JPH0695452B2 - Micro high-speed atomic beam source device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a micro fast atom beam source device for efficiently and simply obtaining a convergent fast atom beam.

<Prior Art> A conventional apparatus for obtaining a convergent high-speed atomic beam has a configuration as shown in FIG. In the figure, 1 is an ion source, 2
Is an electrostatic lens, 3 is an ion beam, 4 is a charge exchanger, 5 is a gas inlet, 6 is a convergent high-speed atomic beam, and an ion source
1, the electrostatic lens 2 and the charge exchanger 4 are arranged in a line inside the vacuum container 7. Reference numeral 8 is a vacuum pump for the vacuum container 7. The operation of this device is as follows. First, the vacuum container 7 is sufficiently evacuated by the vacuum pump 8. The ion source 1 generates a high-speed ion beam 3, which is guided to the electrostatic lens 2 and converged to a desired beam diameter. This is further guided to the charge exchanger 4. Gases such as H ₂ , He, N ₂ and Ar are introduced into the charge exchanger 4 through the gas inlet 5. Inside the charge exchanger 4, the following charge exchange reaction proceeds due to the collision between the ion beam 3 and the gas molecules. The ions contained in the ion beam 3 are represented by M ⁺ , and the gas molecules are represented by A.

M ⁺ + A → M + A ⁺ (1) A ⁺ + wall of charge exchanger → A ... (2) By this reaction, the ions lose their charge and become the atomic beam 6, which is ejected from the charge exchanger 4. When the ion is a negative ion, the reaction in which M ⁺ in the formulas (1) and (2) is replaced with M ⁻ proceeds, and the atomic beam 6 is similarly generated. However, in this case, gas molecules having a high electron affinity such as F ₂ , O ₂ , and Cl ₂ are used.

<Problems to be Solved by the Invention> The above conventional device has the following problems. Ions have large loss of kinetic energy because they collide with gas molecules having large mass. Collision with a gas molecule having a large mass disturbs the direction of motion of the ions significantly, and the focusing property of the atomic beam deteriorates. It is difficult to maintain a high vacuum or an ultrahigh vacuum in the vacuum container in order to introduce the gas into the charge exchanger. It requires a lens, a charge exchanger and a power supply to operate it, which is expensive.

An object of the present invention is to solve the above problems and to provide an inexpensive and simple micro fast atomic beam source device.

<Means for Solving the Problems> The structure of the present invention that achieves such an object is to arrange the cathodes on both sides of the anode and hold the anode at a high potential with respect to the cathode, thereby In an atomic beam generator that generates a glow discharge between cathodes and vibrates electrons between both cathodes around the anode to generate an atomic beam, a part of the cathode has a convex spherical shape with respect to the anode. Providing a convex spherical portion,
A large number of holes are formed in the convex spherical portion to form a particle beam outlet.

<Operation> When the anode is held at a high potential with respect to both cathodes, glow discharge is generated between the anode and both cathodes, and a plasma sheath is formed in the vicinity of each cathode. At the same time, the electrons emitted from each cathode accelerate toward the anode, pass through the anode, reach the cathode on the opposite side, lose the speed, and are further accelerated toward the anode, and the above-described behavior is repeated. A high-frequency vibration, which is called the so-called Barkhausen-Kruss vibration, occurs between the cathodes with the anode as the center. The vibrating particles collide with gas molecules to form plasma, and the positive ions in the plasma are mainly accelerated in the plasma sheath near the cathode. The plasma sheath is formed along a convex spherical portion formed on a part of the cathode, and the positive ions project almost perpendicularly to the plasma sheath. Therefore, since the positive ions travel perpendicularly to the convex spherical surface, they fly so as to converge according to the curvature of the convex spherical surface. In the vicinity of the cathode, the velocity of the electrons oscillating in Barkhausen-Kurz becomes 0, so that the collision probability of the electrons and the positive ions becomes very large, and most of the positive ions are neutralized and the high speed is reached. It becomes an atomic beam. The high-speed atom beam is converged at one point after being emitted from the particle beam outlet formed on the convex spherical surface.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a converging atomic beam source device according to an embodiment of the present invention. FIG. 2 shows a cross section taken along the line AA 'in FIG. As shown in the figure, the both ends of the hollow rectangular parallelepiped cathode case serve as the cathodes 11 and 12, and the cathodes 11 and 12 are grounded, while the cathodes 11 and 12 are provided with a gas introduction port 9. ing. Inside the cathode case, round bar-shaped anodes 10 are arranged above and below the center of the cathode case, and are connected to a power supply 13 provided outside. On the other hand, in the center of the cathode 11, the surface shape is a convex spherical surface when viewed from the anode side (with respect to the inside of the cathode case), and a large number of particle beam outlets 14 vertically formed in the convex spherical surface portion are provided. Yes, the center lines of the holes intersect at one point.

The converging fast atom beam source device of this embodiment having the above configuration is used as follows.

First, an inert gas or an active gas is introduced from the gas introduction port 9 into the cathode case so as to have a pressure of about 10 ^-1 Torr to 10 _-3 Torr,
The anode 10 is held at a high potential of several 100 v to several kv with respect to the cathodes 11 and 12. Then, anode 10, cathode 11, 12
A glow discharge is generated between them and a plasma sheath 15 is formed near the cathodes 11 and 12. On the other hand, at this time, the electrons emitted from the cathodes 11 and 12 accelerate toward the anode 10, pass through the middle of the two anodes 10, and the cathodes 12 and 11 on the opposite side.
The velocity is reached, the velocity is lost, the velocity is further accelerated toward the anode 10, and the above-described behavior is repeated. So-called Barkhausen-
High-frequency vibration, which is called Kurtz's vibration, occurs between the cathodes 11 and 12 with the anode 10 as the center, and the vibrating electrons collide with gas molecules to effectively form plasma. . The positive ions in the formed plasma are mainly accelerated in the plasma sheath 15 formed near the cathode, and the particle beam extraction port 14
It is radiated to the outside of the high-speed atomic beam source device through.

By the way, the positive ions move so as to enter the plasma sheath almost vertically. The plasma sheath in the vicinity of the particle beam outlet provided on the cathode having a convex surface shape in the fast atom beam as in the present invention is considered to be formed following this surface shape. The positive ions that traverse to the particle beam extraction port travel at a right angle to this convex surface shape, so that they are converged at a certain point according to the curvature of the convex surface shape. In the vicinity of the cathode, the velocity of the electrons oscillating in Barkhausen-Kurz is 0, and the collision probability of electrons and positive ions becomes very large in the vicinity, neutralizing the positive ions. We will make fast atoms. Due to such a main mechanism, the ion beam is converged into a high-speed atom beam and emitted from the particle beam outlet into the vacuum.

In this embodiment, two rod-shaped anodes are used as the anode 10. However, as long as they do not interfere with the atoms oscillating in Barkhausen-Kurz or the ions accelerated toward the cathode 11, they have an annular shape or other shapes. Can be used. Furthermore, in this embodiment, the particle beam outlet 14 is provided only on the cathode 11, but the present invention is not limited to this, and it may be provided on both cathodes 11 and 12.

In the micro fast atom beam source device according to the present invention, when operated using Ar gas, 90% or more of the total beam extracted from the particle beam outlet is a fast atom beam, and the remaining
It was measured that a little less than 10% was an ion beam.

<Effects of the Invention> As described specifically above with reference to the examples, the present invention forms a plasma sheath along the convex spherical surface of the cathode and positive ions so as to cross the plasma sheath vertically. As a result, the convergent atomic beam can be extracted inexpensively and easily. That is, the electromagnetic field lens and the charge exchanger are not required as compared with the conventional technique in which the ion beam is converged by the electromagnetic field lens and the micro fast atom beam is further obtained by using the charge exchanger. Moreover, since the positive ions are neutralized by the electrons, the loss of the kinetic energy of the particles can be reduced, and the convergent atomic beam can be efficiently obtained. Since this fast atom beam has no charge,
When this is applied to an insulating sample, there is an advantage that processing such as etching, sputtering, and ion implantation can be locally performed without being affected by the surface potential such as surface charging. Even when a semiconductor sample is irradiated, there is an advantage that surface damage accompanied by an increase in interface charge density, which is a problem in the case of an ion beam, is unlikely to occur.

[Brief description of drawings]

FIG. 1 is a sectional view of a micro fast atom beam source device according to an embodiment of the present invention, FIG. 2 is a view taken along the line AA ′ in FIG. 1,
FIG. 3 is a schematic view of a conventional micro fast atom beam apparatus for obtaining a micro fast atom beam. In the drawings, 1 is an ion source, 2 is an electrostatic lens, 3 is an ion beam, 4 is a charge exchanger, 5 is a gas inlet, 6 is a convergent fast atom beam, 7 is a vacuum vessel, 8 is a vacuum pump, and 9 is a vacuum pump. Is a gas inlet, 10 is an anode, 11 and 12 are cathodes, 13 is a high voltage power supply, 1
4 is a particle beam outlet, 15 is a plasma sheath, and 16 is a convergent high-speed atomic beam.

Claims (1)

[Claims] 1. A cathode is disposed on both sides of the anode to maintain the anode at a high potential with respect to the cathode, thereby causing a glow discharge between the anode and the cathode and between the cathodes with the anode as a center. In an atomic beam generator that vibrates an electron to generate an atomic beam, a convex spherical portion having a convex spherical shape with respect to the anode is provided in a part of the cathode, and a large number of holes are formed in the convex spherical portion. A micro high-speed atom beam source device characterized by being formed into a particle beam outlet.