JP3496254B2 - Method and apparatus for vapor phase synthesis of diamond - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for vapor-phase synthesizing film-like diamond on the surface of a substrate and a synthesizing apparatus therefor.

[0002]

2. Description of the Related Art As a vapor phase synthesis method of diamond, there is a CVD method (chemical vapor deposition method) such as a hot filament CVD method and a plasma CVD method. A typical example of this is the hot filament CVD method, which is reported by Matsumoto et al.
n. J. Apnl. Phys., 21, L183 (198)
Since 2) (see 2), active research and development have been promoted and various methods have been proposed.

In the hot filament CVD method, a filament arranged near the surface of the substrate is heated to a high temperature to heat and excite a gas containing carbon atoms such as methane and hydrogen gas, and the excited state of methane produced by this heat excitation. Etc. to deposit diamond. At this time, graphite-like carbon is produced at the same time as the diamond, but this graphite-like carbon is removed by the atomic hydrogen produced by the heat excitation of hydrogen gas, and only diamond mainly grows on the surface of the base material. The hot filament CVD method has the advantages that the apparatus configuration is extremely simple and that the area of the diamond film to be produced can be increased relatively easily.

In the hot filament CVD method,
As a filament used as a heating excitation member for heating and exciting a gas containing carbon atoms and hydrogen gas, a filament such as tungsten having a circular cross section is wound into a coil (NEW).
DIAMOND, Vol. 6, No. 1, p. 9 to 15), and a plurality of linearly arranged straight lines having a circular cross section (see JP-A-3-115576).
Etc. are known. However, to the best of our knowledge, no heat-exciting members having shapes other than filaments have been studied.

Further, in order to carry out the vapor phase synthesis of diamond at a high speed, it is generally considered necessary to raise the temperature of a mixed gas of a gas containing carbon atoms and hydrogen gas and to input high power. (DIAMOND AN
D RELATED MATERIALS, Vol.1,
P1-12 (1991)).

Therefore, even in the hot filament CVD method, it is necessary to raise the filament temperature or increase the filament diameter to increase the input power in order to increase the growth rate and quality of diamond. Considered ("Powder and Powder Metallurgy", Vol. 34, No. 9, 395-401: J. Appl. Phys., 7).
1, (3) 1485-1493: APPLID OPTI
CS, Vol.29, No.33, P4993-4999
reference).

[0007]

As described above, in the conventional hot filament CVD method, in order to grow high quality diamond at a high speed, the temperature of the filament is increased and the diameter of the filament is increased to increase the input power. Need to be bigger. However, it is not desirable to increase the input power because the ratio of the power cost to the cost is not small.

[0008] In addition, since a large amount of heat is generated in the vacuum container for film formation when the applied power is increased and the filament temperature is raised, many measures have been taken in the cooling method of the substrate support base and the inner wall of the container. This is required (Japanese Patent Laid-Open No. 3-11557).
No. 6 publication). It is said that the proper substrate temperature for diamond growth is about 800 to 1000 ° C., but the higher the temperature of the hot filament, the higher the temperature of the hot filament of the substrate and the high efficiency cooling body. Since the base material is sandwiched between the base material and the base material, there is a risk that the base material is subjected to extremely high thermal strain and cracks or warps greatly.

In view of the above conventional circumstances, the present invention is a method for synthesizing high-quality diamond on the surface of a substrate by a vapor phase synthesis method at a high speed, in a large area, at low power, and at low cost. The purpose is to provide a device.

[0010]

In order to achieve the above object, the method for vapor phase synthesis of diamond provided by the present invention comprises:
In the method of vapor phase synthesizing diamond on the surface of a substrate by heating and exciting a gas containing carbon atoms and hydrogen gas, after heating the hydrogen gas only, the exothermic excitation member made of a porous body is contacted It is characterized in that the gas is supplied to the surface of the heated substrate which is arranged opposite to the excitation member, and at the same time, the gas containing carbon atoms is supplied to the surface of the substrate through a route different from the hydrogen gas.

[0011] Further, a gas phase synthesizing apparatus of the diamond according to the invention for carrying out the above method, the second gas supply for supplying a gas containing a first gas supply passage and the carbon atoms supplying hydrogen gas to the substrate surface Separate passages, and a porous body is formed at the end of the first gas supply passage for supplying hydrogen gas on the substrate side.
The heat-exciting member is provided so as to face the surface of the base material.

[0012]

[Function] In the vapor phase synthesis of diamond, it is known that atomic hydrogen generated by heating and exciting hydrogen gas is greatly related to the formation of diamond, and the related mechanism of diamond formation was also announced. (Appl. Phys. Lett., 56, (23)
P2298-2300). According to it, in order to grow high quality diamond at high speed, it is important to increase the generation amount of atomic hydrogen.

The present inventors have studied the vapor phase synthesis reaction of diamond in the hot filament CVD method, and particularly analyzed the mechanism of atomic hydrogen generation. As a result, atomic hydrogen is almost 100% on the surface of the filament. It was found that the reaction was generated by the heterogeneous catalytic reaction of, and the reaction rate was found to reach several tens of times that of the reaction in the usual gas phase. Further, in the reaction of producing atomic hydrogen, carbon compounds such as methane existing in the gas containing carbon atoms supplied together with hydrogen gas act as catalyst poisons to reduce the amount of atomic hydrogen generated. I understand.

Based on these findings, the exothermic excitation member having a large surface area is used in place of the conventional filament, and the hydrogen gas and the gas containing carbon atoms are separately introduced to the surface of the base material to produce the exothermic excitation member. By contacting only hydrogen gas without contacting gas containing carbon atom with
As a result of being able to generate a large amount of atomic hydrogen, it was found that high quality diamond can be grown at high speed, and the present invention has been completed.

In the present invention, since the surface area of the conventional filament is small, an exothermic excitation member having a plurality of communication holes is used as an alternative exothermic excitation member having a large surface area. As a preferred specific example of the heat generation excitation member having a plurality of communication holes, a structure in which a plurality of tubular bodies of foil or net are arranged so that each communication hole opens near the surface of the base material, or from a porous body There is something. The surface area of the exothermic excitation member having a plurality of communication holes is much larger than the surface area of a conventional filament having a linear or coil shape, and thus it is possible to generate a much larger amount of atomic hydrogen as compared with the conventional one. Is.

The material of the heat generation excitation member having a plurality of communication holes is preferably at least one metal selected from the group consisting of rhenium, molybdenum, tungsten, niobium and tantalum.

The exothermic excitation member having a plurality of communication holes according to the present invention is preferably installed near the end of the first gas supply passage for supplying hydrogen gas on the base material side. Since the number of filaments is large, it is possible to install the filaments farther from the surface of the substrate than the ordinary filaments. However, if the distance between the exothermic excitation member and the substrate surface is too large, the growth of diamond is hindered even if the amount of atomic hydrogen generated is large,
If too close, excessive heat stress is applied to the base material, so that the reaction pressure and the flow rate of hydrogen gas affect it, but the distance between the base material side end of the heat generation excitation member and the base material surface is in the range of 5 to 100 mm. Preferably.

Further, the hydrogen gas and the gas containing carbon atoms are carried by separate gas supply passages without being mixed with each other until reaching the surface of the substrate. That is, the gas containing carbon atoms is supplied to the surface of the base material without passing through the communication holes of the heat generation excitation member having the plurality of communication holes. As a result, the exothermic excitation member can be prevented from being contaminated with the carbon compound in the gas containing carbon atoms, and the generation of atomic hydrogen is not hindered.

As a preferable structure of the gas supply passage, a substantially funnel-shaped cylinder is provided at the end of the first gas supply passage for supplying hydrogen gas on the base material side, and a plurality of communication holes are provided in the funnel-shaped cylinder. Store the heat generation member. On the other hand, the base material side end portion of the second gas supply passage for supplying the gas containing carbon atoms is formed into an annular shape which surrounds the base material and has a gas outlet inside, and the funnel-shaped tube is provided on the annular portion. Place the body in contact with or close to it.

Further, the gas containing carbon atoms from the second gas supply passage may be directly supplied to the surface of the base material without being heated, or may be heated and excited and then supplied to the surface of the base material. In this case, the heat generation excitation member is not particularly limited, but it is simple and preferable to provide a linear or coiled filament near the annular portion of the second gas supply passage. The material of this filament is rhenium, molybdenum, tungsten, similar to the heat generation excitation member having a plurality of communication holes.
It is preferably at least one metal selected from the group consisting of niobium and tantalum.

[0021]

Embodiment 1 As shown in FIG. 1, a normal vacuum container 1 is provided with a first gas supply passage 2 for supplying hydrogen gas and a second gas supply passage 3 for supplying gas containing carbon atoms. And a funnel-shaped cylindrical body 4 made of heat-resistant ceramics and having a maximum inner diameter of 13 mm was attached to the end portion of the first gas supply passage 2 on the base material side. On the other hand, an annular portion 5 having an inner diameter of 50 mm and having a plurality of outlets 6 on the inner circumference was attached to the base material side end portion of the second gas supply passage 3.

A tantalum foil having a thickness of 10 μm and a diameter of 3 mm and a length of 1 is used as the heat generation excitation member having a plurality of communication holes.
Ten cylindrical bodies 7 rolled into a cylindrical shape of 00 mm were arranged with their center lines aligned in parallel, and housed and fixed inside the funnel-shaped cylindrical body 4 of the first gas supply passage. Electrodes were attached to the upper and lower ends of each tubular body 7 and connected to an external power source 8 (only one connecting wire is shown in FIG. 1). Further, a silicon base material 9 having a diameter of 50 mm is placed on the base material support base 10, and the distance between the surface of the base material 9 and the lower end of the heat generation excitation member composed of the ten cylindrical bodies 7 is 20 mm. It was set so that

2 in 10 cylindrical bodies 7 which are heat generation excitation members
When heating was performed by applying an alternating current of 8 A and 30 V, the surface temperature of the heat generation excitation member became 2050 ° C. Further, the temperature of the base material 9 is set to 9 by a heater built in the base material support base 10.
Heated to 00 ° C. In this state, hydrogen gas was supplied from the first gas supply path 2 at a flow rate of 3000 sccm and methane gas was supplied from the second gas supply path 3 at a flow rate of 30 sccm, the total pressure was adjusted to 40 Torr, and film formation was performed for 11 hours. .

The substrate 9 taken out after the film formation had a diameter of 50 m.
A diamond film was formed on the entire surface of m, and the amorphous / diamond peak ratio was about 0.01 over the entire surface as identified by Raman spectroscopy. Therefore, it is a good diamond film. understood. The diamond film had a maximum film thickness of 95 μm, and the film thickness variation was 11%.

Embodiment 2 The annular portion 5 of the second gas supply passage 3 in the device of Embodiment 1
Inside the, one filament of 0.1 mm diameter rhenium wire wound in a coil is placed in an annular shape.
An alternating current of 5 A and 53 V was applied to heat to 1600 ° C. Other configurations of the apparatus were the same as in Example 1, and the film forming conditions were the same as in Example 1 except that the substrate temperature was 850 ° C. and the film forming time was 10 hours.

The substrate taken out after film formation had a diameter of 50 mm.
A diamond film was formed on the entire surface of the film, and this film was identified by Raman spectroscopy.
Since the peak ratio of diamond is about 0.01, it was found that the diamond film was good. The maximum thickness of this diamond film was 105 μm, and the variation in the thickness was 12%.

Embodiment 3 In a normal vacuum container, a first gas supply passage for supplying hydrogen gas and a second gas supply passage for supplying gas containing carbon atoms are separately arranged, and the first gas supply passage A funnel-shaped cylindrical body made of heat-resistant ceramics and having a maximum inner diameter of 13 mm was attached to the end portion on the base material side. On the other hand, an annular portion having an inner diameter of 50 mm and having a plurality of outlets on the inner periphery was attached to the base material side end portion of the second gas supply passage.

As a heat generation excitation member having a plurality of communication holes, a net obtained by knitting a tungsten wire having a wire diameter of 10 μm into 100 mesh is rolled into a cylindrical shape having a diameter of 3 mm and a length of 100 mm, and the center line is 10 cylinders. And arrange them in parallel,
It was housed inside the funnel-shaped cylindrical body of the first gas supply passage. still,
Electrodes were attached to the upper and lower ends of each tubular body and connected to external power sources.

Inside the annular portion of the second gas supply passage, one filament of a rhenium wire having a diameter of 0.1 mm wound in a coil is installed in an annular shape, and 1.5 A, 53 V is attached to this filament.
And was heated to 1600 ° C. Furthermore,
A silicon base material having a diameter of 50 mm was placed on the base material support, and the distance between the surface of the base material and the lower end of the heat generation excitation member composed of the ten cylindrical bodies was set to 20 mm. .

13 heat-exciting members are provided in 10 cylindrical bodies.
When heating was performed by passing an alternating current of A and 30 V, the surface temperature of the exothermic excitation member reached 2000 ° C. The temperature of the base material was heated to 850 ° C. by a heater built in the base material support. In this state, hydrogen gas was supplied at a flow rate of 3000 sccm from the first gas supply path and methane gas was supplied at a flow rate of 25 sccm from the second gas supply path, and the total pressure was 30 Torr.
After adjusting to r, film formation was performed for 10 hours.

The base material taken out after the film formation had a diameter of 50 mm.
A diamond film was formed on the entire surface of the film, and this film was identified by Raman spectroscopy.
Since the peak ratio of diamond is about 0.01, it was found that the diamond film was good. The film thickness of this diamond film was 103 μm at maximum, and the variation in film thickness was 13%.

Example 4 In a normal vacuum container, a first gas supply path for supplying hydrogen gas and a second gas supply path for supplying gas containing carbon atoms are separately arranged, and the first gas supply path A funnel-shaped cylindrical body made of heat-resistant ceramics and having a maximum inner diameter of 13 mm was attached to the end portion on the base material side. On the other hand, an annular portion having an inner diameter of 50 mm and having a plurality of outlets on the inner periphery was attached to the base material side end portion of the second gas supply passage.

A porous molybdenum foam having a diameter of 12 mm and a length of 100 mm is prepared as a heat-exciting member having a plurality of communication holes, and electrodes are attached to the upper and lower sides of the molybdenum foam, respectively, to form a funnel-shaped tubular body for the first gas supply passage. It was stored inside. The porosity of this molybdenum foam (the ratio of pores per unit volume) was 87%. Furthermore, a silicon base material having a diameter of 50 mm was placed on the base material support, and the distance between the surface of the base material and the lower end of the heat generation excitation member made of the molybdenum foam was set to 20 mm.

2 in the molybdenum foam which is the heat generation excitation member
When heating was performed by passing an alternating current of 8 A and 30 V, the surface temperature of the exothermic excitation member became 1980 ° C. The temperature of the base material is 900 ° C by the heater built into the base material support.
Heated to. In this state, hydrogen gas was supplied at a flow rate of 3000 sccm from the first gas supply path and methane gas was supplied at a flow rate of 30 sccm from the second gas supply path, and the total pressure was 40 To.
After adjusting to rr, film formation was performed for 11 hours.

The substrate taken out after film formation had a diameter of 50 mm.
A diamond film was formed on the entire surface of the film, and this film was identified by Raman spectroscopy.
Since the peak ratio of diamond is about 0.01, it was found that the diamond film was good. The maximum thickness of this diamond film was 115 μm, and the variation in the thickness was 12%.

Embodiment 5 In a normal vacuum container, a first gas supply passage for supplying hydrogen gas and a second gas supply passage for supplying gas containing carbon atoms are separately arranged, and the first gas supply passage A funnel-shaped cylindrical body made of heat-resistant ceramics and having a maximum inner diameter of 13 mm was attached to the end portion on the base material side. On the other hand, an annular portion having an inner diameter of 50 mm and having a plurality of outlets on the inner periphery was attached to the base material side end portion of the second gas supply passage.

As a heat-exciting member having a plurality of communicating holes, a net obtained by knitting a niobium wire having a wire diameter of 10 μm into 100 mesh was rolled into a cylindrical shape having a diameter of 3 mm and a length of 100 mm. Were arranged in parallel and housed inside the funnel-shaped cylindrical body of the first gas supply passage. Electrodes were attached to the upper and lower ends of each tubular body and connected to external power sources.

Inside the annular portion of the second gas supply passage, one filament of a rhenium wire having a diameter of 0.1 mm wound in a coil is installed in an annular shape, and 1.5 A, 53 V is attached to this filament.
And was heated to 1600 ° C. Furthermore,
A silicon base material having a diameter of 50 mm was placed on the base material support, and the distance between the surface of the base material and the lower end of the exothermic excitation member composed of the ten cylindrical bodies was set to 20 mm. .

13 heat-exciting members are provided in 10 cylindrical bodies.
When heating was performed by passing an alternating current of A and 30 V, the surface temperature of the exothermic excitation member reached 2000 ° C. The temperature of the base material was heated to 850 ° C. by a heater built in the base material support. In this state, hydrogen gas was supplied at a flow rate of 3000 sccm from the first gas supply path and methane gas was supplied at a flow rate of 25 sccm from the second gas supply path, and the total pressure was 30 Torr.
After adjusting to r, film formation was performed for 10 hours.

The substrate taken out after the film formation had a diameter of 50 mm.
A diamond film was formed on the entire surface of the film, and this film was identified by Raman spectroscopy.
Since the peak ratio of diamond is about 0.01, it was found that the diamond film was good. The film thickness of this diamond film was 113 μm at maximum, and the variation in film thickness was 15%.

Comparative Example 1 A mixed gas supply passage for supplying a mixed gas of hydrogen gas and a gas containing carbon atoms was provided in an ordinary vacuum container, and a heat generation excitation member was provided at the end of the mixed gas supply passage on the base material side. Diameter 0.6
A single filament similar to the conventional one in which a tantalum wire having a diameter of 3 mm was wound into a coil having a diameter of 3 mm and a length of 100 mm was arranged. Further, a silicon base material having a diameter of 50 mm was placed on the base material support, and the distance between the surface of the base material and the lower end of the filament was set to 5 mm.

When the filament was heated by applying an alternating current of 29 A and 31 V, the voltage at the end of the carbonization was 45 V, the current was 29 A, and the surface temperature was 20.
It was 50 ° C. Further, the temperature of the base material was heated to 900 ° C. by a heater built in the base material support. In this state, a mixed gas of 99 vol% hydrogen gas and 1 vol% methane gas was supplied from the mixed gas supply passage at a flow rate of 1000 sccm, the total pressure was adjusted to 40 Torr, and film formation was performed for 11 hours. .

On the substrate taken out after the film formation, a diamond film was formed in a peak shape along the filament, and the maximum value of the film thickness was 12 μm.
No diamond was formed at a place separated by more than mm. When the film was identified by Raman spectroscopy, the peak ratio of amorphous / diamond was about 0.1.

Comparative Example 2 A mixed gas supply passage for supplying a mixed gas of hydrogen gas and a gas containing carbon atoms was provided in a normal vacuum container, and a heat generation excitation member was provided at the end of the mixed gas supply passage on the base material side. Diameter 1.0
mm tungsten wire with a diameter of 3 mm and a length of 100 mm
Only one filament similar to the conventional one wound in a coil shape was arranged. Further, a silicon base material having a diameter of 50 mm was placed on the base material support, and the distance between the surface of the base material and the lower end of the filament was set to 10 mm.

When the filament was heated by passing an alternating current of 100 A, 35 V, the voltage at the end of the carbonization was 51 V, the current was 100 A, and the surface temperature was 2250 ° C. Further, the temperature of the base material was heated to 900 ° C. by a heater built in the base material support. In this state, a mixed gas of 99% by volume of hydrogen gas and 1% by volume of methane gas was supplied from the mixed gas supply path at a flow rate of 1000 sccm, the total pressure was adjusted to 40 Torr, and film formation was performed for 10 hours. .

On the substrate taken out after the film formation, a diamond film was formed in a peak shape along the filament, and the maximum value of the film thickness was 21 μm.
No diamond was formed at a place separated by 2 mm or more. The film was identified by Raman spectroscopy and found to have an amorphous / diamond peak ratio of 0.07.
It was about.

[0047]

According to the present invention, as compared with the conventional hot filament CVD method, it is possible to form a high quality diamond film with low energy and low power at a high speed and in a large area. In addition, the growth rate of the diamond film can be increased without raising the temperature of the heat generation excitation member more than necessary and even if the distance between the heat generation excitation member and the surface of the base material is relatively long. It is possible to significantly suppress the thermal strain on the film.

[Brief description of drawings]

FIG. 1 is a schematic side view in which a specific example of a diamond synthesizing apparatus according to the present invention is disassembled and shown for each part.

[Explanation of symbols]

1 vacuum container 2 First gas supply path 3 Second gas supply path 4 funnel-shaped cylinder 5 annular part 6 outlet 7 tubular 8 power supplies 9 Base material 10 Base material support

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A 61-163195 (JP, A) JP-A 5-890 (JP, A) JP-A 1-203295 (JP, A) JP-A 60- 221395 (JP, A) JP 63-159292 (JP, A) JP 3-69593 (JP, A) JP 3-112897 (JP, A) JP 3-115576 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (6)

(57) [Claims] 1. A method of vapor-synthesizing diamond on the surface of a substrate by heating and exciting a gas containing carbon atoms and hydrogen gas, wherein a heat generated from a porous body heated only with hydrogen gas.
After contacting the excitation member , this is supplied to the surface of the heated base material that is arranged opposite to the exothermic excitation member, and at the same time, the gas containing carbon atoms is supplied to the surface of the base material through a route different from hydrogen gas. A method for vapor phase synthesis of diamond, which comprises: 2. The vapor phase of diamond according to claim 1, wherein a gas containing carbon atoms is brought into contact with a heated linear or coil filament and then supplied to the surface of the heated substrate. Synthesis method. 3. An apparatus for vapor-synthesizing diamond on a surface of a substrate by heating and exciting a gas containing carbon atoms and hydrogen gas, wherein a first gas supply path for supplying hydrogen gas to the surface of the substrate and a carbon atom are provided. A second gas supply path for supplying a containing gas is provided separately, and a heat generation excitation member made of a porous body is provided at the base material side end of the first gas supply path for supplying hydrogen gas, facing the surface of the base material. A vapor-phase synthesis apparatus for diamond, characterized in that 4. A base of a first gas supply path for supplying hydrogen gas.
A funnel-shaped tube is provided at the end on the material side.
The vapor phase synthesizing apparatus for diamond according to claim 3, wherein a heat generation excitation member having a plurality of communication holes is housed therein . 5. A material for a heat generation excitation member having a plurality of communication holes.
Quality is rhenium, molybdenum, tungsten, niobium and
And at least one kind of gold selected from the group consisting of tantalum
The vapor phase synthesizer for diamond according to claim 3 or 4 , which is a genus . 6. A second supply for supplying a gas containing carbon atoms.
There is a gas outlet on the inner side of the path surrounding the base material on the base material side end.
A ring-shaped portion is provided, and a linear or
Is equipped with a coiled filament ,
The diamond vapor phase synthesizing apparatus according to claim 3 .