JPH05320879A - Formation of boron nitride containing film - Google Patents

Abstract

PURPOSE:To increase the content of in-cubic system zinc ore type (c-BN) in a film by forming a boron nitride(BN) contg. film while irradiating with the electromagnetic wave when both the vacuum deposition of boron contg. materials and the irradiation of nitrogen ions are used. CONSTITUTION:Boron contg. materials (simple substance, oxide, nitride, carbide, etc., of boron) are vacuum-evaporated or sputtered to vacuumdeposit them on a substrate in a vacuum vessel. Simultaneously or alternately with the vacuum deposition or after the vacuum deposition, the substrate is irradiated with nitrogen element contg. ions from an ion source to form a BN contg. film. At this time, a BN contg. film is formed while irradiating with electromagnetic waves (e.g. ultraviolet rays, X rays) in the vacuum vessel. As a result, the deposited boron atoms become in the highly excited state to be apt to become c-BN, the content of c-BN in the film being increased, thereby the crystallinity of c-BN is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a boron nitride-containing film, more specifically, a field requiring abrasion resistance and slidability, a field requiring high thermal conductivity, or a semiconductor. The present invention relates to a method for forming a boron nitride-containing film used in a field requiring characteristics.

[0002]

2. Description of the Related Art Boron nitride (BN) has a structure similar to that of hexagonal graphite (h-BN) depending on the crystal structure, and cubic zinc blende type (BN). c-BN), or hexagonal wurtzite type (w-BN). h-BN is C
Since it is a material that is cleavable in the axial direction, it is soft but has excellent slidability.At present, artificially synthesized powder is widely used to reduce the friction coefficient of various sliding parts. ing.

On the other hand, c-BN has high hardness and thermal conductivity second only to diamond, and since it is superior in thermal and chemical stability to diamond, it requires wear resistance such as a cutting tool. It is applied to fields and heat sink materials. Furthermore, c-BN has a bandgap larger than that of diamond, and by doping various impurities, it can be applied as a semiconductor that can operate up to a temperature range that is difficult to use in conventional semiconductor devices, and pn junction can be used for ultraviolet light. It has been reported that the diode also operates as a diode that emits light, and has been attracting attention from the viewpoint of characteristics as a semiconductor.

However, h-BN is easily synthesized in powder form under low pressure, and various PVD methods (Physical Vapor Deposit) are used.
ion) or a CVD method (Chemical Vapor Deposition), it is easily formed into a film, whereas c-BN is
It can be synthesized only in bulk form under high temperature or high pressure, and even if it is synthesized, its manufacturing cost becomes very high, and its application range is limited.

If c-BN is film-synthesized at a low temperature that does not require high pressure and can be formed on a substrate with good adhesion, the aforementioned applications can be dramatically expanded. An example of research by the thermal CVD method, which is one of the attempts, will be described. In this method, a substrate is placed in a reaction chamber and a gas containing a boron element (B) or a source gas containing a nitrogen element (N) is used. Is introduced into the reaction chamber and heated to a temperature close to 1000 ° C. to thermally decompose the raw material gas to form a film on the surface of the substrate.

However, this method has a drawback that the type of substrate is limited because the substrate is required to have heat resistance. For example, about 50 such as high speed tool steel (high speed steel)
It is not possible to use, as a substrate, a mold that causes hardness deterioration at a temperature of 0 ° C. or higher, and a mold that does not allow dimensional accuracy due to deformation at high temperatures. Further, although h-BN has been easily synthesized by the CVD method, an example of synthesizing c-BN has not been reported yet, and the fact is that it is in the research stage.

Further, in the PVD method, a method has been tried in which a target made of boron nitride is sputtered by irradiating a laser to form a boron nitride-containing film on the surface of the substrate. However, like the CVD method, Synthesis of c-BN was not possible. However, in recent years, by actively using ions and plasma, c-BN is produced at low temperature.
A number of attempts have been made to synthesize c. BN, and, although small, cases of successful synthesis of c-BN have been reported. For example, decompose the source gas using plasma,
Compared with the thermal CVD method of thermally decomposing and reacting the raw material gas, the plasma CVD method of reacting has an advantage that a boron nitride-containing film can be synthesized at a low temperature, and the excited state of the raw material gas is high. C-BN is synthesized at a temperature at which thermal damage to the substrate is relatively small.

C using other ions and plasma
Some synthetic examples of -BN have been reported, and c-BN has been reported.
The low-temperature synthesis of is getting industrial attention.
Although the use of plasma, ions, etc. has opened the way to the synthesis of boron nitride-containing films at low temperatures, the adhesion between the substrate and the film has not yet been solved for industrial commercialization.

In the method of synthesizing a film by applying heat to a substrate like the thermal CVD method, which has been tried conventionally, the film is formed at a low temperature in terms of adhesion, even though thermal damage to the substrate poses a problem. There is a tendency that it is superior to the method. c-BN
Although the low temperature synthesis was successful, the present situation is that the method for achieving both a film without thermal damage to the substrate and a film with good adhesion has not yet been established.

Therefore, as a method of forming a BN film with good adhesion on the substrate without thermal damage to the substrate, the inventors have used a substance containing a boron element by vacuum deposition and sputtering. It has been proposed to use a method of irradiating the substrate with ions containing at least nitrogen ions simultaneously with forming a film on the substrate, alternately, or after forming the film.
However, in this method, the c-BN formed in the film is generally in an amorphous state or has low crystallinity, and the hardness, thermal conductivity and semiconductor characteristics of c-BN are insufficient. There was a problem that there was.

In order to improve the crystallinity of this c-BN, for example, there is a method of irradiating inert gas ions or hydrogen ions as nitrogen ions at the same time as nitrogen ions. There has been a problem that the inert gas and hydrogen atoms are mixed in, and the density of the film is lowered to cause the deterioration of the characteristics of c-BN or the long-term stability of the film.

It is also conceivable to heat the substrate at the time of film formation to increase the crystallinity, but in this case, there is a problem that it is unsuitable from the viewpoint of low temperature growth. The present invention has been made in view of the above problems, and provides a method for forming a boron nitride-containing film, which has improved hardness, thermal conductivity, semiconductor characteristics, and the like, and can ensure long-term stability.

[0013]

According to the present invention, vacuum deposition or sputtering of a substance containing a boron element on a substrate in a vacuum vessel and irradiation with ions containing at least nitrogen ions are used together. This provides a method for forming a boron nitride-containing film, which comprises forming the boron nitride-containing film while irradiating an electromagnetic wave when forming the boron nitride-containing film.

The film forming apparatus for carrying out the present invention is equipped with an evaporation source, an ion source and the like. For example, the film forming apparatus as shown in FIG. 1 can be used. In FIG. 1, 1 is a substrate, 2 is a substrate holder, 3 is an evaporation source, 4 is an ion source, and they are housed in a vacuum container 5. The vacuum container 5 is evacuated to a predetermined degree of vacuum by an exhaust device 9 and held. The evaporation source 3 is for heating a boron-containing substance by means of an electron beam, resistance or high frequency to vaporize it, and other arbitrary method such as sputtering can be used. However, when the evaporation rate is not stable in the method in which the boron-containing substance is a sublimable substance and is heated and vaporized, it is preferable to use the sputtering method. Also, the method of the ion source 4 is not particularly limited,
A Kauffman type, a bucket type, or the like can be appropriately used. Further, in the vicinity of the substrate holder 2, a film thickness monitor 6 capable of monitoring the deposition amount of vapor deposition atoms on the substrate 1.
However, an ion current measuring device 7 that can monitor the irradiation amount of ions onto the substrate 1 is also provided. The methods of the film thickness monitor 6 and the ion current measuring device 7 are not particularly limited. For example, a crystal oscillator is used as the film thickness monitor 6, and a Faraday cup or the like is appropriately used as the ion current measuring device 7. Can be used. Further, for example, an ultraviolet irradiation lamp 8 is arranged at a position facing the base 1 as a member for irradiating electromagnetic waves. As the ultraviolet irradiation lamp 8 for irradiating the electromagnetic wave, one using a mercury arc can be used, and in addition, light from an X-ray from an X-ray source or a deuterium lamp can also be used. be able to.

In carrying out the present invention, the substrate is placed in a substrate holder and placed in a vacuum container, for example, 1 ×.
After evacuation to a vacuum degree of 10 ^-6 torr or less, the boron-containing substance is heated from the evaporation source and vaporized to be vapor-deposited on the substrate. As the boron-containing substance vaporized from the evaporation source, simple substance of boron, oxide, nitride, carbide, or the like can be used. Then, at the same time as vapor deposition of the substance, alternately, or after vapor deposition, ions containing at least a nitrogen element are irradiated from an ion source. At this time, it is effective to use nitrogen ions as the ions to be irradiated, but in order to improve the crystallinity of the film in order to form a film with particularly high hardness, nitrogen ions and an inert gas element are used. Those containing ions or hydrogen ions can be used. These can be obtained, for example, by introducing only nitrogen gas or nitrogen gas and an inert gas or hydrogen gas into the ion source. In this case,
Since the vapor-deposited boron atoms are brought into an even more highly excited state by the inert gas ions and hydrogen ions, there is an advantage that the crystallinity of the film is improved and, as a result, particularly high hardness is obtained. The angle of incidence of the ions on the substrate at this time is not particularly limited, and the film may be formed while rotating the substrate in order to make the film thickness of the film formed on the substrate uniform.

In the present invention, the acceleration energy of ions when forming a film is preferably about 40 keV or less. When the ion acceleration energy exceeds 40 KeV, excessive defects are generated in the film, and the hardness and chemical stability of the film deteriorate, which is not preferable. Further, the number ratio (B / N transport ratio) of boron atoms and nitrogen ions that reach the base body when forming the film is preferably about 0.5 to 60. When the B / N transport ratio is less than 0.5, the amount of sputtered boron deposited by irradiation ions becomes excessive, and excessive defects are generated in the film, which deteriorates the hardness and chemical stability of the film. It is not preferable. When the B / N transport ratio is more than 60, the amount of BN contained in the film becomes small, and the characteristics of the BN cannot be sufficiently obtained, which is not preferable. The adjustment of the transport ratio can be performed using the film thickness monitor and the ion current measurement monitor in the film forming apparatus.

Further, in the present invention, the substrate is irradiated with electromagnetic waves at the same time when the boron nitride-containing film is formed. The energy at that time is preferably about 10 ^-2 eV to 10 ⁶ eV. This electromagnetic wave irradiation method is not particularly limited, but when the irradiation energy is less than 10 ^-2 eV,
When the excited state of the boron atom is poor and is larger than 10 ⁶ eV, damage to the film due to irradiation cannot be ignored, which is not preferable.

Further, in the present invention, when a substrate for which thermal damage must be extremely avoided is used, it is preferable to perform film formation while cooling the substrate holder with water.

[0019]

According to the present invention, boron nitride is formed by using a combination of vacuum vapor deposition or sputtering of a substance containing a boron element and irradiation with ions containing at least nitrogen ions in a vacuum container of a film forming apparatus. When forming the inclusion film,
Since the boron nitride-containing film is formed while irradiating an electromagnetic wave, a photon irradiated from an electromagnetic wave irradiation source collides with a vapor-deposited boron atom, or the boron atom absorbs the energy of a photon, and an electron between bands. Occurs, the boron atom becomes highly excited, and a pseudo high temperature and high pressure state is created under non-thermal equilibrium. As a result, the boron atoms are likely to become c-BN which is a high temperature / high pressure phase, and c-BN in the film is
As the BN content increases, the crystallinity of c-BN improves.

[0020]

EXAMPLE An example of a method for forming a boron nitride-containing film according to the present invention will be described. Example 1 Using the apparatus shown in FIG. 1, a substrate 1 made of silicon (100) was placed on a substrate holder 2 and a vacuum container 5 was held at a vacuum degree of 5 × 10 ⁻⁷ torr. After that, an evaporated substance made of boron having a purity of 99.7% is vaporized by using the electron beam evaporation source 4 to form a boron film on the substrate 1, and at the same time, a nitrogen gas having a purity of 5N is supplied to the ion source 4 in the vacuum container 5 for 8 times. × 10
^It was introduced until it became ⁻⁵ torr, ionized in the ion source 4, and the substrate 1 was irradiated with an acceleration energy of 1 KeV at an angle of 0 ° with respect to the normal line standing on the substrate 1. B / at this time
The transport ratio of N was 1. As the ion source 4, a bucket type ion source using a cusp magnetic field was used. Then, the BN film was formed on the substrate 1, and at the same time, the substrate 1 was irradiated with ultraviolet rays from the lamp 8 using a mercury arc. In this way
A 1 μm BN film was formed on the substrate.

Comparative Example 1 Using the same substrate 1 as in Example 1, 5 × 1 was used in the same manner as in Example 1.
After holding the vacuum container 5 at a vacuum degree of 0 ^-7 torr, the purity was 99.7
% Of boron is vaporized by using the electron beam evaporation source 4 to form a boron film on the substrate 1, and at the same time, nitrogen gas having a purity of 5N is supplied to the ion source 4 in the vacuum container 5 at 8 × 10 ^−5. It was introduced until it became torr and ionized in the ion source 4, and the substrate 1 was irradiated with an acceleration energy of 2 keV at an angle of 0 ° with respect to the normal line standing on the substrate 1. At this time, the B / N transport ratio was 1. As the ion source 4, a bucket type ion source using a cusp magnetic field was used. However, unlike Example 1, the substrate 1 was not irradiated with ultraviolet rays. In this way, a 1 μm BN film was formed on the substrate 1.

The crystal structures of the BN films thus formed in Example 1 and Comparative Example 1 were identified by X-ray diffraction using Cu-Kα rays, and the results are shown in FIGS. 2 and 3. The diffraction lines obtained from the BN film were all at the position of 43.3 °, and this was due to c-BN. Therefore, it was found that c-BN was formed in the BN film. It was found that the BN film formed in Example 1 had an excellent crystallization state because the BN film formed in Example 1 had a higher diffraction intensity than that in Comparative Example 1.

The hardness of the BN film was measured by a Vickers hardness tester with a load of 10 g.
It was 500, but it was 3000 in the comparative example. Therefore, it was found that in the example, the crystallization of c-BN was excellent, and as a result, the hardness was significantly improved.

[0024]

According to the method for forming a boron nitride-containing film according to the present invention, a film is formed on a substrate in a vacuum container of a film forming apparatus.
Vacuum deposition or sputtering of a substance containing elemental boron,
When the boron nitride-containing film is formed by using irradiation of ions containing at least nitrogen ions in combination, the boron nitride-containing film is formed while being irradiated with electromagnetic waves, so that the vapor-deposited boron atoms are in a highly excited state. As a result, the boron atom is likely to become c-BN, the c-BN content in the film can be increased, and the crystallinity of c-BN can be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a film forming apparatus used when forming a boron nitride-containing film of the present invention.

FIG. 2 is a diagram showing X-ray diffraction of a boron nitride-containing film formed according to an example of the present invention.

FIG. 3 is a diagram showing X-ray diffraction of a boron nitride-containing film formed according to a comparative example.

[Explanation of symbols]

 1 substrate 5 vacuum container

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoto Kuratani 47 Umezu Takaunecho, Ukyo-ku, Kyoto City Nissin Electric Co., Ltd.

Claims (1)

[Claims] 1. When a boron nitride-containing film is formed on a substrate by vacuum deposition or sputtering of a substance containing a boron element and irradiation with ions containing at least nitrogen ions in a vacuum container. A method for forming a boron nitride-containing film, which comprises forming the boron nitride-containing film while irradiating an electromagnetic wave.