HK1140833B - Lighting optical device, exposure system and exposure method - Google Patents

Description

Optical illumination device, exposure device, and exposure method

The present application is a divisional application entitled "light beam conversion element, optical illumination device, exposure device, and exposure method" filed under the original application No. 200480034124.6 (international application No. PCT/JP2004/016247, international application No. 2004/11/2).

Technical Field

The present invention relates to a light beam conversion element, an optical illumination device, an exposure device, and an exposure method, and more particularly, to an optical illumination device suitable for an exposure device used in the production of microdevices such as semiconductor devices, image pickup devices, liquid crystal display devices, and thin film magnetic heads by photolithography.

Background

In such a typical exposure apparatus, a light beam emitted from a light source passes through an optical integrator (optical integrator) and fly-eye lenses (fly-eye lenses), and a substantial secondary light source of a surface light source is formed by a plurality of light sources. The light beam emitted from the secondary light source (generally, the illumination pupil of the optical illumination device or the illumination pupil distribution formed in the vicinity thereof) is restricted by an aperture stop disposed in the vicinity of the rear focal plane of the fly eye lens, and then enters a condenser lens (condenser lens).

The light beams collected by the condenser lens are overlapped to illuminate a mask having a predetermined pattern formed thereon. The light passing through the pattern of the mask is imaged on a wafer (wafer) by an optical projection system. In this manner, the mask pattern is projection exposed (replicated) onto the wafer. Further, the pattern formed on the mask is highly integrated, and it is essential that the fine pattern is accurately transferred to the wafer, and a uniform illuminance distribution is obtained on the wafer.

For example, japanese patent No. 3246615 filed by the present applicant discloses a technique of forming a tire-shaped secondary light source on the rear focal plane of a fly-eye lens and setting a light flux passing through the tire-shaped secondary light source in a linearly polarized state (hereinafter, referred to as "circularly polarized state") in which the circumferential direction is a polarization direction, in order to realize a suitable illumination condition capable of faithfully reproducing a fine pattern in an arbitrary direction.

[ patent document 1] Japanese patent No. 3246615 publication

However, the conventional technique disclosed in the above-mentioned publication restricts the formation of a tire-shaped secondary light source by a circular light beam formed by a fly-eye lens through an aperture having a tire-shaped opening. As a result, the conventional technique causes a large amount of light loss at the aperture stop, which causes an unsuitable phenomenon in which the amount of light transmitted through the exposure apparatus is reduced.

Disclosure of Invention

The purpose of the present invention is to form a tire-shaped illumination pupil distribution in a circumferentially polarized state while effectively suppressing light loss. Further, the present invention is intended to enable the formation of an annular illumination pupil in a circumferentially polarized state while effectively suppressing the loss of light intensity, and to enable the faithful and high-speed transfer of a fine pattern in an arbitrary direction under appropriate illumination conditions.

In order to achieve the above object, according to a first aspect of the present invention, there is provided an optical illumination device applied to an exposure device for transferring a pattern of a mask onto a photosensitive substrate, the optical illumination device illuminating an irradiated surface on which the mask is disposed with illumination light emitted from a light source, the optical illumination device comprising: a light beam conversion element provided in an optical path between the light source and the irradiated surface, the light beam conversion element including: an element formed of a crystalline optical material having an optical rotation, wherein the light beam conversion element forms a predetermined light intensity distribution in which the cross-sectional shape of the incident light beam of the illumination light is different on a pupil surface of the optical illumination device; and a conical axicon system disposed at: an optical path of the illumination light in an emission side of the element formed using a crystalline optical material, the element formed using a crystalline optical material being: converting the illumination light in a linearly polarized state incident on the element into illumination light in a polarized state having linearly polarized light whose polarization direction is a circumferential direction of a tire-shaped region as a main component, the tire-shaped region being centered on an optical axis of the optical illumination device in the pupil plane, the illumination light in the polarized state being converted by an element formed of the crystalline optical material: the irradiated surface is irradiated via the conical axicon system.

In an embodiment of the present invention, the conical axicon system comprises: a 1 st prism element having a curved surface which is flat on the incident side of the illumination light and has a concave cone shape on the exit side of the illumination light; and a 2 nd prism element disposed on the optical path on the emission side of the 1 st prism element, and having a curved surface which is flat toward the emission side of the illumination light and has a convex cone shape toward the incidence side of the illumination light.

In an embodiment of the present invention, a distance between the 1 st prism element and the 2 nd prism element is variable.

In an embodiment of the present invention, the element formed by using the crystalline optical material is: the crystal optical axis of the crystal optical material is oriented in a direction coincident with the optical axis of the optical illumination device.

In an embodiment of the present invention, the polarization state of the illumination light in the pupil plane is: and a linearly polarized state in which a tangent to a circle centered on the optical axis is aligned with a polarization direction.

In an embodiment of the present invention, the beam transformation element includes: a diffraction surface that distributes the illumination light in a pair of arc-shaped regions that are symmetrical with respect to the optical axis in the tire-shaped region in the pupil surface.

In an embodiment of the invention, the predetermined light intensity distribution is: a tire-shaped light intensity distribution in the tire-shaped region in the pupil plane.

In an embodiment of the invention, the predetermined light intensity distribution is: a multi-polar light intensity distribution in the pupil plane within the tire-shaped region.

In an embodiment of the present invention, the optical illumination device further includes: a wavefront-dividing optical integrator disposed on the optical path on the exit side of the diffraction surface; and a zoom lens disposed on the optical path between the diffraction surface and the optical integrator.

In an embodiment of the present invention, the illumination light is emitted from the light source in a polarized state in which linear polarization is a main component.

In an embodiment of the present invention, the optical illumination device further includes: and a polarization state switching device which is disposed in the optical path on the incident side of the light beam conversion element and switches the polarization state of the illumination light emitted from the light source between a linearly polarized state and a non-polarized state or between two linearly polarized states whose polarization directions are perpendicular to each other.

In an embodiment of the present invention, the polarization state switching device includes: 1/4 wavelength plate, 1/2 wavelength plate, and a depolarizer configured to exit the optical path.

In an embodiment of the invention, a polarization degree of the illumination light emitted from the light source is greater than or equal to 95%.

In order to achieve the above object, according to a second aspect of the present invention, there is provided an exposure apparatus for exposing a pattern of a mask to a photosensitive substrate, the exposure apparatus comprising: the optical illumination device illuminates the mask.

In an embodiment of the present invention, the exposure apparatus includes: a projection optical system that projects an image of the pattern of the mask onto the photosensitive substrate; wherein the image of the pattern is: and a liquid filled in an optical path between the projection optical system and the photosensitive substrate, and projected onto the photosensitive substrate.

In order to achieve the above object, according to a third aspect of the present invention, there is provided an exposure method for exposing a pattern of a mask to a photosensitive substrate, the exposure method comprising: illuminating the pattern of the mask using the optical illumination device; and exposing the pattern of the mask illuminated by the optical illumination device on the photosensitive substrate.

In an embodiment of the present invention, the exposure method includes: projecting an image of the pattern illuminated using the optical illumination device onto the photosensitive substrate; wherein the image of the pattern is: the image of the pattern is projected in a state where an optical path between a projection optical system for projecting the image of the pattern onto the photosensitive substrate and the photosensitive substrate is filled with a liquid.

The optical illumination device of the present invention is different from the conventional device in that a large amount of light loss does not occur in the aperture stop, and a tire-shaped illumination pupil distribution in a polarized state in the peripheral direction can be formed without substantial light loss by utilizing the diffraction action and the optical rotation action of the optical diffraction element of the light beam conversion element. That is, the optical illumination device of the present invention can form a tire-shaped illumination pupil distribution in a polarization state in the peripheral direction while suppressing light quantity loss satisfactorily.

Further, the exposure apparatus and the exposure method using the optical illumination apparatus according to the present invention use the optical illumination apparatus capable of suppressing light loss satisfactorily and forming a tire-shaped illumination pupil distribution in a polarized state in the peripheral direction, and therefore, it is possible to reproduce a minute pattern in an arbitrary direction faithfully and at high speed under appropriate illumination conditions, that is, it is possible to manufacture a good device with high productivity.

In order to make the aforementioned and other objects, features and advantages of the invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

Fig. 1 is a schematic view showing a configuration of an exposure apparatus equipped with an optical illumination apparatus according to an embodiment of the present invention.

FIG. 2 illustrates a secondary light source forming a tire shape in a tire-shaped illumination.

Fig. 3 is a schematic diagram showing a structure of a axicon system arranged in an optical path between a front lens group and a rear lens group of an afocal lens in fig. 1.

Fig. 4 is an explanatory view showing the effect of the conical axicon system on the tire-shaped secondary light source.

Fig. 5 is an explanatory diagram showing the effect of the zoom lens on the tire-shaped secondary light source.

Fig. 6 is a schematic view showing the structure of the first cylindrical lens couple and the second cylindrical lens couple arranged in the optical path between the front lens group and the rear lens group of the afocal lens in fig. 1.

Fig. 7 is a first diagram illustrating the effect of the first cylindrical lens couple and the second cylindrical lens couple on the tire-shaped secondary light source.

Fig. 8 is a second diagram illustrating the effect of the first cylindrical lens couple and the second cylindrical lens couple on the tire-shaped secondary light source.

Fig. 9 is a third diagram illustrating the effect of the first cylindrical lens couple and the second cylindrical lens couple on the tire-shaped secondary light source.

Fig. 10 is a schematic perspective view of the internal structure of the polarization monitor of fig. 1.

Fig. 11 is a schematic diagram showing the structure of the optical diffraction element for circumferentially polarized tire illumination according to the present embodiment.

Fig. 12 is a schematic view showing a tire-shaped secondary light source set in a polarization state in the circumferential direction.

Fig. 13 is an explanatory view showing the operation of the first basic element.

Fig. 14 is an explanatory view showing the operation of the second basic element.

Fig. 15 is an explanatory view showing the operation of the third basic element.

Fig. 16 is an explanatory view showing the operation of the fourth basic element.

FIG. 17 is a diagram showing the optical rotation of crystal.

Fig. 18(a) shows an octapole-shaped secondary light source in a circumferential polarization state formed by eight circular arc-shaped regions spaced apart from each other in the circumferential direction.

Fig. 18(b) shows a quadrupole secondary light source in a circumferential polarization state formed by four arc-shaped regions spaced apart from each other in the circumferential direction.

Fig. 19 shows a tire-shaped secondary light source in a circumferential polarized state formed by octagon-shaped regions that are repeated in the circumferential direction.

Fig. 20(a) shows a hexapole-shaped secondary light source in a circumferential polarization state formed by six regions separated from each other in the circumferential direction.

Fig. 20(b) shows a secondary light source in a circularly polarized state formed by a plurality of regions separated from each other in the circumferential direction and a region on the optical axis.

Fig. 21 shows an example of surface planarization on the light incident side of the optical diffraction element for polarizing tire-shaped illumination in the circumferential direction.

FIG. 22 is a flow chart of a process for fabricating a semiconductor device with micro-devices.

FIG. 23 is a flow chart showing a process for fabricating a liquid crystal display device with micro-devices.

1: light source

4: polarized light state switching device

4 a: 1/4 wave plate

4 b: 1/2 wave plate

5,50: optical diffraction element (light beam transformation element)

6: afocal lens

8: conical axicon system

9,10: cylindrical lens couple

11: zoom lens

12: micro fly eye lens

13: polarization monitor

13 a: a first beam splitter

13 b: a second beam splitter

14: optical light-gathering system

15: mask covering body

16: optical imaging system

31: tire-shaped secondary light source

31A to 31D: arc-shaped region

50A to 50D: basic element

M: mask film

PL: optical projection system

W: wafer

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Fig. 1 is a schematic view showing the structure of an exposure apparatus equipped with an optical illumination apparatus according to an embodiment of the present invention. In fig. 1, a normal direction of a wafer W as a photosensitive substrate is set as a Z axis, a direction parallel to a paper surface of fig. 1 within the plane of the wafer W is set as a Y axis, and a direction perpendicular to the paper surface of fig. 1 within the plane of the wafer W is set as an X axis. The exposure apparatus of the present embodiment is provided with a light source 1 for supplying exposure light (illumination light).

As the light source 1, for example, a KrF Excimer Laser (Excimer Laser) light source which supplies light having a wavelength of 248nm or an ArF Excimer Laser light source which supplies light having a wavelength of 193nm can be used. The approximately parallel light beams emitted from the light source 1 in the Z direction extend in the X direction to form an elongated rectangular cross section, and are incident on a beam expander 2(beam expander) formed by a pair of lenses 2a and 2 b. Each of the lenses 2a and 2b has a negative reflection force and a positive reflection force in the paper plane (YZ plane) of fig. 1. Therefore, the light beam incident on the beam expander 2 is expanded in the paper surface of fig. 1 and shaped into a light beam having a predetermined rectangular cross section.

The substantially parallel light flux having passed through the beam expander 2 having the optical shaping system function is turned in the Y direction by the deflecting mirror 3, passes through the 1/4 wavelength plates 4a, 1/2 wavelength plate 4b, the depolarizer (non-polarizing element) 4c (depolarizer), and the optical diffraction element 5 for tire illumination, and is incident on the Afocal lens (Afocal lens) 6. Here, the 1/4 wavelength plates 4a, 1/2 wavelength plates 4b, and the depolarizer 4c constitute the polarization state switching device 4 as described later. The afocal lens 6 is an optical afocal system, and is set such that the front focal position approximately coincides with the position of the optical diffraction element 5, and the rear focal position approximately coincides with the position of a predetermined plane 7 indicated by a broken line in the figure.

In general, an optical diffraction element has a structure in which a step of the wavelength of exposure light (illumination light) is formed on a substrate, and has an action of diffracting an incident light beam at a desired angle. Specifically, the optical diffraction element 5 for tire-shaped illumination has a function of forming a tire-shaped light intensity distribution in a Far Field (Far Field diffraction region) when a parallel light beam having a rectangular cross section is incident. Therefore, the substantially parallel light beam incident on the optical diffraction element 5 serving as the light beam conversion element forms a tire-shaped light intensity distribution on the pupil surface of the afocal lens 6, and then the substantially parallel light beam is emitted from the afocal lens 6.

In the optical path between the front lens group 6a and the rear lens group 6b of the afocal lens 6, a conical axicon system 8, a first cylindrical lens couple 9, and a second cylindrical lens couple 10 are arranged in this order from the light source side in the pupil plane or in the vicinity of the pupil plane, and the detailed structure and operation of these elements will be described later. For the sake of simplicity of explanation, the roles of the conical axicon system 8, the first cylindrical lens couple 9, and the second cylindrical lens couple 10 are temporarily ignored, and only the basic configurations and roles will be explained.

The light beam transmitted through the afocal lens 6 passes through a Zoom lens 11(Zoom lens) for changing the σ value, and enters a micro fly-eye lens 12 (also called fly-eye lens) as an optical integrator. The micro fly-eye lens 12 is an optical element in which a large number of micro lenses having positive refractive power are arranged in a vertically and vertically dense manner. In general, the micro fly-eye lens is formed by, for example, etching a parallel plane plate to form a micro lens group.

Here, each of the microlens elements constituting the micro fly-eye lens is smaller than each of the lens elements constituting the fly-eye lens. Unlike the fly-eye lens including the lens elements isolated from each other, many micro lenses (micro refraction surfaces) are not isolated from each other and are integrally formed. However, since the lens elements having positive refractive power are arranged in a vertical and horizontal direction, the micro fly-eye lens is a wavefront-dividing type optical integrator similar to the fly-eye lens.

The predetermined surface 7 is positioned in the vicinity of the front focal position of the zoom lens 11, and the entrance surface of the micro fly-eye lens 12 is positioned in the vicinity of the rear focal position of the zoom lens 11. In other words, the zoom lens 11 is disposed such that the predetermined plane 7 and the incident plane of the micro fly-eye lens 12 are substantially in a Fourier transform relationship, that is, the pupil plane of the afocal lens 6 and the incident plane of the micro fly-eye lens 12 are disposed so as to be optically approximately conjugate.

Therefore, on the incident surface of the micro fly-eye lens 12, like the pupil surface of the afocal lens 6, a tire-shaped field centered on the optical axis AX is formed. The overall shape of the tire-shaped field varies similarly with the focal length of the zoom lens 11. Each of the microlenses constituting the micro fly-eye lens 12 has a rectangular cross section similar to the shape of the entire shot formed on the mask M (the shape of the entire exposure region formed on the wafer W).

The light flux incident on the micro fly-eye lens 12 is divided into two components by a plurality of micro lenses, and as shown in fig. 2, a secondary light source having approximately the same light intensity distribution as the field formed by the incident light flux, that is, a secondary light source formed by a tire-shaped substantial surface light source centered on the optical axis AX is formed on the rear focal plane (illumination pupil). The light beam emitted from the secondary light source (generally, the pupil plane of the optical illumination device or the illumination pupil distribution formed in the vicinity thereof) formed on the rear focal plane of the micro fly's eye lens 12 passes through the beam splitter 13a (beam splitter) and the optical condensing system 14, and then, the mask shielding body 15 is illuminated in an overlapping manner.

In this way, the mask blank 15, which is an illumination field stop, forms a rectangular field corresponding to the shape and focal length of each microlens constituting the micro fly-eye lens 12. The internal structure and operation of the polarization monitor 13 incorporating the beam splitter 13a will be described later. The light flux passing through the rectangular opening (light transmitting portion) of the mask shielding body 15 is condensed by the optical imaging system 16, and then the mask M having a predetermined pattern is formed by superimposing illumination thereon.

That is, the optical imaging system 16 forms an image of the rectangular opening of the mask shielding body 15 on the mask. The light beam transmitted through the pattern of the mask M passes through the optical projection system PL to form an image of the mask pattern on the wafer W of the photosensitive substrate. In this way, the wafer is driven and controlled two-dimensionally in a plane (XY plane) orthogonal to the optical axis AX of the optical projection system PL, and the pattern of the mask M is sequentially exposed to each exposure region of the wafer W while collective exposure or scanning exposure is performed.

In the polarization state switching device 4, the 1/4 wavelength plate 4a has its optical crystal axis freely rotatable about the optical axis AX, and converts incident elliptically polarized light into linearly polarized light. 1/2 the wavelength plate 4b has its optical crystal axis rotatable around the optical axis AX and can change the polarization plane of incident linearly polarized light. The depolarizer 4c is formed of a wedge-shaped quartz prism (not shown) and a wedge-shaped quartz prism (not shown) having complementary shapes. The crystal prism and the quartz prism are an integrated prism combination body, and can advance and retreat to and from the illumination light path.

When a KrF excimer laser light source or an ArF excimer laser light source is used as the light source 1, the light emitted from these light sources typically has a polarization degree of 95% or more, and approximately linearly polarized light is incident on the 1/4 wavelength plate 4 a. However, when a right-angled prism as a rear mirror is present in the optical path between the light source 1 and the polarization state switching device 4, if the polarization plane of incident linearly polarized light does not coincide with the P-polarization plane or the S-polarization plane, the linearly polarized light becomes elliptically polarized light due to total reflection by the right-angled prism.

The polarization state switching device 4 may be configured such that light of elliptically polarized light, which is caused by total reflection in the rectangular prism, is incident, for example, converted into linearly polarized light by the action of the 1/4 wavelength plate 4a, and incident on the 1/2 wavelength plate 4 b. When the optical crystal axis of the 1/2 wavelength plate 4b is set to form an angle of 0 degree or 90 degrees with respect to the polarization plane of incident linearly polarized light, the polarization plane of the linearly polarized light incident on the 1/2 wavelength plate 4b passes through without change.

When the optical crystal axis of the 1/2 wavelength plate 4b is set at an angle of 45 degrees with respect to the polarization plane of incident linearly polarized light, the 1/2 wavelength plate 4b converts the linearly polarized light into linearly polarized light whose polarization plane changes by 90 degrees. When the optical crystal axis of the crystal prism of the depolarizer 4c is set at an angle of 45 degrees with respect to the polarization plane of incident linearly polarized light, the linearly polarized light incident on the crystal prism is converted into unpolarized light (i.e., unpolarized light).

In the polarization state switching device 4, the depolarizer 4c is disposed at a position in the illumination optical path such that the optical crystal axis of the crystal prism forms an angle of 45 degrees with respect to the polarization plane of the incident linearly polarized light. When the optical crystal axis of the water prism is set to an angle of 0 degree or 90 degrees with respect to the polarization plane of the incident linearly polarized light, the crystal prism passes the incident linearly polarized light as it is without changing the light polarization plane. Also, for example, when the optical crystal axis of the 1/2 wavelength plate 4b is set to form an angle of 22.5 degrees with respect to the polarization plane of incident linearly polarized light, the light of linearly polarized light incident on the 1/2 wavelength plate 4b is converted into light in an unpolarized state, and includes linearly polarized components that pass directly without changing the polarization plane and linearly polarized components that change only the polarization plane by 90 degrees.

The polarization state switching device 4 is configured such that the linearly polarized light enters the 1/2 wavelength plate 4b as described above, but for simplicity of explanation, it is assumed that, when linearly polarized light in the Z direction (direction of electric field) in fig. 1 (hereinafter, referred to as Z-direction polarized light) enters the 1/2 wavelength plate and the position of the depolarizer 4c in the illumination optical path is determined, the light polarized in the Z direction entering the 1/2 wavelength plate 4b is set such that the optical crystal axis of the 1/2 wavelength plate 4b forms an angle of 0 degree or 90 degrees with respect to the polarization plane (polarization direction) of the Z-direction polarized light entering, and the crystal prism that enters the depolarizer 4c with the Z-direction polarized light does not change. Since the optical crystal axis of the crystal prism is set to form an angle of 45 degrees with respect to the polarization plane of the incident Z-direction polarized light, the incident Z-direction polarized light is converted into unpolarized light.

The light polarized in a non-polarized state by the crystal prism is incident on the optical diffraction element 5 in a non-polarized state by passing through the crystal prism serving as a compensator in order to compensate the proceeding direction of the light. On the other hand, when the optical crystal axis of the 1/2 wavelength plate 4b is set to form an angle of 45 degrees with respect to the polarization plane of the incident Z-direction polarized light, the light polarized in the Z-direction incident on the 1/2 wavelength plate 4b changes only the polarization plane by 90 degrees, and forms linearly polarized light (hereinafter, referred to as X-direction polarized light) in the polarization direction (direction of the electric field) in the X-direction in fig. 1, and enters the crystal prism of the depolarizer 4 c. Since the optical crystal axis of the crystal prism is also set to form an angle of 45 degrees with respect to the polarization plane of the incident X-polarized light, the light polarized in the X-direction incident on the crystal prism is converted into light in an unpolarized state, passes through the crystal prism, and enters the optical diffraction element 5 in the unpolarized state.

On the other hand, when the depolarizer 4c is moved out of the illumination optical path, if the optical crystal axis of the 1/2 wavelength plate 4b is set so that the polarization plane of incident Z-polarized light forms an angle of 0 degree or 90 degrees, the light polarized in the Z-direction incident on the 1/2 wavelength plate 4b passes through the Z-polarized light without changing the polarization plane, and enters the optical diffraction element 5 in the Z-polarized state. On the other hand, when the optical crystal axis of the 1/2 wavelength plate 4b is set to have an angle of 45 degrees with respect to the polarization plane of the incident Z-direction polarized light, the light of the Z-direction polarized light incident on the 1/2 wavelength plate 4b is changed in polarization plane by 90 degrees to become X-direction polarized light, and enters the optical diffraction element 5 in the X-direction polarized state.

As described above, the polarization state switching device 4 can inject light in a non-polarized state into the optical diffraction element by inserting the depolarizer 4c into the illumination optical path and determining the position thereof. When the depolarizer 4c is retracted from the illumination optical path and the optical crystal axis of the 1/2 wavelength plate 4b is set to have an angle of 0 degree or 90 degrees with respect to the polarization plane of the incident Z-polarized light, the light in the Z-polarized state can be incident on the optical diffraction element 5. Further, the depolarizer 4c is retracted from the illumination optical path, and the optical crystal axis of the 1/2 wavelength plate 4b is set to have an angle of 45 degrees with respect to the polarization plane of the incident Z-direction polarized light, so that the light in the X-direction polarized light state is incident on the optical diffraction element 5.

In other words, the polarization state switching device 4 can switch the polarization state of the incident light to the optical diffraction element 5 (in the case where a normal optical diffraction element is used in addition to the optical diffraction element for circularly polarizing tire-shaped illumination of the present invention described later, the polarization state of the light illuminated by the mask M and the wafer W) between the linearly polarized state and the unpolarized state by the operation of the polarization state switching device constituted by the 1/4 wavelength plates 4a and 1/2 wavelength plate 4b and the depolarizer 4 c. In the case of the linearly polarized state, the state can be switched between polarized states orthogonal to each other (between the Z-direction polarized light and the X-direction polarized light).

Fig. 3 is a schematic diagram showing a configuration of a conical axicon system disposed in an optical path between the front lens group and the rear lens group of the afocal lens 6 of fig. 1. The conical axicon system 8 is composed of a first prism element 8a and a second prism element 8b, which are arranged in sequence from the light source side, the surface of the first prism element 8a facing the light source side is a plane and the surface facing the mask side is a concave conical curved surface; the second prism element 8b has a curved surface which is flat on the mask side and convex and conical on the light source side.

The concave conical curved surface of the first prism element 8a and the convex conical curved surface of the second prism element 8b are complementary shapes that can be butted. At least one of the first prism element 8a and the second prism element 8b is configured to be movable along the optical axis AX, and the interval between the concave curved fold surface of the first prism element 8a and the convex curved fold surface of the second prism element 8b is variable.

Here, when the concave conical curved surface of the first prism element 8a and the convex conical curved surface of the second prism element 8b are joined to each other, the conical axicon system 8 functions only as a parallel flat plate, and does not affect the formed tire-shaped secondary light source. However, when the concave conical curved surface of the first prism element 8a is isolated from the convex conical curved surface of the second prism element 8b, the axicon system 8 functions as a so-called beam expander. Therefore, the angle of the incident beam to the predetermined plane 7 can be changed with the change in the interval of the conical axicon system 8.

Fig. 4 is an explanatory diagram illustrating an operation of the axicon system on the tire-shaped secondary light source. Referring to fig. 4, the tire-shaped secondary light source 30a having the smallest distance between the conical axicon system 8 and the focal point of the zoom lens 11 is set to the smallest value (hereinafter, referred to as a "standard state") is formed in such a manner that the width (1/2, which is the difference between the outer diameter and the inner diameter, shown by an arrow mark in the figure) of the secondary light source 30a is not changed and the outer diameter and the inner diameter thereof are changed to form the tire-shaped secondary light source 30b as the distance between the conical axicon system 8 is increased from zero to the predetermined value. In other words, the width of the tire-shaped secondary light source does not change due to the action of the axicon system 8, and only the tire ratio (inner diameter/outer diameter) and the size (outer diameter) change together.

Fig. 5 illustrates the effect of the zoom lens 11 on the tire-shaped secondary light source. Referring to fig. 5, tire-shaped secondary light source 30a formed in a normal state is expanded from a minimum value to a predetermined value by a focal length of zoom lens 11, and is changed to expanded tire-shaped secondary light source 30 having a similar overall shape. In other words, the width and size (outer diameter) of the tire-shaped secondary light source are changed together with the tire ratio being unchanged by the zoom lens 11.

Fig. 6 is a schematic diagram of the structures of the first cylindrical lens couple 9 and the second cylindrical lens couple 10 arranged in the optical path between the front side lens group and the rear side lens group in the afocal lens 6 of fig. 1. In fig. 6, a first cylindrical lens pair 9 and a second cylindrical lens pair 10 are arranged in this order from the light source side. The first cylindrical lens pair 9 is arranged in order from the light source side, and includes, for example, a first cylindrical negative lens 9a having negative refractive power in a YZ plane and no refractive power in an XY plane, and a first cylindrical positive lens 9b having positive refractive power in the same YZ plane and no refractive power in the XY plane.

The other second cylindrical lens couple 10 is provided in order from the light source side, for example, a second cylindrical negative lens 10a having negative refractive power in the XY plane and no refractive power in the YZ plane, and a second cylindrical positive lens 10b having positive refractive power in the same XY plane and no refractive power in the YZ plane. The first cylindrical negative lens 9a and the first cylindrical positive lens 9b are integrally rotated around the optical axis AX. Similarly, the second cylindrical negative lens 10a and the second cylindrical positive lens 10b are integrally rotated around the optical axis AX.

In the state shown in fig. 6, the first cylindrical lens couple 9 has the function of expanding the power of the beam in the Z direction, and the second cylindrical lens couple 10 has the function of expanding the power of the beam in the X direction. Also, the power of the first cylindrical lens couple 9 and the power of the second cylindrical lens couple 10 are set to be the same as each other.

Fig. 7 to 9 are diagrams illustrating the effect of the first cylindrical lens couple 9 and the second cylindrical lens couple 10 on the tire-shaped secondary light source. In fig. 7, the power direction of the first cylindrical lens couple 9 is set to an angle of +45 degrees from the optical axis AX to the Z axis; the power direction of the second cylindrical lens couple 10 is at an angle of-45 degrees from the optical axis to the Z-axis.

Therefore, the power direction of the first cylindrical lens couple 9 and the power direction of the second cylindrical lens couple 10 are orthogonal to each other, and in the combined system of the first cylindrical lens couple 9 and the second cylindrical lens couple 10, the power in the z direction is the same as the power in the x direction. As a result, in the perfect circle state shown in fig. 7, the light flux passing through the combining system of the first cylindrical lens couple 9 and the second cylindrical lens couple 10 is expanded by the same power in the z direction and the x direction, and a perfect circle tire-shaped secondary light source is formed at the illumination pupil.

In contrast to the above, in fig. 8, the power direction of the first cylindrical lens couple 9 is set to an angle of, for example, +80 degrees from the optical axis AX to the Z axis, and the power direction of the second cylindrical lens couple 10 is set to an angle of-80 degrees from the optical axis AX to the Z axis. Therefore, in the combined system of the first cylindrical lens couple 9 and the second cylindrical lens couple 10, the power in the Z direction is small, and the power in the X direction is large. As a result, in the state of a horizontal ellipse shown in fig. 8, the light flux passing through the combining system of the first cylindrical lens couple 9 and the second cylindrical lens couple 10 receives a power of expansion action larger than that in the Z direction in the X direction, and forms a horizontal tire-shaped secondary light source elongated in the X direction at the illumination pupil.

In fig. 9, the power direction of the first cylindrical lens couple 9 is set to an angle of, for example, +10 degrees from the optical axis AX to the Z axis, and the power direction of the second cylindrical lens couple 10 is set to an angle of-10 degrees from the optical axis to the Z axis. Then in the combined system of the first cylindrical lens couple 9 and the second cylindrical lens couple 10, the power in the X direction is small and the power in the Z direction is large. As a result, in the vertically elliptical state shown in fig. 9, the light beam passing through the combining system of the first cylindrical lens couple 9 and the second cylindrical lens couple 10 is subjected to an expanding action of a power greater than that in the X direction in the Z direction, and a vertically elongated tire-shaped secondary light source in the Z direction is formed at the illumination pupil.

Further, the first cylindrical lens pair 9 and the second cylindrical lens pair 10 can be set to any state between the perfect circle state shown in fig. 7 and the transverse ellipse state shown in fig. 8, and can form a secondary light source in a shape of a horizontally long tire having various aspect ratios. Further, by setting the first cylindrical lens pair 9 and the second cylindrical lens pair 10 to any state between the perfect circle state shown in fig. 7 and the vertically elliptical state shown in fig. 9, it is possible to form a secondary light source in the form of a vertically long tire having various aspect ratios.

Fig. 10 is a schematic perspective view of the internal structure of the polarization monitor in fig. 1. Referring to fig. 10, the polarization monitor 13 is provided with a first beam splitter 13a disposed in the optical path between the micro fly-eye lens 12 and the optical condensing system 14. The first beam splitter 13a is an uncoated parallel flat plate (i.e., raw glass) made of, for example, quartz glass, and has a function of extracting reflected light in a polarization state different from that of incident light from the optical path.

The light extracted from the optical path by the first beam splitter 13a is incident on the second beam splitter 13 b. The second beam splitter 13b is in the form of an uncoated parallel plane plate made of, for example, quartz glass, as in the first beam splitter 13a, and has a function of generating reflected light in a polarization state different from that of incident light. Then, the P-polarized light to the first beam splitter 13a is set to be S-polarized light to the second beam splitter 13b, and the S-polarized light to the first beam splitter 13a is set to be P-polarized light to the second beam splitter 13 b.

The light transmitted through the second beam splitter 13b is detected by a first light intensity detector 13 c; the light reflected by the second beam splitter 13b is detected by a second light intensity detector 13 d. The outputs of the first light intensity detector 13c and the second light intensity detector 13d are supplied to a control unit (not shown). The control unit drives the 1/4 wavelength plates 4a and 1/2 wavelength plates 4b and the depolarizer 4c constituting the polarization state switching device 4 as necessary.

As described above, in the first beam splitter 13a and the second beam splitter 13b, the reflectance for P-polarized light and the reflectance for S-polarized light are substantially different. Therefore, in the polarization monitor 13, the reflected light from the first beam splitter 13a includes: for example, about 10% of the S-polarized light component of the incident light to the first beam splitter 13a (the S-polarized light component to the first beam splitter 13a, i.e., the P-polarized light component to the second beam splitter 13 b); and, for example, about 1% of the P-polarized component of the incident light to the first beam splitter 13a (P-polarized component to the first beam splitter 13a, that is, S-polarized component to the second beam splitter 13 b).

The reflected light from the second beam splitter 13b includes: for example, about 0.1% of P-polarized light components (P-polarized light components for the first beam splitter 13a, that is, S-polarized light components for the second beam splitter 13 b) of 10% × 1% of incident light to the first beam splitter 13 a; and, for example, an S-polarized component (S-polarized component to the first beam splitter 13a, that is, a P-polarized component to the second beam splitter 13 b) of about 10% × 1% of incident light to the first beam splitter 13 a.

As described above, in the polarization monitor 13, the first beam splitter 13a has a function of extracting reflected light in a polarization state different from the polarization state of incident light from the optical path in accordance with the reflection characteristics. As a result, since the polarization variation is extremely small due to the polarization characteristics of the second beam splitter 13b, the polarization state (polarization degree) of the light incident on the first beam splitter 13, that is, the polarization state of the illumination light of the mask M can be detected based on the output of the first light intensity detector 13c (information on the intensity of the transmitted light of the second beam splitter 13b, that is, information on the intensity of the light in the polarization state approximately the same as the reflected light from the first beam splitter 13 a).

In the polarization monitor 13, the P-polarized light to the first beam splitter 13a is set to the S-polarized light to the second beam splitter 13b, and the S-polarized light to the first beam splitter 13a is set to the P-polarized light to the second beam splitter 13 b. As a result, the amount of light incident on the first beam splitter 13a, that is, the amount of illumination light of the mask M can be detected based on the output of the second light intensity detector 13d (information on the intensity of light sequentially reflected by the first beam splitter 13a and the second beam splitter 13 b), and is substantially not affected by the change in the polarization state of the incident light from the first beam splitter 13 a.

As described above, the polarization monitor 13 can detect the polarization state of the incident light to the first beam splitter 13a, that is, can determine whether or not the illumination light of the mask M is in a desired non-polarized state or linearly polarized state. Then, when the control section confirms that the illumination light of the mask M (or the wafer W) is not in the predetermined unpolarized state or linearly polarized state based on the detection result of the polarization monitor 13, the control section drives and adjusts the 1/4 wavelength plates 4a and 1/2 wavelength plate 4b and the depolarizer 4c constituting the polarized state switching device 4 to adjust the state of the illumination light of the mask M to a desired unpolarized state or linearly polarized state.

The optical diffraction element 5 for tire illumination may be provided in the illumination optical path in place of an optical diffraction element (not shown) for quadrupole illumination, so that quadrupole illumination can be performed. The optical diffraction element for quadrupole illumination has a function of forming a quadrupole light intensity distribution in a Far Field (Far Field) when a parallel light beam having a rectangular cross section is incident. Therefore, the light beam passing through the optical diffraction element for quadrupole illumination forms a quadrupole illumination field of four circular illumination fields centered on the optical axis AX on the incident surface of the micro fly-eye lens 12. As a result, a quadrupole secondary light source similar to the field formed by the incident surface is also formed at the rear focal plane of the micro fly-eye lens 12.

The diffractive optical element 5 for tire illumination is provided in the illumination optical path in place of a diffractive optical element for circular illumination (not shown), and can perform normal circular illumination. The optical diffraction element for circular illumination has a function of forming a circular light intensity distribution in a far field when a parallel light beam having a rectangular cross section is incident. Therefore, the light beam passing through the optical diffraction element for circular illumination forms a quadrupole field formed by a circular field centered on the optical axis AX on the incident surface of the micro fly-eye lens 12. As a result, a circular secondary light source similar to the illumination field formed on the incident surface is also formed on the rear focal plane of the micro fly-eye lens 12.

The diffractive optical element 5 for tire illumination is set in the illumination optical path in place of another diffractive optical element (not shown) for multi-pole illumination, and can perform various multi-pole illumination (such as dipole illumination and octapole illumination). Similarly, the diffractive optical element 5 for tire illumination can be replaced with a diffractive optical element (not shown) having appropriate characteristics in the illumination optical path to perform various forms of anamorphic illumination.

In the present embodiment, the optical diffraction element 50 for the tire-shaped illumination of the so-called circumferential polarization is provided in the illumination optical path instead of the optical diffraction element 5 for the tire-shaped illumination, and the tire-shaped illumination of the circumferential polarization can be performed by the deformed illumination in which the light beam passing through the tire-shaped secondary light source is set to the circumferential polarization state. Fig. 11 is a schematic view of the structure of the optical diffraction element for tire illumination polarized in the circumferential direction according to the present embodiment. Fig. 12 is a schematic view of the tire-shaped secondary light source set in the circumferential polarization state.

Referring to fig. 11 and 12, the circumferentially polarized illumination optical diffraction element 50 of the present embodiment is configured by four types of basic elements 50A to 50D having the same rectangular cross section and different in thickness (length in the optical axis direction) in the light transmission direction (Y direction), and arranged in a vertically and horizontally dense manner. Here, the thickness of the first basic element 50A is the largest, the thickness of the fourth basic element 50D is the smallest, and the thickness of the second basic element 50B is larger than the thickness of the third basic element 50C.

The optical diffraction element 50 includes approximately the same number of first basic elements 50A, second basic elements 50B, third basic elements 50C, and fourth basic elements 50D, and these four basic elements are arranged randomly. Diffraction surfaces (shown by oblique lines in the figure) are formed on the mask side of the basic elements 50A to 50D, and the diffraction surfaces of the basic elements 50A to 50D are aligned on a single plane orthogonal to the optical axis AX (not shown in fig. 11). As a result, the surface of the optical diffraction element 50 on the mask side is planar, but the surface of the optical diffraction element 50 on the light source side is uneven due to the difference in thickness between the basic elements 50A to 50D.

As described above, the structure of the diffraction surface of the first base element 50A can be formed in the tire-shaped secondary light source 31 shown in fig. 12 as a pair of arc-shaped regions 31A that are symmetrical with respect to the Z-direction axis passing through the optical axis AX. That is, as shown in fig. 13, the first base element 50A has a function of forming a pair of circular-arc-shaped light intensity distributions 32A (corresponding to the pair of circular-arc-shaped areas 31A) symmetrical with respect to the Z-direction axis passing through the optical axis AX in the far field 50E of the optical diffraction element 50 (extending to the far fields of the respective base elements 50A to 50D).

The diffraction surface of the second basic element 50B has a structure in which a Z-direction axis passing through the optical axis AX is rotated by-45 degrees about the Y-axis (45 degrees in the counterclockwise direction in fig. 12), and then a pair of symmetrical circular arc-shaped regions 31B are formed about the Z-direction axis. That is, as shown in fig. 14, the second base element 50B has a function of forming a pair of symmetrical circular-arc light intensity distributions 32B (corresponding to a pair of circular-arc regions 31B) about a Z-axis passing through the optical axis AX of the far field 50E by rotating the axis by-45 degrees about the Y-axis.

The structure of the diffraction surface of the third basic element 50C can form a pair of symmetrical figure arc-shaped areas 31C with respect to an axis passing through the optical axis AX in the X direction. That is, as shown in fig. 15, the third base element 50C has a function of forming a pair of circular arc-shaped light intensity distributions 32C (corresponding to the pair of circular arc-shaped regions 31C) symmetrical with each other on the axis in the X direction passing through the optical axis AX in the far region 50E.

The diffraction surface of the fourth basic element 50D has a structure in which a pair of arc-shaped regions 31D symmetrical to the Z-axis passing through the optical axis AX are formed after the axis is rotated by +45 degrees along the Y-axis (rotated by 45 degrees in the clockwise direction in fig. 12). That is, as shown in fig. 16, the fourth base element 50D has a function of forming a pair of symmetrical circular arc light intensity distributions 32D (corresponding to a pair of circular arc regions 31D) with respect to the Z-direction axis passing through the optical axis AX of the far field 50E by rotating +45 degrees with respect to the Y-axis. The sizes of the arc-shaped regions 31A to 31D are approximately the same, and the eight arc-shaped regions 31A to 31D are not overlapped with each other and are not separated from each other, and constitute a tire-shaped secondary light source 31 centered on the optical axis AX.

In the present embodiment, the basic elements 50A to 50D are made of crystal of optically active material, and the optical crystal axes of the basic elements 50A to 50D are set to approximately coincide with the optical axis AX. Hereinafter, the optical rotation of the crystal will be briefly described with reference to FIG. 17. Referring to fig. 17, the optical crystal axis of a parallel planar plate-shaped optical element 35 formed of crystal having a thickness d is arranged to coincide with the optical axis AX. In this case, the polarization direction of the incident linearly polarized light is rotated by an angle θ around the optical axis AX by the optical rotation of the optical element 35.

In this case, the rotation angle θ of the polarization direction due to the optical rotation of the optical element 35 can be expressed by the following formula (1) depending on the thickness d of the optical element 35 and the optical rotation power ρ of the crystal.

θ＝d·ρ (1)

In general, the optical rotation ability ρ of crystal tends to be larger as the wavelength of light used is shorter, and as described on page 167 of "applied optics II" in Japanese document, the optical rotation ability ρ of crystal is 153.9 degrees/mm for light having a wavelength of 250.3 nm.

In the present embodiment, the thickness dA is set in the first base element 50A, and when light of linearly polarized light in the polarization direction of the Z direction is incident, the emitted linearly polarized light is directed in the polarization direction of the Z direction, which is a direction rotated by 180 degrees along the Y axis in the Z direction, as shown in fig. 13. As a result, the polarization direction of the light flux passing through the pair of circular arc-shaped light intensity distributions 32A formed in the far field 50E is set to the Z direction. The polarization direction of the light beam passing through the pair of arc-shaped regions 31A shown in fig. 12 also becomes the Z direction.

The second basic element 50B is set to have a thickness dB, and when linearly polarized light in the Z-direction is incident as shown in fig. 14, the emitted linearly polarized light is directed in a direction +135 degrees around the Y-axis in the Z-direction, that is, in a polarization direction in the Y-45 degree around the Z-axis. As a result, the polarization direction of the light flux passing through the pair of circular arc-shaped light intensity distributions 32B formed in the far field 50E is also a direction rotated by-45 degrees along the Y axis from the Z direction. In the pair of arc-shaped regions 31B shown in fig. 12, the polarization direction of the light beam passing therethrough is also rotated by-45 degrees from the Z direction along the Y axis.

The third basic element 50C is set to have a thickness dC, and when light of linearly polarized light in the Z-direction is incident as shown in fig. 15, the emitted linearly polarized light is directed in the direction of +90 degrees around the Y-axis in the Z-direction, that is, in the polarization direction in the X-direction. As a result, the polarization direction of the light flux passing through the pair of circular arc-shaped light intensity distributions 32C formed in the far field 50E also becomes the X direction. In the pair of arc-shaped regions 31C shown in fig. 12, the polarization direction of the light beam passing therethrough is also the X direction.

The fourth basic element 50D is set to have a thickness dD such that, when light of linearly polarized light in the Z-direction is incident, the emitted linearly polarized light is directed in the polarization direction in which the Z-direction is rotated by +45 degrees along the Y-axis, as shown in fig. 16. As a result, the polarization direction of the light flux passing through the pair of circular arc-shaped light intensity distributions 32D formed in the far field 50E is +45 degrees from the Z direction along the Y axis. In the pair of arc-shaped regions 31D shown in fig. 12, the polarization direction of the light beam passing therethrough is also +45 degrees from the Z direction along the Y axis.

In the present embodiment, in the case of the circumferential polarization tire-shaped illumination, the optical diffraction element 50 for the circumferential polarization tire-shaped illumination is provided in the illumination optical path, and the linearly polarized light in the polarization direction of the Z direction is incident on the optical diffraction element 50. As a result, a tire-shaped secondary light source 31 (tire-shaped illumination pupil distribution) as shown in fig. 12 is formed on the rear focal plane (i.e., the illumination pupil or its vicinity) of the micro fly's eye lens 12, and the light flux passing through the tire-shaped secondary light source 31 is set in a polarized state in the circumferential direction.

In the polarization state in the circumferential direction, the light fluxes in the arc-shaped regions 31A to 31D constituting the tire-shaped secondary light source form a linearly polarized state in the polarization direction approximately coincident with the tangential direction of the circle in the circumferential direction around the optical axis AX of the arc-shaped regions 31A to 31D.

In the present embodiment, the optical transforming element 50 for forming a predetermined light intensity distribution on a predetermined plane according to an incident light beam includes: a first basic element 50A which is made of an optical material having optical rotation and forms a first area distribution 32A among the predetermined light intensity distributions in accordance with the incident light beam; and a second basic element 50B made of an optical material having optical rotation property and forming a second area distribution 32B among the predetermined light intensity distributions according to the incident light beam, wherein the first basic element 50A and the second basic element 50B have different thicknesses in a light transmission direction.

In this way, the aperture stop of the present embodiment, unlike the conventional art, generates a large amount of light loss, and can form the tire-shaped secondary light source 31 in a polarized state in the circumferential direction substantially without light loss due to the diffraction action and the optical rotation action of the optical diffraction element 50 serving as the light beam conversion element.

In a preferred embodiment of the present invention, the thickness of the first basic element 50A and the thickness of the second basic element 50B are set so that the polarization direction of the linearly polarized light forming the first area distribution 32A is different from the polarization direction of the linearly polarized light forming the second area distribution 32B when the linearly polarized light is incident. It is preferable that the positions of the first area distribution 32A and the second area distribution 32B are determined so that at least a part of a predetermined tire-shaped area centered on a predetermined point on the predetermined surface and the light flux passing through the first area distribution 32A and the second area distribution 32B have a polarization state in which linear polarization having the circumferential direction of the predetermined tire-shaped area as the polarization direction is the main component.

At this time, the predetermined light intensity distribution has an outer shape substantially the same as that of the predetermined tire-shaped region, and the polarization state of the light flux passing through the first region distribution 32A has a linearly polarized component almost coincident with a tangential direction of a circle centered at the predetermined point at the center position thereof in the circumferential direction of the first region distribution 32A; and the polarization state of the light flux passing through the second area distribution 32B has a linearly polarized component almost coincident with a tangential direction of a circle centered at the specified point at the central position in the circumferential direction of the second area distribution 32B. Or, the predetermined light intensity distribution is a multipolar distribution distributed in the predetermined tire-shaped region, that is, the polarization state of the light beam distributed through the first region has a linearly polarized component almost coincident with a tangential direction of a circle centered at the predetermined point at the center position thereof in the circumferential direction of the first region distribution; and the polarization state of the light beam distributed through the second region preferably has a linearly polarized component almost coincident with a tangential direction of a circle centered at the specified point at the central position thereof in the circumferential direction of the distribution along the second region.

Furthermore, in a preferred embodiment of the present invention, the first basic element and the second basic element are formed by using an optical material having an optical rotation ability of 100 degrees/mm or more with respect to the light with the wavelength used. And wherein the first basic element and the second basic element are formed using crystal. Furthermore, the beam transformation element comprises the first basic element and the second basic element with the same number. And the first basic element and the second basic element have diffraction effect or refraction effect.

Furthermore, in a preferred embodiment of the present invention, the first basic element forms at least two first area distributions on the predetermined plane according to the incident light beam; and the second basic element forms at least two second area distributions on the predetermined plane according to the incident light beam. Also, the beam conversion element may further include: a third basic element 50C formed of an optical material having optical rotation property, forming a third area distribution 32C in the predetermined light intensity distribution in accordance with the incident light beam; and a fourth basic element 50D formed of an optical material having optical rotation property, forming a fourth area distribution 32D in the determined light intensity distribution in accordance with the incident light beam.

In addition, in the present embodiment, the light beam transformation element 50 can form a predetermined light intensity distribution different from the cross-sectional shape of the incident light beam on a predetermined plane; the light beam transformation element is provided with a diffraction surface or a refraction surface for forming the determined light intensity distribution on the determined surface; the predetermined light intensity distribution is distributed in at least a part of a predetermined tire-shaped area centered on the predetermined point on the predetermined plane, i.e., a so-called predetermined tire-shaped area; and a light beam output from the light beam conversion element and passing through the predetermined tire-shaped region, the light beam having a polarized state in which linearly polarized light having a circumferential direction of the predetermined tire-shaped region as a polarized direction is a main component.

In this way, the aperture stop of the present embodiment, unlike the conventional art, generates a large amount of light loss, and can form the tire-shaped secondary light source 31 in a polarized state in the circumferential direction substantially without light loss due to the diffraction action and the optical rotation action of the optical diffraction element 50 serving as the light beam conversion element.

In a preferred embodiment of the present embodiment, the predetermined light intensity distribution has a multi-pole shape or a tire-like shape. Preferably, the light beam conversion element is formed using an optical material having optical rotation.

In addition, the optical illumination device of the present embodiment utilizes the light beam from the light source to illuminate an illuminated surface, and the optical illumination device includes the light beam transforming element for transforming the light beam from the light source to form an illumination pupil distribution at or near an illumination pupil of the optical illumination device. With this configuration, the optical illumination device of the present embodiment can form a tire-shaped illumination pupil distribution in a polarization state in the circumferential direction while suppressing light quantity loss satisfactorily.

Here, it is preferable that the beam conversion element is configured to be exchangeable with other beam conversion elements having different characteristics. Further, it is preferable that a wavefront-dividing type optical integrator is additionally provided in an optical path between the light beam conversion element and the irradiated surface, and the light beam conversion element forms the predetermined light intensity distribution in accordance with an incident light beam on an incident surface of the optical integrator.

In the optical illumination device according to a preferred embodiment of the present invention, at least one of the light intensity distribution on the predetermined surface and the polarization state of the light beam emitted from the light beam conversion element passing through the predetermined tire-shaped region is set in consideration of the influence of the optical element disposed in the optical path between the light source and the surface to be illuminated. In addition, it is preferable that the polarization state of the light beam emitted from the light beam conversion element is set to a polarization state in which the light irradiated on the irradiation surface is S-polarized light as a main component.

Furthermore, the exposure apparatus of the present embodiment is an exposure apparatus including the above-mentioned optical illumination apparatus, wherein the illumination apparatus is used to illuminate a mask, so that the exposure apparatus exposes the pattern of the mask on a photosensitive substrate. Here, it is preferable that at least one of the light intensity distribution on the predetermined surface and the polarization state of the light beam emitted from the light beam conversion element passing through the predetermined tire-shaped region is set in consideration of the influence of an optical element disposed in the optical path between the light source and the surface to be irradiated. Further, it is preferable that the polarization state of the light beam emitted from the light beam conversion element is set to a polarization state in which the light irradiated on the irradiation surface is S-polarized light as a main component.

In addition, the exposure method of the present embodiment includes: an illumination process for illuminating a mask by using the optical illumination device; and an exposure step of exposing the pattern of the mask to light on the photosensitive substrate. Here, it is preferable that at least one of the light intensity distribution on the predetermined surface and the polarization state of the light beam output from the light beam conversion element passing through the predetermined tire-shaped region is set in consideration of the influence of an optical element disposed in the optical path between the light source and the surface to be irradiated. Further, it is preferable that the polarization state of the light beam emitted from the light beam conversion element is set to a polarization state in which the light irradiated on the irradiation surface is S-polarized light as a main component.

In other words, the optical illumination device of the present embodiment can form a tire-shaped illumination pupil distribution in a circumferential polarization state while suppressing light amount loss satisfactorily. As a result, the exposure apparatus of the present example uses the optical illumination apparatus capable of suppressing the light quantity loss well and forming the illumination pupil distribution in a tire shape in a polarization state in the circumferential direction, and thus can reproduce a fine pattern in an arbitrary direction faithfully and with high yield under appropriate conditions.

In the circumferential direction polarized tire illumination based on the tire-shaped illumination pupil distribution in the circumferential direction polarized state, the light irradiated to the wafer W as the irradiated surface is in a polarized state mainly containing S-polarized light. The "S-polarization" here is a linear polarization (polarization in which electric vector vibration is incident in a vertical direction) in which a polarization direction perpendicular to an incident surface is maintained. However, the definition of the incident surface is a surface including a normal line and a light incident direction on the boundary surface of the medium (irradiated surface; surface of the wafer W) when the light reaches the boundary surface.

In the above-described embodiment, the optical diffraction element 50 for circumferentially polarized tire-shaped illumination is configured by using four kinds of basic elements 50A to 50D having the same rectangular cross section and randomly arranging the same number of basic elements in a vertically, horizontally, and densely. However, the number, cross-sectional shape, number, arrangement, etc. of the basic elements may be varied.

In the above-described embodiment, the optical diffraction element 50 formed using the four basic elements 50A to 50D forms the tire-shaped secondary light source 31 centered on the optical axis AX from the eight arc-shaped regions 31A to 31D that are not overlapped with each other and are not arranged apart from each other. However, the number, shape, arrangement, and the like of the regions constituting the tire-shaped secondary light source are not limited to these examples, and various modifications are possible.

Specifically, as shown in fig. 18(a), for example, an optical diffraction element composed of four basic elements may be used to form a secondary light source 33a having eight circular arc-shaped regions spaced apart from each other in the circumferential direction and having an octapole-shaped polarization state. As shown in the circle 18(b), for example, a quadrupole secondary light source 33b in a polarized state in the circumferential direction may be formed by an optical diffraction element composed of four basic elements, in which four arc-shaped regions are arranged apart from each other in the circumferential direction. In the octapole-shaped secondary light source or the quadrupole-shaped secondary light source, the shape of each region is not limited to the circular arc shape, and may be, for example, a circular shape, an elliptical shape, or a fan shape. As shown in fig. 19, for example, a tire-shaped secondary light source 33c in a polarized state in the circumferential direction in which eight arc-shaped regions are arranged so as to overlap each other in the circumferential direction may be formed by an optical diffraction element composed of four basic elements.

In addition to the quadrupole or octapole secondary light sources arranged in the circumferential polarization state with four or eight regions spaced apart from each other in the circumferential direction, a hexapole secondary light source in the circumferential polarization state with six regions spaced apart from each other in the circumferential direction is also preferable as shown in fig. 20 (a). As shown in fig. 20(b), a secondary light source may be composed of a plurality of multipolar secondary light sources in a circumferential polarization state in which regions are arranged apart from each other in the circumferential direction, and a central polar secondary light source in a non-polarized state or a linearly polarized state in which regions on the optical axis are formed. Two secondary light sources may be formed in a polarized state in the circumferential direction by two regions separated from each other in the circumferential direction.

In the above-described embodiment, as shown in fig. 11, the four types of basic elements 50A to 50D are formed individually, and then these elements are combined to form the optical diffraction element 50. However, the present invention is not limited to the above, and the optical diffraction element 50 may be configured such that the diffraction surfaces on the emission side and the concave-convex surfaces on the incident side of the respective basic elements 50A to 50D are formed integrally on one crystal substrate by, for example, etching.

In the above-described embodiment, the basic elements 50A to 50D (i.e., the optical diffraction element 50) are formed of crystal. However, the optical element is not limited to this, and other suitable optical materials having optical rotation properties may be used to form each basic element. In this case, it is preferable to use an optical material having an optical rotation ability of 100 degrees/mm or more with respect to light of a wavelength to be used. That is, when an optical material having a small optical rotation ability is used, the thickness required for the element is too large to obtain a desired rotation angle in the polarization direction, which is not preferable because it causes a loss of light amount.

In the above-described embodiment, the illumination pupil distribution (secondary light source) is formed in a tire shape, but not limited to this, and a circular illumination pupil distribution may be formed at the illumination pupil or its vicinity. Further, the tire-shaped illumination pupil distribution or the multipole-shaped illumination pupil distribution can be further increased to form, for example, a central region distribution including the optical axis, and thus, a tire-shaped illumination having a central pole or a plural-pole illumination having a central pole can be realized.

In the above-described embodiment, the illumination pupil distribution in the state of polarization in the circumferential direction is formed at or near the illumination pupil. However, the polarization direction may be changed by polarization aberration (repetition) of an optical system (an optical illumination system or an optical projection system) on the wafer side of the optical diffraction element of the beam varying element. In this case, the polarization state of the light beam passing through the illumination pupil formed at or near the illumination pupil is appropriately set in consideration of the influence of the polarization aberration of these optical systems.

In an optical system (an optical illumination system or an optical projection system) on the wafer side of the beam conversion element, the polarization characteristics of the reflection element arranged may cause a phase difference in the reflected light in each polarization direction, depending on the polarization aberration. In this case, it is also necessary to appropriately set the polarization state of the light beam passing through the illumination pupil distribution formed at or near the illumination pupil, in consideration of the influence of the phase difference due to the polarization characteristics of the reflective element.

In an optical system (an optical illumination system or an optical projection system) on the wafer side of the beam conversion element, the polarization characteristics of the arranged reflection element may cause the reflectance of the reflection element to change depending on the polarization direction. In this case, it is preferable to set the distribution in the number of the respective basic elements by adding a compensation amount to the light intensity distribution formed at the illumination pupil or the vicinity thereof in consideration of the reflectance in each polarization direction. The transmittance of the optical system on the wafer side of the beam conversion element can be corrected by the same method when the transmittance changes depending on the direction of polarization.

In the above-described embodiment, the surface of the optical diffraction element 50 on the light source side is formed with the uneven shape having the step difference depending on the thickness of each of the basic elements 50A to 50D. In this regard, as shown in fig. 21, the correction element 36 is attached to the incident side of the basic elements other than the first basic element 50A having the largest thickness, that is, the second basic element 50B, the third basic element 50C, and the fourth basic element 50D, so that the surface of the light source side (incident side) of the optical diffraction element 50 can be made planar. In this case, the correction element 36 is formed by using an optical material having no optical rotation.

In the above-described embodiments, only an example in which the illumination pupil is formed at or near the illumination pupil and the light flux passing therethrough is a light flux having a linearly polarized component in the circumferential direction will be described. However, the present invention is not limited to this, and the desired effect of the present invention can be obtained by only using the state of polarization of the light beam distributed through the illumination pupil as a state in which the linear polarization whose polarization direction is the circumferential direction is the main component.

In this embodiment, an optical diffraction element including a plurality of basic elements having a diffraction function is used as the light beam conversion element, and a light intensity distribution having a different shape from the cross-sectional shape of the incident light beam is formed on a predetermined surface according to the incident light beam. However, the present invention is not limited to this, and for example, a plurality of basic elements having a diffraction surface approximately equivalent to the diffraction surface and optical property of each basic element, that is, a plurality of basic elements having refraction function may be used, and the optical refraction element formed by the plurality of basic elements may be a beam transformation element.

In the exposure apparatus of the above embodiment, the mask (cross mark) is illuminated by the optical illumination device (i.e., illumination process); the pattern for transfer formed on the mask is exposed on the photosensitive substrate by an optical projection system (exposure process), whereby microdevices (semiconductor device, imaging device, liquid crystal display device, thin film magnetic head, etc.) can be manufactured. Next, a procedure for manufacturing a semiconductor device, which is a micro device, by forming a predetermined circuit pattern on a wafer or the like, which is a photosensitive substrate, using the exposure apparatus of the above embodiment will be described with reference to a flowchart of FIG. 22.

First, in step 301 of fig. 22, a metal film is evaporated on a group of wafers. Next, in step 302, a photoresist is coated on the metal film of the group of wafers. Next, in step 303, the pattern image on the mask is sequentially exposed and copied to the respective irradiation regions on the set of wafers by the optical projection system using the exposure apparatus of the above embodiment. Thereafter, in step 304, the photoresist on the set of wafers is developed, and thereafter, in step 305, etching is performed on the set of wafers using the photoresist pattern as a mask, and a circuit pattern corresponding to the pattern on the mask is formed in each shot region on each wafer. Thereafter, a process such as forming a further upper circuit pattern is performed to manufacture an element such as a semiconductor element. According to the method for manufacturing a semiconductor device, a semiconductor device having an extremely fine circuit pattern can be manufactured with good productivity.

The exposure apparatus of the above embodiment can form a predetermined pattern (circuit pattern, electrode pattern, etc.) on a substrate (glass substrate), and can also manufacture a liquid crystal display device which is one of microdevices. An example of the process is described below with reference to the flowchart of fig. 23. In the pattern forming step 401 in fig. 23, the pattern of the mask is transferred and exposed on a photosensitive substrate (such as a resist-coated glass substrate) by using the exposure apparatus of the above-described embodiment, and then a so-called photolithography etching step is performed. In the photolithography and etching step, a predetermined pattern including a plurality of electrodes and the like is formed on a photosensitive substrate. Thereafter, the exposed substrate is subjected to various processes such as a development process, an etching process, and a resist stripping process to form a predetermined pattern on the substrate, and then is transferred to a color filter formation process 402.

Next, in the color filter forming step 402, a plurality of color filters are formed in which three dots corresponding to R (red), G (green), and B (blue) are combined and arranged in an array, or R, B, G in which three color filter groups in stripes are arranged in a plurality of horizontal scanning line directions. After the color filter forming process 402, a component assembling process 403 is performed. In the element assembling step 403, a liquid crystal panel (liquid crystal element) is assembled using the substrate having a predetermined pattern produced in the pattern forming step 401, the color filter produced in the color filter forming step 402, and the like.

In the element assembling step 403, for example, liquid crystal is injected between the substrate having a predetermined pattern obtained in the pattern forming step 401 and the color filter obtained in the color filter forming step 402, thereby forming a liquid crystal panel (liquid crystal element). Thereafter, in the module assembling step 404, a circuit for causing the assembled liquid crystal panel (liquid crystal element) to perform a display operation, a backlight module, and the like are mounted to complete the liquid crystal display element. According to the above method for manufacturing a liquid crystal display element, a liquid crystal display element having an extremely fine circuit pattern can be manufactured with good productivity.

In the above-mentioned embodiment, the light source for exposure is light from KrF excimer laser (wavelength: 248nm) or ArF excimer laser (wavelength: 193nm), but the present invention is not limited thereto, and other suitable laser light sources include, for example, F for supplying laser light having a wavelength of 157nm₂Laser light sources and the like are also applicable to the present invention. In the above-described embodiments, the present invention is described by taking an exposure apparatus equipped with an optical illumination apparatus as an example, but it is obvious that the present invention can be applied to a general optical illumination apparatus for illuminating an illuminated surface other than a mask or a wafer.

In the above-described embodiment, it is preferable to use a method of filling the optical path between the optical projection system and the photosensitive substrate with a medium (typically, a liquid) having a refractive index of more than 1.1, that is, a so-called liquid immersion method. In this case, as a method of filling the liquid in the optical path between the optical projection system and the photosensitive substrate, there is a method of partially filling the liquid disclosed in international patent application No. WO 99/049504; or a method of moving a stage holding a substrate to be exposed in a liquid bath, as disclosed in Japanese patent laid-open No. 6-124873; or a method of forming a liquid groove of a predetermined depth on a stage and holding a substrate therein as disclosed in Japanese patent laid-open No. Hei 10-303114, and the like. International patent application WO99/049504, Japanese patent laid-open No. Hei 6-124873, and Japanese patent laid-open No. Hei 10-303114 are incorporated herein by reference.

Further, it is preferable that the liquid has a high refractive index as high as possible in order to be transparent to exposure light, and is stable even to a resist applied to an optical projection system or a substrate surface. In the case where, for example, a KrF excimer laser or an ArF excimer laser is used as the exposure light, pure water or deionized water can be used as the liquid. The exposure light source used was F₂In the case of a laser, the liquid may be F₂Fluorine-based liquids such as laser-transparent fluorine-based oils and perfluorinated polyethers (PFPE).

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (17)

1. An optical illumination device applied to an exposure device for transferring a pattern of a mask onto a photosensitive substrate, the optical illumination device illuminating an irradiated surface on which the mask is disposed with illumination light emitted from a light source, the optical illumination device comprising:

a light beam conversion element provided in an optical path between the light source and the irradiated surface, the light beam conversion element including: an element formed of a crystalline optical material having an optical rotation, wherein the light beam conversion element forms a predetermined light intensity distribution in which the cross-sectional shape of the incident light beam of the illumination light is different on a pupil surface of the optical illumination device; and

a conical axicon system disposed between: an optical path of the illumination light in an exit side of the element formed using the crystalline optical material,

the element formed using the crystalline optical material is: rotating the polarization direction by the optical rotation of the crystalline optical material to convert the illumination light in the linearly polarized state incident on the element into illumination light in the polarized state mainly composed of linearly polarized light in which the polarization direction is the circumferential direction of a tire-shaped region centered on the optical axis of the optical illumination device, the illumination light in the polarized state being converted by the element formed of the crystalline optical material: the irradiated surface is irradiated via the conical axicon system.

2. The optical illumination device according to claim 1, wherein:

the conical axicon system comprises:

a 1 st prism element having a curved surface which is flat on the incident side of the illumination light and has a concave cone shape on the exit side of the illumination light; and

and a 2 nd prism element disposed on the optical path on the emission side of the 1 st prism element, and having a curved surface which is flat toward the emission side of the illumination light and has a convex cone shape toward the incidence side of the illumination light.

3. The optical illumination device according to claim 2, wherein:

the 1 st prism element is spaced from the 2 nd prism element by a variable distance.

4. The optical illumination device according to claim 1, wherein:

the element formed using the crystalline optical material is: the crystalline optical axis of the crystalline optical material is oriented in a direction coincident with the optical axis.

5. The optical illumination device according to claim 1, wherein:

the polarization state of the illumination light in the pupil plane is: and a linearly polarized state in which a tangent to a circle centered on the optical axis is aligned with a polarization direction.

6. The optical illumination device as claimed in claim 1, wherein the beam transformation element comprises:

a diffraction surface that distributes the illumination light in a pair of arc-shaped regions that are symmetrical with respect to the optical axis in the tire-shaped region in the pupil surface.

7. The optical illumination device according to claim 6, wherein:

the determined light intensity distribution is: a tire-shaped light intensity distribution in the tire-shaped region in the pupil plane.

8. The optical illumination device according to claim 6, wherein:

the determined light intensity distribution is: a multi-polar light intensity distribution in the pupil plane within the tire-shaped region.

9. The optical illumination device according to claim 6, characterized by further comprising:

a wave surface division type optical integrator, the optical path arranged on the exit side of the diffraction surface, and

and a zoom lens disposed on the optical path between the diffraction surface and the optical integrator.

10. The optical illumination device according to claim 1, wherein:

the illumination light is emitted from the light source in a polarized state in which linearly polarized light is the main component.

11. The optical illumination device according to claim 10, further comprising:

and a polarization state switching device which is disposed in the optical path on the incident side of the light beam conversion element and switches the polarization state of the illumination light emitted from the light source between a linearly polarized state and a non-polarized state or between two linearly polarized states whose polarization directions are perpendicular to each other.

12. The optical illumination device according to claim 11, wherein:

the polarization state switching device includes:

1/4 wavelength plate, 1/2 wavelength plate, and a depolarizer configured to exit the optical path.

13. The optical illumination device according to claim 10, wherein:

the degree of polarization of the illumination light emitted from the light source is 95% or more.

14. An exposure apparatus that exposes a pattern of a mask to a photosensitive substrate, the exposure apparatus comprising:

the optical illumination device of any one of claims 1 to 13, illuminating the mask.

15. The exposure apparatus according to claim 14, characterized by comprising:

a projection optical system that projects an image of the pattern of the mask onto the photosensitive substrate;

wherein the image of the pattern is: and a liquid filled in an optical path between the projection optical system and the photosensitive substrate, and projected onto the photosensitive substrate.

16. An exposure method of exposing a pattern of a mask to a photosensitive substrate, the exposure method characterized by comprising:

illuminating the pattern of the mask using the optical illumination device of any one of claims 1 to 13; and

the pattern of the mask illuminated by the optical illumination device is exposed on the photosensitive substrate.

17. The exposure method according to claim 16, characterized by comprising:

projecting an image of the pattern illuminated using the optical illumination device onto the photosensitive substrate;

wherein the image of the pattern is: the image of the pattern is projected in a state where an optical path between a projection optical system for projecting the image of the pattern onto the photosensitive substrate and the photosensitive substrate is filled with a liquid.