JP3101695B2 - Multilayer film for soft X-ray optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multilayer film for a soft X-ray optical element, and more particularly to a multilayer film for a soft X-ray optical element having a small absorption loss and a large optical refractive index in a soft X-ray wavelength region.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG. FIG.
FIG. 3 is a view showing a cross section of a general multilayer film for a soft X-ray optical element comprising a Mo / Si layer. Reference numeral 1 denotes a substrate, 2 denotes a low refractive index layer made of a Mo layer, and 3 denotes a high refractive index layer made of a Si layer. This multilayer film is the most widely researched and developed Mo
/ Si is an example of a soft X-ray reflection multilayer film, in which a high refractive index layer composed of a light element layer is formed of Si, and a low refractive index layer composed of a heavy element layer is formed of Mo. The Si layer in question here usually has a polycrystalline structure in which amorphous or microcrystals are aggregated.

[0003]

In the soft X-ray wavelength region, since the optical constant of the substance is close to 1, when a multilayer mirror is formed, the reflection at each interface of the multilayer film is small, and many interfaces are required. It is known that Each substance forming the multilayer film has an inherent absorption loss,
When the number of layers is multi-layered, it becomes difficult to form a multi-layered film having a high reflectance because absorption loss increases.

According to the present invention, a cage-like layer made of a cluster crystal such as Si ₂₀ , Si ₃₄ or Si ₄₆ is used as a high refractive index layer made of a light element layer, instead of a conventional high refractive index layer having an amorphous or polycrystalline structure. An object of the present invention is to provide a multilayer film for a soft X-ray optical element which uses a material having a structure, significantly reduces absorption loss as compared with a conventional multilayer film, and shows a high refractive index as a result.

[0005]

In a multilayer film for a soft X-ray optical element which reflects and transmits soft X-rays by alternately laminating substances having different optical refractive indices in a soft X-ray wavelength region, a high refractive index A multilayer film for a soft X-ray optical element in which layers were formed using a low-density material was formed .

The low-density material has a cage structure.
Si _20, Si _34, to constitute a soft X-ray multilayer film for optical element is any one selected from among Si _46.

[0007]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a cross section of an embodiment of a multilayer film for a soft X-ray optical element comprising a Mo / Si ₂₀ layer of the present invention. 1 indicates the substrate. Reference numeral 2 denotes a low-refractive-index layer formed of a heavy element layer, which is formed of Mo in this example. Selection of the material of the low refractive index layer composed of this heavy element layer
Considering the wavelength of the target soft X-ray, it is selected as a combination that can obtain a high reflectance. Reference numeral 3 denotes a high refractive index layer made of a light element layer, which is formed using Si _{20 in} this example.

FIG. 2 is an enlarged view of the Si ₂₀ layer of the Mo / Si ₂₀ multilayer film shown in FIG. Substrate 1 is subjected to polishing smooth, 2 low refractive index layer made of Mo layer, 3 is a high refractive index layer made of Si _20. FIG. 3 is a diagram showing a simple substance constituting the Si ₂₀ layer. This Si ₂₀ is a material having a cage structure composed of cluster crystals. In other words, the simple substance constituting the basis of the structure of the Si ₂₀ layer forms a dodecahedron composed of regular pentagonal faces. There are 20 vertices and each vertex is 20 in total
Si atoms are occupied and the inside is hollow. As a material for forming this light element high refractive index layer, Si ₃₄ or Si ₄₆ can be used in addition to Si _20. Also, as another light element high refractive index layer, a structure of C ₆₀ or C ₇₀ is used. Can also be used. These are all materials having a cage-like structure composed of cluster crystals.

FIG. 4 is a diagram showing the wavelength dependence of the optical refractive index n of a normal Si film and a Si ₂₀ film. The dotted line in FIG. 4 indicates the wavelength dependence of the refractive index n of ordinary Si,
The solid line shows the wavelength dependence of the refractive index n of Si ₂₀ . The calculation of the reflectance was performed with an incident angle of 10 ° and a number of layers of 101. FIG. 5 is a diagram showing the wavelength dependence of the absorption coefficient k of a normal Si film and a Si ₂₀ film. The dotted line in FIG. 5 shows the wavelength dependence of the absorption coefficient k of ordinary Si, and the solid line shows the wavelength dependence of the absorption coefficient k of Si ₂₀ . The calculation of the reflectance was performed with the incident angle being 10 ° and the number of layers being 101.

FIG. 6 is a graph showing the soft X-ray reflectivity of a multilayer film for a soft X-ray optical element having a normal structure composed of Mo / Si layers and a multilayer film for a soft X-ray optical element of the present invention composed of ₂₀ layers of Mo / Si. It is a figure which shows a wavelength dependence. The dotted line in FIG. 6 shows the wavelength dependence of the reflectance of the multilayer film in which the high refractive index layer is formed of ordinary Si, and the solid line shows the wavelength of the reflectance of the multilayer film of the present invention in which the high refractive index layer is formed of Si _20. Show dependencies. The calculation of the reflectivity was performed with the incident angle of 10 ° and the number of layers of 101.
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[0011] As described above, the multilayer film of conventional construction consisting of Mo / Si layers, as is apparent from FIG. 6 showing the wavelength dependence of the multilayer film of this invention having the Mo / Si ₂₀ layers, wide soft X-ray An improvement in the reflectance in the wavelength region is observed.

[0012]

As described above, according to the present invention, instead of forming a high refractive index layer composed of a light element layer using a conventional amorphous or polycrystalline layer, these cluster crystals are used. By using a cage-shaped material made of such a material, the density of the multilayer film can be reduced, the absorption loss in the film can be reduced, and the reflectance, transmittance, and proof stress can be improved.

[Brief description of the drawings]

FIG. 1 illustrates an embodiment.

FIG. 2 is an enlarged view showing a part of FIG. 1;

FIG. 3 is a diagram showing the structure of Si ₂₀

FIG. 4 is a diagram showing wavelength dependence of a refractive index.

FIG. 5 is a diagram showing wavelength dependence of an absorption coefficient.

FIG. 6 is a graph showing the wavelength dependence of the reflectance of a multilayer film.

FIG. 7 illustrates a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Low refractive index layer which consists of a double element layer 3 High refractive index layer which consists of a light element layer

Continuation of the front page (56) References JP-A-8-5975 (JP, A) JP-A-6-230194 (JP, A) JP-A-6-184738 (JP, A) JP-A-6-242297 (JP) , A) Japanese Patent Application Laid-Open No. 5-142397 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21K 1/06

Claims (1)

(57) [Claims] In a soft X-ray wavelength region, a high refractive index layer is provided.
In soft X-ray multilayer film for optical element for reflecting and transmitting the soft X-rays to a substance of high refractive index layer are laminated alternately, the material of the high refractive index layer, Si ₂₀ having a cage-like structure,
A multilayer film for a soft X-ray optical element, wherein the multilayer film is selected from Si ₃₄ and Si ₄₆ .