JP2586836B2 - Ion source device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion source device which supplies electrons from an electron emission source and converts an ionized gas into plasma by DC discharge to generate an ion beam.

[0002]

2. Description of the Related Art Conventionally, as typical ion source devices used for ion beam sputtering, ion beam mixing, ion assist and the like, there are a Kauffman type ion source device, a bucket type ion source device and the like.

(Conventional Example 1) A conventional Kauffman-type ion source device has a configuration shown in FIG.
Reference numeral 1 denotes a case made of a non-magnetic metal such as stainless steel, 2 denotes a plasma generation chamber formed by the case 1, 3 denotes a filament provided in the generation chamber 2, such as tungsten W, lanthanum boride LaB _{6, and the} like. Consists of Reference numeral 4 denotes a filament power supply for heating the filament 3, and reference numeral 5 denotes a cylindrical anode provided in the generation chamber 2.

[0006] Reference numeral 6 denotes a gas inlet to the generation chamber 2, and reference numeral 7 denotes an ion beam extraction electrode group, which includes a first electrode 8, a second electrode 9,
It is composed of a third electrode 10. Reference numeral 11 denotes a cylindrical permanent magnet or electromagnet provided outside the housing 1 for generating a magnetic field.

An arc power supply 12 has an anode connected to the anode 5 and a cathode connected to the housing 1 via the resistor 13, and applies an anode voltage to the anode 5. An acceleration power supply 14 has an anode connected to the cathode of the arc power supply 12 and applies a positive acceleration voltage lower than the anode voltage to the first electrode 8 having the same potential as the housing 1. Reference numeral 15 denotes a deceleration power supply for applying a negative voltage to the second electrode 9.

The filament 3 is a thermoelectron emission source as a cathode, and emits thermoelectrons e 'while being kept at a high temperature by resistance heating of the filament power supply 4, for example, 2400 ° C. for tungsten and 130 ° C. for lanthanum boride.
Heated to about 0 ° C.

On the other hand, an ionized gas, for example, a rare gas such as argon (Ar) or a reactive gas such as oxygen gas is introduced into the plasma generation chamber 2 from the gas inlet 6.

The discharge between the filament 3 and the anode 5 generates a plasma 16 of the introduced ionized gas, and the ions in the plasma are converted into an ion beam by the beam extraction operation of the electrode group 7 to the sputtering chamber or the like. Drawn out.

At this time, the magnetic field of the magnet 11 improves the generation efficiency of the plasma 16 or improves the confinement of the plasma 16.

(Conventional Example 2) A conventional bucket type ion source device has a configuration shown in FIG. 3, and the points different from the configuration of FIG. 2 are as follows. Without the anode 5 of FIG.
The anode of the arc power supply 12 is directly connected to the housing 1,
Is an anode, and the anode of the acceleration power supply 14 is connected to the housing 1 directly or via a resistor to the first electrode 8 of the electrode group 7 via the insulator 17, and the permanent magnet 11 is composed of a plurality of annular bodies. In that a cusp magnetic field is formed inside the housing 1. The operation is almost the same as in FIG.

(Conventional Example 3) A conventional hollow cathode type ion source device has a configuration shown in FIG. 4 and differs from FIG. 3 in the following point. A cathode housing 19 made of a non-magnetic metal is attached to the left opening of the housing 1 via an insulator 18 without the filament 3, and the cathode housing 19 is inserted into the left opening of the housing 19 via an insulator 20. A cover plate 21 made of a magnetic metal is mounted, and a cathode chamber 22 is formed.

A hollow cathode 23 is provided in the cathode chamber 22, and a heater coil 25 is wound around an outer periphery of a tubular body 24 integrally formed on the cover plate 21, and a thermionic emission material is provided on an inner surface of the tubular body 24. The hollow cathode 23 is provided, the heater coil 25 is heated by the power supply 4, and the thermionic emission material 26 is heated via the tubular body 24.

The cover plate 21 is provided with a gas inlet 27 to the inside of the tubular body 24. The cathode of the arc power supply 12 is connected to the cover plate 21 and the cylindrical body 24, and is also connected to the cathode housing 19 and the first electrode 8 via the resistor 13.

Then, an ionized gas is introduced into the production chamber 2 from the introduction port 6, and a rare gas for hollow discharge such as argon is introduced from the introduction port 27 into the inside of the cylindrical body 24. A discharge is generated between the housing 1 to be formed and the hollow cathode 23, a hollow discharge of a rare gas is generated in a space inside the cylindrical body 24, and thermionic electrons are emitted from the thermionic emission material 26 by thermionic emission based on the hollow discharge. e ′ is released, and the thermoelectrons e ′ are introduced into the generation chamber 2 by the anode voltage.

Therefore, the plasma 16 is generated in the generation chamber 2 by the discharge between the housing 1 and the hollow cathode 23,
The discharge is continued by the thermoelectrons e ′ supplied from the cathode 23, the ionized gas is ionized from the gas inlet 6, and an ion beam is extracted through the electrode group 7, as in the case of FIG.

(Conventional Example 4) On the other hand, JP-A-62-93834 (H01J 27)
/ 08) describes an ion source device provided with an electron source that emits ionized electrons by plasma generation.

This ion source device has an electron generation chamber and a plasma generation chamber (corresponding to the generation chamber 2). And
Plasma is generated in the generation chamber by high-frequency discharge in the electron generation chamber.

Further, an electron extraction electrode is provided between the electron generation chamber and the plasma generation chamber, the electrode being electrically insulated from the housings of the two chambers. electron extraction electrode polarity of the DC voltage becomes a positive potential (electron extraction voltage) V ₁ is applied to the electron generation chamber.

[0019] By the application of the DC voltage V _1, only electrons from the electron generating chamber by the action of the electron gun with an electron extraction electrode is led out are accelerated and supplied to the plasma generation chamber through the electron extraction electrode.

The plasma generation chamber generates a DC discharge (arc discharge) using the extracted electrons to generate plasma, and an ion beam is extracted from the plasma via a beam extraction electrode.

[0021]

SUMMARY OF THE INVENTION The conventional FIGS.
The ion source device of the present invention comprises a filament 3 as an electron emission source.
Is provided in the generation chamber 2 to maintain the filament 3 at a high temperature and generate thermoelectrons e ′ necessary for generation of the plasma 16 by using the thermoelectron emission phenomenon.
The material evaporates due to the high temperature heating, and in addition, is exposed to severe conditions such as sputtering by ion bombardment.

Therefore, when the filament 3 is greatly consumed and the ionized gas is argon, there is a problem that it is possible to use only about 50 hours with tandexten and about 100 hours with lanthanum boride, and the ionized gas is a reactive gas such as oxygen. In the case of (1), there is a problem that the filament 3 is rapidly oxidized and consumed in an extremely short time.

Next, in the ion source apparatus shown in FIG. 4, hollow discharge for thermionic emission is performed using a rare gas in a cathode chamber 22 separate from the plasma generation chamber 2 to which the ionized gas is supplied. 3 can be used for a long time as compared with the apparatus shown in FIG. 3, but since the thermoelectron emitting material 26 is subjected to sputtering by ion bombardment at a high temperature, even if the ionized gas is a rare gas such as argon, 100 to There is a problem that only 200 hours can be used.

Moreover, since the ionized gas of the generation chamber 2 slightly flows into the cathode chamber 22, when the ionized gas is oxygen or the like, the thermoelectron emission material 2 is reduced in a shorter time than when the rare gas is used.
6 is consumed.

In addition, since the rare gas for hollow discharge in the cylindrical body 24 is mixed with the ionized gas in the plasma generation chamber 2, the generated plasma 16 is mixed with the rare gas for hollow discharge and the rare gas for hollow discharge. However, there is a problem that a plasma of only the ionized gas cannot be generated, and a desired ion beam cannot be obtained.

Next, in the ion source device described in the above publication, necessary electrons are generated not by thermionic emission but by plasma generation, so that the electron emission source uses consumable materials such as the filament 3 and the hollow cathode 25. Formed without
It can be used for a long time, and a desired ion beam can be obtained by plasma generation using only ionized gas.

However, since only electrons are extracted from the electron generation chamber and supplied to the plasma generation chamber by the so-called electron gun method, the two chambers are electrically insulated from the two chambers between the electron generation chamber and the plasma generation chamber. an electron extraction electrode, it is necessary to apply a DC voltage V ₁ of the electronic acceleration between the housing and the electron extraction electrode of the electron generating chamber, construction course from complication, as described below In addition, there is a problem in that the supply amount of electrons in the plasma generation chamber is limited and reduced, and the ion beam generation efficiency is poor and the amount is small.

That is, by applying a DC voltage V ₁ between the housing of the electron generation chamber and the electron extraction electrode, a space charge layer of only electrons is formed between the plasma of the electron generation chamber and the electron extraction electrode, Since the amount of electrons extracted is limited by this layer, the amount of electrons supplied to the plasma generation chamber is limited and reduced, and the amount of ion beam generation is small.

The present invention uses a plasma generation method of high-frequency discharge, which is cheaper than microwave discharge or the like, without using the thermionic emission phenomenon of a consumable material and without providing an electrode or the like for electron acceleration. With the configuration, the plasma of the ionized gas is generated without limitation of the electron supply amount (drawing amount), the material consumption of the electron emission source is completely eliminated, and a long time use is enabled, and the plasma generation of only the ionized gas is performed. It is an object of the present invention to make it possible to efficiently form a high-quality ion beam.

[0030]

In order to achieve the above-mentioned object, an ion source device according to the present invention is provided with a gas introduction port for ionization, and a sub-electrode for electron emission by high-frequency discharge based on application of a high-frequency voltage. An insulator sub-housing for generating plasma;
A main housing connected to the sub-housing, a lid plate formed integrally with the sub-housing on the main housing side of the sub-housing, an electron emission hole formed in the lid plate, and an electrode in the sub-housing. At a lower potential than the main housing,
A DC power supply supplies electrons from the electron emission holes into the main housing and generates main plasma in the main housing by DC discharge, and an ion beam extraction electrode for extracting an ion beam from the main plasma.

[0031]

In the ion source device of the present invention configured as described above, a sub-plasma for emitting electrons is generated by high-frequency discharge in the sub-housing based on application of a high-frequency voltage, and electrons ionized by the generation of the plasma are generated. The electrons necessary for plasma generation of the ionized gas are supplied into the main housing through the electron emission holes of the cover plate.

Further, a main plasma is generated in the main housing by a DC discharge using the supplied electrons, and an ion beam is extracted from the main plasma by an ion beam extraction electrode.

The cover plate is integrally formed of an insulator with the sub-housing, and the high-frequency electrode in the sub-housing has a lower potential than the main housing by the DC power supply, and electrons are transferred to the main housing by a potential difference between the main and sub-plasmas. Supplied to the body.

At this time, a double sheath of both plasmas is formed at the interface between the main plasma and the sub-plasma near the electron emission holes.
Since electrons are emitted from the sub-plasma side to the main plasma side, and ions flow into the sub-plasma side from the main plasma side, there is no formation of a space charge layer of only electrons which is a problem in the electron gun system of the above publication, and It is efficiently released into the main plasma without restriction on the supply amount.

Therefore, it is not necessary to use a thermionic emission material such as a filament which is intensely consumed unlike the conventional art, and the electron emission source has an extremely long life and can be used for a long time. Further, when the same gas as the ionized gas in the main plasma chamber is used as the gas used for generating the sub-plasma, the main plasma is generated only with a desired gas and a high-quality ion beam is formed.

In addition, since the main plasma is generated without any limitation on the amount of supplied electrons, a large amount of ion beams can be efficiently formed. Since the high-frequency discharge for generating plasma is generated based on the application of the high-frequency voltage, the power supply is formed at a lower cost than when the high-frequency discharge is generated based on microwave power supply or the like.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment applied to a bucket type ion source device will be described with reference to FIG. In the figure,
The same reference numerals as those in FIGS. 2 to 4 denote the same or corresponding components, and reference numeral 28 denotes a sub-housing formed of heat-resistant glass (insulator), which forms a sub-plasma chamber 29.

Reference numeral 30 denotes an ionization gas inlet formed in the sub-housing 28, and reference numeral 31 denotes a high-frequency power source. One of the cylindrical high-frequency electrodes provided on the outer periphery of the sub-housing 28 and the sub-housing 28
A high-frequency voltage for discharge is applied to the other plate-shaped high-frequency electrode 33 positioned inside the cell.

Reference numeral 34 denotes a sub-housing 2 at the right opening of the sub-housing 28.
8 is a cover plate formed integrally with the cover plate 8, 35 is an electron emission hole formed in the cover plate 34, 36 is a non-magnetic metal main housing corresponding to the housing 1 of FIG. Through the sub-housing 28
And a main plasma chamber 37 is formed.

The anode of the arc power supply 12 is
6 and its cathode is connected to the high-frequency electrode 33 and the first electrode 8, and these electrodes 33 and 8 are fixed at a lower potential than the main housing 36.

In this state, a high-frequency voltage in the order of MHz is output from the high-frequency power supply 31, and this voltage is
When the voltage is applied to the sub-plasma chamber 29, a high-frequency discharge is generated in the sub-plasma chamber 29, and a gas for electron emission such as a rare gas introduced into the sub-plasma chamber 29 from the inlet 30 is ionized.
8 is generated.

The electrons e generated by the ionization due to the generation of the sub-plasma 38 are drawn out from the emission hole 35 to the main plasma chamber 37 at an anode voltage of about 40 to 120 V and supplied.

Next, in the main plasma chamber 37, based on a DC discharge using the supplied electrons e, an ionized gas such as a rare gas from the inlet 6 is ionized, and a main plasma 39 is generated. The discharge is sustained by the supply.

At this time, the main plasma 39 is efficiently confined by the cusp magnetic field of the magnet 11 and the electrode group 7
And stable main plasma 3 over a large area in the vicinity of
9 is generated.

Then, the ions are extracted from the main plasma 39 as an ion beam to a sputtering chamber or the like by the beam extracting action of the electrode group 7. By the way, the electron emission hole 3
The cover plate 34 on which 5 is formed has the same potential as the sub-housing 28 and has no electron acceleration function.

Then, the discharge electrode 3 is turned on by the arc power supply 12.
3 is fixed at a lower potential than the main housing 36,
Is lower in potential than the main plasma 39, so that the electrons e
The plasma is supplied to the main plasma chamber 37 according to the potential difference between the sub-plasmas 39 and 38.

At this time, a double sheath of the two plasmas 38, 39 is formed at the boundary surface between the main and sub-plasmas 39, 38 near the electron emission hole 35, and electrons e are emitted from the sub-plasma 38 side to the main plasma 39 side. Since ions flow from the main plasma 39 to the sub-plasma 38 side, there is no formation of a space charge layer of only electrons, which is a problem in the electron gun system of the above-mentioned publication, and electrons e are efficiently supplied to the main plasma 3
9 and released.

Since the high-frequency discharge in the sub-plasma chamber 29 uses a high-frequency power supply 31 which is less expensive than a microwave generator, the apparatus is formed at low cost.

The gas introduced into the sub-plasma chamber 29 has no influence even if a gas other than the rare gas is used, and the same gas as the ionized gas in the main plasma chamber 37 is introduced into the sub-plasma chamber 29. Can be.

It is preferable to provide a permanent magnet or an electromagnetic coil for generating a magnetic field outside the sub-plasma chamber 29 to increase the density of the sub-plasma 38. Further, it is needless to say that this embodiment can be applied to a Kauffman-type ion source device.

[0051]

Since the present invention is configured as described above, the following effects can be obtained. In the sub-housing 28 as an electron emission source, a sub-plasma 38 for electron emission is generated by high-frequency discharge, and by this generation, electrons required for plasma generation in the main housing 36 are formed. Since the consumable material such as a filament and a thermionic emission material is heated to a high temperature and maintained as in the related art, the material is consumed more than in the case where the thermionic emission phenomenon is used. In addition, the electron emission source has an extremely long life, and a long continuous operation of several hundred hours or more can be performed.

A gas other than a rare gas can be used as the ionization gas used for the generation of the sub-plasma, and there is no restriction on the type of the ionization gas. When the same gas is used, the main housing 36
The main plasma 39 becomes a plasma of only a desired ionized gas, and a high-quality ion beam can be formed.

Further, even when a reactive gas such as oxygen is used for generating an ion beam, there is no oxidative consumption,
Generation of plasma can be stably maintained for a long period of time.

Further, the high-frequency electrode 33 in the sub-housing 28 is held at a lower potential than the main housing 36 by the DC power source (arc power source) 12, and the sub-plasma 38 in the sub-housing 28 is The potential becomes lower than that of the main plasma 39, and the supply of electrons from the sub housing 28 to the main housing 36 through the electron emission holes 35 accelerates the electrons by the electrode voltage between the two housings 28 and 36. Primary and secondary plasmas 3
This is performed according to the potential difference of 9, 38.

At this time, a double sheath of the plasmas 39 and 38 is formed at the boundary between the plasmas 39 and 38 in the vicinity of the electron emission hole 35, and a space charge layer of only electrons, which is a problem in the electron gun system, can be formed. In addition, electrons can be efficiently emitted into the main plasma 39 without limitation of the supply amount, and a large amount of ion beams can be efficiently formed with a simple configuration that does not use electrodes for electron acceleration (for extraction).

Further, since a high-frequency power supply 31 which is less expensive than a microwave generator is used for high-frequency discharge in the sub-housing 28,
The device is formed at low cost.

Therefore, the plasma generation method of high-frequency discharge, which is cheaper than microwave discharge or the like, does not use the thermionic emission phenomenon of the consumable material, and has a simple structure without providing an electrode for electron acceleration. The plasma of ionized gas is generated without restriction on the supply amount (drawing amount), the material consumption of the electron emission source is completely eliminated, and a long-time use is enabled, and the plasma generation of only the ionized gas is enabled. An ion beam can be efficiently formed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of the present invention.

FIG. 2 is a configuration diagram of an example of a conventional device.

FIG. 3 is a configuration diagram of another example of the conventional device.

FIG. 4 is a configuration diagram of still another example of the conventional device.

[Explanation of symbols]

 7 Ion beam extraction electrode group 12 Arc power supply 28 Sub-housing 30 Gas inlet 32, 33 High frequency electrode 34 Cover plate 35 Electron emission hole 36 Main housing 38 Sub-plasma 39 Main plasma

Continuing from the front page (72) Inventor Shuichi Nogawa 47, Takaune-cho, Umezu, Ukyo-ku, Kyoto (56) References JP-A-62-93834 (JP, A)

Claims (1)

(57) [Claims] An ionization gas inlet is formed, an insulator sub-housing for generating a sub-plasma for electron emission by high-frequency discharge based on application of a high-frequency voltage, and an insulating sub-housing connected to the sub-housing. A main housing, a lid plate formed integrally with the sub-housing on the main housing side of the sub-housing, an electron emission hole formed in the lid plate, and an electrode in the sub-housing being attached to the main housing. Hold it at a lower potential than the housing,
A DC power supply for supplying electrons from the electron emission holes into the main housing and generating a main plasma in the main housing by DC discharge; and an ion beam extraction electrode for extracting an ion beam from the main plasma. Characterized ion source device.