JPH02238402A - Multilayered film - Google Patents

Abstract

PURPOSE:To prevent the decrease in the X-ray reflectivity of the multilayered films and the peeling of the multilayered films by constituting the compsn. of one thin film of the plural multilayered films of boron and nitrogen. CONSTITUTION:The multilayered films are formed by using a compd. BN consisting of the boron (B) and nitrogen (N) having about the same complex index of refraction as that of a single element in the light element layer. The multilayered films are formed by alternately laminating 20 layers each of BN 10 and W 11 by a sputtering method. The BN layers are respectively indicated as B1 to B20 and the W layers respectively as A1 to A20. The degradation in the X-ray reflectivity of the multilayered films with age and the peeling of the multilayered films from a substrate are prevented in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer film suitable for reflecting light in the soft X-ray region.

[Conventional technology]

Multilayer films have been widely used as antireflection films for visible light. In recent years, soft xg area (10~1
With the progress of light source development and research, multilayer films are attracting attention as optical elements that can be used in the soft X-ray region.

FIG. 4 shows the structure of a multilayer film for soft X-rays in which heavy elements and light elements are alternately laminated. In the figure, 1 is a layer of a heavy element with a high X-ray reflectance and is called the A layer, and 2 is a layer of a light element with a low X-ray reflectance and is called B/Pl. 3 is a substrate. In order to efficiently reflect soft XG with the multilayer film having the above structure, it is necessary that the difference between the X-ray reflectance of the A layer and the X-ray reflectance of the B layer be large. For that purpose, A
A heavy element with a high X-ray reflectance is used for the layer, and a light element with a low X-ray reflectance is used in the B layer.

Conventionally used multilayer films include, for example, if a multilayer film made of W and C is expressed as W/C, W/C, Mo/Si.
All/Cu. Au/C, Ta/C. Cu/C, Re/
C, W/Be, etc. [Problem to be solved by the invention] W/C. Au/C. Ta/C. Cu/C. Re/C,W
/Be In a multilayer film such as e, the B layer, which is formed of single elements such as Be and C, has a weak bond between atoms and the light elements that make up the B layer have a small atomic radius. It has a tendency to leave Aff and spread easily to Aff. For example, the currently used C film is a graphite-like film, and the carbon in the graphite is more likely to decompose and diffuse into the A layer than in diamond. Additionally, diamond-like thin films with strong bonds that are difficult to decompose and diffuse are being created, but because they grow in island-like shapes, it is currently difficult to create ultra-thin films with flat surfaces. On the other hand, Be used in W/Be also has a weak bond between Be and tends to grow in an island shape, leaving the B layer and diffusing into the A layer. Furthermore, in a multilayer film of metals such as Cu/Jldl, An and Cu tend to diffuse into each other due to the nature of the metals. Due to such mutual diffusion, the X-ray reflectance of the A layer decreases and at the same time the X-ray reflectance of the B layer increases, resulting in a problem in that the reflectance of the multilayer film decreases. Furthermore, since the mutual diffusion between the B layer and the A layer is promoted by time and temperature increase due to light irradiation on the multilayer film, there is a problem that the reflectance of the multilayer film decreases over time. Substances A and B used in conventional multilayer films are often a combination that forms a compound, and the formed compound is also stable, and it is possible for the compound to form over several to several tens of layers at the interface. many. For example, in the most commonly used W/C multilayer film, W and C combine at the interface to form WC, which is chemically stable and easily formed. Also, B
When Si is used in the layer, in most cases it combines with atoms in the A layer to form silicide. By forming several to several dozen layers of compounds at the interface, the A layer and B layer
There was a problem in that the difference in reflectance between layers was reduced, and the reflectance of the multilayer film was significantly lowered.

Also, Be. When layer B is formed with C, etc., it is difficult to form a single-crystal thin film with strong bonds between elements, so it tends to grow in granular form, and the interface with layer A becomes uneven, causing irregular scattering of X-rays and There was a problem in that the reflectance of the calendar membrane decreased significantly. Also. Using Be, C, etc., extremely thin Be.
When using a Citl film, it is chemically stable and has good adhesion to the substrate and heavy element layer when the substrate is kept at a low temperature.
Currently, it is difficult to form flat thin films. Therefore, there was a problem in that the multilayer film peeled off from the substrate over time. Furthermore, when a multilayer film using such light elements is irradiated with strong light such as SR light, heat is instantaneously applied to the multilayer film, the temperature locally increases, and the light elements in the multilayer film are heated. The problem was that the multilayer film would peel off from the substrate because the thin film was chemically unstable and had poor adhesion. In addition, conventional C, Be, Cu, Si
When the substrate is heated during formation, there is a problem in that compounds with heavy elements are formed at the interface or rapidly diffused into the heavy element layer. As mentioned above, in the conventional multilayer film, at the interface between layer A and layer B, the atoms forming layer A and the atoms forming layer B may diffuse into each other or form a compound. Or, due to unevenness on the interface, the soft X-ray reflectance of the heavy element layer A decreases and at the same time the reflectance of the light element layer B increases, making it difficult to maintain the reflectance difference. There is a problem that the reflectance of the multilayer film cannot be obtained as per the designed value, and furthermore, there is a problem that the multilayer film peels off because the adhesion of the B layer to the substrate or the A layer is poor.

The present invention uses a thin film made of a single light element with weak inter-element bonding for a multilayer film. The object of the present invention is to obtain a multilayer film that solves the problems of a decrease in X-ray reflectance and peeling of the multilayer film.

[Means to solve the problem]

The above purpose is to create a compound B consisting of boron (B) and nitrogen (N) that has a complex refractive index comparable to that of a single element in the light element layer.
This is achieved by forming a multilayer film using N. [Operation] The complex refractive index of the above-mentioned substance is expressed as n=1−δ−iβ, where δ and β take values specific to the material.

δ in the soft X-ray region of simple C and B elements and even BN compounds
is shown in Figure 5. C. Figure 6 shows β in the soft X-ray region for B element alone and also for BN compounds. δ is C for 0 to 100 people
, B, and BN show almost the same size. Especially C
and B temporarily decrease at the absorption edge (44 and 31 people, respectively), and BN slightly decreases at the absorption edge of B and N, but have almost the same slope and magnitude. Also, from FIG. 6, β is C. for wavelength λ of O and λ<20 people. B. It is almost the same as BN, and for 20 people λ〈44 people, the size is BN＜B＜C
become. 44 people × λ〈70 people, CABN<B,
When there are 70 people and λ, B<C<BN. Therefore, B.N.
The δ and β of the film are comparable to those of a film made of simple element C, which is commonly used as a multilayer film material, or depending on the wavelength (λ> 70 people), it is better as a multilayer film material and has a small complex refractive index. It has the following characteristics. In addition to exhibiting optical values comparable to or superior to conventional single elements as mentioned above, BN compounds have a very high melting point of 3000°C and are chemically stable. ing. Therefore, compared to conventional films made of single elements, they have the advantage of being stable even when subjected to local heating, without decomposition or diffusion, and without deterioration over time. Furthermore, as can be seen from the high melting point of B
The bond between B and N is strong, and the simple B. While C easily forms compounds with heavy elements, BN does not form compounds with heavy elements, so it does not mix with the heavy element layer at the interface, and has the advantage that there is very little risk of decomposition and diffusion into the heavy element layer. has.

In addition, in order to form a film that strongly adheres to the substrate, it is effective to apply heat during the formation of the thin film, but conventionally heating has not been possible because light elements diffuse or form compounds. However, since BN is thermally stable compared to single-element thin films, there is little risk of it decomposing and diffusing even if heat of several hundred degrees is applied during fabrication. It has the advantage of being easy to make thin films. Furthermore, since the substrate can be heated, it has the advantage that thin films can be produced using the CVD method, which generally produces stronger bonds and flat thin films than the sputtering method. In addition, since BN has two components, BN
It has the advantage that it can be easily controlled by slightly changing the compositions of and N.

〔Example〕

Next, embodiments of the present invention will be explained with reference to the drawings. Fig. 1 is a block diagram showing an embodiment of a multilayer film according to the present invention, Fig. 2 is a diagram showing the structure of an X-ray reflectance measurement system for the multilayer film, and Fig. 3
The figure shows experimental values and theoretical values for the X-ray reflectance of the multilayer film of the above example. FIG. 1 shows an embodiment of the present invention in which BN is used for the B layer and the WtitA layer, and the wavelength is 39.8.
We designed and manufactured a multilayer film that reflects human soft X-rays most strongly at an incident angle of 70°. The multilayer film shown in FIG. 1 is formed by alternately stacking 20 layers each of BNIO and Wll by a sputtering method, and the BN layer has 20 layers each of Bl. B2,...B20, W layers are each made of Al
．． The thickness of each layer is indicated as A2, . . . A20. The X-ray reflectance measurement of the multilayer film was carried out using the configuration shown in FIG. That is, the substrate 3
The uppermost surface (W layer A20) of the multilayer film sequentially formed above was irradiated with incident X-rays 12 such that the incident angle 13 was O, and reflected X-rays 14 were measured. The characteristic X-rays (M-rays) of Ag (silver) having a wavelength of 39.8 were used as the incident XIil2, and the results of measuring the reflected X-rays l4 are shown in Figure 3.
In FIG. 3, the horizontal axis shows the incident angle, and the vertical axis shows the X-ray reflectance, where the solid line is the measured value 15 and the dotted line is the calculated value 16. As shown in the figure, the measured value 15 and the calculated value 16 are in almost good agreement, indicating that BN is effective as a multilayer film composition. Moreover, instead of the above W, Au. Re% Bi. Mo.
Ta. Similar results can be obtained using Rh and the like.

The values of δ and β of the above-mentioned BN compound may be on the same level as a film made of simple element C, which is generally used as a multilayer film material, or depending on the wavelength, it may have the excellent advantage of having a small complex refractive index as a multilayer film material. are doing. In addition, the above B
The N compound has a very high melting point of 3000° C., is chemically stable, and has the advantage of being stable without decomposition or diffusion even when subjected to local heating, and does not change over time.

Furthermore, since the BN compound does not form a compound with a heavy element, it does not mix with the heavy element layer at the interface, and there is very little possibility that it will decompose and diffuse into the heavy element. In addition, BN compounds, which are thermally stable compared to single-element thin films, do not have the risk of decomposing and diffusing even when heated to several hundred degrees during fabrication, and can be formed into flat thin films with good adhesion by heating the substrate. can be easily formed. Furthermore, since the BN compound has two components, it has the advantage that the stress within the film, which causes grain growth, can be easily controlled by slightly changing the composition of B and N. There is.

Although the multilayer film in this embodiment was formed by sputtering, it is also possible to use CVD, which can form a thin film with stronger bonding than the sputtering method described above.

〔Effect of the invention〕

As mentioned above, the multilayer film according to the present invention has a refractive index of . In a multilayer film formed by laminating a plurality of different thin films alternately, the composition of one of the plurality of thin films is a compound consisting of boron (B) and nitrogen (N). , since the above multilayer film is thermally stable and does not change over time,
It can be used not only as a mirror for SR light that needs to reflect strong light, but also as a mirror for a plasma light source that generates strong light in a pulsed manner.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing an embodiment of a multilayer film according to the present invention;
Figure 2 is a diagram showing the configuration of the X-ray reflectance measurement system for the multilayer film, Figure 3 is a diagram showing experimental values and theoretical values for the X-ray reflectance of the multilayer film, and Figure 4 is a diagram showing the multilayer film. Figure 5 shows the basic structure of B and C for X-rays in the wavelength range 0-100.
．． A diagram showing the value of the optical constant δ of BN, Figure 6 is the above-mentioned B and C.
, BN is a diagram showing the value of the optical constant β of BN. 1... A layer of heavy elements 2... B layer of light elements
O...BH layer patent applicant Nippon Telegraph and Telephone Corporation Representative Patent Attorney Junnosuke Nakamura Figure 6 Figure 2 Figure IQ: BN layer Figure 1 Figure 3 Illustration supplement (self-proposed) April 1999 ■． Display of the case Patent application filed on March 13, 1999 (1) 2. Name of the invention Multilayer film 3. Relationship with the case of the person making the amendment

Claims (1)

[Claims] 1. In a multilayer film formed by alternately laminating a plurality of thin films each having a different refractive index, one of the plurality of thin films has a composition consisting of boron (B) and nitrogen (N). A multilayer film characterized by: