JPH09326352A - Illumination optics - Google Patents

Abstract

(57) Abstract: An illumination optical device capable of illuminating an elongated rectangular region with high illumination efficiency by using a circular light source such as a mercury lamp. A multi-light source image forming means is arranged in order from a light source side.
A first lens group formed of an assembly of a plurality of first lens elements having a predetermined rectangular cross section, and a plurality of second lens elements having a predetermined hexagonal cross section or a predetermined polygonal cross section having seven or more sides. And a second lens group composed of an aggregate. The optical axis of each of the plurality of first lens elements is substantially parallel to the optical axis of the illumination optical device and substantially coincides with the optical axis of the corresponding second lens element of the plurality of second lens elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical apparatus, and more particularly to an illumination optical apparatus suitable for a projection exposure apparatus used in the manufacturing process of semiconductor elements, liquid crystal display elements and the like.

[0002]

2. Description of the Related Art Conventionally, there is known a projection exposure apparatus of a so-called step-and-repeat system which sequentially projects and exposes an entire mask pattern onto each shot area of a photosensitive substrate. Further, in recent years, a scan type projection exposure apparatus has been proposed in order to realize higher throughput while ensuring higher resolution. In the scanning type projection exposure apparatus, projection exposure is performed while scanning the mask and the photosensitive substrate with respect to the projection optical system. At this time, the region illuminated by the illumination optical device on the mask, that is, the illumination region, has an elongated rectangular shape having a short side along the scanning direction and a long side along the direction orthogonal to the scanning direction. It is common.

[0003]

Therefore, in the scan type projection exposure apparatus, the fly-eye integrator is constituted by a group of lens elements having a rectangular cross section similar to the shape of the illumination area, so that the light amount loss can be avoided as much as possible. Therefore, it is desirable to secure a predetermined lighting efficiency. However, when a circular light source having a predetermined size such as a mercury lamp is used, a conventional fly-eye integrator including a lens element having a rectangular cross section causes a significant loss of light amount at its exit surface. Therefore, the present applicant has disclosed an illumination optical device equipped with a fly-eye integrator having a special configuration in order to avoid the above-described loss of light amount on the exit surface of the fly-eye integrator as much as possible (Japanese Patent Laid-Open No. 8-31736). Issue).

In the illumination optical device disclosed in Japanese Patent Laid-Open No. 8-31736, a lens element having a rectangular cross section similar to the shape of the illumination area is arranged on the incident side of the fly-eye integrator. On the other hand, on the exit side of the fly-eye integrator, a lens element having a rectangular cross section that includes the formed circular light source image as much as possible is arranged. As described above, by using the fly-eye integrator having the entrance-side lens element and the exit-side lens element having different cross-sectional shapes, it is possible to reduce the light amount loss on the exit surface and increase the illuminance in the illumination area. However, due to restrictions on the power (refractive power) of the relay lens of the illumination optical device, multiple circular light source images formed on the exit surface of the fly-eye integrator overlap each other, so avoiding a certain amount of light loss on the exit surface. I couldn't.

The present invention has been made in view of the above problems, and an object thereof is to provide an illumination optical device capable of illuminating an elongated rectangular region with high illumination efficiency using a circular light source such as a mercury lamp. And

[0006]

In order to solve the above problems, in the present invention, a substantially circular light source having a predetermined size and a plurality of light source images are formed based on the light flux from the light source. And a condenser optical system for converging light fluxes from the plurality of light source images formed through the multi-light source image forming means to illuminate a surface to be illuminated in a superimposed manner. In the illumination optical device, the multi-light source image forming means includes, in order from the light source side, a first lens group formed of an assembly of a plurality of first lens elements having a predetermined rectangular cross section, and a predetermined hexagonal cross section or seven A second lens group composed of an assembly of a plurality of second lens elements having a predetermined polygonal cross section having the above sides, and the optical axis of each of the plurality of first lens elements is the illumination optical device. Almost flat with the optical axis of In, and to provide an illumination optical apparatus characterized by substantially coincides with the optical axis of the corresponding second lens element of the plurality of second lens elements.

According to a preferred aspect of the present invention, in the plurality of first lens elements, the short sides of the rectangular cross section of each first lens element are in contact with each other, and each first lens element is in contact with each other.
The long sides of the rectangular cross section of the lens element are adjacent 4
A plurality of second lens elements arranged so as to abut half of corresponding long sides of the rectangular cross-sectional shape of the two first lens elements.
The lens elements are arranged such that each side of the hexagonal cross-sectional shape of each second lens element abuts a corresponding side of the hexagonal cross-sectional shape of the adjacent six second lens elements.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a multi-light source image forming means such as a fly-eye integrator is arranged in order from the light source side.
It has a first lens group composed of an assembly of a plurality of first lens elements, and a second lens group composed of an assembly of a plurality of second lens elements. Here, the optical axis of each of the first lens elements substantially coincides with the optical axis of the corresponding second lens element. Then, each first lens element has a predetermined rectangular cross section similar to the shape of the illumination region to be formed on the illuminated surface. Further, each second lens element has a predetermined hexagonal cross section or seven or more hexagonal cross sections so as to include each circular light source image formed on the exit surface of the fly-eye integrator (that is, the exit surface of the second lens element) as much as possible. It has a predetermined polygonal cross section with sides.

Specifically, the first lens element is linearly arranged such that the short sides of its cross-sectional shape are in contact with each other. In addition, each of the linearly arranged first lens elements is arranged such that the long sides of the cross-sectional shape thereof are offset from each other by half and contact each other.
Further, the plurality of second lens elements are arranged so that the respective sides of the cross-sectional shape are in contact with each other. As described above, in the illumination optical device of the present invention, the first lens element has a rectangular cross section similar to the shape of the illumination region, and the second lens element has a hexagonal cross section that includes a circular light source image as much as possible. Therefore, even if a circular light source such as a mercury lamp is used, the light amount loss is suppressed on the exit surface of the fly-eye integrator, and the elongated rectangular region can be illuminated with high illumination efficiency.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view schematically showing a configuration of an illumination optical device according to an embodiment of the present invention. In FIG. 1, the Z axis is set along the optical axis AX, and the X axis and the Y axis are set in directions orthogonal to each other in a plane perpendicular to the optical axis AX.
In addition, FIG. 2 shows the second fly-eye integrator 7 of FIG.
It is the figure which looked at the central part along with optical axis AX. This embodiment shows an example in which the illumination optical device is applied to a projection exposure apparatus for manufacturing a semiconductor element.

The illustrated illumination optical device includes a light source 1 which is, for example, a mercury lamp. The light source 1 is positioned at a first focus position of a condenser mirror (elliptic mirror) 2 having a reflecting surface formed of a spheroidal surface. Therefore, the illumination light flux emitted from the light source 1 forms a substantially circular light source image at the second focal position of the elliptical mirror 2. At the second focal position of the elliptical mirror 2 on which a circular light source image is formed, a shutter 3 having a circular opening portion having substantially the same size as the light source image is provided. Therefore, by selectively opening and closing the opening of the shutter 3, the light from the light source 1 is effectively captured and made incident on the subsequent collimator lens 4, or the incidence on the collimator lens 4 is completely blocked. You can The state in which the opening of the shutter 3 is open will be described below.

In the opened state of the shutter 3, the light flux from the light source image is condensed through the collimator lens 4 and then
It is incident on the first fly-eye integrator 5. The light flux that has entered the first fly-eye integrator 5 is two-dimensionally divided by the plurality of lens elements that form the first fly-eye integrator 5. Then, a plurality of light source images corresponding to the number of lens elements are formed at the rear focus position of the first fly-eye integrator 5 (that is, near the exit surface). The cross section of the light flux incident on the first fly-eye integrator 5 is substantially circular, and the light source image formed on its exit surface is also substantially circular. Therefore, each lens element forming the first fly-eye integrator 5 has a square cross section, and the entire shape of the first fly-eye integrator 5 is substantially circular.

Light fluxes from a plurality of light source images formed on the exit surface of the first fly-eye integrator 5 are condensed via a relay lens 6 and then illuminate the second fly-eye integrator 7 in a superimposed manner. The second fly-eye integrator 7 includes, in order from the light source side, a first lens group 71 including an assembly of first lens elements 7a having an elongated rectangular cross section, a plane parallel plate 72, and a second lens element having a hexagonal cross section. Second lens group 73 composed of an assembly of 7b
It is composed of

The first lens element 7a is a plano-convex lens having a convex surface facing the light source side, and the plane of this plano-convex lens is supported by the surface of the plane parallel plate 72 on the light source side. The second lens element 7b is a plano-convex lens having a flat surface facing the light source side, and the flat surface of the plano-convex lens is supported by the exit side surface of the plane-parallel plate 72. The number of the first lens elements 7a is equal to the number of the second lens elements 7b, and the second lens elements 7a corresponding to the optical axes of the respective first lens elements 7a
The optical axis of the lens element 7b is parallel to the optical axis AX and coincides with each other.

Still referring to FIG. 2, the cross-sectional shape of each first lens element 7a has long sides in the X direction and Y
It is an elongated rectangle having a short side in the direction. And the first
The lens element 7a is linearly arranged along the Y direction so that the short sides of the cross-sectional shape contact each other. In addition, each first lens element 7a linearly arranged along the Y direction abuts half of the corresponding long sides of the cross-sectional shapes of the four first lens elements 7a whose long sides of the cross-sectional shape are adjacent. Thus, they are arranged alternately along the X direction. On the other hand, the second lens element 7
The cross-sectional shape of b is hexagonal, and the side of the cross-sectional shape of each second lens element 7b is arranged so as to abut the corresponding side of the six adjacent second lens elements 7b.

Therefore, the light beam incident on the second fly-eye integrator 7 is two-dimensionally divided by the plurality of first lens elements 7a forming the first lens group 71, and is subjected to the condensing action. Next, each of the divided light fluxes passes through the plane-parallel plate 72, and then the second lens group 7
Each of the plurality of second lens elements 7b forming the third lens element 7b enters the corresponding second lens element 7b. The light flux incident on each second lens element 7b forms a plurality of light source images corresponding to the number of lens elements of the first fly-eye integrator 5 in the vicinity of the exit surface thereof.
That is, in the vicinity of the exit surface of the second fly-eye integrator 7, a number of light source images represented by the product of the number of lens elements of the first fly-eye integrator 5 and the number of lens elements of the second fly-eye integrator 7. It is formed.

The light beams from a large number of light source images formed on the exit surface of the second fly-eye integrator 7 are subjected to the condensing action of the condenser lens 8 and then superposed on the mask 9 on which a predetermined circuit pattern is formed. Uniform illumination. In this way, the second fly-eye integrator 7 is placed on the mask 9.
An elongated rectangular illumination area similar to the cross-sectional shape of each first lens element 7a forming the first lens group 71 is formed. The light flux that has passed through the mask 9 forms an image of the mask pattern on the photosensitive substrate via a projection optical system (not shown).

FIG. 3 shows the second fly-eye integrator 7.
FIG. 9 is a diagram schematically showing the overall shape of a light source image formed on the exit surface of each second lens element 7b that constitutes the central portion of FIG. As described above, a plurality of light source images corresponding to the number of lens elements of the first fly-eye integrator 5 are formed on the exit surface of each second lens element 7b. Therefore, on the exit surface of each second lens element 7b,
A substantially circular light source image (consisting of a plurality of light source images corresponding to the number of lens elements of the first fly-eye integrator 5) corresponding to the entire shape of the first fly-eye integrator 5 is formed. In FIG. 3, for simplicity of explanation, the overall shape of the light source image formed on the exit surface of each second lens element 7b is approximated by a circle.

As shown in FIG. 3, a substantially circular light source image is formed on the exit surface of the second fly-eye integrator 7 so as to partially overlap each other. The degree of overlap of the circular light source images on the exit surface of the second fly-eye integrator 7 depends on the specifications of the optical members designed to suppress the light amount loss as much as possible. FIG.
It is a figure explaining the light quantity loss in the exit surface of the fly eye integrator disclosed by Japanese Patent No. 736. FIG. 5 is a diagram for explaining the light amount loss on the exit surface of the second fly-eye integrator 7 according to the present embodiment.

As shown in FIG. 4 (a), Japanese Patent Laid-Open No. 8-31
In the illumination optical device disclosed in Japanese Patent No. 736, each lens element on the exit side of the fly-eye integrator has a rectangular cross section. Each lens element is arranged so as to include the circular light source image formed on its exit surface along the long side direction. Therefore, as shown in FIG. 4B, both ends (indicated by hatched portions in the figure) along the short side direction of each lens element in the circular light source image are considered to be a cause of light amount loss without contributing to illumination. Become. JP-A-8-317
In the case of the illumination optical device disclosed in Japanese Patent Laid-Open No. 36-36, when a trial calculation is performed based on a typical design example, the light amount loss on the exit surface of the fly-eye integrator is about 14%.

On the other hand, as shown in FIG. 5A, in the illumination optical apparatus according to this embodiment, each lens element 7b on the exit surface side of the second fly-eye integrator 7 has a hexagonal cross section. Each lens element 7b is arranged so as to substantially include the circular light source image formed on its exit surface. Therefore, as shown in FIG.
Of the circular light source image, the portion protruding from the exit surface of each lens element 7b, that is, the portion that causes the light amount loss without contributing to the illumination is small. In the case of the present embodiment, a trial calculation based on a typical design example shows that the light amount loss on the exit surface of the second fly-eye integrator 7 is about 6%.

In the embodiment described above, the first fly-eye integrator 5 and the relay lens 6 are interposed in the optical path between the shutter 3 and the second fly-eye integrator 7. However, the first fly-eye integrator 5 and the relay lens 6 are omitted, and the shutter 3
Also, the light flux that has passed through the collimator lens 4 can be directly incident on the second fly-eye integrator 7.

Further, in the above-described embodiment, the second lens element of the second fly-eye integrator 7 has a hexagonal sectional shape. However, depending on the arrangement of the circular light source image formed on the exit surface of the second fly-eye integrator 7, the cross-sectional shape of the second lens element is a polygon based on a hexagon (a polygon having seven or more sides). ). Furthermore, in the above-mentioned embodiments, the present invention is applied to the illumination optical device for the projection exposure apparatus, but the present invention can also be applied to other suitable illumination optical devices.

[0024]

As described above, according to the present invention, the first lens element has a rectangular cross section similar to the shape of the illumination area, and the second lens element has a hexagonal cross section that includes a circular light source image as much as possible. Have. Therefore, even if a circular light source such as a mercury lamp is used, the light amount loss is suppressed on the exit surface of the fly-eye integrator, and it is possible to illuminate an elongated rectangular region with high illumination efficiency and little unevenness in illuminance.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a configuration of an illumination optical device according to an embodiment of the present invention.

FIG. 2 is a diagram of a central portion of a second fly-eye integrator 7 in FIG. 1 viewed along an optical axis AX (Z axis).

FIG. 3 is a diagram schematically showing the overall shape of a light source image formed on the exit surface of each second lens element 7b forming the central portion of the second fly-eye integrator 7.

FIG. 4 is a diagram illustrating a light amount loss on an exit surface of a fly-eye integrator disclosed in Japanese Patent Laid-Open No. 8-31736.

FIG. 5 is a diagram illustrating a light amount loss on the exit surface of the second fly-eye integrator 7 according to the embodiment of the present invention.

[Explanation of symbols]

 1 Light Source 2 Elliptical Mirror 3 Shutter 4 Collimator Lens 5 First Fly-Eye Integrator 6 Relay Lens 7 Second Fly-Eye Integrator 8 Condenser Lens 9 Mask 71 First Lens Group 72 Parallel Plane Plate 73 Second Lens Group 7a First Lens Element 7b Second lens element

Claims (2)

[Claims] 1. A substantially circular light source having a predetermined size, a multi-light source image forming means for forming a plurality of light source images based on a light flux from the light source, and the multi-light source image forming means. In an illumination optical device comprising a condenser optical system for converging light fluxes from the formed plurality of light source images and illuminating a surface to be illuminated in a superimposed manner, the multi-light source image forming means is arranged from the light source side. In order, a first lens group composed of an assembly of a plurality of first lens elements having a predetermined rectangular section, and a plurality of second lenses having a predetermined hexagonal section or a predetermined polygonal section having seven or more sides. A second lens group composed of an assembly of elements, wherein an optical axis of each of the plurality of first lens elements is substantially parallel to an optical axis of the illumination optical device, and the plurality of second lens groups are provided.
An illuminating optical device characterized in that it substantially coincides with an optical axis of a corresponding second lens element of the lens elements. 2. The plurality of first lens elements are composed of four first lens elements in which short sides of a rectangular cross section of each first lens element are in contact with each other and long sides of a rectangular cross section of each first lens element are adjacent to each other. The plurality of second lens elements are arranged so as to contact half of the corresponding long sides of the rectangular cross-sectional shape of the first lens element, and the plurality of second lens elements have six hexagonal cross-sectional shapes adjacent to each other. The illumination optical device according to claim 1, wherein the illumination optical device is arranged so as to come into contact with a corresponding side of the hexagonal sectional shape of the second lens element.