JPH06289193A - Fast atomic beam source - Google Patents

Abstract

PURPOSE:To obtain a fast atomic beam source having a low energy with the low electric discharge voltage, by supplying the thermoelectrons from the thermal filament in the anode upstream part and supplying a large quantity of thermoelectrons to an electric discharge part on the downstream of the anode. CONSTITUTION:The reaction gas 5 such as argon is introduced into an outer cylinder 23, and a dc high voltage is applied between a plate shaped anode 22 and a cathode 21. Simultaneously with the introduction of the gas 5, a filament 6 is heated to emit thermoelectron. The thermoelectron gas 5 is introduced into an electric discharge part, passing through a gas flow-out hole 9, and electric discharge is performed by the dc high voltage between the electrodes 21 and 22, and plasma 6 is generated. Since, in the electric discharge part, the gas 5 contains a large quantity of electrons, electric discharge can be maintained with the low electric discharge voltage. In the plasma 6, the cations and electrons of the gas 5 are generated, and the cations are accelerated towards the cathode 21, and the large energy is obtained. The cation contacts the atom of the gas 5 staying in the vicinity of the cathode 21 and looses its positive electric charge, and changes to the neutral fast atom, and irradiates the fast atomic beam 8. In such a way, the fast atomic beam having low energy can be obtained by the low electric discharge voltage.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fast atomic beam source,
In particular, it relates to a fast atom beam source capable of efficiently emitting a low energy atom beam at a low discharge voltage.

[0002]

2. Description of the Related Art Atoms and molecules that are in thermal motion in the atmosphere at room temperature have a kinetic energy of about 0.05 eV. Atoms / molecules that fly with much larger kinetic energy than this are called “fast atoms”, and when they flow in a beam in one direction, they are called “fast atom beams”. The high-speed atomic beam can be used for processing such as shaving the solid surface or modifying it, and is particularly electrically neutral, so that it is not limited to the application to the metal and semiconductor fields,
Plastic, which was not good at the conventional ion beam method,
It is also effective in machining insulators such as ceramics. In addition, a low-energy high-speed atomic beam does not damage the work piece, and is therefore suitable for fine processing of semiconductors.

FIG. 2 shows a conventional high-speed atom beam source for generating a high-speed atom beam of gas atoms, which emits a beam of argon atoms having a kinetic energy of 0.5 to 10 keV. An example is shown. In the figure, 1 is a cylindrical cathode also serving as an envelope, 2 is a donut-shaped anode, 3 is a high voltage DC power supply of 0.5 to 1 kV, 4 is a gas nozzle, 5 is argon gas, 6 is plasma, and 7 is A fast atom beam emission hole, and 8 denotes a fast atom beam.

This fast atom beam source operates as follows. That is, each component except the DC high-voltage power supply 3 is contained in a vacuum container, and after the vacuum container is sufficiently evacuated, argon gas 5 is injected into the cylindrical cathode 1 from the gas nozzle 4. Then, a high DC voltage is applied between both electrodes by a high DC power supply 3 so that the anode 2 has a positive potential and the cathode 1 has a negative potential.

As a result, an electric discharge is generated between the cathode 1 and the anode 2, plasma 6 of argon gas is generated, and argon ions and electrons are generated. At that time, the electrons emitted from the bottom surface on one end side of the cylindrical cathode 1 are accelerated toward the anode 2, pass through the central hole of the anode 2, and reach the bottom surface on the other end side of the cylindrical cathode 1. The electrons that have reached the bottom surface on the other end side lose their speed and are reversed here, are accelerated again toward the anode 2, pass through the holes of the anode 2 again, and reach the bottom surface on the one end side of the cathode 1. Such repetitive motion of electrons causes high frequency vibration between both end faces of the cylindrical cathode 1 via the anode 2, and during the motion, it collides with argon gas to generate a large number of argon ions.

The argon ions in the plasma 6 thus generated are accelerated toward the end surface of the cylindrical cathode 1 to obtain sufficient kinetic energy. Also, the cylindrical cathode 1
The space in the vicinity of both end faces is a turning point of electrons that oscillate at high frequency, and is a region where many low-energy electrons are present. Argon ions incident on this region collide with electrons and recombine to return to argon atoms. In ion-electron collisions, the mass of the electron is negligibly small compared to the argon ion, so that the kinetic energy of the argon ion is inherited by the atom as it is with almost no loss and becomes a fast atom. Therefore, in this case, the kinetic energy of the fast atom is determined by the discharge sustaining voltage by the DC high voltage power source 3 being, for example, 1 kV
In case of, the value is about 1 keV. The fast atoms are emitted as a fast atom beam 8 to the outside through an emission hole 7 formed in the end face of the cylindrical cathode 1.

[0007]

However, in this conventional high-speed atomic beam source, in order to increase the emission amount of the high-speed atomic beam, it is necessary to increase the discharge voltage by using a magnet as considered from the above structure. There are only methods such as combined use and increasing the pressure of the reaction gas. As a result, there are many problems in use, such as an increase in the energy of the fast atom beam, an increase in the size of the apparatus, and a widening of the energy width of the fast atom beam, which is difficult to use.

The present invention has been made in view of the problems of the prior art.
It is an object of the present invention to provide a fast atom beam source capable of efficiently emitting a fast atom beam having a high particle beam flux and a low energy at a low discharge voltage.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to a cathode having a fast atom emission hole, an anode arranged to face the cathode at a predetermined interval, and an outer cylinder containing the cathode and the anode. A gas nozzle for introducing a reaction gas into, and a DC high voltage power source for applying a positive potential to the anode and a negative potential to the cathode,
A hot filament is provided upstream of the anode in the outer container.

[0010]

According to the present invention, a large amount of electrons are supplied to the discharge portion downstream of the anode by supplying thermoelectrons by the hot filament upstream of the anode. Therefore, discharge can be maintained at a low voltage in the discharge portion between the anode and the cathode, and a low-energy high-speed atomic beam can be emitted.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 illustrates a schematic configuration of a fast atom beam source showing an embodiment of the present invention. In this embodiment, the same symbols are used for the components having the same functions and operations as those of the conventional example described with reference to FIG.

As shown in FIG. 1, a plate-shaped cathode 21 and a plate-shaped anode 22 which are opposed to each other with a predetermined distance are arranged in an insulator (ceramic) outer cylinder 23 and sufficiently housed in a vacuum container (not shown). Exhausted to. The cathode 21 and the anode 22 are connected to a DC high voltage power supply 3 arranged outside the vacuum container, a negative DC potential is applied to the cathode 21 and a positive DC high voltage is applied to the anode 22, and a discharge unit is provided between both electrodes. Is configured.
Further, the plate cathode 21 has a large number of high-speed atomic beam emission holes 7 formed on its surface so that the high-speed atomic beam 8 can be emitted.
The gas nozzle 4 is for introducing the reaction gas 5 into the outer cylinder 23 from the outside of the vacuum container, and the portion of the gas flow in the outer cylinder 23 between the gas nozzle 4 and the plate-shaped anode 22 serves as the anode upstream portion. . The plate-like anode 22 is provided with a through hole 9 for the reaction gas 5. The reaction gas 5 passes from the gas nozzle 4 through the upstream portion of the anode and through the through-hole 9 in the plate-like anode 22 to both electrodes 21, It flows into the discharge part between 22.

A hot filament 26 is provided upstream of the plate-shaped anode 22 in the outer cylinder 23. Hot filament 2
6 is made of platinum or L _a B ₆ and is connected via a variable resistor 25 to a power source 24 arranged outside the vacuum container.

Next, the operation of the high-speed atomic beam source constructed as described above will be explained. First, the inside of the vacuum container in which the high-speed atomic beam source and the object to be processed are housed is sufficiently exhausted, and then a reaction gas 5 such as argon is introduced into the outer cylinder 23 through the gas nozzle 4. Then, a DC high voltage is applied from the DC high voltage power supply 3 between the plate anode 22 and the plate cathode 21, and at the same time when the reaction gas 5 is introduced, the filament 26 is heated to emit thermoelectrons.

At the upstream portion of the plate-like anode 22, the released thermoelectrons and the reaction gas 5 are distributed through the flow holes 9 of the plate-like anode 22.
Through the plasma into the discharge part on the downstream side, and the discharge is generated by the high DC voltage applied between the electrodes 21 and 22.
Is generated. In the discharge part, the reaction gas 5 contains a large amount of electrons emitted by the hot filament in advance,
Discharge can be maintained at a low discharge voltage.

In the plasma 6 of the discharge part, cations and electrons of the reaction gas 5 are generated, but the cations are accelerated toward the cathode 21 to which a negative potential is applied, and obtain large energy. The accelerated cations contact the atoms of the reaction gas 5 remaining in the vicinity of the plate-like cathode 21 to lose positive charges and become neutral fast atoms, or lose positive charges by recombination with electrons. And becomes a fast atom, and is emitted as a fast atom beam 8 from the fast atom emission hole 7.

Since the hot filament 26 is heated to a high temperature, if the introduced gas 5 is highly reactive, it may easily react with the gas 5 and may be deteriorated or cut. The use of platinum or L _a B ₆ hardly reacts with the gas 5 in the hot filament 26, it is possible to prevent deterioration of the filaments, the cutting.

A magnetic field is preferably further provided in a portion of the outer cylinder 23 upstream of the plate-like anode 22 where the hot filament 26 is arranged to generate thermoelectrons. That is, for example, the outer cylinder 23
By providing a cylindrical electromagnet or permanent magnet so as to surround the, a magnetic field is formed in the anode upstream portion of the outer cylinder 23. When such a magnetic field is formed, the electron cyclotron resonance effect can be utilized and more effectively ionized electrons can be supplied to the discharge portion between the cathode 21 and the anode 22. Therefore, by providing a magnetic field in the upstream part of the anode, it is possible to obtain a lower discharge voltage, that is, a low-energy fast atom beam.

[0019]

As described above, in the fast atom beam source of the present invention, a large amount of thermoelectrons are generated by the hot filament in the upstream part of the anode and supplied to the discharge part. Therefore, the DC high-voltage power supply can be kept low in order to generate the plasma of the reaction gas in the discharge part, and the low-energy high-speed atomic beam can be obtained. This effect is further promoted by providing a magnetic field in the upstream part of the anode.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a fast atom beam source according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional high-speed atomic beam source.

[Explanation of symbols]

 1 Cylindrical Cathode 2 Donut-shaped Anode 3 DC High Voltage Power Supply 4 Gas Nozzle 5 Reactive Gas 6 Plasma 7 Atom Emission Hole 8 High Speed Atomic Beam 9 Gas Flow Hole 21 Plate Cathode 22 Plate Anode 23 Insulator (Ceramic) Outer Cylinder 24 Power Supply 25 variable resistor 26 hot filament

Claims (5)

[Claims] 1. A cathode having a fast atom emission hole, an anode arranged to face the cathode at a predetermined distance, and a gas nozzle for introducing a reaction gas into the cathode and an outer cylinder containing the anode. A high-speed atomic beam source, comprising: a high-voltage direct-current power supply for applying a negative potential to the cathode and a positive potential to the anode, and a hot filament provided upstream of the anode in the outer container. 2. The fast atom beam source according to claim 1, further comprising a magnetic field provided upstream of the anode. 3. The fast atom beam source according to claim 1, wherein platinum is used for the hot filament. 4. The fast atom beam source according to claim 1, wherein the hot filament uses L _a B ₆ . 5. The cathode having the atom emission holes is a plate-shaped cathode, the anode is a plate-shaped anode having a gas flow hole, and the cathode and the anode are installed to face each other in an outer cylinder. The fast atom beam source according to claim 1, 2, 3, or 4.