JPS6396840A - Ion source - Google Patents

Abstract

PURPOSE:To obtain an ion source with less impurities by performing d-c separation of a high frequency coil from an earth potential and performing d-c connection of the coil with an acceleration electrode. CONSTITUTION:A high-frequency coil 2 is connected with a high-frequency source 9 through coupling capacitors 11 and 12, where d-c separation from the high-frequency source 9 is performed. A middle point 13 of the high-frequency coil 2 is connected with an acceleration electrode 5. Therefore, and a mean potential of the high-frequency coil 2 is equal to the potential of the acceleration electrode 5 and also equal to that of plasma. Hence, no electric field occurs between the plasma and the high-frequency coil 2, so that ions in the plasma are not accelerated in the direction of the high-frequency coil and an insulating material of an vacuum container 1 is not sputtered. Therefore, sputtered materials do not invade the plasma, and so ion beams with less impurities are generated. Hence, a clean etching device without contamination at a time of processing can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion source, and particularly to an ion source suitable for dry etching.

[Conventional technology]

In recent years, dry etching using an ion beam has come to be used in thin-film magnetic head processes and the like. Conventionally, ion sources for dry etching have generated ions using filament type hot cathode arc discharge, but in dry etching, CFa, SFs or CO
Fluorine threads such as No. 2 and chlorine-based gases that become extremely active when decomposed are used. As a result, there was a maintenance problem in that the filament wore out within a few hours. Therefore, it is conceivable to use high frequency electrodeless discharge to generate ions. A method for efficiently generating ions using high-frequency electrodeless discharge is described in Journal of Vacuum Science Technology A3 (8) 1
Pages 1218 to 1221 of the 576th issue of 985 (J
, Vac, Sci, Technol, A 3 (3
) May/Juna1985. P121g~
There is a method discussed in P.1221). In this method, since the high-frequency coil is placed inside the vacuum container, there is a risk that the coil may be damaged.In order to avoid this, a method of placing the high-frequency coil outside as shown in FIG. 6 may be considered.

That is, the ion source includes a high-frequency coil 2 provided on the outer periphery of a vacuum container 1 made of an insulating material such as glass or ceramics, and an end plate having a gas introduction tube 4 attached to one end of the vacuum container 1. 10 is provided, and at the other end, an accelerating electrode 5 and a decelerating electrode 6 are provided, each having a large number of holes in a disk.
A potential of V is applied to the deceleration electrode 6 by a power source 8.
A potential of about 00V is applied. The high-frequency coil is connected to a high-frequency power source 9 with one end at ground potential, and the vacuum vessel 1
A plasma is generated from the gas introduced into the inside of the chamber from the gas introduction pipe at a pressure of 10'''' 8 Torr. Only ions are extracted through the acceleration electrode 5 and the deceleration electrode 6, and are irradiated onto the workpiece to perform etching.

7-[Problems to be solved by the invention] □By the way, this method does not take into consideration the fact that the insulator of the vacuum container is sputtered by ions, and there is a problem that impurities adhere to the workpiece. Ta. That is, since the plasma in the vacuum container 1 is in contact with the accelerating electrode 5, its potential is the same as that of the accelerating electrode 5. On the other hand, the potential of the high-frequency coil is, on average, the ground potential. Therefore, a voltage approximately equal to the accelerating electrode voltage is applied between the plasma and the high-frequency coil, accelerating ions in the plasma toward the wall of the vacuum chamber. As a result, the vacuum vessel insulator is sputtered by these ions, sputtered atoms of the insulator are mixed into the plasma, and the impurities are also introduced into the ion beam, causing the problem of contaminating the workpiece.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ion source with fewer impurities that eliminates the drawbacks of the prior art.

[Means for solving problems]

The above object is achieved by electrically disconnecting the high frequency coil from the ground potential and electrically connecting it to the accelerating electrode.

[Effect]

That is, the average potential of the high-frequency coil is approximately the voltage of the accelerating electrode, and no large voltage is applied between the plasma and the high-frequency coil. Therefore, the ions in the plasma are accelerated in the direction of the high-frequency coil and do not sputter the insulator in the vacuum container, making it possible to generate an ion beam with few impurities and providing a clean etching device that does not cause contamination during processing. .

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The high frequency coil 2 is connected to the high frequency power source 9 via coupling capacitors 11 and 12, and is separated from the high frequency power source in terms of direct current. and midpoint 1 of high frequency coil 2
3 is connected to the acceleration type [5. Therefore, the average potential of the high-frequency coil 2 becomes the potential of the accelerating electrode 5, and the same potential as that of the plasma. As a result, no electric field is generated between the plasma and the high-frequency coil, and ions in the plasma are no longer accelerated in the direction of the high-frequency coil.

Sputtering of the insulator in the vacuum container is eliminated. Therefore, a sputtered material does not enter the plasma, an ion beam with few impurities can be generated, and a clean etching apparatus that does not cause contamination during processing can be provided.

FIG. 2 shows a second embodiment of the invention. In this case, one end 14 of the high frequency coil 2 and the accelerating electrode 5 are connected in a direct current manner, and the same effect as the embodiment shown in FIG. 1 can be achieved.

FIG. 3 shows a third embodiment of the present invention, in which the vacuum vessel 1 consists of an insulating cylinder 15 and a metal cylinder 16, and a large number of permanent magnets are arranged around the outer circumference of the metal cylinder 16 with alternating polarities. This is an example in which the present invention is applied to an ion source, and in this case as well, the same effects as in FIG. 1 can be achieved.

FIG. 4 shows a fourth embodiment of the present invention.

In this embodiment, the intermediate point 13 of the high frequency coil and the accelerating electrode are connected via a choke coil 18, and in this case as well, the same effects as in the embodiment shown in FIG. 1 can be achieved.

FIG. 5 shows a fifth embodiment. In this case, the high-frequency coil and the high-frequency power source are separated in a DC manner via the high-frequency transformer 19, and the intermediate point 13 of the high-frequency coil 2 is connected to the accelerating electrode 5. In this case, too, the embodiment of FIG. The same effect can be achieved.

Further, the effects of the present invention can also be achieved by further disposing a power source between the high frequency coil and the accelerating electrode so that the high frequency coil has a positive potential with respect to the accelerating electrode.

〔Effect of the invention〕

According to the present invention, an electric field that drives ions toward the wall of the vacuum chamber does not act between the high-frequency coil and the plasma, and the insulator of the vacuum chamber is not sputtered, resulting in an ion beam with few impurities. It is possible to provide a clean etching device that can generate a clean etching system that does not cause contamination during processing.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is a block diagram of a second embodiment of the present invention, Fig. 3 is a block diagram of a third embodiment of the present invention, and Fig. 4 is a block diagram of a third embodiment of the present invention. FIG. 5 is a block diagram of a fourth embodiment of the present invention, FIG. 5 is a block diagram of a fifth embodiment of the present invention, and FIG. 6 is a block diagram of a sixth embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Vacuum container, 2... High frequency coil, 4... Gas introduction pipe, 5... Acceleration electrode, 6... Deceleration electrode, 9...
...High frequency heavy ring 1 mouth 20th figure 3 figure 4

Claims (1)

[Claims] 1. An insulating vacuum container equipped with an exhaust device, a high frequency coil provided for generating plasma in a space within the vacuum container, and a high frequency power source provided in the high frequency coil are connected, and an acceleration electrode and a deceleration electrode for ion extraction;
In the ion source, the high-frequency coil is disposed on the outer periphery of the vacuum container and insulated from the high-frequency power supply in a direct-current manner, and a part of the high-frequency coil and the accelerating electrode are connected in a direct-current manner. An ion source characterized in that it is electrically connected. 2. In claim 1, the high-frequency coil is disposed on the outer periphery of the vacuum container, is insulated from the high-frequency power supply in terms of direct current, and further includes a substantially intermediate point of the high-frequency coil, An ion source characterized in that it is electrically connected to an accelerating electrode in a direct current manner. 3. In claim 1, the high-frequency coil is disposed on the outer periphery of the vacuum container and is DC-insulated from the high-frequency power source, and further:
An ion source characterized in that a positive potential higher than that of the accelerating electrode is applied to the high-frequency coil.