JP2861753B2 - Substrate coated with boron nitride containing film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to abrasion resistance, lubrication, moderate slidability, releasability and heat resistance of cutting tools, dies, optical element molding dies, magnetic heads and various sliding parts. The present invention relates to a substrate coated with a boron nitride-containing film capable of improving these properties and having good adhesion to the substrate on a substrate requiring one or more properties such as properties.

[0002]

2. Description of the Related Art Boron nitride (BN) has a crystal structure similar to cubic zinc blende type (c-BN), a structure similar to hexagonal graphite (h-BN), or hexagonal crystal. It is roughly classified into wurtzite type (w-BN) and the like. h-BN also has properties similar to graphite,
Since it has cleavage properties in the C-axis direction, it is soft but has excellent slidability. Currently, artificially synthesized powder is widely used as a solid lubricant to lower the friction coefficient of various sliding members. Have been.

[0003] Also, c-BN has the second highest hardness next to diamond, and is superior in thermal and chemical stability to diamond. Therefore, it is applied to fields requiring wear resistance such as cutting tools. In addition, it is used as a heat sink material by utilizing its features of insulating properties and high thermal conductivity. w-BN also has high hardness and excellent thermal and chemical stability, and like c-BN, has been applied to fields requiring wear resistance centered on tools.

[0004] h-BN is easily synthesized into a powder at low temperature, and various physical vapor deposition (PVD) methods and chemical vapor deposition (C
It is easily synthesized into a film by the VD) method. But,
Since c-BN and w-BN have been synthesized artificially under high temperature and high pressure, their production costs are extremely high, and the synthesized form is bulk. , Its application range was limited. Then, c
-An attempt to synthesize a thin film of BN and w-BN,
It is performed by various PVD methods and CVD methods.

As an example, an attempt to form a BN-containing film using a thermal CVD method will be described. A gas containing boron (B) and a gas containing nitrogen (N) as source gases in a reaction chamber in which a substrate is placed. By introducing a gas or the like containing the two elements and heating the mixture to a temperature close to 1000 ° C., the raw material gas is thermally decomposed, and an attempt was made to form a BN-containing film on the base using decomposition products. Although the h-BN-containing film was easily formed by the technique, the c-BN-containing film was not formed.

In the PVD method, for example, a method of sputtering a target made of BN by laser irradiation to form a BN-containing film on the opposing substrate surface has been attempted, but a c-BN-containing film is synthesized. Did not. However, in recent years, the raw material gas is turned into plasma by applying electric power to generate chemically active ions and radicals, and a chemical reaction on the surface of the substrate is promoted by these active particles to form a thin film by a plasma CVD method. BN-containing film or w-
BN-containing films have come to be formed.

[0007] This plasma CVD method has an advantage that a dense film can be obtained at a low temperature as compared with the thermal CVD method. Therefore, the hardness is deteriorated at a certain temperature or more, for example, in high-speed tool steel (high-speed steel). It can also be used in the case of using a substrate or a mold or the like that does not allow deviation in dimensional accuracy due to deformation at high temperature. However, a film formed by a plasma CVD method tends to have lower adhesion to a substrate than a film formed at a high temperature.

Recently, a film containing a B element is vacuum-deposited or sputtered to form a film on a substrate at the same time, alternately, or after the film is formed, and then irradiated with an ion species containing at least an N element. The vaporized atoms collide with the irradiated ions, the vaporized atoms are pushed into the substrate, and recoil in the substrate, forming a mixed layer of the constituent atoms at the interface between the substrate and the film. It has been found that the adhesion to the film is improved. According to this method, as a result of collision between the evaporated atoms and the irradiated ions, the evaporated atoms are excited, and c-BN and w-BN are synthesized in a non-thermal equilibrium at a low temperature.

[0009]

However, although the c-BN film and the w-BN film are synthesized with good adhesion to the substrate at a low temperature by this method, they are coated with the c-BN or w-BN film. When the substrate is put to practical use, especially when the substrate slides or comes into contact with other articles to cause friction and wear, the adhesion is sufficient to withstand long or repeated use. The property has not been obtained, and it has not yet been put to practical use in industry.

Accordingly, the present invention provides a BN-containing film having high hardness, excellent chemical stability, and good adhesion to various substrates, thereby providing abrasion resistance, sliding performance, release performance, and the like. An object of the present invention is to provide a substrate excellent in the above.

[0011]

Means for Solving the Problems The present inventor has conducted studies to solve the above-mentioned problems, and has found the following facts. Since c-BN and w-BN have high hardness among BN having various crystal structures, the hardness of the base is improved by coating with a film containing these. However, c-BN and w-BN generate excessive internal stress during film formation and are chemically stable, so that a film containing them has poor adhesion to a substrate. Therefore, if B atoms that are not bonded to N atoms are mixed into the c-BN or w-BN-containing film, the internal stress is eliminated, and the film leaks to the substrate.
The adhesion of the film to the substrate is improved.

On the other hand, the chemical stability of the film, such as heat resistance, is reduced by the incorporation of B atoms. Therefore, the substrate coated with the BN-containing film further includes a B atom which is not bonded to N atoms. Need to be coated with a BN-containing film containing no. However, since the inner film containing B atoms and the outer film not containing B atoms have greatly different crystal structures, the outer film is easily peeled off.

Therefore, c-BN or w-BN is provided between the two films.
By forming an intermediate film containing at least one of the above and h-BN in addition to the B atoms not bonded to the N atoms, peeling of the outer film is prevented. This is because the outer membrane is h-
When BN is included, the intermediate film contains a material having the same structure as the outer film and a material having the same structure as the inner film, thereby alleviating the mismatch between the outer film and the inner film. This is because the internal stress generated at the time is reduced.

Further, the outer membrane does not contain h-BN, and c-
When at least one of BN and w-BN is included, the outer film is brittle, and generally, when a substrate coated with such a film is used in a field where abrasion resistance is required, the outer film becomes more fragile. Cracks are easily formed in the film. However, in the present invention, also in this case, the outer film is prevented from peeling off by forming the intermediate film. The reason is that the h-BN contained in the intermediate film
In the crystal, the C planes of the crystal are connected by van der Waals force, and when stress is applied from the outside, the C planes are displaced to relieve the stress. This is because the stress applied to the outer layer is relaxed to prevent the outer film from cracking, and as a result, the adhesion of the outer film to the substrate as a whole can be improved.

Based on the above findings, the present invention relates to a substrate coated with a BN-containing film, wherein at least one of a B atom not bonded to an N atom, c-BN and w-BN is provided on the substrate. Is formed, a film containing at least one of c-BN, w-BN, and h-BN, and a B atom that is not bonded to an N atom, is formed thereon, and c is further formed thereon. A substrate coated with a BN-containing film, wherein a film containing at least one of BN, w-BN, and h-BN and containing no B atom bonded to an N atom is formed. Is what you do.

It is desirable that the number ratio of B atoms to N atoms (B / N composition ratio) contained in the BN-containing film decreases in order from the inner film to the outer film. As a result, the B / N composition ratio does not greatly differ between the inner film and the intermediate film and between the intermediate film and the outer film, and the adhesion between the respective BN-containing films and further the adhesion between the films and the substrate can be further improved. it can. In addition, as a manufacturing method of the said base, the following can be considered, for example. .

That is, the substrate is supported by a holder in a vacuum chamber for film formation, and a substance containing a B element is applied to the substrate by vacuum deposition and / or sputtering.
Irradiating ions from the ion source alternately or after the application, B
An N-containing film is formed on the substrate. As the B element-containing substance used in the method, in addition to B alone,
One or more of B compounds such as boron oxide, boron nitride, boron carbide, boron sulfide, phosphorus boride, borohydride, and various metal borides are used.

The ion species used in the above method may be any as long as it acts on evaporated B atoms to form a BN film.
For example, N atom ions, N molecule ions, nitrogen compound ions such as ammonia ions (NH ₃ ⁺ ), B compound ions such as boron nitride ions (BN ⁺ ), and ion species containing these N elements include argon. A mixture of an inert gas ion such as an ion (Ar ⁺ ) and a hydrogen atom ion (H ⁺ ) is used.

The crystal structure of BN formed in each film,
The control of the crystallinity of N and the B / N composition ratio are controlled by the ratio of the number of B atoms to the number of N atoms reaching the substrate (B / N transport ratio),
This is performed by appropriately combining the conditions of the ion species, the acceleration energy of the irradiation ions, and the current density. The B / N transport ratio is desirably from 0.5 to 60. If the B / N transport ratio is less than 0.5, the collision of the irradiated ions with the evaporating substance becomes excessive and the number of defects in the film increases. Stability decreases. When it is larger than 60, it is contained in the film,
Since the proportion of B atoms that do not bond to N atoms increases, and the proportion of BN contained in the film decreases accordingly, various properties of BN cannot be sufficiently exhibited. By controlling the B / N transport ratio so that the B / N composition ratio becomes greater than 1, B atoms that do not bond to N atoms can be generated in the film.

The B / N transport ratio is controlled by, for example, monitoring the amount of vapor deposition on the substrate by using a film thickness monitor such as a quartz crystal film thickness meter, for example, by using a Faraday cup having a secondary electron suppressing electrode. It can be performed by monitoring the amount of ion irradiation on the substrate using an ion current measuring device. As these ion species, these N
When a mixture of an inert gas ion such as an argon ion (Ar ⁺ ) and a hydrogen atom ion (H ⁺ ) with an ion species containing an element is used, the B atom can be further excited, and c-BN, This is advantageous for the synthesis of w-BN.

The acceleration energy of the irradiation ions is preferably larger than 50 eV and smaller than 40 KeV. 50e
If it is smaller than V, the thickness of the mixed layer formed at the interface between the substrate and the film and between the films by the ion irradiation becomes small, and the two layers sandwiching the mixed layer cannot be sufficiently adhered. On the other hand, when it is larger than 40 KeV, defects in the film increase, and the hardness and chemical stability of the film decrease.

When the acceleration energy is increased within the above range, the formation amount of h-BN and a-BN increases, and when the acceleration energy is reduced, the formation amount of c-BN and w-BN increases. In the above method, when synthesizing c-BN, w-BN and h-BN, B having an amorphous structure is used.
Although N (a-BN) is easily mixed, the mixed a-BN does not hinder the function of the BN-containing film of the present invention. Even if each of the above-mentioned BN-containing films is formed to contain a-BN. Good.

For example, in order to enhance the crystallinity, a mixture of nitrogen ions and inert gas ions is used as the irradiation ion species, or as described above, the acceleration energy of the irradiation ions is set to a low value of 2 KeV or less. Use things. However, when a mixture of nitrogen ions and inert gas ions is used, the number of gas systems connected to the ion source increases accordingly, increasing the cost required for the apparatus and complicating gas flow control and film formation operations. And the labor required to ensure the reproducibility of the film increases. Further, when the acceleration energy of the irradiation ions is set to a low value of, for example, 2 KeV or less, the adhesion between the film and the base is inferior to the case where ions having a high acceleration energy are used. Therefore, in order to improve the adhesion, it is desirable that the acceleration energy is increased only when forming a film near the interface between the substrate and the film, and then the acceleration energy is sequentially switched to a lower acceleration energy. However, in this case, the voltage range of the power source used for the ion source is wider than in the case where all the steps of ion irradiation are performed with high acceleration energy.
The cost required for the apparatus is increased, and the film forming operation is complicated.

Therefore, allowing a-BN to be mixed into the film is simpler in the structure of the apparatus and facilitates control during film formation, so that the production cost can be reduced or the production efficiency can be improved. can do. Therefore, in the production of the substrate of the present invention, it is preferable to aggressively mix a-BN, especially when priority is given to reducing the production cost and increasing the production efficiency. The mixing amount of a-BN is not particularly limited as long as it is within a range where each BN film can be confirmed to have a desired crystal structure.

The angle of incidence of ions on the substrate is not particularly limited, and the film may be formed while rotating the substrate. There is no particular limitation on the type of the ion source, for example, a Kauffman type,
A bucket type or the like is conceivable. Further, for a substrate for which thermal damage must be sufficiently avoided, it is preferable to form a film while cooling the substrate by cooling the substrate holder with water.

The material of the base is not particularly limited, and may be, for example, a material made of various ceramics, metals, or polymers.

[0027]

The substrate coated with the BN-containing film of the present invention comprises
The N-containing film has three layers, of which the inner film in contact with the substrate is a film containing B atoms and at least one of c-BN and w-BN, and the outer film is c-BN, w-BN, h −
A film containing at least one of BN, and the intermediate film is a film containing at least one of B atoms, c-BN and w-BN, and h-BN,
The outer film of the film has excellent chemical stability, the inner film has high hardness, and has good adhesion to the substrate.
Since the intermediate film containing h-BN having an intermediate structure of the N-containing film and having a cleavage property in the C-axis direction improves the adhesion between the two films, the substrate as a whole is high in hardness and chemically stable It is covered with a BN-containing film having excellent adhesion and good adhesion to the substrate. Even if the BN crystal contained in the outer film is only h-BN, since the BN-containing film formed thereunder has a high hardness, the substrate is entirely covered with the BN-containing film having a high hardness. It was done.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged sectional view of a part of a substrate according to one embodiment of the present invention, and FIG. 2 shows a schematic configuration of a film forming apparatus used for manufacturing the substrate. In FIG. 2, 1 is a substrate, 2
Is a holder for supporting the base 1, 3 is an evaporation source for evaporating a substance containing a B element, 4 is an ion source for irradiating ions, 5 is the number of B atoms deposited on the base 1 and its thickness. Is a film thickness monitor for measuring the number of ions, and 6 is an ion current measuring device for measuring the number of ions applied to the substrate 1. These are accommodated in the vacuum container 7. The inside of the container 7 can be set to a desired degree of vacuum by the exhaust device 8.

In producing the substrate according to the present invention, the substrate 1 is first supported on the holder 2 and then the vacuum vessel 7 is prepared.
The inside is set to a predetermined degree of vacuum. After that, using the evaporation source 3, the B element-containing substance 3 a is vacuum-deposited on the base 1 by means such as an electron beam, a resistor, a laser, or a high frequency. Instead of the vacuum deposition, a film may be formed on the base 1 by sputtering the B element-containing substance 3a by means of an ion beam, a magnetron, a high frequency or the like.

Simultaneously or alternately with the vacuum deposition (or sputtering) of the B element-containing substance 3a, or after the deposition (or sputtering), ions 4a are irradiated from the ion source 4 onto the deposition surface. By the film forming operation described above, as shown in FIG. 1, B atoms not bonded to N atoms
And an inner film 11 containing at least one of c-BN and w-BN is formed, and a B atom which is not bonded to an N atom, and at least one of c-BN and w-BN, and h An intermediate film 12 containing -BN is formed,
Further, an outer film 13 containing at least one of c-BN, w-BN, and h-BN is formed outside thereof.

B formed in each of the films 11, 12 and 13
The control of the crystal structure of N, the degree of crystallinity of the BN, and the B / N composition ratio are performed by controlling the ratio of the number of B atoms to the number of N atoms reaching the substrate (B / N transport ratio), the ion species, and the irradiation ions. The acceleration energy and the current density conditions are appropriately combined. In the substrate 1 coated with the films 11, 12, and 13, the film 11 has high hardness by containing c-BN and / or w-BN, and has high hardness by containing B atoms.
Film 13 is excellent in adhesion to c-BN or w-BN.
In the case of containing h-BN, excellent hardness is obtained, and in the case of containing h-BN, the chemical stability is excellent in any case. Even when the film 13 contains only h-BN of the BN crystal, the films 11 and 12 have high hardness, so that the substrate as a whole has high hardness. The film 12 is the film 1
1 and 13, both membranes 11
And 13 can be improved in adhesion. When the outer film 13 does not contain h-BN, the film 13 is brittle and easily cracks.
BN relaxes the stress applied from the outside to prevent this crack from occurring, and can improve the adhesion of the film 13 and thus the entire film to the substrate 1. Accordingly, the substrate 1 is covered with films 11, 12, and 13 having high hardness, excellent chemical stability, and good adhesion to the substrate 1.

Next, a specific example of the method of manufacturing the substrate of the present invention using the film forming apparatus shown in FIG. 2 and a substrate coated with a BN-containing film obtained by the method will be described. Example A high-speed tool steel (SKH-5) was manufactured using the apparatus shown in FIG.
Substrate 1 consisting of 1) (25 mm × 25 mm × thickness 3 m)
m) is placed on the substrate holder 2 and the inside of the vacuum vessel 7 is 5 × 10
^The degree of vacuum was set to ^-7 Torr. Thereafter, the 99.9% pure boron pellet 3a was vaporized using the electron beam evaporation source 3 to form a film on the substrate 1. At the same time, nitrogen gas having a purity of 5N (99.999%) is introduced into the ion source 4 until the inside of the vacuum vessel 7 reaches 5 × 10 ⁻⁵ Torr, and ionized, and the ions 4a are accelerated at an acceleration energy of 20 KeV to the substrate 1. The substrate 1 was irradiated at an angle of 0 ° with respect to the normal line set in the above. Note that a bucket type ion source using a caps magnetic field was used as the ion source.

In the film forming operation, the B / N transport ratio is adjusted in consideration of the sputtering efficiency of boron atoms by nitrogen ions and the like so that the B / N composition ratio becomes 35. The film 11 was formed. Next, B pellets having a purity of 99.7% were used as evaporating substances,
The B / N transport ratio was adjusted so that the B / N composition ratio became 15 under the same conditions as when the film was formed.
An nm film 12 was formed.

Further, B having a purity of 99.7% as an evaporating substance
Using a pellet, the B / N transport ratio is adjusted so that the B / N composition ratio becomes 1 under the same conditions as when the film 11 was formed, and a film 13 having a thickness of about 500 nm was formed on the film 12. did. In order to examine the crystal structure of BN in each film formed in the above-described embodiment and the bonding state of B atoms in the film, the films 11, 12, and 13 in the embodiment were individually formed on the same substrate as in the embodiment. BN of the same thickness (500 nm)
The structure of the film was analyzed by infrared absorption spectroscopy (IR) and photoelectron spectroscopy (XPS).

According to IR, the crystal structure of BN contained in each film is such that the film 11 contains only c-BN and the film 12 contains c-BN.
BN and h-BN were contained, and the film 13 contained only h-BN. According to the XPS, the film 11 and the film 12
Had a B atom not bonded to an N atom. As a result of both analyses, the structure of each of the films was as follows.

Film 11: c-BN + B atoms (B / N composition ratio = 35) Film 12: c-BN + h-BN + B atoms (B / N composition ratio = 15) Film 13: h-BN only (B / N composition ratio) = 1) Since only the crystal structure affects the characteristics of the film-coated substrate, the crystallinity of each crystal structure, that is, the content of a-BN was not analyzed.

The hardness and the film adhesion of the substrate according to the example and the substrates (comparative examples 1, 2, and 3) in which the films 11, 12 and 13 in the above example were individually coated were measured. However, the following results were obtained. The hardness is 1
Using a scratch tester with an AE sensor using a diamond indenter, the film was scratched while increasing the load continuously from 0, and the load at which the AE signal rapidly rose was measured using a scratch tester with an AE sensor using a diamond indenter. The peeling load was evaluated based on the magnitude of the value.

Hardness (Kg / cm ² ) Adhesion (N) Example 3500 30 Comparative Example 1 3500 30 Comparative Example 2 2800 26 Comparative Example 3 1200 15 The substrate according to the example and the substrate according to the comparative example 1 have high hardness,
The substrate according to Comparative Example 2 was coated with a film having high adhesion, and the substrate according to Comparative Example 2 was coated with a film having substantially the same adhesiveness as the substrate according to the example, but the hardness was inferior to the substrate according to the example, The substrate according to Comparative Example 3 was inferior in both hardness and adhesion to the substrate according to the example.

Next, the substrates according to Examples and Comparative Examples 1 to 3 were exposed to an air atmosphere at 700 ° C. for 3 hours, and the oxidation state of the film was examined. The oxidation state was determined by examining the state of the photoelectron peak of the B atom by XPS, and the following results were obtained. Examples Not oxidized. Comparative Example 1 Oxidized.

Comparative Example 2 Oxidized. Comparative Example 3 Not oxidized. The substrates according to Comparative Examples 1 and 2 had inferior oxidation resistance as compared with the substrates according to Example and Comparative Example 3. From the above results, it can be seen that the substrates according to the examples are excellent in all of chemical stability, hardness and adhesion.

[0041]

According to the present invention, the BN-containing film having high hardness, excellent chemical stability, and good adhesion to various substrates has abrasion resistance and sliding performance. And a substrate excellent in mold release performance and the like. Further, a is contained in the film to such an extent that it does not hinder the above-mentioned effects.
By mixing -BN, production cost can be reduced and production efficiency can be increased.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a part of an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a film forming apparatus used for manufacturing the base shown in FIG.

[Description of Signs] 1 Base 11 Inner film 12 Intermediate film 13 Outer film 3 Evaporation source 3a Deposition material 4 Ion source 4a Ion 5 Film thickness monitor 6 Ion current measuring instrument 7 Vacuum container 8 Exhaust device

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-247627 (JP, A) JP-A-5-247625 (JP, A) JP-A 5-2855062 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C23C 14/00-14/58 C01B 21/064

Claims (2)

(57) [Claims] 1. A substrate coated with a boron nitride-containing film, the substrate comprising at least one of a boron atom not bonded to a nitrogen atom and at least one of a cubic zinc blende type and a hexagonal wurtzite type. A film containing boron nitride having a crystal structure is formed, on which a boron atom not bonded to a nitrogen atom, and at least one crystal structure of a cubic zinc blende type and a hexagonal wurtzite type are formed. A film containing boron nitride having a crystal structure similar to that of boron nitride and hexagonal graphite is formed, and on top of this a film similar to cubic zinc blende type, hexagonal wurtzite type, and hexagonal graphite Containing boron nitride having a crystal structure of at least one of the following types, wherein a film containing no boron atoms not bonded to nitrogen atoms is formed. Substrate coated with a membrane. 2. The substrate coated with the boron nitride-containing film according to claim 1, wherein each of the boron nitride-containing films contains boron nitride having an amorphous structure.