JPH0618108B2 - Electron cyclotron type ion source - Google Patents

Description

The present invention relates to an ion source used for dry etching or thin film formation in semiconductor technology, for example, an electron cyclotron that does not require a microwave transmission circuit. EC
R) type ion source.

[Prior Art] Conventionally, as this kind of ion source, there is a document; TAMB
A, K. YAMAGUCHI, S.M. TANAKA, M .;
YAMAWAKI, Y. SAKAMOTO: Nucle
ar Instruments and Method
s in Physics Research B37
/ 38 (1989) 173-175. Have been reported to. In this example, a microwave oscillating tube and a plasma generating section are provided in one rectangular waveguide so as to be in close proximity to each other, and an electron cyclotron resonance magnetic field is provided in the plasma generating section so as to surround the waveguide between them. An electromagnetic coil for generating a region is provided, and an ion beam is extracted from the plasma generated in the plasma generation unit and irradiated onto a sample such as a semiconductor substrate. In this ECR type ion source, the three-dimensional circuit group is simplified by adopting the matching by the plunger provided at the end of the waveguide.

[Problems to be Solved by the Invention] In practice, the diameter of the extraction beam is 20 in the field of semiconductor technology.
In many cases, 0 mm or more is required. However, in the conventional ECR type ion source having the above-mentioned configuration, the diameter of the extracted ion beam is limited by the diameter of the rectangular waveguide due to its operating principle. Therefore, in order to obtain an ion beam with a practical diameter, the diameter of the rectangular waveguide must be increased, which results. The diameter of the electromagnetic coil provided so as to surround this waveguide must be increased. For this reason, the whole apparatus becomes large in size corresponding to the need for the three-dimensional circuit group. Moreover, high electric power is required to generate a magnetic field of a required strength in the electromagnetic coil in the large-diameter waveguide.

Therefore, an object of the present invention is to provide an electron cyclotron type ion source capable of omitting a three-dimensional circuit group, obtaining an ion beam having a large diameter without increasing the size of the entire apparatus, and requiring high power. That is.

[Means for Solving the Problems] An electron cyclotron type ion source according to the present invention has one end wall formed with an ion beam extraction port, the other end wall, and an outer peripheral wall through which microwaves pass, and A flat cylindrical inner cylinder in which a plasma space into which a plasma generating gas is introduced is formed, an outer cylinder provided around the outer circumference of the inner cylinder to define an annular oscillation space, and the inner cylinder. Means for exciting microwaves in the oscillation space so that the microwaves enter the plasma space from almost the entire circumference of the outer peripheral wall of the inner cylinder, and at least the other end wall side of the one end wall and the other end wall of the inner cylinder. A permanent magnet provided along the outer peripheral wall and near the outer peripheral wall to form an electron cyclotron resonance magnetic field region near the outer peripheral wall of the plasma space, and an electrode for extracting ions generated in the plasma space from the ion beam extraction port And is provided.

[Operation] In the electron cyclotron type ion source having the above configuration,
An electron cyclotron resonance magnetic field region is formed on the outer peripheral side of the plasma space by a permanent magnet. Then, when the plasma generating gas is introduced in a state where the microwave is supplied to the magnetic field region through the outer peripheral wall, the introduced gas is ionized. Ions are accelerated in the electron cyclotron resonance magnetic field region, and plasma is generated in this region. An ion beam is extracted from the plasma to the outside through the extraction port.

[Embodiment] An electron cyclotron type ion source according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

In the figure, reference numeral 1 indicates a cylindrical outer cylinder, and reference numeral 2 indicates an inner cylinder arranged inside the outer cylinder 1 and coaxially therewith. These cylinders form an annular oscillation space 3 around the entire circumference of these tubes.
The dimension is set so that is specified. The outer cylinder 1 is made of a material that reflects microwaves, for example, metal, and the inner cylinder 2 is a material that transmits microwaves.
For example, it is made of ceramic. The outer cylinder 1 formed of a reflective material functions as a reflection plate that reflects microwaves excited in the oscillation space 3 and constitutes a microwave matching element. The upper end opening and the lower end opening of the cylinders 1 and 2 are formed by the disc-shaped upper plate 4 and the lower plate 5,
Each is closed and seals the oscillation space 3 and defines a circular plasma space 6 inside the inner cylinder 2. A plurality of microwave oscillating tubes 7 are mounted on the upper plate 4 at predetermined intervals in the circumferential direction so as to be located on the oscillation space 3. In this embodiment, four microwave oscillating tubes 7 are arranged at intervals of 90 °. The antenna 7a of each of the oscillation tubes 7 penetrates the upper plate 4 and projects into the oscillation space 3 to excite microwaves in the space 3. Further, in the oscillation space 3, a metal partition plate 8 is provided so as to cut off between the adjacent antennas 7a. As a result, the ring-shaped oscillation space 3
Are divided into four 90 ° compartments, and one antenna 7a is arranged in each compartment so that the microwaves excited by the respective antennas 7a do not affect each other in the oscillation space 3. Therefore, the microwave excited in the oscillation space 3 enters the inner cylinder from almost the entire circumference of the outer peripheral wall of the inner cylinder 2.

Magnetic field generating means 9 and 10 are provided on the outer surfaces of the upper plate 4 and the lower plate 5 near the outer periphery of the plasma space 6, respectively. These magnetic field generating means jointly generate an electron cyclotron resonance magnetic field region along the inner and outer circumferences of the plasma space to accelerate plasma electrons and confine them in the magnetic field. In this embodiment, these magnetic field generating means 9 and 10 are arranged at a predetermined interval in the circumferential direction, near the outer peripheral wall of the inner cylinder and along the same, and each of them has a cylindrical shape of 12 small diameters. It is composed of permanent magnets 9a and 10a.
The upper magnet 9a and the lower magnet 10a are arranged so that their magnetic pole surfaces face each other so as to form a cup-shaped magnetic field. Of course, the upper magnet 9a and the lower magnet 10a may be arranged such that different magnetic pole surfaces face each other so as to generate a mirror-type magnetic field. Further, the magnetic field generating means may be formed by a ring-shaped permanent magnet.

At the center of the lower plate 5, an ion beam extraction port 11 composed of a large number of small holes is formed, and the ion beam from the plasma space 6 is emitted to the outside through the extraction port 11. As shown in the drawing, the outlet 11 has a circular shape and its outer periphery is located near the lower magnet 10a. That is, the lower magnet 10a is arranged in a narrow annular portion between the outer periphery of the outlet 11 and the outer peripheral wall of the inner cylinder 2. On the lower side of the lower plate 5, electrodes 12 and 13 for extracting the ion beam, which are mesh electrodes, are electrically insulated from each other by an insulator 14.

In use, the inside of the plasma space 6 is evacuated by a vacuum pump (not shown), an etching gas or the like is supplied, and a microwave is supplied by a microwave oscillating tube. As a result, the electrons generated by the ionization in the plasma space 6 are trapped by the magnetic field generated along the entire circumference near the inner circumference of the plasma chamber, and are further ionized by being accelerated by microwaves in the electron cyclotron resonance region. To help. On the other hand, the plasma ions are deviated from the electron cyclotron resonance region and gathered at the extraction electrodes 12 and 13 to which a voltage is applied at the center of the plasma chamber, and the ion beam is emitted to the outside from the extraction port 11.

In the electron cyclotron type ion source having the above-mentioned configuration, the oscillation tube 7
2.54GHz microwave (wavelength is 120m
An example of the dimension of each member will be described below in the case of obtaining a plasma with a large diameter by using the one that excites m).

The diameter of the inner cylinder 2, that is, the plasma space 6 is set to 300 mm, and the antenna 7a is installed at the opposite wavelength from the outer circumference of the plasma space 6. As a result, a pair of opposing antennas 7a
The distance is 420 mm. The outer cylinder 1 is installed so as to be apart from the antenna 7a by a half wavelength. As a result, the outer cylinder 1 has a diameter of 5
It becomes 40 mm. In the electron cyclotron type ion source having the above-described configuration in which the extraction port 11 is formed as large as possible so that the outer periphery thereof is located near the lower magnet 10a as shown in the figure, the diameter is about 540 mm and the size is small as a whole. It is possible to obtain an ion beam having a large diameter (the diameter of the ion beam coincides with the diameter of the extraction port, and the diameter of the extraction port is determined from the diameter of the inner cylinder 2 to alert the annular portion where the permanent magnet 10a is provided). It is almost the length of the hole minus the length of the hole.
And, since no magnet coil is used, high power is not required. Further, in the plasma chamber, an electron cyclotron resonance magnetic field region is formed near the outer circumference of the plasma chamber, and microwaves are introduced into the plasma chamber from a plurality of symmetrical directions, so that plasma with excellent characteristics is generated. As a result, there is an effect that the intensity distribution in the radial direction of the ion beam extracted from each becomes uniform.

Although the four microwave oscillating tubes are arranged at equal intervals in the above embodiment, they need not be arranged at equal intervals. Even in this case, a part of the microwave transmitted from the microwave transmission tube is reflected by the inner peripheral surface of the outer cylinder 1 and propagates in the transmission space, so that it is supplied to the plasma chamber from almost the entire circumference of the inner cylinder.
However, in order to make the plasma more uniform, it is preferable to arrange them symmetrically with respect to the plasma chamber.

[Advantages of the Invention] The electron cyclotron ion source according to the present invention can obtain a large-diameter ion beam with a uniform intensity distribution without using a three-dimensional circuit group and without making the entire apparatus large and complicated. . Moreover, since no electromagnetic coil is used,
From this point as well, the device can be downsized and does not require large power.

[Brief description of drawings]

The drawings are for explaining an electron cyclotron type ion source according to one embodiment of the present invention. FIG. 1 is an overall plan view, and FIG. 2 is a partial sectional view. 1 ... Outer cylinder, 2 ... Inner cylinder, 3 ... Oscillation space, 6 ... Plasma space, 7 ... Microwave oscillation tube, 9, 10 ... Magnetic field generating means. 9a. 10a ... Permanent magnet, 11 ... Ion beam outlet.

Claims (1)

[Claims] 1. A plasma chamber is formed when a plasma generating gas is introduced into the chamber, which has one end wall having an ion beam extraction port, another end wall, and an outer peripheral wall through which a microwave passes. A flat cylindrical inner cylinder, and an outer cylinder that is provided on the outer periphery of the inner cylinder to surround the inner cylinder and defines an annular oscillation space,
Means for exciting microwaves in the oscillation space so that the microwaves enter the plasma space from substantially the entire circumference of the outer peripheral wall of the inner cylinder, and at least the other end of one end wall and the other end wall of the inner cylinder. On the wall side, along the outer peripheral wall, near the outer peripheral wall, a permanent magnet that forms an electron cyclotron resonance magnetic field region near the outer peripheral wall of the plasma space, and the ion beam extraction port for the ions generated in the plasma space Electron cyclotron type ion source having an electrode to be extracted from.