JPH04202663A - Formation of boron nitride film and apparatus therefor - Google Patents

Abstract

PURPOSE:To form baron nitride having high quality and high purity on the surface of a substrate by arranging members constituted of baron nitride at least on the surface at a spatial area close to or in contact with an excited plasma area. CONSTITUTION:In a reaction chamber 2, an Si substrate 3 is set to a substrate holder 4, to which a raw material gas contg. B2H6 and NH3 is introduced from a gas introducing port 9, and vacuum evacuation is executed from an exhaust port 10 into a prescribed pressure. Next, a high frequency voltage is impressed from a high frequency power source generator 8 on the lower electrode 5 arranged oppositely to the substrate 3. Thus, plasma in the above raw material gas is excited to form a BN thin film on the surface of the above substrate 3. In the above plasma CVD apparatus 1, BN members 11 and 12 are arranged at an area close to or in contact with the above plasma area. In this way, the direct exposure of the constituting members of the above apparatus 1 to the plasma is prevented, and the inhibition of the crystallization of a BN film caused by the mixing of impurities generated from the above is prevented to obtain the BN film having good crystallinity and high purity.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method and apparatus for forming a boron nitride film.

In detail, hard boron nitride (cubic boron nitride (abbreviated as C-BN) and Wurtz type boron nitride (abbreviated as w-BN)) is extremely hard and highly heat resistant, and has high thermal conductivity and electrical insulation properties. Excellent hexagonal boron nitride (h-B
The present invention relates to a method and apparatus for forming (abbreviated as N). The boron nitride according to the present invention can be effectively used in fields that require excellent properties such as hardness, heat resistance, oxidation resistance, and chemical stability, such as materials for cutting tools and wear-resistant tools.

Further, the hexagonal boron nitride according to the present invention can be applied as an electronic material due to its high thermal conductivity and electrical insulation properties.

[Conventional technology]

such as cubic boron nitride and Wurtz type boron nitride,
So-called hard boron nitride has a hardness second only to diamond, and has better heat resistance, oxidation resistance, and
Furthermore, since it is highly chemically stable, it is no exaggeration to say that it is an ideal material for cutting tools, wear-resistant tools, and other tools. However, synthesis of hard boron nitride requires extremely high pressure and high temperature, which is higher than that of diamond.
Not only is the shape of the product severely restricted, but the synthesis cost is also high due to the use of an extremely expensive ultra-high pressure generator, so its range of use is naturally limited.

Recently, a method has been developed for synthesizing hard boron nitride by depositing it on the surface of a substrate from the gas phase, without using ultra-high pressure or high temperature, as in the case of diamond. According to this vapor phase synthesis technology, there are very few restrictions on the product shape, and since no ultra-high pressure generator is used, it is thought that the synthesis cost will be extremely low.

Gas phase synthesis technologies for hard boron nitride include, for example: ■ ion beam method in which metallic boron is melted and evaporated with an HCD electron gun and reacted with nitrogen plasma in the atmosphere to precipitate boron nitride on a substrate; A reactive sputtering method involves sputtering with hydrogen or nitrogen and reacting with nitrogen plasma in the atmosphere to precipitate and synthesize boron nitride on the substrate.Furthermore, ■ reacting diborane with nitrogen or ammonia in high frequency plasma such as microwaves. Many methods have been proposed, including a plasma CVD method in which boron nitride is deposited and synthesized on a substrate.

[Problem to be solved by the invention]

However, none of the above-mentioned conventional methods has succeeded in precipitating and synthesizing single-phase cubic boron nitride or Wurtz-type boron nitride from the gas phase on a substrate; A mixture of hard type boron nitride and hexagonal boron nitride, which is a thermodynamically low-pressure phase, was obtained. Hexagonal boron nitride is not suitable as a tool material due to its low hardness, and vapor-phase synthetic boron nitride according to the prior art has not yet been able to withstand practical use as a tool material.

Hexagonal boron nitride has excellent thermal conductivity and high electrical insulation. In addition, hexagonal boron nitride has a layered structure similar to graphite, and by inserting various atoms and molecular species between the layers to form interlayer compounds, it is also possible to control physical properties such as electrical conductivity. be. Improving crystallinity is an important issue from the viewpoint of application to electronic materials, but hexagonal boron nitride formed by conventional vapor phase synthesis techniques has low crystallinity.

In view of the current situation, the present invention provides a method and apparatus for forming high quality and/or high purity cubic boron nitride, Wurtz type boron nitride and/or hexagonal boron nitride on the surface of a substrate. It is.

[Means to solve the problem]

The present invention, which solves the above problems, provides a method for forming a boron nitride film on a substrate from a gas phase in plasma, in which a member at least on the surface of which is made of boron nitride is provided in a spatial region adjacent to or in contact with an excited plasma region. It is characterized by placing.

Furthermore, the present invention provides an apparatus for forming a boron nitride film by physical vapor deposition or chemical vapor deposition, which includes plasma generation means,
The present invention provides the above-mentioned device, characterized in that a member having at least a surface made of boron nitride is disposed in a spatial region close to or in contact with the excited plasma region.

[Effect]

The present inventors believe that one of the causes of the problems of the prior art described above is that elements other than boron and nitrogen, which are film constituents, are mixed in as impurities from the constituent materials of the film forming apparatus that are in contact with or in the vicinity of the plasma. I came up with this idea.

In other words, in conventional vapor phase synthesis technology, the sputtering phenomenon of the constituent materials due to the interaction between the plasma and the surface of the constituent members of the film forming apparatus (for example, quartz tubes, stainless steel, etc.) that are in contact with or in the vicinity of the plasma causes damage to the constituent materials. The contained elements are released into the plasma and deposited as impurities along with boron nitride on the substrate exposed to the plasma.

In addition, the impurity elements released into the plasma chemically combine with boron or nitrogen, and nitrides/borides made of the impurity elements are formed and deposited on the substrate, resulting in the desired high quality and high purity boron nitride film. can't get it.

In the present invention, in a method for forming boron nitride in which a boron nitride film is deposited on the surface of a substrate from a gas phase, a member having at least a surface made of boron nitride is disposed in a spatial region in contact with or close to plasma, and a member forming a film forming apparatus is used. Avoid direct exposure to plasma. In this case as well, the boron nitride member in contact with or in the vicinity of the plasma is emitted into the plasma by sputtering etc. due to interaction with the plasma, but the elements mixed into the plasma are boron and nitrogen, and in this gas phase Even if the boron and nitrogen released in the process chemically react in the gas phase, only boron nitride is formed, so there is almost no adverse effect on the formation of a high-quality, high-purity boron nitride film. Therefore, it is possible to prevent the incorporation of impurities that inhibit improvement of the crystallinity of the boron nitride film, and to form a boron nitride film with good crystallinity and high purity.

The boron nitride forming at least the surface of the arrangement member may be cubic, Wurtzian, or hexagonal. These may be provided in contact with the base material on which the boron nitride film is formed, or may be provided by coating the inner surface of the reaction chamber with boron nitride.

Further, the vapor phase synthesis of boron nitride in the present invention may be performed by any known means as long as it uses plasma.

Specifically, sputtering method using physical vapor deposition, laser ablation method, ion blating method, etc., RF plasma CVD method using chemical vapor deposition, DCCVD method, EC
This is a method that uses plasma in cyclotosonic resonance plasma CVD, microwave plasma CVD, etc.

The boron nitride film formed on the surface of the substrate according to the present invention is one of cubic boron nitride, wurtzian boron nitride, and hexagonal boron nitride.

The specific method and apparatus of the present invention will be explained in detail in the following examples, but the present invention is not limited thereto.

〔Example〕

Example 1 and Comparative Example 1 The present invention and the conventional method were compared using a parallel plate high frequency plasma CVD apparatus 1 shown in FIG.

In the embodiment of the present invention, a member II and a member 12 each having a structure whose surface is coated with hexagonal boron nitride are provided on the inner wall portion of the reaction chamber 2 exposed to plasma (a spatial region close to the plasma).

The member 12 is placed on top of the surface of the lower electrode 5. The appropriate thickness of the member 12 is about 1 to 3 m+. When forming a cubic boron nitride film, high-density plasma is required, so if the thickness is less than 1 won, sputtering of the member will be large, making it impractical for long-term use. Further, if the distance is 3 m or more, it becomes difficult for high frequency waves to propagate on the electrode surface.

After installing the 3i board 3 on the board holder 4, open the exhaust hole 1.
The inside of the reaction chamber 2 was evacuated to 3 X I Q -' Torr or less by operation of a vacuum evacuation device (not shown) connected to 0, and the Si substrate 3 was heated to 700° C. by a heater 7. After that, diborane gas is introduced from the gas inlet 9 for 0.2S.
CC■, ammonia gas 2sec, H2 gas 1
Q gsccm and 1 Q sccm of Ar gas were introduced, respectively, and a conductance valve (
(not shown) to adjust the pressure inside the reaction chamber 2 to 4QTorr.
was held at After that, 1 3.5 connected to the lower electrode 5
A 6 MHz high frequency power oscillator 8 was operated to supply 300 W of high frequency power to form plasma between the substrate holder 4 and the lower electrode 5. Furthermore, the DC power supply 6 connected to the board holder 4 is operated to apply a voltage of -400 V to the board boulder 4.
A DC bias voltage of was applied. In this state, boron nitride was deposited on the substrate for 1 hour.

When the infrared absorption spectrum of the obtained film was first measured, no absorption due to hexagonal boron nitride was observed, and only absorption due to cubic boron nitride was observed.

Next, transmission electron beam diffraction was performed, but only the diffraction lines of cubic boron nitride were observed.Also, similar results were obtained by applying radio frequency (RF) bias instead of applying DC bias in the above method. Obtained. (
Example 1).

For comparison, a similar analysis was conducted on a substrate coated with boron nitride for one hour under the same conditions as in Example 1, except that the boron nitride members 11 and 12 were not provided using the above method. In the external absorption spectrum, absorption was mainly due to cubic boron nitride, but absorption from impurities and impurity nitrides and borides was also observed, and diffraction lines of impurities were also observed in transmission electron diffraction.

Specifically, since the reaction chamber was made of stainless steel in this example, absorption caused by nitrides and/or borides of iron (Fan), chromium (Cr), and nickel (Ni) was confirmed.

Table 1 below shows the half-width of the diffraction line peak from the (111) plane of cubic boron nitride, which was measured to evaluate the crystallinity of the formed boron nitride film (the smaller the half-width, the better the crystallinity). and the results of film composition analysis by X-ray excitation photoelectron spectroscopy (XPS). From Table 1, it can be confirmed that the present invention can improve the crystallinity of cubic boron nitride and reduce the impurities in the film.

Example 2 and Comparative Example 2 Using the sputtering apparatus shown in FIG. 2, the present invention and the conventional method were compared.

As in Example 1, a member 33 made of cubic boron nitride was placed in the spatial region near the plasma generation region. Specifically, the cylindrical member 3 was placed at a distance of 3 cm from the outer circumferential side of the lower electrode 23 and the target 24 . After installing the SUS substrate 22 on the substrate holder 21 and metal boron as a target on the lower electrode 23, the inside of the reaction chamber is evacuated by the operation of a vacuum evacuation device (not shown) connected to the exhaust port 25.
x l Exhaust to below Q-'Torr and connect the SUS board 22
was heated to 650'C by heater 27. After that, 2 sccm of nitrogen gas and 4 seconds of Ar gas were introduced from the gas inlet 028, and the exhaust port 25
By adjusting the conductance valve 29 provided in the reaction chamber 2,
The pressure inside the substrate holder 21 and the lower part was maintained at 4X I O-'' Torr.Then, the 13.56 MHz high frequency power oscillator 30 connected to the lower electrode 23 was operated to supply 400 W of high frequency power, and the substrate holder 21 and the lower Plasma was formed between the electrodes 23. Furthermore, the DCt connected to the substrate 21
The source 31 was operated to apply a DC bias voltage of -200 V to the substrate holder 21. In this state, boron nitride was deposited on the SUS substrate for 1 hour. Note that a magnet 32 was installed below the metal boron target 24 to improve sputtering efficiency.

When the infrared absorption spectrum of the obtained film was first measured, no absorption due to hexagonal boron nitride was observed, and only absorption due to cubic boron nitride was observed. Next, transmission electron beam diffraction was performed, but only the diffraction lines of cubic boron nitride were observed. Note that instead of applying a DC bias voltage to the substrate holder 21, high frequency (RF
) Similar results were obtained even when a bias was applied. (Example 2).

For comparison, a similar analysis was performed on a substrate coated with boron nitride for one hour under the same conditions as described above, except that no boron nitride member was provided, and the infrared absorption spectrum showed that cubic boron nitride Although the absorption was the main one, absorption of impurities and impurity nitrides and/or borides was also observed, and diffraction lines of impurities were also observed in transmission electron diffraction. Specifically, the reaction chamber in this example Since the material was made of stainless steel, absorption caused by nitrides and/or borides of iron (Fe), chromium (Cr), and nickel (Ni) was confirmed (Comparative Example 2).

Table 2 below shows the half-width of the diffraction line peak from the (111) plane of cubic boron nitride, which was measured to evaluate the crystallinity of the formed boron nitride film (the smaller the half-width, the better the crystallinity). and the results of film composition analysis by X-ray excitation photoelectron spectroscopy (XPS). From Table 1, it can be confirmed that the present invention can improve the crystallinity of cubic boron nitride and reduce the impurities in the film.

Example 3 and Comparative Example 3 The present invention and the conventional method were compared using a microwave plasma CVD apparatus shown in FIG. As in Example 1, a member 119 whose surface was coated with cubic boron nitride was provided near the plasma generation region. The film forming conditions were as follows.

Substrate: Sj Substrate temperature 2600°C Source gas: B 2HI/Nx= 1/5
Q sccm pressure: 4
QTorr microwave input power input power crab 200 W: 2 hours When the infrared absorption spectrum of the obtained film was first measured, only absorption due to cubic boron nitride was observed. Next, transmission electron beam diffraction was performed, but only the diffraction line of cubic boron nitride was observed (Example 3).

For comparison, a similar analysis was performed on a substrate coated with boron nitride for 1 hour under the same conditions except that the boron nitride member was not provided using the above method, and the infrared absorption spectrum showed that cubic boron nitride was not present. Although absorption was the main one, absorption of impurities and impurity nitrides and/or porides was also observed, and diffraction lines of impurities were also observed in transmission electron diffraction. Specifically, since the reaction chamber in this example was a quartz tube, absorption caused by silicon (S i ) and oxygen (◯) was confirmed (Comparative Example 3).

Table 3 below shows the half-width of the diffraction line peak from the (002) plane of hexagonal boron nitride, which was measured to evaluate the crystallinity of the formed boron nitride film (the smaller the half-width, the better the crystallinity). and the results of film composition analysis by X-ray excitation photoelectron spectroscopy (XPS). From Table 1, it can be confirmed that the present invention can improve the crystallinity of hexagonal boron nitride and reduce the impurities in the film.

〔Effect of the invention〕

As explained above, when forming a boron nitride film by vapor phase synthesis technology, the present invention provides high quality and high This makes it possible to form a pure boron nitride film.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining embodiments of the present invention, in which fig. 2
FIG. 3 shows Example 3 of the case where the sputtering equipment is used.
The case is shown in which a microwave plasma CVD apparatus is used. Agents 1) Sun Moon Agent
Ryo Hagiwara - Agent Anzai
Atsuo Figure 1 Figure 5j-2, 1IrEIr:I; itail R% Koshikudai

Claims (2)

[Claims] (1) A method for forming a boron nitride film on a substrate from a gas phase in plasma, characterized by arranging a member at least on the surface of which is made of boron nitride in a spatial region close to or in contact with an excited plasma region. The above method. (2) An apparatus for forming a boron nitride film by physical vapor deposition or chemical vapor deposition, which has a plasma generating means, characterized in that a member having at least a surface made of boron nitride is disposed in a spatial region adjacent to or in contact with an excited plasma region. The above device.