JPH05320878A - Formation of boron nitride containing film - Google Patents

Abstract

PURPOSE:To form a boron nitride(BN) film with good adhesive property at low temp. by generating negative charged particles in a vessel when both the vacuum deposition of boron contg, materials and the irradiation of boron ions are used to form the BN contg. film in the vacuum vessel. CONSTITUTION:Boron contg. materials (simple substance, oxide, nitride, carbide, etc., of boron) are vacuum-evaporated or sputtered to vaccumdeposit 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, by discharging high-frequency from a high-frequency applying coil, etc., negative charged particles, such as negative ions or electrons are generated in the vacuum vessel and the positive charge accumulated in the formed BN contg. film is neutralized to dissolve charge-up, thereby the generation of pinholes is prevented.

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) and the like. Since h-BN is a substance having cleavability in the C-axis direction, it is soft but excellent in slidability. In addition, since it is easily synthesized into powder at low pressure and is easily formed into a film by various PVD methods (Physical Vapor Deposition) and CVD (Chemical Vapo Deposition), the friction coefficient of various sliding parts can be improved. Widely used to lower.

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. In addition, 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 high temperature region that is difficult to use in conventional semiconductor devices, and by pn junction, it can be used for ultraviolet light It has been reported that it can also function as a diode that emits light, and has attracted attention from the viewpoint of the characteristics as a semiconductor. However, c-BN 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. Therefore, if c-BN is film-synthesized at a low temperature that does not require high pressure and can be formed on the substrate with good adhesion, the above-mentioned applications can be dramatically expanded.

Therefore, in recent years, many attempts have been made to synthesize c-BN at a low temperature by positively using ions and plasma, and there have been a few successful cases of synthesizing c-BN. It came to be reported. For example, plasma CVD in which a source gas is decomposed and reacted using plasma
The method is thermal CVD for thermally decomposing and reacting the raw material gas.
Compared with the method, it has the advantage that a boron nitride-containing film can be synthesized at a low temperature, and the excited state of the source gas is also high, so that c-BN is synthesized at a temperature at which thermal damage to the substrate is relatively small .. Also, some examples of synthesizing c-BN using other ions and plasma have been reported.
The low temperature synthesis of BN is getting attention. However, the adhesiveness between the substrate and the film has not yet been solved in industrially synthesizing the boron nitride-containing film at low temperature by utilizing plasma, ions, and the like.

Therefore, as a method of forming a BN film having good adhesion on the substrate without thermal damage to the substrate, the inventors have used a substance containing a boron element by vacuum deposition or 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, according to this method, when BN is formed in the film, BN is an insulator regardless of the crystal structure, so that positive charges due to irradiation ions are accumulated in the film during the formation of the film, Causes a phenomenon of charge-up. As a result, the accumulated charges cause a local dielectric breakdown in the film, resulting in the formation of pinholes, which results in various properties such as the insulating property of the film, weather resistance, and the role of protecting the substrate. There was a problem of reducing long-term stability.

The present invention has been made in view of the above problems, and provides a method for forming a boron nitride-containing film capable of preventing the occurrence of pinholes and improving the properties such as insulation and weather resistance. Is.

[0007]

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 an ion containing at least nitrogen ions in a vacuum container. There is provided a method for forming a boron nitride-containing film, wherein negatively-charged particles are generated in the vacuum container when the contained film is formed.

The film forming apparatus for carrying out the present invention comprises an evaporation source, an ion source and the like, and 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 the exhaust device 11 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. The method of the ion source 4 is not particularly limited, and a Kauffman type, a bucket type, or the like can be used as appropriate. 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, a high frequency applying coil 10 is arranged inside the vacuum container 5, and the high frequency applying coil 10 is connected to a high frequency power source 9 and a matching circuit 8 outside the vacuum container 5.

In carrying out the present invention, the substrate is placed on a substrate holder, placed in a vacuum container, evacuated by an evacuation device, and then the boron-containing substance is heated from the evaporation source to be vaporized to be placed on the substrate. Vapor deposition. 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 those containing nitrogen ions and inert gas element ions and hydrogen ions can be used depending on the type of the substrate. They are,
For example, it can be obtained by introducing only nitrogen gas or nitrogen gas and an inert gas or hydrogen gas into the ion source. The angle of incidence of ions on the substrate at this time is not particularly limited, and film formation may be performed while rotating the substrate so that a film having a uniform film thickness is formed on the substrate.

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. In addition, the number ratio (B / N transport ratio) of boron atoms and nitrogen ions that reach the substrate 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.

Further, in the present invention, negatively charged particles are generated in the vacuum container at the same time when the boron nitride-containing film is formed. The method for generating the negatively charged particles is not particularly limited, but for example, in order to obtain matching between the incident wave and the reflected wave with respect to the high frequency discharge in the vacuum container with a high frequency power source that generates a frequency of 13.56 MHz. Negatively charged particles such as negative ions or electrons can be generated by the high-frequency discharge using the matching circuit of. At this time, the output of the applied high frequency is preferably about 10 W or more. Further, the gas pressure in the vacuum container when the high frequency discharge is generated is 1 × 10.
^-6 torr or more is preferable, and if it is less than this, high frequency discharge cannot be stably maintained. The introduction of the gas when the high frequency discharge is generated may be performed by introducing the gas into the vacuum container from the ion source, or may be performed by separately providing a gas introduction port for the high frequency discharge.

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.

[0013]

According to the present invention, when a boron nitride-containing film is formed by using a combination of vacuum vapor deposition or sputtering of a substance containing a boron element in a vacuum container and irradiation with ions containing at least nitrogen ions, By generating negatively charged particles such as negative ions or electrons in a vacuum container, the positive charges accumulated in the formed boron nitride-containing film are neutralized by the ions irradiated from the ion source, or irradiation is performed. Ions are irradiated to the substrate in a neutralized form. As a result, the positively charged ions generated by the formation of the boron nitride-containing film are not accumulated in the boron nitride-containing film, the charge-up is eliminated, and the occurrence of pinholes is prevented.

[0014]

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 3 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 a temperature of 8 × 10
^It was introduced until it reached ⁻⁵ torr, 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 to 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, at the same time as forming the BN film on the substrate 1, a high-frequency discharge with an output of 200 W was generated in the vacuum container 5. In this way, a 1 μm BN film was formed on the substrate.

Example 2 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 3 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 is introduced until it becomes torr, ionized in the ion source 4, and the base 1 is accelerated with an energy of 20 KeV.
Irradiation was performed 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 3. The ion source 4
Used a bucket type ion source with a cusp magnetic field. Then, at the same time when the BN film is formed on the substrate 1, 200 W
A high-frequency discharge having an output of 1 was generated in the vacuum container 5. In this way, a 1 μm BN film was formed on the substrate.

Example 3 The same substrate 1 as in Example 1 was used, and 5 × 1 was used 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 3 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 is introduced until it becomes torr, ionized in the ion source 4, and the base 1 is accelerated with an energy of 200 eV.
Irradiation was performed 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 3. The ion source 4
Used a bucket type ion source with a cusp magnetic field. Then, at the same time when the BN film is formed on the substrate 1, 200 W
A high-frequency discharge having an output of 1 was generated in the vacuum container 5. In this way, a 1 μm BN film was formed on the substrate.

Comparative Example 1 The same substrate 1 as in Example 1 was used, and 5 × 1 as in Example 1 was used.
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 3 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 high frequency discharge was not generated in the vacuum container 5. In this way, a 1 μm BN film was formed on the substrate.

Comparative Example 2 Using the same substrate 1 as in Example 2, 5 × 1 was used in the same manner as in Example 2.
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 3 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 is introduced until it becomes torr and ionized in the ion source 4, and the base 1 is accelerated with an acceleration energy of 20 keV.
Irradiation was performed 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 3. The ion source 4
Used a bucket type ion source with a cusp magnetic field. However, unlike Example 2, the high frequency discharge was not generated in the vacuum container 5. In this way, 1 μm on the substrate 1
BN film was formed.

Comparative Example 3 Using the same substrate 1 as in Example 3, 5 × 1 was used in the same manner as in Example 3.
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 3 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 is introduced until it becomes torr, ionized in the ion source 4, and the base 1 is accelerated with an energy of 200 eV.
Irradiation was performed 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 3. The ion source 4
Used a bucket type ion source with a cusp magnetic field. However, unlike Example 3, the high frequency discharge was not generated in the vacuum container 5. In this way, 1 μm on the substrate 1
BN film was formed.

Thus, Examples 1 to 3 and Comparative Examples 1 to 1
When the structure of the BN film formed by 3 and 3 was examined by infrared absorption (IR), it was found to consist of c-BN. Further, when the surfaces of these BN films were observed by a scanning electron microscope (SEM), no pinhole was observed in the BN films formed in Examples 1 to 3. On the other hand, Comparative Examples 1 to
Pinholes were observed in the BN film formed in No. 3.

[0021]

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,
At the time of forming a boron nitride-containing film by using together with irradiation of ions containing at least nitrogen ions, since negatively charged particles are generated in the vacuum container, at low temperature,
A boron nitride-containing film having good adhesion can be formed.

Further, by generating negatively charged particles such as negative ions or electrons in the vacuum container, the positive charges accumulated in the formed boron nitride-containing film are neutralized, or the irradiated ions are neutralized. The substrate can be irradiated in a harmonized form. Therefore, the positively charged ions generated by the formation of the boron nitride-containing film are not accumulated in the boron nitride-containing film, the charge-up can be eliminated, the occurrence of pinholes can be prevented, and It becomes possible to form a high quality boron nitride-containing film.

[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.

[Explanation of symbols]

 1 Substrate 5 Vacuum Container 11 Film Forming Device

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

Claims (2)

[Claims] 1. A vacuum container for forming a boron nitride-containing film by using vacuum deposition or sputtering of a substance containing a boron element in a vacuum container together with irradiation of ions containing at least nitrogen ions. A method for forming a boron nitride-containing film, characterized in that negatively charged particles are generated therein. 2. The negatively charged particles generated in the vacuum container are
The method for forming a boron nitride-containing film according to claim 1, wherein the boron ions are negative ions or electrons.