JPH0786560B2 - Method for manufacturing X-ray transmission window - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an X-ray transmission window having a large transmittance for X-rays and a low transmittance for ultraviolet light, visible light, and infrared light, and a method for manufacturing the same. .

[Conventional technology]

Although there are various X-ray detectors, a silicon semiconductor detector in which lithium is diffused has been widely used in recent years.

Normally, this semiconductor detector needs to be cooled to the liquid nitrogen temperature to operate. In order to insulate the detector cooled to low temperature and to prevent condensation and contamination on the surface, the semiconductor element part of the detector is installed inside the vacuum chamber, and the X-ray coming from outside the vacuum chamber maintains the vacuum. However, a method of leading to a detector in a vacuum chamber through a window having a high X-ray transmittance is adopted.

Further, the semiconductor detector usually outputs a signal not only to X-rays but also to ultraviolet rays, visible rays or infrared rays. Therefore, an X-ray transmission window is installed in front of the detector so that ultraviolet rays, visible rays or infrared rays can be emitted. There is also a need for a measure to block infrared rays and have sensitivity only to X-rays.

Regarding the material characteristics required for the X-ray transmission window, it is desired that the transmittance for X-rays is good, that is, the absorption coefficient is small, the thickness can be made thin, and the mechanical strength is high. The absorption coefficient is a value peculiar to a substance, and usually depends on the wavelength of X-rays and the density of the substance. The smaller the approximate atomic number, the smaller the absorption coefficient. The thinner the thickness, the higher the transmittance. Therefore, it is desirable that the thickness be as thin as possible.

For this purpose, a Be thin plate having a thickness of about 10 μm has been conventionally used.

[Problems to be Solved by the Invention]

However, the conventional beryllium thin plate is manufactured by rolling a metal beryllium plate, but it is difficult to uniformly roll it to a thickness of 10 microns or less, and even if it can be manufactured, it has a mechanical strength as a window. Since there is a shortage, there is a problem that it is not practical. Therefore, X-
There has been a fatal defect that the transmittance of low energy X-rays of 10 Å or more at the wavelength of rays is extremely lowered and the operation of the X-ray detector is restricted.

Further, the X-rays are absorbed in the substance and are easily converted into heat, which causes a problem of thermal deformation and mechanical destruction due to the temperature rise of the window material, so that the absorbed heat can be quickly diffused. It is preferable that the thermal diffusivity or thermal conductivity is large and the thermal expansion coefficient is small.

Various materials have been investigated for the purpose of the X-ray transmission window, but up to now, there has been no practical material other than beryllium. Diamond is a light element and has a high transmittance for X-rays, a large mechanical strength and a high thermal conductivity, and is a stable window material excellent in moisture resistance and heat resistance, but it is expensive and There was a problem that only a maximum area of about 5 mm was available. Further, diamond has a problem in manufacturing technology that it is difficult to form a thin plate because diamond has a high degree and is not easily polished. There is also a problem that diamond is transparent to visible light and ultraviolet light and is not suitable for use in transmitting only X-rays.

An object of the present invention is to provide an X-ray transmission window and a method for manufacturing the same that solve the above problems.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, a method for manufacturing an X-ray transmission window according to the present invention includes a film forming step, a window forming step, and a thin film forming step, and a metal beryllium thin film is laminated on a polycrystalline diamond thin film. In the method for manufacturing an X-ray transmission window, the film forming step is a step of forming a polycrystalline diamond thin film on the substrate, and the window forming step is a step of partially removing the substrate. This is a process of forming a window consisting only of a crystalline diamond thin film, and the thin film forming process is a process of forming a metal beryllium thin film in the window portion on the polycrystalline diamond thin film.

The method of manufacturing an X-ray transmission window according to the present invention has a film forming step, a window forming step, and a thin film forming step, and is formed by laminating a metal beryllium thin film on a polycrystalline diamond thin film.
-A method of manufacturing a linear transmission window, wherein the film forming step is a step of forming a tungsten or molybdenum film on a silicon substrate, and further forming a polycrystalline diamond thin film on the tungsten or molybdenum film. This is a process of partially removing the substrate to form a window composed of only the polycrystalline diamond thin film, and the thin film forming step is a process of forming a metal beryllium thin film on the polycrystalline diamond thin film.

[Action / Principle]

 Next, the present invention will be described.

FIGS. 1 (a) to 1 (d) are process diagrams showing a method for manufacturing an X-ray transmission window according to the present invention.

In FIG. 1 (d), according to the present invention, a diamond polycrystal thin film 11 made of an aggregate of diamond fine crystal grains is formed in a window 12a having a predetermined shape, and the diamond polycrystal thin film 11 is formed.
By using a window in which the metal beryllium thin film 10 is provided in a multi-layered structure, the various drawbacks described above are eliminated.

Next, the manufacturing method of the present invention will be described with reference to the drawings. FIG. 1A shows a process of forming a diamond polycrystalline thin film 11 on a substrate 12. For forming the polycrystalline diamond thin film 11, a mixed gas of methane gas and water was used.
No. 0, a so-called hot filament method vapor phase synthesis technique, or a plasma vapor phase synthesis method utilizing microwave excitation of a mixed gas of methane and hydrogen as described in JP-A-58-110494. Available. FIG. 2 shows an outline of a hot filament method gas phase synthesis apparatus as an example. In FIG. 2, the substrate 21 on which the diamond polycrystalline thin film is to be synthesized is heated by the substrate heating device 22 to about 600 ° C.
Keep at about 900 ℃. A mixed gas of methane gas (CH ₄ ) 23 and hydrogen (H ₂ ) 24 was introduced into the synthesis reactor 25, and
Pyrolysis is excited by the tungsten filament 26 provided above the substrate 21 and heated to about 2000 ° C. to deposit diamond on the substrate 21. 27 is an exhaust device for evacuating the inside of the synthesis reaction device 25. The details of the thermal decomposition process of methane gas and the formation process of diamond by this method are still unclear at present and are controversial. In any case, any method may be used as long as the polycrystalline diamond thin film 11 can be formed. The synthesis conditions are particularly important because the grain size of the crystal grains forming the thin film and the amount of impurities other than diamond existing at the crystal grain boundaries in the film determine the X-ray transmission coefficient and the uniformity of the film. In the present invention,
As the structure of the diamond polycrystalline thin film produced by the vapor phase synthesis method, a structure composed of diamond crystal grains and a non-diamond substance, that is, graphite or amorphous carbon containing hydrogen is used. The role of the amorphous phase is to suppress abnormal grain growth of diamond and form a film structure composed of fine grains. That is, usually in the growth of diamond, carbon in methane gas is deposited as diamond on the diamond seed crystal, but grain growth is stopped when the non-diamond phase is deposited on the surface of the diamond. If the non-diamond phase is not deposited, it becomes a film composed of large grains, the surface has large irregularities, and it becomes a film in which intergranular vacancies exist, and there is a problem that it is difficult to attach a beryllium thin film on it. The ratio depends on the film synthesis conditions, for example, the mixing ratio of methane gas and hydrogen gas, the substrate temperature, the gas pressure, and other deposition conditions of the polycrystalline diamond thin film, so it is necessary to control the synthesis conditions so that the desired characteristics are obtained. There is. Diamond polycrystalline thin film obtained by controlling the deposition conditions of the thin film,
The diamond polycrystal thin film containing diamond particles having a grain size of about 0.05 μm to 0.2 μm and amorphous carbon containing graphite or hydrogen at the crystal grain boundaries can have sufficiently high transmittance in the X-ray region.

In FIG. 1 (a), silicon may be used as the material for the substrate 12, but it is not necessarily a silicon substrate, and any substrate capable of adopting the manufacturing process shown in FIG. 1 may be used. There is no particular problem. The thickness of the diamond polycrystalline thin film 11 may be selected so that the mechanical strength of the film and the value of X-ray transmittance have desired characteristics.

As shown in FIG. 1 (b), the substrate 12 on which the diamond polycrystalline thin film 11 was formed was used a photoresist 13 to partially remove the substrate 12 while leaving only the diamond polycrystalline thin film 11. A resist pattern is formed by the pattern forming process. Next, the substrate 12 is removed by etching using the mask 14 in a substrate etching process to form a window 12a in which only the diamond polycrystalline thin film 11 is left as shown in FIG. 1 (c). To do. Board 1
In the case of a silicon substrate, the etching of 2 may be performed by immersing it in a mixed solution of hydrofluoric acid and nitric acid. Then the first
As shown in FIG. 3D, a metal beryllium thin film 10 is formed on the diamond polycrystalline thin film 11 by vapor deposition or sputtering. Through the above steps, an X-ray transmission window having a multilayer film composed of the polycrystalline diamond thin film 11 coated with the beryllium thin film 10 on the substrate 12 can be manufactured.

As described above, according to the present invention, it is possible to use a window in which a metal beryllium thin film is provided on a diamond polycrystalline thin film whose film uniformity is improved by reducing the grain size, so that a high transmittance is obtained in the X-ray region. In the visible light region, an X-ray transmission window having low transmittance can be easily manufactured.

〔Example〕

 Hereinafter, description will be given based on examples of the present invention.

Example 1 A vapor phase synthesis apparatus as shown in FIG. 2 was used to form a diamond polycrystalline thin film. The gas conditions during the reaction were such that the concentration of methane in hydrogen gas was 0.5% to 5%, the synthesis pressure was 10 Torr, and the substrate temperature was 600 ° C to 950 ° C on the surface of the silicon substrate. Under the above conditions, the thickness of the polycrystalline diamond thin film was set to approximately 0.3 μm. Then, a photoresist is coated on the front surface and the back surface of the substrate to a thickness of 3 μm by a spin coating method, and then only the portion of the back surface where the substrate should be removed is removed to form an etching window. To remove the substrate, use hydrofluoric acid (HF), nitric acid, and
The substrate is completely removed by immersing in a mixed solution of acetic acid and etching to leave only the diamond polycrystalline thin film. After that, the remaining photoresist is removed by a resist remover, and then a metal beryllium thin film having a thickness of 0.1 μm is formed into a multi-layer structure by an evaporation method according to the manufacturing process shown in FIG. Can be completed.

Using the X-ray transmission window produced by the method described above, the transmittance of visible light to X-rays was evaluated. The light transmittance was calculated by dispersing the light from the light source with a spectroscope, irradiating the portion of the polycrystalline diamond thin film, and measuring the intensity of the transmitted light. The transmittance was sufficiently low at approximately 5% or less in the visible to infrared and infrared regions. Results for the X-ray region are shown in FIG. As shown in FIG. 3, the method of the present invention can increase the transmittance in the X-ray region.
In the conventional beryllium window, it becomes 10% or less at a wavelength of 10 angstroms, but in comparison to this, good characteristics are exhibited at a transmittance of 10% or more up to a wavelength of 30 angstroms.

Example 2 A tungsten film and a molybdenum film are formed on a silicon substrate as a substrate for forming a diamond polycrystalline thin film at a substrate temperature.
A film having a thickness of 3 μm formed by sputtering at 400 ° C. was used.

The same method as in Example 1 was used to form the diamond polycrystalline thin film. According to the manufacturing process shown in FIG. 1, a window made of only a multilayer thin film of beryllium and diamond is formed on the substrate by the same method as that of the first embodiment.

The light transmittance was calculated by dispersing the light from the light source with a spectroscope, irradiating the portion of the polycrystalline diamond thin film, and measuring the intensity of the transmitted light. The transmittance was low in the range from ultraviolet light to visible light and infrared light, and the transmittance was sufficiently low at about 5% or less. Results for the X-ray region are shown in FIG. As shown in FIG. 3, an X-ray transmission window having a high transmittance in the X-ray region can be produced by the method of the present invention.

〔The invention's effect〕

According to the method of the present invention, a stable X-ray transmission window having a high X-ray transmittance, a low transmittance for ultraviolet rays and visible light, and excellent moisture resistance and heat resistance can be produced at a low cost, so that it is practical. Above is extremely beneficial. Further, as is clear from the manufacturing process, it is clear that it does not depend on the kind of the substrate, and the effect of the present invention is not impaired even if any substrate is used.

Furthermore, the present invention focuses on the difference in the coefficient of thermal expansion between the polycrystalline diamond thin film and the metal beryllium thin film, and since the metal beryllium thin film is formed on the polycrystalline diamond thin film, it is lower than the deposition temperature of the polycrystalline diamond thin film. The metal beryllium thin film can be formed at a temperature, and cracks in the metal beryllium thin film can be prevented.

Further, the metal beryllium thin film reacts with carbon at a high temperature such as when forming a polycrystalline diamond thin film to generate a carbide,
Although the original X-ray transparency is impaired, according to the present invention, since the metal beryllium thin film is formed on the polycrystalline diamond thin film, the metal beryllium thin film is formed at a temperature higher than that of the polycrystalline diamond thin film. Since it is performed at a low temperature, there is an effect that it is possible to prevent a decrease in X-ray transparency.

[Brief description of drawings]

1 (a), (b), (c), and (d) are process drawings showing a method for manufacturing an X-ray transmission window according to the present invention, and FIG. 2 shows a method for forming a diamond polycrystalline thin film. Figure explaining, third
The figure is a diagram showing the characteristics of the transmission window obtained by the methods of Example 1 and Example 2. 10 …… Beryllium thin film 11 …… Diamond polycrystalline thin film, 12 …… Substrate 12a …… Window, 13 …… Photoresist 14 …… Mask 21 …… Diamond forming substrate 22 …… Substrate heating device, 23 …… Methane gas 24 …… Hydrogen gas, 25 …… Synthesis reactor 26 …… Tungsten filament, 27 …… Exhaust device

Claims (2)

[Claims] 1. A method of manufacturing an X-ray transmission window, comprising a film forming step, a window forming step, and a thin film forming step, wherein a metal beryllium thin film is laminated on a polycrystalline diamond thin film. The film process is a process of forming a polycrystalline diamond thin film on the substrate, and the window forming process is a process of partially removing the substrate to form a window made of only the polycrystalline diamond thin film. The step is a process of forming a metal beryllium thin film on a window portion on the polycrystalline diamond thin film, the method for manufacturing an X-ray transmission window. 2. A method of manufacturing an X-ray transmission window, comprising a film forming step, a window forming step, and a thin film forming step, wherein a metal beryllium thin film is laminated on a polycrystalline diamond thin film. The film process is a process in which a tungsten or molybdenum film is formed on a silicon substrate, and a polycrystalline diamond thin film is further laminated thereon. In the window forming process, the substrate is partially removed to remove the polycrystalline diamond thin film. A method of manufacturing an X-ray transmission window, which is a process of forming a window consisting of only a single layer, and the thin film forming step is a process of forming a metal beryllium thin film on the polycrystalline diamond thin film.