JPS63117992A - Device for synthesizing diamond in vapor phase - Google Patents

Abstract

PURPOSE:To synthesize a diamond even on a relatively large substrate in a vapor phase by using a Rigitano coil as a plasma producing means, and transmitting a microwave through a coaxial cable. CONSTITUTION:A reaction chamber 8 is independently provided, the substrate 7 is arranged at a specified position in the reaction chamber 8 by a holder 9, and the Rigitano coil 10 is arranged to surround the substrate 7. A gaseous mixture obtained by mixing gaseous H2 and gaseous CH4 in a specified ratio is introduced at a fixed flow rate into the reaction chamber 8 through a supply pipe 16, a specified amt. of the introduced gaseous mixture is sucked and exhausted through an exhaust pipe 17, and the pressure in the reaction vessel 8 is kept at a preset value. Meanwhile, the Rigitano coil 10 is connected to a waveguide through the coaxial cable 18 and a converter 19. The gaseous mixture is supplied into the reaction chamber 8, plasma is produced around the substrate 7 by the Rigitano coil 10, and hence thin diamond film is synthesized on the substrate 7 in a vapor phase.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a diamond vapor phase synthesis apparatus.

[Prior Art] Diamond has long been widely used mainly in cutting tools because of its high hardness. On the other hand, in recent years, attention has been paid to its high thermal conductivity and its potential to be used as a semiconductor by doping with impurities. The application of diamond has been studied, and the latter property has also been applied to the field of electronic technology such as semiconductor devices, and techniques for forming diamond are being rapidly developed.

The synthesis method for diamond uses graphite as a carbon raw material,
40,000 to 70,000 atmospheres using Ni, Cr, Mn, etc. as a catalyst, 10
A high-pressure method is known in which synthesis is carried out at high temperatures and pressures of 00 to 2000°C, but gas phase synthesis methods have also been developed in which gaseous hydrocarbons are used as carbon raw materials and carried out under low-pressure conditions. It has been pointed out that the disadvantage of diamond synthesis using the vapor phase synthesis method is that the diamond crystals are smaller compared to the high-pressure method. The advantage that it is easy to form has attracted attention, and it is positioned as a useful technology.

FIG. 2 is a schematic explanatory diagram showing a conventional diamond vapor phase synthesis apparatus. The device is a technology that applies microwaves, and its outline is as follows.

In Fig. 2, the microwave (2.45 GHz) oscillated from the magnetron oscillator 1 is transmitted to the isolator 2.
, power monitor 3, tuner 4, and waveguide 5 in the stated order, and irradiates a substrate 7 installed in a quartz reaction tube 6 provided through the waveguide 5. Although a metal material such as Ta, Co, W, or Mo may be used as the substrate 7, a St wafer is generally used, and the substrate 7 is placed at a predetermined position by a support base 9 made of quartz. ing. Then, in the reaction tube 6, from the reaction tube population 11 side, a mixed gas of H2 gas and CH4 gas mixed at a predetermined ratio (for example, CH41%-H299%) is supplied at about 100 S.
CCM (Standard Cubic[:ent
per minute).

A predetermined amount of the introduced mixed gas is suctioned and exhausted from the exhaust port 13 side, and the inside of the reaction tube 6 is maintained at a predetermined pressure (for example, 40 to 50
Torr).

When oscillating radio waves (approximately 300 W) such as microwaves are introduced into the reaction tube 6 into which the mixed gas is supplied in this way, the mixed gas component molecules are decomposed into atoms, ions, and radicals by high-energy electrons. A steady plasma is generated within the reaction tube 6. The substrate 7 is placed in the plasma generation region 14, and diamond crystals are deposited on the substrate 7 using carbon in the mixed gas as a raw material. and board 7
Depending on the type of diamond and processing conditions, diamonds can be obtained in different forms, such as microcrystals or thin films.

In the diamond vapor phase synthesis apparatus shown in FIG. 2, if a St wafer is used as the substrate 7, the substrate temperature will be approximately 850°C under the above-mentioned processing conditions, and a Crystalline diamond precipitates at a growth rate. Reference numeral 15 in FIG. 1 is a plunger, which is used to adjust the reflection of microwaves so that the substrate 7 is accurately located at the center of the plasma generation region 14.

A member designated by reference numeral 20 is an applicator, which functions to prevent the reaction tube 6 from being excessively heated by supplying cooling water from the supply pipe 21 and discharging it from the discharge pipe 22.

[Problems to be Solved by the Invention] However, in the vapor phase synthesis apparatus as shown in FIG. 2, there is a problem in that the size of the substrate 7 can only be approximately 1010×10. The reason for this is as follows. That is, microwaves used for gas phase synthesis are industrially limited, and 2.45 GHz is common, but the diameter of the reaction tube 6 is set to half the wavelength of the microwave (about 6 GHz).
cm) or higher, microwaves will leak to the outside, so
The diameter of the reaction tube 6 must be limited to 6 cm or less. Furthermore, if the plasma generation region 14 generated in the reaction tube 6 spreads too much, problems such as excessive heating of the inner wall of the reaction tube 6 will occur due to the generated plasma, so the diameter of the plasma generation region 14 is adjusted to about 3 cm. ing. Under such conditions, in order to uniformly form a diamond film on the substrate 7 without disturbing the plasma, the size of the substrate 7 is limited to the above-mentioned size.

The present invention was made under these circumstances, and
The purpose is to provide a diamond vapor phase synthesis apparatus that can perform vapor phase synthesis of diamond even on a relatively large substrate without limiting the size of the substrate depending on the wavelength or the like.

[Means for Solving the Problems] The configuration of the present invention that achieves the above object is an apparatus for vapor phase synthesis of diamond on a substrate by generating plasma in a reaction chamber in which a substrate is disposed. A rigid coil is arranged in the reaction chamber so as to surround the substrate, and a microwave is transmitted to the wall surface of the rigid coil via a coaxial cable, and the rigid coil is arranged to surround the substrate. This device is a diamond vapor phase synthesis device whose main feature is that plasma is generated in the surrounding area.

[Function] Although the present invention is constructed as described above, the main feature is that a rigidano coil is employed as a means for generating plasma. By transmitting microwaves to the rigidano coil via a coaxial cable, plasma is generated around the substrate surrounded by the rigidano coil, and a thin diamond film is formed on the substrate.

The size of the rigidano coil in the present invention can be selected independently of the microwave frequency, and there is no restriction in principle. Therefore, by increasing the power of manually generated microwaves in accordance with the size of the rigidano coil, the plasma generation area can be enlarged, making it possible to form a diamond thin film even on a relatively large substrate. It will be like that.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Embodiment FIG. 1 is a schematic explanatory diagram of an embodiment of the present invention. Also in the present invention, the magnetron oscillator 1 shown in FIG. Isolator 2. Power monitor 3. The tuner 4 and waveguide 5 are used as they are and are given the same reference numerals in FIG.

In the present invention, a reaction chamber 8 is provided independently as shown in FIG.
At the same time, a rigid coil 10 is arranged so as to surround the substrate 7. Then, add H2 gas and CH.

A mixed gas obtained by mixing gases at a predetermined ratio is introduced into the reaction chamber 8 at a constant flow rate through the supply pipe 16, and a predetermined amount of the introduced mixed gas is sucked and exhausted through the exhaust pipe 17, and the gas is exhausted into the reaction chamber 8. is a predetermined pressure (for example, about 2 Torr).

On the other hand, the rigid coil 10 is connected to the waveguide 5 via a coaxial cable 18 and a transducer 19.

In FIG. 1, microwaves (2.45 GHz) oscillated from a magnetron oscillator 1 are transmitted to an isolator 2.
, power monitor 3, tuner 4, and waveguide 5 in this order, the signal is then converted into an electrical signal by a converter 19, and further transmitted to the wall surface of the rigidano coil 10 via a coaxial cable 18. When the microwave is transmitted to the rigidano coil 10, plasma is generated within the rigidano coil 10, but the substrate 7 is generated within the plasma generation region 14.
is located.

In the apparatus shown in FIG. 1, a gas mixture of H2 gas and CH4 gas in a predetermined ratio is supplied into the reaction chamber 8 through the supply pipe 16, and plasma is generated around the substrate 7 by the rigidano coil. As a result, a diamond thin film is synthesized on the substrate 7 in a vapor phase. By adopting such a configuration, the size of the substrate 7 can be increased without any restrictions, and the conventional technical problem that the size of the substrate 7 is limited depending on the microwave frequency can be solved. It was.

Note that the configuration of the rigidano coil 10 is not limited in any way, and any configuration conventionally known in the field of nuclear fusion can be adopted. For example, Figure 3 (1
), a so-called slot-type rigidano coil 10a has a zigzag-shaped gap 25a (approximately 2 mm) formed in a metal cylindrical member.

Alternatively, as shown in FIG. 3(2), a so-called helical rigid coil 25b in which a spiral gap 25b is formed in a metal cylindrical member may be used.

The present inventors conducted an experiment using the vapor phase synthesis apparatus shown in FIG. That is, the output of the microwave is set to IKW, and a mixed gas of H2 gas and CH4 gas (CH4
1%-H299%) was fed at a flow rate of 503 CCM.

The pressure in the reaction chamber 8 was adjusted to 2 Torr by exhausting a predetermined amount of the mixed gas from the exhaust pipe 17, and
A St wafer was used. When the reaction was allowed to continue for 15 hours, diamond particles with a diameter of about 0.5 μm were observed to be formed on the substrate 7.

The structure of the vapor phase synthesis apparatus according to the present invention is basically as shown in FIG. 1, but various other structures can also be adopted.

FIG. 4 is a schematic explanatory diagram showing the main parts of another embodiment of the present invention. Particularly when the pressure in the reaction chamber 8 is below ITorr, the generated plasma may expand too much and the expected effect may not be achieved. The configuration shown in FIG. 4 is designed to avoid the above-mentioned situation. That is, if an electromagnet 30 is placed near the reaction chamber 8 and a magnetic field is created in the reaction chamber 8, conditions are created in which electron cyclone resonance (ECR) occurs within the reaction chamber 8 (in the case of a 2.45 GHz microwave). Approximately 9
000 Gauss), the expansion of the plasma generated in the reaction chamber 8 can be prevented and the plasma can be confined within the reaction chamber, making it possible to achieve efficient gas phase synthesis.

FIG. 5 is a schematic explanatory diagram showing the main parts of still another embodiment of the present invention. In this embodiment, the downstream side (lower side in FIG. 5) of the reaction chamber 8 into which the mixed gas is introduced is a reaction chamber 8a having a relatively large capacity, and a substrate 7 with a wide area is installed in the reaction chamber 8a. Then, diamond is deposited on this substrate 7. At this time, the substrate 7 needs to be heated to 800 to 1000° C. by the auxiliary heater 31. It is also possible to employ a configuration in which a part where a magnetic field is applied and a plasma is generated by the rigidano coil 10 and a part where the substrate 7 is placed are provided separately.

[Effects of the Invention] As described above, according to the present invention, the size of the substrate is not limited by frequency or the like, and diamond vapor phase synthesis can be performed even on a relatively large substrate.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an embodiment of the present invention, FIG. 2 is a schematic explanatory diagram showing a conventional diamond vapor phase synthesis apparatus, and FIG. 3 (1) is a perspective view of a slot-type rigidano coil 10a.
FIG. 3(2) is a perspective view of the helical rigidity coil 10b, FIG. 4 is a schematic explanatory diagram showing the main parts of another embodiment of the present invention, and FIG. 5 is a diagram of still another embodiment of the present invention. FIG. 2 is a schematic explanatory diagram showing main parts. 1... Magnetron oscillator 5... Waveguide 7... Substrate 8... Reaction chamber 10.10a, lob... Rigitano coil 18...
·coaxial cable

Claims (1)

[Claims] An apparatus for vapor phase synthesis of diamond on the substrate by generating plasma in a reaction chamber in which a substrate is disposed, wherein a rigidano coil is disposed in the reaction chamber so as to surround the substrate, and the rigidano coil is arranged to surround the substrate. A diamond vapor phase synthesis apparatus characterized in that microwaves are transmitted to the wall surface of the substrate via a coaxial cable, and plasma is generated around the substrate by the rigidano coil.