JPH0940494A - Hard carbon film and its formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hard carbon film having high film hardness and an excellent adhesion property to a substrate by changing the compsn. of the hard carbon film to be formed on the substrate in its thickness direction in such a manner that specific conditions are attained. SOLUTION: The compsn. of the film 21 is changed in its thickness direction in such a manner that the hydrogen concn. near 21a the boundary with the substrate (e.g.; Ni alloy substrate) 20 is 60 to 40% and the hydrogen concn. near 21b the surface of the film is 30 to 10% or that the internal stress near 21a the boundary with the substrate is 5 to 6GPa and the internal stress near 21b the surface of the film is 7 to 8GPa or that the hardness near 21a the boundary with the substrate is 500 to 2000Hv and the hardness near 21b the surface of the film is 3000 to 3400Hv.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hard carbon film formed on a substrate and a method for forming the hard carbon film.

[0002]

2. Description of the Related Art Hard carbon coatings, like diamond, have excellent hardness, resistivity, chemical stability, etc.
It holds great promise as a coating material for surface modification. However, the substrates on which such a hard carbon coating can be directly formed with good adhesion have been limited to limited substrates such as silicon and glass. Therefore, a hard carbon coating could not be formed on a substrate such as a metal substrate or a ceramic substrate with good adhesion.

In order to solve such a problem, a method has been proposed in which an intermediate layer of silicon or the like is provided between a substrate such as a ceramic substrate and a hard carbon film to improve the adhesion (Japanese Patent Laid-Open No. 1-1999). 317197).

[0004]

According to the above-mentioned method of providing the intermediate layer, the adhesion between the substrate and the hard carbon coating can be improved, but a material different from carbon, which is a constituent element of the hard carbon coating, can be used. Since it is used as a raw material for the intermediate layer, there is a problem that the manufacturing process becomes complicated. Also, when providing an intermediate layer between the substrate and the hard carbon coating,
There was a demand to further improve the adhesion. In particular, when a hard carbon film having a high film hardness is formed, it is difficult to obtain good adhesion.

An object of the present invention is to provide a hard carbon film having a high film hardness and excellent adhesion to a substrate, and a method for forming the same, which solves the conventional problems.

[0006]

The hard carbon coating of the present invention is a hard carbon coating formed on a substrate, which is formed near the interface with the substrate, that is, on the substrate side, and near the surface of the coating, that is, the surface side. Characterized by changing the composition of the coating in the thickness direction, the composition on the substrate side is a composition with good adhesion, and the composition on the coating surface side is a composition with excellent adhesion and other properties such as hardness. There is. Such a change in the composition of the coating film in the thickness direction can be expressed as a hydrogen concentration. Further, such changes in composition cause changes in internal stress, hardness, conductivity, refractive index, and the like. Therefore, the hard carbon coating of the present invention can be represented by specifying these properties.

The hard carbon coating according to the first aspect of the present invention has a hydrogen concentration of 60 to 40% near the interface with the substrate.
And the hydrogen concentration near the surface of the coating is 30 to 10
%, The composition of the film is changed in the thickness direction.

The hard carbon coating according to the second aspect of the present invention has an internal stress of 5 to 6 GPa in the vicinity of the interface with the substrate.
And the internal stress near the surface of the coating is 7 to 8 GP.
It is characterized in that the composition of the coating is changed in the thickness direction thereof as indicated by a.

The hard carbon coating according to the third aspect of the present invention has a hardness of 500 to 2000 near the interface with the substrate.
Hv, and hardness near the surface of the coating is 3000 to
It is characterized in that the composition of the coating is changed in the thickness direction so as to be 3400 Hv.

The hard carbon coating according to the fourth aspect of the present invention has a conductivity of 10 ⁻⁴ to 10 ⁻⁷ near the interface with the substrate.
([Omega] cm) is ^-1, it is characterized in that the conductivity in the vicinity of the surface of the film has changed the composition of the coating in the thickness direction such that ^{10 -1 0 ~10 -11 (Ωcm)} -1.

The hard carbon coating according to the fifth aspect of the present invention has a refractive index of 1.0 to 1.5 near the interface with the substrate.
And the refractive index near the surface of the coating is 2.0 to 2.
No. 5, the composition of the coating is changed in the thickness direction.

The% of hydrogen concentration represents atomic%, and can be measured by, for example, secondary ion mass spectrometry (SIMS). The internal stress can be measured from the amount of deformation of the substrate. When a film is formed on a thin substrate in a stressed state, the substrate exhibits a flexure determined by its shape and elastic constant. Therefore, the internal stress can be evaluated by detecting this flexure amount. This flexure method is described, for example, in "Stress Physics" Vol. 66, No. 7 (198).
7), pages 923-924. here,
The internal stress is calculated from the radius of curvature of the flexure of the substrate obtained by the Newton ring method.

The hardness of the film is Vickers hardness, and the conductivity can be calculated from the voltage / current characteristics between two metal electrodes formed on the film. The refractive index can be calculated from the measured values of the transmittance and the reflectance.

The substrate in the present invention is not particularly limited, and a silicon substrate or a glass substrate can be used, but Ni substrates, Al substrates, stainless steel substrates, ceramics, which have been particularly problematic in conventional adhesion, have been used. It is useful for steel substrates or substrates made of alloys such as Ni, Al and stainless steel.

Further, the term "substrate" used in the claims of the present specification includes a substrate having an underlayer and the like formed thereon. Therefore, a substrate having a silicon layer formed on a Ni alloy substrate is also included as a substrate. In such a case, “near the interface with the substrate” means near the interface with the underlying layer such as a silicon layer.

The hard carbon coating of the present invention is characterized in that the composition of the coating is changed in the thickness direction. Such a change in the composition of the coating film may be changed stepwise by a multi-layer structure having at least a two-layer structure, or may be continuously changed by an inclined structure.

The method of forming the hard carbon coating of the present invention is not particularly limited, but it can be formed by, for example, the CVD method. For example, by using a plasma CVD method, a high frequency voltage is applied to the substrate holder, and the self-bias voltage generated in the substrate holder is changed as the film formation progresses, thereby changing the composition of the hard carbon film in the thickness direction. Can be made.

That is, the manufacturing method of the present invention is a method of forming the hard carbon coating of the present invention on a substrate placed on a substrate holder, and generating plasma containing a reaction gas as a raw material of the hard carbon coating, The composition of the film is changed in the thickness direction by changing the self-bias voltage generated in the substrate holder that irradiates the plasma with the progress of the film formation.

The self-bias voltage generated in the substrate holder is, for example, from when the film is formed in the vicinity of the interface with the substrate, that is, from the beginning of the film formation to the vicinity of the surface of the film, that is, the end of the film formation. The composition of the coating can be changed by changing the voltage from 0 to -150V.

An electron cyclotron resonance (ECR) plasma CVD apparatus can be used as a plasma generating means in the plasma CVD method. By using such an apparatus, the plasma density can be further increased, and high quality can be obtained at low temperature. Can be formed.

[0021] In the hard carbon film of action the present invention, and by changing the composition of the coating in the thickness direction, in the vicinity of the interface between the substrate and good film composition of adhesion near the surface of the coating, the hardness, The composition has good properties such as electrical conductivity and chemical stability required for the hard carbon coating. Therefore, the hard carbon coating of the present invention can be a hard carbon coating having good adhesion to the substrate and having necessary characteristics such as film hardness.

[0022]

FIG. 1 is a sectional view showing a hard carbon coating of an embodiment according to the present invention. In the embodiment shown in FIG. 1, the substrate 2
A hard carbon film 21 is formed on the surface of the film. The hard carbon coating 21 is formed so as to have an inclined structure whose composition continuously changes from the substrate 20 toward the surface of the coating 21. That is, the hydrogen concentration is formed so as to decrease from the interface vicinity 21a toward the film surface vicinity 21b. Similarly, the internal stress, the film hardness, and the refractive index are increased, and the conductivity is decreased.

FIG. 2 is a cross-sectional view showing another embodiment of the hard carbon coating according to the present invention. In the embodiment shown in FIG. 2, a hard carbon coating 22 is formed on the substrate 20. The hard carbon coating 22 has a two-layer structure including coating layers 22a and 22b. The coating layer 22a has a coating composition having good adhesion to the substrate 20, has a relatively high hydrogen concentration and conductivity, and has a relatively high internal stress, hardness, and refractive index as compared with the coating layer 22b. It is formed to be low.

The hard carbon coating in the present invention may have a two-layer structure as shown in FIG. 2, or may have a multi-layer structure of three or more layers. Ultimately, as the number of layers is increased, a graded structure in which the composition continuously changes as shown in FIG. 1 is obtained.

FIG. 3 is a schematic sectional view showing an example of an ECR plasma CVD apparatus capable of forming a hard carbon film according to the embodiment of the present invention. Referring to FIG. 3, inside vacuum chamber 8, plasma generation chamber 4 and a reaction chamber in which substrate 13 is installed are provided. One end of the waveguide 2 is attached to the plasma generation chamber 4, and the microwave supply means 1 is provided at the other end of the waveguide 2. The microwave generated by the microwave supply means 1 is transmitted to the waveguide 2
And, it is guided to the plasma generation chamber 4 through the microwave introduction window 3. The plasma generation chamber 4 is provided with a discharge gas introduction pipe 5 for introducing a discharge gas such as argon (Ar) gas into the plasma generation chamber 4. A plasma magnetic field generator 6 is provided around the plasma generation chamber 4.

A drum-shaped substrate holder 12 is installed in the reaction chamber in the vacuum chamber 8 so as to be rotatable about a rotation axis perpendicular to the paper surface of FIG. A motor (not shown) is connected. A plurality of (24 in this embodiment) Ni alloy substrates 13 are mounted on the outer peripheral surface of the substrate holder 12 at equal intervals. The high frequency power supply 10 is connected to the substrate holder 12.

A metal cylindrical shield cover 14 is provided around the substrate holder 12 about 5 m from the substrate holder 12.
It is provided at a distance of m. This shield cover 1
4 is connected to the ground electrode. This shield cover 14 prevents a discharge between the substrate holder 12 and the vacuum chamber 8 other than the film forming location from occurring due to a radio frequency (RF) voltage applied to the substrate holder 12 when forming a film. It is provided for.

An opening 15 is formed in the shield cover 14. Plasma drawn from the plasma generation chamber 4 through the opening 15 is radiated to the substrate 13 mounted on the substrate holder 12. A reaction gas introduction pipe 16 is provided in the vacuum chamber 8. The tip of the reaction gas introduction pipe 16 is located above the opening 15.

FIG. 4 is a plan view showing the vicinity of the tip of the reaction gas introducing pipe 16. Referring to FIG. 4, the reaction gas introducing pipe 16 includes a gas introducing portion 16a for introducing CH ₄ gas into the vacuum chamber from the outside, and a gas releasing portion 16b connected to the gas introducing portion 16a in a vertical direction. It consists of The gas releasing portion 16b is arranged in a direction perpendicular to the rotation direction A of the substrate holder 12, and the opening 1
It is provided so as to be located on the upstream side in the rotation direction above 5. A plurality of holes 17 are formed in the gas releasing portion 16b in a direction of about 45 degrees downward. In this embodiment, eight holes 17 are formed. The distance between the holes 17 is
It is formed so that it gradually narrows from the center toward both sides. By forming the holes 17 at such intervals, the CH ₄ gas introduced from the gas introducing portion 16a is released substantially uniformly from the holes 17.

An example of forming a hard carbon film as shown in FIG. 1 on a Ni alloy substrate using the above film forming apparatus will be specifically described below. First, the vacuum chamber 8
The inside is evacuated to 10 ⁻⁵ to 10 ⁻⁷ Torr, and the substrate holder 12 is rotated at a speed of about 10 rpm. Next, Ar gas is supplied from the discharge gas introduction pipe 5 at 5.7 × 10 ⁻⁴ Torr and the microwave supply means 1 to 2.45 G.
A microwave of 100 W at a frequency of 100 Hz is supplied to irradiate the surface of the substrate 13 with the Ar plasma formed in the plasma generation chamber 4. At the same time, while supplying CH ₄ gas at 1.3 × 10 ⁻³ Torr from the reaction gas pipe 16, RF power of 13.56 MHz is supplied from the high frequency power source 10 to the substrate holder 1.
2 When RF power is applied to the substrate holder 12, as shown in FIG. 5, the self-bias voltage generated on the substrate is 0 V at the initial stage of film formation and 15 at the end of film formation.
The RF power was adjusted and applied so as to be −150 V after a minute.

Through the above steps, a hard carbon coating having a film thickness of 1200Å was formed on the Ni alloy substrate. FIG. 6 is a diagram showing the relationship between the self-bias voltage generated in the substrate holder and the refractive index, conductivity, hardness, internal stress, and hydrogen concentration of the hard carbon film formed at the self-bias voltage. . These measured values were obtained by forming a hard carbon coating on the apparatus shown in FIG. 3 under the condition that the self-bias voltage generated in the substrate holder was constant, and measuring each characteristic of the obtained hard carbon coating. It is a numerical value. FIG. 6 shows the relationship between these characteristics obtained by forming a film by changing the self-bias voltage and measuring the characteristic values.

As is apparent from FIG. 6, when the self-bias voltage is 0 V, the refractive index is about 1.0, the conductivity is about 10 ⁻⁴ (Ωcm) ⁻¹ , and the hardness is about 850 Hv. , The internal stress is about 5 GPa, and the hydrogen concentration is 6
It turns out that it is about 0%. When the self-bias voltage is −150 V, the refractive index is about 2.5, the conductivity is about 10 ⁻¹¹ (Ωcm) ⁻¹ , and the hardness is 340.
It can be seen that it is about 0 Hv, the internal stress is about 8 GPa, and the hydrogen concentration is about 10%.

Therefore, with the progress of film formation, in the hard carbon film of the above example in which the self-bias voltage was changed from 0 to -150 V, changes in the respective characteristics as shown in FIG. 6 occurred in the thickness direction. It is believed that Therefore, the vicinity 21a of the interface between the hard carbon film 21 and the substrate 20 is
In Table 3, the composition has a small hardness but a small internal stress, and it can be seen that the composition has excellent adhesion to the substrate 20. Further, it is understood that the hardness and the like are high in the vicinity 21b of the coating surface, and the composition has a high hardness desired as a hard carbon coating.

In addition to the hard carbon coating having a graded structure as shown in FIG. 1 (Example 1), a hard carbon coating having a two-layer structure as shown in FIG. 2 was further formed. The conditions for forming the film were the same as in Example 1 except for the self-bias voltage. As shown in FIG. 7, the self-bias voltage was set to 0 V for 5 minutes from the start of film formation to −150 V for 10 minutes until 15 minutes thereafter. By such a process, on the Ni alloy substrate,
A hard carbon coating having a film thickness of 1200Å was formed. The coating film formed with the self-bias voltage of 0 V is the portion of the coating layer 22a shown in FIG. 2, and the coating film formed with the self-bias voltage of -150 V is the portion corresponding to the coating layer 22b.

For comparison, a hard carbon film was formed under the same conditions as in Examples 1 and 2 except that the self-bias voltage generated in the substrate holder was kept constant at -150 V during film formation (Comparative Example). 1) and a hard carbon coating (Comparative Example 2) were prepared by keeping the self-bias voltage constant at 0 V during the coating formation.

Examples 1 and 2 obtained as described above
In addition, the hard carbon coatings of Comparative Examples 1 and 2 were evaluated for adhesion. The evaluation of the adhesion was performed by an indentation test with a constant load (load = 1 kg) using a Vickers indenter. The number of samples was set to 50, and the number of peeled hard carbon coatings on the Ni alloy substrate was counted and evaluated.
Table 1 shows the evaluation results.

[0037]

[Table 1]

As is clear from Table 1, the hard carbon coatings of Examples 1 and 2 according to the present invention have a significantly smaller number of peeling occurrences than the hard carbon coating of Comparative Example 1. Therefore, it can be seen that according to the present invention, a hard carbon film having excellent adhesion to the substrate can be obtained.

Further, the above Examples 1 and 2 and Comparative Example 1
The hardness of the hard carbon coatings Nos. 2 and 2 were measured, and the results are shown in Table 2.
It was shown to.

[0040]

[Table 2]

As is clear from Table 2, the hard carbon coatings of Examples 1 and 2 according to the present invention have high hardness equivalent to that of Comparative Example 1. As shown in Table 1, the hard carbon film of Comparative Example 2 has a small number of peeling occurrences and is excellent in adhesion, but it is understood that the film hardness is very low.

From the above results, it can be seen that the hard carbon coating according to the present invention is a hard carbon coating having a sufficiently high film hardness and excellent adhesion. In the above example, the hard carbon film was formed using the ECR plasma CVD apparatus,
The hard carbon coating of the present invention is not limited to such a forming method.

In the above embodiment, the hard carbon film is directly formed on the substrate. However, in order to further improve the adhesiveness, a base layer such as a silicon layer is formed on the substrate. It may be used as a substrate on which a hard carbon coating is formed.

[0044]

According to the present invention, it is possible to obtain a hard carbon coating having desired properties such as hardness, resistivity and chemical stability that the hard carbon coating has and having excellent adhesion to the substrate.

Further, the hard carbon coating of the present invention can be directly formed on a substrate such as a Ni alloy which could not be formed with good adhesion in the past, to obtain a coating with good adhesion. Therefore, it is possible to form a hard carbon coating having good adhesion without complicating the manufacturing process.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a hard carbon coating of an embodiment according to the present invention.

FIG. 2 is a sectional view showing a hard carbon coating of another embodiment according to the present invention.

FIG. 3 ECR used in an embodiment according to the present invention
The schematic sectional drawing which shows a plasma CVD apparatus.

4 is a plan view showing the vicinity of the opening of the ECR plasma CVD apparatus shown in FIG.

FIG. 5 is a diagram showing a relationship between a film forming time and a self-bias voltage in an example according to the present invention.

FIG. 6 shows the self-bias voltage, refractive index, conductivity, hardness,
The figure which shows the relationship with internal stress and hydrogen concentration.

FIG. 7 is a diagram showing a relationship between a film forming time and a self-bias voltage in an example according to the present invention.

[Explanation of symbols]

 20 ... Substrate 21 ... Hard carbon coating 21a ... Portion of hard carbon coating near interface with substrate 21b ... Hard carbon coating near surface 22 ... Hard carbon coating 22a ... Substrate side coating layer 22b ... Surface side coating layer

Front page continuation (72) Inventor Seiichi Kiyama 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (7)

[Claims] 1. A hard carbon coating formed on a substrate, wherein the hydrogen concentration in the vicinity of the interface with the substrate is 60 to 40%.
And the hydrogen concentration near the surface of the coating is 30 to 10
%, The hard carbon coating is characterized in that the composition of the coating is changed in the thickness direction. 2. A hard carbon coating formed on a substrate, wherein the internal stress in the vicinity of the interface with the substrate is 5 to 6 GPa.
And the internal stress near the surface of the coating is 7 to 8 GP.
The hard carbon coating characterized in that the composition of the coating is changed in the thickness direction as shown in (a). 3. A hard carbon coating formed on a substrate, wherein the hardness in the vicinity of the interface with the substrate is 500 to 2000.
Hv, and hardness near the surface of the coating is 3000 to
A hard carbon coating characterized in that the composition of the coating is changed in the thickness direction so that it is 3400 Hv. 4. A hard carbon film formed on a substrate, having a conductivity of 10 ⁻⁴ to 10 ⁻⁷ near an interface with the substrate.
(Ωcm) ⁻¹ , and the hardness of the coating composition is changed in the thickness direction so that the electrical conductivity in the vicinity of the surface of the coating is 10 ⁻¹⁰ to 10 ⁻¹¹ (Ωcm) ^−1. Carbon coating. 5. A hard carbon coating formed on a substrate, wherein the refractive index in the vicinity of the interface with the substrate is 1.0 to 1.5.
And the refractive index near the surface of the coating is 2.0 to 2.
5 is a hard carbon coating characterized in that the composition of the coating is changed in its thickness direction. 6. The hard carbon coating according to claim 1, wherein the substrate is made of at least one selected from Ni, Al, stainless steel, ceramics, and alloys thereof. 7. A method for forming a hard carbon coating according to claim 1 on a substrate placed on a substrate holder, comprising a reaction gas as a raw material of the hard carbon coating. Formation of a hard carbon coating characterized by changing the composition of the coating in the thickness direction by generating plasma and changing the self-bias voltage generated in the substrate holder irradiating the plasma with the progress of coating formation. Method.