JP3115472B2 - Method and apparatus for generating induction plasma - 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 and an apparatus for generating a plasma by induction of a high-frequency voltage.

[0002]

2. Description of the Related Art When an electric field is formed in a space by a high-frequency voltage, electrons reciprocate in the space. As the electrons repeat impact ionization with the neutral gas, ions increase and plasma is formed. In the plasma induced by the high-frequency voltage, it is not necessary to dispose electrodes directly in the space, so that contamination of impurities generated from the electrodes can be avoided. For this reason, in the fields of plasma chemistry and plasma CVD, the high-frequency induction plasma is often used for material deposition and edging.

FIG. 5 is a sectional view showing a configuration of a conventional induction plasma generating apparatus. Flanges 4 and 9 are attached to the upper and lower sides of the cylindrical insulating container 2, and an upper lid 5 covers the upper flange 4. An insulating tube 11 is fixed to the centers of the flanges 4 and 9. The coil 1 is disposed between the insulating tube 11 and the insulating container 2 via a support (not shown) together with the cooling water 3. The coil 1 is formed by winding an outer periphery of an insulating tube 11 in a spiral shape in an axial direction with a conductor covered with an insulating coating, and both ends thereof are connected to a high-frequency power supply 10.

In FIG. 5, an insulating tube 8A for passing the carrier gas 8 and an insulating gas blowing tube 13 for passing the seed gas 7 are arranged at the center of the upper lid 5.
Further, a lateral hole 7 communicating with the inside of the insulating tube 11 is provided in the upper lid 5.
A and 6A are provided, respectively, for guiding the seed gas 7 and the sheath gas 6 into the inside of the insulating tube 11. Insulation tube 1
1, between the upper inner peripheral surface and the outer peripheral surface of the gas injection pipe 13
The spacer 6B is interposed. This spacer 6B
It is formed in a spiral shape, so that the sheath gas 6
Is induced to flow spirally. The entire apparatus shown in FIG. 5 is housed in a vacuum vessel (not shown).

[0005] The mechanism by which the induction plasma 12 is formed inside the insulating tube 11 will be described below with reference to FIG. Side hole 7
The seed gas 7 is caused to flow into the vacuum inside the insulating tube 11 via A. The seed gas 7 is, for example, an inert gas such as Ar, and serves as a seed of the induction plasma 12. At the same time, a sheath gas 6 such as Ar is also flown into the insulating tube 11 through the lateral hole 6A. The sheath gas 6 forms 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 flows from the high-frequency power supply 10 to the coil 1 in this state, an axial high-frequency magnetic field is generated inside the insulating tube 11. Further, an induced current around the axis of the insulating tube 11 is formed in the seed gas 7 to cancel the magnetic field. Although the seed gas 7 initially has neutral molecules, initial electrons slightly contained in the gas vibrate in the insulating tube 11 in the circumferential direction by a high-frequency magnetic field. The electrons collide with the neutral molecules and ionize, and the seed gas 7 enters a plasma state due to an increase in ions and electrons. The induction plasma 12 shown in FIG. 5 is formed by the above-described mechanism. In the induction plasma 12, an induction current flows, and the temperature of the region reaches several thousands to tens of thousands of degrees due to Joule heating.

[0006] The sheath gas 6 is for preventing the induction plasma 12 from directly touching the inner wall surface of the insulating tube 11. The outer peripheral side of the induced plasma 12 is cooled by flowing the sheath gas 6 in a spiral shape along the inner wall surface of the insulating tube 11, and the induced plasma 12 is kept stationary on the central axis side of the insulating tube 11. By flowing the cooling water 3, the coil 1 and the insulating tube 11 are cooled, and the sheath gas 6 is also cooled, thereby preventing the sheath gas 6 itself from being turned into plasma.

In FIG. 5, when the induction plasma 12 is formed, the carrier gas 8 flows from the upper part of the insulating tube 8A and is mixed into the induction plasma 12. Induction plasma 1
The carrier gas 8 and the seed gas 7 are caused to react by the high temperature of 2, and the reaction gas is taken out from the lower part of the insulating tube 11. The carrier gas 8 may be a gas alone or a mixture of a gas and a powder. The induction plasma 12 is used for plasma processing such as film formation and edging on a semiconductor surface. The present invention can also be used in an apparatus for decomposing chlorofluorocarbon, which is a cause of destruction of the ozone layer, by plasma.

[0008]

However, the above-mentioned conventional apparatus has a problem that the temperature distribution of the induced plasma formed is not uniform. That is, since the induction current flowing in the induction plasma is at a high frequency, most of the induction current flows on the outer peripheral surface of the induction plasma due to the skin effect,
The high temperature region was offset to the outer peripheral side, and the internal temperature rise was not sufficient. FIG. 6 is a characteristic diagram showing the result of actually measuring the temperature distribution of the induction plasma by spectroscopy. The radius r from the central axis of the induction plasma 12 formed inside the insulating tube 11 having a diameter of 2R is marked on the horizontal axis, and the temperature T at the axial center of the induction plasma 12 is marked on the vertical axis. The characteristic curve 20 is the characteristic of the device of FIG. The temperature near the position (r = R ₁ ) near the inner wall of the insulating tube 11 is the highest, and the temperature near the central axis (r = O) is the lowest. This is because, as described above, most of the induced current flows on the outer peripheral side of the induced plasma 12 due to the skin effect. It is noted that the temperature decreases at the outermost position (r = R ₂ ) of the induction plasma 12 because the cooling by the cooling water 3 and the sheath gas 6 are spirally performed on the inner wall surface of the insulating tube 11 as shown in FIG. It is because it flows along. Induction plasma 1 as shown by characteristic curve 20
If the temperature of each part in 2 is distributed from 10,000 degrees K to 15,000 degrees K, the reaction of the sheath gas or the carrier gas becomes insufficient depending on the location, leading to a reduction in plasma processing capability.

An object of the present invention is to make the temperature distribution in the induction plasma as uniform as possible.

[0010]

According to the method of the present invention, a seed gas is blown into the inside of the insulating tube from one end in the axial direction of the insulating tube and wound around the outer periphery of the insulating tube. Generating an induced plasma in the insulating tube by passing an alternating current through the coil,
Stirring gas may be blown from the peripheral wall of the insulating tube toward the induction plasma formed inside the insulating tube.

According to the present invention, there is provided an insulating tube, a gas blowing tube provided at one end of the insulating tube in an axial direction for blowing a seed gas toward the inside of the insulating tube, and an insulating tube. A coil wound around the outer periphery of the coil and an AC power supply connected to the coil, a nozzle for injecting the stirring gas is provided on the peripheral wall of the insulating tube, and a direction for injecting the stirring gas from the nozzle is provided. Is directed to the induction plasma formed inside the insulating tube. In such a configuration, it is preferable that the direction in which the stirring gas is injected from the nozzle is oriented in a direction inclined toward the gas blowing pipe with respect to the radial direction of the insulating pipe.

[0012]

According to the structure of the present invention, the nozzle for injecting the stirring gas is provided on the peripheral wall of the insulating tube, and the direction for injecting the stirring gas of the nozzle is directed toward the induction plasma formed inside the insulating tube. Can be As a result, the induction plasma is agitated by the stirring gas, and the outer peripheral portion, which tends to be high in temperature due to the skin effect, mixes with the inner portion, in which the temperature does not easily rise. Therefore, the temperature distribution of the induction plasma becomes uniform as a whole.

[0013] In this configuration, the direction in which the stirring gas is injected from the nozzle is directed to the direction inclined toward the gas blowing pipe with respect to the radial direction of the insulating pipe. Since the stirring gas is injected against the flow of the seed gas from the gas injection pipe, the inside of the induction plasma is sufficiently stirred and the temperature distribution of the induction plasma becomes more uniform.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a sectional view showing a configuration of a plasma generator according to an embodiment of the present invention. An insulating ring 15 is hermetically interposed midway in the axial direction of the insulating tube 11. A hole is penetrated obliquely downward through the insulating ring 15 to form a nozzle 15A. On the other hand, a ventilation hole 17 is also provided in the flange 9, and a guide pipe 16 for a stirring gas 18 is provided between the ventilation hole 17 and the nozzle 15A. The other configuration is the same as the conventional configuration described with reference to FIG. The same portions are denoted by the same reference numerals, and the detailed description will not be repeated.

FIG. 2 is a sectional view taken along the line AA of FIG. The guide tube 16 rising from below branches into three horizontal guide tubes 19. The other end of the guide tube 19 is connected to three nozzles 15A provided on the insulating ring 15, respectively. Returning to FIG. 1, the same stirring gas 18 as the seed gas 7 such as Ar or the sheath gas 6 is used. The stirring gas 18 blown from the outside of the flange 9 into the ventilation hole 17 is injected into the inside of the insulating tube 11 from the three nozzles 15A via the guide tubes 16 and 19. The nozzle 15A is disposed above the induction plasma 12, and injects the stirring gas 18 toward the induction plasma 12 from obliquely above. As a result, the induction plasma 12 is stirred gas 1
The outer peripheral portion, which tends to be heated by the skin effect and is likely to be heated by the skin effect, mixes with the inner portion that is hardly heated. Therefore, the entire temperature distribution of the induction plasma 12 becomes uniform. Therefore, the reaction between the seed gas 7 and the carrier gas 8 proceeds efficiently, and the plasma processing capability of the apparatus is improved.

FIG. 3 is a sectional view showing a configuration of an induction plasma generating apparatus according to another embodiment of the present invention. An insulating ring 15 is hermetically interposed in the axial direction of the insulating tube 11 so that the emission direction of the nozzle 15 becomes horizontal toward the induction plasma 12. The rest is the same as the configuration of FIG. The BB cross section in FIG. 3 has the same configuration as that in FIG. 2, and the nozzles 15 </ b> B are equally arranged at three places on the insulating ring 15.

In the case of FIG. 3 as well, the induction plasma 12 is agitated by the stirring gas 18 so that the outer peripheral portion, which tends to be high in temperature, mixes with the inner portion, which is hardly heated. Therefore, the temperature distribution of the induction plasma 12 becomes uniform as a whole. FIG. 4 is a cross-sectional view showing a configuration of an induction plasma generator according to still another embodiment of the present invention. The insulating ring 15 is hermetically interposed in the axial direction of the insulating tube 11 such that the injection direction of the nozzle 15 is obliquely upward toward the induction plasma 12. The rest is the same as the configuration of FIG. 4 has the same configuration as that of FIG. 2, and the nozzles 15 </ b> C are equally arranged at three places on the insulating ring 15.

In FIG. 4, since the stirring gas 18 is injected against the flow of the seed gas 7 from the gas injection pipe 13, the inside of the induction plasma 12 is sufficiently stirred and the temperature distribution of the induction plasma 12 is reduced. Become more uniform. FIG.
In each of the apparatuses shown in FIGS. 4 to 4, the insulating ring 15 is provided with three nozzles. If the nozzles are arranged at equal pitches on the insulating ring 15 and are arranged in large numbers, the effect of stirring the induction plasma 12 is excellent and the temperature distribution of the induction plasma 12 is improved.

The temperature distribution of the induction plasma 12 in the above embodiment was measured by spectroscopy. The result is shown in FIG. 6 in comparison with the conventional apparatus. The characteristic curve 21 is the case of the apparatus of FIGS. 1 and 2, and the characteristics of both are almost the same. The characteristic curve 22 is for the device of FIG.
Each of the characteristic curves 21 and 22 has a somewhat lower maximum temperature than the characteristic curve 20, but has a uniform temperature distribution as a whole. Further, in the case of the apparatus shown in FIG. 3 in which the stirring gas is injected against the seed gas, the temperature distribution of the induction plasma 12 is more uniform as shown by the characteristic curve 22 than in the other cases.

[0020]

As described above, according to the present invention, an induction plasma is provided in which a nozzle for injecting a stirring gas is provided on the peripheral wall of an insulating tube, and a direction for injecting the stirring gas from the nozzle is formed inside the insulating tube. Turned to Thereby, the induction plasma is stirred by the stirring gas. Therefore, the temperature distribution of the induction plasma becomes uniform as a whole, and the plasma processing capability of the apparatus is improved.

In such a configuration, the direction in which the stirring gas is injected from the nozzle is directed to the direction inclined toward the gas blowing pipe with respect to the radial direction of the insulating pipe. Since the stirring gas is injected against the flow of the seed gas from the gas injection pipe, the inside of the induction plasma is sufficiently stirred and the temperature distribution of the induction plasma becomes more uniform. Therefore, the plasma processing capability of the apparatus is further improved.

[Brief description of the 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 taken along line AA of FIG. 1;

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

FIG. 4 is a sectional view showing a configuration of an induction plasma generator according to still another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a configuration of a conventional induction plasma generator.

FIG. 6 is a characteristic diagram showing a temperature distribution of induction plasma.

[Explanation of symbols]

1: coil, 7: seed gas, 11: insulating tube, 13: gas blowing tube, 18: stirring gas, 10: AC power, 12:
Induction plasma, 15A, 15B, 15C: Nozzle

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadahiro Sakuta Examiner in the company 2-3-7 Higashi Murai, Matsuto City, Ishikawa Prefecture (56) References JP-A-3-67498 (JP, A) Hei 6-35717 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05H 1/46 H05H 1/30

Claims (3)

(57) [Claims] A method for generating an induced plasma in an insulating tube by blowing a seed gas into the insulating tube from one axial end of the insulating tube and passing an alternating current through a coil wound around the outer periphery of the insulating tube. A method for generating induction plasma, characterized by blowing a stirring gas from a peripheral wall of an insulating tube toward an induction plasma formed inside the insulating tube. 2. The method according to claim 1, further comprising: an insulating tube; a gas blowing tube provided at one end of the insulating tube in an axial direction for blowing seed gas toward an inside of the insulating tube; It consists of a coil wound around the outer circumference of the insulating tube and an AC power supply connected to the coil. A nozzle for injecting the stirring gas is provided on the peripheral wall of the insulating tube, and the stirring gas for the nozzle is injected. An induction plasma generating apparatus characterized in that the direction of the induction plasma is directed to the induction plasma formed inside the insulating tube. 3. A nozzle according to claim 2, wherein the direction of injection of the stirring gas from the nozzle is directed to a direction inclined toward the gas injection pipe with respect to the radial direction of the insulating pipe. Induction plasma generator.