JP2002040327A - Optical integrator of wavefront splitting type and illuminating optical device provided with the optical integrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical integrator of wavefront splitting type which enables to obtain a uniform illuminance distribution over almost the whole of illuminated field which is formed even when the sizes of respective micro lenses are made small and the number of wavefront splitting is set in large numbers. SOLUTION: This optical integrator of wave front splitting type has a large number of micro lenses which are arranged two-dimensionally, wavefront-splits an incident luminous flux and forms a large number of light sources. Each micro lens has a regularly hexagonal incident face which inscribes with a circle of diameter d and a regularly hexagonal emission face which inscribes with the circle of diameter d and, when the focal distance of each micro lens is f and the wavelength of the incident luminous flux is λ, the condition of (d/2)2/(λ.f)>=3.05 is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavefront splitting type optical integrator and an illumination optical apparatus having the optical integrator, and more particularly to an illumination optical apparatus suitable for an exposure apparatus and a microscope for manufacturing a micro device by a lithography process. It concerns the device.

[0002]

2. Description of the Related Art Semiconductor devices, imaging devices, liquid crystal display devices,
In a typical exposure apparatus for manufacturing a micro device such as a thin-film magnetic head, a light beam emitted from a light source enters a micro fly's eye, and forms a secondary light source including a large number of light sources on a rear focal plane. . The luminous flux from the secondary light source is restricted via an aperture stop arranged near the rear focal plane of the micro fly's eye, and then enters the condenser lens.

The light beam condensed by the condenser lens illuminates a mask on which a predetermined pattern is formed in a superimposed manner. The light transmitted through the mask pattern forms an image on the photosensitive substrate via the projection optical system. Thus, the mask pattern is projected and exposed (transferred) on the photosensitive substrate. Note that the pattern formed on the mask is highly integrated, and it is essential to obtain a uniform illuminance distribution on the photosensitive substrate in order to accurately transfer this fine pattern onto the photosensitive substrate.

[0004] The micro fly's eye is a wavefront splitting optical integrator composed of a large number of minute lenses arranged densely and vertically. Generally, a micro fly's eye is formed by, for example, performing an etching process on a parallel flat glass plate to form a group of minute lenses. Here, each micro lens constituting the micro fly's eye is smaller than each lens element constituting the fly's eye lens.

[0005]

As described above, in the case of an exposure apparatus for transferring a fine pattern onto a photosensitive substrate, it is essential to obtain a uniform illuminance distribution on the mask and on the photosensitive substrate. . Therefore, in order to reduce uneven illuminance, it is desired to increase the number of micro lenses constituting the micro fly's eye, that is, to increase the number of wavefront divisions.

When a micro fly's eye is manufactured by etching or the like, it is difficult to deeply etch a glass plate, and it is easier to manufacture a microlens having a smaller size. However, if the size of each microlens is simply reduced, the surrounding illuminance in the illumination field formed on the irradiated surface that is optically conjugate to the incident surface is reduced by the diffraction limit with respect to the incident surface of each microlens. There are inconveniences.

The present invention has been made in view of the above-mentioned problems, and even if the size of each microlens is reduced and the number of wavefront divisions is set to be large, a uniform illumination field is formed over substantially the entire illumination field. It is an object of the present invention to provide a wavefront splitting type optical integrator and an illumination optical device including the optical integrator, which can obtain a proper illuminance distribution.

[0008]

According to a first aspect of the present invention, there is provided a multi-lens array comprising: a plurality of minute lenses arranged two-dimensionally; In the wavefront splitting type optical integrator that forms the above, each microlens has a rectangular entrance surface and a rectangular exit surface, and the focal length of each microlens is f,
The length of one side of the entrance surface of each microlens is d1, the length of the other side of the entrance surface of each microlens is d2, and the exit surface of each microlens corresponds to one side of the entrance surface. When the length of the side to be set is D1, the length of the side corresponding to the other side of the entrance surface on the exit surface of each microlens is D2, and the wavelength of the incident light beam is λ, (d1 / 2) (D1 / 2) / (λ · f) ≧ 3.05 (d2 / 2) (D2 / 2) / (λ · f) ≧ 3.05 Provide an optical integrator.

According to a preferred aspect of the first invention, the length d1 of one side of the incident surface is substantially larger than the length d2 of the other side of the incident surface, and (d1 / 2) ( D1 / 2) / (λ · f) ≧ 3.05.

According to a second aspect of the present invention, there is provided a wavefront splitting type optical integrator having a plurality of two-dimensionally arrayed minute lenses and dividing an incident light beam into a wavefront to form a plurality of light sources. Is a rectangular entrance surface,
And a circular or regular hexagonal exit surface, the focal length of each microlens is f, the length of one side of the entrance surface of each microlens is d1, and the other of the entrance surfaces of each microlens is When the length of the side is d2, the diameter of the circular exit surface of each microlens or the diameter of a circle circumscribing the regular hexagonal exit surface is D, and the wavelength of the incident light beam is λ, (d1 / 2) It satisfies at least one of the conditions of (D / 2) / (λ · f) ≧ 3.05 (d2 / 2) (D / 2) / (λ · f) ≧ 3.05. An optical integrator is provided.

According to a preferred aspect of the second invention, the length d1 of one side of the incident surface is substantially larger than the length d2 of the other side of the incident surface, and (d1 / 2) ( D / 2) / (λ · f) ≧ 3.05.

According to a third aspect of the present invention, there is provided a wavefront splitting optical integrator having a plurality of two-dimensionally arrayed minute lenses and dividing an incident light beam into a wavefront to form a plurality of light sources. Has a regular hexagonal entrance surface inscribed in a circle with a diameter d or a circle with a diameter d, and a regular hexagonal exit surface inscribed in a circle with a diameter d or a circle with a diameter d, Let f be the focal length of each microlens
And an optical integrator characterized by satisfying a condition of (d / 2) ² /(λ·f)≧3.05 when a wavelength of the incident light beam is λ.

According to a fourth aspect of the present invention, there are provided light source means for supplying a light beam, and the optical integrators of the first to third inventions for forming a large number of light sources based on the light beam from the light source means. A light guiding optical system for guiding light beams from the plurality of light sources to the surface to be illuminated.

According to a preferred aspect of the fourth invention, the light guide optical system includes: a condenser optical system for condensing light beams from the plurality of light sources to form an illumination field in a superimposed manner; An imaging optical system for forming the image of the illumination field on the irradiated surface based on the light beam from the optical system, and optically forming the positions of the plurality of light sources in the optical path of the imaging optical system. An aperture stop for blocking unnecessary light flux is provided at a substantially conjugate position.

According to a fifth aspect of the present invention, there is provided an illumination optical apparatus combined with an exposure apparatus having a projection optical system for forming an image of a pattern on a mask disposed on a surface to be irradiated on a photosensitive substrate. Light source means for supplying, and multiple light beam superimposing means for forming a large number of light sources based on the light beams from the light source means and forming an illumination field which is an area on a predetermined surface on which the light beams from the multiple light sources are superimposed. And an illumination imaging optical system that forms the image of the illumination field on or near the mask, wherein the illumination imaging optical system is disposed at a position optically conjugate with the pupil of the projection optical system. An illumination optical device having an aperture stop provided.

According to a sixth aspect of the present invention, there is provided an illumination optical device according to the fourth or fifth aspect, and a projection optical system for projecting and exposing a mask pattern set on the surface to be irradiated onto a photosensitive substrate. An exposure apparatus characterized by comprising:

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, as shown in FIG. 1, consider the case where both the entrance surface and the exit surface of each micro lens constituting an optical integrator are formed in a regular hexagonal shape having the same size. In this case, the peripheral illuminance in the illuminated field formed on the illuminated surface that is optically conjugate with the incident surface is reduced by the diffraction limit with respect to the incident surface of each microlens. When the diameter of a circle circumscribing the regular hexagonal incident surface and the exit surface is d, the numerical aperture of each microlens is NA, the focal length of each microlens is f, and the wavelength of the incident light beam is λ, diffraction occurs. The width b of the peripheral portion on the incident surface that contributes to the reduction in illuminance due to the limit is expressed by the following equation (a). b = 0.61 · (λ / NA) = 0.61 · λ / {(d / 2) / f} (a)

In order to obtain a uniform illuminance distribution over almost the entire illuminated field formed on the surface to be illuminated, the width b must be smaller than 1/10 of the size d of the incident surface. It is desirable that conditional expression (b) be satisfied. 0.61 · {λ / (d / 2) / f} ≦ d / 10 (b) When the conditional expression (b) is modified, a relationship expressed by the following conditional expression (1) is obtained. (D / 2) ² /(λ·f)≧3.05 (1)

Further, in order to obtain a more uniform illuminance distribution over substantially the entire illumination field, the above-mentioned width b must be smaller than 1/100 of the size d of the incident surface, that is, the following conditional expression (c) Is more desirably satisfied. 0.61 · {λ / (d / 2) / f} ≦ d / 100 (c) When the conditional expression (c) is modified, a relationship represented by the following conditional expression (1 ′) is obtained. (D / 2) ² /(λ·f)≧30.5 (1 ′) As described above, the case where both the entrance surface and the exit surface of the optical integrator are regular hexagons having the same size has been described. The same applies to the case where both surfaces are circular in the same size.

Next, as shown in FIG. 2, consider a case where the entrance surface of each microlens constituting the optical integrator is formed in a rectangular shape and its exit surface is formed in a regular hexagonal shape. In this case, the length of the long side of the rectangular incident surface is d1, and the length of the short side of the rectangular incident surface is d1.
2, the diameter of a circle circumscribing the exit surface of the regular hexagon is D, the numerical aperture of each microlens is NA, the focal length of each microlens is f, and the wavelength of the incident light beam is λ. The width b of the peripheral portion on the incident surface that contributes to the reduction in illuminance due to the limit is expressed by the following equation (d). b = 0.61 · λ / {(D / 2) / f} (d)

In order to obtain a uniform illuminance distribution over substantially the entire illuminated field formed on the surface to be illuminated, the width b must be smaller than 1/10 of the size d1 in the long side direction of the incident surface. ,
Alternatively, it is desirable that the size is smaller than 1/10 of the size d2 in the short side direction, that is, the following conditional expression (e) or (f) is satisfied. 0.61 · λ / {(D / 2) / f} ≦ d1 / 10 (e) 0.61 · λ / {(D / 2) / f} ≦ d2 / 10 (f)

By transforming conditional expressions (e) and (f),
The following relational expressions (2) and (3) are obtained. (D1 / 2) (D / 2) / (λ · f) ≧ 3.05 (2) (d2 / 2) (D / 2) / (λ · f) ≧ 3.05 (3)

Further, in order to obtain a more uniform illuminance distribution over substantially the entire illumination field, the width b is smaller than 1/100 of the size d1 in the long side direction of the incident surface or the short side. It is further desirable that the size be smaller than 1/100 of the size d2 in the direction, that is, the following conditional expression (g) or (h) is satisfied. 0.61 · λ / {(D / 2) / f} ≦ d1 / 100 (g) 0.61 · λ / {(D / 2) / f} ≦ d2 / 100 (h)

By transforming conditional expressions (g) and (h),
The following relational expressions (2 ') and (3') are obtained. (D1 / 2) (D / 2) / (λ · f) ≧ 30.5 (2 ′) (d2 / 2) (D / 2) / (λ · f) ≧ 30.5 (3 ′)

When the exit surface is a perfect regular hexagon, the ratio between the length d1 of the long side and the length d2 of the short side of the rectangular incident surface satisfies the relationship shown in the following equation (i). There is a need. d1: d2 = 3: √ (3) / 2 or 1.5: √ (3) (i) Here, √ (3) represents the square root of 3. Incidentally, the shape of the incident surface of the optical integrator needs to be set to be similar to the shape of the illumination area (illumination field) to be formed on the irradiated surface. Therefore, the incident surface is actually set to a required rectangular shape, and the shape of the exit surface is set to a hexagonal shape close to a regular hexagon according to the shape of the incident surface. Although the case where the exit surface of the optical integrator has a regular hexagonal shape has been described above, the same applies to the case where the exit surface is circular. The exit surface of the optical integrator is preferably similar in shape to the shape of the light source. In the case of a lamp light source, a substantially circular shape or a regular hexagonal shape is effective.

Next, as shown in FIG. 3, a case will be considered in which both the entrance surface and the exit surface of each microlens constituting the optical integrator are formed in a rectangular shape. In this case, the length of the long side of the rectangular incident surface is d1, the length of the short side of the rectangular incident surface is d2, and the length of the rectangular exit surface corresponds to the direction of the long side of the incident surface. D1 is the length along the direction corresponding to the short side direction of the entrance surface of the rectangular exit surface, D2 is the numerical aperture of each microlens, and the focal length of each microlens is f, and the wavelength of the incident light beam is λ, the width b1 along the long side direction and the width b2 along the short side direction of the peripheral portion on the incident surface contributing to the reduction in illuminance due to the diffraction limit are:
It is represented by the following equations (j) and (k). b1 = 0.61 · λ / {(D1 / 2) / f} (j) b2 = 0.61 · λ / {(D2 / 2) / f} (k)

In order to obtain a uniform illuminance distribution over substantially the entire illuminated field formed on the irradiated surface, the width b1 must be smaller than 1/10 of the size d1 in the long side direction of the incident surface. Alternatively, it is desirable that the width b2 is smaller than 1/10 of the size d2 of the incident surface in the short side direction, that is, the following conditional expression (m) or (n) is satisfied. 0.61 · λ / {(D1 / 2) / f} ≦ d1 / 10 (m) 0.61 · λ / {(D2 / 2) / f} ≦ d2 / 10 (n)

By transforming conditional expressions (m) and (n),
The following relational expressions (4) and (5) are obtained. (D1 / 2) (D1 / 2) / (λ · f) ≧ 3.05 (4) (d2 / 2) (D2 / 2) / (λ · f) ≧ 3.05 (5)

Further, in order to obtain a more uniform illuminance distribution over almost the entire illumination field, the width b1 is smaller than 1/100 of the size d1 in the long side direction of the incident surface, or The width b2 is 1 of the size d2 in the short side direction of the incident surface.
/ 100, that is, the following conditional expression (p)
Or it is more desirable that (q) be satisfied. 0.61 · λ / {(D1 / 2) / f} ≦ d1 / 100 (p) 0.61 · λ / {(D2 / 2) / f} ≦ d2 / 100 (q)

By transforming conditional expressions (p) and (q),
The following relational expressions (4 ') and (5') are obtained. (D1 / 2) (D1 / 2) / (λ · f) ≧ 30.5 (4 ′) (d2 / 2) (D2 / 2) / (λ · f) ≧ 30.5 (5 ′)

Finally, as shown in FIG. 4, consider the case where both the entrance surface and the exit surface of each of the microlenses constituting the optical integrator are formed in the same rectangular shape. In this case, the length of the long side of the rectangular entrance surface and the exit surface is d1, the length of the short side of the rectangular entrance surface and the exit surface is d2, the numerical aperture of each microlens is NA, and Let the focal length of the micro lens be f
When the wavelength of the incident light beam is λ, the width b along the long side direction of the peripheral portion on the incident surface that contributes to the reduction in illuminance due to the diffraction limit is expressed by the following equation (r). . b = 0.61 · λ / {(d1 / 2) / f} (r)

In order to obtain a uniform illuminance distribution over substantially the entire illuminated field formed on the illuminated surface, the width b must be smaller than 1/10 of the size d1 of the incident surface in the long side direction. ,
Alternatively, it is desirable that the size is smaller than 1/10 of the size d2 in the short side direction, that is, the following conditional expression (s) or (t) is satisfied. 0.61 · λ / {(d1 / 2) / f} ≦ d1 / 10 (s) 0.61 · λ / {(d2 / 2) / f} ≦ d2 / 10 (t)

By transforming conditional expressions (s) and (t),
The following relational expressions (6) and (7) are obtained. (D1 / 2) ² /(λ·f)≧3.05 (6) (d2 / 2) ² /(λ·f)≧3.05 (7)

Further, in order to obtain a more uniform illuminance distribution over substantially the entire illumination field, the width b is smaller than 1/100 of the size d1 in the long side direction of the incident surface or the short side. It is more desirable that the size is smaller than 1/100 of the size d2 in the direction, that is, the following conditional expression (u) or (v) is satisfied. 0.61 · λ / {(d1 / 2) / f} ≦ d1 / 100 (u) 0.61 · λ / {(d2 / 2) / f} ≦ d2 / 100 (v)

By transforming conditional expressions (u) and (v),
The following relational expressions (6 ′) and (7 ′) are obtained. (D1 / 2) ² /(λ·f)≧30.5 (6 ′) (d2 / 2) ² /(λ·f)≧30.5 (7 ′)

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 5 is a diagram schematically illustrating a configuration of the illumination optical device according to the first embodiment of the present invention. FIG. 6 shows FIG.
1 is a diagram schematically showing a configuration of an epi-illumination type microscope provided with the illumination optical device of FIG. FIG. 7 is a diagram schematically showing a configuration of a transmission illumination type microscope provided with the illumination optical device of FIG. In the first embodiment, the present invention is applied to an illumination optical device of a microscope.

Referring to FIG. 5, the illumination optical device according to the first embodiment includes, for example, a halogen lamp 10 as a light source for supplying illumination light. Halogen lamp 1
The light beam from 0 becomes a substantially parallel light beam via a collimating lens 11 and enters a micro fly's eye 12 as a wavefront splitting optical integrator. As shown in FIGS. 1 and 5, the micro fly's eye 12 is an optical element composed of a large number of microlenses having a positive refractive power arranged densely vertically and horizontally, and each microlens has an entrance surface and an exit surface. Both are formed in a regular hexagonal shape (size d) of the same size. The micro fly's eye 12 is formed by, for example, performing an etching process on a parallel flat glass plate to form a micro lens group.

Therefore, the light beam incident on the micro fly's eye 12 is two-dimensionally divided by a large number of microlenses, and a substantially planar light source (hereinafter referred to as a "secondary light source") comprising a large number of light sources is provided on the rear focal plane. ) Is formed. The luminous flux from the secondary light source formed on the rear focal plane of the micro fly's eye 12 is condensed via a condenser lens 14 after being restricted by an aperture stop 13 disposed in the vicinity thereof, and is then focused on the rear focal plane. The territory is formed. A field stop 15 is disposed at the position where the illumination field is formed (that is, at the rear focal plane of the condenser lens 14). As described above, the collimating lens 11, the micro fly's eye 12, and the condenser lens 14 form a large number of light sources based on the light flux from the light source 10, and form an area on a predetermined surface on which the light flux from the large number of light sources is superimposed. And a multi-beam superimposing means for forming an illumination field.

The luminous flux from the illumination field that has passed through the field stop 15 illuminates an object surface (sample surface) 17 to be observed via an imaging optical system 16. Here, the field stop 15 and the object surface 17 as an irradiation surface are optically conjugated via an imaging optical system 16. Therefore, the object plane 17
On the upper side, an illumination area is formed as an image of the opening of the field stop 15 (that is, an image of an illumination field). An aperture stop 18 is arranged near the pupil plane of the imaging optical system 16 to block unnecessary light that causes flare or the like. Here, if one of the aperture stops 13 and 18 is arranged, the basic performance of the illumination optical device is satisfied. However, in order to favorably suppress the occurrence of flare, both the aperture stops 13 and 18 are arranged. It is desirable to arrange 18. Further, the aperture stops 13 and 18 preferably have a variable aperture.

Referring to FIG. 6, in the epi-illumination type microscope in which the illumination optical device of the first embodiment is incorporated, the light beam from the illumination field formed at the position of the field stop 15 is transmitted to the imaging optical system 16. The light enters the beam splitter 61 via the front lens group 16a. The light flux reflected by the beam splitter 61 illuminates the object plane through the rear lens group 16b of the imaging optical system 16 to illuminate the object plane. The light reflected from the object surface enters the beam splitter 61 via the first objective lens 62 (that is, the rear lens group 16b of the imaging optical system 16). The light transmitted through the beam splitter 61 forms an observation object image 64 via the second objective lens 63. This observation object image 64 is enlarged and observed through the eyepiece 65.

On the other hand, referring to FIG. 7, in a transmission illumination type microscope in which the illumination optical device of the first embodiment is incorporated,
A light beam from the illumination field formed at the position of the field stop 15 illuminates the object plane from below through the imaging optical system 16. The light transmitted through the object surface forms an observation object image 64 via the first objective lens 62 and the second objective lens 63. This observation object image 64 is enlarged and observed through the eyepiece 65. 6 and 7, the aperture stop 18
Are not shown.

In the first embodiment, the micro fly eye 1
2 is configured to satisfy the above conditional expression (1). Therefore, in the illumination field formed at the position of the field stop 15, and further in the illumination area (illumination field) formed on the object plane 17 which is the illuminated surface, the width of the peripheral portion where the illuminance is reduced is suppressed to be small. A uniform illuminance distribution can be obtained over the whole. If the micro fly's eye 12 is configured so as to satisfy the conditional expression (1 '), the width of the peripheral portion where the illuminance is reduced can be further reduced, and a more uniform illuminance distribution can be obtained over almost the entirety. it can.

FIG. 8 is a view schematically showing a configuration of an exposure apparatus provided with an illumination optical device according to a second embodiment of the present invention. In the second embodiment, the present invention is applied to an exposure apparatus for manufacturing a liquid crystal display element using an ultra-high pressure mercury lamp as a light source. Referring to FIG. 8, the apparatus according to the second embodiment includes a light source 20 formed of an ultra-high pressure mercury lamp that supplies light including, for example, an i-line. Light source 20
Is positioned at the first focal position of the elliptical mirror 21 having an elliptical reflecting surface rotationally symmetric with respect to the optical axis AX. Therefore, the illumination light flux emitted from the light source 20 is reflected by the elliptical mirror 21.
The light source image is formed at the second focal position of the light source.

The divergent light beam from the light source image formed at the second focal position of the elliptical mirror 2 is converted into a substantially parallel light beam by the collimating lens 22, and then passed through a wavelength selection filter (not shown) to a wavefront splitting type. To the optical integrator 23. In the wavelength selection filter, only i-line light (365 nm) is selected as exposure light. In addition,
In the wavelength selection filter, for example, g-line (436 nm)
Light, h-line (405 nm) and i-line light can be selected simultaneously, g-line light and h-line light can be selected simultaneously, and h-line light and i-line light can be selected. Light and light can be selected at the same time.

In the optical integrator 23, as shown in FIG. 8, a plane parallel plate 23c having a predetermined thickness is interposed between the first minute lens group 23a on the incident side and the second minute lens group 23b on the exit side. Thus, these are integrally configured. Here, the first minute lens group 23 on the incident side
As shown in FIG. 2 (a), a is composed of a large number of rectangular (d1 × d2) minute lenses having a positive refractive power and arranged densely vertically and horizontally. In addition, the second minute lens group 23 on the emission side
As shown in FIG. 2 (b), b is composed of a large number of regular hexagonal (size D) microlenses having a positive refractive power and densely arranged vertically and horizontally. The first minute lens group 23a on the incident side and the second minute lens group 23b on the exit side are formed by, for example, a molding method such that the optical axes of the corresponding minute lenses exactly match.

In this case, the optical integrator 2
The micro lenses constituting the third micro lens 3 are one of the first micro lenses in the first micro lens group 23a on the incident side and the second micro lens on the exit side.
It is composed of one second minute lens corresponding to the first minute lens in the minute lens group 23b. Further, the focal length of the minute lens constituting the optical integrator 23 is the combined focal length of the first minute lens and the second minute lens. The first minute lens group 23 on the incident side
It is also possible to interpose a parallel flat plate 23c having a predetermined thickness between a and the second microlens group 23b on the emission side, and to join them with an adhesive or the like. For a more detailed configuration of the optical integrator 23, refer to
Reference can be made to the disclosure of JP-A-31736 (for example, FIGS. 6 and 7).

Thus, the optical integrator 2
A secondary light source composed of a large number of light sources is formed on the rear focal plane of No. 3. The light beam from the secondary light source is restricted by an aperture stop 24 arranged near the rear focal plane of the optical integrator 23, and then enters the condenser lens 25. The aperture stop 24 is provided with a projection optical system P described later.
L is disposed at a position optically conjugate to the entrance pupil plane of L (position of the illumination pupil), and has an opening for defining the range of the secondary light source contributing to illumination. The aperture stop 24 is arranged on the front focal plane of the condenser lens 25.

Accordingly, the light beam condensed via the condenser lens 25 illuminates the illumination field stop 26 for defining an illumination area (illumination field) of the mask M described later in a superimposed manner. The light beam passing through the rectangular opening of the illumination field stop 26 illuminates the mask M on which a predetermined transfer pattern is formed in a superimposed manner via the imaging optical system 27. Thus, on the mask M, an image of the opening of the illumination field stop 26, that is, a rectangular illumination area similar to the cross-sectional shape of the first microlens of the optical integrator 23 is formed. An aperture stop 28 is arranged near the pupil plane of the imaging optical system 27 (position optically conjugate with the entrance pupil plane of the projection optical system PL) to block unnecessary light that causes flare or the like. ing.

The mask M is held on a mask stage (not shown) that can move two-dimensionally along the mask surface. The position coordinates of the mask stage are measured and controlled by an interferometer (not shown). The light flux transmitted through the pattern of the mask M forms an image of the mask pattern on the plate P, which is a photosensitive substrate, via the projection optical system PL. The plate P is held on a plate stage (not shown) that can move two-dimensionally along the plate surface. The position coordinates of the plate stage are measured and controlled by an interferometer (not shown).

In this way, by performing the batch exposure or the scan exposure while driving and controlling the plate P two-dimensionally in a plane orthogonal to the optical axis of the projection optical system PL, each exposure region of the plate P The pattern is sequentially exposed. In batch exposure, so-called step-and-
According to the repeat method, the mask pattern is collectively exposed to each exposure area of the plate P. On the other hand, in the scan exposure, according to the so-called step-and-scan method, optical scanning is performed in the short side direction of the rectangular incident surface of the optical integrator 23 (that is, in the short side direction of the rectangular illumination area formed on the mask M). By performing scan exposure while moving the mask M and the plate P relative to the projection optical system PL along a direction (scan direction) corresponding to the target, the pattern of the mask M is exposed in each exposure area of the plate P. It is sequentially exposed.

In the second embodiment, the optical integrator 23 is configured to satisfy at least one of the conditional expressions (2) and (3). Therefore, in the illumination area (exposure area) formed on the mask M, which is the irradiation surface, and thus on the plate P, the width of the peripheral portion where the illuminance decreases is kept small, and the illuminance distribution is uniform over almost the entire area. Can be obtained.
If the optical integrator 23 is configured to satisfy at least one of the conditional expressions (2 ′) and (3 ′), the width of the peripheral portion where the illuminance is reduced is further reduced, and almost the entire width is reduced. It is possible to obtain a more uniform illuminance distribution throughout.

When the scan exposure is performed in the second embodiment, the illuminance distribution along the scan direction (the direction optically corresponding to the short side direction of the rectangular incident surface of the optical integrator 23) depends on the effect of the scan exposure. , The two conditional expressions (2) and (3)
Of these, it is preferable to satisfy the conditional expression (2) along the long side direction of the rectangular incident surface of the optical integrator 23. Similarly, when performing scan exposure in the second embodiment, it is more preferable to satisfy the conditional expression (2 ′).

In the second embodiment, the first minute lens group 23a on the incident side is composed of a large number of rectangular minute lenses, and the second minute lens group 23b on the exit side is composed of a large number of regular hexagonal minute lenses. It is configured. However, as shown in FIG. 3, the first micro lens group 23a on the incident side is composed of many rectangular (d1 × d2) micro lenses, and the second micro lens group 23b on the exit side is composed of many rectangular ( A modified example composed of (D1 × D2) microlenses is also possible. In the case of this modification, it is preferable that at least one of the conditional expressions (4) and (5) is satisfied, and at least one of the conditional expressions (4 ′) and (5 ′) is satisfied. It is more preferable to satisfy the expression. Then, when performing scan exposure in the modified example,
It is preferable to satisfy the conditional expression (4) along the long side direction of the rectangular incident surface, and it is more preferable to satisfy the conditional expression (4 ′).

FIG. 9 is a view schematically showing a configuration of an exposure apparatus provided with an illumination optical device according to a third embodiment of the present invention. In the third embodiment, the present invention is applied to an exposure apparatus for manufacturing a semiconductor device using an excimer laser light source. Referring to FIG. 9, the device of the third embodiment includes:
As the light source 30 for supplying exposure light (illumination light), for example, 248 nm (KrF) or 193 nm (Ar
An excimer laser light source for supplying light having a wavelength of F) is provided. The substantially parallel light beam emitted from the light source 30 is shaped into a light beam having a predetermined rectangular cross section via a beam expander (not shown), and then the micro fly eye 3
Incident on 1.

The micro fly's eye 31 is composed of a large number of square microlenses having a positive refracting power and densely arranged vertically and horizontally. Thus, a large number of light sources are formed on the rear focal plane of the micro fly's eye 31. Light beams from a number of light sources formed on the rear focal plane of the micro fly's eye 31 pass through the first condenser lens 32,
The light enters the wavefront splitting type optical integrator 33. As shown in FIG. 9, the optical integrator 33 includes a first micro fly's eye 33 arranged on the incident side.
a and the second micro fly's eye 33b arranged on the emission side
It is composed of

Here, the first micro fly's eye 33a on the incident side and the second micro fly's eye 33b on the exit side are shown.
Is composed of a large number of rectangular microlenses having positive refractive power, which are densely arranged vertically and horizontally, as shown in FIG. Then, the first micro lens constituting the first micro fly's eye 33a on the incident side and the second micro fly's eye 3
The second micro lens constituting 3b is formed in a rectangular shape (d1 × d2) of the same size. Further, the first micro fly's eye 33 is set so that the optical axis of each first micro lens and the optical axis of each corresponding second micro lens exactly match.
a and the second micro fly's eye 33b are aligned.

In this case, the optical integrator 3
The microlenses constituting No. 3 are composed of a first microlens constituting the first micro fly's eye 33a on the incident side and a second micro lens constituting the second micro fly's eye 33b on the exit side. Then, the optical integrator 33
Is the combined focal length of the first and second microlenses described above. In addition,
It is preferable to dispose a cover glass on the entrance side and the exit side of the optical integrator 33. Also, the first
The radius of curvature of the first micro lens constituting the micro fly's eye 33a and the second micro lens constituting the second micro fly's eye 33b are slightly different from each other so that the front focal position of the micro lens constituting the optical integrator 33 is set to the second position. 1 micro fly eye 33a
In addition, the rear focal point may be configured to be the exit side space of the second micro fly's eye 33b. In this case,
There are advantages in terms of light quantity and laser resistance.

Thus, the optical integrator 3
A secondary light source composed of a large number of light sources is formed on the rear focal plane of No. 3. The luminous flux from the secondary light source is restricted by an aperture stop 34 arranged near the rear focal plane of the optical integrator 33, and then the second condenser lens 35
Incident on. The light beam condensed through the second condenser lens 35 passes through the rectangular opening of the illumination field stop 36, and illuminates the mask M via the imaging optical system 37 in a superimposed manner. Thus, a rectangular illumination area similar to the cross-sectional shape of each microlens of the optical integrator 33 is formed on the mask M. In the vicinity of the pupil plane of the imaging optical system 37, an aperture stop 38 for blocking unnecessary light causing flare or the like is arranged.

The mask M is held on a mask stage (not shown) that can move two-dimensionally along the mask surface. The position coordinates of the mask stage are measured and controlled by an interferometer (not shown). The light flux transmitted through the pattern of the mask M forms an image of the mask pattern on the wafer W as a photosensitive substrate via the projection optical system PL. The wafer W is held on a wafer stage (not shown) that can move two-dimensionally along the wafer surface. The position coordinates of the wafer stage are measured and controlled by an interferometer (not shown).

As described above, the batch exposure or the scan exposure is performed while the wafer W is two-dimensionally driven and controlled in a plane orthogonal to the optical axis of the projection optical system PL. The pattern is sequentially exposed. In the collective exposure, a mask pattern is collectively exposed to each exposure region of the wafer W according to a so-called step-and-repeat method. On the other hand, in the scan exposure, the mask M and the wafer W are moved along a direction (scan direction) optically corresponding to the short side direction of the rectangular incident surface of the optical integrator 33 according to a so-called step-and-scan method. Projection optical system P
By performing the scanning exposure while moving relative to L, the pattern of the mask M is sequentially exposed on each exposure area of the wafer W.

In the third embodiment, the optical integrator 33 is configured to satisfy at least one of the conditional expressions (6) and (7). Therefore, in the illumination area (exposure area) formed on the mask M, which is the irradiation surface, and thus on the wafer W, the width of the peripheral portion where the illuminance decreases is kept small, and the illuminance distribution is uniform over almost the entire area. Can be obtained. Also, the optical integrator 33 satisfies the conditional expression (6 ′).
If at least one of the conditional expressions (7 ′) and (7 ′) is satisfied, the width of the peripheral portion where the illuminance is reduced can be further reduced, and a more uniform illuminance distribution can be obtained over almost the entirety. .

When the scan exposure is performed in the third embodiment, the illuminance distribution along the scan direction (the direction optically corresponding to the short side direction of the rectangular incident surface of the optical integrator 33) depends on the effect of the scan exposure. , The two conditional expressions (6) and (7)
Of these, it is preferable to satisfy the conditional expression (6) along the long side direction of the rectangular incident surface of the optical integrator 23. Similarly, when performing scan exposure in the third embodiment, it is more preferable to satisfy the conditional expression (6 ′).

In the case of scan exposure using a pulse oscillation light source as in the third embodiment, the phase difference between the illumination light of any two adjacent microlenses in the optical integrator 33 changes randomly for each pulse. Is desirable. As shown in FIG. 10, when the numerical aperture of the incident light beam is NA2 and the size of the minute lens along the scanning direction is d2, the coherence area on the incident surface is λ.
/ NA2, it is illuminated with a set of phase differences that differ by d2 / (λ / NA2). It is necessary that the number of the sets is at least 10 or more, that is, the following conditional expression (8) is satisfied. Further, it is more desirable that the lower limit value of conditional expression (8) is equal to or larger than the number of pulses (usually 30 to 50). 10 <d2 / (λ / NA2) (8)

In each of the above embodiments, the present invention is applied to an illumination optical device of a microscope or an exposure apparatus. However, the present invention is not limited to this, and may be applied to other general illumination optical devices. Can be applied.

In the above-described second and third embodiments, the light from the peripheral portion where the illuminance is low in the illumination field formed on the rear focal plane of the condenser lenses 25 and 35 is reduced by the aperture stop 24. And 34 may or may not be blocked. When the light beam from the peripheral portion is blocked, the width of the peripheral portion where the illuminance is reduced according to the present invention is kept small, so that the light amount loss in the aperture stops 24 and 34 can be kept small.

[0066]

As described above, in the optical integrator according to the present invention, even if the size of each microlens is reduced and the number of wavefront divisions is set to be large, a uniform illumination field is formed over substantially the entire illumination field. An illuminance distribution can be obtained. Therefore, the illumination optical device incorporating the optical integrator of the present invention can illuminate the irradiated surface with a uniform illuminance distribution over almost the entirety. Further, in the exposure apparatus incorporating the illumination optical device of the present invention,
The mask is illuminated with a uniform illuminance distribution over almost the entirety, and a fine pattern of the mask can be transferred well.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which an entrance surface and an exit surface of each microlens are formed in a regular hexagonal shape of the same size in an optical integrator.

FIG. 2 is a diagram showing a state in which an entrance surface of each microlens is formed in a rectangular shape and an exit surface thereof is formed in a regular hexagonal shape in the optical integrator.

FIG. 3 is a diagram illustrating a state in which both an entrance surface and an exit surface of each microlens are formed in a rectangular shape in the optical integrator.

FIG. 4 is a diagram showing a state in which an entrance surface and an exit surface of each microlens of each microlens are formed in a rectangular shape having the same size in the optical integrator.

FIG. 5 is a diagram schematically showing a configuration of an illumination optical device according to the first embodiment of the present invention.

6 is a diagram schematically showing a configuration of an epi-illumination type microscope provided with the illumination optical device of FIG.

7 is a view schematically showing a configuration of a transmission illumination type microscope including the illumination optical device of FIG. 5;

FIG. 8 is a diagram schematically illustrating a configuration of an exposure apparatus including an illumination optical device according to a second embodiment of the present invention.

FIG. 9 is a diagram schematically illustrating a configuration of an exposure apparatus including an illumination optical device according to a third embodiment of the present invention.

FIG. 10 is a diagram illustrating a numerical aperture of a light beam incident on any two adjacent minute lenses in the optical integrator and a size of the minute lens in a scanning direction.

[Description of Signs] 10, 20, 30 Light source 12, 23, 33 Optical integrator 13, 24, 34 Aperture stop 14, 25, 35 Condenser lens 15, 26, 36 Field stop 16, 27, 37 Imaging optical system 18, 28,38 aperture stop M mask PL projection optical system P plate W wafer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H052 AC18 BA02 BA03 BA07 BA09 BA12 5F046 BA03 CA02 CB05 CB08 CB12 CB13 CB23

Claims (9)

[Claims] 1. A wavefront splitting optical integrator having a plurality of two-dimensionally arrayed microlenses and splitting an incident light beam into a wavefront to form a plurality of light sources. Surface and a rectangular exit surface, the focal length of each microlens is f, the length of one side of the entrance surface of each microlens is d1, and the length of the other side of the entrance surface of each microlens is D2, and the length of the side corresponding to one side of the incident surface on the exit surface of each microlens is D1.
When the length of the side corresponding to the other side of the entrance surface on the exit surface of each microlens is D2 and the wavelength of the incident light beam is λ, (d1 / 2) (D1 / 2) / ( An optical integrator that satisfies at least one of the following conditions: λ · f) ≧ 3.05 (d2 / 2) (D2 / 2) / (λ · f) ≧ 3.05. 2. The length d1 of one side of the incident surface is substantially larger than the length d2 of the other side of the incident surface, and (d1 / 2) (D1 / 2) / (λ · 2. The optical integrator according to claim 1, wherein a condition of f) ≧ 3.05 is satisfied. 3. A wavefront splitting optical integrator having a plurality of two-dimensionally arrayed microlenses and splitting an incident light beam into a wavefront to form a plurality of light sources. Surface, and a circular or regular hexagonal exit surface, the focal length of each microlens is f, the length of one side of the entrance surface of each microlens is d1, and the entrance surface of each microlens is When the length of the other side is d2, the diameter of the circular exit surface of each microlens or the diameter of a circle circumscribing the regular hexagonal exit surface is D, and the wavelength of the incident light beam is λ, d1 / 2) (D / 2) / (λ · f) ≧ 3.05 (d2 / 2) (D / 2) / (λ · f) ≧ 3.05 Optical integrator characterized by the following. 4. The length d1 of one side of the incident surface is substantially larger than the length d2 of the other side of the incident surface, and (d1 / 2) (D / 2) / (λ · 4. The optical integrator according to claim 3, wherein the condition of f) ≧ 3.05 is satisfied. 5. A wavefront splitting optical integrator having a plurality of two-dimensionally arranged microlenses and dividing an incident light beam into a plurality of light sources, wherein each microlens has a diameter of d. It has a regular hexagonal entrance surface inscribed in a circle or a circle having a diameter d, and a regular hexagonal exit surface inscribed in a circle having a diameter d or a circle having a diameter d. The focal length of each microlens Where f is the wavelength of the incident light beam and λ is the wavelength of the incident light beam, and the following condition is satisfied: (d / 2) ² /(λ·f)≧3.05. 6. A light source means for supplying a light beam, an optical integrator according to claim 1 for forming a large number of light sources based on a light beam from said light source means, A light guiding optical system for guiding light beams from a number of light sources to the surface to be illuminated; 7. A condenser optical system for condensing light beams from the plurality of light sources to form an illumination field in a superimposed manner, and the light guide optical system based on the light beams from the illumination field. An imaging optical system for forming an image of the illumination field on the irradiation surface, and unnecessary at a position optically substantially conjugate to the formation positions of the multiple light sources in the optical path of the imaging optical system. The illumination optical device according to claim 6, further comprising an aperture stop for blocking a light beam. 8. An illumination optical device combined with an exposure device having a projection optical system for forming an image of a pattern on a mask disposed on a surface to be irradiated on a photosensitive substrate, wherein a light source means for supplying a light beam; A plurality of light sources based on the light beams from the light source means, and a multi-beam superimposing means for forming an illumination field which is an area on a predetermined surface on which the light beams from the many light sources are superimposed; and An illumination imaging optical system that forms an image of the illumination field in the vicinity of the mask, wherein the illumination imaging optical system has an aperture stop disposed at a position optically conjugate with a pupil of the projection optical system. An illumination optical device, comprising: 9. An illumination optical device according to claim 6, further comprising: a projection optical system for projecting and exposing a mask pattern set on the irradiation surface onto a photosensitive substrate. An exposure apparatus, comprising: