JPH0695480B2 - Ion neutralizer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ion neutralizer for efficiently neutralizing the charge of ions in order to generate a fast atom beam.

[Prior Art] FIG. 2 is a schematic configuration diagram of a neutralizer disclosed so far. In the figure, 1 is a cylindrical envelope with a thick central portion,
Reference numeral 2 is a circular filament for emitting thermoelectrons, 3 is an ion beam, 4 is a fast atom beam, 5 is a power source for heating the filament 2, and 6 is a DC bias power source. The operation of this ion neutralizer is as follows.

The filament 2 is stretched around the central axis of the envelope 1, and is housed in the thick and central portion of the envelope 1. Put the components other than the power supplies 5 and 6 in a vacuum container. The circular filament 2 is heated by the power source 5 to emit a large amount of thermoelectrons. The envelope 1 is biased by the DC power supply 6 to a potential lower than the filament 2 by several volts.
Therefore, the thermoelectrons emitted from the filament 2 are repelled by the wall of the envelope 1 and are concentrated near the central axis of the envelope 1 to form a high-density electron cloud there. When the ion beam 3 is incident on this electron cloud, collision / recombination of ions / electrons occurs, and the ion beam 3 is converted into a fast atom beam 4. In ion-electron collision at the time of electron recombination, the mass of the electron is much smaller than that of the ion, so that the kinetic energy of the ion is hardly lost and is inherited by the atom as it is to form the fast atom beam 4. .

[Problems to be Solved by the Invention] In the conventional ion neutralizer described above, the electron cloud density is adjusted by the heating power source 2 and the bias power source 6 of the filament 2, but a sufficient electron cloud density is obtained. However, it was difficult to efficiently generate high-speed atoms.

An object of the present invention is to provide an ion neutralizer that forms a high-density electron cloud and efficiently generates a fast atom beam.

[Means for Solving the Problems] The present invention provides a cylindrical anode, a needle-shaped cathode installed along the central axis of the anode, and a magnetic field line applied along the central axis of the anode. It is characterized by comprising a magnet installed outside the anode and a discharge DC voltage power supply for applying a voltage between the anode and the cathode.

The greatest feature of the present invention is to form a high-density electron cloud by applying a magnetic field to the glow discharge. The density of the electron cloud is increased by thermionic filament and bias voltage. The electrode configuration is fundamentally different from the conventional method.

[Embodiment] FIG. 1 is a view showing an embodiment of the present invention. In the figure, 3 and 4 indicate the same components as the same numbers in FIG. Further, 21 is a cylindrical anode, 22 is a needle cathode, 23 is a magnet, and 24 is a DC high voltage power supply for discharge.

The needle-shaped cathode 22 is installed so as to match the central axis of the cylindrical anode 21. The magnet 23 is, for example, a ring-shaped magnet, and is installed so as to surround the cylindrical anode 21 so that the magnetic force lines are substantially parallel to the central axis of the cylindrical anode 21. Components other than 24 are housed in a vacuum container.

The operation of the ion neutralizer having the above configuration is as follows.

In a vacuum vessel, for example, argon gas is injected at about 10 ⁻⁴ Torr, and a high voltage DC power supply 24 applies a high DC voltage between the anode 21 and the cathode 22 to cause glow discharge between the anode 21 and the cathode 22. It is generated and plasma is formed. In this discharge, the cathode
The electrons emitted from 22 are once accelerated toward the anode 21, but the electrons fly in a circular motion because the magnetic lines of force are applied perpendicularly to this motion direction. Since the radius of gyration of the circular motion is smaller as the velocity of the electron is smaller, the radius of gyration is very small in the vicinity of the cathode 22 and the space density of the electron is extremely high. When the ion beam 3 is incident on a space having a high electron density, collisions / recombination occurs between ions and electrons, and a high-speed atomic beam is generated. When the argon gas pressure inside the anode 21 is high, collisions of ions and gas molecules occur in addition to collisions of ions and electrons, and high-speed atoms with low kinetic energy are generated. With a gas pressure of
Since the mean free path of gas molecules is several tens of centimeters or more, the collision probability of ions and gas molecules is so small that it can be ignored. Needless to say, if oxygen is used as the gas to be injected, a fast atom beam of oxygen can be obtained.

In the present invention, three factors, that is, injection gas pressure, discharge voltage, and magnetic field strength, are provided as factors for controlling the electron cloud density that controls the generation efficiency of fast atoms. Then, the electron cloud density can be increased to efficiently generate a fast atom beam.

EFFECTS OF THE INVENTION According to the present invention, the degree of freedom in controlling the electron cloud density is high, and the electron cloud density can be increased by increasing the magnetic field strength to efficiently generate a high-speed atomic beam.

The fast atom beam can be used for thin film formation by sputter deposition, fine pattern processing by sputter etching, and material evaluation by secondary ion mass spectrometry, similarly to the fast ion beam. In particular, since the fast atom beam is non-chargeable, it is effective not only for metals and semiconductors but also for insulators such as plastics and ceramics, which are not good at the ion beam method. In that sense, obtaining an ion neutralizer that produces a large amount of fast atoms is very useful for improving the efficiency of processing and analysis.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an ion neutralizer shown as an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a conventional ion neutralizer. 3 ... Ion beam, 4 ... Fast atom beam, 21 ... Cylindrical anode, 22 ... Needle cathode, 23 ... Magnet, 24 ... DC high-voltage power supply for discharge.

Claims (1)

[Claims] 1. An ion neutralizer for neutralizing the charge of ions to generate a high-speed atom beam by injecting an ion beam into an electron cloud. A cylindrical anode and a central axis of the anode are provided. A needle-like cathode installed alongside the magnet, a magnet installed outside the anode so that magnetic field lines are applied along the central axis of the anode, and a DC high voltage for discharge for applying a voltage between the anode and the cathode. An ion neutralizer characterized by being composed of a power supply.