JP3246615B2 - Illumination optical device, exposure apparatus, and exposure method - Google Patents

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, for example, a semiconductor element or a liquid crystal display element.

[0002]

2. Description of the Related Art A projection exposure apparatus for transferring a pattern of a photomask or a reticle (hereinafter, collectively referred to as a "reticle") onto a photosensitive substrate when a semiconductor element or a liquid crystal display element is manufactured by photolithography. Is used. In such a projection exposure apparatus, it is required to print a finer pattern at a high resolution with an increase in integration of semiconductor elements and the like. As a method for realizing this, a phase shift reticle method utilizing the interference effect of light from transparent portions having different reticle pattern areas is disclosed in Japanese Patent Publication No. Sho.
It is disclosed in Japanese Patent Publication No. 2-50811. When this method is applied to a line-and-space image, the 0th-order diffracted light basically disappears, and an image is formed by only ± 1st-order diffracted light.
Even with a projection optical system having the same numerical aperture, a finer line and space image can be printed at a 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 of printing a fine pattern with a high resolution and a relatively deep depth of focus by devising an illumination optical system ( For example, March 1992, Applied Physics Alliance Lecture Meeting 30-a-NA-
See 3, 4). In the following, the method is referred to as the "multi-tilt 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 'that intersects the x-axis and the y-axis forming the rectangular coordinate system at 45 °, respectively, and this axis x'
And four small light sources 11 </ b> A to 11 </ b> A along an axis symmetric 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 a line-and-space pattern mainly having a long edge parallel to the x-axis or a long edge parallel to the y-axis.

FIG. 8B shows a schematic configuration of a projection exposure apparatus using the equivalent light source unit 10 of FIG. 8A as a light source. In FIG. Is irradiated on 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 a pupil plane (entrance pupil plane) 10A of the projection optical system 13, and an aperture stop 13a is provided on this pupil plane. 0 from that reticle 12
Order diffracted light (also denoted by reference numeral 15A) and first order diffracted light 1
6A is emitted almost symmetrically with respect to the optical axis AX.
The first order diffracted light 15A and the first order diffracted light 16A
After that, the light enters the wafer 14 as a photosensitive substrate at substantially the same incident angle θ. In this case, since the 0th-order diffracted light 15A and the 1st-order diffracted light pass near the periphery of the pupil symmetrically with respect to the optical axis AX, the resolution up to the performance limit of the projection optical system 13 can be obtained.

[0005] Further, as in the conventional case, the 0th-order diffracted light is not reflected on the wafer 1.
In the method of vertically incident on the beam 4, the depth of focus is shallow because the wavefront aberration of the 0th-order diffracted light and the wavefront aberration of the other diffracted lights with respect to the defocus amount of the wafer 14 are greatly different. On the other hand, in the configuration shown in FIG. 8B, the 0th-order diffracted light and the 1st-order diffracted light enter the wafer 14 at the same incident angle, so that the wafer 14 is located before and after the focal position of the projection optical system 13. 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 oblique illumination method, a 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 a line and space pattern 9 in a direction of 45 ° with respect to the x-axis or the y-axis, if 10A is the pupil of the projection optical system, , FIG.
The diffracted light from the two small light sources 11B and 11D among the four small light sources 11A to 11D in FIG.
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 uniformly. as a result,
The contrast of the pattern on the wafer 14 will be reduced.

This will be shown by simple numerical calculations. The intensity of the ± 1st-order diffracted light with respect to the intensity of the 0th-order diffracted light is 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 the line and space pattern long in the y-axis direction is as follows as the sum of the image intensity distributions of the respective small light sources.

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. On the other hand, in the case of a line-and-space pattern long in a 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), the following is obtained.

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

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

## EQU4 ## Cx> Cx '

Accordingly, a decrease in the contrast of a pattern long in a direction crossing the x-axis at 45 ° is shown. For example, when the width of the line is equal to the width of the space, the intensity a of the ± 1st-order diffracted light is 2 / π, so that the following expression is obtained. Cx = 0.006, Cx ′ = 0.529

In the above description, the case of the multiple oblique illumination method has been described as an example. However, for example, even when the annular illumination method or the like is used, it is desired to further improve the image contrast. In view of the above, the present invention provides an illumination optical device that illuminates a reticle or the like by positively utilizing illumination light inclined with respect to an optical axis, and an exposure device using such an illumination optical device.
In the optical method , when the pattern of the reticle or the like is a line-and-space pattern whose longitudinal direction is perpendicular to the incident surface of the illumination light, the pattern of the reticle or the like is projected by the projection optical system. It is an object of the present invention to sometimes improve the contrast of the image by devising the illumination optical device side.

[0013]

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

The second illumination optical device is, for example, as shown in FIG.
As shown in (1), 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 the illumination light, 2 decentered with respect to the optical axis of the focusing optical system
Form a secondary light source and illuminate a predetermined area from an oblique direction
Inclined light forming means for forming a slope light (24) is arranged between the light source (20) and its condensing optical system (26), its
To illuminate a predetermined area in an oblique direction (oblique illumination)
Converts the inclined light, polarizing means for forming an illumination light linearly polarized in the direction orthogonal to the incident surface of the inclined light (25
B, 25C) are arranged between the inclined light forming means (24) and the condensing optical system (26). This place
In this case, the inclined light forming means includes a first polyhedron plate having a concave portion.
Rhythm (32) and second polyhedral prism (3
3). Further, the exposure apparatus of the present invention
Is a lighting device of the present invention for illuminating a reticle as the object.
The optical device and its reticle pattern image are projected onto the photosensitive substrate.
And a projection optical system (13) for shadowing. An exposure method according to the present invention illuminates a reticle as an object using the illumination optical device of the present invention, and transfers a pattern of the reticle.

[0015]

The principle of the present invention will be described below with reference to an example of a multiple oblique illumination method for illuminating an object with illumination light from four decentered small light sources. First, according to the first illumination optical device of the present invention, for example, as shown in FIG. 3, inclined light (27B, 27C) for illuminating a predetermined area 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 oscillates in the direction perpendicular to the incident surface).
are doing. Note that the linearly polarized light means a state in which the vibration direction of the electric vector of the light wave is within one plane, and the vibration direction of the electric vector is defined as the direction of the linearly polarized light. The term “incident surface” is defined as a surface that includes, when light reaches a boundary surface of a medium, a normal line of the surface at that point and a light incident direction. FIG. 1 is a simplified view of the illumination optical device shown in FIG.

FIG. 1A shows an equivalent light source unit 10 such as a secondary light source unit of the illumination optical apparatus shown in FIG. 3. In FIG. 1A, an x-axis and a y-axis forming a rectangular coordinate system are shown. The four small light sources 11A to 11D are arranged along an axis x 'which intersects at 45 ° and an axis symmetrical with respect to the axis x' and the y axis.

FIG. 1B shows a schematic configuration of a projection exposure apparatus using the illumination optical device shown in FIG. 3, and in FIG. 1B, an equivalent light source unit 10 shown in FIG. Is equal to A principal ray 15A of the exposure light from the small light source 11A of the equivalent light source unit 10 is applied to the reticle 12 obliquely with respect to the optical axis AX via a condenser lens system not shown. The principal ray 15A is inclined light (27B, 27B) shown in FIG.
Corresponds to C). The incident surface of the principal ray 15A is shown in FIG.
According to the present invention, the principal ray 15A is linearly polarized in a direction perpendicular to the plane of FIG. 1B (the electric vector oscillates in a direction perpendicular to the plane of FIG. 1B). The light enters the reticle 12. Similarly, in FIG. 1A, light from each of the small light sources 11B to 11D is linearly polarized in a direction indicated by an arrow in FIG. )).

The 0th-order diffracted light (also denoted by reference numeral 15A) and the 1st-order diffracted light 16A from the reticle 12 enter 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 a direction parallel to the x-axis or the y-axis in FIG. Since the illumination light diffracted in the x or y direction by the polarization direction is at 45 ° to the pattern, the illumination light has the same image forming state as the random polarization. Therefore, the contrast is the same as in the conventional example.

On the other hand, if the pattern formed on the reticle 12 is a line and space pattern 9 which is long in a direction perpendicular to the x 'axis in FIG. The first-order diffracted light of the illumination light 15A enters the pupil of the projection optical system 13. In addition, FIG.
In this case, 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 (light whose electric vector oscillates in a direction perpendicular to the plane of FIG. 1B) whose polarization direction (the direction in which the electric vector oscillates) is parallel to the surface of the wafer 14. . Therefore, the interference effect on the wafer 14 is larger than that of the case of random polarization, and a high-contrast image is formed. For this reason, 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 conventional disadvantage that the contrast is reduced. .

Here, 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 represented by P-polarized light (light in which the vibration direction of the electric vector is in the incident plane) and S-polarized light (light in which the vibration direction of the electric vector is perpendicular to the incident plane). Shown. 0th order diffracted light 1
Assuming that the incident angles of the 5A and the 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
(X) is simply shown as follows using the amplitude distribution Us (x).

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.

[6] ^{_{Is (x) = a 0 2}} + a 1 2 + 2a 0 a 1 · cos _{[(2π / λ) (sinθ 0} -sinθ 1) x ], where the coefficients a ₀ and a _1, respectively 0-order diffracted light And 1
This 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 zero-order diffracted light through the projection optical system 13, so that the contrast Cs of the S-polarized light is as follows.

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
You must 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 indicated, the following expression 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 )

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

Equation 9] Ip (x) = | Up ( x) | 2 = a 0 2 + a 1 2 + 2a 0 a 1 × (cosθ 0 cosθ 1 + sinθ 0 sinθ 1) × cos _{[(2π / λ) (sinθ 0} - sin θ ₁ ) x]

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

Equation 10] Compared _{Cp = 2a 0 a 1 cos (} θ 0 -θ 1) / (2a 0 2 + a 1 2) and (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 great difference between the case of P-polarized light and the case of S-polarized light. Since the randomly polarized light is considered to be the average of the P-polarized light and the S-polarized light, the contrast is (1/2) (1 + 0.
68) = 0.84.

As described above, the use of S-polarized light causes a large difference in contrast. That is, when illumination light having a polarization state as shown in FIG. 1A is used, a line-and-space pattern whose edge is parallel to a direction crossing the x-axis and the y-axis at 45 ° is conventionally used. In this case, the contrast is expected to increase by about 20%, which is effective for fine patterns.

Although the above description has been made with reference to the multiple oblique illumination method as an example, when the present invention is applied to, for example, an annular illumination method, for example, as shown in FIG. The light from the light source in the direction perpendicular to the plane of incidence,
That is, the light 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 decentered by the illumination light from the light source is formed. The secondary light source is, for example, an equivalent light source 10 shown in FIG.
If so, the above description applies to the present invention as it is.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. In this embodiment, 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 according to 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 the collected illumination light is collimated. Lens 2
The light enters the fly-eye lens 23 (optical integrator) via the second lens 2. A planar secondary light source is formed on the focal plane on the emission 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. Further, polarizing plates 25A to 25D are respectively attached to the four openings of the spatial filter 24 on the reticle side (or on the light source 20 side). However, FIG.
Shows only the polarizing plates 25B and 25C. FIG.
4A is a front view of the spatial filter 24 of FIG. 3 as viewed from the reticle side, and FIG. 4B is a cross-sectional view taken along line AA of FIG. 4A. As shown in
The spatial filter 24 has a 90 ° angle around the optical axis AX.
Four openings 24a to 24d are formed at intervals, and these openings are respectively covered with polarizing plates 25A to 25D. Further, the polarization directions of the polarizing plates 25A to 25D are set to the tangential directions of the circumference around the optical axis AX as indicated by arrows. Therefore, the spatial filter 24
Illumination light emitted from the openings 24a to 24d is linearly polarized in a direction substantially parallel to a tangential direction of a circle around the optical axis AX.

Referring back to FIG. 3, the spatial filter 24 forms four secondary light sources decentered with respect to the optical axis AX.
The illumination light emitted from the four secondary light sources passes through the polarizing plates 25A to 25D, 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 focal point (light source side focal point) of the condenser lens system 26, and the pattern forming surface of the reticle 12 is 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 enter the reticle 12 obliquely with respect to the optical axis AX via the condenser lens system 26, respectively. Each of the principal rays 27B and 27C is linearly polarized in a direction perpendicular to the plane of incidence (on the paper) of 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, the reticle 12 is parallel or perpendicular to a straight line connecting the openings 24a and 24c in FIG. When a line-and-space pattern having a long edge in the direction is formed, the pattern can be projected onto the wafer 14 through the projection optical system 13 with better contrast than before. Here, in the apparatus shown in FIG. 3, the incident side surface of the fly-eye lens 23 and the object surface (the reticle 12 or the wafer 14) are conjugated to each other, and the exit side surface (the secondary light source 10) of the fly-eye lens 23 is projected. The pupil plane 10A of the optical system 13 is conjugated. In addition to the configuration of FIG. 3, another large polarizing plate is disposed between the fly-eye lens 23 and the spatial filter 24, and a part or all of the four openings 24 a to 24 d of the spatial filter 24 A two-wavelength plate may be provided to adjust the rotation angle of each half-wavelength plate. This also allows the optical axis A as shown in FIG.
Illumination light polarized in the tangential direction of the circumference around 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 at every opening of the spatial filter 24.

Further, for example, by using a laser light source that emits a linearly polarized laser beam as a light source, the entire spatial filter 24 shown in FIG. 3 as an equivalent light source can be illuminated with linearly polarized illumination light. It is only necessary to provide an appropriate half-wave plate in the rotation direction in a part or all of the four openings 24a to 24d of the spatial filter 24. In this case, it is sufficient to provide a half-wave plate in some of the openings, but providing a half-wave plate in all of the openings is more effective in reducing variations in illumination. When the polarization direction is adjusted using a half-wave plate as described above,
Lighting efficiency is good because there is no loss of illumination light.

When illuminating the spatial filter 24 shown in FIG. 3 as an equivalent light source by using a device that generates illumination light of circular polarization as a whole, each opening of the spatial filter 24 has an appropriate rotation direction. It is preferable to provide a / 4 wavelength plate.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a projection exposure apparatus of the present example. In FIG.
After passing through the bending mirror 28 and the input lens 29, the light beam becomes a substantially parallel light beam. The elliptical mirror 21 and the folding mirror 2
8 and the shutter 30 is arranged.
By closing 0 with the drive motor 31, the supply of the 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 a KrF laser beam or the like can be used in addition to a mercury lamp. When using an excimer laser light source,
Instead of the optical system from the elliptical mirror 21 to the input lens 29, a beam expander or the like is used.

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 polyhedral prism 33 is divided into four light beams at equal angles around the optical axis with the optical axis as the center.

The light beams divided into four light beams are used as fly eye lenses 34A, 34B, 34C and 3
4D is incident. Although only the fly-eye lenses 34A and 34B are shown in FIG. 5, the two fly-eye lenses 34C and 34C sandwich the optical axis in a direction perpendicular to the plane of FIG.
4D is arranged. And the fly-eye lens 34
The light beam emitted from A is converted into a substantially parallel light beam via a guide optical system including lens systems 35A and 36A, and is incident on the first group fly-eye lens 37A. Similarly,
The light beam emitted from the second group fly-eye lens 34B is converted into a substantially parallel light beam through a guide optical system including lens systems 35B and 36B, and the first group fly-eye lens 3
Although not shown in the figure, the light fluxes which have entered the second group fly-eye lenses 34C and 34D enter the first group fly-eye lenses 37C and 37D via guide optical systems, respectively, although not shown.

First group fly-eye lenses 37A-37D
Are arranged at 90 ° intervals around the optical axis. A planar secondary light source is formed on the reticle-side focal plane of each of the first group fly-eye lenses 37A to 37D, and variable aperture stops 38A to 38D are arranged on the formation surface of the secondary light sources. 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 stops 13A and 13B and the polarizing plates 39A and 39B are shown.

The illumination light emitted from the variable aperture stops 38A to 38D 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, respectively, and is focused on the reticle 12. Illuminate with almost uniform illuminance. The pattern of the reticle 12 is transferred by the projection optical system 13 onto the wafer 14 on the wafer stage WS at a predetermined reduction magnification β. The polarization directions of the polarizing plates 39A to 39D are parallel to the tangential direction of the circumference around the optical axis AX. For example, the principal ray 43A of the light beam transmitted through the polarizing plate 39A from the variable aperture stop 38A 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.
It is provided at the front focal point (light source side focal point) of the condenser lens system of the combined system of the auxiliary condenser lens 40 and the main condenser lens, and this position is substantially conjugate with the pupil plane 10A of the projection optical system 13.

According to this embodiment, the wafer 14 having a line and space pattern in a predetermined direction on the reticle 12 is also provided.
The contrast of the upper 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, for example, positions 44A and 4 between the relay optics, respectively.
4B, or may be arranged at another position. In the case where the illumination light from the light source 20 is already linearly polarized light, 1 is used instead of the polarizing plates 39A and 39B.
A / 2 wavelength 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 240 having a ring-shaped opening 240a as shown in FIG. 6A is changed from the spatial filter 24 of the first embodiment shown in FIG. It shows an example provided on the side. Due to the arrangement of the spatial filter 240, the exit side of the fly-eye lens 23
As shown in FIG. 3A, an annular secondary light source 45 decentered from the optical axis AX is formed, and the light from the annular secondary light source 45 passes through the condenser lens 26 and the reticle 12 as shown in FIG. The light reaches the pupil plane 10A (the entrance pupil plane) of the projection optical system 13 via the optical path. Here, in order to simplify the description, considering the state 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: FIG.
As shown in (b), an annular 0th-order diffracted light 45A similar to the annular light source 45 and an annular 1st-order diffracted light 45B obtained by laterally shifting the annular 0th-order diffracted light 45A are formed.

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

It should be noted that the present invention is not limited to the above-described embodiment, but can adopt various configurations without departing from the spirit of the present invention.

[0043]

According to the present invention, since the illumination light obliquely incident on the object is polarized in the direction perpendicular to the plane of incidence, the pattern on the object is perpendicular to the plane of incidence of the illumination light. In the case of a line-and-space pattern whose longitudinal direction is set in a desired direction, there is an advantage that the contrast of the image can be greatly improved when the pattern of the object is projected by the projection optical system.

[Brief description of the 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 in FIG. 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 according to the first embodiment of the present invention.

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

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

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

7A is a diagram illustrating a polarization state of illumination light from an equivalent light source according to a third embodiment, and FIG. 7B is a diagram illustrating an equivalent light source according to a modification of the third embodiment.

FIG. 8A is a diagram illustrating an equivalent light source of a plurality of oblique illuminations,
FIG. 9B 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.

FIG. 9 is a diagram illustrating a case where a specific pattern is illuminated by a plurality of oblique illuminations.

[Explanation of symbols]

 DESCRIPTION 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 Polarizer 26 Condenser lens system

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027

Claims (5)

(57) [Claims] 1. An illumination optical device for uniformly illuminating a predetermined area on an object with illumination light from an illumination optical system, wherein the illumination optical system forms inclined light for illuminating the predetermined area from an oblique direction. Forming means, and the predetermined area
By converting the slope light for illuminating obliquely, illumination optical apparatus characterized by having a polarization means for forming an illumination light linearly polarized in the direction orthogonal to the incident surface of the inclined light. 2. An illumination optical apparatus comprising: a light source for supplying illumination light; and a condensing optical system for uniformly illuminating a predetermined area on an object with the illumination light. to form a secondary light source eccentrically arranged tilting light forming means for forming a slope light to illuminate the predetermined area in an oblique direction between the condensing optical system and the light source with respect to the diagonal of the predetermined area by converting the slope light for illuminating from the direction, polarization means for forming an illumination light linearly polarized in the direction orthogonal to the incident surface of the inclined light between the focusing optical system and the inclined light forming means An illumination optical device, which is arranged. 3. The illumination optical device according to claim 1, wherein the inclined light forming means has a first polyhedral prism having a concave portion and a second polyhedral prism having a convex portion. Wherein exposure and having an illumination optical device according to claim 1 or 2 for illuminating a reticle as the object, a projection optical system for projecting a pattern image of the reticle onto a photosensitive substrate device . 5. An exposure method comprising illuminating a reticle as the object using the illumination optical device according to claim 1 and transferring a pattern of the reticle.