Patent Application
20090135396
1. Field
The present invention relates to illumination optical apparatus, exposure apparatus, and device manufacturing methods and, more particularly, to an illumination optical apparatus suitable for an exposure apparatus for manufacturing such devices as semiconductor devices, imaging devices, liquid-crystal display devices, and thin-film magnetic heads by a lithography process.
2. Description of the Related Art
The photolithography process for manufacturing the semiconductor devices and others is carried out using an exposure, apparatus for projecting a pattern image of a mask (or reticle) through a projection optical system onto a photosensitive substrate (a wafer, a glass plate, or the like coated with a photoresist) to effect an exposure thereof. The ordinary exposure apparatus is arranged to form a pattern of one kind in one shot area (unit exposure region) on the photosensitive substrate.
In contrast to it, a method proposed for improvement in throughput is a double exposure method of effecting exposures of patterns of two kinds in a superimposed state in one shot area on a photosensitive substrate to form one synthetic pattern (cf. Japanese Patent Application Laid-open No. 2000-21748).
It is important for the exposure apparatus of the double exposure method to individually illuminate, for example, regions on two masks separate from each other, e.g., to individually illuminate the regions under required illumination conditions according to characteristics of transfer patterns.
An object of the present invention is to provide an illumination optical apparatus capable of individually illuminating two regions separate from each other, under required illumination conditions. Another object of the present invention is to provide an exposure apparatus capable of performing an exposure of a fine pattern at high throughput on a photosensitive substrate by the double exposure method, using the illumination optical apparatus individually illuminating two regions separate from each other, under required illumination conditions.
A first embodiment of the present invention provides an illumination optical apparatus comprising: a first illumination system including a first illumination optical path and illuminating a first illumination region; and a second illumination system including a second illumination optical path independent of the first illumination optical path and illuminating a second illumination region,
wherein the first illumination system includes a first variable system which varies a shape or size of a light intensity distribution on an illumination pupil of the first illumination system,
wherein the second illumination system includes a second variable system which varies a shape or size of a light intensity distribution on an illumination pupil of fee second illumination system, and
wherein the first variable system and the second variable system vary the light intensity distribution on the illumination pupil of the first illumination system and the light intensity distribution on the illumination pupil of the second illumination system independently of each other.
A second embodiment of the present invention provides another illumination optical apparatus comprising: a first illumination system including a first illumination optical path and illuminating a first illumination region; and a second illumination system including a second illumination optical path independent of the first illumination optical path and illuminating a second illumination region,
wherein the first illumination system includes a first polarization setting unit which sets a polarization state of light to illuminate the first illumination region, to a desired polarization state,
wherein the second illumination system includes a second polarization setting unit which sets a polarization state of light to illuminate the second illumination region, to a desired polarization state, and
wherein the first polarization setting unit and the second polarization setting unit vary the polarization state of the light to illuminate the first illumination region and the polarization state of the light to illuminate the second illumination region, independently of each other,
the illumination optical apparatus further comprising a light splitting member which splits incident light into two beams, guides one of the two beams to the first illumination optical path, and guides the other beam to the second illumination optical path.
A third embodiment of the present invention provides an exposure apparatus comprising the illumination optical apparatus of the first aspect or the second aspect and performing an exposure of a pattern illuminated by the illumination optical apparatus, on a photosensitive substrate.
A embodiment aspect of the present invention provides a device manufacturing method comprising: effecting the exposure of the pattern on the photosensitive substrate, using the exposure apparatus of the third embodiment; developing the substrate in which said pattern has been transferred; forming a mask layer of a shape corresponding to the pattern on a surface of the photosensitive substrate; and processing the surface of the photosensitive substrate through the mask layer.
A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.
Embodiments of the present invention will be described on the basis of the accompanying drawings.
The light source 1 applicable herein can be, for example, an ArF excimer laser light source which supplies light with the wavelength of about 193 nm or a KrF excimer laser light source which supplies light with the wavelength of about 248 nm. A light beam emitted along the optical axis AX from the light source 1 is expanded into a beam of a required sectional shape by a shaping optical system 2 and the expanded beam is incident to a half mirror 3. The beam transmitted by the half mirror 3 is guided to a first illumination system which illuminates a first illumination region on a first mask M1. On the other hand, the beam reflected by the half mirror 3 is reflected by a path folding mirror 4 and then is guided to a second illumination system which illuminates a second illumination region on a second mask M2. The half mirror stated herein does not always have to be limited to one having a light quantity ratio of 1:1 in division of incident fight. In the present embodiment, the half mirror 3 for amplitude division of incident light may be replaced by a polarization beam splitter for polarization division of incident fight.
Since the first illumination system and the second illumination system have much the same basic configuration, the configurations and actions thereof will be described mainly with focus on the first illumination system. In the description thereof, the description of the second illumination system corresponding to the first illumination system will be given in parentheses. The first beam transmitted by the half mirror 3 and guided to the first illumination system (the second beam reflected by the half mirror 3 and guide to the second illumination system) travels through a first polarization setting unit 10 (second polarization setting unit 20) and a diffractive optical element 11 (21) to enter an afocal lens 12 (22). The diffractive optical element 11 (21) is arranged to be able to be set in or off an illumination optical path of the first illumination system (second illumination system) and is arranged to be replaceable with another diffractive optical element which forms a different light intensity distribution in its far field. The replacement of the diffractive optical element 11 (21) is performed by a driving unit (not shown) which operates based on a command from a control unit 5. For simplicity of description, it is assumed hereinafter that the diffractive optical element 11 arranged in the optical path of the first illumination system and the (diffractive optical element 21 arranged in the optical path of the second illumination system both are diffractive optical elements for annular illumination.
The first polarization setting unit 10 (second polarization setting unit 20) has the following elements arranged in order from the light entrance side: quarter wave plate 10a (20a) which is so arranged that the crystal optic axis thereof is rotatable around the optical axis AX1 (AX2) and which converts elliptically polarized light incident thereto into linearly polarized light; half wave plate 10b (20b) which is so arranged that the crystal optic axis thereof is rotatable around the optical axis AX and which changes the polarization direction of linearly polarized light incident thereto; depolarizer (depolarization element) 10c (20c) which can be set in or off the illumination optical path. The first polarization setting unit 10 (second polarization setting unit 20) has such a function that, in a state in which the depolarizer 10c (20c) is set off the illumination optical path, it converts the light from the fight source 1 into linearly polarized light with a desired polarization direction and makes the linearly polarized light incident to the diffractive optical element 11 (21) and, in a state in which the depolarizer 10c (20c) is set in the illumination optical path, it converts the light from the fight source 1 into substantially unpolarized light and makes the unpolarized fight incident to the diffractive optical element 11 (21). The first polarization setting unit 10 (second polarization setting unit 20) is controlled by a driving unit (not shown) which operates based on a command from the control unit 5. Concerning the detailed configuration and action of the polarization setting units, reference can be made, for example, to U.S. Pat. Published Application No. 2006/0055834. The teachings of U.S. Pat. Published Application No. 2004/0055834 are incorporated herein by reference.
The afocal lens 12 (22) is an afocal system (afocal optic) so set that a front focal point of a front lens unit 12a (22a) is approximately coincident with the position of the diffractive optical element 11 (21) and that a rear focal point of a rear lens unit 12b (22b) is approximately coincident with a position of a predetermined plane FP1 (FP2) indicated by a dashed line in the drawing. In general, a diffractive optical element is made by forming level differences with a pitch nearly equal to the wavelength of the exposure light (illumination light) in a substrate and has an action to diffract an incident beam at desired angles.
Specifically, the diffractive optical element 11 (21) for annular illumination has such a function that when a parallel beam with a rectangular cross section is incident thereto, it forms an annular light intensity distribution in its far field (or Fraunhofer diffraction region). Therefore, a nearly parallel beam incident to the diffractive optical element 11 (21) forms an annular light intensity distribution on the pupil plane of the afocal lens 12 (22) and is then emitted in an annular angle distribution from the afocal lens 12 (22). In the optical path between the front lens unit 12a (22a) and the rear lens unit 12b (22b), an axicon system 13 (23) is located on or near the pupil plane of the afocal lens 12 (22). For simplicity of the description, it is assumed hereinafter that the axicon system 13 in the first illumination system and the axicon system 23 in the second illumination system both are conical axicon systems. The configuration and action of the conical axicon system 13 (23) will be described later.
The beam passing through the afocal lens 12 (22) travels through a zoom lens (power-varying optical system) 14 (24) for variation in σ value (σ value= mask-side numerical aperture of the illumination system/mask-side numerical aperture of the projection optical system) and is then incident into a micro fly's eye lens (or fly's eye lens) 15 (25). The micro fly's eye lens 15 (25) is an optical element consisting of a large number of micro lenses with a positive refracting power arrayed vertically and horizontally and densely. In general, a micro fly's eye lens is made, for example, by forming the micro lens group in a plane-parallel plate by etching.
Each micro lens forming the micro fly's eye lens is smaller than each lens element forming the fly's eye lens. In the micro fly's eye lens, different from the fly's eye lens consisting of lens elements isolated from each other, the large number of micro lenses (micro refracting faces) are integrally formed without being isolated from each other. However, the micro fly's eye lens is an optical integrator of the same wavefront division type as the fly's eye lens, in that the lens elements with positive refracting power are arranged vertically and horizontally.
The position of the predetermined plane FP1 (FP2) is located near the front focal point of the zoom lens 14 (24) and the entrance surface of the micro fly's eye lens 15 (25) is located near the rear focal point of the zoom lens 14 (24). In other words, the zoom lens 14 (24) establishes a substantial Fourier transform relation between the predetermined plane FP1 (FP2) and the entrance surface of the micro fly's eye lens 15 (25) and, therefore, keeps the pupil plane of the afocal lens 12 (22) approximately optically conjugate with the entrance surface of the micro fly's eye lens 15 (25).
Therefore, for example, an annular illumination field (annular fight intensity distribution) centered on the optical axis AX1 (AX2) is formed on the entrance surface of the micro fly's eye lens 15 (25) as on the pupil plane of the afocal lens 12 (22). The overall shape of this annular illumination field similarly varies depending upon the focal length of the zoom lens 14 (24). Each micro lens forming the micro fly's eye lens 15 (25) has a rectangular cross section similar to the shape of the first illumination region (second illumination region) to be illuminated on the first mask M1 (second mask M2) (and, therefore, similar to the shape of an exposure region to be formed on the wafer W).
The beam incident into the micro fly's eye lens 15 (25) is two-dimensionally divided by the large number of micro lenses and forms a secondary light source with a light intensity distribution approximately identical with the illumination field formed by the incident beam, i.e., a secondary light source consisting of a substantial surface illuminant of an annular shape centered on the optical axis AX1 (AX2), on or near the rear focal plane of the micro fly's eye lens. Beams from the secondary light source formed on or near the rear focal plane of the micro fly's eye lens 15 (25) travel through a condenser optical system 16 (26) to superposedly illuminated a mask blind 17 (27).
In this way, a rectangular illumination field according to the shape and focal length of each micro lens forming the micro fly's eye lens 15 (25) is formed on the mask blind 17 (27) as an illumination field stop. Beams passing through a rectangular aperture (light transmitting portion) of the mask blind 17 (27) are subjected to a converging action of an imaging optical system 18 (28) and thereafter superposedly illuminate the first illumination region (second illumination region) on the first mask M1 (second mask M2) on which a predetermined pattern is formed. Namely, the imaging optical system 18 (28) forms an image of the rectangular aperture of the mask blind 17 (27) on the first mask M1 (second mask M2). The imaging optical system 18 (28) is composed of a front lens unit 18a (28a) and a rear lens unit 18b (28b) and a path folding mirror PM1 (PM2) is located between the two lens units 18a (28a) and 18b (28b). For clarity of the drawing, reference symbols 18, 28 are omitted from illustration.
The first mask M1 is held on a first mask stage MS1 and the second mask M2 on a second mask stage MS2. More specifically, the second mask M2 is located with a spacing along the Y-direction from the first mask M1 and at the same height as the first mask M1 along the Z-direction. A first beam passing through the first illumination region on the first mask M1 and a second beam passing through the second illumination region on the second mask M2 travel through a so-called double-headed projection optical system PL to form a pattern image of the first mask M1 and a pattern image of the second mask M2 on the wafer (photosensitive substrate) W held on a wafer stage WS. The double-headed projection optical system PL is an optical system having two effective view fields spaced from each other, and one effective image region. The first embodiment, as schematically shown in
The first beam, which formed the annular light intensity distribution on the rear focal plane of the micro fly's eye lens 15 or on the illumination pupil (illumination pupil of the first illumination system) near it, forms the first illumination region IR1 of a rectangular shape elongated in the Y-direction on the first mask M1, as shown in
Namely, a pattern corresponding to the first illumination region IR1 is annularly illuminated in a pattern region PA1 on the first mask M1, while a pattern corresponding to the second illumination region IR2 is annularly illuminated in a pattern region PA2 on the second mask M2. In this manner, as shown in
In the first embodiment, while the first mask M1, the second mask M2, and the wafer W are synchronously moved along the X-direction with respect to the projection optical system PL, one synthetic pattern is formed in one shot area on the wafer W by superimposed scanning exposures of the pattern of the first mask M1 and the pattern of the second mask M2. By two-dimensionally stepping the wafer W along the XY plane with respect to the projection optical system PL and repeating the above-described superimposed scanning exposures, the synthetic pattern of the pattern of the first mask M1 and the pattern of the second mask M2 is sequentially formed in each of shot areas on the wafer W.
The conical axicon system 13 (23) is composed of the following elements arranged in order from the light source side (light entrance side): first prism member 13a (23a) with a plane on the light source side and with a refracting surface of a concave conical shape on the mask side (light exit side); second prism member 13b (23b) with a plane on the mask side and with a refracting surface of a convex conical shape on the light source side. The concave conical refracting surface of the first prism member 13a (23a) and the convex conical refracting surface of the second prism member 13b (23b) are complementarily formed so as to be able to contact each other. At least one of the first prism member 13a (23a) and the second prism member 13b (23b) is arranged as movable along the optical axis AX1 (AX2) so that the spacing can be varied between the concave conical refracting surface of the first prism member 13a (23a) and the convex conical refracting surface of the second prism member 13b (23b). The variation in the spacing along the optical axis AX1 (AX2) between the first prism member 13a (23a) and the second prism member 13b (23b) in the conical axicon system 13 (23) is implemented by a driving unit (not shown) which operates based on a command from the control unit 5.
The action of the conical axicon system 13 (23) and the action of the zoom lens 14 (24) will be described below with focus on the annular secondary light source. In a state in which the concave conical refracting surface of the first prism member 13a (23a) and the convex conical refracting surface of the second prism member 13b (23b) contact each other, the conical axicon system 13 (23) functions as a plane-parallel plate and causes no effect on the annular secondary light source formed. However, as separation is effected between the concave conical refracting surface of the first prism member 13a (23a) and the convex conical refracting surface of the second prism member 13b (23b), the outside diameter (inside diameter) of the annular secondary light source varies while the width of the annular secondary light source (half of a difference between the outside diameter and the inside diameter of the annular secondary light source) is kept constant. Namely, the separation results in varying the annular ratio (inside diameter/outside diameter) and the size (outside diameter) of the annular secondary light source.
The zoom lens 14 (24) has a plurality of optical elements movable along the optical axis AX1 (AX2) and has a function to similarly (isotropically) enlarge or reduce the overall shape of the annular secondary light source. For example, when the focal length of the zoom lens 14 (24) is increased from a minimum value to a predetermined value, the overall shape of the annular secondary light source is similarly enlarged. In other words, the width and size (outside diameter) of the secondary light source both vary, without change in the annular ratio of the annular secondary light source, by virtue of the action of the zoom lens 14 (24). The focal length of the zoom lens 14 (24) is changed by a driving unit (not shown) which operates based on a command from the control unit 5. In this manner, the annular ratio and size (outside diameter) of the annular secondary light source can be controlled by the actions of the conical axicon system 13 (23) and the zoom lens 14 (24).
When another diffractive optical element for multi-pole illumination (not shown) is set instead of the diffractive optical element 11 (21) for annular illumination in the illumination optical path, multi-pole illumination (dipolar illumination, tripolar illumination, quadrupolar illumination, pentapolar illumination, or the like) can be implemented. Specifically, for example, the diffractive optical element for dipolar illumination (or for quadrupolar illumination) has such a function that when a parallel beam with a rectangular cross section is incident thereto, it forms a light intensity distribution of a dipolar shape (or quadrupolar shape) in its far field. Therefore, beams passing through the diffractive optical element for dipolar illumination (or for quadrupolar illumination) form, for example, an illumination field pattern of a dipolar shape (or quadrupolar shape) consisting of two (or four) illumination fields symmetric with respect to the optical axis AX, on the entrance surface of the micro fly's eye lens 15 (25). As a result, the secondary light source of the same dipolar shape (or quadrupolar shape) as the illumination field pattern formed on the entrance surface of the micro fly's eye lens is formed on or near the rear focal plane of the micro fly's eye lens 15 (25).
When a diffractive optical element for circular illumination (not shown) is set instead of the diffractive optical element 11 (21) for annular illumination in the illumination optical path, ordinary circular illumination can be implemented. The diffractive optical element for circular illumination has such a function that when a parallel beam with a rectangular cross section is incident thereto, it forms a circular light intensity distribution in its far field. Therefore, a beam passing through the diffractive optical element for circular illumination forms, for example, an illumination field of a circular shape centered on the optical axis AX, on the entrance surface of the micro fly's eye lens 15 (25). As a result, the secondary light source of the same circular shape as the illumination field formed on the entrance surface of the micro fly's eye lens is formed on or near the rear focal plane of the micro fly's eye lens 15 (25).
For example, in the case of the quadrupolar illumination, the control unit 5 sets a pyramid axicon system (not shown), instead of the conical axicon system 13 (23) (or in addition to the conical axicon system 13 (23)), on or near the pupil plane of the afocal lens 12 (22). For example, in the case of the dipolar illumination, the control unit 5 sets a V-groove axicon system (not shown), instead of the conical axicon system 13 (23) (or in addition to the conical axicon system 13 (23)), on or near the pupil plane of the afocal lens 12 (22). The pyramid axicon system has refracting surfaces of the shape corresponding to side faces of a pyramid centered on the optical axis, and the V-groove axicon system has refracting surfaces of a V-shaped cross section approximately symmetric with respect to a predetermined axis passing the optical axis. Concerning the configurations and actions of the pyramid axicon system and the V-groove axicon system, reference can be made, for example, to Japanese Patent Application Laid-open No. 2002-231619 and U.S. Pat. Published Application No. 2004/0263817 corresponding thereto. The teachings of U.S. Pat. Published Application No. 2004/263817 are incorporated herein by reference.
In the first embodiment, the plurality of interchangeable diffractive optical elements including the diffractive optical element 11 constitute the first shape varying system which varies the shape of the light intensity distribution on the illumination pupil of the first illumination system, and the plurality of interchangeable diffractive optical elements including the diffractive optical element 21 constitute the second shape varying system which varies the shape of the light intensity distribution on the illumination pupil of the second illumination system. Similarly, the conical axicon system 13, the pyramid axicon system, and the V-groove axicon system constitute the first shape varying system which varies the shape of the light intensity distribution on the illumination pupil of the first illumination system, and the conical axicon system 23, the pyramid axicon system, and the V-groove axicon system constitute the second shape varying system which varies the shape of the fight intensity distribution on the illumination pupil of the second illumination system. Furthermore, the zoom lens 14 constitutes the first power varying system which varies the size of the fight intensity distribution on the illumination pupil of the first illumination system, and the zoom lens 24 constitutes the second power varying system which varies the size of the light intensity distribution on the illumination pupil of the second illumination system.
In the first embodiment, exposure information of the photosensitive substrate, i.e., information about various masks to be sequentially used for exposures according to the step-and-scan method, is fed through an input unit 6 like a keyboard to the control unit 5. Based on the information from the input unit 6, the control unit 5 independently controls the replacement and arrangement of the diffractive optical element in the first illumination system and the replacement and arrangement of the diffractive optical element in the second illumination system. In addition, based on the information from the input unit 6, the control unit 5 also independently controls, the spacing adjustment of the axicon system in the first illumination system and the spacing adjustment of the axicon system in the second illumination system. Furthermore, based on the information from the input unit 6, the control unit 5 also independently controls the adjustment of the focal length of the zoom lens 14 in the first illumination system and the adjustment of the focal length of the zoom lens 24 in the second illumination system. In this manner, the first shape varying system and first power varying system and the second shape varying system and second power varying system vary the light intensity distribution on the illumination pupil of the first illumination system and the light intensity distribution on the illumination pupil of the second illumination system, independently of each other.
Yet furthermore, based on the information from the input unit 6, the control unit 5 independently controls the first polarization setting unit 10 which sets the polarization state of the light to illuminate the first illumination region IR1 on the first mask M1, to a desired polarization state and the second polarization setting unit 20 which sets the polarization state of the light to illuminate the second illumination region IR2 on the second mask M2, to a desired polarization state. In this manner, the first polarization setting unit 10 and the second polarization setting unit 20 vary the polarization state of the light to illuminate the first illumination region IR1 on the first mask M1 and the polarization state of the light to illuminate the second illumination region IR2 on the second mask M2, independently of each other.
As described above, the illumination optical apparatus of the first embodiment is able to individually illuminate the first illumination region IR1 on the first mask M1 and the second illumination region IR2 on the second mask M2, under required illumination conditions with the shape or size of the light intensity distribution on the illumination pupil, the polarization state of illumination light, or the like as a parameter.
Since in the exposure apparatus of the first embodiment the polarization setting units 10, 20 are arranged in the respective optical paths divided by the half mirror 3, the first illumination region IR1 on the first mask M1 and the second illumination region IR2 on the second mask M2 can be individually illuminated under optional polarization states even when there is a polarization characteristic of the half mirror 3 (e.g., such a characteristic that polarization states are different from each other between the beams divided by the half mirror 3). When a polarization beam splitter is used in place of the half mirror 3, this effect will appear prominent.
As a consequence, the exposure apparatus of the first embodiment is able to perform the exposures of the micro patterns of the two masks M1 and M2 with high accuracy and high throughput on the wafer W by the double exposure method, using the illumination optical apparatus individually illuminating the two illumination regions IR1 and IR2 spaced from each other, under the required illumination conditions.
An example of the effect achieved based on the configuration of the first embodiment will be described below with reference to
Specifically, for example, when the pattern on the first mask M1 is dominated by a unidirectional pattern elongated along the Y-direction, X-directional dipolar illumination as shown in
Similarly, for example, when the pattern on the second mask M2 is dominated by a unidirectional pattern elongated along the X-direction, Z-directional dipolar illumination as shown in
In the above-described first embodiment, the first mask M1 and the second mask M2 are located at the same height along the Z-direction. However, without having to be limited to this, it is also possible to locate the first mask M1 and the second mask M2 at mutually different heights along the Z-direction, as shown in a first modification example of
In the above-described first embodiment, the polarization state of the light to illuminate the first illumination region IR1 on the first mask M1 is set in the desired polarization state by the action of the first polarization setting unit 10 in the first illumination system, and the polarization state of the light to illuminate the second illumination region IR2 on the second mask M2 is set in the desired polarization state by the action of the second polarization setting unit 20 in the second illumination system. However, without having to be limited to this, it is also possible to adopt a modification, example wherein a polarization beam splitter 3A is located instead of the half mirror 3 and wherein the installation of the first polarization setting unit 10 and the second polarization setting unit 20 is omitted, as shown in
In the third modification example of
When the depolarizers 3C and 3D both are set off the illumination optical path, the first illumination region IR1 on the first mask M1 is illuminated with light in a linearly polarized state with the polarization direction along the Y-direction and the second illumination region IR2 on the second mask M2 is illuminated with light in a linearly polarized state with the polarization direction along the X-direction. When only the depolarizer 3C is set in the illumination optical path, the first illumination region IR1 is illuminated with the light in the unpolarized state and the second illumination region IR2 is illuminated with the light in the linearly polarized state with the polarization direction along the X-direction. When only the depolarizer 3D is set in the illumination optical path, the first illumination region IR1 is illuminated with the light in the linearly polarized state with the polarization direction along the Y-direction and the second illumination region IR2 is illuminated with the light in the unpolarized state. As a result, the first illumination region IR1 and the second illumination region IR2 are illuminated with the light beams in the mutually different polarization states and, therefore, the first illumination region IR1 and the second illumination region IR2 can be illuminated with light in their respective desired polarization states.
In the third modification example of
In the fourth modification example of
The common power-varying optical system ZL is an optical member corresponding to the zoom lenses 14, 24 in
On the other hand, when the pair of diffractive optical element DO and micro fly's eye lens MF are set in the second posture, the light reflected by the polarization beam splitter 3A passes through the second shutter SH2 and then travels through the diffractive optical element DO, common power-varying optical system ZL, micro fly's eye lens MF, common condenser optical system CL, mask blind 17, etc. to illuminate the first illumination region IR1 on the first mask M1. At this time, the first shutter SH1 blocks passage of light to avoid occurrence of harmful light.
In the fourth modification example of
In the fourth modification example of
It is also possible to apply the major configuration of the fourth modification example of
In the second embodiment of
In the second embodiment, the light from the light source 1 is converted into a required sectional shape by the shaping optical system 2, the light is then converted into light in an unpolarized state by the depolarizer 31, and thereafter the unpolarized light is incident to the half mirror 3. The light transmitted by the half mirror 3 is guided to the first illumination system and then travels through the diffractive optical element 11 and afocal lens 41 to enter the rod integrator 42. On the other hand, the light reflected by the half mirror 3 is reflected by the path folding mirror 4 to be guided to the second illumination system, and the light travels through the diffractive optical element 21 and afocal lens 51 to enter the rod integrator 52. The afocal lens 41 (51) has a front lens unit 41a (51a) and a rear lens unit 41b (51b). The rear focal point of the front lens unit 41a (51a) is approximately coincident with the front focal point of the rear lens unit 41b (51b) and the front lens unit 41a (51a) and the rear lens unit 41b (51b) constitute an afocal optical system as a whole.
The rod integrators 42, 52 are rods of the internal reflection type made of an optical material, for example, like silica or fluorite and form light source images as many as the number of internal reflections along a plane passing a converging point and being parallel to the entrance surface of the rod by making use of total reflections on the boundary surface between the inside and the outside, i.e., the internal surface. Most of the light source images formed are virtual images, but only the light source image at the center (converging point) is a real image. Namely, the beam incident into the rod integrator 42, 52 is divided in angle directions by internal reflections to form a secondary light source consisting of a large number of tight source images along the plane passing the converging point and being parallel to the entrance surface of the rod integrator. Beams from the secondary light source formed on the entrance side by the rod integrator 42, 52 are superposed on the exit surface thereof and then are incident to the imaging optical system 18, 28.
Namely, the beams from the rod integrator 42 in the first illumination system travel through the imaging optical system 18 to illuminate the first illumination region IR1 oh the first mask ML
When the first polarizing plate 43 is inserted in the optical path between the front lens unit 18a and the rear lens unit 18b of the imaging optical system 18, for example, only the light in the linearly polarized state with the polarization direction along the Z-direction passes through the first polarizing plate 43 and the first illumination region IR1 is illuminated with the light in the linearly polarized state with the polarization direction along the Y-direction. On the other hand, when the first polarizing plate 43 is retracted from the optical path of the imaging optical system 18, the first illumination region IR1 is illuminated with the light in the unpolarized state.
Similarly, the beams from the rod integrator 52 in the second illumination system travel through the imaging optical system 28 to illuminate the second illumination region IR2 on the second mask M2. When the second polarizing plate 53 is inserted in the optical path between the front lens unit 28a and the rear lens unit 28b of the imaging optical system 28, for example, only the light in the linearly polarized state with the polarization direction along the X-direction passes through the second polarizing plate 53 and the second illumination region IR2 is illuminated with the light in the linearly polarized state with the polarization direction along the X-direction. On the other hand, when the second polarizing plate 53 is retracted from the optical path of the imaging optical system 28, the second illumination region IR2 is illuminated with the light in the unpolarized state.
The illumination optical apparatus of the second embodiment is also able to individually illuminate the first illumination region IR1 and the second illumination region IR2 under the required illumination conditions with the shape or size of the light intensity distribution on the illumination pupil, the polarization state of illumination light, or the like as a parameter, as in the first embodiment. When the aforementioned axicon system (conical axicon system, pyramid axicon system, V-groove axicon system, or the like) is arranged in the optical path of the front lens unit 41a (51a), the shape of the light intensity distribution formed on the illumination pupil of the first illumination system (second illumination system) can be varied. When the afocal lens 41 (51) is constructed as an afocal zoom lens, the size of the light intensity distribution formed on the illumination pupil of the first illumination system (second illumination system) can be varied.
In the above-described second embodiment, the first mask M1 and the second mask M2 are located at the same height along the Z-direction. However, without having to be limited to this, the first mask M1 and the second mask M2 can also be located at mutually different heights along the Z-direction, as shown in a fifth modification example of
In the above-described second embodiment, the half mirror 3 is used as a light splitting member, the light from the common light source 1 is split into two beams by the half mirror 3, one of the split beams is guided to the first illumination system, and the other split light is guided to the second illumination system. However, without having to be limited to this, it is also possible to adopt a modification example wherein a polarization beam splitter 3A is arranged in place of the half mirror 3, as shown in
In the above-described second embodiment, one rod integrator 42 is arranged in the first illumination system and one rod integrator 52 in the second illumination system. In other words, the light beam from the common light source 1 is split before the rod integrators 42, 52, one of the split beams is made incident to one rod integrator 42, and the other split beam is made incident to the other rod integrator 52. However, without having to be limited to this, it is also possible to implement the splitting of the beam in a rod integrator by a combination of three rods 61a, 61b, 61c and a polarization beam splitter 62 as shown in an eighth modification example of
In the eighth modification example of
In the ninth modification example of
The above-described first embodiment and second embodiment adopt the configuration wherein the beam incident along the optical path of the first illumination system is reflected by the path folding mirror PM1 to be guided to the first mask M1 and wherein the beam incident along the optical path of the second illumination system independent of the first illumination system is reflected by the path folding mirror PM2 to be guided to the second mask M2. However, without having to be limited to this, it is also possible to adopt a configuration wherein a beam incident along a common optical path is split by a half mirror 66, light transmitted by the half mirror 66 is reflected by a path folding mirror 67 to be guided to the first mask M1, and light reflected by the half mirror 66 is guided to the second mask M2, as shown in a tenth modification example of
Incidentally, when coherency is high between two types of illumination states during simultaneous execution of double exposures, the pattern formed on the wafer is likely to be affected by interference of light. Therefore, the temporal coherency of the double exposures can be reduced by adopting a configuration as shown in an eleventh modification example of
In a case where two laser light sources 73, 74 with mutually different polarization directions of emitted light and two exposure device bodies 75, 76 are combined through a half mirror 77 as in a twelfth modification example of
In each of the above-described embodiments, the present invention was explained in association with the double exposures to form one synthetic pattern by superimposing two types of patterns in a single shot area on the photosensitive substrate (wafer). However, without having to be limited to this, the present invention can also be applied similarly to multiple exposures to form one synthetic pattern by superimposing three or more types of patterns in a single shot area on the photosensitive substrate. In each of the above embodiments, one synthetic pattern is formed by the scanning exposures of the first pattern and the second pattern in the superimposed state in one shot area on the photosensitive substrate. However, without having to be limited to this, it is also possible to adopt a method of perforating a scanning exposure or one-shot exposure of the first pattern in a first shot area on the photosensitive substrate and then performing a scanning exposure or one-shot exposure of the second pattern in a second shot area on the photosensitive substrate.
In each of the above embodiments, the pattern image of the first illumination region of the first mask and the pattern image of the second illumination region of the second mask are formed on the photosensitive substrate. However, without having to be limited to this, it is also possible to form pattern images of two illumination regions of a single mask on the photosensitive substrate. In each of the above embodiments, the pattern image of the first illumination region of the first mask and the pattern image of the second illumination region of the second mask are formed in alignment on the photosensitive substrate. However, without having to be limited to it, it is also possible to form the pattern image of the first illumination region of the first mask and the pattern image of the second illumination region of the second mask in parallel on the photosensitive substrate. In this case, the projection optical system PL applicable can be, for example, a double-headed projection optical system PL of another type consisting of a refracting system and folding mirrors as shown in
In the aforementioned embodiments, the masks can be replaced with a pattern forming device that forms a predetermined pattern based on predetermined electronic data. Use of this pattern forming device minimizes the effect on synchronization accuracy even when the pattern surface is vertical. The pattern forming device applicable herein can be, for example, a DMD (Digital Micromirror Device) including a plurality of reflective elements driven based on predetermined electronic data. The exposure apparatus with the DMD is disclosed, for example, in Japanese Patent Applications Laid-open No. 8-313842 and Laid-open No. 2004-304135. Besides the non-emission type reflective spatial optical modulators like the DMD, it is also possible to use a transmissive spatial optical modulator or a self-emission type image display device.
In the foregoing embodiments, it is also possible to apply a technique of filling the optical path between the projection optical system and the photosensitive substrate with a medium having; the refractive index larger than 1.1 (typically, a liquid), so called a liquid immersion method. In this case, one of the following methods can be adopted as the technique of filling the optical path between the projection optical system and the photosensitive substrate with the liquid: the technique of locally filling the optical path with the liquid as disclosed in International Publication WO99/49504; the technique of holding the substrate as an object to be exposed, by a stage and moving the stage in a liquid bath as disclosed in Japanese Patent Application Laid-open No. 6-124873; the technique of forming a liquid bath of a predetermined depth on a stage and holding the substrate in the bath as disclosed in Japanese Patent Application Laid-open No. 10-303114. The teachings of International Publication WO99/49504, and Japanese Patent Application Laid-open Nos. 6-124873 and 10-303114 are incorporated herein by reference.
The exposure apparatus of the foregoing embodiments are manufactured by assembling various sub-systems containing their respective components as set forth in the scope of claims in the present application, so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. For ensuring these various accuracies, the following adjustments are carried out before and after the assembling: adjustment for achieving the optical accuracy for various optical systems; adjustment for achieving the mechanical accuracy for various mechanical systems; adjustment for achieving the electrical accuracy for various electrical systems. The assembling steps from the various sub-systems into the exposure apparatus include mechanical connections, wire connections of electric circuits, pipe connections of pneumatic circuits, etc, between the various sub-systems. It is needless to mention that there are assembling steps of the individual sub-systems, before the assembling steps from the various sub-systems into the exposure apparatus. After completion of the assembling steps from the various sub-systems into the exposure apparatus, overall adjustment is carried out to ensure various accuracies as the entire exposure apparatus. The manufacture of exposure apparatus is desirably performed in a clean room in which the temperature, cleanliness, etc. are controlled.
The exposure apparatus according to the above-described embodiments can be used to manufacture micro devices (semiconductor devices, imaging devices, liquid-crystal display devices, thin-film magnetic heads, etc.) through a process of illuminating masks (reticles) by the illumination optical apparatus (illumination block) and effecting exposures of transfer patterns formed on the masks, on a photosensitive substrate by use of the projection optical system (exposure block). The below will describe an example of a method of manufacturing semiconductor devices as micro devices by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate by means of the exposure apparatus of the above embodiments, with reference to the flowchart of
The first block 301 in
Thereafter, devices such as semiconductor devices are manufactured through blocks including formation of circuit patterns in upper layers. The above-described semiconductor device manufacturing method permits us to obtain the semiconductor devices with extremely fine circuit patterns at high throughput. The blocks 301-305 are arranged to perform the respective blocks of deposition of metal on the wafer, application of the resist onto the metal film, exposure, development, and etching, but it is needless to mention that the process may be modified as follows: prior to these blocks, an oxide film of silicon is formed on the wafer, a resist is then applied onto the silicon oxide film, and thereafter the blocks of exposure, development, and etching are carried out.
The exposure apparatus of the above embodiments can also be used to manufacture a liquid-crystal display device as a micro device by forming predetermined patterns (circuit pattern, electrode pattern, etc.) on plates (glass substrates). An example of a method in this case will be described below with reference to the flowchart of
The next color filter forming block 402 is to form a color filter in which a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arrayed in a matrix pattern or in which sets of filters of three stripes of R, Q, and B are arrayed in the horizontal scan line direction. After the color filter forming block 402, a cell assembling block 403 is executed. The cell assembling block 403 is to assemble a liquid crystal panel (liquid crystal cell) using the substrate with the predetermined pattern obtained in the pattern forming block 401, the color filter obtained in the color filter forming block 402, and others.
In the cell assembling block 403, the liquid crystal panel (liquid crystal cell) is manufactured, for example, by pouring a liquid crystal into between the substrate with the predetermined pattern obtained in the pattern forming block 401 and the color filter obtained in the color filter forming block 402. The subsequent module assembling block 404 is to attach various components such as electric circuits and backlights for display operation of the assembled liquid crystal panel (liquid crystal cell) to complete the liquid-crystal display device. The above-described manufacturing method of the liquid-crystal display device permits us to obtain the liquid-crystal display device with extremely fine circuit patterns at high throughput.
The illumination optical apparatus according to the one embodiment of the present invention is configured to vary the shape or size of the light intensity distribution on the illumination pupil of the first illumination system illuminating the first illumination region and the shape or size of the light intensity distribution on the illumination pupil of the second illumination system illuminating the second illumination region, independently of each other. As a consequence, the illumination optical apparatus is able to individually illuminate the first illumination region and the second illumination region separate from each other, under the required illumination conditions with the shape or size of the light intensity distribution on the illumination pupil as a parameter.
In the illumination optical apparatus according to the another embodiment of the present invention, the first polarization setting unit setting the polarization state of the light to illuminate the first illumination region and the second polarization setting unit setting the polarization state of the light to illuminate the second illumination region are arranged in the respective optical paths split by the light splitting member. As a consequence, the illumination optical apparatus is able to individually illuminate the first illumination region and the second illumination region separate from each other, in optional polarization states even when there is a polarization characteristic of the light splitting member.
As a consequence, the exposure apparatus of the embodiment of the present invention is able to perform the exposure of the fine pattern at high throughput on the photosensitive substrate by the double exposure method and, therefore, to manufacture good devices at high throughput, using the illumination optical apparatus individually illuminating the two mutually separate regions under the required illumination conditions.
Each of the aforementioned embodiments used the KrF excimer laser light source or the ArF excimer laser light source as the light source, but the present invention does not have to be limited to these: the present invention can also be applied to the exposure apparatus using any other appropriate light source, e.g., an F2 laser light source. Each of the aforementioned embodiments described the present invention using the example of illumination optical apparatus mounted on the exposure apparatus and adapted to illuminate the masks, but it is apparent that the present invention can be applied to the generally-used illumination optical apparatus for illuminating any illumination target surface other than the masks. As described above, the present invention is not limited to the above-described embodiments but can be carried out in various configurations without departing from the spirit and scope of the present invention. Also, the components disclosed in the embodiments may be assembled in any combination for embodying the present invention. For example, some of the components may be omitted from all components disclosed in the embodiments. Further, components in different embodiments may be appropriately combined.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-191348 | Jul 2006 | JP | national |
This is a continuation application of a PCT application No. PCT/JP2007/063644 filed on Jul. 9, 2007, claiming the benefit of priorities from Japanese Patent application No. 2006-191348 filed on Jul. 12, 2006, and incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2007/063644 | Jul 2007 | US |
| Child | 12244868 | US |
