JP3265030B2 - X-ray spectral reflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectroscopic element for selecting soft X-rays and an X-ray spectral reflector required for an X-ray microscope or an X-ray telescope.

[0002]

2. Description of the Related Art It is used for the chemical state, chemical composition, impurity concentration of various materials such as semiconductor materials, soft X-rays necessary for high sensitivity analyzer of light elements, fine processing for LSI, biological observation and plasma observation. In X-ray telescopes such as those for X-ray microscopes and solar corona observation, multilayer films have been used to select monochromatic or quasi-monochromatic soft X-rays or X-rays. In general, the multilayer film is formed by regularly stacking a light element layer 2 and a heavy element layer 1 on a substrate such as silicon or quartz with a constant thickness of several tens of degrees to several hundreds of degrees, as shown in FIG. . The multilayer film has an advantage that the reflectance is higher than that of a diffraction grating or a crystal particularly in a soft X-ray wavelength region. In the conventional single-layer film, the light is not reflected as the light approaches the vertical incidence, and the reflectance is hardly less than 0.000001. However, for example, when the wavelength is about 13 nm, molybdenum (Mo) is used for the heavy element layer and the light element layer is used. A multi-layer film using silicon (Si) (Mo / Si multi-layer film) has a high reflectivity of about 50 to 80% in the vicinity of normal incidence and has a high reflectivity even when the wavelength is about 20 °. A multilayer film (W / C multilayer film) using tungsten (W) and carbon (C) as a light element layer is about 7% near the direct incidence, compared to a spectroscopic element using a diffraction grating or crystal. Since a reflectance higher by one digit or more can be obtained, application to a soft X-ray or an apparatus or method using X-rays is being studied. From the standpoint of various soft X-rays and X-ray applications, the higher the reflectivity or the more stable, the higher the utility value. For example, from the viewpoint of spectroscopic analysis, as the reflectance increases, the sensitivity and accuracy are improved in proportion to the reflectance, and the processing time is shortened from the viewpoint of processing. Further, when the intensity of the soft X-ray source or the X-ray source to be used is increased, an improvement in heat resistance is required in order to withstand the heat load caused by the intensity.

[0003]

However, for example, in a W / C multilayer film (150 pairs), a wavelength of 40
The reflectance at about Å is about 7% near the direct incidence, and although the reflectance is higher than that of a diffraction grating or a crystal-based spectral element, the industry has always demanded a multilayer film having a higher reflectance. . In this case, in general, when a substance having a smaller atomic number, that is, a substance having a lower density is used in place of C, the reflectance of the multilayer film with respect to soft X-rays and X-rays becomes higher due to the relationship between the optical constant and the density of the substance. Become. However, the only solid substances having a lower density than C are lithium (Li), beryllium (Be), and boron (B). this house,
Li has a melting point as low as 186 ° C. as it is, and a multilayer film using this as a light element layer has extremely poor heat resistance. Also,
Be is toxic by itself, causing skin irritation,
It is known to absorb the lungs if absorbed. For this reason,
Since it is necessary to handle the apparatus for manufacturing the multilayer film and care for the breathing method and clothes when the apparatus is used and to handle the equipment very strictly, not only the time is required for the manufacture but also great difficulty is involved. B has a surface with excellent physical properties, but is much inferior to C with respect to the smoothness of the layer interface required for improving the reflectance,
The surface roughness of the layer C can be formed to about 2 to 4 ° measured by an optical roughness meter or a stylus type roughness meter, while the surface roughness of the layer B is about 7 to 20 °, which is about twice as large as that of C. As a result, even if a multilayer film having the same structure is produced by using the heavy element layer of the same substance and applying the light element layers C and B respectively, the reflectance is C. There is a problem that it is higher.

Further, barium (Ba), calcium (C)
If a), magnesium (Mg), strontium (Sr), or the like is used, it is possible to produce a multilayer film having a high reflectance in terms of calculation. However, since these substances alone do not exist stably in the atmosphere, they are actually produced. There is also a problem that it is difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a soft X-ray source having a high soft X-ray reflectivity and an X-ray reflectivity, and an X-ray spectral reflector which can be used for a high intensity soft X-ray source and an X-ray source. I do.

[0006]

An object of the present invention is to provide an X-ray spectroscopic reflector having a multilayer structure in which a plurality of layer pairs each composed of a heavy element layer and a light element layer are stacked and having a Bragg diffraction effect. This is achieved by including fluorine in at least one layer of the film structure or by forming a layer made of fluoride. Specifically, the configuration is as described in the claims. That is, in the X-ray spectroscopic reflecting mirror having a Bragg diffraction effect, which has a multilayer structure in which a plurality of layer pairs each composed of a heavy element layer and a light element layer are stacked as described in claim 1 , The heavy element layer is made of barium fluoride, and the light element layer is made of an X-ray spectral reflector made of carbon. Further, in the X-ray spectroscopic reflecting mirror having a Bragg diffraction effect, which has a multilayer structure in which a plurality of layer pairs each composed of a heavy element layer and a light element layer are stacked, as described in claim 2 , The heavy element layer is made of strontium fluoride, and the light element layer is an X-ray spectroscopic reflector made of carbon. The X-ray spectroscopic reflector having a Bragg diffraction effect, which has a multilayer structure in which a plurality of layer pairs each composed of a heavy element layer and a light element layer are stacked, as described in claim 3 , wherein the multilayer film structure The heavy element layer is made of molybdenum, and the light element layer is an X-ray spectroscopic reflector made of a 1: 1 mixture of aluminum fluoride and beryllium fluoride.

[0007]

Since fluorine has the highest electronegativity among all atoms, it can produce stable compounds with many elements. Therefore, when fluorine is added to a material that is not stable in the air and is difficult to actually produce, or a multilayer film that does not exist stably even when produced, the above-described disadvantage can be improved. . For example, lithium (Li)
Has a density of 0.534, which is the smallest among single solid substances, so that a multilayer film using this as a light element layer should improve the reflectance. However, it easily reacts with oxygen and burns at 200 ° C. in oxygen to change to lithium oxide. Also,
It easily reacts with nitrogen and the like. However, when fluorine is added to the above Li, the melting point becomes high, and it is possible to form a stable and highly reflective multilayer film. As the amount of fluorine increases and the composition of lithium fluoride (LiF) increases, the melting point increases to about 840 ° C. In addition, calcium (Ca), which is highly deliquescent, and barium (B), which easily forms an oxide in air.
When fluorine is added to a), strontium (Sr), or toxic beryllium (Be), it is possible to form a stable or non-toxic multilayer film with high reflectance.

When such a multilayer spectroscopic element using a multilayer film is applied to various analyses using X-rays or soft X-rays, the reflectivity of the multilayer film is improved, and the sensitivity and accuracy are improved. Since the heat resistance of the spectral characteristics is also improved, the fluctuation with time is reduced, and the accuracy and accuracy of the analysis can be improved. Further, when the multilayer spectroscopic element is applied to X-ray lithography, the reflectance is improved and the productivity is improved, or the exposure time can be shortened. The exposure time can be accurately determined. Further, it is possible to obtain an effect that the life of the multilayer film itself is extended.

[0009]

Next, embodiments of the present invention and reference examples will be described with reference to the drawings. FIG. 1 is a diagram showing the relationship between the material of the multilayer film and the reflectivity in Reference Example 1 of the X- ray spectroscopic mirror. FIG. 2 is a diagram showing a heavy element layer using any of LiF, Be, B, and C for the light element layer. FIG. 3 is a diagram showing a state of a multilayer film reflectance with a period length of 20 ° using W. FIG. 3 shows a light element layer made of a material obtained by adding fluorine (F) to Li and a period length of 20 ° using W as a heavy element layer. FIG. 4 is a diagram illustrating a state of soft X-ray reflectivity in a multilayer film.

[0010]Reference Example 1  Use LiF, Be, B, or C for the light element layer
Four types of multilayer films using W for the elementary layer were formed by sputtering.
Formed. Each of the above multilayer films has a light element layer thickness
The period length, which is the sum of the thickness of the heavy element layer and the
Up to 30 °, the ratio of the thickness of the light element layer to the thickness of the heavy element layer
Was 2: 3 and 150 pairs were laminated. Substrate is Si wafer
Ha. Tilt 3 degrees from an angle perpendicular to the surface of each multilayer film
Reflectance and period length when soft X-rays are incident at an angle of
FIG. 1 shows the relationship with the material. Among these, many with a cycle length of 20 °
FIG. 2 shows the relationship between the soft X-ray reflectivity and the wavelength in the layer film.
You. In the wavelength range of about 25 to 40 degrees, reflection
W / C and W / Be, which were considered to be high,
It was confirmed that LiF had higher reflectance.

[0011]Reference example 2  5%, 10%, 15%, 20%, 3% by weight of F in Li
Use 0% added material for the light element layer and add W to the heavy element layer
The cycle length is set to 20 °, the thickness of the light element layer and the heavy element
The ratio of the thickness of the layers is 2: 3.
Prepared by sputtering method, perpendicular to the surface of the multilayer film
When soft X-rays are incident at an angle of 3 degrees from the angle
The soft X-ray reflectivity was compared. FIG. 3 shows the results.
Their reflectivity is higher than that using LiF for the light element layer.
Is getting higher.

[0012]Reference Example 3  Use Ca and calcium fluoride (CaF) for the light element layer
Using nickel (Ni) for the element layer, the cycle length is 30Å.
The ratio of the thickness of the light element layer to the heavy element layer is 2: 3 and 1
A multilayer film made by stacking 00 pairs is produced by a sputtering method,
Comparison of reflectance when soft X-rays are incident on the above multilayer film
And the change with time in air retention was examined. That
As a result, the reflectivity is 24 for the Ni / Ca multilayer film at a wavelength of 50 °.
%, And 28% for the Ni / CaF multilayer film. Each of the above multilayers
When the surface roughness of the film is measured with an optical roughness meter, Ni
/ Ca multilayer film is as large as 6 to 9 °, whereas Ni / Ca
It has been confirmed that the F multilayer film has high smoothness of about 4 to 6 mm.
Was. That is, by adding fluorine, high smoothness is obtained.
And the resulting high reflectivity
Was confirmed. In addition, air at a temperature of 20 ° C. and a humidity of 55%
After standing for 24 hours in the inside, the soft X-ray reflectivity was measured.
The Ni / Ca multilayer film has been reduced to 19%, while Ni
In the / CaF multilayer film, no change in reflectance was observed.
That is, by mixing fluorine with Ca,
The effect that the change can be suppressed was confirmed.

[0013]Reference example 4  Magnesium fluoride (MgF) is used for the light element layer,
The period length is set to 30 ° using Ni for the elementary layer,
The ratio of the thickness to the thickness of the heavy element layer is 2: 3, and 100 is laminated.
The multi-layer film was made by sputtering,
Compare the reflectivity when soft X-rays are incident, and
The time-dependent change in the retention of was observed. As a result, the reflectance is
At a wavelength of 50 °, the Ni / Mg multilayer film shows 28%.
The Ni / MgF multilayer film showed 31%. That is, fluorine
It was confirmed that the addition of
Was. In addition, at 24 o'clock in the air at a temperature of 20 ° C and a humidity of 55%
After standing for a while, the soft X-ray reflectivity was measured.
The Ni / MgF multilayer was reduced to 25% in the film.
No change in reflectance was observed in the film. That is, M
By mixing fluorine with g, it is possible to suppress changes over time.
The effect of cutting was confirmed.

[0014]Example 1  Use Ba and barium fluoride (BaF) for the heavy element layer
The cycle length is set to 30 ° using C for the elementary layer, and the thickness of the light element layer is
The ratio of the thickness of the heavy element layer to the thickness of the heavy element layer was 2: 3, and 100 layers were stacked.
A multilayer film is formed by a sputtering method, and a soft X
Compare the reflectivity of incident light, and keep it in the atmosphere.
The time-dependent change in retention was examined. As a result, the reflectivity is
At 48 °, the Ba / C multilayer film has a BaF / C ratio of 19%.
The multilayer film showed 21%. Adjust the surface roughness of the multilayer film
When measured with an optical roughness meter, the Ba / C multilayer film has a thickness of 8 ~.
While it is as large as 11 °, the BaF / C multilayer film has a thickness of 6 to
It was confirmed that the smoothness was as high as about 9 °. That is,
Addition of fluorine increases the smoothness, which causes reflection
It was confirmed that the rate increased. The above multilayer film was heated at a temperature of 20
Soft X-ray reflection after standing in air at 55 ° C and humidity of 55% for 24 hours
When the ratio was measured, it decreased to 14% for the Ba / C multilayer film.
On the other hand, in the BaF / C multilayer film, the change in the reflectance was
I was not able to admit. That is, Ba is mixed with fluorine.
This confirms the effect that changes over time can be suppressed.
Was done.

[0015]Example 2  Sr and strontium fluoride (SrF) used for heavy element layer
Then, use C for the light element layer to make the cycle length 30 °,
The ratio of the thickness of the elementary layer to the thickness of the heavy element layer is 2: 3 and 100: 100.
The laminated multilayer film was prepared by a sputtering method,
Compare the reflectance when soft X-rays are incident on the film, and
The change with time in holding in air was examined. As a result, the reflection
The ratio is 28% for a Sr / C multilayer film at a wavelength of 48 °.
The SrF / C multilayer film showed 30%. The above multilayer film
When the surface roughness of the surface is measured with an optical roughness meter, Sr / C
In the case of a multi-layer film, it is as large as 5 to 8 °, whereas SrF / C multi-layer film
It was confirmed that the film had a high smoothness of about 3 to 6 °.
That is, the smoothness is increased by the addition of fluorine.
As a result, it was confirmed that the reflectance increased. The above multilayer film
Is left in the air at a temperature of 20 ° C and a humidity of 55% for 24 hours,
When the soft X-ray reflectivity was measured, the Sr / C multilayer film showed 24
%, Whereas the SrF / C multilayer film reflects
No change in rate was observed. That is, fluorine is added to Sr.
By mixing, the effect that change over time is suppressed
confirmed.

[0016]Example 3  Use molybdenum (Mo) for the heavy element layer and fluorine for the light element layer.
Aluminum fluoride (AlF₃) -Beryllium fluoride (Be
F₂Using a 1: 1 mixture of
And the ratio of the thickness of the light element layer to the thickness of the heavy element layer is 2: 3.
Fifty pairs of laminated multilayer films were produced by a sputtering method.
In the X-ray diffraction evaluation, W, AlF₃, BeF₂
Is detected, but the peak of Be is observed.
Did not. That is, there is no or very few Be
Therefore, the produced multilayer film contains Be element as a component.
Is non-toxic or extremely
It was confirmed that there was little. In addition, soft X
The reflectivity when a line was incident was examined. As a result, the reflectance
Has the effect of exhibiting a high value of 42% at a wavelength of 160 °.
It was also confirmed. That is, fluorine is mixed with Be.
As a result, it becomes a non-toxic multilayer film and has a soft X-ray reflectivity.
It was also confirmed that it became higher.

Although only a few examples have been exemplified in the above embodiments, it is presumed that, as a matter of course, even in combinations of substances other than those described above, a substance whose stability, detoxification, and high melting point can be obtained by adding fluorine. It is needless to say that the use of is effective in forming a multilayer film with high reflectivity, a multilayer film with excellent safety, or a multilayer film with excellent heat resistance.

[0018]

The X-ray spectral reflector according to the present invention has the features described in the claims.
As described range, has a multi-layer film structure composed of heavy element layer and a light element layer <br/> plurality of layer pairs are stacked, a X-ray reflecting mirror having a Bragg diffraction effect, the multilayer Film structure
At least one layer of the structure contains fluorine , or
With made of fluoride layers, the multilayer film structure is easily used to stabilize, next use can <br/> elements help high reflectivity, depending further substances can also precluding toxicity, also, By increasing the melting point of the light element having a low melting point, a multilayer structure having improved heat resistance can be obtained. By applying multi-layered film spectroscopy device of the present invention to various analyzes utilized such as X-rays and soft X-rays, increased and the sensitivity and accuracy improved reflectance variation with time because the heat resistance is higher spectral characteristics And the precision and accuracy of the analysis can be improved. Further, by applying the present invention to X-ray lithography, it is possible to increase the productivity by improving the reflectance or shorten the exposure time. In addition, the change in reflectivity is small and the proper exposure time can be accurately determined, and further, the multilayer film structure has an excellent effect of prolonging its life.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a material of a multilayer film and a reflectance in a first embodiment of an X-ray spectral reflecting mirror according to the present invention.

FIG. 2 is a diagram showing a state of a multilayer film reflectivity with a period length of 20 ° using any one of LiF, Be, B, and C for a light element layer and using W for a heavy element layer.

FIG. 3 is a view showing the state of soft X-ray reflectivity in a multilayer film having a period length of 20 ° using W as a light element layer using a material in which Li is added to fluorine and using a heavy element layer as W;

FIG. 4 is a diagram showing a structure of a multilayer film.

Continuation of the front page (56) References JP-A-4-34400 (JP, A) JP-A-2-306202 (JP, A) JP-A-4-326098 (JP, A) JP-A-3-115898 (JP) JP-A-64-81908 (JP, A) JP-A-64-81909 (JP, A) JP-A-64-81911 (JP, A) JP-A-4-169899 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G21K 1/06

Claims (3)

(57) [Claims] 1. An X-ray spectroscopic reflector having a multilayer structure in which a plurality of layer pairs each composed of a heavy element layer and a light element layer are stacked and having a Bragg diffraction effect, wherein the heavy element layer of the multilayer film structure is a fluorine element. An X-ray spectroscopic reflector comprising barium halide and a light element layer comprising carbon. 2. An X-ray spectroscopic mirror having a multilayer structure in which a plurality of layer pairs including a heavy element layer and a light element layer are stacked and having a Bragg diffraction effect. An X-ray spectroscopic mirror comprising strontium halide and a light element layer comprising carbon. 3. An X-ray spectroscopic mirror having a multilayer structure in which a plurality of layer pairs each composed of a heavy element layer and a light element layer are stacked and having a Bragg diffraction effect, wherein the heavy element layer of the multilayer structure has molybdenum. An X-ray spectroscopic mirror, wherein the light element layer comprises a 1: 1 mixture of aluminum fluoride and beryllium fluoride.