CN101078813B

CN101078813B - Polarizing transforming element, optical lighting device, exposure device and exposure method

Info

Publication number: CN101078813B
Application number: CN200710110950.XA
Authority: CN
Inventors: 谷津修; 重松幸二; 广田弘之; 松山知行
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 2004-02-06
Filing date: 2005-01-14
Publication date: 2014-09-24
Anticipated expiration: 2025-01-14
Also published as: CN101078814A; CN101078888B; CN101078814B; CN101320136A; CN100409045C; CN1914525A; CN101078811B; CN101078812B; CN101078813A; CN101078811A; CN101320136B; CN101078888A; CN101078812A

Abstract

A polarization conversion element capable of converting, with a limited light quantity loss, a linearly polarized incident light having a polarization direction in an almost single direction into a circumferentially polarized light having a polarization direction in an almost circumferential direction. A polarization conversion element (10) for converting the polarization state of an incident light into a specified polarization state. It is formed of an optical material having optical rotation, for example, quartz, and has a thickness distribution changing in a circumferential direction. The thickness distribution is so set that a linearly polarized light having a polarization direction in an almost single direction is converted into a circumferentially polarized light having a polarization direction in an almost circumferential direction. It has a plurality of circumferentially divided areas (10A-10D), and two arbitrary adjacent areas in the plurality of areas are different in thickness from each other. Also, two arbitrary facing areas in the plurality of areas have optical rotation angles almost equal to each other.

Description

Polarization conversion element, optical illumination device, exposure device, and exposure method

The present application is a divisional application entitled "polarization conversion element, optical illumination device, exposure device, and exposure method" filed as application No. 200580003186.5 (international application No. PCT/JP2005/000407), 2005, 01 th, 14 th.

Technical Field

The present invention relates to a polarization conversion device, an optical illumination device, an exposure apparatus, and an exposure method, and more particularly to an exposure apparatus used in a photolithography process for manufacturing microdevices such as a semiconductor device, an image capturing device, a liquid crystal display device, and a thin film magnetic head.

Background

In some typical exposure apparatuses, a light beam emitted from a light source passes through a fly eye lens as an optical integrator (optical integrator) to form a secondary light source of a substantially planar light source composed of 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 a diaphragm disposed in the vicinity of the rear focal plane of the fly-eye lens, and then enters the condenser lens.

The light beam condensed by the condenser lens is overlapped with the mask formed with a predetermined pattern to illuminate. The light passing through the mask pattern is imaged on the wafer by the projection optical system. Then, the mask pattern is projection-exposed (transferred) on the wafer. Further, when the pattern formed on the mask is highly integrated, it is essential to accurately transfer the fine pattern to the wafer and obtain a uniform illuminance distribution on the wafer.

For example, japanese patent No. 3246615 by the inventor discloses that in order to realize an illumination condition for faithfully transferring a fine pattern in an arbitrary direction, an annular secondary light source is formed on the rear focal plane of a fly-eye lens, and a light flux passing through the annular secondary light source is set so that the polarization direction in the circumferential direction is in a linearly polarized state (hereinafter, simply referred to as "circumferential polarization state").

However, the technology of the above publication uses a circular light beam formed by a fly-eye lens to restrict an aperture having a circular annular aperture, thereby forming a circular annular secondary light source. As a result, the conventional technique is not suitable because the aperture causes a large amount of light loss and the throughput of the exposure apparatus is low.

Disclosure of Invention

In view of the above-described problems, the present invention provides a polarization conversion element capable of converting incident light in a linearly polarized state having a polarization direction in approximately a single direction into light in a circumferentially polarized state having a polarization direction in approximately a circumferential direction, and preventing loss of light amount.

It is another object of the present invention to provide an optical illumination device capable of converting incident light in a linearly polarized state having a polarization direction in approximately a single direction into light in a circumferentially polarized state having a polarization direction in approximately a circumferential direction by using a polarization conversion element, and capable of forming a band-shaped illumination pupil distribution in the circumferentially polarized state while preventing light quantity loss satisfactorily.

The present invention also provides an exposure apparatus and an exposure method, which can prevent light loss well by using an optical illumination device, form a zonal illumination pupil distribution in a polarization state in the circumferential direction, and transfer a fine pattern faithfully and with high yield by using an appropriate illumination condition.

In order to solve the above-described problems, a first embodiment of the present invention provides a polarization conversion element that converts the polarization state of incident light into a predetermined polarization state and forms a thickness variation distribution in the circumferential direction using an optical material having optical rotation.

According to a second embodiment of the present invention, there is provided an optical illumination device including a light source that supplies illumination light, and the polarization conversion element of the first embodiment is arranged in an optical path between the light source and an illuminated surface.

In a third embodiment of the present invention, there is provided an optical illumination device for illuminating an illuminated surface with illumination light from a light source,

the light intensity distribution formed on the illumination pupil surface or the surface conjugate to the illumination pupil surface of the optical illumination device has an average specific polarization ratio RSP of the 1 st direction polarized light in the predetermined effective light source region_h(Ave) represents the average specific polarization ratio with respect to the 2 nd direction polarization in RSP_v(Ave) represents, satisfies

RSP_h(Ave)＞70％，RSP_v(Ave)＞70％。

In addition, the air conditioner is provided with a fan,

RSP_h(Ave)＝Ix(Ave)/(Ix+Iy)Ave；

RSP_v(Ave)＝Iy(Ave)/(Ix+Iy)Ave。

here, ix (ave) is a light flux reaching a point on the image plane through a predetermined effective light source region, and the intensity of the polarization component is averaged in the 1 st direction. Iy (Ave) is a light flux reaching a point on the image plane through a predetermined effective light source region, and the intensity of the polarized light component is averaged in the 2 nd direction. (Ix + Iy) Ave is the intensity average of the total beam intensity passing through the defined active source area. The illumination pupil plane of the optical illumination device may be defined as a plane corresponding to the optical fourier transform relationship of the illuminated surface, and when the optical illumination device is combined with the projection optical system, a plane in the optical illumination device optically conjugate to the aperture of the projection optical system may be defined. The surface conjugate to the illumination pupil surface of the optical illumination device is not limited to the surface in the optical illumination device, and for example, when the optical illumination device is combined with a projection optical system, the surface in the projection optical system may be used. Further, the surface may be a surface in a polarization measuring device for detecting the polarization state of the optical illumination device (or the projection exposure device).

In a fourth embodiment of the present invention, there is provided an exposure apparatus comprising the optical illumination device of the second or third embodiment, through which a pattern on a mask is exposed onto a photosensitive substrate.

The fifth embodiment of the present invention provides an exposure method for exposing a pattern on a mask onto a photosensitive substrate using the optical illumination device of the second or third embodiment.

In accordance with a sixth aspect of the present invention, there is provided a method of manufacturing a polarization conversion element for converting a polarization state of incident light into a predetermined polarization state, the method including: preparing an optical material with optical rotation; and setting a thickness distribution of the optical material that varies in a circumferential direction.

The polarization conversion element of the present invention is formed using an optical material having optical rotation such as crystal, for example, and has a thickness distribution that varies in the circumferential direction. Here, the thickness distribution is set, for example, such that light in a linearly polarized state having a polarization direction in approximately a single direction is converted into light in a circumferentially polarized state having a polarization direction in approximately a circumferential direction. As a result, the present invention can realize a polarization conversion device that can convert incident light in a linearly polarized state having a polarization direction in approximately a single direction into light in a circumferentially polarized state having a polarization direction in approximately a circumferential direction, while preventing loss of light quantity. In particular, since the polarization conversion device is formed using an optical material having optical rotation, there is an advantage that the wavelength plate is relatively easy to manufacture.

In the optical illumination device of the present invention, since the polarization conversion device is used, the incident light in the linearly polarized state having the polarization direction in approximately one direction can be converted into the light in the circularly polarized state having the polarization direction in approximately the circumferential direction, and the annular illumination pupil distribution in the circularly polarized state can be formed while preventing the loss of the light amount. Further, the exposure apparatus and the exposure method of the present invention can form a zonal illumination pupil distribution in a circumferentially polarized state by using an optical illumination apparatus while preventing light quantity loss satisfactorily, and can transfer a fine pattern faithfully and with high productivity under appropriate illumination conditions, and further, can produce a device with satisfactory 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 of an exposure apparatus according to an embodiment of the invention.

FIG. 2 shows an illustration of the operation of the conical cylindrical lens system with respect to the annular band-shaped secondary light source.

FIG. 3 shows the function of the telescopic lens relative to the belt-shaped secondary light source.

Fig. 4 is a schematic oblique view of the internal structure of the polarization monitor of fig. 1.

Fig. 5 is a schematic diagram illustrating an internal structure of the polarization conversion element of fig. 1.

FIG. 6 is an explanatory diagram of optical rotation of a crystal.

FIG. 7 is a schematic diagram of a belt-shaped secondary light source set to a circumferentially polarized state by the action of a polarization conversion element.

FIG. 8 is a schematic diagram of a belt-shaped secondary light source set to a radial polarization state by the action of a polarization conversion element.

FIG. 9 is a schematic diagram showing a plurality of polarization conversion elements that can be switched.

Fig. 10 is a schematic diagram showing a plurality of polarization conversion elements 10a to 10e mounted on a turntable 10T as the exchange mechanism of fig. 9.

Fig. 11A to 11E are schematic structural diagrams of various polarization conversion elements 10a to 10E, respectively.

Fig. 12A to 12C are schematic diagrams showing an example of the secondary light source set to the circumferential polarization state by the action of the polarization conversion element.

Fig. 13 is a schematic structural diagram of the polarization conversion element 10f disposed rotatably around the optical axis AX.

Fig. 14A to 14C are schematic diagrams showing an example of the secondary light source set to the circumferentially polarized state by the action of the polarization conversion element 10 f.

Fig. 15A to 15C are schematic diagrams showing an example of a secondary light source that is rotatable around the optical axis AX and is obtained by a polarization conversion element including 8 fan-shaped basic members.

Fig. 16 is a schematic diagram showing an example of a position (near the incident side) directly in front of the conical prism system 8 in which the polarization conversion element is arranged in the vicinity of the pupil of the illumination optical system.

Fig. 17 is a schematic diagram illustrating a variation shown in fig. 16 to satisfy the conditional expressions (1) and (2).

Fig. 18 is a schematic diagram showing an example of a position of the polarization conversion element disposed in the vicinity of the pupil of the illumination optical system and in the vicinity of the pupil of the imaging optical system 15.

Fig. 19 is a schematic structural view of a wafer plane polarization monitor 90 for detecting the polarization state and the light intensity of light illuminating the wafer W.

Fig. 20 is a schematic diagram showing a 4-division circumferential polarization belt illumination using a 4-division polarization conversion element 10f to obtain a belt-shaped secondary light source 31.

FIG. 21 illustrates an actual process for obtaining a semiconductor device as a micro device.

FIG. 22 shows the actual process for obtaining the liquid crystal display device as a micro device.

1: light source 4: polarized light state conversion unit

4 a: 1/4 wavelength plate 4 b: 1/2 wave plate

4 c: a depolarizer 5: diffractive optical element

6: afocal lens 8: conical cylindrical mirror system

9: the telescopic lens 10: polarization conversion element

10A to 10D: each basic element 10E: central region

11: micro fly-eye lens 12: polarization monitor

12 a: the beam splitter 13: light collecting system

14: mask shield plate 15: imaging optical system

104 c: polarization-absorbing member M: mask (C)

PL: projection optical system W: wafer

Detailed Description

FIG. 1 is a schematic view of an exposure apparatus according to an embodiment of the invention. In fig. 1, a direction along a normal line of a photosensitive substrate, i.e., a wafer W, is set as a Z-axis, a direction parallel to a paper surface of fig. 1 within the surface of the wafer W is set as a Y-axis, and a direction perpendicular to the paper surface of fig. 1 within the surface of the wafer W is set as an X-axis. Referring to fig. 1, the exposure apparatus of the present embodiment includes a light source 1 for supplying exposure light (illumination light).

As the light source 1, for example, a KrF excimer laser source which supplies 248nm wavelength light or an ArF excimer laser source which supplies 193nm wavelength light can be used. The approximately parallel light beam emitted from the light source 1 in the Z direction has a rectangular cross section elongated in the X direction and enters a beam expander 2(expander) constituted by a pair of lenses 2a and 2 b. The respective lenses 2a and 2b have negative refractive power and positive refractive power in the plane of paper (in YZ plane) of fig. 1, respectively. Therefore, the light beam incident on the beam expander 2 is enlarged in the paper of fig. 1 and shaped into a light beam having a predetermined rectangular cross section.

The approximately parallel light beam passing through the beam expander 2 as a shaping optical system is bent and deflected in the Y direction by the reflecting mirror 3, passes through the 1/4 wavelength plate 4a, the 1/2 wavelength plate 4b, the depolarizer (depolarizer)4c, and the diffractive optical element 5 for wheel illumination, and enters the afocal lens 6. Here, the 1/4 wavelength plate 4a, the 1/2 wavelength plate 4b, and the depolarizer 4c constitute the polarization state converter 4, as will be described later. The afocal optical system is set to: the front focal position of the afocal lens 6 is approximately matched with the position of the diffractive optical element 5, and the rear focal position is approximately matched with the position of the predetermined surface 7 as shown by the broken line in the figure.

In general, a diffractive optical element has a substrate formed with a height difference of about the wavelength of light (illumination light) for exposure, and diffracts an incident beam at a desired angle. Specifically, the diffractive optical element 5 for wheel illumination has a function of forming a wheel-shaped light intensity distribution in a far-field (or Fraunhofer diffraction region) when a parallel light beam having a rectangular cross section is incident.

Therefore, the approximately parallel light flux incident on the diffractive optical element 5 serving as the light flux conversion element forms a zonal light intensity distribution on the pupil surface of the afocal lens 6, and then the approximately parallel light flux is emitted from the afocal lens 6. A conical cylindrical lens (axicon) system 8 is disposed at or near the pupil plane in the optical path between the front lens group 6a and the rear lens group 6b of the afocal lens 6, and the detailed configuration and operation thereof will be described later. For the sake of simplicity, the conical cylindrical mirror system 8 is omitted, and the basic structure and operation will be described below.

The light beam passing through the afocal lens 6 passes through a zoom lens 9(zoom lens) for changing the σ value and a polarization conversion element 10, and is incident on a micro fly's eye lens (or fly's eye lens) 11 serving as an optical integrator (optical integrator). The structure and operation of the polarization conversion element 10 will be described later. The micro fly's eye lens 11 is an optical element composed of a plurality of micro lenses having positive refractive power arranged in a vertically and horizontally dense manner. Generally, a micro fly-eye lens is manufactured by, for example, applying an etching process to a parallel plane plate to form a micro lens group.

Next, each microlens constituting the micro fly-eye lens is smaller than each lens element (lens element) constituting the fly-eye lens. In addition, unlike a fly's eye lens comprising lens units isolated from each other, a plurality of micro-lenses (micro-refractive surfaces) are integrally formed without being isolated from each other. However, the micro fly's eye lens is a wavefront-dividing type optical integrator similar to the fly's eye lens in that the lens units having positive refractive power are arranged vertically and horizontally.

The position of the predetermined surface 7 is arranged in the vicinity of the front focal position of the telescopic lens 9, and the incident surface of the micro fly-eye lens 11 is arranged in the vicinity of the rear focal position of the telescopic lens 9. In other words, the telescopic lens 9 is disposed such that the predetermined surface 7 and the incident surface of the micro fly-eye lens 11 are substantially in a fourier transform relationship, and further, such that the pupil surface of the afocal lens 6 and the incident surface of the micro fly-eye lens 11 are substantially optically conjugate.

Next, the entrance surface of the micro fly's eye lens 11 is formed with a belt-like irradiation range centered on the optical axis AX, for example, in the same manner as the pupil surface of the afocal lens 6. The overall shape of the belt-like irradiation field changes similarly depending on the focal length of the telescopic lens 9. Each of the microlenses constituting the micro fly-eye lens 11 has a rectangular cross section, which is similar to the shape of the mask M in which the irradiation field is to be formed (and thus the shape of the exposure field on the wafer W).

The light flux incident on the micro fly's eye lens 11 is two-dimensionally divided by a plurality of micro lenses, and a secondary light source having a light intensity distribution approximately equal to the formed irradiation range, that is, a secondary light source constituted by a substantially planar light source in a shape of a circular band with the optical axis AX as the center is formed by the incident light flux on the rear focal plane or the vicinity thereof (and further on the illumination pupil). The secondary light beam formed from the rear focal plane of the micro fly's eye lens 11 or its vicinity passes through the beam splitter 12a (beam splitter) and the light collecting system 13, and then is illuminated with the mask blank in an overlapping manner.

Then, the mask blank 14, which is the illumination field stop, forms a rectangular illumination range corresponding to the shape and focal length of each microlens constituting the micro fly-eye lens 11. The polarization monitor 12 has a beam splitter 12a provided therein, and the internal structure and function thereof are as described below. The light beam passing through the rectangular opening (light-transmitting portion) of the mask blank 14 is subjected to the condensing action of the imaging optical system 15, and then is superimposed on the mask M on which a predetermined pattern is formed.

That is, the imaging optical system 15 forms an image of the rectangular opening of the mask sheet 14 on the mask M. The light beam passing through the pattern of the mask M passes through the projection optical system PL, and an image of the mask pattern is formed on the photosensitive substrate, i.e., the wafer W. Then, the wafer W is subjected to full-scale or scanning exposure in a plane (XY plane) perpendicular to the optical axis AX of the projection optical system PL by two-dimensionally driving and controlling the wafer W, and the pattern of the mask M is sequentially exposed to each exposure region of the wafer W.

In the polarization state switching unit 4, the 1/4 wavelength plate 4a is configured to be rotatable about the crystal optical axis about the optical axis AX, and converts the incident elliptically polarized light beam into a linearly polarized light beam. The 1/2 wavelength plate 4b is configured to be rotatable about a crystal optical axis about the optical axis AX, and changes the polarization plane of incident linearly polarized light. The depolarizer 4c is formed by a wedge-shaped quartz prism and a wedge-shaped quartz prism having complementary shapes. A prism assembly in which a quartz prism and a quartz prism are integrated is configured so as to be freely insertable into and removable from an 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 generally has a polarization degree of 95% or more, and the light polarized in approximately a straight line is incident on the 1/4 wavelength plate 4 a. However, in the case of a rectangular prism as a back reflector in the optical path between the light source 1 and the polarization state switching unit 4, the polarization plane of incident linearly polarized light does not coincide with the P-polarization plane or the S-polarization plane, and the linearly polarized light is converted into elliptically polarized light by total reflection by the rectangular prism.

The polarization state switching unit 4 receives an elliptically polarized light beam due to total reflection by the rectangular prism, for example, converts the elliptically polarized light beam into a linearly polarized light beam by the action of the 1/4 wavelength plate 4a, and receives the linearly polarized light beam on the 1/2 wavelength plate 4 b. When the optical axis of the crystal of the 1/2 wavelength plate 4b is set to 0 degree or 90 degrees with respect to the polarization plane of the incident linearly polarized light, the linearly polarized light beam incident on the 1/2 wavelength plate 4b passes through without changing the polarization plane.

The optical axis of the crystal of the 1/2 wavelength plate 4b is changed to linearly polarized light only by 90 degrees in accordance with the case where the polarization plane of the incident linearly polarized light is set at 45 degrees, and the polarization plane of the linearly polarized light beam incident on the 1/2 wavelength plate 4b is changed. Further, the crystal optical axis of the crystal prism of the depolarizer 4c is changed to unpolarized light (unpolarized) in accordance with the case where the polarization plane of the incident linearly polarized light is set to 45 degrees.

In the polarization state switching section 4, when the depolarizer 4c is positioned in the illumination optical path, the crystal optical axis of the crystal prism is set at 45 degrees with respect to the polarization plane of the incident linearly polarized light. When the crystal optical axis of the crystal prism is set at an angle of 0 degree or 90 degrees with respect to the polarization plane of the incident linearly polarized light, the polarization plane of the linearly polarized light incident on the crystal prism passes through without changing. When the crystal optical axis of the 1/2 wavelength plate 4b is set to an angle of 22.5 degrees with respect to the polarization plane of incident linearly polarized light, the linearly polarized light incident on the 1/2 wavelength plate 4b is converted into unpolarized light containing linearly polarized light components whose polarization planes do not change but pass through the linearly polarized light components and linearly polarized light components whose polarization planes change only by 90 degrees.

The polarization state switching unit 4 is configured such that linearly polarized light is incident on the 1/2 wavelength plate 4b as described above, and linearly polarized light having a polarization direction (electric field direction) in the Z direction of fig. 1 (hereinafter, referred to as Z-direction polarized light) is incident on the 1/2 wavelength plate 4b for the sake of the following brief description. When the depolarizer 4c is positioned in the illumination optical path, the polarization plane (polarization direction) of the crystal optical axis incident on the 1/2 wavelength plate 4b with respect to the Z-direction polarization is set to 0 degree or 90 degrees, and the Z-direction polarization incident on the 1/2 wavelength plate 4b passes through the Z-direction polarization whose polarization plane does not change, and enters the crystal prism of the depolarizer 4 c. The crystal optical axis of the crystal prism is set to an angle of 45 degrees with respect to the incident Z-direction polarized polarization plane, and thus the incident Z-direction polarized light of the crystal prism is converted into unpolarized light.

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

On the other hand, when the depolarizer 4c is moved away from the illumination optical path, and the polarization plane of the crystal optical axis incident on the 1/2 wavelength plate 4b with respect to the Z-direction polarization is set to 0 degree or 90 degrees, the light polarized in the Z-direction incident on the 1/2 wavelength plate 4b passes through without changing, and is incident on the diffractive optical element 5 in the Z-direction polarization state. On the other hand, when the polarization plane of the crystal optical axis incident on the 1/2 wavelength plate 4b is set to 45 degrees with respect to the Z-direction polarization, the polarization plane of the Z-direction polarized light incident on the 1/2 wavelength plate 4b changes by 90 degrees to X-direction polarized light, and the light enters the diffractive optical element 5 in the X-direction polarized state.

As described above, the polarized-light-state switching unit 4 can cause the non-polarized-light-state light to enter the diffractive optical element 5 by determining the positioning of the depolarizer 4c inserted in the illumination optical path. The depolarizer 4c is moved away from the illumination optical path, and the polarizing plane of the crystal optical axis of the 1/2 wavelength plate 4b polarized in the Z direction is set to 0 degree or 90 degrees with respect to the incident polarized light in the Z direction, so that the light polarized in the Z direction can be incident on the diffractive optical element 5. The depolarizer 4c is set apart from the illumination optical path, and the polarization plane of the crystal optical axis of the 1/2 wavelength plate 4b is set to 45 degrees with respect to the incident Z-direction polarization, so that the X-direction polarized light can be incident on the diffractive optical element 5.

In other words, the polarization state switching unit 4 can switch the polarization state of the incident light to the diffractive optical element 5 (and further the polarization state of the light illuminating the mask M and the wafer W) between the linearly polarized state and the unpolarized state, and can switch between the mutually perpendicular polarization states (between the Z-direction polarization state and the X-direction polarization state) in the case of the linearly polarized state, by the action of the polarization state switching unit composed of the 1/4 wavelength plates 4a, 1/2 wavelength plate 4b, and the depolarizer 4 c.

In the polarization state switching unit 4, the 1/2 wavelength plate 4b is retracted from the illumination optical path together with the depolarizer 4c, and the desired angle is set by the crystal optical axis of the 1/4 wavelength plate 4a with respect to the incident elliptically polarized light, so that circularly polarized light can be incident on the diffractive optical element 5. In general, the polarization state of the incident light to the diffractive optical element 5 can be set to a linearly polarized state in which the polarization direction is present in any direction by the action of the 1/2 wavelength plate 4 b.

Then, the conical prism system 8 is composed of a1 st prism portion 8a having a plane opposite to the light source side and a concave conical refraction surface opposite to the mask side, and a2 nd prism portion 8b having a plane opposite to the mask side and a convex conical refraction surface opposite to the light source side along the light source side. The concave conical refraction surface of the 1 st prism portion 8a and the convex conical refraction surface of the 2 nd prism portion 8b are engageable and complementary shapes. At least one of the 1 st prism portion 8a and the 2 nd prism portion 8b is configured to be movable along the optical axis AX. The interval between the concave conical refractive surface of the 1 st prism portion 8a and the convex conical refractive surface of the 2 nd prism portion 8b is variable.

Here, in a state where the concave conical refractive surface of the 1 st prism portion 8a and the convex conical refractive surface of the 2 nd prism portion 8b are joined to each other, the conical prism system 8 functions as a parallel plane plate without affecting the formed annular secondary light source. However, when the concave conical refractive surface of the 1 st prism portion 8a and the convex conical refractive surface of the 2 nd prism portion 8b are separated from each other, the conical prism system 8 functions as a so-called beam expander. Therefore, as the interval of the conical cylindrical mirror system 8 is changed, the incident light angle to the predetermined plane 7 is changed.

FIG. 2 is a schematic diagram of a conical cylindrical lens system for a circular band-shaped secondary light source. Referring to fig. 2, in a state where the interval of the conical cylindrical mirror system 8 is set to zero and the focal length of the telescopic lens 9 is set to the minimum value (hereinafter, referred to as a standard state), the minimum annular secondary light source 30a is formed, and the width (1/2: the difference between the outer diameter and the inner diameter, indicated by an arrow in the figure) of the conical cylindrical mirror system 8 is increased from zero to the predetermined value, and the outer diameter is increased together with the inner diameter to be changed to an annular secondary light source 30 b. In other words, the width of the annular secondary light source does not change by the action of the conical cylindrical mirror system 8, and the annular ratio (inner diameter/outer diameter) thereof changes together with the size (outer diameter).

FIG. 3 shows the function of the telescopic lens relative to the belt-shaped secondary light source. Referring to fig. 3, the belt-shaped secondary light source 30a formed in the normal state is expanded from the minimum value to a predetermined value by the focal length of the telescopic lens 9, and the overall shape is similarly expanded and changed to a belt-shaped secondary light source 30 c. In other words, the belt ratio of the belt-shaped secondary light source does not change by the action of the telescopic lens 9, and the width thereof changes together with the size (outer diameter).

Fig. 4 is a schematic oblique view of the internal structure of the polarization monitor of fig. 1. Referring to fig. 4, the polarization monitor 12 includes: and a1 st beam splitter 12a disposed on an optical path between the micro fly-eye lens 11 and the light collecting system 13. The 1 st beam splitter 12a is in the form of an uncoated parallel plate (i.e., a plain glass) formed of, for example, quartz glass, and has a function of taking out reflected light in a polarization state different from that of incident light from an optical path.

The light extracted from the optical path by the 1 st beam splitter 12a enters the 2 nd beam splitter 12 b. The 2 nd beam splitter 12b is, similarly to the 1 st beam splitter 12a, in the form of an uncoated parallel plate made of, for example, quartz glass, and has a function of generating reflected light in a polarization state different from that of incident light. Next, the P-polarization with respect to the 1 st beam splitter 12a is set to the S-polarization with respect to the 2 nd beam splitter 12b, and the S-polarization with respect to the 1 st beam splitter 12a is set to the P-polarization with respect to the 2 nd beam splitter 12 b.

The light transmitted through the 2 nd spectroscope 12b is detected by the 1 st light intensity detector 12c, and the light reflected by the 2 nd spectroscope 12b is detected by the 2 nd light intensity detector 12 d. The outputs of the 1 st and 2 nd light intensity detectors 12c and 12d are supplied to a control unit (not shown). The control unit drives the 1/4 wavelength plates 4a and 1/2 wavelength plate 4b and the depolarizer 4c constituting the polarization state switching unit 4 as necessary.

As described above, the 1 st beam splitter 12a and the 2 nd beam splitter 12b have substantially different reflectances for P-polarized light and S-polarized light. Therefore, the reflected light from the 1 st beam splitter 12a of the polarization monitor 12 includes, for example, about 10% of the S-polarized light component of the incident light to the 1 st beam splitter 12a (the S-polarized light component to the 1 st beam splitter 12a is the P-polarized light component to the 2 nd beam splitter 12 b), and, for example, about 1% of the P-polarized light component of the incident light to the 1 st beam splitter 12a (the P-polarized light component to the 1 st beam splitter 12a is the S-polarized light component to the 2 nd beam splitter 12 b).

The reflected light from the 2 nd beam splitter 12b contains, for example, a P-polarized component (the P-polarized component for the 1 st beam splitter 12a is the S-polarized component for the 2 nd beam splitter 12 b) of about 10% × 1% of the incident light to the 1 st beam splitter 12a to 0.1%, and an S-polarized component (the S-polarized component for the 1 st beam splitter 12a is the P-polarized component for the 2 nd beam splitter 12 b) of about 1% × 10% of the incident light to the 1 st beam splitter 12a to 0.1%.

In this way, the 1 st beam splitter 12a has a function of extracting reflected light in a polarization state different from the polarization state of the incident light from the optical path in response to the reflection characteristic of the polarization monitor 12. As a result, the polarization state (polarization degree) of the incident light to the 1 st beam splitter 12a and further the polarization state of the illumination light to the mask M can be detected based on the output of the 1 st photometric detector 12c (the transmitted light intensity data of the 2 nd beam splitter 12b, that is, the intensity data of the light having the same polarization state about the reflected light from the 1 st beam splitter 12 a) with little influence of the polarization fluctuation by the 2 nd beam splitter 12 b.

The polarization monitor 12 is set such that the P-polarization with respect to the 1 st beam splitter 12a is the S-polarization with respect to the 2 nd beam splitter 12b, and the S-polarization with respect to the 1 st beam splitter 12a is the P-polarization with respect to the 2 nd beam splitter 12 b. As a result, the light quantity (intensity) of the incident light to the 1 st beam splitter 12a and the light quantity of the illumination light to the mask M can be detected based on the output of the 2 nd light intensity detector 12d (intensity data on the sequentially reflected light from the 1 st beam splitter 12a and the 2 nd beam splitter 12 b) without being substantially affected by the change in the polarization state of the incident light to the 1 st beam splitter 12 a.

Then, the polarization monitor 12 is used to detect the polarization state of the incident light to the 1 st beam splitter 12a, and further, it is possible to determine whether the illumination light to the mask M is in the desired non-polarization state, linearly-polarized state, or circularly-polarized state. The control unit determines whether or not the illumination light to the mask M (and hence the wafer W) is in a desired non-polarized state, linearly polarized state, or circularly polarized state based on the detection result of the polarization monitor 12, and drives and adjusts the 1/4 wavelength plates 4a and 1/2 wavelength plate 4b and the depolarizer 4c constituting the polarized state switching unit 4, thereby adjusting the illumination light to the mask M to be in a desired non-polarized state, linearly polarized state, or circularly polarized state.

Further, 4-pole illumination can be performed by setting the diffraction optical element (not shown) for 4-pole illumination in the illumination optical path instead of the diffraction optical element 5 for wheel illumination. The 4-pole diffractive optical element for illumination has a function of forming a 4-pole light intensity distribution in a far field when a parallel light beam having a rectangular cross section is incident thereon. Therefore, the light flux passing through the 4-pole diffractive optical element for illumination forms a 4-pole illumination region composed of 4 circular illumination regions centered on the optical axis AX, for example, on the incident surface of the micro fly eye lens 11. As a result, the rear focal plane of the micro fly-eye lens 11 or its vicinity is formed into a 4-pole secondary light source in the same manner as the irradiation region formed on the incident surface.

Further, a diffractive optical element for circular illumination (not shown) is set in the illumination optical path instead of the diffractive optical element for wheel illumination 5, so that general circular illumination can be performed. A diffractive optical element for circular illumination has a function of forming a circular light intensity distribution in its far field when a parallel light beam having a rectangular cross section is incident thereon. Therefore, the light beam passing through the circular illumination diffractive optical element forms a 4-pole illumination area, which is composed of a circular illumination area centered on the optical axis AX, for example, on the incident surface of the micro fly eye lens 11. As a result, the rear focal plane of the micro fly-eye lens 11 or its vicinity is formed into a circular secondary light source in the same manner as the irradiation region formed on the incident surface.

Further, instead of the diffractive optical element 5 for wheel illumination, a diffractive optical element (not shown) for multipole illumination can be set in the illumination optical path to perform various multipole illuminations (2-pole illumination, 8-pole illumination, and the like). Similarly, the diffractive optical element having appropriate characteristics, instead of the diffractive optical element 5 for the wheel band illumination, can be set in the illumination optical path to perform various forms of variable illumination.

Fig. 5 is a schematic diagram illustrating an internal structure of the polarization conversion element of fig. 1. FIG. 6 is an explanatory diagram of optical rotation of a crystal. FIG. 7 is a schematic diagram of a belt-shaped secondary light source set to a circumferentially polarized state by the action of a polarization conversion element. The polarization conversion element 10 according to the embodiment of the present invention is arranged directly in front of the micro fly's eye lens 11, that is, at or near the pupil of the illumination optical devices (1 to PL). Therefore, in the case of the belt illumination, a light flux having a cross section of about a belt shape and having the optical axis AX as the center is incident on the polarization conversion element 10.

Referring to fig. 5, the polarization conversion element 10 has an effective region having an overall optical axis AX as a central annular band shape, and the effective region having the annular band shape is formed by basic elements equally divided into 8 sectors in the circumferential direction with the optical axis AX as the center. In these 8 basic elements, a pair of basic elements opposing each other across the optical axis AX have the same characteristics as each other. That is, the 8 basic elements include 2 basic elements each of 4 kinds of basic elements 10A to 10D different from each other in thickness (length in the optical axis direction) along the light passing direction (Y direction).

Specifically, the thickness of the 1 st element 10A is the largest, the thickness of the 4 th element 10D is the smallest, and the thickness of the 2 nd element 10B is larger than the thickness of the 3 rd element 10C. As a result, one surface (for example, an incident surface) of the polarization conversion element 10 is planar, and the other surface (for example, an emission surface) is uneven due to the difference in thickness of the basic elements 10A to 10D. The both surfaces (incident surface and emission surface) of the polarization conversion element 10 may be formed in an uneven shape.

In the present embodiment, each of the basic elements 10A to 10D is made of crystal as a crystal material, which is an optical material having optical activity, and the crystal optical axis of each of the basic elements 10A to 10D is set to approximately coincide with the optical axis AX, that is, approximately coincide with the traveling direction of incident light. Hereinafter, the optical rotation of the crystal will be briefly described with reference to FIG. 6. Referring to fig. 6, the optical axis of the crystal of the parallel-plate optical member 100 made of crystal having the thickness d is aligned with the optical axis AX. In this case, the polarization direction of the incident linearly polarized light is emitted in a state rotated by an angle θ with respect to the optical axis AX by the optical rotation of the optical member 100.

At this time, the rotation angle (rotation angle) θ in the polarization direction due to the optical rotation of the optical member 100 is expressed by the following formula (a) using the thickness d of the optical member 100 and the optical rotation energy ρ.

θ＝d.ρ(a)

In general, the optical rotation energy ρ of crystal tends to be wavelength-dependent (optical rotation energy values different depending on the wavelength of light used: optical dispersion), and specifically, the shorter the wavelength of light used, the greater the optical rotation energy ρ of crystal. According to the description on page 167 of "applied optics II", the optical rotation energy ρ of crystal is 153.9 degrees/mm with respect to light having a wavelength of 250.3 nm.

In this embodiment, the thickness dA of the 1 st basic element 10A is set so that, when linearly polarized light polarized in the Z direction enters, linearly polarized light having a polarization direction in the Z direction is emitted in a direction in which the Z direction is rotated by +180 degrees around the Y axis. Therefore, in this case, as in the belt-like secondary light source 31 shown in fig. 7, the polarization direction of the light flux that is subjected to the optical rotation action of the pair of 1 st basic elements 10A, and the light flux that passes through the pair of circular arc-shaped regions 31A formed, is in the Z direction.

The 2 nd basic element 10B is set to have a thickness dB, and when linearly polarized light polarized in the Z direction enters, the Z direction rotates by +135 degrees around the Y axis, that is, the Z direction rotates by-45 degrees around the Y axis, and linearly polarized light in the polarization direction exits. Therefore, in this case, as shown in fig. 7, in the belt-like secondary light source 31, the polarization direction of the light beam subjected to the optical rotation action of the pair of 2 nd basic elements 10B passing through the pair of circular arc-shaped regions 31B formed is a direction in which the Z direction is rotated by-45 degrees about the Y axis.

The 3 rd basic element 10C is set to have a thickness dC, and when linearly polarized light polarized in the Z direction enters, linearly polarized light in the X direction exits in a direction in which the Z direction is rotated by +90 degrees around the Y axis. Therefore, in this case, as in the belt-like secondary light source 31 shown in fig. 7, the polarization direction of the light flux that is subjected to the optical rotation action of the pair of 3 rd basic elements 10C, and passes through the pair of arc-shaped regions 31C formed, is in the X direction.

The 4 th basic element 10D is set to have a thickness dD, and when linearly polarized light polarized in the Z direction enters, linearly polarized light in the polarization direction exits in a direction in which the Z direction is rotated by +45 degrees around the Y axis. Therefore, in this case, as shown in fig. 7, in the belt-shaped secondary light source 31, the polarization direction of the light flux that is optically acted on by the pair of 4 th basic elements 10D and passes through the pair of arc-shaped regions 31D formed is a direction in which the Z direction is rotated by +45 degrees around the Y axis.

The polarization conversion element 10 can be obtained by combining 8 basic elements formed separately, or the polarization conversion element 10 can be obtained by forming a crystal substrate of a parallel plane plate into a desired uneven shape (step). When the polarization conversion element 10 is not removed from the optical path, normal circular illumination is possible, and a circular central region 10E is set to have a size equal to or larger than 3/10, preferably equal to or larger than 1/3, in the radial direction of the effective region of the polarization conversion element 10 and to have no optical rotation. The central region 10E may be formed of an optically inactive material such as quartz, or may be a simple circular opening. However, the central region 10E is not an essential element of the polarization conversion element 10. The size of the central region 10E is determined by the boundary between the region in the circumferential polarization state and the non-region.

In the present embodiment, when the circularly polarized light is circularly illuminated (i.e., the deformed illumination in which the light beam passing through the circularly polarized secondary light source is set to the circularly polarized state), the linearly polarized light having the Z-direction polarization is incident on the polarization conversion element 10. As a result, the rear focal plane of the micro fly's eye lens 11 or its vicinity is formed with a band-shaped secondary light source (a band-shaped pupil distribution) 31 as shown in fig. 7, and the light flux passing through the band-shaped secondary light source 31 is set to be in a circumferentially polarized state. In the circumferential polarization state, the light flux passing through each of the arc-shaped regions 31A to 31D constituting the annular secondary light source 31 follows the circumferential direction of each of the arc-shaped regions 31A to 31D, and the polarization direction of the linearly polarized state at the center position is approximately aligned with the tangential direction of a circle having the optical axis AX as the center.

Next, in the present embodiment, unlike the conventional technique in which the loss of light amount occurs due to a large aperture, the secondary light source 31 in the form of a band in the polarization state in the circumferential direction can be formed without substantial loss of light amount due to the optical rotation action of the polarization conversion element 10. In other words, with the illumination optical device of the present embodiment, the loss of light amount is suppressed well, and a zonal illumination distribution in the polarization state in the circumferential direction can be formed. In addition, in the present embodiment, since the polarization function of the optical element is used, the polarization conversion element can be easily manufactured, and the thickness tolerance of each typical basic element can be set very gently, thereby achieving an excellent effect.

In addition, according to the circumferential polarization annular illumination of the annular illumination pupil distribution in the circumferential polarization state, the light irradiated on the wafer W as the final illuminated surface is in a polarization state in which S-polarized light is the main component. Here, the S-polarized light is linearly polarized light having a polarization direction perpendicular to the incident surface (polarized light in which the direction electric vector perpendicular to the incident surface vibrates). However, the incident surface is defined as the interface (irradiated surface: surface of wafer W) when light reaches the medium, and includes the normal line of the interface at that point and the surface of the incident light.

As a result, the optical performance (depth of focus, etc.) of the projection optical system can be improved for the circumferential direction polarizing band illumination, and a mask pattern image with high contrast on a wafer (photosensitive substrate) can be obtained. That is, according to the embodiments of the present invention, since the illumination optical device that can favorably suppress the loss of the light amount and form the annular illumination pupil distribution in the polarization state in the circumferential direction is used, the fine pattern can be transferred with fidelity and high productivity under the appropriate illumination condition.

Next, in the present embodiment, the linearly polarized light having the X-direction polarization direction is made incident on the polarization conversion element 10, and as shown in fig. 8, the light beam passing through the annular secondary light source 32 is set to the radial direction polarization state, and radial direction polarization annular illumination (deformed illumination in which the light beam passing through the annular secondary light source 32 is set to the radial direction polarization state) is performed. In the radially polarized state, the light fluxes passing through the arc-shaped regions 32A to 32D constituting the annular secondary light source 32 respectively follow the circumferential direction of the arc-shaped regions 32A to 32D, and the linearly polarized state at the center position is approximately aligned with the radius of a circle having the optical axis AX as the center.

The light irradiated to the wafer W as the final illuminated surface is in a polarized state mainly composed of P-polarized light according to the radial polarized band illumination of the radial polarized band illumination pupil distribution. Here, the P-polarized light is linearly polarized light in a polarization direction parallel to the above-defined incident surface (polarized light in which the electric vector vibrates in a direction parallel to the incident surface). As a result, the light reflectance of the resist applied to the wafer is reduced by the radial direction polarizing stripe illumination, and a good mask pattern image can be obtained on the wafer (photosensitive substrate).

In the above embodiment, the light beam incident on the polarization conversion element 10 is switched between the linearly polarized state having the polarization direction in the Z direction and the linearly polarized state having the polarization direction in the X direction, thereby realizing the circumferential polarization wheel band illumination and the radial polarization wheel band illumination. However, without being limited thereto, for example, with respect to an incident beam in a linearly polarized state having a polarization direction in the Z direction or the X direction, the circumferential-direction polarized wheel band illumination and the radial-direction polarized wheel band illumination can be realized by switching the polarization conversion element 10 between the 1 st state shown in fig. 5 and the 2 nd state of rotating only 90 degrees around the optical axis AX.

In the above embodiment, the polarization conversion element 10 is disposed directly in front of the micro fly-eye lens 11. However, the present invention is not limited to this, and the polarization conversion element 10 may be disposed at or near the pupil of the general illumination devices (1 to PL), for example, at or near the pupil of the projection optical system PL, at or near the pupil of the imaging optical system 15, directly in front of the conical prism system 8 (at or near the pupil of the afocal lens 6), or the like.

Therefore, if the polarization conversion element 10 is disposed in the projection optical system PL and the imaging optical system 15, the effective diameter required for the polarization conversion element 10 is likely to be large, which is not preferable in view of the current situation where it is difficult to obtain a large crystal substrate of high quality. Further, if the polarization conversion element 10 is disposed immediately in front of the conical prism system 8, the effective diameter required for the polarization conversion element 10 can be reduced, but the distance to the wafer W on the final irradiated surface is long, and factors that change the polarization state, such as coating for preventing lens reflection and a reflective film of a mirror, are liable to be involved in the optical path, which is not preferable. That is, the reflection preventing coating of the lens and the reflection film of the mirror are easily deteriorated by the reflectance of the polarization state (P-polarization and S-polarization) and the incident angle, and further easily changed in polarization state.

In the above embodiment, at least one surface (for example, the emission surface) of the polarization conversion element 10 is formed in a concave-convex shape, and the polarization conversion element 10 has a discretely (discontinuously) varied thickness distribution in the circumferential direction. However, the present invention is not limited to this, and at least one surface (for example, an emission surface) of the polarization conversion element 10 may be formed in a curved surface shape, as long as the polarization conversion element 10 has a thickness distribution that varies approximately discontinuously in the circumferential direction.

In the above embodiment, the polarization conversion element 10 is configured by 8 fan-shaped basic elements corresponding to 8 divisions of the effective band-shaped region. However, the present invention is not limited to this, and the polarization conversion element 10 may be configured by 8 fan-shaped basic elements corresponding to 8 divisions of a circular effective region, 4 fan-shaped basic elements corresponding to 4 divisions of a circular or annular effective region, or 16 fan-shaped basic elements corresponding to 16 divisions of a circular or annular effective region, for example. That is, the effective region shape of the polarization conversion element 10, the number of effective region divisions (the number of basic elements), and the like may be variously modified.

In the above examples, the various basic elements 10A to 10D (and further the polarization conversion element 10) were formed using crystal forms. However, without being limited thereto, each basic element may be formed using another appropriate optical material having optical activity. In this case, an optical material having optical rotation energy of 100 degrees/mm or more depending on the wavelength of light to be used may be used. That is, if an optical material having a small optical power is used, the thickness required to obtain a rotation angle required for the polarization direction is too large, which is not preferable due to the loss of light amount.

In the above embodiment, the polarization conversion element 10 may be fixedly set in accordance with the illumination optical path, or the polarization conversion element 10 may be removably set in accordance with the illumination optical path. In the above embodiment, the S-polarized light with respect to the wafer W and the wheel band illumination are combined as an example, but the S-polarized light with respect to the wafer W may be combined with the multipolar illumination of 2-pole, 4-pole, or the like and the circular illumination. In the above embodiment, the illumination condition to the mask M and the imaging condition (numerical aperture and aberration) to the wafer W, for example, the type of the pattern of the mask M, can be automatically set.

FIG. 9 is a schematic diagram showing a plurality of polarization conversion elements that can be switched. Further, a modification of fig. 9 has a structure similar to that of the embodiment shown in fig. 1, for example, and is different in that it has a turn table 10t (turret) that allows a plurality of polarization conversion elements to be exchanged.

Fig. 10 is a schematic diagram showing a plurality of polarization conversion elements 10a to 10e mounted on a turntable 10T as the exchange mechanism of fig. 9. As shown in fig. 9 and 10, in the modification, a plurality of types of polarization conversion elements 10a to 10e are provided on a turntable 10T rotatable about an axis parallel to the optical axis AX, and the plurality of types of polarization conversion elements 10a to 10e are exchangeable with each other by the rotation action of the turntable 10T. In fig. 9, only the polarization conversion elements 10a and 10b among the plurality of types of polarization conversion elements 10a to 10e are shown. The exchange mechanism as the polarization conversion element is not limited to the turntable 10T, and may be a slider, for example.

Fig. 11A to 11E are schematic structural diagrams of various polarization conversion elements 10a to 10E, respectively. In fig. 11A, the 1 st polarization conversion element 10a has the same structure as the polarization conversion element 10 of the embodiment shown in fig. 5. In fig. 11B, the 2 nd polarization conversion element 10B has a similar configuration to the polarization conversion element 10a shown in fig. 11A, but is different in that a polarization resolving member 104c is provided in the central region 10E. This polarization resolving member 104c has the same structure as the depolarizer 4c shown in fig. 1, and has a function of converting incident linearly polarized light into unpolarized light.

In fig. 11C, the 3 rd polarization conversion element 10C has a similar structure to the polarization conversion element 10A shown in fig. 11A, but is different in that the size of the central region 10E is large (the widths of the 1 st to 4 th basic elements 10A to 10D are narrow). In fig. 11D, the 4 th polarization conversion element 10D has a similar configuration to the polarization conversion element 10C shown in fig. 11C, and is different in that a polarization absorbing member 104C is provided in the central region 10E.

In fig. 11E, the 5 th polarization conversion element 10E is composed of 6 basic elements 10C, 10F, and 10G in combination, instead of 8 basic elements. The 5 th polarization conversion element 10e is constituted by basic elements 10C, 10F, 10G divided into 6 segments in the circumferential direction and the like with the optical axis AX as the center and a circular effective region centered on the optical axis AX. In these 6 fan-shaped basic elements 10C, 10F, and 10G, a pair of basic elements opposing each other with the optical axis AX interposed therebetween have the same characteristics. That is, the 6 basic elements 10C, 10F, and 10G include 2 basic elements 10C, 10F, and 10G of 3 types, each of which has a different thickness (length in the optical axis direction) along the light transmission direction (Y direction).

Next, the basic element 10C has the same functional members as the 3 rd basic element 10C shown in fig. 7, and the functional description thereof will be omitted. The thickness dF of the basic element 10F is set, and when linearly polarized light having a polarization direction is incident in the Z direction, the light having linearly polarized light having a polarization direction in which the Z direction is rotated by +150 degrees around the Y axis, that is, the Z direction is rotated by-30 degrees around the Y axis is emitted. The basic element 10G is set to have a thickness dG, and when linearly polarized light in the polarization direction enters in the Z direction, linearly polarized light in the polarization direction rotated by +30 degrees in the Z direction is emitted around the Y axis. Instead of the central region 10E, a polarization absorbing member 104c may be provided.

Referring back to fig. 10, the turret 10T is provided with an opening 40 on which a polarization conversion element is not mounted, and in the case of polarized illumination other than the circularly polarized illumination, the opening 40 is positioned in the illumination optical path in the case of unpolarized illumination having a large σ value (σ value is the mask-side numerical aperture of the illumination optical device/the mask-side numerical aperture of the projection optical system).

As described above, although the central region 10E is formed of a circular opening or a material having no optical rotation or the polarization resolving member 104c is exemplified as the central portion of the polarization conversion elements 10a to 10E placed on the turret 10T, a polarization conversion element (a polarization conversion element formed of a fan-shaped basic element) having no central region 10E or polarization resolving member 104c may be disposed.

Fig. 12A to 12C are schematic diagrams showing an example of the secondary light source set to the circumferential polarization state by the action of the polarization conversion element. Fig. 12A to 12C are redrawn as a polarization conversion element for easy understanding.

Fig. 12A shows a 8-pole secondary light source 33 in a case where a diffractive optical element (beam conversion element) that forms an 8-pole light intensity distribution in the far field (or in the Fraunhofer diffraction region) is provided in the optical path and a polarization conversion element 10a or 10b is provided in the illumination optical path, instead of the diffractive optical element 5. Therefore, the light flux passing through the 8-pole secondary light source 33 is set to be in a circumferentially polarized state. In the circularly polarized state, the light beams passing through the 8 circular regions 33A to 33D constituting the 8-pole secondary light source 33 are linearly polarized in a polarization direction in which the 8 circular regions 33A to 33D are combined in the circumferential direction of a circle, that is, in which the tangential direction of the circle combined with the 8 circular regions 33A to 33D approximately coincides. In fig. 12A, the 8-pole secondary light source 33 is exemplified by 8 circular regions 33A to 33D, but the shape is not limited to 8 regions having a circular shape.

Fig. 12B shows a 4-pole secondary light source 34 in a case where a diffractive optical element (beam conversion element) that forms a 4-pole light intensity distribution in the far field (or in the Fraunhofer diffraction region) is disposed in the optical path and a polarization conversion element 10c or 10d is disposed in the illumination optical path, instead of the diffractive optical element 5. Therefore, the light flux passing through the 4-pole secondary light source 34 is set to be in a circumferentially polarized state. In the circumferential polarization state, the light fluxes passing through the 4 regions 34A and 34C constituting the 4-pole secondary light source 34 are respectively combined into the circumferential direction of a circle by the 4 regions 34A and 34C, that is, the linear polarization state is a polarization direction approximately coincident with the tangential direction of the circle combined by the 4 regions 34A and 34C. In fig. 12B, the 4-pole secondary light source 34 is exemplified by 4 elliptical regions 34A and 34C, but the shape is not limited to 4 elliptical regions.

Fig. 12C shows a 6-pole secondary light source 35 in a case where a diffractive optical element (beam conversion element) that forms a 6-pole light intensity distribution in the far field (or in the Fraunhofer diffraction region) is provided in the optical path and a polarization conversion element 10e is provided in the illumination optical path, instead of the diffractive optical element 5. Therefore, the light flux passing through the 6-pole secondary light source 35 is set to be in a circumferentially polarized state. In the circumferential polarization state, the light fluxes passing through the 6 regions 35C, 35F, and 35G constituting the 6-pole secondary light source 35 are respectively linearly polarized in a polarization direction in which the 6 regions 35C, 35F, and 35G are combined in the circumferential direction of a circle, that is, in which the tangential direction of the circle combined with the 6 regions 35C, 35F, and 35G is approximately coincident. In fig. 12C, the 6-pole secondary light source 35 is exemplified by 6 approximately trapezoidal regions 35C, 35F, and 35G, but the 6 regions are not limited to approximately trapezoidal shapes.

In the above-described embodiments and modifications, the polarization conversion element may be fixed around the optical axis, and the polarization conversion element may be rotated around the optical axis. Fig. 13 is a schematic configuration diagram of a polarization conversion element 10f provided to be rotatable around an optical axis.

In fig. 13, the polarization conversion element 10f is composed of 4 basic elements 10A and 10C. The polarization conversion element 10f has a belt-like effective region centered on the optical axis AX as a whole, and the belt-like effective region is equally divided into 4 basic elements 10A, 10C in a fan shape in the circumferential direction around the optical axis AX. Of the 4 basic elements 10A, 10C, a pair of basic elements opposed to each other across the optical axis AX have the same characteristics as each other. That is, the 4 basic elements 10A and 10C include 2 basic elements 10A and 10C of 2 types, respectively, which are different in thickness (length in the optical axis direction) along the light passing direction (Y direction).

Here, since the basic element 10A is a member having the same function as the 1 st basic element 10A shown in fig. 7, and the basic element 10C is a member having the same function as the 3 rd basic element 10C shown in fig. 7, the description of the function thereof will be omitted. Instead of the central region 10E, a polarization absorbing member 104c may be provided.

The polarization conversion element 10f is rotatably set around the optical axis AX, for example, around the optical axis AX by +45 degrees or-45 degrees. Fig. 14A to 14C are schematic diagrams showing an example of the secondary light source set to the circumferentially polarized state by the action of the polarization conversion element 10 f. In fig. 14, the polarization conversion element 10f is shown in duplicate for ease of understanding.

Fig. 14A shows a 2-pole secondary light source 36(36A) in a case where a diffractive optical element (beam conversion element) that forms a 2-pole light intensity distribution in the far field (or in the Fraunhofer diffraction region) is disposed in the optical path and the polarization conversion element 10f is disposed in the illumination optical path in a state where the rotation angle is 0 degrees (reference state). Here, the light flux passing through the secondary light source 36(36A) is set to be the vertical polarization direction.

Fig. 14B shows a 4-pole secondary light source 37 in a case where a diffractive optical element (beam conversion element) that forms a 4-pole light intensity distribution in the far field (or in the Fraunhofer diffraction region) is disposed in the optical path, and the polarization conversion element 10f is disposed in the illumination optical path in a state where the rotation angle is 0 degrees (reference state). Here, the light flux passing through the secondary light source 37 is set to the circumferential polarization direction. In fig. 14B, the light intensity distribution of the 4-pole shape is limited to the vertical direction (Z direction) and the horizontal direction (X direction) in the paper surface.

In the circularly polarized state, the light beams passing through the 4 circular regions 37A and 37C constituting the 4-pole secondary light source 37 respectively have a linearly polarized state in which the polarization direction approximately coincides with the circumferential direction of the circle formed by joining the 4 circular regions 37A and 37C, that is, the tangential direction of the circle formed by joining the 4 circular regions 37A and 37C. In fig. 14B, the 4-pole secondary light source 37 is shown as being composed of 4 circular regions 37A and 37C, and the shape of the 4 regions is not limited to a circular shape.

Fig. 14C shows a 4-pole secondary light source 38 in a case where, instead of the diffractive optical element of fig. 14B, a diffractive optical element (light beam conversion element) forming a 4-pole light intensity distribution is disposed in the optical path with the +45 degrees (-135 degrees) direction in the paper plane and the-45 degrees (+135 degrees) direction in the paper plane being limited in the far field (or Fraunhofer diffraction area), and the polarization conversion element 10f is disposed in the illumination optical path by being rotated at a rotation angle of +45 degrees (45 degrees with respect to the reference state).

In fig. 14C, the 1/2 wavelength plate 4b in the polarization state switching unit 4 is rotated around the optical axis, and linearly polarized light having a polarization direction of +45 degrees (-135 degrees direction) is incident on the polarization conversion element 10 f. Here, the basic element 10A has a function of rotating the polarization direction of the incident linearly polarized light by 180 degrees ± n × 180 degrees (n is an integer), and the basic element 10C has a function of rotating the polarization direction of the incident linearly polarized light by 90 degrees ± n × 180 degrees (n is an integer), and the light flux passing through the 4-pole secondary light source 38 is set to the circularly polarized state.

In the circumferentially polarized state shown in fig. 14C, the light fluxes passing through the 4 circular regions 38B and 38D constituting the 4-pole secondary light source 38 respectively have a linearly polarized state in which the circumferential direction of the circle formed by combining the 4 circular regions 38B and 38D, that is, the polarization direction approximately coincides with the tangential direction of the circle formed by combining the 4 circular regions 38B and 38D. In fig. 14C, the 4-pole secondary light source 38 is illustrated as an example including 4 circular regions 38B and 38D, and the shape of the 4 regions is not limited to a circular shape.

In this way, by the changing operation of the polarization direction of the polarization state switching unit 4 and the rotation action of the polarization switching element 10f, the polarization state in the circumferential direction can be realized even when the 4-pole secondary light source is limited to the +45 degrees (-135 degrees) direction and the-45 degrees (+135 degrees) direction, the 4-pole secondary light source is limited to the 0 degrees (+180 degrees) direction and the 90 degrees (270 degrees) direction, that is, the vertical and horizontal directions, and the 2-pole secondary light source is limited to the 0 degrees (+180 degrees) direction or the 90 degrees (270 degrees) direction, that is, the vertical and horizontal directions.

The polarization conversion element, which is formed by 8 fan-shaped basic elements equally divided in the circumferential direction with the optical axis AX as the center, may be rotated around the optical axis AX. As shown in fig. 15A, for example, if a polarization conversion element (for example, a polarization conversion element 10a) composed of 8 basic elements is rotated by +45 degrees around an optical axis AX, the light beams passing through 8 circular regions 39A to 39D constituting the 8-pole secondary light source 39 have a linearly polarized state in which the polarization direction is rotated by-45 degrees with respect to the circumferential direction of the circle formed by joining the 8 circular regions 39A to 39D (the tangential direction of the circle formed by joining the 8 circular regions 39A to 39D).

In addition, as shown in fig. 15B, when the light flux passing through each of the 8 circular regions constituting the 8-pole secondary light source passes through the light flux in the 8 circular regions, and the long axis direction is elliptically polarized in the polarization direction rotated by only +45 degrees in the circumferential direction of the circle combined with the 8 circular regions (the tangential direction of the circle combined with the 8 circular regions), the polarization state in the approximately circumferential direction can be obtained by rotating only +45 degrees around the optical axis AX by the polarization conversion element (for example, the polarization conversion element 10a) shown in fig. 15A, as shown in fig. 15C.

Fig. 16 is a schematic diagram showing an example in which the polarization conversion element is arranged in a position near the pupil of the illumination optical system, and a position just in front of the conical prism system 8 (a position near the incident side). In the example of fig. 16, the size of the image projected onto the central region 10E of the entrance surface of the micro fly's eye lens 11 and the size of the images of the respective basic elements 10A to 10D projected onto the entrance surface of the micro fly's eye lens 11 are changed by the magnification change action of the telescopic lens system 9, and the radial width of the images of the respective basic elements 10A to 10D projected onto the entrance surface of the micro fly's eye lens 11 around the optical axis AX is changed by the operation of the conical prism system 8.

Therefore, as shown in the modification example shown in fig. 16, in the case where the polarization conversion element in the central region 10E (or the polarization absorbing member 104c) is provided on the light source side of the optical system (the telescopic lens 9) having a function of converting magnification, the size of the central region 10E can be determined in consideration of the fact that the region occupied by the central region 10E is changed by the conversion magnification of the telescopic lens 9.

In the modification shown in fig. 16, in the case where the polarization conversion element having the central region 10E (or the polarization absorbing member 104c) is provided on the light source side than the optical system (the conical prism system 8) having the function of changing the duty ratio, as shown in fig. 17, it is preferable that at least one of the following conditions (1) and (2) is satisfied.

(1)(10in+ΔA)/10out＜0.75

(2)0.4＜(10i n+ΔA)/10out.

Wherein,

10 in: the effective radius of the central region 10E of the polarization conversion element 10,

10 out: the outer effective radius of the polarization conversion element 10,

Δ A: the inner radius of the beam passing through the optical system is increased by the portion having the function of changing the belt ratio.

In the case where the condition (1) is not satisfied, the zonal region in which the polarization state in the circumferential direction is changed by the polarization conversion element 10 is narrowed, which is not preferable because the zonal or multipolar secondary light source having a small zonal ratio cannot be used to perform the circumferential polarization illumination. In the case where the condition (2) is not satisfied, the diameter of the light beam that can pass through the central region of the polarization conversion element 10 becomes significantly small, and for example, when the polarization conversion element 10 does not move outward from the illumination optical path, the polarization state does not change, and it is not preferable because the small σ illumination cannot be performed.

As shown in fig. 18, the polarization conversion element may be disposed at a position near the pupil of the illumination optical system, and more specifically, may be disposed at a position near the pupil of the imaging optical system 15 for projecting the image of the mask 14 onto the mask, rather than at a position near the mask side of the micro fly eye lens 11. In the embodiments shown in fig. 16 and 18, as in the embodiments of fig. 9 to 11, a plurality of switchable polarization conversion elements may be provided.

In the above embodiment, when the optical system (the illumination optical system and the projection optical system) on the wafer W side has polarization aberration (retardation) as compared with the polarization conversion element 10, the polarization direction changes due to the polarization aberration. In this case, it is preferable that the direction of the polarization plane to be rotated can be set by the polarization conversion element 10in consideration of the influence of the polarization aberration of the optical system. When a reflection member is disposed in the optical path on the wafer W side by the polarization conversion element 10, a phase difference occurs in each polarization direction by the reflection of the reflection member. At this time, the direction of the rotated polarizing surface may be set by the polarization conversion element 10in consideration of the beam phase difference due to the polarization characteristics of the reflecting surface.

Next, an example of the evaluation method of the polarization state is explained. In this embodiment, the wafer W serving as a photosensitive substrate is held on the side of a wafer stage (substrate stage), and the polarization state of a light beam reaching the wafer W serving as a photosensitive substrate is detected by using a wafer plane polarization monitor 90 that can be inserted and removed. The wafer surface polarization monitor 90 may be provided in the wafer stage, or the wafer stage may be provided on another measurement stage.

Fig. 19 is a schematic structural view of a wafer plane polarization monitor 90 for detecting the polarization state and the light intensity of light illuminating the wafer W. As shown in fig. 19, the wafer plane polarization monitor 90 includes a pinhole member 91 that can be positioned at or near the wafer W. The light passing through the pinhole 91a of the pinhole member 91 passes through an alignment lens 92 (collimating lens) disposed at or near the image plane position of the projection optical system PL, such as the front focal position, to become a substantially parallel light flux, and is reflected by a reflecting mirror 93 and then incident on a relay lens system 94(relay lens). The approximately parallel light beam having passed through the relay lens system 94 passes through an 1/4 wavelength plate 95 as a phase shift element and a polarizing beam splitter 96 as a polarizing element, and reaches a detection surface 97a of a two-dimensional CCD97 (Charge Coupled Device). Here, the detection surface 97a of the two-dimensional CCD97 is substantially optically conjugate with the exit pupil of the projection optical system PL, and further substantially optically conjugate with the illumination pupil surface of the illumination optical device.

The 1/4 wavelength plate 95 is configured to be rotatable about the optical axis, and the 1/4 wavelength plate 95 is connected to a setting unit 98 that is set to be rotatable about the optical axis. In this way, when the polarization degree of the illumination light with respect to the wafer W is not 0, the setting unit 98 rotates the 1/4 wavelength plate 95 around the optical axis, thereby changing the light intensity distribution on the detection surface 97a of the two-dimensional CCD 97. Therefore, the wafer surface polarization monitor 90 can measure the polarization state of the illumination light by a method of rotating the phase shift element from the detection result by detecting the change of the light intensity distribution on the detection surface 97a while rotating the 1/4 wavelength plate 95 around the optical axis by using the setting unit 98.

Further, a method of rotating the phase shift element, for example, the optical pencil, applied optics to the optical technician, described in the He field, is described in detail in communications (communications) of New technologies, Inc. In practice, the pinhole member 91 (and hence the pinhole 91a) is moved two-dimensionally along the wafer surface, and the polarization state of the illumination light is measured at a plurality of positions on the wafer surface. At this time, the wafer plane polarization monitor 90 detects a change in the light intensity distribution on the two-dimensional detection surface 97a, and can measure the distribution of the polarization state in the pupil of the illumination light based on the detected distribution data.

In the wafer plane polarization monitor 90, a 1/2 wavelength plate may be used in place of the 1/4 wavelength plate 95 as the phase shift element. Using a phase shifting element, the polarization state, that is, for measuring 4 Stokes parameters, is changed along the relative angle of the phase shifting element and the optical axis of the polarizing element (polarizing beam splitter 96), while the phase shifting element or the polarizing element is withdrawn from the optical path, and the change in the light intensity distribution on the detection surface 97a is detected in at least 4 different states as necessary. In the present embodiment, the 1/4 wavelength plate 95 as the phase shifter is rotated around the optical axis, the polarizing beam splitter 96 as the polarizer may be rotated around the optical axis, and both the phase shifter and the polarizer may be rotated around the optical axis. Instead of or in addition to these operations, one or both of the 1/4 wavelength plate 95 as a phase shifter and the polarizing beam splitter 96 as a polarizing element may be inserted into and removed from the optical path.

The wafer-plane polarization monitor 90 changes the polarization state of light by the polarization characteristics of the mirror 93. In this case, the measurement result of the wafer-plane polarization monitor 90 is corrected based on the influence of the polarization state of the polarization characteristic of the mirror 93 obtained by a necessary calculation based on the polarization characteristic of the mirror 93 known in advance, and the polarization state of the illumination light can be accurately measured. Further, not limited to the mirror, the polarization state of the illumination light can be accurately measured by changing the polarization state caused by other optical members such as a lens to correct the measurement result in the same manner.

The evaluation of the polarization state distribution in the pupil of the illumination light will be specifically described below. First, the light beams that reach a point (or a minute area) on the image plane through a point (or a minute area) on the pupil calculate the corresponding specific polarization degrees DSP one by one. In the following description, the XYZ coordinate system of fig. 1, 16, and 18 is used. One point (minute region) on the pupil corresponds to one pixel of the two-dimensional CCD97, and one point (minute region) on the image plane corresponds to the XY coordinate system of the pinhole 91 a.

When the intensity of the X-direction polarization component (polarization in the X-direction vibration direction on the pupil) of a specific light beam passing through a point (or a minute region) on the pupil and reaching a point (a minute region) on the image plane is Ix, and the intensity of the Y-direction polarization component (polarization in the Y-direction vibration direction on the pupil) of the specific light beam is Iy,

(3)DSP＝(Ix-I y)/(Ix+Iy)。

the specific polarization degree DSP corresponds to the total intensity S₀Subtracting the vertical linear polarization intensity S from the horizontal linear polarization intensity₁And (S)₁/S₀) The same is true.

Further, since the intensity of the X-direction polarization component (polarization in the X-direction vibration direction on the pupil) of a specific light beam that passes through a point (or a minute region) on the pupil and reaches a point (a minute region) on the image plane is Ix, and the intensity of the Y-direction polarization component (polarization in the Y-direction vibration direction on the pupil) of the specific light beam is Iy, the specific polarization ratio RSP of horizontal polarization (polarization in which diffracted light corresponding to a mask pattern extending in the horizontal direction on the pattern plane becomes S-polarized light) can be defined by the following equations (4) and (5)_hA specific polarization ratio RSP with respect to vertical polarization (polarization in which diffracted light corresponding to a mask pattern extending in a vertical direction in a pattern plane becomes S-polarized light)_v。

(4)RSP_h＝Ix/(Ix+I y)，

(5)RSP_v＝Iy/(I x+Iy)，

Wherein RSP is used when the ideal non-polarized illumination is used_h，RSP_vBoth are 50%, RSP when the ideal horizontal bias is applied_hAt 100%, RSP when ideal vertical polarization_vIs 100%.

When the polarization degree V is defined by the following expressions (6) to (9) for one of the light beams that have passed through one point (or a minute region) on the pupil and reached one point (a minute region) on the image plane, the average polarization degree V (ave) can be defined by the following expression (10) for the light beam that has passed through the desired effective light source region and reached one point (a minute region) on the image plane.

(6)V＝(S₁ ²+S₂ ²+S₃ ²)^1/2/S₀

＝(S₁’²+S₂’²+S₃’²)^1/2

(7)S₁’＝S₁/S⁰

(8)S₂’＝S₂/S₀

(9)S₃’＝S₃/S₀

Wherein S₀For full strength, S₁Subtracting the vertical linear polarization intensity from the horizontal linear polarization intensity, S₂Subtracting the intensity of the 135 degree linear polarization from the intensity of the 45 degree linear polarization, S₃The intensity of the right-handed circular polarized light is subtracted by the intensity of the left-handed circular polarized light.

(10)V(Ave)＝∑[S₀(x_i，y_i).V(x_i，y_i)]/∑S₀(x_i，y_i)。

In the formula (10), S₀(x_i，y_i) Is to pass through the desired effective light source area (x)_i，y_i) All the intensity S of the light reaching one point (or micro region) on the image plane₀，V(x_i，y_i) Is to pass through the desired effective light source area (x)_i，y_i) The degree of polarization of light reaching a point (or a micro area) on the image plane.

And, the light beam reaching a point (micro area) on the image plane corresponding to the light beam passing through the desired effective light source areaThe average specific polarization ratio RSP with respect to horizontal polarization can be defined by the following formula (11)_h(Ave), an average specific polarization ratio RSP with respect to vertical polarization can be defined by the following formula (12)_v(Ave)。

(11)RSP_h(Ave)＝Ix(Ave)/(Ix+Iy)Ave

＝∑[S₀(x_i，y_i).RSP_h(x_i，y_i)]/∑S₀(x_i，y_i)，

(12)RSP_v(Ave)＝Iy(Ave)/(Ix+Iy)Ave

＝∑[S₀(x_i，y_i).RSP_v(x_i，y_i)]/∑S₀(x_i，y_i)，

Wherein Ix (Ave) is the area (x) passing through the determined effective light source_i，y_i) The intensity average of the X-direction polarization component (polarization in the X-direction vibration direction on the pupil) of the light reaching a point (micro region) on the image plane, Iy (Ave) is the intensity average of the light passing through the predetermined effective light source region (X)_i，y_i) The intensity of the Y-direction polarization component (polarization in the Y-direction vibration direction on the pupil) of the light reaching a point (micro region) on the image plane is averaged, RSP_h(x_i，y_i) Is passed through a determined effective light source area (x)_i，y_i) And a specific polarization ratio, RSP, of horizontally polarized light of the light reaching a point (micro region) on the image plane_v(x_i，y_i) Is passed through a determined effective light source area (x)_i，y_i) And a specific polarization ratio of the light reaching a point (micro area) on the image plane in the vertical polarization. Also, (Ix + Iy) Ave is the intensity average of the entire light beam passing through the specified effective light source area.

Herein, RSP is the ideal unpolarized illumination_h(x_i，y_i)，RSP_v(x_i，y_i) Both are 50%, RSP when the ideal horizontal bias is applied_h(x_i，y_i) Is composed of100% when desired vertically biased RSP_v(x_i，y_i) Is 100%.

Then, the light source correspondingly passes through the determined effective light source area (x)_i，y_i) The average specific polarization degree dsp (ave) of the light beam reaching a point (micro area) on the image plane can be defined by the following equation (13).

(13)DSP(Ave)＝(Ix-Iy)Ave/(Ix+I y)Ave

＝{∑[Ix(x_i，y_i)-Iy(x_i，y_i)]/∑[Ix(x_i，y_i)+Iy(x_i，y_i)]}

＝S₁’(Ave)

＝{∑S₁/∑S₀}

Here, (Ix-Iy) Ave passes through the determined effective light source area (x)_i，y_i) The light beam reaching a point (micro area) on the image plane passes through a predetermined effective light source area (X) on the average with the intensity of the polarization component in the X direction_i，y_i) On the other hand, Ix (x) is the average of the intensity differences of polarization components in the Y direction of the light beam reaching a point (micro region) on the image plane_i，y_i) Is passed through a determined effective light source area (x)_i，y_i) The intensity of the polarization component in the X direction, Iy (X) of the light beam reaching a point (micro region) on the image plane_i，y_i) Is passed through a determined effective light source area (x)_i，y_i) And the intensity of the polarization component in the Y direction of the light beam reaching a point (micro region) on the image plane, S₁' (Ave) is in a predetermined effective light source area (x)_i，y_i) S of₁' average of ingredients.

In equation (13), DSP (Ave) is 0 for ideal unpolarized illumination, 1 for ideal horizontally polarized illumination, and-1 for ideal vertically polarized illumination.

Now, the illumination optical apparatus, and thus the exposure apparatus, of the present embodiment are effective at a given levelLight source area (x)_i，y_i) Average specific polarization ratio RSP of_h(Ave), RSPv (Ave) satisfies

RSP_h(Ave)＞70％，RSP_v(Ave)＞70％，

It can be seen that within a given effective light source area is linearly polarized. Herein, when the average specific polarization ratio RSP_h(Ave)，RSP_vWhen (Ave) does not satisfy the above-described condition, the imaging performance cannot be improved upward for a fine pattern having a line width in a specific direction (pitch) because a polarizing surface is not in a desired linearly polarized state in a predetermined direction, such as in a circularly polarized wheel band illumination, a circularly polarized quadrupole illumination, or a circularly polarized dipole illumination.

In the case of 4-division circumferential-direction polarized light belt illumination using the 4-division polarization conversion element 10 as shown in fig. 13, the secondary light source 31 in the belt shape may be 4-division as shown in fig. 20, and the average specific polarization ratio RSP for each of the divided regions 31a1, 31a2, 31C1, and 31C2 may be set_h(Ave)，RSP_v(Ave) evaluation was performed.

With the exposure apparatus of the above embodiment, microdevices (semiconductor devices, imaging devices, liquid crystal display devices, thin film electromagnetic heads, etc.) can be manufactured by illuminating the mask (cross mark) with illumination optical means (illumination step) and exposing the pattern formed for mask transfer to a photosensitive substrate using a projection optical system (exposure step). Hereinafter, an actual method of forming a circuit pattern on a wafer or the like serving as a photosensitive substrate to obtain a semiconductor device serving as a microdevice by using the exposure apparatus of the above embodiment will be described with reference to a flowchart of fig. 21.

First, in step 301 of fig. 21, a metal film is deposited on a batch of wafers. In the next step 302, photoresist is coated on the metal films on the wafers of the batch. Then, in step 303, the image of the pattern on the mask is sequentially exposed and transferred to each shot area on the batch of wafers by using the exposure apparatus of the above embodiment through the projection optical system. Thereafter, after the photoresist on the batch of wafers is developed in step 304, etching is performed by using the photoresist pattern on the batch of wafers as a mask in step 305, so that a circuit pattern corresponding to the pattern on the mask is formed on each shot region of each wafer. Then, by forming a circuit pattern on an upper layer, an element such as a semiconductor element is manufactured. According to the above method for manufacturing a semiconductor device, a semiconductor device having an extremely fine circuit pattern can be manufactured with good productivity.

In the exposure apparatus of the above embodiment, a liquid crystal display device as a micro device can be obtained by forming a predetermined pattern (circuit pattern, electrode pattern, etc.) on a plate (glass substrate). The following description will be made as an example with reference to a flowchart of fig. 22. In fig. 22, in a pattern forming step 401, a so-called photolithography process is performed by transferring a pattern of an exposure mask onto a photosensitive substrate (e.g., a glass substrate coated with a photoresist) using the exposure apparatus of the above-described embodiment. By this photolithography process, a predetermined pattern including a plurality of electrodes is formed on the photosensitive substrate. Thereafter, the exposed substrate is subjected to a developing step, an etching step, a photoresist removing step, and the like, to form a predetermined pattern on the substrate, followed by a color filter forming step 402.

In the color filter forming step 402, a plurality of filters are arranged in a matrix corresponding to 3 dots of red, green, and blue, or 3 filters of red, green, and blue are arranged in a plurality of horizontal scanning line directions to form color filters. Next, after the color filter forming step 402, a cell combining step 403 is performed. In a cell assembly step 403, a liquid crystal panel (liquid crystal cell) is obtained by assembling the substrate having the predetermined pattern obtained in the pattern formation step 401, and using the color filter obtained in the color filter formation step 402.

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

In the above-mentioned examples, KrF excimer laser light (wavelength 248nm) or ArF excimer laser light (wavelength 193nm) was used as the exposure light, but the present invention is not limited thereto, and other suitable light sources, for example, F which supplies laser light having a wavelength of 157nm, are used₂A laser light source, etc., and the present invention can be applied. Further, although the exposure apparatus including the illumination optical device is described as an example in the above embodiment, it is understood that the present invention may be applied to a general illumination optical device for illuminating an illuminated surface other than a mask or a wafer.

In the above-described embodiment, a method of filling the optical path between the projection optical system and the photosensitive substrate with a medium (typically a liquid) having a refractive index of 1.1 or more, that is, a so-called liquid immersion method, may be used. In this case, as a method of filling the liquid in the optical path between the projection optical system and the photosensitive substrate, a partially filled liquid as disclosed in international publication No. WO99/49504, a method of moving a stage holding the substrate to be exposed in a liquid bath is also disclosed in japanese patent laid-open publication No. 6-124873, and a method of forming a liquid bath of a predetermined depth on the stage and holding the substrate therein and the like are also disclosed in japanese patent laid-open publication No. 10-303114.

Further, as the liquid, a liquid which is transparent to exposure light and has a high refractive index and is stable against the projection optical system and the resist applied to the substrate surface is preferably used, and for example, in the case of using KrF excimer laser light or ArF excimer laser light as the exposure light, pure water or deionized water can be used as the liquid. Further, F is used as exposure light₂In the case of laser, as the liquid, F-permeable liquid may be used₂The laser beam is a fluorine-based liquid such as fluorine-based oil or fluorinated polyether (PFPE).

Claims

1. A polarization conversion element that can be used in combination with an illumination optical system and converts a polarization state of incident light traveling along an optical path of the illumination optical system into a predetermined polarization state, the polarization conversion element being characterized in that:

the polarization conversion element has a plurality of regions divided in a circumferential direction;

the polarization conversion element is formed by optical material with optical activity and has a thickness distribution changing in the circumferential direction;

wherein the thickness profile is set to:

converting the incident light in a linearly polarized state having a polarization direction in a single direction into light in a circumferentially polarized state having a polarization direction in a circumferential direction or light in a radially polarized state having a polarization direction in a radial direction in each of the plurality of regions;

the polarization conversion element is provided so as to be rotatable about an optical axis along the illumination optical system.

2. A polarization conversion element according to claim 1, wherein the thicknesses of any 2 adjacent regions among the regions are different.

3. A polarization conversion element according to claim 2, wherein any 2 of the regions have equal rotation angles.

4. A polarization conversion element according to claim 3, wherein the opposite arbitrary 2 regions have equal thicknesses.

5. A polarization conversion element according to claim 4, wherein each of the regions has a fan shape.

6. A polarization conversion element according to claim 1, wherein the optical material forming the polarization conversion element is formed of a crystalline material whose crystalline optical axis is set to the traveling direction of the incident light.

7. A polarization conversion element according to claim 1, wherein the polarization conversion element is disposed so as to be freely insertable and removable from the predetermined optical path.

8. An optical illumination device, comprising:

the polarization conversion element according to any one of claims 1 to 7, which is provided so as to be freely insertable and removable from an optical path of illumination light.

9. The optical illumination device of claim 8, wherein the polarization conversion element is disposed at or near a pupil of the optical illumination device.

10. The illumination device as claimed in claim 8, further comprising a phase member disposed in the optical path of the incident side of the polarization conversion element for changing the polarization direction of the incident light in the linearly polarized state.

11. The illumination device as claimed in claim 10, wherein the phase member has an 1/2 wavelength plate freely rotatable on a crystal optical axis as a center of an optical axis of the illumination device.

12. The optical illumination device of claim 10, further comprising a2 nd phase element disposed in the optical path on the incident side of the phase element for converting incident light in the elliptically polarized state into light in the linearly polarized state.

13. The illumination device as claimed in claim 12, wherein the 2 nd phase element has an 1/4 wavelength plate freely rotatable on a crystal optical axis which is a center of an optical axis of the illumination device.

14. The illumination device as claimed in claim 8, further comprising a duty ratio changing optical system for changing a duty ratio of the secondary light source formed at a pupil of the illumination device.

15. The optical illumination device according to claim 14, wherein the polarization conversion element is disposed in an optical path on an incident side of the belt ratio changing optical system, and satisfies:

(10in+ΔA)/10out＜0.75

0.4 < (10in + Δ A)/10out, wherein

10 in: the effective radius of the central region of the polarization conversion element,

10 out: the outer effective radius of the polarization conversion element,

Δ A: an increased portion of an inner radius of the light beam passing through the belt ratio altering optical system.

16. The optical illumination device according to claim 8, wherein the optical material forming the polarization conversion element is formed of a crystalline material whose crystalline optical axis is set to a traveling direction of the incident light.

17. An optical illumination device that illuminates an illumination target surface, the optical illumination device comprising:

a polarization conversion element for converting a polarization state of incident light traveling along an optical path of the illumination light into a predetermined polarization state;

the polarization conversion element has a plurality of regions divided in the circumferential direction,

a polarization conversion element for converting the incident light in a linearly polarized state having a polarization direction in a single direction into light in a circularly polarized state having a polarization direction in a circumferential direction or light in a radially polarized state having a polarization direction in a radial direction in each of the plurality of regions;

the polarization conversion element is provided so as to be rotatable about an optical axis along the optical illumination device.

18. An optical lighting device as recited in claim 17, wherein said lighting device comprises:

a1 st light flux conversion element disposed on an optical path of the illumination light, and configured to convert a light intensity distribution in a cross-sectional direction of the incident light into a zonal light intensity distribution different from the light intensity distribution;

and a2 nd beam conversion element which is replaceable with the 1 st beam conversion element, wherein the 2 nd beam conversion element converts a light intensity distribution in a cross-sectional direction of incident light into a multipolar light intensity distribution different from the light intensity distribution.

19. An exposure apparatus characterized by comprising:

the optical illumination device according to claim 8, wherein a predetermined pattern is exposed onto the photosensitive substrate by the optical illumination device.

20. An exposure method characterized by comprising:

the optical illumination device according to claim 8, wherein a predetermined pattern is exposed on the photosensitive substrate.

21. A method for manufacturing a device, comprising:

exposing a predetermined pattern on a photosensitive substrate by using the optical illumination device according to claim 8; and

and developing the exposed photosensitive substrate.

22. An exposure apparatus characterized by comprising:

the optical illumination device according to any one of claims 17 to 18, wherein a predetermined pattern is exposed onto the photosensitive substrate by the optical illumination device.

23. An exposure method characterized by comprising:

the optical illumination device according to any one of claims 17 to 18, wherein a predetermined pattern is exposed on a photosensitive substrate.

24. A method for manufacturing a device, comprising:

a step of exposing a predetermined pattern onto a photosensitive substrate using the optical illumination device according to any one of claims 17 to 18; and

and developing the exposed photosensitive substrate.