JPH02199742A - Ion source - Google Patents

Abstract

PURPOSE:To heighten the ionization efficiency with simple constitution for obtaining a relatively big current by arranging an anode having potential different from a second plasma generation chamber between a first plasma generation chamber and the second plasma generation chamber. CONSTITUTION:Besides providing a first plasma generation chamber 6 with an anode 4, a second plasma generation chamber 8 is provided with an anode 7, both of these are connected to an acceleration power supply 16. Potential of the second plasma generation chamber 8 impressed by relatively negative voltage as compared with the anode 7 pulls electrons generated inside the second plasma generation chamber 8 as a second electron beam 11 to advance in the reverse direction to that of an electron beam 10 and rush into the first plasma generation chamber 6. This second electron beam 11 also concerns with ionization by collision of ionization gas inside the first plasma generation chamber 6 so that an ion generation rate inside the first plasma generation chamber 6 is heightened. Thereby, ionization efficiency can be heightened while lightening space charge of ions in ion pulling so that a bigger amount of an ion current can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] - The present invention relates to an ion source, particularly an electron beam-excited ion source.

[Conventional technology]

2. Description of the Related Art Conventionally, there is an electron beam excitation type ion source as shown in FIG. 2 as an ion source that generates plasma and obtains an ion beam through interaction between an electron beam and an ionized substance.

In this ion source, in a vacuum volume #119, an electron beam 10 emitted from a cathode 1 having a pore (not shown) in the center is accelerated in two stages by electric potentials applied to an extraction electrode 3 and an anode 4. The electron beam 10 enters the plasma generation chamber 6 and ionizes the ionized substance introduced from the ionized substance introduction port 9 by collision with the electron beam 10, thereby generating plasma.

Then, ions are extracted from this plasma according to the potential difference between the extraction electrode 3 and the anode 4, and the ion beam 1
I got 2. Therefore, in this ion source, the cathode 1.
Wehnelt 2. An electric field applied between the extraction electrode 3 and the anode 4 is used to generate and accelerate an electron beam, and also to draw and accelerate the ion beam.

One way to increase the ion production rate is to increase the electron beam current, but the maximum value of the electron beam current that can be obtained is determined according to the magnitude of the electric field between the cathode 1 and the extraction electrode 3. Therefore, in order to obtain a large amount of electron beam current, it is necessary to increase the electron beam acceleration voltage. Further, in order to extract ions with a practical amount of current from the plasma, it is desirable that the extraction voltage be high.

Therefore, the accelerating voltage of the electron beam must be at least several KV.1 In the figure, 5 is an electromagnetic lens, 15 is an extraction power source,
16 is an acceleration power source, 17 is a bias power source, and 13° and 14 are exhaust ports.

[Problem to be solved by the invention]

By the way, in order to ionize an ionized substance by the impact ionization effect of an electron beam, the ionization efficiency is often highest when the energy of the electron beam is several hundred eV, although it depends on the type of the ionized substance. However, due to the above-mentioned reasons, in the electron beam excited ion source, the energy of the electron beam is at least several KV, so the ionization efficiency of the ionized substance is relatively low, and therefore it is difficult to obtain a large amount of ion beam current. was there.

The object of the present invention has been made in view of the above-mentioned drawbacks.
An object of the present invention is to provide an electron beam-excited ion source that can increase ionization efficiency and obtain a relatively large current with a relatively simple configuration.

[Means to solve the problem]

In order to achieve the above object, the ion source according to the present invention generates plasma upon receiving an electron beam emitted from an electron gun having a cathode with a pore in the center, and extracts a plasma from the plasma. an electron beam-excited ion source that causes the ion beam to travel backward in the path of the electron beam and is ejected from the pore of the cathode; A second plasma generation chamber is provided, and an anode having a different potential from that of the second plasma generation chamber is arranged between the first plasma generation chamber and the second plasma generation chamber. .

[Effect]

In the ion source of the present invention, plasma is generated in the second plasma generation chamber by the electron beam being incident on the second plasma generation chamber located behind the first plasma generation chamber. Charged particles are extracted from this plasma by the potential difference between the plasma generation chamber and the anode, enter the first plasma generation chamber, and participate in ionization, so the ionization efficiency in the first plasma generation chamber increases, and therefore The ion current drawn from the plasma generation chamber can be increased.

〔Example〕

Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 3 is a block diagram of a second embodiment of the present invention. In each figure,
Components that are the same as those in FIG. 2 are given the same numbers, and explanations of other than essential parts will be omitted.

In FIG. 1, the metal ion source of the present invention has a conventional plasma generation chamber (first plasma generation chamber) 6 in a vacuum vessel 19 and a plasma generation chamber (second plasma generation chamber) 8 above it. They are set up consecutively. An ionized substance inlet 9 is passed through the insulating tube 18 into this second plasma generation chamber 8.
Open. In addition to providing an anode 4 for the first plasma generation chamber 6, an anode 7 is provided for the second plasma generation chamber 8, both of which are connected to an acceleration power source 16. Also.

The second plasma generation chamber 8 is connected to the extraction power source 15 .

The cathode 1, which has a pore (not shown) in the center, is made of a directly heated filament made of W, and the thermoelectrons generated by heating this are shaped and accelerated by the voltage applied to the Wehnelt 2. It is accelerated by two stages due to the potential difference between the voltage applied to the cathode 1 by the power source 16 and the voltage applied to the extraction electrode 3 by the extraction power source 15, and the potential difference between the anode 4 and the extraction electrode 3, and further focused by the electromagnetic lens 5. first electron beam 10
As a result, the plasma enters the first plasma generation chamber 6. The current of the first electron beam 10 is controlled by adjusting the voltage applied to the Wehnelt 2 by the bias power supply 17.
The first electron beam 1 entering the first plasma generation chamber 6
0 generates plasma by colliding and ionizing the ionized substance (hereinafter referred to as ionized gas) introduced as a gas from the ionized substance introduction port 9. After this, the electron beam lO of the cylinder 1 passes through the anode 7 and enters the second plasma generation chamber 8. The first electron beam 10 collides with and ionizes the ionized gas in the second plasma generation chamber 8 to generate plasma.

Due to the potential of the second plasma generation chamber 8 to which a relatively negative voltage is applied compared to the anode 7, the electrons generated in the second plasma generation chamber 8 become a second electron beam 11. It is pulled and moves in the opposite direction to the electron beam 10,
It enters the first plasma generation chamber 6. Since this second electron beam 11 also participates in the collision ionization of the ionized gas in the first plasma generation chamber 6, the ion generation rate in the first plasma generation chamber 6 increases. In the first embodiment, the cathode 1
In order to improve the degree of vacuum in the vicinity, the ionized gas is placed in an insulating tube 1.
8 into the second plasma generation chamber 8, and differential pumping is used. The ionized gas does not necessarily need to be introduced from the second plasma generation chamber 8, and may be introduced from the first plasma generation chamber 6.

In the exhaust configuration shown in FIG. 1, the pressure in the second plasma generation chamber 8 is the highest, so relatively high-density plasma is generated, and the second electron beam 11 with a relatively large current can be extracted. Furthermore, by using the extraction power source 15 as the power source for applying voltage to the second plasma generation chamber 8, there is no need to add a new power source; In addition, it is of course possible to adopt a configuration in which the potential of the second plasma generation chamber 8 can be varied independently. Further, the voltage applied to the second plasma generation chamber 8 is set to be positive compared to the voltage applied to the anode 7.

Ions are drawn from the second plasma generation chamber 8.

These ions may be used for ionization in the first plasma generation chamber 6.

The ion beam 12 is formed by ions generated in the first plasma generation chamber 6 being extracted in the opposite direction to the first electron beam lO according to the potential difference between the extraction electrode 3 and the anode 4; Since the electron beam 11 can reach the vicinity of the extraction electrode 3, the space charge of the ions can be relaxed during ion extraction, and a larger amount of ion beam current can be extracted.

Next, a second embodiment will be explained. The basic configuration is the same as that of the first embodiment, but in the second embodiment, as shown in FIG. 2 plasma generation chamber 8
It is located inside. By doing this, the second electron beam 11 is extracted, and the reflected electrons of the first electron beam 10 are extracted as the third electron beam 21.
The amount of electron beam current entering the first plasma generation chamber 6 is increased.

〔Effect of the invention〕

As described above, according to the present invention, an electrode having a relatively simple structure can be used in a conventional electron beam-excited ion source.

By adding a plasma generation chamber, the ionization efficiency can be increased, and the space charge of ions can be relaxed during ion extraction, so that a larger amount of ion current can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a first embodiment of the present invention, and FIG. 2 is a block diagram of a conventional electron beam-excited ion source. FIG. 3 is a block diagram of a second embodiment of the present invention. 1... Cathode 2... Wehnelt 3.
...Extraction electrodes 4,7...Anode 5...
・Electromagnetic lens 6...first plasma generation chamber 8・
...Second plasma generation chamber 9...Ionized substance inlet 11...Second electron beam 13.14...Exhaust port 16...Acceleration power source 18...Insulating tube 20...Target 10... First electron beam 12... Ion beam 15... Extraction power source 17... Bias power source 19... Vacuum vessel 21... Third electron beam

Claims (1)

[Claims] (1) A plasma is generated by receiving an electron beam emitted from an electron gun having a cathode with a pore in the center, and an ion beam extracted from the plasma is traced back along the path of the electron beam. In addition, an electron beam-excited ion source emitted from the pore of the cathode is provided with a first plasma generation chamber and a second plasma generation chamber having different potentials sequentially from the direction of incidence of the electron beam. An ion source characterized in that an anode having a different potential from that of the second plasma generation chamber is disposed between a plasma generation chamber and a second plasma generation chamber.