JPH04124258A - Formation of boron nitride thin film - Google Patents

Abstract

PURPOSE:To form the BN thin film essentially consisting of a c-BN structure on the surface of a base body at a low temp. by irradiating the surface of the base body with rare gaseous ions and nitrogen ions at specific irradiation energy and irradiation quantity ratio simultaneously with the vapor deposition of an evaporating material contg. boron on the surface of the base body. CONSTITUTION:An evaporating source 3 is heated in a vacuum device to deposit the evaporating material 4 contg. a boron element B by evaporation on the surface of the base body 2. This base body is irradiated with at least >=1 kinds of the rare gaseous ions 6a and the nitrogen ions 6b from an ion source 5 simultaneously with the above-mentioned vapor deposition. The value of this irradiation energy is set at 100 to 500eV in order to form the BN thin film having the extremely few damages and defects of the crystal structure. The ratio of the irradiation quantity of the rare gaseous ions 6a and nitrogen ions 6b with which the base body 2 are irradiated is set in a 0.05 to 2.0 range. Further, the ratio (B/N compsn. ratio) of the number of the particles of the boron and nitrogen in the BN thin film formed on the surface of the base body 2 is so adjusted as to be kept within a 0.5 to 3.0 range. The boron nitride (BN) thin film which consists essentially of the c-BN structure and has high hardness is formed on the base body 2 at the low temp. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a boron nitride thin film that forms a hard boron nitride thin film on the surface of cutting tools, molds, magnetic heads, and other mechanical/mechanical parts and semiconductor devices. This relates to a forming method.

[Conventional technology]

Boron nitride (hereinafter abbreviated as BN) is classified into cubic zinc blende type boron nitride (hereinafter abbreviated as c-BN) and hexagonal graphite type boron nitride (hereinafter h-B) depending on its crystal structure.
(abbreviated as N), hexagonal wurtzite boron nitride (hereinafter referred to as w
-BN) can be roughly divided into three types.

c-BN has a hardness second only to diamond, and is also excellent in thermal conductivity, insulation, and chemical stability, so it is used as a coating thin film in a wide range of fields such as semiconductors and cutting tools. There is. It is also expected to be used as a material for heat sinks due to its insulating properties and high thermal conductivity.

However, at present, in order to obtain c-BN, it must be synthesized artificially under high temperature and high pressure. The form is granular.

Since it can only be obtained in the form of a solid powder, its range of applications is also limited. Therefore, c-BN was heated at low temperature.
Research into methods of forming thin films under low pressure is chemical vapor deposition (CV).
D method) and physical vapor deposition method (PVD method).

For example, in the chemical vapor deposition method (CVD method), a substrate on which a thin film is to be deposited is placed in a reaction chamber and heated to a temperature of 500°C or higher, and then a gas containing boron element (B) and nitrogen element (
A mixed gas with a gas containing N) is introduced into the reaction chamber and subjected to a thermal decomposition reaction to form a BN thin film on the surface of the substrate.

In addition, in the physical vapor deposition method (PVD method), a target containing boron element (B) is sputtered with ion species in a nitrogen gas atmosphere, and sputtered particles are deposited on the surface of the substrate to form a BN thin film. Law. Furthermore, the flying particles of boron element (B) are ionized,
There is an ion plating method in which these particles are accelerated to several eV to several KeV using an electric field and deposited on the surface of a substrate to form a BN thin film.

[Problem to be solved by the invention]

However, in the chemical vapor deposition method (CVD method), it is necessary to maintain the substrate at a high temperature (approximately 500°C or higher), and the substrate deteriorates due to heat, making it impossible to form a BN thin film.
There is a drawback that the substrates on which the BN thin film is formed are limited. In addition, the BN thin film formed by this method has a soft h
-BN tends to become a thin film, and the above-mentioned characteristics of c-BN cannot be fully utilized.

Also, in the physical vapor deposition method (PVD method), only a thin film mainly composed of h-BN can be obtained, similar to the chemical vapor deposition method (CVD method).

An object of the present invention is to provide a method for forming a boron nitride thin film that can form a BN thin film mainly having a c-BN structure on the surface of a substrate at low temperatures.

[Failure to solve the problem]

The method for forming a boron nitride thin film of the present invention includes simultaneously depositing an evaporative material containing boron on the surface of a substrate, and simultaneously applying at least one type of rare gas ion and nitrogen ion to a 100 eV
The number of boron and nitrogen particles in a boron nitride (BN) thin film formed by irradiation with an irradiation energy of ~500 eV and a ratio of the dose of the rare gas ion to the nitrogen ion of 0.05 to 2.0. The ratio (B/N composition ratio) of 0.5 to 3.0
That is.

An example of a BN thin film forming apparatus for the boron nitride thin film forming method of the present invention will be described with reference to FIG.

In a vacuum device (not shown), a base 2 is fixed to a holder 1 that can be water-cooled by circulating water. An evaporation source 3 and an ion source 5 are arranged at positions facing the base 2.

This evaporation source 3 can be heated to a high temperature by an electron beam, laser beam, high frequency, etc.
An evaporated substance 4 containing B) is introduced.

The ion source 5 is a Kaufmann type or a packet type using a Kasub magnetic field for confining plasma, and uses a mixture of a gas made of at least one kind of rare gas element and a gas made of nitrogen element. This device ionizes and irradiates the surface of the substrate 2 with rare gas ions 6a and nitrogen ions 6b.

Furthermore, a film thickness meter 7 and a current measuring device 8 are arranged within the vacuum apparatus.

This film thickness meter 7 is for measuring the film thickness of the vapor deposited substance 4 deposited on the surface of the substrate 2 and the number of boron particles, and is, for example, a vibrating film thickness meter using a quartz crystal resonator, etc. It is. The current measuring device 8 is used to measure the amount of nitrogen ions 6b that are irradiated onto the substrate 2. For example, the current measuring device 8 is used to measure the amount of nitrogen ions 6b that are irradiated onto the substrate 2. This is a current measuring device, etc.

In the above configuration, the evaporation source 3 is heated to deposit the evaporation substance 4 containing boron element (B) on the surface of the substrate 2, and at the same time, at least one type of rare gas ion 6a and nitrogen are evaporated from the ion source 5. irradiation with ions 6b.

At this time, the value of the irradiation energy of the rare gas ions 6a and the nitrogen ions 6b is set to 1 in order to form a BN thin film with extremely little damage or defects in the crystal structure.
00eV~50. OeV.

Note that the lower limit of the irradiation energy range is 100 eV or more due to the performance of the actual ion source 5 and the inability to obtain a current density sufficient for practical use, and the upper limit of the irradiation energy range is 100 eV or more due to the performance of the actual ion source 5 and the inability to obtain a current density sufficient for practical use. In order to further reduce thermal damage to the formed BN thin film, the voltage is set to 500 eV or less.

Further, the ratio of the irradiation amount between the rare gas ions 6a and the nitrogen ions 6b irradiated to the substrate 2 (in other words, the ratio between the rare gas and nitrogen gas supplied to the ion source 5) is set in the range of 0.05 to 2.0. Irradiate with. When the ratio of the irradiation doses is smaller than this range, that is, when the ratio of the irradiation doses between the rare gas ions 6a and the nitrogen ions 6b is less than 0.05, the BN bond in the BN thin film formed by the rare gas ions 6a There is insufficient excitation energy given to the nitrogen ions 6b, and the effect on the reaction between the boron-containing evaporated substance 4 and the nitrogen ions 6b becomes insufficient. Further, if the ratio of the irradiation amount between the rare gas ions 6a and the nitrogen ions 6b is larger than 2.0, the irradiation amount of the nitrogen ions 6b is insufficient, and the reaction between the boron-containing evaporation substance 4 and the nitrogen ions 6b is delayed. The progress becomes insufficient, and a BN thin film mainly having a c-BN structure cannot be formed.

Furthermore, the ratio of the number of particles of boron to nitrogen in the BN thin film formed on the surface of the substrate 2 (hereinafter abbreviated as B/N composition ratio) is adjusted so that the film is in the range of 0.5 to 3.0. Thickness gauge 7. The current measuring device 8 is used to measure and control the amount of the deposited material 4 and the amount of irradiation of the rare gas ions 6a and nitrogen ions 6b. If the B/N composition ratio is outside this range, and the B/N composition ratio is larger than 3.0, too much boron will be deposited on the substrate 2, and the content of C-BN in the BN thin film will decrease. or 0
．． If it is smaller than 5, there will be too much nitrogen that cannot chemically bond with boron in the formed BN thin film, and the desired high hardness,
This is because a thermally and chemically stable BN thin film cannot be obtained.

Note that the rare gas element supplied to the ion source 5 to form the rare gas ions 6a is He (helium).

At least one type of rare gas such as Ne (neon), Ar (argon), Kr (krypton), and Xe (xenon) is supplied.

Under these conditions, the rare gas ions 6a react with the nitrogen ions 6b and boron in the evaporated substance 4 in an excited state, resulting in c-BN, which could only be formed under high temperature and high pressure conditions in the past. The formation of a structured BN thin film can be promoted.

Next, another example of the BN thin film forming apparatus will be explained based on FIG. 2.

In a vacuum device (not shown), a substrate 2 is fixed to a holder l that can be cooled by circulating water, and a film thickness gauge 7 and a current measuring device 8 similar to those described above are arranged on both sides of the holder l. . An evaporation source 3 and two ion sources 5.degree. 5' are arranged at positions facing the substrate 2.

The evaporation source 3 and the ion source 5.5' are similar to the BN thin film forming apparatus shown in FIG. 1 and described above. An evaporative substance 4 containing boron (B) is introduced.

The ion source 5 ionizes a gas made of at least one type of rare gas element and irradiates the surface of the substrate 2 with rare gas ions 6a, and the ion source 5' ionizes a gas made of nitrogen element, The surface of the substrate 2 is irradiated with nitrogen ions 6b.

In this way, by arranging two ion sources 5' that irradiate rare gas ions 6a and nitrogen ions 6b as ion sources, it is possible to individually control the irradiation energy of rare gas ions 6a and nitrogen ions 6b. The amount of irradiation of the rare gas ions 6a to bring the reaction conditions into an excited state and the amount of irradiation of the nitrogen ions 6b that react with boron contained in the evaporated substance 4 can be adjusted individually.

〔Example〕

Example 1 In the apparatus shown and explained in FIG. 1, a base body 2 made of a silicon single crystal wafer is placed in a holder 1 with its cut surface [+00] facing an evaporation source 3 and an ion source 5.
After fixing to
A high vacuum of 10-@(Torr) or less was maintained. At the same time, the evaporation source 3 is heated with an electron beam to deposit the evaporation substance 4 on the surface of the substrate 2, and at the same time, a packet-type ion source 5 is heated with a mixed gas consisting of a rare gas consisting of Ar (argon) gas and nitrogen gas. was supplied, and the surface of the substrate 20 was irradiated with rare gas ions 6a made of Ar (argon) and nitrogen ions 6b.

At this time, the irradiation energy of the rare gas ions 6a and the nitrogen ions 6b is set to 300 eV, the ratio of the irradiation amount of the rare gas ions 6a and the nitrogen ions 6b is set to 0.1, and the current density of the rare gas ions 6a and the nitrogen ions 6b is 0゜15 (A
/cnf), the boron evaporation rate is controlled to 1 [in/sec] so that the B/'N composition ratio of the formed BN thin film becomes 1, and the evaporated substance 4 made of boron reaches the substrate 2.
The number of BN particles and the number of nitrogen particles were measured using a film thickness meter 7 and a current measuring device 8, and a BN thin film of 5,000 mL was formed.

Note that the respective supply amounts of the rare gas consisting of Ar (argon) and the nitrogen gas, which are mixed and supplied to the evaporation source 5, are precisely controlled and supplied by a mass flow controller. Also,
During the formation of the BN thin film, the base 2 is kept at room temperature (RT=23° C.) by constantly cooling the boulder 1 with water.

Example 2 Substrate 2 of the same material as Example 1. Evaporated substances4. The formation conditions were the same as in Example 1 except that the evaporative substance 4 was simultaneously vaporized using rare gas ions 6a and nitrogen ions 6b, and the ratio of the irradiation amount between rare gas ions 6a and nitrogen ions 6b was set to 0.8. 5 on the surface of the substrate 2 by controlling each condition to meet the conditions.
000 C] BN thin film was formed.

Example 3 Substrate 2 of the same material as Example 1. Evaporated substances4. The formation conditions are the same as in Example 1 except that the evaporation substance 4 is simultaneously vaporized using rare gas ions 6a and nitrogen ions 6b, and the ratio of the irradiation amount of rare gas ions 6a and nitrogen ions 6b is set to 1.5. 5 on the surface of the substrate 2 by controlling each condition to meet the conditions.
000 C] BN thin film was formed.

Comparative Example Substrate 2 of the same material as Example 1. Evaporated substances4. Formation other than supplying only nitrogen gas without supplying the rare gas to the ion source 5 and irradiating the substrate 2 with only the nitrogen ions 6b while simultaneously depositing the evaporative substance 4 using the rare gas ions 6a and nitrogen ions 6b Each condition was controlled to be the same as in Example 1, and a BN thin film of 5000 ml was formed on the surface of the substrate 2.

Each of Examples 1 to 3 and Comparative Example B formed under the above conditions
In order to confirm the structure and properties of the N thin film, CuKa line (
X-ray diffraction using λ = 1.5406 people) and Knoop hardness (Hk) were measured.

As a result, regarding X-ray diffraction, all the BN thin films of each example and comparative example showed a c-BN structure at a diffraction angle 2θ=
A diffraction peak was observed at 43.3, and it was confirmed that both were BN thin films containing a c-BN structure. However, when examining the crystallinity from the diffraction intensity, the BN thin film of Example 2 was compared to the BN thin film of Comparative Example. c
It was confirmed that the -BN structure has excellent crystallinity.

In addition, the Knoop hardness (Hk) is expressed as the value of the Knoop hardness (Hk) for the ratio of the irradiation amount between the rare gas ions 6a made of Ar (argon) and the nitrogen ions 6b (hereinafter abbreviated as Ar/N ion ratio). As shown in FIG. 3, the Knoop hardness (Hk) of the BN thin film of the comparative example formed by irradiating the substrate 2 with only nitrogen ions 6b (Ar/N ion ratio = 0) is 1200 (kg/mm'). , whereas Ar
/N ion ratio to 0.1. 0.8. The Knoop hardness (Hk) of the BN thin films of Examples 1 to 3, which was set to 1.5, was 310
0.4200, 3000 (kg/mm2) and about 2.
The Knoop hardness (Hk) is 5 to 3.5 times higher, and the formation of a BN thin film with a hard c-BN structure is observed.

In addition, under the formation conditions of Example 2 and Comparative Example, the boron deposition rate was increased to 3.5 (input/5ee) and B/N
The Knoop hardness (Hk) was measured by forming a BN thin film under the same conditions as Example 2 and Comparative Example, except that the composition ratio was changed from 1 to 3,5, and the Knoop hardness (Hk) was compared to the B/N composition ratio. The hardness (Hk) is shown in FIG. 4 along with the values of Example 2 and Comparative Example.

As a result, the Knoop hardness (Hk
) becomes smaller, especially in the region where the B/N composition ratio is greater than 3, the difference in Knoop hardness (Hk) from the comparative example is small, and the Knoop hardness (Hk) when the B/N composition ratio of the comparative example is changed to 3 or 5 is small. Hardness (Hk) value (1450, 2450 (kg/Tou2))
When compared with the curve, the Knoop hardness (Hk) reverses when the B/N composition ratio reaches a boundary of about 4.6.

In this way, at the same time as the deposition substance 4 containing boron is deposited on the surface of the substrate 2, rare gas ions 6a consisting of Ar (argon) ions and nitrogen ions 6b are irradiated with an irradiation energy of 300 eV to change the B/N composition. When forming a BN thin film with a ratio of 1, the Ar/N ion ratio was set to 0.1 in Example 1.
In Example 2, it was set to 0.8, and in Example 3, it was set to 1.5. Therefore, the crystal structure of the formed BN thin film,
The structure is mainly based on the structure, and has a high Knoop hardness (Hk).
It is possible to form a BN thin film having .

〔Effect of the invention〕

The method for forming a boron nitride thin film of the present invention includes simultaneously depositing an evaporative material containing boron and at least one type of rare gas ion and nitrogen ions at a voltage of 100 eV to 500 eV.
The surface of the substrate is irradiated with an irradiation energy of V and an irradiation dose ratio of rare gas ions and nitrogen ions of 0.05 to 2°0, and the ratio of the number of particles of boron and nitrogen (B/N composition ratio) 0.
5 to 3.0, a boron nitride (BN) thin film having a c-BN structure as a main component and having high hardness can be formed at a low temperature.

In addition, since the irradiation energy value of rare gas ions and nitrogen ions is relatively low at 100 eV to 500 eV, the boron nitride (BN) thin film that is formed has very little damage or defects inside. ) A thin film can be formed.

Furthermore, since the gases supplied to the ion source and irradiated as ions are only rare gases and nitrogen gas, other active gases (hydrogen gas, etc.) used in the past are not used, and crystallization is even more effective. It is possible to form a boron nitride (BN) thin film with excellent properties and adhesion to the substrate.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of a thin film forming apparatus for the boron nitride thin film forming method of the present invention, Fig. 2 is a conceptual diagram of another thin film forming apparatus, and Fig. 3 is the Ar/N ion ratio of each example and comparative example. FIG. 4 is a graph of Knoop hardness (Hk) versus B/N composition ratio of Example 2 and Comparative Example. 2... Substrate, 3... Evaporation source, 4... Evaporation substance, 5
．． 5'...Ion source, 6a...Rare gas ion, 6b
...Nitrogen ion, 7.. Film thickness meter, 8.. Current measuring device. Figure 4 B/N composition ratio of ions/nitrogen ions

Claims (1)

[Claims] Simultaneously with the vapor deposition of an evaporative substance containing boron on the surface of the substrate, at least one type of rare gas ion and nitrogen ion are irradiated with an irradiation energy of 100 eV to 500 eV and a ratio of the irradiation amount between the rare gas ion and the nitrogen ion. 0.
Boron nitride (BN) formed by irradiation at 05 to 2.0
A method for forming a boron nitride thin film in which the ratio of the number of boron to nitrogen particles (B/N composition ratio) in the thin film is 0.5 to 3.0.