JP3390803B2 - Diamond synthesis method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond synthesizing method and apparatus for synthesizing diamond by using Synchrotron Radiation (hereinafter abbreviated as "SR light").

[0002]

2. Description of the Related Art As a conventional technique for artificially synthesizing diamond of this kind, there is a method disclosed in Japanese Patent Laid-Open No. 6-24896 as a typical method using laser light, and laser ablation is used. As a typical method, there is a method disclosed in JP-A-6-234594. The method disclosed in the former publication is a method of synthesizing diamond on a substrate in a vapor phase by using a raw material gas in which a compound containing a carbon atom is diluted with hydrogen gas, and a laser beam within a predetermined range is used as the raw material. By irradiating in gas or on the substrate, the compound and hydrogen gas are decomposed to synthesize diamond on the substrate.
Further, the method disclosed in the latter publication is a method of forming a diamond thin film by causing carbon particles to fly by a laser ablation on a target made of graphite provided in a reaction chamber and reacting the carbon particles by a photochemical reaction on a substrate. Is.

[0003]

The method disclosed in the former publication has a problem that the reproducibility is not good because it is a vapor phase synthesis method based on photodecomposition of a source gas by laser light. Further, there is a problem that a diamond peak at 1333 cm ^-1 in Raman spectroscopic analysis is hard to appear. In addition, there is a problem that the substrate temperature must be kept high. Further, since the method disclosed in the latter publication uses laser ablation generated by irradiating a target made of graphite with laser light, the density of diamond nucleation is low and a thin film is formed rather than being formed. There is a problem in terms of film quality that a lump of particles is generated. Further, there is a problem that the efficiency of the synthesis of diamond becomes weak unless the substrate needs to be irradiated with SR light and the substrate is not heated to a high temperature.

[0004]

The present invention has been made in view of the above circumstances, and the means therefor are as follows.
In Claim 1, SR light is irradiated to a coagulation target substance obtained by coagulating a gaseous or liquid fluid substance containing at least carbon and hydrogen atoms to cause ablation to generate diamond on a substrate. There is a method of synthesizing diamond. According to a second aspect of the present invention, in the means of the first aspect, a diamond synthesis method is used in which laser light is irradiated and then SR light is irradiated to generate ablation. Claim 3
In, the ablation is generated in the presence of a gas containing nitrogen or boron.

According to another aspect of the present invention, there is provided a reaction chamber, and a supply device for supplying a gaseous or liquid fluid substance containing at least carbon and hydrogen atoms into the reaction chamber.
A solidification device for solidifying the supplied gaseous or liquid fluid substance to form a solidification target substance, a holding table for holding the solidification target substance in the reaction chamber, and a solidification target held on the holding table. SR to substance
The diamond synthesizing apparatus has a device for irradiating light and a substrate for diamond production provided in the reaction chamber facing the ablation caused by the irradiation of SR light. According to a fifth aspect of the present invention, in the means of the fourth aspect, the diamond synthesizing device is a device for irradiating the solidification target material held on the holding table with laser light and SR light.

According to a sixth aspect of the present invention, there is provided a reaction chamber, a holding base for holding a solidification target substance obtained by solidifying a gaseous or liquid fluid substance containing at least carbon and hydrogen atoms in the reaction chamber, and the holding table. An apparatus for irradiating a solidification target substance held on a table with SR light,
The diamond synthesizing apparatus has a substrate for diamond production provided in the reaction chamber facing the ablation caused by the SR light irradiation. According to a seventh aspect of the present invention, in the means of the sixth aspect, the diamond synthesizing device is a device for irradiating the solidification target substance held on the holding table with laser light and SR light. In the eighth aspect, the diamond synthesizing apparatus has a gas containing nitrogen or boron in the reaction chamber.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described. According to this diamond synthesis method, SR light is irradiated to a solidification target material obtained by solidifying a gaseous or liquid fluid material containing at least carbon and hydrogen atoms to cause ablation to generate diamond on a substrate. There is a method of synthesizing diamond. As a first embodiment of a diamond synthesizing apparatus for embodying this method, as shown in FIGS. 1 and 2, a reaction chamber 1 and a gaseous state containing at least carbon and hydrogen atoms in the reaction chamber 1 are used. Alternatively, an SR having a holding table 4 for holding the solidification target material 3 obtained by solidifying the raw material 2 which is a liquid fluid substance, and an SR light source for irradiating the solidification target material 3 held on the holding table 4 with SR light 5 The apparatus 6 and the substrate 7 for diamond production provided in the reaction chamber 1 facing the ablation caused by the irradiation of the SR light 5, and the raw material 2
Is a device capable of being jetted and introduced above the holding table 4 through the raw material supply pipe 8.

Examples of the raw material 2 containing at least carbon and hydrogen atoms include paraffin hydrocarbons (C _n H _{2n + 2} ) such as methane, olefin hydrocarbons (C _n H _2n ) such as ethylene, acetylene and the like. Acetylene hydrocarbon,
Examples thereof include alcohols such as methanol, ethers such as methyl ether, aldehydes such as methanal, ketones such as acetone, and aromatic compounds such as benzene. Whether these substances are gases or liquids,
Alternatively, it may be a solid or powdery substance dissolved in a solvent to form a liquid, or may be a mixture of a gas and a liquid. In short, fluids of gases, liquids and any of the above substances in which gas and liquid are mixed can be used as the raw material of the present invention.

Since the holding table 4 is connected to the cooler (solidifying device) 11 cooled by the refrigerant 10 supplied through the refrigerant supply pipe 9 so as to be capable of conducting heat, it is easy to maintain the low temperature state. . As the refrigerant 10, a material suitable for the solidification temperature of the raw material 2 is appropriately selected from liquid nitrogen, liquid helium, dry ice, ice, and the like. Although the cooler 11 is illustrated as being directly cooled by these refrigerants 10, it may be cooled by other means such as refrigeration or a cooler. The holding table 4 is preferably made of a metal plate having good thermal conductivity, such as copper or stainless steel, but may be made of another material. The holder 4 and the cooler (solidifying device) 11 may be formed separately as in this embodiment, or may be integrally formed so that one of them also serves as the other. Are included in.

A substrate 7 for diamond production made of silicon, quartz, a metal plate or the like is provided in the reaction chamber 1 so as to face the holding table 4, and the substrate 7 is provided.
Diamond is generated on the surface of the holding table 4 facing the. In the present invention, diamond is generated even if the substrate 7 is not kept at a high temperature by the heat source 12.
A heat source 12 may be provided in order to control the film quality and enhance the production efficiency.

The inside of the reaction chamber 1 is decompressed and maintained in a vacuum state by an exhaust device 13 such as a turbo molecular pump so that ablation easily occurs.
However, since it is possible to synthesize diamond by ablation of SR light even in oxygen, this exhaust device 13
Is not essential, but has the advantage of increasing production efficiency if used. Further, the SR light 5 emitted from the SR device 6 is
When the solidification target material 3 is irradiated with light passing through the condensing mirror 14, there is an advantage that ablation is efficiently generated, but since ablation can be sufficiently generated even when the condensing mirror 14 is not passed, It is not a mandatory requirement.

Unlike the laser light, the SR light 5 emitted from the SR device 6 has the characteristics that the wavelength is continuous light and the phases are scattered. However, it is possible to cause a core-electron excitation reaction in a substance irradiated with soft X-rays and vacuum ultraviolet rays having a wavelength shorter than that of laser light. In addition, the photon flux (phs./sec·mA·mm ² · 0.1% bw), which represents the amount of light that passes through a unit area in a unit time, is a value larger than the “threshold” that causes ablation of the coagulation target substance. Must-have. For this reason, increasing the amount of stored electrons in the SR device 6 and
The distance from the device 6 to the target material is made as short as possible to increase the value of photon flux. In addition, a condenser is also provided in the beam line to increase the photon flux in a unit area. In this way, achieving a high flux density is a requirement for a light source that causes SR ablation.

Next, a process of synthesizing diamond using the above-mentioned apparatus will be described. First, a raw material 2 which is a gaseous or liquid fluid substance containing at least carbon and hydrogen atoms is jetted through a raw material supply pipe (supply device) 8 onto the upper surface of a holding table 4 cooled by a cooler 11. . Then, the raw material 2 is solidified on the upper surface of the holding table 4. At this time, when the raw material 2 is a gas, it solidifies in a frost-like state, and when it is a liquid, it solidifies like ice to become the solidification target substance 3. By irradiating the coagulation target material 3 with the SR light 5 having a photon flux amount larger than the above-mentioned threshold value, an explosive bond cleavage occurs on the surface of the coagulation target material, which is a decomposed fragment thereof. A phenomenon in which carbon, radicals containing carbon, and hydrogen become a plasma state and scatter at supersonic speed while emitting light, that is, ablation occurs, and these scattered fragments and carbon grow and accumulate on the substrate, The film is formed.

In the case of the present invention in which the target substance is a solidified gas or liquid fluid substance containing at least atoms of carbon and hydrogen, carbon is converted into atomic or molecular units by irradiation of such SR light 5. Diamond is generated due to bond cleavage and ablation, but in the case of a conventionally used solid such as graphite, bond cleavage occurs only in atomic units, and therefore it is replaced with the solidification target substance 3. Even if used as a raw material, diamond is not generated. In addition, hydrogen required for diamond production is supplied from the outside.

In the above-described first embodiment, the raw material 2 is continuously supplied to the upper surface of the holding table 4 so as to supplement the solidification target substance 3 reduced by the ablation, so that the ablation is continuously performed for a long time. It can be generated, and as a result, a thick film of diamond can be formed on the substrate 7.

When the raw material 2 is a liquid or a mixture of liquid and gas, it takes some time for the upper surface of the holding table 4 to freeze and solidify. May leak from the top surface. In order to prevent this, it is desirable to surround the upper surface of the holding table 4 in a container shape.

Next, an apparatus of the second embodiment for embodying the method of the present invention will be described with reference to FIG. The difference from the first embodiment described above is that, as is apparent from the figure, since the mass of the solidification target substance 4 that has been frozen and solidified in advance like ice is placed on the upper surface of the holding table 4,
That is, the raw material supply pipe 8, the refrigerant supply pipe 9, and the cooler 11 are no longer required.

According to the diamond synthesizing apparatus of the second embodiment, the solidification target material 3 is placed on the upper surface of the holding table 4, and the ablation is completed when the total mass of the solidification target material 3 disappears. The thickness of the deposited diamond film depends on the solidification target material
It will be only for.

Even in the case of this embodiment, if the holding table 4 is cooled, it is possible to prevent the solidification target material 3 from being melted, which is effective when the ablation time is long and continuous. is there.

Further, the solidification target material 3 is placed on the holding table 4.
The agglomerates may be continuously supplied by a supply device. In this case, since the ablation can be continuously generated for a long time, as in the case of the first embodiment, the thick diamond film It can be expected to be generated.

In the first and second embodiments described above, S
If the coagulated ablation substance is activated by irradiating the laser beam before irradiating the R light, the ablation by the SR light is performed more actively, so that the diamond generation can be efficiently performed. In this case,
Similar to the device for irradiating SR light, a device for irradiating laser light is separately provided.

In the first and second embodiments described above, if a gas such as nitrogen or boron is put in the reaction chamber 1, the gas and carbon produced by ablation act on the substrate 7 Since a p-type semiconductor diamond film is deposited on the substrate, this method can be adopted if necessary. Also in this case, the gas such as nitrogen or boron may be continuously supplied from the outside of the reaction chamber 1 in a required amount through a supply pipe or the like.

[0023]

[Experimental equipment, premise explanation]

(1) As the SR device as the SR light source, a superconducting small SR device (in Ritsumeikan University SR Center) was used. The relationship between the photon flux of this light source and the wavelength (photon energy) is as shown in FIG. That is, the wavelength is a region that includes vacuum ultraviolet rays and soft X-rays and causes an inner-shell electron excitation reaction of the irradiated substance, and the photon flux has a high flux density that can cause SR ablation. As the beam line, the BL-14 white light irradiation beam line of the SR device was used. In this beam line, the light beam emitted from the light source point is condensed (longitudinal direction) and guided to the position of the solidification target substance on the upper surface of the holding table of the reaction chamber.
The SR light was used in the state of white light without selecting the wavelength with a spectroscope. (2) The reaction chamber has a diameter of 20 cm and a longitudinal length of 25.
cm. (3) Gaseous acetone was used as a raw material. (4) Liquid nitrogen was used as the refrigerant. (5) A 10 mm × 15 mm quartz substrate was used as the substrate. The distance from the solidification target material to the substrate is 1
It is 0 mm. (6) A turbo molecular pump was used as the exhaust device.

[Experimental Conditions] (1) SR light was irradiated for 60 minutes with white light including wavelengths in the visible light region from soft X-rays. (2) The raw material acetone was supplied to the upper surface of the holding table at a rate of 0.1 to 0.2 cc / min. (3) The substrate was brought to room temperature without heating. (4) Liquid nitrogen was used as the refrigerant. The temperature of the holding table was constantly maintained at -80 ° C. This caused acetone to solidify like frost on the upper surface of the holding table. (5) The degree of vacuum in the reaction chamber was 2 × 10 ⁻⁶ Torr.

[Experimental Results] Plasma was observed from the window of the reaction chamber during the experiment. After the experiment, the thickness of the thin film formed on the substrate was measured and found to be 50n at the thin part.
m was 150 nm at a thick portion. Further, when Raman spectroscopic analysis was performed on this thin film, a Raman spectrum as shown in FIG. 5 was shown. In FIG. 5, 133
Since a diamond peak occurs at 3 cm ^-1 ,
It was confirmed that the produced thin film was a diamond film.

[0026]

According to the diamond synthesizing method and apparatus of the present invention, it is possible to synthesize at a room temperature without raising the temperature of the substrate, as compared with the conventional method using laser light or laser ablation. Also, there is an advantage that the device is sufficient. Further, the produced diamond has an advantage that it can be a high-quality diamond having a high density. Further, since the gaseous or liquid fluid substance containing at least carbon and hydrogen atoms as the raw material can be gas or liquid, there is an advantage that the range of selection of the raw material is expanded.

In addition, since the raw material has fluidity, as shown in the first embodiment, continuous supply to the reaction chamber through a supply pipe or the like is possible, and as a result, continuous synthesis for a long time is possible. Can be maintained, the efficiency of the synthesis work can be improved, and large diamonds can be produced.

When a solidification target substance obtained by freezing and solidifying a liquid raw material is used, there is an advantage that diamond can be synthesized with a simpler apparatus as shown in the second embodiment.

Further, when the laser light is irradiated before the SR light, there is an advantage that the ablation due to the SR light easily occurs and the diamond production efficiency is improved.

In addition, if the ablation is performed in an atmosphere of gas such as nitrogen or boron, there is an advantage that p-type semiconductor diamond useful in the semiconductor industry can be synthesized.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a main part of FIG.

FIG. 3 is an enlarged explanatory view of a second embodiment of the present invention corresponding to FIG.

FIG. 4 is a graph showing the relationship between photoflux and photon energy.

FIG. 5 is a graph showing a Raman spectroscopic analysis result of a thin film formed on a substrate.

[Explanation of symbols]

1 Reaction chamber 2 raw materials 3 coagulation target substances 4 holding table 5 SR light (synchrotron radiation) 6 SR device 7 substrate 8 Raw material supply pipe (supply device) 11 Cooler (Coagulator)

Front page continued (72) Inventor Takeo Matsubara 1-1-1 Nojihigashi, Kusatsu City, Shiga Ritsumeikan University Biwako Kusatsu Campus SR Center (56) Reference JP-A-59-137396 (JP, A) HEI 6-234594 (JP, A) JP HEI 8-259388 (JP, A) HEI 8-325096 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C30B 1 / 00-35 / 00 H01L 21/205 CA (STN) JISST file (JOIS)

Claims (8)

(57) [Claims] 1. A solidification target substance obtained by solidifying a gaseous or liquid fluid substance containing at least carbon and hydrogen atoms is irradiated with synchrotron radiation to cause ablation, and diamond is deposited on a substrate. A method for synthesizing diamond, which comprises producing the diamond. 2. A laser irradiation is applied to a coagulation target material obtained by coagulating a gaseous or liquid fluid material containing at least carbon and hydrogen atoms, and then synchrotron radiation is applied to generate ablation. A method for synthesizing diamond, characterized in that diamond is produced on the substrate. 3. The method for synthesizing diamond according to claim 1, wherein the ablation is generated in the presence of a gas containing nitrogen or boron. 4. A reaction chamber, a supply device for supplying a gaseous or liquid fluid substance containing at least carbon and hydrogen atoms into the reaction chamber, and the supplied gaseous or liquid fluid substance. A solidification device that solidifies to form a solidification target material, a holding table that holds the solidification target material in the reaction chamber, a device that irradiates the solidification target material held on the holding table with synchrotron radiation, and A diamond synthesizing apparatus comprising: a substrate for diamond production, which is provided in the reaction chamber so as to face ablation caused by irradiation with synchrotron radiation. 5. A reaction chamber, a supply device for supplying a gaseous or liquid fluid substance containing at least carbon and hydrogen atoms into the reaction chamber, and the supplied gaseous or liquid fluid substance. A solidification device that solidifies to form a solidification target material, a holding table that holds the solidification target material in the reaction chamber, and a device that irradiates the solidification target material held on the holding table with laser light and synchrotron radiation light. And a substrate for diamond production provided in the reaction chamber facing the ablation caused by irradiation with the synchrotron radiation. 6. A reaction chamber, a holding table for holding a solidification target material obtained by solidifying a gaseous or liquid fluid material containing at least carbon and hydrogen atoms in the reaction chamber, and a holding table held by the holding table. A diamond comprising: a device for irradiating the solidified target substance with synchrotron radiation, and a substrate for diamond production provided in the reaction chamber facing the ablation caused by the irradiation of the synchrotron radiation. Synthesizer. 7. A reaction chamber, a holding table for holding a solidification target material obtained by solidifying a gaseous or liquid fluid material containing at least carbon and hydrogen atoms in the reaction chamber, and a holding table held by the holding table. An apparatus for irradiating the solidified target material with laser light and synchrotron radiation, and a substrate for diamond production provided in the reaction chamber facing the ablation caused by the irradiation of the synchrotron radiation. And diamond synthesizing equipment. 8. The gas containing nitrogen or boron is present in the reaction chamber.
The diamond synthesizing apparatus according to any one of 1 to 7.