JP2648599B2 - Method of making multilayer reflector for X-ray or vacuum ultraviolet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a reflecting mirror for radiation with a wavelength of not less than X-rays and not more than vacuum ultraviolet rays and having a wavelength of 200 nm or less, the incidence angle of which is almost perpendicular to a reflecting surface. The present invention relates to a method of manufacturing a reflecting mirror that receives a regular incident angle.

[Prior art] Conventionally, a reflector having a high reflectance when radiation is incident on a reflection surface at a right angle or near to the reflection surface with respect to radiation having a wavelength shorter than the vacuum ultraviolet region having a wavelength of 200 nm or less. Did not exist, and only an reflectance of 1% or less could be obtained at an incident angle near perpendicular to the reflecting surface.

On the other hand, in the oblique reflection mirror which gives a relatively high reflectance, it is necessary to adjust the incident angle to 1 degree or less from the reflection surface or in the range of 1 to 3 degrees.

In addition, since the light is incident on the reflecting surface at a small angle, the reflecting surface needs to be large even for small incident light, and its use is difficult and its application range is limited. Met.

In the case of the oblique incidence reflecting mirror, the degree of freedom of the optical system configuration is small, and it is indispensable to polish the reflecting mirror itself so as to have a highly accurate flatness over a wide area of the reflecting surface. Accurate support and means of precise adjustment are also important, and there are many inconveniences in practical use.

In order to eliminate these difficulties, a reflector using a multilayer reflector utilizing interference of a multilayer thin film has been proposed as a target for radiation from a wavelength of 2000 ° to a visible wavelength.

The wavelength range longer than the wavelength 2000 Å, a thin layer and Zn consisting MgF ₂
In the case of a multilayer reflector in which two thin layers of a dielectric material such as a thin layer made of S are alternately stacked, a reflectance of approximately 80 to 100% is obtained even at normal incidence.

However, in a reflector using a reflector consisting of this dielectric alternating layer, the absorption of radiation in the wavelength range of 1000 mm or less increases rapidly, and the dielectric alternating layer that can be used as a reflector is used. There is almost no constituent material.

On the other hand, for a single-layer metal film such as Al, Au, and Pt, the reflectance sharply decreases in proportion to the wavelength λ- ⁴ for radiation in the short wavelength range of 700 ° or less, and the short wavelength of 200 ° or less It is 1% or less at normal incidence for radiation in the region.

In order to eliminate such a drawback, a reflector using a metal multilayer film in which two kinds of metal materials having different complex refractive indices are alternately laminated as a reflector has been used.

In the X-ray and vacuum ultraviolet region, the reflectivity of most materials is the complex index of refraction (n +
ik, hereinafter simply referred to as the refractive index. ), And the real part n is approximately 1.0 (n = 1−δδ = 10 ⁻¹ to 10 ⁻³ ), so that the reflectivity of Fresnel at the boundary between the vacuum and the material thin film is very small, 0.1 It is a size of an order of magnitude or less.

In addition, even at the boundary between the laminated thin films of different materials, the reflectance does not exceed several% for one boundary surface.

However, high reflectivity can be achieved by adopting a structure with a film thickness such that different materials are alternately laminated to form a multilayer structure and the reflection from each layer boundary is intensified by interference and the reflectivity of the multilayer film reflector is maximized as a whole. Becomes possible.

Further, it is known that by selecting a combination of different materials so that the difference in the refractive index between adjacent layers becomes large, it is possible to realize a reflecting mirror that gives a high reflectance together with the structure of the film thickness. Have been.

Among the combinations of materials known to date, there are transition metals as low refractive index materials, and many of high refractive index materials use semiconductor elements such as carbon and silicon.

Representative examples include a combination of tungsten and carbon, and a combination of molybdenum and silicon.

[Problems to be Solved by the Invention] However, when a combination of two kinds of materials is actually selected to realize a theoretically possible high reflectance,
Conventionally, it has been extremely difficult to obtain the expected high reflectance even when two kinds of materials are alternately laminated by means such as vapor deposition.

Observation of the cut surface of the prototype multilayer film body with an electron microscope shows that there are characteristic voids commonly referred to as voids in the film, the filling rate is about 0.7 to 0.9, and the dense bulk material It became clear that a different porous layer film was easily formed.

When the filling factor of the layer film is smaller than 1, it means that the density of the layer film is lower than that of the bulk material, and the reflectance is naturally lower than the reflectance theoretically determined by the optical constant of the bulk material used. Only will be obtained.

Furthermore, when these layer films are observed by electron beam diffraction and X-ray diffraction, it has been found that an amorphous, amorphous layer film capable of obtaining only a so-called halo diffraction pattern is formed.

If the structure of the layer film becomes closer to amorphous,
There are innumerable voids, and the synchrotron orbital synchrotron radiation,
Alternatively, when high-intensity light such as laser plasma X-ray radiation is irradiated, the reflector of the reflector is locally heated and has a disadvantage that the multilayer structure is easily destroyed.

Therefore, it has durability against local heating,
It is required that it is chemically stable against the overall temperature rise and that there is no diffusion of the constituent material of the layer film.

The present invention has been completed with the aim of avoiding or eliminating the above-mentioned problems, the aim being to achieve a reflection equal to the optical properties of the bulk material and thus substantially equal to a high theoretical value. It has excellent thermal resistance when irradiated with synchrotron orbital radiation, as well as in a normal storage state, and the presence of one or more crystallized layer films adjacent to each other causes The present invention provides a method for producing a multilayer mirror for X-rays and vacuum ultraviolet rays having excellent heat resistance and chemical stability, in which diffusion of metal ions is remarkably prevented as compared with the case where an amorphous layer film is present. That is.

Means for Solving the Problems An object of the present invention is to provide a method for producing a multilayer reflector for X-ray or vacuum ultraviolet rays by alternately stacking two kinds of layer films having different refractive indexes. Forming at least one of the two layer films at a temperature at which a crystallized substance including a crystal grain boundary having a size equal to or greater than the wavelength of the X-ray or vacuum ultraviolet light to be reflected is formed. And the crystallization material is a metal containing one or more platinum group metals, or contains one or more elements selected from the group consisting of Be, B, C and Si, or Pb and Bi The alloy consisting of, as a main component, or one or more transition metal elements, or one or more compounds selected from the group consisting of carbides, nitrides, and oxides of Si and B, respectively. By selecting a membrane material for It is achieved Te.

The reflector made according to the present invention is irradiated with high-intensity light such as synchrotron orbital radiation, and has a specific crystallized single crystal so that the performance of the reflector is secured even if it is locally heated. Elemental substances or crystallized compounds
It is used and configured as a layer film of a multilayer reflector,
As a layer film composed of these specific substances, a layer containing at least one of platinum group metals, ruthenium Ru, rhodium Rh, and palladium Pd is particularly preferably used.

As another layer alternately laminated, it is more preferable that at least one of beryllium Be, boron B, carbon C, and silicon Si is combined as a layer film and as an amorphous, preferably crystallized layer film.

Further, as another more preferred layer film, particularly, the melting point is 20
Aluminum nitride AlN, beryllium nitride Be ₃ N ₂ , titanium nitride
TiN, nitriding Niobu NbN, vanadium nitride VN, zirconium nitride ZrN, boron nitride BN, hafnium nitride HfN, tantalum nitride TaN, Ta ₂ N, boride aluminum AlB _2, titanium boride Ti
B ₂ , vanadium boride V ₃ B ₄ , VB, tungsten boride WB, hafnium boride HfB, zirconium boride ZrB, boron carbide B
₄ C, molybdenum carbide Mo ₂ C beryllium carbide Be ₂ C, silicon carbide
SiC, vanadium carbide V ₂ C, tungsten carbide WC, W ₂ C,
Hafnium carbide HfC, Niobium carbide NbC, Tantalum carbide TaC
Titanium carbide TiC, zirconium carbide ZrC, aluminum oxide Al ₂ O ₃ , beryllium oxide BeO, chromium oxide Cr ₂ O ₃ , hafnium oxide HfO ₂ , titanium oxide TiO ₂ , cerium oxide CeO ₂ ,
It is preferable to use zirconium oxide ZrO ₂ or the like.

The substances listed here include those with a high refractive index and those with a low refractive index. What is necessary is just to form an alternating layer in combination so that it may be higher than the other refractive index.

In the present invention, in order to form each layer of at least one substance into a crystallized layer film, a substrate used when forming a multilayer reflective film, for example, SiC, Si, Zordur, Cer-Vi
t, the temperature of the fused quartz is raised to a high temperature, for example, from about 300 ° C. to about 600 ° C., and electron beam vapor deposition and cluster ion vapor deposition of UHV, which are easily crystallized, are performed as a film forming method.

The multilayer mirror for X-rays or vacuum ultraviolet rays obtained according to the present invention has a sufficiently smooth surface, for example, a surface polished to a roughness of 10 ° or less in rms value, or a curved surface corresponding to the wavelength of the radiation of interest. On the substrate 1 of FIG.
The layer film 2 of the first type substance and the layer film 3 of the second type substance are alternately laminated. X of the present invention
The reflectivity provided by the multilayer reflector for line / vacuum ultraviolet light varies depending on the refractive index difference between the two kinds of materials alternately laminated, the absorptance of each layer film, the number of layer films, the wavelength of irradiated radiation, and the like.

The difference in the refractive index between the two materials that are alternately stacked is 10 layers.
When 0 layer pairs are used, it is practically preferably 0.01 or more.

In order to provide a refractive index difference between the respective layer films of the alternating layer films, a material having a high refractive index and a material having a low refractive index with respect to X-rays and radiation in a vacuum ultraviolet region may be used. Examples of the substance having a low refractive index and a high melting point include borides, nitrides, carbides, and oxides of the above-mentioned transition metals. Examples of the substance having a high refractive index and a high melting point include beryllium, aluminum, and boron. Or silicon nitride, carbide, oxide
No.

Here, the transition metal is an element having an electron vacancy in 3d, 4d, and 5d orbitals scandium Sc, titanium Ti, vanadium V, chromium Cr, iron Fe, nickel Ni, cobalt Co, zirconium Zr, niobium Nb, molybdenum Mo, Techchinium T
c, rhodium Rh, tungsten W, rhenium Re, osmium Os, iridium Ir, platinum Pt, and copper Cu, palladium Pd, silver Ag, and gold Au filled with 3d, 4d, and 5d orbitals.

The thickness of each layer film is approximately 1/4 of the wavelength of the target radiation, and the same material is a layer film that is repeatedly laminated with one layer of another material interposed therebetween. When the reflected light at the boundary between the films satisfies the condition that they all interfere so as to stress each other, or when the absorption loss in each layer film and the decrease in reflectivity due to phase shift are compared, the reflectivity of the multilayer film as a whole is Is determined by satisfying one or both of the following conditions.

At that time, the layer thickness may be the same for all the layer films of the same material, or may be different from each other so that the reflectance is maximized by changing the thickness of the layer film for each layer. .

Also, since the reflectance increases as the number of layer films increases, the number of layer films is preferably 5 or more. However, if the number is excessive, the influence of the absorption layer becomes remarkable. Then, it is appropriate to stop to about 200 layer pairs.

The reflector of the alternating layer film of the two crystallized substances according to the present invention is much more durable than the conventional one, but furthermore, another substance is present on the surface of the uppermost layer film. Needless to say, a protective layer made of a chemically stable material having a low absorption capacity may be added.

For a better understanding of the invention, the following examples are given.

[Example 1] Using an ultrahigh vacuum electron beam evaporation apparatus shown in Fig. 2, an alternate layer film of Ru and Si, a total of 41 layer films, was sequentially formed by evaporation to obtain a soft X-ray having a wavelength of 114 °. A multilayer reflector was manufactured. The first material 2 in FIG. 1 was made of Ru and the second material 3 was made of Si, and the thickness of each layer was set to 36.4 ° and 23.5 °, and vapor deposition was started from Ru, and 41 layers were sequentially and alternately laminated.

In the apparatus shown in FIG. 2, two electron guns of an electron beam evaporation source are arranged opposite to the substrate 2 at symmetrical positions, and each electron gun hearth has a purity of 3N, that is, 99.9% of Ru and 9N, that is, 9
9.9999999% Si was installed.

A circular flat substrate 2 having a flatness of λ / 50 (λ = 6328 °) and a surface roughness of 5 ° rms or less and having a diameter of 2 inches and a thickness of 10 mm was mounted on the heater surface of the substrate holder, It takes 2 hours before vapor deposition at 1400 ℃
Until it reaches. Then, after the degree of vacuum in the vapor deposition device was restored to 8 × 10 ⁻¹⁰ Torr, the temperature of the substrate 2 was reduced to 8 × 10 ⁻¹⁰ Torr.
The temperature was set at 00 ° C. and maintained at or above this temperature during the subsequent deposition.

The shutters on both hearths and the main shutter were initially closed, and both Ru and Si in both hearths were pre-heated with an electron beam for 30 minutes to 1 hour, during which the respective deposition rates were 10Å / min and 20Å. / min
A quartz oscillator (not shown) placed close to both hearths provided feedback for maintaining the deposition rate at a predetermined value.

Thereafter, the shutters on both hearths were alternately opened to perform vapor deposition, and 41 layers having a predetermined layer thickness were stacked.

During this time, the degree of vacuum in the evaporation apparatus was set to 1 × 10 ⁻⁹ Torr,
The temperature was controlled within the range of 800-830 ° C.

After the deposition process was completed, electron diffraction was performed.As a result, an alternating layer equal to a single crystal film of Ru and Si was obtained in a spot-like manner.
It was confirmed that about 350 mm for Si and about 200 mm for Si.

Irradiation with synchrotron orbital radiation at an incident angle of 10 degrees resulted in a reflectance of 59.8%.

Example 2 In the same manner as in Example 1, tungsten carbide W ₂ C was used as a high absorption layer film 2 on a polished SiC substrate by the ion beam evaporation apparatus shown in FIG. Then, silicon Si was deposited to a thickness of 39.8 mm, 21 layers of W ₂ C and 20 layers of Si were deposited and deposited.

Therefore, the final deposited layer film is high absorption tungsten carbide.

During the deposition, the temperature of the substrate was 450 ° C. to 600 ° C. The higher the temperature, the more excellent the crystallinity of the layer film was obtained. The deposition phase was close to the spot.

Depositing first W ₂ C purity 3N (99.9%), and Si6N (99.9999
%) Are charged into crucibles 3 and 4, respectively.

The degree of vacuum in the vacuum vessel 13 was adjusted to 2 × 10 ⁻⁸ Torr, and the ionization current and acceleration voltage of each evaporation source were 125 m for W ₂ C.
A, 1.4 kV, and Si were set to 2.0 mA and 1.5 kV, respectively.

By adjusting the temperature in crucibles 3 and 4, the deposition rate is 5-10
The vapor deposition was performed so as to be Å / min.

When the thus-prepared multilayer mirror for soft X-rays and vacuum ultraviolet rays was irradiated with a 124.0 ° ray at an incident angle of 10 °, a reflectance of 48.5% was obtained.

[Comparative Example] Soft X-ray / vacuum consisting of an amorphous layer film obtained by vapor deposition with an electron gun while maintaining the substrate temperature of Ru and Si as in Example 1 at room temperature and at a low temperature cooled by liquid nitrogen. A multilayer reflector for ultraviolet light was manufactured.

When this reflector was attached to a soft X-ray spectrometer using synchrotron orbital synchrotron radiation and irradiated with SR light for a total of 15 hours, peeling of the layer film and local melting on the surface of the layer film occurred, and the reflectance was reduced. It has decreased to a few percent.

On the other hand, both reflecting mirrors manufactured in Examples 1 and 2 are:
Similarly, when attached to a soft X-ray spectrometer that uses synchrotron orbital synchrotron radiation,
There was no damage beyond 200 hours and no decrease in the reflectivity occurred.

[Effect of the Invention] The multilayer mirror for X-ray / vacuum ultraviolet light of the present invention only has a higher reflectivity to radiation of wavelengths in the soft X-ray / vacuum ultraviolet region than the conventional amorphous layer. Not
Conventionally, the reflecting surface was significantly damaged in a short time due to irradiation with synchrotron orbital radiation or the like. However, the reflecting mirror of the present invention has sufficient durability to withstand long-time continuous irradiation.

In particular, the present invention combines a plurality of flat or curved reflecting mirrors as a reflecting mirror for an enlargement / reduction optical system in the X-ray region, and a reflection for a laser resonator for a soft X-ray vacuum ultraviolet region. The reflection boundary of the present invention can be widely used as a useful part for an optical device in the region of X-ray optics, which has not existed conventionally, such as a mirror, and further for a reflection type dispersion element having a reflection boundary having a lattice structure. .

[Brief description of the drawings]

FIG. 1 is a schematic view for explaining the configuration of a cut end face of a reflecting surface body for a reflecting mirror made according to the present invention, and FIG. 2 is a view for manufacturing a reflecting mirror made according to the present invention. FIG. 3 is an explanatory view of a configuration of an ultrahigh vacuum electron beam evaporation apparatus used, and FIG. 3 is an ion beam evaporation apparatus used similarly. [List of symbols in the figure] FIG. 1 1... Substrate 3... 2nd substance 2... 1st substance 4... Protective film 2 FIG. ...... Substrate, 6 ... Ruthenium 3 ... Main shutter, 7 ... Silicon 4 ... Shutter, 8 ... Shutter 5 ... Electron gun, 9 ... Quartz vibrator Fig. 3 Ion beam evaporation apparatus 1 ... Substrate Holder heater 2 Substrate 8, Accelerator plate 3 Evaporation source (example Si) 9, 9 Si ion beam 4 Evaporation source (example Ru), 10 Ru ion beam 5 Ionization unit , 11 ... Acceleration power supply 6 ... Ionization unit, 12 ... Acceleration power supply 7 ... Acceleration plate, 13 ... Bell jar

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-7400 (JP, A) JP-A-62-226047 (JP, A) JP-A-61-128199 (JP, A) JP-A-61-128199 165701 (JP, A)

Claims (2)

(57) [Claims] 1. A method for producing a multilayer mirror for X-ray or vacuum ultraviolet radiation by alternately stacking two kinds of layer films having different refractive indexes, wherein at least one of the two kinds of layer films is used. The formation is performed by vapor deposition at a temperature at which a crystallized substance including a crystal grain boundary having a size equal to or larger than the wavelength of the X-ray or vacuum ultraviolet light to be reflected is formed, and the crystallized substance is formed of platinum. A metal containing one or more group metals, or containing one or more elements selected from the group consisting of Be, B, C, and Si, or an alloy containing Pb and Bi as a main component, or a transition It is characterized in that the film material is selected so as to be composed mainly of at least one kind of a metal simple substance, or at least one compound selected from the group consisting of carbide, nitride and oxide of Si and B respectively. Multi-layer coating for X-ray or vacuum ultraviolet How to create a mirror. 2. The method according to claim 1, wherein said vapor deposition is performed at a temperature of 300 ° C. or higher.