JP2963455B1 - Method for forming boron nitride film - Google Patents

Abstract

An object of the present invention is to provide a film forming method for forming a long-life cubic boron nitride film having excellent adhesion, excellent wear resistance and strength on a substrate of cemented carbide or high-speed steel. SOLUTION: Ti is provided on a substrate 1 subjected to a bombardment process.
After the N film 2 is formed, a Ti film, a B film, and a third buffer film I composed of a BN film having a stepwise changed composition ratio are covered, and then a cBN film 4 is formed thereon.
A cubic boron nitride film having excellent adhesion to the substrate 1 and a long life is obtained.

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 cubic boron nitride film, and more particularly to a method for forming a cubic boron nitride film having a high hardness, a low friction coefficient,
A cubic boron nitride film, which has better properties such as heat resistance than other materials, is applied to the surface of tool members such as cutting tools and wear-resistant tools to achieve a longer life of these members. The present invention relates to a method for forming a crystalline boron nitride film with good reproducibility.

[0002]

2. Description of the Related Art Cubic boron nitride (cBN) has the second highest hardness next to diamond, has excellent thermal and chemical stability, and has lower reactivity with iron-based materials than diamond. Therefore, the cBN sintered body obtained by sintering under ultra high pressure and high temperature is cut into a suitable size by a wire electric discharge machine, brazed to a carbide tip, end mill, etc. for cutting. It is used as a tool and as a material for wear-resistant articles.

However, as described above, the production of a cBN compact requires synthesis at an ultra-high pressure and high temperature, so that it is difficult to obtain a complex-shaped one, and the mass productivity is low.
In addition, the production range is extremely limited because of the high production cost and the like. Further, since the processing step is complicated and the processing temperature is high, it has not been widely used because it cannot be applied to high-speed steel small tools which are mass-produced tools.

[0004] Therefore, in order to take advantage of the above-mentioned properties of cBN, a molded body having a low-cost and improved abrasion resistance and corrosion resistance of the substrate is formed by forming a coating layer of cBN on the surface of the substrate. Attempts to gain are widely made. Such cBN coating is attempted to deposit a cBN film on the surface of a base material by a CVD method, a PVD method, or the like.
Coating by vapor phase synthesis of cBN has become industrially possible.

[0005]

The cBN film obtained by the above-mentioned vapor phase synthesis method has a large internal stress irrespective of the production method, so that it tends to peel off after the film formation. If it exceeds 1 μm, it will peel off. In order to prevent such cBN film peeling,
For example, in Japanese Patent Application Laid-Open No. H8-60339, a Ti film is formed as an intermediate layer at the interface of the base material, and thereafter, boron ion plating is performed while changing the nitrogen composition to form a gradient layer of boron and nitrogen. CBN via graded layer
A method of obtaining a cBN film of about 0.5 μm by forming a layer has been proposed.

However, cBN by such a film forming method is used.
With a film, it is difficult to obtain a practical adhesion strength because peeling occurs in a cutting test.

As a countermeasure for improving the adhesion of the cBN film to the base material, Japanese Patent Application Laid-Open No. H8-60339 described above discloses a method in which boron ions are implanted into a cBN layer formed via an inclined layer, and then the temperature is increased to about 800 ° C. Japanese Patent Application Laid-Open No. 9-95774 discloses a method of annealing a boron-excess boron nitride film formed on a substrate in a nitrogen or inert gas atmosphere at 200 to 1000 ° C.
Japanese Patent Application Laid-Open No. 8-165558 proposes a method of forming an intermediate layer of titanium nitride and boron carbide on the surface of a substrate. Further, Japanese Patent Application Laid-Open
Japanese Patent No. 18025 discloses that a mixing layer of titanium nitride and boron nitride is formed by simultaneously depositing boron by ion implantation and injecting a nitrogen gas and an inert gas onto an intermediate layer made of a titanium nitride film provided on a base material. A method for doing so is disclosed.

[0008] Among the cBN films formed on the base material by the above-mentioned methods, there are some which have no abnormality in the cutting test.
The temperature conditions, such as temperature rise near the ion source, substrate heating, and annealing treatment, exceed 500 ° C., and the hardness of high-speed steel cannot be maintained. It is assumed that.

The cBN film has a thickness of 0.8 to 1.0 μm.
At m, the cBN structure tends to change. Therefore, when the cBN film is a thick film of 1.0 μm or more, cB
The characteristics of the N film may be degraded. Also, the cBN film is
It is an aggregate of cBN microcrystals and may contain grain boundary impurities at crystal grain boundaries, and these grain boundary impurities are said to be weak in weather resistance. For this reason, in the case where the cBN film is deposited on the outermost surface by the method described above, there is a problem that the cBN film on the outermost surface is gradually deteriorated due to the influence of humidity in the air, the volume is expanded, and the cBN film is peeled off. is there.

In view of the above, the present invention provides a method for cBN on a substrate.
In forming the film, as a result of studying to improve the adhesion of the cBN film to the substrate interface and to improve the weather resistance,
A general-purpose tool material can be obtained by interposing an N film and further changing the film formation conditions to several stages by changing the film formation conditions to several stages in place of the conventionally known gradient composition layer or mixing layer. It is intended to provide a film forming method capable of coping with high-speed steel.

[0011]

According to the first aspect of the present invention,
a: a step of bombarding the substrate; b: a step of forming a Ti film and / or a TiN film on the interface of the bombarded substrate; c: the Ti film and / or TiN
Ti film, B film on the film and B with composition ratio changed stepwise
A method for forming a boron nitride film, comprising: a step of forming a buffer film I made of an N film; and d: a step of forming a cBN film on the buffer film I.

According to a second aspect of the present invention, a: a step of performing a bombarding process on the substrate; b: a step of forming a Ti film and / or a TiN film on the interface of the substrate subjected to the bombarding process;
c: Ti film, B on the Ti film and / or TiN film
A step of forming a buffer film I made of a BN film having a composition ratio changed stepwise and a step of forming a cBN film on the buffer film I are repeated a plurality of times to form a multilayer film of cBN. In this case, a method of forming a boron nitride multilayer film is characterized in that a step of forming a buffer film II composed of a B film and a Ti film is interposed in forming a TiN film on a cBN film in this repeated step.

According to a third aspect of the present invention, in the film forming method according to the second aspect, the outermost surface is replaced with TiN instead of a cBN film.
It is characterized in that it is a film. According to a fourth aspect of the present invention, in any one of the film forming methods of the first to third aspects, the TiN film has an odd multilayer structure of three or more layers.

According to the first aspect of the present invention, in forming a boron nitride film on a substrate, first, a Ti film and / or a TiN film is formed on a bombarded substrate, and then a T film is formed.
A buffer film I composed of an i film, a B film, and a BN film having a composition ratio changed stepwise is formed, and then a cBN film is formed thereon. The TiN film is used to measure the adhesion to the substrate. In addition, the formation of the buffer film I composed of a Ti film, a B film, and a BN film in which the composition ratio is changed stepwise is performed by directly forming the buffer film I on the TiN film.
When a BN film is formed, it is intended to prevent a phenomenon that peeling is likely to occur at the interface between the two in the atmosphere. Further, the composition ratio is changed stepwise after the Ti film and the B film as the buffer film I. Forming a BN film, the cB
By setting the B / N ratio of the BN film at the interface where the N film is formed to a composition close to 1, it is possible to obtain higher practical adhesion to the cBN film.

According to a second aspect of the present invention, there is provided a method of forming a cBN multilayer film by repeating the film forming method of the first aspect.
Buffer film II consisting of B film and Ti film between film and TiN film
This improves the adhesion between the cBN film and the TiN film, thereby enabling a multilayer structure of the cBN film.

This is because when the cBN film has a thickness of about 0.8 to 1.0 μm, it tends to become a thin film having a structure different from the cBN structure. Therefore, in order to obtain a practically applicable cBN film while maintaining the cBN structure, it is desired that the film thickness be up to about 0.8 μm. Therefore, in the present invention, TiN / B having a thickness of 0.5 to 2.0 μm is used.
By using a multilayer laminate structure with N as a basic unit, 0.5 to
A multilayer film of 20 μm can be obtained.

According to a third aspect of the present invention, the boron nitride film obtained in the second aspect of the present invention has a cBN film as the outermost surface layer, and as described above, there is a possibility that the boron nitride film is peeled off due to deterioration of weather resistance. The film is covered with TiN film and cBN
It is intended to improve the weather resistance by preventing the film from being directly exposed to the atmosphere.

According to a fourth aspect of the present invention, the TiN film formed in the first to third aspects of the present invention has a multilayer structure having three or more odd-numbered crystal structures different from each other, thereby eliminating surface roughness due to crystal grains. The effect of filling the pinhole in the film can be achieved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a film forming method according to the present invention will be described. The method of the present invention can be performed by various ion plating methods such as an arc discharge type ion plating method, a reactive ion plating method, and a magnetic field excitation type ion plating method. Particularly preferred is a magnetic field excitation type ion plating method in which the steps up to the film formation step can be performed by one apparatus.

FIG. 5 shows an example of an apparatus used in such a magnetic field excitation type ion plating method. The substrate 1 is mounted on a substrate holder 32 in a vacuum chamber 21. An etching prevention plate 33 is provided below. The lower evaporation source 22 in the vacuum chamber 21 is provided with a crucible 24 containing an evaporation material 23 and an electron gun 25 for heating and evaporating the evaporation material 23.

A cathode 41 for emitting thermoelectrons and an anode 43 facing the cathode 41 are provided below the substrate 1, and a pair of magnets 46a and 46b accommodated in the parallel magnetic field generating magnets 46a and 46b are located in the same horizontal plane. Magnet 45a,
45b are disposed, and the magnet case 46 is provided.
Inverted L-shaped yokes 47a, 47b for increasing the uniform magnetic flux density distribution in the vicinity of the substrate 1 are provided on the back surfaces of the substrates a, 46b. Reference numeral 48 denotes a mesh plate made of an iron-based material.

After the vacuum chamber 21 is evacuated, Ar gas or the like is introduced from the gas nozzle 38, a voltage is applied to the cathode 41 and the anode to generate plasma between the magnets 45a and 45b, and at the same time, an electron beam as an evaporation source 26 is operated to evaporate the evaporation material, and the high-frequency power 3 applied to the substrate 1
4, the evaporating material 23 is formed on the substrate 1 as a reaction product film.

In the above method, when a boron nitride film is formed on a substrate, bombardment is performed for cleaning the substrate. In the present invention, in order to make the cleaning effect remarkable, the following order is used. Perform three types of bombard.

(A) Glow discharge bombard: Ar gas, H ₂ gas or a mixed gas of Ar + H ₂ is introduced into a vacuum chamber in which a substrate has been set and evacuated, and the substrate is subjected to high frequency or negative voltage applied to the substrate. Glow discharge is caused between the vacuum walls to clean the substrate surface for 10 to 20 minutes. (B) High vacuum bombard: 4 to 8 × introduced into vacuum chamber
An Ar gas of 10 ^-2 Pa is discharged between an anode on which a parallel magnetic field is superimposed and a cathode which is a thermionic emission filament, and a high frequency or negative voltage applied to a substrate by Ar ions generated by this discharge is applied to the substrate. Clean the surface for 10-20 minutes. (C) Ti bombard: In a vacuum chamber having a high vacuum of about 1 × 10 ⁻³ Pa, Ti in the crucible is evaporated by an evaporation source, and Ar gas of 1 to 3 × 10 ⁻² Pa is introduced. Ar
A gas or Ti is discharged between an anode on which a parallel magnetic field is superimposed and a cathode which is a thermionic emission filament, and the high frequency or negative voltage applied to the base material mainly by Ti ions generated by this discharge is applied to the substrate surface. Clean for 3-10 minutes.

When a boron nitride film is formed on a substrate by the method of the present invention, first, a Ti film and / or a TiN film are formed on the interface of the substrate. And / or apply the characteristics of the TiN film, and by this formation, the adhesion characteristics of the cBN film, which varies depending on the type of the substrate, can be avoided. In addition, by forming the TiN film, there is an advantage that a technique already established as a technique for improving the adhesive force at the substrate interface can be used. Further, under the conditions for forming a cBN film according to the method of the present invention, since the distance between the ion source and the substrate is short, the etching power of the substrate by the generated ions is large, and the etching resistance of the thin film formed at the substrate interface is emphasized. Also in this regard, the TiN film is excellent.

The TiN film is also used as the outermost surface layer in the film forming method of the present invention from the viewpoint of weather resistance. However, this TiN film layer needs to maintain pinholes and smoothness in the film. is there. For this purpose, TiN having different crystal structures is used.
If the layers are alternately stacked, the surface roughness due to crystal grains is reduced, and the effect of filling pinholes can be expected. For this reason, the TiN film has a thickness of 0.2 to 1.0.
μm, an odd-numbered multilayer structure of 3 to 9 layers, an odd-numbered layer having a composition ratio of Ti: N of 1: 1, and an even-numbered layer having a number of N less than 1 are arranged.

On the substrate on which the TiN film is thus formed,
Cannot directly form a cBN film due to the problem of adhesion.
Then, Ti film, B film, BN film with composition ratio changed step by step
The cBN film is formed after the buffer film I
You. This BN film is formed by forming a B film after forming a Ti film.
To form a buffer film that slopes the composition ratio of B and N from 0 to 1.
In the method of forming, the hBN layer which is easily peeled is formed.
Avoiding the easily peelable hBN layer
Ar gas and N after the formation of the B film for the purpose of _Twogas
Flow rate ratio, substrate bias (high frequency power) amount, deposition time
By controlling in four stages, B / N becomes higher as the layer becomes higher.
= 1 is formed. Thus formed
Form a 0.3-0.8 μm cBN film on the buffer film I
Thus, the boron nitride film of the present invention is obtained.

When the cBN film has a thickness of about 0.8 to 1.0 μm, the film tends to have a structure different from the cBN structure. To obtain a practically applicable cBN film while maintaining the cBN structure, the thickness is 0.8 μm.
It is desired to be up to the extent. Therefore, in the present invention, a multilayer film of 0.5 to 20 μm can be obtained by forming a multilayer structure having a basic unit of TiN / BN having a thickness of 0.5 to 2.0 μm. In this case, if the TiN film is formed directly on the cBN film, the peeling of the TiN film occurs as described above. However, by forming the buffer film II composed of the B film and the Ti film on the cBN film, This enables a film to be formed.

[0029]

Next, the present invention will be described in detail with reference to examples. Example 1 A high-speed steel straight drill having a diameter of 3.4 mm was used as a substrate, and the straight drill was used to form a boron nitride film in the following order using, for example, a film forming apparatus (magnetic field excitation type ion plating apparatus) shown in FIG. A film was formed. The material used is 99.
9% pure boron, 99% pure titanium, 99.99%
Purity of Ar, and 99.99% pure N _2.

(A). Substrate cleaning The above-mentioned drill was attached to the substrate holder 22 in the vacuum chamber 21 as the substrate 1 and the inside of the chamber was evacuated to 2 × 10 ⁻⁴ Pa,
After maintaining the substrate temperature at 250 ° C., first, the following three types of bombarding were successively performed as substrate cleaning. (1) Glow discharge bombard: Ar of 2.5 to 40 Pa
A gas was introduced, a glow discharge was caused between the substrate and the vacuum wall by high-frequency power of 100 to 200 W applied to the substrate, and the surface of the substrate was cleaned for 20 minutes. (2) High vacuum bombard: Then, 6.7 × 10 ^-2 Pa
Ar gas was introduced into the tank, and a discharge was applied between the anode voltage of 65 V applied in the parallel magnetic field and the cathode of 300 W to produce an anode current of 15 A. The Ar ions generated by this discharge applied 200 W to the substrate. 300W
The surface of the substrate was cleaned with the high-frequency power. (3) Ti bombard: Ti is heated and evaporated with a 5.5 kW electron gun, an Ar gas of 2.0 × 10 ⁻² Pa is introduced, and an anode voltage of 65 V applied in a parallel magnetic field, and 3
Due to the Ti ions ionized by the discharge having the anode current of 15 A between the cathodes of 00 W, 360
Cleaning was performed for 2 minutes by applying a high frequency bias of W (FIG. 1A).

(B). Next, a TiN film 2 was formed on the surface of the substrate 1 cleaned as described above as follows. That is, 5.5k of Ti
2.0 × 10 ^-2 Pa by heating and evaporating with a W electron gun 25
Is introduced from the gas nozzle 38, and a discharge is applied between the anode 43 applied with 50 V in a parallel magnetic field and the 300 W cathode 41 so as to have an anode current of 20 A to ionize Ti. (RF) 34 was applied, and N ₂ gas was introduced for 3 minutes to form a 0.3-0.7 μm TiN film 2 as shown in FIG. The TiN film was supplied at a rate of 150 mL / min for the first minute and the next 1 minute for the introduction amount of the N ₂ gas for 3 minutes.
75mL / min per minute, and 150m for the last minute
By changing it to L / min, as shown in FIG. 2 (a), the intermediate layer 2b has a higher N than the upper and lower layers 2a, 2c.
_The three-layered TiN film ₂ having a small amount of _two was formed.

(C). Formation of cBN film (C) -1 Formation of buffer film I When a cBN film having a thickness of 0.1 μm or more is formed on the substrate 1 on which the TiN film 2 is formed, the TiN film and the cBN film are In order to maintain the adhesion, a Ti film, B
Film, consisting of a BN film with a composition ratio changed step by step
A 0.3 μm buffer film I (FIG. 2 (b)) was formed 3 in the same manner as the above-mentioned TiN film formation, but under the following conditions (FIG. 1 (c)). Conditions for Ti film formation: Ti gun electron gun output 5.5 kW Anode voltage 50 V Anode current 10 A Cathode current 300 W Introduced Ar gas pressure 2.0 × 10 ^-2 Pa RF output 200 W Film formation time 15 seconds Conditions for B film formation : Electron gun output of B 6.0 kW Anode voltage 40 V Anode current 10 A Cathode current 300 W Introduced Ar gas pressure 6.7 × 10 ^-2 Pa Introduced Ar gas amount 12 mL / min RF output 150 W Film forming time 15 seconds Composition ratio is stepwise The film formation conditions of the BN film changed to
After the film was formed for 15 seconds, N ₂ gas was simultaneously introduced at the same pressure as the Ar gas pressure, and the flow rate ratio, RF output and film formation time of the _two were set as follows: N ₂ : Ar = 1: 1, RF = 220 W, 15 seconds N ₂ : Ar = 1.5: 1, RF = 220 W, 15 seconds N ₂ : Ar = 1.5: 1, RF = 250 W, 45 seconds N ₂ : Ar = 1.5: 1, RF = 300 W, 120 seconds, so that as the BN layer formed on the B film layer goes from the lower layer to the upper layer, the amount of N _{2 is} increased to form a boron-excess amorphous BN. By using a BN film whose outermost surface is close to B / N = 1, it is possible to sufficiently maintain the adhesion to the cBN film formed on this layer.

(C) -2. Next, the electron gun output of B is 6.0 kW, the anode voltage is 40 V, the anode current is 10 A, the cathode current is 300 W, the introduced gas pressure is 6.7 × 10 ⁻² Pa, and the Ar is introduced on the buffer film I formed above. A gas amount of 12 mL / min, an introduced N ₂ gas amount of 18 mL / min, an RF output of 360 W and a film formation time of 4 minutes were used to form a 0.3 to 0.8 μm cBN film 4, as shown in FIG. Thus, a boron nitride film of the present invention was obtained.

Embodiment 2 After forming the cBN film of (C) -2 in Embodiment 1 described above, subsequently, a B film and a Ti film 5 were formed in the vacuum chamber 21 in the same manner as in Embodiment 1. 0.1-0.3 μm
(Where the film thickness ratio is B / Ti = 1)
(FIG. 2C) was formed under the following condition (D), and the TiN film forming step of (B) and the cBN film forming step of (C) of Example 1 were repeated for one cycle (total 2). Cycle) Figure 3
A multilayer film of boron nitride having a structure as shown in FIG. Also,
In the same manner, a film forming process of three cycles is performed, and the outermost surface layer is made of T
FIG. 4 shows a multilayer thin film configuration of boron nitride as an iN film. In this case, the formation of the outermost surface TiN film was performed under the following condition (E). (D). Film formation of buffer film II (D) -1 Film formation of B film Electron gun output of B 6.0 kW Anode voltage 40 V Anode current 10 A Cathode current 300 W Introduced gas pressure 6.7 × 10 ^-2 Pa Introduced Ar gas amount 12 mL / min RF output 150 W Film formation time 15 seconds (D) -2 Ti film formation Ti electron gun output 5.5 kW Anode voltage 50 V Anode current 10 A Cathode current 300 W Introduced gas pressure 2.0 × 10 ^-2 Pa Introduced Ar gas Amount 12 mL / min RF output 200 W Film formation time 15 seconds (E). Formation of TiN film Ti electron gun output 5.5 kW Anode voltage 50 V Anode current 20 A Cathode current 300 W Introduced gas pressure 2.0 × 10 ^-2 Pa Introduced Ar gas amount 12 mL / min N ₂ gas amount 150 mL / min for the first minute min Next 1 minute 75 mL / min Next 1 minute 150 mL / min RF output 200 W Film formation time 3 minutes

In order to identify whether or not the coating thus obtained contains a cubic boron nitride phase, the vicinity of the cutting edge of the drill on which the coating was formed was subjected to Fourier transform infrared absorption spectroscopy (FT-IR). As a result of the measurement, it was confirmed that the film contained a large amount of the cBN phase as shown in FIG.

Next, in Example 2, three cycles of film formation were performed to form a cBN multilayer film having a thickness of 3.5 μm.
As a comparative test, an untreated φ3.4 mm high-speed steel straight drill (Comparative product 1) and a high vacuum arc discharge type ion plating method were used to form a TiN film on a TiN film. 0μm deposited φ
Using a 3.4 mm high speed steel straight drill (commercial product, comparative product 2), drill rotation speed: 500 rpm, work material: SUS304, cutting speed: 5.3 m / min, feed amount: 0.1 to When a cutting test was performed under the cutting conditions of 0.35 mm / rev (one rotation), cutting material: no lubrication, and hole depth: 10 mm, the drill that formed the film of the present invention recorded 47 times of drilling. On the other hand, the comparative product 1 is 5 times,
The result of the comparison product 2 was obtained 16 times, and the life of the film was 9 times or more that of the untreated product by the film formation of the present invention, and was about 3 times as long as that of the commercial product.

From the above test results, it was recognized that the cBN laminate film having excellent adhesion to the cutting tool was formed on the cutting tool according to the film forming method of the present invention.
Moreover, the use of a high-speed steel drill has confirmed a remarkably longer life than that of a commercially available product, which clearly shows that this film forming method can form a film at a relatively low temperature of about 500 ° C.

[0038]

As described above, the film forming method of the present invention can be applied to a variety of types of substrates, in particular, a cBN film cannot be directly formed in terms of adhesion by applying a TiN film first. It is also possible to apply a cBN film and a multilayer film structure to apply it to cutting tools such as high-speed steel and cemented carbide. A longer life can be expected because the film surface appears. In addition, even if a crack is formed in the cBN film surface during cutting, the cBN film surface can be stopped at the TiN film surface, and the cBN film surface can be covered with the TiN film to improve weather resistance. However, it is possible to sufficiently prevent the problem that the cBN film is degraded due to the influence of the humidity in the atmosphere and the like, and separation occurs at the grain boundary portion in the cBN film.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a procedure and a configuration of an embodiment of a film forming method of the present invention.

FIG. 2 is a schematic plan view showing a film configuration of a TiN film and buffer films I and II to be implemented by the film forming method of the present invention.

FIG. 3 is a schematic sectional view showing the configuration of another embodiment of the film forming method of the present invention.

FIG. 4 is a schematic sectional view showing the configuration of still another embodiment of the film forming method of the present invention.

FIG. 5 is a schematic view showing an example of a film forming apparatus used to carry out the method of the present invention.

FIG. 6 shows IR of a cBN film obtained by the film forming method of the present invention.
It is a spectrum diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 TiN film 3 Buffer film I 4 cBN film 5 Buffer film II 21 Vacuum tank 23 Evaporation material 25 Electron gun 33 Etching prevention plate 41 Cathode for thermionic emission 43 Anodes 45a, 45b Magnet

Claims (4)

(57) [Claims] 1. A step of performing a bombardment treatment on a substrate; b. A step of forming a Ti film and / or a TiN film on an interface of a substrate subjected to the bombardment treatment; and c: Ti on the Ti film and / or TiN film. Membrane, B
A step of forming a buffer film I made of a BN film in which the composition ratio is changed stepwise; and d: a step of forming a cBN film on the buffer film I. Film formation method. 2. A step of performing a bombardment treatment on a substrate; b. A step of forming a Ti film and / or a TiN film on the interface of the substrate subjected to the bombardment treatment; and c: Ti on the Ti film and / or TiN film. Membrane, B
A step of forming a buffer film I composed of a BN film having a composition ratio changed stepwise, and a step of forming a cBN film on the buffer film I a plurality of times to form a multilayer film of cBN. In this case, a method of forming a TiN film on a cBN film in the repetition step includes a step of forming a buffer film II composed of a B film and a Ti film. 3. The method for forming a boron nitride film according to claim 1,
3. The method according to claim 2, wherein the outermost surface is a TiN film instead of the cBN film. 4. The method for forming a boron nitride film according to claim 1,
4. The method for forming a boron nitride film according to claim 1, wherein the TiN film has an odd multi-layer structure of three or more layers.