JPH08255697A - High frequency discharge method, discharge device therefor, and high frequency discharge treatment device using this discharge device - Google Patents

Abstract

PURPOSE: To eliminate the loss of electrons resulted from the electrostatic coupling of an antenna with a plasma even when the surface of an antenna conductor is not covered with a dielectric. and prevent the abnormal rise of the plasma potential by covering the circumference of the looped antenna conductor with a magnetic force line. CONSTITUTION: When a high frequency power source 13 is operated to apply a high frequency power to an antenna 11, the process gas supplied into a vessel is excited and laid in plasma state. In this state, a workpiece is subjected to a plasma working such as etching or CVD. When a DC power source 14 is operated at this time to apply a DC power to the antenna 11, the circumference of the antenna 11 can be covered with a magnetic force line. Thus, the electrons in the plasma are insulated from the surface of the antenna 11 by the magnetic force line, and the potential of the plasma can be prevented from being abnormally raised by the electrostatic coupling of the antenna 11 with the ions, and the spattering by the ions can be also prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thin film element, a high frequency discharge method used for a plasma source such as a particle beam source and an analyzer, a discharge apparatus therefor and a high frequency treatment apparatus using the discharge apparatus.

[0002]

2. Description of the Related Art A device having a thin film whose constituent elements are metals, semimetals, semiconductors, oxides, nitrides, boron, etc.
A wide variety of storage devices such as LSIs, magnetic recording devices, optical recording devices, communication devices such as semiconductor lasers and photoelectric conversion devices, flat-panel displays, display devices such as solid-state imaging devices, energy devices such as solar cells, etc. It has been applied to major parts of equipment and is expected to develop technically as an essential part for making devices smaller and having higher performance.

Miniaturization of the structure of the thin film element as described above,
As the performance is advanced, a plasma process in which various raw materials are decomposed by using discharge plasma or a solid material is sputtered to perform CVD or etching is used as a manufacturing method thereof. Therefore, as a plasma source, inductively coupled high-frequency plasma in the presence or absence of a magnetic field is in the limelight.

Generally, the inductively coupled high frequency plasma in a magnetic field or a magnetic field is generated by a loop antenna placed outside the vacuum container. This method is usually called an external antenna method. That is, in the case of this external antenna method, a magnetic field generated by a high frequency current flowing through the antenna is applied to the process gas in the vacuum container through a dielectric window such as quartz or ceramic formed in the vacuum container to generate plasma. It has become. At this time, the high frequency power is coupled with the plasma through the induction electromagnetic field.

As the process gas, a raw material gas is used in the case of CVD and a reactive gas for etching is used in the case of etching. However, a strong electrostatic field is also generated around the antenna, accelerating the ions and causing damage to the dielectric window. This not only shortens the life of the dielectric window, but also causes impurities such as etching and C
This will deteriorate the process such as VD.

Such electrostatic coupling between the antenna and the plasma can be prevented by applying Faraday shield, but this shield also weakens the electromagnetic coupling most necessary for plasma generation. There are drawbacks.

The external antenna method for electromagnetically coupling through the above-mentioned dielectric window has the drawback that the window material is more easily mechanically damaged than metal, and is also difficult to apply to the process of conductive materials. Sometimes.

That is, in the former case, one of the factors that deteriorate the mechanical strength is that it is consumed by a process such as etching and the life is limited. In the latter case, a conductive thin film is deposited on the inner surface of the dielectric window, and the electromagnetic coupling necessary for plasma generation is interrupted by the eddy current flowing in the film, so that the discharge may stop.

As a method of solving such a problem, it is conceivable to directly arrange a metal antenna in a vacuum container and employ an internal antenna system in which a high-frequency current is passed. In this case as well, a conductive film is deposited on the surface of the antenna, but since the antenna is originally made of metal, there is no problem.

However, in this method, the antenna directly contacts the plasma generated in the vacuum vessel, so that the loss of electrons increases due to electrostatic coupling, the plasma potential rises abnormally, and arcing occurs and discharge occurs. Becomes unstable and the plasma density cannot be increased.

The above-mentioned abnormal increase in plasma potential can be prevented by covering the surface of the metal antenna with a dielectric to insulate it. However, in the case of an antenna insulated with a dielectric, as in the case of the above-mentioned dielectric window, sputtering occurs because ions hit the dielectric on the surface of the antenna, causing problems such as generation of impurities and shortening of the life of the antenna. Will occur.

[0012]

As described above, when the antenna is installed outside the vacuum container, the window member may be prematurely damaged or impurities are generated. When the antenna is installed inside the vacuum container, the antenna may be damaged. Since the plasma is directly touched, the plasma potential is abnormally increased to cause arcing, the discharge becomes unstable, and the plasma density cannot be increased.

If the surface of the antenna is coated with a dielectric material in order to increase the plasma density, the generation of impurities due to sputtering and the early damage of the antenna may occur.

The object of the present invention described in claim 1 is to:
It is an object of the present invention to provide a high-frequency discharge method capable of preventing an abnormal increase in plasma potential by eliminating the loss of electrons caused by the electrostatic coupling between the antenna and the plasma without coating the surface of the antenna conductor with a dielectric. .

The object of the present invention set forth in claim 2 is:
It is an object of the present invention to provide a high-frequency discharge device capable of eliminating an electron loss caused by electrostatic coupling between an antenna and plasma and preventing an abnormal rise in plasma potential even if the surface of the antenna conductor is not covered with a dielectric.

The object of the present invention set forth in claim 3 is:
Even if the surface of the antenna provided in the container is not covered with a dielectric, by eliminating the loss of electrons due to the electrostatic coupling between the antenna and the plasma, the workpiece can be removed without causing an abnormal rise in the plasma potential. It is an object of the present invention to provide a high-frequency discharge treatment device capable of treating.

[0017]

In order to solve the above-mentioned problems, the invention described in claim 1 generates a discharge plasma by causing a high-frequency current to flow in a loop antenna conductor to generate a fluctuating magnetic field. In the high frequency discharge method, there is provided a high frequency discharge method characterized by covering the periphery of the antenna conductor with magnetic lines of force.

According to a second aspect of the present invention, there is provided a high frequency discharge method according to the first aspect of the invention, in which the antenna conductor is covered with magnetic lines of direct current or low frequency.

According to a third aspect of the present invention, there is provided a high frequency discharge device for generating discharge plasma by causing a high frequency current to flow in a loop antenna conductor to generate a fluctuating magnetic field. A high-frequency discharge device comprising: a high-frequency power source for flowing a high-frequency current; and a magnetic force line generating means for generating magnetic force lines covering the loop antenna.

According to a fourth aspect of the invention, in the invention of the third aspect, the magnetic force line generating means is a DC power source or a magnet. A fifth aspect of the present invention is the high-frequency discharge device according to the third aspect, wherein the loop-shaped antenna has a plurality of turns.

According to a sixth aspect of the present invention, in a high-frequency electric discharge treatment apparatus for treating a workpiece with an electric discharge plasma, a container in which the workpiece is installed and a process gas is supplied, and the container. A loop-shaped antenna provided inside, a high-frequency power source that excites the process gas to generate plasma by generating a fluctuating magnetic field by applying a high-frequency current to the antenna, and a magnetic field line that covers the periphery of the antenna. A high-frequency discharge treatment device is provided with a magnetic force line generating means for generating the magnetic force lines.

According to a seventh aspect of the present invention, in the high frequency electric discharge processing apparatus according to the sixth aspect, the magnetic force line generating means is a DC power source or a magnet.
The invention described in claim 8 is the high-frequency electric discharge processing device according to the invention of claim 6, wherein the loop-shaped antenna has a plurality of turns.

[0023]

According to the inventions of claims 1 and 3, when the magnetic field lines surround the anten, electrons are prevented from reaching the antenna surface. Therefore, the antenna surface is not covered with a dielectric. In addition, it is possible to prevent the antenna from being sputtered due to an abnormal increase in the plasma potential due to electrostatic coupling between the antenna and the plasma.

According to the second and fourth aspects of the present invention, it is possible to surely cover the periphery of the antenna with magnetic field lines of either DC or low frequency. According to the invention of claim 5, by making the number of turns of the antenna plural, the strength of the magnetic field formed by this antenna is enhanced, and the probability that the ions collide with the surface of the antenna becomes low.

According to the sixth aspect of the present invention, even if the antenna is provided in the container, the workpiece can be plasma-processed without causing the generation of impurities and the early life of the antenna.
According to the invention of claim 7, it is possible to surely cover the periphery of the antenna with a magnetic field line of either DC or low frequency.

According to the eighth aspect of the invention, by making the number of turns of the antenna plural, the strength of the magnetic field formed by this antenna is enhanced, and the probability of ions colliding with the antenna surface is reduced.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows the high-frequency discharge treatment apparatus of the present invention, in which 1 is a stainless steel container. This container 1
An exhaust pipe 3 having an exhaust pump 2 in the middle is connected to the bottom of the exhaust pipe 3. By operating the exhaust pump 2, the inside of the container 1 is depressurized.

A supply pipe 4 for a process gas such as a reactive gas for etching or a raw material gas for CVD is connected to the upper portion of the container 1. The supply pipe 4 communicates with a process gas supply unit (not shown). Therefore, the process gas is supplied into the container 1. A table 6 is provided in the container 1 and the table 6 is provided.
A workpiece 7 to be etched or CVD is placed on the bull 6 as described later.

Further, inside the container 1, there is provided a loop-shaped antenna 11 made of a conductive material. In this embodiment, the antenna 11 is formed with a plurality of turns, for example, two turns, and both ends thereof are led out from the peripheral wall of the container 1 to the outside in an airtight manner. One end of the antenna 11 led out is grounded, and the other end is connected to the drive controller 12.

As shown in FIG. 1, the drive control section 12 comprises a high frequency power source 13 and a DC power source 14 as a magnetic force generating means, which are connected in parallel to the other end of the antenna 11. Note that the number of turns of the antenna 11 is not limited at all, and may be one instead of a plurality of turns, but a plurality of turns is preferable to enhance the magnetic field.

When the high frequency power source 13 is operated to apply the high frequency power of the antenna 11, the high frequency power excites the process gas supplied into the container 1,
The gas becomes a plasma state. Therefore, the workpiece 7 in the container 1 is subjected to plasma processing such as etching and CVD according to the type of process gas supplied to the container 1.

When DC power is applied to the antenna 11 by operating the DC power supply 14, the periphery of the antenna 11 can be covered with magnetic lines of force as described later. Therefore, the electrons in the plasma are insulated from the surface of the antenna 11 by the magnetic lines of force, so that not only the plasma potential is prevented from abnormally rising due to electrostatic coupling between the antenna 11 and the ions, but also the sputtering by the ions is prevented. It can also be prevented from occurring.

FIG. 6 illustrates a case where the periphery of the antenna 11 is covered with the magnetic field lines B 1. That is, consider a case where a high-frequency current flows along the linear-cylindrical antenna 11 with the radius a placed in the plasma P.

First, a cylindrical coordinate system (r, θ, z) is taken as shown in the figure. At this time, high-frequency charges appear on the surface of the conductor (antenna 11), and the charged particles in the plasma P are accelerated in the r direction. Since electrons are lighter than ions, more electrons are absorbed by the antenna 11, and as a result, the plasma potential rises abnormally. Further, the surface of the antenna 11 is negatively charged on a time average, and is attracted to the negative potential, and positive ions hit the surface of the antenna 11 to cause metal sputtering.

However, when the surface of the antenna 11 is covered in the θ direction by the magnetic force line B, the electron e is bent by the Lorentz force as shown by the arrow, so that it becomes difficult to reach the surface of the antenna 11. That is, since the electrons are insulated from the magnetic field generated by the magnetic force lines B 1, it is prevented that the electrons are absorbed by the antenna 11 and the plasma potential rises abnormally. Further, since the surface of the antenna 11 is not negatively charged, positive ions are less likely to hit the surface of the antenna 11 to cause sputtering.

The condition for the magnetic force lines B 1 to function effectively is that the magnetic force lines B 1 do not interlink with the surface of the antenna 11, and in the case of FIG. It may be in a helical shape.

In the embodiment shown in FIG. 1, the direct current I _DC is superposed on the high frequency current I _RF and is fed to the antenna 11. However, as shown in FIG. 5, a permanent magnet or an electromagnet is provided near the antenna 11. You may make it arrange | position the magnet 21. Since the magnet 21 itself fluctuates with a high-frequency potential and accompanies a linear Kaps magnetic field, it is possible to insulate the surroundings of the antenna 11 by the magnetic field line B.

That is, the DC power source 14 is used as a means for generating magnetic lines of force according to the usage pattern of the antenna 11 or the like.
The magnet 21 may be used. Next, the experimental results of the present invention will be described. The antenna 11 was installed in a stainless steel container 11 as a one-turn copper loop antenna having a diameter of about 10 cm, and a high-frequency current of 13.56 MHz was passed through the antenna 11 while a direct current I _DC was passed. Hydrogen was used as the process gas for discharge, and the pressure inside the container 1 was
The plasma potential Vp was measured when the direct current I _DC was changed while maintaining the high frequency power constant at 40 W for both 0.6 mTorr and 2 mTorr.

The results are shown in FIG. The plasma potential Vp on the vertical axis of this figure is a value measured at a position 3 cm away from the surface of the antenna 11. It was confirmed that when the DC current I _DC was 100 A or less and the magnetic field was weak, the plasma potential Vp was high, arcs frequently occurred, and the discharge became unstable. However, as the DC current I _DC increases, the plasma potential Vp decreases as is apparent from the figure. As a result, the increase in plasma density could be confirmed.

In FIG. 4, the relationship between the high frequency power W and the direct current I _DC was measured using hydrogen gas pressure as a parameter. From this experiment, it was found that the higher the high frequency power W, the higher the minimum DC current I _DC required to stabilize the discharge. That is, as described with reference to FIG. 3, as the direct current I _DC increases, the plasma potential Vp decreases and the discharge can be stabilized. However, as can be seen from FIG. 4, in order to stabilize the discharge, the gas pressure must be reduced. The higher is, the larger the direct current I _DC is required. This can be considered because the effect of the magnetic field on the electrons is weakened by the collision.
To enhance the magnetic field, the DC current I _DC flowing through the antenna 11 may be increased or the number of turns of the antenna 11 may be increased.

That is, the DC power source 14 causes the antenna 1
The plasma potential Vp can be lowered by forming a magnetic field around the antenna 11 by passing a DC current I _DC to the antenna 1. If the plasma potential Vp becomes low, the antenna 1
Since the impact of the ions on 1 is also reduced, the antenna 11 is prevented from being damaged.

Moreover, when the plasma potential is lowered by flowing the direct current I _DC , the plasma density is increased. Therefore, the plasma density can be increased without increasing the gas pressure as in the conventional case, so that the high-frequency discharge can be reduced in pressure, and if the plasma density can be increased, the diameter can be increased. Become.

[0043]

As described above, according to the first and second aspects of the present invention, the antenna used for generating the discharge plasma is covered with magnetic lines of force, so that the lines of magnetic force in the plasma are used. The electrons are insulated from the antenna.

Therefore, the plasma potential is prevented from rising abnormally, and the antenna is prevented from being sputtered by the ions to be damaged in an early stage. Moreover, unlike the conventional case, the antenna is not covered with a dielectric to insulate and insulate the plasma potential. Since the abnormal rise is prevented, it is possible to provide a high frequency discharge method that does not cause the generation of impurities.

According to the third and fourth aspects of the present invention, by covering the periphery of the antenna with magnetic lines of force, the antenna is not sputtered by the ions and is not damaged at an early stage, and impurities are not generated. A discharge device can be provided.

According to the fifth aspect of the present invention, by making the number of turns of the loop-shaped antenna plural, the magnetic field formed around the antenna by the lines of magnetic force can be enhanced, so that the discharge can be stabilized. it can.

According to the sixth and seventh aspects of the present invention, it is possible to provide a high-frequency electric discharge treatment apparatus capable of performing electric discharge treatment on a workpiece without causing early damage to the antenna or generation of impurities.

According to the eighth aspect of the present invention, the number of turns of the loop-shaped antenna is plural, whereby the magnetic field formed around the antenna by the lines of magnetic force can be enhanced to stabilize the discharge. Therefore, it becomes possible to precisely perform the electric discharge treatment on the workpiece in the container.

[Brief description of drawings]

FIG. 1 is a schematic view of a high frequency discharge device of the present invention.

FIG. 2 is a schematic view of a high frequency discharge treatment apparatus using the high frequency discharge apparatus.

FIG. 3 is a graph showing the relationship with the plasma potential when the DC power supply is changed.

FIG. 4 is a graph showing the relationship between high frequency power and DC current, with gas pressure as a parameter.

FIG. 5 is an explanatory diagram for generating lines of magnetic force by a magnet around an antenna.

FIG. 6 is an explanatory diagram illustrating a relationship between magnetic force lines and movement of electrons when magnetic force lines are generated around the antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 7 ... Workpiece, 11 ... Antenna, 12 ... Drive control part, 13 ... High frequency power supply, 14 ... DC power supply, 21 ... Magnet

Claims (8)

[Claims] 1. A high-frequency discharge method for generating discharge plasma by flowing a high-frequency current to a loop-shaped antenna to generate a fluctuating magnetic field, wherein the antenna is covered with magnetic lines of force. Method. 2. The high frequency discharge method according to claim 1, wherein the antenna is covered with a magnetic field line of direct current or low frequency. 3. A high-frequency discharge device for generating a discharge plasma by causing a high-frequency current to flow in a loop-shaped antenna to generate a fluctuating magnetic field, and a high-frequency power source for supplying a high-frequency current to the loop-shaped antenna, A high frequency electric discharge device comprising: a magnetic force line generating means for generating a magnetic force line that covers the periphery of the loop-shaped antenna. 4. The high frequency discharge device according to claim 3, wherein the magnetic force line generating means is a DC power source or a magnet. 5. The high frequency discharge device according to claim 3, wherein the loop-shaped antenna has a plurality of turns. 6. A high-frequency electric discharge treatment apparatus for treating a workpiece with an electric discharge plasma, a container in which the workpiece is installed and a process gas is supplied, and a loop provided in the container. -Shaped antenna, a high-frequency power source that excites the process gas to generate plasma by generating a fluctuating magnetic field by flowing a high-frequency current through the antenna, and a magnetic force line generation unit that generates magnetic force lines covering the antenna. A high-frequency discharge treatment device characterized in that 7. The high frequency electric discharge processing apparatus according to claim 6, wherein the magnetic force line generating means is a DC power source or a magnet. 8. The high frequency electric discharge processing apparatus according to claim 6, wherein the loop-shaped antenna has a plurality of turns.