JPH117900A - Electron beam stimulated plasma generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the attrition in an opening part for leading out electrons from a discharge part and prevent a material in the opening part from being included in a reaction gas plasma to have a bad effect on the plasma process. SOLUTION: A narrow path 10 for leading out electron beams from a discharge part 7 is formed out of a metal plate or insulating material electrically insulated from each electrode, preferably, alumina, aluminum nitride or quartz. The narrow path 10 of the discharge part 7 may be provided in the direction having an angle of, for example, 90 deg. to the direction of connecting an intermediate electrode 2 to a discharge electrode 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of an electron beam generator of an electron beam excited plasma generator, and more particularly to the structure of a bottleneck for extracting electrons from a discharge chamber.

[0002]

2. Description of the Related Art Various electron beam excited plasma generators have been developed as plasma guns used in plasma processing apparatuses, that is, plasma ion plating apparatuses, plasma CVD apparatuses, plasma sputtering apparatuses, plasma etching apparatuses, and the like. The electron beam excited plasma apparatus includes an electron beam generator that generates an electron beam, and a plasma process chamber that generates plasma by exciting with the electron beam to cause various reactions.

An electron beam generator is arranged in the order of a cathode, an intermediate electrode, a discharge anode and an accelerating electrode. When a discharge voltage is applied between the cathode and the discharge electrode, thermions emitted from the cathode are supplied to the cathode portion. The plasma acts on the inert gas to generate plasma and fills the discharge chamber between the intermediate electrode and the discharge anode. When an accelerating voltage is applied between the discharge anode and the accelerating electrode, electrons are extracted from the plasma through a draw-out path opened at the center of the discharge anode, accelerated, and a large current electron beam is supplied to the plasma process chamber. The electron beam converts a gas supplied to the plasma process chamber into plasma, and performs various kinds of processing on the target substrate.

Conventionally, a cathode, an intermediate electrode, a discharge anode, and an accelerating electrode are coaxially arranged in a straight line, an electron outlet formed of a conductive material is used as a discharge anode, and an electron beam is focused at the center of each electrode. It was designed to linearly penetrate into the plasma process chamber through the formed communication hole and react with the gas inside. Such a linear arrangement is very natural considering the process of extracting an electron beam from the formed plasma and accelerating it. However, since holes are directly formed in the discharge anode for generating plasma and an electron beam is extracted therefrom, ions in the plasma collide with the surface of the discharge anode at high speed.

In a process plasma generated by an electron beam in an electron beam-excited plasma generator, the inside of a process plasma is substantially equipotential, and this equipotential range is slightly increased from a process chamber through an accelerating electrode, and further through a discharge passage. It has an outer shell shape penetrating inside, and its potential is almost equal to the potential of the accelerating electrode. In the conventional plasma apparatus, the potential of the draw-out bottle has the same value as that of the discharge anode, and a large potential difference is generated at a very short distance between the outer shell of the plasma in the draw-out narrow passage and the draw-out narrow passage. When a voltage was applied, the ions in the plasma in the extraction bottleneck collided with the extraction bottleneck with a large energy of about 100 eV. Such collisions not only cause the anode to be worn out, but also when used in a film formation process, the anode material removed by the collisions becomes impurities and mixes into the formed film, so that a high-quality film is formed. It was difficult to do. In addition, there is a problem that it is deposited at a place where insulation is required, causes insulation failure, and makes discharge unstable.

Japanese Patent Application Laid-Open No. 4-58445 discloses that
An example is disclosed in which the periphery of the side facing the acceleration anode corresponding to the acceleration electrode of the through hole of the acceleration cathode corresponding to the discharge anode is covered with an insulator, but the wall of the through hole is exposed in a state where the metal electrode is exposed. In addition, they are arranged coaxially from the cathode to the discharge anode to the acceleration electrode. Therefore, electrons from the cathode directly collide with and flow into the vicinity of the through-hole, causing damage to the electrode.In addition, ions in the plasma body directly attack and damage the electrode surface of the through-hole, and the scraped-off electrode material is removed. It will still be an impurity in the thin film to be formed.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an opening for preventing electrons from being drawn out from a discharge portion formed between an intermediate electrode and a discharge anode and extracting electrons from a discharge portion. It is an object of the present invention to provide an electron beam excited plasma generator configured to prevent a substance to be mixed from entering a reaction chamber and adversely affecting a plasma process.

[0008]

In order to solve the above-mentioned problems, an electron beam excited plasma generator according to the present invention, which is arranged in the order of a cathode, an intermediate electrode, a discharge anode and an acceleration electrode, comprises:
A draw-out path for extracting an electron beam from a discharge portion formed between the intermediate electrode and the discharge anode is electrically insulated from each electrode. In the plasma generator of the present invention, since the draw-out bottleneck is insulated from the discharge anode,
The potential difference between the drawing bottleneck and the plasma generated in the vicinity of the bottleneck is reduced, so that ions in the plasma do not collide with the drawing bottleneck at a high speed, and contamination generated when the scraped bottle member enters the process chamber. Nation can be suppressed.

The draw-out path may be a metal plate insulated from other electrodes, but may be formed of an insulating material. Further, it is preferable that the insulating material used for the drawing bottleneck is formed of alumina. Further, it is more preferable to use aluminum nitride or quartz. When a draw-out bottleneck is formed by an insulator, the structure of the discharge chamber is simplified since insulation with the discharge anode is easy, and particularly, alumina (Al
₂ O ₃ ) is excellent in heat resistance and degassing properties, and when formed of aluminum nitride (AlN), thermal conductivity and thermal shock resistance are further improved, and quartz (Si)
In the case of O ₂ ), an electron beam excited plasma generator having a long life and easy maintenance can be provided because the sputtering rate by ions is small.

In order to solve the above problems, an electron beam excited plasma generator of the present invention, which is arranged in the order of a cathode, an intermediate electrode, a discharge anode and an acceleration electrode, comprises a discharge part formed between the intermediate electrode and the discharge anode. Is characterized by being provided in a direction having an angle of, for example, 90 degrees with respect to a direction connecting the intermediate electrode and the discharge anode. If the drawing bottleneck is arranged at a position deviated from the trajectory of the electrons due to the discharge, electrons do not directly flow into the drawing bottleneck portion, so that the material forming the bottleneck is not separated and present near the process plasma. . Therefore, there is an effect that impurities mixed in the plasma process chamber are reduced.

It is preferable that the draw-out path is electrically insulated from the discharge anode and the like. Insulation from the discharge anode or the like makes it difficult for ions in the plasma to collide with the extraction bottleneck, and further reduces the bottleneck material mixed into the plasma, thereby enabling a favorable plasma process to be performed. Usually, the degree of vacuum in the discharge chamber is 0.05
Torr to 0.5 Torr, 0.1 mTorr to 1 mTo in the acceleration chamber
rr, but within this range, the inner diameter of the draw-out bottleneck is 4 mm or more and 8 mm or less, and the length is 1 mm or more and 20 mm or less.
mm or less.

If the opening area of the drawing bottleneck is too large,
The density of the plasma in the discharge chamber for extracting the electron beam is insufficient, and the electron extraction efficiency is reduced. On the other hand, if the opening area is too small, the pressure difference between the discharge chamber and the plasma process chamber increases, and the plasma generated in the draw-out path connects the plasma in the discharge chamber with the plasma in the plasma process chamber, making it difficult to accelerate electrons. Or the gas pressure in the discharge chamber is too high, so that the electron beam energy after acceleration is lost in the draw-out path before entering the process chamber, and the plasma density in the plasma reaction chamber decreases, causing the same harm. Also, since heat concentration occurs, the inner surface of the insulating sleeve will peel off when an insulating material is used in the bottleneck, and if metal is used in the bottleneck, it will glow due to red heat causing vaporization and contamination in the reaction chamber. Cause cations and adversely affect the process. If the drawing bottleneck is too long, it is difficult to extract and accelerate electrons. If the drawing bottleneck is too short, the thickness of the bottleneck portion becomes insufficient, and the strength cannot withstand a pressure difference. Such a situation does not occur within the above dimensional range.

Further, in the electron beam excited plasma generating apparatus of the present invention, a magnetic field applying mechanism is provided in the discharge part, so that lines of magnetic force can be formed in parallel with the discharge anode. Electrons spiral into the lines of magnetic force parallel to the surface of the discharge anode where electrons injected into the discharge part are absorbed, so that the residence time in the discharge part increases and the probability of collision with inert gas molecules such as argon increases. This has the effect of increasing efficiency and improving efficiency.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electron beam excited plasma generator according to the present invention will be described in detail with reference to the drawings.

[0015]

FIG. 1 is a block diagram for explaining the principle of a first embodiment of an electron beam excited plasma generating apparatus according to the present invention. In the electron beam excited plasma generator of this embodiment, a cathode 1, an intermediate electrode 2, a discharge anode 3, an acceleration electrode 4, and a sample stage 5 are arranged in this order. The electron beam excited plasma generator includes a cathode chamber 6 partitioned by the intermediate electrode 2, a discharge chamber 7 between the intermediate electrode 2 and the discharge anode 3, an acceleration chamber 8 between the discharge anode 3 and the acceleration electrode 4, and an acceleration electrode 4. The plasma processing chamber 9 is divided. Each of the intermediate electrode 2 and the acceleration electrode 4 has a through hole at the center. An insulator disk 10 made of ceramic such as alumina, aluminum nitride, or quartz and having a through hole at the center is fitted into the center of the discharge anode 3.

The cathode chamber 6 is provided with a gas nozzle 11 to which an inert gas such as argon gas Ar is supplied, and the acceleration chamber 8 is provided with an exhaust port 12 connected to a vacuum device. A heating power supply 13 is connected to the cathode 1 with a built-in filament. Cathode 1 is lanthanum hexaboride L
comprising a disk made of a suitable material such as aB _6, tungsten W, and is connected to the cathode of the DC power supply 14 for discharge. The intermediate electrode 2 is connected to the discharge anode 3 via the resistor 15.
Is directly connected to the anode of the discharge power supply 14.
An acceleration power supply 16 for applying an acceleration potential is connected between the discharge anode 3 and the acceleration electrode 4.

An argon gas serving as a plasma species is supplied to the cathode chamber 6 at a pressure of less than 1 Torr. When a current flows from the heating power supply 13 to the cathode 1, thermoelectrons are emitted to the surroundings, and when a voltage of the discharge power supply 14 is applied to the discharge anode 3, the discharge between the cathode 1 and the intermediate discharge electrode 2 is mediated. Discharge occurs between the anodes 3. This discharge turns the inert gas into a plasma, and the argon plasma 17 fills the discharge chamber 7. The degree of vacuum in the discharge chamber 7 is maintained at an appropriate value in the range of 0.05 Torr to 0.5 Torr.

The degree of vacuum in the acceleration chamber 8 is 0.1 m
Since the operation is performed at about 1 mTorr to 1 mTorr, the discharge chamber 7
In order to maintain the degree of vacuum at a predetermined value, it is preferable that the inner diameter of the draw-out path 3 is 4 mm or more and 8 mm or less, and the length is 1 mm or more and 20 mm or less. Since the discharge anode 3 of this embodiment is disposed around the insulator disk 10 having a draw-out narrow path, the discharge current flows avoiding the draw-out narrow path. For this reason, even if a large current of electrons flows in and something jumps out of the electrode surface, there is little fear that it will be mixed in a subsequent process. The reaction gas is supplied from a reaction gas supply port 29 provided in the plasma process chamber 9, and most of the reaction gas is exhausted from an exhaust port 30. The pressure in the plasma process chamber 9 is kept constant during film formation by a pressure adjusting mechanism (not shown).

When a voltage of an accelerating power supply 16 is applied between the discharge anode 3 and the accelerating electrode 4, an electron flow is extracted from the plasma 17 in the discharge chamber 7, accelerated and accelerated to increase the speed, and accelerated.
To the plasma process chamber 9 to ionize and dissociate gas molecules in the chamber to form a plasma, thereby forming a reaction gas plasma 1
8 is generated. The plasma gas is processed according to each purpose, and reacts with the sample 19 mounted on the sample stage 5 to form a product. The acceleration chamber 8 is evacuated from the exhaust port 12 so that the inert gas in the discharge chamber 7 and the reaction gas in the plasma process chamber 9 are not mixed. The inside of the reaction gas plasma 18 is substantially equipotential, and this equipotential range has an outer shell shape that slightly enters the inside of the discharge chamber 7 from the process chamber 9 through the accelerating electrode 4 and the draw-out path, The potential is substantially equal to the potential of the acceleration electrode 4.

If the extraction bottleneck has the same potential as the discharge anode 3, a high voltage difference is generated across a very thin boundary film having a thickness of about 1 mm, so that cations having high energy in the plasma are extracted at high speed. However, in the configuration of the present embodiment, since the draw-out path is made of an insulator, the collision of high-energy ions with a steep voltage gradient and high speed can be effectively avoided. A similar effect can be obtained when the drawing bottleneck is a conductor which is electrically insulated from other electrodes and is at a floating potential.

When the surface of the draw-out path is made of alumina, aluminum nitride, or quartz, it withstands high temperature of plasma, especially withstands thermal shock based on thermal history such as sudden rise during operation, and under high vacuum. Therefore, a high-quality reaction gas plasma with few impurities can be obtained because the amount of gas generated from the inside is small even when receiving heat. Further, aluminum nitride is a ceramic, but has a high thermal conductivity and promotes heat dissipation, so that problems due to deformation of the apparatus and thermal stress can be avoided. Also, quartz has a very low sputtering rate due to ions, so that wear can be minimized.

In this embodiment, the draw-out path member 10
Is fitted in the discharge anode 3, but the discharge anode 3 having a hole larger than the bottleneck may be concentrically bonded to the upstream surface of the bottleneck member 10. Even with such a configuration, electrons do not flow into the draw-out bottleneck, and ions in the generated plasma do not collide at high speed. It is also possible to provide a magnetic field applying mechanism composed of an air-core coil or a permanent magnet in order to facilitate the passage of electrons through the through-hole of the intermediate electrode 2, the draw-out path, and the acceleration electrode 4.

[0023]

Embodiment 2 FIG. 2 is a block diagram for explaining the principle of a second embodiment of the electron beam excited plasma generator according to the present invention. The electron beam excited plasma generator of the present embodiment
The third embodiment is different from the first embodiment in that the process chamber 9 is disposed immediately behind the discharge chamber 7 and the wall surface 31 of the process chamber is connected to the power source 16 for acceleration to form an acceleration electrode. The remaining items have the same effects as the corresponding elements of the first embodiment. In particular, bottleneck 1
The role of 0 is not different from that of the first embodiment. With such an arrangement, the installation space for the apparatus is reduced, and the distribution of plasma in the process chamber is equalized, and the reaction with the sample 19 on the sample stage 5 is homogenized.

[0024]

Third Embodiment FIG. 3 is a block diagram for explaining the principle of a third embodiment of the electron beam excited plasma generator according to the present invention. The electron beam excited plasma generator of the present embodiment differs from the first embodiment in that the side wall of the discharge chamber is formed as a discharge anode, and a draw-out path is arranged at a position shifted from the trajectory of electrons due to discharge. Thus, FIG. 3 shows only parts different from those in FIG.

Referring to FIG. 3, a draw-out path 20 formed of an insulator is arranged on an extension of a straight line connecting the cathode 1 and the intermediate electrode 2. On the other hand, the side wall of the discharge chamber 7 is formed of a metal insulated from the intermediate electrode 2 and is connected to a discharge power supply to form a discharge anode 21. In the present embodiment, the electromagnetic coil 22 is provided outside the discharge anode 21 to form magnetic lines of force parallel to the discharge anode 21.

According to the electron beam excited plasma generator of the present embodiment, the discharge current flows between the cathode 1 and the discharge anode 21 which is the side wall of the discharge chamber 7, so that the electrons do not flow directly into the draw-out path. In addition, since the magnetic field lines parallel to the surface of the discharge anode 21 exist, the electrons coming toward the discharge anode 21 cling to the magnetic field lines and cause a spiral motion, so that the residence time of the electrons in the discharge part 7 increases, and the inert gas molecules and This has the effect of increasing the probability of collision and increasing the efficiency of plasma conversion.

The plasma 23 for taking out the electron beam formed in this way fills the discharge chamber 7, and the electron beam is taken out from the draw-out path 20 by the action of an acceleration electrode (not shown), accelerated, and supplied to the process chamber. The reaction gas is turned into plasma to form a reaction gas plasma 24. Although the outer shell of the reaction gas plasma 24 is close to the extraction bottleneck 20, the potential of the extraction bottleneck 20 is dragged by the potential of the reaction gas plasma 24 so that a large potential difference does not occur. It is possible to suppress the inclusion of a bottle-path forming substance which has crashed into the surface of the substrate as impurities in the plasma.

[0028]

Fourth Embodiment FIG. 4 is a block diagram for explaining the principle of a fourth embodiment of the electron beam excited plasma generator according to the present invention. The electron beam excited plasma generator of the present embodiment is different from the first embodiment in that the extraction bottleneck is provided at a position shifted from the trajectory of the discharge electrons by providing the extraction bottleneck on the side wall of the discharge chamber. Therefore, FIG. 4 illustrates only parts different from those in FIG.

Referring to FIG. 4, a discharge anode 25 having a large area is arranged on an extension of a straight line connecting the cathode 1 and the intermediate electrode 2. Although the discharge chamber 7 is formed between the intermediate electrode 2 and the discharge anode 25, the discharge anode 25 has no through hole. On the other hand, a draw-out narrow passage 26 formed of an insulator passes from the cathode 1 through the through hole of the intermediate electrode 2 to the discharge anode 2.
5 in a direction perpendicular to the straight line.
The configuration downstream of the draw-out path 26 is the same as in the first embodiment.

According to the electron beam excited plasma generator of this embodiment, the discharge current flows between the discharge anode 25 facing the cathode 1 and the electrons do not flow directly into the draw-out path 26. The plasma 27 for taking out the electron beam formed by the electron beam fills the discharge chamber 7, and by the action of the accelerating electrode 4, the electron beam is taken out of the plasma 27 for taking out the electron beam through the narrow path 26 to the acceleration chamber 8 and accelerated. Then, the reaction gas is turned into plasma in the process chamber to form a reaction gas plasma 28. Also in the apparatus of the present embodiment, it is possible to prevent the discharge anode 25 from being worn, and to suppress the ions in the reaction gas plasma 28 from scraping the surface of the extraction bottleneck 26 to be included as impurities in the plasma. it can.

[0031]

As described in detail above, the electron beam excited plasma generating apparatus of the present invention has a small discharge anode wear, and the substance constituting the opening is mixed into the reaction chamber and adversely affects the plasma process. And a high quality plasma process can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of an electron beam excited plasma generator according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a main part of a third embodiment of the present invention.

FIG. 4 is a block diagram showing a main part of a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cathode 2 Intermediate electrode 3, 21, 25 Discharge anode 4, 31 Acceleration electrode 5 Sample table 6 Cathode chamber 7 Discharge chamber 8 Acceleration chamber 9 Plasma process chamber 10 Insulator disk with a draw-out path 11 Gas supply port 12 Exhaust port 13 Heating Power supply 14 Discharge power supply 15 Resistor 16 Acceleration power supply 17, 23, 27 Current extraction plasma 18, 24, 28 Reactive gas plasma 19 Sample 20, 26 Extraction path 22 Electromagnetic coil 29 Reaction gas supply port 30 Exhaust port

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/203 H01L 21/203 Z 21/3065 H05H 1/46 A H05H 1/46 H01L 21/302 B

Claims (8)

[Claims] 1. A cathode, an intermediate electrode, a discharge anode, and an accelerating electrode are arranged in this order, and electrons are extracted from a discharge portion formed between the intermediate electrode and the discharge anode via an extraction bottleneck, accelerated by the acceleration electrode, and accelerated by the acceleration electrode. An electron beam excited plasma generator for converting a gas in an outside process chamber into a plasma, wherein the draw-out path is electrically insulated from each electrode. 2. An electron beam excited plasma generator according to claim 1, wherein said draw-out path is formed of an insulating material. 3. The electron beam excited plasma generator according to claim 2, wherein the material of said insulating material is one of alumina, aluminum nitride and quartz. 4. A cathode, an intermediate electrode, a discharge anode, and an accelerating electrode are arranged in this order, and electrons are extracted from a discharge portion formed between the intermediate electrode and the discharge anode via an extraction bottleneck and accelerated by the acceleration electrode to form a bottleneck. An electron beam excitation plasma apparatus for converting a gas in a process chamber outside into an electron beam, wherein the extraction bottleneck is provided in a direction at an angle to a direction connecting an intermediate electrode and a discharge anode. Plasma generator. 5. An electron beam excited plasma generator according to claim 4, wherein said draw-out path is electrically insulated from each electrode. 6. The electron beam excited plasma generator according to claim 1, wherein the drawing narrow path has a diameter of 4 mm or more and 8 mm or less. 7. The drawing bottleneck is 1 mm or more and 20 mm or more.
The electron beam excited plasma generator according to any one of claims 1 to 6, having the following length. 8. A magnetic field application mechanism is provided in the discharge unit,
8. The electron beam excited plasma generator according to claim 1, wherein magnetic lines of force are formed in parallel with the discharge anode.