JP2006063369A - Hard carbon nitride film manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a carbon nitride film of high hardness by realizing the film having firm and dense chemical bond of nitrogen with carbon by increasing the nitrogen content of the carbon nitride film. <P>SOLUTION: In the method for depositing a hard carbon nitride film on the surface of a work, raw carbon materials are heated and sublimed by utilizing hollow cathode discharge while introducing gaseous nitrogen or ammonium gas, and nitrogen and carbon are activated by inducing microwave plasma discharge in a vicinity of the surface of the work at the same time, and the hard carbon nitride film is vapor-deposited on the surface of the work. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method capable of producing a carbon nitride film harder than a diamond-like carbon (DLC) film for the purposes of wear resistance, slidability, decoration, adhesion resistance, releasability, and the like.

The production of hard carbon nitride films by conventional methods includes reactive DC sputtering, reactive RF sputtering, laser ablation, ion implantation, ion-assisted DC sputtering, ion-assisted dynamic mixing, arc ion plating, as PVD (physical vapor deposition) methods. Hollow cathode discharge (HCD) ion plating and the like, and CVD (chemical vapor deposition) methods include RF plasma CVD and the like.
As raw materials in these methods, graphite is used as a carbon source and nitrogen gas is used as a nitrogen source in the PVD method. In the CVD method, a hydrocarbon such as CH ₄ is used as a carbon source, and nitrogen gas is used as a nitrogen source.
Further, only the above-described method is used to form a carbon nitride film from these raw materials, and no additional active means for decomposition of the raw materials and film formation are incorporated.

In the conventional method, since no means for increasing the chemical activity of carbon and nitrogen, which are constituent elements of the carbon nitride film, is added, the theoretical stoichiometric composition β-C ₃ N as a hard film of the carbon nitride film. The composition ratio N / C of ₄ is much smaller than 1.33, and is almost 0.5 in most cases, and less than 1 at most. According to the theoretical calculation results for β-C ₃ N ₄ (AYLiu and MLCohen, Science, 245 (l989) 841), this substance has the same crystal structure as β-S ₃ N ₄ and contains diamond. Although it is said that the volume modulus of elasticity surpasses that of diamond, that is, hardness superior to diamond, an ultra-hard carbon nitride film having such characteristics has not been obtained.
Therefore, the present invention provides a method for producing a carbon nitride film having high hardness by increasing the nitrogen content of the carbon nitride film and making the chemical bond between nitrogen and carbon strong and dense. For the purpose.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, and when forming a carbon nitride film using hollow cathode discharge, by inducing microwave plasma discharge near the surface of the material to be processed, I found out that the problem was solved.
Generally, a discharge in a frequency region of 1 GHz or more is called a microwave plasma discharge, but 2.45 GHz is most often used. Since the microwave is sent to the plasma generation unit through the waveguide and electric power can be locally injected, it is possible to generate high-density plasma as compared with plasma obtained by other discharges. Therefore, excitation and ionization of gas molecules are promoted, and a large amount of radicals and ions as active species are generated efficiently. By supplying this microwave energy to nitrogen and carbon immediately before entering the material to be treated, they are chemically activated, thereby having a high N / C composition ratio and a fine hard carbon nitride. The method of forming a film is the present invention.
That is, the method for producing a hard carbon nitride film according to the present invention is a method for forming a hard carbon nitride film on the surface of a material to be processed as claimed in claim 1, wherein nitrogen gas or ammonia is formed in the processing chamber. While introducing the gas, the raw material carbons are heated and sublimated using hollow cathode discharge, and at the same time, microwave plasma discharge is induced near the surface of the material to be treated to activate nitrogen and carbon, A hard carbon nitride film is deposited on the surface of the film.
The method for producing a hard carbon nitride film according to claim 2 is characterized in that, in the method for producing a hard carbon nitride film according to claim 1, a hollow cathode current of the hollow cathode discharge is set to 150 to 300A.
A method for producing a hard carbon nitride film according to claim 3 is the method for producing a hard carbon nitride film according to claim 1 or 2, wherein the amount of nitrogen gas introduced is 50 to 500 sccm, and the film is formed at that time. The inside pressure is set to 0.04 to 0.6 Pa.
The method for producing a hard carbon nitride film according to claim 4 is the method for producing a hard carbon nitride film according to claim 1 or 2, wherein the ammonia gas is introduced in an amount of 30 to 400 sccm, and the film is formed at that time. The inside pressure is 0.05 to 0.7 Pa.
The method for producing a hard carbon nitride film according to claim 5 is the method for producing a hard carbon nitride film according to claim 3 or 4, wherein the direct current applied voltage of the gas introduction nozzle for introducing the nitrogen gas or ammonia gas is used. Is 0 to 200V.
The method for producing a hard carbon nitride film according to claim 6 is the method for producing a hard carbon nitride film according to any one of claims 1 to 5, wherein the plasma generated during the hollow cathode discharge is converged by a coil magnetic field. It is characterized by doing.
The method for producing a hard carbon nitride film according to claim 7 is the method for producing a hard carbon nitride film according to claim 6, wherein the coil magnetic field is arranged around a hearth containing raw material carbons. It is generated by a coil.
The method for producing a hard carbon nitride film according to claim 8 is characterized in that, in the method for producing a hard carbon nitride film according to claim 6 or 7, the coil current applied to the coil is 120 to 240A. And
The method for producing a hard carbon nitride film according to claim 9 is the method for producing a hard carbon nitride film according to claim 1 to 8, wherein an input power of the microwave plasma discharge is set to 300 to 3000 W. Features.

  As described above, according to the present invention, while introducing nitrogen gas or ammonia gas into the processing chamber, the raw material carbons are heated and sublimated using a hollow cathode discharge, and at the same time, microscopic material is placed near the surface of the material to be processed. By depositing a hard carbon nitride film on the surface of the material to be processed while generating a wave plasma discharge, a dense and hard film having a larger N / C chemical composition ratio than when no microwave plasma discharge is applied Can be obtained.

The method for producing a hard carbon nitride film of the present invention is such that the N / C composition ratio is made higher and dense when producing a hard carbon nitride film harder than a dense diamond-like carbon (DLC) film. A high-quality hard carbon nitride film can be produced on the surface of any material to be processed made of glass, metal, ceramics, semiconductor, or the like.
In the present invention, in order to increase the film formation rate, carbon such as solid graphite as a raw material is heated and sublimated with a high-current electron beam, and is deposited on the surface of the material to be treated together with introduced nitrogen gas or ammonia gas. Cathode discharge is used, and nitrogen and carbon immediately before being incident on the surface of the material to be processed are activated by microwave plasma discharge.
In hollow cathode discharge, while introducing nitrogen gas or ammonia gas into the vacuum exhaust system, argon gas is flowed from the hollow cathode discharge gun to the raw solid graphite in the copper water-cooled hearth, and this argon gas is supplied to the hollow cathode discharge gun. And the water-cooled hearth are ionized by a DC voltage applied to obtain a large current, and the raw solid graphite is heated and sublimated. The large current of the hollow cathode discharge promotes ionization of the introduced nitrogen gas or ammonia gas and carbon, and a high deposition rate of the hard carbon nitride film can be realized.
In the hollow cathode discharge, an electron beam with a large current of 100 to 1000 A can be obtained at a low voltage of 30 to 40 V, but it is close to a voltage of an ionization voltage (near 100 V) at which the ionization of atoms is maximized. Therefore, the probability of collision between atoms and electrons is extremely high, so that the ionization of the evaporation material is extremely large. Therefore, the larger the hollow cathode current, the higher the deposition rate, but if it is too large, the surface of the resulting hard carbon nitride film becomes rough, so a hard carbon nitride film is formed by vapor deposition utilizing hollow cathode discharge. For this purpose, the hollow cathode current is suitably 150 to 300A.
In addition, the cleaning effect of the to-be-processed material surface can be heightened by carrying out the acceleration collision by the electric field which applied the ionized argon gas to the to-be-processed material.
When the nitrogen gas or the argon gas is introduced from the gas introduction nozzle provided in the hollow cathode discharge gun or from the hollow cathode discharge gun and introduced from the gas introduction nozzle, a DC potential is applied to the gas introduction nozzle. It is preferable to promote ionization of nitrogen gas or ammonia gas. In this case, it is preferable that the DC applied voltage to the gas introduction nozzle for introducing the ammonia gas is 0 to 200V.
Further, in order to obtain a good film quality, when the nitrogen gas is used, the amount introduced is preferably about 50 to 500 sccm, and the pressure in the processing chamber at that time is preferably about 0.04 to 0.6 Pa. In the case of using the ammonia gas, the introduction amount is preferably about 30 to 400 sccm, and the pressure in the processing chamber at that time is preferably about 0.05 to 0.7 Pa.
In addition, by forming a coil magnetic field during hollow cathode discharge, the generated plasma is converged by this coil magnetic field, and ionization of nitrogen, carbon, and argon is promoted, and the formed hard carbon nitride film has excellent adhesion and hardness. As a result, the hardness of the film is improved and the film formation rate can be increased.
The coil magnetic field is preferably generated by a coil disposed around a hearth containing raw material carbons. In this case, by setting a coil current to be supplied to the coil to 120 to 240 A, HV3100 A film with a hardness of ˜3600 is formed.
The hardness of the hard carbon nitride film increases approximately linearly with the increase in the coil current.
Unlike the case of the hard carbon film, the hardness of the hard carbon nitride film increases substantially linearly in proportion to the increase of the coil current without applying a bias voltage to the object to be processed. It will be.
Note that the object to be processed may be in a state in which a floating potential, a ground potential, or an external potential is applied.
The externally applied potential can be any potential of direct current, high frequency, or low frequency.
In this case, -200 V, 1-2 A for direct current, 200 V, 2-3 A for commercial frequency alternating current, and 100-500 W for high-frequency potential.
Further, the microwave for microwave plasma discharge, which is a feature of the present invention, guides a 2.45 GHz microwave oscillated by a microwave oscillator through a waveguide and introduces it into the vacuum chamber through quartz glass.
In order to sustain the microwave plasma discharge in the vicinity of the surface of the material to be processed and to activate the nitrogen and carbon immediately before being incident on the surface of the material to be strengthened, the above-mentioned microwave plasma discharge is applied. The power is set to 300 to 3000W. As a result, the N / C composition ratio and the density of the hard carbon nitride film are increased, and the hardness is increased as compared with the case where no microwave is added, so that a film of HV4000 or more is manufactured.
FIG. 1 shows an example of an apparatus for carrying out the method for producing a hard carbon nitride film of the present invention. In the figure, 1 shows a stainless steel processing chamber, and this processing chamber 1 has a vacuum exhaust system (not shown). It is connected and can be adjusted to the pressure in the processing chamber 1.
A copper water-cooled hearth 2 is provided at the bottom of the processing chamber 1 so that the raw graphite C or the like can be accommodated in the hearth 2.
A tantalum hollow cathode discharge gun (hereinafter referred to as “HCD gun”) 4 communicated with an argon supply pipe 3 is disposed immediately above the water-cooled hearth 2. The water-cooled hearth 2 and the HCD gun 4 are communicated with an HCD gun power source 5.
In the figure, reference numeral 6 denotes a nitrogen gas or ammonia gas introduction nozzle communicated with the gas supply passage 7, which is arranged adjacent to the side of the water-cooled hearth 2 so that nitrogen gas or ammonia gas can be introduced into the processing chamber 1. ing. The gas introduction nozzle 6 is connected to a nozzle bias power source 8 so that a bias voltage can be applied.
Thus, argon gas is flowed from the HCD gun 4 into the raw solid graphite C in the water-cooled hearth 2, and energized from the HCD gun power source 5 while introducing nitrogen gas or ammonia gas into the treatment nitrogen 1 from the gas introduction nozzle 6. The argon gas and nitrogen gas or ammonia gas are ionized by a DC voltage applied between the HCD gun 4 and the water-cooled hearth 2 to obtain a large current, and the raw material solid carbon is heated and sublimated to produce a carbon nitride film. It can be made to.
Further, a coil 10 communicated with a coil power source 9 is disposed around the water-cooled hearth 2 so that the ionized argon gas plasma can be converged.
In addition, a processing material holder 11 is provided on the ceiling portion in the processing chamber 1 so that the processing material A can be supported, and the processing material A is attached by a heater 12 provided on the back surface of the processing material holder 11. It can be heated to a predetermined temperature.
The substrate can be heated or heated to obtain a hard carbon nitride film at room temperature, but in order to improve the adhesion between the hard carbon nitride film and the object to be processed, it is preferable to heat it. In this case, it is preferable to heat to 400 ° C. or lower.
Further, a workpiece bias power source 13 is communicated with the workpiece holder 11 so that an arbitrary bias such as direct current, high frequency, and low frequency can be applied as necessary.
Further, the 2.45 GHz microwave oscillated by the microwave oscillator 14 is guided by the waveguide 15, enters the vacuum chamber 1 through the quartz glass 16, and generates a microwave plasma discharge in the vicinity of the material A to be processed. Thus, nitrogen and carbon immediately before being incident on the surface of the material to be processed are activated so that their chemical bonds become strong, and a high-quality hard carbon nitride film can be produced. In addition, what is shown by 17 in a figure is a plunger.

  Next, specific examples of the method for producing the hard carbon nitride film of the present invention will be described.

Example 1
A Si wafer was installed as a material to be processed, and after the processing chamber of FIG. 1 was evacuated to about 10 ⁻³ Pa, argon gas was introduced from a tantalum HCD gun and adjusted to a pressure of 20 Pa.
Thereafter, a 50 V voltage was superimposed between the HCD gun and Haas, and a high frequency voltage was applied thereto to cause glow discharge of argon gas. In order to converge the plasma of argon gas, a current of about 100 A was passed through the coil, and a voltage of 350 V at maximum was applied between the auxiliary electrode provided in the gun and the gun in order to promote the discharge between the gun and the hearth. After the arc discharge between Gunn and Haas ignited, the processing chamber was evacuated by oil diffusion without changing the flow rate of argon gas, and the pressure was set to about 0.1 Pa.
As a first step, the material to be treated was cleaned under the following conditions. That is, the HCD gun current was 100 A, the flow rate of nitrogen gas or ammonia gas was 0 sccm, the coil current was 180 A, the material to be treated—the installation voltage—800 V, and the cleaning time was 5 minutes.
Next, a carbon nitride film was deposited in the second stage. That is, the apparatus conditions were changed as follows in one minute from the cleaning conditions.
The HCD gun current was 150 A, the argon gas flow rate from the HCD gun was 10 sccm, the nitrogen gas flow rate from the gas introduction nozzle was 200 sccm, the coil current was 200 A, no potential was applied to the material to be processed, and the nozzle-ground voltage was 50 V.
The output power for the microwave plasma discharge was 500 W, and a carbon nitride film having a thickness of 5.8 μm was obtained in 60 minutes. The pressure during film formation at this time was 0.32 Pa.
The film formation rate was 97 nm / min, the chemical composition ratio N / C of the obtained film was 0.99 according to EPMA (Electron Probe Microanalyzer), and the hardness was HV4100.

(Comparative Example 1)
A carbon nitride film was produced in the same manner as in Example 1 except that the output power for microwave plasma discharge was not added and was set to 0 W. The pressure during film formation was 0.34 Pa.
The film formation rate was 100 nm / min, the obtained chemical composition ratio N / C was 0.75, and the hardness was HV3300.

(Example 2)
As in Example 1, a Si wafer is used as the material to be processed, the first stage cleaning is performed as in Example 1, and the hard carbon nitride film is deposited in the second stage using an HCD gun current 150A and an HCD gun. The argon gas flow rate from the scooter was 0 sccm, the ammonia gas flow rate from the HCD gun was 100 sccm, the ammonia gas flow rate from the gas introduction nozzle was 0 sccm, the coil current was 200 A, and no potential was applied to the workpiece.
The output power for the microwave plasma discharge was 500 W, and a 6.5 μm thick carbon nitride film was obtained in 100 minutes. The pressure during film formation at this time was 0.20 Pa.
The film formation rate was 65 nm / min, the chemical composition ratio N / C of the obtained film was 1.30, and the hardness was HV4400.

(Comparative Example 2)
A carbon nitride film was produced in the same manner as in Example 2 except that the output power for microwave plasma discharge was not added and the power was set to 0 W. The pressure during film formation was 0.19 Pa.
The film formation rate was 66 nm / min, the obtained chemical composition ratio N / C was 1.07, and the hardness was HV3600.
The above results are summarized in Table 1.

From Table 1 above, it was found that in Examples 1 and 2, a hard carbon nitride film having a high N / C composition ratio and high hardness was obtained as compared with Comparative Examples 1 and 2.
Further, in Example 2 using ammonia gas having higher reactivity than nitrogen gas in Example 1, a hard carbon nitride film having a higher N / C composition ratio and higher hardness than that in Example 1 is obtained. It turns out that it is obtained.

Explanatory drawing of one Embodiment of the manufacturing apparatus of the hard carbon nitride film of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing chamber 2 Copper water-cooled hearth 3 Argon (nitrogen or ammonia) supply pipe 4 Hollow cathode discharge gun 5 HCD gun power supply 6 Nitrogen gas or ammonia gas introduction nozzle 7 Gas supply path 8 Nozzle bias power supply 9 Coil power supply 10 Coil 11 Material Holder 12 Heater 13 Material Bias Power Supply 14 Microwave Oscillator 15 Waveguide 16 Quartz Glass 17 Plunger A Material A C Graphite

Claims (9)

  A method for forming a hard carbon nitride film on the surface of a material to be processed, in which a raw material carbon is superheated and sublimated using a hollow cathode discharge while introducing nitrogen gas or ammonia gas in a processing chamber, At the same time, a microwave plasma discharge is induced near the surface of the material to be processed to activate nitrogen and carbon, and a hard carbon nitride film is formed on the surface of the material to be processed by vapor deposition. Method.   2. The method for producing a hard carbon nitride film according to claim 1, wherein a hollow cathode current of the hollow cathode discharge is set to 150 to 300A.   3. The method for producing a hard carbon nitride film according to claim 1, wherein the amount of nitrogen gas introduced is 50 to 500 sccm, and the pressure at that time is 0.04 to 0.6 Pa.   The method for producing a hard carbon nitride film according to claim 1 or 2, wherein the ammonia gas is introduced in an amount of 30 to 400 sccm, and the pressure at that time is 0.05 to 0.7 Pa.   The method for producing a hard carbon nitride film according to claim 3 or 4, wherein a direct-current applied voltage of a gas introduction nozzle for introducing the nitrogen gas or ammonia gas is set to 0 to 200V.   6. The method for producing a hard carbon nitride film according to claim 1, wherein the plasma generated during the hollow cathode discharge is converged by a coil magnetic field.   The method for producing a hard carbon nitride film according to claim 6, wherein the coil magnetic field is generated by a coil disposed around a hearth containing raw material carbons.   The method for producing a hard carbon nitride film according to claim 6 or 7, wherein a coil current applied to the coil is 120 to 240A.   The method for producing a hard carbon nitride film according to claim 1, wherein an input power of the microwave plasma discharge is set to 300 to 3000 W.

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