JPH0837098A - Plasma generating device - Google Patents

Abstract

PURPOSE:To provide a plasma generating device capable of efficiently guiding electrons from a plasma source into a vacuum chamber and generating dense plasma. CONSTITUTION:The plasma generated in a case 5 is focused in the axial direction of the electron beam from a cathode 2 by the effect of the magnetic field generated by a coil 4, and electrons accelerated by the accelerating electric field of an anode 3 are extracted to a vacuum chamber 7. Since the electrons in the plasma rarely flow into the case 5 and a shield plate 12, most of the electrons are accelerated by the accelerating electric field of the anode 3 located at an opening section of the shield plate 12 facing the vacuum chamber 7 and are efficiently extracted to the vacuum chamber 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optimum plasma generator for use in ion plating, plasma CVD equipment and the like.

[0002]

2. Description of the Related Art In a plasma generator such as an ion plating device, plasma is formed in a vacuum chamber, the film forming material is ionized by the plasma, and the ionized material is attached to a substrate in the chamber. To generate plasma in this chamber,
An electron source is provided in the chamber, and electrons from the electron source are introduced into the chamber. Recently, a plasma source is used as this electron source.

FIG. 1 shows a plasma generator using a plasma source as an electron source. In the figure, reference numeral 1 denotes a plasma source, and the plasma source 1 is provided at an end of the case 2, a cylindrical case 5 arranged so as to enclose the cathode 2, a ring-shaped anode 3, a magnetic field generating coil 4, a cathode 2. It is composed of a gas inlet 6. The plasma source 1 is mounted in a vacuum chamber 7 so as to be built therein. The cathode 2 is made of a wire made of a thermionic emission material such as tungsten. The cathode 2 is connected to a heating power source 8 and is configured to be heated to a temperature at which thermoelectrons can be emitted. The anode 3 is electrically insulated from the case 5 by an insulator 9.

The anode 3 is connected to the cathode 2 via a discharge DC power source 10 and a resistor R _1.
Is applied with a voltage of +50 V to +150 V with respect to the cathode 2, and plays a role of extracting and accelerating the electrons in the plasma generated in the case 5 and introducing them into the vacuum chamber 7. The case 5 serves as a discharge chamber for maintaining stable discharge between the cathode 2 and the anode 3. Further, the case 5 is connected to the discharge power source 10 via a resistor R ₃ of about several hundred Ω. As a result, the case 5 is applied with a voltage equal to or higher than the ionization voltage of the argon gas with respect to the average potential of the cathode 2, and is configured to function as a discharge trigger. In addition, the cathode 2, the anode 3,
The discharge circuit composed of the discharge DC power supply 10 is connected to the vacuum chamber 7 by a high resistance R ₂ .

The coil 4 is an electromagnet that forms a magnetic field parallel to the direction in which electrons are extracted from the plasma generated in the case 5, and the magnetic field focuses the discharge plasma in the case 5 to make the electron beam an anode. It also has a role of guiding the electron beam extracted from the anode 3 to the vacuum chamber 6 to a distance from the anode 3 while helping to pass the electron beam from the anode 3. Although not shown in detail, the case 5 and the anode 3 have a structure in which cooling water can circulate. Next, the operation of such a configuration will be described.

First, the inside of the case 5 is evacuated to a high vacuum by a vacuum exhaust system (not shown), and then an inert gas such as argon gas is introduced into the case 5 through the gas introduction port 6. In this case, the pressure in the case 5 is set higher than 10 ⁻² Torr. After the inside of the case 5 is set to a predetermined pressure, a current is supplied from the heating power source 8 to the cathode 2 to electrically heat it, and the cathode is heated to a temperature at which thermionic electrons can be emitted. As a result, thermoelectrons are emitted from the cathode 2, and a discharge is generated between the cathode 2 and the anode 3 and between the cathode 2 and the case 5. Case 5 by this discharge
The argon gas inside is ionized, and plasma is generated in the case 5.

The plasma thus generated is focused in the axial direction of the electron beam from the cathode 2 under the influence of the magnetic field created by the coil 4, and the electrons accelerated by the accelerating electric field of the anode 3 are evacuated to the vacuum chamber 7. Be drawn to. The electrons drawn into the vacuum chamber 7 excite the active gas or the reaction gas introduced from the gas introduction port 11 into the vacuum chamber 7 to generate plasma, thereby forming a deep plasma in the vacuum chamber 7.

Since the discharge circuit of the plasma source 1 and the vacuum chamber 7 are connected by a high resistance, the discharge current drawn from the anode 3 to the vacuum chamber 7 becomes difficult to flow into the vacuum chamber 7 and is almost impossible. Will return in the direction of the anode 3. That is, the plasma source 1
Acts such that the electron beam extracted from the anode 2 makes a U-turn and is returned to the anode 3.

[0009]

The plasma source having the above-mentioned structure has the following problems. That is, most of the electrons in the plasma inside the case 5 flow directly into the anode 3 without being extracted to the vacuum chamber 7. Therefore, the discharge current drawn into the vacuum chamber 7 is considerably reduced with respect to the discharge current between the cathode 2 and the anode 3. In order to solve this point, it is conceivable to strengthen the magnetic field by the coil 4 to prevent the electrons extracted from the plasma in the case 5 from axially compressing and directly flowing into the anode 3.
However, with this method, the discharge current flowing directly into the anode 3 can be reduced, but the plasma generated by the electron beam extracted from the anode 3 to the vacuum chamber 7 is affected by the magnetic field, and thus the anode 3
The electron beam extracted from the anode 3 cannot spread in the vicinity, and the behavior that the electron beam is U-turned and returned to the anode 3 is hindered, and the discharge output that can be injected into the vacuum chamber 7 cannot be increased.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a plasma generator capable of efficiently introducing electrons from a plasma source into a vacuum chamber to generate a dense plasma. It will be realized.

[0011]

A plasma generator according to the present invention comprises a case into which a plasma gas is supplied, a cathode and an anode, and the inside of the case is heated by thermoelectrons generated by heating the cathode. A plasma source configured to form a plasma in the interior of the plasma source, and a vacuum chamber into which electrons accelerated by the anode are introduced from plasma generated in the case of the plasma source are introduced into the plasma source. It is characterized in that a shield plate is provided on the front surface of the anode facing the plasma formed in the above.

[0012]

In the plasma device according to the present invention, a shield plate is provided on the front surface of the anode facing the plasma formed in the case of the plasma source to prevent electrons extracted from the plasma from flowing into the anode.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. 2 shows an embodiment of the present invention,
The same or similar components as those of the conventional apparatus of FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In this example,
This is different from the conventional device shown in FIG. 1 in that a shield plate 12 is arranged on the front surface of the anode 3. This shield plate 12
Are arranged so as to cover the surface of the anode 3 exposed to the plasma formed in the case 5. The shield plate 12 is arranged so as to be insulated from the anode 3 and the case 5, and is placed in a floating state or installed with a high resistance. Alternatively, it may be fixed to the case 5 installed via a high resistance and electrically connected to the case 5. The operation of such a configuration will be described below.

First, as in the conventional device shown in FIG. 1, a case 5 is used.
The inside is evacuated to a high vacuum by a vacuum exhaust system (not shown),
Then, an inert gas such as argon gas is introduced into the case 5 through the gas introduction port 6. In this case, the pressure in the case 5 is set higher than 10 ⁻² Torr. After the inside of the case 5 is set to a predetermined pressure, an electric current is supplied to the cathode 2 from a heating power source to energize and heat the cathode 2 to a temperature at which the thermoelectrons can be emitted. As a result, thermoelectrons are emitted from the cathode 2, and discharge is generated between the cathode 2 and the case 5 and between the cathode 2 and the shield plate 12. Due to this discharge, the argon gas inside the case 5 is ionized, and plasma is generated inside the case 5.

The plasma thus generated is focused in the axial direction of the electron beam from the cathode 2 under the influence of the magnetic field created by the coil 4, and the electrons accelerated by the accelerating electric field of the anode 3 are vacuum chamber 7. Be drawn to. At this time, the electrons in the plasma are difficult to flow into the case 5 and the shield plate 12, so most of them are accelerated by the acceleration electric field of the anode 3 existing in the opening of the shield plate facing the vacuum chamber 7, and the vacuum chamber 7 To be efficiently extracted. Here, regarding the influence of the magnetic field by the coil 4, it was confirmed that the coil magnetic field strength during the operation of the plasma source was 100 gauss to 300 gauss at the center of the coil, and that the coil operates practically without any problem.

The electrons drawn into the vacuum chamber 7 excite the active gas or the reaction gas introduced into the vacuum chamber 7 to turn them into plasma and form a deep plasma in the vacuum chamber 7. Since the discharge circuit of the plasma source 1 and the vacuum chamber 7 are connected by a high resistance, the discharge current drawn from the anode 3 to the vacuum chamber 7 becomes difficult to flow into the vacuum chamber 7, and most of the anode 3 It will return to the direction. That is, the plasma source 1 behaves such that the electron beam extracted from the anode 3 makes a U-turn and is returned to the anode 3. Therefore, the shield plate should not be arranged in front of the surface of the anode 3 facing the vacuum chamber 7.

The plasma source 1 is not limited to being built in the vacuum chamber 7, but the plasma source may be externally attached to the wall of the vacuum chamber.

[0018]

As described above, in the plasma generator according to the present invention, the shield plate is provided on the front surface of the anode facing the plasma formed in the case of the plasma source so that the electrons extracted from the plasma are It was configured to prevent it from flowing into the anode before being drawn into the vacuum chamber. As a result, electrons can be efficiently supplied from the plasma source into the vacuum chamber, and dense plasma can be formed in the chamber. Further, since it is not necessary to increase the magnetic field strength in order to prevent the electrons from flowing into the anode, the problem of the conventional device in which the electrons are introduced only into a narrow area in the vacuum chamber is solved.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional plasma generator.

FIG. 2 is a diagram showing an embodiment of a plasma generator according to the present invention.

[Explanation of symbols]

 1 Plasma Source 2 Cathode 3 Anode 4 Magnetic Field Generation Coil 5 Case 6 Gas Inlet 7 Vacuum Chamber 8 Heating Power 9 Insulator 10 Discharge Power 11 Gas Inlet 12 Shield Plate

Claims (3)

[Claims] 1. A case in which a plasma gas is supplied inside, a plasma source including a cathode and an anode, and configured to form plasma in the case by thermoelectrons generated by heating the cathode. In a plasma generator provided with a vacuum chamber into which electrons accelerated by the anode and extracted from plasma generated in the case of the plasma source are introduced, a front surface of the anode facing the plasma formed in the case, A plasma generator provided with a shield plate. 2. The plasma generator according to claim 1, wherein the shield plate has a floating potential. 3. The plasma generator according to claim 1, wherein the shield plate is grounded via a high resistance.