JP2001085293A - Illumination optical system and exposure system provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination optical system capable of producing converted illumination such as zonal illumination, quadruple illumination while reducing an optical loss at an aperture to a small amount. SOLUTION: This illumination optical system includes angled optical flux forming means 4, 5 for converting an optical flux from a light source 1 into a plurality of optical fluxes having angle components, optical flux shape converting means 6, 7 for forming, for example, zonal optical intensity distribution based on the optical fluxes, an optical integrator 8 which receives the optical fluxes to form a secondary light source having a zonal optical intensity distribution, and a light introducing optical system 10 for introducing the optical fluxes from the optical integrator 8 into a mask 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating optical apparatus and an exposure apparatus having the illuminating optical apparatus. The present invention relates to an illumination optical device suitable for an exposure apparatus.

[0002]

2. Description of the Related Art In a typical exposure apparatus of this kind,
The light beam emitted from the light source enters the fly-eye lens,
Thereafter, a secondary light source including a large number of light source images is formed on the side focal plane. The light beam from the secondary light source is restricted via an aperture stop arranged near the rear focal plane of the fly-eye lens, and then enters the condenser lens. The aperture stop limits the shape or size of the secondary light source to a desired shape or size according to a desired illumination condition (exposure condition).

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

In recent years, the size of the secondary light source formed by the fly-eye lens has been changed by changing the size of the opening (light transmitting portion) of the aperture stop arranged on the exit side of the fly-eye lens. A technique for changing the illumination coherency σ (σ value = aperture stop diameter / pupil diameter of the projection optical system, or σ value = exit side numerical aperture of the illumination optical system / incident side numerical aperture of the projection optical system). Is attracting attention. In addition, by setting the shape of the opening of the aperture stop arranged on the emission side of the fly-eye lens to an annular shape or a four-hole shape (ie, a quadrupole shape), the secondary light source formed by the fly-eye lens is formed. Attention has been paid to a technology for improving the depth of focus and the resolving power of a projection optical system by limiting the shape to an annular shape or a quadrupole shape.

[0005]

As described above, in the prior art, the secondary light source is limited to have a ring shape or quadrupole shape to perform deformed illumination (zone deformed illumination or quadrupole deformed illumination). To
A light beam from a relatively large secondary light source formed by a fly-eye lens is limited by an aperture stop having an annular or quadrupole aperture. In other words, in the annular deformation illumination and the quadrupole deformation illumination in the related art, a substantial part of the light beam from the secondary light source is blocked by the aperture stop, and does not contribute to illumination (exposure). As a result, there is a disadvantage that the illuminance on the mask and the wafer is reduced due to the light amount loss in the aperture stop, and the throughput as the exposure apparatus is also reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides an illumination optical device capable of performing deformed illumination such as annular illumination or quadrupole illumination while favorably suppressing a light quantity loss in an aperture stop. An object of the present invention is to provide an exposure apparatus including the illumination optical device.

[0007]

According to a first aspect of the present invention, there is provided an illumination optical apparatus for illuminating a mask having a predetermined pattern, a light source for supplying a light beam. An angle beam forming unit that converts a light beam from the light source unit into a light beam having a plurality of angle components with respect to a reference optical axis and causes the light beam to enter a first predetermined surface; Based on the luminous flux having the plurality of angle components, a light intensity distribution that is weak in a region including the reference optical axis or in a region near the reference optical axis and strong in an outer peripheral portion away from the reference optical axis. A light beam shape converting means for forming on a second predetermined surface;
An optical integrator that receives the light beam having passed through the predetermined surface to form a secondary light source having a light intensity distribution having the same tendency as the light intensity distribution, and a light guide optics for guiding the light beam from the optical integrator to the mask And an illumination optical device.

In the present invention according to claim 1, it is preferable to adopt any one of the following constitutions (1) to (18). (1) It is preferable that the angle light beam forming means changes the plurality of angle components of the light beam incident on the first predetermined surface. (2) The light beam incident on the first predetermined surface is preferably a convergent light beam as a whole. (3) The divergent light beam forming device converts the substantially parallel light beam from the light source device into light beams diverging at various angles with respect to the reference optical axis, and the divergent light beam forming device. A first optical system for condensing the divergent light beam formed through the element and guiding the divergent light beam to the first predetermined surface.

(4) In the configuration of the above (3), it is preferable that the first optical system optically conjugates the divergent light beam forming element and the first predetermined surface. (5) In the configuration of (3) or (4), it is preferable that the first optical system has a variable power optical system. (6) In the configuration of the above (5), the variable power optical system includes:
Preferably, the plurality of angle components of the light beam incident on the first predetermined surface are changed. (7) In any one of the above constitutions (3) to (6), the light intensity distribution on the pupil plane of the first optical system is preferably substantially uniform. (8) In the configuration of the above (5), the variable power optical system includes:
It is preferable to change the width of the annular light source or the plurality of light sources formed as the secondary light source without changing the center height.

(9) In any one of the constitutions (3) to (8), it is preferable that the divergent light beam forming element is configured to be insertable into and removable from an illumination light path. (10) In any one of the above configurations (3) to (9),
It is preferable that the divergent light beam forming element splits a light beam from the light source means into a wavefront. (11) In the configuration according to claim 1, the divergent light beam forming element has a microlens array configured to be insertable into and removable from an illumination light path, and the first optical system is formed as the secondary light source. It is preferable to have a first variable power optical system for changing the width of the annular light source or the plurality of light sources without changing the center height. (12) In the configuration of the above (11), the first variable power optical system includes a focal plane of the micro lens array and the first variable power optical system.
It is preferable to have an afocal zoom lens that optically conjugates with the predetermined surface.

(13) Claim 1 or the above (1) to (1)
In any one of the constitutions 2), the light beam shape converting means includes a light beam converting element disposed near the first predetermined surface, and a second light beam guiding device for guiding the light beam from the light beam converting device to the second predetermined surface. It is preferable to have an optical system. (14) In the configuration of the above (13), it is preferable that the second optical system has a variable power optical system. (15) In the configuration of the above (13) or (14),
The light beam conversion element is weak in a far field (or Fraunhofer diffraction region) in a region including the reference optical axis or in a region near the reference optical axis, and becomes strong in an outer peripheral portion away from the reference optical axis. Preferably, a light intensity distribution is formed, and the second optical system preferably forms the light intensity distribution formed in the far field (or Fraunhofer diffraction region) on the second predetermined surface.

(16) In any one of the constitutions (13) to (15), it is preferable that the light beam converting element is provided so as to be freely inserted into and removed from an illumination light path. (17) In the configuration according to any one of (1) to (12), the light beam shape converting means is a ring-shaped light beam that radially diverges a thin light beam incident on the first predetermined surface. Or a light flux conversion element for converting into a plurality of light fluxes, and based on a ring-shaped light flux or a plurality of light fluxes formed via the light flux conversion element, a ring-shaped illumination field or the illumination field on the incident surface of the optical integrator. A second optical system for forming a plurality of illumination fields decentered with respect to the reference optical axis. (18) In the configuration of the above (17), the light beam conversion element includes a diffractive optical element configured to be detachable from an illumination optical path and having a diffraction surface positioned on the first predetermined surface. The second optical system preferably has a ring-shaped light source formed as the secondary light source or a second variable power optical system for changing the outer diameter of the plurality of light sources without changing the ring ratio. .

According to a second aspect of the present invention, in an illumination optical device for illuminating a mask having a predetermined pattern, a light source means for supplying a substantially parallel light beam;
A divergent light beam forming element for converting the substantially parallel light beam from the light source means into a divergent light beam having a plurality of angle components with respect to a reference optical axis; and condensing the divergent light beam to a first predetermined surface. A first optical system for guiding the light, a light beam converting element disposed near the first predetermined surface, a second optical system for guiding a light beam from the light beam converting device to a second predetermined surface, An optical integrator that receives the light beam passing through the second predetermined surface to form a secondary light source having a predetermined light intensity distribution, and a light guide optical system for guiding the light beam from the optical integrator to the mask. The first and second optical systems have first and second variable power optical systems, and the light beam conversion element and the second optical system are configured to control the reference optical axis based on a light beam from the first optical system. Weakly in the region including or around the reference optical axis. One provides an illumination optical apparatus, and forming a light intensity distribution such that stronger on the second predetermined plane in the reference optical axis from a remote peripheral portion.

In the present invention according to claim 2, it is preferable to adopt any one of the following constitutions (19) to (25). (19) In the configuration of claim 2, it is preferable that the divergent light beam forming element splits the substantially parallel light beam from the light source means into a wavefront. (20) In the constitution of claim 2 or (19),
The light beam guided to the first predetermined surface is preferably a convergent light beam as a whole.

(21) Claim 2 or (19) or above
In any one of the constitutions (20), the first optical system includes:
It is preferable that the divergent light beam forming element and the first predetermined surface are optically conjugate. (22) In the configuration according to claim 2 or any one of (19) to (21), the light beam conversion element includes a region including the reference optical axis or a reference light in a far field (or Fraunhofer diffraction region). It is preferable to form a light intensity distribution that is weak in a region near an axis and strong in an outer peripheral portion distant from the reference optical axis, and the second optical system is arranged in the far field (or Fraunhofer diffraction region). The light intensity distribution to be formed is
Is preferably formed on a predetermined surface.

(23) Claim 2 or (19) or above
In any one of the constitutions of (22), the first optical system includes:
Preferably, the plurality of angle components of the light beam incident on the first predetermined surface are changed. (24) In any one of the constitutions (2) and (19) to (22), the first variable power optical system may have a center height of the light intensity distribution formed on the second predetermined surface. It is preferable to change the width without changing the width. (25) In any one of the constitutions (2) or (19) to (23), the second variable power optical system is configured such that the reference light in the light intensity distribution formed on the second predetermined surface is provided. It is preferable to change the distance from the reference optical axis to the outside while maintaining a constant ratio of the distance from the axis to the inside and the distance from the reference optical axis to the outside.

Further, according to the present invention, in an illumination optical device for illuminating a mask having a predetermined pattern, a light source means for supplying a substantially parallel light beam, and the substantially parallel light beam from the light source means are provided. A divergent light beam forming element for converting the light beam into a divergent light beam having a plurality of angular components with respect to a reference optical axis; and a first optical system for condensing the divergent light beam and guiding the divergent light beam to a first predetermined surface. A light beam conversion element disposed in the vicinity of the first predetermined surface, a second optical system for guiding a light beam from the light beam conversion element to a second predetermined surface;
An optical integrator that receives the light beam having passed through the predetermined surface to form a secondary light source having a predetermined light intensity distribution, and a light guide optical system for guiding the light beam from the optical integrator to the mask. The first optical system optically conjugates the divergent light beam forming element and the first predetermined surface, and the light beam conversion element and the second optical system, based on a light beam from the first optical system, A light intensity distribution is formed on the second predetermined surface such that the light intensity distribution is weak in a region including a reference optical axis or in a region near the reference optical axis and strong in an outer peripheral portion away from the reference optical axis. An illumination optical device is provided.

In the third aspect of the present invention, it is preferable to adopt any one of the following constitutions (26) to (33). (26) In the configuration of the third aspect, it is preferable that the first optical system has a first variable power optical system. (27) In the configuration of (26), it is preferable that the first variable power optical system has an afocal zoom lens.

(28) In the configuration of (26) or (27), the first variable power optical system changes a center height of the light intensity distribution formed on the second predetermined surface. Preferably, the width is changed. (29) In any one of the constitutions (3) and (26) to (28), it is preferable that the light intensity distribution on the pupil plane of the first optical system is substantially uniform. (30) In the third aspect, in any one of the above (26) to (29), it is preferable that the second optical system has a second variable power optical system. (31) In the configuration of the above (30), it is preferable that the second variable power system makes the light flux conversion element and the second predetermined surface substantially have a Fourier transform relationship.

(32) Claim 3 or (26)-
(31) In any one of the constitutions (31), the second variable power optical system is configured such that a distance from the reference optical axis to an inner side from the reference optical axis in the light intensity distribution formed on the second predetermined surface and the reference optical axis. It is preferable to change the distance from the reference optical axis to the outside while maintaining the ratio of the distance to the outside constant. (33) In any one of the constitutions (3) or (26) to (32), the light beam conversion element may include a region including the reference optical axis or the reference light in a far field (or Fraunhofer diffraction region). It is preferable to form a light intensity distribution that is weak in a region near an axis and strong in an outer peripheral portion distant from the reference optical axis, and the second optical system is arranged in the far field (or Fraunhofer diffraction region). The light intensity distribution to be formed is
Is preferably formed on a predetermined surface.

Further, in the present invention according to any one of the first, second or third aspects and the above-mentioned constitutions (1) to (33), any one of the following constitutions (34) to (35) is adopted. Is preferred. (34) Claim 1, 2 or 3, and the above (1)-
In any one of the constitutions (33), it is preferable that an incident surface of the optical integrator is positioned at the second predetermined surface. (35) Claim 1, 2 or 3, and the above (1)-
(34) In any one of the constitutions (34), the light guide optical system comprises:
A condenser group for condensing a light beam from the secondary light source to illuminate a third predetermined surface in a superimposed manner;
And a relay group for forming an image on the predetermined surface.

According to the present invention, there is provided an exposure apparatus for transferring a pattern on a mask onto a photosensitive substrate, wherein the exposure apparatus comprises any one of claims 1, 2 and 3, and any one of the above constitutions (1) to (35). An illumination optical device according to the present invention, and a projection optical system for transferring the pattern onto the photosensitive substrate. In the above exposure apparatus, the divergent light beam forming element, the first variable power optical system, the light beam conversion element, and the second light beam
It is preferable to further include control means for controlling at least one of the variable power optical systems.

According to the present invention, there is provided an exposure method for transferring a pattern on a mask onto a photosensitive substrate, and the method according to any one of claims 1, 2 and 3, and any one of the above constitutions (1) to (35). The illumination optical device illuminates the mask and transfers the illuminated pattern onto the photosensitive substrate. In the above-described exposure method, at least one of the divergent light beam forming element, the first variable power optical system, the light beam conversion element, and the second variable power optical system is controlled based on information on the pattern of the mask. It is preferable to control.

[0024]

DETAILED DESCRIPTION OF THE INVENTION In a typical embodiment of the invention,
In the optical path between the light source means and the optical integrator, an angle light beam forming means and a light beam shape converting means are arranged. Specifically, the angle beam forming unit includes a divergent beam forming element such as a microlens array for converting a substantially parallel beam from the light source unit into a beam diverging at various angles with respect to the reference optical axis. And an optical system such as an afocal zoom lens for condensing a divergent light beam formed via a microlens array and guiding the light to a diffraction surface of a diffractive optical element as a light beam conversion element described later. . Therefore, the substantially parallel light flux from the light source means passes through the microlens array and the afocal zoom lens, and then enters the diffractive optical element as a light flux having a plurality of angle components with respect to the reference optical axis.

On the other hand, the light beam shape converting means includes a light beam converting element such as a diffractive optical element for converting an incident thin light beam into a ring-shaped light beam or a plurality of light beams radiating radially, and a diffractive optical element. To form a ring-shaped illumination field or a plurality of illumination fields decentered with respect to a reference optical axis on an incidence surface of an optical integrator such as a fly-eye lens based on the ring-shaped light beam or the plurality of light beams formed by And an optical system such as a zoom lens. In general, a plurality of illumination fields or secondary light sources decentered with respect to a reference optical axis is, for example, a dipole or multipole (triple, quadrupole,..., Octupole) illumination. In the following description, a quadrupole illumination field or a secondary light source will be described as an example.

Thus, an angle beam forming means comprising the micro lens array and the afocal zoom lens,
By the action of the light beam shape converting means including the diffractive optical element and the zoom lens, an annular illumination field or a quadrupole illumination field is formed on the incident surface of the fly-eye lens. As a result, an annular or quadrupolar secondary light source is similarly formed on the rear focal plane of the fly-eye lens. The luminous flux from the annular or quadrupolar secondary light source formed by the fly-eye lens in this manner is limited by an aperture stop having an opening corresponding to the size and shape of the secondary light source, and is then illuminated. Are superimposedly illuminated.

As described above, according to the present invention, an annular or quadrupolar secondary light source can be formed based on the luminous flux from the light source means with almost no loss of light amount. As a result, it is possible to perform annular deformation illumination and quadrupole deformation illumination while favorably suppressing the light amount loss in the aperture stop that restricts the light flux from the secondary light source. It is needless to say that ordinary circular illumination can be performed while satisfactorily suppressing loss of light amount by retracting the microlens array from the illumination optical path.

Further, in the present invention, by changing the magnification of the afocal zoom lens, it is possible to change both the outer diameter and the annular ratio of the annular or quadrupolar secondary light source. Further, by changing the focal length of the zoom lens, it is possible to change the outer diameter of the annular or quadrupole secondary light source without changing the annular ratio.
As a result, by appropriately changing the magnification of the afocal zoom lens and the focal length of the zoom lens, it is possible to change only the annular ratio without changing the outer diameter of the annular or quadrupolar secondary light source. Can be.

As described above, in the illumination optical device of the present invention, while the loss of light amount in the aperture stop for limiting the secondary light source is suppressed favorably, deformed illumination such as orbicular deformed illumination or quadrupole deformed illumination and a normal circular illumination are used. Lighting can be performed. In addition, the simple operation of changing the magnification of the afocal zoom lens or changing the focal length of the zoom lens allows the loss of light amount at the aperture stop to be suppressed well and the parameters of the deformed illumination (the limited secondary light source (Size and shape) can be varied.

Therefore, in the exposure apparatus incorporating the illumination optical apparatus of the present invention, the resolution and depth of focus of the projection optical system suitable for the fine pattern to be exposed and projected can be obtained by appropriately changing the type and parameters of the modified illumination. Can be. As a result, good projection exposure with high throughput can be performed under high exposure illuminance and good exposure conditions. Further, in the exposure method of exposing the pattern of the mask disposed on the surface to be irradiated to the photosensitive substrate using the illumination optical device of the present invention, projection exposure can be performed under favorable exposure conditions. , A good device can be manufactured.

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically illustrating a configuration of an exposure apparatus including an illumination optical device according to an embodiment of the present invention. FIG.
1, the Z axis along the normal direction of the wafer 13 as a photosensitive substrate, the Y axis in a direction parallel to the plane of FIG. 1 in the wafer plane, and the Y axis in a direction perpendicular to the plane of FIG. 1 in the wafer plane. The X axis is set individually. In FIG. 1, the illumination optical device is set to perform annular illumination.

The exposure apparatus shown in FIG. 1 is provided with, as a light source 1 for supplying exposure light (illumination light), for example, an excimer laser light source for supplying light having a wavelength of 248 nm or 193 nm. A substantially parallel light flux emitted from the light source 1 in the Z direction has a rectangular cross section elongated in the X direction, and has a pair of cylindrical lenses 2a and 2a.
b enters the beam expander 2. Each of the cylindrical lenses 2a and 2b is positioned in the plane of FIG.
(In the Z plane), each of which has a negative refractive power and a positive refractive power, and which includes the optical axis AX and is orthogonal to the paper (XZ).
(In a plane) as a parallel plane plate. Therefore, the light beam incident on the beam expander 2 is enlarged in the plane of FIG. 1 and shaped into a light beam having a predetermined rectangular cross section.

A substantially parallel light beam passing through a beam expander 2 as a shaping optical system is deflected in the Y direction by a bending mirror 3 and then enters a microlens array 4 for annular deformation illumination. As shown in FIGS. 1 and 2, the microlens array 4 is an optical element including a large number of regular hexagonal microlenses (microlenses) 4a arranged densely and vertically and horizontally. Generally, a microlens array is formed by, for example, performing etching on a parallel flat glass plate to form a group of microlenses.

Here, each micro lens constituting the micro lens array is smaller than each lens element constituting the fly-eye lens. Also, unlike a fly-eye lens composed of lens elements that are isolated from each other, the microlens array has a large number of microlenses formed integrally without being isolated from each other.
However, a microlens array is the same as a fly-eye lens in that lens elements having positive refractive power are arranged vertically and horizontally. In FIGS. 1 and 2,
For clarity of the drawing, the number of microlenses 4a constituting the microlens array 4 is set to be much smaller than the actual number.

Therefore, the light beam incident on the microlens array 4 is two-dimensionally divided by a large number of microlenses, and one microlens is provided on the rear focal plane.
Two light source images are formed. Light beams from a large number of light source images formed on the rear focal plane of the microlens array 4 become divergent light beams each having a regular hexagonal cross section and enter the afocal zoom lens 5. As described above, the microlens array 4 constitutes a divergent light beam forming element for converting a substantially parallel light beam from the light source 1 into light beams diverging at various angles with respect to the optical axis AX.

The microlens array 4 is configured to be freely inserted into and removed from the illumination optical path, and to be switchable with the microlens array 40 for quadrupole illumination. The configuration and operation of the microlens array 40 for quadrupole deformation illumination will be described later. Further, the afocal zoom lens 5 is configured so that the magnification can be continuously changed within a predetermined range while maintaining an afocal system (a non-focus optical system).

Here, the micro lens array 4 for annular deformation illumination and the micro lens array 40 for quadrupole deformation illumination
And the retreat of the microlens arrays 4 and 40 from the illumination light path is performed by the first drive system 22 that operates based on a command from the control system 21. The magnification change of the afocal zoom lens 5 is performed by the second drive system 23 that operates based on a command from the control system 21.

The light beam passing through the afocal zoom lens 5 enters a diffractive optical element (DOE) 6 for annular deformation illumination. At this time, the divergent light flux from each light source image formed on the rear focal plane of the microlens array 4 converges on the diffraction surface of the diffractive optical element 6 while maintaining a regular hexagonal cross section. That is, the afocal zoom lens 5 optically couples the rear focal plane of the microlens array 4 and the diffraction plane of the diffractive optical element 6. Then, the numerical aperture of the light beam condensed on one point on the diffraction surface of the diffractive optical element 6 changes depending on the magnification of the afocal zoom lens 5.

Generally, a diffractive optical element is formed by forming a step having a pitch on the order of the wavelength of exposure light (illumination light) on a glass substrate, and has a function of diffracting an incident beam to a desired angle. Specifically, as shown in FIG. 3A, the diffractive optical element 6 for annular deformation illumination has an optical axis AX.
A thin light beam perpendicularly incident in parallel with the light beam is radially diverged according to one predetermined divergence angle. In other words, a thin light beam that is perpendicularly incident on the diffractive optical element 6 along the optical axis AX is
The light is diffracted along all directions at an equal angle about the optical axis AX. As a result, the thin luminous flux perpendicularly incident on the diffractive optical element 6 is converted into a divergent luminous flux having a ring-shaped cross section. As described above, the diffractive optical element 6 constitutes a light beam conversion element for converting an incident fine light beam into a ring-shaped light beam that diverges radially.

Therefore, as shown in FIG. 3B, when a thick parallel light beam is perpendicularly incident on the diffractive optical element 6,
Also at the focal position of the lens 31 disposed behind the diffractive optical element 6, a ring-shaped image (ring-shaped light source image) 32
Is formed. That is, the diffractive optical element 6 forms a ring-shaped light intensity distribution in the far field (or Fraunhofer diffraction region). The lens 31 is
A ring-shaped light intensity distribution formed in the far field (or Fraunhofer diffraction region) is formed on the rear focal plane.

Here, as shown in FIG. 3C, when a thick parallel light beam incident on the diffractive optical element 6 is inclined with respect to the optical axis AX, a ring-shaped image formed at the focal position of the lens 31 is formed. Moving. That is, when the thick parallel light beam incident on the diffractive optical element 6 is inclined along a predetermined surface (the paper surface in FIG. 3), a ring-shaped image 3 formed at the focal position of the lens 31 is formed.
3 moves its center along a predetermined surface in the direction opposite to the direction in which the light beam is inclined, without changing its size.

As described above, the micro lens array 4
The divergent light flux from each light source image formed on the rear focal plane of
The light converges on the diffraction surface of the diffractive optical element 6 while maintaining the regular hexagonal cross section. In other words, a light beam having a large number of angle components is incident on the diffractive optical element 6, and the incident angle is defined by a light beam range of a regular hexagonal pyramid. Therefore, as shown in FIG. 4A, each ridge line of a regular hexagonal pyramid-shaped light beam range is centered on a ring-shaped image 47 (shown by a broken line in the figure) formed by a light beam that is perpendicularly incident on the diffraction optical element 6. The light beam incident at the maximum angle corresponding to
To 46 (shown by solid lines in the figure). FIG.
(B) shows a state in which ring-shaped images 41 to 47 thus formed at the focal position of the lens 31 are superimposed.

In practice, an infinite number of light beams having a large number of angular components defined by a light beam range of a regular hexagonal pyramid shape are incident on the diffractive optical element 6, so that the focal position of the lens 31 is infinitely ring-shaped. Are superimposed to form an annular (annular) image as a whole as shown in FIG. Note that FIG. 5 shows that the image superimposed on the focal position of the lens 31 has a ring shape as a whole by superimposing more ring-shaped images than in FIG.

The diffractive optical element 6 is configured to be insertable into and removable from the illumination optical path, and is configured to be switchable between a diffractive optical element 60 for quadrupole deformation illumination and a diffractive optical element 61 for normal circular illumination. ing. The configuration and operation of the diffractive optical element 60 for quadrupole deformation illumination and the diffractive optical element 61 for normal circular illumination will be described later. Here, the diffractive optical element 6 for annular deformation illumination and the diffractive optical element 6 for quadrupole deformation illumination
Switching between 0 and the diffractive optical element 61 for normal circular illumination is performed by the third drive system 24 that operates based on a command from the control system 21.

Referring to FIG. 1 again, the light beam having passed through the diffractive optical element 6 enters the zoom lens 7. Here, the zoom lens 7 has the same action as the lens 31 shown in FIG. In the vicinity of the rear focal plane of the zoom lens 7,
An incident surface of a fly-eye lens 8 as an optical integrator is positioned. Accordingly, the light beam having passed through the diffractive optical element 6 forms an annular illumination field on the rear focal plane of the zoom lens 7 and thus on the incident surface of the fly-eye lens 8. The outer diameter of this annular illumination field changes depending on the focal length of the zoom lens 7. As described above, the zoom lens 7 has a substantially Fourier transform relationship between the diffractive optical element 6 and the entrance surface of the fly-eye lens 8. The change in the focal length of the zoom lens 7 is performed by the fourth drive system 25 that operates based on a command from the control system 21.

The fly-eye lens 8 is constituted by arranging a large number of lens elements having a positive refractive power densely and vertically. Each lens element constituting the fly-eye lens 8 has a rectangular cross section similar to the shape of the illumination field to be formed on the mask (and, consequently, the shape of the exposure area to be formed on the wafer). The entrance side surface of each lens element constituting the fly-eye lens 8 is formed in a spherical shape with a convex surface facing the incident side, and the exit side surface is formed in a spherical shape with a convex surface facing the exit side. .

Therefore, the light beam incident on the fly-eye lens 8 is two-dimensionally divided by a large number of lens elements, and a light source image is formed on the rear focal plane of each lens element on which the light beam has entered. In this way, on the rear focal plane of the fly-eye lens 8, a number of annular light sources (hereinafter, referred to as “secondary light sources”) having the same annular field as the illumination field formed by the light beam incident on the fly-eye lens 8 are formed. A light beam from the annular secondary light source formed on the rear focal plane of the fly-eye lens 8 enters an aperture stop 9 arranged near the light source. The aperture stop 9 is supported on a turret (rotary plate: not shown in FIG. 1) rotatable around a predetermined axis parallel to the optical axis AX.

FIG. 6 is a diagram schematically showing a configuration of a turret in which a plurality of aperture stops are arranged in a circumferential shape. As shown in FIG. 6, the turret substrate 400 is provided with eight aperture stops having light transmission areas indicated by oblique lines in the figure along the circumferential direction. The turret substrate 400 is configured to be rotatable around an axis passing through the center point O and parallel to the optical axis AX. Therefore, by rotating the turret substrate 400, one aperture stop selected from eight aperture stops can be positioned in the illumination optical path. The rotation of the turret substrate 400 is performed by the fifth drive system 26 that operates based on a command from the control system 21.

On the turret substrate 400, three annular aperture stops 401, 403 and 405 having different annular ratios are formed. Here, the annular aperture stop 401 is r11 /
It has an annular transmission region having an annular ratio of r21. The annular aperture stop 403 has an annular transmission region having an annular ratio of r12 / r22. The annular aperture stop 405 is r13 / r
It has an annular transmission region having an annular ratio of 21.

The turret substrate 400 has three quadrupole aperture stops 402, 404, and 40 having different orbital ratios.
6 are formed. Here, the four-pole aperture stop 402 is
It has four eccentric circular transmissive regions in an annular region having an annular ratio of r11 / r21. 4-pole aperture stop 404
Has four eccentric circular transmissive regions within an annular region having an annular ratio of r12 / r22. 4-pole aperture stop 4
Reference numeral 06 has four eccentric circular transmission regions in an annular region having an annular ratio of r13 / r21. Further, two circular aperture stops 407 and 408 having different sizes (diameter) are formed on the turret substrate 400.
Here, the circular aperture stop 407 has a circular transmission area having a size of 2r22, and the circular aperture stop 408 has a circular transmission area having a size of 2r21.

Therefore, three annular aperture stops 401,
By selecting one of the annular aperture stops 403 and 405 and positioning it in the illumination optical path, the annular luminous flux having three different annular ratios is accurately restricted (defined),
It is possible to perform three types of annular deformation illumination having different annular ratios. Also, three quadrupole aperture stops 402, 404 and 4
The four eccentric light beams having three different ring zone ratios are accurately limited by selecting one of the four-pole aperture stop of the aperture stop in the illumination optical path, and the three eccentric light beams having three different ring zone ratios are selected.
Different types of quadrupole illumination can be provided. Further, by selecting one of the two circular aperture stops 407 and 408 and positioning it in the illumination optical path, two types of normal circular illumination having different σ values can be performed.

In FIG. 1, an annular secondary light source is formed on the rear focal plane of the fly-eye lens 8, so that one aperture selected from three annular aperture stops 401, 403 and 405 is used as the aperture stop 9. An annular aperture stop is used. However, the configuration of the turret shown in FIG. 6 is exemplary,
The type and number of the aperture stops to be arranged are not limited to this. In addition, without being limited to the turret type aperture stop, an aperture stop capable of appropriately changing the size and shape of the light transmission region may be fixedly mounted in the illumination optical path. Further, instead of the two circular aperture stops 407 and 408, an iris diaphragm capable of continuously changing the circular aperture diameter can be provided.

The light from the secondary light source through the aperture stop 9 having the annular aperture (light transmitting portion) is subjected to a light condensing action of the condenser optical system 10 as a light guiding optical system, and then is subjected to a predetermined light. The mask 11 on which the pattern is formed is uniformly illuminated in a superimposed manner. The light flux transmitted through the pattern of the mask 11 forms an image of the mask pattern on the wafer 13 as a photosensitive substrate via the projection optical system 12. Thus, the projection optical system 12
The batch exposure or the scan exposure is performed while the wafer 13 is two-dimensionally driven and controlled in a plane (XY plane) orthogonal to the optical axis AX. Is done.

In the batch exposure, a so-called step
According to the AND repeat method, the mask pattern is collectively exposed to each exposure region of the wafer. In this case, the shape of the illumination area on the mask 11 is a rectangular shape close to a square, and the cross-sectional shape of each lens element of the fly-eye lens 8 is also a rectangular shape close to a square. On the other hand, in scan exposure, according to a so-called step-and-scan method, a mask pattern is scanned and exposed on each exposure region of a wafer while the mask and wafer are relatively moved with respect to a projection optical system. In this case, the mask 11
The shape of the illumination area above is a rectangular shape having a ratio of the short side to the long side of, for example, 1: 3, and the cross-sectional shape of each lens element of the fly-eye lens 8 is a rectangular shape similar to this.

FIG. 7 is a diagram schematically showing the configuration from the microlens array 4 to the entrance surface of the fly-eye lens 8. The magnification of the afocal zoom lens 5, the focal length of the zoom lens 7, and the fly-eye FIG. 4 is a diagram illustrating the relationship between the size and shape of an annular illumination field formed on an incident surface of a lens. In FIG. 7, a light ray 70 incident along the optical axis AX at the center of the microlens arranged on the optical axis AX of the microlens array 4 is emitted along the optical axis AX. The microlens array 4 is composed of microlenses having a size (a size corresponding to the diameter of a circle circumscribing a regular hexagon) and a focal length f1.
After passing through the afocal zoom lens 5, the light ray 70
The light enters the diffractive optical element 6 along the optical axis AX.

The diffractive optical element 6 has an angle θ with respect to the optical axis AX based on the light beam 70 perpendicularly incident along the optical axis AX.
To form a light beam 70a emitted. The light ray 70a emitted from the diffractive optical element 6 at an angle θ reaches the incident surface of the fly-eye lens 8 via the zoom lens 7 having the focal length f2. At this time, the position of the light ray 70a on the incident surface of the fly-eye lens 8 has a height of y from the optical axis AX.
On the other hand, a light ray 71 incident parallel to the optical axis AX on the uppermost edge of the microlens arranged on the optical axis AX of the microlens array 4 is emitted at an angle t with respect to the optical axis AX.
The light beam 71 is transmitted to the afocal zoom lens 5 having a magnification m.
After that, the light enters the diffractive optical element 6 at an angle t ′ with respect to the optical axis AX.

The light beam 71 incident on the diffractive optical element 6 at an angle t 'with respect to the optical axis AX has an angle (θ +
The light beam is converted into various light beams including the light beam 71a emitted at t ′). The light ray 71a emitted from the diffractive optical element 6 at an angle (θ + t ′) with respect to the optical axis AX passes through the zoom lens 7 and enters the optical axis AX at the incident surface of the fly-eye lens 8.
To a height of (y + b). Furthermore, the light beam 72 incident on the lowermost edge of the microlens disposed on the optical axis AX of the microlens array 4 in parallel with the optical axis AX is emitted at an angle t with respect to the optical axis AX. After passing through the afocal zoom lens 5, the light beam 72 enters the diffractive optical element 6 at an angle t 'with respect to the optical axis AX.

The light beam 72 incident on the diffractive optical element 6 at an angle t ′ with respect to the optical axis AX is at an angle (θ−
The light beam is converted into various light beams including the light beam 72a (not shown) emitted at t ′). Angle (θ-t ') with respect to optical axis AX
The light beam 72a emitted from the diffractive optical element 6 at the point (a) reaches the height (y-b) from the optical axis AX on the incident surface of the fly-eye lens 8 via the zoom lens 7.

Thus, the range in which the divergent light flux from each light source image formed near the rear focal plane of the microlens array 4 reaches the incident surface of the fly-eye lens 8 is centered on the height from the optical axis AX to y. As a range having the width 2b. That is, as shown in FIG.
The annular illuminated field formed on the entrance surface of the lens, and thus the annular secondary light source formed on the rear focal plane of the fly-eye lens 8 have a center height y from the optical axis AX and a width 2b. Will have.

Here, the exit angle t from the microlens array 4 and the incident angle t 'to the diffractive optical element 6 are represented by the following equations (1) and (2). t = a / (2 · f1) (1) t ′ = t / m = a / (2 · f1 · m) (2) Further, the center height y and the maximum height (y +
b) and the minimum height (y−b) are given by the following equations (3) to
Each is represented by (5). y = f2 · sinθ (3) y + b = f2 (sinθ + sint ′) (4) y−b = f2 (sinθ−sint ′) (5)

Accordingly, the inner diameter φi of the annular secondary light source
The annular zone ratio A defined by the ratio of the outer diameter φo to the outer diameter φo is expressed by the following equation (6).

A = φi / φo = 2 (y−b) / (2 (y + b)) = (sinθ−sint ′) / (sinθ + sint ′) = (sinθ−sin (a / (2 · f1 · m)) )) / (Sinθ + sin ((a / (2 · f1 · m))) (6)

The outer diameter φo of the ring-shaped secondary light source is expressed by the following equation (7).

## EQU2 ## φo = 2 (y + b) = 2 · f2 (sin θ + sint ′) = 2 · f2 (sin θ + sin (a / (2 · f1 · m))) (7)

Thus, referring to the equations (2) to (6), when the magnification m of the afocal zoom lens 5 changes, the center height y of the annular secondary light source does not change, but only its width 2b. Changes. That is, by changing the magnification m of the afocal zoom lens 5, it is possible to change both the size (outer diameter φo) of the annular secondary light source and its shape (annular ratio A).

Further, referring to the equations (3) to (7), when the focal length f2 of the zoom lens 7 changes, the ring height A and the center height y of the ring-shaped secondary light source do not change. It can be seen that both widths 2b change. That is, by changing the focal length f2 of the zoom lens 7, the outer diameter φo can be changed without changing the annular ratio A of the annular secondary light source. As described above, by appropriately changing the magnification m of the afocal zoom lens 5 and the focal length f2 of the zoom lens 7, only the annular ratio A is changed without changing the outer diameter φo of the annular secondary light source. can do.

As described above, when the annular microlens array 4 and the diffractive optical element 6 for annular deformation are used, the annular secondary light source is formed based on the light beam from the light source 1 with almost no loss of light amount. As a result, it is possible to perform annular deformation illumination while satisfactorily suppressing the light amount loss in the aperture stop 9 that limits the light flux from the secondary light source.

As described above, the micro lens array 4
Is configured to be insertable into and removable from the illumination optical path, and to be switchable with the microlens array 40 for quadrupole deformation illumination. The diffractive optical element 6 is configured to be freely inserted into and removed from the illumination optical path, and is configured to be switchable between a diffractive optical element 60 for quadrupole deformation illumination and a diffractive optical element 61 for normal circular illumination. Hereinafter, a quadrupole deformation illumination obtained by setting the microlens array 40 in the illumination optical path instead of the microlens array 4 and setting the diffractive optical element 60 in the illumination optical path instead of the diffractive optical element 6 will be described. I do.

As shown in FIGS. 1 and 8, the microlens array 40 is composed of a large number of square-shaped microlenses 40 having positive refracting power arranged vertically and horizontally. Therefore, the micro lens array 40
A large number of light source images are formed on the rear focal plane. Light beams from the respective light source images enter the afocal zoom lens 5 as divergent light beams each having a square cross section. The light beam having passed through the afocal zoom lens 5 enters a diffractive optical element 60 for quadrupole deformation illumination. At this time, the divergent light flux from each light source image formed on the rear focal plane of the microlens array 40 converges on the diffraction surface of the diffractive optical element 60 while maintaining a square cross section.

As shown in FIG. 9A, the four-pole modified illumination diffractive optical element 60 radially diverges a thin light beam perpendicularly incident parallel to the optical axis AX according to one predetermined exit angle. It is converted into four light beams. In other words, the optical axis AX
The thin light beam that is vertically incident along is diffracted at equal angles around the optical axis AX along four specific directions, resulting in four thin light beams. More specifically, a thin light beam that is perpendicularly incident on the diffractive optical element 60 is converted into four light beams, and a square connecting the passing points of the four light beams passing through the rear surface parallel to the diffractive optical element 60 is a square. The center of the square will be on the axis of incidence on the diffractive optical element 60.

Therefore, as shown in FIG. 9B, when a thick parallel light beam is perpendicularly incident on the diffractive optical element 60, the focal position of the lens 91 disposed behind the diffractive optical element 60 is also 4 Point images (point light source images) 92
Is formed. Here, as shown in FIG. 9C, when the thick parallel light beam incident on the diffractive optical element 60 is inclined with respect to the optical axis AX, the four images formed at the focal position of the lens 91 move. That is, when a thick parallel light beam incident on the diffractive optical element 60 is tilted along a predetermined plane, the four point images 93 formed at the focal position of the lens 91 are not tilted along the predetermined plane. Move in the opposite direction.

As described above, the micro lens array 4
The divergent luminous flux from each light source image formed on the back focal plane of the diffractive optical element 60 is maintained while maintaining a square cross section.
Converges on the diffraction plane. In other words, the diffractive optical element 60
A light beam having a large number of angle components is incident on the light source, and the angle of incidence is defined by a light beam range of a regular quadrangular pyramid.
That is, an infinite number of light beams having a large number of angle components defined by the light beam range of a regular quadrangular pyramid shape
0, an infinite number of point images are superimposed on the focal position of the lens 91, and 4 points as shown in FIG.
A polar image is formed. Therefore, the diffractive optical element 60
Forms a quadrupole illumination field on the rear focal plane of the zoom lens 7 and consequently on the entrance plane of the fly-eye lens 8. As a result, as shown in FIG. 11, a secondary light source having the same quadrupolar shape as the illumination field formed on the incident surface is also formed on the rear focal plane of the fly-eye lens 8.

Switching from the micro lens array 4 to the micro lens array 40 and the diffractive optical element 6
The switching from the annular aperture stop 9 to the aperture stop 9a is performed corresponding to the switching from to the diffractive optical element 60. The aperture stop 9a is one quadrupole aperture stop selected from three quadrupole aperture stops 402, 404 and 406. Thus, the microlens array 40 for quadrupole deformation illumination
Also when the diffractive optical element 60 is used, a quadrupole secondary light source can be formed with little loss of light amount based on the light beam from the light source 1, and as a result, an aperture for restricting the light beam from the secondary light source Quadrupole deformation illumination can be performed while satisfactorily suppressing the light amount loss in the stop 9a.

As shown in FIG. 11, the size and shape of the quadrupolar secondary light source can be defined in the same manner as the annular secondary light source. In this case, the size a of each micro lens constituting the micro lens array 40 is defined as a size corresponding to a diameter of a circle circumscribing a square having a sectional shape. By changing the magnification m of the afocal zoom lens 5 in the same manner as in the case of the annular deformation illumination, both the outer diameter φo of the quadrupole secondary light source and the annular ratio A can be changed. Further, by changing the focal length f2 of the zoom lens 7, the outer diameter φo of the quadrupole secondary light source can be changed without changing the ring zone ratio A. As a result, by appropriately changing the magnification m of the afocal zoom lens 5 and the focal length f2 of the zoom lens 7, the outer diameter φ of the quadrupole secondary light source
Only the zone ratio A can be changed without changing o.

Next, the micro lens arrays 4 and 4
0 are retracted from the illumination optical path, and the diffractive optical element 6 or 60 is replaced with a diffractive optical element 6 for circular illumination.
A normal circular illumination obtained by setting 1 in the illumination optical path will be described. In this case, a light beam having a rectangular cross section enters the afocal zoom lens 5 along the optical axis AX. The luminous flux incident on the afocal zoom lens 5 is enlarged or reduced in accordance with the magnification, and emitted from the afocal zoom lens 5 along the optical axis AX as a luminous flux having a rectangular cross section. Incident.

Here, the diffractive optical element 61 for circular illumination is used.
Has a function of converting an incident rectangular light beam into a circular light beam. Therefore, the circular luminous flux formed by the diffractive optical element 61 forms a circular illumination field centered on the optical axis AX on the incident surface of the fly-eye lens 8 via the zoom lens 7. As a result, a circular secondary light source centered on the optical axis AX is also formed on the rear focal plane of the fly-eye lens 8. In this case, by changing the focal length f2 of the zoom lens 7, the outer diameter of the circular secondary light source can be appropriately changed.

The micro lens arrays 4 and 40
From the illumination optical path and diffractive optical element 61 for circular illumination
Is switched from the annular aperture stop 9 or the quadrupole aperture stop 9a to the circular aperture stop 9b. The circular aperture stop 9b is one circular aperture stop selected from two circular aperture stops 407 and 408, and has an opening having a size corresponding to a circular secondary light source. In this way, by retracting the conical prism 4 from the illumination optical path, a circular secondary light source is formed with almost no loss of light amount based on the light beam from the light source 1,
Normal circular illumination can be performed while satisfactorily suppressing the light amount loss in the aperture stop that restricts the light flux from the secondary light source.

Hereinafter, the switching operation of the illumination in this embodiment will be specifically described. First, information relating to various masks to be sequentially exposed according to the step-and-repeat method or the step-and-scan method is input to the control system 21 via input means 20 such as a keyboard. The control system 21 stores information such as the optimum line width (resolution) and depth of focus for various masks in an internal memory unit, and responds to an input from the input unit 20 to the first drive system 22 to the first drive system 22. 5 supplies an appropriate control signal to the drive system 26.

That is, when performing annular deformation illumination under the optimum resolution and depth of focus, the first drive system 22 moves the microlens array 4 of annular deformation illumination in the illumination optical path based on a command from the control system 21. Position. The third drive system 24 positions the diffractive optical element 6 for annular deformation illumination in the illumination optical path based on a command from the control system 21. Then, in order to obtain an annular secondary light source having a desired size (outer diameter) and an annular ratio at the rear focal plane of the fly-eye lens 8, the second drive system 23 responds to a command from the control system 21. The fourth drive system 25 sets the focal length of the zoom lens 7 based on a command from the control system 21 based on the magnification of the afocal zoom lens 5. In addition, in order to limit the annular secondary light source in a state where the light amount loss is suppressed well, the fifth drive system 26 rotates the turret based on a command from the control system 21 to set a desired annular aperture stop. Position in the illumination light path. Thus, an annular secondary light source can be formed on the basis of the light beam from the light source 1 with little loss of light amount. As a result, the ring stop can be formed with almost no light loss at the aperture stop for limiting the light beam from the secondary light source. Band deformation illumination can be performed.

Further, if necessary, the magnification of the afocal zoom lens 5 is changed by the second drive system 23 or the focal length of the zoom lens 7 is changed by the fourth drive system 25, so that the fly-eye lens 8 The size and annular ratio of the annular secondary light source formed on the rear focal plane can be appropriately changed. In this case, the turret rotates in accordance with the change in the size of the annular secondary light source and the annular ratio, and an annular aperture stop having a desired size and annular ratio is selected and positioned in the illumination optical path. You. Thus, various annular deformation illuminations can be performed by appropriately changing the size and annular ratio of the annular secondary light source with little loss of light amount in the formation and limitation of the annular secondary light source. .

In the case of performing quadrupole deformation illumination with an optimum resolution and depth of focus, the first drive system 22 is controlled by the control system 21.
, The microlens array 40 for quadrupole deformation illumination is positioned in the illumination optical path based on the instruction from. In addition, the third drive system 24 positions the diffractive optical element 60 for quadrupole deformation illumination in the illumination optical path based on a command from the control system 21. The fly-eye lens 8 has a desired size (outer diameter) and shape (ring zone ratio) on the rear focal plane of the fly-eye lens 8.
In order to obtain a polar secondary light source, the second drive system 23 is controlled by the afocal zoom lens 5 based on a command from the control system 21.
The fourth drive system 25 sets the focal length of the zoom lens 7 based on a command from the control system 21. Further, in order to limit the quadrupole secondary light source in a state in which the light quantity loss is suppressed well, the fifth drive system 26 rotates the turret based on a command from the control system 21 to provide a desired 4-pole aperture stop. Are positioned in the illumination light path. Thus, a quadrupolar secondary light source can be formed based on the light beam from the light source 1 with almost no light amount loss. As a result, the light amount loss can be satisfactorily suppressed in the aperture stop that restricts the light beam from the secondary light source. In addition, it is possible to perform quadrupole deformation illumination.

Further, the fly-eye lens 8 is changed by changing the magnification of the afocal zoom lens 5 by the second drive system 23 or changing the focal length of the zoom lens 7 by the fourth drive system 25 as necessary. The size and shape of the quadrupole secondary light source formed on the rear focal plane can be changed as appropriate. In this case, the turret rotates according to the change in the size and shape of the quadrupole secondary light source, and a quadrupole aperture stop having a desired size and shape is selected and positioned in the illumination light path. In this manner, in a state in which the loss of light amount is properly suppressed in forming and limiting the quadrupole secondary light source, various quadrupole deformation illuminations are performed by appropriately changing the size and shape of the quadrupole secondary light source. be able to.

Further, when performing ordinary circular illumination under the optimum resolution and depth of focus, the first drive system 22 retracts the microlens arrays 4 and 40 from the illumination optical path based on a command from the control system 21. . Further, the third drive system 24 positions the diffractive optical element 61 for normal circular illumination in the illumination optical path based on a command from the control system 21.
Then, in order to obtain a circular secondary light source having a desired size (outer diameter) on the rear focal plane of the fly-eye lens 8, the second drive system 23 performs an afocal operation based on a command from the control system 21. The magnification of the zoom lens 5 is set, and the fourth drive system 25 sets the focal length of the zoom lens 7 based on a command from the control system 21. Further, in order to limit the circular secondary light source in a state where the light quantity loss is suppressed well, the fifth drive system 26 rotates the turret based on a command from the control system 21 to illuminate a desired circular aperture stop. Position in the optical path. When an iris diaphragm capable of continuously changing the circular aperture diameter is used, the fifth drive system 26 sets the aperture diameter of the iris diaphragm based on a command from the control system 21. In this way, a circular secondary light source can be formed with almost no loss of light amount based on the light beam from the light source 1, and as a result, the light amount loss can be favorably suppressed in the aperture stop that restricts the light beam from the secondary light source. Usually circular illumination can be performed.

Further, if necessary, the focal length of the zoom lens 7 is changed by the fourth drive system 25, so that the size of the circular secondary light source formed on the rear focal plane of the fly-eye lens 8 is increased. Can be appropriately changed. In this case, the turret rotates according to the change in the size of the circular secondary light source, and a circular aperture stop having an opening of a desired size is selected and positioned in the illumination light path. In this way, various ordinary circular illuminations can be performed by appropriately changing the σ value while favorably suppressing the light amount loss in the formation and limitation of the square secondary light source.

As described above, in the above-described embodiment, the deformed illumination such as the ring-shaped deformed illumination and the quadrupole deformed illumination and the normal circular light are suppressed while the light amount loss in the aperture stop for limiting the secondary light source is suppressed favorably. Lighting can be performed. In addition, by the simple operation of changing the magnification of the afocal zoom lens or changing the focal length of the zoom lens,
It is possible to change the parameters of the deformed illumination and the normal circular illumination while favorably suppressing the light amount loss at the aperture stop. Therefore, the resolution and the depth of focus of the projection optical system suitable for the fine pattern to be exposed and projected can be obtained by appropriately changing the type and parameters of the deformed illumination. As a result, good projection exposure with high throughput can be performed under high exposure illuminance and good exposure conditions.

The wafer subjected to the exposure step (photolithography step) by the exposure apparatus of the above-described embodiment undergoes a development step, and then an etching step of removing portions other than the developed resist, and an unnecessary step after the etching step. The wafer process is completed through a resist removal step for removing the unnecessary resist and the like. Then, when the wafer process is completed, in the actual assembling process, dicing for cutting the wafer into chips for each printed circuit, bonding for providing wiring and the like to each chip, and packaging for packaging each chip Through these steps, a semiconductor device (LSI or the like) is finally manufactured as a device.

In the above description, an example in which a semiconductor element is manufactured by a photolithography process in a wafer process using a projection exposure apparatus has been described. An element, a thin-film magnetic head, and an imaging element (such as a CCD) can be manufactured. Thus, in the case of the exposure method for manufacturing a device using the illumination optical device of the present invention, since projection exposure can be performed under favorable exposure conditions, a good device can be manufactured.

In the embodiment described above, the microlens array as the divergent light beam forming element and the diffractive optical element as the light beam converting element can be configured to be positioned in the illumination light path by, for example, a turret method. In addition, for example, a known slider mechanism can be used to insert, remove, and switch the microlens array and the diffractive optical element.

In the above-described embodiment, the shape of the microlenses constituting the microlens array for annular deformation illumination is set to a regular hexagon. This is because a circular microlens cannot be densely arranged and causes a loss of light quantity, and thus a regular hexagon is selected as a polygon close to a circle. However, the shape of each microlens constituting the microlens array for annular deformation illumination is not limited to this, and another appropriate shape can be used. Similarly, although the shape of the microlenses constituting the microlens array for quadrupole deformation illumination is set to be square, other suitable shapes including, for example, rectangular shapes can be used. Further, in the above-described embodiment, the refractive power of the microlenses constituting the microlens array is defined as positive refractive power. However, the refractive power of this microlens may be negative.

Further, in the above-described embodiment, the afocal zoom lens is used. However, a focal zoom lens is used instead of the afocal zoom lens, and a rectangular light beam is converted into a circular light beam in front of the microlens array. It is also possible to adopt a configuration in which a diffractive optical element for performing the operation is arranged. In the above-described embodiment, one fly-eye lens is used. However, the present invention can be applied to a double fly-eye system using two fly-eye lenses.

Further, in the above-described embodiment, the diffractive optical element 61 is positioned in the illumination optical path when performing ordinary circular illumination. However, the use of the diffractive optical element 61 can be omitted.

In the above-described embodiment, a microlens array is used as the divergent light beam forming element. However, if necessary, a fly-eye lens, a diffractive optical element, or the like may be used. Further, in the above embodiment, the diffractive optical element is used as the light beam converting element. However, the present invention is not limited to this. For example, a refractive optical element such as a microlens array or a microlens prism can be used. Incidentally, a detailed description of the diffractive optical element that can be used in the present invention is described in U.S. Pat.
It is disclosed in Japanese Patent Publication No. 0,300.

Further, in the above-described embodiment, an aperture stop for limiting the light flux of the secondary light source is arranged near the rear focal plane of the fly-eye lens. However, in some cases, a configuration in which the cross-sectional area of each lens element constituting the fly-eye lens is set to be sufficiently small to omit the arrangement of the aperture stop and not restrict the light flux of the secondary light source at all is also possible. Further, in the above-described embodiment, the present invention has been described by taking the projection exposure apparatus having the illumination optical device as an example. However, the present invention is applied to a general illumination optical device for uniformly illuminating an irradiated surface other than a mask. It is clear that you can.

In the above-described embodiment, the aperture stop 9 is provided by the condenser lens 10 as a light guide optical system.
, The light from the secondary light source formed at the position is condensed and the mask 11 is illuminated in a superimposed manner. Between the condenser lens 10 and the mask 11, an illumination field stop (mask blind), The image of the illumination field stop is used as a mask 11
A relay optical system formed above may be arranged. In this case, the light guide optical system includes a condenser lens 10 and a relay optical system. The condenser lens 10 collects light from a secondary light source formed at the position of the aperture stop 9 and illuminates the light in a superimposed manner. This illuminates the field stop, and the relay optical system forms an image of the opening of the illumination field stop on the mask 11.

In the above-described embodiment, the fly-eye lens 8 which is a wavefront splitting type integrator is used as the optical integrator. The optical system closer to the mask 11 than the zoom lens 7 may be configured as follows. That is, a condensing optical system is added downstream of the zoom lens 7 to form a conjugate plane of the diffractive optical element 6 as a light beam conversion element. Then, the rod-type integrator is arranged so that the incident end is positioned near the conjugate plane. Then, a relay optical system for forming an image of the illumination field stop disposed on the exit end face or near the exit end face of the rod type integrator on the mask 11 is arranged. In the case of this configuration, the second predetermined surface is a pupil surface of the combined system of the zoom lens 7 and the condensing optical system, and the secondary light source is formed on the pupil surface of the relay optical system (the virtual image of the secondary light source is Formed near the entrance end of the rod-type integrator). In this case, the light guide optical system is a relay optical system for guiding the light beam from the rod type integrator to the mask.

Further, in the above-described embodiment, the light intensity distribution is such that it is weak in a region including the reference optical axis or in a region near the reference optical axis and strong in an outer peripheral portion distant from the reference optical axis. A light intensity distribution (ring-shaped distribution) in which the light intensity is increased in a ring-shaped (donut-shaped) region surrounding the optical axis of the illumination optical device, substantially on the predetermined surface around the optical axis of the illumination optical device. Intensity distribution (quadrupole distribution) in which the intensity is increased in four regions arranged at angular intervals.
However, on a predetermined surface, a light intensity distribution such that the intensity is increased in a plurality of regions at four or more places arranged at substantially equal angular intervals around the optical axis of the illumination optical device (for example, in the case of eight places) : 8-pole distribution). In other words, in the above-described embodiment, an example is shown in which a quadrupole secondary light source is formed. However, for example, a dipole (second) secondary light source, or 8
A multipole secondary light source such as a pole (eighth) can also be formed.

Further, in the above embodiment, the fly-eye lens 8 is formed by integrating a plurality of element lenses, but these may be formed as a micro lens array. The micro lens array is one in which a plurality of minute lens surfaces are provided in a matrix on a light transmitting substrate by a method such as etching. In terms of forming a plurality of light source images, there is substantially no functional difference between the fly-eye lens and the micro lens array, but the size of the aperture of one element lens (micro lens) is extremely large. The micro lens array is advantageous in that it can be made smaller, the manufacturing cost can be greatly reduced, and the thickness in the optical axis direction can be made very thin.

In this embodiment, K is used as the light source.
Since exposure light having a wavelength of 180 nm or more such as an rF excimer laser (wavelength: 248 nm) and an ArF excimer laser (wavelength: 193 nm) is used, the diffractive optical element can be formed of, for example, quartz glass. When a wavelength of 200 nm or less is used as the exposure light, the diffractive optical element may be made of fluorite, quartz glass doped with fluorine, quartz glass doped with fluorine and hydrogen, having a structure determination temperature of 1200 K or less and an OH group. Quartz glass with a concentration of 1000 ppm or more, a structure determination temperature of 1200 K or less, and a hydrogen molecule concentration of 1 × 10 ¹⁷ molecu
Quartz glass of les / cm ³ or more, structure determination temperature of 120
A quartz glass having a temperature of 1200 K or less, a hydrogen molecule concentration of 1 × 10 ¹⁷ molecules / cm ³ or more, and a chlorine concentration of 50 p or less.
It is preferably formed of a material selected from the group of quartz glass having a value of pm or less.

The quartz glass having a structure determination temperature of 1200 K or less and an OH group concentration of 1000 ppm or more is disclosed in Japanese Patent No. 2770224 by the present applicant. Quartz glass having a molecular concentration of 1 × 10 ¹⁷ molecules / cm ³ or more, quartz glass having a structure determination temperature of 1200 K or less and a chlorine concentration of 50 ppm or less, and a structure determination temperature of 1200 K or less and a hydrogen molecule concentration of 1 × 10 ¹⁷ molecu
Quartz glass having a les / cm ³ or more and a chlorine concentration of 50 ppm or less is disclosed in Japanese Patent No. 2936138 by the present applicant.

[0098]

As described above, in the illumination optical apparatus according to the present invention, while suppressing the loss of light quantity in the aperture stop for restricting the secondary light source, the illumination optical apparatus such as the annular deformation illumination and the quadrupole deformation illumination can be used. Deformed illumination and usually circular illumination can be provided. In addition, by performing a simple operation of changing the magnification of the afocal zoom lens or changing the focal length of the zoom lens, it is possible to change the parameters of the deformed illumination while favorably suppressing the loss of light amount at the aperture stop.

Therefore, in the exposure apparatus incorporating the illumination optical apparatus of the present invention, the resolution and depth of focus of the projection optical system suitable for the fine pattern to be exposed and projected can be obtained by appropriately changing the type and parameters of the modified illumination. Can be. As a result, good projection exposure with high throughput can be performed under high exposure illuminance and good exposure conditions. Further, in the exposure method of exposing the pattern of the mask disposed on the surface to be irradiated to the photosensitive substrate using the illumination optical device of the present invention, projection exposure can be performed under favorable exposure conditions. , A good device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a configuration of an exposure apparatus including an illumination optical device according to an embodiment of the present invention.

FIG. 2 is a view schematically showing a configuration of a microlens array 4 for annular deformation illumination.

FIG. 3 is a diagram illustrating the operation of a diffractive optical element 6 for annular deformation illumination.

FIG. 4 is a second diagram illustrating the operation of the diffractive optical element 6 for annular deformation illumination.

FIG. 5 is a view showing a ring-shaped illumination field formed on an incident surface of a fly-eye lens 8;

FIG. 6 is a diagram schematically illustrating a configuration of a turret in which a plurality of aperture stops are arranged in a circumferential shape;

FIG. 7 is a diagram schematically showing a configuration from a micro lens array 4 to an entrance surface of a fly-eye lens 8, and illustrates a magnification of an afocal zoom lens 5, a focal length of the zoom lens 7, and a fly-eye lens 8; It is a figure explaining the relation with the size and shape of the annular illumination field formed in an entrance surface.

FIG. 8 is a diagram schematically showing a configuration of a microlens array 40 for quadrupole deformation illumination.

FIG. 9 is a view for explaining the operation of the diffractive optical element 60 for annular deformation illumination.

FIG. 10 is a view showing a fourth example formed on the incident surface of the fly-eye lens.
It is a figure which shows a polar illumination field.

FIG. 11 is a diagram showing a quadrupolar secondary light source formed on the rear focal plane of the fly-eye lens 8;

[Explanation of symbols]

 Reference Signs List 1 light source 4, 40 micro lens array 5 afocal zoom lens 6, 60, 61 diffractive optical element 7 zoom lens 8 fly eye lens 9 aperture stop 10 condenser optical system 11 mask 12 projection optical system 13 wafer 20 input means 21 control system 22 ~ 26 drive system

Claims (4)

[Claims] 1. An illumination optical apparatus for illuminating a mask having a predetermined pattern, comprising: a light source unit for supplying a light beam; and a light beam from the light source unit, wherein a plurality of angle components with respect to a reference optical axis. An angle light beam forming unit that converts the light beam into a light beam having the plurality of angle components via the first predetermined surface, based on the light beam having the plurality of angle components, A light beam shape converting means for forming a light intensity distribution on a second predetermined surface such that the light intensity distribution is weak in a region near the reference optical axis and strong in an outer peripheral portion distant from the reference optical axis; An optical integrator that receives the light beam passing through a predetermined surface and forms a secondary light source having a light intensity distribution having the same tendency as the light intensity distribution; and guiding the light beam from the optical integrator to the mask. The illumination optical apparatus characterized in that it comprises guiding optical system and the. 2. An illumination optical device for illuminating a mask having a predetermined pattern, comprising: a light source means for supplying a substantially parallel light beam; A divergent light beam forming element for converting the divergent light beam into a divergent light beam having a plurality of angle components; and a first divergent light beam for condensing the divergent light beam and guiding the divergent light beam to a first predetermined surface.
An optical system, a light beam conversion element disposed in the vicinity of the first predetermined surface, a second optical system for guiding a light beam from the light beam conversion element to a second predetermined surface, and the second predetermined surface. An optical integrator for receiving the passed light beam to form a secondary light source having a predetermined light intensity distribution; and a light guiding optical system for guiding the light beam from the optical integrator to the mask. The optical system has first and second variable power optical systems, and the light beam conversion element and the second optical system are configured to include a region including the reference optical axis or the region based on a light beam from the first optical system. An illumination optical device, wherein a light intensity distribution is formed on the second predetermined surface such that the light intensity distribution is weak in a region near a reference optical axis and strong in an outer peripheral portion away from the reference optical axis. 3. An illumination optical apparatus for illuminating a mask having a predetermined pattern, comprising: light source means for supplying a substantially parallel light beam; A divergent light beam forming element for converting the divergent light beam into a divergent light beam having a plurality of angle components; and a first divergent light beam for condensing the divergent light beam and guiding the divergent light beam to a first predetermined surface.
An optical system, a light beam conversion element disposed in the vicinity of the first predetermined surface, a second optical system for guiding a light beam from the light beam conversion element to a second predetermined surface, and the second predetermined surface. An optical integrator that receives the passed light beam and forms a secondary light source having a predetermined light intensity distribution; and a light guide optical system that guides the light beam from the optical integrator to the mask. The first optical system includes: The divergent light beam forming element and the first predetermined surface are optically conjugated, and the light beam conversion element and the second optical system adjust the reference optical axis based on the light beam from the first optical system. An illumination optical device that forms a light intensity distribution on the second predetermined surface such that the light intensity distribution is weak in a region including or in the vicinity of the reference optical axis and strong in an outer peripheral portion distant from the reference optical axis. . 4. An illumination optical device according to claim 1, further comprising: a projection optical system for projecting and exposing a pattern of the mask onto a photosensitive substrate. Exposure equipment.