JP2000173521A - Electron beam source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron beam source capable of emitting a large diameter electron beam with homogeneous current density, with a simple structure. SOLUTION: An electron beam exciting plasma generation device 10 has a cathode 1 for plasma generation as an electron beam source to emit the electronic beam toward a sample 7, an auxiliary anode 2 with an open hole 2a to let the plasma penetrate, a porous anode 3 for plasma generation with a plurality of open holes 3a to let electrons in plasma penetrate, a porous electrode 4 for electron acceleration with a plurality of open holes 4a corresponding to each open hole 3a of the anode 3 to let electrons in plasma penetrate. A permanent magnet 8 is provided between the auxiliary anodes 2 and the anode 3 to generate a specific magnetied field to widen discharging current I (current of electrons) in plasma in radial direction. The permanent magnet 8 constitutes a circular member which extends around the central axis L of the discharging current I in plasma, and electric field B runs out radially in the direction which is almost orthogonal to the axis L of the discharging current in plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam source, and more particularly to an electron beam source for plasma generation used for various plasma processing such as dry etching and film formation of semiconductors and plasma cleaning.

[0002]

2. Description of the Related Art As a conventional electron beam source for generating plasma, for example, an electron beam source described in Japanese Patent Application Laid-Open No. 62-234857 is known. The electron beam source includes a cathode (cathode) and an anode (anode) having a plurality of through holes for generating plasma between the cathode and transmitting electrons in the generated plasma.
A large-diameter electron beam having a uniform current density by forming the anode from a plurality of electrode elements and controlling the flow of each current between the formed electrode elements and the cathode. Is trying to release. In this electron beam source, the electrode elements are insulated from each other, and a resistor is connected between each electrode element and the cathode.

[0003]

However, in this type of electron beam source, the anode for transmitting electrons generally needs to be suppressed to a predetermined thickness (usually about 0.5 to 1 mm). The above-mentioned JP-A-62-2348.
In the case where an anode is formed from a plurality of electrode elements as in the electron beam source described in Japanese Patent Application Laid-Open No. 57-57, there is a difficulty in manufacturing such as insulation between the electrode elements and connection of a resistor to each electrode element. In addition, there is a problem that it is difficult to keep each electrode element of the anode composed of a plurality of electrode elements and the cathode parallel to each other, thereby increasing the manufacturing cost.

The present invention has been made in view of the above points, and an object of the present invention is to provide an electron beam source having a simple structure capable of emitting a large-diameter electron beam having a uniform current density. Aim.

[0005]

The present invention has a plasma generating cathode and a plurality of through holes for generating plasma between the plasma generating cathode and transmitting electrons in the generated plasma. A plasma generating porous anode, and a magnetic field generating means provided between the plasma generating cathode and the plasma generating porous anode to generate a predetermined magnetic field so as to radially expand the flow of electrons in the plasma. An electron beam source characterized in that:

In the present invention, it is preferable that the magnetic field generating means generates a magnetic field radially extending in a direction substantially perpendicular to the flow of electrons in the plasma. Preferably, the magnetic field generating means is made of a permanent magnet, and in particular, the permanent magnet is made of an annular member extending around a central axis of the flow of electrons in the plasma, and the inner and outer peripheral surfaces of the annular member are It is preferable that each has a different magnetic pole.

According to the present invention, since a magnetic field is formed in the middle of the path of the electrons in the plasma, the electrons traveling in the magnetic field are trapped by the magnetic field and make a spiral motion, and the substantial mean free path Becomes shorter. Therefore, the electrons easily collide with the gas particles in the space, and the flow of the electrons in the plasma is expanded in the radial direction. Therefore, according to the present invention, a large-diameter electron beam having a uniform current density can be emitted by a simple structure in which a magnetic field generating means is provided between a cathode for plasma generation and a porous anode for plasma generation. Therefore, simplification of the device and simplification of manufacture can be achieved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views showing an embodiment of an electron beam source according to the present invention. Here, FIG. 1 is a schematic diagram showing an electron beam excited plasma generator provided with an electron beam source, and FIG. 2 is a diagram showing a configuration of a permanent magnet (magnetic field generating means) in the electron beam source shown in FIG.

As shown in FIG. 1, an electron beam excited plasma generator 10 includes a substantially cylindrical container 10a, in which an electron beam source for emitting an electron beam toward a sample 7 is provided. A cathode 1 for plasma generation, an auxiliary anode 2 having a through hole 2a for transmitting plasma, a porous anode 3 for plasma generation having a plurality of through holes 3a for transmitting electrons in the plasma, An electron accelerating porous electrode 4 having a plurality of through holes 4a for transmitting electrons in plasma is provided corresponding to each through hole 3a of the porous anode 3.

Here, a heating power supply 11 is connected to the plasma generating cathode 1, and the plasma generating cathode 1 is heated by energization. A discharge power source 12 is connected between the cathode 1 for plasma generation and the porous anode 3 for plasma generation via a resistor 14.
And a plasma generating porous anode 3 for generating plasma. Further, a cathode for plasma generation 1
A discharge power source 12 is connected via resistors 14 and 15 to the auxiliary anode 2 disposed between the auxiliary anode 2 and the plasma generating porous anode 3. The through hole 2a of the auxiliary anode 2 has an opening area (about 3 mm in diameter) that can prevent gas from flowing from the plasma generating porous anode 3 side to the plasma generating cathode 1 side. In the plasma processing state, the cathode 1 functions as a partition for protecting the plasma generating cathode 1 from oxygen gas (O ₂ ) or the like. Furthermore, an acceleration power source 1 is provided between the plasma generating porous anode 3 and the electron accelerating porous electrode 4 via a switching element SW.
3 is connected to accelerate the electrons drawn between the plasma generating porous anode 3 and the electron accelerating porous electrode 4 through the through holes 3 a of the plasma generating porous anode 3.

A discharge current (flow of electrons) in the plasma is provided between the auxiliary anode 2 and the plasma-generating porous anode 3.
A permanent magnet (magnetic field generating means) 8 for generating a predetermined magnetic field is provided so as to expand I in the radial direction.

FIG. 2 is a diagram showing a permanent magnet used in the electron beam source shown in FIG. As shown in FIG. 2, the permanent magnet 8 is formed by combining eight fan-shaped magnet members 8a, and as a whole, forms an annular member extending around the central axis L of the discharge current I in the plasma. The inner peripheral surface and the outer peripheral surface of the annular member are magnetized to the N pole and the S pole, respectively, and the central axis of the discharge current I in the plasma flowing toward the permanent magnet 8 at the front surface of the permanent magnet 8. L
A magnetic field B extends radially in a direction substantially perpendicular to the magnetic field B.

The electron beam excited plasma generator 1
0 container 10a is provided with supply ports 41a and 41b and a discharge port 41c.
Is supplied with an argon gas (Ar) through a supply port 41a, and a region between the electron acceleration porous electrode 4 and the sample 7 is supplied with a toluene gas (C ₇₎ through a supply port 41b. H ₈ ), methane gas (CH ₄ ), ethylene gas (C ₂
H ₄ ), oxygen gas (O ₂ ) and the like are supplied.

An insulating member 40 is coated on the inner peripheral surface of a region between the auxiliary anode 2 and the sample 7 in the container 10a,
Most of the discharge current flows to the plasma generating porous anode 3. An insulating member 40 is also inserted between the container 10a and the plasma generating cathode 1, the auxiliary anode 2, the plasma generating porous anode 3, and the electron accelerating porous electrode 4.

Further, a cooling mechanism (not shown) is provided in the wall surface of the container 10a and in the auxiliary anode 2 for water-cooling a portion heated by the plasma.

Next, the operation of the present embodiment having such a configuration will be described.

First, with the switching element SW turned off, all of the heating power supply 11, the discharge power supply 12, and the acceleration power supply 13 are turned on. Thus, the voltage _Vf is applied to the plasma generating cathode 1 by the heating power supply 11, and the plasma generating cathode 1 is heated. At the same time, the discharge power supply 12 causes the space between the plasma generating cathode 1 and the auxiliary anode 2 and between the plasma generating cathode 1 and the plasma generating porous anode 3.
Voltage V _d is given, a plasma of argon gas supplied from the supply port 41a between the plasma generating cathode 1 and the plasma generating porous anodic 3 by the discharge current (Ar) is generated between the.

At this time, a permanent magnet 8 is provided between the auxiliary anode 2 and the plasma-generating porous anode 3, and a magnetic field B radially extends in a direction substantially perpendicular to the central axis L of the discharge current I in the plasma. , The discharge current I flowing in the vicinity of the central axis L, out of the discharge current I in the plasma flowing toward the permanent magnet 8, is diverted outward. Further, the electrons in the discharge current I are trapped in the magnetic field B and make a spiral motion, and the substantial mean free path is shortened. This makes it easier for electrons to collide with gas particles in space,
As a result, the discharge current I is expanded in the radial direction. For this reason, the current density of the discharge current I that reaches the plasma generating porous anode 3 through the permanent magnet 8 becomes substantially uniform over the entire cathode-side electrode surface of the plasma generating porous anode 3.

Next, the switching element SW is turned on. Thus, _a voltage Va is applied between the plasma generating porous anode 3 and the electron accelerating porous electrode 4 by the accelerating power supply 13, and plasma is generated between the plasma generating porous anode 3 and the electron accelerating porous electrode 4. Holes 3a of the porous anode 3 for use
The electrons extracted through are accelerated.

The electrons accelerated in this manner are extracted through the respective through holes 4a of the porous electrode 4 for electron acceleration, and the accelerated electrons supply a supply port between the porous electrode 4 for electron acceleration and the sample 7. Toluene gas (C ₇
Plasma such as H ₈ ) is generated, and a predetermined plasma process is performed on the sample 7. Specifically, for example, a sample 7 such as a semiconductor, a mechanical component, or a magnetic recording component is arranged, and a gas (for example, toluene gas) containing carbon and hydrogen is provided in a region between the sample 7 and the electron accelerating porous electrode 4. By supplying (C ₇ H ₈ ), methane gas (CH ₄ ), and ethylene gas (C ₂ H ₄ ) to generate plasma, a diamond-like carbon thin film can be formed on the surface of the sample 7.
Further, by supplying oxygen gas (O ₂ ) to the region between the sample 7 and the electron accelerating porous electrode 4 to generate plasma, the surface of the sample 7 can be plasma-cleaned.

At this time, as described above, the current density of the discharge current I reaching the plasma generating porous anode 3 is substantially uniform over the entire cathode-side electrode surface of the plasma generating porous anode 3. Therefore, the electrons (electron beams) extracted through the through holes 4a of the electron accelerating porous electrode 4 also
A substantially uniform current density is obtained over the entire electrode surface of the electron accelerating porous electrode 4, and a substantially uniform plasma treatment can be performed on the surface of the sample 7.

As described above, according to the present embodiment, the uniform current density can be obtained by a simple structure in which the permanent magnet 8 is provided between the plasma generating cathode 1 (auxiliary anode 2) and the plasma generating porous anode 3. , A large-diameter electron beam having the following characteristics can be emitted, thereby simplifying the apparatus and facilitating manufacture.

In the above-described embodiment, a permanent magnet is used as the magnetic field generating means. However, the present invention is not limited to this as long as it can generate a predetermined magnetic field. Means can be used.

Further, in the above-described embodiment, the distribution of the magnetic field B is represented by the central axis L of the discharge current I in the plasma.
The distribution in which the magnetic field B extends radially in a direction substantially perpendicular to the direction is adopted. However, the distribution is not limited to this as long as the discharge current I in the plasma can be expanded in the radial direction. Can be adopted.

Further, in the above embodiment,
As the permanent magnet 8, the central axis L of the discharge current I in the plasma
The inner and outer peripheral surfaces of the annular member extending around are magnetized to the N and S poles, respectively. However, if the discharge current I in the plasma can be expanded in the radial direction, The present invention is not limited to this, and any shape and magnetization mode can be adopted. Specifically, for example, a disk-shaped member arranged substantially perpendicular to the central axis L of the discharge current I in the plasma and having both front and rear surfaces magnetized to N pole and S pole, respectively, can be adopted.

[0026]

Next, a specific embodiment of an electron beam excited plasma generator equipped with the electron beam source shown in FIGS. 1 and 2 will be described.

[0027] As an example embodiment, by supplying a toluene gas (C ₇ H ₈₎ in the region between the electron accelerating porous electrode 4 and the specimen 7 through the supply port 41b, a silicon substrate as a sample 7 ( 8c diameter
An experiment for forming a diamond-like carbon film on the surface of m) was performed. Note that the voltage _Vf of the heating power supply 11 is 8 V,
Voltage V _d is 60V of discharge power supply 12, the voltage V _a of the acceleration power supply 13 is set to 100 V, the resistor 14 2～5Omu, resistor 15 was 200 [Omega. The pressure in the region between the plasma generating cathode 1 and the auxiliary anode 2 is 0.2 Torr,
The pressure in the region between the sample and sample 7 was 2 × 10 ⁻³ Torr. Further, as the permanent magnet 8, an annular member having an outer diameter of 3 cm, an inner diameter of 1.5 cm, and a thickness of 10 mm in its entire shape was used. Further, as the plasma-generating porous anode 3, one having about 1200 through-holes 4 a having a diameter of about 1 to 2 mm formed in a disk made of carbon having a diameter of 10 cm and a thickness of 1 mm was used.

Comparative Example As a comparative example, an experiment was performed under the same conditions as in the above example except that the permanent magnet was omitted.

Evaluation Results FIGS. 3 and 4 are diagrams showing the experimental results of the above example and comparative example, respectively, and show the radial distribution of the thickness of diamond-like carbon formed on the silicon substrate. As shown in FIG. 3, in the above embodiment, the diameter is 8 cm.
The distribution width of the film thickness in the radial direction of the silicon substrate is ± 10
%, And a diamond-like carbon film having a substantially uniform thickness over the entire surface of the silicon substrate could be formed. In contrast, in the comparative example, as shown in FIG. 4, the distribution width of the film thickness in the radial direction of the silicon substrate having a diameter of 8 cm is ± 25%, and the film thickness is considerably large over the entire surface of the silicon substrate. Only a diamond-like carbon film with variation could be formed.

[0030]

As described above, according to the present invention, a simple structure in which a magnetic field generating means is provided between a cathode for plasma generation and a porous anode for plasma generation makes it possible to provide a large-diameter, uniform current density. An electron beam can be emitted, so that the device can be simplified and its manufacture can be facilitated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an electron beam excited plasma generator provided with an embodiment of an electron beam source according to the present invention.

FIG. 2 is a perspective view showing a permanent magnet used in the electron beam source shown in FIG.

FIG. 3 is a diagram showing a radial distribution of film thickness when a diamond-like carbon film is formed on a silicon substrate by the electron beam source shown in FIGS. 1 and 2;

FIG. 4 is a diagram showing a radial distribution of film thickness when a diamond-like carbon film is formed on a silicon substrate by a conventional electron beam source.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 cathode for plasma generation 2 auxiliary anode 2 a through hole 3 porous anode for plasma 3 a through hole 4 porous electrode for electron acceleration 4 a through hole 7 sample 8 permanent magnet 10 electron beam excited plasma generator 11 heating power supply 12 discharge power supply 13 acceleration power supply 14,15 resistance SW switching element

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shigekazu Tada 1-4, Kasumigaoka, Kamifukuoka-shi, Saitama Confor Kasumigaoka No. 13, Building 1105 (72) Inventor Yuichi Sakamoto 5-1 Narita Higashi, Suginami-ku, Tokyo −34

Claims (4)

[Claims] A plasma generating cathode; a plasma generating porous anode having a plurality of through holes for generating plasma between the plasma generating cathode and transmitting electrons in the generated plasma; An electron beam provided between the cathode for plasma generation and the porous anode for plasma generation, and magnetic field generating means for generating a predetermined magnetic field so as to radially expand the flow of electrons in the plasma. source. 2. An electron beam source according to claim 1, wherein said magnetic field generating means generates a magnetic field radially extending in a direction substantially perpendicular to the flow of electrons in said plasma. 3. An electron beam source according to claim 1, wherein said magnetic field generating means comprises a permanent magnet. 4. The permanent magnet comprises an annular member extending around a central axis of the flow of electrons in the plasma, wherein an inner peripheral surface and an outer peripheral surface of the annular member have different magnetic poles. The electron beam source according to claim 3.