JP4182224B2 - Method for forming hard carbon nitride film - Google Patents

Description

  The present invention relates to a method for forming a hard carbon nitride film used for a cutting tool, a die, a wear-resistant component, a protective film of a storage medium such as an optical disk and a magnetic disk, and the like.

In recent years, it has been pointed out that carbon nitride C ₃ N ₄ having a structure similar to β-type silicon nitride may have a hardness higher than that of diamond, and a technique for forming a hard carbon nitride film on various substrates has been proposed. Various proposals have been made. (For example, see Patent Documents 1 to 3)
JP 11-350140 A JP 2001-254172 A JP 2002-38269 A

The techniques described in Patent Documents 1 and 2 are based on a substrate disposed in a vacuum vessel, and a material containing nitrogen or nitrogen-containing material gas plasma serving as a film nitrogen source and carbon serving as a film carbon source. A gas plasma is supplied and a pulse voltage is applied to the substrate to form a carbon nitride film.
However, in these techniques, since the nitrogen source and the carbon source of the film supplied separately react on the substrate, it is difficult to increase the nitrogen content in the film (about 20% at most), and the hardness Therefore, it was impossible to obtain a hard carbon nitride film having high and desired properties. Further, the pulse voltage applied to the substrate is in the order of kV and the pulse width is applied as an extremely short pulse of about several microseconds, which requires a large-scale power supply device and control device.

  On the other hand, the technique described in Patent Document 3 was developed by the present inventors and the like, and when a raw material gas containing a cyanide compound is converted into plasma and a carbon nitride film is synthesized on the substrate, the substrate is formed at the initial stage of film formation. Is biased to a negative voltage of 0 to -60V. According to this technique, the nitrogen content in the carbon nitride film can be significantly increased as compared with the techniques described in Patent Documents 1 and 2, but the negative voltage biased to the substrate is −60V. If it is larger, a film may not be formed by sputtering, and there is a problem that a homogeneous hard carbon nitride film cannot be formed efficiently.

  Therefore, the present invention eliminates these problems of the prior art and provides a method for efficiently forming a hard carbon nitride film having a high hardness, a smooth surface and a uniform surface on a substrate without requiring large-scale and expensive equipment. The purpose is to provide.

  As a result of intensive studies, the present inventors have solved the above problem by applying a very slow pulse voltage to the substrate when forming a carbon nitride film on the substrate by converting the source gas containing cyanide into plasma. And the present invention has been completed.

That is, the present invention employs the following configurations 1 to 8 .
1. When a carbon nitride film is formed on a substrate by activating the source gas containing a cyanide compound into a plasma, a high frequency pulse with a pulse period of 10 to 10000 seconds is applied to the substrate with an on / off ratio of 50/50 to 80/20. A method for forming a hard carbon nitride film, wherein
2. 2. The method for forming a hard carbon nitride film according to 1, wherein the temperature of the substrate is maintained at 0 to 100 ° C.
3. 3. The method for forming a hard carbon nitride film according to 1 or 2, wherein the high-frequency pulse bias voltage is −50 to −200V.
4). 4. The method for forming a hard carbon nitride film according to any one of 1 to 3, wherein the source gas is a mixed gas of a cyanide compound and an inert gas.
5. 5. The method for forming a hard carbon nitride film according to any one of 1 to 4, wherein the substrate has a surface selected from silicon, silicon carbide, and silicon nitride.
6). The method for forming a hard carbon nitride film according to any one of 1 to 5, wherein the hardness of the hard carbon nitride film is 20 to 60 GPa.
7). 7. The method for forming a hard carbon nitride film according to any one of 1 to 6, wherein the nitrogen content of the hard carbon nitride film is 20 to 50% in atomic ratio.
8). The hard carbon nitride film according to any one of 1 to 7, wherein any one of direct current, alternating current, high frequency, microwave, and ECR is used as plasma generating means, and plasma is generated at a pressure of 10 ^{−4 to 1} Torr. Forming method.

  According to the present invention, hard carbon nitride having a hardness of about 20 to 60 GPa, particularly about 45 to 60 GPa, and a nitrogen content of about 20 to 50% in terms of atomic ratio, which has been extremely difficult to generate by the prior art. The film can be formed efficiently on the surface of the substrate at a low cost. The present invention makes it possible to efficiently form a hard carbon nitride film having a high hardness, a smooth surface and a uniform surface on a substrate without requiring large-scale and expensive equipment, and has practical value. It is extremely expensive.

In the present invention, when forming a carbon nitride film on the substrate by activating the source gas containing a cyanide compound into a plasma, the substrate has a pulse period of 0.1 to 100,000 seconds, preferably 10 to 10,000 seconds, Preferably, a high-frequency pulse of 100 to 1000 seconds is applied at an on / off ratio of 50/50 to 80/20.
Although cyanide halides and various organic compounds can be used as the source gas, cyanogen bromide, iodine cyanide, chlorine cyanide, hydrogen cyanide, acetonitrile, dicyan and the like are practically used. It is preferable. These cyan compounds can be used alone or in admixture of two or more.
These cyan compounds are usually used by mixing with an inert gas such as argon, helium or nitrogen. The mixing ratio of the cyanide compound and the inert gas is preferably such that the partial pressure of the cyanide compound is 0.0001 to 100%, particularly 0.001 to 40%.

Although there is no restriction | limiting in particular as a board | substrate which forms a hard carbon nitride film, It is preferable to use the board | substrate which has the surface selected from silicon | silicone, silicon carbide, silicon nitride, etc. Examples of such a substrate include a substrate made of these materials themselves, or a substrate in which a film made of these materials is formed on a substrate made of other materials.
When the substrate temperature is maintained at about 0 to 100 ° C. by cooling the substrate stage with water or the like, the hardness of the obtained carbon nitride film is preferable.

In the present invention, the raw material gas containing the above cyanide compound is activated by plasma, and a carbon nitride film is formed on the substrate. However, the plasma generation means is not particularly limited, but is usually direct current, alternating current, high frequency, microscopic Waves, ECR, etc. are used. The pressure is preferably about 10 ^{−4 to 1} Torr.

In the present invention, when a carbon nitride film is formed on a substrate, a high frequency pulse having a pulse period of 0.1 to 100,000 seconds, preferably 10 to 10,000 seconds, more preferably 100 to 1000 seconds is applied to the substrate. Apply at 50 / 50-80 / 20. The voltage of the high frequency pulse is preferably 0 to −200V, particularly −50 to −200V.
In the prior art proposed by the present inventors described in Patent Document 3, a dense and hard carbon nitride film is generated by continuously applying a negative high-frequency bias voltage to the substrate. When the negative voltage to be biased is -40V, particularly larger than -60V, a film may not be formed by sputtering, and there is a problem that a homogeneous hard carbon nitride film cannot be formed efficiently. In the present invention, by applying the above extremely slow pulse voltage to the substrate, it is possible to prevent the formation of the film from being hindered by sputtering when the negative voltage is increased, and an efficient and uniform hard carbon nitride film is formed. It was effective in forming.

  According to the present invention, hard carbon nitride having a hardness of about 20 to 60 GPa, particularly about 45 to 60 GPa, and a nitrogen content of about 20 to 50% in terms of atomic ratio, which has been extremely difficult to generate by the prior art. The film can be formed efficiently on the surface of the substrate at a low cost.

Next, examples of the present invention will be described with reference to the drawings. However, the following specific examples do not limit the present invention.
(Example 1)
FIG. 1 is a schematic view showing an example of an apparatus used in the method for forming a hard carbon nitride film of the present invention. In this apparatus, on the substrate 11 placed on the substrate stage 12 in the reduced-pressure reaction chamber 8, the raw material gas containing a cyanide compound is activated by converting it into plasma, and a hard carbon nitride film is formed on the substrate 11. Is formed.

The procedure for forming a hard carbon nitride film on the substrate 11 using this apparatus will be described below.
First, the reaction chamber 8 is evacuated to about 10 ⁻³ Torr using the mechanical booster pump 1 and the rotary pump 2. Thereafter, the valve 3 is released, and argon is introduced into the plasma generation chamber 5 using a glass tube such as quartz through the drying chamber 4 filled with phosphorus pentoxide. Next, a microwave of 2.45 GHz and 100 W is input to the waveguide 7 from the microwave oscillator 6 to generate argon gas plasma. The generated plasma is drawn out from the plasma generation chamber 5 and guided to the reaction chamber 8, and the reaction and decomposition are performed with the cyanide vapor introduced through the drying chamber 9 and the nozzle 10 filled with phosphorus pentoxide in the reaction chamber 8, Cyanide decomposition products are deposited on the substrate 11 to form a carbon nitride film.
At that time, cooling water is introduced into the water channel 13 from the outside and circulated through the substrate stage 12. Further, a high frequency of 13.56 MHz is applied from the outside to the substrate stage 12 using the high frequency power supply 14 and the matching box 15, and the negative DC bias voltage value generated on the substrate stage 12 is converted into a voltage passed through the filter circuit 16. Read with 17 in total.

In this example, a silicon substrate having a length of 1 cm, a width of 1 cm, and a thickness of 0.2 mm was used, and the substrate temperature was 30 ° C. Further, the flow rate of argon was 3000 Torr · l · s ⁻¹ , bromine cyanide was used as the cyanide compound, and the flow rate was 0.03 Torr · l · s ⁻¹ .
And the negative bias voltage applied to a board | substrate was set to -40V and -100V. Further, a digital delay pulse generator 18 is connected to the high-frequency power source 14, and the period is 100 and 1000 seconds, and the on / off time ratios are 50/50, 60/40, 70/30, 80/20, and 90/10, respectively. The high frequency power supply was pulsed under the conditions.

  The carbon nitride film is formed under the conditions of on / off time ratios of 50/50, 60/40, 70/30, and 80/20, the film thickness is 0.5 to 1 μm, and the nitrogen content is 30 in terms of atomic ratio. -50%. The result of measuring the film hardness with a micro indentation hardness tester is shown in FIG. The hardness value of the film was 15 to 50 GPa, and the larger the negative bias voltage and the larger the on / off time ratio, the higher the hardness value was. Further, FIG. 3 shows the result of Raman spectroscopic analysis of the carbon nitride film manufactured under the condition of an on / off ratio of 80/20. In FIG. 3, a G band derived from a two-dimensional structure and a D band derived from a grain boundary or a three-dimensional structure are observed. As a result of analysis, the strength of the D band increases as the hardness value increases. There was a trend. From this, it was found that the D band of the film produced in this example was mainly caused by a three-dimensional network structure. As described above, a wide range of hard carbon nitride films can be synthesized by changing the substrate bias voltage and the on / off time ratio.

(Example 2)
FIG. 4 is a schematic view showing another example of an apparatus used in the method for forming a hard carbon nitride film of the present invention. In this apparatus, the same parts as those in the apparatus of FIG. The procedure for forming a hard carbon nitride film on the substrate 11 using this apparatus will be described below.
First, the inside of the reaction chamber 8 is evacuated to about 10 ⁻⁶ Torr using the turbo molecular pump 19 and the rotary pump 2. Thereafter, the valve 3 is opened, and argon is introduced into the plasma production chamber 5 made of stainless steel through the drying chamber 4 filled with phosphorus pentoxide. Next, a microwave of 2.45 GHz and 70 W is input from the microwave oscillator 6 to the antenna 21 through the coaxial cable 20 to generate argon gas plasma. At that time, a magnetic field of 875 G is generated using the permanent magnet 22 and the electrons are resonantly accelerated to generate a stable plasma at a low pressure of about 10 ⁻³ Torr. The generated plasma is drawn out from the plasma generation chamber and guided to the reaction chamber 8, where it reacts and decomposes with the cyanide vapor introduced through the drying chamber 9 and the nozzle 10 filled with phosphorus pentoxide, and carbonizes the decomposition product of the cyanide compound. A carbon nitride film is formed by depositing on the silicon substrate 11. At that time, cooling water is introduced into the water channel 13 from the outside and circulated through the substrate stage 12. Further, a high voltage of 13.56 MHz is applied from the outside to the substrate stage 12 using the high frequency power supply 14 and the matching box 15, and a negative DC bias voltage value generated on the substrate stage 12 is passed through the filter circuit 16. Read with 17.

In this example, a silicon carbide substrate having a length of 1.5 cm, a width of 1.5 cm, and a thickness of 0.5 mm was used, and the substrate temperature was 30 ° C. The flow rate of argon was 100 Torr · l · s ⁻¹ , chlorine cyanide was used as the cyanide compound, and the flow rate was 1 Torr · l · s ⁻¹ .
And the negative bias voltage applied to a board | substrate was changed between -40--100V. Furthermore, a digital delay pulse generator 18 is connected to the high-frequency power source, and the conditions of periods of 100 and 1000 seconds, on / off time ratios of 50/50, 60/40, 70/30, 80/20, and 90/10, respectively. Below, the high frequency power supply was pulsed and compared with the case of 100/0 (continuous bias). In this embodiment, a self-bias of about −10 V is generated in the substrate stage 12 even in the case of the pulse off.

In the case of continuous bias, and in the case of on / off time ratios of 80/20 and 90/10, the influence of sputtering was high, and formation of a carbon nitride film was not recognized. The carbon nitride film was formed under the conditions of on / off time ratios of 50/50, 60/40, and 70/30, and the film thickness was 0.1 to 0.5 μm. When cyanogen bromide was used as a raw material, the nitrogen content was 20-35% in terms of atomic ratio, and the film hardness was measured with a microindentation hardness tester. The hardness value was 10 GPa. The hardness value when a pulse bias was applied from the outside was 40 to 60 GPa. As a result of the experiment, the larger the on / off time ratio, the lower the film thickness and the higher the hardness value. When acetonitrile was used as a raw material, the nitrogen content was 5-25% in atomic ratio, and the film hardness was measured with a microindentation hardness tester. As a result, the hardness value was 1 to 2 GPa regardless of whether or not an external bias was applied. A soft film was obtained. In addition, infrared and Raman spectroscopic analyzes were performed on the produced carbon nitride film. In the infrared spectrum (see FIG. 5) of the carbon nitride film prepared using cyanogen bromide as a raw material at an on / off ratio of 70/30, the band of G band, D band, and CN single bond at 1200-1500 cm ^−1. Was observed, and no vibration of a hydrogen-terminated structure such as NH was observed at 3200-3500 cm ⁻¹ . Furthermore, both G band and D band were observed in the Raman spectrum. On the other hand, in the infrared spectrum of the carbon nitride film using acetonitrile as a raw material, the band of the CN single bond was not observed, and the band of the hydrogen termination structure was strongly observed. Furthermore, no peak was observed in the Raman spectrum.

(Example 3)
FIG. 6 is a schematic view showing another example of an apparatus used in the method for forming a hard carbon nitride film of the present invention. In this apparatus, the same parts as those in the apparatus of FIG. The procedure for forming a hard carbon nitride film on the substrate 11 using this apparatus will be described below.
First, the inside of the apparatus is evacuated to about 10 ⁻⁶ Torr using the turbo molecular pump 19 and the rotary pump 2. Thereafter, the valve 3 is released, and a mixed gas of argon, nitrogen and cyanide is introduced into the quartz glass plasma generation chamber 5 through the drying chamber 4 filled with phosphorus pentoxide. Next, a microwave of 2.45 GHz and 100 W is input from the microwave oscillator 6 to the waveguide 7 to generate plasma. Cyanide decomposition products are deposited on the silicon carbide substrate 11 to form a carbon nitride film. At that time, cooling water is introduced into the water channel 13 from the outside and circulated through the substrate stage 12. Further, a high voltage of 13.56 MHz is applied from the outside to the substrate stage 12 using the high frequency power supply 14 and the matching box 15, and a negative DC bias voltage value generated on the substrate stage 12 is passed through the filter circuit 16. Read with 17.

In this example, a silicon carbide substrate having a length of 1.5 cm, a width of 1.5 cm, and a thickness of 0.5 mm was used, and the substrate temperature was 30 ° C. Further, the flow rate of argon 1000Torr · l · ^{s -1,} the nitrogen flow rate using cyanide iodine as 200Torr · l · ^{s -1,} and cyanide, the flow rate thereof and 0.01Torr · l · ^{s -1} did.
And the negative bias voltage applied to a board | substrate was changed between -40--100V. Furthermore, a digital delay pulse generator 18 is connected to the high-frequency power source, and the conditions of periods of 100 and 1000 seconds, on / off time ratios of 50/50, 60/40, 70/30, 80/20, and 90/10, respectively. The high frequency power supply was pulsed below.

The carbon nitride film was formed under the conditions of on / off time ratios of 50/50, 60/40, 70/30, and 80/20, and the film thickness was 0.1 to 0.5 μm. The nitrogen content was 25-45% by atomic ratio, and the film hardness was 40-60 GPa as a result of measuring the film hardness with a microindentation hardness tester. Further, the generated result of performing infrared and Raman spectroscopic analysis of carbon nitride film, G band 1200-1500cm ^-1, D band and C-N single bond bands were observed, the 3200-3500cm ^-1 N- No vibrations of hydrogen-terminated structures such as H were observed. Furthermore, both G band and D band were observed in the Raman spectrum.

It is a schematic diagram which shows an example of the apparatus used for the formation method of the hard carbon nitride film of this invention. It is a figure which shows the result of having measured the film | membrane hardness of the carbon nitride film obtained in Example 1. FIG. It is a figure which shows the result of having performed the Raman spectroscopic analysis of the carbon nitride film obtained in Example 1. FIG. It is a schematic diagram which shows the other example of the apparatus used for the formation method of the hard carbon nitride film of this invention. It is a figure which shows the infrared spectrum of the carbon nitride film produced using cyanogen bromide as a raw material. It is a schematic diagram which shows the other example of the apparatus used for the formation method of the hard carbon nitride film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mechanical booster pump 2 Rotary pump 3 Valves 4 and 9 Drying chamber 5 Plasma generation chamber 6 Microwave oscillator 7 Waveguide 8 Reaction chamber 10 Nozzle 11 Substrate 12 Substrate stage 13 Water channel 14 High frequency power supply 15 Matching box 16 Filter circuit 17 Voltmeter 18 Digital Delay Pulse Generator 19 Turbo Molecular Pump 20 Coaxial Cable 21 Antenna 22 Permanent Magnet

Claims (8)

When a carbon nitride film is formed on a substrate by activating the source gas containing a cyanide compound into a plasma, a high frequency pulse with a pulse period of 10 to 10000 seconds is applied to the substrate with an on / off ratio of 50/50 to 80/20. A method for forming a hard carbon nitride film, wherein   The method of forming a hard carbon nitride film according to claim 1, wherein the temperature of the substrate is maintained at 0 to 100 ° C.   3. The method of forming a hard carbon nitride film according to claim 1, wherein the high-frequency pulse bias voltage is -50 to -200V.   4. The method for forming a hard carbon nitride film according to claim 1, wherein the source gas is a mixed gas of a cyanide compound and an inert gas.   5. The method for forming a hard carbon nitride film according to claim 1, wherein the substrate has a surface selected from silicon, silicon carbide, and silicon nitride.   The method for forming a hard carbon nitride film according to claim 1, wherein the hardness of the hard carbon nitride film is 20 to 60 GPa.   The method for forming a hard carbon nitride film according to claim 1, wherein the nitrogen content of the hard carbon nitride film is 20 to 50% in atomic ratio. Hard nitriding according to any one of claims 1 to 7, wherein any one of direct current, alternating current, high frequency, microwave, and ECR is used as the plasma generating means, and plasma is generated at a pressure of 10 ^{-4 to 1} Torr. A method for forming a carbon film.

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