JPH07101798A - Production of diamond film and device therefor - Google Patents

Abstract

PURPOSE:To form a high-quality diamond film having good flatness at a high rate. CONSTITUTION:A boron nitride insulator 40, a carbon source gas inlet 32, a substrate 2 and a copper substrate holder 3 are set below the plasma jet(PJ) gas 1 in a vacuum chamber 5, an electrode 10 (positive electrode) has a plasma nozzle 18 to throttle a plasma gas into the PJ gas, a carbon source gas inlet 19 is concentrically arranged, and a gaseous mixture of hydrogen and hydrocarbons is supplied to the PJ gas. The gaseous mixture is also supplied around the PJ gas from a gas inlet 32 on the downstream side. Although the optimum distance between the gas inlet 32 and the substrate 2 depends on the inside of a vacuum chamber 5, arc power and the cooled state of the substrate 2, the gas inlet 32 is set 10-80mm above the substrate 2 to efficiently flatten the formed diamond film. The carbon source gas is distributed from the inlet 19 of the gas inlet 32, and the distribution ratio affects the flatness of the formed film and is controlled to 1:1 to 1:4 to produce an intended effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond film manufacturing apparatus and manufacturing method, and more particularly to a manufacturing apparatus and manufacturing method for vapor phase synthesizing a diamond film using a plasma jet by arc discharge.

[0002]

2. Description of the Related Art In recent years, various low-pressure vapor phase synthesis methods for diamond films have been proposed, and there are mainly three types. First,
First, there is the hot filament CVD method. This is 800
Providing a tungsten filament directly above the substrate heated to ~ 1000 ° C, heating the filament to 2000 ° C or higher, and blowing hydrogen and hydrocarbon gas (for example CH ₄ ) through the filament onto the substrate to grow a diamond film on the substrate. Is the way.

As a second method, microwave plasma C
The VD method is known. This is a method of generating plasma in a mixed gas of hydrogen and a hydrocarbon gas by a microwave of several hundred watts and growing a diamond film on a substrate placed in the plasma. The substrate is heated by the microwave, The temperature is about 700 to 900 ° C.

In these two synthetic methods, atomic hydrogen is
This atomic hydrogen plays an important role in promoting the decomposition of CH ₄ and also in selectively etching synthetic materials such as amorphous carbon other than diamond. However, a hot filament C that heats the filament to a high temperature
In the VD method, there are many troubles in which the filament is broken, which is not practical. Further, considering the melting point of tungsten, the filament temperature is about 2000 ° C., and at a temperature higher than that, there is a problem that the wire breaks and the raw material gas cannot be decomposed sufficiently. In addition, the synthesis method using microwave plasma has a problem that it is difficult to apply it to a large-area sample due to the restriction of the size of the plasma chamber, and the decomposition of the source gas, especially hydrogen, is insufficient. .

A third method is a synthesis method using an ion beam. This is to grow a diamond film by applying a carbon ion beam to the substrate. However, there is a problem that the diamond becomes a large amount of impurities such as amorphous.

Therefore, as proposed in Japanese Patent Laid-Open No. 63-176399 or Japanese Patent Laid-Open No. 1-201097, for example, a method of effectively utilizing the raw material gas is to generate an arc discharge in the opposing electrodes. There is known a synthesis method in which a raw material gas is passed through an arc discharge to form a gas plasma, and the gas plasma is blown as a plasma jet gas to a substrate by a narrowing portion to deposit and form diamond on the substrate. The formation of the diamond film by the plasma jet method generally has the configuration shown in FIG. This synthesizing method is considered to be a film forming method capable of obtaining a diamond film of the highest speed and high purity.

[0007]

However, even in the plasma jet method using this arc discharge, a difference occurs depending on the plasma diameter, and the film thickness distribution formed on the substrate is thick in the central portion and thin in the peripheral portion. Becomes Therefore, there is a limit to the width even if it is attempted to form a large area, and if it is carried out in the step of forming a diamond film such as a heat sink or a tool, a post-process for correcting the uneven film thickness is required. Therefore, there is a problem in use, which causes a large cost increase. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a manufacturing apparatus and a manufacturing method of a diamond film that synthesizes a high-quality diamond film with high efficiency and has a good film thickness distribution. Is.

[0008]

In order to achieve the above object, the diamond film manufacturing apparatus according to the first invention has the following constitution. That is, it has a vacuum container and an arc discharge mechanism that causes an arc discharge between a positive electrode portion and a negative electrode opposite to each other in the vacuum container, and at least a non-film forming plasma source gas is jetted at the time of arc discharge and the positive electrode is In a diamond film manufacturing apparatus including a gas supply means for causing a carbon source gas to flow from a portion and spraying the gas plasma on a substrate arranged downstream of the gas plasma, the inlet of the carbon source gas is the first positive electrode of the positive electrode portion. And a second inlet provided in the second positive electrode, the position of the second inlet is an intermediate position between the position of the first inlet and the substrate. It is installed in.

Further, in the second invention of the manufacturing apparatus, the first inlet of the carbon source gas has an annular shape which blows out evenly to the plasma jet portion directly below the arc discharge location. The second introduction port has an annular shape that blows out evenly with respect to the gas plasma jet in the vicinity of the substrate away from directly below the arc discharge. A further related configuration of the third invention is that the position of the first introduction port is the plasma ejection port, and the distance between the plasma ejection port and the substrate exceeds 10 mm and is approximately 100 mm. Is the height, the position of the second introduction port,
It is installed between 10 and 80 mm above the substrate. In a further related configuration of the fourth invention, the height of the second positive electrode from the substrate is fixed at any of the intermediate positions, and the inner diameter of the second positive electrode is 2 times the inner diameter of the ejection port.
It is about 5 times larger. In a further related configuration of the fifth invention, the carbon source gas is a hydrocarbon gas or a gas body of an organic compound, or a mixed gas of a hydrocarbon gas or a gas body of an organic compound and hydrogen gas, or a hydrocarbon gas or It is characterized in that it is one of a mixed gas of a gas body of an organic compound and a group 0 element gas.

As a second aspect of the invention, the method for producing a diamond film is such that an arc discharge is generated in the space of a positive electrode and a negative electrode which are placed opposite to each other in a vacuum container, and at least a plasma source gas is flown during the arc discharge and a carbon source is supplied from the positive electrode. Including a gas, spraying the substrate placed downstream of the gas plasma, in the diamond film manufacturing method of forming a diamond film, in the carbon source gas from the first inlet directly under the arc discharge portion, the substrate That is, the ratio of the flow rate with the carbon source gas from the second inlet provided above is between 1: 1 and 1: 4. The configuration of the related invention of this production method is such that a carbon source gas from the first inlet and a carbon source gas from the second inlet are a gas body of a hydrocarbon gas or an organic compound, or a hydrocarbon gas or an organic compound. It is characterized in that either a mixed gas of the above gas body and hydrogen gas or a mixed gas of a hydrocarbon gas or an organic compound gas body and a Group 0 element gas is used.

[0011]

[Operation] In a vacuum container, an arc discharge is generated between the negative electrode and the positive electrode, and a mixed gas of a Group 0 element gas and hydrogen gas is introduced as a plasma source gas from the plasma source gas introduction port between the electrodes to enhance the hydrogen gas. At the same time as dissociating, by introducing a raw material gas containing carbon from the raw material gas introduction port, the gas containing carbon is decomposed, and this gas plasma is ejected from the ejection port of the electrode end to form a plasma jet, which is applied to the substrate. The diamond is sprayed to form a film on the substrate. When diamond is formed by this method, a film having a film thickness distribution in which the central portion of the plasma jet is thick and the peripheral portion thereof is thin is obtained. Further, if the second positive electrode is arranged below the positive electrode and a plasma jet is formed by another power source and a diamond film is formed, then the peripheral portion of the substrate becomes thicker and the central portion becomes thinner. Therefore, when the height of the second positive electrode from the substrate is set to a predetermined value and the diamond film is formed by the plasma jet of the both positive electrodes, the combined film thickness of the two becomes a substantially uniform film thickness. Since the film is formed in double, the film formation speed is high. In the case where the height is limited due to the device, it is realized by using the second positive electrode whose inner diameter is adjusted. Further, since the introduction of the carbon source gas is uniform so that the supply of the carbon source gas is uniform, a more uniform film can be formed.

[0012]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a schematic structural sectional view of a manufacturing apparatus according to an embodiment of the present invention. In FIG. 1, a plasma jet gun 1, a ring-shaped insulator 40 made of boron nitride, a cylindrical positive electrode 10 made of copper, a substrate 2 and a substrate support 3 made of copper have a pressure of 5 Torr to 5 atmospheres (3800 Torr). It is provided in the vacuum container 5 which is maintained at a predetermined pressure within the range. The plasma jet gun 1 has a rod-shaped electrode (negative electrode) 7 made of tungsten formed on a tip portion 7a having one end formed in a needle shape with an acute angle and a flange portion 7b formed at the other end from the flange portion 7b side. An electrode cooling part 8 made of copper, a gas introduction part 9 made of Teflon, and a cylindrical electrode (positive electrode) 10 made of copper are provided. The main structure of the plasma jet gun 1 remains almost the same as the conventional structure shown in FIG.

The electrode cooling section 8 and the cylindrical electrode 1 are also provided.
0 are provided with hollow portions 108 and 110, respectively. Cooling water pipe 14 connected to the cylindrical electrode 10
The cooling water supplied from b flows out from the hollow portion 110 of the cylindrical electrode 10 to the cooling water pipe 14a. Similarly, the cooling water supplied from the cooling water pipe 15b connected to the electrode cooling unit 8 is supplied to the hollow portion 108 of the electrode cooling unit 8,
The cooling water pipe 15a connected to the electrode cooling section 8 discharges the cooling water to prevent wear of both electrodes due to heat of arc discharge generated between the rod-shaped electrode 7 and the cylindrical electrode 10.

The gas introducing section 9 has a raw material gas introducing pipe 1
6 is provided, and further, this gas introduction pipe 16
An opening is formed at one end of the rod-shaped electrode 7 so that the gas supplied from the rod-shaped electrode 7 is sent to the tip portion 7a of the rod-shaped electrode 7. Further, in order to cause arc discharge between the rod-shaped electrode 7 and the cylinder-shaped electrode 10, the rod-shaped electrode 7 and the cylinder-shaped electrode 10 are connected to an arc discharge power supply 17.
The arc discharge power source 17 is connected so that the rod-shaped electrode 7 side having the tip portion 7a formed at an acute angle has a negative potential in order to effectively generate the arc discharge. Further, in the cylindrical electrode 10, on the surface opposite to the gas introduction portion 9, there is provided a plasma ejection port 18 for narrowing gas plasma to generate plasma jet gas. A carbon source gas introduction port 19 is arranged so as to overlap with the plasma ejection port 18. The inlet 19 is concentric with the plasma jet 18 and has the same inner diameter, and the carbon source gas from the gas supply pipe 19 a from the outside is hollowed out so as to reach the periphery of the jet 18 and is introduced into the jet 18. On the other hand, the introduction ports 19 are evenly opened.

A ring-shaped insulator 40 forming a plasma passage is connected to communicate with the plasma jet port 18.
Further, a ring-shaped carbon source gas introduction part 32 made of copper is provided, which serves as a second positive electrode. In addition, the discharge power source 21
In addition to the cylindrical electrode 10 that is the first positive electrode, it is connected to the rod-shaped electrode (negative electrode) 7. Then, a gas introduction pipe 32a is connected to the carbon source gas introduction part 32, and a carbon source gas is supplied from the outside. The copper ring-shaped gas introduction portion 32 is provided with gas supply ports 32b evenly around the ejection port 18. This gas introduction part 3
Since No. 2 is arranged downstream of the plasma jet port 18, a mixed gas of hydrogen and hydrocarbon is supplied to the periphery of the plasma jet gas. In addition, the ring-shaped carbon source gas introduction part 32
Although not shown in the figure, cooling water is introduced and cooled, heating by plasma is suppressed, and wear of the ring-shaped source gas introduction part 32 is prevented.

A substrate support 3 is installed below the ring-shaped insulator 40 and the ring-shaped gas inlet 32 downstream of the plasma jet port 18, and the substrate 2 is placed on the substrate support 3. Has been done. The substrate support 3 is supplied with cooling water by a cooling water pipe 20b in order to maintain the substrate 2 at a predetermined temperature (about 800 ° C. in this embodiment).
It is hollow so that it can be discharged from a. This is because the gas temperature of the plasma jet ejected from the plasma ejection port 18 reaches several thousands to several tens of thousands of degrees, so that the substrate 2 should be heated in order to bring the substrate temperature to 600 to 1100 ° C. which is the synthesis range of diamond. This is because it needs to be cooled.

The distance between the plasma ejection port 18 and the substrate 2 changes depending on the inside of the vacuum chamber 5, the arc power, and the cooling condition of the substrate 2. In our experiment, the diamond film formation was 10 to 100 mm. It was possible. The ring-shaped gas introduction part 32 is installed between 10 and 80 mm above the substrate 2 to obtain the flattening effect of the diamond film to be formed. When the height of the gas introducing portion 32 was 20 mm, the inner diameter of the gas introducing portion 32 was optimally 10 mm. In addition, when the position of the ring-shaped gas introduction part 32 is fixed and the optimum film forming condition is set, it is possible to deal with it by changing the ring diameter. Depending on the above ratio, the plasma jet 18
The inner diameter of the ring-shaped gas introducing portion 32 is about 2 to 5
It can be doubled in size. In the range other than this, it is difficult to obtain a uniform diamond film.

Further, the introduction of the carbon source gas is distributed from two places of the carbon source gas introduction port 19 and the ring-shaped gas introduction part 32, and the distribution ratio also affects the flattening effect of the film to be formed,
Ring-shaped gas introduction part 32 for carbon source gas introduction port 19
The effect was obtained in the ratio of the amount of gas introduced into the range of 1: 1 to 1: 4. In this embodiment, the plasma jet 1
The distance between the substrate 8 and the substrate 2 is 40 mm, and the ring-shaped gas introduction part 32 is placed at a distance of 20 mm above the substrate 2 and the plasma ejection port 1
It is installed on the same axis as 8. Further, the distribution ratio of the gas introduction amount containing carbon to the ring-shaped gas introduction part 32 to the carbon source gas introduction port 19 was set to 1: 2.

Next, the method for synthesizing the diamond film of this embodiment will be described. First, after evacuating the vacuum vessel 5, argon, which is a group 0 element gas having a high ionization degree, is introduced into the plasma jet gun 1 through the gas introduction pipe 16, and the pressure in the vacuum vessel 5 is set to 40 Torr. . After that, an arc discharge is generated by the arc discharge power supply 17 between the rod-shaped electrode 7 (negative electrode) and the cylindrical electrode 10 (positive electrode). In order to generate an arc discharge, a high frequency wave may be superposed between the rod-shaped electrode 7 and the cylindrical electrode 10, or a spark discharge may be generated by an igniter or the like, and then the arc discharge may be transferred. In this embodiment, arc discharge is performed under the conditions of a DC voltage of 40 V and a current of 60 A.

When the discharge is stable, a plasma source gas, for example, a mixed gas of 50 vol% of argon and 50 vol% of H ₂ gas is flowed through this gas discharge pipe 16 at a flow rate of 12 liters per minute. Plasma is generated, and this gas plasma is passed through the narrowed portion of the plasma ejection port 18 to form a plasma jet. From the carbon source gas inlet 19, methane gas 80cc / min and hydrogen gas 120cc / mi
A mixed gas of n is introduced. Here, the hydrocarbon gas as a carbon source gas represented by methane gas may be introduced from the gas introduction pipe 16, but since the tungsten electrode rod may be carbonized and the discharge may not be stable for a long time, carbonization may occur. It is desirable that a hydrogen gas is provided at the downstream of the discharge part and introduced from there. Then, the methane gas introduced from the carbon source gas inlet 19 is blown onto the plasma jet of the above-mentioned plasma source gas to form a plasma jet gas. Furthermore, 160cc / min of methane gas and 40cc / mi of hydrogen gas were introduced from the ring-shaped raw material gas inlet 32.
An n 2 mixed gas is introduced and supplied around the plasma jet. Film formation was performed for 60 minutes under the above conditions. In the present embodiment, the temperature of the central part of the plasma is 3000 ° C. or higher, and the discharge part inside the plasma gun rises more than that.

Next, the ring-shaped gas introduction part 32 is installed above the substrate, and the ratio of the gas introduction amount to the ring-shaped gas introduction part 32 with respect to the carbon source gas introduction port 19 is adjusted. The reason why the film flattening effect is obtained will be described below. A diamond film is formed by the conventional DC arc plasma jet method.
A diamond film having a film thickness distribution as shown in (1) can be obtained. The cause of having such a film thickness distribution is that the gas containing carbon is plasma-ejected, and the hydrogen as the plasma source gas and the group 0 gas are thermally decomposed by the heat of arc discharge and mixed with the jetted plasma. Therefore, it is considered that the carbon active species that contribute to diamond synthesis are concentrated in the center of the plasma jet, and the temperature distribution of the substrate is high in the central portion of the plasma jet and low in the periphery thereof. But,
The substrate temperature distribution is at the center and 10mm away from the center.
The temperature decreased only by about 50 ℃, and the main factor seems to be the spatial distribution of active carbon species that are the raw material of diamond.

Therefore, by supplying a gas containing carbon to the periphery of the plasma jet from the second gas inlet,
As a result of investigating the film thickness distribution of the diamond film to be formed, as shown in FIG. 3 (2), the diamond film growing only in the peripheral part, that is, in the crater shape without forming the central part. It was confirmed that the distribution of was obtained. And
This crater-like distribution tends to have a smaller crater diameter as the carbon source gas is supplied on the upstream side of the plasma jet, and a larger crater diameter as the carbon source gas is supplied closer to the substrate downstream of the plasma jet. It was revealed. Therefore, the distribution of the diamond film formed by supplying the carbon source gas from the plasma ejection portion, which is the conventional inlet of the carbon source gas (Fig. 3 (1)), and the second side in the peripheral portion of the plasma jet on the downstream side of the distribution By combining the distribution of the diamond film obtained by supplying the carbon source gas from the inlet (Fig. 3 (2)), the diamond film to be formed is flattened, that is, flattened as shown in Fig. 3 (3). Is possible. That is,
By appropriately adjusting the height of the second inlet by adjusting the amount of plasma gas supplied from above, it is possible to achieve a substantially uniform diamond film thickness on the substrate.

The evaluation results of surface deposits on the substrate 2 actually formed under the above conditions for 60 minutes will be described. In addition,
As the substrate 2, a tungsten metal plate having a size of 25 mm square is used, and the surface is preliminarily finely scratched by polishing so that a diamond film can be easily synthesized. A Raman spectroscope and an electron microscope were used to observe the deposits on the substrate 2.

FIG. 4 shows the center of the diamond film formed (FIG. 4 (a)), 5 mm from the center (FIG. 4 (b)), and 10 mm from the center.
The Raman spectrum at the position (Fig. 4 (c)) is shown. From these results, sharp peaks near 1333 cm ^−1, which show the peak of diamond, were similarly observed at each position, and it is understood that an extremely high-quality diamond film is uniformly formed. Further, FIG. 5 shows the results of measuring the surface distribution of the obtained film. From this measurement result, it can be seen that the flatness of the film is good. Further, the obtained film was observed by an electron microscope, and it was also confirmed that an automorphic surface showing a diamond polycrystal was clearly grown. Further, regarding the synthesis rate of the diamond film, in the present embodiment, the thickest portion has a thickness of 80 μm, and the diamond film can be deposited at a sufficiently high synthesis rate of 1 μm / min or more.

[0025]

As described above, according to the present invention, the carbon source gas which is the source gas is introduced into the plasma jet port in the region where the gas plasma is generated, and at the same time, the space between the plasma jet port and the substrate is increased. By introducing the carbon source gas from the arranged source gas introduction part, a high quality diamond film can be formed at high speed and with good flatness. Due to this effect,
It can greatly contribute to the reduction of processing cost when applied to a heat sink of diamond film, a cutting tool, or the like.

[Brief description of drawings]

FIG. 1 is a schematic structural sectional view of a diamond film manufacturing apparatus according to a first embodiment of the present invention.

FIG. 2 is an example of a main part of a conventional diamond film forming apparatus using a plasma jet method.

FIG. 3 is an explanatory diagram showing a film thickness distribution of a diamond film depending on the introduction position of a gas containing carbon and a flattening effect by the combination thereof.

FIG. 4 is a characteristic diagram showing the Raman spectrum of the formed diamond film. (A) is the center of the film, (b) is 5 mm from the center.
Position, (c) shows the Raman spectrum at a position 10 mm from the center.

FIG. 5 is a characteristic diagram showing the measurement results of the surface distribution of the formed diamond film.

[Explanation of symbols]

 1, 1'Plasma jet gun 2 Substrate 3 Substrate support 5 Vacuum container 7 Rod-shaped electrode (negative electrode) 8 Electrode cooling part 9 Plasma source gas introduction part 10 Cylinder-shaped electrodes 14, 15 Cooling water passage (a, b) 16 Gas introduction Pipe 17 Power source for arc discharge 18 Plasma jet 19 Carbon source gas inlet (first positive electrode) 19a Gas supply pipes 20a, 20b Cooling water passage 21 Power source for plasma current 32a Gas supply pipe 32b Ring-shaped carbon source gas inlet (Second positive electrode) 40 Ring-shaped insulator

Claims (7)

[Claims] 1. A vacuum container and an arc discharge mechanism for causing an arc discharge between a positive electrode portion and a negative electrode opposite to each other in the vacuum container, and at least a non-film forming plasma source gas is jetted at the time of arc discharge. With the carbon source gas from the positive electrode portion together with, in the diamond film manufacturing apparatus provided with a gas supply means for spraying the substrate arranged in the gas plasma downstream, the inlet of the carbon source gas, the positive electrode portion of the One of the first inlet provided in the positive electrode and the second inlet provided in the second positive electrode, the position of the second inlet, the position of the first inlet and the substrate A diamond film manufacturing apparatus, which is installed at an intermediate position. 2. The first inlet of the carbon source gas has an annular shape that uniformly blows out to the plasma jet portion directly below the location of the arc discharge, and the second inlet is the arc discharge. The diamond film manufacturing apparatus according to claim 1, wherein the diamond film manufacturing apparatus has an annular shape that blows out evenly with respect to the gas plasma jet near the substrate that is separated from immediately below. 3. The position of the first introduction port is the plasma ejection port portion, and the distance between the plasma ejection port and the substrate is more than 10 mm and up to about 100 mm, The diamond film manufacturing apparatus according to claim 1 or 2, wherein the position of the second inlet is set between 10 and 80 mm above the substrate. 4. The carbon source gas is a hydrocarbon gas or an organic compound gas body, or a mixed gas of a hydrocarbon gas or an organic compound gas body and hydrogen gas, or a hydrocarbon gas or an organic compound gas body. 0
The diamond film manufacturing apparatus according to claim 1, wherein the diamond film manufacturing apparatus is a mixed gas with a group element gas. 5. The height of the second positive electrode from the substrate is fixed at any of the intermediate positions, and the inner diameter of the second positive electrode is 2 to 5 times larger than the inner diameter of the ejection port. The diamond film manufacturing apparatus according to claim 1, wherein 6. An arc discharge is caused in a space of a positive electrode and a negative electrode which are opposed to each other in a vacuum container, and at least a plasma source gas is caused to flow at the time of the arc discharge, and a carbon source gas is caused to flow from the positive electrode, so that the gas plasma is downstream. In a diamond film manufacturing method of forming a diamond film by spraying on the substrate arranged in, the carbon source gas from the first inlet directly under the arc discharge part, from the second inlet provided on the substrate A diamond film manufacturing method, characterized in that the ratio of the flow rate with the carbon source gas is between 1: 1 and 1: 4. 7. The carbon source gas from the first inlet and the carbon source gas from the second inlet are a hydrocarbon gas or an organic compound gas body, or a hydrocarbon gas or an organic compound gas body and hydrogen. Mixed gas with gas, or hydrocarbon gas or gas of organic compound and 0
The method for producing a diamond film according to claim 6, wherein any one of a mixed gas with a group element gas is used.