JPS63179527A - Plasma generating apparatus - Google Patents

Abstract

PURPOSE:To prevent glow discharge in a gas path, by introducing process gas into a discharge chamber between both high frequency electrodes so that the gas is not brought into contact with the electrodes before the gas enters into the discharge chamber, and making the distance of a gas introducing path in the direction of an electric field shorter than the thickness of an ion sheath in the discharge chamber. CONSTITUTION:An electric insulator 13 comprising Teflon, alumina and the like is provided between a planar electrode 1 and a tubular electrode 2. A gas introducing tube 14 comprising an insulator is inserted into the electric insulator in the lateral direction. An annular slit-shaped gas flowing path 15 is formed in the insulator 13 and a quartz pipe 5 so as to communicate the introducing tube and a discharge chamber 3. A length (width) d1 of the gas flowing path in the direction of a high frequency electric field (direction of arrows) is thin and shorter than a thickness d2 of an ion sheath 16, which is generated between a plasma region in the discharge chamber and the electrode 1. Process gas is not brought into contact with the electrodes 1 and 2 before the gas enters into the discharge chamber 3. The gas is introduced through a space, in which the distance in the direction of the applied electric field is less than the thickness of the ion sheath. Therefore, glow discharge is not generated in the gas flowing path 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion source, a plasma generation device used in plasma etching, reactive ion etching, plasma CVD, etc.

[Prior Art 1] FIG. 3 shows an example of a conventional ion source for extracting ions from plasma. In this example, plasma is generated using high-frequency discharge, and 1 is a flat electrode, 2 is a cylindrical electrode for forming a discharge chamber 3 between the flat electrode, and both are connected to a high-frequency discharge. 1ii714 supplies high-frequency power at a desired frequency.

The flat electrode and the cylindrical electrode are electrically insulated, and the discharge chamber is surrounded by an electrical insulator 5 such as a quartz glass tube,
Electrodes 1 and 2 are protected. Reference numeral 6 denotes an outer casing at ground potential, and a process gas introduction passage 7 made of an electrically insulating material such as a Teflon tube is formed through the outer casing, the flat electrode 1, and the quartz glass tube 5. The passage is connected to an external gas supply source (tank) via a flow control valve 8,
A desired gas is introduced into the discharge chamber 3 at a predetermined pressure. At the outlet of the discharge chamber, that is, on the side opposite to the flat electrode, there are a mesh-shaped accelerating electrode 9 and an extraction electrode 10.
and a ground electrode 11 are arranged in this order, and extract ions while accelerating them from within the plasma region 12 generated in the discharge chamber, and project them downward. A positive potential is applied to the acceleration electrode, and a negative potential is applied to the extraction electrode from respective DC power sources.

In such a device, when a desired gas is introduced into the discharge chamber through the passage 7 and high-frequency power is supplied between the electrodes 1 and 2 from the high-frequency electric wire #i4, a high-frequency discharge is generated within the discharge chamber.
Plasma is generated in the area indicated by 12. A positive potential is applied to the acceleration electrode 9 in contact with this plasma region, and the extraction electrode 1
By applying a negative potential to zero, ions in the plasma region are extracted while being accelerated as a beam. This ion beam is then used for purposes such as etching and CVD.

[Problems to be Solved by the Invention] However, in the conventional device described above, the passage 7 for introducing the process gas is formed in the electrode 1, and the gas is introduced from a portion with a potential. Even if it is made of an electrical insulator such as a Teflon tube, the passage between the earth potential outer casing 6 and the adjustment valve 8 has a length in the direction of the electric field, and glow discharge (portion A) occurs in this part. arise. Due to this discharge, the main discharge inside the discharge chamber 3 becomes extremely unstable, and there is also local heating due to the glow discharge, which may damage some passages and electrodes, and furthermore, cause a large power loss. There are drawbacks.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional drawbacks, it is an object of the present invention to provide a novel plasma generating device in which no glow discharge occurs in the process gas introduction passage.

Means for Solving Problem E] The present invention includes a flat electrode, and a substantially cylindrical electrode arranged electrically insulated from the electrode to form a discharge chamber between the flat electrodes. and a high-frequency power source that supplies high-frequency power between the flat electrode and the cylindrical electrode, and means for introducing a process gas into the discharge chamber,
An electrical insulator is interposed between the flat electrode and the cylindrical electrode, and a passage for introducing a process gas is formed in the insulator, and the direction of the electric field in a portion close to both electrodes is determined at least within the passage. The plasma generating device is characterized in that the length is shorter than the thickness of the ion sheath generated within the discharge chamber.

[Operation of the Invention] The present invention relates to a plasma generation device that utilizes high frequency waves, and the process gas is introduced into the discharge chamber from between both high frequency electrodes so that it does not come into contact with the electrodes before entering the discharge chamber. Glow discharge within the gas passage is prevented by making the distance of the introduction path in the electric field direction shorter than the thickness of the ion sheath inside the discharge chamber.

[Embodiment] FIG. 1 is a sectional view showing an embodiment of the present invention, and the same reference numerals as in FIG. 3 indicate the same constituent members.

In the present invention, an electrical insulating material 13 such as Teflon or alumina is inserted between the electrodes 1 and 2, and a gas introduction tube 14 made of an insulating material is inserted into the electrical insulating material from the lateral direction. The insulator 13 and the quartz tube 5 are connected to the insulator 13 and the quartz tube 5 through an annular and slit-shaped gas inflow path 15 so as to communicate with each other.
to form. Figure 2 is an enlarged view of the main parts of Figure 1.
The discharge chamber and gas inflow path are shown. As can be seen from the figure, the length and thickness (dl) of the gas inflow path in the direction of the high-frequency electric field (in the direction of the arrow) are made very thin, and the gas flow is generated between the plasma region formed in the discharge chamber and the electrode 1. It is shorter than the thickness d2 of the ion sheath 16.

In the above, the electrode 2 is a cylindrical electrode, but it does not need to be cylindrical and may have any shape. Further, it does not have to be completely cylindrical; for example, four flat plates or curved plates may be used and electrically connected to each other to form a substantially cylindrical electrode. Furthermore, d is thinner than the thickness of the ion sheath.
The part of the gas flow path formed in the direction L may be limited to the part close to the high frequency electrodes 1 and 2, and in the part where the electric field strength is not high enough to generate a glow discharge, the gas flow path (
tube) may be placed.

[Effect 3] With the above configuration, the process gas will not come into contact with the electrode before entering the discharge chamber, and the gas will be removed from the space where the distance in the direction of the applied electric field is less than the thickness of the ion sheath. This eliminates the occurrence of glow discharge in the gas inflow path, improves the stability of the main discharge, prevents local damage, and further reduces power loss. You can expect it.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
FIG. 3 is an enlarged view of the main parts of the device, and FIG. 3 is a sectional view of the conventional device. 1.2: High frequency electrode 3: Discharge chamber 4: High frequency power supply 6: Outer casing 7: Gas introduction passage 8: Flow rate adjustment valve 9: Accelerating electrode 10: Extraction electrode 11: Earth electrode 12: Plasma region 13: Electrical insulator 14 :Gas introduction tube

Claims (3)

[Claims] (1) A flat electrode, a substantially cylindrical electrode arranged electrically insulated from the electrode and for forming a discharge chamber between the flat electrode, and a cylindrical In an apparatus comprising a high-frequency power source for supplying high-frequency power to an electrode, and a means for introducing a process gas into the discharge chamber, an electrical insulator is interposed between the flat electrode and the cylindrical electrode, and the process A passage for introducing gas is formed in the insulator, and the length of at least a portion of the passage close to the electrodes in the direction of the electric field is formed to be shorter than the thickness of the ion sheath generated in the discharge chamber. Plasma generator. (2) The plasma generating device according to claim 1, wherein the discharge chamber formed by the flat electrode and the cylindrical electrode is lined with an electrical insulator such as a quartz glass tube. (3) The plasma generating device according to claim 1 or 2, wherein the cylindrical electrode is formed by combining a plurality of plate electrodes.