JPH0757893A - Method and device for generating induction plasma - Google Patents

Abstract

PURPOSE:To form an induction plasma having a large diameter and an uniform temperature distribution. CONSTITUTION:An induction plasma generating device is formed of a first coil 1 spirally wound in the axial direction, a plasma seed gas 7 axially carried in the inner part of the first coil 1, and a second coil 15 spirally wound on the outer circumference of the first coil 1 in the axial direction. Alternate currents having different frequencies are carried to the first coil 1 and the second coil 15, and the alternate current having a frequency lower than the first coil 1 is carried to the second coil 15, Thus, the plasma seed becomes plasma state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for generating plasma by inducing high frequency voltage.

[0002]

2. Description of the Related Art When a high-frequency voltage forms an electric field in a space, electrons reciprocate in the space. The electrons are repeatedly ionized by collision with the neutral gas, so that the number of ions increases and plasma is formed. Since the plasma induced by the high frequency voltage does not need to directly dispose the electrode in the space, it is possible to avoid mixing of impurities generated from the electrode. Therefore, in the field of plasma chemistry and plasma CVD, this high frequency induction plasma is often used for material film formation and edging processing.

FIG. 4 is a sectional view showing the structure of a conventional induction plasma generator. Flange 4 and 9 are attached to the upper and lower sides of a cylindrical insulating container 2, and an upper lid 5 covers the upper flange 4. An insulating pipe 11 is fixed to the centers of the flanges 4 and 9. The first coil 1 is arranged between the insulating pipe 11 and the insulating container 2 together with the cooling water 3 via a support (not shown). The first coil 1 is formed by spirally winding the outer circumference of an insulating tube 11 in an axial direction with a conductor coated with insulation, and both ends of the first coil 1 are provided with a high frequency power source 10
It is connected to the.

In FIG. 4, an insulating tube 8A for passing the carrier gas 8 and an insulating tube 13 for passing the plasma seed gas 7 are arranged in the center of the upper lid 5. Further, the upper lid 5 has lateral holes 7A communicating with the inside of the insulating pipe 11,
6A is provided to guide the plasma seed gas 7 and the sheath gas 6 to the inside of the insulating tube 11. The spacer 6B provided on the outer wall of the insulating tube 13
Are formed in a spiral shape, which guides the sheath gas 6 to flow in a spiral shape. Note that FIG.
The entire apparatus is stored in a vacuum container (not shown).

The mechanism by which the inductive plasma 12 is formed inside the insulating tube 11 will be described below with reference to FIG. Side hole 7
The plasma seed gas 7 is caused to flow into the vacuum inside the insulating tube 11 via A. The plasma seed gas 7 is Ar, for example.
An inert gas such as is used as a seed of the induction plasma 12. At the same time, a sheath gas such as Ar is also flown into the insulating tube 11 through the lateral hole 6A. The sheath gas 6 becomes a spiral flow (indicated by a dotted line) along the inner wall surface of the insulating tube 11 due to the interposition of the spiral spacer 6B. When a high-frequency current is passed from the high-frequency power supply 10 to the first coil 1 in this state, an axial high-frequency magnetic field is generated inside the insulating tube 11. Furthermore, an induced current is formed in the plasma seed gas 7 to cancel this magnetic field. In the plasma seed gas 7, the molecules themselves are initially neutral, but the initial electrons minutely contained in this gas vibrate in the insulating tube 11 in the circumferential direction by the high-frequency magnetic field.
The electrons collide and ionize with neutral molecules, and the number of ions and electrons increases, so that the plasma seed gas 7 enters a plasma state. The induction plasma 12 in FIG. 4 is formed by the above-mentioned mechanism, and an induction current flows in the induction plasma 12 and the temperature in that region reaches several thousands to tens of thousands degrees due to Joule heating.

[0006] The sheath gas 6 is for preventing the induction plasma 7 from directly contacting the inner wall surface of the insulating tube 11. The sheath gas 6 is cooled by flowing it in a spiral shape along the inner wall surface of the insulating tube 11 to prevent the sheath gas 6 itself from being turned into plasma. The first coil 1 and the sheath gas 6 are cooled by flowing the cooling water 3.

In FIG. 4, when the induction plasma 12 is formed, the carrier gas 8 is caused to flow from the upper part of the insulating tube 8A and mixed into the induction plasma 12. Induction plasma 1
The high temperature of 2 causes the carrier gas 8 and the plasma seed gas 7 to react with each other, and the reaction gas is taken out from the lower portion of the insulating tube 11. The carrier gas 8 may be a gas alone or a mixture of gas and powder. The induction plasma 12 is used for plasma processing such as film formation and edging on the semiconductor surface.

[0008]

However, the conventional device as described above has a problem that when the induction plasma having a large diameter is formed, the temperature distribution in the induction plasma becomes non-uniform. In the conventional device, a high frequency current of several MHz or more, generally on the order of 10 MHz, was applied to the first coil. Therefore, most of the induced current flows on the outer peripheral surface of the induced plasma due to the skin effect, the high temperature region is biased toward the outer peripheral side, and the internal temperature rise is not sufficient. Therefore, conventionally, there was a limit to the practical use of induction plasma having a diameter of 50 to 60 mm. In a practical apparatus such as plasma processing, the plasma processing capability is improved by using induction plasma having a uniform temperature distribution and a diameter as large as possible.

An object of the present invention is to form an induction plasma having a uniform temperature distribution even if its diameter is increased.

[0010]

In order to achieve the above object, according to the method of the present invention, a plasma seed gas is axially flown inside a first coil spirally wound in an axial direction, The outer circumference of the first coil, or the outer circumference of the plasma seed gas flowing from the inside of the first coil to the downstream side is spirally wound around the second coil with the second coil, and the first coil and the second coil have alternating frequencies different from each other. It is assumed that the plasma seed gas is turned into plasma by passing an alternating current having a frequency lower than that of the first coil while passing a current.

In order to achieve the above object, according to the present invention, a first coil spirally wound in an axial direction, a plasma seed gas flowing axially inside the first coil, and a first coil The first coil and the second coil are supplied with alternating currents of different frequencies, and the second coil is composed of a second coil wound around the outer circumference of the coil in a spiral shape in the axial direction. It is assumed that an alternating current having a lower frequency is applied.

Further, the first coil wound in a spiral shape in the axial direction, the plasma seed gas flowing in the axial direction of the first coil and the outer periphery of the plasma seed gas flowing from the inside of the first coil to the downstream side. Is composed of a second coil spirally wound in the axial direction, alternating currents of different frequencies are applied to the first coil and the second coil, and the second coil has a lower frequency than the first coil. In this configuration, a plurality of first coils are arranged, and each plasma seed gas flowing out from the inside of the first coil to the downstream side is collectively surrounded by the second coil in the axial direction. It shall be wound in a spiral shape.

[0013]

According to the structure of the present invention, the outer circumference of the first coil,
Alternatively, the outer periphery of the plasma seed gas flowing from the inside of the first coil to the downstream side is wound with a second coil, and an alternating current having a frequency lower than that of the first coil is passed through the second coil. An induction plasma is first formed by the first coil, and an induction current of the second coil flows in the induction plasma. Since the frequency of the current flowing through the second coil is lower than that of the first coil, the skin effect is weakened, and the induced current is more likely to flow not only to the outer circumference of the induction plasma but also to the inner side. Since the high temperature region formed by Joule heating expands to the inner side of the induction plasma, it is possible to form induction plasma with a uniform temperature distribution even if the diameter increases.

In such a structure, a plurality of first coils are arranged, and each plasma seed gas flowing out from the inside of the first coil to the downstream side is collectively wrapped with the second coil in the axial direction in a spiral shape. . With this configuration, a plurality of induction plasmas are formed by the first coil, and the induction current of the second coil flows in a state where the induction plasmas are collected. Even if the diameter of each induction plasma formed by the first coil is small, since they are put together, an induction plasma having a large diameter and a uniform temperature distribution is formed.

[0015]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a sectional view showing the configuration of an induction plasma generator according to an embodiment of the present invention. Another insulating container 16 is arranged on the outer periphery of the insulating container 2, and the upper and lower flanges 40, 90 are provided.
It is fixed to. The second coil 15 immersed in the flow of the cooling water 17 is arranged in the insulating container 16 and connected to the alternating power source 14. The second coil 15 is made of an electrically insulating conductor and is wound around the outer circumference of the insulating container 12. Others are similar to those of the conventional device shown in FIG. The same parts are designated by the same reference numerals, and detailed description thereof is omitted.

In FIG. 1, the frequency of the high frequency power source 10 is several MHz to several tens of MHz, but the frequency of the alternating power source 14 is several tens of kHz to several hundreds of kHz. Although the induction plasma 12 is formed by the first coil 1, the induction current by the second coil 2 easily flows into the induction plasma 12 because the skin effect is weakened. Therefore, the temperature of the induction plasma becomes uniform even inside. Therefore, FIG.
The inner diameter d of the insulating tube 13 in the conventional device is 50 to 60
mm was the limit, but in the device of FIG.
Even if it is expanded to 00 mm and configured, a uniform induction plasma 1
2 can be obtained. A few hundred meters with the device of FIG.
Even if the induction plasma having a diameter of m is formed, the entire temperature is uniform, so that the plasma treatment can be performed in a large area, and the efficiency of the plasma treatment is significantly improved.

FIG. 2 is a sectional view showing the structure of an induction plasma generator according to another embodiment of the present invention. 4 is that the insulating container 21 is provided between the flanges 41 and 42, and the insulating container 2 is arranged on the flange 41. Further, insulating tubes 22 and 23 are provided inside the insulating container 21,
A spiral spacer 60B is interposed between the spacers 3 and 3. The flange 41 is provided with a lateral hole 80A for passing the carrier gas 80 and a lateral hole 60A for passing the sheath gas 60, both of which communicate with the inside of the insulating tube 22. On the other hand, the second coil 15 immersed in the cooling water 20 is arranged inside the insulating container 21 and is connected to the alternating power source 14. The second coil 15 is made of a conductor coated with insulation,
The outer circumference of the insulating tube 22 is wound. The carrier gas 8 is sent from the upper lid 5 in FIG. 4, but is sent from the lateral hole 80A of the flange 41 in the apparatus of FIG. Also, as in Fig. 1, the first coil has several MHz to several tens MH.
A high frequency current of z is applied, and an alternating current of several 10 kHz to several 100 kHz is applied to the second coil.

In FIG. 2, the induction plasma 18 formed inside the first coil 1 is formed by the same mechanism as the induction plasma 12 in FIG. The induction plasma 18 advances downward according to the flow of the plasma seed gas 7 and is fed into the insulating tube 22 having a wide inner diameter. Therefore, the induction plasma 18 has a larger diameter and becomes the induction plasma 19. Since the second coil 15 is arranged outside the induction plasma 19, an induction current is induced,
The entire induction plasma 19 is heated. Since the sheath gas 60 flows out through the spiral spacer 60B, it flows spirally along the inner wall surface of the insulating pipe 22 like the sheath gas 6. The sheath gas 60 prevents the induction plasma 19 from directly contacting the insulating tube 22. In this state, the carrier gas 80 is flown through the lateral hole 80A and mixed into the induction plasma 19.

With the configuration shown in FIG. 2, the upper insulating tube 1
The inner diameter d of 1 does not necessarily have to be 50 to 60 mm or less. The induction plasma 18 need only be ignited, and the temperature distribution inside the induction plasma 18 need not be uniform. When the plasma 18 flows downward and becomes the induction plasma 19, the whole is uniformly heated by the induction current by the second coil 15. For example, even if the inner diameter d of the insulating tube 11 is 100 mm and the inner diameter D of the insulating tube 22 is 300 mm, the diameter is several tens.
It is possible to form an induction plasma having a uniform temperature of 0 mm inside.

FIG. 3 is a sectional view showing the structure of an induction plasma generator according to a further different embodiment of the present invention. The difference from the configuration of FIG. 2 is that a plurality of first coils 1 are arranged on the upper side of the upper flange 43 so that the induction plasma 18 can be formed inside the insulating tube 11. A plurality of induction plasmas 18 are collectively packaged inside the insulating tube 22 to grow into one induction plasma 24.

With the structure of FIG. 3, the inner diameter d of the upper insulating tube 11 is not necessarily 50 to 6 as in the case of FIG.
It does not need to be 0 mm or less. The induction plasma 18 need only be ignited, and the internal temperature distribution need not be uniform. When the plasma 18 flows downward and becomes the induction plasma 24, the whole is uniformly heated by the induction current by the second coil 15. Although FIG. 3 shows an example of two induction plasmas 18, the diameter of the induction plasma 24 can be increased by further increasing the number. For example, even if four insulating tubes 11 are arranged and the inner diameter d is 100 mm and the inner diameter D of the insulating tube 22 is 500 mm, the diameter is 1 more than that of the conventional one.
It is possible to form an inductive plasma that has an order of magnitude larger than that of the inner plasma with a uniform temperature.

[0022]

As described above, according to the present invention, the outer circumference of the first coil or the outer circumference of the plasma seed gas flowing from the inside of the first coil to the downstream side is wound by the second coil, and the first coil is wound around the second coil. An alternating current of lower frequency than the coil is passed. By this method, even if the diameter of the induction plasma is greatly increased from 50 mm to 60 mm and formed to several hundreds mm, the temperature distribution is uniform even inside, and the efficiency of plasma treatment is greatly improved.

Further, in the above, a plurality of first coils are arranged, and each plasma seed gas flowing out from the inside of the first coil to the downstream side is collectively wrapped with the second coil in a spiral shape in the axial direction. It As a result, if the number of induction plasmas formed by the first coil is increased, it is possible to form induction plasmas having a diameter that is an order of magnitude larger than that of the prior art, with a uniform temperature distribution. Therefore, the efficiency of plasma processing is further improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an induction plasma generator according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the configuration of an induction plasma generator according to another embodiment of the present invention.

FIG. 3 is a sectional view showing the configuration of an induction plasma generator according to a further different embodiment of the present invention.

FIG. 4 is a sectional view showing the configuration of a conventional induction plasma generator.

[Explanation of symbols]

1: first coil, 2, 16, 21: insulating container, 8A, 1
1, 13, 22, 23: Insulation pipe, 3, 17, 20: Cooling water, 40, 41, 42, 43, 90: Flange, 5: Upper lid, 6: Sheath gas, 7: Plasma seed gas, 8: Carrier gas 10: high frequency power supply, 12, 18, 19, 2
4: Induction plasma, 14: Alternating power source, 15: Second coil, 80A, 60A, 7A, 6A: Side hole, 6B, 60
B: Spacer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tadahiro Sakuta 2-3-7 Muraihigashi, Matsuto-shi, Ishikawa Prefecture

Claims (4)

[Claims] 1. A plasma seed gas in which a plasma seed gas is caused to flow in the axial direction inside a first coil that is spirally wound in the axial direction and flows out to the downstream side from the outer periphery of the first coil or the inside of the first coil. The coil is wound around the outer circumference of the coil in the axial direction with a second coil, and alternating currents of different frequencies are applied to the first coil and the second coil. A method of generating induction plasma, characterized in that the plasma seed gas is turned into plasma by energizing the plasma. 2. An apparatus for carrying out the method according to claim 1, wherein a first coil spirally wound in an axial direction, and a plasma seed gas flowing in the first coil in the axial direction are provided. The first coil and the second coil are spirally wound around the outer periphery of the first coil in the axial direction, and alternating currents having different frequencies are applied to the first coil and the second coil. An induction plasma generator characterized in that an alternating current having a frequency lower than that of one coil is applied. 3. An apparatus for carrying out the method according to claim 1, wherein a first coil spirally wound in an axial direction, a plasma seed gas flowing axially in the first coil, and It is composed of a second coil spirally wound in the axial direction around the outer periphery of the plasma seed gas flowing from the inside of one coil to the downstream side, and alternating currents having different frequencies are applied to the first coil and the second coil. In addition, the induction plasma generator is characterized in that an alternating current having a frequency lower than that of the first coil is applied to the second coil. 4. The one according to claim 3, wherein a plurality of first coils are arranged, and each plasma seed gas flowing from the inside of the first coil to the downstream side is bundled together and the second coil spirals in the axial direction. An induction plasma generator characterized by being wound into a shape.