JPS63941A - High frequency ion source - Google Patents

Abstract

PURPOSE:To reduce magnetic effect at an extension electrode and lower a divergence angle of a beam by arranging a high frequency coil, which generates plasma with electrostatic dissociation of the gas inside a vacuum vesel, with its central axis in pararell with the extension electrode. CONSTITUTION:By connecting a vacuum vessel 1 on the same side as an ion source to a vacuum vessel 2 on the same sade as a processing chamber, required gas is introduced therein from an air inlet 5 after both vessels are exhausted into a high vacuum through an air outlet 4. Then, high frequency power is fed by a high frequency power source 8 to a high frequency coil 7 arranged with its central axis orthogonalized with normal direction of an extension electrode 13. A high frequency ion source is formed by dissociating the gas in the vessel 1 to generate plasma, and drawing an ion beam 14 from the plasma to implant it on a workpiece 15. Accordingly, high frequency magnetic field at the extension electrode 13 can be lowered to check diffraction of the ion beam 14, reducing a divergence angle of the beam and enabling it to be formed in a pararell beam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion source that generates plasma using a high-frequency current, and particularly to a method that can improve the beam divergence angle without impairing the beam extraction characteristics. C. Conventional technology]. As an ion source that generates plasma using conventional direct current,
For example, Vacuum 34 Volume 3-4 (1984) 4
Pages 55-462 (Vacuum 3 4, 3-4,
(1984) pp455-462) Figure
There is something mentioned in 1. In this method, first,
A filament is lit, and then plasma is generated by a discharge using the filament as a cathode and the vacuum container as an anode. In DC type ion sources with such filaments, when using halogen-based compound gases, which have recently become widely used, the life of the filament may be extremely short due to its chemically active nature. Kaisho 52-
Electrodeless systems such as those disclosed in Publication No. 143981 have been reviewed. In this method, a high-frequency coil is arranged around an insulating container, and a high-frequency current supplied by a high-frequency power source is passed through the high-frequency coil to obtain an electrodeless discharge. Furthermore, as a method to enhance the plasma generation effect, Journal of Vacuum Science Technology A3 No. 3 (1985) pp. 1218-1221 (J. Vac. Sci. T
achnolA3 (3) (1985) pp121
11-1221), a vacuum container impregnated with a high-frequency coil has been developed. [Problems to be solved by the invention] In addition to the long life and high efficiency mentioned above, the needs for ion sources also include the problem of low divergence angle required in microprocessing in the semiconductor field. 6 This suppresses the divergence angle of the beam,
The aim is to make it as close to a parallel beam as possible.

However, in the above-mentioned configuration in which the extraction electrode is placed on the central axis of the high-frequency coil, the high-frequency magnetic field of the extraction electrode increases, and the ion beam extracted by the extraction electrode is diffracted by the magnetic field, causing the beam to spread. The problem was that it was unavoidable.

An object of the present invention is to provide a long-life ion source that can achieve low beam divergence without impairing beam generation efficiency.

[Means for solving problems]

The above objective is achieved by arranging the central axis of the high-frequency coil impregnated in the vacuum container parallel to the extraction electrode. [Operation] The areas where the magnetic field is strongest around the high-frequency coil are inside the coil, around the coil conductor, and near the coil on the central axis. The first point of the present invention is to locate the extraction electrode as far away from this area as possible. The second point is to draw out the direction of the magnetic flux applied to the extraction electrode part as much as possible so that it is parallel to the electrode surface. Due to the nature of high-frequency magnetic fields, parallel components of a conductor cannot penetrate the conductor due to the skin effect. The high frequency magnetic field of the extraction electrode part can be realized by arranging the central axis of the high frequency coil parallel to the extraction electrode surface.

〔Example〕

The present invention will be explained below using detailed examples. The embodiment shown in FIG. 1 includes a vacuum vessel 1 on the ion source side and a vacuum vessel 2 on the processing chamber side.
are connected through an insulator 3 in a structure that can maintain a vacuum. The principle of operation is that the inside of the vacuum container 1.2 is first evacuated to a high vacuum of, for example, IXIO-'Torr or less, through the gas exhaust port 4 by a vacuum evacuation means (not shown).
A desired gas is continuously introduced into the vacuum chamber 1 through a desired gas supply port 5 by a gas supply means (not shown), and balanced with the exhaust speed of the manual exhaust system at, for example, IX10''-8 Torr. In this state, high-frequency power is supplied from a high-frequency current 8 installed externally to a high-frequency coil 7 sealed and held by a high-frequency current introduction terminal 6.The high-frequency power supply 8 is a 13.56 M& Although the frequency of
Alternatively, an electromagnetic shield or the like is required as a measure against electromagnetic wave leakage into the external space. In this way, plasma is normally ignited in the vacuum vessel 1 by supplying high-frequency power to the high-frequency coil 7, but if the atmospheric gas pressure is low and it is difficult to ignite the plasma, an auxiliary point (not shown) may be used. The plasma can be ignited by lighting an arc filament or by instantaneously increasing the gas pressure with a gas supply means. Next, a positive potential is applied to the vacuum vessel 1 and the extraction electrode 11 connected thereto, and a negative potential is applied to the extraction electrode 12 using the external DC power supplies 9 and 10 to create an electric field in the extraction electrode section 13. The positive ions are accelerated and become an ion beam 14. The light is incident on a workpiece 15 held by a holder (not shown). Depending on the machining accuracy and shape of the workpiece 15, this holder is provided with functions such as rotational movement, tilting mechanism, orbital movement when there are multiple workpieces, or a combination of these functions, but the specific configuration will be omitted. With the above configuration, the magnetic field generated by the high-frequency coil 7 is as shown in 16, and by arranging the central axis of the high-frequency coil 7 in a direction orthogonal to the normal direction of the lead-out electrode part 13, the lead-out electrode part 13
At the position, the strength is weak and the direction is parallel to the extraction electrode surface 13, confirming that the desired characteristics are obtained. In this embodiment, the central axis of the high-frequency coil 7 is linear, and the configuration is suitable for an ion source with a relatively small diameter.

The embodiment shown in Figure 2 is a high-frequency coil viewed from the axial direction, and unlike the circular structure of the embodiment, it has a rectangular cross-sectional structure. Depending on the configuration of the workpiece, an ion beam with a rectangular or square cross section may be desired, and in that case, it is efficient to have a rectangular or cubic configuration for the ion source side vacuum vessel. This embodiment is suitable for such a case.

Figures 3 and 4 show a high-frequency coil 7 with a double solenoid structure.
This is what is shown. Figure 3 is a view from the extraction electrode side, and Figure 4 is a view from the perpendicular direction. In this case as well, since the central axis 15 of the high-frequency coil 7 is perpendicular to the line direction of the extraction electrode, the same effect as described above can be obtained. This embodiment is suitable for the configuration of a medium-sized ion source.

Figure 5 shows a large-scale ion source suitable for processing many workpieces simultaneously. The ion source structure at this time is a donut-shaped structure having a center i111117, and both the vacuum chamber 1 and the extraction electrode part 13 are donut-shaped. The high-frequency coil 7 enters through the insulated lead-in terminal 6, and exits through another lead-in terminal after making approximately one turn, as shown in the plan view of FIG. At this time, a double solenoid structure as shown in FIG. 3 is also possible, but this embodiment is more advantageous when considering impedance matching with the high frequency power source. In this embodiment, a coil of approximately one turn is considered, but up to several turns are permitted. In addition, in this configuration example, physically the central axis of the coil is 17 in the figure. However, considering the magnetic field generated by the coil 7 in this example, the shape shown in 16 is obtained due to the skin effect of the vacuum container. Therefore, the central axis here should be considered as 18, and by aligning the axis 18 of the high frequency coil with the central axis 18 of the vacuum container, the same effect as described above can be obtained.

In the above configuration, a permanent magnet 19 is attached to the outer periphery of the vacuum container 1.
The beam extraction efficiency is improved by arranging a so-called cusp magnetic field.

〔Effect of the invention〕

According to the present invention, it is possible to reduce the influence of the magnetic field on the extraction electrode portion and reduce the beam divergence angle.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of one embodiment of the present invention, Fig. 2 is a plan view of the main part of another embodiment of the invention, Fig. 3 is a front view of the main part of Fig. 2, and Fig. 4 is a front view of the main part of Fig. 2. 3 is a front view, FIG. 5 is a longitudinal sectional view of FIG. 2, and FIG. 6 is a front view of the main part of FIG. 2.

Claims (1)

[Scope of Claims] 1. A vacuum container, a vacuum evacuation means for evacuating the gas in the vacuum container, a gas supply means for supplying a desired gas to the vacuum container, a high frequency power source, and a high frequency power source from the high frequency power source. a high-frequency coil for supplying output power to the gas in the vacuum container to ionize the gas and create plasma; and an extraction electrode mechanism for extracting ions in the plasma as a beam, the generation of the high-frequency coil A high-frequency ion source, characterized in that the high-frequency ion source is arranged so that the direction of the magnetic field does not coincide with the normal direction of the extraction electrode. 2. The high-frequency ion source according to claim 1, wherein the direction of the central axis of the high-frequency coil is orthogonal to the normal direction of the extraction electrode. 3. The high-frequency ion source according to claim 1, wherein the high-frequency coil is arranged so that the direction of the high-frequency coil substantially coincides with the central axis of the vacuum container. 4. The high-frequency ion source according to claim 1, 2, or 3, wherein the vacuum vessel is provided with a permanent magnet for generating a magnetic field for confining plasma around the vacuum vessel.