JPS61288348A - Ion source device - Google Patents

Abstract

PURPOSE:To prevent discharge from becoming unstable, by providing an anode member inside the inner circumferential surface of a plasma generation container which also serves as an anode and is fitted with a plurality of permanent magnets on the outer circumferential surface of the container, to keep the anode member at a high temperature to prevent a high-molecular product from clinging thereto. CONSTITUTION:A cylindrical plasma generation container 2A, which also serves as an anode and is fitted with permanent magnets 7A on the outer circumferential surface of the container, and a lid 2B, which is provided with an inlet port 1 for introducing a gas including a CF4 gas or the like and is fitted with a cathode 3 made of a hairpin-shaped tungsten filament, are combined with each other to constitute an ion source device. A cylindrical anode member 4 made of stainless steel or the like is spot-welded to a magnetic member 9, which is held on the inner circumferential surface of the container 2A by the attractive forces of the permanent magnets 7A. As a result, the anode member 4 can be caused to act at a high temperature so that an electrically-insulating high-molecular substance produced by discharge is prevented from clinging to the anode member. The discharge can thus be stabilized.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an ion source device, and particularly to an ion source device suitable for a reactive ion beam etching device that microfabricates the surface of a workpiece using chemical reactions and sputtering. Regarding the source device.

[Background of the invention]

In general, ion source devices, especially high-output ion source devices, generate various discharges such as glow discharge, arc discharge, and high-frequency discharge in a low-pressure discharge chamber, and the gas in the discharge chamber is turned into plasma by this discharge, and the plasma is It is configured to extract ions.

By the way, among such ion source devices, one in which a cusp magnetic field is formed within the discharge chamber in order to generate highly spatially uniform plasma is disclosed in, for example, Japanese Patent Laid-Open No. 56
It is disclosed in Japanese Patent Application Laid-Open No. 57-185653, etc.

However, when a plasma is created by ionizing a compound gas (fluorine, chlorine compound, etc.) using an ion source device that uses the cusp magnetic field described above, high molecular weight insulating products are generated in the plasma due to the plasma polymerization reaction of the compound gas. Deposits on the walls of the generation container.

Because the plasma generation vessel is the anode, which is the positive electrode of DC arc discharge, it has been found that there are problems with the basic operation of the ion source, such as unstable discharge or no discharge, and it is stable against compound gases. There is a risk that it will not be possible to maintain a constant discharge.

[Purpose of the invention]

The present invention has been made in view of the above points, and its purpose is to prevent the discharge from becoming unstable or stopping even if the plasma generation container also serves as an anode. An object of the present invention is to provide an ion source device that can maintain stable discharge against a compound gas.

[Summary of the invention]

The present invention achieves the intended purpose by providing an anode electrode on the inner periphery of a plasma generation container which also serves as an anode and has a plurality of permanent magnets on its outer periphery.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail based on embodiments of the drawings.

FIG. 1 shows an embodiment of the ion source device of the present invention.

As shown in the figure, a normal ion source device also serves as an anode,
and a substantially cylindrical plasma generation container 2A having a plurality of permanent magnets 7A on its outer periphery, and this plasma generation container 2.
A plasma generating container which forms a part of A, has a plurality of permanent magnets 7B on its outer periphery, and has a gas inlet 1 for introducing a gas containing a compound gas such as CF4 or a mixed gas of CF4 and Ar. An upper lid 2B, a cathode 3 using a hairpin-shaped tungsten filament supported by the plasma generation container upper lid 2B and arranged on the central axis of the plasma generation container 2A, and extracting ions from the formed plasma. It is roughly composed of extraction electrodes 5 and 6 having a large number of small holes which irradiate the workpiece as a beam as shown by the arrow. The above plurality of permanent magnets 7
A and 7B are provided along the outer periphery of the container so that the north and south poles face the central axis of the cylinder, creating a line cusp magnetic field inside the container. Furthermore, permanent magnet 7A,
A water cooling pipe 8 is installed between the rows of permanent magnets 7A and 7B.
, 7B is prevented from deteriorating in performance due to temperature rise. In this embodiment, an anode electrode 4 is provided on the inner periphery of the plasma generation container 2A. This anode electrode 4 is made of non-magnetic stainless steel with a plate thickness of 0.5 mm and a length of 150 mm.
It has a structure in which a cylinder of +++11 is divided in half in the direction along the central axis, and the installation is supported by spot welding to one end of a magnetic material 9 made of iron, and the other end of the magnetic material 9 is attracted by a permanent magnet 7A. By doing so, it is held and fixed inside the plasma generation container 2A.

In such a configuration, a gas containing a compound gas such as CF4 or a mixed gas of CF and Ar is introduced from the gas inlet 1, and a DC voltage is applied to the cathode 3 made of a tungsten filament and the anode electrode 4. 3
Plasma is created by ionizing the gas with thermionic electrons. An ion beam is extracted from this plasma by extraction electrodes 5 and 6 and irradiated onto the workpiece.

Therefore, as described above, if the anode electrode 4 is provided inside the plasma generation container 2A, the anode electrode 4 is not thermally cooled because it is electrically connected to the plasma generation container 2A. Accelerated electrons flow between the anode electrode 4 and the plasma and heat the anode electrode 4, so that the anode electrode 4 operates at a considerably higher temperature than the plasma generation container 2. Therefore, the anode electrode 4 will not have any insulating polymer substances generated due to the discharge of the compound gas attached to it, and this will prevent the discharge from becoming unstable or no longer occurring. There are no operational problems, and stable discharge can be maintained even with compound gases. In addition, since the anode electrode 4 is fixed using magnetism, maintenance work such as replacing and cleaning the 7-node electrode 4 itself is easy, and
If a part of the magnetic material 9 supporting the anode electrode 4 is insulated, a potential different from that of the plasma generation container 2A can be applied to the anode electrode 4, which has the effect of improving the confinement of electrons or ions. Furthermore, since the anode electrode 4 is at room temperature when the ion source is initially energized and started operating, there is a risk that insulating polymer products produced by the plasma will adhere and the discharge will become unstable. In this case, stable discharge can be continued by creating plasma with Ar gas or H2 gas, preheating the anode electrode 4 to a high temperature, and then switching to a compound gas such as CF. In addition, in this case,
It has been confirmed that by providing a temperature sensor such as a thermocouple on the anode electrode 4, stable discharge can be performed when the temperature of the anode electrode 4 reaches 150° C. to 200° C. or higher. Furthermore, by keeping the anode electrode 4 at a high temperature, it is possible to prevent the deposition of insulating polymer products, but low-molecular solids such as carbon will accumulate, so maintenance such as replacement and cleaning of the anode electrode 4 is required. Work must be done frequently. At this time, if hydrogen plasma is used, polymers such as fluorine and chlorine deposited on the anode electrode 4 will be decomposed by the reduction action of the hydrogen ions, so the fluorine etc. contained in the carbon will be converted into volatile matter and pumped into the vacuum pump. By discharging it out of the system, stable discharge can be restored, and at the same time, the anode electrode 4 can be replaced,
This has the effect of making maintenance work such as cleaning less complicated.

Next, an application example of the present invention is shown in FIGS. 2 and 3.

The application example shown in FIG. 2 uses electrons extracted from plasma by electrodeless discharge such as high frequency plasma or microwave plasma, or a hollow cathode, instead of the small tungsten filament as the cathode described above. For this reason, in the example shown in FIG. 2, a glass cylinder 10a having a gas inlet 10b and an RF coil 11 at R1 is attached to an upper lid 2B of the plasma generation container having a permanent magnet 7B, and an electron extraction electrode 12. Insulating spacer 13
It is provided through a 300° C. to serve as a source of electrons.

The other configurations are the same as the embodiment shown in FIG.

With this configuration, stable discharge can be maintained, and since there is no filament, maintenance work such as filament replacement can be omitted.6 Next, the application example shown in Figure 3 is similar to that shown in Figure 1. A workpiece 15 is placed at the positions of extraction electrodes 5 and 6 in the ion source device having the configuration shown, and etching is made possible by directly exposing the workpiece 15 to plasma, similar to that shown in FIG. Of course, this method has the effect of reducing damage to the workpiece due to ion beam impact.

〔Effect of the invention〕

According to the ion source device of the present invention described above, since the anode electrode is provided on the inner periphery of the plasma generation container which also serves as an anode and has a plurality of permanent magnets on the outer periphery, it is possible to heat the anode electrode to a high temperature. This type of ion source can be It is very effective for equipment.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the ion source device of the present invention, and FIGS. 2 and 3 are cross-sectional views showing application examples of the present invention, respectively. 1.10b... Gas inlet, 2A... Plasma generation container, 2B... Plasma generation container top lid, 3... Cathode, 4... Anode electrode, 5, 6... Extraction electrode, 7A . 7B... Permanent magnet, 8... Water cooling pipe, 9... Magnetic material, 10a... Glass cylinder, 11... RF coil,
12...Electron extraction electrode, 13...Insulating spacer, 15...Sheep! Figure No. 2m

Claims (1)

[Claims] 1. An ion source device that generates plasma by ionizing a compound gas by direct current discharge between a cathode and an anode in a plasma generation container that also serves as an anode and has a plurality of permanent magnets around its outer periphery, An ion source device characterized in that an anode electrode is provided on the inner periphery of the plasma generation container. 2. The ion source device according to claim 1, wherein the anode electrode is fixed to the inner periphery of the plasma generation container via a magnetic material. 3. The ion source device according to claim 2, wherein a part of the magnetic material is insulated. 4. The ion source device according to claim 1, wherein the cathode is comprised of a filament provided within a plasma generation container. 5. The ion source device according to claim 1, wherein plasma generated by high frequency electrodeless discharge such as a high frequency plasma source or a microwave plasma source is used as the cathode. 6. A plurality of extraction electrodes are provided for extracting ion beams from the plasma created by ionizing the compound gas by DC discharge between the cathode and the anode, and the workpiece is irradiated with the ion beam extracted by the extraction electrodes. An ion source device according to claim 1, characterized in that: 7. The ion source device according to claim 1, wherein the workpiece is irradiated with plasma generated by ionizing a compound gas by direct current discharge between the cathode and the anode.