JPS61183198A - Production of diamond film - Google Patents

Abstract

PURPOSE:To produce a diamond film having high hardness and superior char acteristics at the high rate of formation by introducing an org. compound contg. oxygen as a constituent atom into a reaction chamber together with gases for forming the diamond and by growing the diamond on a substrate in a vapor phase. CONSTITUTION:The substrate is placed in the reaction chamber, and the org. compound contg. oxygen as one or more constituent atoms such as (CH3)2O, CH3OH or CH3COOH is introduced into the chamber together with gases for forming diamond such as H2 and CH3. the molar ratio of the org. compound to H2 is preferable about 0.0001-0.5. The internal pressure of the chamber is then regulated to about 10<-5>-100 Torr, the substrate is kept at about 400-1,400 deg.C, and plasma CVD is carried out. The org. compound prevents H from intruding a film during the formation and accelerates the activation of CH4 or other hydrocarbon, so a high hardness diamond film having a low hydrogen content is formed on the surface of the substrate. The rate of deposi tion is increased and the cost of the production of the diamond film is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a diamond film that improves the diamond properties of the film and increases the film formation rate.

[Prior art]

Diamond has come to be synthesized under ultra-high pressure and ultra-high temperature using expensive equipment, but on the other hand, it is being used in an even wider range of applications by taking advantage of its excellent properties such as hardness and thermal conductivity, as well as its semiconducting properties. In order to answer this question and efficiently synthesize diamond, low-pressure vapor phase synthesis technology is being researched, and for example, diamond synthesis using plasma CVD has been proposed.

According to this plasma CVD method for diamond synthesis, a mixed gas consisting of hydrocarbon gas and hydrogen gas is introduced into a reaction chamber, and plasma is generated using radio frequency, microwave, DC voltage, etc., and a diamond film is formed on the surface of the substrate. It is something to do. (Japanese Patent Application Laid-Open No. 158774/1983,
(Refer to Japanese Unexamined Patent Publication No. 59-3098) [Problems to be solved by the invention] However, if only a mixed gas consisting of hydrocarbon gas and hydrogen gas is used as the diamond-forming gas, the diamond formation rate is low, and the diamond formation rate is about 1 μm. To obtain a film thickness of 3
The current situation is that it takes up to 4 hours.

Furthermore, even in the diamond film obtained by this plasma (4D method), excellent diamond properties such as high hardness have not yet been achieved to a satisfactory level, and further improvement of these properties is desired.

[Purpose of the invention]

Therefore, the present invention was completed in order to solve the problem, and its purpose is to provide a method for manufacturing a diamond film that increases the diamond production rate and reduces the manufacturing cost.

Another object of the present invention is to provide a method for producing a diamond film having excellent diamond properties such as high hardness.

[Summary of the invention]

According to the present invention, the reaction system in which the substrate is installed7. A method for producing a diamond film is provided in which a generation gas 8 is introduced and diamond is grown in a vapor phase on the surface of the substrate from the gas 8, characterized in that the gas contains oxygen atoms. be done.

[Means to solve the problem]

The present invention is suitable for all vapor phase growth techniques for producing diamond, and will be described in detail below using plasma CVD as an example.

Instead of using hydrocarbon gas, hydrogen gas, or the like as the gas for producing diamond by plasma CvD, the present invention makes this gas contain oxygen atoms.

It has been found that the oxygen atoms can be obtained by introducing, for example, oxygen gas into the diamond-forming gas, and that a diamond film can be formed at high speed by this method.

As described in the examples below, plasma CVD according to the present invention includes high frequency plasma CVD, microwave plasma CVD1 electron cyclotron resonance + (ECR) plasma CVD, and the present invention also uses methods such as chemical transport method. objectives can be achieved.

It was confirmed. According to such plasma CVD, electrons in the plasma space have significantly greater kinetic energy than ions and neutral molecular species. For this purpose, hydrocarbons collide with electrons in the plasma space and are excited, accelerating the reaction rate with a relative decrease in the activation energy of the reaction, and furthermore, the hydrocarbons dissociate into atomic forms and are heated to a predetermined temperature. Carbon atoms are deposited in a diamond shape on the surface of the substrate.

Diamond-generating gases often contain hydrogen atoms, such as hydrogen atoms in hydrocarbon gas, and hydrogen gas is used to generate hydrogen plasma as described in JP-A-58-185117. may be introduced. Such hydrogen atoms work to generate hydrogen plasma to efficiently generate the plasma, or to react with and remove graphitic carbon produced as a diamond film is formed.

However, activated hydrocarbons and carbon in the plasma space collide with hydrogen gas and hydrogen after decomposition, causing recombination and losing their activity.

Therefore, even if many hydrocarbons reach the substrate, only a small portion of them will form diamonds, and the majority will be released back into the gas phase.

Therefore, in the present invention, when oxygen is added to this plasma space, C
This is based on the knowledge that 90" ionic species are generated and these react with hydrocarbons to promote activation, resulting in a significant increase in the rate of diamond film formation.

Furthermore, according to the present invention, since the diamond-forming gas contains a large amount of hydrogen, hydrogen is incorporated during film formation and deteriorates the original high hardness characteristics and high thermal conductivity. It has been found that by introducing hydrogen, which tends to be incorporated during film formation, is extracted, and as a result, the diamond properties of the film are significantly improved.

The inventor repeatedly conducted various experiments and found that my
o Vickers hardness: 7000 to 12000 kg/xx
The film-forming time was 1 to 50 times per hour.
It was possible to increase the level to µ.

According to the invention, hydrocarbons are used as diamond-forming gases, such as methane, ethane, propane, butane, ethylene, propylene.

There are saturated or unsaturated chain hydrocarbons such as acetylene, allenecyclopropane, cyclobutane, benzene, toluene, and oxy-15, alicyclic hydrogen ash, aromatic hydrocarbons, etc., and depending on the type of hydrocarbon, hydrogen Hydrogen gas may be added to generate plasma. Furthermore, there is no problem in replacing all or part of this hydrogen gas with a neutral gas such as argon or helium.

Furthermore, according to the present invention, in addition to adding oxygen gas to the diamond-forming gas to provide an oxygen atom supply source, Co, CO
It is also effective to use oxygen compounds such as 2, H+O, NO+, No2, N20, etc., carbides, and hydrides.

Furthermore, a gas in which a hydrocarbon serving as a carbon supply source and oxygen atoms are combined may be used as the diamond-forming gas according to the present invention. For example C1IH40, (CHa)g.

, CHa○Fl, C2H50H, CHa○H, C
There are alcohols, ethers, and organic acids such as HsCOOH.
Even with these K, hydrogen gas may be added to generate hydrogen plasma (although there is no problem in replacing all or part of the hydrogen gas with a neutral gas such as argon or helium.

In addition, the diamond-forming gas according to the present invention may be used alone or in combination with each of the above-mentioned hydrocarbons and oxygen atom-containing hydrocarbons.

In the manufacturing method of the present invention, in addition to the type of diamond-generating gas, it is desirable to set the ratio of these gas components within a predetermined range.

In other words, with regard to diamond-forming gases consisting of oxygen-containing gases such as hydrogen gas, hydrocarbon gas, diatomic molecules such as Co, 02°Cow, etc., and 8-atom molecules, hydrocarbons are The molar ratio of gas is set to 0.
It is preferable to set it in the range of 0005 to 100, and more preferably in the range 1 of α001 to 0.1.

Although it depends on the type of gas, it is best to set the molar ratio of oxygen-containing gas (to hydrocarbon gas) in the range of 0.0001 to 2, preferably in the range of O,0OO2 to 0.2. . This is because within these ranges, the effect that a diamond film having excellent diamond properties can be formed at a relatively high speed becomes remarkable.

In addition, regarding the diamond-forming gas consisting of hydrocarbon gas containing oxygen atoms and hydrogen gas, although it depends on the type of gas, the molar ratio of the hydrocarbon gas to hydrogen gas is α
0001 to 0.5, preferably 0.005 to 0.1
It has been confirmed that by setting the diamond film in the range of , the effect that a diamond film having excellent diamond properties can be formed at a relatively high speed becomes remarkable.

Furthermore, in the manufacturing method of the present invention, the temperature of the substrate on which the diamond film is formed and the gas pressure during film formation are preferably set within predetermined ranges.

According to the inventor's experiments, the substrate temperature was set at 400 to 1400.
It was confirmed that the object of the present invention could be achieved by setting the temperature within the range of 0.degree. C. and the gas pressure within the range of 10 to 100 Torr.

Next, high frequency plasma CVD, microwave plasma CVD
, KC:R plasma CVD methods to produce a diamond film from a diamond producing gas will be described in sequence.

[Example 1] Four high-frequency current coils were installed outside a quartz tube serving as a reaction chamber.
It was formed into a spiral shape, and a base body was installed inside it, which was set at a predetermined temperature. Based on the high-frequency plasma CVD method, a high-frequency current of 13.56 MHz was passed through the coil, and a diamond-generating gas was introduced into the quartz tube as shown in Table 1, the gas pressure was set, and plasma was generated. .

For each diamond film thus obtained, the deposition rate using a scanning electron microscope, the hardness using micro-Vickers, the hydrogen content in the film using secondary ion mass spectrometry, and the oxygen content in the film using Auger electron spectroscopy were measured. As is clear from Table 1, the deposition rate and hardness were significantly higher for sample numbers 1 to 6 of the present invention, and the hydrogen content in the film was also lower than that of the comparative example.
It was significantly smaller than sample numbers 7 and 8), and a high quality diamond film was obtained.

[Example 2] In this example, when forming a film using a 145 GHz microwave based on the microwave plasma CVD method, a diamond-generating gas was introduced as shown in Table 2. , plasma was generated while the substrate temperature and gas pressure were also set within predetermined ranges.

For each diamond film thus obtained, the deposition rate, Vickers hardness, hydrogen content in the film, and oxygen content in each film were measured in the same manner as in Example 1, and the results shown in Table 2 were obtained. It was done.

As is clear from Table 2, sample numbers 9 to 19 of the present invention
It can be seen that the precipitation rate and hardness were significantly increased. In addition, regarding sample number 21, it was observed that the diamond was not uniformly formed into a film, but formed into a granular film with a portion of the substrate surface being exposed.

[Example 3] In this example, the inventor filed a patent application No. 58-20800.
A diamond film was formed based on a method that combined an ion beam with an ECR plasma CVD method as proposed in Publication No. 6. Then, the diamond-generating gas is added to the third
The materials were introduced as shown in the table, and plasma was generated while the substrate temperature and gas pressure were also set within predetermined ranges.

For each diamond film thus obtained, the deposition rate, hardness, hydrogen content and oxygen content in the film were measured in the same manner as in Example 1, and the results shown in Table 3 were obtained. .

As is clear from Table 3, sample numbers 22 to 3 of the present invention
It can be seen that for No. 2, the precipitation rate and hardness were significantly increased.

〔Effect of the invention〕

As shown in the above examples, the diamond film produced by the method of the present invention has a lower hydrogen content than conventionally known diamond films and has excellent diamond characteristics, such as excellent hardness. I understand. Furthermore, the deposition rate is also much higher, and a method for manufacturing a diamond film is provided that reduces manufacturing costs.

Claims (1)

[Claims] In a method for manufacturing a diamond film, in which a diamond-forming gas is introduced into a reaction chamber in which a substrate is installed, and diamond is grown in a vapor phase from the gas onto the surface of the substrate, the gas contains oxygen atoms. Characteristic diamond film manufacturing method.