Patent Application
20090115989
The present invention relates to illumination optical apparatus, exposure apparatus, and exposure methods and, more particularly, to an illumination optical apparatus suitable for exposure apparatus for manufacturing devices such as semiconductor devices, imaging devices, liquid-crystal display devices, and thin-film magnetic heads by lithography.
In a typical exposure apparatus of this type, a beam emitted from a light source travels through a fly's eye lens as an optical integrator to form a secondary light source as a substantial surface illuminant consisting of a large number of light sources. Beams from the secondary light source (a light intensity distribution formed at or near an illumination pupil) are condensed by a condenser lens to illuminate a mask with a predetermined pattern therein in a superimposed manner.
Light having passed through the pattern of the mask is guided through a projection optical system to be focused on a wafer. In this manner, the mask pattern is projected (or transferred) onto the wafer to effect exposure thereof. Since the pattern formed in the mask is a highly integrated pattern, a uniform illuminance distribution must be achieved on the wafer in order to accurately transfer this fine pattern onto the wafer.
For realizing an illumination condition suitable for faithfully transferring the fine pattern in any direction, the applicant discloses the technology of forming the secondary light source of annular shape on the rear focal plane of the fly's eye lens and making such a setting that a beam through the annular secondary light source is in a linearly polarized state in which the direction of polarization is its circumferential direction (which will be referred to hereinafter simply as “circumferential polarization state”) (e.g., Patent Document 1).
Patent Document 1: US2006/0203214
The projection exposure of a specific pattern with light in a specific linear polarization state, without being restricted only to the above-described circumferential polarization state, is effective to improvement in resolution of the projection optical system. More generally, the projection exposure with light in a specific polarization state (which is a broad concept embracing an unpolarized state) according to the mask pattern is effective to improvement in resolution of the projection optical system.
However, in the case where the mask (or the wafer eventually) is attempted to be illuminated with light in a desired polarization state, when an optical member to change the polarization state of light is interposed in the illumination light path, the light will not be focused in the desired polarization state and this could result in degrading the imaging performance of the projection optical system eventually. Particularly, the polarization state of light passing a peripheral region is more likely to vary than that of light passing a central region of an effective region of a lens.
The present invention has been accomplished in view of the above-described problem and an object of the invention is to provide an illumination optical apparatus capable of illuminating a surface to be illuminated with light in a desired polarization state through adjustment of a polarization distribution on the illumination pupil plane or on the surface to be illuminated. Another object of the invention is to provide an exposure apparatus and an exposure method capable of imaging a fine pattern in a desired polarization state on a photosensitive substrate and thereby implementing faithful and excellent exposure, using the illumination optical apparatus capable of illuminating the surface to be illuminated with light in the desired polarization state.
In order to solve the above problem, a first aspect of the present invention provides an illumination optical apparatus which illuminates a surface to be illuminated on the basis of light from a light source, comprising:
a first polarizing member arranged as rotatable around an optical axis of the illumination optical apparatus or around an axis substantially parallel to the optical axis; and
a second polarizing member arranged as rotatable around the optical axis or around the axis substantially parallel thereto in an optical path between the first polarizing member and the surface to be illuminated,
wherein each of the first polarizing member and the second polarizing member provides incident light with variations in a polarization state different according to respective positions of incidence.
A second aspect of the present invention provides an illumination optical apparatus which illuminates a surface to be illuminated on the basis of light from a light source, comprising:
a phase member arranged as rotatable around an optical axis of the illumination optical apparatus or around an axis substantially parallel to the optical axis, at or near a pupil plane of the illumination optical apparatus, and adapted to provide incident light with phase amounts varying according to respective positions of incidence.
A third aspect of the present invention provides an illumination optical apparatus which illuminates a surface to be illuminated on the basis of light from a light source, comprising:
a phase member arranged as rotatable around an optical axis of the illumination optical apparatus or around an axis substantially parallel to the optical axis, near the surface to be illuminated, at a position optically conjugate with the surface to be illuminated, or near the conjugate position, and adapted to provide incident light with phase amounts varying according to respective positions of incidence.
A fourth aspect of the present invention provides an illumination optical apparatus which illuminates a surface to be illuminated on the basis of light from a light source, comprising:
a polarization distribution adjusting member which adjusts a polarization distribution of light on an illumination pupil plane,
wherein the polarization distribution adjusting member comprises an optical rotation member arranged as rotatable around an optical axis of the illumination optical apparatus or around an axis substantially parallel to the optical axis and adapted to provide incident light with optical rotation amounts varying according to respective positions of incidence.
A fifth aspect of the present invention provides an illumination optical apparatus which illuminates a surface to be illuminated on the basis of light from a light source, comprising:
a polarization distribution adjusting member which adjusts a polarization distribution of light on the surface to be illuminated,
wherein the polarization distribution adjusting member comprises an optical rotation member arranged as rotatable around an optical axis of the illumination optical apparatus or around an axis substantially parallel to the optical axis and adapted to provide incident light with optical rotation amounts varying according to respective positions of incidence.
A sixth aspect of the present invention provides an exposure apparatus for effecting exposure of a photosensitive substrate with a predetermined pattern, comprising:
the illumination optical apparatus of any one of the first aspect to the fifth aspect which illuminates the predetermined pattern or the photosensitive substrate.
A seventh aspect of the present invention provides an exposure method for effecting exposure of a photosensitive substrate with a predetermined pattern, comprising:
illuminating the predetermined pattern or the photosensitive substrate, using the illumination optical apparatus of any one of the first aspect to the fifth aspect.
An eighth aspect of the present invention provides a device manufacturing method comprising:
exposing a photosensitive substrate with a predetermined pattern, using the exposure apparatus of the sixth aspect; and
developing the photosensitive substrate exposed.
A ninth aspect of the present invention provides an adjustment method for an illumination optical apparatus which illuminates a surface to be illuminated on the basis of light from a light source, comprising:
measuring a polarization state of light illuminating the surface to be illuminated; and
rotating at least one of a first polarizing member disposed in an optical path of the illumination optical apparatus and a second polarizing member disposed in an optical path between the first polarizing member and the surface to be illuminated, around an optical axis of the illumination optical apparatus or around an axis substantially parallel to the optical axis, based on the polarization state measured.
A tenth aspect of the present invention provides a method for manufacturing an illumination optical apparatus which illuminates a surface to be illuminated on the basis of light from a light source, comprising:
preparing a first polarizing member and a second polarizing member rotatable around an optical axis of the illumination optical apparatus or around an axis parallel to the optical axis; and
rotationally adjusting at least one of the first polarizing member and the second polarizing member, according to the adjustment method of the ninth aspect.
Embodiments of the present invention will be described on the basis of the accompanying drawings.
With reference to
The polarization state switch 3 has a quarter wave plate 3a the crystal optic axis of which is rotatable around the optical axis AX and which converts incident elliptically polarized light into linearly polarized light, a half wave plate 3b the crystal optic axis of which is rotatable around the optical axis AX and which changes the polarization direction of incident linearly polarized light, and a depolarizer (depolarizing element) 3c which can be set inserted and retracted the illumination light path, in the order named from the light source side. The polarization state switch 3, with the depolarizer 3c being set off the illumination light path, has a function of converting the light from the light source 1 into linearly polarized light with a desired polarization direction and letting the linearly polarized light into the diffractive optical element 4, and, with the depolarizer 3c being set in the illumination light path, it has a function of converting the light from the light source 1 into substantially unpolarized light and letting the unpolarized light into the diffractive optical element 4.
The afocal lens 5 is an afocal system (afocal optical system) so set that a front focal position of a front lens unit 5a thereof is approximately coincident with the position of the diffractive optical element 4 and that a rear focal position of a rear lens unit 5b thereof is approximately coincident with a position of a predetermined plane 6 indicated by a dashed line in the drawing. In general, a diffractive optical element is made by forming steps with a pitch approximately equal to the wavelength of the exposure light (illumination light) in a substrate and has the action to diffract an incident beam at desired angles.
Specifically, the diffractive optical element 4 for annular illumination has the following function: when a parallel beam with a rectangular cross section is incident thereto, it forms a light intensity distribution of an annular shape in its far field (or a Fraunhofer diffraction region). Therefore, a nearly parallel beam incident to the diffractive optical element 4 as a beam converting element forms a light intensity distribution of an annular shape on the pupil plane of the afocal lens 5 and then it is emitted in an annular angular distribution from the afocal lens 5. A conical axicon system 7 is disposed at or near the pupil plane of the afocal lens 5 in the optical path between the front lens unit 5a and the rear lens unit 5b of the afocal lens 5. The configuration and action of the conical axicon system 7 will be described later.
The beam having passed through the afocal lens 5 travels through a zoom lens 8 for variation in a value (σ value=mask-side numerical aperture of the illumination optical apparatus/mask-side numerical aperture of the projection optical system) and through a polarization distribution adjusting member 9 to enter a micro fly's eye lens (or fly's eye lens) 10. The configuration and action of the polarization distribution adjusting member 9 will be described later. The micro fly's eye lens 10 is an optical element consisting of a large number of microscopic lenses with a positive refracting power arranged vertically and horizontally and densely. In general, a micro fly's eye lens is made, for example, by forming a microscopic lens group in a plane-parallel plate by etching.
Each microscopic lens forming the micro fly's eye lens is smaller than each lens element forming a fly's eye lens. In the micro fly's eye lens, different from the fly's eye lens consisting of lens elements apart from each other, the large number of microscopic lenses (fine refracting faces) are integrally formed without being apart from each other. However, from the aspect that the lens elements with the positive refracting power are arranged vertically and horizontally, the micro fly's eye lens is a wavefront-splitting type optical integrator of the same kind as the fly's eye lens.
The position of the predetermined plane 6 is located near the front focal position of the zoom lens 8 and the entrance surface of the micro fly's eye lens 10 is located near the rear focal position of the zoom lens 8. In other words, the zoom lens 8 arranges the predetermined plane 6 and the entrance surface of the micro fly's eye lens 10 substantially in the Fourier transform relation and, in turn, sets the pupil plane of the afocal lens 5 and the entrance surface of the micro fly's eye lens 10 approximately optically conjugate with each other. The polarization distribution adjusting member 9 is located immediately before the micro fly's eye lens 10 and is thus set approximately optically conjugate with the pupil plane of the afocal lens 5.
Therefore, for example, an annular illumination field is formed around the optical axis AX on the entrance surface of the micro fly's eye lens 10, as on the pupil plane of the afocal lens 5. The overall shape of this annular illumination field varies in a similarity state depending upon the focal length of the zoom lens 8. Each microscopic lens forming the micro fly's eye lens 10 has a rectangular cross section similar to a shape of an illumination field to be formed on a mask M (or a shape of an exposure region to be formed on the wafer W eventually).
The beam incident to the micro fly's eye lens 10 is two-dimensionally split by the large number of microscopic lenses to form on or near the rear focal plane thereof (or on the illumination pupil eventually), a secondary light source with a light intensity distribution approximately identical to the illumination field formed by the incident beam, i.e., a secondary light source consisting of a substantial surface illuminant of an annular shape around the optical axis AX. Beams from the secondary light source formed on or near the rear focal plane of the micro fly's eye lens 10 travel through a condenser optical system 11 to illuminate a mask blind 12 in a superimposed manner.
In this manner, a rectangular illumination field according to the shape and focal length of each microscopic lens forming the micro fly's eye lens 10 is formed on the mask blind 12 as an illumination field stop. Beams through a rectangular aperture (light transmitting portion) of the mask blind 12 are converged by an imaging optical system 13 to illuminate the mask M with a predetermined pattern therein in a superimposed manner. Namely, the imaging optical system 13 forms an image of the rectangular aperture of the mask blind 12 on the mask M.
A beam transmitted by the pattern of the mask M held on a mask stage MS travels through a projection optical system PL to form an image of the mask pattern on the wafer (photosensitive substrate) W held on a wafer stage WS. In this manner, the pattern of the mask M is sequentially transferred into each of exposure areas on the wafer W by one-shot exposure or scanning exposure while two-dimensionally driving and controlling the wafer stage WS in a plane (XY plane) perpendicular to the optical axis AX of the projection optical system PL, i.e., while two-dimensionally driving and controlling the wafer W.
Quadrupole illumination can be implemented when a diffractive optical element for quadrupole illumination (not shown) is set instead of the diffractive optical element 4 for annular illumination in the illumination light path. The diffractive optical element for quadrupole illumination has the following function: when a parallel beam with a rectangular cross section is incident thereto, it forms a light intensity distribution of a quadrupole shape in its far field. Therefore, beams through the diffractive optical element for quadrupole illumination form, for example, a quadrupolar illumination field pattern consisting of four circular illumination fields around the optical axis AX on the entrance plane of the micro fly's eye lens 10. As a result, a secondary light source pattern of the same quadrupolar shape as the illumination field pattern formed on the entrance plane is also formed on or near the rear focal plane of the micro fly's eye lens 10.
Furthermore, conventional circular illumination can also be implemented when a diffractive optical element for circular illumination (not shown) is set instead of the diffractive optical element 4 for annular illumination in the illumination light path. The diffractive optical element for circular illumination has the following function: when a parallel beam with a rectangular cross section is incident thereto, it forms a light intensity distribution of a circular shape in its far field. Therefore, a beam through the diffractive optical element for circular illumination forms, for example, an illumination field of a circular shape around the optical axis AX on the entrance plane of the micro fly's eye lens 10. As a result, a secondary light source of the same circular shape as the illumination field formed on the entrance plane is also formed on or near the rear focal plane of the micro fly's eye lens 10.
Furthermore, a variety of multi-pole illuminations (dipole illumination, octupole illumination, etc.) can also be implemented when diffractive optical elements for other multi-pole illuminations (not shown) are used instead of the diffractive optical element 4 for annular illumination in the illumination light path. Similarly, any one of modified illuminations of various forms can also be implemented when a diffractive optical element with an appropriate property (not shown) is set instead of the diffractive optical element 4 for annular illumination in the illumination light path.
The conical axicon system 7 is composed of a first prism member 7a with a plane on the light source side and a refracting surface of a concave conical shape on the mask side, and a second prism member 7b with a plane on the mask side and a refracting surface of a convex conical shape on the light source side, in the order named from the light source side. The refracting surface of the concave conical shape of the first prism member 7a and the refracting surface of the convex conical shape of the second prism member 7b are formed in complementary shapes so as to be able to abut on each other. At least one of the first prism member 7a and the second prism member 7b is arranged as movable along the optical axis AX so as to make the space variable between the refracting surface of the concave conical shape of the first prism member 7a and the refracting surface of the convex conical shape of the second prism member 7b. The action of the conical axicon system 7 and the action of the zoom lens 8 will be described below with focus on the annular or quadrupolar secondary light source.
In a state in which the concave conical refracting surface of the first prism member 7a and the convex conical refracting surface of the second prism member 7b are in contact with each other, the conical axicon system 7 functions as a plane-parallel plate and has no effect on the annular or quadrupolar secondary light source formed. However, as the concave conical refracting surface of the first prism member 7a is separated away from the convex conical refracting surface of the second prism member 7b, the outside diameter (inside diameter) of the annular or quadrupolar secondary light source varies while the width of the annular or quadrupolar secondary light source (half of a difference between the outside diameter and the inside diameter of the annular secondary light source; half of a difference between a diameter (outside diameter) of a circle circumscribed to the quadrupolar secondary light source and a diameter (inside diameter) of a circle inscribed in the quadrupolar secondary light source) is kept constant. Namely, the separation results in varying the annular ratio (inside diameter/outside diameter) and the size (outside diameter) of the annular or quadrupolar secondary light source.
The zoom lens 8 has a function to enlarge or reduce the overall shape of the annular or quadrupolar secondary light source in proportion. For example, when the focal length of the zoom lens 8 is increased from a minimum to a predetermined value, the overall shape of the annular or quadrupolar secondary light source is similarly enlarged. In other words, the action of the zoom lens 8 is to vary both the width and size (outside diameter), without change in the annular ratio of the annular or quadrupolar secondary light source. In this manner, the annular ratio and size (outside diameter) of the annular or quadrupolar secondary light source can be controlled by the actions of the conical axicon system 7 and the zoom lens 8.
The exposure apparatus of the present embodiment is provided with a polarization state measuring unit 14 for measuring a polarization state of illumination light (exposure light) incident to the wafer W, which is mounted on the wafer stage WS for holding the wafer W. The measurement result by the polarization state measuring unit 14 is supplied to a control unit 15. The detailed configuration and action of the polarization state measuring unit 14 are disclosed, for example, in Japanese Patent Application Laid-open No. 2005-5521. The polarization state measuring unit 14 is used to measure the polarization state in the pupil of the illumination light incident to the wafer W, so as to determine whether the illumination light is in an appropriate polarization state in the pupil. Japanese Patent Application Laid-open No. 2005-5521 is incorporated herein by reference.
The control unit 15 drives the polarization state switch 3 according to need and further drives the polarization distribution adjusting member 9 as described below, based on the measurement result by the polarization state measuring unit 14, to adjust the polarization state of the illumination light on the mask M (or on the wafer W eventually) to a desired polarization state.
On the other hand, the first correction optical member 22 and the second correction optical member 24 are made of an amorphous optical material, for example, like silica glass (or a crystal optic material like fluorite) and have a wedge-shaped sectional shape as the first optical-rotation optical member 21 and the second optical-rotation optical member 23. Specifically, in a standard state shown in
Similarly, in the standard state shown in
The first optical-rotation optical member 21 and the first correction optical member 22 are integrally held and arranged as rotatable around the optical axis AX. Similarly, the second optical-rotation optical member 23 and the second correction optical member 24 are integrally held and arranged as rotatable around the optical axis AX. The control unit 15 controls the integral rotation of the first optical-rotation optical member 21 and the first correction optical member 22 and the integral rotation of the second optical-rotation optical member 23 and the second correction optical member 24.
As described above, the first optical-rotation optical member 21 and the second optical-rotation optical member 23 are made of rock crystal with optical activity and the thickness thereof in the optical-axis direction linearly varies along the predetermined direction perpendicular to the optical axis AX (or along the X-direction in the standard state of
In this case, linearly polarized light incident to the optical member 100 is emitted in a state in which the direction of polarization thereof is rotated by θ around the optical axis AX, by virtue of the optical activity of the optical member 100. At this time, the rotation angle (optical rotation angle; optical rotation amount) 0 of the polarization direction due to the optical activity of the optical member 100 is represented by Formula (a) below, where d is the thickness of the optical member 100 and p the optical activity of rock crystal.
θ=d×p (a)
In general, the optical activity ρ of rock crystal has wavelength dependence (a property showing different values of optical activity depending upon wavelengths of used light: optical activity dispersion) and, specifically, it tends to increase with decrease in the wavelength of used light. According to the description on page 167 in “Oyo Kogaku II,” the optical activity ρ of rock crystal for light having the wavelength of 250.3 nm is 153.9°/mm. For simplifying the description, it will be assumed hereinafter that the first optical-rotation optical member 21 and the second optical-rotation optical member 23 have the same configuration and that the first correction optical member 22 and the second correction optical member 24 have the same configuration. It will also be assumed that in the standard state shown in
A distribution of optical rotation amounts provided for the incident light to the first optical-rotation optical member will be described with reference to
S(x)=(x/t)×tan α (1)
On the other hand, when the first optical-rotation optical member 21 is rotated by an angle of +β around the optical axis AX from the standard state shown in
S(x)=(x/t)×tan α×cos β (2)
In the standard state shown in
On the other hand, when the first optical-rotation optical member 21 is rotated by an angle of +β around the optical axis AX and the second optical-rotation optical member 23 is rotated by an angle of −β around the optical axis AX from the standard state shown in
This is because the optical rotation distribution S(y) along the y-direction by the first optical-rotation optical member 21 and the optical rotation distribution S(y) along the y-direction by the second optical-rotation optical member 23 cancel each other whereas the optical rotation distribution S(x) along the x-direction in Eq (2) by the first optical-rotation optical member 21 and the optical rotation distribution S(x) along the x-direction in Eq (2) by the second optical-rotation optical member 23 are combined in a summational manner with each other. As a result, just as in the case of the standard state shown in
In this case, as apparent with reference to Eq (2), as the magnitude |β| of the rotation angles of the first optical-rotation optical member 21 and the second optical-rotation optical member 23 increases from 0°, the change rate of the optical rotation distribution S(x) by the polarization distribution adjusting member 9 monotonically decreases. However, when the magnitude |β| of the rotation angles of the first optical-rotation optical member 21 and the second optical-rotation optical member 23 reaches 90°, the sum of the thickness in the optical-axis direction of the first optical-rotation optical member 21 and the thickness in the optical-axis direction of the second optical-rotation optical member 23 becomes constant along the x-direction, and incident light in an optional linearly polarized state passes with the polarization direction maintained, without being subjected to the optical rotation action of the polarization distribution adjusting member 9.
In the present embodiment, when the polarization state of light is measured with the polarization state measuring unit 14, for example, during circular illumination, the result of the measurement can be as shown in
Specifically, the control unit 15 rotates the first optical-rotation optical member 21 forming the polarization distribution adjusting member 9, by the required angle +β around the optical axis AX and rotates the second optical-rotation optical member 23 by the required angle −β around the optical axis AX, based on the measurement result by the polarization state measuring unit 14. As a result, by virtue of the action of optical activity of linear change along the X-direction of the polarization distribution adjusting member 9, the linearly polarized states in the region from the center to the periphery along the X-direction can be corrected (or adjusted) into the desired X-directionally linearly polarized state, without substantially changing the linearly polarized state in the region from the center to the periphery along the Y-direction on the illumination pupil plane, as shown in
In the illumination optical apparatus (1-PL; 1-13) of the present embodiment, as described above, the polarization distribution on the illumination pupil plane is adjusted by the action of optical activity of the polarization distribution adjusting member 9, whereby the wafer W can be illuminated with light in the desired polarization state. Since the exposure apparatus of the present embodiment uses the illumination optical apparatus capable of illuminating the wafer W with light in the desired polarization state, the exposure apparatus is able to focus the image of the fine pattern of the mask M in the desired polarization state on the wafer W and thereby to implement faithful and excellent exposure. In the above-described embodiment, the first optical-rotation optical member 21 can be regarded, for example, as a first polarizing member and the second optical-rotation optical member 23 can be regarded, for example, as a second polarizing member.
The polarization distribution adjusting member 9 in the above-described embodiment is constructed using the optical-rotation optical members (21, 23) of the wedge-shaped sectional shape in which the thickness in the optical-axis direction linearly varies along the predetermined direction perpendicular to the optical axis AX.
However, without having to be limited to the wedge-shaped sectional shape, a variety of modification examples of the polarization distribution adjusting member can be contemplated, using optical-rotation optical members with other appropriate sectional shapes in which the thickness in the optical-axis direction varies along the predetermined direction perpendicular to the optical axis AX. Typical modification examples of the polarization distribution adjusting member will be described below.
The illumination optical apparatus according to the embodiment comprises the optical rotation member arranged as rotatable around the optical axis, for example, at the position of the illumination pupil plane or at the position optically conjugate with the surface to be illuminated and adapted to provide incident light with optical rotation amounts varying according to respective positions of incidence. As a consequence, the polarization distribution of light on the illumination pupil plane or on the surface to be illuminated can be adjusted by the optical activity of this optical rotation member.
Since the illumination optical apparatus of the embodiment is arranged to adjust the polarization distribution on the illumination pupil plane or on the surface to be illuminated as described above, it is able to illuminate the surface to be illuminated with light in a desired polarization state. Therefore, the exposure apparatus and exposure method of the embodiment are able to image the fine pattern in the desired polarization state on the photosensitive substrate and thereby implement faithful and excellent exposure, using the illumination optical apparatus capable of illuminating the surface to be illuminated with light in the desired polarization state, and, in turn, to manufacture excellent devices.
Like the first optical-rotation optical member 31, the second optical-rotation (rotary polarization) optical member 33 is made, for example, of rock crystal and has a plane 33a on the light source side and a refracting face 33b of a concave and V shape on the mask side. Like the first correction optical member 32, the second correction optical member 34 is made, for example, of silica glass (or fluorite or the like) and has a refracting face of a convex and V shape (a surface complementary to the V-shaped refracting face 33b) 34a on the light source side and a plane 34b on the mask side. The first optical-rotation optical member 31 and the first correction optical member 32 are arranged as integrally rotatable around the optical axis AX, and the second optical-rotation optical member 33 and the second correction optical member 34 are arranged as integrally rotatable around the optical axis AX.
It will be assumed hereinafter for simplification of description that the first optical-rotation optical member 31 and the second optical-rotation optical member 33 have the same configuration, the first correction optical member 32 and the second correction optical member 34 have the same configuration, and the first optical-rotation optical member 31 and the second optical-rotation optical member 33 are positioned in the same posture in the standard state shown in
Therefore, the optical rotation distribution S(x) provided for linearly polarized light incident to respective points along the x-direction on the plane 31a being an entrance plane of the first optical-rotation optical member 31 is represented by Eq (3) below, where a is an inclination angle of the two inclined faces forming the V-shaped refracting face 31b of the first optical-rotation optical member 31 and t the thickness of rock crystal necessary for a 360-degree rotation of the polarization direction of incident linearly polarized light.
S(x)=(|x|/t)×tan α (3)
On the other hand, when the first optical-rotation optical member 31 is rotated by an angle of +p around the optical axis AX from the standard state shown in
S(x)=(|x|/t)×tan α×cos β (4)
Therefore, it is also the case in the first modification example that when the first optical-rotation optical member 31 is rotated by the angle +β around the optical axis AX and the second optical-rotation optical member 33 is rotated by the angle −β around the optical axis AX from the standard state shown in
In this case, as apparent with reference to Eq (4), as the magnitude |β| of the rotation angles of the first optical-rotation optical member 31 and the second optical-rotation optical member 33 increases from 0°, the change rate of the optical rotation distribution S(x) by the polarization distribution adjusting member 9A monotonically decreases. However, when the magnitude |β| of the rotation angles of the first optical-rotation optical member 31 and the second optical-rotation optical member 33 reaches 90°, the sum of the thickness in the optical-axis direction of the first optical-rotation optical member 31 and the thickness in the optical-axis direction of the second optical-rotation optical member 33 becomes constant along the x-direction and incident light in an optional linearly polarized state passes with the polarization direction maintained, without being subjected to the action of optical activity of the polarization distribution adjusting member 9A.
In the first modification example, when the polarization state of light is measured with the polarization state measuring unit 14, for example, during circular illumination, the measurement result can be as shown in
Specifically, the control unit 15 rotates the first optical-rotation optical member 31 forming the polarization distribution adjusting member 9A, by the required angle +β around the optical axis AX and rotates the second optical-rotation optical member 33 by the required angle −β around the optical axis AX, based on the measurement result by the polarization state measuring unit 14. As a result, by virtue of the action of optical activity of linear change along the X-direction of the polarization distribution adjusting member 9A, the linearly polarized states in the region from the center to the periphery along the X-direction can be corrected (or adjusted) into the desired X-directionally linearly polarized state, without substantially changing the linearly polarized state in the region from the center to the periphery along the Y-direction on the illumination pupil plane, as shown in
Just like the first optical-rotation optical member 41, the second optical-rotation (rotary polarization) optical member 43 is made, for example, of rock crystal and has a plane 43a on the light source side and a refracting face 43b of a concave and cylindrical shape on the mask side. Just like the first correction optical member 42, the second correction optical member 44 is made, for example, of silica glass (or fluorite or the like) and has a refracting face of a convex and cylindrical shape (a surface complementary to the concave refracting face 43b) 44a on the light source side and a plane 44b on the mask side. The first optical-rotation optical member 41 and the first correction optical member 42 are arranged as integrally rotatable around the optical axis AX and the second optical-rotation optical member 43 and the second correction optical member 44 are arranged as integrally rotatable around the optical axis AX.
It will be assumed hereinafter for simplification of description that the first optical-rotation optical member 41 and the second optical-rotation optical member 43 have the same configuration, that the first correction optical member 42 and the second correction optical member 44 have the same configuration, and that the first optical-rotation optical member 41 and the second optical-rotation optical member 43 are positioned in the same posture in the standard state shown in
Therefore, the optical rotation distribution S(x) provided for linearly polarized light incident to respective points along the x-direction on the plane 41a being an entrance plane of the first optical-rotation optical member 41 is represented by Eq (5) below, where a is a coefficient to define the cylindrical shape of the concave refracting face 41b of the first optical-rotation optical member 41 and t the thickness of rock crystal necessary for a 360-degree rotation of the polarization direction of the incident linearly polarized light.
S(x)=ax2/t (5)
On the other hand, when the first optical-rotation optical member 41 is rotated by an angle of +β around the optical axis AX from the standard state shown in
S(x)=(ax2/t)×cos β (6)
It is therefore also the case in the second modification example that when the first optical-rotation optical member 41 is rotated by the angle +β around the optical axis AX and the second optical-rotation optical member 43 is rotated by the angle −β around the optical axis AX from the standard state shown in
In this case, as apparent with reference to Eq (6), as the magnitude |β| of the rotation angles of the first optical-rotation optical member 41 and the second optical-rotation optical member 43 increases from 0°, the change rate of the optical rotation distribution S(x) by the polarization distribution adjusting member 9B monotonically decreases. However, when the magnitude |β| of the rotation angles of the first optical-rotation optical member 41 and the second optical-rotation optical member 43 reaches 90°, the sum of the thickness in the optical-axis direction of the first optical-rotation optical member 41 and the thickness in the optical-axis direction of the second optical-rotation optical member 43 becomes constant along the x-direction and incident light in an optional linearly polarized state passes with the polarization direction maintained, without being subjected to the action of optical activity of the polarization distribution adjusting member 9B.
In the second modification example, as described above, the control unit 15 also rotates the first optical-rotation optical member 41 forming the polarization distribution adjusting member 9B, by the required angle −β around the optical axis AX and rotates the second optical-rotation optical member 43 by the required angle −β around the optical axis AX, based on the measurement result by the polarization state measuring unit 14. As a result, by virtue of the action of optical activity of quadratic change along the X-direction of the polarization distribution adjusting member 9B, the linearly polarized state in the region from the center to the periphery along the X-direction can be corrected (or adjusted) into the desired X-directionally linearly polarized state, without substantially changing the linearly polarized state in the region from the center to the periphery along the Y-direction on the illumination pupil plane. In the above-described second modification example, the first optical-rotation optical member 41 can be regarded, for example, as a first polarizing member and the second optical-rotation optical member 43 can be regarded, for example, as a second polarizing member.
Just like the first optical-rotation optical member 51, the second optical-rotation (rotary polarization) optical member 53 is made, for example, of rock crystal and has a plane 53a on the light source side and a refracting face 53b of a higher-order noncircular-cylindrical (aspheric-cylindrical) shape on the mask side. Just like the first correction optical member 52, the second correction optical member 54 is made, for example, of silica glass (or fluorite or the like) and has a refracting face of a higher-order noncircular-cylindrical (aspheric-cylindrical) shape (a surface complementary to the refracting face 53b) 54a on the light source side and a plane 54b on the mask side. The first optical-rotation optical member 51 and the first correction optical member 52 are arranged as integrally rotatable around the optical axis AX and the second optical-rotation optical member 53 and the second correction optical member 54 are arranged as integrally rotatable around the optical axis AX.
It will be assumed hereinafter for simplification of description that the first optical-rotation optical member 51 and the second optical-rotation optical member 53 have the same configuration, that the first correction optical member 52 and the second correction optical member 54 have the same configuration, and that the first optical-rotation optical member 51 and the second optical-rotation optical member 53 are positioned in the same posture in the standard state shown in
Therefore, the optical rotation distribution S(x) provided for linearly polarized light incident to respective points along the x-direction on the plane 51a being an entrance plane of the first optical-rotation optical member 51 is represented by Eq (7) below, where a0-an are coefficients to define the higher-order non-cylindrical shape of the refracting face 51b of the first optical-rotation optical member 51 and t the thickness of rock crystal necessary for a 360-degree rotation of the polarization direction of the incident linearly polarized light.
S(x)=(anxn+an-1xn-1+ . . . +a1x+a0)/t (7)
On the other hand, when the first optical-rotation optical member 51 is rotated by an angle of +p around the optical axis AX from the standard state shown in
S(x)={(anxn+an-1xn-1+ . . . +a1x+a0)/t}×cos β (8)
It is therefore also the case in the third modification example that when the first optical-rotation optical member 51 is rotated by the angle +β around the optical axis AX and the second optical-rotation optical member 53 is rotated by the angle −β around the optical axis AX from the standard state shown in
In this case, as apparent with reference to Eq (8), as the magnitude |β| of the rotation angles of the first optical-rotation optical member 51 and the second optical-rotation optical member 53 increases from 0°, the change rate of the optical rotation distribution S(x) by the polarization distribution adjusting member 9C monotonically decreases. However, when the magnitude |β| of the rotation angles of the first optical-rotation optical member 51 and the second optical-rotation optical member 53 reaches 90°, the sum of the thickness in the optical-axis direction of the first optical-rotation optical member 51 and the thickness in the optical-axis direction of the second optical-rotation optical member 53 becomes constant along the x-direction and incident light in an optional linearly polarized state passes with the polarization direction maintained, without being subjected to the action of optical activity of the polarization distribution adjusting member 9C.
In the third modification example, as described above, the control unit 15 also rotates the first optical-rotation optical member 51 forming the polarization distribution adjusting member 9C by the required angle +β around the optical axis AX and rotates the second optical-rotation optical member 53 by the required angle −β around the optical axis AX, based on the measurement result by the polarization state measuring unit 14. As a result, by virtue of the action of optical activity of higher-order change along the X-direction of the polarization distribution adjusting member 9C, the linearly polarized state in the region from the center to the periphery along the X-direction can be corrected (or adjusted) into the desired X-directionally linearly polarized state, without substantially changing the linearly polarized state in the region from the center to the periphery along the Y-direction on the illumination pupil plane. In the above-described third modification example, the first optical-rotation optical member 51 can be regarded, for example, as a first polarizing member and the second optical-rotation optical member 53 can be regarded, for example, as a second polarizing member.
In the above description the polarization distribution adjusting member is provided with the two sets of optical-rotation optical members and correction optical members, but it is also possible to two-dimensionally adjust the polarization distribution on the illumination pupil plane, using the polarization distribution adjusting member provided with only one set of an optical-rotation optical member and a correction optical member. In the above description the first set of optical-rotation optical member and correction optical member and the second set of optical-rotation optical member and correction optical member have the same configuration, but it is also possible to adopt different configurations for the first set and the second set.
In the above description the first set of optical-rotation optical member and correction optical member and the second set of optical-rotation optical member and correction optical member are rotated by the same angle in opposite directions, but it is also possible to two-dimensionally adjust the polarization distribution on the illumination pupil plane, by rotating the first set and the second set independently of each other. When the spacing between the optical-rotation optical member and the correction optical member is relatively large, this spacing can cause a change in in-plane ray distribution density to easily give rise to light-quantity unevenness (illuminance unevenness); therefore, the spacing between the optical-rotation optical member and the correction optical member is preferably set as small as possible.
In the above description the face shapes of the optical-rotation optical members are set so as to achieve the optical rotation distribution without change in the polarization state of light of axial rays, and this is because the polarization state is more likely to deviate from the desired state in the peripheral region than in the central region (axial region) on the illumination pupil plane. However, without having to be limited to this, it is also possible to contemplate a variety of modification examples as to the face shapes of the optical-rotation optical members (and thus as to the optical rotation distribution).
In the above description the correction optical members are used to correct deflection of rays due to the angle deviation action of the optical-rotation optical members, but it is also possible to omit the disposition of the correction optical members in the polarization distribution adjusting member. In the above description the optical-rotation optical members are made of rock crystal, but, without being limited to rock crystal, the optical-rotation optical members can also be made of another appropriate optical material with optical activity. It is also possible to subject incident light to the action of optical activity by form birefringence.
In the above-described first modification example, it is sometimes difficult to highly accurately process the ridge-line portions (top portions or bottom portions) of the V-shaped refracting faces of the optical-rotation optical members and the correction optical members. In this case, light-quantity unevenness is likely to occur because of processing error in the ridge-line portions and it is thus preferable to reduce influence of the processing error, for example, by defocusing the ridge-line portions somewhat from the plane optically conjugate with the illumination pupil plane.
In the foregoing third modification example, the refracting faces of the higher-order noncircular-cylindrical shapes of the optical-rotation optical members and correction optical members are desirably defined by differentiable continuous functions. When this configuration is not satisfied, for example, discontinuous light-quantity unevenness becomes likely to occur because of influence of processing error made according to a tolerance during processing of parts.
In the above description the optical-rotation optical members are rotated around the optical axis, but it is also possible to adjust the polarization distribution on the illumination pupil plane, by moving the optical-rotation optical members in a direction perpendicular to the optical axis (generally, in a direction intersecting with the optical axis). In this case, the offset component (O-order component) in the polarization distribution can be adjusted throughout the entire illumination pupil plane including the axial region, in the aforementioned embodiment and first modification example; the inclination component (first-order component) in the polarization distribution can be adjusted in the second modification example; the (n−1)th-order component in the polarization distribution can be adjusted in the third modification example. The polarization distribution can also be adjusted according to a diversity of forms by rotating the optical-rotation optical members around an axis parallel to the optical axis in a state in which the optical-rotation optical members are moved in the direction perpendicular to the optical axis.
In the polarization distribution adjusting member 9D shown in
The second optical-rotation optical member 35 and the second correction optical member 36 are arranged as integrally rotatable around the optical axis AX. When the polarization distribution adjusting member 9D of the fourth modification example is in the standard state shown in
The polarization state of illumination light onto the wafer W can be adjusted into a desired polarization state, by similarly changing the relative rotation angles of the first optical-rotation optical member 31 and the second optical-rotation optical member 35 as in the aforementioned embodiment and modification examples. In the above-described fourth modification example, the first optical-rotation optical member 31 can be regarded, for example, as a first polarizing member and the second optical-rotation optical member 35 can be regarded, for example, as a second polarizing member.
In the polarization distribution adjusting member 9E shown in
The second optical-rotation optical member 45 and the second correction optical member 46 are arranged as integrally rotatable around the optical axis AX. When the polarization distribution adjusting member 9E of the fifth modification example is in the standard state shown in
The polarization state of illumination light onto the wafer W can be adjusted into a desired polarization state by similarly changing the relative rotation angles of the first optical-rotation optical member 41 and the second optical-rotation optical member 45 as in the aforementioned embodiment and modification examples. In the above-described fifth modification example, the first optical-rotation optical member 41 can be regarded, for example, as a first polarizing member and the second optical-rotation optical member 45 can be regarded, for example, as a second polarizing member.
In the polarization distribution adjusting member 9F shown in
The second optical-rotation optical member 55 and the second correction optical member 56 are arranged as integrally rotatable around the optical axis AX. When the polarization distribution adjusting member 9F of the fifth modification example is in the standard state shown in
The polarization state of illumination light onto the wafer W can be adjusted into a desired polarization state, by similarly changing the relative rotation angles of the first optical-rotation optical member 51 and the second optical-rotation optical member 55 as in the aforementioned embodiment and modification examples. In the above-described sixth modification example, the first optical-rotation optical member 51 can be regarded, for example, as a first polarizing member and the second optical-rotational optical member 55 can be regarded, for example, as a second polarizing member.
The above described use of the single polarization distribution adjusting member, but it is also possible to use two or more polarization distribution adjusting members. The following will describe such examples with reference to
In the above description the optical-rotation optical members used were those with the thickness distribution of one-fold rotational symmetry or two-fold rotational symmetry with respect to the optical axis AX, but, without being limited to this, it is also possible to use optical-rotation optical members with a thickness distribution of any other rotational symmetry such as three- or more-fold rotational symmetry (except for infinite-fold rotational symmetry with respect to the rotation axis).
In the above description each optical-rotation optical member (polarizing member) in the polarization distribution adjusting member was formed of a single optical member, but it may also be composed of an aggregate (assembly) of a plurality of optical-rotation optical elements.
In
The entire polarization distribution adjusting member 47 has an optical rotation distribution of rotation asymmetry (two-fold rotation symmetry in the present modification example) approximate to the optical rotation distribution of the first optical-rotation optical member 41 in the fifth modification example shown in
The polarization distribution adjusting member 48, as shown in
The entire polarization distribution adjusting member 48 has an optical rotation distribution of rotation asymmetry (two-fold rotation symmetry in the present modification example) approximate to the optical rotation distribution of the second optical-rotation optical member 45 in the fifth modification example shown in
It is noted herein that the following sums are equal to each other: the sum of the first thickness of the optical-rotation optical element 47A and the fourth thickness of the optical-rotation optical element 48A; the sum of the second thickness of the optical-rotation optical elements 47B, 47D and the fifth thickness of the optical-rotation optical elements 48B, 48D; the sum of the third thickness of the optical-rotation optical elements 47C, 47E and the sixth thickness of the optical-rotation optical elements 48C, 48E.
This configuration enables the eleventh modification example to achieve the function equivalent to that of the polarization distribution adjusting member shown in the fifth modification example. In the eleventh modification example shown in
The above-described eleventh modification example used the plurality of optical-rotation optical elements of the plane-parallel plate shape, but the plurality of optical-rotation optical elements do not have to be limited to the plane-parallel plate shape.
The accuracy of approximation of optical rotation distribution can be improved by using the optical-rotation optical elements 470B-470E, 480B-480E of the wedge shape instead of those of the plane-parallel plate shape. The entrance surfaces 470Aa-470Ea, 480Aa-480Ea of these optical-rotation optical elements 470A-470E, 480A-480E may be changed from the planar shape into a curved shape such as a concave cylindrical surface or a convex cylindrical surface. In the twelfth modification example, the aggregate of optical-rotation optical elements 470A-470E can be regarded as a first polarizing member and the aggregate of optical-rotation optical elements 480A-480E can be regarded, for example, as a second polarizing member.
In cases where the polarization distribution adjusting member is constructed using the optical-rotation optical elements of the shapes other than the plane-parallel plate shape, e.g., those of the wedge shape or curved shape, it is preferable to combine the optical-rotation optical elements with correction optical elements having faces complementary to those of the optical-rotation optical elements of the shapes other than the plane-parallel plate shape, as in the thirteenth modification example of
In the thirteenth modification example, as described above, each set of an optical-rotation optical element and a correction optical element has the form of the plane-parallel plate shape as a whole, and thus they can maintain the traveling direction of light passing through the polarization distribution adjusting members 471, 481. In the thirteenth modification example, the aggregate of optical-rotation optical elements 470A-470E can be regarded as a first polarizing member, and the aggregate of optical-rotation optical elements 480A-480E can be regarded, for example, as a second polarizing member.
The twelfth modification example and the thirteenth modification example described above showed the examples in which the plurality of optical-rotation optical elements (and correction optical elements) were held by the holding member, but, without being limited to this configuration, the plurality of optical-rotation optical elements may also be arrayed on a single optically transparent substrate.
In
The polarization distribution adjusting member 26, as shown in
In the fourteenth modification example, in order to keep the thickness approximately constant in the direction of the optical axis AX of the polarization distribution adjusting members, correction optical members 251A, 251B, 251D are provided on the respective optical-rotation optical elements 25A, 25B, 25D, and correction optical members 261B-261E are provided on the respective optical-rotation optical elements 26B-26E. The whole polarization distribution adjusting member 26 has an optical rotation distribution of rotation asymmetry (two-fold rotation symmetry in the present modification example) equivalent to the optical rotation distribution of the polarization distribution adjusting member 48 in the eleventh modification example shown in
In the fourteenth modification example shown in
In the fourteenth modification example shown in
In the fourteenth modification example shown in
In the fourteenth modification example the plurality of optical-rotation optical elements (polarizing optical elements) 25A-25E, 26A-26E were integrated on one optically transparent substrate 25F, 26F, but the plurality of optical-rotation optical elements (polarizing optical elements) may be held so as to be sandwiched between two optically transparent substrates.
In the fifteenth modification example, the configurations of the plurality of optical-rotation optical elements 27A-27E, 28A-28E integrated along one direction crossing the optical axis AX are the same as those of the plurality of optical-rotation optical elements 25A-25E, 26A-26E shown in the fourteenth modification example, and the description thereof is omitted herein.
The fifteenth modification example is different in the configuration from the fourteenth modification example in that the plurality of optical-rotation (rotary polarization) optical elements 27A-27E are sandwiched between two optically transparent substrates 27F, 27G arranged in juxtaposition along the direction of the optical axis AX and in that the plurality of optical-rotation (rotary polarization) optical elements 28A-28E are sandwiched between two optically transparent substrates 28F, 28G arranged in juxtaposition along the direction of the optical axis AX. The optically transparent substrates 27G, 28G in the fifteenth modification example are provided with shield portions 27G1-27G4, 28G1-28G4 so as to overlap the optical-rotation optical elements 27A-27E, 28A-28E, in order to prevent unwanted light which could appear in the boundary regions of the optical-rotation optical elements 27A-27E, 28A-28E. This configuration achieves uniform illumination while preventing the unwanted light from the boundary regions of the optical-rotation optical elements (polarizing optical elements).
In the fifteenth modification example, each optical-rotation optical element may also be provided with a correction optical element as in the aforementioned fourteenth modification example and the shape of each optical-rotation optical element may be a wedge shape. In the fifteenth modification example, the aggregate of optical-rotation optical elements 27A-27E can be regarded as a fist polarizing member and the aggregate of optical-rotation optical elements 28A-28E can be regarded, for example, as a second polarizing member.
In the eleventh to fifteenth modification examples, the plurality of optical-rotation optical elements (phase elements or polarizing optical elements) were integrated in one direction in the plane crossing the optical axis, but the direction of integration of the optical-rotation optical elements in not limited to only one direction; for example, they may also be integrated in a two-dimensional matrix.
In
As apparent from the A-A arrow view of
The whole polarization distribution adjusting member 29 has an optical rotation distribution equivalent to that of the polarization distribution adjusting member 47 in the eleventh modification example shown in
In the above-described sixteenth modification example, the shape of each of the optical-rotation optical elements (phase elements or polarizing elements) was the rectangular shape, but the shape of the optical-rotation optical elements (phase elements or polarizing elements) is not limited to the rectangular shape; for example, they may have a hexagonal shape as in the seventeenth modification example shown in
In
The polarization distribution adjusting members 29, 37 of the sixteenth modification example and the seventeenth modification example described above had the optical rotation distribution varying only in one predetermined direction crossing the optical axis AX, but they may have a two-dimensional distribution in the plane crossing the optical axis AX, for example, as in the ninth modification example of
The contour of each optical-rotation optical element (phase element or polarizing element) does not have to be limited to the rectangular or hexagonal shape, but may be any other polygonal shape. However, in order to minimize light-quantity loss, it is preferable to adopt a shape permitting close packing arrangement, e.g., the rectangular shape or the hexagonal shape. The shape of the optical-rotation optical elements does not have to be limited to the same shape, but it is also possible to adopt a combination of shapes permitting close packing arrangement, e.g., a combination of a regular pentagon with a rhombus, a combination of a regular heptagon with a pentagon, or a combination of a regular octagon with a square.
Since light-quantity unevenness is likely to occur in the boundary regions of the optical-rotation optical elements (phase elements or polarizing elements) as in the aforementioned eleventh to seventeenth modification examples, it is preferable to reduce the influence of the boundary regions, for example, by defocusing the polarization distribution adjusting member somewhat from the plane optically conjugate with the illumination pupil plane or from the plane optically conjugate with the surface to be illuminated.
In the above description the polarization distribution on the illumination pupil plane is adjusted by locating the polarization distribution adjusting member at the position immediately before the micro fly's eye lens 10. However, without being limited to this, the polarization distribution on the illumination pupil plane can also be adjusted by locating the polarization distribution adjusting member at or near the pupil position of the illumination optical apparatus (1-PL), e.g., at or near the pupil 61 of the afocal lens 5, at or near the pupil of the imaging optical system 13, or at one of a position immediately before, a position 62 immediately after, and a position near the micro fly's eye lens 10.
In the above description, the polarization distribution adjusting member includes the first polarizing member (first optical-rotation optical member 21, 31, 41, 51) and the second polarizing member (second optical-rotation optical member 23, 33, 43, 53) arranged adjacent to each other on the illumination light path, but, without being limited to this, they may also be arranged so as to be approximately conjugate with each other through an optical system in the illumination optical apparatus. For example, the first polarizing member may be located at or near the pupil 61 of the afocal lens 5 and the second optical member may be located at one of the position immediately before, the position 62 immediately after, and the position near the micro fly's eye lens 10, or at or near the pupil of the imaging optical system 13.
When the polarizing member of the first set (e.g., the set of first optical-rotation optical member 21, 31, 41, 51 and correction optical member 22, 32, 42, 52) is different in the configuration from the polarizing member of the second set (e.g., the set of second optical-rotation optical member 23, 33, 43, 53 and correction optical member 24, 34, 44, 54), these sets of polarizing members may be arranged adjacent to each other in the illumination light path, or, without being limited to this, they may also be arranged so as to be approximately conjugate with each other through an optical system in the illumination optical apparatus.
In order to adjust the polarization distribution on the illumination pupil plane, the polarization distribution adjusting member is preferably located in the portion of the beam where the sectional shape thereof is changed by the beam shape changing member. In this case, it is preferable to locate the polarization state switch for adjusting the polarization state of the entire beam cross section nearer to the light source than the beam shape changing member. This configuration permits the polarization state switch to adjust the overall offset component in the polarization state on the illumination pupil plane, and permits the polarization distribution adjusting member to adjust the distribution of local polarization states in the illumination pupil plane.
In the above description, the polarization distribution adjusting member is located at or near the pupil position of the illumination optical apparatus (1-PL) to adjust the polarization distribution on the illumination pupil plane. However, without being limited to this, it is also possible to adjust the polarization distribution on the wafer W being a surface to be illuminated, by locating the polarization distribution adjusting member at or near the position optically conjugate with the surface to be illuminated (W) in the illumination optical apparatus (1-PL). In this case, specifically, the polarization distribution adjusting member is located, for example, at a position 65 immediately before and/or at a position 66 immediately after the mask M, at a position 63 immediately before or at a position 64 immediately after the mask blind 12, or at a position 67 immediately before the wafer W. The polarization distribution adjusting member is preferably located in the optical path between the micro fly's eye lens as a wavefront-splitting type optical integrator, and the surface to be illuminated. It is also possible to locate two polarization distribution adjusting members one at or near the pupil position of the illumination optical apparatus (1-PL) and the other at or near the position optically conjugate with the surface to be illuminated (W) in the illumination optical apparatus (1-PL). It is also possible, for example, to locate the polarization distribution adjusting member at a position 68 different from the pupil position of the illumination optical apparatus (1-PL) and the position optically conjugate with the surface to be illuminated (W).
In the case of the scan type (scanning) exposure apparatus, the polarization distribution along an orthogonal direction perpendicular to a scanning direction is more important than the polarization distribution along the scanning direction in a still exposure region on the wafer W being a surface to be illuminated, by virtue of scan averaging effect. Therefore, when the polarization distribution adjusting member in each of the aforementioned embodiment and modification examples is applied to the scan type exposure apparatus, the first set of optical-rotation optical member and correction optical member and the second set of optical-rotation optical member and correction optical member had better be rotated by the same angle in opposite directions, so as to adjust only the polarization distribution along the orthogonal direction.
In the above description, the configuration from the light source 1 to the projection optical system PL is assumed to constitute the illumination optical apparatus for illuminating the wafer W as the surface to be illuminated, but we can also assume that the configuration from the light source 1 to the imaging optical system 13 constitutes an illumination optical apparatus for illuminating the mask M as a surface to be illuminated. In this case, the polarization distribution adjusting member for adjusting the polarization distribution on the mask M as a surface to be illuminated is located near the surface to be illuminated (M) in the illumination optical apparatus (1-13), or at or near a position optically conjugate with the surface to be illuminated (M).
In the above description, the optical rotation members (optical-rotation optical members) for providing the incident light with optical rotation amounts varying according to respective positions of incidence were rotated, but in general, it is feasible to adjust the polarization distribution of light on the illumination pupil plane or on the surface to be illuminated, by rotating a phase member for providing the incident light with phase amounts varying according to respective positions of incidence. This phase member may be an optical rotation member for providing phase differences different according to respective directions of rotation of circularly polarized light (i.e., for providing a required optical rotation distribution for linearly polarized light to be resolved into left-hand and right-hand circularly polarized light components with an equal amplitude and equal velocity), like the optical-rotation optical members in the aforementioned embodiment and each modification example. This phase member may be a phase shift member for providing phase differences different according to respective directions of vibration of linearly polarized light, e.g., like a wave plate. This phase shift member may be one made of a birefringent optical material such as rock crystal, may be one of a shape to exhibit form birefringence, or may be an optical member with stress birefringence. It is also possible to use a combination of an optical rotation member with a phase shift member.
The exposure apparatus according to the above-described embodiment can manufacture micro devices (semiconductor devices, imaging devices, liquid-crystal display devices, thin-film magnetic heads, etc.) through a process of illuminating a mask (reticle) by the illumination optical apparatus (illumination block) and exposing a photosensitive substrate with a transfer pattern formed in a mask, by the projection optical system (exposure block). An example of a method for obtaining semiconductor devices as micro devices by forming a predetermined circuit pattern in a wafer or the like as a photosensitive substrate by means of the exposure apparatus of the above embodiment will be described below with reference to the flowchart of
The first block 301 in
The exposure apparatus of the above embodiment can also manufacture a liquid-crystal display device as a micro device by forming predetermined patterns (circuit pattern, electrode pattern, etc.) on plates (glass substrates). An example of a method in this case will be described below with reference to the flowchart of
The next color filter forming block 402 is to form a color filter in which a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arrayed in a matrix pattern or in which sets of filters of three stripes of R, Q and B are arrayed in the horizontal scan line direction. After the color filter forming block 402, a cell assembling block 403 is executed. The cell assembling block 403 is to assemble a liquid crystal panel (liquid crystal cell) using the substrate with the predetermined pattern obtained in the pattern forming block 401, the color filter obtained in the color filter forming block 402, and others.
In the cell assembling block 403, the liquid crystal panel (liquid crystal cell) is manufactured, for example, by pouring a liquid crystal into between the substrate with the predetermined pattern obtained in the pattern forming block 401 and the color filter obtained in the color filter forming block 402. The subsequent module assembling block 404 is to attach various components such as electric circuits and a backlight for display operation of the assembled liquid crystal panel (liquid crystal cell) to complete the liquid-crystal display device. The above-described manufacturing method of the liquid-crystal display device permits us to obtain the liquid-crystal display device with extremely fine circuit patterns at high throughput.
The aforementioned embodiment used the ArF excimer laser light (the wavelength: 193 nm) or the KrF excimer laser light (the wavelength: 248 nm) as the exposure light, but the exposure light does not have to be limited to these: the present invention can also be applied to any other appropriate laser light source, e.g., an F2 laser light source for supplying the laser light at the wavelength of 157 nm.
The foregoing embodiment was the application of the present invention to the illumination optical apparatus for illuminating the mask or the wafer in the exposure apparatus, but, without having to be limited to this, the present invention can also be applied to commonly-used illumination optical apparatus for illuminating a surface to be illuminated except for the mask or the wafer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005325787 | Nov 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/321607 | 10/30/2006 | WO | 00 | 10/14/2008 |
