JPH05271938A - Method for synthesizing diamond - Google Patents

Abstract

PURPOSE:To efficiently produce high quality diamond excellent in adhesion and crystallinity by impressing negative bias voltage on a substrate put in a magnetic field, treating the substrate with plasma of a carbon-contg. compd. and forming diamond on the substrate by a vapor phase method. CONSTITUTION:A substrate electrode 1 with a substrate 3 put on the top and a counter electrode 2 are placed opposite to each other at a fixed interval in a reaction tube in the longitudinal direction, plural magnets 4 are arranged under the substrate electrode 1 and a magnetic field is formed so that lines of magnetic force from the magnets 4 pierce the substrate 3. Negative bias voltage is impressed on the substrate 3, a carbon-contg. compd. such as methane or methanol is converted into plasma by a microwave plasma process and the substrate 3 is treated with the plasma to form initial nuclei of diamond on the surface of the substrate 3. A diamond film is then formed on the surface of the substrate 3 in a prescribed thickness by CVD or other vapor phase method with ethane, ethanol, etc. By this method, high quality diamond can easily be mass-produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synthesizing diamond, and more specifically, it has a high generation density of nuclei for forming diamond (diamond initial nuclei) and has a uniform distribution in a diamond forming surface on a substrate. The present invention relates to a method for synthesizing diamond capable of generating initial nuclei, excellent in adhesion to a substrate, and capable of efficiently producing high-quality diamond having excellent crystallinity.

[0002]

2. Description of the Related Art Since diamond has high hardness and wear resistance, it is widely used for tools such as cutting and polishing. In addition, since it has excellent electrical properties, it is also regarded as a promising material for semiconductor devices. In order to industrially respond to such uses, it is necessary to utilize synthetic diamond without depending on expensive natural diamond. Therefore, a technology for mass-producing high-quality diamond while maintaining a certain quality. Development is strongly demanded. As described above, in recent years, the tendency to use synthetic diamond has been increasing, and along with this, the development and improvement of the diamond synthesis method have become more and more important. In particular, research on techniques for forming diamond as a thin film on various substrates by a vapor phase synthesis method such as a CVD method has been actively conducted, and a diamond-coated member obtained by the vapor phase synthesis method is used as a cutting tool,
Technical development for practical use as a polishing tool, a sliding member, etc., or as a semiconductor device, etc. is underway. According to this vapor phase synthesis method, reduction in manufacturing cost and mass production can be expected.

However, the diamond film obtained by the vapor phase synthesis method usually contains graphite or DLC.
Carbonaceous components other than diamond, such as (diamond-like carbonaceous material), are often contained, which causes problems such as deterioration of quality and non-uniformity. Further, in order to improve the productivity, a device for facilitating the formation of the diamond film is required. In the conventional method, as shown below, these points have not been sufficiently solved.
That is, when a diamond film is formed on a substrate by a vapor phase synthesis method, if diamond is synthesized as it is without performing any treatment on the surface of the substrate, the generation density of initial nuclei for forming diamond is low, Moreover, it is not possible to obtain a high quality diamond film having excellent adhesion.

Therefore, a mechanical method such as a lapping process using diamond abrasive grains or a so-called scratching process such as an ultrasonic process in an organic solvent such as acetone is carried out, and the diamond is initially formed on the substrate. It is common to generate nuclei and use this as a growth point to form a diamond film. However, in this method,
For example, the production efficiency of diamond is still insufficient, which is unsatisfactory as an industrial production method, and there is a problem that it is difficult to maintain a certain quality in the obtained product.

As a method for improving this, a method of applying a negative bias voltage to the substrate and performing plasma treatment using a mixed gas of methane and hydrogen containing high-concentration methane to generate diamond nuclei at a high density is proposed. Has been done [App
l. Phys. Lett. , 58 (10), 1036-
1038 (1991)]. However, even in this method, since the synthesis conditions of diamond are not optimal, carbon having a weak bonding force, that is, glassy carbon or the like is deposited, so that the crystallinity of diamond is low, and the adhesion to the substrate is poor, and a high-quality diamond film is obtained. Not obtained.

[0006]

The present invention has been made to improve the above circumstances. An object of the present invention is to efficiently form high-quality diamond having a small amount of impurities such as graphite and DLC (diamond-like carbonaceous material) and excellent crystallinity on the surface of various substrates with a high generation density of initial diamond nuclei. Another object of the present invention is to provide a method for synthesizing diamond, which has the advantages that diamond having excellent in-plane uniformity and adhesion to a substrate can be easily mass-produced.

[0007]

According to the present invention for solving the above-described problems, a carbon-containing compound or a mixture of a carbon-containing compound and hydrogen is placed on a substrate which is placed in a magnetic field and to which a negative bias voltage is applied. A method of synthesizing diamond, which comprises forming a diamond on the substrate by a gas phase method after a treatment with gas plasma.

In the present invention, the substrate is placed in a magnetic field and a negative bias voltage is applied. The material of the substrate is not particularly limited, various materials commonly used for synthesizing diamond by a known vapor phase synthesis method (for example, various metals, alloys, cemented carbides, semiconductors,
Ceramics, glass, etc.) can be appropriately selected and used. When a specific example, for example, WC-Co-based WC-based cemented carbide, such as, TiN, Si ₃ N ₄ or the like nitride ceramics, SiC, carbide ceramics of TiC or the like, aluminas, oxides such as glass A wide variety of materials such as semiconductors, semi-metals such as silicon, and semiconductors can be given. The shape of the substrate is not particularly limited.

In the method of the present invention, the magnetic field is applied to the inside or outside of the substrate electrode and the counter electrode in the reaction tube used when performing the plasma treatment described later.
It can be formed by providing a magnet. In addition,
Here, the magnet for forming the magnetic field may be a permanent magnet, an electromagnet or a coil. As a specific example of forming a magnetic field, for example, as shown in FIG. 1, a reaction tube in which a substrate electrode 1 having a substrate 3 arranged above and a counter electrode 2 are vertically opposed to each other and are arranged at a constant interval (see FIG. (Not shown), a plurality of magnets 4 are provided below the substrate electrode 1.
A magnetic field in which the magnetic field lines of the magnet 4 penetrate through the substrate 3.

In this case, there are various modes of arranging a plurality of magnets under the substrate electrode. For example, the substrate electrode is a disc, and the substrate placed on the substrate is also a disc. In some cases, the N pole of the magnet is arranged in the center of the disk below the substrate electrode so that the magnet is surrounded by
A mode in which the S poles of a plurality of magnets are arranged concentrically can be mentioned. Alternatively, the N pole of the magnet may be arranged at the center of the disc, and the ring-shaped magnet (S pole) may be arranged so as to surround the magnet. In the case of this mode, the magnetic field lines emitted from the N pole of the magnet arranged at the center of the disk of the substrate electrode are formed so as to penetrate the substrate and then return to the S pole of the magnets arranged concentrically. .. As another aspect, for example, when the substrate electrode is a disk and the substrate mounted on the disk is also a disk, the N of the magnet is located below the substrate electrode and in the center of the disk. There can be mentioned a mode in which a pole or a south pole is arranged and the north and south poles of a plurality of magnets are concentrically and alternately arranged so as to surround the magnet.

As another specific example of magnetic field formation, the example shown in FIG. 2 can be given. As shown in FIG. 2, in a reaction tube (not shown) in which a substrate electrode 1 on which a substrate 3 is arranged and a counter electrode 2 are vertically opposed to each other and arranged at a constant interval, the substrate electrode An example can be given in which a pair of magnets 4 are arranged so as to face each other so that magnetic field lines 5 parallel to these electrodes are formed in the space between 1 and the counter electrode 2.

As another specific example of magnetic field formation, the example shown in FIG. 3 can be given. As shown in FIG. 3, in a reaction tube (not shown) in which a substrate electrode 1 on which a substrate 3 is placed and a counter electrode 2 are vertically opposed to each other and arranged at a constant interval, the counter electrode The first solenoid coil 6a is arranged on the upper part and the second solenoid coil 6b is arranged on the lower part of the substrate electrode 1,
An example can be given in which the magnetic force lines 5 are formed from the inner space of a to the outer space, and the magnetic force lines 5 are formed from the inner space of the second solenoid coil 6b to the outer space.

In the above three examples of magnetic field formation, all the magnets are arranged inside the reaction tube, but in the present invention, the magnets may be arranged outside the reaction tube. In the present invention, it is essential only that the magnet is arranged inside or outside the reaction tube so that a magnetic field is formed in the vicinity of the diamond formation region on the substrate. Moreover, it is preferable that the direction of the magnetic field in the vicinity of the diamond formation region on the substrate is perpendicular to the direction of the electric field formed by a negative bias voltage described later.

The magnetic field strength of the magnetic field is usually 50 G or more, and particularly preferably 300 G to 1,000 G. If the magnetic field strength is less than 50 G, the effect of applying the magnetic field may be lost and inconvenience may occur. The negative bias voltage applied to the substrate is, for example, DC of the substrate electrode.
Bias in the range of -500 to -5V, preferably -4
It should be in the range of 00 to -20V. In addition, in order that the bias voltage is in the range of -500 to -50V, RF
A single method or a method of applying an RF + DC bias is also suitably adopted.

In the present invention, the substrate which is placed in the magnetic field and to which the negative bias voltage is applied is subjected to the plasma treatment of the carbon-containing compound or the mixed gas of the carbon-containing compound and hydrogen. As the mixed gas used in the plasma treatment to which the negative bias voltage is applied, a gas containing a carbon-containing gas and a hydrogen gas, which is commonly used as a general diamond synthesis gas, or can be used Things can be used.

The carbon-containing compound is not particularly limited as long as it contains at least a carbon-containing compound, and may be a mixed gas containing hydrogen gas or the like, which is commonly used as a general diamond synthesis gas. The thing which can be used, or what can be used can be used. Specific examples of the carbon-containing compound include various hydrocarbons (specifically, for example, methane, ethane, propane,
A wide variety of hydrocarbons such as alkanes such as butane, pentane and hexane, alkenes such as ethylene, propylene, butene and pentene, aromatic hydrocarbons such as benzene and toluene, cycloalkanes such as cyclopentane and cyclohexane), Oxygenated hydrocarbons (specifically, for example, alcohols such as methanol, ethanol, propanol, ethylene glycol, benzyl alcohol, etc., ketones such as acetone, methyl ethyl ketone, cyclohexanone, acetophenone, carboxylic acids such as acetic acid, propionic acid, etc. A wide variety of oxygen-containing hydrocarbons such as acids, ethers such as dimethyl ether, diethyl ether, and tetrahydrofuran), and various carbon-containing compounds such as CO and CO ₂ .

Of these, methane, methanol, acetone, CO and the like are particularly preferable. In addition, these may be used individually by 1 type, and may be used together, such as mixing 2 or more types. When the mixed gas of the carbon-containing compound and hydrogen is used, the carbon-containing compound based on the whole mixed gas of the carbon-containing compound and hydrogen is usually 0.05 to 99% by volume, preferably 0.1 to 99% by volume. It is desirable that the ratio is 80%.

The method of converting the carbon-containing compound into plasma is not particularly limited, and plasma treatment methods by various methods such as plasmaization method used in general vapor phase synthesis method of diamond or diamond film are applied. It is possible. Specifically, for example, a microwave plasma method, a high frequency plasma method, a hot filament method, an ECR method, or a combination thereof can be used. Among these, in particular, a plasma treatment method by a microwave plasma method or the like can be preferably used.

The reaction conditions for the plasma treatment may be conventional. For example, the pressure of the reaction system is usually 10 ⁻⁵ Torr.
It is above, and it is particularly preferable that it is 10 ⁻³ Torr or above. Further, the substrate temperature can be suitably selected by appropriately selecting it in the range of room temperature to 1,000 ° C. In the present invention, the plasma treatment time is
Usually, it is preferably 1 second to 30 minutes.

In the present invention, as described above, the substrate, which is placed in the magnetic field and to which the negative bias voltage is applied, is treated with the plasma of the carbon-containing compound so that the diamond initial nuclei are formed on the surface of the substrate. Can be efficiently produced in high density in a short time, and high-quality diamond excellent in crystallinity and adhesion to a substrate can be uniformly manufactured on the surface of the substrate. Thus, in the present invention, it is important to perform the step of treating the substrate with the plasma of the carbon-containing compound while applying a negative bias voltage to the substrate in the presence of a magnetic field. By performing in the presence of a magnetic field, the time required to process the substrate with plasma can be significantly shortened compared with the case where it is not performed in the presence of a magnetic field, and the density of initial diamond nuclei generated on the surface of the substrate is increased. It is possible to produce a diamond having excellent in-plane uniformity, crystallinity, and adhesion to a substrate.

In the method of the present invention, the substrate may be further treated with hydrogen gas plasma after the above plasma treatment. The hydrogen gas used for the treatment of hydrogen gas with plasma is not particularly limited, but usually hydrogen gas purified to high purity is used. Further, when hydrogen gas is used in the plasma treatment described above, the hydrogen gas can be continuously used.

As a method for converting hydrogen gas into plasma,
There is no particular limitation, and as in the case of the above-mentioned plasma treatment of the carbon-containing compound, various plasma treatment methods such as the plasmaization method used in the vapor phase synthesis method of general diamond or diamond film can be applied. Is.
Specifically, for example, a microwave plasma method, a high frequency plasma method, a hot filament method, an ECR method and the like, or a combination method thereof can be mentioned. Among these, in particular, a plasma treatment method by a microwave plasma method or the like is preferably adopted. The reaction conditions for the treatment with hydrogen gas plasma are almost the same as the conditions for the plasma treatment of the carbon-containing compound described above.
The time for treatment with hydrogen gas plasma is usually 1 second to 30 minutes per treatment. Further, in the present invention, the plasma treatment to which a negative bias voltage is applied and the hydrogen plasma treatment may be alternately performed.

In the method of the present invention, after the pretreatment as described above is performed, diamond is formed on the substrate by a gas phase synthesis method using a carbon source gas. Examples of the carbon source gas include paraffinic hydrocarbons such as methane, ethane, propane and butane; olefinic hydrocarbons such as ethylene, propylene and butylene; acetylene,
Acetylene-based hydrocarbons such as allylene; Diolefin-based hydrocarbons such as butadiene and allene; Alicyclic hydrocarbons such as cyclopropane, cyclobutane, cyclopentane and cyclohexane; Aromatic such as cyclobutadiene, benzene, toluene, xylene and naphthalene Hydrocarbons; ketones such as acetone, diethyl ketone, benzophenone; alcohols such as methanol and ethanol; other oxygen-containing hydrocarbons; amines such as trimethylamine and triethylamine; other nitrogen-containing hydrocarbons; carbon dioxide gas, one Carbon oxides, carbon peroxides; In addition, although not a simple substance, the Hazardous Substances of the Fire Law, such as gasoline, Class 4, Class 1, kerosene, turpentine oil, second oil such as camphor oil, and third oil such as heavy oil Fourth oils such as oils, gear oils and cylinder oils can also be used. Further, the above various compounds may be mixed and used.

Among these, preferred are paraffin hydrocarbons such as methane, ethane and propane, alcohols such as ethanol and methanol, ketones such as acetone and benzophenone, amines such as trimethylamine and triethylamine, carbon dioxide gas, It is carbon oxide, and carbon monoxide is particularly preferable. These may be used alone or in combination of two or more as a mixed gas. Further, these may be used as a mixture with an active gas such as hydrogen or an inert gas such as helium, argon, neon, xenon or nitrogen.

For forming the diamond, various known diamond vapor phase synthesis methods such as a CVD method, a PVD method, a PCVD method, or a combination thereof can be used. ,Normal,
Various hot filament methods including the EACVD method, various direct current plasma CVD methods including the thermal plasma method, microwave plasma CVD methods including the thermal plasma method, and the like can be preferably used.

The conditions for forming diamond are not particularly limited, and the reaction conditions usually used in the above vapor phase synthesis method can be applied. For example, as the reaction pressure,
Usually, 10 ⁻⁶ to 10 ³ Torr is preferable, and 1 to 8 is particularly preferable.
It is preferably in the range of 00 Torr. When the reaction pressure is lower than 10 ⁻⁶ Torr, the diamond formation rate may be slow. Also, if higher than 10 ³ Torr, as compared to the effect obtained when the 10 ³ Torr, there is no further effect.

The surface temperature of the substrate cannot be unconditionally specified because it depends on the means for activating the carbon source gas, etc., but it is usually 300 to 1,000 ° C., preferably 450 to 950 ° C. It is better to stay within the range. If this temperature is lower than 300 ° C., the formation of a crystalline diamond film may be insufficient. Further, when the temperature exceeds 1,000 ° C., the formed diamond film is easily etched.

The reaction time is not particularly limited, and it is preferable to appropriately set the reaction time according to the diamond formation rate so that the diamond film has a desired thickness. The thickness of the diamond film formed on the surface of the base material cannot be uniformly determined because it depends on the purpose of use of the diamond-coated member and the like, but in the case of a tool, it is usually 5 μm or more, preferably 10 to 50 μm or more. Appropriate. If the diamond film is too thin, it may not be possible to sufficiently cover the surface of the substrate.

As described above, since high quality diamond can be produced by subjecting the substrate to a specific pretreatment, a high performance diamond coated member can be obtained. According to the method of the present invention, high-purity diamond (that is, high-quality diamond film) is formed on various substrates.
Can be formed efficiently. Further, according to this method, it is possible to obtain a high-quality diamond having a constant quality or a product using diamond such as a diamond-coated member without quality variations. Furthermore, this method has the advantage that it is extremely easy to mass-produce diamond or its products, and is a method industrially extremely advantageous for producing diamond and various diamond-using products.

[0030]

The present invention will be described in more detail below with reference to examples of the present invention and comparative examples thereof, but the present invention is not limited to these examples. (Example 1) An approximately 25 mm square Si wafer was used as a substrate. This substrate was placed in a diamond synthesizer as shown in FIG. Here, in FIG. 4, reference numeral 1 denotes a disk-shaped substrate electrode, and this substrate electrode 1 is arranged on the upper surface of a disk-shaped support 7 arranged inside the reaction tube 9. .. An Si wafer, which is the substrate 3, is placed on the upper surface of the substrate electrode 1. A counter electrode 2 is arranged inside the reaction tube 9 so as to face the substrate electrode 1. At the lower portion of the support body 7, at a position corresponding to the center of the support body 7,
A pole magnet is arranged, and an S pole magnet is arranged in a ring shape at a position corresponding to the peripheral portion of the support 7. A waveguide 10 for irradiating the microwave 8 toward the substrate is connected to the reaction tube 9, and a second waveguide is sandwiched between the reaction tube 9 and a position opposite to the waveguide 10. 11 is connected. A reflecting plate (not shown) for reflecting microwaves is arranged in the second waveguide 11, and the microwave reflected by the reflecting plate and the microwave traveling in the waveguide 10 are arranged. It interferes with 8. This reaction tube 9
A processing gas or the like is introduced from the upper part of the. A voltage of direct current (DC) -100 V was applied to this substrate, a mixed gas of methane gas 20 sccm and hydrogen gas 50 sccm was introduced into the reaction tube as a processing gas,
Irradiate microwaves with an average output of 350 W to reduce the substrate temperature to 9
The substrate surface was treated for 5 minutes with the generated plasma at 00 ° C. and the reaction internal pressure at 10 Torr. After this pretreatment, a mixed gas of 0.5% by volume of methane gas was introduced into the reaction tube as a raw material gas, the internal pressure was set to 40 torr, the substrate temperature was set to 900 ° C., and the microwave of frequency 2.45 GHz was introduced to generate plasma. The diamond synthesis reaction by the CVD method was performed for 10 minutes. After the synthesis reaction, the number of initial diamond nuclei was counted by observing the surface of the substrate with SEM. The results are shown in Table 1. As a result of Raman analysis of the obtained diamond, a strong peak at 1,333 cm ⁻¹ due to diamond was observed. The full width at half maximum was 10 cm ^-1 , and formation of high-purity diamond was confirmed.

(Examples 2 to 4) In the pretreatment of the substrate,
The same procedure as in Example 1 was repeated except that the reaction internal pressure and the treatment time were changed to the conditions shown in Table 1. Table 1 shows the evaluation of the generation density of initial diamond nuclei.

(Comparative Example 1) The pretreatment of the substrate was performed in the same manner as in Example 1 except that the magnet was not arranged in the apparatus. Table 1 shows the generation density of initial diamond nuclei, the film formation rate, and the evaluation of diamond adhesion.

(Comparative Examples 2 to 4) In the pretreatment of the substrate,
The same procedure as in Comparative Example 1 was repeated except that the reaction internal pressure and the treatment time were changed to the conditions shown in Table 1. Table 1 shows the evaluation of the generation density of initial diamond nuclei.

[0034]

[Table 1]

[0035]

According to the present invention, the substrate, which is placed in the magnetic field and to which the negative bias is applied, is treated with the plasma of the carbon-containing compound, and by such pretreatment, the diamond initial nuclei are shortened on the substrate. Since a specific method is used in which diamond (diamond film) is formed on this substrate by a vapor phase method after being generated at a high density in time, graphite or DLC is formed on the surface of various substrates.
High-performance diamond that can efficiently form high-quality diamond (that is, high-purity diamond with high crystallinity) with less unwanted impurities (non-diamond components) such as (diamond-like carbonaceous material) and with good adhesion. It is possible to provide a practically remarkably advantageous diamond synthesis method, which has the advantages that a coating member or high-quality diamond with little variation in quality can be easily mass-produced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of formation of a magnetic field.

FIG. 2 is an explanatory diagram showing an example of formation of a magnetic field.

FIG. 3 is an explanatory diagram showing an example of formation of a magnetic field.

FIG. 4 is an explanatory diagram showing a process of performing a plasma treatment on a substrate to which a negative bias voltage is applied in a magnetic field.

[Explanation of sign]

 1 Substrate electrode 2 Counter electrode 3 Substrate 4 Magnet 5 Magnetic field line 6a First solenoid coil 6b Second solenoid coil 7 Support 8 Microwave 9 Reaction tube 10 Waveguide 11 Second waveguide

Claims (1)

[Claims] 1. A substrate, which is placed in a magnetic field and to which a negative bias voltage is applied, is treated with plasma of a carbon-containing compound or a mixed gas of a carbon-containing compound and hydrogen, and then the substrate is exposed to air. A method for synthesizing diamond, which comprises forming diamond by a phase method.