JP2833164B2 - Apparatus and method for producing diamond film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus and a method for producing a diamond film, and more particularly to a method for producing a diamond film in a gas phase by using arc discharge.

[Conventional technology]

In recent years, low-pressure gas-phase synthesis of diamond films has been proposed, and the synthesis methods can be roughly classified into the following three types.

The first method is called a hot filament CVD method, in which a tungsten filament is provided directly above a substrate heated to 800 to 1000 ° C., and the filament is heated to 2000 ° C. or more, and hydrogen and a hydrocarbon gas (eg, CH ₄ ) are used. Is sprayed onto a substrate through a filament to grow a diamond film on the substrate. The second is microwave plasma CVD
In this method, a plasma is generated in a mixed gas gas of hydrogen and hydrocarbon gas by a microwave of several hundred watts, and diamond is grown on a substrate placed in the plasma.The substrate is heated by the microwave. The temperature is about 700-900 ° C. In the above two synthetic methods, atomic hydrogen plays an important role. Atomic hydrogen promotes the decomposition of CH ₄ and also selectively etches synthetic materials other than diamond, such as amorphous carbon. The third is a synthesis method using an ion beam, in which a diamond ion film is grown by applying a carbon ion beam to a substrate.

[Problems to be solved by the invention]

However, the above-mentioned conventional diamond production method proposed at present has a speed of several μm /
Very slow with Hr, for example, thickness as a substrate for heat sink
Attempting to synthesize a diamond film of 100 μm or more took an extremely long time, and was not practical in terms of cost.

The present inventors have previously found that DC arc discharge is extremely effective for high-speed synthesis of diamond films. Arc discharge is characterized in that the electron temperature is close to the gas temperature, and the gas temperature is as high as several thousand degrees ゜ k or more. Therefore, the decomposition of the H ₂ gas and the hydrocarbon gas supplied as the source gas for diamond proceeds significantly compared to the hot filament CVD or the microwave PCVD method using glow discharge. As a result, the diamond synthesis method using the DC arc discharge can achieve a synthesis speed 10 to 100 times faster than the conventional synthesis method.

As a synthesis method using a DC arc discharge, as shown in Japanese Patent Application No. 62-256805 previously proposed by the present applicant, a raw material gas is passed through an arc discharge to form a gas plasma, and this gas plasma is formed by a throttle section. The method of forming a plasma jet and spraying the plasma jet on the substrate is effective in that the source gas can be effectively used. However, the following facts were also found in the present synthesis method.

The gas plasma blown as a plasma jet has a high gas temperature of several thousand ゜ k. When diamond is grown on a substrate under low pressure, if the temperature of the diamond growth surface on the substrate exceeds 1000 ° C., the generation rate of impurity carbon such as graphite (carbon other than diamond) increases. Therefore, in the arc discharge plasma jet type synthesis method, the cooling of the substrate and the control of its temperature become very important. Further, even when cooling is performed well, the temperature of the diamond growth surface seems to be different as the film thickness of the growing diamond increases. Diamond is a very good heat conductor, but as the diamond thickness increases (synthesis time increases), the heat insulation effect increases the surface level, and consequently the impurity carbon contamination rate increases. The present inventors have found that this is the case. Third
The figure shows the data indicating this, 1Hr, 5H
FIG. 9 shows Raman shift data of a Raman spectrometer for a diamond film in which the synthesis of r and 10Hr is interrupted. The film thickness is increased corresponding to the synthesis time, and the diamond film thickness is 30 μm at 1 Hr, 150 μm at 5 Hr, and 300 μm at 10 Hr. Higher the longer third diagram the synthesis time according to the Raman spectrum of the data, i.e., the peak of the impurity carbon graphite or the like of 1600 cm ^-1 and near 1370 cm ^-1 vicinity higher the diamond film becomes thicker is to be seen conspicuously . That is, it has been found that as the film thickness increases, the growth surface temperature of the diamond increases to 1000 ° C. or higher, and such impurities are formed.

The present invention has been made based on the discovery of the above fact, and provides a manufacturing apparatus and a manufacturing method capable of obtaining high-purity diamond irrespective of the diamond film thickness (or synthesis time). It is intended to be.

[Means for solving the problem]

In order to achieve the above object, the apparatus for producing a diamond film according to the present invention includes a vacuum vessel maintained at a predetermined degree of vacuum; a positive electrode and a negative electrode arranged in the vacuum vessel so as to face each other; An electric power source for arc discharge that electrically connects to the positive electrode and the negative electrode and applies a predetermined electric power to cause arc discharge in the space between the positive electrode and the negative electrode; and a gas source is generated by flowing at least a plasma source gas into the arc discharge. Gas supply means for blowing the gas plasma containing gas onto a substrate disposed downstream thereof; detection means for detecting a cause of an increase in the temperature of the surface of the diamond film grown on the substrate; and The diamond is grown during the growth of the diamond film in accordance with the factor detected by the detection means so that the temperature becomes a predetermined temperature. It is characterized in that it comprises cooling means for cooling the film.

Further, the method for producing a diamond film according to the present invention is characterized in that a gas plasma is generated by flowing at least a plasma source gas through an arc discharge, and the gas plasma containing a carbon source gas is blown onto a substrate disposed downstream of the gas plasma. In the method of depositing and forming a diamond film on the substrate, detecting a factor that raises the temperature of the surface of the diamond film growing on the substrate, and detecting the temperature so that the temperature of the surface of the diamond film becomes a predetermined temperature. The method is characterized in that the diamond film is cooled during the growth of the diamond film depending on the factors.

〔Example〕

 Hereinafter, the present invention will be described using embodiments shown in the drawings.

FIG. 1 is a view showing an outline of a manufacturing apparatus used in one embodiment of the present invention, and FIG. 2 is a plasma jet gun shown in FIG.
FIG. 1 is a cross-sectional view showing a substrate 2 and a substrate support 3. The plasma jet gun 1 is provided with an electrode cooling portion 8 made of copper, a gas introduction portion 9 made of Teflon, and a cylindrical electrode 10 made of copper around a rod-shaped electrode 7 made of tungsten having one end formed at an acute angle. I have. Electrode cooling unit 8
And the cylindrical electrode 10 has a hollow portion 108, which is a hollow portion,
110 are provided.

Cooling water is supplied to the electrode cooling section 8 and the cylindrical electrode 10 from cooling water pipes 140a and 150a, respectively.
It is discharged from the cooling water pipes 150b and 140b. This prevents electrode wear due to the heat of the arc discharge generated between the rod-shaped electrode 7 and the cylindrical electrode 10.

The gas introduction unit 9 is provided with a raw material gas introduction pipe 16, and is further opened at one end of the rod-shaped electrode 7 so that gas supplied from the gas introduction pipe 16 is sent to the tip 7 a of the rod-shaped electrode 7. Is configured. Further, in order to cause an arc discharge between the rod-shaped electrode 7 and the cylindrical electrode 10, an arc discharge power supply 17 is connected between the rod-shaped electrode 7 and the cylindrical electrode 10 so that the cylindrical electrode 10 has a positive potential. Have been. In addition, the gas inlet 9 of the cylindrical electrode 10
On the opposite side, a plasma outlet 18 as a throttle is provided.

The substrate 2 is placed on the substrate support 3 downstream of the plasma ejection port 18. In this embodiment, a silicon single crystal plate is used as the substrate 2. The substrate support 3 is hollow so that cooling water can be supplied from the cooling water pipe 20a and discharged from the cooling water pipe 20b to maintain the substrate at a predetermined temperature (about 800 ° C. in this embodiment). This is the plasma spout
Since the gas temperature of the plasma jet ejected from 18 reaches several thousands to tens of thousands of degrees, it is necessary to cool the substrate 2 mainly to keep the substrate temperature at 600 to 1100 ° C., which is the diamond synthesis region. Because. Also, plasma spout
A hydrocarbon gas inlet 19 is provided near 18.

Since these devices are operated under reduced pressure in the range of 5 Torr to 5 atm, they are housed in a vacuum vessel 100 except for the arc discharge power supply 17 as shown in FIG.

In FIG. 1, reference numerals 1, 2, and 3 denote plasma jet guns, substrates, and substrate supports 3 described with reference to FIG.
And 30 is a non-contact thermometer, 31 is a window, 32 is a gear, 33
, A support base up-down mechanism; 34, a step motor; and 35, a microcomputer. The plasma jet gas is sprayed from the plasma jet gun 1 onto the substrate 2, and diamond is deposited on the substrate 2. The surface temperature of the diamond film growing on the substrate 2 is measured through the window 31 by the non-contact thermometer 30 and the signal is obtained from the set value of the diamond film surface temperature previously input into the microcomputer 35. When the temperature rises, the substrate support 3 is lowered by driving the support up / down mechanism 33 via the step motor 34 and the gear 32, and the substrate 2 is separated from the plasma jet gun 1 so that the surface temperature becomes the set value. Operate. Conversely, if the diamond film surface temperature falls below the set value, the substrate support 3
To keep the diamond film surface temperature constant. Here, the support base vertical mechanism moves up and down by rotating the gear 32,
The gear 32 is a microcomputer that sends signals from the non-contact thermometer 30
It is rotated by the step motor 34 with the feedback of 35.

Incidentally, as a specific configuration of the non-contact thermometer 30, one having a mechanism as shown in FIG. 5 can be adopted. That is, the surface radiance intensity (changed with temperature) of the substrate 2 is changed by the lens 30a.
After passing through the optical filter 30b, the light intensity is measured by a detector 30c such as a diode array. Since the spectrum of the heat radiator follows the blank radiation formula, the light intensity increases as the temperature rises, and the temperature can be determined by measuring the intensity of the radiance at a certain wavelength.

The set value of the surface temperature of the diamond film is a value within the range since the synthesis of diamond is possible in the range of 600 to 1000 ° C. The optimum temperature differs depending on the gas composition, pressure, and the like. It is appropriate that the control temperature range is within ± 5 ° C.

Next, a method for synthesizing a diamond film using the above-described apparatus will be described. First, after evacuating the inside of the vacuum vessel 100, argon, which is a Group 0 gas having a high degree of ionization, is introduced into the plasma jet gun 1 from the gas introduction pipe 16, and the pressure inside the vacuum vessel 100 is set to 50 Torr. Thereafter, an arc discharge is generated between the rod-shaped electrode 7 (negative electrode) and the cylindrical electrode 10 (positive electrode) by the arc discharge power supply 17. When the discharge was stabilized, a mixed gas of 60 vol% of argon and 40 vol% of H _{2 was} supplied to the arc discharge through a gas introduction pipe 16.
/ min flow rate to obtain gas plasma. Further, methane gas was introduced at 60 cc / min and hydrogen gas was introduced at 200 cc / min from the hydrocarbon gas inlet 19. Here, the hydrocarbon gas typified by methane gas may be introduced from the working gas introduction pipe 16, but since the tungsten electrode rod is carbonized and the discharge is not stabilized for a long time, the hydrocarbon gas discharge section is downstream. It is desirable to introduce the gas through the gas inlet 19 of the first embodiment. Vacuum container
The pressure inside 100 is exhausted to keep it at 50 Torr. The arc discharge was performed under the conditions of a voltage of 40 V and a current of 50 A. The gas plasma was passed through the plasma outlet 18 to form a plasma jet, and methane gas introduced from the hydrocarbon gas inlet 19 was blown onto the plasma jet to form a plasma jet gas. The center temperature of the plasma is 3000 ℃ in gas temperature.
That is all, and the discharge part inside the gun has risen further. Then, a red-purple plasma jet gas is sprayed on the substrate 2 to precipitate and form diamond.

Next, a method of controlling the surface temperature of the diamond film to a value near the set value in forming the diamond film will be described.

The microcomputer 35 starts the control shown in FIG. 6 in response to the start of the arc discharge by the arc discharge power supply 17. This control is performed by repeatedly executing steps 200 to 240 while the arc discharge is being performed.

First, in step 200, the detection data T indicating the outermost surface temperature of the diamond film detected by the non-contact thermometer 30 is input from the non-contact thermometer 30 and the set value data stored in the microcomputer 35 in advance. Read To and allowable deviation data D. As the set value data To, for example, 900 ° C. is set as the set value of the outermost surface temperature of the diamond film, and as the allowable deviation data D, a value corresponding to 20 ° C. is set. This is because when the outermost surface temperature of the diamond film is 800 ° C or lower, the possibility that amorphous carbon called i-carbon is generated increases, and when the temperature is 1000 ° C or higher, the possibility that impurity carbon such as graphite is generated increases. Because you do.

In step 210, it is determined whether or not the difference between the detection data T and the set value data To is equal to or smaller than the allowable deviation data D. If this determination is YES, the process returns to step 200. But,
If the detection data T is lower than the set value data To by the allowable deviation data D or more, the determination in step 210 is NO, and the process proceeds to step 240 via step 220. In this step 240, an ascending signal is sent to the stepping motor 34 to raise the support base up-and-down mechanism 33. As a result, the temperature of the diamond surface rises and approaches the set value.

If the detected data T is higher than the set value data To by the allowable deviation data D or more, the process proceeds from step 210 to step 230 via step 220. In this step 230, a lowering signal is sent to the step motor 34 to lower the support base vertical mechanism 33. As a result, the temperature of the diamond surface decreases and approaches the set value.

Therefore, by performing the above feedback control,
Maintain the temperature of the diamond surface between 880 ° C and 920 ° C.

Thus, according to the present example, as a result of synthesizing a diamond film under the above conditions, the synthesis speed was 30 μm / Hr, and the synthesis was possible at a considerably high speed. Then, the temperature of the surface of the diamond film is detected, and the temperature of the surface is controlled to a set value according to the detected temperature. The set value is always accurately controlled without depending on the thickness (or the synthesis time), and as a result, a diamond film with high purity can be obtained. FIG. 4 shows Raman shift data of a diamond film Raman analyzer in which synthesis of 1Hr, 5Hr, and 10Hr was continued from the start of synthesis according to the present embodiment.

From the results of the Raman spectrum, it was found that even when the film thickness became close to 300 μm, only a slight peak of impurity carbon was observed, which had a great effect on improving the purity of the diamond film.

As described above, the present invention has been described using the above embodiments. However, the present invention is not limited thereto, and various modifications can be made as shown below, for example, without departing from the gist of the present invention.

(1) Although the above-described embodiment uses the support base up-and-down mechanism 33 as means for adjusting the surface temperature of the diamond film, the temperature may be adjusted by the arc discharge power supply 17. That is, the diamond film surface temperature signal from the non-contact thermometer 30 is fed back to the arc discharge power supply 17 via the microcomputer 35, and the discharge power may be controlled.If the surface temperature increases, the power is reduced, Conversely, if the surface temperature decreases, the power is increased. However,
In this case, if the change in power is large, the discharge itself becomes unstable.

The surface temperature is adjusted by feeding back the temperature signal of the non-contact thermometer 30 and changing the amount or temperature of the cooling water in the cooling water pipes 20a and 20b for cooling the substrate support 3. May be. However, since the control by the water temperature or the amount of water has a problem in responsiveness, and it is difficult to perform delicate temperature control, the control is performed in combination with the above-described method of moving the support base up and down mechanism 33 up or down, or the method of controlling discharge power. It is desirable.

(2) In the above embodiment, the temperature of the surface of the diamond film is directly detected using the non-contact thermometer 30 as a cause of the change in the temperature of the surface of the diamond film according to the present invention. Since the temperature varies depending on the thickness of the diamond film or the synthesis time, the temperature of the surface may be detected indirectly by detecting them. When the synthesis conditions change, the relationship between the film thickness or the synthesis time of the diamond film and the temperature of the surface of the diamond film also changes, so it is necessary to control the change in consideration of the change.

(3) Although the arc discharge plasma jet method is used in the above embodiment, the same effect as that of the above embodiment can be obtained by the arc discharge method having the structure shown in Japanese Patent Application No. 62-5527. That is, arc discharge is generated between the electrodes facing each other by an arc discharge electrode, and a mixed gas of hydrogen, methane, and argon is used as a source gas containing a plasma source gas and a carbon source gas from a source gas introduction pipe as in the above-described embodiment. Flow at the same ratio and flow rate.

Then, as in the above-described embodiment, a factor that changes the temperature of the surface of the diamond film grown on the substrate is detected, and the temperature of the surface of the diamond film is controlled to a predetermined temperature according to the detected factor. It is good to do.

〔The invention's effect〕

As described above, according to the present invention, a factor that changes the temperature of the surface of a diamond film grown on a substrate is detected, and the temperature of the surface of the diamond film is set to a predetermined temperature according to the detected factor. Control
There is an effect that a highly pure diamond film can be obtained.

In addition, if the temperature of the surface of the diamond film is directly detected as the factor, there is an effect that the detection accuracy of the temperature is increased and the controllability is improved.

[Brief description of the drawings]

FIG. 1 is a view showing an outline of a manufacturing apparatus used in a first embodiment of the present invention, FIG. 2 is a sectional view showing a plasma jet gun, a substrate, and a substrate support table in FIG. 1, and FIG. Raman shift data of the Raman spectrometer of the technology.
Raman shift data of the Raman spectrometer of the embodiment shown in the figure, FIG. 5 is a diagram for explaining the mechanism of the non-contact thermometer, and FIG. 6 is a flowchart showing control of the microcomputer in FIG. 1 ... Plasma jet gun, 2 ... Substrate, 3 ... Substrate support, 17 ... Power supply for arc discharge, 30 ... Non-contact thermometer, 33 ...
… Supporting mechanism, 34… Step motor, 100… Vacuum container.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Hattori 14 Iwatani, Shimowasumi-machi, Nishio-shi, Aichi Pref. Japan Automotive Parts Research Institute Co., Ltd. Field surveyed (Int. Cl. ⁶ , DB name) C30B 1/00-35/00

Claims (4)

(57) [Claims] 1. A vacuum vessel maintained at a predetermined degree of vacuum, a positive electrode and a negative electrode disposed in the vacuum vessel so as to face each other, and electrically connected to the positive electrode and the negative electrode, and in a space between the positive electrode and the negative electrode. An electrode for arc discharge for applying a predetermined electric power to cause arc discharge, a substrate for generating gas plasma by flowing at least a plasma source gas in the arc discharge, and disposing the gas plasma containing a carbon source gas downstream thereof Gas detecting means for detecting a cause of an increase in the temperature of the surface of the diamond film grown on the substrate; andthe detecting means so that the temperature of the surface of the diamond film becomes a predetermined temperature. Cooling means for cooling the diamond film during the growth of the diamond film according to the detected factor. Yamondo film production apparatus. 2. The diamond film manufacturing apparatus according to claim 1, wherein said detecting means detects a temperature of a surface of said diamond film as said factor. 3. A gas plasma is generated by flowing at least a plasma source gas through an arc discharge, and a diamond film is deposited on the substrate by spraying the gas plasma containing a carbon source gas on a substrate disposed downstream thereof. In the method of forming, while detecting a factor that raises the temperature of the surface of the diamond film grown on the substrate, the temperature of the surface of the diamond film becomes a predetermined temperature, according to the detected factor, A method of manufacturing a diamond film, wherein the diamond film is cooled during the growth of the diamond film. 4. The method according to claim 3, wherein the factor is a temperature of a surface of the diamond film.