JPH08201590A - Optical element for reflection - Google Patents

Abstract

PURPOSE: To provide an optical element for reflection (for example, an optical element for reflection having an equal function to a theoretical mirror for Koehler's illumination) fulfilling both of strict accuracy of shape and accuracy of roughness. CONSTITUTION: On the curved surface 4 of a base plate 1 having a curved surface 4, a reflection part 2 having a plurality of reflection plane or a rough reflection plane 6 isolated by a groove 3 is contacted to make an optical element for reflection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection optical element, and more particularly to a reflection optical element suitable for an illumination system of X-ray optical equipment such as an X-ray reduction projection exposure apparatus and an X-ray microscope.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of semiconductor integrated circuit devices, in order to improve the resolution of an optical system which is limited by the diffraction limit of light, conventional X-rays are replaced with X-rays having a shorter wavelength. The projection lithography technique used has been developed. The X-ray reduction projection exposure apparatus used in this technique is mainly composed of an X-ray source, an illumination optical system, a mask, an imaging optical system, a wafer stage and the like.

The X-ray source includes synchrotron radiation and laser plasma X.
A radiation source or the like is used. The illumination optical system is composed of an oblique incidence mirror that reflects X-rays obliquely incident on the reflection surface, a multilayer mirror whose reflection surface is formed of a multilayer film, and a filter that reflects or transmits only X-rays of a predetermined wavelength. Then, the mask is illuminated with X-rays having a desired wavelength.

The mask includes a transmission type mask and a reflection type mask. The transmissive mask has a pattern formed by providing a substance that absorbs X-rays in a predetermined shape on a thin membrane made of a substance that transmits X-rays well.
On the other hand, the reflective mask is, for example, a pattern formed by providing a portion having a low reflectance in a predetermined shape on a multilayer film that reflects X-rays.

The pattern formed on such a mask is transferred onto the resist by forming an image on a wafer coated with a photoresist by a projection imaging optical system composed of a plurality of multilayer film mirrors and the like. To be done. Since X-rays are absorbed by the atmosphere and attenuated, all the optical paths thereof are maintained at a predetermined vacuum degree. Generally, in diffraction-limited imaging in which the aberration of the optical system is sufficiently small and the influence of the aberration can be ignored, the resolving power of the optical system depends not only on the performance of the imaging system but also on the object (mask in the case of lithography). It depends on the lighting method.

The ratio of the numerical aperture of illumination light to the incident numerical aperture of the image forming system is called a coherence factor σ. The case of σ = 0 is called image formation by coherent illumination, and in this case, the object is illuminated with a parallel light flux incident from a single direction. At this time, as shown in FIG. 9, the transfer function (OTF) of the optical system is NA / λ (NA is the exit side numerical aperture of the imaging system, λ
Indicates a constant value up to the spatial frequency determined by the wavelength of the illumination light), but when it exceeds this spatial frequency, it becomes 0 and is not resolved.

On the other hand, the case of σ = 1 is called image formation by incoherent illumination. In this case, the object is illuminated with a ray having a divergence angle that fills the entire entrance side aperture of the image forming system. At this time, the OTF gradually decreases as the spatial frequency increases, but does not become 0 up to the spatial frequency of 2NA / λ. Therefore, although the image contrast is reduced, incoherent illumination can resolve a pattern with a higher spatial frequency. Therefore, in the illumination optical system of the exposure apparatus, which requires a diffraction-limited resolution, partial incoherent illumination of 0 <σ <1 is used in consideration of the resolution and the contrast.

In the case of illuminating a wide area of, for example, about 120 × 120 mm on a mask in an actual exposure apparatus, it is required to satisfy the conditions of the partial coherent illumination as described above and make the illuminance uniform. It As an illumination optical system that satisfies such a condition, a Koehler illumination optical system as shown in FIG. 10 is widely and generally used. The function of the Koehler illumination optical system will be briefly described below.

The light beam emitted from the light source 19 is first converted into a parallel light beam by the first lens 20, and then enters the optical integrator 21. The optical integrator 21 spatially splits the parallel light flux and focuses each of the split light fluxes, so that a multiplexed image 22 of the light source 19 is formed. In an exposure apparatus that uses ultraviolet light, a fly-eye lens is generally used as the optical integrator 21.

Next, the light rays diverging from the light source image 22 are converted into parallel light fluxes by the second lens 23,
Illuminate the object 24. Ray bundles emitted from different light source images 22 enter the object 24 from different directions. At this time, on the way (first lens 20 and optical integrator 2
The thickness of the parallel light flux (between 1) determines the NA (numerical aperture) of the illumination light, and the divergence angle from the multiplexed light source image 22 determines the size of the illumination area. Since the light emitted from the point light source is converted into a parallel light flux to illuminate the object, the illuminance unevenness is small. Moreover, it is easy to change the numerical aperture of the illumination.

In order to realize the Koehler illumination optical system as described above in the X-ray projection exposure apparatus, all the optical systems equivalent to those shown in FIG. 10 are reflective optical systems (for example, those using a multilayer film mirror). ) Must be configured. As an optical element for multiplexing such light sources, a Koehler illumination mirror as shown in FIG. 11 has been proposed by JB Murphy et al. (Appl. Opt., 32 (34) 6920 (1993)).

The proposal of such a mirror for Koehler illumination is theoretical, and there is no real thing. This is because the mirror for Koehler illumination requires both strict shape accuracy and roughness accuracy (surface accuracy) of its reflecting surface, and is extremely difficult to manufacture. However, if such a mirror for Koehler illumination is present, it can be used for an X-ray optical system to which a lens optical system cannot be applied, such as the above-mentioned X-ray projection exposure apparatus, and other optical systems. Extends to a variety of devices.

For example, in the fields of medicine and biotechnology, which have been rapidly advancing in recent years, ordinary visible light (λ = about 400 nm
As a high-resolution microscope that has a higher resolution than a microscope that uses 800 nm) and that can also clearly observe living samples (hereinafter referred to as biological samples, such as cells, bacteria, sperms, chromosomes, mitochondria, flagella). , X-ray microscopes using soft X-rays having a wavelength λ of 2 to 5 nm instead of visible light have been studied and are being developed.

For example, FIG. 12 shows a simple structure and optical system of such an X-ray microscope. In FIG. 12, the X-rays emitted from the X-ray generator 12 are condensed by the X-ray illumination optical system 13 and applied to the sample in the sample capsule 14. Then, the X-ray transmitted through the sample forms an image of the sample on the X-ray imaging device 16 by the X-ray magnifying optical system 15. The optical path length from the X-ray generator 12 to the X-ray imaging device 16 is, for example, about 2 m.

Reference numeral 17 is a vacuum container, and 18 is an exhaust device for evacuating the inside of the container. If the Koehler illumination mirror can be used for the X-ray illumination optical system 13, the Koehler illumination optical system can be configured.

[0016]

The Koehler illumination mirror must satisfy the function of reflecting the light beam from the split plane and converging it to one point in order to spread the light beam from the point light source and to eliminate the unevenness. I have to. The reflection surface shape of the Koehler illumination mirror is similar to the reflection concave surface of the continuous concave mirror, but different from the reflection surface shape of the continuous concave mirror. The reflecting surface of the mirror for Koehler illumination is formed by arranging a plurality of planes so as to be separated from each other, and the arrangement is such that the normal line at the center of each plane is gathered at one point.

Conventionally, the reflection mirror, whether it is axially symmetric or a free-form surface, has been mainly processed and manufactured by an NC machine tool. However, in such a conventional processing method,
It has not been possible to fabricate a reflection optical element that requires strict shape accuracy and roughness accuracy like the Koehler illumination mirror.

Therefore, the reflection optical element, which requires strict shape accuracy and roughness accuracy, as proposed by the Koehler illumination mirror, is merely theoretical and cannot be used in practice ( There is a problem that there is no real thing). The present invention has been made in view of the above problems, and a reflection optical element satisfying strict shape accuracy and roughness accuracy (for example, a reflection optical element having a function equivalent to that of the theoretical Koehler illumination mirror). The purpose is to provide.

[0019]

Therefore, a first aspect of the present invention is "for reflection, which is formed by joining a reflective member having a plurality of reflective flat surfaces or reflective substantially flat surfaces separated by grooves to the curved surface of a substrate having a curved surface. An optical element (claim 1) ". Further, the present invention is secondly “the curved surface of the substrate is a spherical surface, and the reflective member is provided on the spherical surface so that each normal line of the plurality of reflective planes or substantially reflective planes passes through the center of the spherical surface. The reflective optical element according to claim 1 (claim 2), which is formed by bonding.

The present invention is thirdly "the reflection optical element according to claim 1 or 2, wherein the substrate and the reflection member are bonded by an anodic bonding method (claim 3)". I will provide a. In the fourth aspect of the present invention, the "X
4. A multilayer film for line reflection is provided, which is characterized in that
A reflective optical element (claim 4) ".

[0021]

A reflecting optical element satisfying strict shape accuracy and roughness accuracy (for example, a reflecting optical element having a function equivalent to that of the theoretical mirror for Kohler illumination) is formed on the curved surface 4 of the substrate 1 having the curved surface 4. It can be realized by a reflection optical element (claim 1) formed by joining a reflection member 2 having a plurality of reflection planes or reflection planes 6 separated by a groove portion 3 (see FIG. 1).

As an example of a method for manufacturing the reflection optical element of the present invention, first, a flat plate member (for example, a silicon wafer) 2a is prepared, and a groove 3 is formed in the member 2a to form the reflection member 2. It is produced (see 1. in FIG. 5). The groove portion 3 can be formed by, for example, a dicing process or an etching process. When the groove 3 is formed by dicing,
The width of the groove 3 is the width of the dicing blade (for example, 20
μm, 100 μm), but the groove 3
In the case of forming by etching, the width can be made smaller.

Since the dicing process does not require a labor-intensive process like the photolithography process in the etching process, the process can be easily performed if a processing machine is prepared. However, as described above, the dicing process has a limit in processing a highly accurate shape such as a thin groove due to mechanical restrictions such as the width of the blade. Therefore, if higher accuracy is required, the process becomes longer, but the groove 3 may be formed by etching.

Next, the curved surface 4 of the substrate 1 having the curved surface 4
Then, the reflection member 2 in which the groove 3 is formed is joined by, for example, an anodic bonding method (see 2. in FIG. 5) to complete the reflection optical element (see 3. in FIG. 5). The anodic bonding method will be described in detail later. When the curved surface 4 of the substrate 1 and the reflecting member 2 are joined, particularly when the curved surface 4 of the substrate 1 which is the joining surface is a concave surface, the flat surface (joint surface) of the reflecting member 2 which is closest to the concave surface is joined. Therefore, air is likely to be accumulated at the joint.

Therefore, to prevent air accumulation,
It is preferable to provide holes 5 for venting air in the substrate 1 or the reflecting member 2 (see FIG. 1, an example in which the holes 5 are provided in the substrate 1). When the air vent hole 5 is provided in the substrate 1, the hole 5 affects the deformation of the reflecting surface portion of the reflecting member 2 located thereabove, and therefore the reflecting surface portion 6 which is not particularly required to have optical characteristics.
It is preferable to provide the substrate portion located on the lower side of a with the minimum necessary size.

When the air vent hole 5 is provided in the reflecting member 2, it is preferable to provide the hole 5 in the reflecting surface portion where optical characteristics are not particularly required. Therefore, the air vent hole 5 is preferably provided in the center of the substrate 1 or the reflection member 2 with a minimum size. Heretofore, an example of the method for producing the reflective optical element of the present invention has been shown.

By joining the curved surface 4 of the substrate 1 and the reflecting member 2 according to the reflecting optical element of the present invention, the shape accuracy of the curved surface 4 of the substrate is transferred to the reflecting member 2 after joining. That is, the joining surface of the reflecting member 2 is deformed following the joining of the curved surface 4 of the substrate after joining, whereby the shape accuracy of the curved surface 4 of the substrate is transferred to the reflecting member 2 after joining (see 3. in FIG. 5). The bonding surface of the reflecting member 2 is deformed following the curved surface 4 of the substrate after bonding, but in the present invention, the groove portion 3 for separating a plurality of reflecting surfaces (reflection planes or reflection substantially planes) 6 is provided on the reflection surface side of the reflection member 2. ing. Therefore, the stress generated when the joint surface of the reflecting member 2 is deformed is reduced by the groove 3
It is possible to suppress the deformation of the plurality of reflecting surfaces 6 by concentrating it on the portion where the groove is formed (groove portion forming portion).

Further, in the reflecting member 2, the larger the difference in rigidity between the reflecting surface 6 portion and the groove portion 3 forming portion, the more the stress is concentrated on the groove portion 3 forming portion, thereby suppressing deformation of the plurality of reflecting surfaces 6. Will increase. However, when the difference in rigidity is too large and the deformation of the groove 3 due to stress concentration on the portion is excessive, the accuracy of the shape of the curved surface 4 of the substrate is less likely to be transferred to the reflecting member 2 after joining.

Therefore, it is preferable to provide a rigidity difference in consideration of both the deformation suppression of the reflection surface 6 and the transfer of the shape accuracy. In order to increase the rigidity difference, for example, the thickness of the reflecting surface 6 portion is made larger than that of the groove portion 3 forming portion, or the width (length of one side) of the groove portion 3 is set to the reflecting surface 6 portion (groove portion 3). It is sufficient to reduce the width (length of one side) of each reflection surface portion (separated by). It should be noted that making the width of the groove 3 smaller than the width of the portion of the reflective surface 6 means that the reflective surface 6
It is also preferable to increase the area of the whole and to increase the function as a reflective optical element.

The plane projection shape of the groove 3 is preferably a shape that can be easily processed and can be easily displayed in a plane coordinate system. For example, the rotationally symmetric lattice shape shown in FIG. 1A is preferable. In the reflection optical element of the present invention, the curved surface 4 of the substrate 1 is a spherical surface, and the normal surface of the plurality of reflection planes or the reflection approximate plane 6 passes through the center C of the spherical surface. The reflection optical element (claim 2) formed by bonding the reflection member 2 has a function equivalent to that of the theoretical mirror for Kohler illumination.

The normal lines of the plurality of reflection planes or reflection planes 6 pass through the center of the spherical surface (curved surface 4).
In order to join the reflection member 2 to the spherical surface, for example, the planar projection shape of the groove portion 3 may be formed into a rotationally symmetric lattice shape shown in FIG. Further, the reflective optical element of the present invention is preferably one in which the curved surface 4 of the substrate and the reflective member 2 are bonded by an anodic bonding method (claim 3).

As a joining method, a joining method using an adhesive such as an organic adhesive, a metal adhesive used for brazing or soldering, a glass adhesive, laser welding, seam welding, ultrasonic welding And the like, and the anodic bonding method. The joining method by welding includes a method of joining two members through a joining material and a method of joining two members directly without a joining material.

When the substrate curved surface 4 and the reflecting member 2 are joined by a joining method using an adhesive or a joining material among such joining methods, the curved surface of the substrate (the joining surface of the substrate) 4 and the joining surface 4 of the reflecting member 2 are joined. ', An adhesive layer or a bonding material layer will be interposed, but if the thickness of this layer is large, the curved surface of the substrate 4
It becomes difficult to transfer the shape accuracy of the above to the reflecting member 2 after joining.

Further, when an adhesive layer or a bonding material layer is interposed between the curved surface of the substrate (bonding surface of the substrate) 4 and the bonding surface 4'of the reflecting member 2, the bonding strength decreases due to the difference in thermal expansion coefficient and plasticity. And the problem of deterioration of joint strength due to aging. When the substrate 1 and the reflecting member 2 are joined by a welding method that does not use a joining material, it is necessary to heat the substrate 1 or the reflecting member 2 to the melting point or the softening point or higher, so that the joining is performed while maintaining the shape accuracy. Is difficult.

Therefore, as the joining method, it is possible to join at a relatively low temperature, and it is not necessary to use a joining material.
Therefore, the shape accuracy of the curved surface 4 of the substrate is adjusted so that the reflecting member 2 after joining
The anodic bonding method is preferable because it enables accurate transfer.
The anodic bonding method is a bonding method that enables bonding at a temperature lower than the original (when no DC voltage is applied) bonding temperature by applying a DC voltage between two members to be bonded. It can be applied to joining (for example, glass or ceramics) and metals (unit metal, alloy, semiconductor).

When performing anodic bonding, it is preferable to first polish and smooth each bonding surface of the dielectric and metal to be bonded. This smoothing has the effect of increasing the bonding strength. For example, it is preferable that the surface roughness be 0.05 μm or less. In anodic bonding, the bonding surfaces of both materials are superposed, heated at a temperature lower than the softening point of the dielectric and the melting point of the metal, and a relatively high DC voltage is applied between the two materials, Bonding is done. The polarity at this time is
Set the metal side to + and the dielectric side to-.

The heating temperature depends on the combination of materials and the smoothness of the joint surface, but is often 300 to 600 ° C. The better the smoothness of the joint surface and the smaller the hardness of the dielectric material, the lower the heating temperature the joint becomes possible. The applied voltage is a DC voltage, and in the case of an AC voltage, no junction is made. Also, the polarity must be + on the metal side. The magnitude of the applied voltage depends on the combination of materials, the smoothness of the joint surface, and the heating temperature, but it is often 200 to 2000 V, and about 1000 V is generally suitable. The upper limit is
It is the upper limit value that does not cause destruction by sparks.

Voltage application time (bonding completion time)
Depends on the heating temperature and the applied voltage, but the higher the heating temperature and the higher the applied voltage, the shorter the time, and generally about several minutes. Anodic bonding is generally carried out in air, but it can also be carried out in an atmosphere of oxygen, steam, nitrogen, hydrogen, argon, vacuum or homing gas.

In order to increase the bonding strength by anodic bonding, it is preferable to select a combination having a small difference in the coefficient of thermal expansion between the dielectric material and the metal which are the materials to be bonded. For example,
A combination in which the difference in coefficient of thermal expansion is 50% or less is preferable. Examples of dielectrics suitable for anodic bonding include soft glass (for example, borosilicate glass), hard glass, optical glass, ceramics (for example, β-alumina ceramics),
There are fused quartz, sapphire, porcelain and the like, and as metals suitable for combination with each of these dielectrics, for example, kovar, chromium alloy, tantalum, silicon, germanium, molybdenum, tungsten, G
aAs and the like.

Even in the case of a combination of the above-mentioned suitable dielectric material and a metal material having a difference in coefficient of thermal expansion from the dielectric material of more than 50%, the bonding strength can be increased by forming the metal material into a thin film. Is. Examples of such metals include copper,
Examples include iron, nickel, iron-nickel alloys, chromium, aluminum, magnesium, titanium and beryllium. Of the combinations of the above materials, the one particularly suitable for anodic bonding is a combination of borosilicate glass and silicon in terms of versatility and processing accuracy. In anodic bonding by this combination, bonding can be performed at a relatively low bonding temperature and in a short time.

When an X-ray reflection multilayer film is provided on the reflection surface of the reflection optical element of the present invention (claim 4), the element can be used as an X-ray optical element. Examples of the multilayer film for X-ray reflection include Mo / Si, Mo / Si compound, Ru /
Si, Ru / Si compound, Rh / Si, Rh / Si compound, W / C, W / Si, Ni / C, Cr / C, Mo / B
₄ C, Mo / SiC, Ru / B ₄ C, Ni / V ₂ O ₅ ,
Among the combinations of Cr / V ₂ O ₅ , any one of them can be used by alternately stacking a plurality of times.

The method of manufacturing an optical element (claim 4) having a reflection surface provided with a multilayer film for X-ray reflection is broadly divided into the following:
There are a method of performing anodic bonding after forming the multilayer film and a method of forming the multilayer film after performing anodic bonding. When the degree of curvature (for example, curvature) of the joint surface between the substrate and the reflecting member is small,
It is easy to form a desired multi-layered film (alternating multi-layered film in which the film thickness ratio of constituent layers and the film thickness of each constituent layer are constant) even after bonding, but when the degree of curved surface (for example, curvature) is large, the desired multilayered film can be formed after bonding. When a multilayer film is to be formed, the film forming process such as setting film forming conditions becomes complicated. Therefore, the degree of curvature of the joint surface (eg curvature)
When the value is large, it is advisable to form a multilayer film before joining.

In the present invention, by proposing both methods, it is possible to provide a method for producing an optical element (claim 4) having a reflecting surface provided with a multilayer film for X-ray reflection, regardless of the shape of the joint surface.
The reflection optical element according to the present invention can be used in an optical system of various devices (for example, an illumination optical system such as a microscope). Further, the optical element having the multilayer film formed thereon can be applied to an illumination optical system of an X-ray microscope or an X-ray lithography apparatus. In addition, the method for producing the reflective optical element of the present invention can be applied not only to the optical element but also to various mechanical system elements.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0045]

Embodiment 1 FIG. 1 is a plan view of an optical element of this embodiment (a).
FIG. 3B is a cross-sectional view (b), in which the optical element has a reflecting member 2 having a plurality of reflecting surfaces (reflecting surfaces or reflecting substantially flat surfaces) 6 separated by a groove 3 on the curved surface 4 of a substrate 1 having a curved surface 4. It is a reflection optical element formed by joining.

The curved surface 4 of the substrate 1 is a spherical surface with good shape accuracy, and the reflecting member 2 is joined to the spherical surface so that each normal of the plurality of reflecting surfaces 6 passes through the center C of the spherical surface. Has been done. Borosilicate glass is used as the material of the substrate 1.
Silicon was used as the material of the reflecting member 2. Further, the substrate 1 and the reflecting member 2 were joined by the anodic joining method.

The procedure for producing the optical element of this example will be described below. First, a flat plate-shaped member 2a made of silicon was prepared, and the groove 3 was formed in the member 2a by a dicing method or an etching method to manufacture the reflecting member 2 (see 1. in FIG. 5). In the etching method, SiO ₂ was vapor-deposited on the flat plate-shaped member (silicon wafer) 2a, and the resist 8 was further applied, and then photolithography was performed using a mask. Next, SiO ₂ dry etching was performed, and the groove 3 was formed by wet etching using KOH or the like by utilizing the difference in etching rate depending on the plane orientation.

As shown in FIG. 1 (a), the plane projection shape of the groove portion 3 is a rotationally symmetric lattice shape which can be easily processed and is easily displayed in a plane coordinate system.
In the reflecting member, in order to increase the rigidity difference between the reflecting surface portion and the groove portion forming portion, the thickness of the reflecting surface portion and the length of one side are larger than the width of the groove portion 3 and the thickness of the groove portion forming portion. That is, the width of the groove portion 3 was 100 μm, the thickness of the groove portion forming portion was 150 μm, and the thickness of the reflecting surface portion was 2 mm and the length of one side was 2 mm.

Before performing anodic bonding, first, the reflection surface portion of the reflection member 2 was polished to have a maximum surface roughness of 0.001 μm or less. Further, the respective bonding surfaces of the reflecting member (silicon) 2 and the substrate (borosilicate glass) 1 to be bonded were polished and smoothed (maximum surface roughness of 0.05 μm or less). Anodic bonding is performed using a reflective member (silicon) 2 and a substrate (borosilicate glass) 1
Is heated to about 400 ° C., the polarity of the reflection member (silicon) 2 side is set to +, the polarity of the substrate (borosilicate glass) 1 side is set to −, and a DC voltage of about 600 V is applied for about 10 minutes. Joining is completed.

When the substrate 1 and the reflecting member 2 are anodically bonded,
While the maximum deformation amount of 1 μm was generated in the groove portion forming portion, almost no deformation was generated in the reflecting surface portion, and the maximum surface roughness of the reflecting surface 6 portion could be maintained at 0.001 μm or less. It should be noted that, depending on the curved surface shape of the substrate that is the bonding surface, the value of the maximum deformation amount is further increased. In that case, by further increasing the thickness of the reflection surface 6 portion, the deformation amount of the reflection surface 6 is increased. Should be within the range of surface roughness accuracy required for the optical system.

When the curved surface 4 of the substrate 1 and the reflecting member 2 are bonded together, particularly when the curved surface 4 of the substrate 1 which is the bonding surface as in this embodiment is concave, the reflecting member closest to the concave surface is Since the bonding is performed from the flat surface (bonding surface) portion, air is likely to be accumulated in the bonding portion. Therefore, in this embodiment, the holes 1 for venting air are provided in the substrate 1 so that air cannot be collected. Since the air vent hole 5 affects the deformation of the reflecting surface portion of the reflecting member 2 located thereabove, the substrate portion located below the reflecting surface portion (central portion) 6a which is not particularly required to have optical characteristics. The minimum size required.

[0052]

[Embodiment 2] FIG. 2 is a sectional view of an optical element of the present embodiment. In the optical element, a dielectric layer 9 is provided on the curved surface of a substrate 1 having a curved surface, and the substrate 1 is provided with the dielectric layer 9 interposed therebetween.
The reflecting optical element is formed by joining a reflecting member 2 having a plurality of reflecting surfaces (reflecting surfaces or reflecting planes) separated by a groove 3.

The curved surface of the substrate 1 is a spherical surface, and the reflecting member 2 is joined to the spherical surface so that the respective normals of the plurality of reflecting surfaces 6 pass through the center of the spherical surface. The dielectric layer 9 was provided by depositing Pyrex glass (borosilicate glass) on the substrate 1. The thickness of the dielectric layer 9 is preferably 0.2 to 2 μm, but in the present embodiment, it is 0.1.
It was 4 μm.

Stainless steel was used as the material of the substrate 1 and a silicon wafer was used as the material of the reflecting member 2. Also, the substrate 1
The reflection member 2 and the reflection member 2 were bonded by the anodic bonding method. When the substrate 1 and the reflection member 2 were anodically bonded, the groove formed portion was deformed by a maximum deformation amount of 1 μm, while the reflection surface portion was hardly deformed and the maximum surface roughness was 0.001 μm.
The reflective surface 6 of m or less could be obtained.

[0055]

Third Embodiment FIG. 3 is a sectional view of an optical element of this embodiment. In the optical element, a metal layer (silicon thin film layer) 10 is provided on a joint surface of a reflection member 2 having a plurality of reflection surfaces (reflection surfaces or reflection planes) separated by a groove 3, and the metal layers 10 are provided. The reflection member 2 via the substrate 1 having a curved surface
The optical element for reflection is formed by joining the curved surface of the optical element. Although the thickness of the metal layer 10 is preferably 0.2 to 2 μm, it is 0.4 μm in this embodiment.

The curved surface of the substrate 1 is a spherical surface, and the reflecting member 2 is joined to the spherical surface so that the normals of the plurality of reflecting surfaces 6 pass through the center of the spherical surface. Borosilicate glass was used as the material of the substrate 1 and the reflection member 2. Further, the substrate 1 and the reflecting member 2 were joined by the anodic joining method. When the substrate 1 and the reflection member 2 are anodically bonded,
The maximum deformation amount of 1 μm was generated in the groove forming portion, whereas the deformation was hardly generated in the reflecting surface portion, and the reflecting surface 6 having the maximum surface roughness of 0.001 μm or less could be obtained.

[0057]

Fourth Embodiment FIG. 4 is a sectional view of an optical element of this embodiment. The optical element is the curved surface 4 of the substrate 1 having the curved surface 4.
And a reflection member 2 having a plurality of reflection surfaces (reflection surfaces or reflection planes) separated by a groove portion 3 are joined to each other, and an X-ray reflection multilayer film 7 is formed on the reflection surface 6. It is a reflection optical element.

The curved surface 4 of the substrate 1 is a spherical surface, and
The reflecting member 2 is joined to the spherical surface so that each normal line of the plurality of reflecting surfaces 6 passes through the center of the spherical surface. Borosilicate glass was used as the material of the substrate 1, and silicon was used as the material of the reflecting member 2. Further, the substrate 1 and the reflecting member 2 were joined by the anodic joining method. The multilayer film 7 was formed on the reflective surface 6 before anodic bonding. That is,
First, the multilayer film 7 was formed on the flat plate-shaped member (silicon wafer) 2a (see 1. in FIG. 6). For film formation, a film forming apparatus such as an ion beam sputtering apparatus or a magnetron sputtering apparatus was used. The multilayer film 7 was formed by depositing 50 to 100 pairs of Mo / Si.

Next, the flat plate-shaped member 2a on which the multilayer film 7 is formed
Although the groove 3 is formed in the groove 3, the above-described etching process is not preferable because the multilayer film 7 may be deteriorated. Therefore, in this example, the groove 3 was formed by the dicing process to manufacture the reflecting member 2 (see 2. in FIG. 6). Next, the reflection member 2 was bonded onto the spherical surface of the substrate 1 by anodic bonding (see 3. in FIG. 6). At that time, the substrate 1
A larger reflective member 2 is used, and the electrode 11 is
It suffices to join a. When a reflecting member having the same size as the substrate 1 is used, the multilayer film 7 is not formed on the end reflection surface of the reflecting member 2, or the end portion of the reflecting member 2 of the formed multilayer film is not formed. The multilayer film 7 on the reflecting surface may be peeled off, and the electrode 11a may be bonded to the end reflecting surface.

When the substrate 1 and the reflecting member 2 are anodically bonded,
While the maximum deformation amount of 1 μm was generated in the groove forming portion, almost no deformation was generated in the reflecting surface portion, and an optical element having a reflecting surface 6 having a maximum surface roughness of 0.001 μm or less could be manufactured (FIG. 6). 4)). As the X-ray reflective multilayer film 7, a Mo / Si alternating multilayer film was used. The optical element of this example could be used as an X-ray optical element.

[0061]

Fifth Embodiment FIG. 4 is a sectional view of an optical element of this embodiment. The optical element is the curved surface 4 of the substrate 1 having the curved surface 4.
And a reflection member 2 having a plurality of reflection surfaces (reflection surfaces or reflection planes) separated by a groove portion 3 are joined to each other, and an X-ray reflection multilayer film 7 is formed on the reflection surface 6. It is a reflection optical element.

The curved surface of the substrate 1 is a spherical surface, and the reflecting member 2 is joined to the spherical surface so that the normals of the plurality of reflecting surfaces pass through the center of the spherical surface. Borosilicate glass was used as the material of the substrate 1, and silicon was used as the material of the reflecting member 2. Further, the substrate 1 and the reflecting member 2 were joined by the anodic joining method. The multilayer film 7 was formed on the reflecting surface 6 after anodic bonding (see 2.3 in FIG. 7) (see 4. in FIG. 7). That is, first, after manufacturing an optical element in the same process as in Example 1 (see 1.2.3. In FIG. 7), the multilayer film 7 was formed on the reflecting surface 6 of the optical element.

This method of forming the multi-layer film 7 on the reflecting surface 6 of the optical element is one of the manufacturing methods generally used for the optical element using the multi-layer film. Since this general method can be used, the X-ray optical element can be manufactured more easily than in the case of Example 6 in which the multilayer film 7 is formed on the reflecting surface before the anodic bonding without making a large change in work. Workability was good.

The X-ray reflection multilayer film 7 contains Mo / Si.
The alternate multilayer film of was used. The optical element of this example could be used as an X-ray optical element.

[0065]

Sixth Embodiment FIG. 4 is a sectional view of an optical element of this embodiment. The optical element is the curved surface 4 of the substrate 1 having the curved surface 4.
And a reflection member 2 having a plurality of reflection surfaces (reflection surfaces or reflection planes) separated by a groove portion 3 are joined to each other, and an X-ray reflection multilayer film 7 is formed on the reflection surface 6. It is a reflection optical element.

The curved surface 4 of the substrate 1 is a spherical surface, and
The reflecting member 2 is joined to the spherical surface so that each normal line of the plurality of reflecting surfaces 6 passes through the center of the spherical surface. Borosilicate glass was used as the material of the substrate 1, and silicon was used as the material of the reflecting member 2. Further, the substrate 1 and the reflecting member 2 were joined by the anodic joining method. The multilayer film 7 was formed on the reflective surface 6 before anodic bonding. That is,
First, a flat plate-shaped member 2a made of silicon is prepared, and the groove 3 is formed on the member 2a by a dicing method or an etching method.
To form the reflection member 2 (see 1. in FIG. 8).

Next, after polishing the reflecting surface portion of the reflecting member 2 to a maximum surface roughness of 0.001 μm or less, a multilayer film 7 is formed on the reflecting member 2 (see 2. in FIG. 8). Further, the reflecting member 2 was joined to the spherical surface of the substrate 1 by anodic bonding (see 3. in FIG. 8), and the X-ray reflective optical element of this example was manufactured (see 4. in FIG. 8). The X-ray reflection multilayer film 7 has M
An alternating multilayer film of o / Si was used. The optical element of this example could be used as an X-ray optical element.

The reflection optical element according to the above-described embodiments can be applied as a mirror for Koehler illumination which can multiplex point light sources. Further, by forming an X-ray reflective multilayer film on the reflecting surface, it can be applied as a Koehler illumination mirror even in an X-ray optical system in which a lens optical system cannot be assembled. As a result, the performance of the X-ray illumination optical system in an X-ray microscope, an X-ray lithography apparatus, etc. can be improved.

The embodiment also discloses a method of manufacturing an optical element according to the present invention. However, compared with a method of manufacturing an optical element of the same shape by machining or the like, substrate preparation, groove formation,
Even in all of the three steps, which are roughly divided into anodic bonding, the time required for processing is short, and since general-purpose technology can be applied, it is easy in terms of processing technology level. In the examples, three types of manufacturing methods are disclosed for forming the X-ray reflective multilayer film, but the steps are the same as those for forming the multilayer film on a normal substrate, and a short process can be performed without using a special device. The optical element can be manufactured in time.

[0070]

As described above, the reflection optical element of the present invention satisfies both strict shape accuracy and roughness accuracy, and therefore has a function equivalent to that of the theoretical mirror for Koehler illumination. It can be put to practical use as an optical element for reflection.

[Brief description of drawings]

FIG. 1 is a plan view (a) and a sectional view (b) of an optical element of Example 1.

FIG. 2 is a sectional view of an optical element of Example 2.

FIG. 3 is a sectional view of an optical element of Example 3.

FIG. 4 is a cross-sectional view of optical elements of Examples 4, 5, and 6.

5A to 5C are process explanatory diagrams of the method for manufacturing the optical element of Example 1. FIGS.

6A to 6C are process explanatory diagrams of a method of manufacturing the optical element of Example 4. FIGS.

7A to 7C are process explanatory diagrams of a method of manufacturing the optical element of Example 5. FIGS.

FIG. 8 is a process explanatory view of a method for manufacturing an optical element of Example 6.

FIG. 9 is an explanatory diagram showing the relationship between OTF and spatial frequency at each value of σ.

FIG. 10 is an explanatory diagram illustrating the concept of a Koehler illumination optical system.

FIG. 11 is an explanatory diagram illustrating a concept of a theoretical mirror for Kohler illumination.

FIG. 12 is a configuration diagram of a general X-ray microscope.

[Explanation of symbols for main parts]

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Reflecting member 2a ... Flat plate member 3 ... Groove part 4 ... Curved surface (joint surface) of substrate 4 '... Bonding surface of reflecting member 5 ... Air vent hole 6・ ・ ・ Reflecting surface 7 ・ ・ ・ X-ray reflection multilayer film 8 ・ ・ ・ Resist 9 ・ ・ ・ Dielectric (borosilicate glass) layer 10 ・ ・ ・ Metal (silicon) layer 11 ・ ・ ・ Electrode 11a Member side electrode 11b ... Substrate side electrode 12 ... X-ray generator 13 ... X-ray illumination optical system 14 ... Sample capsule 15 ... X-ray magnifying optical system 16 ... X-ray imaging device 17・ ・ ・ Vacuum container 18 ・ ・ ・ Exhaust device 19 ・ ・ ・ Light source 20 ・ ・ ・ First lens 21 ・ ・ ・ Optical integrator 22 ・ ・ ・ Multiplexed light source image 23 ・ ・ ・ Second lens 24 ・..Object 25 ... Incident light
that's all

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoto Majima 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (4)

[Claims] 1. A reflective optical element comprising a substrate having a curved surface and a reflective member having a plurality of reflective flat surfaces or reflective substantially flat surfaces separated by a groove portion, which are bonded to the curved surface. 2. The curved surface of the substrate is a spherical surface, and the reflective member is bonded to the spherical surface so that the normals of the plurality of reflective flat surfaces or the reflective substantially flat surfaces pass through the center of the spherical surface. The reflective optical element according to claim 1, wherein: 3. The substrate according to claim 1, wherein the substrate and the reflecting member are bonded by an anodic bonding method.
The reflective optical element described. 4. An optical element for reflection according to claim 1, wherein a multilayer film for X-ray reflection is provided on the reflection surface.