JP2003043223A - Beam splitter and wave plate made of crystal material, and optical device, exposure device and inspection device equipped with the crystal optical parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a beam splitter which can maintain preferable optical performance without having substantial influences of birefringence even when a birefringent crystal material such as fluorite is used. SOLUTION: The beam splitter is made of a crystal belonging to the cubic system. The incident direction of a beam to the beam splitter and the exiting direction of the beam from the beam splitter are preliminarily controlled to be almost coincident with the crystalline axis [100] of the crystal or with a crystalline axis optically equivalent to the above crystalline axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam splitter and a wave plate made of a crystalline material, and an optical device provided with these crystalline optical components, and particularly to photolithography of microdevices such as semiconductor elements and liquid crystal display elements. The present invention relates to an optical component suitable for an optical system related to an exposure apparatus used when manufacturing in a process.

[0002]

2. Description of the Related Art When forming a fine pattern of an electronic device (microdevice) such as a semiconductor integrated circuit or a liquid crystal display, a photomask (also called a reticle) is formed by proportionally enlarging a pattern to be formed by about 4 to 5 times. The pattern is subjected to reduction exposure transfer onto a photosensitive substrate (substrate to be exposed) such as a wafer using a projection exposure apparatus. In this type of projection exposure apparatus, the exposure wavelength thereof continues to shift to the short wavelength side in order to cope with the miniaturization of semiconductor integrated circuits.

At present, the exposure wavelength is 248 nm of a KrF excimer laser, but the shorter wavelength Ar is used.
193 nm of the F excimer laser is also in the stage of practical application. Further, a projection exposure apparatus using a light source that supplies light in a wavelength band called a so-called vacuum ultraviolet region, such as an F ₂ laser having a wavelength of 157 nm and an Ar ₂ laser having a wavelength of 126 nm, has been proposed. Further, since high resolution can be achieved by increasing the numerical aperture (NA) of the projection optical system, not only development for shortening the exposure wavelength but also development of a projection optical system having a larger numerical aperture is possible. Has been done.

In this type of projection optical system, the residual aberration must be extremely small in order to realize high resolution. For that purpose, it is needless to say that an inspection optical system for measuring the residual aberration of the projection optical system is necessary, and that the inspection optical system itself is required to have the residual aberration extremely suppressed. .
Further, in order to improve the performance of a semiconductor integrated circuit, particularly to improve the operating speed, dimensional uniformity of patterns in the circuit is extremely important. Since it is necessary to make the exposure amount uniform in order to make the pattern size uniform, an extremely high illuminance uniformity is required for the illumination optical system that supplies the illumination light to the reticle.

As described above, there is a limit to optical materials (lens materials) having good transmittance and uniformity for exposure light in the ultraviolet region having a short wavelength. In a projection optical system using an ArF excimer laser as a light source, synthetic quartz glass can be used as a lens material, but one type of lens material cannot satisfactorily correct chromatic aberration. Calcium crystals (fluorite) are used. On the other hand, F ₂
In a projection optical system using a laser as a light source, usable lens materials are practically limited to calcium fluoride crystals (fluorite). The material of the lens and the material of the transmissive optical component that can be used in the inspection optical system and the illumination optical system are also limited to fluorite.

[0006]

Recently, it has been reported that birefringence occurs even in cubic calcium fluoride crystals (fluorite) with respect to ultraviolet rays having such a short wavelength. In an ultra-high precision optical system such as a projection optical system used for manufacturing an electronic device, the aberration caused by the birefringence of the lens material is fatal, and the lens configuration in which the influence of the birefringence is substantially avoided. And the adoption of lens design is essential. Also, for the inspection optical system for measuring the residual aberration of the projection optical system, it is essential to use optical components and lens configurations that substantially avoid the influence of birefringence.

The present invention has been made in view of the above-mentioned problems, and even if a birefringent crystal material such as fluorite is used, it is possible to obtain good optical properties without being substantially affected by birefringence. An object of the present invention is to provide a beam splitter and a wave plate capable of ensuring performance. It is another object of the present invention to provide an optical device including crystal optical components such as a beam splitter and a wave plate which have good optical performance without being substantially affected by birefringence.

[0008]

In order to solve the above-mentioned problems, in the first invention of the present invention, in a beam splitter formed of a crystal belonging to a cubic system, the incident direction of a light beam to the beam splitter and the above-mentioned The emission direction of the light beam from the beam splitter is the crystal axis [10] of the crystal.
[0] or a crystal axis that is substantially equivalent to the crystal axis that is optically equivalent to the crystal axis.

According to a second aspect of the present invention, in a beam splitter formed of a crystal belonging to a cubic system, the beam splitter has a pair of prism members having a triangular prism shape, and one of the prism members transmits a light beam passing therethrough. Is set so as to substantially coincide with the crystal axis [100] of the crystal or a crystal axis optically equivalent to the crystal axis, and in the other prism member, the traveling direction of the light flux passing therethrough is the crystal of the crystal. Provided is a beam splitter, which is set so as to substantially coincide with an axis [111] or a crystal axis optically equivalent to the crystal axis.

According to a preferred aspect of the first invention or the second invention, the beam splitter is a polarization beam splitter. Further, the crystal is preferably a calcium fluoride crystal or a barium fluoride crystal.

According to a third aspect of the present invention, in a wave plate formed of a crystal belonging to a cubic system, the traveling direction of a light beam passing through the wave plate is the crystal axis [110] of the crystal or the crystal axis. Provided is a wave plate, which is set so as to substantially coincide with an optically equivalent crystal axis.

According to a preferred aspect of the third aspect of the present invention, the thickness is about 6 cm along the traveling direction of the luminous flux, and the thickness is about 157.
It functions as a quarter-wave plate for a light beam having a wavelength of nm. Alternatively, about 12 along the traveling direction of the light flux.
It preferably has a thickness of cm and functions as a half-wave plate for a light beam having a wavelength of about 157 nm.

According to a preferred aspect of the third invention,
It has an incident surface that is substantially perpendicular to the traveling direction of the light flux, and an exit surface that is substantially inclined with respect to a surface that is perpendicular to the traveling direction of the light flux. Further, the crystal is preferably a calcium fluoride crystal or a barium fluoride crystal.

According to a fourth aspect of the present invention, there is provided an optical device comprising a crystal optical component of at least one of the beam splitter according to the first aspect or the second aspect and the wave plate according to the third aspect. To do.

A fifth invention of the present invention provides an illumination optical system characterized in that the wavelength plate according to any one of the third invention is arranged in the optical path of the illumination light.

According to a sixth aspect of the present invention, there is provided an illumination optical system according to the fifth aspect for illuminating a mask and a projection optical system for forming an image of a pattern formed on the mask on a photosensitive substrate. Provided is an exposure apparatus characterized by being provided.

According to a seventh aspect of the present invention, in an inspection device for inspecting a projection optical system for forming an image of a pattern formed on a mask on a photosensitive substrate, the projection optical system is irradiated with inspection light. An irradiation optical system,
There is provided an inspection device comprising the optical device of the fourth invention.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing a configuration of an inspection device including a crystal optical component according to an embodiment of the present invention. This inspection device measures, for example, the wavefront aberration of the optical system under test. 2 is a diagram schematically showing the configuration of an exposure apparatus having a projection optical system as the test optical system of FIG. First, the configuration and operation of the exposure apparatus will be described with reference to FIG.

The exposure apparatus shown in FIG. 2 includes a light source 21 such as an ArF excimer laser or an F ₂ laser. The light flux supplied from the light source 21 is guided to the illumination optical system 23 via the light transmission system 22. Illumination optical system 23
Is composed of the folding mirrors 23a and 23b shown in the figure, an optical integrator (illuminance equalizing element) not shown, etc., and illuminates the reticle (mask) 33 with a substantially uniform illuminance. The reticle 33 is held by the reticle holder 24 by, for example, vacuum suction, and is held by the reticle stage 25.
It is configured to be movable by the action of.

The light flux transmitted through the reticle 33 is condensed via the projection optical system 31 and forms a projected image of the pattern on the reticle 33 on a photosensitive substrate such as a semiconductor wafer 32. The wafer 32 is also held by the wafer holder 27 by vacuum suction, for example, and is movable by the action of the wafer stage 28. Thus, the wafer 3
By performing batch exposure while moving 2 in steps,
The pattern projection image of the reticle 33 can be sequentially transferred to each exposure area of the wafer 32.

Further, the reticle 3 is attached to the projection optical system 31.
It is also possible to sequentially transfer the pattern projection image of the reticle 33 to each exposure region of the wafer 32 by performing scanning exposure (scan exposure) while moving the wafer 3 and the wafer 32 relatively. When exposing a circuit pattern to an actual electronic device, it is necessary to accurately align and expose the pattern of the next step on the pattern formed in the previous step. An alignment microscope 30 for accurately detecting the position of the position detection mark on 32 is mounted.

When an F ₂ laser or an ArF excimer laser (or an Ar ₂ laser having a wavelength of 126 nm) is used as the light source 21, the optical paths of the light transmitting system 22, the illumination optical system 23 and the projection optical system 31 are, for example, nitrogen or helium. It has been purged with such an inert gas. Particularly, when the F ₂ laser is used, the reticle 33, the reticle holder 24, and the reticle stage 25 include the casing 26.
This casing 26 is isolated from the outside atmosphere by
The inner space of is also purged with an inert gas.

Similarly, the wafer 32 and the wafer holder 27 are provided.
The wafer stage 28 is isolated from the outside atmosphere by the casing 29, and the internal space of the casing 29 is also purged with an inert gas. The optical component 35 arranged in the optical path of the light transmitting system 22 will be described later. Also, assuming that an F ₂ laser is used as the light source 21, the configuration and operation of the inspection device will be described with reference to FIG. 1.

The inspection apparatus shown in FIG. 1 is equipped with a light source 1 consisting of a solid-state laser and a crystal (or fiber etc.) for generating harmonics. The light source 1 emits a light beam having a wavelength substantially equal to 157 nm which is the wavelength of the F ₂ laser. As the light source 1, F ₂ used in the exposure apparatus is used.
A laser light source may be used. The light beam emitted from the light source 1 is deflected by the mirror 2 and expanded by the lenses 3, 4, 5, and 6 which form the beam expander,
It becomes a parallel light beam and enters the polarization beam splitter 7. The luminous flux incident on the polarization beam splitter 7 is as shown in FIG.
Is a linearly polarized light having a plane of polarization along a plane parallel to the plane of FIG.

Therefore, the light beam incident on the polarization beam splitter 7 is transmitted through the polarization splitting surface thereof and is incident on the quarter wavelength plate 8. The light flux converted from linearly polarized light to circularly polarized light by the action of the quarter-wave plate 8 is passed through the lenses 9, 10, 11, 12 which constitute the condenser lens, and onto the virtual object plane 13 shown by the broken line in the figure. The converging point 13C is formed. In addition,
The surface of the lens 12 on the virtual object surface 13 side, that is, the reference surface 12
Reference numeral a denotes a half mirror, which reflects an incident light flux at a predetermined energy ratio. The center of curvature of the reference surface 12a coincides with the condensing point 13C.

Thus, since the incident angle of the light beam on the reference surface 12a is always 0 degree, the light beam reflected by the reference surface 12a is the same as the incident light beam in the condenser lens (12, 11, 10, 9). The light travels along the optical path, is converted into a parallel light flux, and then is incident on the quarter-wave plate 8. On the other hand, the virtual object plane 13
The light flux that has passed through is incident on the optical system to be inspected, for example, the projection optical system 14 (indicated by reference numeral 31 in FIG. 2), and due to the imaging action of the projection optical system 14, the virtual image plane 15 indicated by the broken line in the figure. A condensing point 15C is formed on the top. The light flux diverging via the condensing point 15C enters a concave reflecting mirror 16 having a spherical reflecting surface with the condensing point 15C as the center of curvature.

The light beam reflected by the concave reflecting mirror 16 is condensed on the condensing point 15C, and then is condensed on the condensing point 13C on the virtual object surface 13 via the projection optical system 14. Focus point 13C
The light flux passing through the condenser lens (12, 11, 10, 9)
After being converted into a parallel light flux by, it is incident on the quarter-wave plate 8. In this way, the reference light reflected by the reference surface 12 a and the test light that has reciprocated through the projection optical system 14 return to the quarter-wave plate 8. Here, although both the reference light and the test light incident on the quarter-wave plate 8 are circularly polarized light,
The reference light and the test light emitted from the four-wave plate 8 are 1 /
By the action of the four-wave plate 8, it is converted into linearly polarized light having a polarization plane along a plane perpendicular to the paper surface of FIG.

In this way, the reference light and the test light that have passed through the quarter-wave plate 8 are reflected by the polarization beam splitter 7 and guided to the image pickup device 17 such as a CCD. Then, an interference fringe of the reference light and the test light is formed on the image pickup surface of the image pickup device 17. This interference fringe is caused by a difference in phase information between the reference light and the test light. This difference in phase information means that the test light reciprocates the projection optical system 14 and undergoes a phase change due to its wavefront aberration. caused by. Therefore, the wavefront aberration of the projection optical system 14 as the test optical system can be obtained by measuring the above-mentioned interference fringes and analyzing the amount of deformation.

The wavelength of the F ₂ laser is 15
At present, the optical material that transmits ultraviolet rays having a short wavelength such as 7 nm and has good uniformity is limited to fluorite. Therefore, the lenses 3, 4, 5 and 6, the polarization beam splitter 7, the quarter wave plate 8, and the lenses 9, 10 and 1
Fluorite is used as the optical material for forming the layers 1 and 12. In this case, as described above, fluorspar has birefringence with respect to a light flux having a short wavelength. However, birefringence (refractive index difference between two light beams having orthogonal polarization planes) does not occur for light traveling in the crystal axis [100] direction and the crystal axis [111] direction of the fluorite crystal. . Therefore, the crystal axis [111] or [100] of the fluorite lens and the optical axis A
If it is set so as to coincide with X (and thus the optical axis of the fluorite lens), no birefringence will occur with respect to the image forming light traveling parallel to the optical axis AX.

Actually, in any of the lenses 3, 4, 5, 6 and the lenses 9, 10, 11, 12, the light flux passing through the inside thereof has an opening angle (NA), so it is slight. It will be affected by birefringence. Therefore, referring to FIG. 3, the names of crystal axes in cubic crystals such as fluorite will be described. The cubic system is a crystal structure in which unit cells of a cube are periodically arranged in the direction of each side of the cube. The sides of the cube are orthogonal to each other, and are defined as Xa axis, Ya axis, and Za axis. At this time,
The + direction of the Xa axis is the direction of the crystal axis [100], and Ya
The + direction of the axis is the crystal axis [010] direction, and the + direction of the Za axis is the crystal axis [001] direction.

More generally, the above (Xa, Ya, Z
a) Direction vector (x1, y1, z1) in the coordinate system
When taking, the direction becomes the direction of the crystal axis [x1, y1, z1]. For example, the orientation of the crystal axis [111] matches the orientation of the orientation vector (1,1,1). Further, the orientation of the crystal axis [11-2] is the orientation vector (1,1,-
Match the direction of 2). Of course, in a cubic crystal, the Xa axis, the Ya axis, and the Za axis are optically and mechanically equivalent to each other, and no distinction can be made in an actual crystal. Also, the crystal axis [011],
The arrangement of three numbers such as [0-11], [110], and the crystal axes in which the signs are changed are completely equivalent (equivalent) both optically and mechanically.

In the present invention, when it is necessary to strictly define the relative crystal axis orientation, for example, the crystal axis [01
1] has a plurality of crystal axes that are optically equivalent to [011],
As in [0-11], [110], etc., the notations (lists) are changed with different signs and arrangement positions. However, when it is not necessary to strictly define the relative crystal axis orientation, the crystal axis [011] is used to describe [011], [0-1
A plurality of optically equivalent crystal axes such as 1] and [110] are collectively represented. This is the crystal axis [001]
The same applies to crystal axes other than the crystal axis [011] such as or [111].

Of these crystal axis directions, the crystal axis [10
0] (or the crystal axis optically equivalent to this),
And the crystal axis [111] (or its optically equivalent bond).
For light traveling in the (crystal axis) direction, the birefringence is
Does not happen. On the other hand, in the direction away from these crystal axis directions
Birefringence occurs for traveling light. And the amount of birefringence
Is the crystal axis [011] (or its optically equivalent bond).
It becomes maximum for light traveling in the direction of (crystal axis). This and
The direction of polarization (electric field direction) in the direction of the crystal axis [100].
Refractive index n100 of light and crystal axis [0-11]
The difference from the refractive index n011 of light having a polarization direction is
If the crystal is fluorite, the wavelength is 193 nm ArF laser
3.6 × 10 for light^-7The wavelength is 157
nm F ₂6.5 × 10 for laser light^-7To a degree
is there.

In the inspection apparatus of FIG. 1, in order to substantially avoid the influence of the birefringence, for example, the lens 3 and the lens 4 form a lens pair, and the lenses 9 and 10 form a lens pair. Then, in these four lenses, the crystal axis [111] is made to coincide with the optical axis AX, and in each lens pair, one lens is arranged relative to the other lens by 60 ° relative to the optical axis AX. Similarly,
The lens 5 and the lens 6 form a lens pair, and the lenses 11 and 12 form a lens pair. Then, in these four lenses, the crystal axis [100] is made to coincide with the optical axis AX, and in each lens pair, one lens is arranged relative to the other lens by 45 ° relative to the optical axis AX. In this way, by selecting the crystal axis that matches the optical axis and imparting rotation of a predetermined angle around the optical axis,
It is possible to substantially eliminate the adverse effects of the birefringence of the fluorite lens.

On the other hand, since a crystal material such as fluorite is also used for the polarization beam splitter 7, wavefront aberration due to birefringence may occur depending on how the crystal axis of this crystal material is adopted. . Therefore, also in the polarization beam splitter 7, it is necessary to select the crystal axis direction so that the influence of birefringence does not substantially occur. FIG. 4 is a diagram for explaining selection of crystal axes in the polarization beam splitter. Referring to FIG. 4, the light source 1 (not shown in FIG. 4)
The light flux from the incident light enters the polarization beam splitter 7 along the −Z direction from above in the figure. At this time, the incident light flux on the polarization beam splitter 7 is linearly polarized light having a polarization plane parallel to the YZ plane.

The polarization beam splitter 7 is a cube-type (rectangular parallelepiped) beam splitter composed of triangular prism type members 7a and 7b. A multilayer film 7c having different reflection characteristics and transmission characteristics for S-polarized light and P-polarized light is formed on the joint surface between the members 7a and 7b.
The P-polarized light flux (linearly polarized light having a polarization plane parallel to the YZ plane) incident on the member 7a along the −Z direction from above in the figure passes through the multilayer film 7c and is incident on the member 7b. Then, the light passes through the member 7b and heads downward in the drawing along the −Z direction toward the projection optical system 14 (not shown in FIG. 4).

On the other hand, the return light (test light) from the projection optical system 14 enters the member 7b and the multilayer film 7c along the + Z direction from below in the figure. At this time, the light flux incident on the polarization beam splitter 7 is linearly polarized light (S-polarized light) having a polarization plane parallel to the XZ plane. Therefore, the multilayer film 7c
The test light incident on is reflected in the + Y direction by the multilayer film 7c and guided to the image sensor 17 (not shown in FIG. 4).

As described above, the polarization beam splitter 7
, The light flux is in two orthogonal directions (ie, Z direction and Y direction).
Direction), it is necessary to select a crystal axis that does not cause birefringence in these two orthogonal directions. The crystal axis that does not cause birefringence is the crystal axis [100] and the crystal axes ([010], [001], [-1] which are optically equivalent to the crystal axis.
00], [0-10], [00-1]). Therefore, in the present embodiment, as shown in FIG. 4, in the polarization beam splitter 7, the incident direction of the light flux and the exit direction of the light flux are the crystal axis [100] (or a crystal axis optically equivalent to this crystal axis). By setting them to coincide with each other, the adverse effect of the birefringence of the crystalline material can be substantially avoided.

In the example shown in FIG. 4, the light flux passing through the member 7a constituting the polarization beam splitter 7 is only the incident light flux parallel to the Z direction. Therefore, with respect to the member 7a, even if the incident direction of the light flux is set to coincide with the crystal axis [111] (or the crystal axis optically equivalent to this crystal axis), it is substantially affected by the birefringence. No polarizing beam splitter can be constructed. In this case, the incident side surface of the member 7a is a <111> surface that can be easily processed, which is advantageous in processing the member 7a and forming an antireflection film. Further, in the present embodiment, the polarization beam splitter 7
Although the present invention is applied to the above, it is needless to say that the present invention can be applied to a simple beam splitter without being limited to this.

Next, the quarter-wave plate 8 using a cubic crystal material such as fluorite will be described. Figure 5
It is a figure explaining selection of the crystal axis in a quarter wave plate. Referring to FIG. 5A, in the quarter-wave plate 8, the traveling direction of the light flux is set to coincide with the crystal axis [011] (or a crystal axis optically equivalent to this crystal axis). . Referring to FIG. 5B, which is a view of the quarter-wave plate 8 from the polarization beam splitter 7 side, linearly polarized light having a polarization direction PD is incident along the horizontal direction on the paper surface of FIG. 5B. .

Therefore, as shown in FIG. 5 (b), in the plane orthogonal to the crystal axis [011] (that is, in the plane of the paper of FIG. 5 (b)), the directions that form 45 degrees with respect to the polarization direction PD, respectively. Crystal axes [100], [0-11], [-10
0] and [01-1] match, the rotation azimuth of the crystal material (the rotation angle about the crystal axis [011] matched with the traveling direction of the light flux as the rotation center) is set. In this case, it has a polarization plane in a direction separated by 45 degrees from both sides of the polarization direction PD.
Since the two polarized lights have different refractive indexes, such a crystal optical element has a function as a wave plate.

As described above, for light traveling in the direction of the crystal axis [011], the refractive index of the polarized light in the direction of the crystal axis [100] and the refractive index of the polarized light in the direction of the crystal axis [0-11]. When the crystal is fluorite, the difference is about 6.5 × 10 ^{−7 with} respect to the F ₂ laser light having a wavelength of 157 nm. As a result, an optical path difference of 6.5 nm occurs for an optical path length of 1 cm in the crystal. Therefore, if the length of the crystal along the traveling direction of the light flux is about 24 cm (= 157 / 6.5), this crystal functions as a one-wave plate. Further, if the length of the crystal along the traveling direction of the light flux is about 12 cm, which is ½ thereof, it functions as a ½ wavelength plate. Further, if the length of the crystal along the traveling direction of the light flux is about 1/4, that is, about 6 cm, it functions as a quarter-wave plate.

The quarter-wave plate 8 of the present embodiment is based on this principle, and a quarter-wave plate 8 in which a fluorite crystal having the above-described crystal orientation is set to a length of about 6 cm is used. Is used as. Quarter wave plate 8 having the above configuration
By the action of, the incident linearly polarized light is converted into circularly polarized light and emitted. The circularly polarized light formed through the quarter-wave plate 8 is transmitted through the projection optical system 14 and then reflected by the concave reflecting mirror 16 to be circularly polarized in the reverse direction by this reflection.
It enters the wave plate 8. At this time, the reverse circularly polarized light is converted into linearly polarized light having a polarization direction orthogonal to the polarization direction PD on the paper surface of FIG. 5B and emitted toward the polarization beam splitter 7.

The cross-sectional shape of the quarter-wave plate 8 is shown in FIG.
It is not limited to the form shown in FIG. 5B, but the outer shape and the crystal orientation may be rotated by 45 degrees from FIG. 5B, that is, the form shown in FIG. Needless to say. Further, in the inspection apparatus shown in FIG. 1, since a quarter wavelength plate is required as a component, fluorite having a crystal length of about 6 cm along the traveling direction of the light flux is used. However, if a ½ wavelength plate is required as a constituent element, fluorite having a crystal length of about 12 cm along the traveling direction of the light flux may be used.

The wave plate as described above is an important component also in the projection exposure apparatus. In the projection exposure apparatus, in order to ensure the uniformity of the pattern line width of the transferred circuit pattern, the reticle (mask) has an extremely uniform illuminance.
An illuminating optical system for illuminating is required. However, when a laser is used as the light source, the high coherence causes the interference fringes generated on the mask surface to deteriorate the uniformity of illuminance. To solve this, it is preferable to provide a wavelength plate in the illumination optical system to control the polarization state of the light beam from the light source so that interference fringes are not easily formed on the reticle.

Specifically, as an optical member (crystal optical component) 35 made of a crystal material belonging to the cubic system in the optical path of the light transmitting system 22 of the projection exposure apparatus as shown in FIG. It is preferable to provide a quarter-wave plate as shown. With this configuration, linearly polarized light emitted from the laser light source 21 is converted into circularly polarized light via the quarter-wave plate 35. As a result, it is possible to reduce the coherence of the illumination light flux, which in turn can reduce the interference fringes on the reticle 33.

FIG. 6 is a view showing a modification of the crystal optical component additionally provided in the optical path of the light sending system of the projection exposure apparatus. Figure 6
Referring to, the optical member 35 is composed of members 35a and 35b made of crystals belonging to the cubic system. Here, the member 3 arranged on the light source side (lower side in FIG. 6A)
5a, the traveling direction of the luminous flux and the crystal axis [011] coincide with each other, similarly to the quarter-wave plate shown in FIG. And
As shown in FIG. 6B, which is a view of the member 35a as seen from the light source side, it is 45 with respect to the polarization direction IP of the incident light flux.
The crystal axes [100], [0-11], and
The rotation direction of the crystal material (the crystal axis [0] matched with the traveling direction of the light flux is set so that [-100] and [01-1] match each other].
11] is set as a rotation angle).

Therefore, the member 35a acts as a wave plate, but its length along the traveling direction of the light flux is as shown in FIG.
As shown in (a), since the left and right in the figure are different, the illumination light flux has different polarization states on the left and right, is emitted from the member 35a, and is incident on the member 35b. Here, the member 35b
Then, since the traveling direction of the light flux and the crystal axis [111] coincide with each other, there is no birefringence action. Therefore, the light beam emitted from the member 35a is emitted from the member 35b while the polarization state is maintained. The light flux emitted from the member 35b passes through the illumination optical system 23 and illuminates the reticle 33. Since various polarization states are mixed in this illumination light flux, the reticle 33 is illuminated.
It is possible to sufficiently suppress the generation of the above interference fringes.

In this case, the member 35b is not always necessary. However, without the member 35b, the illumination light beam is largely refracted at the exit end surface of the member 35a.
It is better to provide the member 35b to suppress this refraction.
Also, a similar wave plate is formed even if the light source side member 35a has a structure in which the traveling direction of the light beam and the crystal axis [111] are aligned with each other and the member 35b is configured to match the traveling direction of the light beam with the crystal axis [011]. It goes without saying that you can do it. In the member on the side that does not cause birefringence, the crystal axis [100] may be made to coincide with the traveling direction of the light beam, instead of the crystal axis [111].

In the above embodiment, calcium fluoride crystals (fluorite) are used as the birefringent optical material, but the invention is not limited to this, and other uniaxial crystals such as barium fluoride are used. Crystal (BaF ₂ ), lithium fluoride crystal (LiF), sodium fluoride crystal (NaF),
Other crystal materials that are transparent to ultraviolet rays, such as strontium fluoride crystal (SrF ₂ ) and beryllium fluoride crystal (BeF ₂ ) can also be used. Of these, barium fluoride crystals have already been developed as large crystal materials having a diameter of more than 200 mm, and are promising as lens materials. In this case, the crystal axis orientation of barium fluoride (BaF ₂ ) or the like is also preferably determined according to the present invention.

In the exposure apparatus of each of the above-described embodiments, the reticle (mask) is illuminated by the illumination device (illumination step),
A microdevice (semiconductor element, image sensor, liquid crystal display element, thin film magnetic head, etc.) is manufactured by exposing a photosensitive substrate with a transfer pattern formed on a mask using a projection optical system (exposure step). be able to. Hereinafter, an example of a method for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of each embodiment will be described with reference to the flowchart of FIG. 7. Explain.

First, in step 301 of FIG. 7, 1
A metal film is deposited on a lot of wafers. In the next step 302, photoresist is applied on the metal film on the wafer of the 1 lot. Then step 303
In the above, using the exposure apparatus of each embodiment, the image of the pattern on the mask is sequentially exposed and transferred to each shot area on the wafer of the one lot through the projection optical system. Then, in step 304, the photoresist on the wafer of the one lot is developed, and then in step 30.
5, the circuit pattern corresponding to the pattern on the mask is formed in each shot area on each wafer by performing etching using the resist pattern as a mask on the wafer of one lot.

After that, a device such as a semiconductor element is manufactured by forming a circuit pattern on an upper layer. According to the above semiconductor device manufacturing method,
It is possible to obtain a semiconductor device having an extremely fine circuit pattern with high throughput. Note that step 30
In steps 1 to 305, a metal is vapor-deposited on the wafer, a resist is applied on the metal film, and each step of exposure, development, and etching is performed. Prior to these steps, a silicon film is formed on the wafer. Needless to say, after the oxide film is formed, a resist may be applied on the silicon oxide film, and each step such as exposure, development and etching may be performed.

Further, in the exposure apparatus of each embodiment, a predetermined pattern (circuit pattern,
It is also possible to obtain a liquid crystal display element as a microdevice by forming an electrode pattern or the like). Hereinafter, an example of the method at this time will be described with reference to the flowchart in FIG. In FIG. 8, in a pattern forming step 401, a so-called photolithography step is performed in which the pattern of the mask is transferred and exposed onto a photosensitive substrate (such as a glass substrate coated with a resist) using the exposure apparatus of each embodiment. By this photolithography process, a predetermined pattern including a large number of electrodes and the like is formed on the photosensitive substrate. After that, the exposed substrate undergoes a developing process, an etching process, a reticle peeling process, and the like to form a predetermined pattern on the substrate, and the process proceeds to the next color filter forming process 402.

Next, in the color filter forming step 402, 3 corresponding to R (Red), G (Green) and B (Blue)
Many sets of one dot are arranged in a matrix,
Alternatively, a color filter in which a set of filters of three stripes of R, G, and B is arranged in the horizontal scanning line direction is formed. Then, the color filter forming step 4
After 02, the cell assembling step 403 is executed. In the cell assembly step 403, a liquid crystal panel (liquid crystal cell) is assembled using the substrate having the predetermined pattern obtained in the pattern formation step 401, the color filter obtained in the color filter formation step 402, and the like. In the cell assembly step 403, for example, the pattern formation step 4
A liquid crystal panel (liquid crystal cell) is manufactured by injecting liquid crystal between the substrate having the predetermined pattern obtained in 01 and the color filter obtained in the color filter forming step 402.

After that, in a module assembling step 404, various components such as an electric circuit for performing a display operation of the assembled liquid crystal panel (liquid crystal cell) and a backlight are attached to complete a liquid crystal display element. According to the method of manufacturing a liquid crystal display element described above, a liquid crystal display element having an extremely fine circuit pattern can be obtained with high throughput.

Further, in the above embodiment, the wavelength of 193 nm
ArF excimer supplying wavelength light Laser light source and 157
F that supplies light with a wavelength of nm₂Uses a laser light source
However, without being limited to this, for example, a wavelength of 126 nm
Ar supplying wavelength light Use a laser light source, etc.
You can also

[0058]

As described above, according to the present invention, even if a birefringent crystal material such as fluorite is used, a beam having good optical performance without being substantially affected by birefringence. Splitters and wave plates can be realized. Further, according to the present invention, it is possible to obtain an optical device provided with a crystal optical component such as a beam splitter or a wave plate having good optical performance without being substantially affected by birefringence. As this optical device, for example, a highly accurate inspection device for measuring the wavefront aberration of the projection optical system mounted in the exposure device, and an exposure device capable of sufficiently suppressing the generation of interference fringes on the reticle are realized. can do.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an inspection apparatus including a crystal optical component according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a configuration of an exposure apparatus provided with a projection optical system as a test optical system shown in FIG.

FIG. 3 is a diagram for explaining names of crystal axes in a cubic crystal such as fluorite.

FIG. 4 is a diagram illustrating selection of crystal axes in a polarization beam splitter.

FIG. 5 is a diagram illustrating selection of crystal axes in a quarter-wave plate.

FIG. 6 is a diagram showing a modified example of a crystal optical component additionally provided in the optical path of the light transmission system of the projection exposure apparatus.

FIG. 7 is a flowchart of a method for obtaining a semiconductor device as a micro device.

FIG. 8 is a flowchart of a method for obtaining a liquid crystal display element as a micro device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 light source 2 mirrors 3, 4, 5, 6 lens which comprises a beam expander 7 polarizing beam splitter 8 quarter wave plate 9, 10, 11, 12 lens 12a which constitutes a condenser lens reference surface 13 virtual object surface 14, 31 Projection Optical System 15 Virtual Image Surface 16 Concave Reflector 17 Imaging Device 21 Light Source 22 Light Transmitting System 23 Illumination Optical System 25 Reticle Stage 28 Wafer Stages 26, 29 Casing 30 Alignment Microscope 32 Wafer 33 Reticle

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) G03F 7/20 521 G03F 7/20 521 H01L 21/027 H01L 21/30 515D F term (reference) 2H042 CA06 CA14 CA18 2H049 BA05 BA06 BA07 BA42 BB03 BB61 BC21 2H097 CA06 CA13 GB01 LA10 LA12 2H099 AA00 BA17 CA02 CA05 CA07 DA00 5F046 CB10 CB15

Claims (13)

[Claims] 1. A beam splitter formed of a crystal belonging to a cubic system, wherein the incident direction of the light beam to the beam splitter and the emission direction of the light beam from the beam splitter are the crystal axis [100] of the crystal or the A beam splitter characterized by being set so as to substantially coincide with a crystal axis that is optically equivalent to the crystal axis. 2. A beam splitter formed of a crystal belonging to a cubic system, wherein the beam splitter has a pair of prismatic prism-shaped prism members, and one of the prism members has a traveling direction of a luminous flux passing through the crystal. Crystal axis [100] or a crystal axis that is optically equivalent to the crystal axis of the crystal axis [100] or the crystal axis [111] of the crystal or the crystal axis of the other prism member. A beam splitter characterized by being set so as to substantially coincide with a crystal axis that is optically equivalent to the crystal axis. 3. The beam splitter according to claim 1, wherein the beam splitter is a polarization beam splitter.
Beam splitter described in. 4. The beam splitter according to claim 1, wherein the crystal is a calcium fluoride crystal or a barium fluoride crystal. 5. A wave plate formed of a crystal belonging to a cubic system, wherein a traveling direction of a light beam passing through the wave plate is a crystal axis [110] of the crystal or an optical equivalent of the crystal axis. A wave plate characterized by being set so as to substantially coincide with the axis. 6. The light guide plate according to claim 5, wherein the light guide plate has a thickness of about 6 cm along the traveling direction of the light flux and functions as a quarter-wave plate for a light flux having a wavelength of about 157 nm. Wave plate. 7. A distance of about 12 cm along the traveling direction of the luminous flux.
6. The wave plate according to claim 5, wherein the wave plate has a thickness of about 157 nm and functions as a half-wave plate for a light flux having a wavelength of about 157 nm. 8. The light emitting device according to claim 5, further comprising an entrance surface substantially perpendicular to the traveling direction of the light flux and an exit surface substantially inclined with respect to a surface perpendicular to the traveling direction of the light flux. Wave plate. 9. The wave plate according to claim 5, wherein the crystal is a calcium fluoride crystal or a barium fluoride crystal. 10. A crystal optical component of at least one of the beam splitter according to any one of claims 1 to 4 and the wave plate according to any one of claims 5 to 9. An optical device characterized by. 11. An illumination optical system in which the wave plate according to any one of claims 5 to 9 is arranged in the optical path of the illumination light. 12. An illumination optical system according to claim 11 for illuminating a mask, and a projection optical system for forming an image of a pattern formed on the mask on a photosensitive substrate. An exposure apparatus. 13. An inspection apparatus for inspecting a projection optical system for forming an image of a pattern formed on a mask on a photosensitive substrate, comprising an irradiation optical system for irradiating the projection optical system with inspection light, An irradiation optical system comprises the optical device according to claim 10.