JPH05205691A - Ion implantation device - Google Patents

Abstract

PURPOSE:To provide an ion beam neutralization mechanism for ion implantation device, with which stable and efficient ion beam neutralizing performance is obtained. CONSTITUTION:An ion beam neutralizing mechanism is equipped with a filament 2 located on a cylindrical surface coaxial with the center axis of an ion beam, an electrode 1 provided on another coaxial cylindrical surface situated outermore than the filament, a filament power supply 4 for heating the filament, and an electrode power supply 5 which gives the electrode a potential lower than the filament. Because the energy of electron to be neutralized is low, the neutralization can be done efficiently. Also stable performance can be maintained because it is not likely being affected by the surface condition of constituent parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implanter, and more particularly to a neutralizing mechanism for neutralizing a positively charged ion beam in the ion implanter.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional structure of an ion beam neutralizing mechanism of an ion implanter. In the figure, the filament 22 is placed in a direction perpendicular to the central axis of the ion beam.
Is placed, and the filament is heated by the filament power source 24 to generate thermoelectrons. Since the electrode 21 has a potential of about 20V lower than that of the filament 22 by the electrode power source 25, thermoelectrons are forced to move toward the ion beam side,
Also, the acceleration power source 27 causes the filament 22 to move about 30
It moves toward the secondary electron emission plate 28 at a high potential of 0 V and collides with it to emit secondary electrons.

Then, a positively charged ion beam passes through the group of the secondary electrons and accelerated thermoelectrons, so that they are combined with these electrons and, as a result, the ion beam is neutralized. The ammeter 26 quantitatively indicates the amount of electrons used to neutralize the ion beam.

Of the ion beam neutralizing mechanism of the above-mentioned ion implanter, the power sources 24, 25 and 27 and the ammeter 27 are usually installed in the atmosphere, but the others are installed in vacuum.

[0005]

In the ion beam neutralizing mechanism of the above-described conventional ion implanter, the energy of the electrons to be neutralized is as high as about 20 eV for secondary electrons and about 300 eV for the other electrons, which is high in speed. Since it is moving, the contact time with the ion beam is short and the ion beam and the electron cannot be efficiently coupled. Therefore, the ion beam could not be sufficiently neutralized.

Further, since the emission of secondary electrons largely depends on the surface state of the secondary electron emission plate, the emission ratio changes due to surface contamination, which makes stable emission of secondary electrons difficult, and therefore the ion beam The neutralization performance of was not stable.

[0007]

A feature of the present invention is that in an ion implantation apparatus having an ion beam neutralization mechanism for neutralizing a positively charged ion beam, the ion beam neutralization mechanism is a central axis of the ion beam. And a filament arranged on the coaxial cylindrical surface, an electrode arranged on the coaxial cylindrical surface further outside the filament, a filament power source for heating the filament, and a potential of the electrode lower than the potential of the filament. And an ion implantation device having an electrode power supply for switching.

[0008]

The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention. Figure 1 shows the parts installed in a vacuum,
Power supplies installed in the atmosphere are omitted. As shown in FIG. 1, the ion beam neutralization mechanism of this ion implanter has a coiled filament 2 placed on the coaxial cylindrical surface of the ion beam and a cylindrical filament 2 placed on the outer coaxial cylindrical surface thereof. 1 and an insulator 3 that electrically insulates the filament 2 from the electrode 1. The filament 2 has an inner diameter that is about 1.5 times larger than the size of the ion beam, while the openings on both end surfaces of the electrode 1 have an inner diameter that is about 1.2 times larger than the size of the ion beam. It is possible to prevent the ion beam from colliding with.

FIG. 2 is a vertical sectional view showing the entire structure of FIG. 1, and the operation will be described with reference to this drawing. First, the filament 2 is usually made of tungsten and heated by the electric current from the filament power supply 4. Further, the electrode 1 is set to a potential of several V to several tens of V lower than the potential of the filament 2 by the electrode power source 5. In the absence of an ion beam, the thermoelectrons of several eV generated from the filament 2 have a repulsive force near the electrode 1 and accumulate around the filament 2 because the potential of the electrode 1 is lower than that. Here, when the ion beam charged to several tens KeV of positive energy passes through, the thermoelectrons generate an attractive force between the ion beam and the ion beam, and are mixed and combined in the ion beam, resulting in neutralization of the ion beam. It will be.

FIG. 3 is a vertical sectional view showing the overall construction of the second embodiment of the present invention. Note that, in FIG. 3, the same or similar portions as those in FIGS. 1 and 2 are denoted by the same reference numerals.

In this embodiment, the filament and its power source are improved, and a plurality of small coil-shaped filaments 12a and 12b are arranged on the coaxial cylindrical surface of the ion beam. In this case, the filament power sources 14 are arranged in the same number as the filaments, considering that the electric characteristics of the filaments are not uniform. In the case of this embodiment, the filament can be downsized as compared with the previously stretched embodiment, so that the total length of the filament can be shortened. Therefore, the voltage of the filament power supply can be lowered, and the difference in the filament potential generated in the axial direction of the ion beam becomes small. As a result, the ion beam is neutralized more efficiently.

Further, although the coil-shaped filament is used in the above-mentioned two embodiments, the operation is the same with the rod-shaped filament. However, when the coiled fragment is used, the thermoelectrons move to the ion beam while making a circular motion due to the magnetic field due to the filament current, so that the contact time with the ion beam becomes longer and the efficiency is improved.

[0014]

As described above, according to the present invention, the secondary electrons and the accelerated thermoelectrons are not used for neutralizing the ion beam, but the thermoelectrons having low energy are used.
It is possible to efficiently neutralize the ion beam. Further, since the filament that generates thermoelectrons has a structure that does not easily get dirty and uses the electron emission principle that does not easily depend on the surface state of the component parts, it has the effect of high operational stability.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ion beam neutralization mechanism of an ion implantation apparatus according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing the entire ion implantation apparatus according to the first embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view showing the entire ion implantation apparatus according to the second embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional ion implantation device.

[Explanation of symbols]

 1, 21 Electrodes 2, 12a, 12b, 22 Filament 3 Insulator 4, 14, 24 Filament power supply 5, 25 Electrode power supply 6, 26 Ammeter 27 Acceleration power supply 28 Secondary electron emission plate

Claims (1)

[Claims] 1. An ion implanter having an ion beam neutralization mechanism for neutralizing a positively charged ion beam,
The ion beam neutralization mechanism is a filament arranged on a coaxial cylindrical surface with the central axis of the ion beam, an electrode arranged on a coaxial cylindrical surface further outside the filament, and a filament power source for heating the filament. And an electrode power source for setting the electric potential of the electrode to a lower electric potential than the electric potential of the filament.