JPH07263312A - Lighting optical device - Google Patents

Abstract

PURPOSE:To irradiate an area to be irradiated having a rectangular shape, circular-arcuate shape, etc., on a surface to be irradiated with light in a highly uniform illuminance distribution and at high lighting efficiency by using a light source which emits a luminous flux having, for example, a circular cross section. CONSTITUTION:A luminous flux from a light source 11 is supplied to an optical integrator 2 having a square cross section after condensing the luminous flux with an elliptic mirror 12 and converting the luminous flux into a parallel luminous flux through a collimator lens 13. The luminous flux from the integrator 2 is supplied to another optical integrator 4 through a relay optical system 3 and the luminous flux from the integrator 4 is supplied to a third optical integrator 6 through another relay optical system 5. Then a rectangular area 8 to be irradiated is irradiated with the luminous flux from the integrator 6 through a condenser optical system 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating optical device for illuminating, for example, a rectangular or arcuate illumination area on a surface to be illuminated, and more particularly, exposure for producing a semiconductor element or a liquid crystal display element. It is suitable for application to the illumination system of the device.

[0002]

2. Description of the Related Art In an illumination system for an exposure apparatus used in a photolithography process for manufacturing a semiconductor device, a liquid crystal display device, etc., a reticle (or photomask, etc.) pattern is formed at a high resolution on a substrate (wafer) to be exposed. , Glass plate, etc.), it is required to increase the uniformity of illuminance distribution in the illumination area on the reticle. Furthermore,
In order to extend the life of the exposure light source, it is necessary to guide the illumination light from the exposure light source to the illumination area with high efficiency. Further, as a conventional exposure apparatus, a projection exposure apparatus (stepper or the like) that collectively exposes a reticle pattern to each shot area of a substrate to be exposed has been widely used.

FIG. 5A shows an illumination system used in a conventional collective exposure type exposure apparatus. In FIG. 5A, a light source 11 such as a mercury lamp is placed at the first focal point of an elliptical mirror 12. It is arranged. The light flux emitted from the light source 1 is condensed by the elliptical mirror 12 at the second focal point, and then converted into a parallel light flux by the collimator lens 13. This parallel light flux enters a fly-eye lens 63 composed of an assembly of lens elements 63a having a rectangular cross section, and the fly-eye lens 6
A plurality of light source images are formed on the exit side of 4. An aperture stop 91 having a circular opening is arranged at this light source image position, and the light flux from the light source image in the aperture stop 91 is condensed by a condenser lens 92 to superimpose a reticle R as an irradiated object. Illumination with uniform illuminance.

Under the illumination light, the circuit pattern on the reticle R is transferred onto the wafer W via the projection optical system 93 including the lenses 93a and 93b. The wafer W is
The wafer W is placed in a two-dimensional plane perpendicular to the optical axis of the projection optical system 93.
Is placed on the wafer stage WS which positions the wafer, and when exposure to one shot area on the wafer W is completed,
Exposure is performed by a so-called step-and-repeat method in which another shot area to be exposed on the wafer W is moved to the exposure field of the projection optical system 93 by the wafer stage WS.

In this case, the condenser lens 92 sets the illumination area on the reticle R and the entrance surface of each lens element 93a forming the fly-eye lens 63 to be conjugate with each other. The illumination area on the reticle R is substantially square, and the cross-sectional shape of each lens element 93a of the fly-eye lens 93 (that is, the cross-sectional shape of the incident surface) is also substantially square in order to improve the illumination efficiency. In addition, after being condensed by the elliptical mirror 12, the cross-sectional shape of the light flux passing through the collimator lens 13 is substantially circular, and in order to improve the utilization efficiency of the light flux, as shown in FIG.
The outer shape of the cross section of the fly-eye lens 63 was substantially circular.

[0006]

When the illumination area on the reticle is substantially square as described above, a one-stage fly-eye lens is used to obtain relatively high illuminance distribution uniformity and illumination light. It is possible to improve the utilization efficiency of the and to illuminate the illumination area. By the way, recently, a rectangular or arcuate illumination area on a reticle is illuminated by an illumination system, the reticle is scanned with respect to this illumination area, and an exposure area which is conjugate with the illumination area is exposed in synchronization. An exposure apparatus of a scanning exposure type such as a slit scan type or a step-and-scan type which performs exposure while scanning a substrate is drawing attention. According to such a scanning exposure method, for example, a large reticle pattern can be exposed with a high throughput, and a reticle pattern can be exposed on a substrate to be exposed in a region wider than the exposure field of the projection optical system.

In this case, for example, in FIG. 5A, if the shape of the illumination area on the reticle R is rectangular, in order to improve the utilization efficiency of the illumination light, the illumination area and the fly-eye lens 63 are used. It is desirable that the cross-sectional shape of each of the lens elements 63a is conjugated (similar). Therefore, instead of the fly-eye lens 63, FIG.
It is desirable to use a fly-eye lens 94 having a configuration in which lens elements 94a having a rectangular cross section are bundled as shown in FIG.

However, when the fly-eye lens 94 having the cross-sectional shape as shown in FIG. 5 (c) is used, the number of lens elements arranged in the vertical direction and the number of lens elements arranged in the horizontal direction are significantly different from each other. The number of light fluxes from the light source image to be superimposed greatly differs in the vertical direction and the horizontal direction. Therefore, in the rectangular illumination area on the reticle R, the illuminance distribution uniformity is greatly different between the longitudinal direction and the short side direction, and as a result, uneven illumination occurs.

In this regard, the present applicant has filed Japanese Patent Application No. 5-19
No. 098, 2 optical integrators
We have proposed an illuminating optical device that has a tiered arrangement and has uniform illuminance distribution in the vertical and horizontal directions. However, in this illumination optical device, the outer shape may be a rectangular shape as the first-stage optical integrator. As shown in FIG. 5, the first-stage optical integrator with a rectangular outer shape is used.
When supplying a light flux having a substantially circular cross-sectional shape emitted from the collimator lens 13 of (a), it is conceivable that the light flux is converted into a light flux having an elliptical cross-sectional shape through a beam expander. Even if the cross-sectional shape is elliptical as described above, there is a disadvantage that the light amount loss in the optical integrator at the first stage is large.

In view of the above point, the present invention provides a high illuminance when illuminating a rectangular or arcuate illumination area on a surface to be illuminated using a light source that supplies a light flux having a circular cross section, for example. An object of the present invention is to provide an illumination optical device capable of illuminating the illuminated area with uniform distribution and high illumination efficiency.

[0011]

An illumination optical apparatus according to the present invention includes, for example, as shown in FIG. 1, a light source system (1) for supplying light having a light flux cross section of a predetermined shape (circular shape, etc.), and this light source system. From the light flux from the first multi-light source image forming means (2) forming a plurality of light source images arranged in a substantially square shape or a substantially circular shape, and the light flux from the first multi-light source image forming means,
Second multi-light source image forming means (4) for forming a plurality of light source images arranged in a substantially rectangular shape or a substantially straight shape, and a light flux from the second multi-light source image forming means into a substantially square shape or a substantially circular shape. Third multi-light source image forming means (6) for forming a plurality of arranged light source images, and condenser optics for condensing light fluxes from the plurality of third multi-light source image forming means to illuminate the irradiated surface (R). The system (7) and the position of the light source image formed by the first multi-source image forming means (2) disposed between the first and second multi-source image forming means and the second multi-source image forming means ( 4)
A first relay optical system (3) for conjugating the position of the light source image formed by the second multi-light source image forming means (3). 4)
And a second relay optical system (5) for making the position of the light source image formed by (3) and the position of the light source image formed by the third multi-light source image forming means (6) conjugate.

In this case, one example of the first multi-light source image forming means (2) is a plurality of lens elements (2 having a rectangular cross section.
a). An example of the second multi-light source image forming means (4) is composed of a plurality of lens elements (4a) arranged in at least one row. An example of the third multi-light source image forming means (6) is composed of a plurality of lens elements (6a) having a rectangular cross section.

Further, at least one of the first, second and third multi-light source image forming means is constituted by an internal reflection type optical member (21, 41, 61) as shown in FIG. 3, for example. May be.

[0014]

According to the present invention, the first multi-light source image forming means (2) forms a plurality of light source images arranged in a substantially square or circular shape from the light flux supplied from the light source system (1). To do. That is, when the first multi-light source image forming means (2) is a fly-eye lens, its outer shape is substantially square or circular. Therefore, even if the cross-sectional shape of the light beam supplied from the light source system (1) is, for example, a circular shape, most of the light beam is incident on the first multi-light source image forming means (2), and the light amount loss is small, High lighting efficiency.

Further, a plurality of light source images arranged in a substantially rectangular shape or a linear shape by the second multi-light source image forming means (4) from the light fluxes from the plurality of light source images by the first multi-light source image forming means (2). Is formed. At this time, by adjusting the vertical and horizontal arrangement pitches of the light source images by the second multi-light source image forming means (4), it is possible to reduce the light amount loss on the incident surface of the second multi-light source image forming means (4). Similarly, by adjusting the vertical and horizontal arrangement pitch of the light source images by the third multi-light source image forming means (6), it is possible to reduce the light amount loss on the incident surface of the third multi-light source image forming means (6). Further, since a large number of light source images formed by the second multi-light source image forming means (4) are arranged in a substantially rectangular or linear shape, an area including a rectangular or arcuate illumination area on the irradiated surface (R). Can be illuminated with a uniform illuminance distribution and high illumination efficiency.

Next, when the first and second multi-light source image forming means (2, 4) each comprise a fly-eye lens,
The incident surfaces of the individual lens elements (2a) constituting the first fly-eye lens (2) are respectively conjugated with the incident surface (the outer shape is substantially rectangular or linear) of the second fly-eye lens (4). . Therefore, by making the cross-sectional shape of the lens element (2a) of the first fly-eye lens (2) rectangular (or linear), the illumination efficiency is increased.

In this case, the second fly-eye lens (4)
The outer shape of the second fly-eye lens (4) is substantially rectangular or linear, but the second fly-eye lens (4) can be configured by arranging the lens elements (4a) in one row or a plurality of rows. Next, when the third multi-light source image forming means (6) is composed of a fly's eye lens, the incident surfaces of the individual lens elements (6a) constituting this fly's eye lens (6) are respectively on the irradiated surface (R). It becomes conjugate with the illumination area of. Therefore, by making the cross-sectional shape of the lens element (6a) of the third fly-eye lens (6) rectangular, it is possible to illuminate a rectangular illumination area on the irradiated surface (R) with high illumination efficiency.

Further, at least one of the first, second and third multi-light source image forming means is provided with an internal reflection type optical member (21, 41, 61) such as a rod integrator as shown in FIG. In the case of (1), a plurality of light source images (including virtual images) are formed on the incident surface side of the internal reflection type optical members (21, 41, 61). Therefore, the irradiated surface (R) is the same as when using the fly-eye lens.
The upper illumination area can be illuminated with high uniformity of illuminance distribution.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the illumination optical device according to the present invention will be described below with reference to FIG. The present embodiment is an application of the illumination optical device of the present invention to an illumination system of an exposure apparatus for semiconductor manufacturing. FIG. 1A shows an illumination optical apparatus of the present embodiment. In FIG. 1A, a light source system 1 is an elliptical mirror 12, and a g-line (436 nm) is arranged at a first focus position of the elliptic mirror 12. , I-line (365 nm) or h-line (407
(nm) etc., and a collimator lens 13 and a light source 11 such as a mercury lamp for outputting a light flux (exposure light). The light beam output from the light source 11 forms a light source image at the second focal position of the elliptic mirror 12 by the condensing action of the elliptic mirror 12, and the light beam from this light source image is converted into a parallel light beam by the collimator lens 13. The parallel light flux enters a fly-eye lens type optical integrator 2 as a first multi-light source forming means for forming a plurality of light source images arranged in a substantially square shape. The Y axis is taken parallel to the optical axis of this illumination optical device, the X axis is taken perpendicular to the Y axis and parallel to the paper surface of FIG. 1 (a), and the Y axis is perpendicular to the paper surface of FIG. 1 (a). Take the Z axis vertically.

As shown in FIG. 1B, the optical
The integrator 2 is configured by bundling a plurality of lens elements 2a having a rectangular cross-sectional shape into six rows in the X direction and two columns in the Z direction so that the outer shape is a square shape.
The cross-sectional shape of the lens element 2a is the same as that of the optical integrator 4 (see FIG.
It is formed to be similar to the overall cross-sectional shape of (c). The light flux that has entered each lens element 2a that constitutes the optical integrator 2 is condensed, and a light source image is formed on the exit side of each lens element 2a. Therefore, in FIG. 1A, the lens element 2 is provided on the exit surface (exit side focal surface) A1 of the optical integrator 2.
A plurality of light source images corresponding to the number of a are arranged and formed in a substantially square shape, and a secondary light source is substantially formed here.

An aperture stop 31 having a circular aperture for adjusting the amount of light is arranged in the vicinity of the exit surface A1, and among the plurality of secondary light sources formed by the optical integrator 2, the secondary light source in the aperture stop 31 emits light. The luminous flux is the lens 3
It is condensed by the relay optical system 3 composed of 2 and 33,
The light is incident on a fly-eye lens type optical integrator 4 as a second multi-light source forming means for forming a plurality of light source images arranged in a rectangular shape. As shown in FIG. 1C, the optical integrator 4 includes lens elements 4a having a substantially square cross section, three rows in the X direction, and Z.
It is configured by bundling so as to form a rectangular shape as a whole in nine rows in the direction. The cross-sectional shape of each lens element 7a is configured to be similar to the overall cross-sectional shape of the optical integrator 6 (FIG. 1 (d)) as the third multi-light source image forming means described later. As a result, the light fluxes passing through the respective lens elements 4a forming the optical integrator 4 are condensed and a light source image is formed on the exit side of each lens element 4a. Therefore, in FIG. 1A, a plurality of light source images arranged in a rectangular shape are formed on the exit surface A2 of the optical integrator 4, and a substantially tertiary light source is formed therein.

The luminous flux from the tertiary light source formed by the optical integrator 4 is reflected by the lenses 51 and 52.
Optical system of fly-eye lens type as third multi-light source image forming means for forming a plurality of light source images which are condensed by the relay optical system 5 and are arranged in a substantially square shape.
It is incident on the integrator 6. As shown in FIG. 1D, the optical integrator 6 bundles the lens elements 6a having a rectangular cross section into nine rows in the X direction and three columns in the Z direction so as to form a substantially square shape as a whole. Is configured. This Optical Integrator 6
The light fluxes passing through the respective lens elements 6a constituting the above are condensed respectively, and a light source image is formed on the exit side of each lens element 6a. Therefore, a plurality of light source images arranged in a square shape are formed on the exit surface A3 of the optical integrator 6, and a quaternary light source is formed substantially there.

In FIG. 1A, the number of a plurality of light source images arranged in a square shape on the exit surface A3 of the optical integrator 6 is equal to the number of lens elements 2a constituting the optical integrator 2 by L. L × M × N, where M is the number of lens elements 4a forming the optical integrator 4 and N is the number of lens elements 6a forming the optical integrator 6.

The relay optical system 3 makes the incident surface B1 of the optical integrator 2 and the incident surface B2 of the optical integrator 4 optically conjugate with each other, and
The exit surface A1 of the optical integrator 2 and the exit surface A2 of the optical integrator 4 are optically conjugated. In addition, the relay optical system 5 also optically makes the incident surface B2 of the optical integrator 4 and the incident surface B3 of the optical integrator 6 optically conjugate with each other, and the exit surface A2 of the optical integrator 4 and the exit of the optical integrator 6 The surface A3 is optically conjugated.

The light beam from the fourth-order light source formed by the optical integrator 6 and distributed in a substantially square shape passes through the circular aperture of the aperture stop 71 disposed immediately after the exit surface A3 of the optical integrator 6. Then, the cross-sectional shape is converted into a circular luminous flux. The light flux that has passed through the aperture stop 71 illuminates a rectangular illumination area 8a on the pattern formation surface of the reticle R installed on the irradiation surface R1 via the condenser optical system 7 including the lenses 72 and 73. . The condenser optical system 7 is configured such that its front focal position coincides with the emission surface (emission side focal plane) A3 of the optical integrator 6 and its rear focal position coincides with the irradiated surface R1. Therefore, the light fluxes from the plurality of light source images formed by the optical integrator 6 illuminate the illuminated surface R1 in a superimposed and uniform illuminance distribution by the condensing action of the condenser optical system 7. At this time, the aperture stop 31 immediately after the first-stage optical integrator 2 is replaced, or the aperture stop 31 is replaced.
The amount of light on the irradiated surface R1 is controlled by controlling the opening diameter of the.

Next, the operation of the three-stage optical integrators 2, 4 and 6 of this embodiment will be described. First, the illumination area 8a on the irradiation surface R1 is a rectangle long in the Z direction as shown in FIG.
The pattern inside is projected and exposed on a wafer (not shown) through a projection optical system (not shown). At this time, the reticle R is scanned in the X direction, which is the short-side direction with respect to the illumination area 8a, and the wafer is scanned in a direction conjugate with it, so that the entire pattern of the reticle R is transferred to the shot area of the wafer. .

The rectangular illumination area 8a and the entrance surface B3 of each lens element 6a of the optical integrator 6 are conjugated by the condenser optical system 7. Therefore, in order for most of the light flux incident on each lens element 6a to illuminate the illumination area 8a, each lens element 6
The cross-sectional shape of a needs to be a rectangle that is similar (conjugate) to the illumination area 8a, but this condition is satisfied in this embodiment as already described. Specifically, each lens element 6a has a rectangular parallelepiped shape as shown in FIG. As a result, the light flux incident on the optical integrator 6 is efficiently irradiated onto the illumination area 8a.

Further, the optical integrator 6 has a square sectional shape as a whole.
As the opening of 1, usually a circular opening, a ring-shaped opening, or a plurality of small circular openings inscribed in the circumference are used,
A square figure is selected as a figure circumscribing the circular opening or circumference. To summarize the above, in FIG. 1, assuming that the width in the longitudinal direction (Z direction) of the rectangular illumination area 8a is t and the width in the short side direction (X direction) is s, Z of each lens element 6a of the optical integrator 6 is represented. The width in the direction (longitudinal direction) is m3, and the width in the X direction (transverse direction) is n.
When it is set to 3, it is desirable to satisfy the following relationship.

M3 / n3 = s / t (1) Next, the entrance surface B3 of the optical integrator 6 and the entrance surface B2 of each lens element 4a of the optical integrator 4 are conjugated by the relay lens system 5. There is. Therefore, in order for most of the light flux that has entered each lens element 4a to enter the incident side end surface of the optical integrator 6, the cross-sectional shape of each lens element 4a is similar to (conjugated to) the cross-sectional shape of the optical integrator 6.
However, as described above, this condition is satisfied in this embodiment. Specifically, each lens element 4a has a square prism shape as shown in FIG. As a result, the light flux that has entered the optical integrator 4 efficiently enters the optical integrator 6.

Further, the optical integrator 4 has a rectangular sectional shape as a whole, but this is determined in order to efficiently guide the luminous flux having a circular sectional shape emitted from the collimator lens 13 to the illumination area 8a. It is a thing. To summarize the above, the width of the third optical integrator 6 in the Z direction is M3, and the width in the X direction is N.
Assuming that the width in the Z direction of each lens element 4a of the optical integrator 4 is m2 and the width in the X direction is n2, it is desirable that the following relationship be satisfied.

M2 / n2 = M3 / N3 (2) Since the aperture of the aperture stop 71 is circular, the cross-sectional shape of the final stage optical integrator 6 is as shown in FIG. It is also possible to have a substantially circular shape or a substantially regular hexagonal shape, but in this case, the sectional shape of each lens element 4a of the second stage optical integrator 4 is a regular hexagonal shape, and the entire sectional shape is It may have a substantially rectangular shape.

Further, by means of the relay lens system 3, the incident surface B2 of the optical integrator 4 and the optical
The entrance surface B1 of each lens element 2a of the integrator 2 is conjugated. Therefore, in order for most of the light flux incident on each lens element 2a to be incident on the incident side end surface of the optical integrator 4, the cross-sectional shape of each lens element 2a is similar (conjugate) to the cross-sectional shape of the optical integrator 4. Although it is necessary to make the shape rectangular, this condition is satisfied in this embodiment as already described. Specifically, each lens element 2a has a rectangular parallelepiped shape as shown in FIG. As a result, the light beam that has entered the optical integrator 2 efficiently enters the optical integrator 4.

Further, the optical integrator 2 has a square sectional shape as a whole, but this is because the luminous flux emitted from the light source system 1 has a substantially circular sectional shape.
It is defined in order to efficiently receive the light flux. To summarize the above, the width in the Z direction (longitudinal direction) of the entire second-stage optical integrator 4 is set to M2, X.
When the width in the direction (short direction) is N2, the width in the Z direction (longitudinal direction) of each lens element 2a of the optical integrator 2 is m1, and the width in the X direction (short direction) is n1, the following relationship It is desirable to satisfy.

M1 / n1 = M2 / N2 (3) Within the range where these expressions (1) to (3) are satisfied, the overall outer shape of each optical integrator 2, 4 and 6 and the cross-sectional shape of each lens element are Can be set. Regarding the uniformity of the illuminance distribution, a large number of light source images are formed on the exit surface A3 of the optical integrator 6 at the final stage.
An extremely high illuminance distribution uniformity can be obtained on the illumination area 8a due to the superimposing effect. As described above, according to this embodiment, by stacking the optical integrators in three stages,
The rectangular illumination area 8a is illuminated with a uniform illuminance distribution (Kehler illumination) and with high illumination efficiency by the light flux emitted from the light source system 1 and having a substantially circular cross section.

As described above, the applicant of the present application has proposed an illumination optical device using a two-stage optical integrator in Japanese Patent Application No. 5-19098. Therefore, a comparison is made between the case where the two-stage optical integrator is used and the case where the three-stage optical integrator is used as in the present embodiment. FIG. 4 shows a case in which an excimer laser light source is used as a light source and a fly-eye lens type is used as an optical integrator in an illumination optical device using such a two-stage optical integrator. In the light source system 1B of FIG. 4, the parallel light flux LB output from the excimer laser light source 14 and having a rectangular cross section (see FIG. 4B) passes through the beam shaping optical system including the cylindrical lenses 15 and 16. It is converted into a light beam having a predetermined beam cross section.

The luminous flux emitted from the light source system 1B is shown in FIG.
A plurality of lens elements 42a having a square lens cross section shown in (c) are incident on the optical integrator 42 arranged in one row in a direction perpendicular to the paper surface of FIG. 4 (a). Light source images arranged in one row are formed in a direction perpendicular to the paper surface of FIG. 4A on the emission surface E2 of the optical integrator 42. An aperture stop 55 having a circular aperture is arranged near the exit surface E2, and the aperture stop 5
The light beams from the plurality of light source images in 5 are reflected by the lenses 56 and 5
4 (d) after passing through the relay optical system 5B composed of 7
A plurality of lens elements 62a having a rectangular lens cross section are arranged in a square shape and enter the optical integrator 62 as shown in FIG.

Due to the condensing action of the optical integrator 62, a plurality of light source images arranged in a square shape are formed on the exit surface E3 thereof. An aperture stop 77 having a circular opening is provided at the position of the light source image, and the light flux from the plurality of light source images circularized by the aperture stop 77 causes the condenser optical system 7 including lenses 78 and 79.
The rectangular illumination area 8a on the illuminated surface R2 of the reticle R is illuminated via B. This condenser optical system 7B
Of the optical integrator 62 has its front focus position aligned with the exit surface E3 of the optical integrator 62, and its rear focus position aligned with the illuminated surface R2 of the reticle R.
As a result, the light fluxes from the plurality of light source images formed by the optical integrator 62 are subjected to the condensing action of the condenser optical system 7B, and the illumination area 8 on the reticle R is illuminated.
a is uniformly illuminated in a superimposed manner.

Also, the optical integrator 22
The amount of light in the illumination area 8a of the reticle R was controlled by replacing the aperture stop 55 immediately after the change and changing the aperture diameter of the aperture stop 55. However, in FIG. 4, if the light source system 1 of FIG. 1 is used instead of the light source system 1B, the light source system 1
Since the cross-sectional shape of the light flux from is circular, light amount loss occurs at the incident surface of the optical integrator 42. On the other hand, in the present embodiment of FIG. 1, since the cross-sectional shape of the optical integrator 2 in the first stage is square, the light amount loss in the optical integrator 2 in the first stage is small.

Next, comparing the control of the amount of light on the surface to be illuminated, in the example of FIG. 4, the amount of light is controlled by the aperture stop 55 immediately after the optical integrator 42.
In this case, since the optical integrator 42 has a rectangular shape, if the light flux from here is limited by the circular aperture of the aperture stop 55, the optical integrator 6
The image size of the plurality of light source images on the exit surface of the optical integrator 42 formed on the exit surface of each of the second lens elements 62a changes. When the illumination optical apparatus of FIG. 4 is applied to a projection exposure apparatus, the plane on which the aperture stop 55 is arranged is conjugate with the pupil plane of the projection optical system.

Therefore, due to the change in the aperture diameter of the aperture stop 55, the light source image formed on the pupil plane of the projection optical system may locally change and the image forming performance may be deteriorated. The number of arrayed lens elements 62a of the optical integrator 62 is N
1 (X direction) × N2 (Z direction), the X direction and Z of the local change of the light source image formed on the pupil plane of the projection optical system.
The spatial period in the direction is (N1, N2).

On the other hand, in the present embodiment shown in FIG. 1, three optical integrators are arranged in series, and an aperture stop 31 for controlling the light quantity is provided immediately after the exit surface of the optical integrator 2 in the first stage. I put it in. Therefore, when the array number of each lens element of the optical integrator 4 is M1 (X direction) × M2 (Z direction) and the array of the optical integrator 6 is N1 × N2, it is formed on the pupil plane of the projection optical system. The spatial period of the local change of the light source image in the X and Z directions is (M1 × N
2, M1 × N2), which is advantageous in that the change in the brightness of the light source image formed on the pupil plane of the projection optical system can be localized to a smaller extent and the deterioration of the imaging performance of the projection optical system can be prevented.

Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment illuminates an arcuate illumination area using the embodiment of FIG. 1, and in FIG. 2, parts corresponding to those in FIG. 1 are assigned the same reference numerals and detailed explanations thereof are omitted. 2A is a plan view of the illumination optical device of this embodiment, and FIG. 2B is a front view of the illumination optical device. In these FIGS. 2A and 2B, the illuminated surface R1 is shown.
The upper rectangular illumination area is illuminated with a uniform illuminance distribution. In this embodiment, the field stop 81 is provided on the illuminated surface R1.
Is installed. The aperture of the field stop 81 is a rectangle smaller than the rectangular illumination area, and the shape (size) of the final arc-shaped illumination area depends on the opening shape of the field stop 81.
Is determined.

The light flux passing through the aperture of the field stop 81 passes through the relay lens 82 and the toric reflector 83.
Incident on. At this time, the front focus position of the relay lens 82 coincides with the arrangement surface of the field stop 81, and the relay lens 82
Assuming that the rear focus position is the surface A4, the surface A4 is conjugate with the exit surface A3 of the optical integrator 6, and many light source images are formed on this surface A4.

In this case, the surface A4 on which the light source image is formed
It is assumed that the optical axis AX4 of the optical integrator 6 is perpendicular to, and in the paper surface of FIGS. 2 (a) and 2 (b). Also, using a predetermined constant α, the surface A is placed at a position perpendicular to the surface A4 and at a distance of 1 / (2α) from the optical axis AX4.
5 is set, and the Y axis is taken in the direction parallel to the paper surface of FIG. 2B in the plane A5, and the Z axis is taken perpendicular to the Y axis in the surface A5 (that is, perpendicular to the paper surface of FIG. 2B). . Then, the origin O is taken at a position where the distance from the surface A4 is 3 / (4α) on the Y axis, and the X axis is taken perpendicularly to the YZ plane through the origin O.

Next, as shown in FIG. 2B, a parabola PA defined by Y = αX ² is assumed in the XY plane using the above-mentioned constant α. The axis of symmetry AX1 of this parabola PA
Is the Y axis itself. This parabola PA is rotated about a reference axis AX3 that passes through the optical axis AX4 in the plane A4 and is perpendicular to the Y axis to form a paraboloidal toric rotation surface,
A region surrounded by two parallels and two meridians on the parabolic toric surface of rotation is centered on the intersection of the parabolic toric surface of rotation and the optical axis AX4. Use as a reflective surface. On the reflecting surface of the toric reflector 83, a dielectric multilayer film for increasing the reflectance with respect to the light flux in the wavelength band supplied from the light source system 1 is formed.

In this case, the light flux from one point of the light source image on the surface A4 is converted into a parallel light flux by the toric reflector 83 as shown by the solid line, and the telecentricity is maintained on the surface A5. An arc-shaped illumination area 84 is formed. On the other hand, the light parallel to the optical axis AX4 is reflected by the toric reflection mirror 83, and then is separated from the origin O by 1 / (4α) on the Y axis on the surface A5, that is, from the surface A4 1 / ( Two
Since the light passes through a position separated by α), the illumination region 83 is also formed centering on that position.

In FIG. 2, the focal length f of the toric reflection mirror 83 is 1 / (2α), and the entrance pupil (focal position on the light source side) of the toric reflection mirror 83 is on the surface A4 which is the light source image forming surface. And a toric reflector 83 on the surface A5.
There is a focal position on the illuminated object side. The pattern forming surface of the reticle R is arranged on the surface A5 on which the arcuate illumination region 84 is formed. The reticle R is attached to the Y-shaped illumination area 84 via a reticle stage (not shown).
Scanning is performed at a constant speed in a direction parallel to the axis (short side direction).
Below the reticle R, for example, a projection optical system (not shown) of a mirror projection type, which is both-side telecentric at the same magnification, is provided. In the projection optical system of the mirror projection system, the good image range is an arc,
It is desirable that the illumination area on the reticle R be arcuate. The pattern image of the reticle R in the illumination area 84 is image-projected via the projection optical system onto the wafer W which is scanned in synchronization with the reticle R. As a result, the pattern of the reticle R is sequentially transferred and exposed on the wafer by the scanning exposure method.

As described above, according to this embodiment, since the toric reflector 83 is installed next to the relay optical system 7, the arc-shaped illumination area 84 on the reticle R is finally provided with a high illuminance distribution. It is possible to illuminate with uniformity and high illumination efficiency.
It should be noted that an arc-shaped illumination area 84 as shown in FIG. 2C is formed on the reticle R by the toric reflector 83 in this embodiment, but here, the center of the arc-shaped illumination area 84 is formed. The width of the section is s, the length of the arc (chord) of the arc-shaped illumination area 84 is t, the width of each lens element 6a of the optical integrator 6 in the Z direction (longitudinal direction) is m3, and each of the optical integrator 6 is When the width of the lens element 6a in the X direction (short side direction) is n3, the optical integrator 6 is preferably configured to satisfy the above expression (1). The relative relationship between the optical integrator 6 and the optical integrator 4 preferably satisfies the above expression (2), and the relative relationship between the optical integrator 4 and the optical integrator 2 is as described above. It is more preferable to satisfy the expression (3). Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment is optical
This is an example of illuminating a rectangular illumination area by using an internal reflection type integrator such as a glass rod as an integrator. In FIG. 3, parts corresponding to those in FIG. To do.

FIG. 3A is a plan view of the illumination optical device of this embodiment, and FIG. 3B is a front view of the illumination optical device.
In FIGS. 3A and 3B, the longitudinal direction of the rectangular illumination region 8a on the irradiated surface R1 is the Z axis, and the short side direction is the X axis, and the Y axis is parallel to the optical axis. As shown in FIGS. 3A and 3B, the light source system 1A is arranged at the elliptic mirror 12 and the first focal position of the elliptic mirror 12, and the g-line (436n
m), i-line (365 nm), h-line (407 nm), or other light source 11 such as a mercury lamp. In the light source system 1A, the light from the light source 11 is condensed by the condensing action of the elliptic mirror 12 to form a light source image at the second focal position of the elliptic mirror 12.

The second focal point of the elliptical mirror 12 is positioned on the incident side end face C1 of the optical member 21 (see FIG. 3C) having a rectangular cross section of the internal reflection type as the first multiple light source forming means. The light source image is formed on the incident side end surface C1 of the optical member 21. The optical member 21 is composed of, for example, a glass rod. The light flux from the light source image is repeatedly internally reflected by the optical member 21 and is emitted from the emission side end face D1 of the optical member 21. At this time, a plurality of light source images (virtual images) arranged in a square shape are formed on the incident side end surface C1 of the optical member 21.
Are formed, and a light beam is emitted from the exit side end surface D1 of the optical member 21 as if there were a plurality of light source images on the entrance side end surface C1 of the optical member 21.

The light beam emitted from the internal reflection type optical member 21 is a relay optical system 3A composed of lenses 34 and 35.
And then enters the internal reflection type optical member 41 (see FIG. 3D) having a square cross section as the second multi-light source image forming means. The relay optical system 3A includes the optical member 2
The incident-side end surface C1 of No. 1 and the incident-side end surface C2 of the optical member 41 are optically conjugated, and the exit-side end surface D1 of the optical member 21 and the exit-side end surface D2 of the optical member 41 are optically conjugated. There is.

As a result, the incident side end surface C of the optical member 21 is formed.
The light fluxes from the plurality of square-shaped light source images formed in 1 form a plurality of square-shaped light source images on the incident side end surface C2 of the optical member 41. The light flux from this light source image is repeatedly reflected on the inner surface of the optical member 41, and is emitted from the emission side end face D2 of the optical member 41. At this time, a plurality of light source images (virtual images) distributed in a rectangular shape are formed on the incident side end surface C2 of the optical member 41, and the optical images are generated as if the incident side end surface C2 of the optical member 41 has a plurality of light source images. A light beam is emitted from the emission side end surface D2 of the member 41.

The light flux emitted from the exit side end surface D2 of the optical member 41 passes through the relay optical system 5A composed of the lenses 53 and 54, and the internal reflection type optics having the rectangular cross section as the third multiple light source image forming means. Member 61 (see FIG. 3 (e))
Incident on. In the relay optical system 5A, the incident side end surface C2 of the optical member 41 and the incident side end surface C3 of the optical member 61 are optically conjugate with each other, and the exit side end surface D2 of the optical member 41 is made.
And the exit side end face D3 of the optical member 61 are optically conjugated. Therefore, the light beams from the plurality of light source images formed on the incident side end surface C2 of the optical member 41 are transmitted by the optical member 6.
A plurality of light source images (real images) distributed in a rectangular shape are formed on the incident-side end face C3 of No. 1.

Light fluxes from a plurality of light source images formed on the incident side end face C3 of the optical member 61 are repeatedly internally reflected by the optical member 61 and are emitted from the emission side end face D3 of the optical member 61. At this time, the incident side end surface C3 of the optical member 61
, A plurality of light source images (virtual images) are formed, and together with the plurality of light source images (real images) directly formed by the light flux from the optical member 41, a plurality of light source images distributed in a square shape as a whole are formed. . A light beam is emitted from the exit side end surface D3 of the optical member 61 as if there were a plurality of light source images on the entrance side end surface C3 of the optical member 61.

The light beam emitted from the optical member 61 passes through the condenser lens 74 in the condenser optical system 7A and then enters the aperture stop 75 having a circular aperture. The condenser lens 74 is arranged such that its front focus position coincides with the exit side end surface D3 of the optical member 61, and the condenser lens 74 disposes the incident side end surface C3 of the optical member 61 and the aperture stop 75. It is conjugated with C4. As a result, a light source image distributed in a square shape is formed on the arrangement surface C4 of the aperture stop 75, and is converted into a plurality of light source images distributed in a circular shape by the circular aperture of the aperture stop 75, for example.

The light flux from the light source image in the aperture of the aperture stop 75 is subjected to the condensing action by the condenser lens 76, and illuminates the illumination area 8a on the illuminated surface R1 of the reticle R.
The front focus position of the condenser lens 76 is the aperture stop 75.
Is arranged so as to coincide with the arrangement surface C4 and the rear focal position thereof coincides with the irradiated surface R1. Thus, the light flux from the light source image formed on the arrangement surface C4 of the aperture stop 75 has a rectangular illumination area 8 on the irradiation target surface R1.
Illuminate a with a uniform illuminance.

In the present embodiment, the exit side end surface D3 of the optical member 61 conjugate with the rectangular illumination area 8a is a rectangle similar (conjugated) to the illumination area 8a, so that it is emitted from the optical member 61. The luminous flux efficiently illuminates the illumination area 8a. Further, the two-stage optical members 41 and 61 improve the uniformity of the illuminance distribution in the X direction and the Z direction in the illumination area 8a. In addition, since the image of the light source 11 is formed at the center of the incident side end surface C1 of the first-stage optical member 21, even if the cross-sectional shape of the light beam supplied from the light source system 1A is circular, the light amount loss is small. There is an advantage that does not occur. Here, an optimum configuration example of the optical members 21, 41, 61 used in this embodiment will be described. First, assuming that the width in the long side direction (Z direction) of the illumination area 8a is t and the width in the short side direction (X direction) is s, the Z direction (longitudinal direction) of the third stage optical member 61.
Is v3 and the width in the X direction (short direction) is u3,
Since the illumination area 8a and the exit side end surface of the optical member 61 are conjugated, it is desirable that the following relationship be established.

S / t = u3 / v3 (4) Further, assuming that the image forming magnification of the relay optical system 5A is β _5A , the width of the second stage optical member 41 in the Z direction is v2, and the width in the X direction is u.
If it is 2, it is desirable that the following relationship be established. However, in this embodiment, v2 = u2 holds. u2 = β _5A · u3 (5) Further, assuming that the image forming magnification of the relay optical system 3A is β _3A , the width of the first stage optical member 21 in the Z direction (longitudinal direction) is v1, and the width in the X direction (short side direction). Let u1 be the following relationship. However, in this embodiment, v2 = u2 holds.

U1 = β _3A · u2 (6) By establishing these relationships, the illumination area 8a is illuminated with high illumination efficiency and high illuminance distribution uniformity (Kohler illumination). As the optical members 21, 41, 61, a hollow prismatic inner reflection type optical member may be used instead of the rod glass.

In the present invention, a fly-eye lens type optical integrator and an internal reflection type optical member may be mixed and used as the first multi-source image forming means to the third multi-source image forming means. It goes without saying that it is good. Further, in the above-mentioned embodiment, the light source system uses a system in which a light flux from a light source such as a mercury lamp is condensed by an elliptic mirror, but even when a laser light source is used, the light is emitted from the laser light source. When the cross-sectional shape of the light flux is substantially circular, by applying the present invention and using a three-stage optical integrator, the condition of uniform illuminance distribution and the condition of illumination efficiency can be satisfied.

As described above, the present invention is not limited to the above-mentioned embodiments, and various configurations can be adopted without departing from the gist of the present invention.

[0062]

According to the present invention, since the multistage light source image forming means of three stages are arranged, even if the cross-sectional shape of the light beam supplied from the light source system is, for example, a circular shape, the light source system can generate light from the light source system. The light flux can be taken in efficiently. Therefore, there is an advantage that a rectangular or arcuate illumination area on the illuminated surface can be illuminated with high illuminance distribution uniformity and high illumination efficiency.

Therefore, when the present invention is applied as an illumination system of a projection exposure apparatus having a projection optical system, the illuminance distribution on the pupil plane of the projection optical system on which the light source image is formed can be made uniform, so The system can bring out sufficient resolution and depth of focus performance. Further, when the first multi-light source image forming means is composed of a plurality of lens elements having a rectangular cross section, the incident surface and the irradiated surface of the lens element are conjugated so that the irradiated surface is The rectangular illumination area can be efficiently illuminated.

If the second multi-light source image forming means is composed of a plurality of lens elements arranged in at least one row, the illumination efficiency as a whole can be improved. When the third multi-light source image forming means is composed of a plurality of lens elements having a rectangular cross section, especially the second multi-light source image forming means is a fly-eye lens type optical integrator and the cross-sectional shape is The illumination efficiency in the rectangular shape can be improved.

Further, when at least one of the first, second and third multi-light source image forming means is composed of an internal reflection type optical member, the structure of the optical system can be simplified.

[Brief description of drawings]

1A and 1B are views showing a first embodiment of an illumination optical apparatus according to the present invention, FIG. 1A is a front view of the embodiment as seen from the Z direction, and FIG. 1B is a view showing an incident surface of an optical integrator 2. The figure, (c) is a figure which shows the incident surface of the optical integrator 4, (d) is a figure which shows the incident surface of the optical integrator 6, (e) is a figure which shows an illumination area,
(F) is an enlarged perspective view showing the lens element 2a, (g) is an enlarged perspective view showing the lens element 4a, (h) is the lens element 6
It is an expansion perspective view which shows a.

2A and 2B are diagrams showing a configuration when a second embodiment of the illumination optical device according to the present invention is applied to an exposure apparatus for semiconductor manufacturing, FIG. 2A is a plan view showing the embodiment, and FIG. It is a front view of the Example.

3A and 3B are views showing a configuration when a third embodiment of the illumination optical device according to the present invention is applied to an exposure apparatus for semiconductor manufacturing, FIG. 3A is a plan view showing the embodiment, and FIG. The front view which shows the Example, (c) is the expansion perspective view which shows the optical member 21, (d) is the expansion perspective view which shows the optical member 41, (e).
FIG. 6 is an enlarged perspective view showing an optical member 61.

FIG. 4 is a diagram showing a configuration of an example of an illumination optical device according to a prior application of the applicant.

FIG. 5 is a diagram showing a configuration when a conventional illumination optical device is applied to an exposure apparatus for semiconductor manufacturing.

[Explanation of symbols]

 1 Light source system 2,4,6 Optical integrator 3,5 Relay optical system 3A, 5A Relay optical system 7 Condenser optical system 7A Condenser optical system R1 Irradiated surface R Reticle 8a Illumination area 11 Light source such as mercury lamp 12 Elliptical mirror 13 Collimator lens 21, 41, 61 Internal reflection type optical member 31 Aperture stop 71 Aperture stop 83 Toric reflector

Claims (5)

[Claims] 1. A light source system that supplies light having a light flux cross section of a predetermined shape, and a first multi-light source image that forms a plurality of light source images arranged in a substantially square or circular shape from the light flux from the light source system. Forming means, a second multi-light source image forming means for forming a plurality of light source images arranged in a substantially rectangular shape or a substantially straight shape from the light flux from the first multi-light source image forming means, and the second multi-light source image Third multi-light source image forming means for forming a plurality of light source images arranged in a substantially square shape or a substantially circular shape from the light flux from the forming means, and condensing light fluxes from the plurality of third multi-light source image forming means A condenser optical system for illuminating a surface to be illuminated, a position of a light source image formed by the first multi-light source image forming means and arranged between the first and second multi-light source image forming means, and the second multi-light source. The position of the light source image formed by the image forming means is conjugated And a position of a light source image formed by the second multi-light source image forming means and arranged between the second and third multi-light source image forming means, and the third multi-light source image forming means. A second relay optical system for making the position of the light source image formed by the means conjugate with each other, and an illumination optical device. 2. The illumination optical apparatus according to claim 1, wherein the first multi-light source image forming means includes a plurality of lens elements having a rectangular cross section. 3. The illumination optical device according to claim 1, wherein the second multi-light source image forming means includes a plurality of lens elements arranged in at least one row. 4. The illumination optical apparatus according to claim 1, wherein the third multi-light source image forming means comprises a plurality of lens elements having a rectangular cross section. 5. The illumination optical apparatus according to claim 1, wherein at least one of the first, second and third multi-light source image forming means is composed of an internal reflection type optical member. .