JPH0653120A - Illuminating optic device - Google Patents

Abstract

PURPOSE:To improve image contrast for oblique illumination performed by a plurality of illuminating devices when a reticle pattern is a line-and-space pattern whose lengthwise direction is vertical to the incident plane of the illuminating light. CONSTITUTION:Four apertures 24a-24d of a space filter as a secondary light source forming part are covered with a polarizing plates 24A-25D and the polarizing direction of the polarizing plates 25A-25D is set in the direction of the tangential line of a circumference whose axis is an optical axis AX.

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 suitable for application to an illumination system of a projection exposure apparatus used for manufacturing a semiconductor element, a liquid crystal display element or the like.

[0002]

2. Description of the Related Art A projection exposure apparatus for transferring a pattern of a photomask or a reticle (hereinafter, referred to as a "reticle") onto a photosensitive substrate when a semiconductor element, a liquid crystal display element or the like is manufactured by using a photolithography technique. Is used. In such a projection exposure apparatus, it is required to print a finer pattern with high resolution as semiconductor elements and the like are highly integrated. As a method of achieving this, a phase shift reticle method utilizing the interference effect of light from transparent portions of different reticle pattern areas is disclosed in Japanese Patent Publication No.
It is disclosed in Japanese Patent Publication No. 250811. When this method is applied to line-and-space images, the 0th-order diffracted light basically disappears, and only ± 1st-order diffracted light forms an image,
Even with a projection optical system having the same numerical aperture, a finer line-and-space image can be printed with higher resolution than in the case of a conventional reticle.

As another approach to further increase the resolution, the present applicant has proposed a method in which an illumination optical system is devised to print a fine pattern with a high resolution and a relatively deep depth of focus ( For example, March 1992 Proceedings of the Joint Lecture on Applied Physics 30-a-NA-
3 and 4). In the following, we will refer to that method as the "multi-slope illumination method"
The method will be described with reference to FIG. First, FIG. 8A shows an equivalent light source unit 10 such as a secondary light source unit in an illumination optical system to which the multiple tilt illumination method is applied.
In (a), an axis x ′ and an axis x ′ intersecting the x-axis and the y-axis forming an orthogonal coordinate system at 45 °, respectively.
And four small light sources 11A along an axis symmetrical with respect to the y-axis.
11D is arranged. The arrangement of the small light sources 11A to 11D is suitable when the pattern of the reticle to be transferred is mainly a line-and-space pattern having a long edge parallel to the x-axis or a long edge parallel to the y-axis.

FIG. 8B shows a schematic structure of a projection exposure apparatus using the equivalent light source unit 10 of FIG. 8A as a light source. In FIG. 8B, the small light source 11A of the equivalent light source unit 10 is used. The principal ray 15A of the illumination light is applied to the reticle 12 obliquely with respect to the optical axis AX via a condenser lens system (not shown). The equivalent light source unit 10 is conjugate with the pupil plane (incident pupil plane) 10A of the projection optical system 13, and an aperture stop 13a is provided on this pupil plane. 0 from the reticle 12
First-order diffracted light (also indicated by reference numeral 15A) and first-order diffracted light 1
6A is emitted almost symmetrically with respect to the optical axis AX, and these 0
The first-order diffracted light 15A and the first-order diffracted light 16A are projected by the projection optical system 13.
Then, the light enters the wafer 14 as a photosensitive substrate at substantially the same incident angle θ. In this case, the 0th-order diffracted light 15A and the 1st-order diffracted light pass symmetrically with respect to the optical axis AX near the periphery of the pupil, so that the resolution up to the performance limit of the projection optical system 13 can be obtained.

Further, as in the conventional case, the 0th-order diffracted light is emitted from the wafer 1.
In the method in which the light is incident perpendicularly to No. 4, the depth of focus is shallow because the wavefront aberration of the 0th-order diffracted light and the wavefront aberration of other diffracted light with respect to the defocus amount of the wafer 14 are significantly different. On the other hand, in the configuration of FIG. 8B, since the 0th-order diffracted light and the 1st-order diffracted light are incident on the wafer 14 at the same incident angle, when the wafer 14 is located before and after the focus position of the projection optical system 13. The wavefront aberrations of the 0th-order diffracted light and the 1st-order diffracted light are equal, and the depth of focus is deep.

[0006]

In the multiple tilt illumination method, the line and space pattern 8 in the x-axis direction or the y-axis direction is effective. On the other hand, as shown in FIG. 9, when the long edge is the line-and-space pattern 9 in the direction of 45 ° with respect to the x-axis or the y-axis, 10A is the pupil of the projection optical system. , Fig. 8
The diffracted light from the two small light sources 11B and 11D of the four small light sources 11A to 11D in (a) is the 0th-order diffracted light 15
Only B and 15D pass through the pupil 10A of the projection lens,
Since the first-order diffracted lights 16B and 16D do not pass through the pupil 10A, no pattern is formed on the wafer 14 and the wafer 14 is simply illuminated. as a result,
The contrast of the pattern on the wafer 14 is lowered.

This will be shown by a simple numerical calculation. The intensity of the ± 1st-order diffracted light with respect to the intensity of the 0th-order diffracted light is defined as a, and the small light sources 11A to 11D are regarded as point light sources. At this time, the image intensity distribution I (x) on the x-axis in the case of a line-and-space pattern long in the y-axis direction is as follows as the sum of the image intensity distributions by the small light sources.

## EQU1 ## I (x) = 4 {1 + a ² + 2a · cos [(4π / λ) (sin θ) x]}

Here, the incident angle θ is an angle formed by the 0th-order diffracted light or ± 1st-order diffracted light with the optical axis AX, as shown in FIG. 8B. On the other hand, in the case of a line-and-space pattern long in the direction intersecting the x-axis or the y-axis at 45 °, if the coordinate axis in the 45 ° direction is the x ′ axis, the intensity distribution I
(X ') is as follows.

[Number 2] ^{I (x ') = 2 {} 1 + a 2 + 2a · cos [(4π / λ) (sinθ) x]} +2 {1} = 4 {1+ (a 2/2) + a · cos [(4π / λ) (sin θ) x]}

When the contrasts Cx and Cx 'of the respective intensity distributions are obtained from (Equation 1) and (Equation 2), they are as follows.

[Number 3] Cx = 2a / (1 + a 2), Cx '= a / (1 + a 2/2)

In this case, the following equation holds. Cx-Cx '= a / { (1 + a 2) (1 + a 2/2)}> 0 Therefore, the following equation is established.

[Equation 4] Cx> Cx ′

Thus, a reduction in the contrast of patterns that are long in the direction intersecting the x-axis at 45 ° is shown. For example, when the line and the space have the same width, the intensity a of the ± 1st-order diffracted light is 2 / π, and therefore, the following equation is obtained. Cx = 0.906, Cx '= 0.529

In the above description, the case of the multi-tilt illumination method has been described as an example, but it is desired to further improve the image contrast even when the annular illumination method or the like is used. In view of the above problems, the present invention provides an illumination optical device that positively utilizes illumination light inclined with respect to the optical axis to illuminate a reticle or the like, and the pattern of the reticle or the like is perpendicular to the incident surface of the illumination light. In the case of a line-and-space pattern whose longitudinal direction is the direction, when the pattern of the reticle or the like is projected by the projection optical system, it is possible to improve the contrast of the image by devising the illumination optical device side. The purpose is to

[0013]

A first illumination optical device according to the present invention is, for example, as shown in FIG. 3, an illumination which uniformly illuminates a predetermined area on an object (12) by illumination light from an illumination optical system. In the optical device, the illumination optical system includes an inclined light (27B, 27B) that illuminates a predetermined area from an oblique direction.
C) forming a tilted light and a polarized light for converting the tilted light to form an illumination light that is linearly polarized in a direction orthogonal to the incident surface of the tilted light that obliquely illuminates a predetermined area. And means (25B, 25C).

Further, the second illumination optical device is, for example, as shown in FIG.
As shown in FIG. 3, in an illumination optical device having a light source (20) for supplying illumination light and a condensing optical system (26) for uniformly illuminating a predetermined area on an object (12) with this illumination light, Decentered with respect to the optical axis of the condensing optical system by 2
An inclined light forming means (24) for forming a next light source and illuminating a predetermined area thereof in an oblique direction is arranged between the light source (20) and the condensing optical system (26) to convert this inclined light. Then, the polarizing means (25B, 25C) for forming the illumination light linearly polarized in the direction orthogonal to the incident surface of the inclined light for obliquely illuminating the predetermined area is provided with the inclined light forming means (24) and its condensing optical system. It is arranged between (26).

[0015]

The principle of the present invention will be described below by taking a multi-inclined illumination method for illuminating an object with illumination light from four eccentric small light sources. First, according to the first illumination optical device of the present invention, for example, as shown in FIG. 3, tilted light (27B, 27C) that illuminates a predetermined region of the object (12) from an oblique direction.
Are formed, and these inclined lights (27B, 27C) are linearly polarized in the direction perpendicular to the incident surface (paper surface) with respect to the object (12) (the electric vector vibrates in the direction perpendicular to the incident surface).
is doing. The linearly polarized light means a state in which the vibration direction of the electric vector of the light wave is in one plane, and the vibration direction of the electric vector is defined as the direction of the linearly polarized light. Further, the incident surface is defined as a surface including the normal line of the surface at that point and the incident direction of the light when the light reaches the boundary surface of the medium. The illumination optical device shown in FIG. 3 is simplified as shown in FIG.

FIG. 1A shows an equivalent light source unit 10 such as a secondary light source unit of the illumination optical device shown in FIG. 3, and in FIG. 1A, the x-axis and the y-axis which form the orthogonal coordinate system. Four small light sources 11A to 11D are arranged along an axis x'intersecting at 45 ° and an axis symmetrical to the axis x'and the y-axis.

FIG. 1 (b) shows a schematic structure of a projection exposure apparatus using the illumination optical apparatus of FIG. 3, and in FIG. 1 (b), the equivalent light source section 10 is the equivalent light source section of FIG. 1 (a). Is equal to The chief ray 15A of the exposure light from the small light source 11A of the equivalent light source unit 10 is irradiated onto the reticle 12 obliquely with respect to the optical axis AX via a condenser lens system (not shown). The chief ray 15A is the inclined light (27B, 27
Corresponds to C). The incident surface of the chief ray 15A is shown in FIG.
Since it is parallel to the paper surface of (b), according to the present invention, the chief ray 15A is linearly polarized in the direction perpendicular to the paper surface of FIG. 1 (b) (the electric vector vibrates in the direction perpendicular to the paper surface). It is incident on the reticle 12. Similarly, in FIG. 1A, the light from each of the small light sources 11B to 11D is linearly polarized in the direction of the arrow in FIG. 1A, that is, in the direction perpendicular to the incident surface with respect to the reticle 12, and then in FIG. ) Is incident on the reticle 12.

The 0th-order diffracted light (also indicated by reference numeral 15A) and the 1st-order diffracted light 16A from the reticle 12 are incident on the wafer 14 via the projection optical system 13. First, assuming that the pattern formed on the reticle 12 is a line-and-space pattern long in the direction parallel to the x-axis or the y-axis in FIG. The illumination light diffracted in the x-direction or the y-direction is in the same image formation state as the randomly polarized light because the polarization direction is 45 ° with respect to the pattern. Therefore, the contrast is similar to that of the conventional example.

On the other hand, if the pattern formed on the reticle 12 is the line-and-space pattern 9 which is long in the direction perpendicular to the x'axis of FIG. 1A, the light source 11A emits light. The first-order diffracted light of the illumination light 15A enters the pupil of the projection optical system 13. Incidentally, FIG. 1 (b)
In, the x'axis is parallel to the paper surface. Here, FIG.
As shown in (b), the 0th-order diffracted light 1 of the illumination light 15A
5A and the first-order diffracted light 15B are both S-polarized light whose polarization direction (direction in which the electric vector vibrates) is parallel to the surface of the wafer 14 (light whose electric vector vibrates in a direction perpendicular to the paper surface of FIG. 1B). . Therefore, the interference effect on the wafer 14 becomes larger than that in the case of randomly polarized light, and a high-contrast image is formed. Therefore, as described with reference to FIG. 9, when the light is diffracted in the x ′ direction, a part of the diffracted light goes out of the pupil to reduce the contrast, which is a conventional disadvantage. .

The difference in intensity distribution depending on the polarization direction will be briefly described below. In FIG. 2, the image plane, that is, the state near the surface of the wafer 14 is shown as P-polarized light (light whose electric vector vibration direction is within the incident surface) and S-polarized light (light whose electric vector vibration direction is perpendicular to the incident surface). It is shown using. 0th order diffracted light 1
If the incident angles of the 5A and first-order diffracted light 16A are θ ₀ and θ ₁ , respectively, the intensity distribution Is on the image plane in the case of S-polarized light is
(X) is simply shown as follows using the amplitude distribution Us (x).

[Equation 5] Is (x) = | Us (x) | ² , Vs (x) = a ₀ · exp [−i (2π / λ) (sin θ ₀ ) x] + a ₁ · exp [−i (2π / λ) (sin θ ₁ ) x]

Therefore, the intensity distribution Is (x) is as follows.

Is (x) = a ₀ ² + a ₁ ² + 2a ₀ a ₁ · cos [(2π / λ) (sin θ ₀ −sin θ ₁ ) x] where the coefficients a ₀ and a ₁ are the 0th-order diffracted light, respectively. And 1
It is the intensity (amplitude) of the next-order diffracted light. In the case of a line-and-space pattern having a pitch in the x ′ direction, two of the four small light sources pass only the 0th-order diffracted light through the projection optical system 13, so the contrast Cs of S-polarized light is as follows.

## EQU7 ## Cs = 2a ₀ a ₁ / (2a ₀ ² + a ₁ ² )

On the other hand, in the case of P-polarized light, the x component of polarized light and
We have to consider the z component. When the amplitude distribution Up (x) on the image plane in the case of P-polarized light is represented by a vector and the x component and the z component are shown, the following equation is obtained.

Up (x) = (a ₀ · exp [−i (2π / λ) (sin θ ₀ ) x] · cos θ ₀ + a ₁ · exp [−i (2π / λ) (sin θ ₁ ) x] · cos θ ₁ , a ₀ · exp [−i (2π / λ) (sin θ ₀ ) x] · sin θ ₀ + a ₁ · exp [−i (2π / λ) (sin θ ₁ ) x] ・sin θ ₁ )

Therefore, the intensity distribution Ip (x) on the image plane for P-polarized light is as follows.

Ip (x) = | Up (x) | ² = a ₀ ² + a ₁ ² + 2a ₀ a ₁ × (cos θ ₀ cos θ ₁ + sin θ ₀ sin θ ₁ ) × cos [(2π / λ) (sin θ ₀ − sin θ ₁ ) x]

Therefore, the contrast Cp for P-polarized light is
Is as follows.

[Equation 10] Cp = 2a ₀ a ₁ cos (θ ₀ −θ ₁ ) / (2a ₀ ² + a ₁ ² ) Comparing (Equation 7) and (Equation 10), in the case of P-polarized light,
It can be seen that the contrast becomes cos (θ ₀ −θ ₁ ) times. For example, sin θ ₀ = 0.4, sin θ ₁ = −
Considering the case of 0.4, cos (θ ₀ −θ ₁ ) = 0.
68, which is a large difference between the P-polarized light and the S-polarized light. Since the random polarization is considered to be the average of P polarization and S polarization, the contrast is (1/2) (1 + 0.
68) = 0.84.

As described above, the S-polarized light causes a large difference in contrast. That is, when illumination light having a polarization state as shown in FIG. Also, it is expected that the contrast will increase by about 20%, which is effective for fine patterns.

Although the multi-tilt illumination method has been described above as an example, when the present invention is applied to the annular illumination method, for example, as shown in FIG. The direction from which the light from the light source is perpendicular to the incident surface,
That is, it may be converted into light that is linearly polarized in the tangential direction of a circle centered on the optical axis.

Next, according to the second illumination optical device of the present invention, for example, as shown in FIG.
A secondary light source that is decentered by the illumination light from the light source is formed. The secondary light source is, for example, the equivalent light source 10 of FIG.
If so, the above description is directly applied to the present invention.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a projection exposure apparatus having an illumination optical device according to the present invention will be described below with reference to FIGS. In this example, the present invention is applied to an illumination optical system of a projection exposure apparatus. FIG. 3 shows an illumination optical system of the projection exposure apparatus of the present embodiment. In FIG. 3, illumination light from a light source 20 composed of a mercury lamp is condensed by an elliptical mirror 21, and this condensed illumination light is collimated. The light enters the fly-eye lens 23 (optical integrator) via the lens 22. A planar secondary light source is formed on the focal plane on the exit side (reticle side) of the fly-eye lens 23.

A spatial filter 24 having four openings eccentric to the optical axis AX is provided near the exit end of the fly-eye lens 23. Polarizing plates 25A to 25D are attached to the reticle side (or the light source 20 side) of the four openings of the spatial filter 24. However, FIG.
In, only the polarizing plates 25B and 25C are shown. Figure 4
4A is a front view of the spatial filter 24 of FIG. 3 viewed from the reticle side, and FIG. 4B is a cross-sectional view taken along the line AA of FIG. 4A. As shown in
The spatial filter 24 has a 90 ° angle about the optical axis AX.
Four openings 24a to 24d are formed at intervals, and these openings are covered with polarizing plates 25A to 25D, respectively. The polarization directions of the polarizing plates 25A to 25D are set in the tangential direction of the circumference around the optical axis AX, as indicated by the arrows. Therefore, the spatial filter 24
The illumination lights emitted from the openings 24a to 24d are linearly polarized in a direction substantially parallel to the tangential direction of the circumference centered on the optical axis AX.

Returning to FIG. 3, the spatial filter 24 forms four secondary light sources eccentric with respect to the optical axis AX.
The illumination light emitted from these four secondary light sources passes through the polarizing plates 25A to 25D, respectively, and then enters the reticle 12 via the condenser lens system 26. A spatial filter 24 (polarizing plates 25A to 25D) is provided at the front side focal point (focal point on the light source side) of the condenser lens system 26, and the pattern forming surface of the reticle 12 is related to the condenser lens system 26. There is a relationship between the arrangement plane and the Fourier transform. In this case, for example, the principal rays 27B and 27C emitted from the openings 24b and 24c of the spatial filter 24 respectively enter the reticle 12 obliquely with respect to the optical axis AX via the condenser lens system 26. Further, each of these chief rays 27B and 27C is linearly polarized in a direction perpendicular to the incident surface (paper surface direction) with respect to the reticle 12.

When such an illumination optical system is used, as described in the explanation of the principle of the present invention, for example, it is parallel or perpendicular to the straight line connecting the openings 24a and 24c of FIG. When a line-and-space pattern having a long edge in the direction is formed, the pattern can be projected on the wafer 14 through the projection optical system 13 with a better contrast than before. Here, in the apparatus of FIG. 3, the incident side surface of the fly-eye lens 23 and the object surface (reticle 12 or wafer 14) are configured to be conjugate, and the exit side surface of the fly-eye lens 23 (secondary light source 10) and the projection surface are projected. The pupil plane 10A of the optical system 13 is configured to be conjugate. In addition to the configuration shown in FIG. 3, another large polarizing plate is disposed between the fly-eye lens 23 and the spatial filter 24, and 1 or 4 is provided in some or all of the four openings 24a to 24d of the spatial filter 24. You may arrange | position a 2 wavelength plate and you may make it adjust the rotation angle of each 1/2 wavelength plate. Also by this, the optical axis A as shown in FIG.
Illumination light polarized in the tangential direction of the circumference centered on X is obtained. In this case, depending on the polarization direction of another large polarizing plate, it is not necessary to provide the half-wave plate in all the openings of the spatial filter 24.

Further, for example, when a laser light source that emits a linearly polarized laser beam is used as a light source, the entire spatial filter 24 of FIG. 3 serving as an equivalent light source is illuminated with linearly polarized illumination light. Need only provide a half-wave plate in the appropriate rotation direction on some or all of the four openings 24a to 24d of the spatial filter 24. In this case, the half-wave plate may be provided only in a part of the openings, but it is more effective to provide the half-wave plate in all the openings in order to reduce the variation in illumination. In this way, when the polarization direction is adjusted using the 1/2 wavelength plate,
The illumination efficiency is good because there is no loss of illumination light.

Further, in the case of illuminating the spatial filter 24 of FIG. 3 which is an equivalent light source by using a device which generates circularly polarized illumination light as a whole, each aperture of the spatial filter 24 is rotated in an appropriate rotation direction. A quarter wave plate is preferably provided.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a projection exposure apparatus of this example. In FIG. 5, the illumination light from the light source 20 is an elliptical mirror 21,
After passing through the bending mirror 28 and the input lens 29, it becomes a substantially parallel light beam. The elliptical mirror 21 and the folding mirror 2
A shutter 30 is arranged between the shutter 8 and the shutter 3.
By closing 0 with the drive motor 31, the supply of illumination light to the input lens 29 is stopped at any time. As the light source 1, for example, an excimer laser light source that generates KrF laser light or the like can be used in addition to the mercury lamp. When using an excimer laser light source,
A beam expander or the like is used instead of the optical system from the elliptic mirror 21 to the input lens 29.

Then, in order from the input lens 29,
A first polyhedral prism 32 having a quadrangular pyramid (pyramid) concave portion and a second polyhedral prism 33 having a quadrangular pyramid (pyramid) convex portion are arranged. The illumination light emitted from the second polyhedron prism 33 is divided into four light beams at the same angle around the optical axis with the optical axis as the center.

The light fluxes divided into these four light fluxes are divided into the second group fly-eye lenses 34A, 34B, 34C and 3 respectively.
It is incident on 4D. Although only the fly-eye lenses 34A and 34B are shown in FIG. 5, two fly-eye lenses 34C and 3 are sandwiched with the optical axis in the direction perpendicular to the paper surface of FIG.
4D is arranged. And the fly-eye lens 34
The light flux emitted from A is converted into a substantially parallel light flux via the guide optical system including the lens systems 35A and 36A and is incident on the fly-eye lens 37A of the first group. Similarly,
The light flux emitted from the fly-eye lens 34B of the second group is converted into a substantially parallel light flux via the guide optical system including the lens systems 35B and 36B, and the fly-eye lens 3 of the first group 3
Although not shown, the light fluxes that have entered the first group of fly-eye lenses 37C and 37D enter the first group of fly-eye lenses 37C and 37D through the guide optical system, respectively.

The first group of fly-eye lenses 37A to 37D
Are arranged at 90 ° intervals around the optical axis. Surface-shaped secondary light sources are formed on the reticle side focal planes of the first group of fly-eye lenses 37A to 37D, and variable aperture stops 38A to 38D are arranged on the surfaces on which the secondary light sources are formed. Further, polarizing plates 39A to 39D are arranged on the reticle side of these variable aperture stops 38A to 38D, respectively. In FIG. 5, only the variable aperture diaphragms 13A and 13B and the polarizing plates 39A and 39B are shown.

The illumination light emitted from the variable aperture diaphragms 38A to 38D after passing through the polarizing plates 39A to 39D is appropriately condensed through the auxiliary condenser lens 40, the mirror 41, and the main condenser lens 42, and then is incident on the reticle 12. Illuminate with almost uniform illuminance. The pattern of the reticle 12 is transferred onto the wafer 14 on the wafer stage WS by the projection optical system 13 at a predetermined reduction ratio β. The polarization directions of the polarizing plates 39A to 39D are parallel to the tangential direction of the circumference centered on the optical axis AX. For example, a chief ray 43A of a light flux emitted from the variable aperture stop 38A after passing through the polarizing plate 39A is obliquely incident on the reticle 12 with respect to the optical axis AX while being linearly polarized in a direction perpendicular to the paper surface. The polarizing plates 39A to 39D shown in FIG.
The auxiliary condenser lens 40 and the main condenser lens are provided at a front focal point (focal point on the light source side) of a condenser lens system that is a composite system, and this position is substantially conjugate with the pupil plane 10A of the projection optical system 13.

Also in this example, the wafer 14 having a line-and-space pattern in a predetermined direction on the reticle 12.
The contrast of the above projected image can be improved. Further, since the second group fly-eye lenses 34A to 34D are provided in addition to the first group fly-eye lenses 37A to 37D, the uniformity of the illuminance on the reticle 12 is further improved. In FIG. 5, the polarizing plates 39A and 39B
Are positions 44A and 4 respectively between the relay optics, for example.
It may be arranged at 4B or at another position. Further, when the illumination light from the light source 20 is already linearly polarized light, instead of the polarizing plates 39A and 39B, 1
A half wave plate may be used.

Next, a third embodiment of the present invention will be described with reference to FIGS. In this embodiment, the spatial filter 24 of the first embodiment shown in FIG. 3 described above is changed, and the spatial filter 240 having a ring-shaped opening 240a as shown in FIG. 6A is emitted from the fly-eye lens 23. An example provided on the side is shown. Due to the arrangement of the spatial filter 240, the fly-eye lens 23 has an exit side as shown in FIG.
As shown in (a), a ring-shaped secondary light source 45 decentered from the optical axis AX is formed, and the light from this ring-shaped secondary light source 45 passes through the condenser lens 26 and the reticle 12 as shown in FIG. It reaches the pupil plane 10A (incident pupil plane) of the projection optical system 13 through. Here, in order to simplify the explanation, considering the states of the 0th-order diffracted light and the 1st-order diffracted light due to the diffraction action of the line-and-space pattern of the reticle 12, the pupil plane 10A of the projection optical system 13 has Figure 6
As shown in (b), a ring-shaped 0th-order diffracted light 45A similar to the ring-shaped light source 45 and a ring-shaped 1st-order diffracted light 45B obtained by laterally shifting the ring-shaped 0th-order diffracted light 45A are formed.

In this case, in this example, as shown in FIG. 7A, the illuminating light emitted from the annular light source 45 of the equivalent light source unit 10 is tangential to the circumference around the optical axis AX. A ring-shaped polarizing plate 250 that polarizes the light in the direction is provided on the spatial filter 240. As a result, a high-contrast image can be obtained for a fine pattern. As shown in FIG. 7B, a spatial filter 240 having an opening that divides the annular light source into arc-shaped zones is used, and polarizing plates 250A to 250H are provided on each zone.
The illumination light may be linearly polarized light in the tangential direction of the circumference about the optical axis AX for each zone.

The present invention is not limited to the above-described embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0043]

According to the first and second illumination optical devices of the present invention, since the illumination light that is obliquely incident on the object is polarized in the direction perpendicular to the incident surface, the illumination light on the object is reduced. When the pattern is a line-and-space pattern whose longitudinal direction is the direction perpendicular to the plane of incidence of the illumination light, the contrast of the image is significantly increased when the pattern of the object is projected by the projection optical system. There is an advantage that can be improved.

[Brief description of drawings]

1A is a diagram showing an equivalent light source for explaining the principle of an illumination optical device according to the present invention, and FIG. 1B is a schematic configuration diagram showing a projection exposure apparatus using the equivalent light source of FIG. 1A. is there.

FIG. 2 is a diagram for explaining the principle of the present invention.

FIG. 3 is a configuration diagram showing an illumination optical system of the projection exposure apparatus of the first embodiment of the present invention.

4A is a front view showing the spatial filter 24 and polarizing plates 25A to 25D of FIG. 3, and FIG. 4B is a view of FIG.
It is sectional drawing which follows the A line.

FIG. 5 is a configuration diagram showing a projection exposure apparatus according to a second embodiment of the present invention.

FIG. 6A is a diagram showing an equivalent light source and a spatial filter 240 according to a third embodiment of the present invention, and FIG. 6B is a diagram showing a state of diffracted light at the pupil of the projection optical system 13 by using the spatial filter 240. FIG.

7A is a diagram showing a polarization state of illumination light from an equivalent light source of a third embodiment, and FIG. 7B is a diagram showing an equivalent light source of a modified example of the third embodiment.

FIG. 8A is a diagram showing an equivalent light source for multi-tilt illumination;
8B is a diagram showing a state of diffracted light at the pupil of the projection optical system 13 when the equivalent light source of FIG. 8A is used.

FIG. 9 is a diagram showing a case where a specific pattern is illuminated by a plurality of inclined illuminations.

[Explanation of symbols]

 10 Equivalent Light Source 11A-11D Small Light Source 12 Reticle 13 Projection Optical System 14 Wafer 20 Light Source 22 Collimator Lens 23 Fly Eye Lens 24 Spatial Filter 24a-24d Opening 25A-25D Polarizing Plate 26 Condenser Lens System

Claims (2)

[Claims] 1. An illumination optical device for uniformly illuminating a predetermined area on an object with illumination light from the illumination optical system, wherein the illumination optical system forms inclined light for illuminating the predetermined area in an oblique direction. Illumination comprising: forming means; and polarizing means for converting the inclined light and forming illumination light linearly polarized in a direction orthogonal to an incident surface of the inclined light for obliquely illuminating the predetermined region. Optical device. 2. An illumination optical device having a light source for supplying illumination light and a condensing optical system for uniformly illuminating a predetermined region on an object with the illumination light, wherein the illumination light causes an optical axis of the condensing optical system. Inclined light forming means for forming an eccentric secondary light source to illuminate the predetermined region from an oblique direction is arranged between the light source and the condensing optical system, and the inclined light is converted to the predetermined light. Illumination characterized in that a polarizing means for forming illumination light linearly polarized in a direction orthogonal to an incident surface of inclined light for obliquely illuminating an area is arranged between the inclined light forming means and the condensing optical system. Optical device.