CN1029135C - Apparatus for Vapor Deposition Diamond - Google Patents

Abstract

Apparatus for vapour depositing diamond, comprising an electrode-forming element of a first polarity; electrode forming elements of opposite polarity; the direct current plasma blowpipe, it has direct current power, is used for exerting the voltage between two electrodes, make the gas entered present the thermal plasma; a gas delivery system for introducing a feed gas compound into a plasma; an apparatus for forming a non-equilibrium plasma, comprising a cooling gas supply means provided with a cooling gas nozzle around a plasma torch nozzle for quenching a hot plasma and forming an active non-equilibrium plasma containing at least a radical-converted product and having a high concentration of radicals, for vapor-depositing a plasma jet; and a substrate support mechanism.

Description

The invention relates to a method and device for vapor deposition diamond. More precisely, the present invention relates to a high-efficiency method and device for uniform vapor deposition of diamond, especially a diamond film with sufficient thickness and excellent film quality obtained at a high film deposition rate.

Diamond is an allotrope of carbon, which shows a diamond structure and has a high Mohs hardness with a value of 10; compared with other materials, it has superior thermal conductivity with a value of 2000W/MK.

Diamond-like carbon is also known, which is an allotrope of the same element. Although it is amorphous, it is transparent and insulating. This product also exhibits high thermal conductivity and hardness values, although lower than those of diamond, factors that make it possible to use this substance in a variety of ways.

More precisely, what makes this substance attractive is that it uses its high thermal conductivity value as a substrate material for mounting semiconductor integrated circuits; it uses its high hardness value as a coating layer for tools and the like. Also, diamond-like carbon, when coated on the surface of a titanium metal plate, can be used as a vibration plate of a speaker.

In particular, the thermal conductivity of diamond is 2000W/MK, which is equivalent to four times higher than that of copper, and it also has excellent hardness and insulation properties, so it is an ideal material for heat sinks for semiconductor components and used as a substrate for circuit substrates Material. Moreover, in a wide range of wavelengths, diamond has excellent light transmission, so it is also an excellent optical material. In addition, since diamond has a wide frequency band (5.45 eV) and is a semiconductor with high carrier mobility, it is attractive when used in high-efficiency devices such as high-temperature transistors, high-speed transistors, etc.

For the vapor phase method of synthetic diamond or diamond-like carbon, methods such as chemical vapor deposition (CVD), ion plating, ionization vapor deposition, sputtering, etc. have been proposed and studied. Law and so on. Among them, the CVD method shows the most possibility of mass production. According to the excitation method of the reactant gas, this method can be classified into a hot filament CVD method, a microwave plasma CVD method, an electron accelerated CVD method, and the like.

More precisely, chemical vapor deposition (CVD) such as the hot filament method (S.Matsumoto et al, Japan, J.Appl.Phys, 21 (1981) L183), microwave plasma CVD method (M.Kamo et al., J.Cryst, Growth.62 (1983) 642), electron accelerated CVD method (A.Sawbe et al. , Appl. Phys Lett. 46 (1985) 1467 and so on.

However, according to these preparation methods, the deposition rate of the diamond film is as low as nµm/h or less, and although inexpensive equipment and raw materials are used, the production rate is low and the cost is high, so it is not practical from a practical point of view. feasible. In addition, the high-frequency thermal plasma CVD method (Society of Applied Physics, Spring Season Lecture Mareh 1987) also has disadvantages, that is, the surface is graphitized at a film thickness of 30 μm or higher, so although it can reach 1 μm/min High film deposition rate, but possible to produce thick films. The speed of the thermal plasma generated by high frequency is very low, therefore, the substrate must be placed in contact with the thermal plasma, so the temperature of the substrate surface rises, so thick films can be prepared. In addition, due to the formation of a large volume of thermal plasma, the flow rate of the thermal plasma is very low, which cannot provide a high enough cooling rate for the water-cooled substrate, so that it is impossible to obtain a uniform diamond film.

Therefore, although a variety of deposition methods are available, and deposition of diamond can be realized by each of said methods, the deposition rate of a film with high quality is only 1 μ/h or less, and its quality is only 1 μ/h. It can be detected by measuring the peak of diamond by Raman spectroscopy. In addition, in the case of diamond-like carbon, the deposition rate is very low, only about 10 µm/h, which is a problem for mass production.

In summary, it is necessary to develop a deposition method for rapidly depositing films.

As described above, in terms of the deposition method of the diamond film, various methods have been proposed and studied, but even in the best CVD method, the deposition rate of diamond is only 1 μm/h or less, therefore, the development A CVD method for rapidly depositing films must yet be realized.

Therefore, the object of the present invention is to eliminate the above-mentioned shortcoming of prior art, provide a kind of method for vapor depositing diamond on substrate and have sufficient film thickness and good film quality under relatively high film deposition rate and devices.

Other objects and advantages of the invention will appear from the following description.

According to the present invention, a kind of method of vapor deposition diamond is provided, the method comprises the steps:

Arc discharge is performed while passing discharge gas between the cathode and anode of a thermal plasma chemical vapor deposition device,

free radicalization of gaseous carbon compounds by passing gas into the resulting plasma stream, and

The radicalized plasma stream hits the substrate to be treated, thus forming a diamond film on the substrate.

According to the present invention, also provide a kind of vapor phase deposition method of diamond, this method comprises the steps:

passing a hydrogen-containing gas and a gaseous carbon compound into a thermal plasma generating device having an anode and a cathode;

Free radicalization of gases by direct current arc discharge between electrodes;

injecting hot plasma in a plasma stream into a decompression chamber; and

A diamond film is deposited on the substrate by quenching the plasma stream by impinging the hot plasma stream on a cooled substrate.

According to the present invention, further provide a kind of method of vapor deposition diamond, this method comprises the steps:

By applying direct current between one electrode of one polarity and multiple electrodes of opposite polarity formed on the inner wall of multiple nozzles opened in a closed system, arc discharge is performed, thereby free radicalizing or activating hydrogen and gas containing gaseous carbon compounds , forming a thermal plasma;

Inject plasma flow into the decompression chamber;

A diamond film is deposited on the substrate by quenching the plasma stream by impinging the hot plasma stream on a cooled substrate.

According to the present invention, there is also provided a device for forming a plasma, which is a device for forming a plasma flow, including a device that is equipped with a discharge gas pipeline, a gas pipeline for raw material gas or a gas that transports solid particles, a DC power supply, and electric wires. A closed body, and therein are opened nozzles for spraying plasma streams, the device is characterized in that a plurality of nozzles are opened, the inner walls of each nozzle form electrodes with the same polarity respectively, and a plurality of electrodes with opposite polarities are arranged In a closed system so that they face the inner wall of each nozzle.

According to the present invention, also provide a kind of method of vapor deposition diamond, this method comprises the steps:

passing the gas into a thermal plasma generating device in the form of a torch having an anode and a cathode;

radicalization of the gas by direct current arc discharge between electrodes to form a hot plasma;

The hot plasma is projected as a plasma jet through a nozzle at the tip of the torch.

Injecting cooling gas into the plasma stream to quench the plasma and form an active non-active non Equilibrium plasma; and,

exposing the substrate to a non-equilibrium plasma, whereby on the substrate Deposit a layer of diamond film.

According to the present invention, there is further provided a method for vapor-phase deposition of diamond, the method is to carry out arc discharge through a DC plasma torch with a cathode and an anode, at the same time, a discharge gas is introduced between the cathode and anode, and the radiating the formed plasma on the substrate to be treated to form a diamond film thereon, the method comprising using at least two plasma torches, making a gas of a higher discharge voltage into a plasma in one of the torches, In the remaining torch, a reactive gaseous carbon compound with a lower discharge voltage is made into a plasma, and the two plasmas collide with the substrate in the form of a jet, thereby forming a diamond film.

According to the present invention, also provide a kind of method of vapor deposition diamond, this method comprises the steps:

Using multiple plasma torches,

A plurality of plasma streams in which a carbon source is made into plasma to form a diamond film are caused to collide with each other.

According to the present invention, further provide a kind of method of vapor deposition diamond, this method comprises the steps:

making a plasma of a discharge gas formed by arc discharge and a material containing at least one gaseous carbon compound;

Injection of hot plasma as a plasma stream, and

The plasma is quenched to deposit a diamond film on the substrate, wherein at least a portion of the material destabilizing the arc discharge is fed into the center of the plasma stream initiation end and not through the arc discharge portion.

The invention will be better understood with reference to the following description of the drawings, in which:

Figure 1 illustrates the principle of the thermal plasma CVD method practiced in accordance with the present invention.

Fig. 2 schematically illustrates a thermal plasma CVD apparatus for practicing the present invention;

Figure 3 illustrates an embodiment of the thermal plasma vapor phase synthesis method;

Figure 4 illustrates another embodiment of thermal plasma vapor phase synthesis;

Fig. 5 is a graph showing the temperature change of the equilibrium constant of hydrogen molecular decomposition reaction.

Fig. 6 is a sectional view of a thermal plasma flow generating device of the present invention;

Fig. 7 is a bottom view of a thermal plasma generating device of the present invention;

Figure 8 is a sectional view of another thermal plasma flow generating device of the present invention;

Fig. 9 is a schematic diagram of a vapor phase synthesis device using the plasma flow generating device of the present invention.

Figure 10 (a) illustrates the principle of DC plasma vapor phase synthesis of the present invention, Figure 10 (b), Figure 10 (c) is a cross-sectional view of the plasma torch;

11(a) and (b) are diagrams and photographs, respectively, showing the state of DC plasma flow according to an embodiment of the present invention;

Fig. 12 (a) and (b) are figure and photograph respectively, have shown the state of the plasma flow of the DC plasma vapor phase synthesis according to another embodiment of the present invention;

Figure 13 schematically illustrates the formation of diamond on a substrate according to the plasma CVD method.

Figure 14 schematically illustrates a thermal plasma CVD apparatus for practicing the present invention;

Fig. 15 illustrates the principle of the plasma flow CVD method of the present invention;

Fig. 16 is a general diagram for implementing the plasma flow CVD method device of the present invention;

Figure 17 has shown the crystal structure according to the diamond film of the present invention;

Figure 18 shows the crystal structure of a diamond film according to another embodiment of the present invention;

Figure 19 illustrates the principle of the plasma jet device of the present invention;

Figure 20 is a scanning electron micrograph showing the surface of the diamond film;

Figure 21 is a scanning electron micrograph showing the surface and cross-section of the diamond film;

Figure 22 has shown the X-ray diffraction result of diamond film;

Figure 23 shows the Raman spectrum of the diamond film;

Fig. 24 has shown the gas-cooled direct current plasma flow vapor-phase synthesis device of the present invention;

Figure 25 is a scanning electron micrograph showing the surface of the diamond film;

Figure 26 is a scanning electron micrograph showing the surface and cross-section of the diamond film;

Figure 27 has shown the X-ray diffraction result of diamond film;

Figure 28 shows the Raman spectrum of the diamond film; and

Figure 29 shows the emission spectra of a DC plasma stream according to the present invention and a conventional microwave plasma.

According to the present invention, diamond is deposited on the processed substrate.

Fig. 1 shows the principle of the thermal plasma method used for the CVD of the present invention, in which, while the discharge gas 3 passes between the anode 1 and the cathode 2, a voltage is applied to perform arc discharge, thereby generating a gas having a temperature of 5000°C or higher. arc plasma.

Through the inlet set on the anode 1, the raw material gas 4 is passed into the arc plasma forming part, and is rapidly heated to a high temperature and activated, thereby forming high-density free radicals, and at the same time, the volume to be injected expands to form an ultra-high-speed plasma flow 6 through nozzle 5.

Using the methods described above, attempts have been made to synthesize powders of high melting point compounds such as silicon carbide (SiC) or silicon nitride (Si ₃ N ₄ ). More specifically, experiments have been done in which silane (SiH ₄ ) and methane (CH ₄ ) were fed as raw material gases into an arc plasma for the production of SiC; and SiN ₄ and ammonia ( NH ₃ ), undergo activation and prepare the powder by allowing free radical reactions to occur.

The present invention develops this method for the purpose of forming a film by causing the plasma stream 6 to collide with the substrate 7 to be processed, thereby performing an efficient CVD reaction on the substrate before the short-lived radicals disappear. In addition, during the reaction on the substrate, energy derived from photoexcitation by ultraviolet radiation generated during arc discharge and plasma collision is applied.

Therefore, the present invention produces a density of free radicals much higher than that obtained by the prior art activated by high-temperature electric arc (above 5000°C), and at the same time, transports free radicals to the substrate to be processed and obtains by the excitation and collision from the above-mentioned The energy causes free radical reactions to occur for efficient diamond deposition.

In the process of synthesizing diamond according to the second embodiment of the CVD method of the present invention, a mixture of carbon compounds (such as methane, acetylene, alcohol, propanol, methylamine, dichloroethane, etc.) and hydrogen is decomposed to Activate and deposit diamond on the substrate at a suitable temperature for vapor deposition of diamond (that is, 400-1500°C). In the synthesis of diamond, it is considered that active species (such as hydrogen atoms and hydrocarbon groups) play an important role in the vapor phase. In order to increase the deposition rate of diamond, a high density plasma of such active species can be prepared and delivered to the surface of the substrate.

平衡常数随温度的变化，但在500K时可以看出，几乎全部氢分子离解成氢原子。然而，当该温度下的热等离子体与基片接触时，基片的温度升得太高，很难合成金刚石。Regarding the plasma with high activity and high degree of dissociation of molecules, a thermal plasma is known, in which different chemical species, such as ions, electrons, and neutral particles, have basically the same temperature in the plasma, and the temperature 5000K or higher. Figure 5 shows the dissociation reaction of molecular hydrogen

The equilibrium constant varies with temperature, but at 500K it can be seen that almost all hydrogen molecules dissociate into hydrogen atoms. However, when hot plasma at this temperature comes into contact with the substrate, the temperature of the substrate rises too high, making it difficult to synthesize diamond.

Fig. 3 is an illustration for synthesizing diamond according to the DC discharge thermal plasma flow (VI) method of the present invention.

While transporting the hydrogen-containing gas 17 and the gaseous carbide 18, a DC voltage is applied between the anode 15 and the cathode 16 to discharge the arc 19. At this time, the gas is suddenly heated between the narrow electrodes and becomes into a thermal plasma with a temperature of 5000°C or higher. In this case, the thermal plasma is injected into the chamber 22 through the nozzle 20 as a supersonic plasma stream 21 due to the volume expansion due to the sudden rise in temperature.

Figure 29 shows the emission spectra of a DC plasma stream according to the present invention and a conventional microwave plasma. The two spectral lines are based on the _H2 peak. In microwave plasma, the hydrogen molecular line width and strong emission peak (<480nm, 560~620nm) were measured. But in a DC plasma flow, the emission is weak due to hydrogen molecules. These results imply that the degree of hydrogen dissociation is high for DC plasma flows compared to conventional microwave plasmas.

The diamond film 25 is synthesized by quenching the plasma stream 21 by colliding the plasma stream 21 with the substrate 24 where efficient cooling takes place, and active species such as short-lived hydrogen react on the substrate before disappearing.

In addition, in the reaction on the substrate, the applied kinetic energy is obtained by intense ultraviolet photoexcitation and ultrasonic particle collisions generated by the arc discharge.

Therefore, in the present invention, chemical reactions can be performed with much higher efficiency than in the prior art methods, so that diamond can be synthesized at high deposition rates.

In the present invention, any carbon compound can be used as the raw material gas, but it is preferable to use a hydrocarbon, or a hydrocarbon or halogenated hydrocarbon containing oxygen, nitrogen or halogen in its molecule.

In addition to hydrogen feed gas and carbon compound feed gas, mixing an inert gas (such as argon, nitrogen, etc.) can improve the stability of arc discharge. In this case, although the deposition rate of the film may be lowered, there is a benefit of improving the uniformity of the film surface.

Also, the effect of etching non-diamond carbon can be enhanced by mixing a small amount of an oxidizing gas such as oxygen, water, hydrogen peroxide, carbon monoxide, and the like.

The raw material gas 18 can be added together with the hydrogen discharge gas 17 between the electrodes, but as shown in Figure 4, it can also be added to the In the plasma stream 21. In this case, however, the feed gas must be fed uniformly into the hot plasma stream.

Since hydrogen is used as the discharge gas, which, as shown in Fig. 5, has a high ionization potential and is difficult to discharge, the electrode material should preferably have high heat resistance. Among them, tungsten added with a rare earth element oxide (such as lanthanum oxide, yttrium oxide, cerium oxide, etc.) is an excellent electrode material. In addition, in order to prevent impurities from being entrained in the electrodes, it is best to use high-purity carbon electrodes.

According to the third embodiment of the present invention, since the formed thermal plasma is heated to about 5000°C, it expands suddenly and is ejected through the nozzle. Since the nozzle hole diameter is narrow, only 1-2mm, the area where the spray from a nozzle collides with the cooling substrate is about 25mm ² . In the present invention, plasma streams are emitted through a plurality of nozzles, and therefore, the film deposition area can be enlarged.

Also, the uniformity of the film during deposition can be improved by mixing an inert gas such as hydrogen or helium into the hydrogen discharge gas or the carbon compound feed gas, or both, or by An oxidizing gas such as oxygen, hydrogen peroxide or water is mixed in to remove non-diamond carbon mixed in the etched film.

As shown in FIG. 6, the plasma generating device includes a closed body in which an anode 26 and a cathode 27 supported by an insulating member are formed, and so on. The gas delivery pipe 28 for discharge gas communicates with the closed body, and the gas delivery pipe 29 for raw material gas or gas transporting solid particles communicates with the interior of a plurality of nozzles 31 arranged on the electrode 26 . A DC voltage is applied to the electrodes through the wire 30 to generate a continuous discharge arc between the electrodes, thereby activating the discharge gas and raw material gas to form a high temperature plasma flow 33 .

As shown in Figure 9, for chemical vapor deposition of diamond according to the present invention, the thermal plasma generating device is arranged in the decompression chamber 37, and the chamber 37 is equipped with a water-cooled substrate holder 36 for supporting the substrate opposite to the nozzle 31 35. As shown in FIG. 7 , the apertures of the four nozzles 31 are each 2 mm, the center distance of the nozzles is at least 5 mm, and the substrate 35 (20 mm ² ) is placed 10 mm below the nozzles 31 . The pressure in the chamber was reduced to 100 Torr, hydrogen was added from the discharge gas delivery pipe 28 at a flow rate of 1000 SCCm, and methane was introduced into the nozzle 31 from the feed gas delivery pipe 29 at a flow rate of 100 SCCm. A 2KW direct current was applied between the electrodes, and the plasma stream 33 generated by the arc discharge was quenched by continuously colliding with the substrate for 1 hour, thereby forming a diamond film with a film thickness of about 80 μm and an area of about 4 cm ² . The area of this film is 16 times of the area obtained when only one nozzle is used. As shown in FIG.

According to the present invention, in the method of direct current plasma flow chemical deposition of diamond, high-speed film formation is possible, and the film formation area can be greatly increased, thereby achieving improvement in cost and production.

In the above example, the chemical vapor deposition of diamond was carried out using a plasma flow, but it is also possible to pass a powder containing an inorganic or metallic substance together with a gas (such as hydrogen) through a raw material gas, or a liquid or The gas delivery pipe of the fine solid particles is delivered to the inside of the nozzle 31, and the inorganic or metal substances are melted with the plasma flow, thereby forming a layer of plasma sprayed layer on the substrate.

As shown in FIG. 8 , the fine powder particles of inorganic or metal substances can be transported by hydrogen gas or the like and blown into the plasma flow through the raw material gas or the gas delivery pipe 29 (opened outside the nozzle 31 ) for transporting liquid or fine solid particles. As the metal substance, refractory metals, superalloys, cermets, and the like can be used. As inorganic substances, Y-Ba-Cu-O system, Bi-Sr-Ca-O system superconducting material, ceramics, graphite, glass, etc. can be used. Regarding the inorganic matter, a powder such as Y-Ba-Cu-O system superconducting ceramic powder is fed through a gas delivery pipe to form a plasma spray with a thickness of about 100 μm and an area of 4 cm ² . According to the actual measurement, this plasma sprayed coating shows superconductivity at the temperature of liquid nitrogen, and the resistance value is zero at the absolute temperature of 88.5K.

According to the fourth embodiment of the present invention, instead of the method of quenching the thermal plasma by colliding with the substrate to be cooled, a method of blowing gas into the plasma stream (air cooling method) is employed.

According to the present invention, this method produces a non-equilibrium plasma independent of the substrate because the hot plasma is instantaneously cooled by forcing the plasma stream to mix with the gas at about room temperature. Thus, diamond can be synthesized at a high rate on a substrate by maintaining the material to be processed in a non-equilibrium plasma at a temperature capable of forming diamond. The recommended substrate temperature is 800°C to 1300°C.

Figure 10 (a) shows the principle of diamond synthesis according to the air-cooled DC plasma flow CVD method of the present invention, wherein 38 is the cathode, 39 is the anode, 40 is the discharge gas, 41 is the nozzle, 42 is the plasma flow, and 43 is the cooling gas Nozzle, 44 is a cooling gas, 45 is a substrate, 46 is a diamond film, 47 is an arc power supply, 48 is an electric arc, and 49 is an unbalanced plasma. As far as the plasma torch 50 is concerned, a single-electrode torch as shown in FIG. 10( b ) or a multi-electrode torch as shown in FIG. 10( c ) can be used.

When passing through the discharge gas 40 containing hydrogen and gaseous carbon compounds, a DC voltage is applied between the cathode 38 and the anode 39 to excite The electric arc 48 is discharged, so that the temperature of the discharge gas is suddenly raised to become a thermal plasma with a temperature of 5000° C. or higher around the nozzle 41 . During this operation, the thermal plasma becomes a supersonic plasma stream 42 and is ejected through the nozzle 41 due to volume expansion caused by a sudden increase in temperature.

Hydrogen gas is blown into the plasma stream 42 as a cooling gas 44 to force mixing, thereby quenching the hot plasma and generating non-equilibrium plasma 49 . By exposing the substrate 45 to the non-equilibrium plasma 49, active species such as short-lived hydrogen atoms react with the substrate before disappearing to grow a diamond film 46 on its surface.

Fig. 11(a), (b) and Fig. 12(a)(b) show the state of plasma flow with or without cooling gas passing through. With regard to Fig. 12(a) and (b), it is clear that the length of the plasma stream must be extremely short to quench the hot plasma when gas cooling is used.

Therefore, compared with the direct current plasma flow CVD method that does not pass through the cooling air flow, the present invention has nothing to do with the substrate because the hot plasma flow can be quenched, so there is no limit to the type of substrate used, and the diamond can be placed on any substrate at a high speed. grow.

In the present invention, any hydrocarbon can be used as the raw material gas, but it is preferable to use a hydrocarbon or a halogenated hydrocarbon containing oxygen, nitrogen and halogen in the molecule.

The stability of the arc discharge can be improved by mixing an inert gas (such as hydrogen, helium) with a carbon compound starting discharge gas in addition to hydrogen. In this case, although the film deposition rate may be reduced, the benefit is obtained that the uniformity of the film surface is improved.

Also, by mixing small amounts of oxidizing gases such as water, hydrogen peroxide and carbon monoxide, the effect of removing non-diamond carbon by etching is also enhanced.

Since hydrogen gas having a high ionization potential is used as the discharge gas, the electrode material preferably has high heat resistance. Tungsten which has a rare earth element oxide (such as lanthanum oxide, ytterbium oxide, selenium oxide, etc.) added is an excellent electrode material. In addition, in order to prevent impurities from being entrained in the electrodes, it is best to use high-purity carbon electrodes.

As previously mentioned, prior art methods for synthesizing diamond films do not meet the requirements of industrialization. According to the fifth embodiment of the present invention, a new method for synthesizing diamond films using the principle of plasma flame spraying has been created, so that on the substrate It is possible to synthesize diamond film industrially.

However, in this method, for example, a gas mixture of hydrogen and a compound of gaseous carbon such as methane is used as a gas, and vapor deposition is performed using a thermal plasma flow CVD apparatus to form a diamond film, but a problem arises, This is due to, for example:

(1) The hydrogen discharge voltage is extremely high.

(2) Heat and volume expansion due to methane cracking.

(3) The carbon and electrode reaction caused by the cracking of methane attached to the flame spraying device.

As a result, the substrate temperature and the plasma flow rate are changed, and a uniform diamond film cannot be synthesized.

Figure 13 illustrates the principle of the above-mentioned thermal plasma CVD method. In this method, a voltage is applied through a DC power supply 56 to activate arc discharge, and at the same time, a discharge gas (H ₂ +CH ₄ ) 55 is passed between the anode 53 and the cathode 54 to generate 5000°C or higher temperature arc plasma.

The raw material gas 55 of the arc plasma forming part passed into the plasma torch is rapidly heated to a high temperature to be activated and generate high-density free radicals, thereby expanding in volume and ejected from the nozzle as a plasma stream 58 at supersonic speed.

According to this method, the plasma flow 58 is made to collide with the substrate to be processed, and a high-efficiency CVD reaction on the substrate is realized before the short-lived free radicals disappear, thereby forming the diamond film 60 . The substrate 59 for the above purpose is placed on a water-cooled substrate holder 61, and cooled to a temperature of, for example, 400-1500°C, preferably 800-1300°C by cooling water 62 added to the water-cooled substrate holder 61.

However, as described above, although a diamond film can be effectively vapor-deposited on a substrate, a stable plasma flow cannot be obtained for the above-mentioned reasons, thereby causing a problem that a uniform diamond film cannot be synthesized. In contrast, according to the present invention, as shown in Fig. 14, two plasma torches 64 and 65 are prepared, _H2 gas (or a mixture of hydrogen and inert gas as conventionally prepared) is introduced into one of the torches, and methane ( _CH4 ) gas (or a mixture of methane and an inert gas such as Ar) into another torch. A voltage is applied between the anodes 66, 67 and cathodes 68, 69 by DC power sources 70 and 71 respectively to initiate an arc discharge, whereby plasma streams 72 and 73 are ejected. These plasma streams deposit a uniform diamond film 76 on a substrate 75 placed on a water-cooled substrate holder.

Considering that by allowing a large number of plasmas to collide with each other, the carbon-containing compound is made into a plasma and quenches the compound in the plasma flow, forming a large number of fine diamond nuclei. Therefore, according to the sixth embodiment of the present invention, a smooth diamond film with excellent uniformity can be prepared, which is different from the case where only a small number of diamond nuclei are grown and the surface of the resulting diamond film is not smooth.

Figure 15 illustrates another principle of generating a plasma flow torch installed in a thermal plasma VCD device. 78 of which are anodes, 79 is cathode, 80 is discharge gas or discharge gas containing raw material gas, 81 is cooling gas or cooling gas containing raw material gas, 82 is electric arc, 83 is nozzle, 84 is plasma flow, 85 is vacuum chamber, 86 is substrate seat, 87 is a substrate, and 88 is a diamond film.

Fig. 16 is the overall view of the device implementing the present invention, among which 89 is the first plasma torch, 90 is the second plasma torch, 91 and 92 are arc power supplies for each torch, and 93 and 94 are cooling water devices for each torch , 95 is a substrate controller, 96 is a blowpipe controller, 97 is a vacuum system, 98 is a bullet-shaped gas cylinder, 99 is a flow meter, 100 is a discharge gas or a discharge gas pipeline containing raw material gas, 101 is a raw material gas And (or) cooling air delivery pipe, 102 is the cooling air nozzle.

A silicon substrate 87 of 5 cm ² is placed 100 mm below the blowpipe 87, and after being evacuated to 1×10 Torr by a rotary pump, under the discharge power of 3KW and the system pressure of 100 Torr, discharge gas H ₂ at 50 SCCm, raw material gas _CH4 was added to blowpipe 89 at 500 SCCm. At the same time, 20 SLM of discharge gas and 100 SCCm of feed gas are input into the torch 90 under the condition of discharge power of 1KW. And form a film at the blowpipe which is 35cm away from the substrate and forms an angle of 60 with the substrate. It took 1 hour. It was found by X-ray diffraction and analyzed by Raman spectroscopy that a film showing diamond peaks was formed. FIG. 17 shows a diamond film prepared with two plasma torches according to the present invention, the film thickness is 35 μm, and the film formation rate is 100 μm/hr. Figure 18 shows a diamond film produced by a comparative method using only one plasma torch. According to the present invention, a diamond film having a smooth and uniform surface can be formed at high speed.

In the above-mentioned example, hydrogen is input into the plasma torches 89 and 90 respectively from the discharge gas pipe 100 and methane gas from the feed gas delivery pipe 101, but it is also possible to input both hydrogen and methane gas in the discharge gas delivery pipe 100, or in the Both the cooling gas H ₂ and the methane gas are input into the feed gas pipeline and (or) the cooling gas pipeline 101 . Variations are also possible, for example, feeding discharge gas and feed gas into only one of the blowpipes. And just feed the discharge gas into the other blowpipe and so on. Its essence is to emit a large amount of plasma flow, and make the carbon source into plasma in the plasma flow to form diamond on the substrate. Also, for deposition rate, the angle of the plurality of plasma streams should preferably be perpendicular to the substrate; however, an optimum angle can be predetermined as desired.

As the above-mentioned plurality of plasma streams, DC plasma generation by DC arc discharge has been mentioned, but various multiple plasmas such as RF plasma streams of high-frequency discharge, light generated by laser photoelectric arc discharge, etc. can also be used. Arc plasma flow, plasma flow generated by microwave plasma flow AC discharge by microwave discharge method, etc. As for the atmosphere for generating plasma, it is preferably under reduced pressure, but atmospheric pressure or elevated pressure can also be used for diamond formation. In addition, this method can also be used to synthesize diamond powder.

According to the sixth embodiment of the present invention, the diamond film can be prepared at a high speed and its surface is smooth and even with the direct current plasma flow CVD method, so the application range of the coating can be expanded to a very wide range, and the heat sink used for semiconductor devices Or diamond circuit substrates can be easily completed.

The diamond film epitaxial growth method of the seventh embodiment of the present invention includes injecting a raw material containing a carbon source into the plasma by quenching hot plasma and growing diamond.

In the diamond growth method, hydrogen is usually used as the discharge gas, and any carbon compound can be used as the raw material gas of the carbon source, but it is best to use a hydrocarbon or a hydrocarbon containing elements such as O, N, and halogen in the molecule. or organic matter. An inert gas such as Ar, He, etc. can also be mixed in the discharge gas or the raw material gas. In this case, the stability of the plasma can be further improved, but the film deposition rate is lowered. Also, in order to enhance the etching effect of non-diamond carbon (such as amorphous carbon), a small amount of an oxidizing gas such as O ₂ , H ₂ O, CO, etc. may also be mixed in the raw material gas.

In addition, semiconductor diamond can also be obtained by mixing trace gases such as B ₂ H ₂ , NH ₃ , PH ₃ etc. into the raw material gas or feeding these trace gases into the plasma flow alone.

The raw material gas is input to the center of the initiation end of the plasma flow without passing through the arc discharge part. For this purpose, it is preferable to use the plasma jet spraying device of the present invention described below. When the plasma jet device of the present invention is used for plasma flame spraying of high-temperature superconducting oxides (Ba-Y-Ca-O system, Bi-Sr-Ca-Cu-O system, etc.), the fine powder of superconducting oxides Together with a carrier gas, it is fed into 109 as shown in Fig. 19, melted in the plasma flow and forms an effective film on the substrate. Of course, a plasma atmosphere, an oxidation atmosphere, an oxygen atmosphere, an air atmosphere, etc. may also be used in this case.

As shown in Figure 19, the plasma jet device of the present invention has a feed hole 109 for raw material gas (or gas containing raw material powder), which extends along the central axis of the inner electrode 103 and has a nozzle 106 positioned at the outer electrode 104 Center nozzle 108 . The arc 113 discharges between the outer electrode 104 and the electrode 103 , but the raw material gas (or raw powder gas) 109 will not be in contact with the arc 113 . In this way, the formation of a uniform arc 113 is not hindered. In addition, since the raw material gas 109 (or the gas containing raw material powder) is released to the central part of the plasma flow 107 initiation end, the plasma flow 107 is formed The plasma distribution is uniform. For vapor deposition or thermal plasma, the use of this plasma flow is conducive to the formation and growth of deposition products, thereby producing a uniform and smooth film.

Note that by using such an apparatus for generating diamond and a raw material other than diamond as a substrate, polycrystalline diamond can be synthesized on its surface.

Fig. 19 illustrates the principle of forming a diamond film using the device of the present invention.

This device is suitable for feeding the raw material gas into the plasma flow through the nozzle installed in the center of the negative plate so that the raw material gas can be uniformly input into the plasma flow, thereby improving the uniformity of the film thickness, or when the raw material gas is carbon In the case of the compound, the generation of graphite can be suppressed. in the figure. 103 is the cathode, 104 is the anode, 105 is the discharge gas, 106 is the nozzle, 107 is the plasma flow, 108 is the raw material gas outlet, 109 is the raw material gas, 110 is the substrate, 111 is the diamond film, 112 is the arc power supply, 113 is the arc.

When hydrogen as the discharge gas flows from a flow rate of 20 liters per minute and methane gas flows as a raw material gas at a flow rate of 0.2 liters per minute, a DC voltage of 90V and a current of 10A are applied between the cathode and anode for laser arc 113 discharge, so that the nozzle The discharge gas around 106 is heated to become a hot plasma flow at or above 5000°C. In this case, the hot plasma flow becomes the ultrasonic plasma flow 107 , which is ejected through the nozzle 106 due to the volume expansion caused by the sharp increase in temperature. The raw material gas is directly input into the plasma flow without passing through the discharge part, thereby being decomposed and activated. The plasma flow is quenched after colliding with a molybdenum substrate of 5×5×0.5 mm, and a diamond film is formed as a result. Therefore, a polycrystalline diamond film with a thickness of 200 μm is obtained within 1 hour. When measuring the surface roughness, it was found that Rmax was 10 μm, which was greatly improved compared with the method prepared by simultaneously inputting raw material gas and discharge gas (Rmax was 50 μm).

In this device, since the arc does not contain raw material gas, a stable discharge is obtained. Also, since all the raw material gas is fed into the plasma flow, the generation of graphite can be suppressed.

As far as diamond growth is concerned, since the use of hydrogen is advantageous, only because the high ionization potential may cause discharge difficulties, it is best to use electrode materials with high heat resistance and stable discharge. Among them, tungsten added with lanthanum oxide, yttrium oxide, cerium oxide, etc. is an excellent electrode material. Also, in order to avoid impurity entrainment in the electrode, it is best to use a high-purity carbon electrode.

The plasma jet apparatus of the present invention is advantageously used for diamond synthesis as previously described, but can of course be used for other purposes as well.

Example

The present invention is now further illustrated by, but not limited to, the following examples in which all parts and percentages are by weight unless otherwise noted.

Example 1

FIG. 2 is a schematic diagram of a thermal plasma device for implementing the present invention, and the plasma flow generation part shown in FIG. 1 is represented as a plasma torch 8 .

A substrate seat 9 facing the plasma torch 8 is placed in the device, the substrate seat is water-cooled, and the substrate 7 to be processed is placed on it.

Also, this device is connected to a vacuum system 10 .

Secondly, the plasma torch 8 is connected to the discharge gas delivery pipe 11 for feeding the discharge gas between the discharge electrodes 1 and 2, and the raw material gas delivery pipe 12 for delivering the raw material gas to the arc plasma. An arc power source 13 is also provided to supply power to the discharge electrodes, and a bias power source 14 to concentrate free radicals on the substrate 7 to be processed.

Next, as an example, a 30 mm ² silicon substrate is processed, and the distance between the substrate and the plasma torch 8 is kept at 300 mm.

First, use the vacuum system 10 to evacuate the inside of the device to 1×10 ^-3 Torr, then feed hydrogen (H ₂ ) through the discharge gas delivery pipe 11 at a flow rate of 1000 SCCM, and feed methane gas ( CH ₄ ), use the vacuum pumping system 10 to keep the vacuum degree in the chamber at 100 Torr, after that, the arc power supply is 2KW, and the bias voltage is 300V.

Then, after thermal plasma CVD, the thickness of the diamond film formed within 1 hour was about 10 μm, and analysis by X-ray diffraction and Raman spectroscopy showed only diamond peaks.

The deposition rate is an order of magnitude higher or higher compared to prior art CVD, which has a deposition rate of 1 µm or less.

According to the present invention, since extremely high-density free radicals can be generated, compared with the prior art, the speed of forming the diamond film is an order of magnitude higher, thereby meeting the requirements for large-scale integrated circuit substrates.

Example 2

The anode 15 and the cathode 16 in Fig. 3 are all made of tungsten with 2% (weight) yttrium oxide added thereto, the plasma torch is the result of water cooling, and the torch is fixed on the controller (not shown) in the chamber 22 , and with variable direction nozzle 20.

The water-cooled substrate seat 23 can move vertically or horizontally, and the distance between the nozzle and the substrate can also be changed.

5mm ² , 0.2mm thick silicon wafer is fixed on the substrate holder 23, after the chamber 22 is evacuated to ² ×10 ^-3 Torr, as shown in Fig. The flow rate, and methane gas as the raw material gas 18 was flowed between the electrodes at a flow rate of 40 cc/min at a pressure of 1 kg/cm ² while the pressure in the chamber 22 was maintained at 100 Torr. From a constant current arc source, a constant current of 10 A was passed between the electrodes and held for about 5 minutes until the voltage was constant. At this time, the voltage is 72V.

The water-cooled substrate holder 23 slowly approached the nozzle 20, and the distance between the nozzle and the substrate was fixed at 5 mm. In this state, the diamond was synthesized for one hour. The synthesized diamonds were evaluated by scanning electron micrographs (SEM), X-ray diffraction, Raman spectroscopy and hardness measurements.

As shown in FIG. 20, the surface of the diamond film is composed of diamond crystals that are regularly arranged and gathered together. The SEM of Fig. 21 shows the middle part of the cross-sectional view of the diamond film, the lower part of the cross-sectional view of the silicon substrate and the upper part of the surface of the diamond film. Therefore, it can be seen that a slightly uneven diamond surface is uniformly formed. Figure 22 shows the X-ray diffraction pattern of the diamond film, the diamond crystal planes (111), (220), (331) are very clear, and (331) and (440) can still be distinguished. Figure 23 represents the Raman spectrum of the diamond film. In the figure, the intrinsic peak of diamond can still be distinguished at a wave number of 1333 cm, and it is also easy to see that no other carbonaceous substances such as graphite appear.

Regarding HV500 Vickers hardness, due to the high hardness of the sample, it is difficult to distinguish the indentation, but the actual measurement shows that the pressure reaches 8000kg/cm ² or higher. It can be seen from the above data that the synthesized diamond is a high-quality polycrystalline film. Moreover, the measured film thickness is 80 μm, and the rate of synthesizing high-quality diamond is 10 times or higher than that of the prior art 80 μm/h.

In addition, under this condition, when the synthesis took 10 hours, the film thickness at the central part of the substrate became 1 mm, and the film thickness at the peripheral part thereof became 0.6 mm. Likewise, even with X-ray diffraction and Raman spectroscopy, only diamond peaks were obtained, and the presence of graphite was not detected.

Example 3 (Figure 4)

Use a molybdenum plate of 10 × 10 × 0.2mm as the substrate, as shown in Figure 4, as the hydrogen of the discharge gas 17 with 20 liters/min, the hydrogen is passed into with 20 liters/min, as the raw material gas 18 containing 2% Hydrogen in acetone was added into the plasma flow at 2 liters/minute, and diamond was synthesized for one hour under the condition of arc current 20A, voltage 60V, nozzle-substrate distance 10mm. The film thickness was 60 μm, and the film quality was similar to Example 2.

Embodiment 4-9 (Fig. 3 and Fig. 4)

In addition, when the reaction conditions are changed, such as changing the feed gas between the electrodes or inputting the gas into the thermal plasma flow formed between the electrodes, the diamond film formation speed is summarized in the table below. The quality of the obtained diamond film is similar to Example 2. (See the text after the table)

According to the plasma flow CVD method of the present invention, high-quality diamond can be deposited at a speed of 80 μm/h, which is much higher than the speed of the prior art, thereby enabling the practical application of cheap diamond by vapor phase synthesis. made great progress. When the diamond synthesized according to the method is used in semiconductor radiators or circuit substrates, the cost can be greatly reduced and the performance can be improved.

Example 10 (Figure 24)

Fig. 24 illustrates the diamond synthesis device of the air-cooled DC plasma flow CVD method implemented according to the present invention, wherein 115 is a plasma torch, 116 is a discharge gas delivery pipe, 117 is a cooling gas delivery pipe, 114 is an arc power supply, and 118 is a blowpipe Cooling water pipeline, 119 is the substrate seat, 120 is the substrate, 121 is the vacuum chamber, 122 is the vacuum system, 123 is the blowpipe controller, 124 is the flow meter, 125 is the gas cylinder, 126 is the cooling gas injection port, And 127 is a substrate controller.

The plasma torch has a water-cooled construction and is made of tungsten to which 2% by weight yttrium oxide has been added together with the cathode and anode 38 . The respective positions and orientations of the plasma torch 115 and the substrate holder 119 can be controlled by the controller, resulting in uniform diamond film growth on large area substrates or materials having complex surface shapes to be processed. Also, although not shown in FIG. 24, the substrate holder 119 may be provided with a heater for heating the substrate or a water cooling device for controlling the temperature of the substrate.

Example 11 (Figure 24)

Use a 5×5×0.2mm silicon wafer as the substrate, evacuate the vacuum chamber to 2×10 ^-3 Torr, use hydrogen as the discharge gas at a pressure of 1kg/cm ² at a rate of 20 liters/min, and methane gas at a pressure of 1kg /cm ² flowed between the electrodes at a flow rate of 80 ml/min, and hydrogen as a cooling gas flowed at a pressure of 1 kg/cm ² at a rate of 20 liters/min to maintain the vacuum chamber pressure at 200 Torr. Through the four cooling air nozzles 126 placed 3 mm below the blowpipe nozzle, the cooling air supplied by the cooling air source pipe 117 shown in FIG. 24 is sprayed to the plasma flow. A constant current of 10A supplied by the constant current arc power supply 114 flows between the electrodes of the plasma torch 115 and is kept for 5 minutes until the voltage stabilizes. At this time, the voltage is 65V. By slowly moving the substrate holder 119 toward the nozzle of the blowpipe 115, the nozzle-substrate surface distance was fixed at 5 mm, and the film was formed for 10 minutes under such conditions. The as-prepared diamonds were evaluated based on scanning electron micrographs (SEM), X-ray diffraction, Raman spectroscopic analysis and hardness measurements.

The SEM shown in Figure 25 shows that the diamond surface has gold Corundum crystals, which are regularly arranged and clustered together.

On the other hand, the SEM in Fig. 26 shows that the middle part is the diamond cross section, the lower part is the silicon substrate cross section, and the upper part is the surface of the diamond film. It can also be seen that a slightly uneven diamond film surface is uniformly formed.

It can also be seen that the synthesized diamond is a dense polycrystal with a clear uniform shape and a film thickness of 15 μm.

Figure 27 shows that the X-ray diffraction pattern of the diamond film has a CuKα ₁ line, and the extremely obvious diamond crystal planes (111), (220), (331), and (331) and (400) are still discernible. So only the diamond spikes of the cubic crystals were measured. Figure 28 shows the Raman spectrum of the diamond film. From the figure, it can be seen that there is also an inherent peak in diamond at a wave number of 1333 cm ^-1 , and it can be seen that there are other carbonaceous materials, such as graphite peaks.

According to actual measurement, the Vickers hardness value is the same as that of natural diamond, about 10000kg/cm ² under a load of 500 grams.

It can be seen from the above results that the synthesized diamond is a high-quality polycrystalline film. It can also be seen that the film deposition rate is as high as 100 μm/h.

Example 12 (Figure 24)

Under the film-forming condition of embodiment 11, use a platinum plate of 10 * 10 * 1mm as the substrate, and make the plasma torch scan the platinum plate with a speed of 2mm/h, and form a thick 0.4mm diamond film on the platinum substrate . The diamond film is peeled off from the substrate to form a diamond plate of 10×10×0.4 mm.

Examples 13-17 and 18 (Figure 24) and Comparisons 1-4

The results of multiple diamond synthesis under different conditions are shown below. (See the text after the table)

Example 19

In the above examples, no gas cooling was used:

Use a 5×5×0.2mm silicon wafer as a substrate, and after the vacuum chamber is evacuated to 2×10 ^-3 Torr, under a pressure of 1kg/cm ² , hydrogen gas flows as a discharge gas at a flow rate of 2 liters/min. Under the pressure of 1kg/ ^cm2 , methane gas flows between the electrodes at a flow rate of 400ml/min, thereby maintaining the pressure of the vacuum chamber at 100 Torr, and passing a current of 10A through the torch of the constant current arc power supply and maintaining it for 5 minutes until the voltage is constant. Now the voltage is 6.5V, and the substrate seat 119 in Fig. 24 is slowly approached to the blowpipe, and the distance between the nozzle and the substrate is fixed at 15mm. In this state, the deposition of the film is completed, and lasts one hour, and A high-quality diamond film with a thickness of 60 μm was obtained.

In the above example, as a method of forming an active non-equilibrium plasma with a high free concentration by quenching, in the example shown the cooling gas collides with the plasma ejected from the four gas cooling nozzles of the plasma, but the cooling Gas can also be injected towards the plasma axis. The cooling gas can also be sprayed against the plasma stream in only one direction to create a temperature profile or a free radical concentration profile can be created.

According to the CVD method of the gas-cooled direct-current plasma flow of the present invention, compared with the direct-current plasma flow CVD method not using air cooling, since the hot plasma can be quenched, it has nothing to do with the substrate, so diamond can be grown on any substrate. High-quality diamond can be produced at a high film deposition rate of about 100 µm/hour without cooling the substrate. This greatly widens the application range of the diamond coating.

Through the vapor phase synthesis method, the practical application of low-cost diamond has been greatly advanced, and when used in heat sinks or semiconductor circuit substrates, the diamond synthesized by this method will greatly reduce the cost and improve the performance , so diamond heat sinks or diamond circuit substrates for semiconductors are easy to implement.

Examples 20 and 21 (Figure 14)

Utilize the apparatus shown in Fig. 13 (embodiment) and Fig. 14 (embodiment 20), the silicon substrate of 10 * 10 * 0.5mm thickness is placed on the substrate seat that cools with cooling water, and by using tungsten as electrode A plasma torch deposits a diamond film on the substrate.

In the device shown in Figure 14, when a mixed gas of hydrogen (flow rate 20 L/min) and methane (flow rate 0.2 L/min) is introduced for discharge, the discharge voltage with a central value of 90 V fluctuates between ±20 V, and The shape of the plasma stream was greatly changed, and a diamond film with a thickness of 180 μm was deposited within one hour. The film had only unique diamond peaks when analyzed by X-ray diffraction and Raman spectroscopy.

On the other hand, in the device shown in Figure 14, when hydrogen and methane are respectively fed into each torch for discharge at a rate of 20 liters/minute (hydrogen) and 0.2 liters/minute (methane), the discharge of the hydrogen torch The voltage is very stable, its value is 100V±2V, the discharge voltage of the methane torch is 30V±2V, the shape of the plasma flow is stable, and a uniform diamond film with a film thickness of about 150 μm is obtained.

As described above, according to the present invention, since hydrogen gas and carbon compound gas (such as methane) are input as separate plasma streams, diamonds can be formed very stably and efficiently as compared with the method of introducing a gas mixture of hydrogen gas and methane gas for discharge. Therefore, it can meet the requirements of large-scale integrated circuits for substrates. Likewise, bypass heated filaments, microwave discharges, and RF discharges can also be utilized in accordance with the present invention rather than DC arc discharges.

Example 22 (Figure 19)

Figure 19 and Figure 24 schematically illustrate the implementation of the method of the present invention A plasma flow CVD device used in the figure, 115 is the plasma torch, 116 is the discharge gas input pipe, 114 is the arc power supply, 118 is the cooling water pipeline of the torch, 119 is the substrate seat, 120 is the diamond substrate, 121 is a vacuum chamber, 122 is a vacuum system, 123 is a blowpipe controller, 124 is a flow meter, 125 is a gas storage cylinder, 126 is a raw material gas input pipe, and 127 is a substrate controller.

The plasma torch 115 is a water-cooled construction made of tungsten with 2% (therapeutic) yttria added together with cathode and anode. The position and the direction of plasma torch 115 and substrate seat 119 are controlled by controller 124,127 respectively, and they all can move with respect to plasma current and substrate, thereby even can grow diamond film or diamond evenly on large area of substrate. Form a diamond film on materials with complex surface shapes. Although not shown in the schematic diagram, in order to control the temperature of the substrate, a heater for heating the substrate or a water cooling mechanism may be installed.

Use IIa type 2×2×0.5mm synthetic diamond substrate, after the vacuum chamber is evacuated to 2×10 ^-3 Torr, under the pressure of 1kg/cm ² , hydrogen is used as discharge gas at a flow rate of 20 liters/min. The feed gas methane was flowed at a flow rate of 0.1 liter/minute to keep the pressure of the vacuum chamber at 120 Torr.

The current of 20A is passed into the torch from the constant current arc power supply and maintained for 5 minutes until the voltage is constant. At this time, the voltage is 50V. When the substrate is slowly brought close to the torch, the distance between the nozzle and the substrate is fixed at 15mm , forming a film in this state for one hour.

When the manufactured diamond is analyzed by Raman spectroscopy and hardness measurement, Raman spectroscopy analyzes the only diamond peak, and the Vickers hardness is equal to the hardness of natural diamond, which is 10000 when the load is 500 grams. The diamond film thickness is 150 μm, and the film formation rate is 150 μm/hour.

Likewise, X-ray diffraction according to Laue's method, and low energy electron diffraction (LEED) confirmed that the single crystal diamond film was grown epitaxially on the underlying diamond substrate.

In this example it was found that the arc voltage fluctuated by about 10%. Therefore, the voltage fluctuation was 20% compared with the method of introducing a gas mixture of hydrogen and methane for discharge (as shown in Fig. 13), and the stability of the arc was also improved.

In this example, no generation of graphite was found yet.

Example 23

In addition, under the film-forming conditions of Example 22, B ₂ H ₆ was mixed into the raw material gas as a dopant gas at a flow rate of 0.1 ml/min, and the film-forming took 10 minutes to obtain a film with 10 ^-2 Ω· P-type semiconductor diamond with m resistivity.

Example 24

Use a silicon wafer (5×5×0.2 mm) as the substrate, vacuumize the vacuum chamber to 2×10 ^-3 Torr, and under the pressure of 1 kg/cm ² , discharge the hydrogen at a flow rate of 20 liters/min, methane The raw material gas was flowed through the vacuum chamber at a flow rate of 0.5 liter/minute so that the pressure of the vacuum chamber was maintained at 100 Torr.

A current of 20A is passed into the torch from a constant current arc power supply and maintained for about 5 minutes until the voltage is constant, and the voltage is 50V at this time. The substrate was slowly brought close to the blowpipe, and the distance from the nozzle to the substrate was fixed at 20 mm, and the film was formed in this state for one hour.

The prepared diamond films were evaluated by X-ray diffraction, Raman spectroscopy and hardness measurement. As a result, through X-ray diffraction, there is only a unique diamond peak in Raman spectrum analysis. The hardness value of the paper-dimensional paper is equal to the hardness value of natural diamond, which is about 10000 under a load of 500g, and the diamond film thickness is 200μm/hour.

When the surface roughness of the as-synthesized diamond film was measured, it was found that the Rmax was about 10 μm, which was greatly improved compared with the Rmax of 50 μm obtained after the feed gas contained the discharge gas input.

In this example, the arc voltage fluctuation of 10% was found in the process of synthesizing diamond, compared with the arc voltage fluctuation of 20% in the method of introducing a gas mixture of hydrogen and methane gas for discharge, and the stability of the arc was also improved. improve.

In addition, in this embodiment, no graphite was generated at the peripheral portion of the substrate.

Example 25

With the molybdenum sheet of 5 * 5 * 0.5mm as substrate, methane is input with the flow velocity of 0.2 liters/min as raw material gas, makes the voltage on the positive and negative electrode be 90V, and electric current is 10A, under the film-forming condition of embodiment 26, Similar results can be obtained.

Figure 19 shows a cross-sectional view of the plasma jet device, but the cathode 103 and the anode 104 can be symmetrically distributed, and the feed gas nozzles and nozzles 106 of the cathode 103 can be polygonal (rectangular, etc.) or elliptical, but uneven discharge characteristics. Also, comb-shaped tooth-shaped heat-resistant insulating material can be housed on the electrode if necessary, which will not affect the discharge and is conducive to large-area coating.

As far as the substrate is concerned, in addition to diamond, quartz glass, tungsten, molybdenum, etc. can also be used for film formation without surface treatment.

As for the discharge atmosphere, it is preferable to use the discharge atmosphere under reduced pressure for the stability of the arc, but it can also be used under normal pressure and increased pressure. An example of diamond film formation was shown in the above-mentioned embodiment, but the method can also be used for synthesizing diamond powder.

Also, as mentioned above, the plasma jet apparatus of the present invention can also be used for plasma flame spraying of high temperature superconducting oxides such as Ba-Y-Cu-O system.

When using the improved DC plasma flow CVD device of the present invention to generate the diamond film, the deposition rate is about 200 μm/hour, and a very smooth surface and excellent diamond film can be rapidly synthesized. Therefore, the application range of the diamond film can be greatly expanded.

The epitaxial film growth is carried out according to the DC plasma flow CVD method, and the thickness of the epitaxial film obtained at a very high film forming speed of 150 μm/hour is 150 μm.

Diamond heat sinks and diamond semiconductor circuit substrates for semiconductor devices can be easily obtained. In addition, semiconductor diamonds can be synthesized, and can also be used for plasma flame spraying of inorganic substances such as high-temperature superconducting oxides.

Example 4 5 6 7 8 9

Feed gas between electrodes H ₂ 20 H ₂ 20 H ₂ 20 H ₂ 20 H ₂ 20 H ₂ 20

(1/min) CH ₄ 1 CH ₃ OH0.5 Ar10 CH ₄ 1 CH ₃ C10.04 CH ₃ F0.04

H ₂ 01

Added to the jet flow Triethylamine 0.1 Ar2

(1/min) H ₂ 2 H ₂ O ₂ 0.5

Substrate thickness (μm) Si200 Si200 Mo200 Si200 Si200 Si200

Pressure (Torr) 120 120 200 130 120 120

Arc current (A) 10 10 10 10 10 10

Nozzle-substrate spacing 5 5 5 5 5 5 5

(mm)

Film deposition rate 80 45 70 60 60 30

(μm/h)

Example of high-speed preparation of high-quality diamond

Example 13 14 15 16 17 18

Discharge gas H ₂ 20 H ₂ 10 H ₂ 20 H ₂ 20 H ₂ 20 H ₂ 20

(1/min) _Ar10CH4 0.2

_{CH40.06H2O0.1 _}

Cooling air H ₂ 20 H ₂ 20 H ₂ 20 H ₂ 20 H ₂ 20 H ₂ 20

(1/min) CH ₄ 0.5 Acetone 2 CH ₃ C10.5 Acetone 2

Substrate Thickness Si2 Si2 Si2 Si2 Si2 Si2

(mm)

Pressure (Torr) 200 200 200 200 200 200

Current (A) 10 10 10 10 10 10

Nozzle-Substrate 5 5 5 5 5 5 5

Pitch (mm)

Film deposition rate 100 70 80 100 60 10

(μm/hour)

Examples of non-premium diamonds

Comparative example 1 2 3 4

Discharge gas H ₂ 20 H ₂ 10 H ₂ 20 H ₂ 20

(1/min) Ar10 CH ₄ 0.5 CH ₄ 0.08

_{CH40.06H2O0.1 _}

Cooling air H ₂ 20 H ₂ 20 H ₂ 20 H ₂ 20

(1/min) CH ₄ 0.5

Substrate Thickness Si2 Si2 Si2 Si2

(mm)

Pressure (Torr) 200 200 200 200

Arc current (A) 10 10 10 10

Nozzle-Substrate 20 5 5 5

Pitch (mm)

Film deposition rate 300

(μm/hour)

Product None Substrate Fusion Amorphous Carbon None

Claims (4)

1, a kind of device of vapor deposition of diamond, it comprises:

A kind of have first a polar electrode forming element, and this element comprises the nozzle of an injection thermal plasma that wherein has a unlatching and the obturator of discharge gas filling tube;

A kind of electrode forming element that has opposite polarity and in described obturator, place described relatively nozzle;

A kind of direct-current plasma blowpipe, it has a power supply system that contains direct supply, be used between the electrode of described first polar electrode and described opposite polarity, applying volts DS, with a lead, this blowpipe adds pneumatic tube by the described discharge gas between the electrode that has added volts DS and feeds a kind of gas, by interelectrode direct current arc discharge described gas is made plasma body and is penetrated the thermal plasma that is plasma jet that forms through described all nozzles;

A kind of gaseous feed compound that is used for that vapour deposition is used is passed into the unstripped gas gas transmission system of described plasma flow;

A kind of device that forms nonequilibrium plasma, it contains the cold gas feedway, the latter is provided with the cold gas nozzle around described plasma body blowpipe nozzle, be used for cold gas is blowed to described plasma body so that the thermal plasma quenching, and form a kind of active nonequilibrium plasma that contains the free radical product by the formation of starting compound free radical at least and have the high density free radical, so that the plasma jet vapour deposition of carrying; And

A kind of substrate support mechanism is used at above-mentioned nonequilibrium plasma supporting substrate and makes the thermal plasma chemical vapour deposition to described substrate.

2, according to the device of claim 1, wherein the direct-current plasma blowpipe comprises an outer electrode, is used to form obturator (104); With one extend via outer electrode and insulating in electrode (103), the nozzle (106) that described outer electrode has a discharge gas blowing mouth (28) and opens, the side of electrode tip is an electrode nozzle side periphery outside in wherein said, form the arc-over face mutually, open as unstripped gas nozzle 108 in the end face central position of the end of interior electrode along the unstripped gas transfer port (103a) of interior electrode centers axle extension.

3, according to the device of claim 2, wherein electrode is tungsten electrode or the carbon dioxide process carbon electrode that has wherein added a kind of rare earth oxide.

4, according to the device of claim 1, wherein the direct-current plasma blowpipe comprises that is used to form the outer electrode of obturator of nozzle that is used to spray plasma jet of being furnished with discharge gas filling tube, a plurality of unlatchings of unstripped gas filling tube, the inwall of each nozzle forms same polar electrode, and a plurality of electrodes with opposite polarity are arranged in the obturator and relative with the inwall of each nozzle.

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