even when illumination light in an ultraviolet region having a wavelength of 170 nm or less is used, the number of lenses is small, the size of the center is not reduced, and the center shielding ratio is reduced. Low, desired size image side NA
It is another object of the present invention to provide a projection optical system or the like in which chromatic aberration capable of securing an image circle is satisfactorily corrected.

[0011]

In order to solve the above problems, the present invention provides a first optical system for receiving light from a first surface,
A second optical system that forms an image of light passing through the first optical system onto a second surface, the second optical system comprising: a partial reflection surface that transmits and reflects the light; A first meniscus optical element having a concave surface facing the first surface side;
A second meniscus optical element having a concave surface facing the surface side;
A reflection surface having a predetermined opening, and light passing through the first optical system is reflected by the reflection surface via the partial reflection surface, the first optical element and the second optical element, Light reflected on the reflection surface is reflected on the partial reflection surface via the second optical element and the first optical element,
The light reflected on the partial reflection surface is the first optical element,
A projection optical system is provided, which forms an image on the second surface via the second optical element and the opening.

In a preferred aspect of the present invention, the radius of curvature of the surface on the second surface side of the first optical element is R2, and the radius of curvature of the surface on the first surface side of the second optical element is R3. In each case, it is desirable to satisfy the following condition: (1) 0.5 ≦ | R2 / R3 | ≦ 2.0.

Conditional expression (1) defines an appropriate shape of the air lens composed of the first optical element and the second optical element. In the projection optical system of the present invention, the light beam passes through the first optical element and the second optical element three times each. However, the conditional expression (1) indicates that the light beam passes through the first optical element and the second optical element. This is a condition for reducing the spherical aberration that occurs in the first stage, especially the higher-order spherical aberration of the light beam having a large NA transmitted through the first time. When the value exceeds the upper limit of conditional expression (1), an enormous amount of spherical aberration is generated particularly in the first transmission of the light transmitted three times. More preferably, by setting the lower limit of conditional expression (1) to 0.8 and the upper limit to 1.2, the occurrence of higher-order spherical aberration can be reduced more effectively.

In a preferred aspect of the present invention, when the largest radius of curvature is Rmax and the smallest radius of curvature is Rmin among the radii of curvature of the surfaces of the first optical element 1 and the second optical element, (2) It is desirable to satisfy the condition of | Rmax / Rmin | ≦ 2.5.

Conditional expression (2) defines an appropriate ratio between the largest radius of curvature and the smallest radius of curvature of the surfaces of the first optical element 1 and the second optical element. If the upper limit of conditional expression (2) is exceeded, the first optical element 1
And N of the light rays transmitted through the second optical element for the first time
The incident angle of a light beam having a large A becomes large, and a large amount of spherical aberration occurs during the first transmission. More preferably, by setting the upper limit of conditional expression (2) to 1.4, the spherical aberration can be more effectively reduced.

Further, in the present invention, the first optical system G1 has the stop S, emits light from the axial center of the first surface (object surface), passes through the stop S and has the largest NA. Assuming that the angle between the axis and the axis is θ, it is desirable to satisfy the following condition: (3) sin θ> 0.05.

Conditional expression (3) defines the maximum NA of the light beam that exits from the center of the object and passes through the stop. If the lower limit of conditional expression (3) is not reached, not only the luminous flux cannot be sufficiently widened, but also the center blocking ratio cannot be reduced.

In the present invention, it is desirable that an auxiliary optical system having a positive refractive power or a negative refractive power is provided between the first surface and the first lens group. When an auxiliary optical system having a positive refracting power is provided, a light beam having a high NA emitted from the first surface can be converged by the auxiliary optical system, and spherical aberration caused by the subsequent lens system can be corrected. Further, when an auxiliary optical system having a negative refractive power is used, when the projection optical system is considered to form an image from the second surface (image surface) side to the first surface (object surface) side, it is considered in the opposite direction. , The angular magnification of the light beam converging on the first surface can be reduced, and as a result, the overall magnification can be increased.

It should be noted that the present invention is not limited to the above-described first to fourth aspects, and may have, for example, the following configurations (A) to (D).

(A) The projection optical system according to any one of claims 1 to 3, wherein the partial reflection surface is formed on a surface on the first surface side of the first optical element. system.

(B) The projection optical system according to claim 1, wherein the reflection surface is formed on the surface of the second optical element on the second surface side. system.

(C) In an exposure method for exposing a predetermined pattern formed on a mask to a photosensitive substrate, an illumination step of illuminating the mask; And projecting the pattern image of the mask onto the photosensitive substrate using the projection optical system.

(D) The exposure method according to (C), wherein the illuminating step illuminates the mask with exposure light having a wavelength shorter than 170 nm.

However, the present invention is not limited to what is described in claims 1 to 4 and the above (A) to (D), and can take various configurations without departing from the gist of the present invention. Needless to say.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A projection optical system and the like according to numerical embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows a lens configuration of a projection optical system (a catadioptric system) according to a first embodiment, and FIG. 2 is an enlarged view showing the vicinity of the second surface.

The projection optical system of the present embodiment includes a first optical system G1 for receiving light from a first surface (object surface or mask surface) R;
And a second optical system G2 for forming an image of the light passing through the first optical system G1 on a second surface (image surface or wafer surface) W. Then, the first optical system G1 is sequentially arranged from the first surface side.
Meniscus-shaped lens component L with the convex surface facing the first surface side
11, L12, a stop S, a plano-convex lens component L13 having a convex surface facing the second surface, and a meniscus lens component L14 having a convex surface facing the second surface. Further, the second optical system G2 includes a partial reflection surface M that transmits and reflects the light.
1 and a meniscus-shaped first optical element L21 having a concave surface facing the first surface R side having the first surface R1, and a meniscus-shaped second optical element L21 having a concave surface facing the first surface R side having the reflective surface M4 having a predetermined opening AP. An optical element L22. In this embodiment, the first optical system G1 has a negative refractive power, and the second optical system G2 has a positive refractive power. Also, the first optical system G
1 has a central shielding member B that is disposed at or near the position of the aperture stop S and blocks light near the optical axis AX.

In this configuration, light passing through the first optical system G1 is reflected by the reflecting surface M4 via the partial reflecting surface M1, the first optical element L21 and the second optical element L22, and is reflected by the reflecting surface M4. The reflected light is reflected on the partial reflection surface M1 via the second optical element L22 and the first optical element L12, and the light reflected on the partial reflection surface M1 is reflected on the first optical element L
21, an image is formed on the second surface W via the second optical element L22 and the opening AP. The glass materials constituting the projection optical system according to the present embodiment are all fluorite.

In this embodiment, the maximum N emitted from the on-axis object point
The angle θ formed by the light beam A and the optical axis AX when passing through the aperture stop S is sin θ = 0.149, which is considerably outward (direction away from the optical axis). In this way, by sufficiently spreading the light, a high NA of 0.70 is obtained.
And the center shielding ratio can be reduced to 12.0%. The M2 surface of the first optical element L21 and the M3 surface of the second optical element L21 correct high-order spherical aberration. As a result, while maintaining a high NA of 0.70,
An optical system with low aberration can be obtained. Further, since the distance from the mask R to the wafer W is as short as 650 mm, assembly of the optical system is easy. Further, since the maximum effective radius of the glass material is as small as 52.079, it can be easily manufactured even with a partial reflection mirror or a back reflection mirror.

Table 1 shows the specification values of the projection optical system according to the present embodiment. In Table 1, λ is the central wavelength of the exposure light, β
Represents the projection magnification, NA represents the image-side numerical aperture, and φ represents the radius of the image circle on the wafer. Also, the surface number is the order of the surface from the mask side along the direction in which the light beam travels from the mask surface as the object surface to the wafer surface as the image surface,
r is the radius of curvature of each surface (vertical radius of curvature for an aspheric surface):
mm), d is the axial spacing of each surface, that is, the surface spacing (mm),
n indicates the refractive index with respect to the center wavelength (λ = 157.6 nm).

The sign of the surface distance d changes each time it is reflected. Therefore, the sign of the surface interval d is negative in the optical path from the reflecting surface M4 to the partial reflecting surface M1,
Positive in other optical paths. The radius of curvature of the convex surface toward the mask R is positive and the radius of curvature of the concave surface is negative regardless of the incident direction of the light beam.

The height of the aspheric surface in the direction perpendicular to the optical axis is defined as y, and the distance (sag amount) along the optical axis from the tangent plane at the vertex of the aspheric surface to a position on the aspheric surface at the height y )
Is Z, the radius of curvature of the vertex is r, the cone coefficient is κ,
When the n-th order aspherical coefficient is A to D, it is expressed by the following equation.

Z = (y ² / r) / [1+ ｛1- (1 + κ)
・ Y ² / r ² ｝ ^1/2 ] + A ・ y ⁴ + B ・ y ⁶ + C ・ y ⁸ + D ・
y ^{10 In} all the following embodiments, the same reference numerals and aspherical formulas as those in the first embodiment are used.

[0034]

[Table 1] (Main specifications) λ = 157.6 nm ± 12.9 pm β = 1/10 NA = 0.7 φ (radius) = 1.06 mm Δn / Δλ = 2.4 × 10 ⁻⁶ (Δλ = 1 pm) Overall length = 650 mm Center shielding ratio = 12% Focal length of the first lens group G1 = -1729.9174 Focal length of the second lens group G = 51.38921 Surface number rdn 1 115.6154 10.0000 1.5600 2 229.2920 0.4000 3 68.3185 10.0000 1.5600 4 47.3899 53.6060 5 0.0000 8.2456 (Aperture stop) 6 0.0000 12.0000 1.5600 7 -312.9935 4.5163 8 -196.2857 11.9086 1.5600 9 -833.7364 10.6014 10 -109.2635 17.8296 1.5600 11 -112.2434 1.2250 12 -137.7119 15.9581 1.5600 13 -99.4390 -15.9581 14 -137.7119 -1.2250 15 -112.2434 -17.8296 1.5600 16 -109.2635 17.8296 17 -112.2434 1.2250 18 -137.7119 15.9581 1.5600 19 -99.4390 5.0000 (Aspherical surface) Surface 7 κ = 0.00000 A = + 3.1551 × 10 ^-7 B = + 1.4597 × 10 ^-11 C = 0.0 D = -8.0489 × 10 ^-19 (values for conditional expressions) (1) | R2 / R3 | = 0.815 ( ) | Rmax / Rmin | = 1.385 (3) sinθ = 0.149

FIG. 3 is a diagram showing the lateral aberration in the first embodiment. In the aberration diagrams, Y represents the image height, the solid line represents the central wavelength of 157.6 nm, and the broken line represents 157.6 nm + 12.9.
pm = 157.6129 nm, and the dot-dash line is 157.6.
nm-12.9 pm = 157.5871 nm. As is clear from the aberration diagrams, in the first example, the chromatic aberration is favorably corrected for the exposure light having a wavelength width of 157.6 nm ± 12.9 pm. Although not shown, it has been confirmed that various aberrations such as spherical aberration, astigmatism, distortion, and the like are also satisfactorily corrected.

In this embodiment, an aspherical surface may be employed on a plurality of surfaces or on all surfaces.

(Second Embodiment) FIG. 4 shows a lens configuration of a projection optical system according to a second embodiment, and FIG. 5 is an enlarged view showing the vicinity of the second surface.

The projection optical system of this embodiment includes, in order from the first surface R, an auxiliary optical system AO having a positive refractive power in a meniscus shape having a concave surface facing the first surface side, a first optical system G1, First
The projection optical system includes a second optical system G2 that forms an image of the light passing through the optical system G1 on the second surface W. Then, the first optical system G
Reference numeral 1 denotes a biconvex lens component L11 and a meniscus-shaped lens component L1 having a convex surface facing the first surface in order from the first surface.
2, a stop S, a plano-convex lens component L13 having a convex surface facing the second surface, and a meniscus lens component L14 having a convex surface facing the second surface. Further, the second optical system G2
Is a first surface having a meniscus-shaped first optical element L21 having a concave surface facing the first surface R having a partial reflection surface M1 for transmitting and reflecting the light, and a reflection surface M4 having a predetermined opening AP. The second meniscus shape with the concave surface facing the R side
An optical element L22. In this embodiment,
Both the first optical system G1 and the second optical system G2 have a positive refractive power. Further, the first optical system G1 has a center shielding member B which is arranged at or near the position of the aperture stop S and blocks light near the optical axis AX.

In this configuration, light from the first surface R passes through the auxiliary optical system AO and the first optical system G1. The light passing through the first optical system G1 is reflected by the reflecting surface M4 via the partial reflecting surface M1, the first optical element L21 and the second optical element L22, and the light reflected by the reflecting surface M4 is reflected by the first reflecting surface M4. The light reflected on the partial reflection surface M1 via the second optical element L22 and the first optical element L12, and the light reflected on the partial reflection surface M1 passes through the first optical element L21, the second optical element L22, and the opening AP. To form an image on the second surface W. The glass materials constituting the projection optical system according to the present embodiment are all fluorite.

The image forming magnification of this embodiment is as high as 1/15 times, and the size of the mask R does not need to be reduced as compared with an optical system of low magnification. Become.
The angle θ formed by the optical axis AX when the light beam having the maximum NA emitted from the on-axis object point passes through the aperture stop S is sin θ =
0.1077, which is quite outward (direction away from the optical axis). In this way, by sufficiently spreading the light, it is possible to achieve a high NA of NA = 0.70 and to reduce the central shielding ratio to 12.4%. Also, the first
Higher order spherical aberration is corrected by the M2 surface of the optical element L21 and the M3 surface of the second optical element L21. This allows
An optical system with low aberration can be obtained while maintaining a high NA of 0.70. The maximum effective radius of the glass material is 51.
Since it is as small as 279, it can be easily manufactured even with a partial reflection mirror or a back reflection mirror.

Table 2 shows the specification values of the projection optical system according to the present embodiment.

[0042]

(Main specifications) λ = 157.6 nm ± 12.9 pm β = 1/15 NA = 0.7 φ (radius) = 1.12 mm Δn / Δλ = 2.4 × 10 ⁻⁶ (Δλ = 1 pm) Overall length = 850 mm Center shielding ratio = 12.4% Focal length of auxiliary lens AO = 686.26076 Focal length of first lens group G1 = 400.76007 Composite focal length of auxiliary lens AO and first lens group G1 =
448.62198 Focal length of the second lens group G2 = 61.67570 Surface number rdn 1 -142.4514 16.5520 1.5600 2 -235.7960 217.9260 3 169.6890 10.7541 1.5600 4 -812.9002 0.4000 5 83.5799 10.0000 1.5600 6 53.0281 37.0270 7 0.0000 19.5341 (Aperture stop) 8 0.0000 12.0000 1.5600 9 -475.9626 8.2344 10 -126.0091 14.7201 1.5600 11 -109.8183 2.6292 12 -104.2974 20.6176 1.5600 13 -122.1125 1.3015 14 -123.9323 11.5700 1.5600 15 -99.5540 -11.5700 16 -123.9323 -1.3015 17 -122.1125 -20.6176 1.5600 18 -104.2974 20.6176 19 -122.1125 1.3015 20 -123.9323 11.5700 1.5600 21 -99.5540 5.0001 (Aspherical surface data) 9th surface κ = 0.00000 A = + 1.6053 × 10 ^-7 B = + 3.4262 × 10 ^-12 C = -1.3562 × 10 ^-15 D = + 4.7717 × 10 ^-19 (Values corresponding to conditional expressions) (1) | R2 / R3 | = 0.885 (2) | Rmax / Rmin | = 1.245 (3) sin θ = 0.008

FIG. 6 is a diagram showing the lateral aberration in the second embodiment. As is clear from the aberration diagrams, in the second example, the chromatic aberration is favorably corrected for exposure light having a wavelength width of 157.6 nm ± 12.9 pm. Although not shown, it has been confirmed that various aberrations such as spherical aberration, astigmatism, distortion, and the like are also satisfactorily corrected.

In this embodiment, an aspherical surface may be used for a plurality of surfaces or all surfaces.

(Third Embodiment) FIG. 7 is a diagram showing a lens configuration of a projection optical system according to a third embodiment.

The projection optical system of this embodiment includes, in order from the first surface R, an auxiliary optical system AO having a positive refractive power in a meniscus shape having a concave surface facing the first surface side, a first optical system G1, First
The projection optical system includes a second optical system G2 that forms an image of the light passing through the optical system G1 on the second surface W. Then, the first optical system G
1 includes, in order from the first surface, a biconvex lens component L11, a biconcave lens component L12, an aperture stop S, a meniscus-shaped lens component L13 having a convex surface facing the first surface, and a biconvex lens component L14. Have. The second optical system G2 is
A first meniscus-shaped first optical element L21 having a concave surface facing the first surface R having a partial reflection surface M1 for transmitting and reflecting the light, and a first surface R having a reflection surface M4 having a predetermined opening AP. And a meniscus-shaped second optical element L22 having a concave surface facing the lens. In the present embodiment, the first
Both the optical system G1 and the second optical system G2 have a positive refractive power. Further, the first lens group G1 has a center shielding member B which is arranged at or near the position of the aperture stop S and blocks light near the optical axis AX.

In this configuration, light from the first surface R passes through the auxiliary optical system AO and the first optical system G1. The light passing through the first optical system G1 is reflected by the reflecting surface M4 via the partial reflecting surface M1, the first optical element L21 and the second optical element L22, and the light reflected by the reflecting surface M4 is reflected by the first reflecting surface M4. The light reflected on the partial reflection surface M1 via the second optical element L22 and the first optical element L12, and the light reflected on the partial reflection surface M1 passes through the first optical element L21, the second optical element L22, and the opening AP. To form an image on the second surface W. The glass materials constituting the projection optical system according to the present embodiment are all fluorite.

The image forming magnification of this embodiment is 1/4, and a large image circle (radius = 8.2 mm) can be secured. The maximum NA ray emitted from the on-axis object point is the aperture stop S
Is an angle θ with the optical axis AX when passing through
0.2259, and by sufficiently widening the light beam, it is possible to achieve a high NA of NA = 0.75 and to reduce the central shielding ratio to 17.5%. The M2 surface of the first optical element L21 and the M3 surface of the second optical element L21 correct high-order spherical aberration. Thereby, 0.
An optical system with low aberration can be obtained while maintaining a high NA of 75.

Table 3 shows the specification values of the projection optical system according to the present embodiment.

[0050]

[Table 3] (Main specifications) λ = 157.6 nm ± 12.9 pm β = 1/4 NA = 0.75 φ (radius) = 8.2 mm Δn / Δλ = 2.4 × 10 ⁻⁶ (Δλ = 1 pm ) Overall length = 838.7 mm Center shielding ratio = 17.5% Focal length of auxiliary lens AO = 690.02507 Focal length of first lens group G1 = 1321.86989 Composite focal length of auxiliary lens AO and first lens group G1 =
551.92081 Focal length of the second lens group G2 = 119.08312 Surface number rdn 1 -993.8719 40.0000 1.5600 2 -282.2564 330.1612 3 217.9575 43.6730 1.5600 4 -264.4779 0.5000 5 -309.6151 25.0000 1.5600 6 189.8944 31.7290 7 0.0000 0.5000 (Aperture stop) 8 675.5575 25.0000 1.5600 9 213.3482 25.1274 10 616.0815 46.8419 1.5600 11 -417.3740 9.5585 12 -276.7222 50.4668 1.5600 13 -249.0398 2.0087 14 -232.8244 26.2932 1.5600 15 -220.6788 -26.29323 16 -232.8244 -2.0087 17 -249.0398 -50.4668 1.5600 18 -276.7222 50.4668 19 -249.0398 2.0087 20 -232.8244 26.2932 1.5600 21 -220.6788 10.0000 (aspherical data) third surface κ = 0.00000 A = -3.6385 × 10 -8 B = -6.6784 × 10 -13 C = -1.0780 × 10 -16 D = + 1.1604 × 10 - ²¹ Surface 6 κ = 0.00000 A = -1.9907 × 10 ^-8 B = +4.9134 × 10 ^-12 C = -1.9860 × 10 ^-16 D = +7.9218 × 10 ^-21 Surface 9 κ = 0.00000 A = +7.9781 × 10 ^-8 B = -6.6088 × 10 ^-12 C = -8.7313 × 10 ^-17 D = + 7.8698 × 10 ^-21 Surface 10 κ = 0.00000 A = + 4.0045 × 10 ^-8 B = -1.4281 × 10 ^-12 C = + 7 .6350 × 10 ^-18 D = -1.0045 × 10 ^-21 Surface 15 (= 21st surface) κ = 0.00000 A = -1.7120 × 10 ^-9 B = -5.7602 × 10 ^-14 C = -1.0876 × 10 ^-18 D = −2.7175 × 10 ⁻²³ (Values corresponding to conditional expressions) (1) | R2 / R3 | = 1.070 (2) | Rmax / Rmin | = 1.254 (3) sin θ = 0.2259

FIG. 8 is a diagram showing the lateral aberration in the third embodiment. As is clear from the aberration diagrams, in the third example, the chromatic aberration is favorably corrected for exposure light having a wavelength width of 157.6 nm ± 12.9 pm. Although not shown, it has been confirmed that various aberrations such as spherical aberration, astigmatism, distortion, and the like are also satisfactorily corrected.

In this embodiment, aspherical surfaces may be used for all surfaces.

(Fourth Embodiment) FIG. 9 is a diagram schematically showing an overall configuration of a projection exposure apparatus having a projection optical system according to each of the above embodiments. In FIG. 9, the projection optical system 8
9 is set in parallel with the optical axis AX, the X axis is set in a plane perpendicular to the optical axis AX, and the Y axis is set in parallel with the plane of FIG.

The projection exposure apparatus shown in the figure is provided with, for example, an F ₂ laser (having an oscillation center wavelength of 157.6 nm) as a light source for supplying illumination light in the ultraviolet region. The light emitted from the light source 1 uniformly illuminates the mask R on which a predetermined pattern is formed via the illumination optical system 2.

In the optical path from the light source 1 to the illumination optical system 2, one or a plurality of bending mirrors for deflecting the optical path are arranged as necessary. When the light source 1 and the projection exposure apparatus main body are separate bodies, F ₂
An automatic tracking unit for constantly directing the direction of the laser light toward the projection exposure apparatus main body, a shaping optical system for shaping the light beam cross-sectional shape of the F ₂ laser light from the light source 1 into a predetermined size and shape,
An optical system such as a light amount adjustment unit is provided. The illumination optical system 2 includes, for example, a fly-eye lens or an internal reflection type integrator to form a surface light source having a predetermined size and shape, and an optical integrator for defining the size and shape of an illumination area on the mask R. It has an optical system such as a field stop and a field stop imaging optical system that projects an image of the field stop onto a mask. Further, an optical path between the light source 1 and the illumination optical system 2 is sealed by a casing (not shown), and a space from the light source 1 to the optical member closest to the mask in the illumination optical system 2 absorbs exposure light. The gas is replaced with an inert gas such as helium gas or nitrogen, which is a gas having a low rate.

The mask R is held on the mask stage 5 via the mask holder 4 in parallel to the XY plane. A pattern to be transferred is formed on the mask R, and has a rectangular shape (slit shape) having a long side along the Y direction and a short side along the X direction in the entire pattern region.
Are illuminated. The mask stage 5 can be moved two-dimensionally along the mask plane (that is, the XY plane) by the action of a drive system (not shown), and its position coordinates are measured by an interferometer 7 using a mask moving mirror 6. And the position is controlled.

Light from the pattern formed on the mask R forms a mask pattern image on the wafer W as a photosensitive substrate via the catadioptric projection optical system 8. The wafer W is placed on the wafer stage 11 via the wafer holder 10.
Above, it is held parallel to the XY plane. And
In order to optically correspond to a rectangular illumination area on the mask R, the wafer W has a long side along the Y direction and X
A pattern image is formed in a rectangular exposure area having a short side along the direction.

The wafer stage 11 can be moved two-dimensionally along the wafer surface (that is, the XY plane) by the action of a drive system (not shown), and its position coordinate is the interferometer 13 using the wafer moving mirror 12. And the position is controlled.

In the illustrated projection exposure apparatus, the optical member (L11 in the first embodiment, the auxiliary optical system in the second and third embodiments) disposed closest to the mask among the optical members constituting the projection optical system 8. AO) and the optical member (L22 in each embodiment) disposed closest to the wafer so that the inside of the projection optical system 8 is kept airtight, and the gas inside the projection optical system 8 is helium gas. And replaced by an inert gas such as nitrogen.

Further, a mask R and a mask stage 5 are disposed in a narrow optical path between the illumination optical system 2 and the projection optical system 8. (Not shown) is filled with an inert gas such as nitrogen or helium gas.

The wafer W and the wafer stage 11 are arranged in a narrow optical path between the projection optical system 8 and the wafer W, but a casing (not shown) hermetically surrounds the wafer W and the wafer stage 11 and the like. ) Is filled with an inert gas such as nitrogen or helium gas. Thus, over the entire optical path from the light source 1 to the wafer W,
An atmosphere in which the exposure light is hardly absorbed is formed.

As described above, the viewing area (illumination area) on the mask R and the projection area (exposure area) on the wafer W defined by the projection optical system 8 are rectangular in shape having short sides along the X direction. It is. Therefore, the driving system and the interferometer (7,
13) While controlling the position of the mask R and the wafer W using, for example, the mask stage 5 and the wafer stage 11 along the short side direction of the rectangular exposure region and the illumination region, that is, the X direction, and thus the mask R By moving (scanning) the wafer W synchronously, an area having a width equal to the long side of the exposure area on the wafer W and a length corresponding to the scanning amount (moving amount) of the wafer W is obtained. The mask pattern is scanned and exposed.

The projection exposure apparatus according to each of the above embodiments can be manufactured by the following method. First, an illumination optical system for illuminating a pattern on a mask with illumination light having a center wavelength shorter than 170 nm is prepared. Specifically, the center wavelength is prepared an illumination optical system for illuminating the mask pattern by using a F ₂ laser light 157.6 nm. At this time, the illumination optical system is configured to supply illumination light having a spectrum width within a predetermined full width at half maximum.

Next, a projection optical system for forming an image of the pattern on the mask on the photosensitive surface on the photosensitive substrate is prepared. Preparing the projection optical system includes preparing a plurality of refractive optical elements and reflecting mirrors and assembling the plurality of refractive optical elements and the like. Then, by connecting these illumination optical system and projection optical system electrically, mechanically or optically so as to achieve the above-described functions, the projection exposure apparatus according to each embodiment can be manufactured.

[0065] Further, in the above embodiments, the use of the CaF ₂ (calcium fluoride) as the material of refractive optical members constituting the projection optical system, in addition to the CaF ₂ or CaF _2, Alternatively, a crystal material of fluoride such as barium fluoride, lithium fluoride, and magnesium fluoride, or quartz doped with fluorine may be used. However, if it is possible to sufficiently narrow the band of the illumination light for illuminating the mask, it is preferable that the projection optical system be made of a single type of optical material. Furthermore, considering the ease of manufacturing and the manufacturing cost of the projection optical system, it is preferable that the projection optical system be composed of only CaF ₂ .

In each of the above embodiments, the optical path from the light source to the wafer is replaced with helium gas, but a part or all of the optical path may be replaced with nitrogen (N ₂ ) gas. Furthermore, in the above embodiments, using a light source and shiso F ₂ lasers, although narrowing the spectral width by the narrowing device, solid-state lasers instead, a YAG laser having an oscillation spectrum in the 157nm May be used. In addition, a single-wavelength laser beam in the infrared or visible region oscillated from a DFB semiconductor laser or a fiber laser is amplified by, for example, a fiber amplifier doped with erbium (or both erbium and ytterbium) to form a nonlinear optical crystal. Alternatively, a harmonic converted to ultraviolet light may be used.

For example, assuming that the oscillation wavelength of the single-wavelength laser light is in the range of 1.51 to 1.59 μm, a tenth harmonic whose output wavelength is in the range of 151 to 159 nm is output. In particular, when the oscillation wavelength is in the range of 1.57 to 1.58 μm, a 10th harmonic having a generation wavelength in the range of 157 to 158 nm, that is, ultraviolet light having substantially the same wavelength as the F ₂ laser light can be obtained. Further, the oscillation wavelength is set to 1.03 to
When the wavelength is within the range of 1.12 μm, the generated wavelength is 147 to 1
A 7th harmonic within a range of 60 nm is output. In particular, when the oscillation wavelength is in a range of 1.099 to 1.106 μm, a 7th harmonic whose generation wavelength is in a range of 157 to 158 nm, that is, an F ₂ laser Ultraviolet light having substantially the same wavelength as light is obtained. Note that, as the single-wavelength oscillation laser, an ytterbium-doped fiber laser is used.

As described above, when using a harmonic from a laser light source, the harmonic itself has a sufficiently narrowed spectrum width (for example, about 0.01 pm).
It can be used in place of the light source 1 in each of the above embodiments. According to the present invention, after the mask pattern image is collectively transferred to one shot area on the wafer, the wafer is sequentially and two-dimensionally moved in a plane orthogonal to the optical axis of the projection optical system, and the next shot A step-and-repeat method (batch exposure method) for repeating a process of collectively transferring a mask pattern image to an area, or a projection magnification β for exposing a mask and a wafer to a projection optical system when exposing each shot area of the wafer.
Can be applied to both the step-and-scan method (scanning exposure method) in which synchronous scanning is performed using the speed ratio as a speed ratio. In the step-and-scan method, it is sufficient that good imaging characteristics can be obtained in a slit-shaped (elongated rectangular) exposure area. Therefore, a wider shot on a wafer can be obtained without increasing the size of the projection optical system. Areas can be exposed.

In each of the above embodiments, the present invention is applied to a projection exposure apparatus used for manufacturing a semiconductor device. However, not only an exposure apparatus used for manufacturing a semiconductor element, but also an exposure apparatus used for manufacturing a display including a liquid crystal display element and the like, an exposure apparatus for transferring a device pattern onto a glass plate, and a device used for manufacturing a thin film magnetic head The present invention can also be applied to an exposure apparatus that transfers a pattern onto a ceramic wafer, an exposure apparatus used for manufacturing an image pickup device (such as a CCD), and the like. Further, the present invention can be applied to an exposure apparatus that transfers a circuit pattern onto a glass substrate, a silicon wafer, or the like in order to manufacture a reticle or a mask.

It is needless to say that the present invention is not limited to the above-described embodiment, but can take various configurations without departing from the gist of the present invention.

[0071]

As described above, according to the present invention,
For example, when using light having a wavelength of 170 nm or less,
Especially, without increasing the size of the optical system, the center shielding ratio is low, the image-side NA and the image circle of the required size can be secured, and a high resolution of, for example, 0.1 μm or less can be achieved. A projection optical system in which chromatic aberration is well corrected can be realized with a small number of lenses.

Therefore, in the projection exposure apparatus having the projection optical system of the present invention and the exposure method using the projection optical system of the present invention, an extremely fine pattern can be projected and exposed on a photosensitive substrate with high accuracy. . In addition, a relatively simple narrow-band F ₂ laser can be used as an exposure light source, so that a large exposure power can be obtained. further,
Since the maintenance cost of the laser light source is also reduced, it is possible to realize a projection exposure apparatus having a low cost for the laser light source and high productivity.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a lens configuration of a projection optical system according to a first example.

FIG. 2 is another diagram showing a lens configuration of the projection optical system according to the first example.

FIG. 3 is a diagram showing lateral aberration in the first example.

FIG. 4 is a diagram showing a lens configuration of a projection optical system according to Example 2.

FIG. 5 is another diagram showing a lens configuration of a projection optical system according to Example 2.

FIG. 6 is a diagram illustrating lateral aberration in a second example.

FIG. 7 is a diagram illustrating a lens configuration of a projection optical system according to a third example.

FIG. 8 is a diagram showing lateral aberration in the third example.

FIG. 9 is a diagram schematically illustrating an overall configuration of a projection exposure apparatus including a projection optical system according to each embodiment of the present invention.

FIG. 10 is a diagram illustrating a center shielding ratio.

[Explanation of symbols]

 Reference Signs List 1 laser light source 2 illumination optical system R mask 4 mask holder 5 mask stage 6, 12 moving mirror 7, 13 interferometer 8 projection optical system W wafer 10 wafer holder 11 wafer stage AX optical axis G1 first optical system G2 second optical system L11 To L14 Each lens component L21 First optical element L22 Second optical element S Aperture stop M1 Partial reflection surface M4 Reflection surface AP Opening B Center shielding member AO Auxiliary optical system

Continued on the front page F term (reference) 2H087 KA21 PA06 PA07 PA17 PB06 PB07 QA02 QA03 QA07 QA12 QA17 QA21 QA22 QA25 QA26 QA32 QA41 QA42 QA45 QA46 RA12 RA13 RA32 TA04 5F046 AA22 BA03 BA05 CA04 CB12 DA01

Claims (4)

[Claims] A first optical system for receiving light from a first surface;
A second optical system that forms an image of light passing through the first optical system onto a second surface, wherein the second optical system has a partially reflecting surface that transmits and reflects the light; It has a meniscus-shaped first optical element having a concave surface facing the first surface side, a meniscus-shaped second optical element having a concave surface facing the first surface side, and a reflecting surface having a predetermined opening. The light passing through the first optical system is transmitted through the partial reflection surface and the first optical system.
The light reflected on the reflection surface via the optical element and the second optical element, and the light reflected on the reflection surface is reflected on the partial reflection surface via the second optical element and the first optical element. And a light reflected by the partial reflection surface forms an image on the second surface via the first optical element, the second optical element, and the opening. 2. When the radius of curvature of the surface on the second surface side of the first optical element is R2, and the radius of curvature of the surface on the first surface side of the second optical element is R3, 0.5 2. The projection optical system according to claim 1, wherein the following condition is satisfied: .ltoreq. | R2 / R3 | .ltoreq.2.0. 3. The largest radius of curvature among the radii of curvature of the surfaces of the first optical element and the second optical element is R.
3. The projection optical system according to claim 1, wherein the following condition is satisfied: | Rmax / Rmin | ≦ 2.5, where max and the smallest radius of curvature are Rmin. 4. An illumination optical system for illuminating a mask on which a predetermined pattern is formed, and an image of the predetermined pattern of the mask disposed on the first surface is disposed on the second surface. A projection exposure apparatus comprising: the projection optical system according to claim 1 for projecting on a photosensitive substrate.